Mechanism In IEEE Research Articles

Emergency access mechanism in IEEE 802.15.4 for wireless body area sensor networks

IEEE 802.15.4 protocol has attracted much attention in research and industrial communities as candidate technology for wireless body area sensor networks (WBASNs). IEEE 802.15.4 supports the exclusive use of a wireless channel through guaranteed time slot (GTS). However, on one hand, bandwidth underutilization rate may be lower because of the variance between the guaranteed bandwidth and the arrival rate. On the other hand, the waiting time for transmitting emergency notification is getting longer when the GTSs assigned to the nodes increase in WBASNs. To solve these problems, in this article, a new scheme is proposed to reduce transmission delay for the alarm notification in emergent situations. Simulation results are presented to validate the efficiency of the proposed scheme by comparing it with the medium access control (MAC) protocol of IEEE 802.15.4.

STOCHASTIC AUTOMATA NETWORKS FOR MODELLING SCHEDULING SCHEME IN WiMAX NETWORKS

WiMAX (Worldwide Interpretability for Microwave Access) is one of the leader standards of broadband Wireless Access (BWA). This standard becomes a competitor of 4G or LTE (Long Terme Evolution) with the introduction of different class of service flow (UGS, rtPS, nrtPS, BE). Each service class has its own QoS requirements. Even if the standard specify the transmission policy of each service class, it recommends the implementation of an admission control (AC) without any specification. This task is let to the operator. In this paper, we propose an implementation of an AC algorithm mechanism for IEEE 802.16. The performance evaluation of these networks by analytical models is not easy due to the state space explosion, thus we use the Stochastic Automata Networks (SAN) formalism to model our proposed AC mechanism. With the SAN we calculate the rewards of the proposed AC and we show that the proposed solution is efficient.

Achievable Throughput-Based MAC Layer Handoff in IEEE 802.11 Wireless Local Area Networks

We propose a MAC layer handoff mechanism for IEEE 802.11 Wireless Local Area Networks (WLAN) to give benefit to bandwidth-greedy applications at STAs. The proposed mechanism determines an optimal AP with the maximum achievable throughput rather than the best signal condition by estimating the AP's bandwidth with a new on-the-fly measurement method, Transient Frame Capture (TFC), and predicting the actual throughput could be achieved at STAs. Since the TFC is employed based on the promiscuous mode of WLAN NIC, STAs can avoid the service degradation through the current associated AP. In addition, the proposed mechanism is a client-only solution which does not require any modification of network protocol on APs. To evaluate the performance of the proposed mechanism, we develop an analytic model to estimate reliable and accurate bandwidth of the AP and demonstrate through testbed measurement with various experimental study methods. We also validate the fairness of the proposed mechanism through simulation studies.

Performance Optimization with Efficient Polling Mechanism in IEEE 802.16 Networks with Cross-Layer Consideration

IEEE 802.16 standard suite defines a reservation-based bandwidth allocation mechanism. A SS (Subscriber Station) has to be polled to request bandwidth reservation before transmits uplink data to a BS (Base Station). In this mechanism exist two main polling modes: the unicast polling mode and the contention-based polling mode. The different polling operations in MAC (Medium Access Control) result in different PHY (PHYsical layer) frame structure that deeply affect the performance. Therefore, there should be an optimal scheme to adopt these two polling modes in order to optimize the performance. Although the standard defines five service classes to adaptively use the polling modes to fit the QoS (Quality of Service) requirements of different applications, it does not specify exactly a scheme to adopt these two polling modes efficiently and fairly during the polling process. In~this paper, we investigate the polling mechanisms in IEEE 802.16 networks, and focus the attention on the performance caused by different adoption schemes. We also propose a simple but efficient polling mechanism to optimize the performance. The simulation results verify that the performance is conditioned to the fulfillment of the polling mechanisms and our proposed optimal polling scheme can allocate bandwidth more efficient and achieve better performance.

