Technical Handbook for Radio Monitoring VHF/UHF. Edition 2011

Transcription

1 Technical Handbook for Radio Monitoring VHF/UHF Edition 2011

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3 Dipl.- Ing. Roland Prösch Dipl.- Inf. Aikaterini Daskalaki-Prösch Technical Handbook for Radio Monitoring VHF/UHF Edition 2011 Books on Demand GmbH Description of modulation techniques and waveforms with 181 pictures and 75 tables 3

4 Bibliografische Information der Deutschen Nationalbibliothek Die Deutsche Nationalbibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über abrufbar Dipl.- Ing. Roland Prösch, Dipl.- Inf. Aikaterini Daskalaki-Prösch 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

5 Acknowledgement: Thanks for those persons who have supported us in the preparation of this book. 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. 5

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7 Content 1. LIST OF PICTURES LIST OF TABLES GENERAL DESCRIPTION OF WAVEFORMS 24 Analogue Waveforms 24 Amplitude Modulation (AM) 24 Double Sideband reduced Carrier (DSB-RC) 25 Double Sideband suppressed Carrier (DSB-SC) 25 Single Sideband full Carrier 26 Single Sideband reduced Carrier (SSB-RC) 27 Single Sideband suppressed Carrier (SSB-SC) 27 Single Sideband Modulation (SSB) 27 Independent Sideband Modulation (ISB) 28 Vestigal Sideband Modulation (VSB) 29 Frequency Modulation (FM) 30 Wide Frequency Modulation (WFM) 31 Digital Waveforms 32 Amplitude Shift Keying (ASK) 32 Frequency Shift Keying (FSK) 33 Continuous Phase Frequency Shift Keying (CPFSK) 34 Double Frequency Shift Keying (DFSK) 34 Constant Envelope 4-Level Frequency Modulation (C4FM) 35 Minimum Shift Keying (MSK) 36 Tamed Frequency modulation (TFM) 37 Gaussian Minimum Shift Keying (GMSK) 37 Multi Frequency Shift Keying (MFSK) 37 Phase Shift Keying (PSK) 39 Binary Phase Shift Keying (BPSK) 39 Quadrature Phase Shift Keying (QPSK) 41 Offset Quadrature Phase Shift Keying (OQPSK) 43 Staggered Quadrature Phase Shift Keying (SQPSK) 43 Compatible Differential Offset Quadrature Phase Shift Keying (CQPSK) 43 Coherent Phase Shift Keying (CPSK) 44 Differential Coherent Phase Shift Keying (DCPSK) 44 8PSK Modulation 44 Differential Phase Shift Keying (DPSK) 45 Differential Binary Phase Shift Keying (DBPSK) 45 Differential Quadrature Phase Shift Keying (DQPSK) 45 Differential 8 Phase Shift Keying (D8PSK) 45 Quadrature Amplitude Modulation (QAM) 46 7

8 Orthogonal Frequency Division Multiplexing (OFDM) 48 Spread Spectrum (SS) 50 Direct Sequence Spread Spectrum (DSSS) 50 Frequency Hopping Spread Spectrum (FHSS) 51 Incremental Frequency Keying (IFK) 51 Analogue Pulse Modulation 52 Pulse Amplitude Modulation (PAM) 52 Pulse Width Modulation (PWM) 52 Pulse Position Modulation (PPM) 52 Digital Pulse Modulation 53 Pulse Code Modulation (PCM) 53 Delta Modulation 53 Description of modulation states 55 Asynchronous Data Transmission 55 Synchronous Data Transmission 55 Simplex 56 Duplex 56 Half duplex 56 Semi duplex 56 Bit Rate, Symbol Rate, Baud Rate 57 Bit rate 57 Symbol rate 57 Baud rate 57 Data formats 58 NRZ (Non Return to Zero) 59 NRZ (S) (Non Return to Zero - Space) 59 NRZ (M) (Non Return to Zero - Mark) 59 Bi-Ф-L (Biphase Level) 59 Bi-Ф-S (Biphase Space) 59 Bi-Ф- M (Biphase Mark) 59 Coding 60 Code 60 Codes in communication used for brevity 60 An example: the ASCII code 60 Codes to detect or correct errors 61 Error-correcting code (ECC) 61 Forward Error Correction (FEC) 61 Convolutional code 62 Viterbi algorithm 62 Reed-Solomon error correction 63 Overview of the method 63 Properties of Reed-Solomon codes 63 Use of Reed-Solomon codes in optical and magnetic storage 64 Timeline of Reed-Solomon development 64 Satellite technique: Reed-Solomon + Viterbi coding 64 Turbo code 65 Shannon-Hartley theorem 65 8

