Joint Distributed Access Point Selection and Power Allocation in Cognitive Radio Networks

Spectrum management has been identified as a crucial step towards enabling the technology of the cognitive radio network (CRN). Most of the current works dealing with spectrum management in the CRN focus on a single task of the problem, e.g., spectrum sensing, spectrum decision, spectrum sharing or spectrum mobility. In this work, we argue that for certain network configurations, jointly performing several tasks of the spectrum management improves the spectrum efficiency. Specifically, we study the uplink resource management problem in a CRN where there exist multiple cognitive users (CUs) and access points (APs), with each AP operates on a set of non-overlapping channels. The CUs, in order to maximize their uplink transmission rates, have to associate to a suitable AP (spectrum decision), and to share the channels belong to this AP with other CUs (spectrum sharing). These tasks are clearly interdependent, and the problem of how they should be carried out efficiently and distributedly is still open in the literature. In this work we formulate this joint spectrum decision and spectrum sharing problem into a non-cooperative game, in which the feasible strategy of a player contains a discrete variable and a continuous vector. The structure of the game is hence very different from most non-cooperative spectrum management game proposed in the literature. We provide characterization of the Nash Equilibrium (NE) of this game, and present a set of novel algorithms that allow the CUs to distributively and efficiently select the suitable AP and share the channels with other CUs. Finally, we study the properties of the proposed algorithms as well as their performance via extensive simulations.Comment: Accepted by Infocom 2011; Infocom 2011, The 30th IEEE International Conference on Computer Communication

Joint Access Point Placement and Channel Assignment for 802.11 Wireless Local Area Networks

To deploy a multi-cell IEEE 802.11 wireless local area network (WLAN), access point (AP) placement and channel assignment are two primary design issues. For a given pattern of traffic demands, we aim at maximizing not only the overall system throughput, but also the fairness in resource sharing among mobile terminals. A novel method for estimating the system throughput of a multi-cell WLAN is proposed. An important feature of this method is that cochannel overlapping is allowed. Unlike conventional approaches that decouple AP placement and channel assignment into two phases, we propose to solve the two problems jointly for better performance. Due to the high computational complexity involved in exhaustive searching, an efficient local searching algorithm, called patching algorithm, is also designed. Numerical results show that for a typical indoor environment, the patching algorithm can provide a close-to-optimal performance with much lower time complexity.published_or_final_versio

Towards next generation WLANs: exploiting coordination and cooperation

Wireless Local Area Networks (WLANs) operating in the industrial, scientific and medical (ISM) radio bands have gained great popularity and increasing usage over the past few years. The corresponding MAC/PHY specification, the IEEE 802.11 standard, has also evolved to adapt to such development. However, as the number of WLAN mobile users increases, and as their needs evolve in the face of new applications, there is an ongoing need for the further evolution of the IEEE 802.11 standard. In this thesis we propose several MAC/PHY layer protocols and schemes that will provide more system throughput, lower packet delivery delay and lessen the power consumption of mobile devices. Our work investigates three approaches that lead to improved WLAN performance: 1) cross-layer design of the PHY and MAC layers for larger system throughput, 2) exploring the use of implicit coordination among clients to increase the efficiency of random media access, and 3) improved packets dispatching by the access points (APs) to preserve the battery of mobile devices. Each proposed solution is supported by theoretical proofs and extensively studied by simulations or experiments on testbeds

Performance Investigation of Wireless LAN with Variable Channel Width

Today, mostly the wireless LAN is based on preset static channel widths. Considering unique benefits of adapting channel width, which is a fundamental yet under-explored facet in wireless communication, We carried out investigations on the performance of suggested scenario, which are based on IEEE 802.11 and composed of different number of nodes with different channel width (10MHz, 20 MHz and 40 MHz) associated to one AP. This research work makes a strong case for wireless systems that adapt channel width in WLAN. Adapting channel width offers rich possibilities for improving system performance. This thesis provides an outlook of the aforementioned issues associated with wireless communication for instance, fairness problem among users associated to same AP and hidden terminal problem. Some issues are investigated and analyzed with Matlab tool. We found that the variable channel width increases the range of communication, providing the users with the required spectrum, which offers a natural way to both improve flow fairness and balance the load across the APs. Also the increase in channel width increases the throughput of suggested scenario compare to the fixed channel width. In our future work, we also provide possible solutions to the new problems in WLAN with variable channel width