太赫兹无线局域网MAC协议优化设计

针对现有太赫兹无线网络MAC(Medium Access Control)协议中存在的无线局域网场景下原有波束赋形方案不适用、关联请求时段在新入网节点数量受限情况下时隙利用率低,以及网络流量较大时扇区号靠后的节点一直无法获得时隙导致时延陡增的情况,提出了一种适用于无线局域网的高效低时延太赫兹MAC协议(High Efficiency and Low Latency Terahertz MAC,HELL-MAC)。该协议利用中心控制节点与普通节点间的信息交互减少了不必要的波束赋形过程,采用机会性复用关联S-CAP(Sub-channel Access Period)机制提高了时隙利用率,采用公平时隙分配机制提高了时隙分配的公平性,从而减少了波束赋形时间,降低了平均端到端时延,提高了信道利用率。     

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division multiple access (TDMA) slot assignment protocol (ATSA) for vehicular ad-hoc networks. ATSA divides different sets of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks (VeMAC) and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.     

多跳Ad Hoc网络中支持MIMO的分布式拓扑未知时分多址接入协议的研究与分析

针对Ad Hoc网络和MIMO的有效结合,提出了适于多跳Ad Hoc网络的支持MIMO的分布式拓扑未知时分多址接入协议.该协议通过有限域无线网络设计算法在每帧给每个节点分配时隙且无需知道全网拓扑信息,这极大地减小了收集全网拓扑信息的开销.通过预约,每个节点在其分配的无干扰时隙并行发送MIMO链路的所有数据流,并在与其他节点共享的时隙发送MIMO链路的一部份数据流来解决传输冲突.同时推导出保证通过率和最佳帧长.结果显示动态分配MIMO的传输容量和抗干扰能力会极大地提高通过率.     

Performance Analysis of a Bandwidth Guaranteed Medium Access Control Protocol for WDM Local Networks

In this paper, we propose and analyze a bandwidth guaranteed medium access control protocol for broadcast-and-select WDM local networks with a star topology. The proposed protocol is based on a combination of contention and dedicated reservation mechanisms for time slotted WDM networks. Every node accesses the data channel by transmitting request packets in minislots on a separate control channel. There are two types of minislots; dedicated minislots and contention minislots. Nodes requiring bandwidth guarantees, called guaranteed nodes, use dedicated minislots that are assigned by the centralized control node. The remaining nodes, called random-access nodes, share contention minislots using a distributed random access mechanism. The dedicated minislots can guarantee a minimum bandwidth for the guaranteed nodes. The contention minislots enable on-demand services at the optical layer and achieve good fairness for the remaining bandwidth. Here, the data channels are dynamically assigned to the minislots successfully returned on a first-come-first-served (FCFS) basis. This protocol can combine the best of centralized and distributed access protocols such as simplicity, efficiency, and flexibility. We analyze the maximum throughput and verify the results by simulation.     

Reduced‐frame TDMA protocols for wireless sensor networks

Time‐division multiple‐access (TDMA) is a common medium access control paradigm in wireless sensor networks. However, in its traditional form, the TDMA‐based protocols suffer from low channel utilization and high message delay because of a long frame length needed to provide collision‐free transmissions, which is particularly damaging in dense wireless sensor networks. In this paper, we investigate the performance and the energy efficiency of a class of TDMA‐based protocols, called reduced‐frame TDMA, where every TDMA slot is augmented with a short time period dedicated for carrier sense multiple access‐based contention resolution mechanism. Because of their ability to dynamically resolve collisions caused by conflicting slot assignments, the reduced‐frame TDMA protocols can be configured with any frame length, independently of node density. In addition, we present a distributed heuristic slot assignment algorithm that minimizes interslot interference in the presence of limited number of slots per frame. The simulation results indicate that the reduced‐frame TDMA protocols significantly reduce the message delay and increase the maximum throughput without incurring significant penalty in energy efficiency compared with the traditional TDMA scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

A Five-Phase Reservation Protocol (FPRP) for Mobile Ad Hoc Networks

A new single channel, time division multiple access (TDMA)-based broadcast scheduling protocol, termed the Five-Phase Reservation Protocol (FPRP), is presented for mobile ad hoc networks. The protocol jointly and simultaneously performs the tasks of channel access and node broadcast scheduling. The protocol allows nodes to make reservations within TDMA broadcast schedules. It employs a contention-based mechanism with which nodes compete with each other to acquire TDMA slots. The FPRP is free of the hidden terminal problem, and is designed such that reservations can be made quickly and efficiently with negligible probability of conflict. It is fully-distributed and parallel (a reservation is made through a localized conversation between nodes in a 2-hop neighborhood), and is thus scalable. A multihop ALOHA policy is developed to support the FPRP. This policy uses a multihop, pseudo-Bayesian algorithm to calculate contention probabilities and enable faster convergence of the reservation procedure. The performance of the protocol, measured in terms of scheduling quality, scheduling overhead and robustness in the presence of nodal mobility, has been studied via simulations. The results showed that the protocol works very well in all three aspects. Some future work and applications are also discussed.     

