Packet fair queueing algorithms for wireless networks with link level retransmission

When the real-time traffic is transmitted under multi-hop network based on IEEE 802.11, there are many problems like the degradation of throughput, delay and higher frame drop by bottle-neck. We can classify the solution about these problems into three cases, i.e. modification of media access control (MAC) algorithm, definition and usage of required new packet, and use of multi-channel. One of modification of MAC algorithm, i.e., the method which both RTS and ACK are transmitted simultaneously is quite useful to reduce the delay in the real-time traffic. Also routing algorithm has to treat packets differently according to traffic types. The interaction between routing algorithm in network layer and MAC layer is required to differentiate QoS for different traffic type, which results in the cross-layer mechanism. In this paper, proposed cross-layer algorithm, named as differentiated data-driven cut-through medium access (DDCMA), integrates the modified MAC algorithm and modified ad-hoc routing algorithm with cross-layer interaction to provide the efficiently differentiated QoS between real-time and non-real-time traffics. DDCMA is based on existing DCMA in MAC layer and enhanced DSR for network routing and targets for differentiated QoS between real/non-real-time traffics. The performance validation has done extensively using GloMoSim, well-known multihop network simulator.

Media access control (MAC) algorithms have been shown to be critical components in the overall efficiency of military radio communication networks. Many papers at the three most recent MILCOM conferences have focused on combat net radios or ML-STD-188-220B. Several of these compared different MAC algorithms for data only and data and voice networks. The MAC algorithm with the best performance characteristics for a wide class of moderately sized networks appears to be deterministic adaptable priority network access delay (DAP-NAD). The DAP-NAD algorithm can be viewed as a modified implicit token passing algorithm. This paper presents a number of significant extensions and modifications to DAP-NAD, including efficient integration of data and voice. The token passing scheme is modified so that the token effectively jumps over stations that may have transmitted in the last period and allows heavily used or higher priority nodes to have increased transmission opportunities. These modifications are shown to have markedly improved performance for the standard tactical Internet division and below (TIDB) network used to compare other MAC algorithms as well as on 16 node randomly loaded networks. Our modifications to DAP-NAD have further enhanced its ability to handle both data and voice efficiently, which is recognized by calling the MAC algorithm data and voice network access delay (DAV-NAD).

We study an interacting particle system whose dynamics depends on aninteracting random environment. As the number of particles growslarge, the transition rate of the particles slows down (perhapsbecause they share a common resource of fixed capacity). Thetransition rate of a particle is determined by its state, by theempirical distribution of all the particles and by a rapidly varyingenvironment. The transitions of the environment are determined bythe empirical distribution of the particles. We prove thepropagation of chaos on the path space of the particles andestablish that the limiting trajectory of the empirical measure ofthe states of the particles satisfies a deterministic differentialequation. This deterministic differential equation involves the timeaverages of the environment process.   We apply the results on particle systems to understand the behavior of computer networks where users access a shared resource using a distributed random Medium Access Control (MAC) algorithm. MAC algorithms are used in all Local Area Network (LAN), and have been notoriously difficult to analyze. Our analysis allows us to provide simple and explicit expressions of the network performance under such algorithms.

Throughput is a basic measure for communication efficiency. It is defined as the average fraction of time that the channel is employed for useful data propagation. This work considers the problem of analytically estimating the throughput of protocols for media access control (MAC) in mobile ad hoc networks (MANETs). The dynamic and difficult to predict nature of MANETs complicates the analysis of MAC algorithms. We use simple extensions to the interleaving model and evolving graphs, for defining the settings that model the location of mobile nodes.This work improves the understanding on impossibility results, the possible trade-offs and the analysis of fault-tolerant algorithms in MANETs. As the first result in the paper and as motivation for the ones that follow, we show that there is no efficient deterministic MAC algorithm for MANETs. Moreover, we prove a lower bound of the throughput in the radical settings of complete random relocation between every two steps of the algorithm. The lower bound matches the throughput of a strategy that is oblivious to the history of wireless broadcasts.Subsequently, we focus on the analysis of non-oblivious strategies and assume a bound on the rate by which mobile nodes relocate, i.e., randomly changing their neighborhoods. Our analysis is the first to demonstrate a novel throughput-related trade-off between oblivious and non-oblivious strategies of MAC algorithms that depends on the relocation rate of mobile nodes. We present a non-oblivious strategy that yields a randomized, fault-tolerant algorithm that can balance between the trade-offs. The studied algorithm is the first of is kind because it is a “stateful” one that quickly converges to a guaranteed throughput.

