Performance analysis of LT code-based HARQ error control in underwater acoustic sensor networks

Abstract

Underwater acoustic sensor network (UASN) is an emerging technology meant for underwater explorations. In underwater communication, the acoustic signal travels a longer distance with smaller bandwidth. Characteristics of the acoustic channel and the distance between underwater sensor nodes vary with time due to the variations in the water current. This affects the channel quality as well as the topology of the network. Connectivity issues in UASN cause transmission reliability challenges, in transferring the data sensed by various sensor nodes to the other end. Thus, data reliability and energy efficiency are the two critical issues in the case of UASN. The robust signal attenuation leads to the reception of erroneous data or data loss. In this paper, Recursive Luby transform (RLT) code-based Hybrid Automatic Repeat reQuest is proposed to overcome the data reliability issues and to obtain transmission efficiency. RLT is a form of Luby transform code with small degree of distribution. The proposed rateless code-based Hybrid ARQ scheme combines the RLT code and selective retransmission ARQ (RLTCH). The RLT code is adopted for its minimal complexity in encoding and decoding processes. The performance of RLTCH is evaluated by considering the underwater-specific channel characteristics. Simulation results of RLTCH for multi-hop UASN reveal that the proposed technique increase the network throughput with reduced energy consumption and end-to-end delay. Comparative performance studies were conducted to confirm the superiority of RLTCH with other schemes based on parameters such as throughput, packet arrival ratio, delay and energy consumption.