Adaptive mobile access protocol (AMAP) for the message service of a land mobile satellite experiment (MSAT-X)

This paper describes a feasibility study of the adaptive mobile access protocol (AMAP) for MSAT-X, a proposed experimental mobile satellite communication network. The mobiles are dispersed over a wide geographical area and the channel data rate is limited due to the size and cost limitations of mobile antennas. AMAP is a reservation based multiple-access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple-access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize system performance. It has been shown that if messages are generated at a rate of one message per hour, AMAP can support approximately 2000 active users per 2400 bit/s channel with an average delay of 1.4 s.     

Adaptive Mobile Access Protocol (AMAP) for the Message Service of a Land Mobile Satellite Experiment (MSAT-X)

This paper describes a feasibility study of the adaptive mobile access protocol (AMAP) for MSAT-X, a proposed experimental mobile satellite communication network. The mobiles are dispersed over a wide geographical area and the channel data rate is limited due to the size and cost limitations of mobile antennas. AMAP is a reservation based multiple-access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple-access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize system performance. It has been shown that if messages are generated at a rate of one message per hour, AMAP can support approximately 2000 active users per 2400 bit/s channel with an average delay of 1.4 s.     

Spread‐spectrum CDMA packet radio MAC protocol using channel overload detection and blocking

An analytical and simulation performance evaluation is presented for a multi‐access protocol for a data packet radio network with a limited user capacity. The network employs direct‐sequence code division multiple access (DS‐CDMA) in a centralised channel load‐sensing scheme with channel overload (collision) detection and blocking via a separate ancillary channel state information broadcast system. Traffic models that incorporate both a finite population and an infinite population and variable length data messages are considered. Results show that an improved throughput/delay performance can be obtained by implementing a channel overload detection (message dropping) scheme as well as a channel overload avoidance (message blocking) scheme. The channel overload threshold β is fixed at the system's maximum user capacity whereas it is shown that the overload avoidance blocking threshold α should be variable and dependent on the mean message arrival rate. This revised version was published online in July 2006 with corrections to the Cover Date.     

量子消息认证协议

研究了在量子信道上实现经典消息和量子消息认证的方法。给出了一个基于量子单向函数的非交互式经典消息认证加密协议。证明了给出的协议既是一个安全的加密方案,也是一个安全的认证方案。利用该认证加密协议作为子协议,构造了一个量子消息认证方案,并证明了其安全性。与BARNUM等给出的认证方案相比,该方案缩减了通信双方共享密钥的数量。     

一种抗阻断攻击的多方密钥协商协议

 一个非认证的多方密钥协商协议不能对通信参与方和消息进行认证,它必须依赖认证的网络信道或其他的认证方法.分析了Horng在认证广播信道下提出的高效多方密钥协商协议,指出它不能抵抗内部恶意参与方发起的密钥协商阻断攻击,该攻击导致通信的其他诚实参与方不能正确计算出相同的共享密钥.提出了一种安全的多方密钥协商协议,在Horng协议中加入了消息正确性的认证方法,能够检测出组内恶意参与方,并在随机预言模型下证明了提出的协议能够抵抗密钥协商阻断攻击.     

The SRUC Protocol for Satellite Packet Communication--A Performance Analysis

SRUC is an adaptive multiple access protocol which combines the slotted ALOHA protocol and a reservation protocol; it switches from one to the other according to the state of the channel. This paper studies SRUC with a go-back-NARQ scheme (SRUC/GBN) in a satellite communication environment to improve the performance over SRUC with a stop-and-wait ARQ scheme (SRUC/SAW) previously studied. The performance of SRUC/GBN is analyzed in this paper, it is assumed that each user handles one message at a time and that the number of packets in a message is geometrically distributed. An approximate Markovian model for SRUC/GBN is developed which has a multidimensional state vector. The model is analyzed by the technique of equilibrium point analysis. The throughput and average message delay performance is derived. Numerical results from both analysis and simulation are given. The performance of SRUC/GBN is also compared with that of SRUC/SAW and other multiple access protocols.     

Performance analysis of the distributed queuing collision avoidance (DQCA) protocol with link adaptation

DQCA is a near-optimum Medium Access Control (MAC) protocol designed for Wireless Local Access Networks (WLANs). The protocol operates as a random access scheme under low traffic load and switches smoothly and automatically to a reservation scheme as the traffic grows. The inherent feedback mechanism of DQCA facilitates the implementation of a link adaptation algorithm that properly selects the best transmission rate taking into account the state of the wireless channel. This paper presents an analytical model for the evaluation of the performance in terms of throughput and mean message delay in the presence of a time-variant channel response.     

