CAPACITY EVALUATION OF MULTI-CHANNEL WIRELESS AD HOC NETWORKS

In this paper, the capacity of multi-channel, multi-hop ad hoc network is evaluated.In particular, the performance of multi-hop ad hoc network with single channel IEEE 802.11 MAC utilizing different topologies is shown. Also the scaling laws of throughputs for largescale ad hoc networks and the theoretical guaranteed throughput bounds for multi-channel grid topology systems are proposed. The results presented in this work will help researchers to choose the proper parameter settings in evaluation of protocols for multi-hop ad hoc networks.     

A fuzzy logic cooperative MAC for MANET

In both wireless local area networks（WLAN） and mobile ad hoc networks（MANET）, the 1EEE 802.11e medium access control （MAC） protocol is proposed for an effective quality of service （QoS） solution. A number of studies have been done to enhance the performance of 802.11e in MANET by independently adjusting contention window （CW） size of each access category （AC） in every node. However, without the cooperation between the high priority flows and lower priority flows, the QoS goal of high priority flows cannot achieve effectively. In this article, a fuzzy logic based cooperative MAC protocol （FLCMAC） is proposed to cooperate amongst network flows and dynamically adjust access probability of each low priority flow affecting the high priority flows to satisfy their QoS requirement. The simulation results indicate that compared to the enhanced distributed channel access （EDCA） scheme of 802.11e, the FLCMAC consistently excels, in terms of throughput and delay under moderate and heavy background traffic both in single-hop and multi-hop scenarios.     

Interference aware routing for mobile ad hoc networks based on node＇s sending and receiving capabilities

How to efficiently build routes among nodes is increasing important for mobile ad hoc networks （MANETs）. This paper puts forward an interference aware routing protocol called Interference aware cross layer routing protocol （IA-CLR） for MANETs based on the IEEE 802.11 medium access layer （MAC）. By defining the node＇s sending and receiving capabilities, IA-CLR can indicate the interference strength of the link in a real and comprehensive way. Further more, in order to choose the route with minimum bottleneck link interference, a new routing metric is proposed by combining the MAC layer and the network layer for cross layer design. Simulation results show that IA-CLR can significantly improve the performances of network such as the average end-to-end delay, the packets loss ratio and the throughput.     

基于动态定价的帧聚合策略(英文)

Frame aggregation is a wireless link optimization mechanism that aims to reduce transmission overheads by sending multiple frames as the payload of a single MAC frame. It is considered as one of the most efficient methods to improve the wireless channel utilization and the throughput of wireless networks.The static assignment of frame aggregation parameters can result in delay penalties due to variations in traffic type. We propose a frame aggregation scheme which is based on dynamic pricing and queue scheduling for a multitraffic scenario. The scheme adopts a dynamic differential pricing scheme for different types of traffic. Meanwhile, it polls buffer queues in accordance with the optimal aggregation weight factors to maximise the network revenue.Simulation results indicate that the proposed frame aggregation scheme can effectively improve the network revenue and the average throughput, while guaranteeing the delay requirements of all types of traffic.     

Key Technology and Experimental Research in Wireless Mesh Networks

With the increasing popularity and rising demand for high-rate wireless Internet access, traditional wireless access networks such as cellular network and Wireless Local Area Network (WLAN) are facing some challenges. The Wireless Mesh Network (WMN) is emerging as a flexible and low-cost alternative to provide multi-hop communications, supporting applications such as last-mile Internet delivery. The WMN has also become a promising technology in the merging of wireless networks. Some key technologies for the WMN networking, including network configuration, power control, mobility management, access control, and routing protocols, are analyzed; the routing protocol design in WMN and mobile Ad hoc network are compared. An example of WMN testbed based on WLAN and second-layer switching technology is given.     

