This paper investigates system performance for an MC-CDMA (multi-carrier coded-division multiple-access) system, in which an operating environment with both single-cell and multiple-cell configurations and correlated-Nakagami-m statistics for fading channels are adopted. It is worthwhile noting that applying the joint characteristic function to determine the jpdf (joint probability density function) with a generalized Laguerre polynomial yields a simpler method. The traditional difficult methods for explicitly obtaining the jpdf are avoided for the sake of simplification. Some new closed-form formulas for average BER (bit-error rate) with statistical calculation of MAI (multiple-access interference) for MC-CDMA system operation in multi-cell environments were obtained in this study. For achieving accuracy in the derived formulas, an example of an MC-CDMA system with a dual-receiver branch operating in a multiple-cell structure with 12 surrounding cells is presented.

This paper considers a wireless LAN system operated in a multiple-cell environment with universal frequency reuse. A key technical goal is to increase cell-capacity within a cell. A very high-rate wireless LAN system, maximum data rates of over 100 Mbit/s, is proposed that offers an expanded signal-bandwidth compared to that specified in IEEE802.11a. The system employs OFDM and MC/CDMA signals in packet mode. It falls back from OFDM signals with low subcarrier modulation orders to MC/CDMA signals. A link level performance comparison shows that OFDM has superior performance to MC/CDMA at over 32 Mbit/s. Under 16 Mbit/s, however, MC/CDMA can establish wireless link connections unlike OFDM. Thus the fallback technique, which is triggered by the CIR environment, should select OFDM if the data rate exceeds 32 Mbit/s. It should fallback to MC/CDMA if the rate is less than 16 Mbit/s. We also evaluate the proposed scheme in a multiple-cell environment with universal frequency reuse, where the severe co-channel (other-cell) interference is present. We derive a cell capacity criterion for wireless LAN systems, and show that the proposed scheme offers a 2.2 times larger available transmission distance than the OFDM-only scheme. In addition, it is found that the proposed scheme offers a 1.3 times improvement in cell capacity compared to the MC/CDMA-only scheme, even if all other-cell interference is considered.