Millimeter wave systems can meet growing indoor bandwidth requirements
The wireless marketplace has many segments or industries, but the two largest categories are indoor and outdoor. Indoor wireless internet consists of several access technologies – most commonly Wi-Fi and mobile small cells. In the outdoor segment there are more usage scenarios and therefore 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.
In addition to these access applications, 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 up to 10 Gbps full-duplex. What had 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 benefits of using wireless in this role (cheaper, faster and more flexible to use compared to fiber or cable), there were significant barriers to this approach indoors, particularly the requirement that systems in these bands have a clear Line of Site must have operated. Clearly, in an indoor environment with hallways, walls and unique floor plans, virtually building by building, this becomes a barrier too high to overcome if LoS is a requirement.
However, if this obstacle can be overcome, indoor wireless backhaul offers the same benefits as outdoor backhaul systems. Indoor use cases reflect the applications supported by cable and fiber, but changes are afoot that may be better accomplished with a wireless approach than with cable. Indoor networks are now seeing multigigabit access technologies in 5G and Wi-Fi surpass CAT5 and even CAT6 capabilities, and for temporary events, running cables in large private locations takes 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 to be on the same network as information traffic for security reasons. The option is to deploy a second wired network, or to use the new wireless backhaul products coming to market.
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Out vs. In
Outdoor point-to-point systems, as mentioned, can provide full-duplex capacity of up to 10 Gbps and can cover distances of up to 10 miles or more based on frequency. To achieve these specifications, these systems use powerful amplifiers (tens of watts) and large (1.8 meter) satellite dishes with gains up to 40 dBi are used to reach these distances. FCC and other regulatory domains allow these high powers as use of these bands requires a geographic license. Normally the controller specifies maximum output power and maximum antenna gain. Adding these two together gives you the allowable EIRP. An interesting note about these regulations: often the authority will allow an increase in antenna gain for every dB decrease in output power. The logic is simple: a higher gain antenna has a narrower beam, reducing RF “pollution.”
All these implementations require a strict Line of Site between nodes. The latest technologies used for this application are in the 60GHz band. This tire has several attractive features and some limitations.
The good thing is that it is license-free, meaning deployment can be done almost immediately. The band is widely allocated around the world and up to 14 GHz of spectrum is available. More spectrum than all the lower bands combined.
The less good – as with all microwave systems, the higher the frequency, the shorter the range. At 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 range that can be achieved in the 60GHz band when used outdoors.
However – if you are using a 60GHz point-to-point system indoors, the distances you are trying to reach are much more modest (100 meters or less) and oxygen uptake at these distances is not a problem. Sounds great, but you still need to address the LoS issue, and in an indoor deployment this limitation can be significant.
Another advantage of using 60GHz indoors is the absence of interference. Using license-free systems in the outside domain while enabling a quick installation always raises the specter of other license-free systems in that band interfering with your installation. For indoor use, the narrow beam you get with 60GHz, and the fact that there are very few to no other 60GHz systems in use (certainly Wi-Fi IEEE 802.11ad and 802.11ay Access Points have seen very limited adoption), minimizes the possibility of interference.
60GHz finds a home – indoor wireless backbones
Furthermore, 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 when private 5G small cells are deployed, they will all require backhaul in locations where none exists today.
There are approaches that use the license-free 5GHz band in a point-to-point mode, but given the sheer number of 5GHz APs that have been shipped and will be shipped, the noise floor rises in 5GHz. And if the access portion of the network is in the same band as the backhaul system, it’s a recipe for trouble.
Enter 60GHz solutions. You immediately get an abundance of spectrum to support massive data speeds. Furthermore, two factors reduce the possibility of self-interference: channel availability and the inherently short range of 60 GHz. The remaining barrier to this approach is the LoS requirement.
This barrier has now fallen. With a high-gain beamforming antenna array at the front of a well-designed 60GHz radio, it is possible to build a system that can penetrate most interior walls. Drywall, wood and glass can all be irradiated with a properly designed system. Add to that the ability to steer angles up to 90 degrees and indoor wireless backhaul becomes a reality – as in multi-gigabit 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 want to add IoT throughout the building or upgrade their Wi-Fi will need to run new higher capacity cables to new locations. A wireless approach can achieve this without causing disruptions for tenants that are inherent in the construction process of laying new pipes and cables. The same can be said for hotels looking to add door locks, leak detection or increased video security.
Factories and warehouses are leaping toward next-generation applications as defined by Industry 4.0 – machine learning, 3D printing, automation and robotics all offer new levels of efficiency and advanced manufacturing – and they’re all crying out for flexible, high-quality connectivity.
The last example mentioned here, but certainly not the end of the use case universe, would be large public locations. An auditorium can host a hockey match one evening, a concert the next and then a trade fair. Each of these events has its own unique floor plan, requiring network connectivity in locations specific to the event being supported. Exhibition halls are perfect examples of locations that would benefit from a wireless backbone system.
Wrap
The future is teeming with exciting new services and applications across the enterprise and industrial domain, limited only by imagination and connectivity. IT/OT network administrators and CIOs have both in abundance, 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 wide range of enterprise, industrial, public venue and residential sectors.
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