NEC-LIST: DECT Coverage in Metal Tunnel

Hello,

We have to study the coverage of a DECT phone system (1.8 GHz, TDMA)
in a metal tunnel 10 meters width, 5 meters height and 40 meters
depth. Both ends of the tunnel are covered with metal, and as such,
the tunnel looks like a metal box.

Since it is a tunnel, we have selected a bi-directional yagi antenna
for the base station and put it at the tunnel center. By doing this,
we find the voice communication quality is no good, especially when
the hand phone is in motion. What we are thinking is that due to the
reflection of metal wall, the power density distribution in the tunnel
is undetermined. Furthermore, due to the delay signal from the wall
reflection, the signal pulses in one time slot interfere the other
time slot, and as such, degrade the communication quality. We also
wonder if we have selected the correct type of antenna or if we could
use panel antenna to improve the performance. Leaky cable is another
common implementation for tunnel coverage. Advisable to use it here?

Has anybody done a similar study before? We would appreciate it if
he/she could share the experience with us. Is there anyway to reduce
the multiple signal reflected from the wall?

We are also interested to find out any simulation software available
for us to study the coverage in this type of tunnel. Since the signal
is reflected from the wall for different path, probably NEC-BSC could
do the job, as it is employing ray tracing method. Has anybody adopted
NEC-BSC for this kind of study?

Thank you.

Best regards,

Chong Kwan Meng
Received on Thu Apr 06 2000 - 22:15:16 EDT