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 Bandwidth Reservation Multiple Access Protocol for Wireless ATM Local Networks

A bandwidth reservation multiple access scheme(BRMA) is proposed to resolve contention and assignbandwidth among multiple users trying to gain access toa common channel such as in mobile users contending for resources in an ATM-based cellular networkor a wireless local area network (LAN) with shortpropagation delays. The protocol is best suited tosupport variable-bit-rate (VBR) traffic that exhibits high temporal fluctuations. Each mobile user isconnected end-to-end to another user over virtualchannels via the base station that is connected to thewired ATM B-ISDN network. The channel capacity is modeled as a time frame with a fixed duration.Each frame starts with minislots, to resolve contentionand reserve bandwidth, followed by data-transmissionslots. Every contending user places a request for data slots in one of the minislots. If therequest is granted by the base station through adownlink broadcast channel, the user then startstransmission in the assigned slot(s). The number ofassigned slots varies according to the required qualityof service (QoS), such as delay and packet lossprobability. A speech activity detector is utilized inorder to indicate the talkspurts to avoid wastingbandwidth. Due to its asynchronous nature, BRMA is ratherinsensitive to the burstiness of the traffic. Since theassignment of the minislots is deterministic, therequest channels are contention-free and the data channels are collision-free. Hence, in spite ofthe overhead (minislots) in each frame, BRMA provideshigher throughput than Packet Reservation MultipleAccess (PRMA) for the same QoS, especially for high-speed systems. A better delay performance is alsoachieved for data traffic compared to Slotted Alohareservation-type protocol PRMA. In addition, BRMAperforms better in terms of bandwidth efficiency thanthe conventional TDMA or the Dynamic TDMA, wherespeech activity detectors are very difficult toimplement.     

Carrier sense multiple access with improvised collision avoidance and short-term fairness

In this paper, we present a simple method to simultaneously enhance collision avoidance efficiency and short-term fairness of a most popular contention based medium access control protocol, carrier sense multiple access with collision avoidance. The key idea here is to adaptively tune the shape of contention slot selection distribution over the temporal contention window during ongoing collision resolution process which, in the legacy scheme, used to be flat throughout. The tuning mechanism is such designed that it not only maximizes the selection likelihood of relatively less collision prone contention slots over the contention window but also compensates the idle delay that the contending stations have suffered in their recent access attempt. Through rigorous numerical and simulation based analysis, the proposed scheme is shown to enhance the performance of a IEEE 802.11 based distributed wireless network in terms of network throughput efficiency and packet transmission delay while allowing individual stations to share the channel fairly even in short time scale.     

A dynamic ID management protocol for CSMA/IC in ad hoc networks

Contention based MAC protocols are widely used in ad hoc networks because they are suitable, where no central control node exists. However, contention based MAC protocols waste much time because of frequent collisions and long contention times. Moreover, it is hard for them to fairly distribute medium access opportunities. As a result, the problem of unfair medium access may arise under normal network conditions. Recently, another contention based MAC protocol, named the Carrier Sense Multiple Access/ID Countdown (CSMA/IC) was proposed. CSMA/IC resolves medium access contention by comparing the IDs of contending nodes with a simple signaling process. Therefore, medium access collisions never happen as long as each node possesses a unique ID, and the time cost for contention may be smaller than any other contention based MAC protocols if the number of IDs is managed so as to be as small as possible. Furthermore, CSMA/IC may support fair medium access by manipulating the ID of each node properly. In this paper, we propose a novel dynamic ID management protocol which enables a node to acquire a unique ID without any message exchanges and fairly distributed the number of medium access opportunities to all contending nodes. The proposed protocol also makes the contention process of CSMA/IC efficient by dynamically managing the length of the ID field according to the network traffic. The simulation results show that the proposed ID management protocol significantly improves the aforementioned aspects of CSMA/IC MAC protocol compared to previous ID management schemes.     

