Non-orthogonal forward link for future CDMA cellular systems

by Sau, Hong Man

In this thesis we propose the use of non-orthogonal forward link for future CDMA cellular systenis. The non-orthogonal forward lin & uses long PN codes as the spreading codes. The use of long PN codes has a few advantages over the common practice of using orthogonal codes. It ailows the design of a flexible air interface that can easily accommodate multimedia traffic, and has the potential to offer substantial capacity improvement by exploiting future advances in source and channel coding. In addition, it allows hand-off-withoutsignaling which may have application in highly-dynamic propagation environments. We study the novel issue of correlation of interference at different diversity branches in a non-orthogonal forward link. Its efkt on the performance of diversity combining is analysed. Simulation on system capacity, with the correlation effect taken in consideration, reveals that with the use of proper antenna diversity and channel coding techniques, nonorthogonal forward link offers roughly equal capacity comparing to orthogonal forward link, and has the potential to offer substantially higher capacity with future advances in source and channel coding. Performance of hand-off-without-signaling is also analysed.