两种异构CSMA/CA机制OSTS/BSTS无线传感网络公平性、实时性分析比较

IEEE802.15.4作为一种专为低速率无线个人区域网络(WPAN)而设计的低成本、低功耗、低速率的短距离无线通信新标准,为无线传感器网络提供了一种很好的解决方案。本文针对异构、非饱和无线网络,提出了两种新的CS-MA/CA机制:OSTS/BSTS机制;异构节点数据到达率不同,其各自获取的吞吐量不同,由此分析获得异构网络节点的公平性。OSTS/BSTS机制最大的特点是异构节点被赋予了公平的机会来访问信道,不存在优先权等级的问题。这两种机制采用两个半马尔可夫链模型来分别表达两组节点的访问过程,一个宏观马尔可夫链模型来表达信道状态转换过程,结合队列理论模型来分析异构节点的延时量、吞吐量、传输概率等特性,以获取网络实时性、公平性理论模型,并采用NS-2仿真工具对分析结果进行了仿真。     

基于队列理论CSMA/CA机制的无线传感器异构机制OSTS的实时性分析

自从IEEE 802.15.4标准发布以来,基于低功耗、低速率传输的无线传感器网络的应用几乎涉及到现实生活的方方面面;但是关于这个标准的CSMA/CA机制大部分都是基于均匀、饱和的传感器网络应用。文中针对非饱和、带缓存的无线传感器异构网络,提出了一种新的异构的CSMA/CA机制OSTS。该机制采用2个马尔可夫链来分别表示异构节点访问信道的过程、一个宏观马尔可夫链来表达信道状态转移,且结合M/G/1/K队列理论分析数据包传送的实时性能,并相应地改进系统的实时性。文中最大的特点是两组非均匀节点被赋予了公平的机会访问信道,而不存在优先权的问题。此外,详细分析了这种机制的数据包传送时间,包括数据包到达率、包大小、节点数量、缓存大小等参数对系统实时性的影响;这些分析结果与我们采用NS-2工具仿真的结果十分吻合。     

基于IEEE 802．15．4 CSMA／CA机制的无线非均匀传感网络实时性能分析

自从IEEE802．15．4标准发布以来,低功耗、低速率传输的无线传感器网络的应用几乎涉及到现实生活的方方面面．而这个标准的CSMMCA机制性能分析大部分都是基于均匀、饱和的传感器网络。针对非均匀、非饱和的CSMMCA机制．提出了一种离散的性能评估方法。采用两个半马尔可夫链来分别表达两组节点的访问过程、一个宏观马尔可夫链来表达信道状态。最大的特点是两组节点被赋予了公平的机会来访问信道,而不存在优先权的问题。基于这个模型。分析了不饱和、无ACK的IEEE802．15．4信标使能访问机制的数据包传送时间,包括数据包到达率、包大小、节点数量等参数对系统实时性的影响。并且这些分析结果与采用NS=2工具仿真的结果十分吻合。     

基于IEEE802.15.4CSMA/CA机制的无线非均匀传感网络实时性能分析

自从IEEE802.15.4标准发布以来,低功耗、低速率传输的无线传感器网络的应用几乎涉及到现实生活的方方面面,而这个标准的CSMA/CA机制性能分析大部分都是基于均匀、饱和的传感器网络。针对非均匀、非饱和的CSMA/CA机制,提出了一种离散的性能评估方法,采用两个半马尔可夫链来分别表达两组节点的访问过程、一个宏观马尔可夫链来表达信道状态。最大的特点是两组节点被赋予了公平的机会来访问信道,而不存在优先权的问题。基于这个模型,分析了不饱和、无ACK的IEEE 802.15.4信标使能访问机制的数据包传送时间,包括数据包到达率、包大小、节点数量等参数对系统实时性的影响,并且这些分析结果与采用NS-2工具仿真的结果十分吻合。     

