6 research outputs found
Performance Analysis of Distributed MAC Protocols for Wireless Networks
How to improve the radio resource utilization and provide better
quality-of-service (QoS) is an everlasting challenge to the
designers of wireless networks. As an indispensable element of
the solution to the above task, medium access control (MAC)
protocols coordinate the stations and resolve the channel access
contentions so that the scarce radio resources are shared fairly
and efficiently among the participating users. With a given
physical layer, a properly designed MAC protocol is the key to
desired system performance, and directly affects the perceived QoS
of end users.
Distributed random access protocols are widely used MAC protocols
in both infrastructure-based and infrastructureless wireless
networks. To understand the characteristics of these protocols,
there have been enormous efforts on their performance study by
means of analytical modeling in the literature. However, the
existing approaches are inflexible to adapt to different protocol
variants and traffic situations, due to either many unrealistic
assumptions or high complexity.
In this thesis, we propose a simple and scalable generic
performance analysis framework for a family of carrier sense
multiple access with collision avoidance (CSMA/CA) based
distributed MAC protocols, regardless of the detailed backoff and
channel access policies, with more realistic and fewer
assumptions. It provides a systematic approach to the performance
study and comparison of diverse MAC protocols in various
situations. Developed from the viewpoint of a tagged station, the
proposed framework focuses on modeling the backoff and channel
access behavior of an individual station. A set of fixed point
equations is obtained based on a novel three-level renewal process
concept, which leads to the fundamental MAC performance metric,
average frame service time. With this result, the important
network saturation throughput is then obtained straightforwardly.
The above distinctive approach makes the proposed analytical
framework unified for both saturated and unsaturated stations.
The proposed framework is successfully applied to study and
compare the performance of three representative distributed MAC
protocols: the legacy p-persistent CSMA/CA protocol, the IEEE
802.15.4 contention access period MAC protocol, and the IEEE
802.11 distributed coordination function, in a network with
homogeneous service. It is also extended naturally to study the
effects of three prevalent mechanisms for prioritized channel
access in a network with service differentiation. In particular,
the novel concepts of ``virtual backoff event'' and ``pre-backoff
waiting periods'' greatly simplify the analysis of the arbitration
interframe space mechanism, which is the most challenging one
among the three, as shown in the previous works reported in the
literature. The comparison with comprehensive simulations shows
that the proposed analytical framework provides accurate
performance predictions in a broad range of stations. The results
obtained provide many helpful insights into how to improve the
performance of current protocols and design better new ones
Performance Prediction and Tuning for Symmetric Coexistence of WiFi and ZigBee Networks
Due to the explosive deployment of WiFi and ZigBee wireless networks, 2.4GHz ISM bands (2.4GHz-2.5GHz) are becoming increasingly crowded, and the co-channel coexistence of these two networks is inevitable. For coexistence networks, people always want to predict their performance (e.g. throughput, energy consumption, etc.) before deployment, or even want to tune parameters to compensate unnecessary performance degradation (owing to the huge differences between these two MAC protocols) or to satisfy some performance requirements (e.g., priority, delay constraint, etc.) of them. However, predicting and tuning performance of coexisting WiFi and ZigBee networks has been a challenging task, primarily due to the lack of corresponding simulators and analytical models.
