Call Control
Initial Time Alignment
At start of the downlink SACCH transmission, an initial ordered TA
value (received at channel activation) is used in the L1 header of the
SACCH block.
Dynamic Time Alignment
Three inputs are used to calculate the new/next TA order value included
in the L1 header of the downlink SACCH block /GSM:04.04:7.1/:
• The Access Delay measurements on all NBs (normal bursts),
which are received since the last calculation (one SACCH
reporting period)
• The actual used (by MS) TA value which is received in the L1
header /GSM:04.04:7.2/ of the uplink SACCH block
• The previous/init ordered TA value to MS
The ordered TA value must not be changed more than 1 step from the
TA/GSM:05.10:5/ previously ordered.
38.3.3 Asynchronous Handover Detection
By means of the HANDOVER DETECTION procedure /GSM:-
08.58:4.3/, the RBS detects and reports when the MS, at asynchronous
handover, is connecting to a "target" dedicated resource.
Channel combinations supported are defined in section Channel
Activation above.
The RBS measures the access delay of handover accesses received.
This information is included in the PHYSICAL_INFORMATION
message to MS and the HANDOVER_DETECTION message to BSC.
Acceptance of a HANDOVER_ACCESS message is based on:
• Handover Reference (received in HANDOVER message), which
shall match the value received in the related
CHANNEL_ACTIVATION from BSC
• Measured Access Delay, which must not exceed 63 (≥64 not
accepted)
To accept the MS handover access, RBS shall receive:
• Two out of three acceptable HANDOVER_ACCESS messages
(ABs) for channel combination (i)
• Two out of four acceptable HANDOVER_ACCESS messages
(ABs) for channel combination (v) and (vii)
The TA difference between acceptable Access Bursts must be less than
or equal to 4 bit periods.
On acceptance of the MS handover access, the RBS takes the following
actions:
• Opens all logical channels for transceiving on the air (start
Normal Burst reception) and starts active channel measurements
on the dedicated resource
EN/LZT 123 2697 R5A
1998-08-13
247 (306)
© Ericsson Radio Systems AB
— All Rights Reserved —
To Next Page
Loading...
