We present a coherent and systematic review of Random Access Algorithms for packet networks, as developed over three and a half decades. We consider the appropriate user models and we classify the algorithms according...We present a coherent and systematic review of Random Access Algorithms for packet networks, as developed over three and a half decades. We consider the appropriate user models and we classify the algorithms according to the channel sensing constraints imposed. We also present a review of the analytical methodologies required for the performance analysis of these algorithms.展开更多
Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel ...Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay.展开更多
A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slo...A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slotted into a time slot with high channel utilization realized by the choice of two parameters p1 and p2, and the channel load equilibrium. The protocol analyzes the throughput of the MSRM protocol for a load equilibrium state and the throughput based on priority. Simulations agree with the theoretical analysis. The simulations also show that the slotted-time system is better than the continuous-time system.展开更多
In this paper, an adaptive random access strategy is presented for multi-channel relaying networks to address the issue of random access of the non-real-time （NRT） services. In the proposed scheme, NRT services acce...In this paper, an adaptive random access strategy is presented for multi-channel relaying networks to address the issue of random access of the non-real-time （NRT） services. In the proposed scheme, NRT services access the base station （BS） by first accessing the nearest relay node （RN）. When collision occurs, for the sake of fast and efficient access, the user will begin a frequency domain backoff rather than randomly retry in time domain. A remarkable feature of this scheme is that the RN will adaptively determine the maximum allowed frequency backoff window at each access period. This is achieved according to the new arrival rate as well as the number of available access channels. Moreover, to alleviate the interference caused by sub-channel reuse among RNs, a fractional frequency reuse scheme is also considered. The analysis and numerical results demonstrate that our scheme achieves higher throughput, lower collision probability and lower access delay than conventional slotted Aloha as well as the scheme without frequency backoff window adaptation.展开更多
认知无线电系统中,为了尽量避免采用随即接入方式进行信道分配时因主用户的出现造成次用户频繁切换信道的现象,提出了一种基于最小化切换风险的支持多种等级的业务服务质量区分的MHR-DSS(minimum handover risk-diversity service sche...认知无线电系统中,为了尽量避免采用随即接入方式进行信道分配时因主用户的出现造成次用户频繁切换信道的现象,提出了一种基于最小化切换风险的支持多种等级的业务服务质量区分的MHR-DSS(minimum handover risk-diversity service scheme)改进方案,从而降低了次用户切换信道的次数和信道切换风险。仿真结果验证了该方案在减少次用户切换次数和降低切换风险方面的合理性和有效性。展开更多
文摘We present a coherent and systematic review of Random Access Algorithms for packet networks, as developed over three and a half decades. We consider the appropriate user models and we classify the algorithms according to the channel sensing constraints imposed. We also present a review of the analytical methodologies required for the performance analysis of these algorithms.
文摘Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay.
基金Supported by the National Natural Science Foundation of China(Nos. 60362001 and F0424104)the Natural Science Foundationof Yunnan Province (No. 2004F0011R)
文摘A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slotted into a time slot with high channel utilization realized by the choice of two parameters p1 and p2, and the channel load equilibrium. The protocol analyzes the throughput of the MSRM protocol for a load equilibrium state and the throughput based on priority. Simulations agree with the theoretical analysis. The simulations also show that the slotted-time system is better than the continuous-time system.
基金Supported by the National High-Tech Research & Development Program of China (Grant No. 2009AA01Z262)the National Basic Research Program of China (Grant No. 2009CB320400)the National Natural Science Foundation of China (Grant No. 60832009)
文摘In this paper, an adaptive random access strategy is presented for multi-channel relaying networks to address the issue of random access of the non-real-time （NRT） services. In the proposed scheme, NRT services access the base station （BS） by first accessing the nearest relay node （RN）. When collision occurs, for the sake of fast and efficient access, the user will begin a frequency domain backoff rather than randomly retry in time domain. A remarkable feature of this scheme is that the RN will adaptively determine the maximum allowed frequency backoff window at each access period. This is achieved according to the new arrival rate as well as the number of available access channels. Moreover, to alleviate the interference caused by sub-channel reuse among RNs, a fractional frequency reuse scheme is also considered. The analysis and numerical results demonstrate that our scheme achieves higher throughput, lower collision probability and lower access delay than conventional slotted Aloha as well as the scheme without frequency backoff window adaptation.
文摘认知无线电系统中,为了尽量避免采用随即接入方式进行信道分配时因主用户的出现造成次用户频繁切换信道的现象,提出了一种基于最小化切换风险的支持多种等级的业务服务质量区分的MHR-DSS(minimum handover risk-diversity service scheme)改进方案,从而降低了次用户切换信道的次数和信道切换风险。仿真结果验证了该方案在减少次用户切换次数和降低切换风险方面的合理性和有效性。
