Technical Handbook for

Radio Monitoring

VHF/UHF

Edition 2013

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Dipl.- Ing. Roland Prösch Dipl.- Inf. Aikaterini Daskalaki-Prösch

Technical Handbook for

Radio Monitoring

VHF/UHF

Edition 2013

Books on Demand GmbH

Description of modulation techniques and waveforms on VHF/UHF with 232 pictures and 85 tables

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© 2013 Dipl.- Ing. Roland Prösch, Dipl.- Inf. Aikaterini Daskalaki-Prösch Email: roland@proesch.net, k.daskalaki@gmx.de Production and publishing: Books on Demand GmbH, Norderstedt, Germany Cover design: Anne Prösch Cover fotos: Mike Höhn, Roland Prösch Printed in Germany Webpage: technicalhandbook.frequencymanager.de ISBN 9783732241477

Bibliografische Information der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.d-nb.de abrufbar.

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Acknowledgement: Thanks for those persons who have supported us in the preparation of this book. Oscar Diez Disclaimer: The information in this book have been collected over years. The main problem is that there are not many open sources to get information about this sensitive field. Although we tried to verify these information from different sources it may be that there are mistakes. Please do not hesitate to contact us if you discover any wrong description.

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Content

1. LIST OF PICTURES 15

2. LIST OF TABLES 21

3. GENERAL 23

4. DESCRIPTION OF WAVEFORMS 25

Analogue Waveforms 25 Amplitude Modulation (AM) 25

Double Sideband reduced Carrier (DSB-RC) 26 Double Sideband suppressed Carrier (DSB-SC) 26 Single Sideband full Carrier 27 Single Sideband reduced Carrier (SSB-RC) 28 Single Sideband suppressed Carrier (SSB-SC) 28 Single Sideband Modulation (SSB) 28 Independent Sideband Modulation (ISB) 29 Vestigal Sideband Modulation (VSB) 30

Frequency Modulation (FM) 31 Wide Frequency Modulation (WFM) 32

Digital Waveforms 33 Amplitude Shift Keying (ASK) 33 Frequency Shift Keying (FSK) 34

Continuous Phase Frequency Shift Keying (CPFSK) 35 Double Frequency Shift Keying (DFSK) 35 Constant Envelope 4-Level Frequency Modulation (C4FM) 36 Minimum Shift Keying (MSK) 37 Tamed Frequency modulation (TFM) 38 Gaussian Minimum Shift Keying (GMSK) 38 Multi Frequency Shift Keying (MFSK) 38

Phase Shift Keying (PSK) 40 Binary Phase Shift Keying (BPSK) 40 Quadrature Phase Shift Keying (QPSK) 42 Offset Quadrature Phase Shift Keying (OQPSK) 44 Staggered Quadrature Phase Shift Keying (SQPSK) 44 Compatible Differential Offset Quadrature Phase Shift Keying (CQPSK) 44 Coherent Phase Shift Keying (CPSK) 45 Differential Coherent Phase Shift Keying (DCPSK) 45 8PSK Modulation 45 Differential Phase Shift Keying (DPSK) 46 Differential Binary Phase Shift Keying (DBPSK) 46 Differential Quadrature Phase Shift Keying (DQPSK) 46 Differential 8 Phase Shift Keying (D8PSK) 46

Quadrature Amplitude Modulation (QAM) 47 Orthogonal Frequency Division Multiplexing (OFDM) 49

Spread Spectrum (SS) 51 Direct Sequence Spread Spectrum (DSSS) 51 Frequency Hopping Spread Spectrum (FHSS) 52

Incremental Frequency Keying (IFK) 52 Analogue Pulse Modulation 53

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Pulse Amplitude Modulation (PAM) 53 Pulse Width Modulation (PWM) 53 Pulse Position Modulation (PPM) 53

Digital Pulse Modulation 54 Pulse Code Modulation (PCM) 54 Delta Modulation 54

Description of modulation states 56 Asynchronous Data Transmission 56 Synchronous Data Transmission 56 Simplex 57 Duplex 57 Half duplex 57 Semi duplex 57

Bit Rate, Symbol Rate, Baud Rate 58 Bit rate 58 Symbol rate 58 Baud rate 58

Data formats 59 NRZ (Non Return to Zero) 60 NRZ (S) (Non Return to Zero - Space) 60 NRZ (M) (Non Return to Zero - Mark) 60 Bi-Ф-L (Bi-phase Level) 60 Bi-Ф-S (Bi-phase Space) 60 Bi-Ф- M (Bi-phase Mark) 60

Coding 61 Code 61 Codes in communication used for brevity 61 An example: the ASCII code 61 Codes to detect or correct errors 62 Error-correcting code (ECC) 62 Forward Error Correction (FEC) 62 Convolutional code 63 Viterbi algorithm 63 Reed-Solomon error correction 64

Overview of the method 64 Properties of Reed-Solomon codes 64 Use of Reed-Solomon codes in optical and magnetic storage 65 Timeline of Reed-Solomon development 65 Satellite technique: Reed-Solomon + Viterbi coding 65

Turbo code 66 Shannon-Hartley theorem 66

Theorem 66 Examples 67

Used code tables 68 ITA2, ITA2P and ITA3(CCIR342-2) 68 Russian MTK2 69 CCIR476-4, HNG-FEC, PICCOLO MK VI 70

ITA 2 P 71 ITA 3 71 CCIR 476 71 ASCII / CCITT 5 71

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Frequency-division multiple access (FDMA) 75 Time division multiple access (TDMA) 75 Code division multiple access (CDMA) 76 Orthogonal Frequency multiple access (OFDMA) 76

The OSI Reference Model 77 The Physical Layer 77 The Data Link Layer 78 The Network Layer 78 The Transport Layer 79 The Session Layer 80 The Presentation Layer 80 The Application Layer 80

Protocols 81 ACP127 81 STANAG 4406 Messaging 81 STANAG 5066 82 X.25 83 RSX.25 88

Designation of Emissions 89 Determination of Necessary Bandwidths 93

5. VHF MODES 101 ACARS 101 ADS-B 105 AIS 106 AMPS 109 APCO 25 110 ARDIS 112 ATCS 114 ATIS 117 BIIS 118 Bluetooth 119

Bluetooth 1.0 and 1.0B 120 Bluetooth 1.1 120 Bluetooth 1.2 120 Bluetooth 2.0 + EDR 120 Bluetooth 2.1 + EDR 121 Bluetooth 3.0 + HS 121 Bluetooth 4.0 121

Broadcast WFM 122 Pre-emphasis and de-emphasis 123

CCIR-1 123 CCIR-2 124 CCITT 125 CDMA One 125 CDMA2000 126 CDPD 126 Cordless Phone 130

Analogue Standard CT0 131 Analogue Standard CT0 (Extended) 131 Analogue Standard CT1 131 Analogue Standard CT1+ 131 Digital Standard CT2 131

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Digital Standard CT2+ 132 Digital Standard CT3 133

CTCSS 133 DAB 134

DAB Bands and modes 134 Audio codec 135 DAB Error-correction coding 135 DAB Single-frequency networks 136 DAB Bit rates 136 DAB Frequencies 136

DAB+ 140 D-AMPS 141 DCSS 143 DECT 144 DPMR 145

DPMR Mode 1 146 DPMR Mode 2 147 DPMR Mode 3 147 DPMR Framing 147 DPMR Burst Structure 148

DSTAR 150 DSTAR Framing 151 DSTAR Radio Header 151 DSTAR data 153 DSTAR voice 153

DTMF 155 DVB-T 155 EEA 160 EIA 161 EPIRB 162 EPLRS 164 ERMES 165 Data Format 166

Hierarchy 166 EUROSIGNAL 167 EXICOM EX7100 168 Family Radio Service 168 FLEX 170 FMS BOS 173 FSK 441 174 GMDSS-DSC VHF 176 GMRS 178 GSM 179

The system components in GSM 181 MS (Mobile Station) 181 BSS (Base Station System) 182 NSS (Network and Switching Subsystem) 182 OSS (Operations Support System or Operation Subsystem) 182

Overview of the network architecture 183 GSM Interfaces 184 Logical Channels of the radio channel 185

Broadcast Channel (BCH) 187 Common Control Channel (CCCH) 187 Dedicated Control Channel (DCCH) 187

Bursts and frame structure 187 Normal burst 188 Frequency correction burst 189 Synchronization burst 189

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Dummy burst 189 Access burst 189

Frequency Hopping 190 Have Quick 192 ITU Fax and Modem Standards 193

Modem Standards 193 V.19 Modem Standard 194 V.21 Modem Standard 194 V.22 Modem Standard 194 V.22 bis Modem Standard 195 V.23 Modem Standard 196 V.26 Modem Standard 196 V.26bis Modem Standard 197 V.26ter Modem Standard 197 V.27 Modem Standard 197 V.32 Modem Standard 197 V.32bis Modem Standard 197 V.33 Modem Standard 197 V.36 Modem Standard 197 V.37 Modem Standard 197 V.38 Modem Standard 198 V.90 Modem Standard 198

Fax Standards 198 V.17 FAX Standard 199 V.29 FAX Standard 199 V.27bis FAX Standard 199 V.27ter FAX Standard 200 V.34 FAX Standard 200

DSVD and H.324 Standards 200 JT2 201 JT44 202 JT6M 203 LINK 4A/C 203

LINK 4A 204 LINK 4C 204

LINK 11 CLEW 204 LINK 11 SLEW 207 LINK 14 208 LINK Y 209 LINK Z 210 LINK 16 210 LINK 22 211 LTE 212 MDC-600/MDC-1200 215 MDC-4800 216 Mobitex-1200 217 Mobitex-8000 218