9 Theorem 65 Examples 66 Used code tables 67 ITA2, ITA2P and ITA3(CCIR342-2) 67 Russian MTK2 68 CCIR476-4, HNG-FEC, PICCOLO MK VI 69 ITA 2 70 ITA 2 P 70 ITA 3 70 CCIR ASCII / CCITT 5 70 Channel access methods 75 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 ACP STANAG 4406 Messaging 81 STANAG X RSX Designation of Emissions 90 Determination of Necessary Bandwidths VHF MODES 103 ACARS 103 ADS-B 107 AIS 109 AMPS 112 APCO ARDIS 115 ATCS 118 ATIS 120 BIIS 121 Bluetooth 122 Bluetooth 1.0 and 1.0B 123 9

10 Bluetooth Bluetooth Bluetooth EDR 123 Bluetooth EDR 124 Bluetooth HS 124 Bluetooth Broadcast WFM 125 Pre-emphasis and de-emphasis 126 CCIR CCIR CCITT 129 CDMA One 130 CDMA CDPD 132 Cordless Phone 136 Analogue Standard CT0 136 Analogue Standard CT0 (Extended) 137 Analogue Standard CT1 137 Analogue Standard CT Digital Standard CT2 137 Digital Standard CT Digital Standard CT3 138 CTCSS 139 DAB 140 DAB Bands and modes 140 Audio codec 141 DAB Error-correction coding 141 DAB Single-frequency networks 142 DAB Bit rates 142 DAB Frequencies 142 D-AMPS 146 DCSS 149 DECT 150 DSTAR 152 DSTAR Framing 153 DSTAR Radio Header 153 DSTAR data 155 DSTAR voice 155 DTMF 157 DVB-T 158 EEA 163 EIA 164 EPIRB 165 EPLRS 167 ERMES 168 Data Format 169 Hierarchy 169 EUROSIGNAL 170 EXICOM EX FLEX 172 FMS BOS 175 FSK

11 GMDSS-DSC VHF 178 GSM 180 The system components in GSM 182 MS (Mobile Station) 182 BSS (Base Station System) 182 NSS (Network and Switching Subsystem) 183 OSS (Operations Support System or Operation Subsystem) 183 Overview of the network architecture 184 GSM Interfaces 185 Logical Channels of the radio channel 186 Broadcast Channel (BCH) 187 Common Control Channel (CCCH) 188 Dedicated Control Channel (DCCH) 188 Bursts and frame structure 188 Normal burst 189 Frequency correction burst 189 Synchronization burst 189 Dummy burst 190 Access burst 190 Frequency Hopping 191 Have Quick 193 INMARSAT 194 INMARSAT-A 194 INMARSAT Aero H 195 INMARSAT Aero H+ 195 INMARSAT Aero I 195 INMARSAT Aero L 195 INMARSAT Aero Mini-M 195 INMARSAT-B 195 INMARSAT-C 196 INMARSAT Mini-C 197 INMARSAT D 197 INMARSAT D+ 197 INMARSAT-E 197 INMARSAT-M 198 INMARSAT mini-m 198 INMARSAT Fleet F INMARSAT Fleet F INMARSAT Fleet F INMARSAT GAN/M4 200 INMARSAT Regional BGAN 200 INMARSAT Swift INMARSAT TDM channel details 201 ITU Fax and Modem Standards 204 Modem Standards 204 V.19 Modem Standard 205 V.21 Modem Standard 205 V.22 Modem Standard 205 V.22 bis Modem Standard 206 V.23 Modem Standard 207 V.26 Modem Standard 207 V.26bis Modem Standard

