Channel assignment in CDMA systems with Walsh and PN coding
Piotr Z. Gajewski · 2002
Many channels assignment procedures and allocation strategies for cellular network have been discussed for various multi-access methods. The channel allocation both for new calls and for handovered ones should minimise the co-channel interference. In CDMA, channels are creating by spreading and accessing codes. The signal-to-noise ratio (SNR) is generally dependent on the number of users N and correlation coefficients r/sub k,i/ between sequences used for transmission. The codes assignment method based on the Hopfield neural network (HNN) with Kohonen (1982) self-organised future maps (KSOFM) is presented. A two-stage algorithm is proposed for DS-CDMA systems with heterogeneous cells. The cross-correlation coefficients are the main factors of minimised cost function that is calculated for the various traffic and multi-access interference parameters. The simulation model was examined for a number of PN sequences as well as for orthogonal Walsh mapping.