Diversity-Multiplexing Tradeoff in Cognitive Machine-to-Machine Networks

Machine-to-Machine (M2M) communication enables many applications, which require ubiquitous wireless connections among objects and the surrounding environment. A general cognitive M2M network (CM2M) consists of multi-radio systems, involving primary system (PS) and secondary system(s) of cognitive machines under heterogeneous wireless architecture. However, inherited from dynamic spectrum access (DSA) ability of cognitive radio technology, uni- directional opportunistic wireless fading links exist in multi-hop CM2M network and the conventional flow control mechanisms at link level cannot be applied anymore. In many cases, effective end-to-end quality-of-service (QoS) control is also needed to provide reliable data transportation. In addition, emerging multi- user multiple input multiple output (MU-MIMO) technology coherently coordinates the transmission and reception among multiple base stations, leveraging the advantage of MIMO communications based on one-hop physical layer transmission. In this paper, through the exploitation of network coding and MU-MIMO, we develop a novel opportunistic QoS control (OQC) scheme for multi-hop CM2M network. OQC control utilizes the cooperative relaying at session level with the proposed Qos guarantees, realizing diversity-multiplexing tradeoff for session traffic. In particular, the statistical QoS guarantee is first proposed to work with our prior routing design, called SAOR. Furthermore, overlaying the proposed guarantees with the routing algorithm, OQC scheme employs the diversity mode to deal with PS´s opportunistic nature and wireless fading, and utilizes the spatial multiplexing mode to obtain the maximum end-to-end throughput. Performance evaluations show the remarkable improvement of end-to-end delay violation probability for cognitive machines´ traffic in multi-hop CM2M networks, thus enabling great M2M applications.