Millimeter wave systems can meet growing indoor bandwidth requirements

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The Wireless marketplace has many segments or verticals, but the two largest categories are indoor and outdoor. Indoor wireless consists of various access technologies – typically Wi-Fi and cellular small cell. In the outdoor segment there are more uses cases and hence more vertical alignments. The most common of these is cellular, which can then be broken down into macro, micro and pico, or small, cells. A smaller but also important outdoor access technology is the Fixed Wireless Access market.

Along with these access use cases, wireless has long been used to connect cell towers and buildings with point-to-point technology, all deployed in the microwave and millimeter wave bands from 6GHz to 86GHz. These systems can support connection capacities as high as 10Gbps full duplex. What has never been seen on the market until recently is the concept of using microwave or millimeter wave frequencies to perform the same function – indoors. Despite the clear attractions of using wireless in this role – cheaper, faster and more flexible to use when compared to fiber or cable, there were significant obstacles to this approach indoors, primarily the requirement that systems in these bands must have a clear Line of Site to operate. Clearly in an indoor environment with hallways, walls and unique floor plans on an almost per building basis this ends up being a barrier too high to overcome if LoS is a requirement.

If however this obstacle can be overcome, indoor wireless backhaul offers all the same advantages as outdoor microwave backhaul systems. Indoor use cases mirror those supported by cable and fiber, but there are changes afoot that might be better served with a wireless approach as opposed to cable. Indoor networks are now seeing multigigabit access technologies in 5G and Wi-Fi outstripping CAT5 and even CAT6 capabilities and, for temporary events, cable runs in large private venues take time and money for an event that may only last a few days. Furthermore, IoT is exploding, and many CIOs do not want IoT traffic on the same network as the information traffic for security reasons. The option is to deploy a second wired network, or use the new wireless backhaul products coming to the market.

David Sumi

VP of Marketing and PLM at Airvine.

Out versus In

Outdoor point to point systems as noted, can provide up to 10Gbps full duplex in capacity, and based on the frequency can cover distances up to 10 miles or more. To achieve these specifications these systems use high-power amplifiers (tens of watts) and large (6 foot) dish antennas with gains up to 40dBi are used to achieve these distances. FCC and other regulator domains allow these high powers as the use of these bands requires a geographic license. Typically, the regulator will specify a maximum power output and a maximum antenna gain. Adding those two together gets you to the EIRP allowed. One interesting note on these regulations – often the authority will allow an increase in antenna gain for every dB lowering of the power output. The logic is simple – a higher gain antenna has a narrower beam reducing rf “pollution.”

All of these deployments require strict Line of Site between nodes. The newest technologies that are being used for this application are based in the 60GHz band. This band has several attractive qualities, and some limitations.

The Good – it is license free, meaning deployment can be done almost instantly. The band is commonly assigned around the world with up to 14GHz of spectrum available. More spectrum then all the lower bands combined.

The Less Good – like all microwave systems, the higher the frequency the shorter the range. In 60GHz there is an additional range limitation – oxygen absorption. The O2 molecule is just the right size to absorb 60GHz radiation. This is an additional limitation on the ranges that can be achieved in the 60GHz band in outdoor deployments.

But – if you take a 60GHz point to point system indoors, the distances you are trying to achieve are much more modest (100 meters or less) and oxygen absorption at these ranges is not an issue. Sounds great, but you still need to address the LoS issue, and in an indoor deployment this limitation can be significant.

Another benefit for using 60GHz indoors lies in the absence of interference. In the outdoor domain using license free systems while allowing quick install, always brings up the specter of other license free systems in that band interfering with your installation. When used indoors, the narrow beam you get with 60GHz, and the fact that there are very few to no other 60GHz systems in operation (certainly Wi-Fi IEEE 802.11ad and 802.11ay Access Points have seen very limited uptake), minimizes the possibility of interference.

60GHz Finds A Home – indoor Wireless Backbones

In addition, the introduction of higher capacity APs comes with reduced coverage, requiring additional APs to be deployed. IoT means bringing connectivity to locations that are not wired today, and private 5G small cells when deployed will all require backhaul in locations where nothing exists today.

There are approaches that use the license free 5GHz band in a point-to-point mode, but given the massive number of 5GHz APs that have been shipped and will be shipped, the noise floor in 5GHz is rising. And having the access portion of the network in the same band as the backhaul system is a recipe for trouble.

Enter 60GHz solutions. Right off the bat you get plentiful spectrum to support massive data rates. Further, two factors reduce the possibility of self-interference -- channel availability and the inherent short range of 60GHz. The remaining barrier to this approach is the LoS requirement.

This barrier has now fallen. With a high gain beamforming antenna array on the front end of a properly designed 60GHz radio, it is possible to build a system that can penetrate most indoor walls. Drywall, wood and glass can all be blasted through with a properly designed system. Add to that the ability to beam steer up to 90 degrees going around corners and indoor wireless backhaul becomes a reality – as in, multigigabit wireless backbones for indoor connectivity.

Where would you use it?

The use cases for such a system are limited only by one’s imagination. Apartment complexes that wish to add IoT throughout the premise or upgrade their Wi-Fi will need to run new cable with higher capacities to new locations. A wireless approach can do this with no tenant disruptions inherent in the construction process of running new conduit and cables. The same can be said for hotels that wish to add door locks, leak detection or increased video security.

Factories and warehouses are leaping into next generation applications as defined by Industry 4.0 – machine learning, 3D printing, automation and robotics all offer new levels of efficiencies and advanced manufacturing -- and they all cry out for flexible high-performance connectivity.

The last example cited here but by no means the end of the use case universe would be large public venues. An auditorium may host a hockey game one night, a concert the next, and a trade show after that. Each of these events has their own unique floor plan with network connectivity required in locations specific to the event being supported. Exhibition halls are perfect examples of venues that would benefit from a wireless backbone system.


The future teems with exciting new services and applications throughout the enterprise and industrial domains, limited only by imagination and connectivity. IT / OT network administrators and CIOs have both in in abundant supply, and with 60GHz indoor backbones, connectivity is also readily available and combined, they will remove a once insurmountable barrier to the future of networking in a broad array of enterprise, industrial, public venue and residential sectors.

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David Sumi is VP of Marketing and PLM at Airvine and has 30 years of experience in the hardware and software used throughout the wireless networking ecosystem.