A wireless communications system with a transmission speed of 18 Mbit/s is presented using the 2.4 GHz ISM band. This system employs the Carrier Frequency Offset-Spread Spectrum (CFO-SS) scheme and the Dual-Polarization Staggered Transmission (DPST) scheme. The 18 Mbit/s CFO-SS system (named CFO-SS18) was developed and its performance evaluated in fields. In this paper, the detailed operating principle of CFO-SS and DPST schemes, together with the specifications and structures of CFO-SS18, are presented. Results of indoor and field tests obtained by using CFO-SS18 are also presented.

Design of wireless communications systems with a transmission rate of 6 and 10 Mbit/s is presented for the 2.4 GHz Japanese ISM band, in which a spread spectrum technique named "CFO-SS (Carrier Frequency Offset-Spread Spectrum)" scheme is employed. In the CFO-SS system, a single PN code is commonly assigned to all the synchronized multiplexed carriers, and the frequency separation between carriers is determined by the transmission rate of each carrier. To realize the CFO-SS system, a timing acquisition and tracking scheme, an important part of the design, is presented first. Next, bit and packet error performance is investigated under severe multipath environments with/without a RAKE receiver. Degradation by channel bandwidth limitations, frequency inaccuracy of the hardware and co-channel interference (CCI) is also investigated by computer simulation. Simulation results presented confirmed sufficient performance of the CFO-SS system for wireless LAN systems using the 2.4 GHz ISM band.