A Multiaccess Model for Packet Switching with a Satellite Having Some Processing Capability

A multiaccess model for packet switching with a satellite having the capability of interrogating the uplink header and creating the downlink header is proposed. The satellite broadcasts slot assignments, based on the users' reported queue status, to the users for transmission in the next frame. With the protocols being done at both the earth stations and at the satellite, the proposed multiaccess model avoids collisions that are prevalent in schemes of the ALOHA type. The actual model is too complex to handle analytically. We derive analytical equations for a two-group model. Calculated and simulated buffer overflow probabilities as a function of traffic intensity and buffer size are compared. We also evaluate the performance of the actual model in terms of average system delay as a function of traffic intensity by means of computer simulation.     

Delay Analysis of Packet Switching System with a Satellite Having Processing Capability

This correspondence deals with the satellite packet switching system employing a frame format proposed by Ng and Mark [1], and analyzes the average queueing and scheduling delay without a rough approximation made by Ng and Mark [2]. The numerical results indicate that the delay computed by the proposed algorithms is quite different from that given by Ng and Mark, especially in both the regions of low and high traffic intensities.     

Packet Switching in a Multiaccess Broadcast Channel: Performance Evaluation

In this paper, the rationale and some advantages for multiaccess broadcast packet communication using satellite and ground radio channels are discussed. A mathematical model is formulated for a "slotted ALOHA" random access system. Using this model, a theory is put forth which gives a coherent qualitative interpretation of the system stability behavior which leads to the definition of a stability measure. Quantitative estimates for the relative instability of unstable channels are obtained. Numerical results are shown illustrating the trading relations among channel stability, throughput, and delay. These results provide tools for the performance evaluation and design of an uncontrolled slotted ALOHA system. Adaptive channel control schemes are studied in a companion paper.     

Packet Switching in a Multiaccess Broadcast Channel: Dynamic Control Procedures

In a companion paper [1], the rationale for multiaccess broadcast packet communication using satellite and ground radio channels has been discussed. Analytic tools for the performance evaluation and design of uncontrolled slotted ALOHA systems have been presented. In this paper, a Markovian decision model is formulated for the dynamic control of unstable slotted ALOHA systems and optimum decision rules are found. Numerical results on the performance of controlled channels are shown for three specific dynamic channel control procedures. Several practical control schemes are also proposed and their performance compared through simulation. These dynamic control procedures have been found to be not only capable of preventing channel saturation for unstable channels but also capable of achieving a throughput-delay channel performance close to the theoretical optimum.     

Two-Level Multiaccess Schemes for Packet Satellite Systems with Low Duty Factor Terminals

A two-level packet satellite network architecture is proposed to provide efficient communications for a large number of low duty factor terminals. At the first level, disjoint subnets of prioritized users employ a minislotted alternating priorities (MSAP) protocol. At the second level, a time division multiple access (TDMA) or frequency division multiple access (FDMA) uplink, and a time division multiplexed (TDM) or frequency division multiplexed (FDM) downlink is assumed, with the satellite regenerating and reformatting the data appropriately. Examples with a large number of terminals show that the two-level schemes provide superior delay performance over single-level methods for wide ranges of throughput.     

Combined Random/Reservation Access for Packet Switched Transmission Over a Satellite with On-Board Processing: Part I--Global Beam Satellite

A combined random/reservation multiple access (CRRMA) scheme for packet-switched communication over a global beam satellite with on-board processing is proposed and analyzed. Channel time is divided into contiguous slots; each slot containsNminislots for transmission of request packets andN'minislots for data. WithNsubstantially smaller than the number of earth stations, collisions will occur in request packet transmissions. Two channel access algorithms for the CRRMA model are proposed: uncontrolled channel access (UCA) and controlled channel access (CCA). UCA is simpler but has an inherent stability problem particularly when the number of minislotsNis small. The CCA algorithm restricts the transmission of request packets for new arrivals to take place only when the slot is in the FREE state. WithN = 3, the CCA algorithm exhibits good delay-throughput characteristics. AsNincreases, the UCA algorithm offers stable operation. ForN geq 5the simpler UCA algorithm is preferred over CCA.     

任意拓扑野战分组交换网的性能分析

本文提出了一种用于快速计算野战分组交换网性能的方法。这种具有一般性的方法，适用于任意拓扑的野战分组交换网络，克服了只能计算某种规则网络性能的方法的局限性，大量的计算机仿真结果证实了这种分析方法的可行性和有效性。     

考虑光开关稳定响应时间的光分组组装性能分析

在光分组交换中,光分组的组装算法将对交换的性能产生重要的影响.由于当前技术水平的限制,光分组的长度与光开关的稳定响应时间粒度相近,因此光开关的稳定响应时间对光分组组装算法的影响必须加以考虑.为此,提出两种考虑光开关稳定响应时间的光分组组装算法,即Threshold-Based-ST算法和Timer-Based-ST算法.采用仿真实验的方法对所提出的组装算法性能进行评估.仿真结果表明,Threshold-Based-ST算法和Timer-Based-ST算法都存在一个最优的组装参数.     