Over the past few years, mobile networks have emerged as a promising approach for future mobile IP applications. With limited frequency resources, designing an effective MAC (Medium Access Control) protocol is a hot challenge. IEEE 802.11b/g/a/n networks are currently the most popular wireless LAN products on the market [1]. The conventional IEEE 802.11b and 802.11g/a specification provide up to 11 and 54 Mbps data rates, respectively. However, the MAC protocol that they are based upon is the same and employs a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) protocol with binary exponential back-off. IEEE 802.11 DCF (Distributed Coordination Function) is the de facto MAC protocol for wireless LAN because of its simplicity and robustness [2,3]. Therefore, considerable research efforts have been put on the investigation of the DCF performance over wireless LAN [2]. With the successful deployment of IEEE 802.11a/b/g wireless LAN and the increasing demand for real-time applications over wireless, the IEEE 802.11n Working Group standardized a new MAC and PHY (Physical) layer specification to increase the bit rate to be up to 600 Mbps [3]. The throughput performance at the MAC layer can be improved by aggregating several frames before transmission [3]. Frame aggregation not only reduces the transmission time for preamble and frame headers, but also reduces the waiting time during CSMA/CA random backoff period for successive frame transmissions. The frame aggregation can be performed within different sub-layers. In 802.11n, frame aggregation can be performed either by A-MPDU (MAC Protocol Data Unit Aggregation) or A-MSDU (MAC Service Data Unit Aggregation). Although frame aggregation can increase the throughput at the MAC layer under ideal channel conditions, a larger aggregated frame will cause each station to wait longer before its next chance for channel access. Under errorprone channels, corrupting a large aggregated frame may waste a long period of channel time and lead to a lower MAC efficiency [4]. On the other hand, wireless LAN mobile stations that are defined as the stations that access the LAN while in motion are considered in this chapter. The previous paper analyzed the IEEE 802.11b/g/n MAC performance for wireless LAN with fixed stations, not for wireless LAN with mobile stations [5, 6, 7, 8, 9, 10]. On the contrary, Xi Yong [11] and Ha Cheol Lee [12] analyzed the MAC performance for IEEE 802.11 wireless LAN with mobile stations, but considered only IEEE 802.11 and 802.11g/a wireless LAN specification. So, this chapter summarizes all the reference papers and analyzes the IEEE 802.11b/g/a/n MAC performance for wireless LAN with fixed and mobile stations. In other words, we will present the analytical evaluation of saturation

