Logically rearrangeable multihop lightwave networks

The optimization problem of rearrangeable multihop lightwave networks is considered. The authors formulate the flow and wavelength assignment problem, when minimizing the maximum flow in the network, as a mixed integer optimization problem subject to linear constraints. The problem is decomposed into two independent subproblems, the wavelength assignment (or connectivity problem) and the flow assignment (or routing problem). A simple heuristic provides a meaningful formulation to the connectivity problem, in a form similar to a transportation problem. An algorithm is then proposed which finds a heuristic initial logical connectivity diagram and the corresponding routing, and then iterates from that solution by applying branch-exchange operations to the connectivity diagram. The algorithm was tested on illustrative traffic matrices for an 8 node network with two transmitters and two receivers per node, and an improvement in achievable throughput over the Perfect Shuffle interconnection pattern was shown in all cases     

M－DQCA：可调信道访问光波网介质访问控制协议

本文提出了一种可调信道访问光波网以及适合于该网的介质访问控制协议Ｍ－ＤＱＣＡ，利用波分复用技术将双总线光波网分成多个并行信道，用一个信道专门传输等时业务和请求信息，使网络管理得到简化；利用时隙重用技术，提高了网络的吞吐量；拥塞控制方法与多跳网相比简单得多，各用户只需根据本站缓存的情况来控制输入业务的流量。计算机仿真表明，Ｍ－ＤＱＣＡ光波网具有很好的性能。     

WDM-based local lightwave networks. II. Multihop systems

For pt.I see ibid., vol.6, no.3, p.12-27, 1992. A survey of wavelength-division-multiplexing (WDM)-based local lightwave networks is presented. The general characteristics of multihop systems are discussed, and various multihop approaches are reviewed. The construction of optimal structures based on minimizing the maximum link flow and optimizations based on minimization of the mean network packet delay are also reviewed. Regular topologies that have been studied as candidates for multihop lightwave networks, including the perfect shuffle, the de Bruijn graph, the toroid, and the hypercube, are discussed. Near-optimal node placement algorithms and shared-channel multihop systems are also discussed     

The scalable lightwave network

In principle, an optical network employing wavelength routing, wavelength reuse, and multihop packet switching is modularly scalable to very large configurations in both the hardware and software sense. As such, it is a viable architecture for a new ATM-based telecommunications infrastructure The network architecture considered for a new, scalable, broadband telecommunications infrastructure is based on (1) the use of wavelength division multiplexing (WDM) and wavelength routing; (2) the translation of signals from one wavelength to another at the access stations; and (3) the use of multihop ATM packet switching. These principles permit networks to be built whose size is essentially unlimited     

BanyanNet-a bidirectional equivalent of ShuffleNet

A multihop, wavelength division multiplex (WDM) based network, BanyanNet, is proposed for the realization of terabit lightwave networks, BanyanNet can he considered as a the bidirectional equivalent of the popular ShuffleNet. Exploiting its representation, we developed a fast, decentralized, bidirectional routing algorithm for BanyanNet. The performance of BanyanNet is compared to that of the ShuffleNet and bilayered ShuffleNet. For N=p^m×k networks, the p=2 BanyanNet provides better performance in channel efficiency, total and user throughput than the corresponding ShuffleNet, and offers more flexible network configurations than the bilayered and p=4 ShuffleNet     

Multihop packet scheduling in WDM/TDM networks with nonnegligibletransceiver tuning times

This paper addresses the design of packet transmission schedules in photonic slotted wavelength-division multiplexing/time-division multiplexing broadcast-and-select networks with W wavelengths and N nodes. Nodes are equipped with one tunable-wavelength transmitter with nonnegligible tuning times and one fixed-wavelength receiver. A new scheduling algorithm that exploits multihop packet transfer to shorten the duration of scheduling periods is first proposed. A single-hop scheduling algorithm that performs slightly better than previous proposals is then described. A simulation-based analysis of the two algorithms shows that they jointly lead to significant improvements in both throughput and delay with respect to previous single-hop schedules     

A 60 GHz Radio-Over-Fiber Network Architecture for Seamless Communication With High Mobility

