A survey of cross‐layer protocols for IEEE 802.11 wireless multi‐hop mesh networks

There has been an escalation in deployment and research of wireless mesh networks by both the business community and academia in the last few years. Their attractive characteristics include low deployment cost, a low‐cost option to extend network coverage and ease of maintenance due to their self‐healing properties. Multiple routes exist between the sender and receiver nodes because of the mesh layout that ensures network connectivity even when node or link failures occur. Recent advances among others include routing metrics, optimum routing, security, scheduling, cross‐layer designs and physical layer techniques. However, there are still challenges in wireless mesh networks as discussed in this paper that need to be addressed. Cross‐layer design allows information from adjacent and non‐adjacent layers to be used at a particular layer for performance improvement. This paper presents a survey of cross‐layer protocol design approaches applied to the IEEE 802.11 standards for wireless multi‐hop mesh networks that have been proposed over the last few years for improved performance. We summarize the current research efforts in cross‐layer protocol design using the IEEE 802.11 standard in identifying unsolved issues that are a promising avenue to further research. Copyright © 2016 John Wiley & Sons, Ltd.     

A cross‐layer optimization for maximum‐revenue‐based multicast in multichannel multiradio wireless mesh networks

Given a video/audio streaming system installed on a multichannel multiradio wireless mesh network, we are interested in a problem concerning about how to construct a delay‐constrained multicast tree to support concurrent interference‐free transmissions so that the number of serviced mesh clients is maximized. In this paper, we propose a heuristic approach called cross‐layer and load‐oriented (CLLO) algorithm for the problem. On the basis of the cross‐layer design paradigm, our CLLO algorithm can consider application demands, multicast routing, and channel assignment jointly during the formation of a channel‐allocated multicast tree. The experimental results show that the proposed CLLO outperforms the layered approaches in terms of the number of serviced mesh clients and throughputs. This superiority is due to information from higher layers can be used to guide routing selection and channel allocation at the same time. As a result, the CLLO algorithm can explore more solution spaces than the traditional layered approaches. In addition to that, we also propose a channel adjusting procedure to enhance the quality of channel‐allocated multicast trees. According to our simulations, it is proved to be an effective method for improving the performance of the proposed CLLO algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

Fair coding for inter‐session network coding in wireless mesh networks

Because of the broadcast and overhearing capability of wireless networks, network coding can greatly improve throughput in wireless networks. However, our investigation of existing inter‐session network coding protocols found that the short‐term unfairness that existed in 802.11‐based medium access control (MAC) protocols actually decreases the coding opportunity, which in turn compromises the throughput gain of network coding. To alleviate the negative impact of this unfairness, we propose a coding‐aware cross‐layer heuristic approach to optimize the coordination of network coding and MAC layer protocol, named FairCoding, which can significantly increase coding opportunities for inter‐session network coding through a fair short‐term traffic allocation for different coding flows. Experiment evaluation shows that the proposed mechanism can bring more coding opportunities and improve the total throughput of wireless mesh networks by up to 20%, compared with the coding mechanism, without considering the negative impact of the short‐term unfairness. Copyright © 2015 John Wiley & Sons, Ltd.     

Cross‐layer optimization for CDMA/TDD wireless mesh networks

This paper proposes a new cross‐layer optimization algorithm for wireless mesh networks (WMNs). CDMA/TDD (code division multiple access/time division duplex) is utilized and a couple of TDD timeslot scheduling schemes are proposed for the mesh network backbone. Cross‐layer optimization involves simultaneous consideration of the signal to interference‐plus‐noise ratio (SINR) at the physical layer, traffic load estimation and allocation at medium access control (MAC) layer, and routing decision at the network layer. Adaptive antennas are utilized by the wireless mesh routers to take advantage of directional beamforming. The optimization formulation is subject to routing constraints and can be solved by general nonlinear optimization techniques. Comparisons are made with respect to the classic shortest‐path routing algorithm in the network layer. The results reveal that the average end‐to‐end successful packet rate (SPR) can be significantly improved by the cross‐layer approach. The corresponding optimized routing decisions are able to reduce the traffic congestion. Copyright © 2010 John Wiley & Sons, Ltd.     

