基于D2D通信系统中的一种跨层中继选择算法

在D2D通信系统与蜂窝网络共存的场景下,引入中继节点可有效提高D2D链路的吞吐量和D2D用户对蜂窝用户的干扰。文中基于译码转发模式,结合跨层协作通信的思想,提出了一种基于物理层和数据链路层的跨层中继选择算法。该算法结合物理层的信道状态信息和数据链路层的队列状态信息,两个参数进行最优中继节点的选择。并最终通过仿真验证表明,基于跨层中继选择算法可提高通信系统的吞吐量,同时降低了通信系统的平均时延和数据包错误率。     

Low-Complexity Throughput-Based Antenna Selection Method

Antenna selection is a low-cost low-complexity attractive approach in MIMO systems that capture many advantages of these systems. In this paper, our objective is to select the best antennas that maximize throughput with truncated selective repeat automatic repeat request at data link layer in zero-forcing MIMO receivers. We propose a novel binary particle swarm optimization method with throughput as its fitness function for joint transmit and receive antenna selection. The results of simulations demonstrate that the proposed throughput based antenna selection method has better performance compared to capacity based methods, and PSO algorithm can significantly reduce computational complexity.     

A Cross-Layer Routing Scheme Using Adaptive Retransmission Strategy for Wireless Mesh Networks

In this paper, we develop a link quality-based adaptive adjustment mechanism of the MAC maximum retransmission count to reduce collision probability of wireless Mesh networks. Based on statistics acquired in the link layer and the retransmission strategy, a multi-metric cross-layer on-demand routing scheme is proposed for wireless Mesh networks. The proposed scheme uses information such as available link bandwidth, node residual load rate and transmission efficiency of a path adequately to cross-layer routing. The network layer can adaptively select an optimal path to deliver packets based on the acquired statistics of the MAC layer. Extensive simulation results demonstrate that the proposed scheme can reduce link failure probability, improve network throughput, and decrease the end-to-end delay effectively.     

Cross-Layer Design Based Optimized Link State Routing Protocol for Wireless Mesh Networks

A proactive routing protocol CL-OLSR (cross-layer based optimized link state routing) by using a brand-new routing metric CLM (cross-layer metric) is proposed. CL-OLSR takes into account four link quality impact factors in route calculation through the cross-layer operation mechanism: the node available bandwidth, the node load, the link delivery rate, and the link interference, and thus the effect of route selection is optimized greatly. The simulation results show that the proposed CL-OLSR protocol can not only improve the network throughput to a large extent, but also reduce the end-to-end delay, while achieving load balance route results.     

Cross-layer based transmit antenna selection for decision-feedback detection in correlated Ricean MIMO channels

In this paper, we investigate a cross-layer transmit antenna selection (AS) approach for the decision-feedback detector (DFD) over spatially correlated flat Ricean fading multiple-input multiple-output (MIMO) channels. Closed-form expressions for the system throughput with both perfect and imperfect channel estimation are derived. Considering a training-based channel estimation technique, we show that the capacity-based AS is more robust to imperfect channel estimation. However, in all cases, the cross-layer AS delivers higher throughput gains than the capacity-based AS.     

Cross-layer design scheme for multihop communications

A cross-layer design scheme for wireless communications is proposed and the performance evaluated. The scheme combines a truncated automatic repeat request (ARQ) protocol at the data link layer and multihop transmission at the physical layer. Closed-form solutions are derived for the average throughput and the average number of transmissions required to send a packet when the channel surfers from Nakagami-m fading. Finally, the improvement, when the cross-layer design is implemented is shown.     

