Filter Bank Based Multi-Carrier Systems for Future Broadband Wireless Communications

Orthogonal Frequency Division Multiplexing (OFDM) technique has gained increasing popularity in both
wired and wireless communication systems, mainly due to its immunity to multipath fading, which allows for a significant
increase in the transmission rate. By inserting a cyclic prefix (CP) before each transmitted block longer than the length
of the channel, OFDM effectively transforms a frequency selective channel into a parallel of flat-fading channels. This
greatly simplifies both channel estimation and data recovery at receiver. However, these advantages come at the cost of a
loss of 10-25% spectral efficiency due to the insertion of CP, and an increased sensitivity to frequency offset and Doppler
spread as well as transmission nonlinearity accentuated by non-constant modulus of OFDM signals. Additionally, due
to the time-varying nature of wireless channels, training sequence needs to be transmitted periodically for the purpose of
channel estimation. The overhead imposed by training sequence and CP can be up to 50 percent for fast fading channels,
causing significant loss of spectral efficiency.

In this proposal we aim to tackle these problems with the filter bank based multi-carrier system employing a special
pulse shaping filter called IOTA (isotropic orthogonal transform algorithm) to yield good time and frequency localization
properties so that inter-symbol interference (ISI) and inter-carrier interference (ICI) are avoided without the use of CP.
We also investigate a linearly precoded IOTA system which facilitates blind channel estimation, resulting in a spectrally
efficient multi-carrier system without the transmission of training sequence in addition to the elimination of CP.
In order to effectively combat carrier frequency offset and high PAPR problems in the current orthogonal frequency division
multiple access (OFDMA) and single carrier frequency division multiple access (SC-FDMA) based uplink communications,
we propose a novel multiple access scheme which combines IOTA with low density signature (LDS) technique.

The focus of our work will be on the study and utilization of some special properties of IOTA which have been overlooked
by others. We aim to leverage these properties in the equalization, decoding and channel estimation design in order to
achieve optimal performance and maximum capacity with affordable computational complexity. Our goal is to provide
theoretical references and guidelines for successful implementation of IOTA systems for future wireless communications.

This research will not only benefit the communications industry, enhance the UK's economic competiveness but also contribute to the country's academic standing in the areas of broadband communications and advanced signal processing which is identified in the shaping capability: EPSRC Research Portfolio 2011 an area for growth.

This research will contribute to theory, design and development of multi-carrier systems for future communications. Research outcomes from the proposed project will act as enablers of next-generation wired and wireless communication systems beyond 2020, which have adopted multi-carrier modulation as a key component to provide applications like voice/video/data communications, with higher data rates, higher mobility and higher reliability.