Cross‐layer enhancement of error control techniques for adaptation layers of DVB satellites

Abstract

SUMMARYThis paper assesses the way error control is managed jointly by Forward Error Codes (FEC) and Cyclic Redundancy Checks (CRC) in the lower layers of today's Digital Video Broadcasting (DVB) satellites. Mathematical and simulation results clearly show that the outer block codes of the coding schemes used in DVB-S and DVB-S2 (Reed-Solomon and Bose-Chaudhuri-Hocquenghem, respectively) can provide very accurate error-detection information to the receiver in addition to their basic correction task at virtually no cost, making an uncorrected error after decoding an extremely improbable event. For this reason, the workload of CRCs can be ensured safely by the FEC subsystem if a dedicated function allowing the physical layer to share its decoding information with the adaptation layer is set. This particular cross-layer mechanism would allow freeing up the bandwidth currently used by CRCs}which adds up to 10% for more than 35% of the total number of IP packets}and pave the way for an enhanced transport of IP over DVB-S2.

GSE: A flexible, yet efficient, encapsulation for IP over DVB‐S2 continuous generic streams

“…One example is utilizing the integrity check with information that may be available at the output of some DVB-S2 decoders. Theoretical and experimental results show the high probability of detecting channel decoding errors by the BCH decoder [17]. For 17 out of the 21 FEC configurations, detectable events are up to 10 8 times more frequent than undetectable ones, and the ratio is between 10 4 and 10 6 for the remaining 4.…”

“…DVB-S2 uses a powerful FEC code that reduces the probability of an undetected error by several orders of magnitude compared with that of DVB-S [17]. This low probability of undetected error (frames are usually either correctly decoded, or known to be in error) means that GSE does not require a cyclic redundancy check (CRC) for each encapsulated PDU (as in MPE/ULE).…”

“…The required integrity detection can be achieved using either the error detection capabilities of the FEC coding scheme of the physical layer (see Section 6.2), or by introducing a CRC-32 for each frame, carried in the final 4 B of the Datafield. DVB-S2 uses a powerful FEC code that reduces the probability of an undetected error by several orders of magnitude compared with that of DVB-S [17]. This low probability of undetected error (frames are usually either correctly decoded, or known to be in error) means that GSE does not require a cyclic redundancy check (CRC) for each encapsulated PDU (as in MPE/ULE).…”

Cross-layer optimization of TCP throughput for DVB-S2 links

“…Also the approach proposed in [7] provides QoS by introducing a bandwidth allocation fairness parameter, tuned via cross-layer architecture. In [8], enhancements are proposed at the IP layer to manage CRC and FEC codes at layer 1. Moreover, a new resource allocation scheme is proposed in [9] considering the interactions between TCP and MAC layers.…”

Design Issues for the Generic Stream Encapsulation (GSE) of IP Datagrams over DVB-S2

“…/ 6 , 8 / 9 and 9 / 10 , for a resulting family of concatenated Forward Error Coding schemes (FEC) only 0.6 to 0.8 dB away from the Shannon limit [6], easily ensuring the Quasi Error Free (QEF) target of BER < 10 −10 at the input of the network layer. On the other hand, it has been pointed out that in DVB-S2 link layer frames are either correctly decoded or totally messed up in the functioning E s /N 0 domain, and that the probability of resilient or undetected errors after FEC decoding in DVB-S2 has been lowered by more than 3 orders of magnitude [7] compared to DVB-S. As a major consequence for IP, encapsulated datagrams in DVB-S2 should be more protected and less exposed to resilient channel errors than in DVB-S. Combined use of higher order modulations and powerful channel coding allows covering a wide range of E s /N 0 values from -2.35 dB to 16.05 dB, enlarging considerably the functional domain of the new standard over DVB-S, and increasing de facto its raw transmission capacity over more than 35% in terms of spectral efficiency [6] [8].…”