Author
Junaid Syed
Editor’s Note: This is the third installment for our “Meet the RF Experts” series in which contributors to the Understanding the RF Path e-book elaborate on subjects in their areas of expertise.
Chapter Nine in the Understanding the RF Path e-bookis a pretty good primer (if, as the author, I can say so myself) about using microwave links for wireless network backhaul. The chapter includes an overview of backhaul frequencies, typical network architectures and considerations for planning a microwave link. One area I did not discuss in great detail, however, is one that our John Cole has blogged about before. And that is how a class 4 microwave antenna creates a tighter signal pattern that offers significant benefits to operators, including cost and capacity improvements.
We all know that capacity is a big issue in the wireless industry, but not everyone realizes it is important on the backhaul side as well as on the access side. Many operators, though, recognize the need to increase capacity and throughput for backhaul networks. The question, of course, is how best to do so. The theoretical maximum capacity of a microwave link is defined by something called Shannon’s Law, which clearly indicates that capacity depends on two things: channel bandwidth and carrier signal-to-interference ratio. Think of the channel bandwidth as the size of the tube carrying the signal—if you could increase the diameter of that tube, more signal could flow through. However, as everyone also knows in the wireless industry, radio spectrum is a finite resource. Expanding the bandwidth on one channel takes away that spectrum from another channel, or it might not even be possible due to licensing and spectrum rights. In short, trying to improve channel bandwidth is not in itself the preferred method right now.
The other path to increasing capacity is to improve the carrier signal-to-interference ratio. In broad terms, this ratio is a measure of how much of the carrier’s intended radio signal is received at a point over how much disrupting interference distorts it. CommScope believes this area is one where operators can realize significant capacity improvements, foremost by deploying ETSI class 4 microwave antennas. You can read more about this topic in this white paper, but let me summarize the point. Class 4 antennas envelope the radiation pattern more tightly than lower classes. This feature enables operators to mitigate interference with a smaller sized antenna (e.g. a 2-foot instead of a 4-foot), which decreases shipping and tower leasing costs. The more contained radiation pattern also improves that important carrier signal-to-interference ratio, thus boosting capacity. It is one of the latest antenna technology evolutions in microwave backhaul.
Have you read the chapter about microwave backhaul in the Understanding the RF Path e-book?
Do you have any questions about microwave backhaul technology?
Leave me a comment and I will reply with any answers I can provide.