High-throughput time group access MCR-SS-CSMA/CA for wireless ad hoc networks with layered-tree topology

Multi-hop packet transmission error due to packet collision is a serious issue for realizing large-scale wireless ad hoc networks. In order to solve the issues, a multicode-reception spread-spectrum (MCR-SS)-CSMA/CA scheme is proposed as multiple access scheme for layered-tree networks. This scheme is further improved by adding a time group access (TGA) technique to gain higher interference reduction between nodes. The proposed TGA scheme divides the layered-tree network into upper subnets group and lower subnets group, thus reducing collision probability among subnets. Network throughput and data delivery ratio for the proposed scheme are analyzed by simulations based on the IEEE 802.15.4/ZigBee specification. Simulation results show that the proposed schemes can improve packet delivery ratio and network throughput remarkably.     

Toward enhanced wireless coexistence in ISM band via temporal characterization and modelling of 802.11b/g/n networks

This paper presents extensive experimental characterization and empirical modelling of 802.11 temporal behavior. A detailed characterization of 802.11b/g/n homogeneous and heterogeneous network traffic patterns is featured, including idle time distribution and channel utilization. A complete modelling of 802.11 networks in the 2.4 GHz Industrial, Scientific, and Medical band is also presented. Such information can assist the development of other wireless technologies aiming to utilize the crowded Industrial, Scientific, and Medical band more efficiently and to achieve enhanced wireless coexistence. In this work, models are derived for both homogeneous and heterogeneous 802.11 network idle time distributions. Also presented is a case study utilizing 802.15.4 ZigBee transmitter packet size that was adaptively modified based on channel idle time distribution. Results demonstrate superior ZigBee performance and significant enhancement in throughput. Copyright © 2016 John Wiley & Sons, Ltd.     

Impact of MAC frame length on energy efficiency in 6LowPAN

To reach necessary end-to-end connectivity between the Internet and wireless sensor networks （WSNs）, the Internet Engineering Task Force （IETF） IPv6 over low power wireless personal area network （6LowPAN） working group has been established and introduced an adaptation layer for integration of IEEE 802.15.4 physical layer/media access control （PHY/MAC） layers and the upper layers of any Intemet protocol （IP）-based networks, such as the Internet. The energy efficiency is one of the most important performance measures in WSNs because most sensor nodes are only battery powered so we should reduce the energy consumption to the lowest to extend the life of nodes. Therefore the determination of MAC frame length should be carefully considered since that the radio frequency （RF） module consumes most the energy of a sensor node meanwhile the MAC protocol is the direct controller of RF module. In this paper, we provide a star-shaped 6LowPAN non-beacon mode with unslotted carrier sense multiple access with collision avoidance （CSMA/CA） mechanism to access to the channel and model the stochastic behavior of a target end node as the M/G/1 queuing system. Analytical expressions for some parameters such as channel busy probability, packet loss probability and energy efficiency are obtained in this paper and our analytical results can clearly show the impact of MAC frame length on the energy efficiency of a target node in both ideal and lossy channel.     

Analysis of an M/G/1/N queue with vacations and its iterativeapplication to FDDI timed-token rings

We present the analysis of an M/G/1/N queueing system with vacations under a dynamic time-limited service policy. This method is used to develop a procedure for performance analysis of a fiber distributed data interface (FDDI) network serving buffer-limited stations under asynchronous service. An efficient iteration procedure is employed to evaluate the limiting state distribution of the embedded Markov chain representing the system state process. Using supplementary variables and sample biasing techniques, we derive the queue size distribution at an arbitrary instant of time as well as the packet blocking probability and the mean packet delay. By exploiting the subtle structure of conditional supplementary variables and the recursive property of the conditional residual delay, the Laplace-Stieltjes transform of the packet delay distribution and a time-domain approximation of the packet delay distribution are obtained. For the analysis of a heterogeneous multi-station FDDI network, an iterative procedure which uses repeatedly the M/G/1/N vacation model described above is presented. This procedure provides for a numerically efficient analysis method by employing constructions of the approximate vacation time distributions. We illustrate the application of our analytical techniques to both symmetric and nonsymmetric FDDI network systems     

