During the past long period

the mathematical modeling researches for multi-star LAN have been focusing on single-star LAN

for which all models and performance evaluation of the Contention-Collision Cancellation (C-CC) access mode have already finished.As there exists difficulty in math aspect

the breakthrough of mathematical modeling for double-star LAN is very late

and only deduced the time delay which is the mean waiting time of customers generated by the observing terminal A

on the condition that at the observing time point

there is

i

customers in system (

i

is greater than 0

i.e.based on heavy load) and terminal A has 1 customer.In this paper

th

e type I system model for double-star LAN based on heavy load is revaluated

and get the mean period of time from time point to the end of service for the customer generated firstly by terminal A

on the condition that at observing time point

there are

i

customers in system (

i

is greater than 0) and no customer in observing terminal A.This paper consummates the type I mathematical model for double-star LAN

and simulation.The conclusion provides the integrated theoretical foundation to the application of double-star LAN based on heavy load.