Efficient QoS support in a slotted multihop WDM metro ring

A novel distributed access protocol for a slotted wavelength-division-multiplexing (WDM) metro ring employing all-optical packet switching and supporting quality-of-service (QoS) classes is presented and analyzed. Since we assume that there are more nodes than available wavelengths in the network, we obtain a scalable multihop WDM ring as underlying network architecture. By dividing each channel into several time slots and further applying destination release and slot reuse, data packets can be efficiently transmitted and received in a statistically multiplexed manner. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider so-called a posteriori access strategies, different packet selection schemes are proposed and compared. An analytical model based on the semi-Markov process methodology is developed to quantify the performance of one of these schemes. As a key element of the protocol, an efficient QoS support access mechanism is proposed and its performance is evaluated. The new QoS control scheme adopts a frame-based slot reservation strategy including connection setup and termination, which only slightly increases the signaling and node processing overhead. Thus, an efficient hybrid protocol combining connectionless and connection-oriented packet transmissions is proposed     

一种新型的光分组交换环网体系结构

提出了一种以波长为标签的新型全光变长分组交换环网的体系结构、网络节点的光分组数据包收发模型,以及防止光分组冲突的多令牌协议。使用多令牌协议的环网在进行光分组交换时,不需要高速的光子器件,无需使用延迟线、电中继以及解决光分组的冲突问题。通过数值仿真,分析了4节点、8节点和16节点环网巾光分组各种的时延特性以及网络的吞吐量特性。结果表明,当网络负载增大时,数据包的平均时延增大,同时网络节点的吞吐量和资源利用率也随之增大;网络节点数目越多,网络的吞吐率也越大。     

Optimal all-to-all broadcast in WDM optical networks with breakdown or power-off transceivers

All-to-all broadcast is an interesting special case of the packet transmission scheduling in which every pair of nodes has exactly one packet to be transferred. This paper considers the all-to-all broadcast problem in wavelength division multiplexed (WDM) optical star network with some breakdown or power-off transceivers. For reaching high data transmission rates, we will focus the problem on the all-optical scheduling where the traffic reaches its destination in single-hop without being converted to electronic form. Each transmitter is tunable with an associated tuning delay and each receiver is fixed-tuned to one of available wavelengths. In this model, we study two kinds of all-to-all broadcast problems depending on whether each node transmits packets to all nodes including or except itself. We identify the lower bound of the scheduling length for each kind of problems and propose single-hop scheduling algorithms to find the optimal solution in both terms of arbitrary number of wavelengths and value of tuning latency.     

Probabilistic Analysis of Cyclic Packet Transmission Scheduling in WDM Optical Networks

We study the packet transmission scheduling problem with tuning delay in wavelength-division multiplexed (WDM) optical communication networks with tunable transmitters and fixed-tuned receivers. By treating the numbers of packets as random variables, we conduct probabilistic analysis of the average-case performance ratio for the cyclic packet transmission scheduling algorithm. Our numerical data as well as simulation results demonstrate that the average-case performance ratio of cyclic schedules is very close to one for reasonable system configurations and probability distributions of the numbers of packets. In particular, when the number of receivers that share a channel and/or the granularity of packet transmission are large, the average-case performance ratio approaches one. Better performance can be achieved by overlapping tuning delays with packet transmission. We derive a bound for the normalized tuning delay Δ such that tuning delay can be completely masked with high probability. Our study implies that by using currently available tunable optical transceivers, it is possible to build single-hop WDM networks that efficiently utilize all the wavelengths.     

Contention-based reservation protocols in multiwavelength opticalnetworks with a passive star topology

In a multiwavelength optical network with tunable transceivers, an algorithm to make the transmitter and the receiver tuned to the same wavelength simultaneously is needed. The paper proposes contention-based reservation protocols using a separate control channel for multiwavelength optical networks with a passive star topology. First, they present a protocol which can be used in the network where the ratio of the end-to-end signal propagation delay to the transmission time of a data packet is smaller than 1. Also, for a very high speed network where this ratio is greater than 1, the authors present three protocols according to the variability of the packet length and the buffering of the reservation. To access the control channel, all the proposed protocols use the slotted ALOHA protocol. The authors analyze these protocols with a finite population model and investigate the delay-throughput characteristics     

A media-access protocol for packet-switched wavelength divisionmultiaccess metropolitan area networks

