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LTE: What is the content of contention resolution ?

+6 votes
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LTE: What is the content of contention resolution ?
posted Oct 27, 2013 by Ganesh Kumar

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2 Answers

+2 votes

as per 3gpp 36.321 (v-a50) sec-5.1.5 "Contention Resolution", following is stated:-
"UE Contention Resolution Identity included in the MAC control element matches the CCCH SDU transmitted in Msg3"

answer Oct 28, 2013 by anonymous
+1 vote

Contention resolution is required whenever two preambles with same value reach at eNodeB at the same time. Then eNodeB MAC layer can proceed with one of these request so it needs to communicate to the UE which is got selected by eNodeB MAC. This information is carried in contention resolution.

Till msg3 conversation , UE can be identified by C-RNTI. As far as I know "eNodeB send same message3 (RRC Connection Request or RRC Connection Reestablishment Request) along with assigned C-RNTI to the intended UE.

Please correct me if I am wrong.

answer Oct 27, 2013 by Vimal Kumar Mishra
Similar Questions
0 votes

At handover time target ENB will give rach preamble to UE. Is it necessary that target ENB is to be sink with source ENB. How UE will do contention free rach when both or not in sink? Is their any case Contention free rach will fail?

+3 votes

Mostly, the MAC control header for contention resolution is of 56-bits(1-byte for DL contention resolution ID+6-bytes for subPdu len of UE-contention resolution id). Please find the below details for your reference.


Source = \Protocol\3GPP\LTE\MAC\Entity Id 17
Destination = \Protocol\3GPP\LTE\PHY\Entity Id 2
Transport Blocks
Transport Block 1 (Codeword 0) Len = 7 =
MAC subheader 1, type: MCE (DL CONTENTION RESOLUTION ID), sub-header length: 1 =
LCID = 28 (DL CONTENTION RESOLUTION ID)
E = 0
R = 0
SubPdu Len = 6
UE Contention Resolution ID = 5E,0E,95,0C,02,C6


Secondly, when does this header if of more than 56-bits as below. 56-bits for contention resolution and 16-bits for padding. Why does the TB1 size is changed?


Source = \Protocol\3GPP\LTE\MAC\Entity Id 17
Destination = \Protocol\3GPP\LTE\PHY\Entity Id 2
Transport Blocks
Transport Block 1 (Codeword 0) Len = 15 =
MAC subheader 1, type: MCE (DL CONTENTION RESOLUTION ID), sub-header length: 1 =
LCID = 28 (DL CONTENTION RESOLUTION ID)
E = 1
R = 0
SubPdu Len = 6
UE Contention Resolution ID = 40,10,00,00,00,16
MAC subheader 2, type: Padding, sub-header length: 1 =
LCID = 31
E = 0
R = 0

0 votes

Does Other UE knows, whether its a Contention Based or Non-Contention based procedure ?

+2 votes

Say e.g ENB given some random preamble to UE1 to do RACH, but in -case same preamble is selected by UE2(preamble given to UE 1) and doing RACH .
In the above scenario ENB will not give any CRM message to UE's so how contention will be resolved for UE2?

+2 votes

Why do we need only contention free RACH in LAA cells?

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