Five-nines (99.999 percent) availability is a concept that is familiar in wireless engineering. Dick Laine, principal engineer of Aviat Networks, compares five-nines availability to 78-rpm records in our most recent episode of the Radio Head Technology Series.
As he relates, even with scratches and pops, a 78-rpm record still is able to transfer aural information so that you can hear it, i.e., its availability is intact, as it does not drop performance. Scratches and pops only represent degradation in the quality of communication. But when the record is broken, an outage occurs—no record, no communication.
The same goes for wireless communication systems. If a microwave link drops 315 or fewer seconds of microwave communications per year (in increments of up to 10 seconds at a time), it is maintaining five-nines availability. The microwave link is offering 99.999 percent availability for wireless backhaul. Only if the microwave link is unavailable for more than 10 seconds has an outage occurred, for the purposes of determining if microwave communications traffic has been dropped.
Dick goes on to explain about what happened in 1949 when 78-rpm records were superseded by 45-rpm records. Dick got a sneak peek at the top-secret 45-rpm record project when he visited the legendary RCA facility in Camden, New Jersey, which played a crucial role in the development of the modern music, radio and television businesses. Unfortunately, unlike a five-nines microwave link, 78-rpm and 45-rpm records are mostly unavailable nowadays.
As most radio engineers know, Vigants calculations, which are discussed in a broadly cited Bell System Technical Journal article, are widely used to determine reliability or error performance for microwave link design. In Video 2 of Aviat Networks’ popular Radio Head Technology Series, which is now available for viewing, Principal Engineer Dick Laine explains how he uses Vigants calculations in conjunction with the three completely separate ITU-R Fixed Wireless System (FWS) models for TDM.
Because of all these models, he likes to use Vigants calculations as a “sanity check” to see that he is close to the correct result for his path engineering plans. The free Aviat Networks’ Starlink wireless path engineering tool can be used to handle Vigants calculations for Aviat Networks’ and other vendors’ equipment.
Can’t wait to hear more of Dick’s experienced views on microwave radio transmission engineering? You can get ahead of the learning curve by registering for the series and get these videos sent to your inbox as soon as they are released.
Transmission engineering of a microwave link requires creativity and skill. So if you are looking for inspiration as well as high-quality wireless engineering instruction look no further than the “Radio Head Technology Series.” Radio Heads is a collection of videos and podcasts featuring our very own Dick Laine. Dick is arguably the most experienced microwave engineer in the wireless communication business, having spent more than 50 years working with microwave radio from its inception—here at Aviat Networks and our predecessor companies (e.g., Farinon, Harris MCD).
Dick has been involved with nearly every aspect of RF transmission, microwave link and network transmission design, and the effects of geoclimatic conditions on transmission of voice and now IP radio data packets.
In his own unique style, Dick has been teaching basic and advanced concepts for digital microwave transmission in seminars and training classes worldwide. Students who have taken his classes return years later eager to get a refresher from Dick and to hear about some of his great adventures in Asia, the Middle East, Africa and in the Americas.
In the first Radio Heads video titled “Check List for a Successful Microwave Link,” Dick explains the four key objectives or requirements for a well-done microwave link design along with “check list” items that the project manager or transmission engineer evaluates for proper design and deployment of a digital microwave link. If you have not already signed up for this video series, register to view the content.
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As we blogged last summer, the FCC has released 650 MHz of new wireless technology spectrum for Fixed Service wireless communication technology operators. Now Comsearch, a leading provider of spectrum management and wireless engineering services in the US, has highlighted this issue in its latest online newsletter, with an article that includes some very informative coverage maps showing the zones where the new bandwidth is available.
These maps are excellent at conveying the limitations of the newly released spectrum for microwave link applications in the 7 GHz (6.875–7.125) and 13 GHz (12.7–13.1) bands. After taking into account the zones that are reserved for existing Fixed and Mobile Broadcast Auxiliary Service (BAS) and the Cable TV Relay Service (CARS) users, these new bands are only available in about 50 percent of the US land mass covering only 10 percent of the population.
What do you think? Should the FCC loosen the spectrum sharing rules even more for 7GHz and 13GHz bands? Take our poll and tell us: