  Modern radio communication is faced with a problem about how to distribute
restricted frequency to users in a certain space. Since our task is to minimize
the number of repeaters, a natural idea is enlarging coverage area. However,
coverage has restrictions. First, service area has to be divided economically
as repeater's coverage is limited. In this paper, our fundamental method is to
adopt seamless cellular network division. Second, underlying physics content in
frequency distribution problem is interference between two close frequencies.
Consequently, we choose a proper frequency width of 0.1MHz and a relevantly
reliable setting to apply one frequency several times.
  We make a few general assumptions to simplify real situation. For instance,
immobile users yield to homogenous distribution; repeaters can receive and
transmit information in any given frequency in duplex operation; coverage is
mainly decided by antenna height.
  Two models are built up to solve 1000 users and 10000 users situations
respectively. In order to utilize restricted frequency and PL code, three
stratified terms - "cell", "cluster", "group" - are introduced to describe the
models in detail. Under our analysis, 91 repeaters for 1000 users and 469
repeaters for 10000 users are viable results.
  Next, to test stability and sensitivity of models, we give total
consideration to the variation of sum of users, antenna height, and frequency
width and service radius. Evaluation about models is offered qualitatively.
Finally, two practical cases are put forward to gain a partial knowledge of
mountainous area. The brief method in dealing with mountains is classified
discussion in two ideal conditions. It may provide some constructive
suggestions to avoid shortcomings or take proper measures in similar locations.

Networking and Internet Architecture