Reliable, congestion aware transport layer protocol for heterogeneous wireless sensor networks

Abstract

Energy is the biggest concern for any heterogeneous WSNs and achieving high energy efficiency is of paramount importance for the longevity of a heterogeneous WSNs. Communicating in- formation from the sensing region to the sink is a critical task in the entire operation of a heterogeneous WSNs. Such information needs to be reliably communicated, while avoiding any network congestion, from source to sink in order to ensure that application-specific Quality of Service objectives are met for any given scenario. This thesis developed several transport layer protocols to address the issues of congestion control, reliability assurance, simultaneously supporting heterogeneous traffic environment and energy efficiency for a heterogeneous WSNs.The first aim of the proposed research is to develop a congestion control scheme for a heterogeneous WSNs. The envisaged congestion control scheme has dual functionality. Firstly, it should be capable of handling the traffic heterogeneity and secondly, it intelligently assigns the source transmission rates and channel bandwidth for avoiding congested scenarios within the network, thereby avoiding any unnecessary packet retransmissions, due to packet drops caused by congestion. This produces high network good throughput, effective use of channel bandwidth, minimum E-2-E data packet latency etc. All the proposed transport layer protocol schemes e.g. End-to-End Reliable and Congestion Aware Transport Layer Protocol (ERCTP), Lightweight Congestion Aware Reliable Transport protocol (LCART) and Lightweight Congestion Aware Reliable Transport Protocol-implicit (LCARTi) are designed with this aim in mind.The second aim of the proposed research is to develop an intelligent reliability ensuring scheme capable of handling bidirectional reliability issues associated with data and control information flow within the heterogeneous WSNs. The design takes into account the variable nature of reliability assurance based on the nature of the traffic. For instance, multimedia flow is given a high reliability measure in comparison to scalar and non-event information flow, since the multimedia has a high retransmission cost. All the proposed transport layer protocol schemes such as ERCTP, LCART and LCARTi are designed in order to achieve this objective.The third aim of the proposed research is to develop a scheme that simultaneously handles the heterogeneous traffic flows within the same network. The proposed scheme has the intelligence to determine the nature of traffic and to allocate different bandwidth based on this nature in order to meet the stringent requirements as imposed by the application-specific QoS constraints like E-2-E data packet latency, high good throughput etc. All the proposed transport layer protocol schemes such as ERCTP, LCART and LCARTi are designed with this objective in mind.The fourth and final aim of the proposed research is to create a mechanism that merges the common functionalities of different layers of the WSNs communication stack in order to maximise energy efficiency. This involves finding the relationship between the transport and the lower MAC and wireless-physical layers of the WSNs communication stack. This merging will result in better utilization of network resources such as bandwidth, storage etc. and helps to achieve the objective of energy efficiency. Only the LCART and LCARTi designs achieve this proposed research aim.