12 V.26ter Modem Standard 208 V.27 Modem Standard 208 V.32 Modem Standard 208 V.32bis Modem Standard 208 V.33 Modem Standard 208 V.36 Modem Standard 208 V.37 Modem Standard 208 V.38 Modem Standard 209 V.90 Modem Standard 209 Fax Standards 210 Fax Standards 210 V.17 FAX Standard 210 V.29 FAX Standard 210 V.27bis FAX Standard 210 V.27ter FAX Standard 211 V.34 FAX Standard 212 DSVD and H.324 Standards 212 JT2 213 JT JT6M 215 LINK 4A/C 216 LINK 4A 216 LINK 4C 216 LINK 11 CLEW 217 LINK 11 SLEW 220 LINK LINK Y 222 LINK Z 223 LINK LINK MDC-600/MDC MDC Mobitex Mobitex RAM 230 MPT NATEL 233 NMT NOAA Weather Radio 235 Elements of NWR SAME Messages 235 Message Format of NRW SAME 237 Codes of NWR SAME 240 EAS Event (NWR-SAME) Codes 240 ORBCOMM 243 ORBCOMM Downlink 244 ORBCOMM SDPSK modulation 244 ORBCOMM Downlink Data Format 244 ORBCOMM subscriber uplink 246 ORBCOMM uplink GES to Satellite Channels 246 ORBCOMM beacon 246 Packet Radio 247 POCSAG

13 Preamble Structure 248 Batch Structure 249 Frame Structure 249 Address codeword 249 Message codeword 250 Idle Codeword 250 Numeric Message Format 250 Alpha-Numeric Message Format 251 Radiosondes 252 VAISALA RS80 15GH 253 VAISALA RS92 KL 254 VAISALA RS92 SGPD 255 M2 K2 256 Table of Radiosondes 257 RD-LAP 259 RDS/RBDS 261 RDS data structure 262 SENOA MSK Hopping System 265 TACAN 266 TETRA 267 TETRAPOL 273 Thuraya 275 Traffic Light Control Fehler! Textmarke nicht definiert. Trunked Radio 278 Terrestrial Television Analogue 280 Terrestrial Television Digital 285 VDEW 286 VHF Digital Link Modes 287 Frequency Allocation 287 VDL Mode VDL Mode VDL Mode VDL Mode ZVEI ZVEI ZVEI 2 xx tones HINTS FOR RADIO MONITORING 300 Recognizing of PSK-, MSK- and TFM - Signals 300 Different PSK modulation TABLES FOR RADIO MONITORING 302 Allocation of International Call Signs 302 Alphabetical List of Country Codes

14 Selective Calling 311 Allocation of Maritime Identification Digits 315 Notice to Airmen (NOTAM) 320 Weather Forecast (TAF and METAR) 327 TAF 327 METAR 327 Q, X and Z - Code 330 Q-Codes 330 X-Codes 340 Z-Codes 341 Abbreviations INDEX

