Scheme In IEEE Research Articles

An Adaptive GTS Allocation Scheme for IEEE 802.15.4

IEEE 802.15.4 is a new standard uniquely designed for low-rate wireless personal area networks. It targets ultralow complexity, cost, and power for low-rate wireless connectivity among inexpensive, portable, and moving devices. IEEE 802.15.4 provides a guaranteed time slot (GTS) mechanism to allocate a specific duration within a superframe for time-critical transmissions. This paper proposes an adaptive GTS allocation (AGA) scheme for IEEE 802.15.4, which considers low latency and fairness. The scheme is designed based on the existing IEEE 802.15.4 medium access control protocol, and IEEE 802.15.4 devices can receive this AGA service without any modification. A simulation model and an analytical model are developed to investigate the performance of our AGA scheme. The numerical results show that the proposed scheme significantly outperforms the existing IEEE 802.15.4 implementation.

Persistent RCSMA: A MAC Protocol for a Distributed Cooperative ARQ Scheme in Wireless Networks

The persistent relay carrier sensing multiple access (PRCSMA) protocol is presented in this paper as a novel medium access control (MAC) protocol that allows for the execution of a distributed cooperative automatic retransmission request (ARQ) scheme in IEEE 802.11 wireless networks. The underlying idea of the PRCSMA protocol is to modify the basic rules of the IEEE 802.11 MAC protocol to execute a distributed cooperative ARQ scheme in wireless networks in order to enhance their performance and to extend coverage. A closed formulation of the distributed cooperative ARQ average packet transmission delay in a saturated network is derived in the paper. The analytical equations are then used to evaluate the performance of the protocol under different network configurations. Both the accuracy of the analysis and the performance evaluation of the protocol are supported and validated through computer simulations.

Media Access Time-Rearrangement of Wireless LAN for a Multi-Radio Collocated Platform

With the advent of new Radio Access Technologies (RATs), it is inevitable that several RATs will co-exist, especially in the license-exempt band. In this letter, we present an in-depth adaptation of the proactive time-rearrangement (PATRA) scheme for IEEE 802.11 WLAN. The PATRA is a time division approach for reducing interference from a multi-radio device. Because IEEE 802.11 is based on carrier sensing and contention mechanism, it is the most suitable candidate to adapt the PATRA.

A novel localised authentication scheme in IEEE 802.11 based Wireless Mesh Networks

In the paper, we propose an efficient two-factor localised authentication scheme for inter-domain handover and roaming in IEEE 802.11 based service-oriented wireless mesh networks (WMNs). Some important aspects, such as resource-constraint Mobile Stations (MSs) and the ping-pong movement phenomenon when handover roaming across different hotspots occurs, are considered. An analytic model is developed to investigate the efficiency of the proposed scheme. Numerical results are given to demonstrate the superiority of the proposed scheme in terms of the resultant signalling overhead, power consumption, and authentication latency, compared with the legacy authentication schemes without losing the capability of preserving the system security.

An Effective QoS Differentiation Scheme for Wireless Mesh Networks

Wireless mesh networking is emerging as an important architecture for future-generation wireless communications systems. Quality of service provisioning is a challenging issue in WMNs. In this article we study an effective QoS differentiation scheme for IEEE 802.16 WiMAX mesh networks. Both collocated and general topologies are exploited. Illustrative numerical examples are presented to demonstrate the effectiveness of the proposed strategy. The impact of key parameters on performance is discussed for differentiating various services. Moreover, with the proposed scheme, WMN scalability can be greatly improved. The challenges with respect to the integration of WMN and cooperative transmission are discussed, and the fairness problem is addressed with potential solutions.

Performance evaluation of a link adaptation scheme in IEEE 802.11e over IEEE 802.11a WLANs with QoS support

AbstractWireless Local Area Networks (WLANs) represent a powerful technology for accessing data, voice and video services in mobility. The literature dealing with IEEE 802.11 WLANs optimisation for supporting real‐time services performance is plentiful. IEEE Task Group E has been created with the aim of enhancing the Quality of Service (QoS) capabilities of the MAC IEEE 802.11, while several link adaptation algorithms have been proposed to optimise the rate selection in the IEEE 802.11a physical layer. In this work, the knowledge of the application type, provided by the MAC IEEE 802.11e layer, is exploited in a link adaptation strategy for the PHY IEEE 802.11a layer. The performance of the system is studied by using an event‐driven simulator, which implements the specifications of the IEEE 802.11e draft standard and the IEEE 802.11a standard. Simulation results show that the proposed scheme achieves both the link adaptation advantages and the required QoS support to real‐time services. Copyright © 2005 AEIT.