With the onset of multimedia applications, Quality of Service (QoS) in 802.11-based wireless ad hoc networks has been an essential area to look into. Standard wireless protocols such as IEEE 802.11b and IEEE 802.11e have been deemed unsuitable for multimedia traffic transmission in an ad hoc (multihop) network environment due to the unique network characteristics. As an ad hoc network is infrastructureless and distributed in nature, it gives rise to several challenges in QoS provisioning. In this thesis, we focus on the research of three key areas on QoS in ad hoc networks namely, buffer management in the medium access control (MAC) layer, cross-layer design and flow admission control. Firstly, we study MAC layer buffer management in the IEEE 802.11e protocol. The IEEE 802.11e MAC protocol provides QoS for multimedia traffic by probabilistic priority queueing. Ad hoc networks tend to generate a large volume of network control packets for route maintenance and these control packets are typically queued in the highest priority queue. As a result, higher priority control traffic is always being served, consuming most of the bandwidth and results in poor network performance for data traffic. We examine this problem and propose a dynamic buffer management scheme to mitigate it. By setting different threshold levels in different priority queues, we allow lower priority data traffic to be served when the higher priority control traffic is deemed to be excessive. Simulation of our proposed scheme has shown that our approach yielded better network performance compared to the standard protocol in terms of packet delivery ratio and average delay. Secondly, we study the cross-layer interaction between the MAC and Network layers to identify its impact on QoS. We select the IEEE 802.11e MAC protocol and Ad-hoc On Demand Distance Vector (AODV) routing protocol in our study since they are standardized protocols for wireless networks. In IEEE 802.11e MAC protocol, lower priority traffic has a higher probability of being blocked. Hence, the MAC layer will inform the Network layer of a broken link through the link notification function. In this case, AODV will re-route the paths that traverse this link. As a result, higher priority traffic which shares the same link as the lower priority traffic will undergo the same re-routing procedures. We termed this phenomenon path correlation effect. Under high traffic load, the path correlation effect will be more intense and hence degrade the QoS of higher priority traffic. To break the path correlation effect, we propose a cross-layer design called the Bundled Virtual Circuit (BVC). Our proposed BVC scheme not only addresses the path correlation issues, but also provides priority treatment from the Network layer to the MAC layer. Through our simulations, our proposed cross-layer design approach is proven to provide better network performance than the 802.11e/AODV protocols in terms of packet delivery ratio and delay. Finally, we examine flow admission control at the routing layer in ad hoc networks. Standard routing protocols such as AODV performs routing on a shortest path basis. In the presence of multiple routes, hotspots are likely to form among the intermediate nodes and thus lead to network congestion. In addition, existing routes are not well-protected from the introduction of new routes. We propose a flow admission control algorithm to be used with AODV. Our algorithm allows routes to be created through available bandwidth and congestion estimation. During the route discovery phase, each node will be gauged on its estimated available bandwidth and its backlog of packets in the MAC buffer. If a node does not have sufficient bandwidth, or has too many backlogged packets compared to the requested flow rate, it will not participate in the route discovery process. From simulations, our new scheme is able to provide better network performance than the standard AODV protocol in terms of delay. Our work in this thesis focuses on QoS provisioning in ad hoc networks from the MAC and network layer perspectives. By studying the network characteristics and protocols’ behavior, we investigate the various problems of providing QoS in an ad hoc network environment and propose three different schemes to improve the QoS provisioning at the MAC and network layers. We believe that our work is able to provide some insights to the research area on QoS in ad hoc networks.

In this paper we study the correlations that exist between the required transmission power of RTS, CTS, DATA and ACK frames to guarantee a successful 4-way handshake in wireless ad hoc networks based on the IEEE 802.11 distributed coordination function (DCF). From these correlations, and starting from a set of different initial conditions, we can derive a class of power controlled media access control (MAC) algorithms for single channel ad hoc networks based on the existing IEEE 802.11 DCF. From substantial simulations of the different algorithms and comparison to some prominent alternatives, we come to a conclusion that contradicts the intuitively sound, commonly held belief which states that sending control frames at maximum power - to reduce interference on the long data frames - then, the ensuing long data frames at a lower, yet sufficient power level decreases power consumption per carried bit.

