Mechanism In IEEE Research Articles

Improved backoff mechanism for IEEE 802.15.4 MAC protocol

Concerning the impact on network performance of the mobile nodes and the constantly changing data transmission rate,the authors proposed a new backoff scheme for IEEE802.15.4,which used Probability Judgment based on Network Load and Exponentially Weighted Moving Average(PJNL_EWMA) method.According to a real-time monitoring of current network status by probability judgment of network load,this method dynamically adjusted backoff exponent by EWMA when Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) began.Compared with the IEEE802.15.4 standard protocol and MBS(Memorized Backoff Scheme) + EWMA algorithm,the simulation experiments on NS2 platform show that the PJNL_EWMA algorithm not only improves the throughput of the network,but also reduces the packet loss rate and the collision ratio,significantly improving the network performance.

IEEE802.15.4 guaranteed time slot performance analysis and allocation optimization under multi-slot

IEEE802.15.4标准的保障时隙（GTS）机制可分配多个时隙,用于保障实时性数据的传输。针对非竞争接入期多时隙下GTS性能分析的不足,利用网络微积分法分析时延和吞吐量服务曲线及其与能耗的关系,改进IEEE802.15.4传感器节点模型,建模仿真研究GTS参数对网络性能（时延、吞吐量及能耗）的影响。仿真结果表明：根据高低突发性数据率的情况,最优化配置下的GTS可以满足实时性数据的传输。

Improving IPTV Forwarding Mechanism in IEEE 802.16j MMR Networks Based on Aggregation

Internet protocol television (IPTV) service depends on the network quality of service (QoS) and bandwidth of the broadband service provider. IEEE...

Performance Analysis of IEEE 802.15.4e Time Slotted Channel Hopping for Low-Rate Wireless Networks

The release of IEEE 802.15.4e specification significantly develops IEEE 802.15.4. The most inspiring improvement is the enhancement for medium access control (MAC) sublayer. To study the performance of IEEE 802.15.4e MAC, in this paper we first present an overview of IEEE 802.15.4e and introduce three MAC mechanisms in IEEE 802.15.4e. And the major concern here is the Time Slotted Channel Hopping (TSCH) mode that provides deterministic access and increases network capacity. Then a detailed analytical Markov chain model for TSCH carrier sense multiple access with collision avoidance (CSMA-CA) is presented. Expressions which cover most of the crucial issues in performance analysis such as the packet loss rate, energy consumption, normalized throughput, and average access delay are presented. Finally the performance evaluation for the TSCH mode is given and we make a comprehensive comparison with unslotted CSMA-CA in non-beacon enabled mode of IEEE 802.15.4. It can validate IEEE 802.15.4e network can provide low energy consumption, deterministic access and increase network capacity.

CLUSTER BASED TIME DIVISION MULTIPLE ACCESS SCHEDULING SCHEME FOR ZIGBEE WIRELESS SENSOR NETWORKS

In IEEE 802.15.4 ZigBee Wireless Sensor Networks, an efficient scheduling mechanism is required for reliable data transmission. Further, concurrent transmission of huge data through CSMA/CA incurs more packet collision rate. This complicated condition has to be eliminated to improve the system throughput. In this study, we propose to deploy cluster based TDMA scheduling mechanism for IEEE 802.15.4 ZigBee Wireless Sensor Networks. This TDMA slot allocation strategy allocates slots to the nodes based on queue occupancy information. It assigns TDMA slots starting from nodes with high queue occupancy value. Nodes that have high queue occupancy value will probably get long TDMA slot period. We prove the proficiency of our mechanism using Network Simulator 2 (NS-2). Our approach fairly allocates slots to the nodes and considerably reduces packet collision rate.

A Call Admission Control Scheme for Multimedia Support Over IEEE 802.11 Wireless LANs

These days there is an increasing interest for VoIP over wireless LANs. QoS support for real-time services like voice in the IEEE 802.11 WLAN is an important issue. Since IEEE 802.11 uses contention based MAC protocol – the distributed coordination function DCF, it is difficult to support the strict QoS requirements for voice in these networks. In this thesis a call admission scheme called “CAC” is proposed to achieve this goal, without changing the basic channel access mechanism of IEEE 802.11. CAC scheme regulates the arriving traffic in the wireless network to efficiently coordinate the medium among the contending traffic sources so that the network operates at optimal point, supporting the QoS requirements as well as providing better channel utilization. In this proposal, majority of available bandwidth is allocated to voice sources and remaining small amount is allocated for non real-time data traffic. It is expected that the proposed CAC scheme can well support strict QoS requirements, such as high throughput and low delay at the same time achieve a high channel utilization.

