An Integrated Cluster-Based Multi-Channel MAC Protocol for Mobile Ad Hoc Networks

This paper proposes a novel joint clustering and multi-channel medium access control (MAC) protocol for mobile ad hoc networks, based on a scalable two-phase coding scheme. It employs the first-phase codes for differentiating the clusters and the second-phase codes for distinguishing the nodes in a specific cluster. The proposed protocol effectively integrates the procedure of code assignment with dynamic clustering and henceforth substantially reduces the control overhead of code assignment in a code division multiple access (CDMA) based multi-channel MAC protocol while simultaneously combating the hidden terminal problem. Furthermore, the confliction detection and resolution mechanism for the allocation of the first-phase codes as well as the collision avoidance mechanism for the allocation of the second-phase codes in the control channel are also introduced. Analytical framework and extensive simulation results, in terms of control overhead and delay, are provided and compared to the traditional distributed CDMA based multichannel MAC algorithms with or without clustering.     

Location-Aware Two-Phase Coding Multi-Channel MAC Protocol (LA-TPCMMP) for MANETs

In classical code division multiple access (CDMA) based multi-channel medium access control (MAC) protocols for mobile ad hoc networks (MANETs), numerous exchanges of neighborhood information are required for code assignment such that nodes within a two-hop separation will adopt different transmission codes and therefore avoid the hidden terminal problem (HTP). However, such expensive communication overhead for code assignment is not desirable since it will cause an under-utilization of bandwidth, energy inefficiency and longer delays, which can significantly degrade the network performance. In this paper, a novel location-aware multi-channel MAC protocol is presented for a large-scale dense MANETs based on a scalable two-phase coding scheme, where the first-phase code is used for differentiating adjacent cells and the second-phase code is employed for distinguishing nodes in one specific cell. A node knows its first-phase code from its location information and requests its second-phase code from its cell leaden. This protocol eliminates the HTP during data transmission without the periodical exchange of neighborhood information. Furthermore, the mechanism of collision resolution in the control channel is described. The performance of the proposed protocol is analyzed in terms of the control overhead and delay. The theoretical results are confirmed by extensive simulations and it is shown that the new protocol significantly outperforms the classical CDMA-based multi-channel MAC protocols     

Dual busy tone multiple access (DBTMA)-a multiple access controlscheme for ad hoc networks

In ad hoc networks, the hidden- and the exposed-terminal problems can severely reduce the network capacity on the MAC layer. To address these problems, the ready-to-send and clear-to-send (RTS/CTS) dialogue has been proposed in the literature. However, MAC schemes using only the RTS/CTS dialogue cannot completely solve the hidden and the exposed terminal problems, as pure "packet sensing" MAC schemes are not safe even in fully connected networks. We propose a new MAC protocol, termed the dual busy tone multiple access (DBTMA) scheme. The operation of the DBTMA protocol is based on the RTS packet and two narrow-bandwidth, out-of-band busy tones. With the use of the RTS packet and the receive busy tone, which is set up by the receiver, our scheme completely solves the hidden- and the exposed-terminal problems. The busy tone, which is set up by the transmitter, provides protection for the RTS packets, increasing the probability of successful RTS reception and, consequently, increasing the throughput. This paper outlines the operation rules of the DBTMA scheme and analyzes its performance. Simulation results are also provided to support the analytical results. It is concluded that the DBTMA protocol is superior to other schemes that rely on the RTS/CTS dialogue on a single channel or to those that rely on a single busy tone. As a point of reference, the DBTMA scheme out-performs FAMA-NCS by 20-40% in our simulations using the network topologies borrowed from the FAMA-NCS paper. In an ad hoc network with a large coverage area, DBTMA achieves performance gain of 140% over FAMA-NCS and performance gain of 20% over RI-BTMA     

Tone Dual‐Channel MAC Protocol with Directional Antennas for Mobile Ad Hoc Networks

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual‐channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual‐channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out‐of‐band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator.     

