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Content for  TS 25.303  Word version:  16.0.0

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1  ScopeWord‑p. 6

The present document describes all procedures that assign, reconfigure and release radio resources. Included are e.g. procedures for transitions between different states and substates, handovers and measurement reports. The emphasis is on showing the combined usage of both peer-to-peer messages and interlayer primitives to illustrate the functional split between the layers, as well as the combination of elementary procedures for selected examples. The peer-to-peer elementary procedure descriptions and interlayer dependencies are described in the related protocol descriptions /1, 2, 3/ and they are thus not within the scope of the present document.
The interlayer procedures and interlayer dependencies in the present document are informative.

2  References

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TS 25.321: "Medium Access Control (MAC) protocol specification".
TS 25.322: "Radio Link Control (RLC) protocol specification".
TS 25.331: "Radio Resource Control (RRC) protocol specification".
TS 25.304: "UE Procedures in Idle Mode and Procedures for Cell Reselection in Connected Mode".
TS 25.301: "Radio Interface Protocol Architecture".
TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
TS 25.323: "Packet Data Convergence Protocol (PDCP) specification".
TR 21.905: "Vocabulary for 3GPP Specifications".

3  Definitions and abbreviations

3.1  Definitions

For the purposes of the present document, the terms and definitions given in [8] apply.

3.2  Abbreviations

For the purposes of the present document, the following abbreviations apply:
Access Service Class
Dedicated Control SAP
Dedicated transport CHannels
Radio Network Temporary Identity

4  General Description of Connected ModeWord‑p. 7

The connected mode is entered when the RRC connection is established. The UE is assigned a Radio Network Temporary Identity (RNTI) to be used as UE identity on common transport channels. Two types of RNTI exist. The Serving RNC allocates an s-RNTI for all UEs having an RRC connection. The combination of s-RNTI and an RNC-ID is unique within a PLMN. c-RNTI is allocated by each Controlling RNC through which UE is able to communicate on DCCH. c RNTI is always allocated by UTRAN when a new UE context is created to an RNC, but the UE needs its c-RNTI only for communicating on common transport channels.
The UE leaves the connected mode and returns to idle mode when the RRC connection is released or at RRC connection failure.
Within connected mode the level of UE connection to UTRAN is determined by the quality of service requirements of the active radio bearers and the characteristics of the traffic on those bearers.
The UE-UTRAN interface is designed to support a large number of UEs using packet data services by providing flexible means to utilize statistical multiplexing. Due to limitations, such as air interface capacity, UE power consumption and network h/w availability, the dedicated resources cannot be allocated to all of the packet service users at all times.
Variable rate transmission provides the means that for services of variable rate the data rate is adapted according to the maximum allowable output power.
The UE state in the connected mode defines the level of activity associated to the UE. The key parameters of each state are the required activity and resources within the state and the required signalling prior to the data transmission. The state of the UE shall at least be dependent on the application requirement and the period of inactivity.
The different levels of UE connection to UTRAN are listed below:
  • No signalling connection exists
    The UE is in idle mode and has no relation to UTRAN, only to CN. For data transfer, a signalling connection has to be established.
  • Signalling connection exists
    When at least one signalling connection exists, the UE is in connected mode and there is normally an RRC connection between UE and UTRAN. The UE position can be known on different levels:
    • UTRAN Registration Area (URA) level
      The UE position is known on URA level. The URA is a set of cells
    • Cell level
      The UE position is known on cell level. Different transport channel types can be used for data transfer:
    • Common transport channels (RACH / FACH, DSCH)
    • Dedicated transport CHannels (DCH)
Assuming that there exists an RRC connection, there are two basic families of RRC connection mobility procedures, URA updating and handover. Different families of RRC connection mobility procedures are used in different levels of UE connection (cell level and URA level):
  • URA updating is a family of procedures that updates the UTRAN registration area of a UE when an RRC connection exists and the position of the UE is known on URA level in the UTRAN;
  • handover is a family of procedures that adds or removes one or several radio links between one UE and UTRAN when an RRC connection exists and the position of the UE is known on cell level in the UTRAN.

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