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    题名: 以叢集劃分和資源共用達成有效率裝置對裝置群播通訊;Enabling Efficient Device to Device Multicast Communication by Clustering and Resource Sharing
    作者: 簡士哲
    贡献者: 通訊工程研究所
    关键词: 蜂巢式網路;群播;D2D通訊;叢集;資源共用;cellular network;multicast;D2D communication;cluster;resource reuse
    日期: 2017
    上传时间: 2019-07-17 10:47:55 (UTC+8)
    出版者: 通訊工程研究所
    摘要: 由於使用LTE-A的用戶劇增,營運商在無線資源短缺的問題上遇到了巨大的挑戰,因此裝置對裝置通訊 (Device to Device;D2D) 被提出並且被視為是一種有效的通訊方式來減輕無線資源短缺的問題。而在現今的影音串流的蓬勃發展下,基地台採用群播來有效使用無線資源是必須的,但是當基地台做群播時,會因為必須考量通道品質最差的用戶來進行群播,所以整個細胞下的用戶可能都必須使用較差的調變技術。因此本文利用D2D短距離通訊來協助基地台做群播,在D2D的短距離通訊的特性下,D2D通訊可以使用較好的調變技術來進行群播,藉此來克服基地台群播的缺點。而要進行D2D協助群播時,由於是短距離通訊,不可能讓距離很遠的裝置作通訊,所以必須進行叢集化的動作,讓位置相近的裝置適當地形成同一個叢集,也因此必須要有一個有效的叢集化演算法。另外在D2D通訊時也必須適當地選擇無線資源來使用,在LTE-A的架構下,下行資源因為傳遞控制訊號導致使用率遠遠高於上行資源,因此 D2D 通訊選擇上行資源共用是一個較好的選擇。本文選擇D2D通訊與蜂巢式使用者共用上行資源,而一般一個蜂巢式使用者只共用一個D2D通訊使用者,而本文藉由提出的最佳化模型以及叢集劃分來共用多個D2D通訊使用者。最後在結果上發現當一個蜂巢式使用者與多個D2D通訊使用者進行上行資源共用時,有可能可以在不損失D2D通訊的吞吐量的情況下節省更多無線資源。在本文裡也比較了三種不同的叢集演算法:Fuzzy C-means、K-means++和Affinity Propagation,而透過結果可以發現Affinity Propagation比較適合與本文所提出的資源分配機制搭配。
    As the number of users of LTE-A grows rapidly, the operator faces the challenge of wireless resource scarcity. The device to device (D2D) communication has been regarded as a valid way to mitigate this resource scarcity problem. In the meantime, with the booming of video streaming services, the eNB needs to use multicast for higher resource efficiency. When the eNB performs multicast to all users under its serving cell, it needs to consider the worst channel gain user for the multicast to be successful. In this situation, the eNB is forced to use a poor modulation scheme to serve all users. In this thesis, we consider using D2D communication to assist the eNB doing multicast. Since D2D communication works in a short range, the original eNB multicast is broken into two shorter-range multicast segments and a better modulation scheme can be used for both segments, resulting in higher multicast throughput. On the other hand, in assisting multicast, a short-range D2D communication cannot serve all users in the same cell. Therefore we need an effective clustering scheme to group users into multiple clusters, each with geographically close users.In addition, when we want to use D2D communication, we need to choose a wireless channel appropriately. In the LTE-A standard, in contrast to the uplink resources, many downlink resources are allocated for delivering the control signals. For this reason, we consider using the uplink resource for D2D to share with cellular users. In earlier studies, a resource unit is shared between one cellular user and one D2D communication user. But in this thesis, we let a cellular user share the uplink resource with multiple D2D communication users. The feasible resource sharing is found by the optimization model and suitable clustering.From the simulation results, we find that, when the cellular user shares the uplink resource with multiple D2D communication users, it is possible to save more resources without the loss of throughput for D2D communication. Also, we compare the difference among three clustering approach: Fuzzy C-means, K-means++, and Affinity Propagation. According to the simulation result, we find that the Affinity Propagation is more suitable for the resource allocation scheme we propose.
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