The deployment of TH-MC-CDMA systems over two-tier femtocell environments

The time-hopped multi-carrier coded-division multiple-access (TH-MC-CDMA) system is deployed under a two-tier femtocell environment. Femtocells were originally designed to serve a group of subscribers located in a small coverage area, such as a small office, home office, or a house. The coverage area is typically up to about 100 m in radius. The femtocell is applied to serve indoor subscribers, thus, Rayleigh fading is adopted to characterize the propagation channel. The TH-MC-CDMA technique transmits each symbol alternatively with fair time (slotting)/frequency (coding) for each user in hot spots (the area around the 0th femtocell). The signal intensity estimated at a mobile unit located in the second tier, i.e., the femtocell coverage area, is an important issue. This article evaluates the system performance with both bit error rate and outage probability according to the most important parameters. For example, the activating user number, the hopping numbers, subcarrier number, and transmitting power provided by the TH-MC-CDMA system. The analytical results are compared with results from published papers for reliability.