Real-time cross-layer design for a large-scale flood detection and attack trace-back mechanism in IEEE 802.11 wireless mesh networks

IEEE 802.11 WMN is an emerging next generation low-cost multi-hop wireless broadband provisioning technology. It has the capability of integrating wired and wireless networks such as LANs, IEEE 802.11 WLANs, IEEE 802.16 WMANs, and sensor networks. This kind of integration: large-scale coverage, decentralised and multi-hop architecture, multi-radios, multi-channel assignments, ad hoc connectivity support the maximum freedom of users to join or leave the network from anywhere and at anytime has made the situation far more complex. As a result broadband resources are exposed to various kinds of security attacks, particularly DoS attacks.

Algorithm for choosing ARQ feedback types based on IEEE 802.16

ARQ mechanism in IEEE 802.16 can resolve the problems for data transmission on wireless link, but there is no appropriate solution for choosing the ARQ feedback types. The key to the algorithm is to choose an appropriate feedback type to send feedback messages for high resource utilization according to wireless link. Therefore, a new algorithm for choosing proper feedback types in real time was proposed. The simulation results show that the new algorithm can increase resource utilization.

Delay distribution and loss probability of bandwidth requests under truncated binary exponential backoff mechanism in IEEE 802.16e over Gilbert-Elliot error channel

This paper presents the mathematical analysis of the truncated binary exponential backoff (TBEB) mechanism as a contentionresolution for bandwidth requests in the broadcast polling and themulticast polling in the IEEE 802.16e. We derive the delaydistribution and the loss probability of request packets in the TBEBover Gilbert-Elliot error channel, by analytic methods on theassumption of Bernoulli arrival process and the unsaturatedcondition. The optimal contention period of transmissionopportunities for transmitting bandwidth requests can be obtainedwhile satisfying QoS on delay bound and loss bound. Furthermore, wefind the utilization of transmission opportunity to see efficiencyof the bandwidth. Numerical examples show that the analyticalresults are well-matched with simulations, and the performanceevaluations in the broadcast polling and multicast polling arecompared on the mean delay, the loss probability and the utilizationof transmission opportunity. Numerical results address that themulticast polling with more groups has better performance than thebroadcast polling in the sense of shorter delay, lower lossprobability and higher utilization of transmission opportunity.

Wireless Networked Control System using ZigBee/IEEE 802.15.4

In this paper, the use of wireless sensor networks for networked control loop is analyzed. As the non beacon-enabled mode of IEEE 802.15.4/ZigBee does not ensure the stability for the control loop since non mechanism can prevent the perturbation coming from other applications sharing the same network, the quality of control has to be guaranteed for the control loop. Several possible solutions are investigated. The first one is the CSMA/CA with probabilistic priority by adjusting the minimum waiting time. The second one consists on a deterministic priority black burst mechanism in IEEE 802.15.4/ZigBee. The third one is the beacon-enabled mode using the Guaranteed Time Slot (GTS) mechanism.

Analytical Modeling of Contention-Based Bandwidth Request Mechanism in IEEE 802.16 Wireless Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The IEEE 802.16 wireless metropolitan area network (WMAN) standard is a promising and cost-effective, last-mile wireless technology for the provision of broadband Internet access to end users. In this paper, we present an accurate analytical model that describes the contention-based bandwidth (BW) request scheme of the 802.16 standard, which is also known as WiMAX, for the persistent and nonpersistent request generation cases. We first model the contention procedure with a Markov chain, taking into account the exponential back-off procedure as well as the waiting time for a BW assignment and the possible timeout for lost messages. The accuracy of the model is then evaluated by comparing it with simulation results for a wide range of values of the parameters involved. We use this model to accurately calculate the capacity of the contention slots in delivering BW requests, from which the average access delay is also found. These measures are used to determine a proper configuration for the efficient operation of the contention-based BW request scheme. The proposed model provides a useful analytical tool for devising adaptive configuration mechanisms for the contention access mode of the 802.16 medium access control (MAC) layer. </para>

A Review of the Challenges in the Implementation of Next-Generation ZigBee Networking

