Odd-even input-buffered multicast switch

An input buffered packet switch called the odd-even multicast switch is proposed. The packet splitting probability of the proposed switch is derived and the packet output contention is resolved using the cyclic-priority reservation (CPR) algorithm. The throughput and mean packet delay of the proposed switch are compared with a simple input buffered switch. It is found that the proposed switch gives a significant performance improvement at the expense of extra packet splitting overhead     

A Link Adaptive Transport Protocol for Multimedia Streaming Applications in Multi Hop Wireless Networks

Transport layer performance in multi hop wireless networks has been greatly challenged by the intrinsic characteristics of these networks. In particular, the nature of congestion, which is mainly due to medium contention in multi hop wireless networks, challenges the performance of traditional transport protocols in such networks. In this paper, we first study the impact of medium contention on transport layer performance and then propose a new transport protocol for improving quality of service performance in multi hop wireless networks. Our proposed protocol, Link Adaptive Transport Protocol provides a systemic way of controlling transport layer offered load for multimedia streaming applications, based on the degree of medium contention information received from the network. Simulation results show that the proposed protocol provides an efficient scheme to improve quality of service performance metrics, such as end-to-end delay, jitter, packet loss rate, throughput smoothness and fairness for media streaming applications. In addition, our scheme requires few overhead and does not maintain any per-flow state table at intermediate nodes. This makes it less complex and more cost effective.     

A Minimum Interference Cross-Layer Routing Protocol for Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), channel contention and packet collision can seriously affect the performance of routing protocols, which will eventually affect the performance of the whole network. Besides, the arbitrary mobility of nodes makes contention and collision ever-changing and more complex. Thus, it is imperative to analyze the problem of contention and collision so as to build appropriate routes in MANETs. In this paper, by respectively predicting the durations of the contention and collision at every hop along the route, a minimum interference cross-layer routing protocol (MI-CLR) is proposed based on Random Waypoint (RWP) model. The new protocol classifies the interference in the network into two types; the first type of interference can only affect channel contention, while the other affects both channel contention and packet collision. Via taking the two types of interference together into account, we propose a new routing metric to build routes which guarantees that the established routes will not break frequently while having the minimum interference. Simulation results show that the MI-CLR protocol can significantly improve the network performance such as the average end-to-end delay, the packet loss ratio, the routing overhead and the throughput.     

Broadcast storm mitigation techniques in vehicular ad hoc networks

Several multihop applications developed for vehicular ad hoc networks use broadcast as a means to either discover nearby neighbors or propagate useful traffic information to other vehicles located within a certain geographical area. However, the conventional broadcast mechanism may lead to the so-called broadcast storm problem, a scenario in which there is a high level of contention and collisions at the link layer due to an excessive number of broadcast packets. While this is a well-known problem in mobile ad hoc wireless networks, only a few studies have addressed this issue in the VANET context, where mobile hosts move along the roads in a certain limited set of directions as opposed to randomly moving in arbitrary directions within a bounded area. Unlike other existing works, we quantify the impact of broadcast storms in VANETs in terms of message delay and packet loss rate in addition to conventional metrics such as message reachability and overhead. Given that VANET applications are currently confined to using the DSRC protocol at the data link layer, we propose three probabilistic and timer-based broadcast suppression techniques: weighted p-persistence, slotted 1-persistence, and slotted p-persistence schemes, to be used at the network layer. Our simulation results show that the proposed schemes can significantly reduce contention at the MAC layer by achieving up to 70 percent reduction in packet loss rate while keeping end-to-end delay at acceptable levels for most VANET applications.     

Contention resolution in random-access wireless networks based on orthogonal complementary codes

This paper proposes a new method for contention resolution in random-access wireless networks. Using orthogonal complementary codes to design access-request packets, users can reserve channel access successfully, even in severe contentions. Collisions among access-request packets can be resolved and exploited, whereas collisions among data packets are avoided. System throughput and delay performance can be enhanced, because random-access contention becomes transparent. Specifically, system throughput approaches the offered load up to the maximum value one with improved average packet delay performance. A joint layer design approach is proposed with both the physical layer signal-detection algorithm and the medium access-control layer random-access protocol. The performance is analyzed with the consideration of signal detection errors. Simulations are performed to demonstrate its superior performance.     

