一种无线ATM网络的MAC协议

主要研究了无线ATM网络对MAC的需求，并介绍了适用于无线ATM的一种新的MAC方案。该协议支持不同类型信息传输，比如恒定比特率（CBR），可变比特率（VBR），可用比特率（ABR），未指定比特率（UBR）。另外此协议还提供了对宽带ATM主干网的无缝连接。同时也支持与ATM相关的QoS级别。对于该协议关注的各种情况的主要原理进行了讨论。     

Aggregated traffic flow weight controlled hierarchical MAC protocol for wireless sensor networks

It has been discussed in the literature that the medium-access control (MAC) protocols, which schedule periodic sleep–active states of sensor nodes, can increase the longevity of sensor networks. However, these protocols suffer from very low end-to-end throughput and increased end-to-end packet delay. How to design an energy-efficient MAC protocol that greatly minimizes the packet delay while maximizing the achievable data delivery rate, however, remains unanswered. In this paper, motivated by the many-to-one multihop traffic pattern of sensor networks and the heterogeneity in required data packet rates of different events, we propose an aggregated traffic flow weight controlled hierarchical MAC protocol (ATW-HMAC). We find that ATW-HMAC significantly decreases the packet losses due to collisions and buffer drops (i.e., mitigates the congestion), which helps to improve network throughput, energy efficiency, and end-to-end packet delay. ATW-HMAC is designed to work with both single-path and multipath routing. Our analytical analysis shows that ATW-HMAC provides weighted fair rate allocation and energy efficiency. The results of our extensive simulation, done in ns-2.30, show that ATW-HMAC outperforms S-MAC; traffic-adaptive medium access; and SC-HMAC.     

A wireless ATM MAC protocol with combined hybrid ARQ and adaptive scheduling with analysis

A combined hybrid automatic repeat request (ARQ) error control and adaptive scheduling scheme is proposed for time-division multiple access/time-division duplex medium access control (MAC) protocols in wireless asynchronous transfer mode (ATM) networks. Specifically, with the aid of proper channel modeling, the performance of various error-control schemes is evaluated. Accordingly, type-II hybrid ARQ is chosen as the error recovery scheme to combat fading effects, while adaptive fair-queueing is designed to achieve a fair and efficient resource allocation in wireless channels. In particular, the weight of a connection used in the fair-queueing algorithm dynamically adapts in terms of varying channel conditions and the types of services. Various simulations are conducted in typical indoor wireless ATM networks. It is shown that the proposed scheme can achieve a high throughput and transfer reliability with minimized delay and cell loss rate when compared with the conventional MAC layer control.     

Feedback-assisted MAC protocol for real time traffic in high rate wireless personal area networks

During the past decade, there has been much standardization effort for indoor or shot-range networks, as communication devices and applications for such networks populate. As a prominent example of these activities, the IEEE 802.15.3 Task Group (TG) published a standard for high-rate wireless personal area network (HR-WPAN). To support strictly timed multimedia services, the TG adopts a time-slotted channel access protocol controlled by a central device (DEV). Although the channel time allocation algorithm plays a key role in deciding the network performance, it remains unspecified in the standard. Therefore, in this paper, we propose a novel feedback-assisted channel time allocation method for HR-WPAN. After initial channel times are allocated based on packet inter-arrival time statistics, the allocation is dynamically adjusted by utilizing feedback information from each DEV. The feedback information includes the buffer status, the packet transmission delay, and the physical transmission rate. By utilizing this feedback information, the central DEV can allocate sufficient channel time for transmissions of pending packets from a DEV. Moreover, the allocated channel times can be synchronized to the packet arrival times so that the overall transmission delay is reduced. To cope with time-varying wireless channels, a dynamic rate selection algorithm assisted by physical layer information is proposed in this paper. Performance evaluation is carried out through extensive simulations, from which significant performance enhancements are observed.     