Cross‐layer bandwidth and power allocation for a two‐hop link in wireless mesh network

In this paper, a cross‐layer analytical framework is proposed to analyze the throughput and packet delay of a two‐hop wireless link in wireless mesh network (WMN). It considers the adaptive modulation and coding (AMC) process in physical layer and the traffic queuing process in upper layers, taking into account the traffic distribution changes at the output node of each link due to the AMC process therein. Firstly, we model the wireless fading channel and the corresponding AMC process as a finite state Markov chain (FSMC) serving system. Then, a method is proposed to calculate the steady‐state output traffic of each node. Based on this, we derive a modified queuing FSMC model for the relay to gateway link, which consists of a relayed non‐Poisson traffic and an originated Poisson traffic, thus to evaluate the throughput at the mesh gateway. This analytical framework is verified by numerical simulations, and is easy to extend to multi‐hop links. Furthermore, based on the above proposed cross‐layer framework, we consider the problem of optimal power and bandwidth allocation for QoS‐guaranteed services in a two‐hop wireless link, where the total power and bandwidth resources are both sum‐constrained. Secondly, the practical optimal power allocation algorithm and optimal bandwidth allocation algorithm are presented separately. Then, the problem of joint power and bandwidth allocation is analyzed and an iterative algorithm is proposed to solve the problem in a simple way. Finally, numerical simulations are given to evaluate their performances. Copyright © 2008 John Wiley & Sons, Ltd.     

Cross‐layer MAC design for location‐aware wireless sensor networks

In this paper, we propose an optimization of MAC protocol design for wireless sensor networks, that accounts for cross‐layering information, in terms of location accuracy for nodes and residual energy levels. In our proposed solution we encode this cross‐layer information within a decreasing backoff function in the MAC. The protocol is optimized by appropriately selecting priority window lengths, and we have shown that accurate cross‐layer information plays a crucial role in achieving an optimal performance at the MAC layer level. The estimation accuracy can be characterized spatially using a location reliability probability distribution function. We show that this distribution function greatly influences the design of the optimal backoff window parameters, and the overall throughput performance of the MAC protocol. Copyright © 2010 John Wiley & Sons, Ltd.     

无线mesh网中一种基于博弈论的公平性路由协议

提出一种基于博弈论的以树为拓扑结构的公平性路由协议.新的协议综合了先验式路由和按需路由,并且将路由计算和信道资源分配控制分布到树中的每个枝节点上,降低了根节点的负担,使其更适合于无线 mesh网的通信需求.仿真结果表明,新的路由协议改进了AODV、HWMP路由协议的端到端平均延迟和网络吞吐量,并且网络中各个无线节点占有的信道资源基本相近,满足公平性原则.     

Utility‐optimal cross‐layer resource allocation in distributed wireless cooperative networks

In this paper, we propose a distributed cross‐layer resource allocation algorithm for wireless cooperative networks based on a network utility maximization framework. The algorithm provides solutions to relay selections, flow pass probabilities, transmit rate, and power levels jointly with optimal congestion control and power control through balancing link and physical layers such that the network‐wide utility is optimized. Via dual decomposition and subgradient method, we solve the utility‐optimal resource allocation problem by subproblems in different layers of the protocol stack. Furthermore, by introducing a concept of pseudochannel gain, we model both the primal direct logical link and its corresponding cooperative transmission link as a single virtual direct logical link to simplify our network utility framework. Eventually, the algorithm determines its primal resource allocation levels by employing reverse‐engineering of the pseudochannel gain model. Numerical experiments show that the convergence of the proposed algorithm can be obtained and the performance of the optimized network can be improved significantly. Copyright © 2012 John Wiley & Sons, Ltd.     

