As mobile phone and other wireless networks “densify” in the parlance of the day, airwave congestion will inevitably rise causing greater interference. Generally, microwave path planners will use dish antennas that provide tighter radiation patterns with more focused main beams and smaller side lobes to overcome interference that results from congestion.
To indicate the tightness of their radiation patterns ETSI (European Telecommunications Standards Institute) classifies antennas from 1 to 4 with higher classifications having tighter radiation patterns. Until recently, to fight interference in most circumstances wireless transmission engineers would resort to Class 3 antennas for deployment scenarios where “very high interference potential” existed.
However, the situation has changed. More drastic implementation scenarios now drive path planners to invoke more dramatic solutions. That includes use of Class 4 antennas, which are for “extremely high interference potential” situations, according to ETSI. For a more detailed treatment of antenna classifications and radiation patterns, see the ETSI document “Fixed Radio Systems; Point to Point Antennas.”
It’s an urban thing
In most cases, microwave radio congestion that leads to interference problems occurs primarily in urban locations. With wireless backhaul sites in much closer proximity in urban areas than in rural or suburban locales, there it’s more likely that side lobes from microwave transmitters could become sources of secondary RF radiation, which can overlap with point-to-point links between neighboring sites.
For example, according to an Aviat Networks analysis of three wireless sites in South America that recently experienced interference issues, at one site the congestion was so intense as to make one complete channel unusable. Even if Class 3 antennas were used, the interference levels were too high to be able to reactivate the disabled microwave channel.
Wider channels, larger capacity
For situations where the operator needs to increase capacity from a wireless backhaul site, the easiest way remains widening the channel size. But at sites that experience extremely high interference, the operator may not be able to coordinate radio frequency pairs in wide channels with Class 3 antennas. However, moving up to Class 4 antennas would allow the operator to optimize the signal-to-noise ratio and let higher modulations come into play, so wide channels could be coordinated with correspondingly higher data rates.
Smaller is more
In cases of high interference, larger antennas can be used to reduce it. For a subset, smaller Class 4 antennas can be used instead of their oversize Class 3 counterparts. Thus, operators who deploy Class 4 antennas gain the added benefit of dropping down a parabolic dish antenna size as compared to a Class 3 antenna in the same application. In general, smaller dishes advantage the operator due to their lighter weight and lower opex tower charges, albeit with an initially bigger upfront capex. Because Class 4 antennas represent an elevated level of precision tooling and more detailed manufacturing versus lower class antennas, capex of these passive, higher-performance infrastructure pieces always weighs in the balance.
As we’ve seen, Class 4 microwave antennas have many general uses. They also are very good alternative solutions for specific industries. For example, utilities often find it difficult to implement Adaptive Coding and Modulation schemes in their backhauls, so Class 4 antennas can provide another way for them to achieve their connectivity and capacity goals.
Lower frequency bands (i.e., less than 11 GHz) have long had access to Class 4 antennas. More recently, antenna manufacturers such as Commscope have begun to make Class 4 antennas for higher frequency bands (e.g., 13, 15, 18, 23 GHz). And RFS has also expressed interest in supplying higher frequency class 4 antennas.
This overview has provided a broad grounding in Class 4 microwave antenna subject matter, but for more in-depth information please download the Aviat white paper “Use of Class 4 Antennas” for which no signup is necessary.
- September 21, 2012
- Carrier Ethernet, Commscope, Dick Laine, microwave networking, National Telecommunications and Information Administration, Principal Engineer, product marketing, Quality of service, Stuart Little, Tellabs
The Microwave Networking seminar hosted by Aviat Networks in Washington D.C. in Sept 2012 had a large turnout of attendees who listened to speakers present on wireless security, MPLS, Carrier Ethernet and other topics of interest to the backhaul community.
Aviat Networks recently completed the latest in its Technology Seminar series on microwave networking with a two-day event in the Crystal City area of Washington D.C. One observer noted attendees were particularly interested in hearing more about security of wireless backhaul systems and how to make a choice between using IP/MPLS or Carrier Ethernet.
The seminar was packed to capacity with more than 100 attendees from organizations that included various federal government agencies, utility companies, public safety organizations and mobile operators. These seminars focus solely on issues relevant to microwave deployments, related technology, regulatory issues, and deployment considerations—with no product pitches.
Attendees took advantage of an agenda that covered a wide variety of technology topics, including microwave-focused sessions on capacity, Ethernet QoS and OAM, IP/MPLS, security and strategies for lowering the total cost ownership of microwave networking. The highlight of the seminar was again Dick Laine, longtime Aviat Networks principal engineer, who spoke at length about Microwave Path Engineering and designing links using Adaptive Modulation. Dick is one of the foremost authorities in the U.S. on microwave planning and path design, and some attendees travel long distances just to hear him speak and share his experiences of more than 50 years in the microwave networking business. (If you’ve never heard/seen Dick present, register for his free Radio Head Technology Series).
Aviat Networks also welcomed special guest speakers from the NTIA, Comsearch, CommScope, Tellabs and LTI DataComm who graciously contributed their time and effort to provide a deeper understanding for attendees on their topics of expertise.
Keep a lookout for details of the next Technology Seminar that may be coming to a city near you! Or if you would like to be notified directly when our next microwave networking seminar is scheduled, please complete this form.
Stuart D. Little
Director, Product Marketing