A dynamic time-wavelength division multiaccess protocol (DT-WDMA) is proposed for metropolitan-sized multichannel optical networks employing fixed wavelength transmitters and tunable optical receivers. Control information is sent over a dedicated signaling channel and data are sent over channels owned by the transmitters. Time is divided into slots on each channel and slots on the control channel are further split into mini-slots. Fixed time-division multiaccess (TDM) is used within each slot on the control channel. Transmitters indicate their intention to transmit a packet by transmitting the destination address during their appropriate mini-slot in the control channel and then transmit their packet in the next slot on their data channel. Receivers listen to the control channel and tune to the appropriate channel to receive packets addressed to them. A common but distributed arbitration algorithm is used to resolve conflicts when packets from many transmitters contend for the same receiver. Each receiver executes the same deterministic algorithm to choose one of the contending packets. Each transmitter uses the same algorithm to determine the success or failure of its packet     

A hybrid reservation-based MAC protocol for underwater acoustic sensor networks

Due to the characteristics of underwater acoustic channel, such as long propagation delay and low available bandwidth, media access control (MAC) protocol designed for the underwater acoustic sensor network (UWASN) is quite different from that for the terrestrial wireless sensor network. However, for the contention-based MAC protocols, the packet transmission time is long because of the long preamble in real acoustic modems, which increase the packet collisions. And the competition phase lasts for long time when many nodes are competing for the channel to access. For the schedule-based MAC protocols, the delay is too long, especially in a UWASN with low traffic load. In order to resolve these problems, a hybrid reservation-based MAC (HRMAC) protocol is proposed for UWASNs in this paper. In the proposed HRMAC protocol, the nodes reserve the channel by declaring and spectrum spreading technology is used to reduce the collision of the control packets. Many nodes with data packets to be transmitted can reserve the channel simultaneously, and nodes with reserved channel transmit their data in a given order. The performance analysis shows that the proposed HRMAC protocol can improve the channel efficiency greatly. Simulation results also show that the proposed HRMAC protocol achieves better performance, namely higher network throughput, lower packet drop ratio, smaller end-to-end delay, less overhead of control packets and lower energy overhead, compared to existing typical MAC protocols for the UWASNs.     

A channel reuse strategy with adaptive channel allocation for all-optical WDM networks

The fundamental problems of WDM networks are: (1) high rate of control packet loss and (2) high propagation delay for each (re)transmission. In this paper, we minimize the station randomness to access the control architecture introducing a collisions-free access scheme. We propose a synchronous protocol according which at the end of the propagation delay each station applies a distributed algorithm for packet transmission following the data channel collisions and the receiver collisions avoidance algorithms. We introduce two data transmission stages. The time difference between them is one packet transmission time. At the end of the first stage all data channels are free and can be reused by the remaining data packets during the second stage. The proposed protocol ensures a totally collisions-free performance. The main advantage is that the data channels reuse strategy applied during the second stage provides enhanced transmission probability to the rejected packets during the first stage. This allows the data packets to try retransmission in the same cycle without requiring control packets re-coordination that increases propagation delay. Thus, we achieve large number of data packets transmission, even more than the data channels number, providing throughput improvement and delay reduction, comparing with other studies.     

Improved MAC protocol for reverse link packet data transmission in wideband DS-CDMA

This paper introduces and analyses a novel medium access control protocol for reverse links in wideband direct-sequence code-division multiple-access (DS-CDMA) mobile systems. The proposed protocol is particularly efficient when data consists of short packets. The new MAC protocol uses the time taken by the receiver to process the packets (the processing delay) to admit a new packet. When packet arrival is assumed to be Poisson, analysis and simulations show consistently that, for short packets, the new MAC scheme can handle a higher arrival rate than the conventional one, in which the processing delay is not used. The new MAC scheme shows only slight throughput degradation, a high utilization of the packet-switched data channel, and achieves a fair treatment of mobile stations.     

A slotted access control protocol for metropolitan WDM ring networks

In this study we focus on the serious scalability problems that many access protocols for WDM ring networks introduce due to the use of a dedicated wavelength per access node for either transmission or reception. We propose an efficient slotted MAC protocol suitable for WDM ring metropolitan area networks. The proposed network architecture employs a separate wavelength for control information exchange prior to the data packet transmission. Each access node is equipped with a pair of tunable transceivers for data communication and a pair of fixed tuned transceivers for control information exchange. Also, each access node includes a set of fixed delay lines for synchronization reasons; to keep the data packets, while the control information is processed. An efficient access algorithm is applied to avoid both the data wavelengths and the receiver collisions. In our protocol, each access node is capable of transmitting and receiving over any of the data wavelengths, facing the scalability issues. Two different slot reuse schemes are assumed: the source and the destination stripping schemes. For both schemes, performance measures evaluation is provided via an analytic model. The analytical results are validated by a discrete event simulation model that uses Poisson traffic sources. Simulation results show that the proposed protocol manages efficient bandwidth utilization, especially under high load. Also, comparative simulation results prove that our protocol achieves significant performance improvement as compared with other WDMA protocols which restrict transmission over a dedicated data wavelength. Finally, performance measures evaluation is explored for diverse numbers of buffer size, access nodes and data wavelengths.     