We demonstrate a 60 GHz broadband picocellular Radio-over-Fiber network architecture that enables seamless connectivity for highly mobile end-users. Its seamless communication capabilities arise by the supported handover scheme that relies on a novel Moving Extended Cell (MEC) concept. MEC exploits user-centric virtual groups of adjacent cells that transmit the same data content to the user and utilizes a switch mechanism for restructuring the virtual multi-cell area according to the user's mobility pattern, so that a virtual antenna group moves together with the mobile user. We present the theoretical formulation for MEC and show that it can provide zero packet loss and call dropping probability values in high-rate wireless services for a broad range of mobile speeds up to 40 m/sec, independently of the fiber link distances. We also demonstrate the physical layer network architecture and switch mechanism both for a RoF network with a single 60 GHz radio frequency (RF) over each wavelength, as well as for a RoF configuration supporting simultaneous multi-RF channel transmission over each optical wavelength. The performance of the multi-RF-over-lambda network implementation is evaluated via simulations showing successful 100 Mb/s radio signal transmission over fiber links longer than 30 km. To this end, MEC can enable seamless connectivity and bandwidth guarantees in 60 GHz picocellular RoF networks being also capable of serving multiple users over the same wavelength in a RF frequency-division-multiplexed (FDM) approach.     

A scalable multiwavelength multihop optical network: a proposal forresearch on all-optical networks

An architectural approach for very-high-capacity wide-area optical networks is presented, and a proposed program of research to address key system and device issues is described. The network is based on dense multiwavelength technology and is scalable in terms of the number of networked users, the geographical range of coverage, and the aggregate network capacity. Of paramount importance to the achievement of scalability are the notions of wavelength reuse and wavelength translation. A distributed optical interconnect that is wavelength-selective and electronically controllable, permitting the same limited set of wavelengths to be reused among other access stations, is employed. By exercising the wavelength-selective switches, the wavelength-routed connectivity between stations can be reconfigured as needed. A multihop overlay network involving wavelength translation and self-routing fast packet switches permits full connectivity, if desired among the access stations at the individual virtual circuit level. Using just eight wavelengths, such a network could in principle interconnect a population of 100 million users over a nationwide geography with an expected delay equal to that of 12 hops     

Channel sharing in multi-hop WDM lightwave networks: realizationand performance of multicast traffic

A local lightwave network can be constructed by employing two-way fibers to connect nodes in a passive-star physical topology, and the available optical bandwidth may be effectively accessed by the nodal transmitters and receivers at electronic rates using wavelength division multiplexing (WDM). The number of channels, ω, in a WDM network is limited by technology and is usually less than the number of nodes, N, in the network. We provide a general method using channel sharing to construct practical multi-hop networks under this limitation. Channel sharing may be achieved through time division multiplexing. The method is applied to a generalized shuffle-exchange-based multi-hop architecture, called GEMNET. Multicasting-the ability to transmit information from a single source node to multiple destination nodes-is becoming an important requirement in high-performance networks. Multicasting, if improperly implemented, can be bandwidth-abusive. Channel sharing is one approach toward efficient management of multicast traffic. We develop a general modeling procedure for the analysis of multicast (point-to-multipoint) traffic in shared-channel, multihop WDM networks. The analysis is comprehensive in that it considers all components of delay that packets in the network experience-namely, synchronization, queuing, transmission, and propagation. The results show that, in the presence of multicast traffic, WDM networks with ω相似文献   

Protocols for very high-speed optical fiber local area networks using a passive star topology

This paper deals with the problem of interconnection of many high-speed bursty traffic users via an optical passive star coupler. Each user can tune its laser over a range of wavelengths, thus resulting in a wavelength division multiplexed communication. The total number of wavelengths over which user tunability exists could be much smaller than the number of users. Therefore, some form of random access sharing and packet switching may be necessary. We propose several protocols that require each user to have a tunable receiver. The information on "where" and "when" to tune the laser is confined to a control (setup) channel that users tune to when in idle mode. An interconnection between two users lasting for the length of a data packet is set up on the control channel by the transmitting user who informs the receiving user where to tune in order to receive the data packet. No centralized control or coordination is required among the users. After analyzing each protocol, we present the throughput/ delay versus the offered traffic and the delay versus throughput in a sequence of plots. We show that in typical applications an average throughput of up to 0.95 can be achieved at a reasonable average delay using one of these protocols. In our benchmark examples we present an optical local area network (LAN) with a total throughput of 100- Gbit/s in which every user has access to a 1-Gbit/s data rate and the network can support over 1000 users. The protocols can be used in a) large LAN's that do not require a large capacity, b) small LAN's (1 kin) that require a large capacity and c) large LAN's (tens of kilometers) that require a rather large capacity.     

