With the popularity of wireless devices and the increase of computing and storage resources, there are increasing interests in supporting mobile computing techniques. Particularly, ad hoc networks can potentially connect different wireless devices to enable more powerful wireless applications and mobile computing capabilities. To meet the ever-increasing communication need, it is important to improve the network throughput while guaranteeing transmission reliability. Multiple-input-multiple-output (MIMO) technology can provide significantly higher data rate in ad hoc networks where nodes are equipped with multi-antenna arrays. Although MIMO technique itself can support diversity transmission when channel condition degrades, the use of diversity transmission often compromises the multiplexing gain and is also not enough to deal with extremely weak channel. Instead, in this work, we exploit the use of cooperative relay transmission (which is often used in a single antenna environment to improve reliability) in a MIMO-based ad hoc network to cope with harsh channel condition. We design both centralized and distributed scheduling algorithms to support adaptive use of cooperative relay transmission when the direct transmission cannot be successfully performed. Our algorithm effectively exploits the cooperative multiplexing gain and cooperative diversity gain to achieve higher data rate and higher reliability under various channel conditions. Our scheduling scheme can efficiently invoke relay transmission without introducing significant signalling overhead as conventional relay schemes, and seamlessly integrate relay transmission with multiplexed MIMO transmission. We also design a MAC protocol to implement the distributed algorithm. Our performance results demonstrate that the use of cooperative relay in a MIMO framework could bring in a significant throughput improvement in all the scenarios studied, with the variation of node density, link failure ratio, packet arrival rate and retransmission threshold.

Chapter Contents:

• 7.1 Introduction
• 7.2 Background and motivation
• 7.3 Problem formulation and a centralized solution
• 7.3.1 Problem formulation
• 7.3.2 A centralized algorithm
• 7.4 Packet scheduling with relay transmission
• 7.4.1 Determination of transmitter nodes and the number of transmission streams
• 7.4.1.1 Distributed transmitter node selection
• 7.4.1.2 Distributed determination of the number of streams
• 7.4.2 Allocation to antennas
• 7.5 Protocol design
• 7.5.1 Relay operations
• 7.5.1.1 Finding candidate relay nodes
• 7.5.1.2 Triggering of relay transmission
• 7.5.1.3 Constraining the delay of relay transmission
• 7.5.1.4 Broadcast of packet reception status
• 7.5.1.5 Rate determination
• 7.5.2 Protocol details
• 7.5.3 An example
• 7.6 Performance evaluation
• 7.7 Further development
• 7.8 Conclusion
• References

Inspec keywords: access protocols; antenna arrays; mobile computing; ad hoc networks; MIMO communication; wireless channels; relay networks (telecommunication); telecommunication network reliability

Other keywords: MAC protocol; multiantenna arrays; direct transmission; failure ratio; powerful wireless applications; harsh channel condition; distributed algorithm; relay transmission; MIMO technique; node density; MIMO ad hoc networks; storage resources; multiplexing gain; mobile computing techniques; packet arrival rate; centralized scheduling algorithms; single antenna environment; retransmission threshold; wireless devices; cooperative relay transmission; transmission reliability; distributed scheduling algorithms; MIMO technology; multiple-input-multiple-output technology

Subjects: Protocols; Antenna arrays; Reliability; Mobile radio systems