RAM 218 MPT 1327 220 NATEL 221 NMT-450 221 NOAA Weather Radio 222

Elements of NWR SAME Messages 222 Message Format of NRW SAME 224 Codes of NWR SAME 227

EAS Event (NWR-SAME) Codes 227 Packet Radio 229 PMR 230

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POCSAG 231 Preamble Structure 231 Batch Structure 232 Frame Structure 232

Address codeword 232 Message codeword 233 Idle Codeword 233 Numeric Message Format 233 Alpha-Numeric Message Format 234

Radiosondes 235 VAISALA RS80 15GH 236 VAISALA RS92 KL 237 VAISALA RS92 SGPD 238 M2 K2 239 Table of Radiosondes 240

Railnet 241 RD-LAP 243 RDS/RBDS 244

RDS data structure 246 Harris RF 7800V 249 SEM93 254 SENOA MSK Hopping System 257 TACAN 258 TETRA 259 TETRA II 265 TETRAPOL 266 Trunked Radio 268 Terrestrial Television Analogue 269 Terrestrial Television Digital 274 VDEW 275 VHF Digital Link Modes 275 Frequency Allocation 275 VDL Mode 1 277 VDL Mode 2 277 VDL Mode 3 278 VDL Mode 4 279 ZVEI 1 282 ZVEI 2 283 ZVEI 2 xx tones 283

6. RADAR 285 GRAVES 285 METEOR RADAR 287 NAVSPASUR 288

7. SATELLITES 291 COSPAS-SARSAT 291 INMARSAT 292

INMARSAT-A 293 INMARSAT Aero H 293 INMARSAT Aero H+ 293 INMARSAT Aero I 293 INMARSAT Aero L 293 INMARSAT Aero Mini-M 294 INMARSAT-B 294 INMARSAT-C 294

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INMARSAT Mini-C 296 INMARSAT D 296 INMARSAT D+ 297 INMARSAT-E 297 INMARSAT-M 297 INMARSAT mini-M 298 INMARSAT Fleet F33 298 INMARSAT Fleet F55 299 INMARSAT Fleet F77 299 INMARSAT GAN/M4 300 INMARSAT Regional BGAN 300 INMARSAT Swift64 300 INMARSAT TDM channel details 301

INMARSAT Packet Formats 304 INMARSAT-C Raw Frame Example 304 LES ID Structure 304 Packet Descriptor with variable size (1-2 Bytes): 304 Bulletin Board Packet - LES Status / Services Bytes (Byte 9-11) 305 Bulletin Board Packet 306 Signalling Channel Packet 306 Logical Channel Assignment Packet 307 Enhanced Data Report Acknowledgement Packet 307 Logical Channel Clear Packet 308 Inbound Message Acknowledgement Packet 308 Acknowledgement Request Packet 308 Message Packet 309 Multiframe Message Packet 309 Multiframe Message Continued Packet 310 Request Status Packet 310 Distress Test Request Packet 310 Distress Alert Acknowledgement Packet 311 Distress Test Results Packet 311

ORBCOMM 312 ORBCOMM Downlink 313 ORBCOMM SDPSK modulation 313 ORBCOMM Downlink Data Format 313 ORBCOMM subscriber uplink 314 ORBCOMM uplink GES to Satellite Channels 315 ORBCOMM beacon 315

STEREO-A/B 315 STEREO Telemtry 317

Thuraya 317 UHF Satellites 320

8. TABLES FOR RADIO MONITORING 323

Allocation of International Call Signs 323

Alphabetical List of Country Codes 327

Selective Calling 331

Allocation of Maritime Identification Digits 335

Weather Forecast (TAF and METAR) 348

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TAF 348 METAR 348

Q , X and Z - Code 351 Q-Codes 351 X-Codes 361 Z-Codes 362

Abbreviations 371

9. INDEX 379

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1. List of Pictures

Picture 1: Different AM waveforms ................................................................................................. 25 Picture 2: Spectrum and sonagram of an amplitude modulation .................................................... 26 Picture 3: Spectrum of a double sideband suppressed carrier signal ............................................. 27 Picture 4: Spectrum and sonagram of a single sidband modulation with full carrier ..................... 27 Picture 5: Spectrum and sonagram of a single sidband modulation with reduced carrier ............. 28 Picture 6: Spectrum of a single sideband modulation ..................................................................... 29 Picture 7: Spectrum of an independent modulated signal ............................................................... 29 Picture 8: Frequency Modulation .................................................................................................... 31 Picture 9: Spectrum and sonagram of a frequency modulation ...................................................... 31 Picture 10: Spectrum of a wide FM broadcast transmitter ............................................................. 32 Picture 11: Amplitude Shift Keying (ASK) ....................................................................................... 33 Picture 12: Spectrum of an ASK with 100 Bd .................................................................................. 33 Picture 13: Oscilloscope display of an ASK .................................................................................... 34 Picture 14: Frequency Shift Keying (FSK) ...................................................................................... 34 Picture 15: Spectrum of an FSK ...................................................................................................... 34 Picture 16: Spetrum of a CPFSK with 100 Bd ................................................................................. 35 Picture 17: Spectrum of a DFSK ..................................................................................................... 36 Picture 18: IQ Plot of C4FM ........................................................................................................... 36 Picture 19: Sonagram and spectrum of C4FM in idle mode ........................................................... 37 Picture 20: Minimum Shift Keying ................................................................................................... 38 Picture 21: Spectrum of a Tamed Frequency Modulation (TFM 3) with 100 Bd ............................ 38 Picture 22: Spectrum of a MFSK with 12 tones ............................................................................... 39 Picture 23: Phase shift Keying ......................................................................................................... 40 Picture 24: BPSK-A ......................................................................................................................... 40 Picture 25: Phase plane of a BPSK ................................................................................................. 41 Picture 26: Spectrum of a BPSK with 600 Bd ................................................................................. 41 Picture 27: BPSK-B ......................................................................................................................... 41 Picture 28: QPSK-A ......................................................................................................................... 42 Picture 29: QPSK-B ......................................................................................................................... 43 Picture 30: Spectrum of a QPSK with 600 Bd ................................................................................. 43 Picture 31: Phase plane of a QPSK ................................................................................................. 43 Picture 32: Phase plane of an OQPSK (right) compared to QPSK (left) ........................................ 44 Picture 33: Phase Plane of an 8PSK ............................................................................................... 45 Picture 34: Spectrum of an 8PSK with 600 Bd ................................................................................ 46 Picture 35: Example of an 8QAM and 16QAM in the Phase Plane ................................................ 47 Picture 36: Spectrum of a QAM8 with 600 Bd ................................................................................ 48 Picture 37: Spectrum of a QAM16 with 600 Bd .............................................................................. 48 Picture 38: Comparison of FDM and OFDM ................................................................................. 49 Picture 39: Spectrum of an audio OFDM with 45 channels ............................................................ 49 Picture 40: Spectrum of an OFDM for DAB ................................................................................... 50 Picture 41: Function of DSSS .......................................................................................................... 51 Picture 42: Function of FHSS .......................................................................................................... 52 Picture 43: Different types of amplitude modulation ....................................................................... 53

