Interference avoidance and power control strategies for coded frequency hopped cellular systems

In a frequency hopped CDMA (FH-CDMA) system, the principal impairment is interference generated by users sharing the same time-frequency slot. If users have fixed hopping patterns, a system can monitor the average interference in every time-frequency slot. It can then assign a new user to communicate only in the M lowest interference slots out of every N slots in the user's hopping pattern. The transmit power for the new user is then reduced on the average. System capacity is increased since each user generates less interference. The capacity for a FH-CDMA system in which every user transmits M out of every N slots with equal received power for every user is derived. Power control algorithms which allow users to have different signal-to-interference ratio (SIR) requirements have been implemented to maximize the capacity of the system. In addition, error correcting codes not only protect against interference, noise, and fading, but can also increase the capacity by permitting admission of users even when some of the slots have poor SIR.