SCS-MC-CDMA system with best effort cell structure

This paper proposes SCS-MC-CDMA system with best effort cell structure. 4th generation mobile communication (4G) system is expected to offer 100 Mbps or higher data rate communication in the high-frequency microwave band. The system is characterized by relatively long delay paths, high maximum Doppler frequency, high power consumption at the mobile terminals and small cell coverage caused by the high data transmission rates and the high-frequency band. All of these are serious problems that must be solved. The proposed SCS-MC-CDMA system can realize high communication quality even under delay spreads as long as a few microseconds and maximum Doppler frequency as high as 1000 Hz. Channel estimation is accurate since code-multiplexed pilot symbols are used, and MMSEC is adopted to reduce inter-code interference. Concerning power consumption, the system can assign a number of sub-carriers, which may be narrower than the whole bandwidth of the system, to each user according to the user´s data rate requirements. This lowers the power consumption, especially for low data rate users such as voice users. Moreover, the best effort cell structure overcomes the small cell coverage issue by changing the maximum data rate for each user adoptively according to his distance from the base station or channel quality.