|
|
| (98 intermediate revisions by 2 users not shown) |
| Line 1: |
Line 1: |
| == Antenna calculations ==
| | migrated to wireless dev |
| | |
| 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
| |