Byoung Jo CHOI
11 Dec. 1997
Spread spectrum communication uses much larger bandwidth than required by spreading original information signal using noise like sequences. A spread spectrum receiver then uses the synchronized replica of the noise like sequences to recover the original information. Due to this noise like property of the spreading sequences, an eavesdropping is not easy. In cellular radio communication, the autocorrelation property and the cross-correlation property of the spreading sequences are used to achieve multiple access communications, known as CDMA(Code Division Multiple Access). Where perfect synchronism can be achieved, as in the forward link, a set of orthogonal codes is used for code division multiplexing. In reverse link, different users use different pseudo random sequences for their spreading and the base station recovers all the user's signals making use of the knowledge of each spreading sequences.
As the spreading sequences generation is the first step in understanding CDMA mobile communications, I have written several well-known code generators and implemented a code management scheme for multi-rate orthogonal codes. These generators are very general and I hope they can be used in various investigations on the nature of CDMA including simulations for CDMA mobile communications. All the source codes(cdma.tar[102k], cdma.tar.gz[13k], cdma.tar.bz2[11k]) are available.