High performance node page
Antenna calculations
Every HP-node has two 5.15-5.6 GHz antennas. The one as a build in patch antenna and the other is an 5.1-5.8 GHz omni-directional antenna. The idea is that the patch antenna of a node will either be aligned to the omni or the patch antenna of another node. The following calculations is to get an feeling of what distances should be possible between these antennas.
South African Wifi channels:
Channel 1 : 2412 Mhz 11g Channel 48 : 5240 Mhz 11a Channel 2 : 2417 Mhz 11g Channel 52 : 5260* Mhz 11a Channel 3 : 2422 Mhz 11g Channel 56 : 5280* Mhz 11a Channel 4 : 2427 Mhz 11g Channel 60 : 5300* Mhz 11a Channel 5 : 2432 Mhz 11g Channel 64 : 5320* Mhz 11a Channel 6 : 2437 Mhz 11g Channel 100 : 5500* Mhz 11a Channel 7 : 2442 Mhz 11g Channel 104 : 5520* Mhz 11a Channel 8 : 2447 Mhz 11g Channel 108 : 5540* Mhz 11a Channel 9 : 2452 Mhz 11g Channel 112 : 5560* Mhz 11a Channel 10 : 2457 Mhz 11g Channel 116 : 5580* Mhz 11a Channel 11 : 2462 Mhz 11g Channel 120 : 5600* Mhz 11a Channel 12 : 2467 Mhz 11g Channel 124 : 5620* Mhz 11a Channel 13 : 2472 Mhz 11g Channel 128 : 5640* Mhz 11a Channel 36 : 5180 Mhz 11a Channel 132 : 5660* Mhz 11a Channel 40 : 5200 Mhz 11a Channel 136 : 5680* Mhz 11a Channel 44 : 5220 Mhz 11a Channel 140 : 5700* Mhz 11a
HP-Node detailed specs: http://wirelessafrica.meraka.org.za/wiki/images/0/07/WLAN-A0033.pdf
Pigtail detail specs: http://wirelessafrica.meraka.org.za/wiki/images/0/0a/Ca178_cable_assemblies_datasheet.pdf
Wireless adapter detail specs: http://wirelessafrica.meraka.org.za/wiki/images/2/21/Wlm54sag23.pdf
OR the Mikrotik version of the same adapter called a R52H (also manufactured by Compex, but usually cheaper) http://wirelessafrica.meraka.org.za/wiki/index.php/Image:R52H.pdf
Another popular adapter is the DCMA-82 from Wistron. They have better RX sensitivity, but lower output power and they are a bit more expensive than the Compex cards. In some of the discussions that I've seen they state that the DCMA-82 has much cleaner output power, better RX sensitivity, and a lower failure rate/quality issues than Compex's cards. http://wirelessafrica.meraka.org.za/wiki/index.php/Image:DCMA-82.pdf
Node specs summary:
Patch antenna - 21-23 dBi, 16 deg H, 11 deg V, 5.15 -5.6 GHz
5Ghz Omni antenna - 8-11 dBi, 360 deg H, 10 deg V, 5.1 - 5.85 GHz
2.4Ghz Omni antenna - 7.5-8.5 dBi, 360 deg H, 12 deg V, 2.4 - 2.5 GHz
30mm U.FL-SMA pigtail - RG178 cable insertion loss, 2.4 GHZ = -1.1dB, 5.6 GHz = -2dB
Compex WLM54AG23 adapter - IEEE 802.11a/b/g (2.4/5GHz)
- AR5413/5414(AR5006X/XS) Atheros Chipset
- RECEIVER SENSITIVITY 802.11a -
-90 dBm @ 6Mbps
-70 dBm @ 54Mbps
- OUTPUT POWER 802.11a
23dBm @ 6-24Mbps
22dBm @ 36Mbps
19dBm @ 48Mbps
17dBm @ 54Mbps
Mikrotik (Compex) R52H - IEEE 802.11a/b/g (2.4/5GHz)
- AR5413/5414(AR5006X/XS) Atheros Chipset
- RECEIVER SENSITIVITY 802.11a -
-90 dBm @ 6Mbps
-70 dBm @ 54Mbps
- OUTPUT POWER 802.11a
24dBm @ 6-24Mbps
22dBm @ 36Mbps
19dBm @ 48Mbps
Wistron DCMA-82 - IEEE 802.11a/b/g (2.4/5GHz)
- AR5413/5414(AR5006X/XS) Atheros Chipset
- RECEIVER SENSITIVITY 802.11a -
-90 dBm @ 6Mbps
-82 dBm @ 36Mbps
-72 dBm @ 54Mbps
- OUTPUT POWER 802.11a
22.5dBm @ 6-24Mbps
21.5dBm @ 36Mbps
18dBm @ 48Mbps
I could not find any receive sensitivity info for ranges between 6Mbps and 54Mbps for the WLM54AG23. The closest I could find was the specs of another manufacturer card, using the same Atheros chipset as the WLM54AG23. Here is the receive sensitivity info for a WMIA-166AG Dual-Band miniPCI module (802.11a/g) Nominal Temp Range:
6Mbps 10-5 BER @ -90 dBm, typical 9Mbps 10-5 BER @ -89 dBm, typical 12Mbps 10-5 BER @ -88 dBm, typical 18Mbps 10-5 BER @ -86 dBm, typical 24Mbps 10-5 BER @ -82 dBm, typical 36Mbps 10-5 BER @ -78 dBm, typical 48Mbps 10-5 BER @ -72 dBm, typical 54Mbps 10-5 BER @ -68 dBm, typical
The WLM54AG23 is not the best wifi adapter in the market, but it gives a good compromise between price vs performance. If one need to push the limits of a specific link then I would probable select the SR5 from Ubiquity. They have excellent TX power and RX sensitivity.