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Picture 44: Quantization in a PCM ................................................................................................. 54 Picture 45: Delta Modulation .......................................................................................................... 55 Picture 46: Common data formats .................................................................................................. 59 Picture 47: Principle of FDMA ....................................................................................................... 75 Picture 48: Principle of TDMA ....................................................................................................... 75 Picture 49: Principle of OFDMA .................................................................................................... 76 Picture 50: The OSI reference model .............................................................................................. 77 Picture 51: STANAG 5066 layers .................................................................................................... 82 Picture 52: Spectrum of ACARS .................................................................................................... 101 Picture 53: Sonagram of ACARS packets ...................................................................................... 101 Picture 54: Mode S short squitter frame ....................................................................................... 105 Picture 55: Mode S extended squitter frame ................................................................................. 105 Picture 56: PPM of ADS-B ............................................................................................................ 106 Picture 57: Framing of ADS-B ...................................................................................................... 106 Picture 58: AIS frame .................................................................................................................... 106 Picture 59: AIS spectrum and sonogram ....................................................................................... 107 Picture 60: Framing of APCO25 ................................................................................................... 110 Picture 61: Spectrum and sonagram of an ARDIS signal with 4800 Bps ..................................... 112 Picture 62: Spectrum and sonagram of a 4FSK ARDIS signal with 19200 Bps ........................... 113 Picture 63: Framing of MDC-4800 in an ARDIS signal ............................................................... 113 Picture 64: Framing of RD-LAP in an ARDIS signal ................................................................... 114 Picture 65: Spectrum and sonagram of an ATCS signal ............................................................... 115 Picture 66: Structure of a 5 serie address ..................................................................................... 115 Picture 67: Structure of a 7 serie address ..................................................................................... 116 Picture 68: Spectrum of an ATIS 1200 Bd signal with test loop ................................................... 117 Picture 69: Spectrum of BIIS ......................................................................................................... 118 Picture 70: Format of a Bluetooth frame ...................................................................................... 119 Picture 71: Spectrum of a WFM .................................................................................................... 122 Picture 72: Spectrum of FM stereo with sub-channels.................................................................. 123 Picture 73: Spectrum of a CCIR-1 signal ...................................................................................... 124 Picture 74: Spectrum of a CCIR-2 signal ...................................................................................... 124 Picture 75: Spectrum of CCITT signal .......................................................................................... 125 Picture 76: Spectrum of a GMSK with 19200 Bd .......................................................................... 127 Picture 77: CDPD framing of forward channel ............................................................................ 128 Picture 78: CDPD reverse channel framing ................................................................................. 129 Picture 79: Cordless phone standards .......................................................................................... 130 Picture 80: Spectrum of a CT2 signal ........................................................................................... 132 Picture 81: Framing of CT2 .......................................................................................................... 132 Picture 82: Spectrum of a DAB signal .......................................................................................... 134 Picture 83: Spectrum of a DECT signal ........................................................................................ 144 Picture 84: Slot occupation of DECT ............................................................................................ 144 Picture 85: Framing of DECT voice transmission ........................................................................ 145 Picture 86: Spectrogram of DPMR ............................................................................................... 146 Picture 87: DPMR TDMA structure .............................................................................................. 147 Picture 88: DPMR generic burst structure 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Picture 89: DPMR TDMA frame mobile station ............................................................................ 148 Picture 90: DPMR TDMA frame base station ............................................................................... 149 Picture 91: Spectrum of DSTAR on IF level .................................................................................. 150 Picture 92: Audio spectrum of a DSTAR signal ............................................................................ 150 Picture 93: Sonogram of a DSTAR signal with pre- and post carrier ........................................... 151 Picture 94: DSTAR overall framing ............................................................................................... 151 Picture 95: Framing of the DSTAR radio header .......................................................................... 151 Picture 96: Framing of DSTAR data payload ............................................................................... 153 Picture 97: Framing of DSTAR voice payload .............................................................................. 154 Picture 98: Spectrum of a DTMF signal ........................................................................................ 155 Picture 99: Spectrum of DVB-T in 8k mode .................................................................................. 156 Picture 100: Spectrum of DVB-T with 7 MHz bandwidth .............................................................. 157 Picture 101: Scheme of a DVB-T transmission system .................................................................. 158 Picture 102: MPEG-2 framing ...................................................................................................... 159 Picture 103: Spectrum of EEA signal ............................................................................................ 161 Picture 104: Spectrum of EIA signal ............................................................................................. 161 Picture 105: Spectrum of a 400 Bd EPIRB signal ......................................................................... 162 Picture 106: Phase plane of a EPIRB ............................................................................................ 162 Picture 107: Baudrate measurement with phase spectrum of a EPIRB ........................................ 163 Picture 108: Sonagram of an EPIRB ............................................................................................. 163 Picture 109: EPIRB short message format .................................................................................... 163 Picture 110: EPIRB long message format ..................................................................................... 164 Picture 111: Spectrum and sonogram of an ERMES signal .......................................................... 165 Picture 112: ERMES data format .................................................................................................. 166 Picture 113: Spectrum of an EXICOM radio ................................................................................. 168 Picture 114: Spectrogram of FRS .................................................................................................. 169 Picture 115: Spectrum of a FLEX signal 2FSK mode ................................................................... 170 Picture 116: Spectrrum of a FLEX signal 4FSK mode .................................................................. 170 Picture 117: Framing of FLEX ...................................................................................................... 171 Picture 118: FLEX frame information ........................................................................................... 172 Picture 119: Spectrum of a FMS BOS signal ................................................................................ 173 Picture 120: Spectrum and sonagram of a FSK441 signal ........................................................... 174 Picture 121: MFSK oscilloscope for a FSK441 ............................................................................. 175 Picture 122: Spectrum of a GMDSS signal with 511 bit test slip .................................................. 176 Picture 123: Spectrum of a GMDSS signal under real conditions ................................................ 176 Picture 124: Spectrogram of GMRS .............................................................................................. 178 Picture 125: Spectrum of GSM ...................................................................................................... 179 Picture 126: Architecture of the GSM Interfaces .......................................................................... 183 Picture 127: Frequency Reuse ....................................................................................................... 184 Picture 128: Logical Channels in GSM ......................................................................................... 186 Picture 129: Burst types in GSM ................................................................................................... 188 Picture 130: GSM Frame Structure ............................................................................................... 190 Picture 131: Slow Frequency Hopping over three frequencies in GSM ........................................ 191 Picture 132: Spectrum of V.22 modem .......................................................................................... 194 Picture 133: Phase plane of V.22 modem ...................................................................................... 195

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Picture 134: Spectrum of V.22bis modem with 2400 Bps ............................................................. 195 Picture 135: Phase plane of V.22bis modem ................................................................................. 196 Picture 136: Spectrum of V.23 modem .......................................................................................... 196 Picture 137: Spectrum and sonagram of a JT2 signal .................................................................. 201 Picture 138: Spectrum and sonagram of a JT44 signal ................................................................ 202 Picture 139_ Spectrum and sonagram of a JT6M signal .............................................................. 203 Picture 140: Spectrum of a LINK 11 transmission ........................................................................ 205 Picture 141: Spectrum of the LINK 11 single Tone Modem .......................................................... 208 Picture 142: Sonagram of LINK 11 SLEW .................................................................................... 208 Picture 143: Typical spectrum of a LINK 14 signal ...................................................................... 209 Picture 144: Uplink spectrum of LTE ............................................................................................ 212 Picture 145: LTE framing.............................................................................................................. 213 Picture 146: LTE physical resource block PRB ............................................................................ 213 Picture 147: Spectrum of ressource blocks of LTE ....................................................................... 214 Picture 148: Spectrum of a MDC-1200 signal .............................................................................. 215 Picture 149: Frame structure for a MDC-1200 signal ................................................................. 215 Picture 150: Spectrum and sonagram of MDC-4800 signal with 4800 Bps ................................. 216 Picture 151: Framing of MDC-4800 ............................................................................................. 217 Picture 152: Spectrum of a MOBITEX-1200 ................................................................................ 217 Picture 153: Sonagram of a MOBITEX-1200 ............................................................................... 217 Picture 154: Frame structure used in MOBITEX .......................................................................... 219 Picture 155: Spectrum of MPT1327 channel ................................................................................ 220 Picture 156: Spectrum of NWR SAME .......................................................................................... 222 Picture 157: Burst sonagram of NWR SAME ................................................................................ 223 Picture 158: Spectrum of a 1200 bd Packet Radio signal ............................................................. 229 Picture 159: Spectrogram of PMR ................................................................................................ 230 Picture 160: Spectrum of a POCSAG signal ................................................................................. 231 Picture 161: Structure of a POCSAG signal ................................................................................. 232 Picture 162: Structure of the POCSAG batches ............................................................................ 232 Picture 163: Frame Structure ........................................................................................................ 232 Picture 165: Sonagram of a VAISALA RS15GH ........................................................................... 237 Picture 166: Spectrum and sonagram of a RS 92 KL radiosonde ................................................. 237 Picture 167: VAISALA RS92 SGPD IF spectrum .......................................................................... 238 Picture 168: Spectrum of a VAISALA RS92 SGPD ....................................................................... 238 Picture 169: Spectrum of a Mark M2K2 ....................................................................................... 239 Picture 170: Phase spectrum of a Mark2K2 with 400 bd peaks ................................................... 239 Picture 171: Principle of FLASH-OFDM ..................................................................................... 242 Picture 172: Spectrogram of Railnet ............................................................................................. 242 Picture 173: Spectrum and sonagram of a 4FSK used in RD-LAP ............................................... 243 Picture 174: Framing of RD-LAP ................................................................................................. 244 Picture 175: Spectrum of FM broadcast carrier ........................................................................... 245 Picture 176: Spectrum of a RDS signal within a WFM signal ...................................................... 245 Picture 177: RDS data structure ................................................................................................... 246 Picture 178: Spectrum of 2400 Bd MELP signal .......................................................................... 249 Picture 179: Phase constellation of 2400 Bd MELP signal .......................................................... 249

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Picture 180: Harris frequency hopper with a hopping bandwidth of 5 MHz ................................ 250 Picture 181: Selection of one hop of a frequency hopper .............................................................. 250 Picture 182: Spectrogram view of a repeated hop ........................................................................ 251 Picture 183: Measurement of the duration of one frequency hop ................................................. 252 Picture 184: Expanded display of one hop .................................................................................... 252 Picture 185: Shift measurement of one hop ................................................................................... 253 Picture 186: Baudrate measurement of one hop ........................................................................... 253 Picture 187: SEM93 spectrum secure voice in none-ECCM mode ............................................... 254 Picture 188: SEM93 shift measurement in none-ECCM mode ...................................................... 254 Picture 189: SEM93 baud rate measurement in none-ECCM mode ............................................. 255 Picture 190: SEM93 hopping spectrum 1 MHz in ECCM mode ................................................... 255 Picture 191: SEM93 spectrum in ECCM mode ............................................................................. 256 Picture 192: SEM93 measurement of hop length in ECCM mode ................................................. 256 Picture 193: SEM93 baud rate measurement in ECCM mode ...................................................... 257 Picture 194: SEM93 shift measurement in ECCM mode ............................................................... 257 Picture 195: Spectrum of TETRA................................................................................................... 259 Picture 196: Logical Channels in TETRA ..................................................................................... 262 Picture 197: TDMA frame structure of TETRA ............................................................................. 263 Picture 198: Burst structure in TETRA .......................................................................................... 264 Picture 199: TERA II spectrum ...................................................................................................... 266 Picture 200: TERA II single carrier spectrum .............................................................................. 266 Picture 201: Spectrum of a TETRAPOL signal ............................................................................. 267 Picture 202: TETRAPOL frame structure ..................................................................................... 267 Picture 203: Spectrum of TETRAPOL signals ............................................................................... 267 Picture 204: Spectrum of a single trunked radio channel ............................................................. 268 Picture 205: Trunked Radio unused and used channel ................................................................. 269 Picture 206: Scannning and display of television lines ................................................................. 270 Picture 207: Structure of a black & white video signal ................................................................. 271 Picture 208: Structure of a colour video signal ............................................................................. 271 Picture 209: Spectrum of ZVEI 1 Signal ........................................................................................ 282 Picture 210: Sonagram of a reflection on a Meteor trail .............................................................. 286 Picture 211: Spectrogram of a METEOR RADAR at Juliusruh on 53.5 MHz............................... 287 Picture 212: Spectrum of the pulses .............................................................................................. 287 Picture 213: Pulse width measurement ......................................................................................... 288 Picture 214: Meteor reception of the NAVSPASUR ...................................................................... 289 Picture 215: Spectrum of INMARSAT satellite .............................................................................. 295 Picture 216: Spectrum of active earth stations on INMARSAT ..................................................... 295 Picture 217: Spectrum of INMARSAT-C 1200 Bd TDMA ............................................................. 296 Picture 218: Phase plane of INMARSAT-C 1200 Bd BPSK TDMA .............................................. 296 Picture 219: Spectrum of INMARSAT M NCS ............................................................................... 297 Picture 220: Spectrum of INMARSAT- mini-M NCS ..................................................................... 298 Picture 221: INMARSAT bit structure of the signalling channel ................................................... 302 Picture 222: Spectrum of an ORBCOMM 4800 bps SDPSK ......................................................... 313 Picture 223: Phase spectrum of an ORCOMM SDPSK with peaks at 4800 bps ........................... 314 Picture 224: Phase constellation of an ORCOMM SDPSK ........................................................... 314