Backbone Network Design and Performance Analysis: A Methodology for Packet Switching Networks

This paper describes a packet network design and analysis (PANDA) model which captures the important features of different packet technologies. This model evolved from many iterations with technology developers and network planners over several years. The main contribution is a methodology for designing low-cost backbone packet networks with satisfactory performance which is both practical and useful. This methodology is useful for investigating cost/performance tradeoffs of various network capabilities and components, thus providing a means for identifying potential cost and performance bottlenecks for different packet technologies and to guide capability requirements for new technologies.     

A Simple and Comprehensive Saturation Packet Delay Model for Wireless Industrial Networks

With the emerging popularity of the wireless local area network technology, many analytical models for its main medium access control mechanism, Distributed Coordination Function (DCF), have been reported. However, most of them are based on some oversimplifying assumptions, or need very complicated mathematical manipulations. In this paper, a simple and accurate packet delay model has been proposed for the IEEE 802.11 DCF mechanism in saturated traffic and error-prone industrial applications which is based on a modified discrete-time Markov chain model of the DCF mechanism which accounts for the backoff freezing. It estimates various delay parameters including the average, jitter, Cumulative Distribution Function, and the effect of Retry Limit. The simulation results confirm the accuracy of the proposed delay model compared with other similar models in the literature.     

任意拓扑结构战术地域分组交换网的性能分析

本文以战术地域分组交换网为基础建立具有不规则拓扑结构网络模型，在给出网络的拓扑结构、网络用户业务量和路由选择算法的条件下，提出了一种计算网络链路传输业务量的方法，并用于分析网络的传输性能。同时，还用计算机仿真方法对同一网络进行模拟。分析结果说明：这类通信网的路由选择算法的设计应更重视网络内部流量的均匀分配     

采用偏射路由算法的全光分组网络的性能分析

本文提出采用统一的马尔可夫链方法分析存储转发路由和偏射路由算法的网络，并在具体计算偏射概率时，采用了递推的算法。着重分析了偏射路由算法在无存储器、有单个存储器及有两个存储器的情况下，ＭａｎｈａｔｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和ＳｈｕｆｌｅＮｅｔ网络的性能，包括网络吞吐量、数据包的平均跳转次数和数据包跳转次数的概率分布，并对ＭａｎｈａｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和Ｓｈｕｆ－ｆｌｅＮｅｔ两种网络进行了简单的比较。     

Performance Modeling for Packet Networks with Satellite Overflow Channels

In a packet network using medium speed terrestrial connectivity, average end-to-end delay can be reduced by using highspeed satellite overflow channels despite their propagation delay. To investigate networks of this type analytically, we derive a new basic queueing model for overflow systems with buffered traffic. The simple, closed-form expressions facilitate analysis. Approximations are developed for multiple primary systems with a single overflow channel; these agree with simulation. Using the overflow model analysis indicated the following. The reduced queueing delay to the high capacity overflow channel more than compensated for propagation delay. Inherent, broadcast transmission capabilities of satellite channels reduced overall network delay. The high capacity overflow channels permit networks to withstand substantial nodal imbalance and overloads.     

Analytical MMAP-Based Bounds for Packet Loss in Optical Packet Switching with Recirculating FDL Buffers

The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. A crucial issue in packet switched networks is the avoidance of packet losses stemming from contention. In OPS, contention can be solved using a combination of exploitation of the wavelength domain (through wavelength conversion) and buffering. To provide optical buffering, fiber delay lines (FDLs) are used. In this paper, we focus on an optical packet switch with recirculating FDL buffers and wavelength converters. We introduce the Markovian arrival process with marked transitions (MMAP), which has very desirable properties as a traffic model for OPS performance assessment. Using this model, we determine lower and upper bounds for the packet loss rate (PLR) achieved by the aforementioned switch. The calculation of the PLR bounds through matrix analytical methods is repeated for a wide range of traffic conditions, including highly non-uniform traffic, both in space (i.e., packet destinations) and time (bursty traffic). The quality of these bounds is verified through comparison with simulation results.     

An Improved Switching Approach for Networked Systems with Packet Loss

This paper investigates networked control systems subjected to packet loss over the channel between sensor and controller. The packet loss is modeled as an i.i.d. Bernoulli process. An improved switching approach is proposed to compensate packet loss. Based on this, the closed-loop system is modeled as a switching system with two modes, where the switching signal is determined by a switching condition. The stability analysis and controller design framework based on the switching condition is established. The results, which are derived by the switching system theory, are dependent on the packet loss probability. A numerical example has shown the usefulness of the proposed results.