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

16 Picture 43: Different types of amplitude modulation Picture 44: Quantization in a PCM Picture 45: Delta Modulation Picture 46: Common data formats Picture 47: Principle of FDMA Picture 48: Principle of TDMA Picture 49: Principle of OFDMA Picture 50: The OSI reference model Picture 51: STANAG 5066 layers Picture 52: Spectrum of ACARS Picture 53: Sonagram of ACARS packets Picture 54: Mode S short squitter frame Picture 55: Mode S extended squitter frame Picture 56: PPM of ADS-B Picture 57: Framing of ADS-B Picture 58: AIS frame Picture 59: AIS spectrum and sonogram Picture 60: Framing of APCO Picture 61: Spectrum and sonagram of an ARDIS signal with 4800 Bps Picture 62: Spectrum and sonagram of a 4FSK ARDIS signal with Bps Picture 63: Framing of MDC-4800 in an ARDIS signal Picture 64: Framing of RD-LAP in an ARDIS signal Picture 65: Spectrum and sonagram of an ATCS signal Picture 66: Structure of a 5 serie address Picture 67: Structure of a 7 serie address Picture 68: Spectrum of an ATIS 1200 Bd signal with test loop Picture 69: Spectrum of BIIS Picture 70: Format of a Bluetooth frame Picture 71: Spectrum of a WFM Picture 72: Spectrum of FM stereo with sub-channels Picture 73: Spectrum of a CCIR-1 signal Picture 74: Spectrum of a CCIR-2 signal Picture 75: Spectrum of CCITT signal Picture 76: Spectrum of a GMSK with Bd Picture 77: CDPD framing of forward channel Picture 78: CDPD reverse channel framing Picture 79: Cordless phone standards Picture 80: Spectrum of a CT2 signal Picture 81: Framing of CT Picture 82: Spectrum of a DAB signal Picture 83: Spectrum of a DECT signal Picture 84: Slot occupation of DECT Picture 85: Framing of DECT voice transmission Picture 86: Spectrum of DSTAR on IF level Picture 87: Audio spectrum of a DSTAR signal

17 Picture 88: Sonogram of a DSTAR signal with pre- and post carrier Picture 89: DSTAR overall framing Picture 90: Framing of the DSTAR radio header Picture 91: Framing of DSTAR data payload Picture 92: Framing of DSTAR voice payload Picture 93: Spectrum of a DTMF signal Picture 94: Spectrum of DVB-T in 8k mode Picture 95: Spectrum of DVB-T with 7 MHz bandwidth Picture 96: Scheme of a DVB-T transmission system Picture 97: MPEG-2 framing Picture 98: Spectrum of EEA signal Picture 99: Spectrum of EIA signal Picture 100: Spectrum of a 400 Bd EPIRB signal Picture 101: Phase plane of a EPIRB Picture 102: Baudrate measurement with phase spectrum of a EPIRB Picture 103: Spectrum and sonogram of an ERMES signal Picture 104: ERMES data format Picture 105: Spectrum of an EXICOM radio Picture 106: Spectrum of a FLEX signal 2FSK mode Picture 107: Spectrrum of a FLEX signal 4FSK mode Picture 108: Framing of FLEX Picture 109: FLEX frame information Picture 110: Spectrum of a FMS BOS signal Picture 111: Spectrum and sonagram of a FSK441 signal Picture 112: MFSK oscilloscope for a FSK Picture 113: Spectrum of a GMDSS signal with 511 bit test slip Picture 114: Spectrum of a GMDSS signal under real conditions Picture 115: Spectrum of GSM Picture 116: Architecture of the GSM Interfaces Picture 117: Frequency Reuse Picture 118: Logical Channels in GSM Picture 119: Burst types in GSM Picture 120: GSM Frame Structure Picture 121: Slow Frequency Hopping over three frequencies in GSM Picture 122: Spectrum of INMARSAT-C 1200 Bd TDMA Picture 123: Phase plane of INMARSAT-C 1200 Bd BPSK TDMA Picture 124: Spectrum of INMARSAT M NCS Picture 125: Spectrum of INMARSAT- mini-m NCS Picture 126: Spectrum of V.22 modem Picture 127: Phase plane of V.22 modem Picture 128: Spectrum of V.22bis modem with 2400 Bps Picture 129: Phase plane of V.22bis modem Picture 130: Spectrum of V.23 modem Picture 131: Spectrum and sonagram of a JT2 signal Picture 132: Spectrum and sonagram of a JT44 signal

