Multi-rate Vehicular Communications with Systematic Raptor Codes in Urban Scenarios

In an urban environment, vehicle mobility is limited by road structure and obstacles. This gives rise to extremely challenging network design for large data transfers due to unpredictable network dynamics, limited connection lifetime and unstable channel conditions. Conventional approaches using re-transmission schemes do not perform well in these conditions due to nodes leaving the network in the middle of the download. Rateless codes have been identified as a solution to address interrupted downloads with minimal handshaking and overhead requirements. Varying channel conditions calls for the need of multi-rate vehicular communications, where low rate robust communication is used when bad channel is experienced and higher rate modulation is used in good channel conditions. This paper presents a novel coding scheme based on systematic raptor codes for multihop data dissemination that is based on multi-rate vehicular communications. With this scheme, even vehicles which are outside the roadside infrastructure coverage can be provided with reliable access to infrastructure services.