Abstract—Recently, intense interest has focused on the transmission techniques which can support high data rate transmission over wireless channels for applications including wireless multimedia, wireless Internet access, and future-generation mobile communication systems. However, high data rate transmission is limited by inter-symbol interference (ISI) due to the frequency selective fading in multipath fading channels. To meet the strong demand for broadband multimedia services by both nomadic and mobile users, it is important to increase the bit rate of future mobile communications systems. To enhance system capacity, novel technologies or new concepts for improving bandwidth efficiency are indispensable. Orthogonal frequency division multiplexing (OFDM) is one of the promising solutions to this problem. The combination of MCCDMA and OFDM is an effective way to further improve the performance. In this work, an adaptive downlink modulation using OFDM and MC-CDMA is presented for maximizing the system capacity and actualizing QoS (Quality of Service) control of future mobile communications. The basic concept of the proposal method is that a time frame is divided into two sub-frames, one is for OFDM and the other is for MC- CDMA, and the base station (BS) allocates a preferable modulation scheme to each user per each time slot in accordance with their service requirements and link conditions such as the received signal strength indication (RSSI) level and interference signal strength.

Index Terms—OFDM, MC-CDMA, RSSI, CINR

Cite: S Venkatachalam and T Manigandan, "ADAPTIVE MODULATION OF OFDM AND MC-CDMA SYSTEM," International Journal of Electrical and Electronic Engineering & Telecommunications, Vol. 1, No. 1, pp. 1-10, October 2012.