<<

. 72
( 132 .)



>>

SIB11 Measurement control information to be used in the cell


• No UE storage of channel parameters “ eliminates SIB16
• No other public land mobile network (PLMN) identities “ eliminates SIB18

This leaves only the SIBs shown in Table 6.24, with the details of each also presented.


6.17.1 Master information block (MIB)
The MIB contains some basic information about the network, and scheduling information
for the SIBs that are present (optionally the SBs). The network information includes
the supported PLMN types: GSM-MAP, ANSI-41 or both, and for GSM, the PLMN ID,
which is the mobile country code (MCC) + mobile network code (MNC). The scheduling
information provides for each SIB present, the SIB type (SIB1, SIB2, etc.), the number
of segments present in the SIB (SEG COUNT, 1“16), where the ¬rst segment is located
(SIB POS), and how often it repeats on the channel (SIB REP), referenced to the system
frame number (SFN).


6.17.2 System information block 1
This contains the NAS information for the CS and PS domain, and the UE timers and
constants. For idle mode, the parameters listed in Table 6.25 are de¬ned.

Table 6.25 UE timers and constants in idle mode
Timer/ Description Default
counter
T300 RRC connection request retransmission timer 1000 ms
N300 RRC connection request retransmission counter 3
T312 The timer for supervising successful establishment of a 1s
physical channel
N312 Maximum number of successive ˜in sync™ indications received 1
from L1 during the establishment of a physical channel
346 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM


Table 6.26 UE timers and constants in connected mode
Timer/ Description Default
counter
T302 Cell/URA update retransmission timer 4000 ms
N302 Cell/URA update retransmission counter 3
T305 Periodic cell update/URA update timer 30 min
T307 Timer for transition to idle mode, when T305 has expired, and 30 s
the UE detects an ˜out of service area™
T316 Started when the UE detects an ˜out of service area™ in 180 s
URA-PCH/CELL-PCH state
T317 Started when the T316 expires and the UE detects an ˜out of 180 s
service area™


When the UE initiates an RRC connection request, it will start T300 and wait for a
response from the network. If it does not receive an RRC connection setup message, it
will try again, up to a total of N300 attempts. If it fails to receive a network response,
it will return to idle mode. When a UE is establishing a physical channel, it will start
T312. During the T312 time period, it should receive N312 ˜in sync™ indications from L1,
to consider that the physical channel establishment has been successful. If T312 expires
before this, a failure has occurred.
For connected mode, there are several timers and counters that are relevant. Table 6.26
de¬nes some of the more relevant ones.
The T302 timer is started when a UE cell/URA update message is sent; if there is no
response from the network before it expires, then the UE will try again up to a total of
N302 times. Should there still be no response, the UE will enter idle mode.
Should the UE be in CELL FACH, CELL PCH or URA PCH, it will perform periodic
cell/URA updates once T305 expires. If T305 expires and the UE detects it is out of
coverage (out of service area), it will start T307 as a time period to wait for transition
back to coverage. Should it expire, it will move to idle mode. This timer is to prevent
cell/URA update failure as a result of momentary loss of coverage. In CELL PCH or
URA PCH state, if the UE detects out of service area, it will start T316. If T316 expires,
the UE checks for coverage. Should it be in service area, it will perform a cell/URA update
with an indication that it was temporarily out of coverage. However, at expiry should it
still be out of service, it will start T317 and try to do a cell/URA update anyway. If
this does not succeed before T317 expires, it will move to idle mode, and release its
signalling connection resources. These timers are to try to keep the UE connected again,
even if there are temporary losses in coverage. An example might be a user entering a
lift. From the default values, as long as the UE is not out of coverage for up to 6 minutes
(by default), it will remain connected.



6.17.3 System information block 2
This contains the list of UTRAN registration area identities for the cell in which the block
is transmitted. A cell can be a member of up to a maximum of eight URAs.
6.17 BROADCAST SYSTEM INFORMATION 347


Table 6.27 SIB3 parameters
Parameter Description
Sintrasearch Threshold (in dB) for intra-frequency measurements and for the HCS
measurement rules
Sintersearch Threshold (in dB) for inter-frequency measurements and for the HCS
measurement rules
SsearchHCS This threshold is used in the measurement rules for cell reselection when
HCS is used. It speci¬es the limit for cell selection receive level (Srxlev)
in the serving cell below which the UE shall initiate measurements of all
neighbouring cells of the serving cell
Qqualmin Minimum required quality level in the cell in dB
Qrxlevmin Minimum required RX level in the cell in dBm.
Qhyst1s Hysteresis value (Qhyst). It is used for cells if the quality measure for cell
selection and reselection is set to CPICH RSCP
Qhyst2s Hysteresis value (Qhyst). It is used for cells if the quality measure for cell
selection and reselection is set to CPICH Ec/No
Treselections Cell reselection timer value
HCS PRIO HCS priority level (0“7) for serving cell and neighbouring cells
Qhcs Quality threshold levels for applying prioritized hierarchical cell reselection
TCRmax Duration for evaluating allowed amount of cell reselection(s)
NCR Maximum number of cell reselections. Default 8
TCRmaxHyst Additional time period before the UE can revert to low-mobility
measurements
HCS, Hierarchical cell structure: this is where there is an overlay of macro, micro and pico cells.


