A multiple-antenna-multiple-equalizer (MAME) system is proposed for overcoming
cochannel interference (CCI) in code-division multiple access (CDMA) indoor wireless
systems. The main advantage of the MAME system is the enhanced interference
suppression capability as compared with many existing approaches. Thus, the use of the
MAME system can lead to an increase in the capacity of the CDMA system. In the
MAME system, a fractionally-spaced equalizer (FSE) is used to process the signal at each
antenna. The number of antennas or the tap spacing of the FSEs is not fixed and inherent
flexibility is available to the designer. In particular, CDMA indoor wireless systems are
best suited to use the interference suppression capabilities of the MAME system.
It is shown that spectral correlation present in user signals is the reason for the interference
suppression capability of the MAME system. Moreover, the MAME system is
interpreted as a dual-domain diversity combiner. Spatial and bandwidth-domain diversity
are used and the relative importance of the diversity domains is discussed. These discussions
offer new insights into the interference suppression capabilities of the MAME
system and give a clear picture of its workings.
Extensive simulation results are presented to illustrate the performance of the
MAME system under various conditions. Optimal or minimum mean-squared error
(MMSE) results are first presented to illustrate the superior interference suppression performance.
The effects of the number of antennas, tap spacing, receive filtering, spectral
correlation, diversity domains, and near-far conditions on performance are examined and
results obtained support the arguments presented earlier in the thesis.
The FSEs in the MAME system are implemented as adaptive filters and the mean-squared-
error (MSE) performance is investigated. A quasi-Newton (QN) algorithm is
recommended over other adaptive filtering algorithms because of ill-conditioning of the
autocorrelation matrix in the MAME system. Simulation results confirm the superior
convergence performance of the QN algorithm. Decision-directed equalization is also
investigated and bit-error rate (BER) results presented illustrate that the gains in the
MMSE performance will most likely translate into gains in BER performance. The BER
performance in near-far and birth of interferers conditions illustrate that the MAME system
is a promising solution to counter these problems.
The thesis concludes with an indoor wireless strategy based on the MAME system
which offers the following advantages:
1. More users than the processing gain of the CDMA system can share the same
bandwidth.
2. No information about code sequences is needed at the receiver.
3. Simple code sequence allocation schemes can be used at the transmitter.
4. Variable numbers of users can be accommodated.
5. Simple power control and error-correction coding schemes can be used. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/9794 |
| Date | 31 July 2018 |
| Creators | Subramanian, Srikanth |
| Contributors | Shpak, Dale John, Antoniou, Andreas |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
Page generated in 0.0042 seconds