Service Differentiation Schemes in IEEE 802.11 Wireless LANs with Variable Frame Size

Service differentiation in wireless LANs is a growing demand, because of their increasing use for applications with different QoS requirements. This paper analyzes IEEE 802.11e based service differentiation schemes—specifically, differentiating minimum back-off window size, the retransmission limit, and combination of the two— in the presence of channel error. An analytical model is developed that can be used to compute performance measures such as saturation throughput, saturation delay, and frame dropping probabilities of different priority classes, in the presence of channel error. The effect of frame size, the number of contention nodes, transmission collision probability, and channel error conditions on the above-mentioned performance measures are studied. The analysis applies to both basic access and RTS/CTS mechanisms. A model to evaluate the performance under a hybrid access scheme, a mechanism in which both basic access and RTS/CTS mechanisms coexist, is also proposed. The frame lengths are assumed to have a general distribution F(A). It is found that in a channel with nonzero bit error rate (BER), there exists an optimal frame size that maximizes the throughput. This optimal frame size reduces with increase in BER, and is independent of the number of contending nodes.

Performance Analysis of the Contention Resolution Scheme in IEEE 802.16

At present, the mandatory contention resolution that shall be supported by IEEE 802.16 is based on truncated binary exponential backoff algorithm. In this paper, the differences of contention mechanism between IEEE 802.16 and IEEE 802.11 are analyzed. The calculations of performance metrics such as the utilization of transmission opportunity u, the delay of bandwidth request d and the drop probability of bandwidth request pd are presented. Based on simulation results, the effects of contention parameters such as the initial window W, the number of subscriber station n and the number of transmission opportunity Nto are discussed. Some policies to adjust the parameters are also provided. These policies are useful for BS to schedule its uplink bandwidth resource.

Performance Analysis on Coexistence of EDCA and Legacy DCF Stations in IEEE 802.11 Wireless LANs

The distributed coordination function (DCF) scheme of IEEE 802.11 MAC protocol does not support any concepts of quality of service (QoS) but the enhanced distributed channel access (EDCA) scheme in IEEE 802.11e standard provides QoS according to access categories using different access parameters. However, the legacy DCF stations may be used together with EDCA stations. In this letter, we investigate and analyze the performance discrimination when EDCA and DCF stations operate simultaneously

End-to-end QoS framework for heterogeneous wired-cum-wireless networks

With information access becoming more and more ubiquitous, there is a need for providing QoS support for communication that spans wired and wireless networks. For the wired side, RSVP/SBM has been widely accepted as a flow reservation scheme in IEEE 802 style LANs. Thus, it would be desirable to investigate the integration of RSVP and a flow reservation scheme in wireless LANs, as an end-to-end solution for QoS guarantee in wired-cum-wireless networks. For this purpose, we propose WRESV, a lightweight RSVP-like flow reservation and admission control scheme for IEEE 802.11 wireless LANs. Using WRESV, wired/wireless integration can be easily implemented by cross-layer interaction at the Access Point. Main components of the integration are RSVP-WRESV parameter mapping and the initiation of new reservation messages, depending on where senders/receivers are located. In addition, to support smooth roaming of mobile users among different basic service sets (BSS), we devise an efficient handoff scheme that considers both the flow rate demand and network resource availability for continuous QoS support. Furthermore, various optimizations for supporting multicast session and QoS re-negotiation are proposed for better performance improvement. Extensive simulation results showthat the proposed scheme is promising in enriching the QoS support of multimedia applications in heterogeneous wired-cum-wireless networks

Carrier-Grade Ethernet Technologies for Next Generation Wide Area Ethernet

This paper describes an overview of overall carrier-grade Ethernet technologies for next generation wide area Ethernet. In recent years, from access network to metro and core network, we can find many areas where communication services are provided by Ethernet technologies. This comes from the fact that operational efficiency and economical efficiency of Ethernet are far better than that of conventional wide area communication technologies such as SONET and ATM. On the other hand, carrier-grade reliability, operations-administration-maintenance (OAM) and quality of service (QoS) are inferior to SONET and ATM. Various standard schemes in IEEE 802 and ITU-T and vendors' proprietary schemes can leave various approaches to solve these problems. In this paper, the author explains a basic architecture of wide area Ethernet service (Q-in-Q tagging for metro network and Mac-in-Mac encapsulation for core network) at first. Various switch control technologies are then discussed which are deployed or are under evaluation in order to improve (i) reliability (i.e., resiliency) to protect subscribers against network failures, (ii) OAM for providers to perform fault and performance management, and (iii) QoS to guarantee subscriber's service level agreement between a carrier and a subscriber. Finally, a new switching architecture, Global Open Ethernet (GOE), is also introduced as one of promising approaches to realize a next generation carrier-grade Ethernet.

IEEE 802.11 MAC-Level FEC scheme with retransmission combining

In this paper, we evaluate and enhance the performance of a Forward Error Correction (FEC) scheme for IEEE 802.11 Medium Access Control (MAC). A novel retransmission combining technique is proposed to enhance the performance of the MAC-level FEC scheme.,We also identify the problem with the IEEE 802.11a physical (PHY) layer when it is used with the MAC-level FEC. A new PHY frame format, backward compatible with the original format, is proposed to resolve the problem. Finally, we analytically evaluate the error performance of the MAC-level FEC, and its enhanced performance via retransmission combining and new 802.11a PHY frame format in AWGN environment. Additionally, we present and discuss the results from simulations using TCP/UDP traffic in more realistic channel environments.