Modeling and performance evaluation of the IEEE 802.15.4e LLDN mechanism designed for industrial applications in WSNs

The IEEE 802.15.4 standard has been introduced for low latency and low energy consumption in wireless sensor networks. To better support the requirements of industrial applications, where the use of this standard is limited, the low latency deterministic network (LLDN) mechanism of the IEEE 802.15.4e amendment has been proposed. In this paper, we develop a three dimensional Markov chain model for the IEEE 802.15.4e LLDN mechanism. Then, we estimate the stationary probability distribution of this chain in order to derive theoretical expressions of some performance metrics, as the reliability, energy consumption, throughput, delay and jitter. After that, we conduct a comparative study between the IEEE 802.15.4e LLDN and the IEEE 802.15.4 slotted carrier sense multiple access with collision avoidance (CSMA/CA). Numerical results show that the deterministic behavior of the LLDN mechanism significantly reduces the collision probability providing best performances in terms of reliability, energy consumption, throughput and delay compared to the IEEE 802.15.4 slotted CSMA/CA. Finally, the accuracy of our theoretical analysis is validated by Monte Carlo simulations.     

Bridging between ieee 802.15.4 and IEEE 802.11b networks for multiparameter healthcare sensing

In this paper we consider the interconnection of an IEEE 802.15.4 body area network (BAN) in which nodes sense physiological variables such as electrocardiography (EKG), electroencephalography (EEG), pulse oximeter data, blood pressure and cardiac output, with an IEEE 802.11b room/ward WLAN. We model the operation of this two-tier network assuming that 802.15.4 BAN operates in CSMA-CA mode and that the BAN coordinator acts as the bridge which conveys BAN packets to the 802.11b access point. We analyze the two-hop network delay and discuss the mutual interaction of different data streams as well as impact of the number of bridges on packet delay.     

Optimal designs for IEEE 802.15.4 wireless sensor networks

This paper investigates the maximum achievable channel throughput in a single‐channel and single‐hop wireless sensor network using IEEE 802.15.4 Medium Access Control (MAC) protocol. We introduce a simple mean‐field approach to model the Carrier Sense Multiple Access with Collision Avoidance mechanism of the 802.15.4 MAC protocol under unsaturated conditions. We derive a set of expressions such as optimal sensing rate of a sensor node, its corresponding failure probability, and the channel throughput for both saturated and unsaturated networks. With those expressions, we propose several network designs to achieve the optimal throughput by choosing the appropriate MAC parameters. We validate the proposed optimal designs using ns‐2 simulations. Furthermore, we evaluate the network lifetime expectancy of the optimal designs and compare it with the lifetime of network settings under saturated conditions that use the default MAC parameters of IEEE 802.15.4. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance evaluation of an IEEE 802.15.4 sensor network with a star topology

One class of applications envisaged for the IEEE 802.15.4 LR-WPAN (low data rate—wireless personal area network) standard is wireless sensor networks for monitoring and control applications. In this paper we provide an analytical performance model for a network in which the sensors are at the tips of a star topology, and the sensors need to transmit their measurements to the hub node so that certain objectives for packet delay and packet discard are met. We first carry out a saturation throughput analysis of the system; i.e., it is assumed that each sensor has an infinite backlog of packets and the throughput of the system is sought. After a careful analysis of the CSMA/CA MAC that is employed in the standard, and after making a certain decoupling approximation, we identify an embedded Markov renewal process, whose analysis yields a fixed point equation, from whose solution the saturation throughput can be calculated. We validate our model against ns2 simulations (using an IEEE 802.15.4 module developed by Zheng [14]). We find that with the default back-off parameters the saturation throughput decreases sharply with increasing number of nodes. We use our analytical model to study the problem and we propose alternative back-off parameters that prevent the drop in throughput. We then show how the saturation analysis can be used to obtain an analytical model for the finite arrival rate case. This finite load model captures very well the qualitative behavior of the system, and also provides a good approximation to the packet discard probability, and the throughput. For the default parameters, the finite load throughput is found to first increase and then decrease with increasing load. We find that for typical performance objectives (mean delay and packet discard) the packet discard probability would constrain the system capacity. Finally, we show how to derive a node lifetime analysis using various rates and probabilities obtained from our performance analysis model.

