October 13, 2020
One of the most significant contributors to the total cost of ownership of a microwave transmission network is the antenna sub-system.
Microwave antennas can be big, really big! Depending on the link distance and the frequency band, antenna diameters range from around 0.3 meters, all the way up to 3.7 meters (15 feet), or more. If you have a space diversity or MIMO link, you have two antennas at each end. If you have a hub site supporting multiple radio paths, this can require a substantial (and expensive) tower structure to accommodate all those antennas.
Antenna related costs come from many different sources. When you total all these costs, the impact can be quite staggering. Then multiply that for the number of links in your network.
So, what if you could reduce these costs by simply using smaller antennas? The table below shows the impact of antenna weight and loading alone by reducing antennas by one or two sizes. Smaller antennas are cheaper, easier to ship, and easier and faster to install.
To reduce the antenna’s size for a given link is pretty simple – you need more radio system gain. What is system gain? System gain equals the combination of the transmitter output power, plus receiver threshold, less any other system losses from external diplexers, antenna mediation devices, etc. To increase system gain, you essentially need to increase your transmitter power using higher power devices or lower the receiver threshold, usually by using better coding algorithms, or both.
High system gain offsets the reduced performance from the smaller antennas, while all other aspects of the link design are maintained – i.e., capacity, availability (up-time), and path length. Alternatively, you can utilize improved system gain with the same size antennas to enable longer links, more capacity, or more reliability (less outage time), or a combination of all three.
Aviat’s WTM 4000 all-outdoor radio system gain performance is superior to other competitor radios in its class. Based on our internal research, the following charts show the high system gain advantage that WTM 4000 enjoys over two comparable platforms on the market today from leading microwave vendors, for both 1+0 and 4+0 single antenna configurations (2048QAM modulation in a 28 MHz channel).
The charts clearly show a significant benefit from using WTM 4000 instead of the other solutions. In some instances, this can be more than 12 dB, which in the chart above can be equivalent to two antenna sizes on each end of a link, equal to more than 400 kg in weight and wind loading per tower. For larger antennas, even one size down can make a huge difference – in the example above, going down one size from 1.8 to 1.2m diameter can save nearly 600 kg in combined weight and wind loading.
The benefit of smaller antennas really cannot be understated. Going from 1.2m to a 0.6m antenna gives about a 70% CAPEX reduction alone. Shipping, handling, and installation costs will also be reduced. For a link, this savings is doubled. If you have 10, 100, or even 1,000 links in your network they could be implemented with smaller antennas thanks to the high system gain that Aviat’s WTM 4000 radio delivers. In that case, you can see the overall savings multiplied significantly!
In the second part of this series, we will examine the trend for tower outsourcing sweeping through the mobile industry and the dramatic impact on the resulting lease charges that can be achieved by using smaller antennas.