March 5, 2018

Case Study: Can Extra High Power reduce need for Space Diversity?

Q:  Can Extra High Power (EHP) Radios Reduce Need for Space Diversity (SD) in Microwave Networks?

A: Yes.

  • EHP radios can reduce need for SD in some microwave networks by providing an optimum level of system gain, which will reduce fading—the problem SD was intended to mitigate
  • Non-reflective paths will benefit the most from EHP
  • Benefits include decreased numbers of antennas and lower capex
  • For example, in a recent project using EHP radios, Aviat reduced the number of required antennas by 9.27 percent and capex by 5 percent

3 Reasons Your Microwave Network May Not Need Space Diversity

Space diversity (SD) remains an effective method for increasing the availability of a microwave link and has for some time. By using two antennas that connect to the same microwave radio, network planners can increase availability of a given path from just under 99.999 percent to in excess of five-nines—a threshold that must be met in most if not all mission-critical applications.

However, installing an additional antenna of both ends of a backhaul link is a capital expenditure (capex) that must be budgeted for as well as the extra complexity that comes with implementing so much bulky hardware. And ongoing maintenance and support as a portion of operational expenditure (opex) will also be higher.

While in days gone by, transmission engineers needed to rely on SD in situations where atmospheric conditions would cause a link to fade with some predictability, today things are different. With the advent of extra high power (EHP) radios (i.e., >39 dBm) microwave network planners can apply greater system gain to cut through the atmospheric interference and establish a reliable, consistent wireless connection.

Reason No. 1 Microwave Networks Don’t Need SD: Fewer Antennas

To make SD work, a wireless backhaul site needs two antennas. But not if you use EHP radios. EHP microwave radios enable networks to use fewer antennas—as much as 50 percent fewer. Of course, that is the theoretical maximum. But in most real situations, by using EHP radios SD will not be needed. In reality terms, Aviat Networks has seen that a properly designed wireless backhaul network can expect to see a 34 percent reduction in antenna numbers at the majority of sites, as in a recent public safety project.

Reason No. 2 Microwave Networks Don’t Need SD: Smaller Antennas

By not using an SD strategy, not only do microwave sites need fewer antennas when using EHP radios but also smaller antennas, in most situations. In a few situations, antennas may be as much as two sizes smaller. For example, a large number of backhaul sites use 6GHz radios. With standard power radios, these sites generally employ 6-foot diameter parabolic antennas. However, if these sites upgrade to EHP radios, they could use 4-foot antennas as the system gain increase sends more radio signal to the smaller dish area than the standard radio. And if the conditions are right, EHP radios can enable a site to move to a 3-foot antenna.

Reason No. 3 Microwave Networks Don’t Need SD: Lower Capex

Given the reduction in the number and size of antennas, the capex for a microwave backhaul network will be reduced. For example, in a public safety network that has 220 sites that utilize 6-foot antennas when implemented with standard power radios, only 144 sites of those sites need 6-foot antennas when using EHP radios. This leads to a topline reduction of capex of just more than 68 percent.

Perception Equals Reality: There’s More Than Meets the Eye

Of course, in a discussion comparing two different types of hardware in any system as complex as a microwave radio backhaul network, many factors exist to consider, only some of which were addressed here. But the basic thrust of this premise should be clear: Extra high power radios can dramatically impact the material and monetary requirements of backhaul network operators.

To enjoy a deeper perspective on the advantages of EHP radios, please download our new fact sheet. Or if you’d like to cut to the chase, drop us a note and we can begin a dialog about your needs and how we can help.

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