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Selecting airmax product

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Selecting the best AirMax product for each situation

Author: Salvador Bertenbreiter May 22nd 2010

This guide will help you through the process of product selection for your wireless link. It covers 2.4 and 5.8Ghz advantages and disadvantages, wireless link reliability calculation and a list of recommended products for specific uses (point-to-point and multipoint-to-point).

The 2.4 vs. 5.8 dilemma

There isn’t a best band for all scenarios. The choice between using 2.4 or 5 GHz depends on various factors, like: type of wireless link (point-to-point or multi-point to point links) interference, distance, Line of Sight, etc. First, let’s see the advantages and disadvantages of each band:

The advantages of the 2.4GHz band are:

  • A “better” tolerance for trees and small obstacles than 5.8GHz
  • Most compatible with standard Wi-Fi devices, like Wi-Fi phones, laptops and Wi-Fi IP cameras. (This is only an advantage if you want to use an AP to serve this kind of devices, otherwise it isn’t.)
  • Unlicensed in most countries

And the disadvantages of 2.4GHz are:

  • Only three non-overlapped channels.
  • It’s a crowded band; there is a lot of interference from cordless phones, SOHO Wireless Router, other WISPs, Micro-Owen, etc…
  • It has a larger Fresnel zone

The advantages of the 5.8GHz band are:

  • There are higher gain antennas
  • A smaller Fresnel zone.
  • Usually, there is much less interference from other sources.

The disadvantages of the 5.8GHz band are:

  • Much more intolerant to obstacles, like trees or walls, than the 2.4GHz band.

Note: It’s important to remark that Ubiquiti 2.4GHz and 5.8GHz devices are not designed for non-line-of-sight scenarios. In some cases, they could establish a link, but there are no warranties of stability or throughput.

Usually, the 5.8GHz band is used in backhaul links (point-to-point), because it offers a less crowded spectrum and combined with highly directional antennae, offers you a better immunity to external sources of interferences. In some cases of near line of sight or regulatory restrictions, 2.4GHz devices (with a narrow channel width) are used for point-to-point links.

In multipoint-to-point deployments the usually band used is 2.4GHz, but in recent year there had been a migration to 5.8GHz because of the saturation of the 2.4GHz. Before you do a major deployment, it may be very useful to perform a spectrum analysis of the site using AirView to determine which band is the best option. In some cases of extremely crowded sites or legal restrictions to deploy outdoor networks in 2.4GHz or 5.8GHz, you may want to obtain permission from your local authority, if they so required, use the 3.65GHz band.

Link calculation and product selection

Wireless Link Calculator using NanoStation M5
Wireless Link Calculator using Loco M5

Again, there isn’t a best product for all cases. The selection of which product to use depends on link distance, the required throughput, as well as the budget and spectrum interference available.

Before installing the products, it is may be very useful to use a wireless link calculator, to determine the reliability of the wireless link. There are a lot of very powerful wireless link calculator apps; this one ( is very simple for starters.

  • First you need to determine what data rate (and throughput) you need. In this example I must have a throughput of 20Mbps (half-duplex), and I’m planning to use 2x2 MIMO devices with a Channel width of 20MHz in the 5.8GHz band, thus I need a data rate of at least MCS11 or higher (in case of using 40MHz channel MCS9 will be enough).
  • The second step is to determine the total power required for the link. Here, you need to select your first candidate; in my case, the first one is NanoStation M5. Go to the product’s datasheet and see the Tx Power for MCS11, which is 27dBm, and the Rx Sensitivity for MCS11, which is -87dBm. For extra reliability, you can subtract the tolerance margin of the device, in this case it’s -2dB for Tx and -2dB for Rx. So the reliable Tx Power is 25dBm and the reliable Rx Sensitivity is -85dBm, at MCS11 data rate. You also need to know the antenna gain, which in NanoStation M5 is at least 14.6dBi (info available in the datasheet).
  • Thirdly, go to the Wireless Link Calculator Web app. I assume you are using the same device (and antenna) on both sides; if you are using different devices on each side, enter proper data for each product. Enter the following parameters:

  • Tx Power in dBm, which in this case is 25dBm
  • Rx Sensitivity, which is -85dBm for MCS11.
  • Antenna Gain: 14.6dBi for NanoStation M5 (or up to 16dBi for some frequencies).
  • Cable length and type, if apply; in my case it doesn’t apply. So, enter 0m on both sides.
  • Link distance, in my case, the link is 5KM and it uses a 5800MHz frequency.
  • Press the Calculate button, you will get a theoretical link status (in our scenario we’re using Nano M5 and the link is reliable) and theoretical signal level at both sides, in our scenario the security margin is 21dBm (-85dBm minus -68dBm, plus 4dBm, previously subtracted to the Tx power and Rx Sensitivity).
  • If you get an unreliable link or you need extra reliability select a product with higher output power or higher antenna gain. (See list below to know which product is appropriate for each situation)

Note: To get a reliable link you should have at least a margin of 17dBm (including the subtracted from Tx power and Rx Sensitivity).

Here’s a list of products recommended for each scenario. Anyway, you could use any other AirMax products combination (operating in the same frequency) if they have enough SNR (Signal-to-Noise). The list is powerful decreasingly; the first product is the most powerful.

List of recommended devices for each scenario

For short distance Point-to-Point links

Point-to-Point Wireless Link

5.8GHz band

  • NanoBridge M5
  • NanoStation M5
  • NanoStation Loco M5
  • AirWire (for indoor network)

2.4GHz band

  • NanoBridge M2 (Available soon)
  • NanoStation M2

For long distance Point-to-Point links

5.8GHz band

  • Rocket M5 with RocketDish 5G-30dBi antenna (or RocketDish 5G-34dBi)
  • PowerBridge M5
  • NanoBridge M5
  • Bullet M5HP with highly directional antenna (upgrade for existing installations using same antennas)

2.4GHz band

  • NanoBridge M2 (Available soon)
  • Bullet M2HP with highly directional antenna (upgrade for existing installations, using same antennas)

For point-to-multipoint links

Point-to-Multipoint Wireless Link

5.8GHz band

Base Station side

  • Rocket M5 with BaseStation Antenna 5GHz (MIMO BaseStation)
  • Bullet M5 with sectorial/omni antenna (non-MIMO)

Client side

  • PowerBridge M5 (carrier class long distance stations)
  • NanoBridge M5 (for long distance stations)
  • AirGrid M5 (1x1 non-MIMO device, medium throughput)
  • NanoStation M5
  • Loco M5 (short distance stations)

2.4GHz band

Base Station side'

  • Rocket M2 with BaseStation Antenna 2.4GHz (MIMO)
  • Bullet M2 with sectorial antenna (non-MIMO)

Client side

  • NanoBridge M2 (for long distance stations.)
  • AirGrid M2 (1x1 non-MIMO device, medium throughput)
  • NanoStation M2
  • LocoStation M2 (short distance stations)

Extra: For short distance Point-to-multipoint links with laptops and/or Wi-Fi devices as clients (with AirMax disabled)

  • Bullet M2HP with sectorial antenna or omni-directional antenna.
  • PicoStation M2HP
  • NanoStation M2 for directional outdoor hotspots