Design of a medium access control feedback mechanism for cellularTDMA packet data systems

Cellular packet data systems require medium access control (MAC) protocols that allow flexible resource allocation on both the uplink and the downlink. The overhead introduced for managing MAC functions should be minimized, and control fields should be well protected in order to provide robustness to channel errors. The IS-136 TDMA digital control channel specifies shared channel feedback (SCF) procedures and fields for managing uplink resources. However, the SCF mechanism is not well suited to long packet data transactions. We describe a simple and robust packet channel feedback (PCF) mechanism for an IS-136 based TDMA packet data channel by identifying the minimal set of functions and fields required to manage both contention access and reserved access. The proposed scheme has unambiguous state transitions and better performance under error conditions. The PCF scheme provides considerable flexibility in assigning bandwidth to multiple users, and allows the efficient scheduling of contention and reservation opportunities on each subchannel without wasted slots     

A low latency path diversity mechanism for sender-oriented broadcast protocols in VANETs

In vehicular ad hoc networks, many applications require a low latency and high reliability especially the safety applications. Reliable multi-hop broadcast protocols have been widely discussed recently. However, most of them use explicit acknowledgments and timeout retransmissions to provide reliability. The retransmission method incurs delays when a packet loss cannot be detected on time. Acknowledgment messages also increase the MAC layer contention time at each node. In order to provide a high reliability and low latency with a low overhead, we propose a mechanism which utilizes path diversity. In the proposed mechanism, a message is delivered through two different paths. By cooperation of these different paths, broadcast messages can be disseminated with a short delay and a high reliability compared with the acknowledgment based retransmission approach. Since the proposed mechanism does not use any explicit acknowledgment message, the message overhead is low. We evaluate the proposed mechanism using both theoretical analysis and computer simulations.     

Design and analysis of a multilink access subsystem based on theBatcher-banyan network architecture

A multilink access subsystem based on the Batcher-banyan network architecture is proposed. With this subsystem, multiple physical output links connecting a pair of switching nodes can be shared in an effective way. The subsystem is also configurational so that there is no restriction on any particular partition of physical output links. This is accomplished by executing the proposed multilink access algorithm on a modified Batcher sorter. It is shown that the required hardware can be integrated into the Batcher sorter, and the multilink access algorithm can be integrated with the contention resolution three-phase algorithm. The overhead incurred due to the running of the multilink access algorithm is calculated and the asymptotic performance analyses of the resulting single queue multilink access switch are presented. Results show that the proposed architecture has higher capacity than the unilink access counterpart, has low delay, and has low packet loss probability with small buffer size     

有效提高吞吐量的UPMA+ +协议

本文提出了基于有效竞争接入、高效无冲突传输的多址接入协议—UPMA+ +.该协议采用了有效的冲突分解策略和及时重获信道资源的方法,克服了UPMA(根据用户数目妥善安排传输的多址接入)协议中的开销;通过自适应调整竞争接入周期长度和限制无冲突服务周期长度的方法,很好地解决了激活节点快速接入信道和传输节点尽快传输分组之间的矛盾,从而提高了协议的吞吐量.本文还应用排队论的方法对UPMA+ +协议的性能进行了理论分析,计算结果与仿真结果基本一致.     

Split-channel pipelined packet scheduling for wireless networks

To reduce medium access control (MAC) overhead and improve channel utilization, there has been extensive research on dynamically adjusting the channel access behavior of a contending station based on channel feedback information. This paper explores an alternative approach, named pipelined packet scheduling, to reduce the MAC overhead. MAC overheads can be divided into bandwidth-dependent and bandwidth-independent components and these overheads can both be reduced by using split-channel pipelining mechanisms, as demonstrated in this paper. In the past, pipelining mechanisms have not been well studied. This paper introduces two total pipelining schemes that attempt to fully pipeline contention resolution with data transmission. Further, the paper identifies shortcomings of total pipelining in the wireless environment and proposes a partial pipelining approach to overcome these shortcomings. Simulation results show that substantial performance improvement in channel utilization, average packet access delay, and access energy cost can be achieved with a properly designed scheme.     

