CAJ | 학술논문

在认知无线电网络中,传输层端到端(TCP)吞吐率是衡量网络性能的重要指标.前期相关研究大都具有以下两方面缺点:第一,大部分研究只考虑了协议底层参数来优化物理链路性能,对传输层性能有所忽略;第二,目前的研究大都基于马尔可夫决策过程建模,这需要网络具有完全知识,使得这类模型的应用受到很大限制.针对以上问题,本文提出一种新的算法:网络中每个节点通过联合配置物理层调制方式、发射功率、链路层信道接入和TCP拥塞控制因子来找到传输层端到端近似最优吞吐率.由于无线设备对环境感知存在误差,本文将网络模型建模为部分可观测马尔可夫决策过程,并将其转换成信念状态马尔可夫决策过程,采用Q值迭代找到近似最优策略.仿真分析表明,提出的算法能在动态无线环境下以一定的误差限收敛于最优策略,能在功率受限条件下,有效提高传输层端到端吞吐率.
재인지무선전망락중,전수층단도단(TCP)탄토솔시형량망락성능적중요지표.전기상관연구대도구유이하량방면결점:제일,대부분연구지고필료협의저층삼수래우화물리련로성능,대전수층성능유소홀략;제이,목전적연구대도기우마이가부결책과정건모,저수요망락구유완전지식,사득저류모형적응용수도흔대한제.침대이상문제,본문제출일충신적산법:망락중매개절점통과연합배치물리층조제방식、발사공솔、련로층신도접입화TCP옹새공제인자래조도전수층단도단근사최우탄토솔.유우무선설비대배경감지존재오차,본문장망락모형건모위부분가관측마이가부결책과정,병장기전환성신념상태마이가부결책과정,채용Q치질대조도근사최우책략.방진분석표명,제출적산법능재동태무선배경하이일정적오차한수렴우최우책략,능재공솔수한조건하,유효제고전수층단도단탄토솔.
In cognitive radio network (CRN), TCP end to end throughput is one of the key issues to measure its performance. However, most of existing research efforts devoted to TCP performance improvement have two weaknesses as follows. First, most of them only consider the underlying parameters to optimize the physical performance, but the TCP performance is neglected. Second, they are largely formulated as a Markov decision process (MDP), which requires a complete knowledge of network and cannot be directly applied to CRNs. To solve the above problems, a Q-BMDP algorithm is proposed in this paper. Each user in CRN combines modulation type and transmitting power at the physical layer, access channels at the media access control layer and TCP congestion control factor to maximize the TCP throughput. Due to the existence of perception error of environment, this issue is formulated as a partial observable Markov decision process (POMDP) which is then converted to belief state MDP, with Q-value iteration to find the approximately optimal strategy. Simulation and analysis results show that the proposed algorithm can be approximately converged to optimal strategy under a maximum error limit, and can effectively improve TCP throughput in a dynamic wireless network under the premise of the limited power consumption.