Performance of Double-Tier Access-Control Schemes Using a Polling Backbone for Metropolitan and Interconnected Communication Networks

We consider a double-tier communication network architecture for metropolitan area and packet radio networks for controlling the access of network terminals into a single shared broadcast channel. Terminals are organized into local groups in accordance with their geographical proximity or other criteria. Each local group can be associated with a primary station. The latter can serve as an unbuffered repeater for terminal transmissions unto the multiple-access channel. A polling policy is used by the primary stations to gain access into the shared communications backbone. Once a primary station is provided access into the channel, it initiates a local access control procedure. Message delay performance results and bounds are obtained for general reservation local-access procedures. In particular, we analyze and present performance results for a polling/tree-random-access procedure which can be effectively used for many packet radio and cellular digital radio networks, as well as for a polling/positionalpriority scheme for CATV and fiber-optic based networks.     

Idle-signal casting multiple access with collision detection (ICMA-CD) for land mobile radio

A population of mobile terminals communicating with a central station over a packet-switched multiple-access radio channel is investigated. In land mobile radio communication, in which terminals cannot sense the carrier transmitted from other terminals (either because they are out-of-range or obstructed), a central controlled multiple access system in which a central station broadcasts idle/busy information of the access channel is used for multiplexing the packets from the terminals. Idle-signal casting multiple access (ICMA), which is a practical application of this central controlled system, has been used in the Nippon Telegraph and Telephone Public Corp. (NTT) mobile phone system for some years. ICMA-CD, which is an advanced ICMA scheme characterized by collision detection and evaluates its improved throughput, channel capacity and loss probability in a mobile radio fading environment with restrictions on retransmission, is proposed. It is clarified that ICMA-CD is suitable for the mobile multiple access scheme, especially in the case where packet detection delay and collision recovery time are short and offered traffic is heavy.     

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.     

BRAM: The Broadcast Recognizing Access Method

In this paper, we first present the broadcast recognizing access method (BRAM), an access protocol suitable for regulating internode communication in either a radio or (coaxial or fiber) cable based communication system. The method avoids collisions, imposes negligible computational requirements on the nodes attempting to transmit, and is fair in the sense that no node will be indefinitely prevented from transmitting. Next we introduce parametric BRAM which attempts to balance the length of inserted channel idle periods, resulting from scheduling effects, against the probability of allowed message collisions. We show that parametric BRAM can be used to realize a method which balances inserted channel idle time against the probability of message collision to yield enhanced performance. For high message loads, parametric BRAM converges to BRAM, while for low and medium loadings it yields throughputs in excess of BRAM, and other methods. Both BRAM and parametric BRAM are discussed under the assumption of homogeneous message arrival rates at the nodes. We conclude by showing how the parametric BRAM can be applied when the nodes operate with heterogeneous or mixed message arrival rates.     

Packet Switching in Radio Channels: Part I--Carrier Sense Multiple-Access Modes and Their Throughput-Delay Characteristics

Radio communication is considered as a method for providing remote terminal access to computers. Digital byte streams from each terminal are partitioned into packets (blocks) and transmitted in a burst mode over a shared radio channel. When many terminals operate in this fashion, transmissions may conflict with and destroy each other. A means for controlling this is for the terminal to sense the presence of other transmissions; this leads to a new method for multiplexing in a packet radio environment: carrier sense multiple access (CSMA). Two protocols are described for CSMA and their throughput-delay characteristics are given. These results show the large advantage CSMA provides as compared to the random ALOHA access modes.     

Secrecy Capacities for Multiterminal Channel Models

Shannon-theoretic secret key generation by several parties is considered for models in which a secure noisy channel with one input terminal and multiple output terminals and a public noiseless channel of unlimited capacity are available for accomplishing this goal. The secret key is generated for a set A of terminals of the noisy channel, with the remaining terminals (if any) cooperating in this task through their public communication. Single-letter characterizations of secrecy capacities are obtained for models in which secrecy is required from an eavesdropper that observes only the public communication and perhaps also a set of terminals disjoint from A. These capacities are shown to be achievable with noninteractive public communication, the channel input terminal sending no public message and each output terminal sending at most one public message, not using randomization. Moreover, when the input terminal belongs to the set A, it can generate the secret key at the outset and transmit it over the noisy channel, suitably encoded, whereupon the output terminals in A securely recover this key using public communication as above. For models in which the eavesdropper also possesses side information that is not available to any of the terminals cooperating in secrecy generation, an upper bound for the secrecy capacity and a sufficient condition for its tightness are given.     