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Picture 225: Spectrum of the STEREO telemetry .......................................................................... 316 Picture 226: Phase spectrum of the STEREO telemetry ................................................................ 316 Picture 227: Phase constellation of the STEREO telemetry .......................................................... 316 Picture 228: STEREO telemtry frame ........................................................................................... 317 Picture 229: STEREO telemetry packet ........................................................................................ 317 Picture 230: Coverage area of Thuraya (copyright www.thuraya.com) ...................................... 318 Picture 231: UHF satellites transponder layout wide ................................................................... 322 Picture 232: UHF satellites transponder layout narrow............................................................... 322

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2. List of Tables

Table 1: C4FM symbol table ........................................................................................................... 36 Table 2: Bit value for QPSK ............................................................................................................ 42 Table 3: Phase shifts for CQPSK ..................................................................................................... 44 Table 4: Bit values for DQPSK ........................................................................................................ 46 Table 5: Bit values for QAM ............................................................................................................ 47 Table 6: Different description for data levels .................................................................................. 56 Table 7: Code table for ITA2, ITA2P and ITA3 ............................................................................... 68 Table 8: Code table for CCIR476-4, HNG-FEC and PICCOLO MK VI alphabets ........................ 70 Table 9: ASCII table ........................................................................................................................ 74 Table 10: X.25 Packet frame ........................................................................................................... 84 Table 11: Common used transmission modes .................................................................................. 92 Table 12: Terms and their description ............................................................................................. 93 Table 13: Determination of necessary bandwidths for emissions ................................................. 100 Table 14: Main ACARS frequencies .............................................................................................. 103 Table 15: ACARS message format ................................................................................................. 104 Table 16: Data structure of AIS ..................................................................................................... 107 Table 17: ACL packet types in Bluetooth ....................................................................................... 119 Table 18: Tone frequencies of CCIR-1 .......................................................................................... 123 Table 19: Tone frequencies of CCIR-2 .......................................................................................... 124 Table 20: Tone frequencies of CCITT ............................................................................................ 125 Table 21: Frequencies of CT0 ....................................................................................................... 131 Table 22: Frequencies of CT0 extended ........................................................................................ 131 Table 23: Tone frequencies of CTCSS ........................................................................................... 133 Table 24: DAB Broadcast band III ................................................................................................ 138 Table 25: DAB Channel 13 frequencies ........................................................................................ 138 Table 26: DAB L-band frequencies ............................................................................................... 139 Table 27: Main parameter of D-AMPS.......................................................................................... 142 Table 28: DCSS bit structure ......................................................................................................... 143 Table 29: DCSS tone frequencies .................................................................................................. 143 Table 30: Frequency mapping DPMR ........................................................................................... 145 Table 31: Modes of DPMR ............................................................................................................ 146 Table 32: DSTAR radio header flag 1 description ........................................................................ 152 Table 33: DTMF tone frequencies ................................................................................................. 155 Table 34: DVB-T available bitrates ............................................................................................... 158 Table 35: EEA tone frequencies..................................................................................................... 160 Table 36: EIA tone frequencies ...................................................................................................... 161 Table 37: Frequencies for ERMES ................................................................................................ 165 Table 38: EURO tone frequencies ................................................................................................. 167 Table 39: FRS frequencies ............................................................................................................. 169 Table 40: Structure of FMS BOS messages ................................................................................... 173 Table 41: FSK 441 tone/character combination ............................................................................ 175 Table 42: Ten bit error detecting code of GMDSS VHF ............................................................... 177

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Table 43: GMRS frequencies duplex ............................................................................................. 179 Table 44: GMRS frequencies simplex............................................................................................ 179 Table 45: GSM Frequencies .......................................................................................................... 180 Table 46: Different GSM frequency ranges by country ................................................................. 181 Table 47: Power for mobile station (MS) in GSM ......................................................................... 181 Table 48: ITU Modem Standards .................................................................................................. 194 Table 49: ITU Fax Standards ........................................................................................................ 198 Table 50: LINK 11 frequencies ..................................................................................................... 205 Table 51: LTE relation bandwidth resource blocks ...................................................................... 214 Table 52: Frequencies Mobitex ..................................................................................................... 219 Table 53: NATEL tone frequencies ............................................................................................... 221 Table 54: Channel frequencies for PMR ....................................................................................... 230 Table 55: POCSAG numeric character ......................................................................................... 234 Table 56: POCSAG alpha numeric message format ..................................................................... 234 Table 57: Tone frequencies of IRIG telemetry standard ............................................................... 235 Table 58: Overview of types of radiosondes .................................................................................. 241 Table 59: RDS and RBDS program types ..................................................................................... 248 Table 60: TETRA II modulations and datarates ........................................................................... 265 Table 61: Different TV standards ................................................................................................. 273 Table 62: TV standards - signal characterisation ......................................................................... 274 Table 63: Differrent digital terrestrial television standards ........................................................ 274 Table 64: VDEW tone frequencies ................................................................................................ 275 Table 65: Frequencies for VHF Digital Link (VDL) ..................................................................... 276 Table 66: ZVEI 1 tone frequencies ................................................................................................ 282 Table 67: ZVEI 2 tone frequencies ................................................................................................ 283 Table 68: Transmitter locations of NAVSPASUR ......................................................................... 288 Table 69: Receiver locations of NAVSPASUR .............................................................................. 289 Table 70: INMARSAT NCS frequencies ........................................................................................ 292 Table 71: INMARSAT modulation overview ................................................................................. 300 Table 72: INMARSAT TDM channel details ................................................................................. 301 Table 73: INMARSAT bit structure of the signalling channel ....................................................... 301 Table 74: Possible subscriber terminal uplink frequencies ........................................................... 315 Table 75: Logical channels in Thuraya that are common to GSM ............................................... 319 Table 76: International callsigns .................................................................................................. 326 Table 77: Country codes ............................................................................................................... 330 Table 78: Translation of a four digit number ................................................................................ 331 Table 79: Translation of a five digit number ................................................................................. 332 Table 80: Coast station identification numbers by blocks and countries ...................................... 334 Table 81: Allocation of MID's ....................................................................................................... 339 Table 82: Q-codes ......................................................................................................................... 360 Table 83: X-codes .......................................................................................................................... 361 Table 84: Z-codes .......................................................................................................................... 370 Table 85: Abbreviations ................................................................................................................ 378

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3. General

The “Technical Handbook for Radio Monitoring HF” is meanwhile well known and used by many radio listeners (official or private) worldwide. Due to the high amount of systems we decided to separate the description of signals in the VHF/UHF range from those heard on HF. This book has been written to help the listener in identifying the different modes or waveforms which are active throughout the VHF/UHF band.

It will never be complete. But it will give a good overview which techniques are state of the art today. It has to be mentioned that most of the pictures are a result of the decoder HOKA CODE 300-32 and PROCITEC PROCEED. For the wide band spectra we have used an AOR5000 with SDR-14 or PERSEUS on the IF-frequency of 10.7 MHz. This book is divided in four main parts:

Basic information about modulation Waveforms used on VHF/UHF Tables for Radio Monitoirng Abbreviations and Index

The part basic information is giving an overview about common modulation techniques with a short description and how they look like in the spectrum or phase plane display. This part also describes standard expressions from the field of coding, error correction and so on which are often used in the field of radio communication. The following section describes most of the waveforms which can be heard on VHF and UHF. The book is finished with some helpful tables taken from th HF edition, the abbreviation table and index.