A detailed study of a CDMA based approach to enhance ad hoc network performance

Random access schemes operate typically on a contention based common channel, which brings problems with increasing traffic load. These problems are emphasized in a multi-hop wireless ad hoc network environment. Efficient collision avoidance methods are needed, but they also tend to decrease the spatial capacity of the network. With CDMA (Code Division Multiple Access), it is possible to make multiple simultaneous co-located successful transmissions and thus increase network capacity within the limits of multiple access interference (MAI). Bi-code channel access (BCCA) is a method to apply CDMA in ad hoc networking, providing also a common access channel for network connectivity maintenance and self-configuration. With BCCA, collisions are rare, and thus, more straightforward medium access control (MAC) methods can be used. A MAC solution designed especially for BCCA (BC-MAC) and ad hoc networking increases the efficiency of the channel usage. As BCCA is based on receiver code CDMA, the spreading code of the next hop node is needed. A novel network layer spreading code distribution (NSCD) method is proposed for this purpose. The spreading codes are distributed within routing protocol control packets at the route establishment phase.A detailed study on the performance behavior of different methods is provided. Also, interesting aspects considering the ad hoc network operation are discussed. Instead of the widely used unrealistic cut propagation model, a propagation model with realistic MAI calculation is used in this study. It is shown that the use of NSCD increases the network control load only slightly, and that the performance is practically the same as it is with the assumption of known spreading codes. BCCA with its dedicated MAC and NSCD clearly outperforms commonly used methods (like IEEE 802.11) and yet is easy to implement, robust for design parameters under different conditions while maintaining the original idea of ad hoc networking.     

A cross-layer scheme for medium access control with QoS guaranteeing for Ad hoc networks

1 Introduction medium access control (MAC) protocols play a crucial role in determining the performance of Ad hoc networks. However, the design of MAC protocols for Ad hoc networks has traditionally been separated from that of the physical layer. In most …     

A Novel Medium Access Control for Ad hoc Networks Based on OFDM System

1IntroductionIn Ad hoc networks , the nodes share the wirelesschannel under the control of media access control proto-col . Currently,there are two types of MAC protocolsproposedfor Ad hoc networks . The first is hand-shak-ing protocol such as IEEE 802 .11 MAC protocol[1 ~4]and MACAW[5], which controls the access procedureby exchanging the control packets among the activenodes . The secondis busy-tone protocol that introducesadditional busy tone signal to control the medium ac-cess . S…     

一种高效可靠的无人机自组网多跳TDMA协议

设计无人机自组网媒体接入控制(Medium Access Control,MAC)协议时,需要考虑其控制开销和数据传输的可靠性。鉴于此,结合现有无线自组网多跳时分多址接入(Time Division Multiple Access,TDMA)协议和无人机自组网特点,提出了一种高效可靠的无人机自组网多跳TDMA协议。首先采用高效负载均衡的时隙请求信息上传机制,选择一个负载较小的节点转发节点时隙请求信息;然后根据相互通信的父节点删除重复节点的时隙请求信息,减少相同节点的时隙请求信息转发次数;最后通过实时更新节点时隙请求信息机制,提高节点时隙请求信息传输的可靠性。仿真结果表明,该协议在数据传输成功率、平均时延、控制开销方面优于现有协议,可较好地应用在无人机自组网中。     

A Hybrid Token-CDMA MAC Protocol for Wireless Ad Hoc Networks

Token-passing medium access control (MAC) protocols are gaining interest among wireless ad hoc network researchers as they provide unrivaled advantages over the existing IEEE 802.11 standards. This paper introduces a hybrid token-code division multiple access (CDMA) MAC protocol that is based on a token-passing scheme with the incorporation of CDMA. With its unique CDMA feature, the proposed MAC is able to support multiple simultaneous transmissions. The proposed protocol provides both quality of service (QoS) and high network resource utilization while ensuring the stability of the network. This paper examines the performance of the proposed MAC scheme by simulation and compares its performance against that of other MAC protocols that have appeared in the literature. Simulation results demonstrate that our proposed MAC scheme is effective in decreasing the packet delay and significantly shortens the length of the queue. The input traffic model used in the simulation is a two-state Markov-Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multilayered Gilbert-Elliot model.     