Optimum transmission ranges in a direct-sequence spread-spectrummultihop packet radio network

The authors obtain the optimum transmission ranges to maximize throughput for a direct-sequence spread-spectrum multihop packet radio network. In the analysis, they model the network self-interference as a random variable which is equal to the sum of the interference power of all other terminals plus background noise. The model is applicable to other spread-spectrum schemes where the interference of one user appears as a noise source with constant power spectral density to the other users. The network terminals are modeled as a random Poisson field of interference power emitters. The statistics of the interference power at a receiving terminal are obtained and shown to be the stable distributions of a parameter that is dependent on the propagation power loss law. The optimum transmission range in such a network is of the form CK^α where C is a constant, K is a function of the processing gain, the background noise power spectral density, and the degree of error-correction coding used, and α is related to the power loss law. The results obtained can be used in heuristics to determine optimum routing strategies in multihop networks     

An overview of lightwave packet networks

The unique systems opportunities offered by, and the unique systems constraints imposed by, lightwave technology as it applies to the field of distributed packet networks are examined. Single-channel and star topology approaches are first considered. Terabit-capacity lightwave networks are discussed, covering both wavelength-division and time-division multiplexing. Multichannel multihop lightwave networks are then considered, and a particular implementation, the ShuffleNet, is described, and its performance, as well as some simple addressing and routing schemes, is discussed     

Adaptive cell sectorization for CDMA systems

Given the user distribution in a cell, we investigate the two problems of how to appropriately sectorize the cell such that we minimize the total received power and the total transmit power of all the users, while giving each user acceptable quality of service in both cases. For the received power optimization problem, we show that the optimum arrangement equalizes the number of users in each sector. The transmit power optimization is formulated as a graph partitioning problem that is polynomially solvable. We provide an algorithm that finds the best sectorization assignment as well as the optimal transmit powers for all the users. The computational complexity of the algorithm is polynomial in the number of users and sectors. For both the received power optimization and the transmit power optimization, under nonuniform traffic conditions, we show that the optimum arrangement can be quite different from uniform cell sectorization (equal width sectors). We also formulate and solve the transmit power optimization and cell sectorization problem in a multicell scenario that would improve the capacity of a hot spot in the network. We observe that, with adaptive sectorization, where the sector boundaries are determined in response to users' locations, received and transmit power savings are achieved, and the number of users served by the system (system capacity) is increased compared to uniform sectorization of the cell     

Exploiting the attenuation of fiber-optic passive taps to createlarge high-capacity LANs and MANs

A local- or metropolitan-area network (LAN or MAN) that exploits the power losses of fiber-optic passive taps so that wavelengths can be reused in different portions of the network is proposed. This wavelength reuse makes it possible to design a large, high-capacity, multichannel network with many concurrent transmissions. An arbitrary number of nodes is supported by allowing packets to take multiple hops, when necessary, to reach their destinations. In one example configuration, there are two closed circular loops of fiber, one for transmissions in the clockwise direction and one for counterclockwise transmissions. Each node has one passive tap (per fiber), which is used for both a fixed-wavelength transmitter and a fixed-wavelength receiver     

基于协议序列的车辆自组织网络信道接入控制算法

 针对如何提高车辆自组织网络无线信道资源利用率问题,提出了一种分布式车辆间通信信道接入控制算法,该算法具体表示为利用中国余数定理设计一种用户保障协议序列,车辆节点(亦称用户)依据该协议序列决定其对通信信道的接入,无需基站或中心节点的协调,所设计的协议序列确保每个车辆节点在一个序列周期内至少成功发送一次数据.仿真结果表明,采用本文提出的协议序列控制算法比无反馈时隙ALOHA接入控制算法具有更小的传输时延,能够满足车辆自组织网络通信实时性的要求.     

An Assigned-Slot Listen-Before-Transmission Protocol for a Multiaccess Data Channel

In the multiaccess protocol described in this paper, users are each assigned specific slots of time in which to listen to the channel and determine if the channel is busy or idle. If the channel is idle, a ready user may transmit a fixed length message, or packet; otherwise he must wait a random time and try again. When two or more users transmit simultaneously, none are successful and each must retry after a random time. Though we have considered random slot assignment in general, in this paper we treat only fixed assignment. An interesting special case is when only one user is assigned to each sensing slot. Then there can be no collision and none of the channel capacity is wasted on retransmissions; that is, the channel is conflictfree. Delay-throughput performance curves are presented and compared with some other current multiaccess schemes of interest. Stability considerations are also discussed.     

