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QoS Priority Based Femtocell User Power Control for Interference Mitigation in 3GPP LTE-A HetNet
Ishtiaq Ahmad(이쉬티아크),Zeeshan Kaleem(지산),KyungHi Chang(장경희) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.2(네트워크)
In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.
Game Theoretic Approach for Joint Resource Allocation in Spectrum Sharing Femtocell Networks
Ishtiaq Ahmad,Shang Liu,Zhiyong Feng,Qixun Zhang,Ping Zhang 한국통신학회 2014 Journal of communications and networks Vol.16 No.6
In this paper, we study the joint price and power allocationin spectrum sharing macro-femtocell networks. The proposedgame theoretic framework is based on bi-level Stackelberg gamewhere macro base station (MBS) works as a leader and underlaidfemto base stations (FBSs) work as followers. MBS has fixed datarate and imposes interference price on FBSs for maintaining itsdata rate and earns revenue while FBSs jointly adjust their powerfor maximizing their data rates and utility functions. Since theinterference from FBSs to macro user equipment is kept under agiven threshold and FBSs compete against each other for powerallocation, there is a need to determine a power allocation strategywhich converges to Stackelberg equilibrium. We consider two casesfor MBS power allocation, i.e., fixed and dynamic power. MBS canadjust its power in case of dynamic power allocation according toits minimum data rate requirement and number of FBSs willing toshare the spectrum. For both cases we consider uniform and nonuniformpricingwhereMBS charges same price to all FBSs for uniformpricing and different price to each FBS for non-uniform pricingaccording to its induced interference. We obtain unique closedform solution for each case if the co-interference at FBSs is assumedfixed. And an iterative algorithm which converges rapidly isalso proposed to take into account the effect of co-tier interferenceon interference price and power allocation strategy. The results areexplained with numerical simulation examples which validate theeffectiveness of our proposed solutions.
Block Error Rate and UE Throughput Performance Evaluation using LLS and SLS in 3GPP LTE Downlink
Ishtiaq Ahmad,Zeeshan Kaleem,KyungHi Chang 한국통신학회 2013 한국통신학회 학술대회논문집 Vol.2013 No.1
This paper provides a link and system level study of the downlink using OFDMA techniques based on LTE systems. At the link level, the Block Error Rate (BLER) performance curves are generated and 10 % points of BLER curves, calculated under SISO AWGN channel, are considered as reference to generate the SNR-to-CQI mapping. These mapping results are used in system level simulator (SLS) via MIESM link to system interface. Then the UE throughput is evaluated by considering proportional fair (PF), round robin (RR), and best CQI schedulers at different values of UE throughput CDF. In this paper we analyze that the PF scheduler outperforms other schedulers in fairness and average throughput, while the best CQI scheduler performs good under high SINR region. The RR is the best choice when resource allocation is to be done without considering any kind of channel condition.