Mobile communication channels always suffer serious frequency-selective fading due to multipath effect. Traditional spreading codes are characterized by the fact that their time-domain orthogonality is based on fixed chip width across a code period. They often fail to perform well under frequency-selective fading. This paper proposes a new class of CDMA codes, wavelet-packet orthogonal codes capable to retain time-domain orthogonality as well as to offer intra-code subband diversity to mitigate frequency-selective fading. The new codes are constructed by congregating several wavelets with various dilations and shifts. The combination of the wavelets in different nodes in a wavelet-packet full binary tree enables frequency diversity capability. Owing to the even code length, they can be easily used in mobile communications for multi-rate streaming and multi-code spreading. The performance study is carried out using correlation statistics distribution convolution algorithm and the results reveal that wavelet-packet codes, combined with RAKE receiver, perform better than traditional spreading codes in frequency-selective fading channels.
|Number of pages||9|
|Journal||IEICE Transactions on Communications|
|Publication status||Published - 2001 Jul|
All Science Journal Classification (ASJC) codes
- Computer Networks and Communications
- Electrical and Electronic Engineering