Ultra wideband （UWB） network brings both chance and challenge to personal area wireless communications. Compared with other IEEE 802 small range wireless protocols （such as WLAN and Bluetooth）, UWB has both extrem...Ultra wideband （UWB） network brings both chance and challenge to personal area wireless communications. Compared with other IEEE 802 small range wireless protocols （such as WLAN and Bluetooth）, UWB has both extremely high bandwidth （up to 480 Mbpa） and low radiation. Moreover, the structured MAC layer of UWB is the fundamental difference to WLAN. The top one is that only when two UWB devices belong to the same piconet can they communicate with each other directly, which means that we must jointly consider topology formation and routing when deploying UWB networks because the interaction between routing and topology formation makes separate optimization ineffective. This paper tries to optimize UWB network from a cross-layer point of view. Specifically, given device spatial distribution and traffic requirement, we want to form piconets and determine routing jointly, to maximize the overall throughput. We formulate the problem of joint optimization to mixed-integer programming and give a practical lower bound that is very close to the theoretical upper bound in our simulation. Furthermore, our lower bound is much better than an algorithm that only considers topology formation in UWB networks.展开更多
TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary...TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.展开更多
针对城市场景的蜂窝车联网(cellular vehicle to everything,C-V2X)中车辆缓存节点高效选择和合理的缓存文件分配问题,提出了基于跨层信息的C-V2X缓存分配算法(Cross-layer Caching Allocation for C-V2X,CLCA)。该算法在LTE-V2X mode3...针对城市场景的蜂窝车联网(cellular vehicle to everything,C-V2X)中车辆缓存节点高效选择和合理的缓存文件分配问题,提出了基于跨层信息的C-V2X缓存分配算法(Cross-layer Caching Allocation for C-V2X,CLCA)。该算法在LTE-V2X mode3模式下,由基站周期地收集覆盖范围内节点的连接度、信噪比和信道接入时延信息,并重新划分邻居归属,构建跨层信息邻接矩阵,再采用贪婪分配的方法筛选缓存节点,以减少缓存节点数量,节约通信资源并降低开销。进而,以服从Zipf分布的文件流行度分布为基础,采用文件流行度预测概率与历史周期实际流行度概率加权叠加的方式,提高文件流行度预测的准确性,再根据缓存容量合理配置缓存文件。仿真分析表明,该算法可以有效提高节点的文件获取效率,降低文件传输时延,减少基站负载。展开更多
This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cro...This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a.展开更多
针对 ad hoc 网络各协议层的功能都相互关联的特点,提出了一种在 ad hoc 网络中基于网络平均时延最小的跨层自适应流量分配算法(CLATA)。该算法将网络层自适应流量分配信息传递给媒体接入控制(MAC)层,以改进 MAC 层中的冲突退避算法,实...针对 ad hoc 网络各协议层的功能都相互关联的特点,提出了一种在 ad hoc 网络中基于网络平均时延最小的跨层自适应流量分配算法(CLATA)。该算法将网络层自适应流量分配信息传递给媒体接入控制(MAC)层,以改进 MAC 层中的冲突退避算法,实现网络平均时延最小化,提高网络的利用率。仿真实验结果表明,该算法可以动态调整链路之间的流量,并具有快速的自适应性,优化网络资源的利用。展开更多
Efficient radio resource allocation is essential to provide quality of service （QoS） for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing sys...Efficient radio resource allocation is essential to provide quality of service （QoS） for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically a/locates radio resources based on user＇s channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process （dMMPP）, and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users.展开更多
文摘Ultra wideband （UWB） network brings both chance and challenge to personal area wireless communications. Compared with other IEEE 802 small range wireless protocols （such as WLAN and Bluetooth）, UWB has both extremely high bandwidth （up to 480 Mbpa） and low radiation. Moreover, the structured MAC layer of UWB is the fundamental difference to WLAN. The top one is that only when two UWB devices belong to the same piconet can they communicate with each other directly, which means that we must jointly consider topology formation and routing when deploying UWB networks because the interaction between routing and topology formation makes separate optimization ineffective. This paper tries to optimize UWB network from a cross-layer point of view. Specifically, given device spatial distribution and traffic requirement, we want to form piconets and determine routing jointly, to maximize the overall throughput. We formulate the problem of joint optimization to mixed-integer programming and give a practical lower bound that is very close to the theoretical upper bound in our simulation. Furthermore, our lower bound is much better than an algorithm that only considers topology formation in UWB networks.
文摘TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.
文摘针对城市场景的蜂窝车联网(cellular vehicle to everything,C-V2X)中车辆缓存节点高效选择和合理的缓存文件分配问题,提出了基于跨层信息的C-V2X缓存分配算法(Cross-layer Caching Allocation for C-V2X,CLCA)。该算法在LTE-V2X mode3模式下,由基站周期地收集覆盖范围内节点的连接度、信噪比和信道接入时延信息,并重新划分邻居归属,构建跨层信息邻接矩阵,再采用贪婪分配的方法筛选缓存节点,以减少缓存节点数量,节约通信资源并降低开销。进而,以服从Zipf分布的文件流行度分布为基础,采用文件流行度预测概率与历史周期实际流行度概率加权叠加的方式,提高文件流行度预测的准确性,再根据缓存容量合理配置缓存文件。仿真分析表明,该算法可以有效提高节点的文件获取效率,降低文件传输时延,减少基站负载。
基金Supported by the National Natural Science Foundation of China (No.60072048) the Doctoral Program Fund of Ministry of Education of China (No.20010561007).
文摘This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a.
文摘针对 ad hoc 网络各协议层的功能都相互关联的特点,提出了一种在 ad hoc 网络中基于网络平均时延最小的跨层自适应流量分配算法(CLATA)。该算法将网络层自适应流量分配信息传递给媒体接入控制(MAC)层,以改进 MAC 层中的冲突退避算法,实现网络平均时延最小化,提高网络的利用率。仿真实验结果表明,该算法可以动态调整链路之间的流量,并具有快速的自适应性,优化网络资源的利用。
基金the National Natural Science Foundation of China (60632030)the Hi-Tech Research and Development Program of China (2006AA01Z283, 2006DFA11050)
文摘Efficient radio resource allocation is essential to provide quality of service （QoS） for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically a/locates radio resources based on user＇s channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process （dMMPP）, and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users.