Clustering and power management for virtual MIMO communications in wireless sensor networks

Multi-input multi-output (MIMO) is a well-established technique for increasing the link throughput, extending the transmission range, and/or reducing energy consumption. In the context of wireless sensor networks (WSNs), even if each node is equipped with a single antenna, it is possible to group several nodes to form a virtual antenna array, which can act as the transmitting or receiving end of a virtual MIMO (VMIMO) link. In this paper, we propose energy-efficient clustering and power management schemes for virtual MIMO operation in a multi-hop WSN. Our schemes are integrated into a comprehensive protocol, called cooperative MIMO (CMIMO), which involves clustering the WSN into several clusters, each managed by up to two cluster heads (CHs); a master CH (MCH) and a slave CH (SCH). The MCH and SCH collect data from their cluster members during the intra-cluster communications phase and communicate these data to neighboring MCHs/SCHs via an inter-cluster VMIMO link. CMIMO achieves energy efficiency by proper selection of the MCHs and SCHs, adaptation of the antenna elements and powers in the inter-cluster communications phase, and using a cross-layer MIMO-aware route selection algorithm for multi-hop operation. We formally establish the conditions on the transmission powers of CHs and non-CHs that ensure the connectivity of the inter-cluster topology. Simulations are used to study the performance of CMIMO. The simulation results indicate that our proposed protocol achieves significant reduction in energy consumption and longer network life time, compared with non-adaptive clustered WSNs.     

移动WiMAX网络下行链路TCP吞吐量公平性的跨层优化

该文提出了一种移动WiMAX网络中的TCP公平性跨层优化模型,设计了基于此模型的cross-layer TCP改进协议。利用端节点链路层的速率信息和在基站BS(Base Station)处预分配ACK分组所需带宽的策略改善了下行终端的QoS (Quality of Service)指标,保证了下行终端和上行终端的吞吐量公平性。仿真结果表明cross- layer-TCP改进协议能够在保持原有系统吞吐量的前提下改善下行终端的公平性。     

OFDM系统中基于自适应调制和ARQ的PHY-MAC跨层设计

设计了一种适用于正交频分复用（OFDM）的跨层自适应算法。此算法结合自适应调制（AM）和有限自动重传请求（ARQ）技术，能够根据不同的信道状态在物理层和数据链路层联合进行性能优化，可以在保证上层吞吐量一定的条件下提供更小的丢包率。仿真结果表明，通过跨层结构设计的系统和传统的分层结构设计的系统相比有一定的性能增益，在进行高速传输时此增益更为显著。     

传感器网络环境监测时间序列数据的高斯过程建模与多步预测

Accessing to the optimal network was an effective way of ensuring the efficiency of network resources utilization and improving network performance.An access point selection mechanism based on cross-layer awareness for cognitive networks(CN_CLA)was proposed.Firstly,a cross-layer cognitive framework was constructed for obtaining the primary evaluation parameters that influence the performance of network access.Secondly,the fuzzy theory was applied for evaluating the access network performance comprehensively,and the weights in each layer were optimized using the quantum genetic algorithm,and then the access point was selected intelligently.Simulation results show that the proposed method chooses reasonable access networks without intervention of users.Furthermore,it is superior to the traditional methods,including the link capacity scheme,H_RSSI_S and AS_FTM,in terms of throughput,delay,session completion rate,packet loss and other performance indicators.     

Exploiting spatial multiplexing and reuse in multi-antenna wireless ad hoc networks

Efficient exploitation of multiple antenna capabilities in ad hoc networks requires carefully designed cross-layer techniques. The work presented in this paper provides a medium access control (MAC)/physical cross-layer scheme for ad hoc networks to address several of the challenges involved in cross-layer design. Multiple antenna systems can be used to increase data rate by spatial multiplexing, that is communicating multiple parallel streams, and to increase spatial reuse by interference suppression. Our proposed scheme, called HYB, exploits both spatial multiplexing and reuse so a receiver node can receive multiple simultaneous data streams from a desired transmitter while suppressing interference from other transmitters in the neighborhood. HYB partitions the available degrees of freedom in the antenna array between spatial multiplexing and reuse which allows the user to obtain different performance characteristics. The applicability of HYB spans across all wireless environments, including line-of-sight and dense multipath scenarios.Simulations demonstrate the significant performance gains and flexibility offered by HYB. The simulation results also offer key insights into the multi-antenna resource allocation problem in ad hoc networks based on traffic patterns and network/transport layer protocols, and consequently provide guidelines for network configuration/management. We show that throughput increases when the degrees of freedom allocated to spatial multiplexing increases, while fairness increases when the degrees of freedom allocated to spatial reuse increases.     