18 Picture 133_ Spectrum and sonagram of a JT6M signal Picture 134: Spectrum of a LINK 11 transmission Picture 135: Spectrum of the LINK 11 single Tone Modem Picture 136: Sonagram of LINK 11 SLEW Picture 137: Typical spectrum of a LINK 14 signal Picture 138: Spectrum of a MDC-1200 signal Picture 139: Frame structure for a MDC-1200 signal Picture 140: Spectrum and sonagram of MDC-4800 signal with 4800 Bps Picture 141: Framing of MDC Picture 142: Spectrum of a MOBITEX Picture 143: Sonagram of a MOBITEX Picture 144: Frame Structur used in MOBITEX Picture 145: Spectrum of MPT1327 channel Picture 146: Spectrum of NWR SAME Picture 147: Burst sonagram of NWR SAME Picture 148: Spectrum of an ORBCOMM 4800 bps SDPSK Picture 149: Phase spectrum of an ORCOMM SDPSK with peaks at 4800 bps Picture 150: Phase constellation of an ORCOMM SDPSK Picture 151: Spectrum of a 1200 bd Packet Radio signal Picture 152: Spectrum of a POCSAG signal Picture 153: Structure of a POCSAG signal Picture 154: Structure of the POCSAG batches Picture 155: Frame Structure Picture 157: Sonagram of a VAISALA RS15GH Picture 158: Spectrum and sonagram of a RS 92 KL radiosonde Picture 159: VAISALA RS92 SGPD IF spectrum Picture 160: Spectrum of a VAISALA RS92 SGPD Picture 161: Spectrum of a Mark M2K Picture 162: Phase spectrum of a Mark2K2 with 400 bd peaks Picture 163: Spectrum and sonagram of a 4FSK used in RD-LAP Picture 164: Framing of RD-LAP Picture 165: Spectrum of FM broadcast carrier Picture 166: Spectrum of a RDS signal within a WFM signal Picture 167: RDS data structure Picture 168: Spectrum of TETRA Picture 169: Logical Channels in TETRA Picture 170: TDMA frame structure of TETRA Picture 171: Burst structure in TETRA Picture 172: Spectrum of a TETRAPOL signal Picture 173: TETRAPOL frame structure Picture 174: Spectrum of TETRAPOL signals Picture 175: Coverage area of Thuraya (copyright Picture 176: Spectrum of a single trunked radio channel Picture 177: Trunked Radio unused and used channel Picture 178: Scannning and display of television lines

19 Picture 179: Structure of a black&white video signal Picture 180: Structure of a colour video signal Picture 181: Spectrum of ZVEI 1 Signal

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21 2. List of Tables Table 1: C4FM symbol table Table 2: Bit value for QPSK Table 3: Phase shifts for CQPSK Table 4: Bit values for DQPSK Table 5: Bit values for QAM Table 6: Different description for data levels Table 7: Code table for ITA2, ITA2P and ITA Table 8: Code table for CCIR476-4, HNG-FEC and PICCOLO MK VI alphabets Table 9: ASCII table Table 10: X.25 Packet frame Table 11: Common used transmission modes Table 12: Terms and their description Table 13: Determination of necessary bandwidths for emissions Table 14: Main ACARS frequencies Table 15: ACARS message format Table 16: Data structure of AIS Table 17: ACL packet types in Bluetooth Table 18: Tone frequencies of CCIR Table 19: Tone frequencies of CCIR Table 20: Tone frequencies of CCITT Table 21: Frequencies of CT Table 22: Frequencies of CT0 extended Table 23: Tone frequencies of CTCSS Table 24: DAB Broadcast band III Table 25: DAB Channel 13 frequencies Table 26: DAB L-band frequencies Table 27: Main parameter of D-AMPS Table 28: DCSS bit structure Table 29: DCSS tone frequencies Table 30: DSTAR radio header flag 1 description Table 31: DTMF tone frequencies Table 32: DVB-T available bitrates Table 33: EEA tone frequencies Table 34: EIA tone frequencies Table 35: Frequencies for ERMES Table 36: EURO tone frequencies Table 37: Structure of FMS BOS messages Table 38: FSK 441 tone/character combination Table 39: Ten bit error detecting code of GMDSS VHF Table 40: GSM Frequencies Table 41: Different GSM frequency ranges by country

