提高有效吞吐率的P2P TV网络编码数据传输算法  

Network coding data transmission algorithm for P2P TV to improve the goodput ratio

作　　者：张志明[1,2] 周晋[2] 陈震[2,3] 李军[2,3] 

机构地区：[1]清华大学自动化系,北京100084 [2]清华大学信息技术研究院,北京100084 [3]清华大学信息科学与技术国家实验室,北京100084

出　　处：《清华大学学报（自然科学版）》2012年第12期1657-1663,共7页Journal of Tsinghua University(Science and Technology)

基　　金：清华-NEC中国研究院联合项目(20103000062)

摘　　要：在基于网络编码的P2PTV系统中,有些段会因为没有收齐而不能解码,导致这些段中已收编码数据包被迫丢弃,造成系统有效吞吐率的下降。为了提高系统有效吞吐率,该文提出了一种先到先得式(FCFS)数据传输算法。该算法将待播放的缓存划分为2部分,首先主动放弃离播放点较近的那部分(第1部分)中的空段,再将其他待获取的段划分为3类,分别为第1部分中的未收齐非空段、第2部分中的未收齐非空段和第2部分中的空段。这3类段的优先级依次降低,类内各段之间的优先级分别使用贪婪式、最少者优先式和随机式方法确定。最后按照可获得上行带宽的情况,使用循环式策略选取邻居,优先向这些邻居请求优先级较高的那些段。仿真结果表明:当系统上行带宽资源不足时,FCFS数据传输算法的有效吞吐率与控制开销率之和总是接近于系统带宽资源指数。与已有的数据传输算法相比,它改善了系统中用户的上行带宽利用率,减少了被无谓丢弃的数据包数量,提高了系统有效吞吐率。In network coding （NC） based P2P TV systems, some segments may not be able to receive the predetermined number of encoded data packets for decoding. This leads to dropping of the encoded data packets in those segments which reduces the system goodput ratio. The goodput ratio is improved by a first come first served （FCFS） transmission algorithm presented here. The algorithm partitions the buffer into two sections by skipping empty segments in the section close to the playback point （called first section）. Then, it divides the requested segments into nonempty segments in the first section, nonempty segments in the second section and empty segments in the second section. The priorities are highest for the first type. The priorities of the first type are based on the greedy method, the second uses rarest-first and the third uses the random method. High priority segments are obtained from neighbors using the round-robin strategy based on the available uplink bandwidth capacity. Simulations indicate that the sum of the goodput ratio and the control overhead ratio is always close to the peer resource index （PRI） when the system uplink bandwidth capacity is inadequate. The FCFS algorithm improves the utility ratio of the users＇ uplink bandwidth capacity, reduces the number of dropped data packets and increases the system goodput ratio.

关 键 词：计算机网络 P2P TV 网络编码 数据传输算法 

分 类 号：TP1[自动化与计算机技术—控制理论与控制工程]