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4G/LTE - CBRS |
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CBRS
CBRS stands for Citizens Broadband Radio Service. It is a block of spectrum in 3.5 Ghz with the range of 150 Mhz (3.5 (3550 MHz to 3700 MHz) for shared wireless access. This used to be used by US Navy and other DoD members, but freed up for unlicensed wireless application like LTE (Refer to What is CBRS? - LTE in 3.5 GHz Shared Spectrum and What it Means for IoT ) for the details.
As mentioned above, this is unlicensed spectrum meaning that you don't have to pay the cost for the spectrum. You can think of this as similar to ISM band, but how you can get a spectrum in the block. In case of ISM, you can just turn on your device working in the spectrum without any special procedure as long as the device meets the regional transmission requirement (e.g, FCC). However, you need to go through a special procedure to get a section of the frequency band as described in What is CBRS? - LTE in 3.5 GHz Shared Spectrum and What it Means for IoT
CBRS band in FCC
The exact CBRS band may vary depending on countries since each country may have different regulations. In case of North America, the band is allowed as specified by FCC as shown below.
* FSS stands for Fixed Satellite Serivice * PAL stands for Priority Access License
source : 3.5 GHz Band Overview (FCC)
What is the common CBRS band in 3GPP ?
Now the CBRS band is defined in 3GPP as Band 48 (See Why CBRS frequency bands are perfect for private LTE and private 5G networks for further details). NOTE that B48 is TDD based.
Now this band is open for 5G/NR as well (Ref [4])
Do we need any special protocols for CBRS ?
Since CBRS is mainly for spectrum regulation, it wouldn't require any specific protocol in terms of modem protocol. When you use test equipment (network simulator) and try your UE in CBRS band (e.g, LTE B48), it would work and UE would attach to the equipment which does not use any specific protocols for CBRS. But in real deployment, the service provider may require some additional feature since the band may be used by other service provider as well (e.g, something similar to LBT(Listen Before Talk) or additional protocols as specified in CBRS WInnForum Standards)
Reference :
[1] What is CBRS? - LTE in 3.5 GHz Shared Spectrum and What it Means for IoT [2] CBRS - Private LTE Networks for IoT Applications [3] 3.5 GHz Band Overview (FCC) [4] WInnForum Approves 5G NR as a Supported Air Interface for CBRS Band [5] What is Private LTE (Band 48 CBRS) and Why is it Important? [6] Why CBRS frequency bands are perfect for private LTE and private 5G networks [8] Spectrum Sharing at 3.5 GHz
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