5G Millimetre Waves
The purpose of this note is to describes the various millimeter waves spectrum bands for 5G and its relevance for India.
Background
World radiocommunication conferences (WRC) are held every three to four years. In these conferences deliberations are undertaken to define or revise the Radio Regulations - the international treaty governing the use of the radio-frequency spectrum. In the last WRC (2015) at set of 7 bands were shortlisted to be studied for suitability of rolling out 5G services, and these are likely to be finalized in the WRC to be held next year (2019). The picture below describes these bands.
Please note that though the 28 GHz band (27.5 - 29.5) was omitted from these ITU studies, but is now likely to be extensively used by key countries (US, Canada, South Korea, HGK, New Zealand, Singapore, Brazil and others) as a candidate band for deployment of 5G services. Hence, this band (28 GHz) will generate strong 5G ecosystem, and therefore cannot be ignored just because it is not part of the ITU deliberations. However, there are issues that need to be address which are described below.
26 & 28 GHz band
The following is the layout of these two band which are adjacent to each other.
The 26 GHz band starts at 24.25 GHz and ends at 27.5 GHz. The ITU is carrying out sharing studies for this band to analyse coexistence of 5G systems with existing satellite services. These satellite services are of two types, a) Earth to Space (FSS); b) Space to Earth (Met Satellites). Please note that for the 28 GHz band (27.5 to 29.5 GHz) no sharing studies are carried out by ITU, as this is not part of their deliberation.
Coexistence Issue
The coexistence of 5G systems with satellite services is a challenge where the satellite earth station is receiving. The reason is that the satellite signals need to travel large distances (sometime thousands of kms) before they reach the satellite receivers located at the earth, thereby weakening these signals and making them susceptible to interference from the 5G system. Hence, these satellite receivers have to guarded with exclusion zones to prevent interference from the adjacent 5G systems. Sometime the size of these exclusion zones are quite large (tens of kilometers).
Whereas, the coexistence is much easier to manage when 5G system have to coordinate with satellite systems which are transmitting from Earth to Space. The reason is that these satellite receivers (which are prone to interference) are located quite far, and sometime 36,000 Kms for the satellites located in a geosynchronous orbit.
Fortunately, both these scenarios are part of the ITU study for the 26 GHz band, since this band is already used to serve these two types of satellite services (please see figure above, Earth to Space is marked blue, and Space to Earth is marked orange).
Therefore, outcome of the same study can be easily implemented for the 28 GHz band (as already described that ITU is not studying this band) which is currently occupied with only satellite service - transmitting from Earth to Space.
Conclusion
For India, both 26 & 28 GHz band are the lowest hanging fruit for deploying the 5G systems. 26 GHz band is accepted globally, but here the 5G system will have to deal with large exclusion zones to prevent interfering into the satellite receivers. But the 28 GHz band does not have such issue and therefore easier to manage, as the 5G systems are unlikely to interfere with the satellite systems, and any interference from the satellite system into the 5G system will require a much smaller exclusion zones (few hindered meters). Also, just like the 26 GHz band, the 28 GHz band will have good global ecosystem for us to ignore it completely, thereby enabling India to leverage both bands for the purpose of deployment of 5G systems.
(Views expressed are of my own and do not reflect that of my employer)
PS: Find the list of other relevant articles in the embedded link.
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6 年As usual an excellent? thought provoking article bringing out the importance of Millimetre Waves -26 & 28Ghz? for 5G . These bands can actually bring out the true benefits of 5G. However, while the co-existence with Satellite Receivers/Transmitters is an important study which is being carried out by ITU in the 26Ghz band, the two case scenarios of Transmit & Receive for Satellite Users? cannot be perhaps carried out effectively in the 26Ghz band? -which can also serve the purpose to establish co-existence in the 28Ghz band , which perhaps has the fastest developing 5G Ecosystem world over . And the reason for that is? as follows: The 28Ghz band ( 27.5-29.5Ghz ) is called the Ka band . This band is being used by over 150 commercial? satellite constellations with over a dozen with footprint over India. Also this band due to its inherent characteristics lends to high throughput ( approx. 10X ), much? more than the current Ku band satellites. While the current Ku band satellites are perhaps used more for DTH and P2P kind of applications ( akin to NLD services ) , the Ka band would be used exclusively for Broadband Satellites. With reusable frequency techniques and high throughput beams, the Cost/bit or Mbit comes down in some cases by a factor of 300x than at present, thereby making satellite broadband highly competitive . Summary: This Band is vital for Satellite Broadband and for connecting the far flung and remote areas where fiber cannot reach at all and also in areas where laying fiber is not feasible or is time consuming. India needs these satellites in the Ka band and they need to be protected from terrestrial technologies. An interesting aspect of the Ka band ( 28Ghz ) study is that in this band the Satellite is transmitting ( Earth-to-Space) and hence chance of interference from 5G transmitters may be quite less, as pointed out by Parag himself. And while the ' zone exclusion' principle could be adopted for the Earth Stations/Gateways , the thousands of small? satellite broadband remote terminals which are likely to be part of the Ka band ecosystem -this principle would be difficult to apply. Perhaps a Geographical segregation of 5G in Urban Areas and Satellite in Rural & Remote Areas of India seems to? be a more feasible solution, as of now.