Research On Optimal Resource Allocation Strategies In Wireless Relay Networks

Wireless relay has emerged as a promising technique which has the characteristicsof low cost, extending the transmit coverage and enhancing the communication quality.The implementation of wireless relay technique is cooperative diversity and femtocell.By forming virtual MIMO system through sharing antennas of different single-antennaterminals, cooperative diversity can achieve significant diversity gain; In order toimprove the communication quality of indoor wireless users femtocell which is a smallsize base station is deployed in the existing macrocell. Focusing on the research ofresource allocation in the wireless relay networks, the optimal resource allocationstrategies are proposed and the efficiency is proved by simulation results. The maincontribution of this work can be summarized as follows:1. Cooperative system based on decode-and-forwardIn the traditional DF cooperative system, the source node and the relay node havethe same transmit power, therefore the system is not adaptive to the channels whichresults the inefficiency of the power resource. We propose an optimal allocation schemeto allocate the given total transmit power between the source node and the relay node.Fistly, a two-use DF cooperative system based on TDMA is formulated and every usertransmits information for the other one as a relay, then the lower bound expression ofthe outage probability of the destination node is calculated according to the averagestatement information of the channels; Secondly, the optimal power allocation factorthat leads to a lower destination node average outage probability is obtained；Finally, thesimulation results show that, this power allocation scheme can achieve a lowerdestination node outage probability than the equal power allocation scheme.2. Cooperative system based on coded cooperationSince the power allocation between the source node and the relay node is onlyaccording to the level of cooperation, the system resource utilization is inefficiency. Anoptimal allocation scheme applying cooperative level selection combined with powerallocation is proposed based on RCPC codes. The allocation scheme aims to reduce theasymptotic upper bound which is derived from the level of cooperation as well as thechannel state information. The sub-optimal power allocation algorithm is effective inimproving the system resource utilization and is low in implementation complexity. Simulation results show that the asymptotic upper bound is tight and the adaptive powerallocation algorithm proposed in this paper outperforms the power allocation algorithmwhich is only concerned with the level of cooperation.3. two-tie networks deployed femtocellA cooperative game-theoretic dynamic resource allocation (CGDRA) scheme isproposed to management the co-channel interference caused by macrocell andfemtocells sharing the same spectrum in two-tie networks,. The transmit power of themacrocell users is allocated according to the propagation loss and the QoS demands.Then the product of all the femtocells’ data rate is formulated as a utility function of thecooperative game-theoretic model with the constraints of the femtocells’ QoS demandand the total transmit power. An approximate optimal solution with low complexity isobtained by applying both the Dynamic Sub-carrier Allocation (DSA) algorithm andAdaptive Power Allocation (APA) algorithm. So that the frequency resource and thetransmit power of the two-tie network are allocated optimally and the transmit rate canbe improved. Simulation results show that the CGDRA approach obtains a goodtrade-off between the transmit rate and the fairness. The CGDRA approach getssignificant data rate increase compared with the max-min algorithm, and achieves abetter fairness than the max-rate fairness algorithm does.