Dynamic Bit Allocation MC-CDMA For NGN

Third Generation (3G) mobile communication technologies like CDMA2000,WCDMA are already in deployment in many countries and TD-SCDMA will soon be deployed in China in addition with other technologies. These are changing the way we communicate,conduct business,access information,and being entertained over the multimedia super highway.3G services enable users to make video calls to the office and surf the net simultaneously, or play interactive game wherever they may be.Although bandwidth of current 3G technologies promise burst rates up to 384Kb/s and 2Mb/s for vehicular and indoor applications respectively, the average throughput per user is not expected to be more than 171Kb/s during the peak hours.This bandwidth is adequate to meet the needs for voice, basic data communication and wireless internet access,but not enough for new interactive multimedia services such as multi-parity video conference.As such there is demand to develop a new physical layer that can give higher bandwidth.These future networks have been termed NGN (Next Generation Networks).The main features of such a system will be greater capacity and access speed in the downlink.The vision of NGN wireless/mobile systems will be the provision of broadband access,seamless global roaming,and Internet/data/voice everywhere,utilizing for each the most appropriate always connected technology. Multi-Carrier Code Division Multiple Access (MC-CDMA) is a promising candidate for the air interface of NGN wireless networks.MC-CDMA is essentially an Orthogonal Frequency Division Multiplexing (OFDM) technique where the individual data symbols are spread using a spreading code in the frequency domain.The spreading code associated with MC-CDMA provides a multiple access technique as well as interference suppression.It is very efficient in spectrum usage and it is very effective in spectrum selective channel.The NGN networks are predicted to provide packet data transmission rates of 5Mbps in outdoor-macro-cellular environments and up 20Mbps in indoor-micro-cellular environments.In MC-CDMA systems,a number of sub carriers per user are used for the high-rate data transmission,and each data modulated by a different sub carrier is transmitted through a different frequency band.Each data undergoes a different channel condition and arrives with a different error rate at the base station.By transmitting message data through all the sub channels based on the Channel State Information (CSI),a new data transmission scheme called "Dynamic Bit Allocation Multicarrier Code Division Multiple Access for Next Generation Networks" is introduced in this dissertation. In this system,the CSI is assumed to be known to the transmitter. Then the base station transmits the data based on the CSI by using the principle of dynamic bit allocation. Simulated results have shown that adaptive MC-CDMA yields a higher system capacity than a conventional MC-CDMA.