Piggyback of RRC request and Service Request 27

Piggyback of RRC request and Service Request 27, June 2007 NTT Do. Co. Mo, Inc. 1

Background • RAN 2 is currently studying the way to piggyback RRC Connection Request (AS) and Service Request (NAS) in order to shorten the setup time. • AS the assumed AS message size is small, RAN 2 want to shorten the message size as much as possible. And one possible way forward is to re-use the duplicate information elements in NAS. – LS is sent to SA 2, SA 3 (CC: CT 1). 2

Proposal • As the piggyback AS & NAS and re-use of the AS information element are highly related to UE – CN protocol design, the detailed study should also be done in CT 1. – Study point • To clarify the re-usable information element in AS. • To clarify the way to convey the message in S 1 MME. 3

Required Information Element in Service Request (draft study result) Considering the current UMTS service request, 4 information elements seem to be required. UMTS (NAS) Note P-TMSI CKSN • In LTE, RRC connection request (AS) includes S-TMSI 2. To present the type of Service Request Service Type • In LTE, “establishment cause” in RRC might represent the same meaning 3. To Assign the activate bearer PDP Context Status The purpose of the information element 1. To Identify the UE 4. NAS Protocol & message discrimination (note) It has not decided if RRC contains “establishment cause” in RAN 2. NAS Protocol header Protocol discriminator, Skip indicator, Message Type • S-TMSI is the candidate of re-usable information elements so far. • It should be clarified the way to convey the re-used information elements to MME. 4

Ref. Service Request information flow Described based on TS 23. 401. 100. The modified parts are described in red. UE e. Node. B MME Serving GW PDN GW HSS 0. Random Access Preamble / Response 1. RRC Connection Request + NAS Service Request 2. NAS: Service Request+S 1 -AP(FFS) 3. RRC Connection Request Resolution 4. Authentication 5. S 1 -AP: Initial Context Setup Request 6. Radio Bearer Establishment 7. Uplink Data 8. S 1 -AP: Initial Context Setup Complete 9. Update Bearer Request 10. Update Bearer Response 5