Design and performance evaluation of a MAC protocol for wireless local area networks

We propose and analyze, from a performance viewpoint, a Medium Access Control (MAC) protocol for Wireless Local Area Networks (WLANs). The protocol, named Prioritized-Access with Centralized-Control (PACC), supports integrated traffics by guaranteeing an almost complete utilization of network resources. The proposed protocol combines random access for signalling, with collision-free access to the transmission channel. The transmission channel is assumed to be slotted, with slots grouped into frames. Access to transmission slots is controlled by a centralized scheduler which manages a multiclass queue containing the users' requests to access the transmission channel. Three classes of users are assumed: voice traffic (voice), data traffic with real-time constraints (high-priority data), and classical data traffic (low-priority data). A priority mechanism ensures that speech users have the highest priority in accessing the idle slots, since speech packets have a more demanding delay constraint. The remaining channel bandwidth is shared fairly among the high-priority data terminals. The low-priority data terminals use the slots left empty by the other classes. Specifically, access to transmission slots is controlled by the centralized scheduler by managing a transmission cycle for each class of terminals. The voice-terminals cycle has a constant length equal to one frame, while the lengths of the data-terminals cycles are random variables which depend on the number of active voice and data terminals. In this paper we show that the proposed scheme can support the same maximum number of voice terminals as an ideal scheduler, while guaranteeing an almost complete utilization of network capacity. In addition, via a performance analysis, we verify that by limiting the number of real-time data terminals in the network this class of traffic can be statistically guaranteed access delays in the order of 200–300 msec. Hence, the QoS the network gives to the real-time data terminals makes this service suitable for real-time applications such as alarms or low bit rate video. This revised version was published online in June 2006 with corrections to the Cover Date.     

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     

Integrated alerting and system broadcast channel for a wirelessaccess system

A protocol is described which allows a wireless access system to dynamically multiplex the alerting, system information, and priority access request subchannels on its system-wide broadcast channel. These subchannels each have different requirements with respect to the message length and position within the framing structure; the described protocol meets each of their requirements. The protocol efficiently accommodates a wide range of alerting traffic levels and provides for efficient downloading of system information to subscriber units by using excess capacity when alerting traffic is low. It provides error detection capabilities above that provided by the radio channel alone and is easily extendible to accommodate other services such as paging and low bandwidth broadcast messaging. The flexibility provided by this protocol could permit a broad range of network architectures for wireless access     

Slotted idle signal multiple access scheme for two-way centralizedwireless communication networks

We propose a random multiple access scheme named S-ISMA/CD (slotted idle signal multiple access with collision detection) for a centralized wireless communication network where upstream and downstream traffic are transmitted over separate channels. Two versions of the scheme, S-ISMA/CD1 and S-ISMA/CD2, are studied in this paper. The S-G (throughput versus offered load) performance of both schemes are evaluated. We also study the dynamic behavior of the system with finite population of terminals on the upward channel. By using EPA (equilibrium point analysis), a fluid approximation method, the throughput and delay performance is evaluated. As a result, it is shown that both schemes have high channel efficiency although S-ISMA/CD1 has a little better performance on the downward channel while S-ISMA/CD2, is easier in implementation and more reliable in operation     

Performance evaluation of preemptive polling schemes and ARQtechniques for indoor wireless networks

This paper examines a radio-based indoor communication network with a single radio channel shared by several data terminals. By enabling the terminals to communicate with each other and access the resources of a wired network, the system is a potential provider of in-building LAN-like services. In this indoor fading environment, a base-station approach is assumed. In the analysis, a two-state Markov chain model is used to model the nonstationary transmission channel. Two preemptive polling multiple-access schemes combine with ARQ error-control schemes to counteract the effects of a nonstationary transmission channel. The main idea devised is that of making the service interruption dependent on the propagation conditions of the transmission channel by monitoring the outcomes of the data packet transmission attempts. A performance comparison reveals the superiority of the preemptive polling systems with respect to a classical TDMA scheme     

WLAN中基于IEEE802.11u协议的终端节能功耗管理方案

支持IEEE 802.11u标准的移动终端在无线局域网提供的网络服务覆盖范围内可自动接入无线局域网。针对IEEE 802.11u无线局域网的特点,提出了一种基于时间序列感知的PSM（S-PSM）方案。采用IEEE 802.11u标准中定义的公共广播服务（GAS）来广播传输序列信息,所有终端根据该序列信息相应地控制自身的工作状态。为了降低竞争信道的碰撞概率,引入了响应竞争窗口。当接入点（AP）中没有数据分组时,AP 广播GAS帧并激活空闲计时器。所有终端进入睡眠状态直到空闲计时器到期。仿真结果表明,与传统的PSM相比,该方案能显著降低功耗,提升终端能效。     

