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transfer signalling connection to the CN message
and transport the initial NAS
message
Uplink direct This is subsequently used to Direct transfer
transfer transfer all NAS messages to
the CN
Downlink direct This is used to transfer all NAS to Direct transfer
transfer the UE
340 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM



UE BTS RNC



Cell/URA Update



Cell/URA Update Confirm




Figure 6.69 RRC cell/URA update

The UE will initiate a cell update procedure for the following reasons:

• uplink data transfer
• paging response
• radio link failure
• re-entry of service area
• cell reselection
• periodic cell update.

It will initiate a URA update in the following situations:

• URA reselection
• periodic URA update.

For a periodic update, the UE performs this based on the value of timer T305, the
value of which is known from system information (SIB 1). Once this timer expires, the
UE will perform a periodic cell/URA update. The default value of T305 is 30 minutes.
The cell/URA update message will contain the U-RNTI, the update cause, and some
measurement results, such as the measured power of the CPICH. The RNC will reply
with the cell update con¬rm message, which may also be used to allocate a new RNTI
to the UE.


6.16.10 Measurement reporting
For the purposes of handover, the UE must make measurements across the Uu interface
and pass these back to the RNC to allow it to make an informed decision about UE
handover. This measurement reporting is controlled by the RNC using the measurement
6.16 RADIO RESOURCE CONTROL (RRC) 341


Table 6.20 UE measurement criteria
Measurement Description
Intra-frequency Measurements on downlink physical channels in cells at the same
frequency as the active set
Inter-frequency Measurements on downlink physical channels in cells at frequencies that
differ from the frequency of the active set
Inter-RAT Measurements on downlink physical channels in cells belonging to another
radio access technology (RAT) than UTRAN, e.g. GSM
Traf¬c volume Measurements of uplink traf¬c volume
Quality Measurements of downlink quality parameters of a channel, e.g. downlink
transport block error rate
UE-internal Measurements of UE transmission power and UE received signal level


Table 6.21 Cell sets
Cell set Description

Active set Current set of cells in which the UE has an active connection and is
sending and receiving information (i.e. >1 for soft handover)
Monitored set A set of cells, not in the active set, that the UE has been instructed by the
RNC to monitor as possible handover candidates
Detected set All other cells that the UE has detected. Reporting of measurements only
occurs for intra-frequency measurements.


Table 6.22 Measurement control
Measurement Description Example
Command Setup, modify or release a measurement Release
Type Description of what type of measurement the UE Intra-frequency
should make
Object Description of what the UE should measure Cell
Quantity The quantity the UE should measure CPICH Ec/N0
Reporting criteria Indication of when the UE should report the 500 ms
measurement


control command. The different types of measurement that the UE may be asked to make
fall into the broad categories listed in Table 6.20.
The cells that a UE is monitoring are broken into three categories (Table 6.21).
The measurement control message will contain the elements listed in Table 6.22.
For each measurement that has been set up, the UE will pass back the measured quantity
in a measurement report message according to the reporting criteria (Figure 6.70). The UE
receives its initial measurement control information from the broadcast channel in system
information blocks 11 and 12. This provides suf¬cient information and reporting criteria
for the UE to perform measurements and ¬le measurement reports. Any subsequent new
342 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM



UE BTS RNC



Measurement control

Reporting
criteria met
Measurement report

Reporting
criteria met
Measurement report



Figure 6.70 RRC measurement reporting


or updated measurement information can be sent to the UE by the RNC in a measurement
control message.



6.16.11 Active set update

For soft handover (in CELL-DCH), the active set update is used by the RNC to instruct
the UE to modify its active set (Figure 6.71).
The possibilities are:

• add radio link
• delete radio link
• combined add and delete radio link.


UE BTS RNC


NBAP RL establishment/
deletion procedures

Active set update


Active set update complete


Figure 6.71 RRC active set update
6.17 BROADCAST SYSTEM INFORMATION 343


Prior to the update, where a new radio link is being added, the RNC will have made the
appropriate transport link preparations in the network. Upon receipt, the UE will update
its active set and report this back to the RNC with an active set update complete message.