Performance evaluation of an intelligent routed WDM mesh network: An analytical approach

This paper presents an analytical model of an optical mesh network capable of handling WDM traffic intelligently. The router is modeled as a processor to read the instructions in the header of the packet to implement the required algorithm adopting standard queuing concepts. Packet stacking, switching, or routing performance deliberately depends on packet size, node architecture and network parameters. The numerical result shows a huge data transmission through the router with a least dependence on the routing time up to a significant data rate and thus provides a significant improvement in call connection probability.     

Queuing Models for Dimensioning Interactive and Streaming Services in High-Speed Downlink Packet Access Networks

We consider modeling the statistical behavior of interactive and streaming traffics in high-speed downlink packet access (HSDPA) networks. Two important applications in these traffic categories are web-browsing (interactive service) and video streaming (streaming service). Web-browsing is characterized by its important sensitivity to delay. Video streaming on the other hand is less sensitive to delay, however, due to its large frame sizes, video traffic is more affected by the packet loss resulting from a limited buffer size at the base station. Taking these characteristics into account, we consider modeling the queuing delay probability density function (PDF) of the Web-browsing traffic, and modeling the queuing buffer size distribution of video streaming traffic. Specifically, we show that the queuing delay of the Web-browsing traffic follows an exponential distribution and that the queuing buffer size of video streaming traffic follows a weighted Weibull distribution. Model fitting based on simulated data is used to provide simple mathematical formulations for the different parameters that characterize the PDFs under consideration. The provided equations could be used, directly, in HSDPA network dimensioning and, as a reference, to satisfy a certain quality of service (QoS).     

The effects of packet size distributions on output and delayprocesses of CSMA/CD

An unslotted model of the nonpersistent CSMA/CD protocol is considered, and the effect of different packet size distribution functions on the system performance is investigated. Under the assumption that packet sizes obey a general distribution function, an exact analysis of the packet output process on the CSMA/CD channel and the packet delay process at each homogeneous station is presented. Statistics analyzed are the following: (1) the Laplace-Stieltjes transform (LST) of the probability distribution function (PDF) of the packet interdeparture time, (2) the autocorrelation coefficient of the packet interdeparture time, (3) the LST of the PDF of the packet delay, and (4) the LST of the PDF of the waiting time. In addition, explicit expressions for the LSTs, averages and variances of the interdeparture time, packet delay, and waiting time distribution functions are given under the heavy-traffic assumption. In numerical results, typical packet size distribution functions are applied to the analytical result, and their effects on the autocorrelation coefficient of the interdeparture time as well as the averages and coefficients of variation of the interdeparture time, packet delay, and waiting time are examined     

Throughput-delay and stability analysis of an asynchronous spreadspectrum packet radio network

A continuous-time Markov chain model for an asynchronous spread spectrum packet radio network is presented. The network consists of N fully connected nodes and the radios in all nodes are identical. Packets arrive at each node and are retransmitted when lost, both according to Poisson processes with different rates, and packet lengths are exponential in distribution. A simple threshold approximation is used to account for the multiuser interference, and the preamble collision probability at receiving radios to account for the capture effect. The approximate analysis gives results which are very close to those obtained by simulations in most cases. The network stability conditions are discussed and the bistable behavior of the network is demonstrated. Results are given which show the effects on throughput and packet delay performance of the network according to the variations of the network size, the packet retransmission rate, the preamble collision probability at receiving radios, and the threshold value of the radio channel capacity     