Jointly optimal routing and scheduling in packet ratio networks

A multihop packet radio network is considered with a single traffic class and given end-to-end transmission requirements. A transmission schedule specifies at each time instant the set of links which are allowed to transmit. The purpose of a schedule is to prevent interference among transmissions from neighboring links. Given amounts of information are residing initially at a subset of the network nodes and must be delivered to a prespecified set of destination nodes. The transmission schedule that evacuates the network in minimum time is specified. The decomposition of the problem into a pure routing and a pure scheduling problem is crucial for the characterization of the optimal transmission schedule     

System Capacity and Access Control for Multimedia TDMA/SS Networks

In this paper, we study the system capacity and access control for the TDMA/SS (time division multiple access with spread spectrum) cellular networks supporting multimedia services. In the TDMA/SS system, time is divided into frames and each frame is further divided into slots. Only one user is allowed to transmit in a slot and spread spectrum technique is adopted to combat inter-cell interference. A packet can occupy more than one slot, depending on the user's data rate and quality of service requirement. We derive a necessary and sufficient condition for a group of users to be admissible for the TDMA/SS system and prove that its admission region contains that of the TDMA/CDMA system. In the TDMA/CDMA system, time is also divided into frames and each frame consists of several slots. The difference is that every packet occupies exactly one slot and multiple users can transmit their packets in the same slot. Numerical results show that the admission region of the TDMA/SS system can be significantly larger than that of the TDMA/CDMA system. To further increase bandwidth utilization and guarnatee delay bound requirements, several access control schemes are proposed. Simulation results are obtained for these access control schemes.     

Expressnet: A High-Performance Integrated-Services Local Area Network

Expressnet is a local area communication network comprising an inbound channel and an outbound channel to which the stations are connected. Stations transmit on the outbound channel and receive on the inbound channel. The inbound channel is connected to the outbound channel so that all signals transmitted on the outbound channel are duplicated on the inbound channel, thus achieving broadcast communication among the stations. In order to transmit on the bus, the stations utilize a distributed access protocol which achieves a conflict-free round-robin scheduling. This protocol is more efficient than existing round-robin Schemes as the time required to switch control from one active user to the next in a round is minimized (on the order of a carrier detection time), and is independent of the end-to-end network propagation delay. This improvement is particularly significant when the channel data rate is so high, or the end-to-end propagation delay is so large, Or the packet size is so small as to render the end-to-end propagation delay a significant fraction of, or larger than, the transmission time of a packet. Moreover, some features of Expressnet make it particularly suitable for voice applications. In view of integrating voice and data, a simple access protocol is described which meets the bandwidth requirement and maximum packet delay constraint for voice communication at all times, while guaranteeing a minimum bandwidth requirement for data traffic. Finally, it is noted that the voice/data access protocol constitutes a highly adaptive allocation scheme of channel bandwidth, which allows data users to recover the bandwidth unused by the voice application. It can be easily extended to accommodate any number of applications, each with its specific requirements.     

Multiconfiguration multihop protocols: a new class of protocols forpacket-switched WDM optical networks

Wavelength-division multiplexing (WDM) local-area networks based on the optical passive-star coupler have traditionally been classified as being either single-hop or multihop. A single-hop network provides a direct connection between the source and the destination of a packet during the packet transfer duration, but may require some amount of coordination between the nodes which may involve tuning of the transmitters or receivers at each node. Since the time required to tune a tunable optical transmitter or receiver may be high, a single-hop network may incur significant overhead. On the other hand, a typical multihop network requires little or no tuning, but a packet may traverse a number of intermediate nodes between the source and destination nodes. Each hop incurs additional queueing delays at each node and also increases the overall load on each link and on the network. In this paper, we propose a new class of multiconfiguration multihop protocols (MMPs) which use tunable transmitters and receivers to cycle through a number of configurations which together make up a multihop logical topology. This class of protocols offers a trade-off between the tuning required in a single-hop network and the number of hops required in a multihop network. We present a generalized framework for comparing the proposed protocols with existing single-hop and multihop protocols, and we show that these protocols may offer significant performance gains for systems with high tuning delays and a limited number of transmitters and receivers at each node