6.17 BROADCAST SYSTEM INFORMATION
System information is carried in the downlink BCCH channel, which is mapped to the
BCH and optionally the FACH. The BCH is carried at the physical layer in the P-
CCPCH. System information provides the UE with the necessary general parameters for
both system and cell level to enable it to communicate with the network, such as details
of the structure of the RACH and PRACH. The system information is split into a number
of system information blocks (SIB), where similar information is contained in one SIB.
The scheduling and frequency of occurrence of these SIBs is referenced in a master
information block (MIB), which acts like an index to the SIBs contained in the broadcast
channel. Optionally, up to two scheduling blocks (SB) may also be present, which also
contain SIB scheduling information. This is implemented in a hierarchical manner, with
the MIB referencing the SBs, which in turn reference the SIBs (Figure 6.72).
System information is considered an RRC function. However, much of the system
information remains static, and thus to minimize the quantity of signalling traf¬c on the
Iub interface, signalling information is sent to the BTS by the CRNC over NBAP when the
cell is created or restarted. The BTS then transmits this information out on the P-CCPCH.
Subsequently, the RNC will only update the BTS with changes to system information.
In addition, there is some information that changes rapidly and is only available to the
BTS, and it is the responsibility of the BTS to place this information on the BCCH. An
example of this is uplink interference in the cell (SIB7).
The speci¬cations de¬ne 18 different SIBs, with two of those (13 and 15) having a
number of sub-blocks. For example, SIB15 also has SIB15.1, 15.2, etc. Not all of the
SIBs are required to be present on the broadcast channel, and the choice of which ones
are present is dependent on the equipment implementation. Some of the SIBs represent
information about features that may not be currently implemented, and are therefore
irrelevant. An example might be UE positioning information for location-based services.
For all SIBs, with the exception of 15.2, 15.3 and 16, their content is static, and can only


MIB SB 1 SIB 1

SB 2 SIB 2

SIB 3
.
.
.

SIB 18

Figure 6.72 System information structure
344 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM


change when directed by the RNC. For 15.2, 15.3 and 16, the information can vary in
different occurrences of the blocks.
Table 6.23 lists the SIBs relevant to FDD, and the information each presents. Note that
SIB14 and SIB17 are only for the TDD system, and are therefore omitted from the list.
Consider that the initial rollout of a simple UMTS network con¬guration can substan-
tially narrow down the system information it must broadcast, as follows:

• Do not use different parameters for connected mode “ eliminates SIB4, SIB6 and SIB12
• No common packet channel implemented (CPCH) “ eliminates SIB8 and SIB9
• No Dynamic Resource Allocation Control (DRAC) “ eliminates SIB10
• Only GSM“mobile application part (MAP) core network “ eliminates SIB13“SIB13.4
• No UE positioning support “ eliminates SIB15“SIB15.4

Table 6.23 UMTS system information blocks
Information Description
Block
MIB SIB scheduling information
SB1 Optional SIB scheduling information
SB2
SIB1 NAS system information as well as UE timers and counters to be used in idle
mode and in connected mode
SIB2 URA identity
SIB3 Parameters for cell selection and reselection
SIB4 Parameters for cell selection and reselection to be used in connected mode
SIB5 Parameters for the con¬guration of the common physical channels in the cell
SIB6 Parameters for the con¬guration of the common and shared physical channels
to be used in connected mode
SIB7 Fast-changing parameters uplink interference and dynamic persistence level
SIB8 Static CPCH information to be used in the cell
SIB9 CPCH information to be used in the cell
SIB10 Information to be used by UEs having their DCH controlled by a dynamic
resource allocation control (DRAC) procedure
SIB11 Measurement control information to be used in the cell
SIB12 Measurement control information to be used in connected mode
SIB13 ANSI-41 system information
SIB13.1 ANSI-41 RAND information
SIB13.2 ANSI-41 user zone identi¬cation information
SIB13.3 ANSI-41 private neighbour list information
SIB13.4 ANSI-41 global service redirection information
SIB15 Information useful for UE-based or UE-assisted positioning methods
SIB15.1 Information useful for UE positioning differential GPS corrections
SIB15.2 Information useful for GPS navigation model
SIB15.3 Information useful for ionospheric delay, UTC offset and Almanac
SIB15.4 Information useful for OTDOA-based UE positioning method
SIB16 Radio bearer, transport channel and physical channel parameters to be stored
by UE in idle and connected mode for use during handover to UTRAN
SIB18 PLMN identities of neighbouring cells to be considered in idle mode as well
as in connected mode
6.17 BROADCAST SYSTEM INFORMATION 345


Table 6.24 Typical SIB usage
Information Description
block
MIB SIB scheduling information
SB1 Optional SIB scheduling information
SB2
SIB1 NAS system information as well as UE timers and counters to be used in idle
mode and in connected mode
SIB2 URA identity
SIB3 Parameters for cell selection and reselection
SIB5 Parameters for the con¬guration of the common physical channels in the cell
SIB7 Fast-changing parameters uplink interference and dynamic persistence level

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