| With the explosive growth of mobile users,the demand of mobile data traffic has significantly increased over the past decade and will keep increasing even faster.Nowadays,more than 60% of mobile voice traffic and 90% of mobile data traffic originate in the indoor environment.Therefore,the large-scale deployment of femtocells is an inevitable trend.The femtocell service has the characteristics of low power,low cost and low coverage.It can be easily installed by end user in the indoor environment and provide better signal quality for indoor mobile subscribers.However,with the intensive deployment of femtocells,there will be strong co-tier interference and cross-tier interference.In this paper,different resource allocation schemes are proposed under the closed access mechanism and hybrid access mechanism.The content is as follows:Firstly,in the two-tier network model,the systematical capacity could be seriously infected by the cross-tier and co-tier interference.In this paper,a cluster-based resource allocation algorithm has been proposed in order to mitigate such interference.The algorithm consists of three parts: the first part is to allocate the channels to macro user equipment(MUE)by using a modified balance method,and the water-filling algorithm is used to allocate the power.For the second part,an enhanced ant colony optimization is used to cluster femtocells into disjoint groups.Finally,a heuristic algorithm is proposed to allocate the channels and power to femtocell user equipment(FUE).The experimental results show that the algorithm effectively reduces the cross-tier and co-tier interference in the Macrocell-Femtocell network,and improves the fairness and satisfaction among users while ensuring the data rate requirement of the user.Secondly,when a hybrid access mechanism is adopted to arrange the femtocells,a subchannel allocation algorithm based on effective capacity is proposed.The algorithm consists of two parts: at first,the femtocell base station(FBS)is grouped by the enhanced ant colony algorithm,and the FBSs with large interference are divided into different groups.And then,the orthogonal subchannels are used to eliminate the inter-group interference.On the contrary,the FBSs with small interference are divided into same groups,and the subchannels can be used with a same frequency multiplexing technology within the group.Moreover,we compute the number of subchannels for each group according to average effective capacity and allocate the optimal subchannel according to SINR.While protecting the quality of service of registered users,we also improve the efficiency of non-registered users.Finally,the experiment results suggest that the proposed algorithm not only provides the fairness among users,but also improves the users’ satisfaction level. |
