A standard Quadrature Amplitude Modulation constellation (non-gray code) diagram showing a demonstrative 4-bit binary code pattern. (Phase offset and amplitude values may not represent those used in real life) (Photo credit: Chris Watts via Wikipedia)
There’s a new arms race in the microwave industry, and it’s over who can claim support for the highest QAM level. Now two vendors are out in the market fighting it out over who had 2048QAM first, yet go back a little more than 12 months and 512 or 1024QAM had barely hit the market. We even are seeing mentions of 4096QAM in some conference presentations. We here at Aviat Networks view these advances as a good thing for our industry, but this heavy marketing of 2048QAM does no one any favors, as it focuses purely on only one aspect of high modulations—capacity—and ignores several other aspects that need to be understood, namely:
- Capacity improvement diminishes with every higher modulation step
- High modulations come with much lower radio system performance—requires shorter hops and/or larger antennas
- High modulations are much more sensitive to interference—makes link coordination difficult (if not impossible)
- High modulations need higher Tx power, increased phase noise and linearity—increases radio design complexity cost
So as with most things that are presented as a cureall, higher order modulations are a useful tool to help operators address their growing backhaul capacity needs, but the catch is in the fine print. Operators will need to look at all the tools at their disposal, of which 1024/2048QAM is a useful option, albeit one that will require very careful planning and strategic deployment. In general, operators need practical solutions for capacity increases, as detailed in “Improving Microwave Capacity“. In fact, speaking of practicalities, the real challenges with LTE backhaul has very little to do with capacity…as detailed by this article. For the complete “Modulations Arms Race” article, click here.
Director, Corporate Marketing
- Unlocking Capacity Block Through Higher Order Digital Modulation (blog.aviatnetworks.com)
- Microwave Capacity: Examining Techniques to Improve Throughput (blog.aviatnetworks.com)
- Mobile World Congress 2012 Wrap Up (blog.aviatnetworks.com)
- Day 1 at Mobile World Congress 2012 (blog.aviatnetworks.com)
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)
At the UTC Telecom 2012 show, Aviat Networks was able to meet with utilities regarding their networking needs. Bottomline, utilities must work closely with their wireless backhaul and other solution providers in order to implement smart grid capabilities.
UTC Telecom 2012 is the annual show of the utilities industry in North America. New technologies and products were displayed to help the industry with its latest challenges. Also various utilities shared their experiences in implementing new networks to deliver leading edge smart grid capabilities.
The show was extremely well attended with a myriad of vendors including many consulting firms. The key message that I took away was the need for utilities to work very closely with their equipment vendors—especially wireless backhaul solution providers—and consultants to implement next generation networks capable of handling the multitude of applications associated with smart grid.
It was interesting to hear from AltaLink about the findings from its extensive lab testing and network implementation:
- How far do you drive MPLS into the network?
- How do you “tweak” the MPLS settings to accommodate microwave radios adapting in modulation?
- What kind of MTU sizes need to be passed and how well do vendor capacities relate to the particular MTU sizes?
BC Hydro talked to the two critical issues it is struggling with: end-to-end management and security across the entire network. Balance the needs/wants of the IT dept., the communications dept. and various internal administrative groups is a real task! Some people think that only the commercial mobile networks must deal with overzealous users demanding unlimited bandwidth to address their video/gaming/voice applications…what happens when all the utilities’ departments find out that there is bandwidth available?!
Aviat Networks’ Eclipse Packet Node radios and skilled network engineers can help you find the right solution for your smart grid implementation. Whether your utility is just starting to look at the issues or ready to buy the critical components of the network, Aviat Networks is able to help.
Director of Business Development
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.