XMSN: An efficient cross‐layer protocol for mixed wireless sensor networks

The application of wireless sensor networks (WSNs) technology in monitoring systems is demanding more efficient services to fulfill the requirements of the monitoring task. For this purpose, the simultaneous presence of features such as different communication mediums (air and water) used by nodes and various sizes of data generated by heterogeneous nodes are the key obstacles to build a communication protocol, which can ensure the reliable data delivery. This work terms such WSNs as mixed wireless sensor networks (MWSNs) which contains the aforementioned features. In this paper, we introduce a new cross‐layer protocol for mixed wireless sensor network (XMSN) which can adapt these features. The proposed cross layer protocol XMSN for such mixed environment is implemented and analyzed extensively in Castalia simulator. The performance of XMSN is compared with composition of well‐known protocols, namely, CTP plus BoX‐MAC‐2. The result shows that XMSN has better efficiency in terms of end‐to‐end delay, energy consumption, and goodput than that of CTP plus BoX‐MAC‐2 protocol.     

A reliable overlay video transport protocol for multicast agents in wireless mesh networks

A new video transport protocol for multicast agents in wireless mesh networks (WMNs) is proposed in this paper. The proposed protocol enables a significant reduction in the transmission overhead, while providing reliable communication for its use in multicast applications. This proposed reliable protocol provides a practical approach for an overlay peer‐to‐peer multicast facility supported within the application layer. This obviates the need to give upgraded routers capable of handling multicast broadcasting or modify the existing protocol stack. The protocol tolerates partial losses in multimedia transmissions, while supporting control of the delay sensitivity of such transmissions in WMNs. The key issue in this protocol is the ability to detect packet loss, anticipate retransmission requests, and use the anticipated retransmission requests to transmit the lost packets prior to requests from other receiving agents. The proposed protocol allows for the receiver to determine if retransmission of lost packets is required, ensuring the greatest flexibility needed for a reliable multicast protocol. Copyright © 2009 John Wiley & Sons, Ltd.     

Congestion control with dynamic threshold adaptation and cross‐layer response for TCP Vegas over IEEE 802.11 wireless networks

Wireless technologies provide mobile access and enable rapid andcost‐effective network deployment. But a wireless link is generally accompanied by high interference, transmission errors and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection, and thus limit TCP performance. This paper presents a threshold control mechanism with cross‐layer response approach for improving TCP Vegas performance in IEEE 802.11 wireless networks. By making slight modifications to the legacy IEEE 802.11 MAC and TCP, the numerical results reveal that the proposed scheme provides a significant improvement in TCP performance under IEEE 802.11 wireless environments. Copyright © 2013 John Wiley & Sons, Ltd.     

Distributed cross‐layer optimization for wireless regional area network‐based cognitive radio networks

This paper presents a study of a cross‐layer design through joint optimization of spectrum allocation and power control for cognitive radio networks (CRNs). The spectrum of interest is divided into independent channels licensed to a set of primary users (PUs). The secondary users are activated only if the transmissions do not cause excessive interference to PUs. In particular, this paper studies the downlink channel assignment and power control in a CRN with the coexistence of PUs and secondary users. The objective was to maximize the total throughput of a CRN. A mathematical model is presented and subsequently formulated as a binary integer programming problem, which belongs to the class of non‐deterministic polynomial‐time hard problems. Subsequently, we develop a distributed algorithm to obtain sub‐optimal results with lower computational complexity. The distributed algorithm iteratively improves the network throughput, which consists of several modules including maximum power calculation, excluded channel sets recording, base station throughput estimation, base station sorting, and channel usage implementation. Through investigating the impacts of the different parameters, simulation results demonstrates that the distributed algorithm can achieve a better performance than two other schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

TCP throughput and fairness performance in presence of delay spikes in wireless networks

Wireless networks are likely to experience delay spikes exceeding several times the typical round‐trip‐time figures, which can cause spurious timeouts that lead to unnecessary retransmissions and reduction of the TCP sender's transmission rate, and thus, the throughput of the TCP is degraded. This paper presents some research results on the effect of delay spikes caused by handover on TCP performance by using three different mobility models. It is shown that the throughput of TCP connection over a single bottleneck link is decreased in the presence of delay spikes significantly. Furthermore, it is shown that the fairness feature of TCP is also severely affected in the presence of delay spikes. Copyright © 2005 John Wiley & Sons, Ltd.     

