LTE Interview Question-Answer Part 1 | SIB | MIB |Cell Search Procedure | RACH
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- เผยแพร่เมื่อ 28 ต.ค. 2019
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LTE Interview Question Part 1 | SIB | MIB |Cell Search Procedure | RACH
What is Functionality & RACH process?.
RAPID in RACH response and Back of indicator.
There is another case where UE needs to retry PRACH. It is the case where UE received RAR from the network, but the RAPID is not for it (It means that RAR is not for some other UE). In this case, it is highly probable that a Backoff Indicator value is transmitted with RAR to control the PRACH retransmission timing.
Contention Resolution
Same PRACH preamble from multiple UE reaches the NW at the same time. This kind of PRACH collision is called "Contention" and the RACH process that allows this type of "Contention" is called "Contention based" RACH Process.
i) RACH Preamble (RA-RNTI, indication for L2/L3 message size)
ii) Random Access Response (Timing Advance, T_C-RNTI, UL grant for L2/L3 message)
iii) L2/L3 message
iv) Message for early contention resolution
Exactly when & where a UE transmit RACH?
Through PRACH config index, it is determined by SIB2.
Answer:
The set of 64 preamble sequences within a cell are divided into two groups:
This group of sequences can be further divided into 2 sub-groups:
· 'Group A' sequences selected by the UE when the uplink data quantity to be sent is relatively small, or when the UE is in poor coverage.
· 'Group B' sequences selected by the UE when the uplink data quantity to be sent is relatively large, and the UE is in good coverage.
The division of PRACH sequences is illustrated in Figure 167. The number of 'Group B' preamble sequences can be set to 0 by configuring the value of 'Size of RA Preambles in Group A' to equal the value of 'Number of RA Preambles'.
The maximum allowed value for 'Number of RA Preambles' is 64 so it is possible to use all of the sequences for contention based random access, and not reserve any sequences for the non-contention based procedure.
Group A sequences are indexed from 0 to 'Size of RA Preambles in Group A'- 1, where the 'Size of RA Preambles in Group A' parameter ranges from 4 to 60 and is broadcast in SIB2.
Group B sequences are indexed from 'Size of RA Preambles in Group A' to 'Number of RA Preambles'- 1, where the 'Number of RA Preambles' parameter ranges from 4 to 64 and is broadcast in SIB2.
The UE selects a group B sequence if both of the following conditions are satisfied:
Preamble format?
How to determine which preamble format to use PRACH configindex determine which preamble format will use.
Why multiple preamble format? Especially why we need various PRACH format with different length of time?
How does Network knows exactly when UE will transmit the RACH
When do I have to retry? What should be the time delay between the previous transmission and the next transmission?
Do I have to retransmit the PRACH with the same power as previous one? Or try with a little bit higher power? If I have to try with a little bit higher power, how much power do I have to increase?
Back of Indicator:
If ARQ is implemented on RLC Layer the why HARQ is implemented at MAC Layer.
Difference between TX diversity and MIMO??
Difference between Close loop spatial multiplexing and Open loop spatial multiplexing?
HOW and WHEN UE start acquiring SIBs
Minimum of how many SIBs are required for the UE to initiate Attach procedure?
On which channels SIBs are transmitted?
Why SIBs are needed?
How many types of SIBs are there?
I am working in wireless technology where what I learn the same knowledge, technology and technical things shared with you in video format.
How to determined which Preamble format to use ?
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Nice
Best video ever on lte basics
Great
It's very good
Thanks for videos sir
Super bro
Nice ...
Helpful Q/A..
Thanks
Very very good Video Anand, please make such videos
Many Thanks Sir for helping mankind :)
Thanks
Thank you so much sir
Superb
Thanks
Very good
Thanks subhash
very informative
Thanks syed
very good
Thanks
Very Good content but next time please improve audio quality so more folks can learn by watching
Very useful information....thanx
thanks mohsin
@@AnandTechnoSolutions wlcm Sir....I m getting benefited by ur videos...thanks for sharing valuable informations...
Sir I hv to attain some interview within a week...so eagerly waiting for RACH videos....plz upload RACH videos...I vl be thankful to you forever.
thanks a lot sir..can you please make a video on RRC & Mac layer please??
very nice sir ji
please make one detail video in RACH procedure
Thank you
Thanks
Hello Sir, you have covered many interview questions, i really appreciate that. can i please request you make some video on hardware as well, for example DU, BBU, RBS , processors and various cards inside BTS, how to reset cards and all. thanks a lot, keep sharing videos.
Sure will try
Please share how dl synchronisation takes place in terms of physical layer... Correlation
sir kindly make us understand,if only reading is concerned for study then we can study from books also,nice questions but not understandable easily.......highly unsatisfied.....
Please upload protocol testing all video
what is work of DTx 10 symbols, pls explain
please PDF of your teaching- means way of describing at you tube that same PDF need to be attached in link
Please make video on RACH
ok
@@AnandTechnoSolutions thank you
Hi , Please share PDF also whichever you teaches
Hello sir is their any institute or online classes in Telangana state, Hyderabad region regarding this subject
Online class is available
Good questions but memorizing these information will not help an Optimization Engineer to resolve KPIs problems in the network. These are just basic fundamentals
Truth is lte engineers are not at alll in more number
Bhai,train pakadna h kya
very nice sir ji
please make one detail video in RACH procedure
Thank you
Thanks Akram
@@AnandTechnoSolutions Hello sir,
While attending LTE protocol testing job interview, I was stuck on questions "What bugs you faced during conformance testing?" & "How you try to fix the bug?"
It will be really helpful, if you share me some real time faced bugs during conformance testing and their resolution.
My id :- akkiraza.ar@outlook.com
Thanks in Advance