Improve TCP performance with a novel adaptive queue management scheme in IEEE 802.17 RPR optical networks

Resilient Packet Ring (RPR), a novel IEEE 802-series MAC scheme over optical network for Metropontan Area Networks (MAN), provides flexible data efficient delivery and optical transmission reliability. However, RPR fairness scheme causes TCP performance degradation. In this paper, an analytical traffic model is developed to study the impact of congestion control of TCP under RPR AM fairness scheme. Basically, two possible ways may be able to improve this impact, to equip a buffer to accommodate the burst or to employ a robust active queue management (AQM). However, buffer requirement in RPR networks may be different for various network scenarios and AQM scheme should be better for RPR networks. Furthermore, our study shows that TCP works not well if queue management parameters are fixed at a value. Hence, a novel adaptive queue management scheme with RPR feedback information is proposed. Available bandwidth for each ingress-aggregated flow should be passed to its upstream nodes in RPR MAC scheme. Accordingly, queue management design parameters could be adaptively tuned to achieve better queueing behavior. Through detailed simulations in various scenarios, our proposed schemes are able to improve TCP performance obviously.

Improved Performance with Adaptive Dly-ACK for IEEE 802.15.3 WPAN over UWB PHY

Dly-ACK scheme in IEEE 802.15.3 MAC is designed to reduce the overhead of the ACK frame in MAC layer and improve the channel utilization. However, how to using the Dly-ACK is open for implementation. In this paper, we propose an adaptive Dly-ACK scheme for both TCP and UDP traffic. We first point out the problems of applying fixed Dly-ACK scheme to these two traffic scenarios and show that the system performance is rather poor and the causes of these problems are presented. Based on our observations, two enhancement mechanisms for fixed Dly-ACK are then proposed. The first one is to request the Dly-ACK frame adaptively or change the burst size of Dly-ACK according to the transmitter queue status. The second is a retransmission counter to enable the destination DEV to deliver the MAC data frames to upper layer timely and orderly. Simulation results show that, with our enhancements, the system performance can be improved significantly compared with the conventional Imm-ACK and fixed Dly-ACK. We also investigate the impacts of some important parameters such as the buffer size on the system performance. Some important guidelines for the Dly-ACK design are given. Finally, it is worth to point out that our Dly-ACK enhancements are compatible with the standard and it is transparent to the upper layer protocols, i.e., either UDP or TCP.

Distributed power management protocols for multi-hop mobile ad hoc networks

The power management scheme in IEEE 802.11 protocol has three severe challenges: beacon contention, timing synchronization, and reliable neighbor maintenance. These challenges are more serious in large and dense multi-hop mobile ad hoc networks (MANETs). To overcome these challenges and improve the energy efficiency as well as network throughput, we propose three new power management protocols. Especially, our solutions offer the network designers full flexibility in trading energy, latency, and neighbor maintenance’s accuracy versus each other by appropriately tuning system parameters. Analyses and simulations show that the proposed protocols attain both the better energy efficiency and throughput than existing protocols.

Distributed power management protocols for multi-hop mobile ad hoc networks

The power management scheme in IEEE 802.11 protocol has three severe challenges: beacon contention, timing synchronization, and reliable neighbor maintenance. These challenges are more serious in large and dense multi-hop mobile ad hoc networks (MANETs). To overcome these challenges and improve the energy efficiency as well as network throughput, we propose three new power management protocols. Especially, our solutions offer the network designers full flexibility in trading energy, latency, and neighbor maintenance’s accuracy versus each other by appropriately tuning system parameters. Analyses and simulations show that the proposed protocols attain both the better energy efficiency and throughput than existing protocols.

Effectiveness of RTS∕CTS handshake in IEEE 802.11a Wireless LANs

The RTS/CTS reservation scheme in IEEE 802.11a Wireless LANs (WLANs) is employed to improve performance as it shortens packet collision duration and addresses the hidden station problem. An investigation has been conducted into how effective the RTS/CTS handshake is in reducing collision duration for 54 Mbit/s by extending an existing mathematical model for the particular packet overheads and delays defined in 802.11a. The study reveals, for the first time, that the RTS/CTS scheme is not beneficial in most network scenarios for the 54 Mbit/s data rate as currently specified in the 802.11a standard and that RTS/CTS effectiveness in improving throughput and average packet delay performance is uncertain.

Communication quality control scheme by using priority control mechanism for ethernet‐based wireless LANs

AbstractA method that realizes CoS (Class of Service) control in Ethernet is communication quality control based on the user priority specified by IEEE 802.1D Annex H. This paper presents a result of investigation of CoS control scheme in IEEE 802.11 system, which is Ethernet wireless LAN standardized by IEEE 802 Committee. An evaluation is also tried by computer simulation, and it is found that the bounded delay time and the bandwidth guarantee are realized, providing the best effort with higher priority in the contention control. It is also shown that the proposed scheme can be used as protection against the user who sends/receives a large amount of data, constraining the bandwidth. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(3): 53–67, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10029