Method of enhancing frequency diversity in block cdma systems

Abstract

Code division multiple access (CDMA) is a popular multiple access technique that is used to support multiple users simultaneously in a network. Many variants of CDMA exist, including direct sequence (DS) CDMA, multi-carrier (MC) CDMA, cyclic prefixed (CP) CDMA, and chip interleaved block spread (CIBS) CDMA. In addition to these variations, many receiver architectures are often available for implementation in CDMA systems, such as the well-known RAKE receiver, interference cancellation receivers, and receivers that rely on channel equalisation. Many MUI-free techniques rely on user separation in the frequency domain by assigning mutually exclusive sets of tones to each user. The known techniques of multiple access, however, do not allow each individual user to fully exploit the frequency diversity in the channel since each user only utilises a portion of the total available bandwidth to transmit a message. According to the present invention users can enhance and adaptively exploit the frequency diversity in the channel by simply altering the spreading codes that are used in a block CDMA system. MUI-free transmission is maintained by employing the techniques disclosed here. Furthermore, this technique can easily be extended to multiple-input multiple-output (MIMO) systems.

Dependencies are inferred from the claim text.