Link Budget calculation
TRANSMITTER |
|
UNITS |
Mpingwe-Poly |
Mpingwe-Ndirande |
Mpingwe-Limbe |
|
Bridge Power |
dBm |
20 |
20 |
20 |
|
Cable Length |
m |
2 |
2 |
2 |
|
Cable Loss/Metre |
dB/m |
0.22 |
0.22 |
0.22 |
|
Cable Loss |
dB |
0.44 |
0.44 |
0.44 |
|
Connector Loss |
dB |
1.2 |
1.2 |
1.2 |
|
Intentional Radiation |
dBm |
18.36 |
18.36 |
18.36 |
|
Antenna Gain |
dBi |
24 |
17 |
17 |
|
EIRP |
dBm |
42.36 |
35.36 |
35.36 |
|
Antenna Loss |
dB |
0 |
0 |
0 |
|
Age loss |
dB |
0 |
0 |
0 |
FREE SPACE LOSS |
|
|
|
|
|
|
Distance |
m |
6337.7 |
5925 |
3710 |
|
Path Loss |
dBm |
116.04 |
115.45 |
111.39 |
RECEIVER |
|
|
|
|
|
|
Antena Gain |
dBi |
24 |
24 |
24 |
|
Connector Loss |
dB |
1.2 |
1.2 |
1.2 |
|
Cable Loss/Metre |
dB/m |
0.22 |
0.22 |
0.22 |
|
Cable Length |
m |
10 |
10 |
10 |
|
Cable Loss |
dB |
2.2 |
2.2 |
2.2 |
|
Received Signal Level |
dBm |
-53.08 |
-59.49 |
-55.43 |
|
Minimum Received Signal Level |
dBm |
-85 |
-85 |
-85 |
|
Fade Margin |
dBm |
31.92 |
25.51 |
29.57 |
Summary of the results:
- Scheme of the links
- The proposed network has 3 links as shown in the attached link budget spreadsheet, namely: Mpingwe to Polytechnic, Mpingwe to Ndirande dispensary and Mpingwe to Limbe Dispensary.
- Mpingwe to Polytechnic is a point to point link using directional antennas at both Mpingwe and Polytechnic. We plan to use grid antennas HG2424G with a gain of 24dBi and beamwidth of 8degrees. The link length is 6.337km.
- Mpingwe to Ndirande is a point to multi-point link using sectorial antenna ( HG2417P-120 with a Gain of 17 dBi and Beamwidth 120 degrees) at Mpingwe and a directional antenna ( grid HG2424G with a gain of 24dBi and beamwidth of 8degrees) at Ndirande. The link length is 5.925km.
- Similarily, Mpingwe to Limbe is a point to multi-point link using sectorial antenna ( HG2417P-120 with a Gain of 17 dBi and Beamwidth 120 degrees) at Mpingwe and and a directional antenna ( grid HG2424G with a gain of 24dBi and beamwidth of 8degrees) at Ndirande. The link length is 3.71km.
- Based on the required transimitter power, availability of hardware in Malawi or close to Malawi we propose the following radios
- Polytechnic-Radio: Airpoint Nexus Pro total sB3212 v/h with minimun received signal of -85dBm at 11 Mbps and transimitter power adjustable to 23dBm.
- Mpingwe-Radio: Dual Radio airPoint2NexusPRO with minimun received signal of -85dBm at 11 Mbps and transimitter power adjustable to 23dBm.
- Ndirande and Limbe: Single Radio airclient Nexus Total sB3414 with minimun received signal of -85dBm at 11 Mbps and transimitter power adjustable to 23dBm.
- The repeater design
- It was a challenge to come up with the design of the repeater. Two options were examined. Firstly, the Network was to consider Mpingwe as an access point with Limbe,Ndirande and Polytechnic as clients. The advantage is that we use only one radio at Mpingwe. However, the Polytechnic-Mpingwe link is a most critical link to be taken at the same level as the other links to clients. The other option is to have two radios at Mpingwe; a point to point between Mpingwe and Polytechnic and Mpingwe to Limbe and Ndirande (point to multi-point.).
- attenuation/TX power/RX sensitivity/margin for each link
- which equipment? (radio/antenna/cables/adapters/etc...)
- reasons for the technical choices done (for example: how to make a repeater station? there are at least two possible solutions: 1 radio with WDS, 2 radios; which one has been selected, and why?)
- cost/benefit evaluation of different alternatives