  Wireless Communication Networks based on Frequency Division Multiplexing (FDM
in short) plays an important role in the field of communications, in which each
request can be satisfied by assigning a frequency. To avoid interference, each
assigned frequency must be different to the neighboring assigned frequencies.
Since frequency is a scarce resource, the main problem in wireless networks is
how to fully utilize the given bandwidth of frequencies. In this paper, we
consider the online call control problem. Given a fixed bandwidth of
frequencies and a sequence of communication requests arrive over time, each
request must be either satisfied immediately after its arrival by assigning an
available frequency, or rejected. The objective of call control problem is to
maximize the number of accepted requests. We study the asymptotic performance
of this problem, i.e., the number of requests in the sequence and the bandwidth
of frequencies are very large. In this paper, we give a 7/3-competitive
algorithm for call control problem in cellular network, improving the previous
2.5-competitive result. Moreover, we investigate the triangle-free cellular
network, propose a 9/4-competitive algorithm and prove that the lower bound of
competitive ratio is at least 5/3.
