Variable chip rate CDMA

A direct-sequence spread spectrum multiple access scheme called variable chip rate code-division multiple access (VCR-CDMA) is presented. The scheme supports different information bearing data rates for users or devices accessing various multimedia applications by varying the transmission (chip) rates and overlaying the frequency spectra of channels with different data rates. This scheme is applicable to home and office wireless environments that operate in unlicensed shared radio frequency bands. It is suitable for applications where various types of electronic devices and appliances of low duty cycle require tetherless connections to a central controller through a shared wireless medium. By assigning code channels of different chip rates, the total number of simultaneously active channels is increased. By using multiple orthogonal codes and/or codes of a different spreading factor, the multiple data rate capability of this scheme can be enhanced.