Evaluation Of Voice Trunking Performance Using AA2 Over ATM Networks

The urgent market needs for an efficient transport mechanism to carry voice traffic over Broadband Integrated Service Digital Networks (B-ISDN). Asynchronous Transfer Mode (A TM) network has been developed to integrate all types of traffic (e.g. voice, data and video) over B-ISDN networks. ATM Adaptation Layer 2 (AAL2) has been designed for efficient transport of voice, fax, and voice-band data traffic over an A TM virtual circuit. AAL2 allows the VBR sources to generate different packet sizes to be packed in an A TM cell, which increases the number of voice channels and decreases the packetization delay. The growing trend of using A TM has also given great impetus to the use of AAL2 in wire-line trunking (e.g. PBX), which provides a good opportunity for multiplexing many voice channels over a single A TM virtual connection. Voice trunking over A TM using AAL2 is the main subject of this thesis. The efficiency of AAL2 for voice transport in ATM networks is evaluated using a simulation approach. Additionally, the performance and capacity of an ATM multiplexer are analysed based on AAL2 technique. The power of AAL2 trunking and multiplexing high number of voice channels over a single ATM virtual connection makes it an efficient layer to support voice traffic with low delay and high efficiency using low bit rate as a reliable compression technique. In this thesis, the comparison between AAL2 and AAL 1 is made in terms of the number of users that can be carried over Tl AThI trunk. Then the focus is shifted to the use of AAL2 to support Voice and Telephony Over ATM (VTOA) networks. The effect of Timer-Composite Unit (Timer-CD) parameter, number of voice channels and voice coding rate on the packing density and link efficiency is further discussed. The results show that ATM cell packetization delay decreases when the number of users increases. Also, the Timer-CD affects the generation of partially filled cells when it is not set properly. Finally, the use of low coding bit rates to support high number of voice channels makes AAL2 a very efficient layer to carry VTOA networks

Study of Optical OFDM System for Wireless LAN Applications

The advantages of optical fiber make it possible to extend the data rate transmission and propagation distance. Orthogonal frequency division multiplexing (OFDM) as a multicarrier technique (MC) is used in hybrid optical-wireless system designs because it has the best spectral efficiency to radio frequency (RF) interference and lower multipath distortion. In this dissertation, a study and evaluation of optical OFDM based wireless local area network (W-LAN) systems are presented. The baseband of the OFDM signal is fully transmitted and up-converted to a radio frequency signal. Also, to reduce system costs, simple base stations (BSs) are interconnected to a central office (CO) via an optical fiber. All the required operations are achieved in the CO. The directly modulated laser (DML) and continuous wave (CW) laser are used in the system simulations as optical laser sources. Identical rectangular microstrip patch antennas have been used at the transmitter and the receiver as well. The simulations were carried out for different SMF and MMF lengths, and the variable wireless distance between the transmitting and receiving antennas was in a range of 40 dB to 80 dB. The purpose of this work is to provide a framework for integrating wireless and optical technologies in one system with the presence of OFDM technology. The required microstrip patch antenna parameters for the system are analyzed and designed. The microstrip patch antenna (S-parameters) is loaded into the Optisystem communication software tool in Touchstone format. As a result, this achievement gives a greater impetus to design an integrated optical-wireless system, and simulation results validate the proposed technique. Then, the integration of the microstrip patch antenna and optical OFDM system is achieved, and the performance is intensely studied. The entire system has been presented by developing analytical models and simulations. The system performance results are obtained regarding EIRP, SNR, signal constellations and BER. The results show that this integrated optical wireless link is very robust for carrying OFDM based wireless LAN signals over an optical fiber. Moreover, using an active patch antenna in the system helps to increase the coverage service to more than 30 meters when an SMF of 80 km length is utilized