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5. VHF Modes

ACARS

Aircraft Communications Addressing and Reporting System

ACARS (Aircraft Communications Addressing and Reporting System) is a 2400 bps MSK packet-like system used by Civilian Aircraft for onboard flight-deck computer interconnections into ground stations. The centre frequency is on 1800 Hz and a shift of 1200 Hz is used. It is a NRZI coded coherent audio frequency MSK and an AM carrier to use standard AM communication equipment. The spectrum and sonagram of ACARS is shown in the following pictures:

Picture 52: Spectrum of ACARS

Picture 53: Sonagram of ACARS packets

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ACARS is mainly transmitted in the VHF range. The following frequencies are assigned to ACARS:

Frequency in MHz

Mode Used in:

129.125 ACARS Additional channel for USA & Canada

130.025 ACARS Secondary channel for USA and Canada

130.425 ACARS Additional channel for USA

130.450 ACARS Additional channel for USA & Canada

131.125 ACARS Additional channel for USA

131.450 ACARS Primary channel for Japan

131.475 ACARS Air Canada company channel

131.525 ACARS European Channel

131.550 ACARS Primary Channel for USA and Canada Also Primary Channel for Australia

131.725 ACARS Primary channel in Europe

131.825 ACARS Additional European Channel

131.850 ACARS Additional European Channel

136.700 ACARS Additional channel for USA

136.725 VDL4 European Channel

136,750 ACARS Additional European Channel Additional channel for USA

136.775 VDL4 European Channel

136.800 ACARS Additional channel for USA

136.825 ACARS European Channel

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Frequency in MHz

Mode Used in:

ARINC VDL2

136.850 ACARS SITA North American Channel

136.875 VDL2 European Channel

136.900. ACARS SITA

Additional European Channel

136.925 ACARS ARINC

ARINC European Channel

136.950 Exp VDL4 European Channel

136.975 VDL2 European Channel

Table 14: Main ACARS frequencies

As with all high-speed MSK systems, subsequent demodulation is very sensitive to inter-symbol interference. Each message frame consists of at least 50, and up to a maximum of 272 characters or bytes. Each character uses a 7 bit ACSII code with an additional eighth parity bit. This results in a total message transmission duration of between 0.17 and 0.91 seconds. The message frame format is rigidly defined to include synchronization, address, acknowledgment, mode and error checking characters, in addition to the actual message text. Imbedded message label characters indicate the type of message. The exact message format is shown below.

Number of Characters

Purpose Comment

16 Pre-key Transmitter warm-up/Rx AGC adjustment 2 Bit sync Establish bit synchronisation 2 Character sync Establish character synch 1 SOH Indicate start of heading 1 Mode Ground system interface configuration 7 Address Aircraft registration number 1 Ack/Nak Acknowledge/non-acknowledge marker 2 Label Type of message 1 Block ID Message block number 1 STX Indicates start of message text 4 Sequence# Message sequence number 6 Flight number Airline flight number

210 Text Message text

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Number of Characters

Purpose Comment

1 ETX End of text 16 Block Check Seq Error detection polynomial value 1 BCS Suffix last character

Table 15: ACARS message format

The sixteen pre-key characters are all binary 1 values, resulting in the 0.05 second 2400 Hz pulse heard at the start of every message. The block check sequence field contains the value of an error detection polynomial that can be used to determine if the entire message was received free of errors.

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ADS-B

Automatic Dependent Surveillance – Broadcast, Squitter Mode Automatic Dependent Surveillance Broadcast (ADS-B) is a technology transmitting aircraft information like position, airspeed, altitude aso. The waveform is a Pulse Position Modulation (PPM) with a data rate of 1 MBps. In a PPM the pulse is transmitted in the first or second half of the bit period indication a 1 or a 0. There are two types of broadcast from an airplane: the short squitter and the extended squitter (1090ES). The short squitter has a length of 56 Bits and is transmitted once per second.

Picture 54: Mode S short squitter frame

The extended squitter also transmits a 56 bit data field which contains additional information for the ADS-B. The total frame length is 112 bit.

Picture 55: Mode S extended squitter frame

ADS-B is using the satellite based global positioning system to determine an aircraft's precise location in space. The system then converts the position into a digital code, which is combined with other information such as the type of aircraft, speed, flight number, and whether it's turning, climbing, or descending. The digital code, containing all of this information, is updated several times a second and broadcast from the aircraft on a discrete frequency as an extended squitter. Other aircraft and ground stations within about 150 miles receive the data link broadcasts and can display the information on a monitor. Pilots in the cockpit see the traffic on a Cockpit Display of Traffic Information (CDTI). Controllers on the ground can see the ADS-B targets on their regular traffic display screen, along with other radar targets. ADS-B is usually transmitted on 1090 MHz in regulary intervals.

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Picture 56: PPM of ADS-B

Picture 57: Framing of ADS-B

AIS

Automatic Information System for ships

The AIS transponder works on 161.975 MHz and 162.025 MHz in an autonomous and continuous mode, regardless of whether it is operating in the open seas or coastal or inland areas. Transmissions use 9.6 kb GMSK FM modulation using HDLC packet protocols. The data structure is as follows and consists of 256 bit:

Picture 58: AIS frame

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Function No of Bits Description Ramp up 8 Training sequence 24 Synchronisation Start Flag 8 HDLC 0x7E Data 168 CRC/FCS 16 HDLC End Flag 8 HDLC 0x7E Buffering 24 Bit stuffing, distance delay, repeater

delay and jitter

Table 16: Data structure of AIS

These information are transmitted within one slot of 26.67 ms.

Picture 59: AIS spectrum and sonogram

Although only one radio channel is necessary, each station transmits and receives over two radio channels to avoid interference problems, and to allow channels to be shifted without communications loss from other ships. The system provides for automatic contention resolution between itself and other stations, and communications integrity is maintained even in overload situations.

Each station determines its own transmission schedule (slot), based upon data link traffic history and knowledge of future actions by other stations. A position report from one AIS station fits into one of 2250 time slots established every 60 seconds. AIS stations continuously synchronize themselves to each other, to avoid overlap of slot transmissions. Slot selection by an AIS station is randomized within a defined interval, and tagged with a random timeout of between 0 and 8 frames. When a station changes its slot assignment, it pre-announces both the new location and the timeout for that location. In this way new stations, including those stations which suddenly come within radio range close to other vessels, will always be received by those vessels.

The required ship reporting capacity according to the IMO performance standard amounts to a minimum of 2000 time slots per minute, though the system provides 4500 time slots per minute. The SOTDMA broadcast mode allows the system to be overloaded by 400 to 500% through sharing of

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slots, and still provide nearly 100% throughput for ships closer than 8 to 10 NM to each other in a ship to ship mode. In the event of system overload, only targets further away will be subject to drop-out, in order to give preference to nearer targets that are a primary concern to ship operators. In practice, the capacity of the system is nearly unlimited, allowing for a great number of ships to be accommodated at the same time.

The system is backwards compatible with digital selective calling systems, allowing shore-based GMDSS systems to inexpensively establish AIS operating channels and identify and track AIS-equipped vessels, and is intended to fully replace existing DSC-based transponder systems.

A Class A AIS unit broadcasts the following information every 2 to 10 seconds while underway, and every 3 minutes while at anchor at a power level of 12.5 watts. The information broadcast includes:

MMSI number - unique referenceable identification Navigation status (as defined by the COLREGS - not only are "at anchor" and "under way

using engine" currently defined, but "not under command" is also currently defined) Rate of turn - right or left, 0 to 720 degrees per minute (input from rate-of-turn indicator) Speed over ground - 1/10 knot resolution from 0 to 102 knots Position accuracy - differential GPS or other and an indication if (Receiver Autonomous

Integrity Monitoring) RAIM processing is being used Longitude - to 1/10000 minute and Latitude - to 1/10000 minute Course over ground - relative to true north to 1/10th degree True Heading - 0 to 359 degrees derived from gyro input Time stamp - The universal time to nearest second that this information was generated

In addition, the Class A AIS unit broadcasts the following information every 6 minutes:

MMSI number - same unique identification used above, links the data above to described vessel

IMO number - unique referenceable identification (related to ship's construction) Radio call sign - international call sign assigned to vessel, often used on voice radio Name - Name of ship, 20 characters are provided Type of ship/cargo - there is a table of possibilities that are available Dimensions of ship - to nearest meter Location on ship where reference point for position reports is located Type of position fixing device - various options from differential GPS to undefined Draught of ship - 1/10 meter to 25.5 meters [note "air-draught" is not provided] Destination - 20 characters are provided (at Master's discretion) Estimated time of Arrival at destination - month, day, hour, and minute in UTC (at Master's

discretion)

Types of Automatic Identifications Systems

ITU-R Recommendation M.1371-1 describes the following types of AIS:

Class A

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Shipborne mobile equipment intended for vessels meeting the requirements of IMO AIS carriage requirement, and is described above.

Class B

Shipborne mobile equipment provides facilities not necessarily in full accord with IMO AIS carriage requirements. IEC has begun work on a Class B certification standard, which should be completed by 2004 - 2005. The Class B is nearly identical to the Class A, except the Class B:

Has a reporting rate less than a Class A (e.g. every 30 sec. when under 14 knots, as opposed to every 10 sec. for Class A)

Does not transmit the vessel’s IMO number or call sign Does not transmit ETA or destination Does not transmit navigational status Is only required to receive, not transmit, text safety messages Is only required to receive, not transmit, application identifiers (binary messages) Does not transmit rate of turn information Does not transmit maximum present static draught

Class B devices are not yet available. These 3 figure codes have been allocated by the International Telecommunications Union (ITU), and are used to denote the country of registration of a vessel or the location of a shore station using DSC. Note that the numbers are issued on a geographic or regional basis. Large nations normally have a vacant block after the main allocation - these vacant blocks are planned to be used for expansion once the main allocation has been used.

AMPS

Advanced Mobile Phone System Advanced Mobile Phone System (AMPS) is the analogue mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983 and Australia in 1987. It was the primary analogue mobile phone system in North America (and other locales) through the 1980s and into the 2000s. As of February 18, 2008, carriers in the United States were no longer required to support AMPS and companies such as AT&T and Verizon have discontinued this service permanently. AMPS was discontinued in Australia in September 2000. AMPS is a first-generation cellular technology that uses separate frequencies for each conversation. Each channel has a bandwidth of 30 kHz. In AMPS, the cell centers can flexibly assign channels to handsets based on signal strength, allowing the same frequency to be re-used in various locations without interference. This allowed a larger number of phones to be supported over a geographical area.