Recent advances have resulted in queue-based algorithms for medium access control which operate in a distributed fashion, and yet achieve the optimal throughput performance of centralized scheduling algorithms. However, fundamental performance bounds reveal that the "cautious" activation rules involved in establishing throughput optimality tend to produce extremely large delays, typically growing exponentially in 1/(1-r), with r the load of the system, in contrast to the usual linear growth. Motivated by that issue, we explore to what extent more "aggressive" schemes can improve the delay performance. Our main finding is that aggressive activation rules induce a lingering effect, where individual nodes retain possession of a shared resource for excessive lengths of time even while a majority of other nodes idle. Using central limit theorem type arguments, we prove that the idleness induced by the lingering effect may cause the delays to grow with 1/(1-r) at a quadratic rate. To the best of our knowledge, these are the first mathematical results illuminating the lingering effect and quantifying the performance impact. In addition extensive simulation experiments are conducted to illustrate and validate the various analytical results.

Recent advances have resulted in queue-based algorithms for medium access control which operate in a distributed fashion, and yet achieve the optimal throughput performance of centralized scheduling algorithms. However, fundamental performance bounds reveal that the cautious activation rules involved in establishing throughput optimality tend to produce extremely large delays, typically growing exponentially in $$1/(1{-}\rho )$$ 1 / ( 1 - ? ) , with $$\rho $$ ? the load of the system, in contrast to the usual linear growth. Motivated by that issue, we explore to what extent more schemes can improve the delay performance. Our main finding is that aggressive activation rules induce a lingering effect, where individual nodes retain possession of a shared resource for excessive lengths of time even while a majority of other nodes idle. Using central limit theorem type arguments, we prove that the idleness induced by the lingering effect may cause the delays to grow with $$1/(1{-}\rho )$$ 1 / ( 1 - ? ) at a quadratic rate. To the best of our knowledge, these are the first mathematical results illuminating the lingering effect and quantifying the performance impact. In addition extensive simulation experiments are conducted to illustrate and validate the various analytical results.

In vehicular ad hoc networks, vehicles compete for channel access through the medium access control protocol to transmit messages. Most traditional medium access methods assign the same probability to all vehicles accessing the channel and ignore the intrinsic attributes of different vehicles. Attributes regarding the position and role of a vehicle are important factors to be considered when a vehicle is competing for the channel. In this paper, we introduce a new notion of a weight factor in a fair medium access game and propose a game model to adjust each node's channel access probability with complete information in the vehicular environment based on the weight factors of vehicles. The weight of a vehicle represents a specific property, such as the distance between vehicles, the vehicle's role, and so on, which can be used to distinguish priorities of different vehicles during channel competition. We also provide instances of relevant applications by using the distance between vehicles and a vehicle's role. Then, we analyze the incomplete information game in which each node cannot acquire the previous channel access probabilities of other nodes. Moreover, we construct a distributed best‐response learning algorithm based on the medium access game model and demonstrate that the game can converge to a unique and stable equilibrium under certain conditions. Furthermore, we investigate some performance indicators such as channel access delay and normalized throughput and perform extensive numerical analyses compared with the IEEE 802.11p protocol and an existing game‐based medium access control algorithm without consideration of weights. The performance comparison of high‐priority nodes and all nodes in a network is also studied. Finally, we analyze the effects of the proportion of high‐priority nodes on the performance of the channel. The performance improvement after introducing the weight factor is verified by these numerical results.

The Internet is facing two problems simultaneously: there is a need for a faster switching/routing infrastructure and a need to introduce guaranteed qualities-of-service (QoS). Each problem can be solved independently: high performance routers can be made faster by using input-queued crossbars instead of shared memory systems; QoS can be provided using packet fair queueing (PFQ) algorithms. Until now, however, the two solutions have been mutually exclusive-all of the work on PFQ algorithms has required that routers use output-queueing or centralized shared memory. In this paper, we design and implement a packet scheduling algorithm, DF/sup 2/Q (distributed feedback fair queueing), on the basis of CIOQ (combined input output queueing) architecture. The most important feature of this scheduling algorithm is the introduction of a feedback mechanism. We analyze and discuss the performance of DF/sup 2/Q, and the experimental results show that it can avoid internal congestion effectively and improve the efficiency of resource utilization.