MCCA: a high-throughput MAC strategy for next-generation WLANs [medium access control protocols for wireless LANs]

Wireless LAN technology has been shown to he a revolutionary development during the last decade. Recently popularized IEEE 802.11a/g-based products can support up to 54 Mb/s physical layer rate and provide wireless access to the Internet. However, in order to deal robustly with the unreliable wireless nature, the 802.11 medium access control protocol has a relatively large overhead and hence, the throughput performance is much worse than the underlying physical layer rate. Moreover, along with many emerging applications and services over WLANs, such as voice over WLAN and audio/video streaming, the demand lor faster and higher- capacity WLANs has been growing recently. In this article, we propose a new medium access control protocol for the next-generation high-speed WLANs. The proposed medium access control, called multi-user polling controlled channel access, is composed of two components: multi-layer frame aggregation, which performs aggregation at both the medium access control and the physical layers; and multi-user polling, used to reduce the contention overhead and in turn, achieve higher network utilization. Multi-user polling controlled channel access is compared with the 802.11e-enhanced distributed channel access medium access control. Highly enhanced medium access control efficiency can be achieved by applying multi-user polling controlled channel access. We show the improved medium access control performance in terms of the aggregate throughput of non-QoS Hows with relevant QoS requirements.     

Loss-based proportional fairness in multihop wireless networks

Proportional fairness is a widely accepted form of allocating transmission resources in communication systems. For wired networks, the combination of a simple probabilistic packet marking strategy together with a scheduling algorithm aware of two packet classes can meet a given proportional vector of n loss probabilities, to an arbitrary degree of approximation, as long as the packet loss gap between the two basic classes is sufficiently large. In contrast, for wireless networks, proportional fairness is a challenging problem because of random channel variations and contention for transmitting. In this paper, we show that under the physical model, i.e., when receivers regard collisions and interference as noise, the same packet marking strategy at the network layer can also yield proportional differentiation and nearly optimal throughput. Thus, random access or interference due to incoherent transmissions do not impair the feasibility of engineering a prescribed end-to-end loss-based proportional fairness vector. We consider explicitly multihop transmission and the cases of Markovian traffic with a two-priority scheduler, as well as orthogonal modulation with power splitting. In both cases, it is shown that sharp differentiation in loss probabilities at the link layer is achievable without the need to coordinate locally the transmission of frames or packets among neighboring nodes. Given this, a novel distributed procedure to adapt the marking probabilities so as to attain exact fairness is also developed. Numerical experiments are used to validate the design.     

A low overhead load balancing router for network-on-chip

The design of a router in a network-on-chip (NoC) system has an important impact on some performance criteria. In this paper, we propose a low overhead load balancing router (LOLBR) for 2D mesh NoC to enhance routing performance criteria with low hardware overhead. The proposed LOLBR employs a balance toggle identifier to control the initial routing direction of X or Y for flit injection. The simplified demultiplexers and multiplexers are used to handle output ports allocation and contention, which provide a guarantee of deadlock avoidance. Simulation results show that the proposed LOLBR yields an improvement of routing performance over the reported routing schemes in average packet latency by 26.5%. The layout area and power consumption of the network compared with the reported routing schemes are 15.3% and 11.6% less respectively.     

