Module 9 - Wireless Systems and Technologies
Slide 52 of 80 ________________
MMDS Spectrum
Capacity
Example:
MMDS system frequency band - 200 M Hz
Modulation Scheme: - 1.5 bits
per sec (4-QAM)
Aggregate throughput - 200 M Hz x 1.5 = 300 M bps
Modulation Scheme: - 5 bits per
sec (64-QAM)
Aggregate throughput - 200 M Hz x 5 = 1 G bps
Example of an MMDS Network:
A typical MMDS cell structure with a frequency reuse factor of 4
and 12 sector hub antenna. An MMDS network can be designed to handle 15,000 high
speed Internet users (downstream data rate > 140 K bps) or 30,000 voice
customers or 45,000 low speed data customers covering 40 Km radius circ
An MMDS Network Cell
Upstream bandwidth 2150 - 2160 M
Hz
Total
bandwidth
12 M Hz
Bandwidth per channel 800 K Hz
No. of frequency channels 15 freq. channels
Reuse
factor
4
Total
channels
60
Data rate per channel 1 M bps
Total data
rate
60 M bps
Data rate per
line
10 K bps
Total lines per
cell
6,000 10 K bps lines
Number of subscribers per line 5
Subscribers per cell
30,000
Number of
cells
1
Total
subscribers
30,000 subs/region
Downstream
Number of 6 M Hz channels 4
Bit rate per channel
27 M bps
Reuse
factor
4
Total bit
rate
27 x 4 x 4 = 432 M bps
Total
subs
30,000
Cells
1
Subs per
cell
30,000
subs per
line
5
Lines per
cell
6,000
lines bit
rate
432,000 / 6,000 = 72 K bps
________________
N-GEN
Communications Web-based Seminars ©NGCS