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DECT

Digital European Cordless Telephony

The Digital European Cordless Telephony (DECT) is a standard for the 1885 – 1900 MHz band and has a modulation structure which is similar to GSM. DECT is using a standard modulation of GFSK. But the DECT specification allows three other modulation schemes: /2 DBPSK, /4-DQPSK and /8-D8PSK. While the first of these modulation schemes is compatible with GFSK, the last two provide 2 and 4 times the data rate as GFSK. This means that, combined with the high speed data profile, data rates of up to 2 Mbps can be achieved using DECT. The spectrum of a DECT signal is shown in the following picture:

Picture 83: Spectrum of a DECT signal

DECT is using a TDD/TDMA structure with a total of 24 frames or time slots. Each frame has a length of 10 ms. The first 12 frames or slots are allocated for the transmission from the base station to the handset. The second part of 12 frames or slots are for the transmission from the handset to the base station. The following pictures shows the this distribution:

Picture 84: Slot occupation of DECT

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DECT is not assigning frequencies or slots to a special handset/base station. The channels are dynamically allocated when setting up a call. But DECT is selecting the channel with the best quality so during a conversation the connection may be transferred to another channel. The DECT standard allows different slot types which may vary in length. Voice is always transmitted in an unprotected slot with 320 bit of data. Speech is coded with 32 kbps ADPCM. The framing is as follows:

Picture 85: Framing of DECT voice transmission

In addition to voice, DECT also offers several ways to transmit data using DPRS (DECT Packet Radio Service). This consists of a series of profiles that each allow a particular data service. The DECT data services use the protected B field, which consists of 256 data bits and 68 CRC bits. This increased level of protection that any errors can be resolved using ARQ. Data services can use more than one slot pair per connection, and can use these in symmetric or asymmetric mode. This means that in theory at least, one portable can use 23 slots in one direction, and 1 slot in the reverse direction.

DPMR

Digital Private Mobile Radio, dPMR446 DPMR is using a 4FSK with a symbol rate od 2400 bd which gives a data rate of 4800 bps. The shift between carriers is 700 Hz. The access method is FDMA. For voice transmission the AMBE+2 vocoder is used. The codec rate is 3600 bps, 2450 bit are used for the voice and 1150 bit for error correction. DPMR is using a TDMA with 30 ms frames. The symbols are mapped according the following table on the four frequencies:

Di-Bit

Symbol Frequency Shift

01 +1 + 1050 Hz 00 +1 + 350 Hz 10 -1 - 350 Hz 11 -3 - 1050 Hz

Table 30: Frequency mapping DPMR

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The typical spectrum and sonagram centered on 3125 Hz is shown in the following picture:

Picture 86: Spectrogram of DPMR

It can transfer voice and data. This could be i.e. GPS positions or text messaging. DPMR is using a bandwith of 6.25 kHz. The maximum power is 500 mW. DPMR radios are license-free for the use in the 446.100 MHz - 446.200 MHz band within Europe. DPMR is supporting several modes for operation:

Mode Descriptions - License-free (DPMR 446) Mode 1 Direct Peer-to-peer Mode Mode 2 Conventional Repeater Mode Mode 3 Digital Trunking Mode

Table 31: Modes of DPMR

DPMR Mode 1 This is the peer to peer mode of DPMR. This mode can operate on all PMR frequency bands and has no RF power limits of DPMR.

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DPMR Mode 2 The mode 2 operations includes repeaters and other infrastructure. DPMR Mode 3 This mode offers multichannel, multisite trunked radio networks. Management of the radio network starts from the authentication of radios that wish to connect. Calls are set-up by the infrastructure when both parties have responded to the call request. Calls may be diverted to other radios, landline numbers or IP addresses. The infrastructure managing these beacon channels would be capable to placing a call to another radio whether that radio is using the same site or another site within the network. DPMR Framing DPMR is using a TDMA structure with 2 slots. The general timing for the base station and a mobile station is shown in the next figure.

Picture 87: DPMR TDMA structure

Each TDMA burst has a length of 30 ms. Two bursts are forming a TDMA frame of 60 ms. The base station is transmitting a Common Announcement Channel (CACH) between the TDMA bursts. The mobile station is using a guard time between the burst to allow an amplifier ramping and propagation delay. Bursts have either a synchronization pattern or an embedded signalling field located in the center of the burst. Placing the embedded signalling in the middle of a burst allows time for a transmitting MS to optionally transition to the outbound channel and recover Reverse Channel (RC) information.

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DPMR Burst Structure The generic burst structure consists of two 108-bit payload fields and a 48-bit synchronization or signalling field as shown in the next figure.

Picture 88: DPMR generic burst structure

Each burst has a total length of 30 ms but 27,5 ms are used for the 264 bits content, which is sufficient to carry 60 ms of compressed speech, using 216 bits payload. For a vocoder that uses 20 ms vocoder frames, the burst will carry three 72-bit vocoder frames (including FEC) plus a 48-bit synchronization word in a voice burst, that is 264 bits (27,5 ms) used for the burst contents. The center of each burst has a field that carries either synchronization or embedded signalling. This field is placed in the middle of a burst to support RC signaling. On the inbound channel, the remaining 2,5 ms is used for guard time to allow for PA ramping and propagation delay, as shown in the next picture for an inbound frame.

Picture 89: DPMR TDMA frame mobile station

On the outbound channel, this 2,5 ms is used for a Common Announcement Channel (CACH) that carries TDMA frame numbering, channel access indicators, and low speed signalling as shown in the next figure for an outbound frame.

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Picture 90: DPMR TDMA frame base station

The frame synchchronisation (SYNC) is provided by a special sequence of bits that mark the location of the center of a TDMA burst. Receivers may use a matched filter to achieve initial synchronization, using the output of a matched correlator to initialize the symbol recovery parameters to compensate for frequency and deviation errors as well as determine the center of the burst. Once the receiver is synchronized to a channel, it may use pattern matching to detect the presence of SYNC to verify that the channel is still present and determine the type of SYNC to identify the contents of the burst. Multiple SYNC patterns are used to:

differentiate voice bursts from data/control bursts and from RC bursts; differentiate inbound channels from outbound channels.

To accomplish this, the following SYNC patterns have been defined:

BS sourced voice; BS sourced data; MS sourced voice; MS sourced data; MS sourced standalone RC.

For all two frequency BS channel inbound transmissions and all single frequency channel transmissions, the first burst shall contain a synchronization pattern to allow the target receiver to detect the presence of the signal, achieve bit synchronization, and determine the center of the burst. Follow-on bursts contain either SYNC or embedded signaling depending on the burst type and the context. For all two frequency BS channel outbound transmissions, it is assumed that the MS is already synchronized to the outbound channel well before the start of any transmissions directed towards it. Therefore, there is no requirement that the voice header shall contain a synchronization pattern.

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Picture 171: Principle of FLASH-OFDM

The spectrum of this modulation is shown in the following picture:

Picture 172: Spectrogram of Railnet

This hopping pattern ensures that users within the same cell are allocated orthogonal resources but use a different subcarrier every symbol duration in downlink and every 7 symbol durations in uplink direction. So the users within a cell do not interfere with each other. In FLASH-OFDM 113 carriers with a spacing of 11.25 kHz are used. The symbol rate is 10 KBd. The overall bandwidth is

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1.25 MHz and allows a downlink of 3.2 MBps and an upload of 900 kBps. The modulation in the downlink is QPSK, 16QAM, 64 QAM or 256 QAM. In the uplink only QPSK is used. For a Forward error Correction FEC a vector-LDPC codes with a block length from 1344 to 5248 is used in the downlink. For the uplink the block length is 1344. In the uplink FLASH-OFDM uses a turbo equalization on a set of 7 QPSK symbols on 7 contiguous OFDM symbols where the 1 symbol is a reference/pilot symbol. FLASH-OFDM provides high reliability through a link layer that features a fast automatic repeat request (ARQ), which is used to check transmitted data for errors. If an error is found, the message is retransmitted very quickly. Therefore, with loop times at less than 10 milliseconds, FLASH-OFDM ARQ latency is very low. This enables low-latency retransmission of frames received with an error. FLASH-OFDM operates in different frequencies like 450MHz, 700MHz, 800MHz, 1.9GHz and 2.1GHz.

RD-LAP

Radio Data Link Access Protocol RD-LAP is a protocol used i.e. in ARDIS and is using a 4FSK with a shift of 2400 Hz between carriers. The signal is using discrete frequencies of -3600 Hz, -1200 Hz, +1200 Hz and 3600 Hz on the nominal transmission frequency. RD-LAP has a data rate of 19200 Bps and uses FEC and CRC for error correction. The following pictures shows the spectrum and sonagram of a 4FSK used in RD-LAP:

Picture 173: Spectrum and sonagram of a 4FSK used in RD-LAP

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The frame structure in RD-LAP mode consists of a frame preamble (comprising a 24-symbol frame synchronisation pattern and station ID block) followed by one or more'Header’ blocks, one or more 'Intermediate’ blocks and a 'Last’ block. Channel status (S) symbols are included at regular intervals. The first frame of any transmission is preceded by a symbol synchronisation pattern. The framing for the RD-LAP mode is shown in the following picture:

Picture 174: Framing of RD-LAP

RDS/RBDS

Radio Data System, Radio Broadcast Data System Radio Data System (RDS) is a communications protocol standard from the European Broadcasting Union (EBU) for sending digital information using conventional FM radio broadcasts. The RDS system standardises several types of information transmitted, including time, track/artist info and station identification. RDS is a standard in Europe and Latin America since the early 1990s. Radio Broadcast Data System (RDBS) is the official name used for the U.S. version of RDS. The two standards are nearly identical. Slight differences are mainly which numbers are assigned to each of the 31 musical and other program formats the RBDS system can identify. RBDS was approved by the NRSC. RDS and RDBS use a 57kHz subcarrier to carry data at 1187.5 bits per second. The 57 kHz was chosen for being the third harmonic of the pilot tone for FM stereo. This will not cause interference or intermodulation with the pilot tone or with the stereo difference signal at 38 kHz. The data format allows forward error correction (FEC).