This paper presents a System on a Chip (SoC) Field-Programmable Gate Array (FPGA) implementation for Media Access Control (MAC) layer of a fast industrial Wireless Local Area Network (iWLAN) protocol, which is used to control industrial robots in factory automation environments. This protocol is a potential technique for industrial wireless communication system by using the Low overhead Packet Division Multiple Access (PDMA) scheme controlled by MAC layer. In our previous research, the MAC layer hardware was implemented and tested on simulation software, but the SoC design for the MAC layer has not been implemented and real tested on the FPGA. In this paper, we have successfully implemented the SoC system for MAC layer of this high-speed wireless communication protocol on the FPGA.

To realize opportunistic MAC (Media Access Control) layer access and to avoid collision in channel competition among nodes in powerline carrier and wireless converged communications, this paper proposes a channel prediction based access control algorithm of converged communication network. Since the process of occupying channels was unexpected, the semi-Markova process is adopted to predict channel competition activities. This proposed algorithm substantially utilizes channel sensing results and the channel competition condition to predict channel state in the next time and the remainder time. Compared to traditional carrier sensing multiple access algorithm, the simulation result shows the proposed approach can greatly improve the converged network efficiency in terms of collision rate and packet loss rate.

최근 무선 인터넷 수요의 증가와 더불어 IEEE 802.11 WLAN의 표준화 작업도 활발히 진행 중이다. 고속처리량을 위한 IEEE 802.11n의 연구 동향은 크게 두 가지로 MAC 계층에서 패킷 간의 Aggregation을 통하여 시스템 처리량을 높인 결과와PHY 계층에서 MIMO 시스템을 적용하여 데이터 전송속도를 높인 결과로 정리될 수 있다. 그러나 아직까지 MAC 계층과 PHY 계층의 연동을 고려하여 IEEE 802.11n의 성능 분석을 보인 결과는 발표되지 않았다. 본 논문에서는 IEEE 802.11n 시스템에서 MAC 계층과 PHY 계층의 연동을 고려하여 성능을 분석한다. MAC 계층에서의 A-MPDU 기법과 PGY 계층에서 MIMO 방식을 적용한다. 결과적으로 기존의 방식에 비해 데이터 전송속도의 증가와 처리량이 향상되었음을 보인다. 또한, MAC과 PRY의 연동을 고려하여 현실성 있는 시뮬레이터인 NS-2를 사용하기로 한다. IEEE 802.11 WLAN(Wireless Local Area Network) standard is currently developing with increased wireless internet demand. Study trends of IEEE 802.11n for high throughput show two aspects, enhanced system throughput using aggregation among packets in MAC(Medium Access Control) layer, and better data rates adapting MIMO(Multiple-Input Multiple-Output) in PRY(Physical) layer. But, no one demonstrates IEEE 802.11n system performance results considering MAC and PRY connection. This paper adapts A-MPDU(Aggregation-MAC Protocol Data Unit) method in MAC layer and MIMO in PRY layer for IEEE 802.11n system. Consequently, Simulation results show enhanced throughput and data rates compared to existing system. Also, We use NS-2(Network Simulator-2) considering MAC and PRY connection for reality.

In dynamic wireless ad hoc networks (DynWANs), autonomous computing devices set up a network for the communication needs of the moment. These networks require the implementation of a medium access control (MAC) layer. We consider MAC protocols for DynWANs that need to be autonomous and robust as well as have high bandwidth utilization, high predictability degree of bandwidth allocation, and low communication delay in the presence of frequent topological changes to the communication network. Recent studies have shown that existing implementations cannot guarantee the necessary satisfaction of these timing requirements. We propose a self-stabilizing MAC algorithm for DynWANs that guarantees a short convergence period, and by that, it can facilitate the satisfaction of severe timing requirements, such as the above. Besides the contribution in the algorithmic front of research, we expect that our proposal can enable quicker adoption by practitioners and faster deployment of DynWANs that are subject changes in the network topology.