- September 18, 2012
- Antenna diversity, Antennas, China Basin, Dick Laine, horn antenna, microwave, microwave propagation, Principal Engineer, Radio Head Technology Series, Radio Heads, Radiohead, San Francisco, Space Diversity
Horn antennas on the roof of a microwave relay station near Madison St. and 17th Ave, Capitol Hill, Seattle, Washington State, USA. (Photo credit: Vladimir Menkov via Wikipedia)
Between any two microwave radio antennas, there is one direct ray and multiple refractive/ reflective multi-path rays. In the eighth and last installment of our Radio Head Technology Series, Aviat Networks Principal Engineer and master storyteller, Dick Laine, relates how restrictive tower rules for San Francisco’s historic China Basin Building required fine adjustments of a horn antenna to resolve reflective rays from the surrounding bay.
As Dick tells it, to accommodate a Space Diversity arrangement, one horn antenna on the building had to be hung upside down. During the installation process, the alignment for the upside-down diversity antenna created a reflection point 3 miles out into the bay. Because of this installation, the performance was horrible, but at the time no one knew why. For example, when a little speedboat or anything larger went through the reflection point, there would be an outage as the signal was interrupted. There did not seem to be an obvious fix to the alignment issue. The horn antenna did not have a way to check the alignment on the horizontal with a bubble level.
To find out how Dick solved this antenna mystery, register for the Radio Head series (it’s free). Then to put it all in context, Dick goes over Huygens’ Principle as it applies to microwave signal diffraction. And if you ever wondered what happened to periscope antennas, Dick provides some key insight! Tune in to find out!
- The Truth About Terahertz (spectrum.ieee.org)
- GL Conveys the Availability of RF Design Tools (virtual-strategy.com)
- FCC Rule Changes Lower the Cost of Microwave Deployments (aviatnetworks.com)
- Why Bigger is not Always Better for Mobile Backhaul! (aviatnetworks.com)
- Got Protection? Diversity Schemes and Other Methods (aviatnetworks.com)
- Cole Valley Cell Tower Authorization Approved By Planning Commission (tantek.com)
- May 25, 2012
- 45-rpm, 78-rpm, 99.999 percent availability, 99.999% availability, Dick Laine, five-nines, Gramophone record, microwave link, Microwave transmission, Principal Engineer, Radio Head Video Technology Series, Radio Heads, Radiohead, RCA, wireless, wireless engineering
You may not think that 78 rpm records and microwave communications could have anything in common. But our Dick Laine finds the devil in the details between the two in Radio Heads video No. 3
. (Picture: label for 1940s brand of jukebox needles for playing 78 rpm records; photo credit, Infrogmation via Wikipedia)
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.
- Salem Hospital works with NetXperts to provide five-nines of availability (netxperts.com)
- Beyond Five Nines: The New Age of “Uber Reliability” (tellabs.com)
- The Holy Grail of five-nines reliability (searchnetworking.techtarget.com)
- 3 Models for Microwave Link Error Performance? Laine Explains (aviatnetworks.com)
- Dick Laine’s 4 Keys to Successful Transmission Engineering of Microwave Links (aviatnetworks.com)
- May 11, 2012
- Aviat Networks, bell system technical journal, Dick Laine, International Telecommunication Union, Internet Protocol, ITU-R, microwave, microwave link, microwave link design, microwave link error performance, Microwave transmission, Principal Engineer, Radio Head, Radio Head Video Technology Series, Radio Heads, Radiohead, reliability or error performance, Richard Laine, tdm, Time-division multiplexing, Vigants, wireless, wireless engineering
In the second episode of Aviat Networks’ Radio Head Technology Series, Principal Engineer Dick Laine explains ITU-R models for Fixed Wireless Systems.
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.
- April 20, 2012
- Aviat Networks, Dick Laine, Farinon, Harris MCD, microwave, microwave engineer, microwave link, microwave link design, Microwave transmission, network engineering support, Principal Engineer, Radio Head, Radiohead, Richard Laine, Telecommunication, transmission engineering, wireless, wireless engineering
Dick Laine, Principal Engineer, Aviat Networks
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.
If you find this video of value, please pass along the information to your friends and colleagues via Facebook, Twitter, LinkedIn or your other favorite social media network.
- August 23, 2011
- Aviat Networks, backhaul, Dick Laine, Frequency range, Internet Protocol, microwave, Microwave transmission, Principal Engineer, Rain Attenuation, Rain Fade, Rain Fading, Telecommunication, Time-division multiplexing, wireless
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.
- The influence of rain attenuation (sce.carleton.ca)
- The World’s Longest All-IP Microwave Link (aviatnetworks.com)
- Comparison of Multiple Rain Attenuation Models with Three Years of Ka Band Propagation Data Concurrently Taken at Eight Different Locations (spacejournal.ohio.edu)
- Microwave Wireless Backhaul Case Study: Tooele County (Utah) (aviatnetworks.com)
- Proposed Rain Attenuation Model Revised From ITU Used For Prediction in Tropical Climates (aprsaf.org)