One of the key challenges in the implementation of ZigBee networks is the development of algorithms which provide autonomous meshing of beacons with minimal or no interference. This feature is out of the scope of current ZigBee capabilities. The energy and bandwidth constraints and the potential large-scale deployment pose challenges in efficient resource allocation and sensor management. In this review paper, we will focus on the problems which hinder the reliable and low-latency operation of deeply-embedded wireless sensor networks. We will also analyze the proposed solutions which play a key role in bolstering ZigBee as the true mediator in making the current scenario of wireless sensor networks (WSN) networking more reliable and thus paving the way for meeting the challenges and requirements demanded by next-generation ZigBee networks. The Review paper has been divided into two parts. In the first part, we briefly introduce the beaconing mechanism of IEEE 802.15.4 and analyze it from the point of view of mesh networks. In the second part, we review the hidden-node problem from the perspective of IEEE 802.15.4. Finally, we conclude with some remarks on the future scope of ZigBee networking.

Admission Control Based on Rate-Variance Envelop for VBR Traffic Over IEEE 802.11e HCCA WLANs

With the increasing popularity of using wireless local area networks (WLANs) for Internet access, the controlled channel access mechanism in IEEE 802.11e WLANs, i.e., HCF controlled channel access (HCCA), has received much more attention since its inherent centralized mechanism is more efficient in handling time-bounded multimedia traffic. So far, only a few research studies address the admission control problem of variable bit rate (VBR) traffic over HCCA. These existing studies consider each traffic flow individually and, thus, cannot exploit the statistical multiplexing gain among multiple VBR traffic flows. In this paper, we apply the existing statistical multiplexing framework to the studied admission control problem, with all the features of IEEE 802.11e HCCA being taken into consideration. Experimental results show that our proposed admission control scheme achieves significant improvement in network utilization while still satisfying all the quality-of-service (QoS) requirements.

Integrated quality-of-service differentiation over IEEE 802.11 wireless LANs

The fundamental medium access control mechanism in IEEE 802.11 wireless LANs (WLANs)-distributed coordination function (DCF) only supports the best-effort service and does not support quality-of-service (QoS) differentiation. Enhanced distributed channel access (EDCA) in IEEE 802.11e supports delay differentiation. A new approach, EDCA+ , is proposed to enhance QoS over WLANs. It simultaneously achieves bandwidth, delay and jitter differentiation by distinguishing the minimum contention window, the maximum backoff stage or persistent factor and packet-loss rate differentiation by distinguishing the retry limit. Analytical models are proposed to analyse the performance of EDCA+ in terms of throughput, bandwidth, delay, jitter and packet-loss rate. Extensive simulations are also carried out to evaluate the accuracy of the proposed performance models and to compare the performance of DCF, EDCA and EDCA+. The simulation results show that EDCA+ performs better than DCF and EDCA in ensuring integrated QoS, and that the proposed analytical models are valid.

An implicit GTS allocation mechanism in IEEE 802.15.4 for time-sensitive wireless sensor networks: theory and practice

Timeliness guarantee is an important feature of the recently standardized IEEE 802.15.4 protocol, turning it quite appealing for Wireless Sensor Network (WSN) applications under timing constraints. When operating in beacon-enabled mode, this protocol allows nodes with real-time requirements to allocate Guaranteed Time Slots (GTS) in the contention-free period. The protocol natively supports explicit GTS allocation, i.e. a node allocates a number of time slots in each superframe for exclusive use. The limitation of this explicit GTS allocation is that GTS resources may quickly disappear, since a maximum of seven GTSs can be allocated in each superframe, preventing other nodes to benefit from guaranteed service. Moreover, the GTS may be underutilized, resulting in wasted bandwidth. To overcome these limitations, this paper proposes i-GAME, an implicit GTS Allocation Mechanism in beacon-enabled IEEE 802.15.4 networks. The allocation is based on implicit GTS allocation requests, taking into account the traffic specifications and the delay requirements of the flows. The i-GAME approach enables the use of one GTS by multiple nodes, still guaranteeing that all their (delay, bandwidth) requirements are satisfied. For that purpose, we propose an admission control algorithm that enables to decide whether to accept a new GTS allocation request or not, based not only on the remaining time slots, but also on the traffic specifications of the flows, their delay requirements and the available bandwidth resources. We show that our approach improves the bandwidth utilization as compared to the native explicit allocation mechanism defined in the IEEE 802.15.4 standard. We also present some practical considerations for the implementation of i-GAME, ensuring backward compatibility with the IEEE 801.5.4 standard with only minor add-ons. Finally, an experimental evaluation on a real system that validates our theoretical analysis and demonstrates the implementation of i-GAME is also presented.

