At the 2009 NAB Show, Comtech EF Data featured its VersaFEC forward error correction tool. VersaFEC is designed to provide maximum coding gain with the lowest possible latency to support cellular backhaul and other latency-sensitive voice, video and data applications. It is available as a plug-in module for the CDM-625 Advanced Satellite Modem.
VersaFEC is a system of short-block, low-latency Low Density Parity Check (LDPC) codes designed to support latency-sensitive applications. Engineered to provide maximum coding gain while minimizing the end-to-end latency, VersaFEC provides an alternative to existing LDPC and DVB-S2 codes.It offers an expanded choice of modulation and code combinations (ModCods). The 12 ModCod combinations offer equivalent coding gains to Comtech EF Data’s existing LDPC offering, and reduce latency. VersaFEC also supports a patent-pending Adaptive Modulation and Coding (ACM) system. The ModCods were chosen to provide a continuous progression in terms of Eb/No and spectral efficiency, while reducing latency to near-theoretical minimums. For all ModCods, VersaFEC performance is within 0.7dB to 1.0dB of the Shannon Bound. This puts the performance of VersaFEC at or near the DVB-S2 performance with 16kbit blocks. Compared to Turbo Product Codes, VersaFEC generally provides 1dB or more reduction in EB/No. By utilizing smaller block sizes and non-interleaved systematic LDPC codes, VersaFEC can also reduce latency by as much as a factor of 10 compared to alternate FECs.