DVB-S2 Modulator with ACM features

Transcription

1 SIXTH FRAMEWORK PROGRAMME Integrated Multi-layer Optimization in broadband DVB-S.2 SAtellite Networks FP Deliverable D9-F DVB-S2 Modulator with ACM features Contractual Date of Delivery to the CEC M24 Actual Date of Delivery to the CEC Author(s) Participant(s) Workpackage Dissemination Level Nature J. Lauterjung, P. Schmidt (R&S), R&S WP3 Public Report / Prototype Version 1.0 Total number of pages 10 Page 1 of 10

2 Table of Contents 1 INTRODUCTION DVB-S2 MODULATOR MODIFICATION OF THE INPUT FORMAT OF THE DVB-S2 MODULATOR Structure of modified Transport Stream packets (TSP) Structure of ACM control information UP-DATE OF THE USER INTERFACE OF THE DVB-S2 MODULATOR DVB-S2 MODULATOR FIRMWARE UP-DATE ACRONYMS REFERENCES Page 2 of 10

3 1 Introduction This Deliverable D9-F describes the up-dates and modifications of the DVB-S2 modulator based on its specification in D09I [ 2]. The up-dated version of the DVB-S2 modulator was provided to project partner CNES who hosted the first set of implementation tests and the intermediate audit in October and November The basic reference document in this deliverable is the ETSI standard for DVB-S2 [ 1]. Page 3 of 10

4 2 DVB-S2 modulator This section describes the status of the DVB-S2 modulator, as it is used in the laboratory tests and field trials, in comparison with the version described in D09I [ 2]. The major up-dates and modifications of the modulator/ test signal generator are modification of the input format for the MPEG2 Transport Stream as provided by the Bandwidth Manager and Multiplexer (BMM) module; up-date of the user interface of the DVB-S2 modulator; up-date of the firmware implemented on the modulator platform after eliminating several errors or bugs. 2.1 Modification of the input format of the DVB-S2 modulator Structure of modified Transport Stream packets (TSP) The interface between the TS multiplexer and the DVB-S2 modulator R&S SFU in the Forward Link Sub-System FLSS is ASI or SPI optionally. The MPEG-2 TSPs which are transported via this interface are 204 bytes long, i.e. they contain 16 bytes in addition to their normal length of 188 bytes. The first 3 bytes of the additional 16 bytes contain the control information as described below. The remaining 13 bytes contain no information. The table shows the structure of the TSPs. Byte Comment 0 ~ 3 MPEG-2 header 4 ~ 187 MPEG-2 payload 188 ~ 190 ACM control information bytes 0 ~ ~ 203 fill bytes Structure of ACM control information Byte Bit Comment 0 (first) 7 (MSB) 1: start a new BBFRAME 0 6 0: normal frame 1: short frame 0 5 0: pilots off 1: pilots on 0 4 ~ 0 0: no change from previous packet other: MODCOD information 1 7 ~ 0 reserved for future use; set to ~ 0 0: useful packet 1: dummy packet other: reserved for future use Page 4 of 10

5 The mechanism of dummy packets (byte 2 of ACM control information) allows for stuffing the TS to a constant data rate while the MODCOD parameters change. Dummy packets are removed in the input stage of the modulator and are not transmitted byte 16 byte 3 13 byte Figure 1: Packet structure on ASI between BMM and DVB-S2 modulator Page 5 of 10

6 2.2 Up-date of the user interface of the DVB-S2 modulator When the modulator is operated in connection with the BMM module in ACM mode, the stuffing functionality at the modulator input is switched off since the BMM provides a Transport Stream of the correct bit rate for the chosen transmission mode (Figure 2). Figure 2: Graphical User Interface (GUI) for the Input signal Page 6 of 10

7 Figure 3: Graphical User Interface (GUI) displaying the Coding parameters When operated in ACM mode, the DVB-S2 modulator user interface shows those parameters which are set by the BMM, with a grey background. In Figure 3 above, these are the parameters for Constellation (here: QPSK), FECframe (here: Normal), Pilots (here: Off) and Code Rate (here: 5/6). The constellation (or modulation scheme) and the code rate are determined by the MODCOD information, the type of frame and the usage of pilots are chosen during the set up of the BMM. As long as these parameters are controlled by the BMM, they cannot be set manually. Page 7 of 10

8 2.3 DVB-S2 modulator firmware up-date During the internal laboratory tests and especially during the trials in Toulouse where the modules and equipment of several partners were interconnected, some minor issues occurred which could be solved by up-dates of the firmware and the control software of the DVB-S2 modulator. One of these issues was the processing of Transport Streams with a useful signal of very low bit rate and a high percentage of stuffing packets. With an improved buffer management algorithm this could be solved. The other issues concerned the display of certain information on the user interface and the elimination of a bug that led to an unpredictable shut-down of the operating system. It should be mentioned that the actual up-date of the firmware and the control software could normally be carried out comparatively quickly. What is always time-consuming in these circumstances is the testing of all modulator functions after a modification of the firmware/ software. For this purpose, specific test signals were generated and extensive tests of all transmission modes were needed. Page 8 of 10

9 3 Acronyms 16APSK 32APSK 8PSK ACM ASI AWGN BCH BER BMM BW CBR CCM CNI CRC FEC IF LDPC LNB MPEG PER PID PSK PRBS QEF QPSK RF TS TSP VCM 16-ary Amplitude and Phase Shift Keying 32-ary Amplitude and Phase Shift Keying 8-ary Phase Shift Keying Adaptive Coding and Modulation Asynchronous Serial Interface Additive White Gaussian Noise Bose-Chaudhuri-Hocquenghem multiple error correction binary block code Bit Error Ratio Bandwidth Manager and Multiplexer BandWidth Constant Bit Rate Constant Coding and Modulation Carrier to Noise plus Interference ratio Cyclic Redundancy Check Forward Error Correction Intermediate Frequency Low Density Parity Check (codes) Low Noise Block Moving Pictures Experts Group (MPEG TS) Packet Error Rate Packet IDentifier Phase Shift Keying Pseudo Random Binary Sequence Quasi-Error-Free Quaternary Phase Shift Keying Radio Frequency Transport Stream Transport Stream Packet Variable Coding and Modulation Page 9 of 10

10 4 References [ 1] ETSI EN Digital Video Broadcasting (DVB); Second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications [ 2] IMOSAN, Deliverable D09I, DVB-S2 Modulator with ACM features, December 2006 Page 10 of 10