Channel modeling and interference rejection for CDMA automatic vehicle monitoring systems

It is desirable to develop a universal digital receiver which is capable of operating with many different wireless communication systems. Time Dependent Adaptive Filter (TDAF) Processing represents an effective approach for CDMA interference rejection. This technique is especially appropriate at the mobile receiver where there is little prior knowledge of the spreading codes of the other users. This thesis presents enhanced forms of the Time Dependent Adaptive Filter (TDAF), which is an optimal periodically time-varying adaptive filter. It is able to fully exploit the cyclostationarity and spectral correlation in certain DS-SS signals. It is shown how multiple AVM service providers can exist in adjacent channels within the ISM band. It is demonstrated that using the realistic channel models the TDAF can provide substantial improvement in interference rejection over the conventional correlation receiver. Computationally efficient TDAF structures have been also proposed to handle the case of different code repeat intervals for different systems. Results of CDMA overlay system simulation have shown that TDAF processing can achieve tremendous gain in narrowband interference rejection compared to notch/matched filter processing. An input signal which has 45 dB narrowband interference-to-signal power ratio (J/S), the SIR of the TDAF processed output signal can be 20 dB, a 65 dB improvement. The use of TDAF processing and a spectral shaping filter can minimize the impact of adjacent channel interference. Even in an environment which has a 30 dB adjacent channel J/S, the SIR at output is demonstrate to be a 50 dB improvement. System performance shows little degradation by adjacent channel and narrowband interference.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Electrical Engineering

Department dc:contributor.department

Electrical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1994

Author dc:creator

• Zheng, Raymond Sihao

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-07112009-040511

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43690