22 Table 42: Power for mobile station (MS) in GSM Table 43: INMARSAT NCS frequencies Table 44: INMARSAT modulation overview Table 45: INMARSAT TDM channel details Table 46: INMARSAT bit structure of the signalling channel Table 47: ITU Modem Standards Table 48: ITU Fax Standards Table 49: LINK 11 frequencies Table 50: NATEL tone frequencies Table 51: Possible subscriber terminal uplink frequencies Table 52: POCSAG numeric character Table 53: POCSAG alpha numeric message format Table 54: Tone frequencies of IRIG telemetry standard Table 55: Overview of types of radiosondes Table 56: RDS and RBDS programm types Table 57: Logical channels in Thuraya that are common to GSM Table 58: Different TV standards Table 59: TV standards - signal characterisation Table 60: Differrent digital terrestrial television standards Table 61: VDEW tone frequencies Table 62: Frequencies for VHF Digital Link (VDL) Table 63: ZVEI 1 tone frequencies Table 64: ZVEI 2 tone frequencies Table 65: PSK transmitted bit's/phase shifts Table 66: International callsigns Table 67: Country codes Table 68: Translation of a four digit number Table 69: Translation of a five digit number Table 70: Coast station identification numbers by blocks and countries Table 71: Allocation of MID's Table 72: Q-codes Table 73: X-codes Table 74: Z-codes Table 75: Abbreviations

23 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 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. 23

24 4. Description of Waveforms Analogue Waveforms Analogue waveforms are mainly seperated in to different forms: the amplitude modulation in which the carrier frequency is fixed and the amplitude of the signal is modulated related to the information being sent. The other modulation form is the frequency modulation in which the frequency is changed related to the information being sent. The carrier envelope remains on the same level. Amplitude Modulation (AM) Picture 1: Different AM waveforms The Ampitude modulation is mainly used for broadcast transmissions or in aeronautic mobile service on VHF. In a AM the strength of the carrier is varried in relation to the information which shall be send. In a pure AM both sidebands are modulated. The following pictures shows the spectrum and sonagram of a typical amplitude modulation with bioth sidebands and the carrier: 24

25 Quadrature Amplitude Modulation (QAM) Quadrature amplitude modulation (QAM) is a modulation scheme in which two techniques are combined: amplitude modulation and phase shift keying (PSK). A combination of two amplitude levels and a QPSK would result in an 8QAM with 8 states representing 8 different bit sequences as shown in the following table: Bit Sequence Amplitude Level Phase Shift Table 5: Bit values for QAM Picture 35: Example of an 8QAM and 16QAM in the Phase Plane The next two pictures are showing the spectrum of a QAM8 and QAM16 with 600 Bd: 46

26 Picture 36: Spectrum of a QAM8 with 600 Bd Picture 37: Spectrum of a QAM16 with 600 Bd The main differences which can be seen in this spectrum are lower side lobes with a QAM16 compared to a QAM8. 47

