Gap Filler for Satellite DAB to Vehicular and Portable Receivers

Transcription

1 Gap Filler for Satellite DAB to Vehicular and Portable Receivers

2 Contents Satellite DAB Overview System E Standard Specification (CDM/TDM) Gap Filler Implementation Cell Planning Gap Filler ID Summary Page 1

3 What does Gap Filler mean? Technology to improve reception characteristics in areas with poor reception conditions Gap: Areas with poor reception conditions Gap Filler: A technology that fills such a gap by re-transmitting signals Page 2

4 Satellite DAB Provide Multimedia Contents to Vehicular and Portable Receivers By using Satellite Multimedia Contents: Audio, Traffic Information, Car Navigation Weather, Game, Stock Receiver with mobility Satellite only almost impossible Need Complementary Terrestrial Path Gap Filler is required to provide satisfactory Satellite DAB Service Page 3

5 Satellite DAB System A, DH, D, E System A System DH System E Satellite HEO 3 HEO 3 GEO 1 Bandwidth (khz) 1,536 1,840 25,000 Useful Bit Rate (kbps) 1,152 1,584 7,078 Multiplexing OFDM Satellite: TDM-QPSK CDM /Modulation Terrestrial: MCM(OFDM) FEC RCPC RS + CC RS + CC Combined Time diversity Page 4

6 Satellite DAB System A, DH, D, E System A System DH System E Power Amplifier (Satellite) Output Back Off (OBO): 7 db 1 OBO: 0 db (TDM only) (TDM) 2 OBO: 0 db (CDM) OBO: 2 db 3 Power Amplifier (Gap Filler) OBO: 7 db OBO: 7 db MCM(OFDM) only OBO: 2 db CDM only Receiver Single demodulator Dual demodulators Single demodulator Note 1) OFDM Signal Property (Reference: BO ) Note 2) For Gap Filler operation only Note 3) CDM Signal Property (Reference: BO ) Page 5

7 System E Overview Page 6

8 System E Overview Earth Station Send CDM Signal to Satellite through Ku-band Send TDM Signal to Satellite through Ku-band Satellite Send CDM Signal to Receivers through S-band Send TDM Signal to Gap Fillers through Ku-band Gap Filler (frequency conversion) Convert TDM Signal to CDM Signal Send CDM Signal to Receivers through S-band Receiver (Portable, Fixed, Vehicle) Receive CDM signals from both Satellite and any Gap Fillers Page 7

9 System E Specification CDM Specification (ITU-R BO ) Concatenate code (Reed-Solomon + Convolutional Code) QPSK Chip Rate Mcps (Processing Gain 64) PN Period 2048 chip TDM Specification CDM to TDM Multiplexing Concatenated code with QPSK (Same to that of ETS ) Page 8

10 Gap Filler Implementation Ku band Receiver Antenna (Ku band), LNB, Tuner Baseband Signal Processor TDM Demodulator TDM to CDM Converter CDM modulator S band Transmitter DAC, Up Converter, Power Amplifier Processor Control, Monitor, Interface to a Network Page 9

11 Implementation - Baseband Signal Processor TDM Demodulator QPSK Demodulator Coherent Detection Carrier/Clock Recovery Viterbi Decoder Continuous mode Node Synchronization by BER Monitoring Sync Byte Detector Sync Detection Timing Signal Generation Reed-Solomon decoder Indicate Satellite Channel Quality Page 10

12 Implementation - Baseband Signal Processor TDM to CDM Converter Remove Fill Data, Sync Byte and Inverted Sync Byte Serial to Parallel (25.5 msec unit) CDM modulator Short Code: 64 chip Walsh Long Code: 2048 chip (truncated from 4095 m-sequence) RRC filter with roll-off factor 0.22 chipx4 Implementation ( MHz) Page 11

13 Cell Planning - PN Period Chip rate: Mcps Chip duration usec ( ~ 18 m) PN period: 2048 chip In time, 125 usec (~ 37.5 Km) PN period restricts RAKE receiving range at Receiver. Paths whose delay larger than 125 usec shall not be combined. Difficult to combine Paths whose delay larger than 62.5 usec. Pilot Channel structure (Pilot Symbol 50% duty cycle) doubles RAKE receiving range Page 12

14 Cell Planning Processing delay of Gap Filler (GF) should be compensated in order to align the timing of signals from satellite and each GF. (At Earth Station, the transmission timing of TDM and CDM signals should be controlled to compensate GF processing delay.) Delay larger than PN period between multi-paths shall be prohibited. (Inter-GF distance shall be less than 37.5 Km.) At receiver, Searching and Finger management algorithm are required to seamless receiving. They are easier than that of Cellular system. Page 13

15 Gap Filler ID Pilot Channel Control Data Reserve Specific Control Data (e.g. D3) to Gap Filler ID Earth Station, Satellite: Null Data transmit At Gap Filler, its ID is inserted at D3 position Additional Walsh Code Channel Via Walsh Code Channel (e.g. W63) which is not used at Satellite, Gap Filler can send its ID. Page 14

16 Gap Filler ID Pilot Channel Control Data PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS Page 15

17 Gap Filler ID Additional Walsh Code Channel Page 16

18 Summary System E Provide Audio and Video Contents Provide Full Mobility by use of Gap Filler Gap Filler for System E Standard provides TDM path for efficient and reliable Gap Filler operation. Gap Filler ID can be inserted at each Gap Filler. Baseband signal processor and Up converter have already been developed and verified. Page 17