In small-zone (cellular) FM mobile communication systems, greater geographical reuse is achieved when the modulation index is larger. A large index, however, imposes a small number of channels. The spectrum utilization factor in total is thus determined as a synthesis of the available number of channels and geographical frequency reuse. The relationship between the modulation index and spectrum utilization factor is discussed for Rayleigh fading condition, with and without diversity. The spectrum utilization factor for the concentrated traffic model is introduced. It is shown that the optimum peak deviation that realizes the most efficient spectrum utilization is from 3 to 4 kHz for uniform traffic distribution, and 2 kHz for concentrated traffic distribution. These results show that narrow channel spacing, such as 12. 5 kHz, is better than the conventional 25 kHz or wider channel spacing for achieving efficient spectrum utilization. Characteristics for the static condition without fading are also discussed.
ASJC Scopus subject areas
- Computer Science Applications
- Electrical and Electronic Engineering
- Applied Mathematics