| With the rapid development of mobile communication technology,the user demand of data traffic increases rapidly.While the scarcity of spectrum becomes the bottleneck of the rate increase.How to transmit more data with limited spectrum resources,becomes the research hotspot in mobile communication.D2D allows two devices in proximity communicate directly without relaying by the base station.D2D users could use dedicated channels,or reuse the spectrum resources of cellular users.D2D could increase the spectrum utilization effectively.D2D becomes one of the key technologies of 5G.However,D2D users and cellular users sharing the same channel cause interference to each other.Interference environment is more complicated because of D2D communication.D2D brings challenges to interference management.Reasonable interference management scheme could reduce co-channel interference and improve network performance.The contributions of this paper are listed below:1.It has been observed that the users causing strong interference to each other would lead some resource allocation algorithms difficult to converge.Inspiring from ITLinQ algorithm,ITLinQ underlaying Cellular networks(ITLQC)algorithm is proposed to reduce the complexity and increase the convergence rate of the algorithm.ITLQC algorithm makes improvements in three aspects,signaling block,priority allocation,and yielding rules.In order to solve cascade yielding problem,I-MAP is introduced.ITLQC algorithm is used to pre-allocate channels so that two users sharing the same channel wouldn't cause strong interference to each other.Then apply the algorithm which is difficult to converge to determine the resource allocation of D2D users.In the simulation,the performance of the SGDRA algorithm and SGDRA algorithm optimized by the ITLQC algorithm is compared.ITLQC algorithm increases the convergence rate of SGDRA algorithm and increases the energy efficiency of the network.2.Traditional graph-based channel allocation algorithms usually consider strong interference caused by one D2D pair and doesn't consider cumulative strong interference caused by multiple devices.Although the the hypergraph based resource sharing method(HBRSM)considers the problem of cumulative strong interference,the complexity of the algorithm is high,and it cannot precisely simulate the cumulative strong interference.In this paper,we propose the tier-based directed weighted hypergraph coloring(TDWGC)algorithm,which solves the problem of cumulative strong interference with low complexity.The algorithm is composed of two stages.In the first stage,a directed weighted hypergraph is constructed to simulate the interference relationship between users.In the second stage,a maximum potential interference based coloring algorithm(MPICA)is proposed to color the graph.With perfect channel state information(CSI),the algorithm is denoted as directed weighted hypergraph based coloring algorithm with perfect CSI(DWGPC)algorithm.TDWGC algorithm and DWGPC algorithm are collectively called the directed weighted hypergraph based coloring algorithm.The proposed algorithm reduces the complexity significantly compared with HBRSM algorithm.Simulation results also show that the proposed algorithms increase network throughput and protect the QoS of the cellular users compared with HBRSM algorithm.3.Channel allocation adjustment with interaction(CAAI)algorithm is proposed to further optimize the directed weighted hypergraph based coloring algorithms.The CAAI algorithm uses the channel allocation result obtained by the directed weighted hypergraph based coloring algorithm as the initial solution.In each iteration,the channel allocation result is adjusted to reduce the interference to users and decrease the interference of the network.Two constraints are proposed to ensure the convergence of the algorithm.Simulation results show that the CAAI algorithm could converge in a low number of iterations and using CAAI algorithm to optimize DWGPC algorithm could improve the performance of the network. |
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