PBCH SCS may not be always 15KHz on live network

free5G / free5GRAN

free5GRAN is an open-source 5G RAN stack. The current version includes a receiver which decodes MIB & SIB1 data. It also acts as a cell scanner. free5GRAN works in SA mode.

Apache License 2.0

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PBCH SCS may not be always 15KHz on live network #10

Closed gmg2719 closed 3 years ago

gmg2719 commented 3 years ago

Describe the bug A clear and concise description of what the bug is.

To Reproduce

Error happen during build or installation
Error happen during execution (If so, please provide the configuration file) In you code, I found you hard code PBCH SCS to 15KHz. I think this may cause some problem when detect some NR cell with PBCH SCS =30 kHz. May be we should use blind detection of PBCH SCS during cell search procedure.

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System:

OS: [e.g. Ubuntu]
Version [e.g. 20.04]
Libuhd version

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adejavel commented 3 years ago

Hello, could you please mention where did you find this and for which band ? Thanks.

gmg2719 commented 3 years ago

Hi, some TDD NR bands, for example TDD N41, N78, N79 get PBCH SCS 30kHz. You can refer to 3GPP specs or follow the following table :

adejavel commented 3 years ago

Yes sure, it is already implemented in the code. My question was where in the code did you find that the SCS is fixed ? For information, in the current release, we do not implement SS Block patterns. The current statement is that Bands below 3Ghz have a SSB SCS of 15khz and bands above have a SSB SCS of 30khz.

gmg2719 commented 3 years ago

Hi, I just look through part of you code, so I think I was wrong. "The current statement is that Bands below 3Ghz have a SSB SCS of 15khz and bands above have a SSB SCS of 30khz" is the key to unlock my puzzle. I think this may be true at most of the situation. But not always true, my real intention is that bind the SSB SCS property to specific bands may be a future improvement of your code. For these bands with multiple SSB SCS, we should blind detect all of possible situation. For example, n5, n41,n66,n90 is below 3GHz, but they can be with SCS =30kHz

In fact , in my country, SSB SCS of n41 is 30kHz in live network

adejavel commented 3 years ago

Hello, Thanks for the feedback! Indeed, the current version do not take into account account that a specific band can have multiple SS Block patterns. It will be part of a future release. For information, the current version distinguishes the SS Block pattern and SSB SCS based on frequency. If required, you can force SSB SCS by setting band_info variable here to either free5GRAN::BANDWIDTH_15_KHZ for 15khz SCS or free5GRAN::BANDWIDTH_30_KHZ for 30khz SCS.

gmg2719 commented 3 years ago

Thanks, I get it!