Systematic raptor codes for atmospheric optical channels

Abstract

In this paper, a rate-adaptive free-space optical (FSO) communication system using systematic Raptor codes is investigated based on experimental data measured over a 1.87 km terrestrial FSO link in different weather conditions. Using Raptor codes, the FSO communication system can adapt to the channel gain fluctuations caused by atmospheric turbulence and/or adverse weather conditions. To alleviate the burden of synchronizing between transmitter and receiver, messages are packetized and sent in sequence. For each packet, a cyclicredundancy code (CRC) is added resulting in an effective packet erasure channel (PEC). Using experimental data and on-offkeying (OOK) modulation, the performance of the rate-adaptive FSO system is evaluated at different signaling rates. While an uncoded FSO system fails to efficiently operate during adverse weather conditions, the rate-adaptive technique provides reliable FSO communication under clear and rainy weather conditions.

Raptor-Coded Free-Space Optical Communications Experiment

“…In [13], the performance of Raptor codes for FSO channels is demonstrated using channel measurements from an FSO link and offline decoding. This work is extended in [14], where a systematic Raptor code is used to implement a rateadaptive FSO link. The performance of the proposed communication system is evaluated by offline processing using FSO channel measurements.…”