一种基于IEEE 802．11a的PHY—MAC跨层设计

文章基于IEEE802．11a协议,从理论上分析了物理层的编码速率、调制方式,以及MAC层的数据帧长度对吞吐率的影响,提出一种基于PHY和MAC层的跨层算法。仿真结果表明,文章提出的PHY-MAC跨层传输方案能显著提高系统的数据吞吐率。     

Analysis of Cross-Layer Interaction in Multirate 802.11 WLANs

Recent works in empirical 802.11 wireless LAN performance evaluation have shown that cross-layer interactions in WLANs can be subtle, sometimes leading to unexpected results. Two such instances are: (i) significant throughput degradation resulting from automatic rate fallback (ARF) having difficulty distinguishing collision from channel noise, and (ii) scalable TCP over DCF performance that is able to mitigate the negative performance effect of ARF by curbing multiple access contention even when the number of stations is large. In this paper, we present a framework for analyzing complex cross-layer interactions in 802.11 WLANs, with the aim of providing effective tools for understanding and improving WLAN performance. We focus on cross-layer interactions between ARF, DCF, and TCP, where ARF adjusts coding at the physical layer, DCF mediates link layer multiple access control, and TCP performs end-to-end transport. We advance station-centric Markov chain models of ARF, ARF-DCF with and without RTS/CTS, and TCP over DCF that may be viewed as multi-protocol extensions of Bianchi's IEEE 802.11 model. We show that despite significant increase in complexity the analysis framework leads to tractable and accurate performance predictions. Our results complement empirical and simulation-based findings, demonstrating the versatility and efficacy of station-centric Markov chain analysis for capturing cross-layer WLAN dynamics.     

基于多Agent强化学习的Ad hoc网络跨层拥塞控制策略

该文首先证明基于MAC层竞争造成的网络拥塞模型中存在纳什均衡点。其次,基于WOLF-PHC学习策略提出了一种跨层拥塞控制(WCS)机制。它在路由层中选择一对去耦合节点作为转发节点,同时在MAC层对源节点的发送数据进行分流,从而提高链路的空间重用性。仿真结果表明:在不需要交互任何信息的情况下,通过节点之间的相互博弈以后,采用WOLF-PHC算法能够找到每个节点的最佳分流概率进而使整体网络吞吐量达到最大值;同时当外界环境发生改变时,该算法能够较快地找到新的最佳分流概率从而实现对环境的自适应能力。     

Cross-layer QoS Analysis of Opportunistic OFDM-TDMA and OFDMA Networks

Performance analysis of multiuser orthogonal frequency division multiplexing (OFDM-TDMA) and orthogonal frequency division multiple access (OFDMA) networks in support of multimedia transmission is conducted in this work. We take a cross-layer approach and analyze several quality-of-service (QoS) measures that incilude the bit rate and the bit error rate (BER) in the physical layer, and packet average throughput/delay and packet maximum delay in the link layer. The authors adopt a cross-layer QoS framework similar to that in IEEE 802.16, where service classification, flow control and opportunistic scheduling with different subcarrier/bit allocation schemes are implemented. In the analysis, the Rayleigh fading channel in the link layer is modeled by a finite-state Markov chain, and the channel state information (CSI) is assumed to be available at the base station. With the M/G/1 queueing model and flow control results, the analysis provides important insights into the performance difference of these two multiaccess systems. The derived analytical results are verified by extensive computer simulation. It is demonstrated by analysis and simulation that OFDMA outperforms OFDM-TDMA in QoS metrics of interest. Thus, OFDMA has higher potential than OFDM-TDMA in supporting multimedia services.     

Energy Efficiency Investigation for the MB-OFDM UWB Cross-Layer Design

Green communication has become the main concern of many researchers according to the quick evolution of wireless communication applications. For this, in this correspondence we develop a cross-layer framework based on the joint association between Modulation and Coding Scheme together with truncated Selective Repeat Hybrid Automatic Repeat Request type I to examine the global energy consumption per bit of Multiband Orthogonal Frequency Division Multiplexing Ultra Wideband (MB-OFDM UWB) systems. Indeed, we examine a theoretical analysis based on throughput performance investigation when mode selection is performed which is dynamically selected following the Channel State Information. Next, we prove that cross-layer design outperforms the mode selection behavior in terms of outage probability. Then, based on the features of cross-layer MB-OFDM UWB (MB-UWB) design a theoretical framework is derived in terms of Packet Error Rate and overall energy expenditure per bit. Specifically, the closed form relation of energy per bit is determined by exploiting the proprieties of the two link adaptation tools. Correspondingly, since the purpose behind cross-layer design adoption into MB-UWB system is EE improvement, we have compared the impact of different M-QAM modulations into energy consumption per useful bit at various range of distances. The obtained results reveal that cross-layer design is a powerful solution in terms of EE enhancement.