Delay-efficient MAC protocol with traffic differentiation and run-time parameter adaptation for energy-constrained wireless sensor networks

This paper presents an asynchronous cascading wake-up MAC protocol for heterogeneous traffic gathering in low-power wireless sensor networks. It jointly considers energy/delay optimization and switches between two modes, according to the traffic type and delay requirements. The first mode is high duty cycle, where energy is traded-off for a reduced latency in presence of realtime traffic (RT). The second mode is low duty cycle, which is used for non-realtime traffic and gives more priority to energy saving. The proposed protocol, DuoMAC, has many features. First, it quietly adjusts the wake-up of a node according to (1) its parent’s wake-up time and, (2) its estimated load. Second, it incorporates a service differentiation through an improved contention window adaptation to meet delay requirements. A comprehensive analysis is provided in the paper to investigate the effectiveness of the proposed protocol in comparison with some state-of-the-art energy-delay efficient duty-cycled MAC protocols, namely DMAC, LL-MAC, and Diff-MAC. The network lifetime and the maximum end-to-end packet latency are adequately modeled, and numerically analyzed. The results show that LL-MAC has the best performance in terms of energy saving, while DuoMAC outperforms all the protocols in terms of delay reduction. To balance the delay/energy objectives, a runtime parameter adaptation mechanism has been integrated to DuoMAC. The mechanism relies on a constrained optimization problem with energy minimization in the objective function, constrained by the delay required for RT. The proposed protocol has been implemented on real motes using MicaZ and TinyOS. Experimental results show that the protocol clearly outperforms LL-MAC in terms of latency reduction, and more importantly, that the runtime parameter adaptation provides additional reduction of the latency while further decreasing the energy cost.     

Dynamic reservation TDMA protocol for wireless ATM networks

A dynamic reservation time division multiple access (DR-TDMA) control protocol that extends the capabilities of asynchronous transfer mode (ATM) networks over the wireless channel is proposed in this paper. DR-TDMA combines the advantages of distributed access and centralized control for transporting constant bit rate (CBR), variable bit rate (VBR), and available bit rate (ABR) traffic efficiently over a wireless channel. The contention slots access for reservation requests is governed by the framed pseudo-Bayesian priority (FPBP) Aloha protocol that provides different access priorities to the control packets in order to improve the quality-of-service (QoS) offered to time sensitive connections. DR-TDMA also features a novel integrated resource allocation algorithm that efficiently schedules terminals' reserved access to the wireless ATM channel by considering their requested bandwidth and QoS. Integration of CBR, voice, VBR, data, and control traffic over the wireless ATM channel using the proposed DR-TDMA protocol is considered in this paper. Simulation results are presented to show that the protocol respects the required QoS of each traffic category while providing a highly efficient utilization of approximately 96% for the wireless ATM channel     

Mobility management and control protocol for wireless ATM networks

The introduction of wireless ATM (WATM) in customer premises network environments necessitates the design of mobility protocols, since the existing versions of B-ISDN signaling do not support terminal mobility. Such protocols can be deployed either as extensions to the standard signaling capabilities, or as individual solutions that have little or no impact on existing infrastructures (switches, signaling software, etc.). A WATM architecture that adopts the latter approach is presented. After a discussion of the problems encountered in the integration of wireless networking and B-ISDN ATM technologies, a mobility management and control (MMC) protocol is proposed. Finally, in the framework of the proposed MMC protocol, algorithms for implementing mobility procedures (handover and registration) are described     

Priority-guaranteed MAC protocol for emerging wireless body area networks

The newly emerging wireless body area networks (WBANs) are intended to support both medical applications and consumer electronic (CE) applications. These two types of applications present diverse service requirements. To satisfy both medical and CE applications with a uniform medium access control (MAC) protocol becomes a new challenge for the WBAN. Addressing this problem, a priority-guaranteed MAC protocol is proposed in this paper. In this protocol, data channels are separated from control channels to support collision-free high data rate communication for CE applications. Priority-specific control channels are adopted to provide priority guarantee to life-critical medical applications. Traffic-specific data channels are deployed to improve resource efficiency and latency performance. Moreover, in order to further minimize energy consumption and access latency, an asynchronous wakeup trigger mode is proposed as an enhancement to the priority traffic. Monte Carlo simulations are carried out for performance evaluation. As compared with IEEE 802.15.4 MAC and its improved versions, the priority-guaranteed MAC demonstrates significant improvements on throughput and energy efficiency with a tolerable penalty on latency performance of bursty traffic in CE applications. Therefore, the customized priority-guaranteed MAC satisfies the service requirements of WBAN by making tradeoff among the performances of different applications.     

