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61.
62.
We study multi-access control in opportunistic communication systems, and propose two new schemes to address channel asymmetry and throughput-guaranteed admission control, respectively. We first devise a relay-aided opportunistic scheduling (RAOS) scheme, in which a user can choose to communicate with the base station either directly or using multiple hops (relay transmissions). We develop relay/direct link construction algorithms using either a channel-capacity-based criterion or a throughput-based criterion, and devise opportunistic scheduling schemes accordingly. Our results show that in the presence of channel asymmetry across users, the RAOS scheme performs significantly better than Qualcomm's HDR scheme. Next, we propose a traffic-aided smooth admission control (SAC) scheme that aims to guarantee throughput provisioning. Simply put, in the SAC scheme, the admission decision is spread over a trial period, by increasing gradually the amount of the time resource allocated to incoming users. Specifically, using the modified weighted proportional fair (WPF) scheduling, we devise a QoS driven weight adaptation algorithm, and the weights assigned to new users are increased in a guarded manner. Then an admission decision is made based on the measured throughput within a time-out window. A key feature is that we exploit explicitly the traffic information and throughput requirements in devising the back-off time. Our results show that the proposed SAC scheme works well in opportunistic communication systems. 相似文献
63.
64.
基于保护主后备配合依赖关系有向图,提出了通过有向图化简计算保护配合最小断点集(MBPS)的新方法。定义了配合依赖关系有向图化简操作的顺序和原则,按照优先级顺序将保护分类,根据保护后备依赖度最大原则从具有较高优先级的类中选择候选断点,将化简过程中得到的自环顶点选为断点。所述方法适用于环网全网配合和同段配合中MBPS的计算。 相似文献
65.
文章介绍了一种新的继电保护安全措施系统的解决方案。讨论了依据此方案所实现的继电保护安措系统软件。该方案可有效避免因人为原因造成的工作失误,既可提高现场工作效率,又能提高继电保护工作人员安措实施的准确性和条理性。 相似文献
66.
Diversity-and-multiplexing tradeoff and throughput of superposition coding relaying strategy 总被引:1,自引:1,他引:0
While the Network Coding cooperative relaying (NC-relaying) has the merit of high spectral ef-ficiency, Superposition Coding relaying (SC-relaying) has the merit of high throughput. In this paper, a novel concept, coded cooperative relaying, is presented, which is a unified scheme of the NC-relaying and SC-relaying. For the SC-relaying strategy which can be considered one-way coded relaying scheme with multi-access channel, the close-form solution of the outage probabilities of the basic signal and additional signal are obtained firstly. Secondly, the Diversity-and-Multiplexing Tradeoff (DMT) characteristics of ba-sic signal and additional signal are investigated entirely as well as the optimal close-form solutions. The compared numerical analysis shows the evaluation error of throughput based on the close-form solution is about 0.15 nats, which is within the acceptable error range. Due to the mutual effect between the both source signals, the available maximal values of the two multiplexing gains are less than 1. 相似文献
67.
Two-hop relaying systems suffer spectral efficiency loss due to the half-duplex property of relays. This paper proposes an efficient relaying protocol which can recover the spectral efficiency loss but still work with half-duplex relays. However, there exists inter-relay interference which degrades the performance of the protocol. With this consideration, a power control policy is derived to suppress the interference using game theory, and then an algorithm is given to facilitate distributed implementation. Furthermore, impact of deploying more destination antennas on performance of the relaying protocol is investigated. Simulation results show that, with the power control policy, the proposed relaying protocol can achieve high spectral efficiency. 相似文献
68.
本文基于机会中继协作通信系统的优良特性,改进了传统的多中继ARQ(Automatic Repeat Request)协作分集机制,联合物理层与数据链路层优化了无线频谱与能量的利用率,并且首次提出了采用Markov(马尔可夫)吸收链方法的端到端性能分析模型.在此分析模型的基础上,对本文改进的机会协作重传协议进行了端到端成功传输概率、丢包率、时延、吞吐量等性能参数的数值分析,最后用仿真实验对此模型进行了验证,详细讨论了最大重传次数、信道衰落参数、总发送功率等对性能的影响.结果表明,本文改进的机会协作重传协议在节能、抗信道衰落方面,表现出了比直接重传协议和传统的多中继协作重传协议具有更优越的性能. 相似文献
69.
分析、比较两时隙无线双向中继系统采用中继放大转发和解码转发的中断概率性能。首先推导得出中继放大转发中断概率的一个下界,且仿真结果证明该下界是紧致的。然后,计算出中继解码转发中断概率的闭合表达式,得到当信噪比和复用增益足够小时,解码转发优于放大转发,反之,放大转发中断性能更优的结论。最后,通过仿真考查了中继节点的位置、时隙分配和速率分配对中断性能的影响。 相似文献
70.
In this paper,we present a non-transferable utility coalition graph game(NTU-CGG) based resource allocation scheme with relay selection for a downlink orthogonal frequency division multiplexing(OFDMA) based cognitive radio networks to maximize both system throughput and system fairness.In this algorithm,with the assistance of others SUs,SUs with less available channels to improve their throughput and fairness by forming a directed tree graph according to spectrum availability and traffic demands of SUs.So this scheme can effectively exploit both space and frequency diversity of the system.Performance results show that,NTU-CGG significantly improves system fairness level while not reducing the throughput comparing with other existing algorithms. 相似文献