6.17.4 System information block 3
This contains the parameters for cell selection and reselection. It will indicate the cell ID,
which is a unique identi¬er for the cell within the network, a list of information for cell
selection and reselection, plus any cell access restrictions, for example, cell barred. The
cell selection and reselection process is based on the quality of the cell, as measured on
the pilot channel. The cell selection and reselection quality measure can be chosen either
as the CPICH Ec/No or CPICH RSCP.3
The parameters cover the required quality levels and thresholds, in dB, for cell selection
and reselection, and also de¬ne the maximum allowed uplink transmit power (in dBm).
The important parameters are listed in Table 6.27.



6.17.5 System information block 5
This block contains the con¬guration parameters for the common physical channels in
the cell (Table 6.28).

3
The received signal code power (RSCP) is a measure of the received power of the pilot after
despreading. The Ec/No is the energy per chip (Ec) of the pilot, divided by the power density
in the frequency band (No). Ec/No is actually the RSCP/RSSI, where RSSI, the received signal
strength indicator, is the wideband received power within the relevant channel bandwidth.
348 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM


Table 6.28 SIBS parameters
Parameter Description
PICH power offset The power transmitted on the PICH minus the power of the primary
CPICH
AICH power offset The power level of the AICH, AP-AICH and CD/CA-ICH channels
minus the power of the primary CPICH
Primary CCPCH info Indication if transmit diversity is supported
PRACH system Including physical layer information (available signatures, spreading
information list factors, preamble scrambling code, available subchannels), RACH
transport channel information (RACH TFS)
SCCPCH information FACH/PCH information (FACH/PCH TFS), PICH information
(channelization code, no. of PI per frame)


6.17.6 System information block 7
This block contains the fast-changing parameters uplink interference and dynamic persis-
tence level in the cell, as follows:
Uplink interference “ total uplink interference in dBm


6.17.7 System information block 11
This block contains measurement control information to be used in the cell. Again, it
de¬nes whether the CPICH RSCP or Ec/N0 should be used, and the measurement param-
eters for intra-frequency, inter-frequency, inter-RAT (radio access technology), traf¬c
volume and UE internal measurements that should be made. This information is used
by the UE to make measurements and when reporting criteria are ful¬lled, feed the
relevant measurement information back to the RNC during connections for handover
evaluation.


6.18 FRAME PROTOCOLS
On the Iu, Iur and Iub interfaces, transmission blocks are encapsulated in a user plane
frame protocol for transfer across the interfaces. It sits immediately above the transport
layer, which on these interfaces is currently ATM. The frame protocol indicates to the
destination the format of the transmission blocks held within. The format of this frame
protocol is dependent on the interface, the nature of the data being transported, and also
whether it is being transported on dedicated or common/shared channels.


6.18.1 Dedicated user data on the Iub/Iur interface
Once a radio bearer has been established between the UE and RNC for a dedicated user
data channel (DCH), the frame protocol (FP) is used across the Iub and Iur interfaces to
transfer this user data. The FP provides the following services to the user data:
6.18 FRAME PROTOCOLS 349


• transfer of transport blocks across the Iub and Iur interfaces;
• transfer of outer loop power control information between the base station and the
serving RNC;
• synchronization;
• transfer of transport format information from SRNC to base station for DSCH channel;
• transfer of radio interface parameters from SRNC to base station.

The structure of the FP is slightly different in the uplink and the downlink, and both
are now examined.


6.18.1.1 Uplink data frame
The data frame contains the transport blocks that comprise the dedicated channel. A user
may have more than one dedicated channel, so these multiple channels may be transferred
in one user data frame. It also provides synchronization information and reliability by
using frame numbers to check for correct sequencing. The format of the uplink frame is
shown in Figure 6.73(a).

• Header CRC (7 bits): provides error checking on the header.
• Frame type (FT, 1 bit): indicates if this is a control (1) or data (0) frame.
• Connection frame number (CFN, 8 bits): this acts like a sequence number, and is linked
to the system frame number (SFN) used across the Uu interface at layer 1.
• Transport format indicator (TFI, 5 bits): indicates the TFI for each of the data channels
within the payload, extracted from the TFCI received at the physical layer.
• Transport block (TB, variable): this is the actual data block being transported. Its size
is variable and the format is as indicated by the TFI. Each transport block of each
data channel is included in the payload. The transport blocks are padded out to a
byte boundary.
• Quality estimate (QE, 8 bits): this is calculated from the BER of either the transport
channel or the physical channel. The choice is dependent on what was selected during
the NBAP/RNSAP channel establishment procedure. The transport channel BER is the
measured bit error rate on the DPDCH, across a transmission time interval (TTI). It
provides a measure of how much error has been introduced to the data by traversing the
air interface. By including such information, this provides the SRNC with a measure
of the quality of the air interface, which can be used for both macrodiversity and outer
loop power control. The physical BER measurement is performed on the DPCCH and
provides a more general quality estimate of the air interface.
• CRC indicator (CRCI, 1 bit): in addition to the QE, the uplink FP also includes an
indicator for each TB of each DCH to inform the SRNC whether the CRC check on
the data across the air interface was correct (0) or not (1). If there was no CRC check
across the air, then the ¬eld is set to 0.
• Payload CRC (16 bits): this is an optional CRC check on the payload contents.
350 UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM


Header CRC FT Header CRC FT
CFN CFN
header header
spare TFI - DCH 1 spare TFI - DCH 1




...




...
spare TFI - DCH n spare TFI - DCH n
First TB of DCH 1 First TB of DCH 1

...




...
First TB of DCH 1 Pad First TB of DCH 1 Pad
...




...
Last TB of DCH 1 Last TB of DCH 1
...




...
Last TB of DCH 1 Pad Last TB of DCH 1 Pad
...




<<

. 72
( 132 .)



>>