Novel MAC protocol for terahertz ultra-high data-rate wireless networks

Due to having a large bandwidth to support Gbps-level data rate, terahertz communication attracts more and more attention in recent years. However, there are few medium access control （MAC） protocols for terahertz ultra-high data-rate wireless networks, which affects the research and application of terahertz communications. To address this problem and to achieve ultra-high data-rate wireless access with terahertz communication, a novel MAC protocol, called medium access control for terahertz communication （MAC-TC）, is proposed. Through designing a new channel access scheme, a new superframe structure, and related key parameters, MAC-TC can support a maximum data rate up to 10 Gbit/s even higher. Theoretical analysis and simulation results show that our proposed MAC protocol realizes the function of medium access control and attains a maximum data rate of 18.3 Gbit/s, which is 2 times higher than 5.78 Gbit/s, the theoretical maximum data rate of IEEE 802.15.3c standard.     

一种基于预约的无线传感器网络MAC协议

无线传感器网络要求的能量高效,低延时,使得MAC协议的设计充满挑战。近来已经提出了很多基于簇的MAC协议,为减少冲突在簇内部采用TDMA方式来协调簇内各个节点的传输。提出了一种在采用簇结构的基础上,使用预约方式来发送数据的R-MAC（Reservation-MAC）协议。当争用节点少的时候,采用随机争用方式来预约数据的发送;在争用节点多的时候,采用时隙争用方式来预约数据的发送。分析表明,R-MAC能够有效地降低能耗和减少延迟。     

An efficient packet sensing MAC protocol for wireless networks

The Group Allocation Multiple Access with Packet-Sensing (GAMA-PS) protocol for scheduling real-time and datagram traffic in a wireless LAN is specified and analyzed. By maintaining a dynamically-sized cycle that changes in length depending on the amount of network traffic, GAMA-PS is able to efficiently control channel access while ensuring that there are no collisions of data packets. Each cycle contains a contention period and a group-transmission period; a station with data to send competes for membership in the “transmission group” by using packet sensing to successfully complete an RTS/CTS message exchange during the contention period. Once a station is a member of the transmission group, it is able to transmit a collision-free data packet during each cycle; as long as a station has data to send, it maintains its position in the group. This revised version was published online in June 2006 with corrections to the Cover Date.     

A multi-state Q-learning based CSMA MAC protocol for wireless networks

Due to the shared nature of wireless channels, competition among the nodes to access media is inevitable. P-persistent carrier sense multiple access (CSMA) is a medium access control scheme widely used for resource allocation in wireless environments. The probability of transmission highly affects the throughput. We model the wireless nodes as agents in a network game. The strategy of an agent is defined as the probability of transmission. Agents don’t have a priori information about the network (e.g., number of nodes, other agents strategies) and learn their optimal strategy using the historical sensory information including the number of collisions or successful transmissions. In this paper, a multi-state reinforcement learning (RL) method is designed for this purpose. The main challenge in designing an RL agent is to define the states of the environment from agent’s perspective. For this purpose, in this paper, various state representations are proposed in a multi-state Q-learning model. This leads to different agents personalities ranging from cautious agents with risk aversion to aggressive risky agents. We also propose agents with combined personalities of cautiousness and aggressiveness. The performance of the proposed Q-learning agents with different state definitions in comparison with each other and also other benchmarking agents is examined via comprehensive simulation results.     

Efficient reporting node selection-based MAC protocol for wireless sensor networks

Wireless sensor networks rely on the cooperative effort of the densely deployed sensor nodes to report the detected events. As a result, sensor observations are highly correlated in the space domain. Typically, multiple sensor nodes may report the same event. Consequently, redundant information may be transmitted by the different sensor nodes, leading thus to unnecessary energy wastage. In this paper, we investigate the relationship between the spatial correlation and the number of reporting nodes by developing a new analytical model based on the theoretical framework of the CC-MAC (correlation-based collaborative medium access control) protocol (Vuran and Akyildiz in IEEE/ACM Trans Netw 14(2): 316–32912006). We show that the reporting task can be delegated to a small subset of sensor nodes without transgressing the distortion constraint. Building on this result, a simple spatial correlation medium access control protocol is then proposed to achieve further energy conservation and faster reporting latency than CC-MAC.     

