UMTS – WCDMA RRC connection establishment between UE and RNC for UE registration

Explained below is the exchange of RRC messages between UE and RNC before NAS messages are exchanged between UE and MSC. Other UMTS – WCDMA information is posted on my website here.

UE send RRC connection request on uplink Common Control Channel (CCCH) with establishment cause as Registration

Other parameters:-

  • TMSI
  • PLMN identity
  • UE capability
  • AS release [Rel 5,6,7,8 etc]
  • Non critical extensions [multi cell support, FDPCH, MAC-EHS, EDCH, MACi etc]

UTRAN responds back with RRC connection setup message in downlink Common Control Channel (CCCH)


  • TMSI
  • PLMN Identity
  • RRC transaction identifier
  • RRC release [Rel 5,6,7,8 etc]
  • UTRAN DRX cycle lenght coeff
  • U-RNTI
  • new RRC state [cell-FACH, cell-DCH]
  • radio capability update [FDD or TDD]
  • rb identity 1
  • rb mapping [logical ch mapping eg. UL DCH <-> DL DCH, UL RACH <-> DL FACH]
  • rb identity 2
  • rlc info – UL and DL [transmission window size, reset timer, max no. of tx before reset]
  • rb mapping [similar as rb mapping for rb identity 1]
  • rb identity and rb mapping for 3 and 4 [similarly]
  • common transport channel info [TFCS, ctfc]
  • DPCH info [preamble, DPCCH power offset, BLER, Scrambling Code, SF, TPC combination index]
  • P-CPICH info [PSC]

UE responds back with RRC connection setup complete message on uplink Dedicated Control Channel (DCCH)


  • RRC transaction identifier
  • start value for CS and PS domain
  • UE radio capability [PDCP, RLC, Tr Ch, RF, RAT, security, positioning, frequency band for UTRAN and GSM, measurement, CM]
  • Non critical extensions [physical channel cap, etc]
Posted in Wireless
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  1. [...] RRC messages exchanged before exchange of NAS messages are explained here. [...]

  2. [...] post concentrates only on the messaging sequence and flow. More details about RRC and NAS messages can be found in earlier posts. UE send “RRC connection request” on [...]

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