Short-term non-uniform access in IEEE 802.11-compliant WLANs: A study on its impact on the saturation performance

Along with the success of IEEE 802.11-compliant WLANs, the distributed coordinated function (DCF) specified as the contention-based medium access mechanism in IEEE 802.11 has been widely used to support applications in new regimes. A thorough understanding of the characteristics of IEEE 802.11 DCF is therefore a research focus. DCF assumes the binary exponential backoff algorithm (BEBA) [D. Bertsekas, R. Gallager, Data Networks, Prentice Hall, 1992]. Several existing models that characterize BEBA as a p-persistent scheme have ignored several subtle protocol details. This has practically constrained the models from being applied in a broader range of configurations, e.g., small contention window, and from being further extended, e.g., 802.11e EDCA. In this paper, we develop an analytical model that captures the subtlety, and faithfully describes the channel activities as governed by DCF. Based on the devised model, we perform a rigorous analysis on the saturation throughput performance in a single-hop WLAN. We show that the stochastic property of the backoff time, r, may substantially impact the system performance. For example, setting the range of r to [1,CW] instead of [0,CW-1], can degrade the system throughput considerably. We also identify, by clearly defining and thus being able to differentiate the two terms, attempt probability and transmission probability, an erroneous extension made to Bianchi's model [G. Bianchi, Performance analysis of the IEEE 802.11 distributed coordination function, IEEE JSAC, 18(3) (2000) 535-547]. All the findings are corroborated by ns-2 simulation.

PARAMETER DECISION FOR ENHANCING PERFORMANCE OF WIRELESS LANs WITH PRIORITIZED MESSAGES

Distributed coordination function (DCF) is a primary random access mechanism of IEEE 802.11, which is the basic protocol of wireless LAN based on the CSMA/CA protocol. It enables fast installation with minimal management and maintenance costs and is a very robust protocol for the best effort service in wireless medium. The current DCF, however, is known to be unsuitable for real-time applications such as voice message transmission. In this paper, we focus on the performance issues of IEEE 802.11 which accommodates the prioritized messages. Existing results use the initial window size and backoff window-increasing factor as tools to handle the priority of the messages. Instead, we introduce a novel scheme which chooses the backoff timer with arbitrary probabilities. By this, one can greatly reduce the backoff delay of the lower priority messages without degrading the performance of higher priority. Additionally, we provide a step-by-step procedure which determines the system parameters such as the initial window size, backoff window-increasing factor, and the backoff timer choosing probabilities, guaranteeing the quality of service (QoS).

A new call admission control method for providing desired throughput and delay performance in IEEE802.11e wireless LANs

The draft IEEE 802.11e standard aims at providing quality of service (QoS) support in 802.11 wireless local area networks (WLANs). Enhanced distributed coordination function (EDCF), being the fundamental medium access control mechanism in IEEE 802.11e, can only provide service differentiation but offers no QoS guarantees. While service differentiation does not perform well under high traffic load conditions, call admission control (CAC) becomes necessary in order to provide and support the QoS of existing calls. In this paper, we first analyze the saturation throughput and mean access delay performance of differentiated service provided by EDCF. Specifically, we investigate the impact of transmission opportunity (TXOP) and wireless channel errors on the performance of the EDCF. Based on the results from this analysis, we propose a new CAC algorithm that provides the desired throughput and access delay performance. Simulated performance results demonstrate the effectiveness of the proposed CAC algorithm

MAC-Layer QoS Management for Streaming Rate-Adaptive VBR Video over IEEE 802.11e HCCA WLANs

With the increasing popularity of using WLANs for Internet access, the HCCA mechanism in IEEE 802.11e WLANs has received much more attention due to its efficiency in handling time-bounded multimedia traffic. To achieve high network utilization and good end-to-end QoS in the scenario of VBR video over HCCA is a very challenging task because of the dynamics coming from both the network conditions and the video content. In this paper, we propose a cross-layer framework for efficiently delivering multiclass rate-adaptive VBR video over HCCA. The proposed framework consists of three major modules: the MAC-layer admission control, the MAC-layer resource allocation, and the application-layer video adaptation. Experimental results demonstrate the effectiveness of each individual module and the advantage of dynamic interactions among different modules.