Voice and data integration in the air-interface of a microcellularmobile communication system

A multiple-access protocol and a call acceptance algorithm for voice and data integration in a microcellular mobile communication system are presented. The protocol supports circuit-mode voice, burst-mode voice, and data. A hybrid multiplexing scheme with no boundaries performs statistical multiplexing, the call-level (for circuit-mode voice) and the talkspurt/message-level (for burst-mode voice and data). This scheme achieves high utilization of the available bandwidth compared to pure circuit switching, but with a lower quality in the latter two classes, due to delay during channel access on each talkspurt/message. A two-party transaction model for each class is implemented, giving a realistic load on uplink and downlink. A unified access procedure is presented, and the structure of the required control bursts is described. Performance is analyzed using simulation, and the optimum data-segment size is obtained. The maximum acceptable load is determined for various traffic mixes. A call acceptance algorithm is implemented, and typical simulation results for delay and call blocking are given     

Cellular communication schemes using generalized fixed channel assignment and collision type request channels

Schemes for accessing the message channels of base stations in a cellular communication system are considered. Detailed analysis is given for a fixed channel assignment scheme with collision type request channels. The probability Pfthat a request fails to secure a message channel is considered as a performance criterion. That fraction of bandwidth allocated to request channels, which minimizes the failure probability Pf, is determined as well as the optimum Pf. Both are plotted as a function of bandwidth utilization S. Sensitivity of system performance to various parameters is considered. A new fixed channel assignment (FCA) scheme, in which a user can be served by any of the nearest k base stations, has been considered and compared with the standard (k = 1) FCA scheme. A mixed scheme with two message types has also been considered. One message type can be served by any of the nearest three base stations but the other type can be served only by the nearest.     

On Multiple Traffic Type Integration over Wireless TDMA Channels with Adjustable Request Bandwidth

A new medium access control (MAC) protocol for mobile wireless communications is presented and investigated. We explore, via an extensive simulation study, the performance of the protocol when integrating voice, video and data packet traffic over a wireless channel of high capacity (referring to an indoor microcellular environment). Depending on the number of video users admitted into the system, our protocol varies: a) the request bandwidth dedicated to resolving the voice users contention, and b) the probability with which the base station grants information slots to voice users, in order to preserve full priority for video traffic. We evaluate the maximum voice capacity and mean access delay, as well as the aggregate channel throughput, for various voice and video load conditions, and the maximum voice capacity, aggregate channel throughput and average data message delays, for various video, voice and data load conditions. As proven by the comparison with a recently introduced efficient MAC scheme (DPRMA), when integrating voice and video traffic our scheme obtains higher voice capacity and aggregate channel throughput. When integrating all three traffic types, our scheme achieves high aggregate channel throughput in all cases of traffic load.     

Performance Evaluation of an Integrated Access Scheme in a Satellite Communication Channel

A method for realizing a circuit and packet integrated access scheme in a satellite communication channel is considered. Two kinds of terminals are assumed, namely, bursty terminals for handling bursty traffic and heavily loaded terminals for long-holdingtime message traffic. In this method, the channel frame is divided into two subframes: one is for bursty terminals, and the other is for heavily loaded terminals. The subframe for heavily loaded terminals is further divided into two subchannels, a reservation subchannel (consisting of small slots) and a message subchannel. The bursty terminals transmit their packets in their dedicated subframes on the slotted ALOHA protocol. The heavily loaded terminal having a message transmits, first of all, a reservation packet in a randomly selected small slot of the reservation subchannel to reserve slots in the coming message subchannels. One slot in the same position of each of the succeeding message subchannels is reserved for the terminal until the end-of-use flag, transmitted from the terminal, is received by the satellite. Mean transmission delays for both kinds of traffic in this method are analytically obtained. We show that there exists an optimal frame length which minimizes mean transmission delay for one kind of traffic while keeping mean transmission delay for the other kind under some permissible value.     

Group random-access disciplines for multi-access broadcast channels

A group random-access (GILA) control discipline for a multi-access communication channel is presented and studied. A GILA scheme uses only certain channel time periods to allow some network terminals to transmit their information-bearing packets on a random-access basis. The channel can thus be utilized at other times to grant access to other terminals or other message types, by applying as appropriate group random-access, reservation, or fixed access-control procedures. GILA schemes could also be utilized to provide channel access to various network protocol packets. The average packet delay under a GRA discipline is evaluated by a Markov ratio limit theorem. To stabilize the channel, the GRA procedure is controlled dynamically by a control policy that rejects any newly arriving packets within certain time periods. Studying the associated Markov decision problem, the optimal control policy is characterized as yielding a minimal average packet delay under a prescribed maximal packet probability of rejection. This policy is shown to be represented by a single-threshold scheme. For such a scheme, a threshold value that attains the minimum probability of rejection is shown to exist and to yield a desirable control procedure. Performance curves are presented to demonstrate the delay-throughput characteristics induced by GRA procedures.     

