84 research outputs found
Queueing and Stability Analysis of Buffered CSMA/CD Local Networks.
This dissertation develops a joint probability generating function for the message quene lengths in a slotted p-persistent CSMA/CD (Carrier-Sense Multiple-Access with Collision Detection) system with a finite population of buffered users. Each user is assumed to have an independent and identical process of packet generation and an infinite buffer for storing outstanding packets. A closed form formula is obtained for the generating function in case of a two user system. Analytic formulas for the stability condition of a p-persistent CSMA/CD system are derived using the generating function. The range of the transmission probability p that leads to stability is examined through numerical analysis over a wide variety of the user\u27s communication demand, the packet length distribution, the number of users on the network, and the time to detect and abort collided packets
Investigation of the consumer electronics bus
The objectives of this dissertation are to investigate the performance of the Consumer Electronics Bus (CEBus) and to develop a theoretical formulation of the Carrier Sense Multiple Access with Contention Detection and Contention Resolution (CSMA/CDCR) with three priority classes protocol utilized by the CEBus
A new priority channel assigned multiple access with embedded priority resolution (PAMA/PR) theoretical model is formulated. It incorporates the main features of the CEBus with three priority classes. The analytical results for throughput and delay obtained by this formulation were compared to simulation experiments. A close agreement has been found thus validated both theory and simulation models
Moreover, the performance of the CEBus implemented with two physical media, the power line (PL) and twisted pair (TP) communication lines, was investigated by measuring message and channel throughputs and mean packet and message delays. The router was modeled as a node which can handle three priority levels simultaneously. Satisfactory performance was obtained.
Finally, a gateway joining the CEBus to ISDN was designed and its perfor-mance was evaluated. This gateway provides access to ISDN-based services to the CEBus. The ISDN and CEBus system network architecture, gateway wiring, and data and signaling interface between the CEBus and ISDN were designed, analyzed, and discussed. Again, satisfactory performance was 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
A MAC protocol for IP-based CDMA wireless networks.
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.The evolution of the intemet protocol (IP) to offer quality of service
(QoS) makes it a suitable core network protocol for next generation
networks (NGN). The QoS features incorporated to IP will enable future lP-based wireless networks to meet QoS requirements of various multimedia traffic. The Differentiated Service (Diffserv) Architecture is a promising QoS technology due to its scalability which arises from traffic flow aggregates. For this reason, in this dissertation a network infrastructure based on DiffServ is assumed. This architecture provides assured service (AS) and premium service (PrS) classes in addition to best-effort service (BE). The medium access control (MAC) protocol is one of the important design issues in wireless networks. In a wireless network carrying multimedia traffic, the MAC protocol is required to provide simultaneous support for a wide variety of traffic types, support traffic with delay and jitter bounds, and assign bandwidth in an efficient and fair manner among traffic classes. Several MAC protocols capable of supporting multimedia services have been proposed in the literature, the majority of which were designed for wireless A1M (Asynchronous Transfer Mode). The focus of this dissertation is on time division multiple access and code division multiple access (TDMAlCDMA)
based MAC protocols that support QoS in lP-based wireless networks. This dissertation begins by giving a survey of wireless MAC protocols. The survey considers MAC protocols for centralised wireless networks and classifies them according to their multiple access technology and as well as their method of resource sharing. A novel TDMAlCDMA based MAC protocol incorporating techniques from existing protocols is then proposed. To provide the above-mentioned services, the bandwidth is partitioned amongst AS and PrS classes. The BE class utilizes the remaining bandwidth from the two classes because it does not have QoS requirements. The protocol employs a demand assignment (DA) scheme to support traffic from PrS and AS classes. BE traffic is supported by a random reservation access scheme with dual multiple access interference (MAl) admission thresholds. The performance of the protocol, i.e. the AS or PrS call blocking probability, and BE throughput are evaluated
through Markov analytical models and Monte-Carlo simulations.
Furthermore, the protocol is modified and incorporated into IEEE 802.16 broadband wireless access (BWA) network
Modern Random Access for Satellite Communications
The present PhD dissertation focuses on modern random access (RA) techniques.
In the first part an slot- and frame-asynchronous RA scheme adopting replicas,
successive interference cancellation and combining techniques is presented and
its performance analysed. The comparison of both slot-synchronous and
asynchronous RA at higher layer, follows. Next, the optimization procedure, for
slot-synchronous RA with irregular repetitions, is extended to the Rayleigh
block fading channel. Finally, random access with multiple receivers is
considered.Comment: PhD Thesis, 196 page
Robustness of Ethernet-Based Real-Time Networked Control System with Multi-Level Client/Server Architecture
The importance of real-time communication at the device level in a factory
automation setup is a widely researched area. This research is an effort to experimentally
verify if Ethernet can be used as a real-time communication standard in a factory
automation setup, by observing the effects of packet delays, packet loss, and network
congestion on the performance of a networked control system (NCS). The NCS
experimental setup used in this research involves real-time feedback control of multiple
plants like DC motors and a magnetic-levitation system connected to one or more
controllers. A multi-client-multi-server architecture on a local area network (LAN) was
developed using user datagram protocol (UDP) as the communication protocol. Key
observations are as follows. (1) The multi-client-single-server system showed the highest
packet delays compared to single-client-single-server architecture. (2) In the singleclient-
single-server system, as the Ethernet link utilization increased beyond 82 percent, the
average packet delays and steady-state error of the DC motor speed-control system
increased by 2231 percent and 304 percent, respectively. (3) Even under high link utilization, adding
an additional server to the NCS reduced average packet delays considerably. (4) With
large packet sizes, higher packet rates were automatically throttled by Ethernet’s flow
control mechanism affecting the real-time communication negatively. (5) In the multiclient-
multi-server architecture, average packet delays at higher packet rates, and at
higher packet lengths were found to be 40 percent lesser than the those of the single-clientsingle-
server system and 87.5 percent lesser than those of the multi-client-single-server
system
Multiple access protocols for multichannel communication systems
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 108-111).System architecture design, evaluation, and optimization are key issues to developing communication systems that meet the requirements of today and expectations of the future. In this thesis, we introduce the concept of multiple access communication and the need to use efficient transmission techniques to expand both present and future wireless communication networks. We will study two areas regarding multiple access on multichannel communication systems. First, we describe fundamental multiplexing techniques that we can build upon and investigate the performance of different candidate architectures for the transmission of messages from bursty sources on multiple channels. We will consider traditional protocols such as Time Division Multiple Access (TDMA) and Slotted ALOHA (S-ALOHA) alongside a channelized architecture, which is based on the idea of multiplexing by dividing total transmission capacity into a fixed number of frequency channels. We develop mathematical models that describe the overall delay for sending large messages of a fixed length arriving from bursty sources and analyze their performances. We will make real-world parameter assumptions in the context of wireless networks and analyze the performance to develop intuition about the effectiveness of the different architectures. Second, we will investigate channel capacity allocation among mixed traffic, i.e., multiple classes of users. We will consider a first-come first-serve (FCFS) access strategy, a non-preemptive priority scheme, a preemptive resume priority scheme, and several channel capacity allocation schemes. We develop models that describe the overall delay for sending messages and analyze their performance. Our focus will concentrate on two classes of users. This scenario is typical of classes of users with small and large messages to transmit. present quantitative results by making real-world parameter assumptions in the context of wireless networks and analyze the performance to develop intuition about the effectiveness of each architecture.by Serena Chan.M.Eng
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