Analytical model for approximating node throughputs in wireless mesh networks

This paper describes an analytical model and an associated algorithm for assessing the throughputs of each host in wireless mesh networks (WMNs). It provides a framework for studying WMNs, particularly when the performance and parameters in multiple protocol layers have to be jointly evaluated and optimized. From the point of the implementation, a simple recursive formula with N ? 1 iterations is used to obtain the throughput performance of N node WMNs. The produced expressions offer insights into understanding the performance of the individual nodes without referring to a specific medium access control layer or physical layer technology. The model serves as a general tool for capturing the characteristics of the WMNs. Using the model, the complexity of cross‐layer studies is reduced, thus allowing researchers to focus on the modelling of other associated layers. The paper explains the rationale behind the model and provides examples of scenarios for which it is suitable. It is validated using discrete event simulations in the OPNET network simulator. Copyright © 2012 John Wiley & Sons, Ltd.     

Protocols and architectures for channel assignment in wireless mesh networks

The use of multiple channels can substantially improve the performance of wireless mesh networks. Considering that the IEEE PHY specification permits the simultaneous operation of three non-overlapping channels in the 2.4 GHz band and 12 non-overlapping channels in the 5 GHz band, a major challenge in wireless mesh networks is how to efficiently assign these available channels in order to optimize the network performance. We survey and classify the current techniques proposed to solve this problem in both single-radio and multi-radio wireless mesh networks. This paper also discusses the issues in the design of multi-channel protocols and architectures.     

A weighted interference estimation scheme for interface‐switching wireless mesh networks

The co‐channel interference problem in wireless mesh networks (WMN) is extremely serious due to the heavy aggregated traffic loads and limited available channels. It is preferable for mesh routers to dynamically switch channels according to the accurate estimation of co‐channel interference level in the neighborhood. Most developed interference estimation schemes, however, do not consider the impact of interface switching. Furthermore, the interference in wireless networks has been extensively considered as an all‐or‐nothing event. In this paper, we develop a weighted interference estimation scheme (WIES) for interface‐switching WMN. WIES takes a new version of multi‐interface conflict graph that considers the impacts of frequent interface switching as the interference relationship estimation scheme. Besides, WIES uses a weight to estimate the interference level between links. The weight utilizes two empirical functions to denote the impacts of the relative distance and characteristics of traffic loads in WMN. Extensive NS2 simulations show that WIES achieves significant performance improvements, especially when the interference level of the network is high. We also validate that the interference level of networks is affected by several system parameters such as the number of available channels and the ratio between interference range and transmission range. Copyright © 2008 John Wiley & Sons, Ltd.     

Channel‐switching and power control mechanisms for improving network connectivity in wireless mesh networks

A Wireless Mesh Network (WMN) consists of fixed wireless routers, each of which provides service for mobile clients within its coverage area and inter‐connects mesh routers to form a connected mesh backbone. Wireless mesh routers are assigned with a channel or a code to prevent collisions in transmission. With a power control mechanism, each router could be assigned with a power level to control connectivity, interference, spectrum spatial reuse, and topology. Assigning high transmitting power level to a router can enhance the network connectivity but may increase the number of neighbors and worsen the collision problem. How to assign an appropriate power level to each router to improve the network connectivity with a constraint of limited channels is one of the most important issues in WMNs. Given a network topology and a set of channels that has been assigned to mesh routers, the proposed channel‐switching mechanism further reassigns each router with a power level and switches channels of routers to optimize both power efficiency and connectivity. A matrix‐based presentation and operations are proposed to respectively identify and resolve the channel switching problems. Simulation study reveals that the proposed mechanisms increase network throughput and provides a variety of route selection, and thus improves the performance of a given WMN. Copyright © 2009 John Wiley & Sons, Ltd.     