Hybrid Dynamic Channel Assignment in Clustered Wireless Multihop CDMA/TDMA Ad Hoc Networks

A good channel assignment scheme in a multihop ad hoc network should not only guarantee successful data transmissions without collisions, but also enhance the channel spatial reuse to maximize the system throughput. It becomes very inefficient to use fixed channel assignment when the network size grows. Therefore, spatial reuse of channels become more important in a large multihop ad hoc network. In this paper, we consider an ad hoc network with an overlaid CDMA/TDMA structure. We divide each code into time slots to form the channels. A dynamic channel assignment (DCA) strategy called Hybrid-DCA is proposed in a clustered ad hoc network. This DCA strategy is designed to make the best use of available channels by taking advantage of the spatial reuse concept. In Hybrid-DCA, the increase in spatial reuse is achieved by adding certain control overhead. We show that the bandwidth saving due to channel spatial reuse is higher than the additional bandwidth spent on the control overhead.     

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.

Performance of Energy-Efficient Cooperative MAC Protocol with Power Backoff in MANETs

This paper presents an energy-efficient cooperative MAC (EECO-MAC) protocol using power control in mobile ad hoc networks. Cooperative communications improve network performance by taking full advantage of the broadcast nature of wireless channels. The power control technique improves the network lifetime by adjusting the transmission power dynamically. We propose the best partnership selection algorithm, which takes energy consumption into consideration for selection of the optimal cooperative helper to join in the transmission. Through exchanging control packets, the optimal transmission power is allocated for senders to transmit data packets to receivers. In order to enhance energy saving, space–time backoff and time–space backoff algorithms are proposed. Simulation results show that EECO-MAC consumes less energy and prolongs the network lifetime compared to IEEE 802.11 DCF and CoopMAC at the cost of delay. Performance improvement offered by our proposed protocol is apparent in congested networks where nodes have low and limited energy.     

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…     

移动自组网中联合优化设计的MAC/路由协议

文章针对节点数量多、密度大的一类移动自组网提出了一种跨层联合设计的MAC/路由协议.在MAC层上采用基于调度的信道分配算法以减少通信冲突,在网络层上结合使用表驱动路由和基于地理位置的路由来提高协议适应动态拓扑的能力,并设计了适合TDMA MAC协议的高效的消息交互机制.在OPNET仿真平台上与AODV/802.11和G...     

Inducing Multiscale Clustering Using Multistage MAC Contention in CDMA Ad Hoc Networks

This paper proposes a new principle for designing MAC protocols for CDMA-based ad hoc networks - inducing spatial clustering in contending transmitters/receivers. We first highlight the advantages of CDMA in handling quality of service (QoS) requirements, enhancing energy efficiency, and enabling spatial multiplexing of bursty traffic. Then, based on stochastic geometric models and simulation, we show how idealized contention resolution among randomly distributed nodes results in clustering of successful transmitters and receivers, in turn leading to efficient spatial reuse. This motivates the central idea of the paper which is to explicitly induce clustering among contending nodes to achieve even better spatial reuse. We propose two distributed mechanisms to realize such clustering and show substantial capacity gains over simple random access/ALOHA-like and even RTS/CTS-based protocols. We examine under what regimes such gains can be achieved, and how clustering and contention resolution mechanisms should be optimized to do so. We propose the design of ad hoc networks supporting hop-by-hop relaying on different spatial scales. By allowing nodes to relay beyond the set of nearest neighbors using varying transmission distances (scales), one can reduce the number of hops between a source and destination so as to meet end-to-end delay requirements. To that end we propose a multi-scale MAC clustering and power control mechanism to support transmissions with different ranges while achieving high spatial reuse. The considerations, analysis and simulations included in this paper suggest that the principle of inducing spatial clustering in contention has substantial promise towards achieving high spatial reuse, QoS, and energy efficiency in CDMA ad hoc networks.     