Delay and energy consumption analysis of priority guaranteed MAC protocol for wireless body area networks

Wireless body area networks are captivating growing interest because of their suitability for wide range of applications. However, network lifetime is one of the most prominent barriers in deploying these networks for most applications. Moreover, most of these applications have stringent QoS requirements such as delay and throughput. In this paper, the modified superframe structure of IEEE 802.15.4 based MAC protocol is proposed which addresses the aforementioned problems and improves the energy consumption efficiency. Moreover, priority guaranteed CSMA/CA mechanism is used where different priorities are assigned to body nodes by adjusting the data type and size. In order to save energy, a wake-up radio based mechanism to control sleep and active modes of body sensors are used. Furthermore, a discrete time finite state Markov model to find the node states is used. Analytical expressions are derived to model and analyze the behavior of average energy consumption, throughput, packet drop probability, and average delay during normal and emergency data. Extensive simulations are conducted for analysis and validation of the proposed mechanism. Results show that the average energy consumption and delay are relatively higher during emergency data transmission with acknowledgment mode due to data collision and retransmission.     

Review of Energy Conservation Using Duty Cycling Schemes for IEEE 802.15.4 Wireless Sensor Network (WSN)

Energy conservation is one of the crucial issues in wireless sensor network (WSN). A significant solution to conserve energy is done by deploying duty cycle management mechanisms in the WSN applications. This paper reviews several duty cycle mechanisms in WSN such as Duty Cycle Learning Algorithm, adaptive media access control (MAC) protocol for efficient IEEE 802.15.4 (AMPE), distributed duty cycle management (DDCM), distributed duty cycle management low power broadcast (DDCM + LPB) and distributed beacon only period. These mechanisms change their parameters such as idle listening, packet accumulation and delay in the end device transmitting queue to improve the energy conservation in WSN. The performances of these different energy conservation mechanisms have been compared at the MAC layer of IEEE 802.15.4 standard. It is found that the DDCM + LPB has made approximately 100 % enhancement in terms of average energy efficiency as compared to the other mechanisms. DDCM + LPB has significant enhancements by adapting the duty cycle according to the network traffic load condition. Using this mechanism, the duty cycle is increased when the traffic load increases and vice versa. Its energy efficiency also outperforms the conventional DDCM by the average of 10 %.     

A backoff algorithm based on self-adaptive contention window update factor for IEEE 802.11 DCF

The binary exponential backoff (BEB) mechanism is applied to the packet retransmission in lots of wireless network protocols including IEEE 802.11 and 802.15.4. In distributed dynamic network environments, the fixed contention window (CW) updating factor of BEB mechanism can’t adapt to the variety of network size properly, resulting in serious collisions. To solve this problem, this paper proposes a backoff algorithm based on self-adaptive contention window update factor for IEEE 802.11 DCF. In WLANs, this proposed backoff algorithm can greatly enhance the throughput by setting the optimal CW updating factor according to the theoretical analysis. When the number of active nodes varies, an intelligent scheme can adaptively adjust the CW updating factor to achieve the maximal throughput during run time. As a result, it effectively reduces the number of collisions, improves the channel utilization and retains the advantages of the binary exponential back-off algorithm, such as simplicity and zero cost. In IEEE 802.11 distributed coordination function (DCF) protocol, the numerical analysis of physical layer parameters show that the new backoff algorithm performance is much better than BEB, MIMD and MMS algorithm.     

Design and performance evaluation of a packet voice system

A packet voice network has been designed using adaptive delta modulators. Tests were performed to examine the effects of packet length and packet loss rate on digital voice intelligibility. The packet voice network was simulated using a SLAM network model to find queue size requirements as a function of packet size, delay distribution, and expiring time out. The queuing strategy is investigated in order to minimize total information loss during channel acquisition delays.