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Home Research Cost Effective Design and Performance Evaluation for Cooperative Wireless Sensor Networks

Cost Effective Design and Performance Evaluation for Cooperative Wireless Sensor Networks

Contact: Tong Wang (1.,2.), Yulin Hu (3.), Anke Schmeink
(3.) is a joint project with Prof. James Gross

Introduction

Recently, wireless sensor networks (WSNs) have been proven extremely powerful because of their unique features that allow a wide range of applications in the areas of military, environment, health and home. WSNs are usually composed of a large number of densely deployed sensing devices which can transmit their data to the desired destination through multihop relays (see Figure 1). As sensor nodes carry limited, in general irreplaceable power sources, one of the most important constraints for WSNs is the low power consumption requirement. Thus, power conservation is of tremendous importance.

WSN
Figure 1: Cooperative Wireless Sensor Networks.

General Tasks

The focus of our research is on WSNs and the need for cost effective solutions, increased capacity and enhanced performance for data fusion and processing. We consider WSNs that operate in a cooperative way with two or multiple hops. The sensor nodes are battery powered, have a limited lifetime, reduced communications and data processing capabilities. Therefore, a major focus is on low-energy solutions. The aim of our research on algorithms, designs and strategies for WSNs is to achieve high performance by still reducing the power consumption. As a result, the network lifetime will be extended and data processing capabilities will be greatly enhanced. Current topics are:

  1. Low-complexity Channel Estimation
  2. Joint Design Strategies with Resource Allocation
  3. Analysis of Relaying Strategies and Protocol Design

1. Low-complexity Channel Estimation

For this topic, we focus on low complexity channel estimation methods for WSNs. Because most of the research on other layers are based on the assumption of perfect synchronization and available channel state information (CSI) at each node, more accurate estimates of the CSI will bring better performance for WSNs. We investigate the set-membership filtering (SMF) framework and incorporate it into the conventional channel estimation algorithms such as least-mean-square (LMS), recursive least-square (RLS), conjugate gradient (CG), affine projection (AP) and date reusing algorithms, etc. These set-membership channel estimation algorithms can reduce the computational complexity significantly and extend the lifetime of the WSN by reducing its power consumption.

2. Joint Design Strategies with Resource Allocation

For this topic, we investigate strategies to jointly design resource allocation, data fusion, relay selection strategies, and energy harvesting (see Figure 2). The aim of our research is to improve the performance under the constraint of the limited power consumption of the sensor nodes.

Joint design
Figure 2: Joint Design for Cooperative WSNs

3. Analysis of Relaying Strategies and Protocol Design

Analysis of QoS-constrained performance

It has been proved in many research works that Multi-relay Cooperative Automatic Repeat reQuest (CARQ) is a promissing way to improve the efficiency of retransmission and to reduce the delay of transmission. Based on approximate queueing theory, we derive the expressions of delay distribution and effective capacity (with target requirements of delay and delay violation probability) for common CARQ protocols. Please see Figure 3 for the validation.

Energy-efficiency-oriented packet drop mechanism

For the feedback-limited system, we design a distributed way to reduce the potential waste of energy by conditionally introducing a packet drop mechanism to relays.

Energy-efficiency-oriented CARQ protocol design

We analyze the energy efficiency of common CARQ protocols by theoretical means. Our focus is to design an effective and efficient CARQ protocol to maximize the energy efficiency of the system.
Queue performance
Figure 3: The validation of theoretical analysis values (TV) by the means of simulation values (SV) with QoS requirements

"Analysis of Relaying Strategies and Protocol Design" is a joint project with Prof. James Gross, KTH, Sweden.