With massive 5G deployment and the upcoming 5G capacity needs, Multi-gigabit connectivity is the key for all 5G end users. To be able to serve these growing needs, many new cells have to be deployed, to provide coverage in a dense urban environment. 5G network architecture will change the way Mobile Carriers design their networks in order to find ways to cope with network densification.
In cases where fiber is not available or difficult to deploy, wireless backhaul transmission provides an alternative and cost-effective solution to serve the upcoming explosion of 5G connectivity.
Mobile Carriers have long used traditional microwave bands in the range of 6 to 42GHz to backhaul 2G/3G & 4G RAN Mobile services. These bands can serve distances from 100m to more than 100Km depending on the specific frequency used per case.
5G Backhaul migration to Millimeter Wave
Traditional microwave frequency bands, however, have been heavily congested over the last several years. Furthermore, spectrum in the 6 – 42 GHz region, had initially been allocated to serve significantly lower traffic of legacy 2G/3G networks, compared to broadband connectivity and high throughput 5G demands.
On the other hand, the Millimeter wave spectrum provides the opportunity to support these higher capacity needs. Millimeter wave links at the 80GHz E-Band frequency range, have been deployed in the last several years, and reports show a substantial increase of its usage in the global microwave market share.
E-band has been regulated in two separate blocks of 5 GHz each (71-76 and 81-86 GHz), resulting in 10 GHz total available spectrum. Using radio equipment that may now support high channel bandwidths of up to 2000MHz and modulation schemes of up to 256QAM, E-Band links can provide a single carrier point-to-point radio with up to 10Gbps transmission capacity.
The need for 5G high capacity
Existing wireless transmission capacity in the E-Band range may for the time being seem adequate to serve the first 5G deployments. However what about the future to come?
Vendors are now focusing on extending their portfolio with even higher capacity products. Standardization is currently ongoing, in order to be able to exploit commercially new higher frequency bands for Mobile Backhaul, such as W-Band (90 GHz) and D-Band (130 – 174.8 GHz).
W-Band spectrum at 90 GHz, is close to the 80 GHz band, and it is therefore sometimes also referred to, as an “extended E-band” solution, due to close frequency proximity and similar system and propagation characteristics. D-Band, however, when commercially available, will be the first frequency band that will break the 100GHz barrier. With an available spectrum of more than 30 GHz and advanced techniques such as MIMO and antenna beam-forming, D-band links can finally reach up to 100Gbps transmission rate in a single radio unit.
D-Band spectrum characteristics
Millimeter wave frequency bands can usually cover shorter distances, due to signal attenuation caused by the oxygen absorption and water vapor. As a rule of thumb, the higher the frequency, the lower the distance covered.
E-band, in particular, can cover distances of 3-5Km, depending on the average rain density of the geographical region that is being deployed. On the other hand, links in the D-Band frequency range, are intended to cover distances of up to 1Km. These short distances may seem like a limited scope, however, taking into account the network density of 5G deployment and 5G small cell architecture, D-band equipment can cover a wide range of 5G last mile connectivity.
Another advantage of this technology is that due to the nature of this extremely high-frequency band, the form factor of such equipment can be quite small and suitable for use in street furniture such as lamp posts, bus stops, telephone booths, etc. All of the above make D-band, a perfect candidate for deployment in a dense urban environment.
D-Band deployment
Microwave vendors are currently working towards the early prototypes of D-band radio and plan to release a commercially available product by late 2020 and 2021.
At the same time, Operators plan Proof of Concept trials by the end of 2019 and the beginning of 2020. One thing is for sure, D-band equipment will provide the Mobile Operators with an extra competitive edge for massive 5G deployment.
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