Energy and delay trade‐off of the GTS allocation mechanism in IEEE 802.15.4 for wireless sensor networks

AbstractThe IEEE 802.15.4 protocol proposes a flexible communication solution for low‐rate wireless personal area networks (LR‐WPAN) including wireless sensor networks (WSNs). It presents the advantage to fit different requirements of potential applications by adequately setting its parameters. When in beacon‐enabled mode, the protocol can provide timeliness guarantees by using its Guaranteed Time Slot (GTS) mechanism. However, power‐efficiency and timeliness guarantees are often two antagonistic requirements in wireless sensor networks. The purpose of this paper is to analyze and propose a methodology for setting the relevant parameters of IEEE 802.15.4‐compliant WSNs that takes into account a proper trade‐off between power‐efficiency and delay bound guarantees. First, we propose two accurate models of service curves for a GTS allocation as a function of the IEEE 802.15.4 parameters, using Network Calculus formalism. We then evaluate the delay bound guaranteed by a GTS allocation and express it as a function of the duty cycle. Based on the relation between the delay requirement and the duty cycle, we propose a power‐efficient superframe selection method that simultaneously reduces power consumption and enables meeting the delay requirements of real‐time flows allocating GTSs. The results of this work may pave the way for a power‐efficient management of the GTS mechanism in an IEEE 802.15.4 cluster. Copyright © 2006 John Wiley &amp; Sons, Ltd.

A Power-Efficient Access Point Operation for Infrastructure Basic Service Set in IEEE 802.11 MAC Protocol

Infrastructure-based wireless LAN technology has been widely used in today's personal communication environment. Power efficiency and battery management have been the center of attention in the design of handheld devices with wireless LAN capability. In this paper, a hybrid protocol named improved PCF operation is proposed, which intelligently chooses the access point- (AP-) assisted DCF (distributed coordinator function) and enhanced PCF (point coordinator function) transmission mechanism of IEEE 802.11 protocol in an infrastructure-based wireless LAN environment. Received signal strength indicator (RSSI) is used to determine the tradeoff between direct mobile-to-mobile transmission and transmission routed by AP. Based on the estimation, mobile stations can efficiently communicate directly instead of being routed through AP if they are in the vicinity of each other. Furthermore, a smart AP protocol is proposed as extension to the improved PCF operation by utilizing the historical end-to-end delay information to decide the waking up time of mobile stations. Simulation results show that using the proposed protocol, energy consumption of mobile devices can be reduced at the cost of slightly longer end-to-end packet delay compared to traditional IEEE 802.11 PCF protocol. However, in a non-time-critical environment, this option can significantly prolong the operation time of mobile devices.

A novel hidden station detection mechanism in IEEE 802.11 WLAN

The popular IEEE 802.11 wireless local area network (WLAN) is based on a carrier sense multiple access with collision avoidance (CSMA/CA), where a station listens to the medium before transmission in order to avoid collision. If there exist stations which can not hear each other, i.e., hidden stations, the potential collision probability increases, thus dramatically degrading the network throughput. The RTS/CTS (request-to-send/clear-to-send) frame exchange is a solution for the hidden station problem, but the RTS/CTS exchange itself consumes the network resources by transmitting the control frames. In order to maximize the network throughput, we need to use the RTS/CTS exchange adaptively only when hidden stations exist in the network. In this letter, a simple but very effective hidden station detection mechanism is proposed. Once a station detects the hidden stations via the proposed detection mechanism, it can trigger the usage of the RTS/CTS exchange. The simulation results demonstrate that the proposed mechanism can provide the maximum system throughput performance.