     

A Cross-Layer Delay Differentiation Packet Scheduling Scheme for Multimedia Content Delivery in 3G Satellite Multimedia Systems

The design of efficient packet scheduling algorithms, which play a key role in the radio resource management (RRM), is crucial for the multimedia delivery in the satellite digital multimedia broadcasting (SDMB) system. In this paper, a novel packet scheduling scheme, which uses the cross-layer approach in its design, is proposed. This scheme comprises a new service prioritization algorithm and a dynamic rate matching based resource allocation algorithm, aimed at utilizing both the applications' QoS attributes and the physical layer data rate information. The performance of the proposed scheme has been evaluated via simulation. In comparison with existing schemes, the proposed scheme achieves significant performance gain on delay, delay variation and physical channel utilization.      

Delay Analysis Under a General Cut-Through Switching Technique in Computer Networks

A general cut-through switching (GCTS) technique is proposed and analyzed. In GCTS, a message may cut through a node if the node becomes free before the message is completely received there. Under the GCTS mechanism, a message may cut through a node even though the node has more than one message in it. This results in minimizing the end-to-end delay time of messages as compared to the other cut-through mechanisms. Moreover, GCTS is more susceptible to exact mathematical treatment.     

Delay Analysis of Packet Scheduling with Multi-Users Diversity in Wireless CDMA Systems

There have been a number of studies that investigate efficient packet scheduling schemes to support quality of service of multiple real-time data users and to increase capacity of non-real-time users sharing a wireless channel. We consider the problem of scheduling transmissions of multiple data users sharing the same wireless channel so as to satisfy delay or throughput and present a general packet scheduling, called MBCS (Multi-users Best Channel Scheduling) which takes advantage of the multi-user diversity of a mobile wireless system. In this paper, a queuing model that represents radio resource management for supporting packet data services is developed for the purpose of evaluating the performance of wireless CDMA systems. Numerical results show that delay performance of the proposed scheduler is higher than that of the Single-user Best Channel Scheduler (SBCS) depending on the time-varying channel status.Sungkyung Kim is a Ph. D. student in the collage of information & Communications at University of Korea, Seoul, Korea. She received her B.S. and M.S. degree in electrical engineering from Korea University in 1999 and in 2001, respectively. From March 2001 to August 2004, she worked at the Electronics Telecommunications Research Institute, Daejeon, Korea, as a member of research engineer. Her research interests include MAC protocol, radio resource control, packet scheduling, and system performance evaluation at system level in wireless access networks.Chung Gu Kang received his B.S. degree in Electrical Engineering from the University of California, San Diego in 1987 and his M.S. and Ph.D. degrees both in Electrical and Computer Engineering from the University of California, Irvine, in 1989 and 1993, respectively. While working on his Ph.D. dissertation from June 1991 to May 1992, he also was with the Aerospace Corporation in El Segundo, California, as a part-time member of technical staff (MTS). After graduation in 1993, he joined Rockwell International in Anaheim, California, where he has been working on the signaling system no. 7 and other telecommunication systems development. Since March 1994, he has been with College of Information & Communications at the Korea University, Seoul, Republic of Korea, as a full professor. His research interests include next generation mobile radio communication system and broadband wireless networks, with special emphasis on physical layer/medium access control layer design and performance analysis. During the academic year of 2000, he has been a visiting scholar at Center for Wireless Communication and also a visiting professor at Department of Electrical & Computer Engineering in University of California at San Diego (UCSD). He is a member of IEEE COMSOC, IT, and VT, and a member of KICS and KITE.     

Throughput and Packet Delay Analysis for the H-Network: CSMA/CD with Adaptive and Nonadaptive Backoff Protocols

In this work, we present the structure of the H-Network, which is a high data rate (∼ 7 Mbytes/s) local area network used to provide point to point and broadcast communication for the Homogeneous Multiprocessor. We also present the analysis, and obtain the throughput and packet delay characteristics for the H-Network operating under CSMA/CD with adaptive and nonadaptive backoff protocols.     

长传播延时卫星环境中TCP性能分析

卫星通信系统中的长传播延时是影响TCP性能的主要特性之一,对长传播延时卫星环境中TCP在整个动态连接过程中的工作情况进行了分析,综合考虑了单连接情况中连接建立初期不稳定阶段的情况和连接达到稳态阶段时的情况,并给出了Goodput的理论分析和仿真结果,进一步证明了连接的Goodput性能随着卫星链路传播延时的增大而下降。