Method of calculation of parameters of wireless access channel for mobile terminals in millimeter wavelength band

It is proposed a number of new technical solutions to implement the delivery of multimedia signals 4G services with data transfer rate for each subscriber 6–12 Mb/s, which move at a speed of 300–350 km/h with a total capacity of the network over a thousand subscribers. The block diagram (architecture) of transfer network in the millimeter wavelength band is developed. We derived balance equation for the network radio energy, which is the basis of the method for calculating the radio channel parameters. Examples of calculation of radio wireless access parameters to mobile terminals in the millimeter range are presented.     

Spectrum allocation method for cognitive satellite network based on service priorities

By using spectrum allocation technology of cognitive radio into integrated satellite and terrestrial networks,the satellite communication network can share spectrum with the terrestrial network and improve utilization efficiency of frequency spectrum in the satellite communication system.Firstly,a spectrum resource sharing model in integrated satellite and terrestrial networks was introduced,and the scenery that cognitive satellite downlinks use the vacant spectrum of terrestrial network was analyzed.Then,the interference and signal model was analyzed.Finally,considering different priority types of satellite terrestrial terminals,a spectrum allocation scheme based on priority was proposed,which could ensure the total throughput in satellite downlink communication and increase the throughput of high-priority terrestrial terminals.     

Message Path Delays in Packet-Switching Communication Networks

A communication path (in isolation) in a packet-switching store-and-forward communication network, such as a computer or satellite-communication network, is considered. Messages are assumed to arrive according to a Poisson stream, and messagelengths are considered to be random variables governed by an arbitrary distribution. Message lengths are divided into fixed-length packets which are sent independently over theN-channel communication path in a store-and-forward manner, and are reassembled at the destination terminal. Expressions for the distributions of the message waiting and delay times over the path are derived. Also, we obtain the limiting average message waiting times and required buffer sizes at the individual channels. The overall message waiting time is observed to depend only on the minimal channel capacity. The case of exponentially distributed message lengths serves as an illustrating example.     

On a Self-Adjusting Capability of Random Access Networks

We consider a distributed communication network with many terminals which are distributed in space and wish to communicate with each other using a common radio channel. Choosing the transmission range in such a network involves the following tradeoff: a long range enables messages to reach their destinations in a few hops, but increases the amount of traffic competing for the channel at every point. We give a simple model for the per-hop delay in random access networks, analyze this tradeoff, and give the optimal transmission range. When choosing this optimal range, as a function of specified traffic and delay parameters, networks demonstrate an important self-adjusting capability. This capability to adjust to traffic makes heavily loaded networks far better than centralized systems (in which all messages must reach one common destination). Dividing a terminal population into power groups can improve any random access system, especially when the traffic is split between groups in an appropriate way, which we demonstrate. But since networks are hurt by destructive interference less than centralized systems, it is harder to improve them. Using power groups can significantly improve centralized systems, but will lead to a smaller relative improvement in networks. Decomposing the system into a hierarchy of ALOHA levels, with only a small population contending at the top level, can improve centralized systems but does not improve networks.     

基于多业务的NB-IOT网络高并发接入优化方法研究

本文提出了一种基于多业务的窄带物联网高并发接入优化方法,当有海量物联网终端接入NB-IOT网络时,综合考虑终端所在位置的网络覆盖情况、不同业务终端对时延的敏感度要求及终端发起接入的等待时延,将物联网终端聚类到不同的接入优先等级类别。之后,将可用随机接入前导及NPRACH资源优先分配给高接入等级类别中的终端,进行随机接入请求,有效提高终端首次接入成功率和系统容量,减小接入时延。     

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.     

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.     

Distributed protocols for access arbitration in tree-structuredcommunication channels

The problem of arbitrating access to a tree-structured communication channel, with large geographic extent, providing multipoint communication among a set of terminals, is considered. Terminals transmit information in bursts consisting of many packets and compete for the right to transmit bursts. In the simplest case, the channel allows only one terminal to transmit at a time; this can be extended to k concurrent transmitters. Two general approaches are identified. The first is based on the idea of transmit permits or tokens; that is, a terminal must have explicit permission to transmit before starting a burst. The second approach allows terminals to transmit whenever the number of bursts they can observe from their vantage point is less than the limiting number; the network then performs arbitration internally, possibly aborting some bursts in the process, to prevent too many bursts from being active on a link at one time. Several specific access arbitration algorithms based on these approaches are presented and assessed