4 Realities about Rain Fading in Microwave Networks

Posted on by Aviat Networks

Rain fading (also referred to as rain attenuation) at the higher microwave frequencies (“millimeter wave” bands)  has been under study for more than 60 years. Much is known about the qualitative aspects, but the problems faced by microwave transmission engineers—who must make quantitative estimates of the probability distribution of the rainfall attenuation for a given frequency band as a function of path length and geographic area—remains a most interesting challenge, albeit now greatly assisted by computer rain models.

A surprising piece of the puzzle is that the total annual rainfall in an area has almost no correlation to the rain attenuation for that area. A day with one inch of rainfall may have a path outage due to a short period of extremely high localized rain cell intensity, while another day of rain may experience little or no path attenuation because rain is spread over a long period of time, or the high intensity rain cell could miss the microwave hop completely.

Over the years, we have learned a lot about deploying millimeter wave microwave hops for our customers:

  • Rain outage approximately doubles in each higher millimeter wave band, e.g. 18 to 23 GHz
  • Rain outage is directly proportional to path length—assuming a constant fade margin for each hop
  • Rain outage in tandem-connected short hops is the same as for a single long hop—if they have the same fade margin
  • Multipath fading in optimally aligned millimeter wave hops does not occur during periods of heavy rainfall, so the entire path fade margin is available to combat rain attenuation fades

More information about assessing rain-induced attenuation is available in our white paper, Rain Fading in Microwave Networks.

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Fiber Isn’t Everything: Key Role of Microwave in Mobile Backhaul

Posted on by Aviat Networks
Fiber

If fiber is this much of a mess in your wiring closet, just imagine the difficulty of deploying it to your cell site. Image by DrBacchus (Rich Bowen) via Flickr

Last year in August, Aviat Networks presented its argument for why fiber optics technology isn’t everything where backhaul of wireless networks is concerned. If anything, this point has only been reinforced by analyses and anecdotal stories showing that fiber can be overkill for the mobile backhaul requirements of  LTE wireless. Plus, there is the simple truth that fiber cannot be deployed to every cell site due to financial and topological issues. That’s why microwave technology remains the world’s first choice for backhauling wireless networks. So let’s look at last year’s FierceWireless webinar slide presentation and refresh our memories.

These slides present the findings of an Ovum survey of North America’s largest backhaul players to understand their strategies regarding media types used to supply cell-site backhaul.

Ovum found that demand for wireless backhaul equipment in North America will continue to grow as mobile operators upgrade their networks to support higher-speed LTE networking technologies. The most common backhaul strategy for mobile operators in the region comprises leasing services over fiber combined with owning and operating microwave-based facilities. Microwave has a distinct advantage vis-a-vis leased services over the long-term due to the opex associated with leasing.

If you would like to see more, you may register for the on-demand replay of the full webinar. It will also present the latest trends and advancements in microwave transmission technology that support the evolution of mobile backhaul networks to all-IP.

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