27 Channel access methods Frequency-division multiple access (FDMA) FDMA, or frequency-division multiple access, is the oldest and most important of the three main ways for multiple radio transmitters to share the radio spectrum. The other two methods are Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). In FDMA, each transmitter is assigned a distinct frequency channel so that receivers can discriminate among them by tuning to the desired channel. TDMA and CDMA are always used in combination with FDMA, i.e., a given frequency channel may be used for either TDMA or CDMA independently of signals on other frequency channels. Picture 47: Principle of FDMA Time division multiple access (TDMA) Time Division Multiple Access (TDMA) is a technology for shared medium (usually radio) networks. It allows several users to share the same frequency by dividing it into different time slots. The users transmit in rapid succession, one after the other, each using their own timeslot. This allows multiple users to share the same transmission medium (e.g. radio frequency) whilst using only the part of its bandwidth they require. TDMA is used extensively in satellite systems, local area networks, physical security systems, and combat-net radio systems. Picture 48: Principle of TDMA 75

28 Code division multiple access (CDMA) Generically (as a multiplexing scheme), code division multiple access (CDMA) is any use of any form of spread spectrum by multiple transmitters to send to the same receiver on the same frequency channel at the same time without harmful interference. One important application of CDMA is the Global Positioning System, GPS. CDMA's main advantage over TDMA and FDMA is that the number of available CDMA codes is essentially infinite. This makes CDMA ideally suited to large numbers of transmitters each generating a relatively small amount of traffic at irregular intervals, as it avoids the overhead of continually allocating and de-allocating a limited number of orthogonal time slots or frequency channels to individual transmitters. CDMA transmitters simply send when they have something to say, and go off the air when nothing is to transmit. Orthogonal Frequency multiple access (OFDMA) Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of the OFDM digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users as shown in the picture below. This allows simultaneous low data rate transmission from several users. OFDMA can also be described as a combination of frequency domain and time domain multiple access, where the resources are partitioned in the time-frequency space, and slots are assigned along the OFDM symbol index as well as OFDM sub-carrier index. Picture 49: Principle of OFDMA 76

29 Broadcast WFM In the broadcast service, mainly the frequency range from 87.5 MHz to 108 MHz, broadcast transmitter are modulated with a Wide Frequency Modulation WFM. The modulation index is much higher than one. This modulation from has been invented to provide high-fedelity sound over broadcast radios. The following picture shows a typical WFM: Picture 71: Spectrum of a WFM The simplest signal is a FM mono transmission with a bandwidth of 15 khz. In the late 1950 s stereo and sub carriers were added to the WFM broadcast. It was important that FM stereo is compatible with FM mono. Therefore the left and right channel were encoded into the sum (left + right, L+R) and the difference (left right, L-R) between both channels. The mono receiver will use the sum of both signals to listen to both in a single loudspeaker. A stereo receiver will add the L+R and L-R signals to get the left channel and subtract L+R and L-R to get the right channel. The (L+R) main channel signal is transmitted as baseband audio in the range of 30 Hz to 15 khz. The (L R) sub-channel signal is modulated onto a 38 khz double-sideband suppressed carrier (DSBSC) signal occupying the baseband range of 23 to 53 khz. A 19 khz pilot tone, at exactly half the 38 khz sub-carrier frequency and with a precisely defined phase relationship to it, is also generated. This is transmitted at 8 10% of overall modulation level and used by the receiver to regenerate the 38 khz sub-carrier with the correct phase. The final multiplex signal from the stereo generator contains the main Channel (L+R), the pilot tone, and the sub-channel (L R). This composite signal, along with any other sub-carriers (SCA), modulates the WFM transmitter. 125

30 Converting the multiplex signal back into left and right audio signals is performed by a stereo decoder, which is built into stereo receivers. The following picture shows these channels in the spectrum display: Picture 72: Spectrum of FM stereo with sub-channels On WFM signals also digital services are available. These services are modulated to a 57 khz subcarrier which is the third harmonic of the 19 khz stereo pilot tone. This digital service is called Radio Data System RDS. This system works with a data rate of Bps. Pre-emphasis and de-emphasis Random noise has a triangular distribution in the spectrum of a FM system. This results in the effect that noise occurs in the higher frequencies of the baseband. To work against this effect a process has been developed: pre-emphasis and de-emphasis. Before transmitted the higher frequencies will be amplified by a certain amount and after reception reduced by the corresponding amount. Reducing the high frequencies will also reduce the noise of a broadcast signal. The amount of pre-emphasis and de-emphasis is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used, in North America it is 75 µs. This applies to both mono and stereo transmissions and to baseband audio (not to the subcarriers). 126