Packet Delay Statistics of the Multichannel Selective-Repeat Automatic-Repeat-Request

In this paper, we conduct stochastic modeling and analysis of the packet end-to-end delay in a multichannel selective-repeat automatic-repeat-request (MSR-ARQ) protocol. In this protocol, the transmitter continuously transmits packets over multiple parallel channels and retransmits erroneously received packets with either dynamic or static packet-to-channel scheduling policy. Under the assumption that packets are always supplied at the transmitter, denoted by the saturated traffic condition, we analyze the steady state probability distribution function of the delay of an arbitrary packet, which is measured by the duration between the instant at which the packet is transmitted for the first time and the time it departs from the resequencing queue at the receiver. Using the analysis result, we numerically compute the distribution function for chosen values of the number of channels and the error rates to demonstrate the computational effectiveness of the result. With numerical and simulation results, we then study the performance of MSR-ARQ in terms of the mean packet delay and compare the two scheduling policies. It is shown that the dynamic scheduling achieves a better packet delay performance than the static scheduling. With the dynamic scheduling and the presence of difference between the error rates of parallel channels, the mean packet delay decreases as the difference between channels?? error rates increases. Moreover, the number of parallel channels has an insignificant impact on the mean packet delay, which shows that the use of parallel channels is favorable for the wireless or mobile communications to increase the data transmission rate while keeping the mean packet delay at an acceptable level.     

Power-stepped protocol: enhancing spatial utilization in a clustered mobile ad hoc network

While most previous studies on mobile ad hoc networks (MANETs) rely on the assumption that nodes are randomly distributed in the network coverage area, this assumption is unlikely to hold, as nodes tend to be cluttered around hot spots like the site of an accident or disaster. We refer to this as a clustered layout. Intuitively, a MANET with the clustered layout may suffer from serious performance degradation due to the excessive collisions in congested hot spots and space underutilization of sparse areas. In this paper, we propose a power-controlled network protocol, called the power-stepped protocol (PSP), that maximizes the spatial utilization of limited channel bandwidth. Using a number of discrete power levels available for the underlying wireless network hardware, PSP finds the appropriate power level for each node in a distributed and a coordinated manner without causing any serious problem at the medium access control and network routing layers. A unique feature of this approach is the use the chosen radio power for both data and control packets, and thus, it requires neither any special mechanism (e.g., a separate control channel) nor frequent power adjustments. Our extensive ns-2-based simulation results have shown the proposed PSP provides excellent performance in terms of packet delivery ratio and delay, as well as the network capacity.     

An AWG-based WDM-PON architecture employing WDM/TDMA transmission for upstream traffic with dynamic bandwidth allocation

In this article, we examine a candidate architecture for wavelength-division multiplexed passive optical networks (WDM-PONs) employing multiple stages of arrayed-waveguide gratings (AWGs). The network architecture provides efficient bandwidth utilization by using WDM for downstream transmission and by combining WDM with time-division multiple access (TDMA) for upstream transmission. In such WDM-PONs, collisions may occur among upstream data packets transmitted simultaneously from different optical networking units (ONUs) sharing the same wavelength. The proposed MAC protocol avoids such collisions using a request/permit-based multipoint control protocol, and employs a dynamic TDMA-based bandwidth allocation scheme for upstream traffic, called minimum-guaranteed maximum request first (MG-MRF), ensuring a reasonable fairness among the ONUs. The entire MAC protocol is simulated using OPNET and its performance is evaluated in terms of queuing delay and bandwidth utilization under uniform as well as non-uniform traffic distributions. The simulation results demonstrate that the proposed bandwidth allocation scheme (MG-MRF) is able to provide high bandwidth utilization with a moderately low delay in presence of non-uniform traffic demands from ONUs.     