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Picture 175: Spectrum of FM broadcast carrier

Picture 176: Spectrum of a RDS signal within a WFM signal

RDS is modulated on the subcarrier with a QPSK waveform with a data rate of 1187.5 Bps. This is equal to the frequency of the RDS subcarrier divided by 48. Data is transmitted in groups consisting of four blocks. Each block contains a 16 bit information word and a 10 bit check word as shown in the next picture. This means that with the data rate of 1187.5 bit per second approximately 11.4 groups can be transmitted each second. The data groups are structured so that data can be transmitted as efficiently as possible. Different stations will want to transmit different types of data at different times. To cater for this there are a 16 different group structures. Mixing of different types of data within groups is kept to a minimum. However the coding structure is such that messages which need repeating most frequently normally occupy the same position within groups. For example the first block in a group always contains the PI code and PTY and TP are to be found in block 2.

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Picture 177: RDS data structure

RDS data structure In order that a radio knows how to decode the data correctly, each type of group has to be identified. This function is performed by a four bit code occupying the first four bits in the second block. Once generated the data is coded onto the subcarrier in a differential format. This allows the data to be decoded correctly whether the signal is inverted or not. When the input data level is "0" the output remains unchanged but when a "1" appears at the input the output changes its state. With the basic signal generated the spectrum has to be carefully limited. This has to be done to avoid any cross talk in phase locked loop decoders. The power density close to 57 kHz is limited by the encoding each bit as a biphase signal. In addition to this the coded data is passed through a low pass filter. The following information fields are normally contained in the RDS data: Alternative Frequencies (AF) This enables a receiver to re-tune to a different frequency providing the same station when the first signal becomes too weak. This is often utilised in car stereo systems. Clock Time (CT) This time can synchronise a clock in the receiver or the main clock in a car. CT can only be accurate to within 100 ms of UTC. Enhanced Other Networks (EON) Allows the receiver to monitor other networks or stations for traffic programmes, and automatically temporarily tune to that station. Programme Identification (PI)

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This is the unique code which identifies the station. Each station receives a specific code with a country prefix. In the USA, PI is determined by applying a formula to the station's call sign. Programme Service (PS) The programme service is an eight-character static display that represents the call letters or station identity name. Most RDS capable receivers display this information and, if the station is stored in the receiver's presets, will cache this information with the frequency and other details associated with that preset. Programme Type (PTY) This coding of up to 31 pre-defined programme types – e.g. (in Europe): PTY1 News, PTY6 Drama, PTY11 Rock music, – allows users to find similar programming by genre. PTY31 seems to be reserved for emergency announcements in the event of natural disasters or other major calamities. Regional (REG) This is used in countries where national broadcasters run "region-specific" programming such as regional opt-outs on some of their transmitters. This functionality allows the user to "lock-down" the set to their current region or let the radio tune into other region-specific programming as they move into the other region. Radio Text (RT) This function allows a radio station to transmit a 64-character free-form textual information that can be either static e.g. station slogans or in sync with the programming such as the title and artist of the currently-playing song. Traffic Announcement(TA), Traffic Programme(TP) The receiver can often be set to pay special attention to this flag and e.g. stop the tape/pause the CD or retune to receive a Traffic bulletin. The TP flag is used to allow the user to find only those stations that regularly broadcast traffic bulletins whereas the TA flag is used to stop the tape or raise the volume during a traffic bulletin. Traffic Message Channel (TMC) Digitally encoded traffic information. Not all RDS equipments supports this. Often available for Automotive navigation systems. In many countries only encrypted data is broadcast, and so a subscription and appropriate decoder is required to use. The following table lists the RDS and RBDS Programm Type codes and their meanings:

PTY code RDS Programme type (EU) RBDS Programm type (USA)

0 No programme type or undefined No program type or undefined

1 News News

2 Current affairs Information

3 Information Sports

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PTY code RDS Programme type (EU) RBDS Programm type (USA)

4 Sport Talk

5 Education Rock

6 Drama Classic Rock

7 Culture Adult Hits

8 Science Soft Rock

9 Varied Top 40

10 Pop Music Country

11 Rock Music Oldies

12 M.O.R. Music Soft

13 Light classical Nostalgia

14 Serious classical Jazz

15 Other Music Classical

16 Weather Rhythm and Blues

17 Finance Soft Rhythm and Blues

18 Children’s programmes Language

19 Social Affairs Religious Music

20 Religion Religious Talk

21 Phone In Personality

22 Travel Public

23 Leisure College

24 Jazz Music Unassigned

25 Country Music Unassigned

26 National Music Unassigned

27 Oldies Music Unassigned

28 Folk Music Unassigned

29 Documentary Weather

30 Alarm Test Emergency Test

31 Alarm Emergency

Table 59: RDS and RBDS program types

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Harris RF 7800V

FALCON III The RF-7800V Combat Net Radio provides continuous coverage in the 30 to 108 MHz frequency band. It is supporting analogue FM, voice transmission with 2400 Bd MELP, secure voice and data with 16 kbd FSK and up to 192 kbps data transmission. For encryption the CITADEL chipset with a 128 bit key is used. During hopping the datarate per hop can be measured with 20 kbd. The radio also offers several frequency hopping waveforms Quicklook 1A, Quicklook 2, Quicklook 3 and Quicklook-Wide. Quicklook-Wide provides 64 kilobits per second of data throughput while frequency hopping. The following pictures are showing the typical spectrum for a 2400 Bd MELP transmission with 8PSK and the phase constellation.

Picture 178: Spectrum of 2400 Bd MELP signal

Picture 179: Phase constellation of 2400 Bd MELP signal

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METEOR RADAR

A METEOR RADAR is transmitting short electromagnetic circumpolarly pulses towards the sky. If a meteor strikes Earth's atmosphere at speeds of 100,000 mph or more they ionize the air in their path. These luminous ionized trails reflect radio waves. The meteor echo is received by a reception antenna system and is interferometrically analysed, thus estimating the location, the echo amplitude, and the radial velocity of the ionisation trace moving with the neutral wind. From many of such individual observations i.e. the wind field for an altitude range between about 80 and 110 km can be estimated. The follwoing pictures where made by receiving the METEOR RADAR at Juliusruh and Kühlungsborn in Northeast Germany. These radars are transmitting on 32.55 MHz and 53.5 MHz. There peak power is 12 KW. The puls width is 13.3 us.

Picture 211: Spectrogram of a METEOR RADAR at Juliusruh on 53.5 MHz

Picture 212: Spectrum of the pulses

2150 Hz

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Calculating with the frequency distance between two pulse the pulse repetition time is 456 us. In case of rectangle pulses the pulse width has a direct relation to the shape of the spectrum. By measuring the distance between the center of the signal and the first side minimum the pulse time can be estimated.

Picture 213: Pulse width measurement

The frequency distance is 75093 Hz with results in a pulse time of 13.3 us.

NAVSPASUR

The Air Force Space Surveillance System, also known as the Space Fence, is a multistatic radar system that detects orbital objects passing over the US. It is a component of the US space surveillance network, and is claimed to be able to detect objects as small as 10 cm) at a height up to 30000 km. The headquarter of the surveillance system is located at Dahlgren, Virginia. There are three transmitter sites in the system:

Location Frequency Coordinate Lake Kickapoo, Texas 216.983 MHz 33°32′47″N 98°45′46″W Gila River, Arizona 216.970 MHz 33°06′32″N 112°01′45″W Jordan Lake, Alabama 216.990 MHz 32°39′33″N 86°15′52″W

Table 68: Transmitter locations of NAVSPASUR

The master transmitter is located at Lake Kickapoo and has a CW radiated power of 768 kW. There are 6 receiving stations:

Location Coordinate Tattnall, Georgia 32°02′35″N 81°55′21″W Hawkinsville, Georgia 32°17′20″N 83°32′10″W Silver Lake, Mississippi 33°08′42″N 91°01′16″W

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Red River, Arkansas 33°19′48″N 93°33′01″W Elephant Butte, New Mexico 33°26′35″N 106°59′50″W San Diego, California 32°34′42″N 116°58′11″W

Table 69: Receiver locations of NAVSPASUR

A typical reception of an object like a meteor is shown in the following sonagram:

Picture 214: Meteor reception of the NAVSPASUR

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7. Satellites

COSPAS-SARSAT

The international COSPAS-SARSAT programme is a satellite-based search and rescue (SAR) distress alert detection and information distribution system, established in 1979. COSPAS (КОСПАС) is an acronym for the Russian words "Cosmicheskaya Sistema Poiska Avariynyh Sudov" (Космическая Система Поиска Аварийных Судов), which translates to "Space System for the Search of Vessels in Distress". SARSAT is an acronym for Search And Rescue Satellite-Aided Tracking. The system can detect and locate emergency beacons activated by aircraft or ships. These beacons are transmitting in the 406 MHz range. They are the only ones detected and processed by the system. Signals from the older 121.5 MHz and 243 MHz beacons are not recognized anymore. The space segment of the COSPAS-SARSAT system consists of SAR signal repeaters (SARR) and SAR signal processors (SARP) aboard satellites:

9 geosynchronous satellites called GEOSARs and 6 low-earth polar orbit satellites LEOSAR

A SARR/SARP instrument is a small package, that typically is attached to a satellite that is being launched primarily for another purpose. The six operational LEOSAR satellites (with both SARR and SARP instruments) are the SARSAT satellites provided by the United States NOAA and Europe's EUMETSAT. These orbit at an altitude of approximately 850 km. They are:

SARSAT -7 instruments aboard NOAA-15 SARSAT -8 instruments aboard NOAA-16 SARSAT -9 instruments aboard NOAA-17 SARSAT -10 instruments aboard NOAA-18 SARSAT -11 instruments aboard METOP-A SARSAT -12 instruments aboard NOAA-19

The GEOSAR satellites provide continuous coverage of the entire earth below about 70 degrees latitude with a view toward the equatorial sky. Operational SARR are installed on the following six GEOSAR satellites providing continuous coverage of the entire earth below about 70 degrees latitude with a view toward the equatorial sky:

The GOES satellites (USA) GOES 13 at 75° W and GOES 15 at 135° W The INSAT-3A satellite (India) at 93.5° E The Meteosat Second Generation (MSG) satellites (Europe) MSG-1 (also known as

Meteosat-8) at 9.5° E and MSG-2 (also known as Meteosat-9) fixed over the Prime Meridian.

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The Electro-L No. 1 satellite (Russia) at 76° E.

SARR undergoing testing or in a role as an on-orbit spare are installed on the following geostationary satellites:

The GOES satellites (USA) GOES 12 at 60° W and GOES 14 at 105° W Luch 5A (Russia) at 167° E. MSG-3 (EUMETSAT) at 3.4° W.

Typical rescue beacon radios transmit a 5 watt signal for 0.5 second once every 50 seconds. Normally they include a GPS receiver so they can report precise GPS co-ordinates. Aircraft distress radio beacons (ELTs) are automatically activated by g-force switches that detect sudden deceleration during a crash, while maritime radio beacons (EPIRBs) are normally activated by contact with sea water. The 406 MHz distress radio beacon band is 100 kHz wide. The center frequency is 406.05 MHz. Individual beacons transmit in assigned 3 kHz channels. A transmitted distress message is either a 112-bit "short" message or a 144-bit "long" message, both including 49 bits of identification information. If the beacon has a GNSS receiver or position information derived from another local source (such as ship navigation equipment), then that information also is encoded in the transmitted distress message.

The SARR instrument is transmitting the received signals on 1544.5 MHz.

INMARSAT

International Maritime Satellite Organization The INMARSAT system consists of four regions with one satellite for each region according to the following table:

Satellite Position Region NCS Frequency AOR-E 15.5°W Atlantic Ocean Region East 1541.45 MHz IOR 64° W Indian Ocean Region 1537.10 MHz POR 178°E Pacific Ocean Region 1541.45 MHz AOR-W 53°W Atlantic Ocean Region West 1537.70 MHz

Table 70: INMARSAT NCS frequencies

All mobile stations (MES) listen in idle mode to the Network Control Station (NCS) common TDM channel which carries signalling information. When a mobile station identifies its id in a signalling frame it will re-act to the commands received from the NCS. In case of a channel assignment message is received it will tune to the assigned transmit-receive frequency pair. The forward telex traffic channel is also TDM with the same frame structure as the NCS TDM containing 22 time slots of 50 Bd telex channels. The telex return channel is a TDMA (Time Division Multiple Access) channel. Voice traffic is FM SCPC (Single Channel Per Carrier). Telex channels are assigned by each earth station and voice channels only by the NCS.

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INMARSAT-A

INMARSAT-A was the first service to be introduced, becoming commercially available in 1982. An analogue system, it provides two-way direct-dial phone, fax, telex and electronic mail and data communications at rates of up to 9.6 kilobits per second (kbit/s). Later models make possible high-speed data communications at 56/64 kbit/s. Due to the large size and weight of the INMARSAT-A antenna INMARSAT-A MESs are fitted only on larger ships.

The INMARSAT standard A terminals are grouped into various classes according to their capabilities. These are:

1. Class 1 - Standard A ship earth station usable for both telegraph and telephone type traffic. 2. Class 2 - Standard A ship earth station usable for telephone type traffic and reception of

shore-to-ship one way telegraphy. 3. Class 3 - Standard A ship earth station usable for telegraph only traffic.

The forward channel from the NCS is a TDM with 1200 Bd BPSK modulated. For telex traffic also a TDM with 22 * 50 Bd channels is used. For voice traffic in both directions the signal is FM SCPC modulated. The return channel from the Mobile Earth Station (MES) is a 4800 Bd TDMA DBPSK.

INMARSAT Aero H INMARSAT Aero H service offers voice, fax and data communications from almost anywhere in the sky supporting voice, fax, data and STU-III transmissions at data rates up to 9.6 kbps, 4.8 kbps and 2.4 kbps.

INMARSAT Aero H+

INMARSAT Aero H+ offers voice transmissions at 4.8 kbps, fax at 2.4 kbps and real-time PC modem-based data at 2.4 kbps. In addition, Aero H+ offers cockpit data at speeds up to 1.2 kbps.

INMARSAT Aero I

INMARSAT Aero I service offers digital voice transmission at 4.8 kbps, fax at 2.4 kbps, real-time data at 2.4 kbps and cockpit data at up to 1.2 kbps.

INMARSAT Aero L

INMARSAT Aero L service operates in the INMARSAT global beams and provides aircraft with real-time, low-speed, two-way data communications capability. Aero L is a packet data service designed primarily for aircraft operators who require a highly reliable data communications capability.

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INMARSAT Aero Mini-M

INMARSAT Aero Mini-M service offers digital voice, fax and data transmission. The service supports voice transmission up to 4.8 kbps and data or fax transmission up to 2.4 kbps.

INMARSAT-B The INMARSAT-B system was introduced in 1994 and uses digital technology to provide high quality telephone, fax, telex, e-mail and data communications, with the antenna size and weight being approximately the same as for INMARSAT-A. Like INMARSAT-A, INMARSAT-B is capable of high-speed data communications (at up to 64 kbps), making it especially suitable for data-intensive users such as oil and seismological companies which need to exchange large amounts of data on a regular basis.

The communications sub-system is based on the use of digital modulation, coding and processing techniques which have been designed to permit efficiency. Filtered quadrature phase shift keying modulation is used on shore to ship carriers with convolutional forward error correction. Ship to shore uses offset QPSK with FEC also. The speech method used for telephony is 16Kbit/s adaptive predictive coding. Other communications services include 56/64Kbit/s data. The APC voice coded is supporting fax up to 2400bit/s.

The forward channel from NCS or LES to the MES are 6 kbps TDM DPSK, 24 kbps OQPSK for voice and low speed data and 132 kbps OQPSK for high speed data. The return channel uses a 24 kbps TDMA OQPSK modulated.

INMARSAT-C

INMARSAT-C was introduced in 1991 to complement INMARSAT-A by providing a global low cost two-way data communications network using a small terminal that could be fitted on either a large or small vessel. Its compactness makes it especially suitable for smaller vessels such as yachts, fishing vessels or supply craft. The INMARSAT-C system does not provide voice communications but is a means of sending text, data and e-mail messages to and from shore-based subscribers using a store-and-forward technique. This requires the user to prepare the message prior to sending it; it is then transmitted via the land earth station operator who sends it on to its intended destination. The global communications capability of the INMARSAT-C system, combined with its Maritime Safety Information (MSI) broadcasts and distress-alerting capabilities, has resulted in the INMARSAT-C system being accepted by the International Maritime Organisation (IMO) as meeting the requirements of the Global Maritime Distress and Safety System (GMDSS). The GMDSS carriage requirements are mandatory for all merchant ships of over 300 Gross Registered Tonnes (GRT) and all passenger vessels which make international voyages. The following picture shows a typically spectrum of the INMARSAT satellite:

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Picture 215: Spectrum of INMARSAT satellite

Picture 216: Spectrum of active earth stations on INMARSAT

The data rate is 1200 symbols per second modulated in BPSK. This results in a bit rate of 600 Bit/s. Error protection is done by convolutional encoding with R = 1/2 and k = 7. A block or frame of data in the forward direction comprises 10368 symbols (8,64 s). Data is highly interleaved to prevent against

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slow fading. Additionally scrambling is used to ensure an even distribution of logical 1s and 0s for proper bit synchronization. Frame synchronisation is achieved by using an unscrambled unique word at the beginning of the frame. The coding will correct some errors otherwise ARQ is used. The forward channels are continuous time division multiplex (TDM) channels. They are used for message transmission and signalling. In the return direction messages are transmitted by time division multiple access (TDMA) channels assigned by the network control station (NCS). The frame length varies between 2176 symbols and 10368 symbols in steps of 2048 symbols.

Picture 217: Spectrum of INMARSAT-C 1200 Bd TDMA

Picture 218: Phase plane of INMARSAT-C 1200 Bd BPSK TDMA

INMARSAT Mini-C

INMARSAT Mini-C service is an evolution of the existing INMARSAT C technology, combining a transceiver and antenna in one light and compact unit., with the added benefit of a significantly reduced level of power consumption The service offers e-mail, position reporting and polling, fax, telex, short-code addressing and mobile-to-mobile messaging services.

INMARSAT D