Dynamic capacity allocation for quality-of-service support in IP-based satellite networks

In broadband satellite access networks, the efficient management of the return channel transmission capacity is key in reducing the service cost while satisfying the QoS requirements of IP-based multimedia applications. In this article a dynamic capacity allocation scheme based on combined free/demand assignment multiple access is proposed, allowing the return channel capacity to be efficiently shared among many user terminals. Simulation results indicate that the proposed scheme provides adequate DiffServ IP QoS support while maintaining high satellite bandwidth utility and reduced DCA signaling overhead.     

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.     

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).采用基于节点层级号的信标时隙分配机制,根据邻居表和时隙分配信息计算能够提前进入到载波监听多路访问时隙(Carrier Sense Multiple Access,CSMA)的时间,减少了信标时隙的浪费,提高了信道利用率;同时采用基于拓扑信息的信标帧高效广播机制,删除不大于自身层级号的节点和大于且在两跳范围内的非子孙节点的时隙分配信息,降低了网络控制开销.仿真结果表明,ELDM-MAC协议在信道利用率、平均时延和控制开销等方面都优于IEEE1901.1 MAC协议,更适用于宽带电力线通信网络的实际应用场景.     

MF-TDMA卫星通信多站型组网体制研究

分析了多频时分多址(MF-TDMA)卫星通信体制3种组网实现方式的特点和支持多类站型组网能力,并结合发跳收不跳MF-TDMA组网提出了一种基于双职守载波可有效支持多类站型组网的改进体制。首先给出了双职守载波使用方法和载波速率配置原则,分析了组网实现和有效支持多类站型通信机理;然后设计了多载波帧结构,给出了各类站型申请信道资源的方法。     

一种双向链路频谱重叠共享频带的卫星通信系统

提出一种基于C,Ku,Ka频段透明转发器的双向链路频谱重叠共享频带的TDM/FDMA星型网卫星通信系统方案,小站至中心站的反向链路采用FDMA接入方式,中心站至各个小站的前向链路采用TDM广播方式。理论和仿真分析结果表明:该系统的频带效率比常规TDM/FDMA系统提高了1倍,而链路的传输性能仍可以达到实用要求。     

一种MF-TDMA卫星通信混合拓扑网络分析

在分析多频时分多址(MF-TDMA)卫星通信体制特点和发展需求的基础上,提出了一种基于MF-TDMA体制构建多星状与网状一体化混合拓扑网络的方法。首先给出了所提出的混合拓扑网络的特点和应用场景,然后设计了MF-TDMA混合网的多载波帧结构并分析了同步控制技术和各类载波与时隙的配置,最后给出了星状、网状用户地球站间的通信流程和使用载波时隙信道资源的方法。     

一种星地一体化路由设计的卫星IP网络

现有大部分支持IP的卫星系统只是提供一个连接地面路由器的物理通道,难以满足宽带接入、多媒体服务以及星地网络一体化等新的需求.为此,提出了一个分组传输和交换均基于IP的GEO卫星系统,并从传输网络和路由结构两方面进行了描述.并针对星上资源紧张的现状,采用了一种地面路由星上交换的新设计思路.通过星上IP交换可实现大量终端间的单跳通信,一个可扩展的集中式IP路由结构可有效减少通过卫星的路由流量,使得通信效率提高的同时,能实现卫星网络与Internet的无缝兼容.     

Base station networking in personal communications

Base stations in personal communications serve as the interface between portable terminals and their central offices. For many reasons, such as cost-effectiveness, higher reliability, simpler handover, and simple clock distribution, it is desirable to use a network instead of point-to-point links to connect base stations to their central offices. The author considers a base station network that has a regular rectangular mesh topology and an access protocol that is based on the slotted ring. The mesh topology provides clock distribution which can synchronize the timing for time-division multiple access (TDMA) or frequency-division multiaccess (FDMA) radio access when the network is physically regular. The slotted-ring protocol provides simple medium access, simple interface with TDMA or FDMA radio channels and simpler handover processing. The author also discusses how base station networks in different central office zones can be interconnected to form a metropolitan area network for both voice and data traffic     

Critical issues of onboard switching in DVB-S/RCS broadband satellite networks

The next generation of broadband satellite networks is challenged to accommodate multimedia services while concurrently integrating with terrestrial IP networks. With IP applications dominating the Internet, carrying IP traffic over the satellite has been under intensive study. Originally developed to bring digital television home through satellites, the DVB-S and DVB-RCS standards empower interactive satellite communications with economical standardized satellite terminals. Furthermore, onboard switching technology is increasingly gaining attention, due to optimized bandwidth usage, fully meshed network topology through one satellite hop, and quality of service guarantee. This article investigates the onboard switching technologies in DVB-S/DVB-RCS broadband satellite networks. Aside from the network system infrastructure and switch hardware architecture, the QoS mechanisms supported by the switch onboard the satellite are discussed in depth.     

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.     