Quality of Service Based Handover Approach in a WLAN network

As the technology is improving so are the demands of end users and their applications increasing. A wide variety of new applications are being invented daily. These applications have different demands from the underlying network protocol suite. High bandwidth internet connectivity has become a basic requirement to the success of almost all of these areas. For the following concern Wireless networks have recently received a lot of attention. The most promising issue that needs to be taken into account while considering a wireless network is Quality of service (QoS). In this paper work we have considered a handover mechanism for IEEE 802.11 Wi-Fi and perform some modifications in that like firstly we increased the range of the access point and secondly increases the speed of Mobile Node (MN) and then study the effect of these changes on QoS in respective throughput delay and jitter. For the simulation purpose we have make use of wireless simulator NS-2 (Network Simulator version 2). Thus aim of this paper is to study the variations in average throughput, delay and jitter with the increased range of access point and increasing speed of mobile node with the help of NS-2 software.

PABM-EDCF: parameter adaptive bi-directional mapping mechanism for video transmission over WSNs

To support and keep high quality of video transmission over wireless sensor networks, this paper proposes a parameter adaptive bi-directional cross-layer mapping algorithm on the basis of the operation mechanism of IEEE 802.11e Enhanced Distributed Coordination Function (EDCF) supporting video service differentiation, named PABM-EDCF. Instead of classifying video data to a specific access category in 802.11e network, our proposed adaptive cross-layer scheme makes use of the hierarchy characteristic of video stream, dynamically maps video data to the appropriate access categories according to both the significance of the different video frames and the network traffic load. The significance passes from the application layer to the media access layer through a cross-layer architecture. In order to prevent the network congestion and keep the high transmission quality, the proposed algorithm adopts bi-directional floating mapping algorithm and congestion awareness mechanism based on the queue length and frame types. The mapping parameters are updated according to the network condition in time. Our simulation results indicate: the proposed method (a) improves the video transmission quality; (b) optimizes the management and utilization of queue resources; and (c) yields superior performance (under different loads) over 802.11e, static mapping and adaptive mapping schemes.

A Novel Multicast Collision Prevention Mechanism for IEEE 802.11

In this letter, we introduce a novel Multicast Collision Prevention (MCP) mechanism for IEEE 802.11 WLANs. The proposed MCP mechanism has been designed following the operation principles of the IEEE 802.11 standard. Our analysis shows that the proposed MCP mechanism effectively improves the reliability and efficiency of the multicast mechanism defined by the IEEE 802.11 standard. Simulation results also show that our proposal properly interoperates with the 802.11 unicast mechanism.

A refined MAC protocol with multipacket reception for wireless networks

AbstractMedium access control (MAC) protocols making use of multipacket reception (MPR) capability achieve better throughput than conventional MAC protocols. When a wireless network operates with MPR capable nodes and non‐MPR nodes, the MAC protocols must not only utilise the MPR capability to maximise throughput, but must also enable the co‐existence with these two types of nodes. We propose a new MPR MAC protocol to achieve the co‐existence requirement by adopting a request‐to‐send (RTS)/clear‐to‐send (CTS) mechanism in IEEE 802.11 MAC standards. This MPR MAC protocol also improves throughput by allowing additional data transmissions to use the MPR capability fully. We analyse the system throughput of the co‐existence of different link characteristics of nodes, and optimise its throughput by adjusting contention window sizes with respect to certain throughput requirements of the nodes. Copyright © 2010 John Wiley & Sons, Ltd.

On the optimization of the contention resolution mechanism for IEEE 802.16 networks

The IEEE 802.16 standard defines a contention bandwidth request mechanism offering QoS-aware broadband access through a wireless medium. According to the standard, the Base Station (BS) is responsible for granting the requests issued by the Subscriber Stations (SSs). The SSs communicate their requests to the BS by placing their requests into the uplink subframe, using the contention period defined within the subframe for this purpose. The size of contention period, defined in minislots, is fixed by the BS on a frame by frame basis. The remaining part of the uplink subframe is used to carry the data frames. A tradeoff between these two periods of the uplink subframe is required for an effective operation of the system. On the contrary, if the size of the contention is shorten below a certain threshold, the SSs may be unable to place their requests within the time required by the end-user applications. In this paper, we introduce an adaptive mechanism of the contention period size. The proposed mechanism takes into account the varying operation conditions of the system by estimating the number of stations that may be placing a request. Simulation results confirm that our proposal outperforms other mechanisms having recently been reported in the literature.

Performance enhancement of repacking and borrowing mechanisms for IEEE 802.16j multihop resource scheduling

The IEEE 802.16j standard has been proposed to triumph over the shadow fading and path attenuation problems in IEEE 802.16e networks by employing the multihop relay (MR) technology. Taking path selection and spatial reuse into account, numerous dynamic/heuristic scheduling algorithms have been presented for MR networks. Unfortunately, although these scheduling schemes can achieve high efficiency of resource utilization, almost all of their low time complexities considerably rely on expensive operations and sophisticated data structures. To maintain the simplicity and low time complexity of fixed-assignment scheduling while guaranteeing high resource utilization, this paper proposes a repacking and borrowing-based resource scheduling algorithm, RBRS, for IEEE 802.16j MR networks. In the repacking phase, a connection that is served via a direct path can be handed off to a cooperative path to release a part of its allocated base station (BS) resources. Since BS resources are shared by all connections within the BS coverage, repacking can increase the amount of available BS resources to serve the connection attempts that arrive at relay stations (RSs) currently under resource starvation. To complement repacking and further enhance the performance of RBRS, borrowing is applied. In the borrowing phase, over-loaded RSs are capable of borrowing resources from under-loaded RSs, further improving the resource utilization. Our main contributions are twofold: (1) to the best of our knowledge, this paper is the first effort in the literature to investigate the performance enhancement of repacking and borrowing operations for MR networks (including IEEE 802.16j); (2) both analytic and simulation models are developed to validate against each other and to study the performance of RBRS. The simulation results indicate that RBRS requires a low computational time which is comparable to that of fixed-assignment scheduling. Furthermore, by increasing available BS resources and balancing RS resources, RBRS shows near-optimal system capacity and throughput performance at the same time.