Contention free inter-cellular slot reservation

A distributed reservation protocol tailored for cellular wireless networks is presented that facilitates contention free inter-cellular slot allocation and reservation. While reserved slots are protected from inter-cell interference by a busy burst enabled reservation protocol, collisions due to simultaneously accessed unreserved slots by neighboring cells are mitigated by means of resource partitioning patterns. Shifting these partitioning patterns over time allows each cell to successively probe all slots. This ensures that full frequency reuse is maintained, in the way that all cells may utilize the entire frequency band. In effect a contention free inter-cellular slot allocation policy is established that in a distributed manner dynamically controls the spatial reuse, in terms of concurrently accessed radio resources by neighboring cells.     

Efficient QoS support in a slotted multihop WDM metro ring

A novel distributed access protocol for a slotted wavelength-division-multiplexing (WDM) metro ring employing all-optical packet switching and supporting quality-of-service (QoS) classes is presented and analyzed. Since we assume that there are more nodes than available wavelengths in the network, we obtain a scalable multihop WDM ring as underlying network architecture. By dividing each channel into several time slots and further applying destination release and slot reuse, data packets can be efficiently transmitted and received in a statistically multiplexed manner. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider so-called a posteriori access strategies, different packet selection schemes are proposed and compared. An analytical model based on the semi-Markov process methodology is developed to quantify the performance of one of these schemes. As a key element of the protocol, an efficient QoS support access mechanism is proposed and its performance is evaluated. The new QoS control scheme adopts a frame-based slot reservation strategy including connection setup and termination, which only slightly increases the signaling and node processing overhead. Thus, an efficient hybrid protocol combining connectionless and connection-oriented packet transmissions is proposed     

话音/数据综合的多时隙预约多址协议及其性能分析

本文提出了一种综合话音和数据的多时隙预约多址协议.该协议在保证话音终端的优先权的情况下,允许数据终端在报文的传输期间在连续多个帧中预约多个信息时隙.文中对协议进行了理论分析,并推导出了协议的重要性能指标(如话音分组丢失率、数据报文平均接入时延、系统平均吞吐率等)的解析表达式.研究表明,该协议可以支持比IPRMA、NC-IPRMA更高的等效数据终端速率,而且系统平均吞吐率在很大的负载范围内接近最大值.     

一种高效低时延的宽带电力线通信网多跳MAC协议

针对IEEE1901.1宽带电力线通信媒体接入控制(Medium Access Control,MAC)协议涉及到信标时隙利用不充分和控制开销过大等问题,提出了一种高效低时延的宽带电力线通信网多跳MAC协议(Efficient and Low Delay Multi-hop MAC,ELDM-MAC).采用基于节点层级...     

MIMO Ad Hoc网络中基于正交阵列的拓扑未知多址接入协议

针对支持MIMO(Multiple Input Multiple Output)的Ad Hoc网络,提出了基于正交阵列的拓扑未知多址接入协议MIMO_O_TTMA(MIMO Supported Orthogonal Array Based Topology Transparent Multiple Access).协议利用正交阵列为节点分配若干时隙,在每个分配时隙中,节点通过与目的节点交互RTS/CTS(Request To Send/Clear To Send)分组来确定发送的数据流数,以机会地利用MIMO的空间复接来提升网络性能.MIMO_O_TTMA在保证节点在一帧内至少有一个时隙能够无干扰地传输的基础上,允许协议的帧长能在一定的范围内进行灵活选择,从而为协议性能的优化提供了更为有利的条件.为评估MIMO_O_TTMA的性能,利用概率方法分析了协议的吞吐量性能,数值结果表明,与已有拓扑未知MAC(Media Access Control)相比,MIMO_O_TTMA有效提升了网络吞吐量.     

m-DIBCR: MAC Protocol with Multiple-Step Distributed In-Band Channel Reservation

A new medium access control (MAC) protocol to handle packet collisions is proposed. Different from traditional MAC protocols, where only one-step reservation is considered, we propose a multiple-step distributed in-band channel reservation, called m-DIBCR, where m represents the number of steps we consider in the channel reservation. In the protocol, each node maintains m timers, each of which serves as the backoff timer for one of the next m packets to be sent. A node broadcasts the initial values of these timers by piggybacking them in the data packet, and simultaneous transmissions can be avoided when its neighboring nodes overhear these values. Extensive simulations show that, compared with one-step channel reservation, throughput can be dramatically improved by multiple-step channel reservation, especially in networks with high transmission error probabilities and/or a large number of contending nodes.     