A cross‐layer partner‐based fast handoff mechanism for IEEE 802.11 wireless networks

In wireless/mobile networks, users freely and frequently change their access points (APs) while they are communicating with other users. To support the mobility of mobile nodes (MNs), Mobile IPv6 (MIPv6) is used to inform the information of MN's home address and current care‐of‐address (CoA) to its home agent. MIPv6 suffers from a long delay latency and high packet losses (PLs) because MIPv6 does not support micromobility. A Hierarchical Mobile IPv6 (HMIPv6) is proposed which provides micromobility and macromobility to reduce handoff latency (HL) by employing a hierarchical network structure. In this paper, we propose a cross‐layer partner‐based fast handoff mechanism based on HMIPv6, called the PHMIPv6 protocol. Our PHMIPv6 protocol is a cross‐layer, layer‐2 + layer‐3, and cooperative approach. A cooperative node, called a partner node (PN), is adopted in the PHMIPv6 protocol. A new layer‐2 trigger scheme used in the PHMIPv6 protocol accurately predicts the next AP and then invites a cooperative PN in the area of the next AP. With the cooperation of the PN, the CoA can be pre‐acquired and duplicate address detection operation can be pre‐executed by the PN before the MN initializes the handoff request. The PHMIPv6 protocol significantly reduces the handoff delay time and PLs. In the mathematical analysis, we verified that our PHMIPv6 protocol offers a better HL than the MIPv6, HMIPv6, and SHMIPv6 protocols. Finally, the experimental results also illustrate that the PHMIPv6 protocol actually achieves performance improvements in the handoff delay time, PL rate, and handoff delay jitter. Copyright © 2009 John Wiley & Sons, Ltd.     

Cross‐layer design for energy efficient communication in wireless sensor networks

There is a plethora of recent research on high performance wireless communications using a cross‐layer approach in that adaptive modulation and coding (AMC) schemes at wireless physical layer are used for combating time varying channel fading and enhance link throughput. However, in a wireless sensor network, transmitting packets over deep fading channel can incur excessive energy consumption due to the usage of stronger forwarding error code (FEC) or more robust modulation mode. To avoid such energy inefficient transmission, a straightforward approach is to temporarily buffer packets when the channel is in deep fading, until the channel quality recovers. Unfortunately, packet buffering may lead to communication latency and buffer overflow, which, in turn, can result in severe degradation in communication performance. Specifically, to improve the buffering approach, we need to address two challenging issues: (1) how long should we buffer the packets? and (2) how to choose the optimum channel transmission threshold above which to transmit the buffered packets? In this paper, by using discrete‐time queuing model, we analyze the effects of Rayleigh fading over AMC‐based communications in a wireless sensor network. We then analytically derive the packet delivery rate and average delay. Guided by these numerical results, we can determine the most energy‐efficient operation modes under different transmission environments. Extensive simulation results have validated the analytical results, and indicates that under these modes, we can achieve as much as 40% reduction in energy dissipation. Copyright © 2008 John Wiley & Sons, Ltd.     

Aspects for untangling cross‐layer design and policy support

Programming language concepts have inspired some networking design decisions. For example, concepts such as object encapsulation and interface invocation have been borrowed, at the time of their adoption, from an already well established object oriented programming paradigm. The authors suggest in this paper that it may be time again to revisit emerging software engineering programming paradigms to learn from them. More specifically, this paper discusses the practical tangling problem, embedded in conventional layer‐coupling (linking) network software design and highlighted by recent research proposals for cross layer design. The adopted solution is based on the aspect‐oriented programming paradigm. We show its programming efficiency, limitations and role in the seamless enforcement of multiple policy scenarios while emphasizing little design changes. Copyright © 2012 John Wiley & Sons, Ltd.