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Throughput analysis of the IEEE 802.11 distributed coordination function considering erroneous channel and capture effects

This paper presents a performance study of the distributed coordination function (DCF) of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method. The aggregate throughput of a practical wireless local area network (WLAN) strongly depends on the channel conditions. In a real radio environment, the received signal power at the access point from a station is subjected to deterministic path loss, shadowing, and fast multipath fading. The binary exponential backoff (BEB) mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate (BER). To alleviate the low performance of IEEE 802.11 DCF, a new mechanism is introduced, which greatly outperforms the existing methods under a high BER. A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.

Simulation of Hard Hand over (HHO) Mechanism in IEEE 802.16j Transparent Mode networks

different relay modes are defined in IEEE 802.16j WIMAX standard: transparent mode and non-transparent mode. IEEE 802.16j standard supports mobile station mobility; it defines three kinds of hand over mechanism: hard handover, macro diversity handover (MDHO) and fast BS switching (FBSS) In this paper we have simulated the hard hand over mechanism of IEEE 802.16j transparent mode networks using NCTUns Tool. We have used Adaptive modulation and coding scheme. The results show when the mobile station moves form base station 1 (BS1) to base station 2(BS2), it has to disconnect the original connection with BS1 before making a new connection with BS2. And also it shows that the throughput gradually decrease when the mobile station moves to NLOS. Key-Words: - IEEE 802.16j, transparent mode, hand over mechanism, NCTUns, throughput etc

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Traffic-Aware Connection Admission Control Scheme for Broadband Mobile Systems

In this letter we introduce a connection admission control (CAC) mechanism for IEEE 802.16 broadband wireless access Standard. Our scheme is based on bandwidth reservation concept and has been developed considering the problem of "busy hour" in communications traffic variation during a typical day. The proposed solution, which is compatible to the IEEE 802.16 Standard, provides higher priority to VoIP calls compared to other types of traffic in the network. The performance of the proposed scheme is evaluated by means of computer simulations, while an analytical solution is provided as well.

Overhead of ARQ mechanism in IEEE 802.16 networks

Different techniques for error correction such as automatic repeat request, forward error correction or combination of both methods also known as hybrid automatic repeat request are utilized in today's wireless networks. All these techniques require an implementation of control and management mechanisms to ensure its proper work. These mechanisms increase the management overhead and consume a part of network capacity. It leads to the reduction of data throughput dedicated to users. Besides, the control mechanism can negatively influence a packet delay. This paper proposes three alternatives of automatic repeat request mechanism to minimize the management overhead without a negative impact on the packet delay. Description of all proposed mechanisms, their evaluation and comparison with conventional techniques used in the IEEE 802.16 networks are presented in this paper.

Performance Analysis of Quality of Service in PMP Mode WiMax Networks

IEEE 802.16 standard supports point-to-multipoint (PMP) and Mesh topologies. This paper proposes a quality of service (QoS) mechanism for IEEE 802.16 in PMP mode and a base station (BS) scheduler for PMP mode. It also describes the QoS over WiMAX networks. The average WiMAX delay, load, and throughput at the BS were analyzed and compared by applying different schedulers at the BS and fixed nodes.

Traffic Adaptive MAC Mechanism for IEEE 802.15.4 Cluster Based Wireless Sensor Networks with Various Traffic Non-uniformities

This paper proposes a medium access control (MAC) mechanism for the recently developed IEEE 802.15.4 standard, a promising candidate to become the physical (PHY) and MAC layer standard for Wireless Sensor Networks (WSNs). The main concern in WSNs is the energy consumption, and this paper presents a mechanism that adapts properly the duty cycle operation according to the traffic conditions. Various traffic adaption mechanisms have been presented for the MAC layer of the IEEE 802.15.4. However these conventional mechanisms only consider the temporal traffic fluctuations. The proposed mechanism outperforms the conventional mechanism when applied to cluster-tree based WSNs, because it considers not only the temporal fluctuations but also the spatial (geographical) fluctuations, which are intrinsic characteristics of traffic in WSNs with the cluster tree topology. Evaluations showed that the proposed mechanism achieves less energy consumption than the conventional traffic adaptation mechanism, with maintaining almost the same transmission performance.