Mode Selection and Resource Allocation for Deviceto- Device Communications in 5G Cellular Networks 林柏毅 羅傑文
Introduction Mode Selection Resource Allocation Power control
5G(fifth-generation) 遠景 1. 網速的進化，從 Mbps 為單位躍升為 Gbps ，短距離傳輸速率甚至 達到 10~20Gbps ，是目前 LTE 的 100 倍以上。 2. 物物可相連，突破過去蜂巢式基地台的限制可以容納更多裝置 連結使用並具備低延遲性的特性，可以支持的設備數量是 4G 網 絡的 10 倍，將可開啟物聯網時代的新天地。
5G 面臨的問題 未來行動裝置越來越多，要如何在有限頻譜內放入更多的裝置成 為了一大問題 5G 解決方案之一： D2D (Device-to-Device)communication (intel Qualcomm…. 等 )
D2D (Device-to-Device)communication 優點： Reuse spectrum resource, Offloading the traffic load from BS (Base station) 面臨挑戰： mode selection,resource allocation, interference,D2D discovery, Synchronizaton…. 等
Introduction At first, according to mode selection criteria, the system determine whether underlay mode should be used. Second, resource allocation scheme focuses on minimizing overall interference. Last, a power control method is to improve the performance of D2D systems.
D2D system model
Mode Selection SINR of CUE can be express as : The distance between D-Tx & CUE can be calculated as : The original SNR of CUE is given as : After D2D underlay mode has been adopted, the transmission Qos of CUE should be guaranteed.
The underlay mode can be selected.
Resource allocation In order to maximize the total throughput after the introduction of D2D communications, we switch the optimization problem into minimize the interference caused by frequency reuse Resource reuse matrix
heuristic overall optimization resource allocation algorithm (HORA) STEP1:Compute the interference when each D2D pair reuses different CUE resource, the interference is denoted as i i,k,then build the interference matrix I M,N STEP2:Construct the resource reuse indication matrix X M,N STEP3:Build the objective function. The objective is to find the optimal resource allocation method that minimizes the total co- channel interference
Step 4: By using the Hungarian Algorithm [22-24], the optimal C-links assignment matrix X* can be calculated.
Hungarian Algorithm
STEP1 : Row Reduce
STEP2 : Column Reduce
STEP3 : Test for an optimal assignment
STEP4 : Making the final assignment Min= =70
Power control Decrease transmit power of eNB Increase transmit power of D2D
Simulation result