A MAC layer protocol for wireless networks with asymmetric links

We introduce AsyMAC, a MAC layer protocol for wireless networks with asymmetric links and study a protocol stack consisting of AsyMAC and the A⁴LP routing protocol. The two protocols are able to maintain connectivity where the standard IEEE 802.11 MAC protocol coupled with either AODV or OLSR routing protocols may loose connectivity. A comparative study shows that AsyMAC improves on two previously proposed protocols’ accuracy in determining the nodes to be silenced to prevent collisions.     

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.     

MC-LMAC: A multi-channel MAC protocol for wireless sensor networks

In traditional wireless sensor network (WSN) applications, energy efficiency may be considered to be the most important concern whereas utilizing bandwidth and maximizing throughput are of secondary importance. However, recent applications, such as structural health monitoring, require high amounts of data to be collected at a faster rate. We present a multi-channel MAC protocol, MC-LMAC, designed with the objective of maximizing the throughput of WSNs by coordinating transmissions over multiple frequency channels. MC-LMAC takes advantage of interference and contention-free parallel transmissions on different channels. It is based on scheduled access which eases the coordination of nodes, dynamically switching their interfaces between channels and makes the protocol operate effectively with no collisions during peak traffic. Time is slotted and each node is assigned the control over a time slot to transmit on a particular channel. We analyze the performance of MC-LMAC with extensive simulations in Glomosim. MC-LMAC exhibits significant bandwidth utilization and high throughput while ensuring an energy-efficient operation. Moreover, MC-LMAC outperforms the contention-based multi-channel MMSN protocol, a cluster-based channel assignment method, and the single-channel CSMA in terms of data delivery ratio and throughput for high data rate, moderate-size networks of 100 nodes at different densities.     

A hybrid handover protocol for local area wireless ATM networks

While handovers of voice calls in a wide area mobile environment are well understood, handovers of multi-media traffic in a local area mobile environment is still in its early stage of investigation. Unlike the public wireless networks, handovers for multi-media Wireless LANs (WLANs) have special requirements. In this paper, the problems and challenges faced in a multi-media WLAN environment are outlined and a multi-tier wireless cell clustering architecture is introduced. Design issues for multi-media handovers are specified and a fast, continuous and efficient hybrid handover protocol is proposed. The protocol is scalable and supports source and destination mobile handovers in a mutually exclusive manner. Crossover switch (CX) discovery is also introduced to support fast inter-cluster handovers with consideration given to Mobile Quality of Service (M-QoS). The resulting wireless ATM LAN exhibits a distributed mobile location management, call admission control and handover management architecture. A prototype of the proposed handover protocol is implemented into a Cambridge Fairisle ATM switch and the results of handovers for a single Mobile Host (MH) with a single on-going connection are evaluated. It was found that implementing transport mobility for a wireless ATM environment is not practical as the cell re-routing function changes the traffic characteristics and is not scalable to increasing cell rate and to the number of mobile connections. The data-link layer mobility implementation however, is found to work well. The protocol provides symmetric data disruption to traffic flows in both directions and up to seventy-five intra-cluster handovers can be supported in a second. Throughout the experiment, cells arrive in sequence with no cell loss observed during the handover, up to the capacity limit of the ATM switch. Finally, zig-zag handovers and handovers for a single MH with multiple on-going unicast connections are performed in order to evaluate the robustness and performance of the protocol under different MHs' migration and communication environment.Parts of this paper appeared in the ACM First International Conference on Mobile Computing and Networking (MOBICOM'95), Berkeley, California, November 1995 as The Design & Implementation of A Hybrid Handover Protocol For Multi-Media Wireless LANs.C-K Toh is supported by a King's College Cambridge External Research Studentship and a Cambridge Commonwealth Trust Scholarship.     

Analysis of a wireless MAC protocol with client-server traffic andcapture

We analyze an efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN). A fixed frame structure with two periods is used; one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. We consider two different types of client-server traffic models, an open-loop and a closed-loop model. In the open-loop model, a remote station can generate reservation requests for the base station whether or not it has received a response from the base station. In the closed-loop case, the remote station waits for a response before generating a new request. The performance of the MAC protocol was analyzed exactly for both the open and closed-loop traffic models and for cases in which transmission errors and a mean-value type of radio capture model are included. In addition, different policies were considered for the transmission strategy that is used by the remote stations when they attempt to make reservations. We derive exact results for the mean throughput and waiting times as well as for the queue length distributions. We also derive an approximate Markov chain to treat a case in which a fixed-position capture model is used. Several types of behavior are illustrated through the use of numerical examples