移动自组网能量保护策略研究进展

移动自组网是一组带有无线收发装置的移动节点组成的一个支持多跳的临时性的网络自治系统，由于移动自组网的大多数节点是由有限寿命的电池来提供的，因此能量保护策略成为该网络所有协议层的关键问题。本文回顾了移动自组网能量保护策略的研究进展，对有关策略进行了评述，最后结合跨层设计思想给出了基于跨层协同的能量保护构架及其包含的研究方向。     

一种基于跨层的无线Mesh网络路由协议

无线Mesh网络的很多技术特点和优势来自于Mesh多跳路由.因此,路由协议的研究与设计是无线Mesh网络技术的一个重要课题.由于无线Mesh网络有自身负载均衡、路由容错与网络容量等要求,因此运用跨层设计,采用更好的路由参数,使用多径路由等方法已经成为无线Mesh网络路由协议设计的重要思路.根据无线Mesh的网络特点,按照其路由协议的设计要求,分析了路由协议DSR在Mesh网络中的不足,引入跨层设计的方法,提出了采用路由质量路径帧投递率(PFDR)为路由准则,并具有负载平衡、拥塞避免的路由协议CMRP.分析和仿真结果表明,CMRP在保持Mesh网络自身优点的同时,比起DSR在网络性能上有了较大的提升,在吞吐率方面有了很大的提高,相应的时延、抖动参数均有了大幅的下降,更加适用于无线Mesh网络.     

无线传感器MAC层协议的分析和研究

无线传感器网络(Wireless Sensor Network,WSN)一般由部署在监测区域内大量廉价微型传感器节点组成,通过无线通信方式形成一个多跳(mutli hop)的自组织(self organizing)网络系统。MAC层协议设计是无线传感器网络设计中的一个重要研究方面,通过对当前众多MAC协议的研究,提出了一种无线传感器网络MAC层协议的分类方法,通过分析比较典型的MAC层协议,给出了MAC层协议设计的评价标准。     

无线自组织网传输功率控制与跨层优化

无线自组织网节点功率有限，如何有效利用节点电量、改善网络性能是自组网领域研究的关键问题。首先讨论了节点传输功率对各协议层的影响，并归纳出功率控制的设计原则；然后分类介绍和比较了几种主要的控制机制。在传统协议分层研究的基础上，提出了对传输功率控制进行跨层优化的设计思想，并对运用跨层优化的困难给予了阐述；最后给出了传输功率控制领域最新的一些研究方向。     

多跳CC-HARQ中继网络的频谱有效性跨层设计

在瑞利衰落信道中,为改善采用Chase合并混合自动重传请求( CC-HARQ)协议的多跳中继网络的频谱效率性能,考虑发送帧长和发送功率的跨层优化,研究了提升其频谱效率的跨层优化策略。不同于传统的中断概率分析,通过利用对数域线性阈值的平均误帧率估计方法,给出了多跳CC-HARQ协议频谱效率的精确表达式,在发送功率固定时设计了最优发送帧长策略,在发送帧长固定时设计了最优发送功率分配方案,进一步提出了跨层的联合优化方案。仿真结果验证了所设计优化方案在理论上的正确性和有效性,同时在仿真中可以观察到采用跨层的优化策略后,多跳 CC-HARQ中继网络的频谱效率获得了显著的提升,其中跨层的联合优化方案比传统的固定帧长等功率策略在频谱效率上提升了0.014 b/s·Hz-1。     

无线传感器网络视频传输技术研究

对无线传感器网络中的视频传输问题进行了研究。无线传感器网络中传输视频数据的难点,在于如何在节点资源有限的网络中确保视频业务的质量。分析并比较了基于单层协议的视频传输技术和基于多层设计的视频传输技术2类视频传输技术,得出结论：2者各有优缺点,单层协议设计与优化简单、扩展性强,但整体性能不一定最佳;跨层优化设计难度较大,但设计得当,性能优于单层协议。     

移动栅格网中跨层资源管理方法研究

移动栅格网是一种全移动多跳无线栅格网络,采用了面向服务的全IP技术体制和全新的分层协议模型。针对这种新型网络结构和协议模型,提出了一种跨层资源管理方法,通过将呼叫接纳控制、路由选择、资源预留、排队机制以及信道接入机制等进行跨层设计,增加层间协作机制和方法以达到资源利用的优化和业务服务质量的提高。对跨层资源管理的总体框架和思路进行了详细描述,对具体实现途径进行了探讨。     

无线通信的跨层优化

传统的OSI分层结构无法适应无线网络环境，随着越来越多无线应用的出现，人们提出了跨层设计，其主要内容就是通过在协议栈的各层之间（主要是应用层、传输层、网络层、链路层和物理层）传递特定的信息，使协议栈能够根据无线环境的变化来实现对资源的自适应优化配置，从而更有效的利用无线网络资源，提高系统的性能。     