In this dissertation, we addressed the aforementioned problems by presenting simulators and models for the coexistence of WiFi and ZigBee devices. Specifically, based on the energy efficiency and traffic pattern of three practical coexistence scenarios: disaster rescue site, smart hospital and home automation. We first of all classify them into three classes, which are non-sleeping devices with saturated traffic (SAT), non-sleeping devices with unsaturated traffic (UNSAT) and duty-cycling devices with unsaturated traffic (DC-UNSAT). Then a simulator and an analytical model are proposed for each class, where each simulator is verified by simple hardware based experiment. Next, we derive the expressions for performance metrics like throughput, delay etc., and predict them using both the proposed simulator and the model. Due to the higher accuracy of the simulator, the results from them are used as the ground truth to validate the accuracy of the model. Last, according to some common performance tuning requirements for each class, we formulate them into optimization problems and propose the corresponding solving methods. The results show that the proposed simulators have high accuracy in performance prediction, while the models, although are less accurate than the former, can be used in fast prediction. In particular, the models can also be easily used in optimization problems for performance tuning, and the results prove its high efficiency
Game theoretic approach to medium access control in wireless networks
Wireless networking is fast becoming the primary method for people to connect to the Internet and with each other. The available wireless spectrum is increasingly congested, with users demanding higher performance and reliability from their wireless connections. This thesis proposes a game-theoretic random access model, compliant with the IEEE 802.11 standard, which can be integrated into the distributed coordination function (DCF). The objective is to design a game theoretic model that potentially optimizes throughput and fairness in each node independently and, therefore, minimise channel access delay. This dissertation presents a game-theoretic MAC layer implementation for single-cell networks and centralised DCF in the presence of hidden terminals to show how game theory can be applied to improve wireless performance. A utility function is proposed, such that it can decouple the protocol's dynamic adaptation to channel load from collision detection. It is demonstrated that the proposed model can reach a Nash equilibrium that results in a relatively stable contention window, provided that a node adapts its behaviour to the idle rate of the broadcast channel, coupled with observation of its own transmission activity. This dissertation shows that the proposed game-theoretic model is capable of achieving much higher throughput than the standard IEEE 802.11 DCF with better short-time fairness and significant improvements in the channel access delay
Performance and Reliability Evaluation for DSRC Vehicular Safety Communication
<p>Inter-Vehicle Communication (IVC) is a vital part of Intelligent Transportation System (ITS), which has been extensively researched in recent years. Dedicated Short Range Communication (DSRC) is being seriously considered by automotive industry and government agencies as a promising wireless technology for enhancing transportation safety and efficiency of road utilization. In the DSRC based vehicular ad hoc networks (VANETs), the transportation safety is one of the most crucial features that needs to be addressed. Safety applications usually demand direct vehicle-to-vehicle ad hoc communication due to a highly dynamic network topology and strict delay requirements. Such direct safety communication will involve a broadcast service because safety information can be beneficial to all vehicles around a sender. Broadcasting safety messages is one of the fundamental services in DSRC. In order to provide satisfactory quality of services (QoS) for various safety applications, safety messages need to be delivered both timely and reliably. To support the stringent delay and reliability requirements of broadcasting safety messages, researchers have been seeking to test proposed DSRC protocols and suggesting improvements. A major hurdle in the development of VANET for safety-critical services is the lack of methods that enable one to determine the effectiveness of VANET design mechanism for predictable QoS and allow one to evaluate the tradeoff between network parameters. Computer simulations are extensively used for this purpose. A few analytic models and experiments have been developed to study the performance and reliability of IEEE 802.11p for safety-related applications. In this thesis, we propose to develop detailed analytic models to capture various safety message dissemination features such as channel contention, backoff behavior, concurrent transmissions, hidden terminal problems, channel fading with path loss, multi-channel operations, multi-hop dissemination in 1-Dimentional or 2-Dimentional traffic scenarios. MAC-level and application-level performance metrics are derived to evaluate the performance and reliability of message broadcasting, which provide insights on network parameter settings. Extensive simulations in either Matlab or NS2 are conducted to validate the accuracy of our proposed models.</p>Dissertatio
Performance Analysis For Wireless G (IEEE 802.11 G) And Wireless N (IEEE 802.11 N) In Outdoor Environment
This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. the comparison consider on coverage area (mobility), through put and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g
Performance analysis for wireless G (IEEE 802.11G) and wireless N (IEEE 802.11N) in outdoor environment
This paper described an analysis the different
capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. The comparison consider on coverage area (mobility), throughput and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g