Distributed antenna

smart antenna and sector antenna are three techniques to improve the system capacity in wireless communication.In this paper

we compare the channel/Shannon capacity of multiple antennas in the three cases.Assuming the average received signal power in total antennas from each user is the same

we get that distributed antenna and sector antenna have much larger Shannon capacity than smart antenna.This is in contrast with that smart antenna has a better performance than sector antenna in suppressing interference

which results in an improvement in system capacity.We also analyze the capacity of distributed antenna in unlimited case

that is

with large number of users

K

and large number antennas

M

while keeping the number of users per dimension

α

constant.Analysis show tha

t in case of large

α

α

1

the capacity of distributed antenna approaches to that of sector antenna with a constant addition 0.44bit/s/Hz/Dim.It should be noted that if diversity gain by distributed antenna is considered

its capacity is still much larger than that of sector antenna.