Military multi-hop routing protocol

Military tactical network is one of the most important applications of ad hoc network. Currently the existing routing protocols are put forward based on the simple and universal network model which has the ability of multi-hop routing but cannot work efficiently in the special military applications. The narrow bandwidth and limited energy of the wireless network make general routing protocols seem to be more redundant. In order to satisfy military needs properly, this letter makes a detailed analysis of physical nodes and traffic distribution in military network, uses cross-layer design concept for reference, combines traffic characteristic of application layer with routing protocol design. It categorized routing problem as crucial routes and non-crucial routes which adopted separate maintenance methods. It not only realizes basic transmission function but also works efficiently. It is quite fit for military application.     

A Probability Driven Quadri-Stage Contention Protocol for Mobile Ad Hoc Networks

The paper proposes a new contention based Time division multiple access （TDMA） Medium access control （MAC） protocol in wireless ad hoc networks, which can be termed Quadri-stage contention protocol （QSCP）. The QSCP protocol is free of both the ＂hidden terminal＂ and the ＂exposed terminal＂ problems. It is distributive and arbitrarily scalable. In the dedicated contention stage, nodes exchange their ＂Normalized accumulation and dissipation rate of payload （NADROP）＂ messages in 2-hop neighborhood, and then run a contention probability calculation algorithm to decide the probability of sending a contention frame. The algorithm guaran- tees that the number of time slot reserved by a node is proportional to its NADROP value, which can remarkably improve the end-to-end throughput when network load is heavy, and is more efficient in energy consumption. The simulation results demonstrate that QSCP performs better than the existing protocols.     

Novel multi-path routing scheme for UWB Ad hoc network

1 Introduction Ad hoc networks and ultra-wideband communications technology are a key factor in the evolution of wireless communications. In ad hoc networks, wireless hosts can communications with each other in the absence of a fixed infrastructure. These networks typically consist of equal nodes that communication over wireless links without central control .The followings can be used to describe the ad hoc network[1]: ? Dynamic network topology ? Limited resource ? Multi-hop communication …     

Fairness-oriented routing algorithm joint with power control and channel assignment for multi-radio multi-channel wireless mesh networks

The multi-radio multi-channel wireless mesh network （MRMC-WMN） draws general attention because of its excellent throughput performance, robustness and relative low cost. The closed interactions among power control （PC）, channel assignment （CA） and routing is contributed to the performance of multi-radio multi-channel wireless mesh networks （MRMC-WMNs）. However, the joint PC, CA and routing （JPCR） design, desired to achieve a global optimization, was poor addressed. The authors present a routing algorithm joint with PC and CA （JPCRA） to seek the routing, power and channel scheme for each flow, which can improve the fairness performance. Firstly, considering available channels and power levels, the routing metric, called minimum flow rate, is designed based on the physical interference and Shannon channel models. The JPCRA is presented based on the genetic algorithm （GA） with simulated annealing to maximize the minimum flow rate, an non-deterministic polynomial-time hard （NP-Hard） problem. Simulations show the JPCRA obtains better fairness among different flows and higher network throughput.     

Graph coloring based channel assignment framework for rural wireless mesh networks

IEEE 802.11 based wireless mesh networks with directional antennas are expected to be a new promising technology and an economic approach for providing wireless broadband services in rural areas. In this paper, we discuss interference models and address how they can affect the design of channel assignment in rural mesh networks. We present a new channel assignment framework based on graph coloring for rural wireless mesh networks. The goal of the framework is to allow synchronously transmitting or receiving data from multiple neighbor links at the same time, and continuously doing full-duplex data transfer on every link, creating an efficient rural mesh network without interference. Channel assignment is shown to be NP-hard. We frame this channel allocation problem in terms of Adjacent Vertex Distinguishing Edge Coloring （AVDEC）. Detailed assignment results on grid topology are presented and discussed. Furthermore, we design an algorithm. Finally, we evaluate the perform- ance of the proposed algorithm through extensive simulations and show the algorithm is effective to the regular grid topologies, and the number of colors used by the algorithm is upper bounded by A ~ 1. Hence the algorithm guarantees that the number of channels available in standards such as IEEE 802.11a is sufficient to have a valid AVDEC for many grid topologies. We also evaluate the proposed algorithm for arbitrary graphs. The algorithm provides a lower upper bound on the minimum number of channels to the AVDEC index channel assignment problem.     

