Research On Resource Allocation Strategy In Wireless Regional Area Network

In recent years, there has been an increasing growth in wireless services, yielding a hugedemand on the radio spectrum. However, the spectrum resources are scarce and most of themhave been already licensed to existing operators. Recent studies showed that the actuallicensed spectrum remains unoccupied for large periods of time. In order to efficiently exploitthese spectrum holes, cognitive radio (CR) has been proposed. By monitoring and adapting tothe environment, CRs (secondary users) can share the spectrum with the licensed users(primary users), operating whenever the primary user (PU) is not using the spectrum.IEEE802.22wireless regional area network (WRAN) is the first worldwidecommunications networks based on CR, which provides communications services for ruralareas. The802.22Working Group was formed by IEEE in November2004to develop astandard for WRAN.802.22standard that is currently being developed and is based onorthogonal frequency division multiple access and opportunistic use of the VHF/UHF TVbands. WRANs are designed to operate in the TV broadcast bands while ensuring that noharmful interference is caused to the incumbent operation (i.e., digital TV and analog TVbroadcasting) and low-power licensed devices such as wireless microphones.A typical WRAN deployment consists of a WRAN base station (WRAN BS) servingmultiple fixed-location wireless customer premise equipment (CPE). A distinctive feature of802.22WRAN as compared to existing IEEE802standards is the BS coverage range, whichcan go up to100Km if power is not an issue (current specified coverage range is33Km at4Watts CPE EIRP). This dissertation is mainly concerned with the resource allocation strateryin WRAN. The author’s major contributions are outlined as follows:1. Resource allocation has been studied in a cell of WRAN. The renting of resourcesbetween IEEE802.22WRAN cells is base on the OFDMA technology. OFDMA is amodulation and multiple access method used in WRAN cells, which is adopted as the physicallayer protocol. It provides the flexibility required to dynamically allocate spectrum. In atypical OFDMA system, where radio resource is partitioned in both time and frequencydomains. Time domain is divided into time slots and frequency resource into subchannels, acluster of OFDM subcarriers. So we use BIN to denote the minimum radio resource sharingunit allocated for CPEs. We model the spectrum allocation in a cell of WRAN with oneofferor BS (Base Station) and multiple CPEs as auction and the progressive second priceauction is used to solve it. The utility of offeror BS will be reduced when multiple CPEscollude in auction. In order to combat collusion of users, the offeror BS can set an optimalreserve price to improve its utilities. The simulation results show the feasibility of the proposed scheme2. Idle spectrum allocation in multiple cells of WRAN han been studied. Consideringmultiple cells of WRAN scenario in which multiple BSs and secondary users (CPEs) coexist,BSs attempt to sell unused spectrum resources to secondary users for monetary gains whilesecondary users try to acquire spectrum usage permissions from primary users to achievecertain communication goals, which generally introduces reward payoffs for them. In order tosolve the above issues, we consider the spectrum sharing as continuous double auction andpropose a pricing mechanism based on fuzzy logic to optimize the overall spectrum efficiency,meanwhile, keeping the participating incentives of the users based on double-auction rules.3. Subchannels allocation of downlink in a cell of WRAN has been studied whenconsidering coexistence between WRAN and WMs. We propose an accurate and realisticWRAN-WM coexistence model that increases spatial reuse of TV spectrum while protectingsmall-scale incumbents. Based on the proposed model, we formulate the subchannelallocation problem as a mixed-integer nonlinear programming (MINLP) which is NP-hard. Tosolve the problem in real-time, we employ hungarian algorithm based on graph theory. Usingmatlab simulation, the proposed algorithm gets the optimal solution while reducing thecomputational cost significantly.4. Joint power and channel allocation of uplink has been studed in multiple cells ofWRAN when considering coexistence between CPEs and WMs. We propose an accurate andrealistic CPE-WM coexistence model which is the same with the model in chapter4. Basedon the proposed model, we can model the problem of joint channel selection and powerallocation as a potential game. We show that by adopting interference minimization as theplayers’ utility function, a network potential function can be defined and thereby proving thegame to be an exact potential game.5. Raley selection (RS) in a bidirectional cooperative network has been studed. To servethe growing demand of the bidirectional information-exchange, we propose a single relayselection scheme for physical-layer network coding (PNC) in a bidirectional cooperativenetwork consisting of two sources and multiple relays. This RS scheme selects a single bestrelay by maximizing the bottleneck of the capacity region of both information-flows in thebidirectional network. We show that the proposed RS rule minimizes the outage probabilityand that it can be used as a performance benchmark for any relay selection rules with PNC.We derive a closed-form exact expression of the outage probability for the proposed RS ruleand show that it achieves full diversity gain. Finally, numerical results demonstrate thevalidity of our analysis.