Telecommunications & Signal Processing Laboratory

Thesis Abstracts, 1996-1998

Paul Popescu
Chip Timing Recovery for Indoor Wireless Networks Employing Commutation Signalling
M.Eng. Project, July 1996
Supervisors: H. Leib and P. Kabal

This project considers chip timing recovery for indoor wireless networks employing Commutation Signalling. First a general analysis is made, based on the Maximum A Posteriori Probability (MAP) concept, which leads to a synchronizer structure. Two cases are examined, one using a raised-cosine, the other using a half-sine as the chip pulse. It is shown that, once acquisition has taken place and therefore the difference between the incoming waveform and the locally generated clock is of no more than a half chip duration, the synchronizer will lock onto and track the phase of the incoming waveform.

The various blocks are implemented and the system is simulated using Simulink, a system level simulator which is part of Matlab.

Prashant Venkat Krishnamurthy
A Combined Frequency, Code and Time Division Multiple-Access Technique for Broadband Indoor Wireless Communications
M.Eng. Thesis, June 1996
Supervisor: H. Leib

Commutation signalling is an antimultipath technique employing direct-sequence bandwidth spreading for combatting multipath induced ISI. We propose a CDMA-like multiple-access scheme which utilizes this inherent spreading for broadband cellular indoor wireless communications. The intra-cell multiple-access is by time division while the inter-cell interference is reduced via combined frequency and code division. The frequency bands of adjacent cells overlap to increase bandwidth efficiency. We consider the interference between spread-spectrum signals with partially overlapping spectra and apply the results to the analysis of this cellular system. The uplink and downlink are considered with and without cell sectorization. The downlink is used for obtaining certain system design parameters and for comparing the merits of different pulse shapes. We finally compare the proposed scheme with the usual TDMA/FDMA and CDMA schemes. The proposed scheme is found to require less bandwidth compared to the usual TDMA/FDMA scheme. However, CDMA requires a lesser bandwidth than the proposed scheme since it employs powerful very low rate channel coding techniques.