Why in case of Long BSR we don't add logical channel Group id ? Though in short BSR it is must.

Question

What could be the reason for defining logical channel grouping concept in LTE ? Why logical channels can't be used independently ?

Answer 1

UE sends these three different types of BSR's (Short, Long and Truncated) as MAC Control elements and it adds LCG ID and not LC ID in them along with Buffer Size.

And the answer for your question is below

• Short BSR and Truncated BSR format: one LCG ID field and one corresponding Buffer Size field (figure 6.1.3.1-1); or
• Long BSR format: four Buffer Size fields, corresponding to LCG IDs #0 through #3 (figure 6.1.3.1-2).

Refer to 36.321 spec 6.1.3.1 for details, Happy Reading!!!

Comments

@Nagaraja: Thank you. It means Long BSR is for all always for all logical channel groups. That is the reason there is no need to mention it separately. Where as in Short BSR's we have to be specific that for which LCG we are sending this BSR. Did i catch right ?

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Yes. You got it right.