Resequencing delay and buffer occupancy under the selective-repeatARQ

Consider a communication network that regulates retransmissions of erroneous packets by a selective-repeat (SR) automatic repeat request (ARQ) protocol. Packets are assigned consecutive integers, and the transmitter continuously transmits them in order until a negative acknowledgement or a time-out is observed. The receiver, upon receipt of a packet, checks for errors and returns positive/negative acknowledgement (ACK/NACK) accordingly. Only packets for which either NACK or time-out have been observed are retransmitted. Under SR ARQ, the receiver accepts packets that are out of order and must store them temporarily if it has to deliver them in sequence. The resequencing buffer requirements and the resulting packet delay constitute major factors in overall system considerations. The authors derive the distributions of the buffer occupancy and the resequencing delay at the receiver under a heavy traffic situation. This enables the network designer to determine how much buffer capacity at the receiver guarantees certain specified performance measures     

An Arrangement of Channels and Transceivers in Optical Packet Switching Networks

Based on a media access and control（MAC）protocol,an arrangement of channels and transceivers in optical packet switching dense wavelength division multiplexing（DWDM）networks is proposed in this paper.In order to reduce the cost of nodes,fixed transmitters and receivers are used instead of tunable transmitters and receivers.Two fixed transmitters and many fixed receivers are used in each node in the scheme.The average waiting delay of this scheme is analyzed through mathematics and computer simulation.The result shows that the property of the scheme is almost the same as using tunable transmitter and receiver.Furthermore,if the tuning time of tunable transmitters is taken into account,the performance of the tunable transmitter scheme is poor than this scheme at the average waiting delay and throughput of the network.     

Selective-repeat ARQ: the joint distribution of the transmitter andthe receiver resequencing buffer occupancies

A selective-repeat automatic-repeat request (SR ARQ) system model in which packets arrive at the transmitter according to a general renewal process is analyzed. The overall delay of a packet in a system that operates under the SR ARQ protocol consists of the queuing delay at the transmitter and the resequencing delay at the receiver. The joint distribution of the buffer occupancies at the transmitter and at the receiver is derived, and the tow types of delay are compared using numerical examples     

Enhanced binary exponential backoff algorithm for fair channel access in the ieee 802.11 medium access control protocol

The medium access control protocol determines system throughput in wireless mobile ad hoc networks following the ieee 802.11 standard. Under this standard, asynchronous data transmissions have a defined distributed coordination function that allows stations to contend for channel usage in a distributed manner via the carrier sensing multiple access with collision avoidance protocol. In distributed coordination function, a slotted binary exponential backoff (BEB) algorithm resolves collisions of packets transmitted simultaneously by different stations. The BEB algorithm prevents packet collisions during simultaneous access by randomizing moments at stations attempting to access the wireless channels. However, this randomization does not eliminate packet collisions entirely, leading to reduced system throughput and increased packet delay and drop. In addition, the BEB algorithm results in unfair channel access among stations. In this paper, we propose an enhanced binary exponential backoff algorithm to improve channel access fairness by adjusting the manner of increasing or decreasing the contention window based on the number of the successfully sent frames. We propose several configurations and use the NS2 simulator to analyze network performance. The enhanced binary exponential backoff algorithm improves channel access fairness, significantly increases network throughput capacity, and reduces packet delay and drop. Copyright © 2013 John Wiley & Sons, Ltd.     

A slotted MAC protocol for efficient bandwidth utilization in WDM metropolitan access ring networks

The paper proposes an original wavelength-division multiplexing slotted-ring network architecture with nodes that use one fixed transmitter and fixed receivers. It is shown, through theoretical predictions and simulation results, how a simple slotted medium access control protocol can be implemented to achieve fairness between access nodes and efficient bandwidth utilization when used in a metropolitan access network. Performance for both source and destination stripping schemes has been analytically derived and simulated with a realistic self-similar traffic model. A modified node architecture using a tunable receiver has also been considered and the impact of receiver collisions has been evaluated and analyzed. Finally, the effect of using unbalanced traffic sources has also been analyzed and simulated.     

基于规则与感知的水声网络MAC协议

针对水声网络(UAN)媒体访问控制(MAC)协议采用RTS/CTS握手机制,导致信道利用率和网络吞吐量较低的问题,提出一套信道访问规则,基于该规则设计了节点状态感知的水声网络MAC(RP-MAC)协议.当接收节点不在收发状态,并且其他邻居节点也都不在接收状态时,发送节点才会尝试发送一到多个报文给接收节点.节点通过侦听和...