A hybrid multi-channel MAC protocol for wireless ad hoc networks

In a regular wireless ad hoc network, the Medium Access Control (MAC) protocol coordinates channel access among nodes, and the throughput of the network is limited by the bandwidth of a single channel. The multi-channel MAC protocols can exploit multiple channels to achieve high network throughput by enabling more concurrent transmissions. In this paper, we propose a hybrid and adaptive protocol, called H-MMAC, which utilizes multi-channel resources more efficiently than other multi-channel MAC protocols. The main idea is to adopt the IEEE 802.11 Power Saving Mechanism and to allow nodes to transmit data packets while other nodes try to negotiate the data channel during the Ad hoc Traffic Indication Message window based on the network traffic load. The analytical and simulation results show that the proposed H-MMAC protocol improves the network performance significantly in terms of the aggregate throughput, average delay, fairness and energy efficiency.     

MAC protocols using directional antennas in IEEE 802.11 based ad hoc networks

Using directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. The most important benefit includes a reduction of the radio interference. Thus, it can significantly increase the spatial reuse, thereby improving the network throughput. To best utilize directional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In this paper, we present modified MAC protocols suitable for 802.11 based ad hoc networks using directional antennas. Our comprehensive simulation results demonstrate the performance improvement obtained with the proposed protocols. Copyright © 2007 John Wiley & Sons, Ltd.     

基于干扰图的无线自组织网络MAC协议

由于IEEE802．11MAC协议采用了简单的干扰模型，因此产生了隐藏终端和暴露终端这两个严重影响无线自组织网络性能的问题。文章提出了一种新的基于干扰图（Conflict Graph）的MAC协议——CG-MAC来提高无线自组织网络的吞吐量。通过仿真实验，该协议能够同时解决隐藏终端和暴露终端问题．很大程度地提高了网络性能。     

A Cross-layer Approach to Channel Assignment in Wireless Ad Hoc Networks

To improve the capacity of wireless ad hoc networks by exploiting multiple available channels, we propose a distributed channel assignment protocol that is based on a cross-layer approach. By combining channel assignment with routing protocols, the proposed channel assignment protocol is shown to require fewer channels and exhibit lower communication, computation, and storage complexity than existing channel assignment schemes. A multi-channel MAC (MC-MAC) protocol that works with the proposed channel assignment protocol is also presented. We prove the correctness of the proposed channel assignment protocol. In addition, through a performance study, we show that the proposed protocol can substantially increase throughput and reduce delay in wireless ad hoc networks, compared to the IEEE 802.11 MAC protocol and an existing multi-channel scheme.

Energy efficient multi-channel media access control for dense wireless ad hoc and sensor networks

Traditional single-channel MAC protocols for wireless ad hoc and sensor networks favor energy-efficiency over throughput. More recent multi-channel MAC protocols display higher throughput but less energy efficiency. In this article we propose NAMAC, a negotiator-based multi-channel MAC protocol in which specially designated nodes called negotiators maintain the sleeping and communication schedules of nodes within their communication ranges in static wireless ad hoc and sensor networks. Negotiators facilitate the assignation of channels and coordination of communications windows, thus allowing individual nodes to sleep and save energy. We formally define the problem of finding the optimal set of negotiators (i.e., minimizing the number of selected negotiators while maximizing the coverage of the negotiators) and prove that the problem is NP-Complete. Accordingly, we propose a greedy negotiator-election algorithm as part of NAMAC. In addition, we prove the correctness of NAMAC through a rigorous model checking and analyze various characteristics of NAMAC—the throughput of NAMAC, impact of negotiators on network capacity, and storage and computational overhead. Simulation results show that NAMAC, at high network loads, consumes 36 % less energy while providing 25 % more throughput than comparable state-of-art multi-channel MAC protocols for ad hoc networks. Additionally, we propose a lightweight version of NAMAC and show that it outperforms (55 % higher throughput with 36 % less energy) state-of-art MAC protocols for wireless sensor networks.     

