{"title":"Interest of the Sequences Pseudo Noises Codes of Different Lengths for the Reduction from the Interference between Users of CDMA Network","authors":"Nergu\u00e8 Kassahan Kone, Souleymane Oumtanaga","country":null,"institution":"","volume":23,"journal":"International Journal of Electrical and Computer Engineering","pagesStart":2600,"pagesEnd":2604,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/3130","abstract":"The third generation (3G) of cellular system adopted\r\nthe spread spectrum as solution for the transmission of the data in the\r\nphysical layer. Contrary to systems IS-95 or CDMAOne (systems\r\nwith spread spectrum of the preceding generation), the new standard,\r\ncalled Universal Mobil Telecommunications System (UMTS), uses\r\nlong codes in the down link. The system is conceived for the vocal\r\ncommunication and the transmission of the data. In particular, the\r\ndown link is very important, because of the asymmetrical request of\r\nthe data, i.e., more remote loading towards the mobiles than towards\r\nthe basic station. Moreover, the UMTS uses for the down link an\r\northogonal spreading out with a variable factor of spreading out\r\n(OVSF for Orthogonal Variable Spreading Factor). This\r\ncharacteristic makes it possible to increase the flow of data of one or\r\nmore users by reducing their factor of spreading out without\r\nchanging the factor of spreading out of other users. In the current\r\nstandard of the UMTS, two techniques to increase the performances\r\nof the down link were proposed, the diversity of sending antenna and\r\nthe codes space-time. These two techniques fight only fainding. The\r\nreceiver proposed for the mobil station is the RAKE, but one can\r\nimagine a receiver more sophisticated, able to reduce the interference\r\nbetween users and the impact of the coloured noise and interferences\r\nto narrow band. In this context, where the users have long codes\r\nsynchronized with variable factor of spreading out and ignorance by\r\nthe mobile of the other active codes\/users, the use of the sequences of\r\ncode pseudo-noises different lengths is presented in the form of one\r\nof the most appropriate solutions.","references":null,"publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 23, 2008"}