Network Throughput Improvement in Cognitive Networks by Joint Optimization of Spectrum Allocation and Cross-layer Routing


This paper introduces innovative technology development that will improve performance of next-generation cognitive wireless networking among space, air, and ground assets. The paper describes methods to develop a system where cognitive users transmit wideband spread-spectrum signals that are designed to adaptively avoid the interference dynamics of the available spectrum at the receiver. These technological advances can achieve improvement in network throughput, delay, and reliability. Theoretical performance expectations are given. The theoretical approach is translated to the construction of specific software techniques and their implementation within the cross-layer wireless communications architecture. The hardware/software testbed that simulates a dynamic Ad Hoc Software Defined Radio (SDR) network is described, and a series of tests to measure the value of the optimization techniques is given. Preliminary test results and the total expected performance improvements are shown. Cognitive radio networks have emerged as a promising technology to improve the utilization efficiency of the existing radio spectrum. However, in a radio network consisting of a number of primary and secondary users, primary users hold licenses for specific spectrum bands, and can only occupy their assigned portion of the spectrum. Secondary users do not have any licensed spectrum and opportunistically send their data by utilizing idle portions of the primary spectrum. In unlicensed spectrum bands there are potentially many uncoordinated devices. And in a multi-hop network the spectrum environment varies in time and space depending on the activities of primary users, interference, and fading, so the optimal spectrum-spreading channelization may therefore be different at each hop in a multi-hop path. Also as new secondary links are formed and others vanish, routing of data flows from one secondary node to another may frequently change. Therefore, controlling the interaction between routing and spectrum allocation is of fundamental importance. The focus of the research is on developing software enhancements in multi-hop routing and spread spectrum channelization that allow for secondary and primary users to co-exist on a non-interfering basis. The authors are

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