     

End-to-end fair rate optimization in wired-cum-wireless networks

In this paper, we address the end-to-end rate optimization problem in a wired-cum-wireless network, where CSMA/CA based wireless LANs extend a wired backbone and provide access to mobile users. The objective is to achieve proportional fairness amongst the end-to-end sessions in the network. Since the network contains wireless links whose attainable throughput is a (non-convex and non-separable) function of MAC protocol parameters, the problem requires joint optimization at both the transport and the link layers. A dual-based algorithm is proposed in this paper to solve this cross-layer rate optimization problem. It is implemented in the distributed manner, and works at the link layer to adjust scheduling rates for the wireless links in the basic service sets, and at the transport layer to adjust end-to-end session rates. We prove rigorously that the proposed algorithm converges to the globally optimal rates. Simulation results are provided to support our conclusions.     

Performance Analysis of Network Coding Based Two-Way Relay Wireless Networks Deploying IEEE 802.11

In this paper, we investigate the performance analysis of the IEEE 802.11 DCF protocol at the data link layer. We analyze the impact of network coding in saturated and non-saturated traffic conditions. The cross-layer analytical framework is presented in analyzing the performance of the encode-and-forward (EF) relaying wireless networks. This situation is employed at the physical layer under the conditions of non-saturated traffic and finite-length queue at the data link layer. First, a model of a two-hop EF relaying wireless channel is proposed as an equivalent extend multi-dimensional Markovian state transition model in queuing analysis. Then, the performance in terms of queuing delay, throughput and packet loss rate are derived. We provide closed-form expressions for the delay and throughput of two-hop unbalanced bidirectional traffic cases both with and without network coding. We consider the buffers on nodes are unsaturated. The analytical results are mainly derived by solving queuing systems for the buffer behavior at the relay node. To overcome the hidden node problem in multi hop wireless networks, we develop a useful mathematical model. Both models have been evaluated through simulations and simulation results show good agreement with the analytical results.     

一种MIMO-WLAN的跨层速率控制方案

针对下一代无线局域网高速率演进的要求,该文提出一种跨层的多输入多输出(MIMO)系统速率控制算法。首先分析了保证业务误码率的物理层吞吐率最大的速率控制算法存在的不足;然后结合自适应调制编码技术,实现了基于预测的MAC(Media Access Control)层吞吐率最大的跨层速率控制算法。仿真和分析表明算法可以取得近似优化的速率选择结果,能够保证业务的误码率性能,提高业务的吞吐率。该文的算法计算简单、预测准确、运行高效,不仅可以实现闭环速率控制,还可用于帧重传和多业务调度等应用的速率控制。     

Cross-Layer Rate Optimization for Proportional Fairness in Multihop Wireless Networks With Random Access

In this paper, we address the rate control problem in a multihop random access wireless network, with the objective of achieving proportional fairness amongst the end-to-end sessions. The problem is considered in the framework of nonlinear optimization. Compared with its counterpart in a wired network where link capacities are fixed, rate control in a multihop random access network is much more complex and requires joint optimization at both the transport and link layers. This is due to the fact that the attainable throughput on each link in the network is “elastic” and is typically a nonconvex and nonseparable function of the transmission attempt rates. Two cross-layer algorithms, a dual-based algorithm and a penalty-based algorithm, are proposed in this paper to solve the rate control problem in a multihop random access network. Both algorithms can be implemented in a distributed manner, and work at the link layer to adjust link attempt probabilities and at the transport layer to adjust session rates. We prove rigorously that the two proposed algorithms converge to the globally optimal solutions. Simulation results are provided in support of our conclusions.