A token circulation scheme for code assignment and cooperative transmission scheduling in CDMA-based UAV ad hoc networks

Code division multiple access (CDMA) ad hoc networks have been considered a promising multiple-channel networking architecture for connecting tactical platforms in battle fields. In this paper we consider a network of a swarm of unmanned aerial vehicles (UAVs) that are used in a tactical surveillance mission. The UAVs are assumed to have multiuser detection capability and form a CDMA-based ad hoc network. A token circulation scheme is proposed to conduct functions required at the medium access control layer including detection of hidden/lost neighbors, code assignment and schedule-based cooperative transmission scheduling. In the proposed scheme, a token continuously circulates around the network based on the “receive-forward” module. Through circulation of the token, each UAV can detect its hidden and/or lost neighbors in near real-time, assign codes enabling the spatial reuse of code channels without incurring code collision, and schedule data transmissions in a cooperative and distributed manner. In addition, the proposed scheme is able to take advantage of multiuser detection functionality and allows for simultaneous transmissions from multiple transmitters to a same receiver. The performance of the proposed token circulation scheme is evaluated, both analytically and through simulations. It is shown that the latency of the token is at most linearly proportional to the network size, and the average delay of a data packet increases with either the packet generation rate or the network size. The results also show that the proposed token circulation scheme is suitable for large-scale CDMA-based UAV ad hoc networks with even heavy network traffic load.     

A dual reservation CDMA-based MAC protocol with power control for ad hoc networks

This paper proposes a new multi-channel Medium Access Control （MAC） protocol named as Dual Reservation Code Division Multiple Access （CDMA） based MAC protocol with Power Control （DRCPC）. The code channel is divided into common channel, broadcast channel and several data channels. And dynamic power control mechanism is implemented to reduce near-far interference. Compared with IEEE 802.11 Distributed Coordination Function （DCF） protocol, the results show that the proposed mechanism improves the average throughput and limits the transmission delay efficiently.     

Distributed Medium Access Control Next-Generation CDMA Wireless Networks

The next-generation wireless networks are expected to have a simple infrastructure with distributed control. In this article, we consider a generic distributed network model for future wireless multimedia communications with a code-division multiple access (CDMA) air interface. For the medium access control (MAC) of the network model, we provide an overview of recent research efforts on distributed code assignment and interference control and identify their limitations when applied in next-generation wireless networks supporting multimedia traffic. We also propose a novel distributed MAC scheme to address these limitations, where active receivers determine whether a candidate transmitter should transmit its traffic or defer its transmission to a later time. Simulation results are given to demonstrate the effectiveness of the proposed distributed MAC scheme.     

采用TDMA和CSMA混合MAC协议的时隙调整算法

由于车联网(VANET)拓扑动态变化,车辆高速移动以及不同服务质量要求,制定媒体接入控制(MAC)协议面临巨大挑战。在控制信道间隔内采用基于TDMA和CSMA的混合接入协议是最有效的MAC协议之一。基于TDMA和CSMA的混合MAC协议(T-C-MAC)能够依据车辆环境调整TDMA帧长度,并能有效地传输非安全消息。为了提高T-C-MAC协议的性能,提出了一种基于三跳邻居信息的时隙调整(THSA) 算法。通过有效地调整车辆传输时隙,基于THSA的MAC（THSA-MAC）协议能够有效地实施广播服务,提高了安全消息传输率。实验数据表明,THSA-MAC有效地提高了安全消息传递率。     

QoS guarantee and provisioning for realtime digital video over mobile ad hoc cdma networks with cross-layer design

In this article we investigate the trade-offs and the constraints for multimedia over mobile ad hoc CDMA networks, and propose a cross-layer distributed power control and scheduling protocol to resolve those trade-offs and constraints in order to provide high-quality video over wireless ad hoc CDMA networks. In particular, a distributed power control and scheduling protocol is proposed to control the incurred delay of video streaming over multihop wireless ad hoc networks, as well as the multiple access interference (MAI). We also investigate the impacts of Doppler spread and noisy channel estimates upon the end-to-end video quality, and provide a relatively robust system which employs a combination of power control and coding/interleaving to combat the effects of Doppler spread by exploiting the increased time diversity when the Doppler spread becomes large. Thus, more robust end-to-end video quality can be achieved over a wide range of channel conditions