31 (Emergency Position Indicating Radio Beacons), as well as hand-portable versions for smaller Vessels. INMARSAT-M INMARSAT-M was introduced in 1993 to complement the existing INMARSAT-A system by providing global telephone/fax and data communications on an MES which is inexpensive and compact in size. The INMARSAT-M MES is smaller and lighter than an INMARSAT-A MES, making this network suitable for smaller vessels such as fishing vessels and yachts. INMARSAT-M is using 6000 Bps DPSK for the NCS or 8000 Bd OQPSK for voice. For the return channel 3000 Bps DPSK or 8000 Bps OQPSK is used. Picture 124: Spectrum of INMARSAT M NCS INMARSAT mini-m The INMARSAT mini-m system was launched in January 1997 and offers the same services as INMARSAT-M, but in a smaller, more lightweight and compact unit. This MES can be made smaller because it operates only in the spot-beam coverage of the latest INMARSAT-3 satellites. The receive modulation for voice/fax/data is OQPSK with 5.6 kbps SCPC or 6 kbps BPSK TDM. The forward channel uses a data rate of 5.6 kbps OQPSK for voice/fax/data or 3 kbps BPSK TDMA. Picture 125: Spectrum of INMARSAT- mini-m NCS 198

32 INMARSAT Fleet F33 Fleet F33 offers an integrated data service within the spot beam, delivering a data stream at speeds up to 9.6kbit/s although an effective throughput of up to seven times faster can be achieved using integrated compression. This service is best used for fax and sending batched transmissions, such as file transfers via . The Mobile Packet Data Service (MPDS) provides an "always on" service where charges are made for the amount of data sent and received, rather than the time spent online. Offering spot beam data and global voice coverage, Fleet F33 has been designed for vessels that require a smaller antenna, lighter above-deck equipment and a low-cost, simple hardware installation. The following services are possible: Voice 4.8 kbps Data 9.6 kbps dedicated channel (with compression equivalent to up to 40 kbps) Data MPDS 28.8/64 kbps MPDS (Packed data) Fax 9.6 kbps Group 3 fax INMARSAT Fleet F55 The Fleet F55 service allows the user to select either or both of two data services with the INMARSAT spot beams Mobile ISDN or the Mobile Packet Data Service (MPDS). There are some fundamental differences between the two forms of communication, suiting different types of operational needs. Mobile ISDN delivers a data stream at speeds up to 64 kbps. The Mobile Packet Data Service (MPDS) is best where network transmissions need to be of a higher frequency, are less urgent or involve smaller amounts of data. MPDS also lets you stay on line all the time, since you only pay for the amount of data sent and received rather than the time spent online making it ideal for and web browsing. Offering spot beam data and global voice coverage, Fleet F55 has been designed for vessels that require a smaller antenna, lighter above-deck equipment and a low-cost, simple hardware installation. The following services are possible: Voice 4,8 kbps, 64 kbps, 3.1 khz audio Data 64 kbps MPDS (Packed data) 56/ 64 kbps ISDN Fax 9.6 kbps Group 3 fax, 64 kbps Group 4 fax, 3.1 khz audio 199

33 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 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). Picture 165: Spectrum of FM broadcast carrier Picture 166: Spectrum of a RDS signal within a WFM signal RDS is modulated on the subcarrier with a QPSK waveform with a data rate of Bps. This is equal to the frequency of the RDS subcarrier divided by

34 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 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. Picture 167: 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) 262