Comparison of Synchronization Methods for Burst-Mode π/4 DQPSK Demodulators
Date
2001
Authors
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Type
Degree Level
Masters
Abstract
The "burst-mode" of communications is becoming increasingly prevalent in emerging
cost-effective wireless packet data networks. These networks employ various forms of TDMA and TDD techniques and are popular as they require very little overhead in the management of network channel resources.
Since multiple users share common frequency channels in time, fast and reliable
synchronization on a burst by burst basis in the receiver is critical for maintaining
efficient data throughput. An attractive modulation technique ill a burst-mode
environment is π/4 DQPSK. Since noncoherent detection may be performed on
1T'/4 DQPSK; synchronization is inherently rapid as only symbol timing information
needs to be recovered.
Various synchronization techniques are suitable for π/4 DQPSK, but surprisingly
little has been published on the performance of these techniques in burst-mode.
This research examined the performance of several synchronization techniques in
a burst-mode environment. It also compared the digital hardware realizations for
various synchronization techniques and explored trade-offs between performance and
implementation complexity.
A number of synchronization methods were investigated based on some common
criteria: cost, complexity and performance. Four methods were chosen and simulated.
Each method. was evaluated for application to a burst-mode system. The
most viable technique was chosen and a functional π/4 DQPSK demodulator based
on the method. was built and tested in the laboratory.
The most promising method was found to be the maximum amplitude method.
This method proved to be very effective in burst-mode, achieving reliable synchronization
in only a few symbols in simulation; The trade-off for this rapid synchronization
was some degradation in bit error rate tracking performance.
A modification to the maximum amplitude method (named modified maximum
amplitude) was proposed and implemented which improved the tracking performance
while maintaining rapid synchronization performance. Both methods were suitable for implementation in programmable digital hardware using a complex programmable logic device. Additionally, testing results showed both systems to be very robust as synchronization times were consistent over a wide range of Eb/No.
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Citation
Degree
Master of Science (M.Sc.)
Department
Electrical and Computer Engineering
Program
Electrical Engineering