Since the backbone network is mission critical network of
LNR service in deployed WiMAX infrastructure, its reliability
is very important. The measurement of "availability" is often
used to reflect the reliability of a network and imply its failure
duration within a given period [7]. Availability is usually
measured as a ratio of cumulative alarm time to the total
testing period. The alarm is set only when bit error rate (BER)
of one backbone link is more than 10-6. As shown in Figure 7,
all the backbone links from site B1 to site B10 are involved to
perform availability tests. The total testing period lasts for 18
days and all availability results are shown in Table II.