Graduation Year

2013

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Huseyin Arslan

Keywords

Adaptive filtering, Intentional overlapping, Multiple accessing, Multi-user scenarios, Roll-off factor

Abstract

Multicarrier modulation is a transmission technique that is quite convenient for high data rates in wireless communication. Information symbols are partitioned and parallelly sent over multiple narrowband subchannels. Pulse shaping filters are critically important in multicarrier

modulation for determining the characteristics of signal in time and frequency domains. In this thesis, we propose a new pulse shaping approach for multicarrier schemes to increase spectral efficiency in multi-user scenarios. Conventionally, the time-frequency lattice and the prototype filter are designed considering the worst-case of time-varying multipath channel. However, this approach ignores to make use of multi-user diversity and leads to excessive spacings between successive symbols in time and frequency. Unlike the prevalent methods, we investigate user-based filter utilization considering the wireless channel of each user individually to prevent over-design and

improve spectral efficiency. Also, this approach is implemented in a denser time-frequency lattice design. Symbols are allowed to be overlapped (depending on time-frequency dispersion of their individual channels) as long as the signal-to-interference ratios (SIRs) observed by all users are kept above a certain level. Employing user-specific filters to enhance SIR of the user exposed to the most interference provides more overlapping flexibility. Therefore, further improvement in spectral efficiency is achieved in our wireless communication system design.

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