无线自组网MAC层和网络层节能策略

无线自组网固有的分布式、自组织特性使得它具有更多的特殊性,对无线自组网络的设计也提出了更多的挑战。针对无线自组网协议设计中的节能技术进行综述,通过分析无线网络数据传输中能量消耗模型,得出节能设计的基本准则,然后分别对媒体访问控制层和网络层的节能策略进行介绍,给出各自进行节能设计的思路。最后指出无线自组网络的节能策略设计需要综合网络通信协议的各层的特点进行跨层设计。     

无线通信中的跨层设计应用

传统的OSI分层结构无法适应无线网络环境,随着越来越多无线应用的出现,人们提出了跨层设计,其主要内容是通过在协议栈的各层之间传递特定的信息,使协议栈能够根据无线环境的变化来实现对资源的自适应优化配置,从而更有效的利用无线网络资源,提高系统的性能.文章举例说明了此设计.     

下一代无线网络中的跨层设计

下一代无线通信系统必须能够与互联网实现信息交互,这就需要利用通信协议来实现系统与其他通信系统间的互连互通。但是,现有通信协议基于OSI标准,其协议栈按照严格的分层方式工作,很难适应快速变化的无线通信环境。通过对现有协议栈进行改进,加入跨层设计方案则有助于改善下一代无线系统性能。文章简要分析了分层协议栈局限性,讨论了跨层设计原理,并系统地阐述了跨层设计时物理层、链路层、网络层、传输层和应用层协议应考虑的因素。     

Application-driven cross-layer optimization for video streaming over wireless networks

Mobile multimedia applications require networks that optimally allocate resources and adapt to dynamically changing environments. Cross-layer design (CLD) is a new paradigm that addresses this challenge by optimizing communication network architectures across traditional layer boundaries. In this article we discuss the relevant technical challenges of CLD and focus on application-driven CLD for video streaming over wireless networks. We propose a cross-layer optimization strategy that jointly optimizes the application layer, data link layer, and physical layer of the protocol stack using an application-oriented objective function in order to maximize user satisfaction. In our experiments we demonstrate the performance gain achievable with this approach. We also explore the trade-off between performance gain and additional computation and communication cost introduced by cross-layer optimization. Finally, we outline future research challenges in CLD.     

In-network aggregation techniques for wireless sensor networks: a survey

In this article we provide a comprehensive review of the existing literature on techniques and protocols for in-network aggregation in wireless sensor networks. We first define suitable criteria to classify existing solutions, and then describe them by separately addressing the different layers of the protocol stack while highlighting the role of a cross-layer design approach, which is likely to be needed for optimal performance. Throughout the article we identify and discuss open issues, and propose directions for future research in the area     

A New Systematic Framework for Autonomous Cross-Layer Optimization

Cross-layer optimization solutions have been proposed in recent years to improve the performance of wireless users that operate in a time-varying, error-prone network environment. However, these solutions often rely on centralized cross-layer optimization solutions that violate the layered network architecture of the protocol stack by requiring layers to provide access to their internal protocol parameters to other layers. This paper presents a new systematic framework for cross-layer optimization, which allows each layer to make autonomous decisions to maximize the wireless user's utility by optimally determining what information should be exchanged among layers. Hence, this cross-layer framework preserves the current layered network architecture. Since the user interacts with the wireless environment at various layers of the protocol stack, the cross-layer optimization problem is solved in a layered fashion such that each layer adapts its own protocol parameters and exchanges information (messages) with other layers that cooperatively maximize the performance of the wireless user. Based on the proposed layered framework, we also design a message-exchange mechanism that determines the optimal cross-layer transmission strategies, given the user's experienced environment dynamics.     

Cross-layer design: a survey and the road ahead

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.     

UPS: Universal Protocol Stack for emerging wireless networks

Recent devices developed for emerging wireless networks, such as 4G cellular networks, wireless mesh networks, and mobile ad hoc networks, support multiple communication substrates and require execution of multiple protocols within a layer, which cannot be supported efficiently by traditional, layered protocol stack approaches. While cross-layer approaches can be designed to support these new requirements, the lack of modularity makes cross-layer approaches inflexible and hence difficult to adapt for future devices and protocols. Thus, there is a need for a new protocol architecture to provide universal support for cross-layer interactions between layers, while also supporting multiple communication substrates and multiple protocols within a stack. In this paper, we propose Universal Protocol Stack (UPS), which provides such support in a modular way through packet-switching, information-sharing and memory management. To show that UPS is realizable with very low overhead and that it enables concurrent and independent execution of protocols of the same stack layer, first, we present a wireless sensor network test-bed evaluation, where UPS is implemented in TinyOS and installed on individual sensor motes. Two cross-layer routing protocols are implemented and evaluated with UPS and without UPS. We also implemented UPS in the OPNET simulator, where the IP (e.g., Routing Information Protocol (RIP)) and AODV routing protocols are executed concurrently to support networks with both static and mobile wireless nodes. Our implementation shows that the overhead incurred to implement UPS is very low, and little or no modification is required to adapt existing protocols to the UPS framework. Both studies also show the advantage of enabling concurrent protocol execution within a stack layer, improving the successful packet delivery ratio or the total number of packets sent for the investigated scenarios.     