M—DCF：在单区网中实现QoS的媒体访问协议

本文结合IP通信的特点,提出了一种适用于WLAN单区网的改进型媒体访问控制协议M-DCF,并进行了计算机仿真。仿真结果表明,M-DCF可以降低系统总的丢包率,话音业务的丢包率,降低话音帧的时延,从而保证话音业务的服务质量,同时也降低了数据帧的时延。     

Link energy minimization for wireless networks

In this paper, we formalize the problem of minimizing the energy dissipated to successfully transmit a single information bit over a link, considering circuit power consumption, packetization and retransmission overhead, bit/packet error probability, and the duty cycle of the transceiver. We optimize the packet length and transmit power as a function of distance between the transmitter and the receiver for different modulation schemes. We propose a general unconstrained energy consumption model that provides a lower bound on the energy dissipated per information bit. A practical unconstrained physical layer optimization scheme is also provided to illustrate the utilization of the model. Furthermore, minimized energy consumptions of different modulation schemes are compared over an additive white Gaussian noise (AWGN) channel. We extend this general energy consumption model by considering two particular constraints: fixed average power and fixed average rate. We explore the impact of the average power and the information rate constraints on energy consumption and determine the optimum constellation size, packet length, and duty cycle.     

High-capacity multiservice optical label switching for the next-generation Internet

This article presents an optical label switching technology geared toward the next-generation Internet, and highlights its promising potential to accommodate packet, burst, and circuit traffic in a unified optical layer. In particular, we provide detailed discussions on an architecture design for a high capacity optical label switching router by considering enabling optical technologies. In pursuit of an effective contention resolution scheme, we investigate an end-to-end solution by incorporating a traffic shaping function at the network edge with wavelength, time, and space dimensions contention resolution in the core network. Experimental results indicate that this scheme is capable of achieving very low packet loss rates. Furthermore, due to its natural compatibility with GMPLS architecture, optical label switching has great potential for a seamless upgrade of today's optical networks toward the next generation Internet.     

Saturation throughput analysis of IEEE 802.11 in the presence of non ideal transmission channel and capture effects

In this paper, we provide a saturation throughput analysis of the IEEE 802.11 protocol at the data link layer by including the impact of both transmission channel and capture effects in Rayleigh fading environment. Impacts of both non-ideal channel and capture effects, specially in an environment of high interference, become important in terms of the actual observed throughput. As far as the 4-way handshaking mechanism is concerned, we extend the multi-dimensional Markovian state transition model characterizing the behavior at the MAC layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel. This way, any channel model characterizing the physical transmission medium can be accommodated, including AWGN and fading channels. We also extend the Markov model in order to consider the behavior of the contention window when employing the basic 2-way handshaking mechanism. Under the usual assumptions regarding the traffic generated per node and independence of packet collisions, we solve for the stationary probabilities of the Markov chain and develop expressions for the saturation throughput as a function of the number of terminals, packet sizes, raw channel error rates, capture probability, and other key system parameters. The theoretical derivations are then compared to simulation results confirming the effectiveness of the proposed models.     

An optical packet contention resolution supporting QoS differentiation with LRWC wavelength converters for OPS

The wavelength conversion is regarded as an effective way to resolve the optical packet contention in the wavelength domain for optical packet switching. An optical packet switching node, based on shared-per-node equipped with limited range wavelength converters and parametric wavelength converters (SPN-LP), is designed to further reduce optical packet loss probability. A novel optical packet contention resolution with priority differentiation wavelength scheduling algorithm to support quality of service (QoS) for the SPN-LP architecture is put forward in the article. The simulation results show that proposed optical packet resolution enables a good QoS differentiation, namely the high priority contending optical packet has the sufficient low packet loss probability.     

Queue‐based multiple path load balancing routing protocol for MANETs

Congestion in the network is the main cause for packet drop and increased end‐to‐end transmission delay of packet between source and destination nodes. Congestion occurs because of the simultaneous contention for network resources. It is very important to efficiently utilize the available resources so that a load can be distributed efficiently throughout the network. Otherwise, the resources of heavily loaded nodes may be depleted very soon, which ultimately affects network performances. In this paper, we have proposed a new routing protocol named queue‐based multiple path load balancing routing protocol. This protocol discovers several node‐disjoint paths from source to destination nodes. It also finds minimum queue length with respect to individual paths, sorts the node‐disjoint paths based on queue length, and distributes the packets through these paths based on the minimum queue length. Simulation results show that the proposed routing protocol distributes the load efficiently and achieves better network performances in terms of packet delivery ratio, end‐to‐end delay, and routing overhead. Copyright © 2016 John Wiley & Sons, Ltd.