There are lots of wifi/antenna/distance calculators available on the WEB. Most of these calculators cannot calculate the max distance for a link, you have to specify the distance and it will calculate you dBm margin. Links to a couple of Wifi/antenna/distance calculators:
http://www.radiolabs.com/stations/wifi_calc.html http://www.zytrax.com/tech/wireless/calc.htm http://www.widgetbox.com/widget/wifi-link-calculator http://www.wifiextreme.com.au/index.php?main_page=page_5 http://www.rflinx.com/help/calculations http://www.olotwireless.net/castella/radio.htm
Here are some formulas use to calculate a link budget:
Free space loss = 36.56 + 20Log10(Frequency) + 20Log10(Dist in miles) mW to dBm = 10Log10(milliWatts) + 30 dBm to mW = 10(dBm/10) RX Power = Margin - RX sensitivity Theoretical margin = TX power budget + RX power budget - free space loss SAD factor = Theoretical margin/TX power budget * 100 and shows the percentage of spare power on transmission.
(Free Space Loss) = 92.5 + (20 Log fequency) + (20 log km distance)
Free space loss @ 5400GHz:
1km = -107.07dB 11km = -128.028dB 2km = -113.09dB 12km = -128.784dB 3km = -116.61dB 13km = -129.479dB 4km = -119.11dB 14km = -130.123dB 5km = -121.05dB 15km = -130.722dB 6km = -122.63dB 16km = -131.282dB 7km = -123.97dB 17km = -131.809dB 8km = -125.13dB 18km = -132.305dB 9km = -126.15dB 19km = -132.775dB 10km = -127.07dB 20km = -133.221dB
The following are the minimum and maximum link calculations for our HPNode with a 5Ghz patch to omni link under ideal conditions with a decent fresnel zone. Just note that one very seldom get ideal conditions in real life installations. These calculations are done to get a feeling for what to expect from our equipment. Link distance calculations was done with these calculator at http://www.swisswireless.org/wlan_calc_en.html. I've first played around with the Free-space-loss values in the Link Budget tool until I would get a 6dB margin. They recommend to take a sufficient security margin (5-6 dB or more on large distances). Then I've used the Free space loss tool to convert my Free-space-loss value to a km distance. Lets do some calculations to see what we get.
Patch - Omni:
Min link distance @ 54Mbps 0.9km: Max link distance @ 54Mbps 1.55km: patch min = 21dBi patch max = 23dBm omni min = 8dBi omni max = 11dBm pigtail = -2dBm pigtail = -2dBm TX power = 17dBm TX power = 17dBm RX sensitivity = -70dBm RX sensitivity = -70dBm Free space loss = -106dB Free space loss = -111dB link margin = 6dB link margin = 6dB
Min link distance @ 24Mbps 6.9km: Max link distance @ 24Mbps 12.3km: patch min = 21dBi patch max = 23dBm omni min = 8dBi omni max = 11dBm pigtail = -2dBm pigtail = -2dBm TX power = 23dBm TX power = 23dBm RX sensitivity = -82dBm RX sensitivity = -82dBm 34km free space = -124dB Free space loss = -129dB link margin = 6dB link margin = 6dB
Min link distance @ 6Mbps 17km: Max link distance @ 6Mbps 30.9km: patch min = 21dBi patch max = 23dBm omni min = 8dBi omni max = 11dBm pigtail = -2dBm pigtail = -2dBm TX power = 23dBm TX power = 23dBm RX sensitivity = -90dBm RX sensitivity = -90dBm 34km free space = -132dB Free space loss = -137dB link margin = 6dB link margin = 6dB
The following are the minimum and maximum link calculations for our HPnodes with a 5Ghz patch to patch link under ideal conditions with a decent fresnel zone. Just note that one very seldom get ideal conditions in real life installations. These calculations are done to get a feeling for what to expect from our equipment. Link distance calculations was done with these calculator at http://www.swisswireless.org/wlan_calc_en.html. I've first played around with the Free-space-loss values in the Link Budget tool until I would get a 6dB margin. They recommend to take a sufficient security margin (5-6 dB or more on large distances). Then I've used the Free space loss tool to convert my Free-space-loss value to a km distance. Lets do some calculations to see what we get.
Patch - Patch:
Min link distance @ 54Mbps 3.9km: Max link distance @ 54Mbps 6km: patch min = 21dBi patch max = 23dBm pigtail = -2dBm pigtail = -2dBm TX power = 17dBm TX power = 17dBm RX sensitivity = -70dBm RX sensitivity = -70dBm Free space loss = -119dB Free space loss = -123dB link margin = 6dB link margin = 6dB
Min link distance @ 24Mbps 30.9km: Max link distance @ 24Mbps 38.9km: patch min = 21dBi patch max = 23dBm pigtail = -2dBm pigtail = -2dBm TX power = 23dBm TX power = 23dBm RX sensitivity = -82dBm RX sensitivity = -82dBm Free space loss = -137dB Free space loss = -139dB link margin = 6dB link margin = 6dB
Min link distance @ 6Mbps 77.6km: Max link distance @ 6Mbps 123km: patch min = 21dBi patch max = 23dBm pigtail = -2dBm pigtail = -2dBm TX power = 23dBm TX power = 23dBm RX sensitivity = -90dBm RX sensitivity = -90dBm Free space loss = -145dB Free space loss = -149dB link margin = 6dB link margin = 6dB