Cross-Layer Design for QoS Support in Multihop Wireless Networks

Due to such features as low cost, ease of deployment, increased coverage, and enhanced capacity, multihop wireless networks such as ad hoc networks, mesh networks, and sensor networks that form the network in a self-organized manner without relying on fixed infrastructure is touted as the new frontier of wireless networking. Providing efficient quality of service (QoS) support is essential for such networks, as they need to deliver real-time services like video, audio, and voice over IP besides the traditional data service. Various solutions have been proposed to provide soft QoS over multihop wireless networks from different layers in the network protocol stack. However, the layered concept was primarily created for wired networks, and multihop wireless networks oppose strict layered design because of their dynamic nature, infrastructureless architecture, and time-varying unstable links and topology. The concept of cross-layer design is based on architecture where different layers can exchange information in order to improve the overall network performance. Promising results achieved by cross-layer optimizations initiated significant research activity in this area. This paper aims to review the present study on the cross-layer paradigm for QoS support in multihop wireless networks. Several examples of evolutionary and revolutionary cross-layer approaches are presented in detail. Realizing the new trends for wireless networking, such as cooperative communication and networking, opportunistic transmission, real system performance evaluation, etc., several open issues related to cross-layer design for QoS support over multihop wireless networks are also discussed in the paper.     

Cross-layer feedback architecture for mobile device protocol stacks

Applications using traditional protocol stacks (e.g., TCP/IP) from wired networks do not function efficiently in mobile wireless environments. This is primarily due to the layered architecture and implementation of protocol stacks. One mechanism to improve the efficiency of the stack is cross-layer feedback, that is, making information from within one layer available to another layer of the stack. For example, TCP retransmissions can be reduced by making it aware of network disconnections or handoff events. We highlight the need for a cross-layer feedback architecture and identify key design goals for an architecture. We present our ECLAIR architecture, which satisfies these design goals. We describe a prototype implementation that validates ECLAIR. We also discuss other cross-layer architectures and provide a cross-layer design guide.     

Cross-Layer Optimized Conditions for QoS Support in Multi-Hop Wireless Networks with MIMO Links

Recent advances in antenna technology made it possible to build wireless devices with more than one antenna at affordable costs. Because multiple antennas offer wireless networks a potential capacity increase, they are expected to be a key part of next-generation wireless networks to support the rapidly emerging multimedia applications characterized by their high and diverse QoS requirements. This paper developed methods that exploit the benefits of multiple antennas to enable multi-hop wireless networks with flow-level QoS capabilities. The authors first propose a cross-layer table-driven statistical approach that allows each node to determine the amount of spatial reuse and/or multiplexing, offered by the multiple antennas that are available to it. The authors then use the developed statistical approach to derive sufficient conditions under which flow rates are guaranteed to be feasible. The derived conditions are multi-layer aware in the sense that they account for cross-layer effects between the PHY and the MAC layers to support QoS at higher layers. The authors evaluate and compare the derived sufficient conditions via extensive simulations. The authors show that the conditions result in high flow acceptance rates when used in multi-hop wireless networking problems such as QoS routing and multicommodity flow problems. The authors also demonstrate the importance and the effect of considering cross-layer couplings into the development of flow acceptance methods.     

A cross-layer protocol for exploiting cooperative diversity in multi-hop wireless ad hoc networks

Cooperative communication has emerged to reap the benefits of spatial diversity. To fully exploit cooperative diversity, we propose a medium access control and routing enabled cross-layer cooperative transmission (MACR-CCT) protocol for improving the performance in multi-hop wireless ad hoc networks (MWAN). Different from previous cooperative protocols that determine a receiver in one hop according to a non-cooperative routing protocol first and then select a cooperative relay, MACR-CCT selects the cooperative relay together with the receiver in one hop to exploit fully cooperative diversity, so that the receiver is selected for higher cooperative gain and closer distance to destination, and the relay is selected to achieve the better throughput performance while considering transmission error. Furthermore, considering that there are multiple source–destination pairs in MWAN, MACR-CCT takes interference mitigation into account to further improve network throughput when selecting the cooperative relay. Besides, we propose a theoretical model to analyze the throughput performance. Finally, we take advantage of simulation results to validate the effectiveness of our analytical model and show that our proposed MACR-CCT protocol can significantly outperform existing packet transmission mechanisms in terms of throughput and delay under the multi-hop multi-flow network scenario.