A two-tier frequency reuse scheme

The race toward higher throughputs for cellular network users is getting more difficult everyday. On the one hand cellular network operators wish to increase benefits by offering new services to users, but on the other hand spare radio resource are shrinking away. The spreading of WiFi-3G dual mode devices is making this fight even harder. The new ”Femtocell” technology is expected to be the rescuer of cellular network operators. This ”mini” cellular base station will provide high indoor coverage and throughput to indoor users relying on regular home access connections to the internet. However the big challenge remaining is to efficiently allocate spectrum to this technology. As spectrum licenses are very expensive most operators do not hold enough to completely separate the femtocell and macrocell layers. Coexisting femtocells and macrocells lead to severe interference scenarios. We propose here a double frequency reuse scheme, which allows a femtocell to reuse the frequency already in use by adjacent sectors of the overlaying macrocell. We present three solutions: full, partial or mixed frequency reuse. Each has advantages and drawbacks, and may be more suitable than the others in some specific configurations. Thanks to our scheme we preserve the radio resource management efficiency without affecting the system performance.