一种VSAT数据通信网络报文传输协议的分析

本文描述并分析了一种适用于多信道ＶＳＡＴ卫星数据通信网的报文传输协议，特别是考虑了无线信道误码率对传输协议的影响，分析表明利用Ｓ－ＲＥ－ＡＬＯＨＡ作为预订信道的多址方式及按报文占用数据信道方法可以减小报文传输延时并增加系统吞吐量。     

Industrial IEEE 802.3 networks with short delivery time for urgentmessages

Two solutions are investigated for introducing priority mechanisms in the CSMA/CD (carrier-sense multiple access with collision detection) protocol defined in the IEEE 802.3 standard to provide short delivery times for urgent messages even when the overall traffic on the channel is heavy. Thus the CSMA/CD protocol, attractive because of its low cost, also becomes suitable for a class of industrial control applications. The proposed schemes can easily be implemented by using already-available chips and boards because they are based on the dynamic management of a transmission parameter, the slot time; this feature is already present in the standard IEEE 802.3, where it is set statically when the network is configured. The first configuration considered implements a message priority scheme, where the priority level for the station can be updated at each new message transmission, varying the slot time according to the message characteristics. The second configuration introduces a fixed-station-priority mechanism which allows each node in the network to be assigned to a specific priority class     

Self-healing group key distribution with time-limited node revocation for wireless sensor networks

A novel key distribution scheme with time-limited node revocation is proposed for secure group communications in wireless sensor networks. The proposed scheme offers two important security properties: the seal-healing re-keying message distribution which features periodic one-way re-keying with implicitly authentication, efficient tolerance for the lost re-keying messages, and seamless Traffic Encryption Key (TEK) switch without disrupting ongoing data transmissions; and the time-limited dynamic node attachment and detachment, so that both forward and backward secrecy is assured by dual directional hash chains. It is shown that the communication and computation overhead of the proposed protocol is light, and the protocol is robust under poor communication channel quality and frequent group node topology change.     

An outband paging protocol for energy-efficient mobile communications

A new protocol is proposed for reducing the power consumption of battery-powered terminals in a mobile computing environment. We exploit the fact that, in a mobile data network, mobile terminals do not continuously receive data and therefore they need not continuously operate their receivers. Nevertheless, they need to check their traffic condition periodically, that is, whether there are pending data for them or not. The proposed energy-efficient protocol is based on a paging procedure wherein a dedicated channel is used to alert (page) terminals with pending traffic. Each terminal may check its traffic condition whenever it decides to by monitoring the paging channel. The protocol is evaluated through an approximated theoretical model and through computer simulation. We focus on deriving approximate formulas for the mean message delay, the message delay variance and the power consumption. It is shown that the proposed protocol can achieve considerable power saving at a cost of increased message delivery delay.     

一种无线组网中的TDMA时隙调整协议

提出了一种适于无线组网环境下传输战术消息的无中心动态分布式时隙分配协议。协议将时隙分为固定微时隙和分配微时隙,节点间通过调整分配微时隙的数量来适应节点消息量的变化,提高了信道利用率。通过分析和仿真表明该协议能够为系统提供较高的吞吐量,通过调整可以满足局部节点消息量增加时的时延要求,能够更好地适应无线组网环境传输实时消息的特点。     

Repetitive signaling using a noisy feedback channel

Several feedback coding schemes considered recently are repetitive signaling schemes. The sender retransmits the message, if necessary, on the basis of information received over the feedback channel. This paper considers a repetitive signaling scheme in which the user's estimate of the transmitted message is sent over the feedback channel to the sender with high energy if the user is uncertain of the estimate and with lower energy if otherwise. The sender retransmits the message with high energy if it decides the user's estimate is incorrect. This scheme is applied to a wide-band, additive-white-Gaussian-noise, average-power-constrained feedback communication system. Orthogonal signals are used for transmission over both forward and feedback channels. A lower bound is obtained for the probability of error when arbitrary decision rules are used. This lower bound is achieved asymptotically for long block duration by using decision rules implemented with correlation receivers. The resulting asymptotic error performance is superior to that of any feedback coding scheme previously considered for use in a wide-band additive-white-Gaussian-noise system for any values of the forward and feedback channel capacities.     

一种利用信道侦听的动态TDMA协议

针对TDMA网络节点间业务量不均匀时,会造成信道资源严重浪费的情况,提出了一种利用信道侦听的CS-TDMA协议。该协议在TDMA协议的基础上,节点通过接收到各节点的数据包数量估算相应节点的业务量大小。当某节点时隙剩余时,向其统计中业务量最大的一个节点发送ATS信息,通知该节点占用剩余时隙发送数据,直至时隙结束。仿真结果表明,CS-TDMA协议较TDMA协议在传输时延、吞吐量、数据接收率上均有所提高,尤其在节点间业务量大小不均匀时,时延性能提升更加明显。     

Performance Analysis of Replication ALOHA for Fading Mobile Communications Channels

This paper describes an ALOHA random access protocol for fading communications channels. A two-state Markov model is used for the channel error process to account for the channel fading memory. The ALOHA protocol is modified to send multiple contiguous copies of a message at each transmission attempt. Both pure and slotted ALOHA channels are considered. The analysis is applicable to fading environments where the channel memory is .short compared to the propagation delay. It is shown that smaller delay may be achieved using replications and, in noisy conditions, can also improve throughput.