Domestic and regional satellite systems

The technical characteristics of domestic and regional satellite systems are discussed. Spacecraft technology is reviewed, communication payload technology developments are discussed, and resources and economics are considered. It is seen that, compared to the installation of terrestrial microwave or optical cable networks in remote and harsh areas, satellite systems offer both lower costs and shorter time to bring on line. Proven technology and mature hardware is available for regions where orbit/spectrum space is still plentiful. As in North America, the sequence of growth is likely to be C-band and then K -band. Corresponding earth station advances in efficient modulation techniques and time-division multiple access will increase the capacity per transponder channel, while frequency and spatial reuse will provide more channels per satellite     

一种适用于卫星通信TDMA体制的混合双工传输方法

提出了一种适用于卫星通信时分多址(TDMA)体制的混合双工传输方法,即星地链路收、发采用频分双工(FDD),地面终端收、发采用时分双工(TDD)。该方法通过对卫星覆盖范围内用户终端的地理位置和传输时间进行分析,设计了一种混合双工传输帧结构以及上、 下行链路的收、发信号定时策略,解决了卫星通信 FDD 模式上、下行链路频率间隔小导致的用户终端收、发信号相互干扰问题,有效降低了卫星天线的隔离度要求,进而减少了卫星天线的尺寸,对于小型武器平台的卫星通信能力提升具有重要意义。     

An IP transport and routing architecture for next-generationsatellite networks

Over the past several years, a number of new satellite systems have been proposed to provide high-speed Internet and multimedia services to businesses and home users. These proposals have been driven by the desire of network operators to reach end users that do not have cost effective access to other alternatives such as fiber, DSL, and cable, and by the availability of new spectrum (Ka-band) for use by new satellite services. The proposed systems generally employ multiple high-power spot beams, an onboard fast packet switch, and a demand-assigned multiple access scheme to provision IP-based services. In this article we concentrate on a geosynchronous satellite system where packet transport and switching within the satellite system are based on ATM. We describe an IP/ATM interworking and IP routing architecture that is driven by three main requirements: (1) the ability to support ATM SVCs between hundreds of thousands of satellite terminals by a single ATM switch located onboard; (2) a scalable IP routing architecture that does not result in large volumes of routing traffic to be transported over the satellite; and (3) the ability to segment the satellite terminals for routing and administrative control by ISPs and enterprise networks     

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.     

Doppler as a new dimension for multiple access in LEO satellite systems

The problem of flow control for little LEO satellite communications systems is studied. In these systems the satellite functions as a ‘bent pipe’ transponder for messaging between small terminals and a command and data acquisition (CDA) earth station. A novel scheme for averting traffic overflow on the inbound channel (from terminal to CDA), which we call ‘Doppler-based multiple access’ (DBMA), is introduced. In DBMA the CDA specifies a subset of the visibility footprint as a region of eligibility (ROE). Only terminals located in the ROE are permitted to transmit. By varying the size and location of the ROE, effective flow control on the inbound channel is achieved. The ROEs are specified in terms of parameters of the Doppler frequency shift versus time curve observed at terminals on the outbound downlink channel (from satellite to terminal). The effectiveness and elegance of the DBMA protocol are illustrated through computer simulation. © 1997 John Wiley & Sons, Ltd.     

Multiwavelength control protocols for WDM networks with restricted data channel collision

A new network architecture which uses several wavelengths as control channels for co‐ordination of packet transmissions on data channels for single‐hop WDMA networks and passive star topology is introduced in this paper. The presented multiwavelength control architecture distributes control information over the total control channels and in conjunction with a suitable network interface, reduces the headers electronic processing bottleneck at each end station. Also, the access schemes decrease the contention on data channels by avoiding part of the data channel collision. Some cases of multiple access protocols for asynchronous and synchronous (re)transmission categories are suggested. The proposed schemes adopt the slotted ALOHA protocol for the access to control and data multichannel systems in which the data packets transmission starts immediately after the control packets transmission. An analytic model is developed and analysed for performance measures evaluation based on Poisson approximations statistics and a finite population. The effect of receiver collision is analysed and estimated by the average rejection probability at destination. Also, numerical results are discussed for various numbers of control and data channels. Copyright © 2000 John Wiley & Sons, Ltd.     

Design and performance evaluation of an RRA scheme for voice‐data channel access in outdoor microcellular environments

In PCS networks, the multiple access problem is characterized by spatially dispersed mobile source terminals sharing a radio channel connected to a fixed base station. In this paper, we design and evaluate a reservation random access (RRA) scheme that multiplexes voice traffic at the talkspurt level to efficiently integrate voice and data traffic in outdoor microcellular environments. The scheme involves partitioning the time frame into two request intervals (voice and data) and an information interval. Thus, any potential performance degradation caused by voice and data terminals competing for channel access is eliminated. We consider three random access algorithms for the transmission of voice request packets and one for the transmission of data request packets. We formulate an approximate Markov model and present analytical results for the steady state voice packet dropping probability, mean voice access delay and voice throughput. Simulations are used to investigate the steady state voice packet dropping distribution per talkspurt, and to illustrate preliminary voice-data integration considerations. This revised version was published online in June 2006 with corrections to the Cover Date.     

A logarithmic lower bound for time‐spread multiple‐access (TSMA) protocols

Time‐Spread Multiple‐Access (TSMA) protocols are scheduled access protocols for mobile multi‐hop radio networks that guarantee deterministic access to the shared channel regardless of the possibility of radio interference. In scheduled access methods, time is considered to be slotted and time slots are cyclically organized into frames. In general, the shorter the frame, the more efficient the protocol. An Ω(log log n) lower bound is known on the minimum length of the frame of TSMA protocols in networks with n nodes. In this note we improve that lower bound by characterizing the multiple access to the radio channel as a combinatorial problem. The proposed characterization allows us to prove that no TSMA protocols can successfully schedule the transmissions of the nodes of a multi‐hop radio network in frames with less than log n time slots. This revised version was published online in August 2006 with corrections to the Cover Date.     

VSAT communications networks-an overview

The very-small-aperture-terminal (VSAT) fixed satellite communication network is a star network in which many dispersed micro terminals attempt to send data in a packet form through a random access/time-division multiple-access (RA/TDMA) satellite channel with transmission delay. The basic concept of the VSAT and its service potential are discussed. Two classes of traffic are addressed, namely business-oriented low-rate-data traffic and bulk data traffic of corporate networks. Satellite access, throughput, and delay are considered. The size of the network population that can be served in an RA/TDMA environment is calculated. User protocols are examined. A typical VSAT business scenario is described