A survey, classification and comparative analysis of medium access control protocols for ad hoc networks

Recent technological advances in wireless communications offer new opportunities and challenges for wireless ad hoc networking. In the absence of the fixed infrastructure that characterizes traditional wireless networks, control and management of wireless ad hoc networks must be distributed across the nodes, thus requiring carefully designed Medium Access Control (MAC) layer protocols. In this article we survey, classify, and analyze 34 MAC layer protocols for wireless ad hoc networks, ranging from industry standards to research proposals. Through this analysis, six key features emerge: (1) channel separation and access; (2) topology; (3) power; (4) transmission initiation; (5) traffic load and scalability; and (6) range. These features allow us to characterize and classify the protocols, to analyze the tradeoffs produced by different design decisions, and to assess the suitability of various design combinations for ad hoc network applications. The classification and the tradeoff analysis yield design guidelines for future wireless ad hoc network MAC layer protocols.     

Power-Controlled MAC Protocols with Dynamic Neighbor Prediction for Ad hoc Networks

1　IntroductionMobileadhocnetworksareasetofmobilenodeswhichformandself configurethenetworkwithoutthepre deployedcentraladministrativein frastructure (e.g .thebasestationofWLAN) .Thedemandforadhocnetworkshasbeenbloominginthepastyearsinthecommercialandmilitaryappli cations ,becauseonlyadhocnetworkscanbeappliedinthesituationswherethecentraladministrativein frastructurecan tbe pre installed (e .g .battlefields,disasterrescue)orisnoteconomicaltoinstallbecauseoftemporaryuse (e .g .ameetingintherent…     

Design and performance of an enhanced IEEE 802.11 MAC protocol for multihop coverage extension

Ad hoc communication is gaining popularity, not only for pure ad hoc communication networks but also as a viable solution for coverage extension in wireless networks. Especially for upcoming WLAN hotspots, this is an interesting option to decrease installation costs. In this article we introduce a new MAC protocol that needs only marginal changes to the standard and enables efficient multihop networking. We advocate the use of multiple IEEE 802.11 channels, where one channel is reserved as a common signalling channel for the task of assigning the others (data channels) among wireless terminals. The proposed MAC protocols are based on a four-way handshake over the common signalling channel, while data transmission occurs on a dedicated channel. We propose a further optimization applying multiple wireless network interface cards. This improvement in performance comes at the price of a slightly more complex hardware. Two different simulation models are implemented to investigate our approach. The first model investigates the MAC protocol and its improvements, while the second model analyzes the multihop performance in terms of delivery ratio and transmission delay. BY means of numerous simulations we present the performance of our MAC approach in comparison with two standard approaches in terms of bandwidth, packet delivery, and transmission delay. For our performance evaluation we apply the IEEE 802.11a technology, but we note that our approach can also be used for IEEE 802.11b.     

Does the IEEE 802.11 MAC protocol work well in multihop wireless adhoc networks?

The IEEE 802.11 MAC protocol is the standard for wireless LANs; it is widely used in testbeds and simulations for wireless multihop ad hoc networks. However, this protocol was not designed for multihop networks. Although it can support some ad hoc network architecture, it is not intended to support the wireless mobile ad hoc network, in which multihop connectivity is one of the most prominent features. In this article we focus on the following question: can the IEEE 802.11 MAC protocol function well in multihop networks? By presenting several serious problems encountered in an IEEE 802.11-based multihop network and revealing the in-depth cause of these problems, we conclude that the current version of this wireless LAN protocol does not function well in multihop ad hoc networks. We thus doubt whether the WaveLAN-based system is workable as a mobile ad hoc testbed