Integrated video and voice transmission using packet reservation multiple access

This paper proposes a new protocol for the integration of voice and video transmission over the packet reservation multiple access (PRMA) system that is a modification of reservation‐ALOHA protocol. We focus on low bit‐rate video applications like video conferencing and visual telephony for wireless communications. The ITU–T H.263 standard provides a solution to the need for low bit‐rate video compression under 64 kbytes/s. The proposed protocol assumes that each voice terminal follows a traffic pattern of talk spurts and silent gaps with fixed permission probability (p=0.3), and each video terminal has the higher permission probability (p=1) to access the available slot based on ITU–T H.263 standard. Again, we present a ‘pseudo‐reservation’ scheme to release slots reserved by video terminals according to the contents of each video transmission buffer, and the active voice terminals can temporarily access the additional slots to improve the performance without sacrificing the video capacity of the system. The packet dropping probability of the active voice terminals and bandwidth utilization of the system are superior to the original PRMA, as indicated in simulation results. Copyright © 2001 John Wiley & Sons, Ltd.     

A multiple access protocol with explicit and implicit reservation

A new version of a MAC‐level protocol is introduced and investigated, operating in a cellular environment, where a base station co‐ordinates mobile users within each cell. The channel multiplexing structure is based on time division, and the slots in each frame are dynamically assigned to the users and their service classes by the cell base station. Decisions are taken on the basis of binary channel feedback information (collision/no collision), by assuming independence in the presence of packets at the mobile stations, and aim at maximizing the one‐step throughput in the current frame. The frame is divided into two periods: the first (short) one contains a number of minislots, equal to the number of ‘real’ slots (i.e. those capable of containing a fixed size packet) of the second part. At the beginning of the frame, the access rights are computed and broadcast to the users; the enabled stations that have a packet to transmit respond, by sending a short burst that contains their ID in a minislot. This most recent feedback is used at the base station to update the parameters of the decision algorithm, which is then re‐applied to yield the final access rights for the second part of the frame. The performance of the scheme is analysed by simulation in the presence of mixed voice and data traffic, and compared with those of a reservation random access protocol using the same algorithm in a single‐phase fashion (RRA‐ISA) and PRMA. Copyright © 2001 John Wiley & Sons, Ltd.     

A schedule‐based medium access control protocol for mobile wireless sensor networks

Recent advances in body area network technologies such as radio frequency identification and ham radio, to name a few, have introduced a huge gap between the use of current wireless sensor network technologies and specific needs of some important wireless sensor network applications such as medical care, disaster relief, or emergency preparedness and response. In these types of applications, the mobility of nodes can occur, leading to the challenge of mobility handling. In this paper, we address this challenge by prioritizing transmissions of mobile nodes over static nodes. This is achieved by using shorter contention windows in reservation slots for mobile nodes (the so‐called backoff technique) combined with a novel hybrid medium access control (MAC) protocol (the so‐called versatile MAC). The proposed protocol advocates channel reuse for bandwidth efficiency and management purpose. Through extensive simulations, our protocol is compared with other MAC alternatives such as time division multiple access and IEEE 802.11 with request to send/clear to send exchange, chosen as benchmarks. The performance metrics used are bandwidth utilization, fairness of medium access, and energy consumption. The superiority of versatile MAC against the studied benchmark protocols is established with respect to these metrics. Copyright © 2012 John Wiley & Sons, Ltd.     

The RRA‐ISA multiple access protocol with and without simple priority schemes for real‐time and data traffic in wireless cellular systems

A multiple access protocol, based on a Reservation Random Access (RRA) scheme, is derived for a wireless cellular network carrying real-time and data traffic. Given a TDMA framed channel and a cellular structure, the aim of the protocol is that of maximizing the one-step throughput over an entire frame. This is achieved by deciding on the access rights at the cell base station, which then broadcasts this information at the beginning of the frame. The decision is made on the basis of binary channel feedback information (collision/no collision) over the previous frames, as well as of long term averages of packet generation rates at the mobile stations, assuming independence in the presence of packets at the latter. The resulting protocol has therefore been termed Independent Stations Algorithm (ISA), and the overall scheme RRA-ISA. As in other RRA protocols, time constrained (e.g., voice) traffic operates in a dynamic reservation mode, by contending for a slot in the frame with the first packet of a burst, and then keeping the eventually accessed slot for the duration of the burst; packets of the time constrained traffic unable to access a slot within a maximum delay are dropped from the input buffer. No such constraint is imposed on data traffic. Together with the “basic” version of the access algorithm, three other variants are presented, which exploit three simple different priority schemes in the RRA-ISA “basic” structure, in order to give a prominence to the voice service. The aim of these variants is to improve the performance in terms of the maximum number of stations acceptable in the system, by slightly increasing the data packets delay. All the proposed schemes are analyzed by simulation in the presence of voice and data traffic. Several comparisons show a relevant performance improvement (in terms of data delay and maximum number of voice stations acceptable within a cell) over other protocols that use ALOHA as a reservation mechanism (RRA-ALOHA or PRMA schemes). This revised version was published online in June 2006 with corrections to the Cover Date.