channel switching
DESCRIPTION
UMTSTRANSCRIPT
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1/14RAN Feature Presentation Jul 27, 2005 1
Channel Switching
Capability
Optimizes the utilization of radio resources, by switching UEs to the
most suitable transport channel based on traffic volume (throughput),
radio resources availability, radio conditions and mobility.
Only applies to PS data (Interactive/background).
Channel Switching
Impacting features
Admission Control Congestion Control
Soft Handover
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Channel type switching
DATA
Common Channel (Cell_FACH)
Packet Packet Packet
Dedicated Channel (Cell_DCH)
TTime-out
Release dedicatedchannel
Switch to
common
Switch to
dedicated
User 1
Channel Switching
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Channel rate switching
Distance
from RBS
or
Load in
the cell
Down-switch
e.g. 384 128 64 Kbps
Up-switch
e.g. 64 128 384 Kbps Bit rate
Distance
from RBSor
Load in
the cell
Channel Switching
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Overview of trigger mechanisms
Channel Switching
Down-switch from dedicated
to common channel to resolvecongestion
Admission Control
Down-switch from one
dedicated channel to another,e.g. from 64/384 to 64/128 to
free up radio resources
Channel SwitchingAlgorithms
Congestion Control
Soft Handover
Down-switch from 64/384 or 64/128 to
64/64 if Admission Control denies adding
a radio link to the Active Set
Channel
Switching
Down/up switch based on
coverage and user activity
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Single RAB State Transitions
Channel Switching
Idle Mode
RACH/FACH
(max. 32 kbps)
Common Channel (Cell_FACH)
Cell_DCH 64/64 kbps UL/DL
Cell_DCH 64/128 kbps UL/DL
Cell_DCH 64/384 kbps UL/DL
Dedicated Channel (Cell_DCH)
Connected Mode
1. Common to Dedicated
1
2. Dedicated to dedicated
Single RAB2b
2b 2a
2a
3. Dedicated to common
3
4. Common to Idle Mode
4
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1. Common to Dedicated Evaluation cont
Channel Switching
Monitors if the UE shall be switched from a common to a dedicated transport
channel due to large amount of user data buffered in the RNC or the UE.
or
UL RLC
buffer load
DL RLC
buffer load
u lRlcBufUpswi tch [256 by tes]
d lR lcBufUpswi tch [512 by tes]
X
XUp-switch
Up-switch
A request is sent to
Admission Control to
perform an up-switch
from Cell_FACH to
Cell_DCH 64/64 kbps
Idle Mode
RACH/FACH
Common Channel
(Cell_FACH)
Cell_DCH
64/64 kbps UL/DL
Cell_DCH
64/128 kbps UL/DL
Cell_DCH
64/384 kbps UL/DL
Dedicated Channel
(Cell_DCH)
Connected Mode
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2a. Dedicated to Dedicated Coverage triggered
Down-Switch Evaluation cont
Channel Switching
Monitors if a switch to a lower rate radio bearer is required due to coverage.
Idle Mode
RACH/FACH
Common Channel
(Cell_FACH)
Cell_DCH
64/64 kbps UL/DL
Cell_DCH
64/128 kbps UL/DL
Cell_DCH
64/384 kbps UL/DL
Dedicated Channel
(Cell_DCH)
Connected Mode Pcode
DL TX code power > [Power Alarm Threshold], defined as Max Code Power
downswi tchPwrMargin. A down-switch to Cell_DCH with lower bitrate is
requested. Timer coverageTimer starts.
DL TX code power < [Power
Alarm Threshold]
reportHysteresiswhile the
timer is running, the down-
switch request is cancelled.
DL TX code power > [Power Alarm
Threshold]reportHysteresisand
timer coverageTimer expires. Thedown-switch is executed.
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2b. Dedicated to Dedicated Up-Switch Evaluation
Channel Switching
Monitors if the throughput becomes close to the max user bandwidth and switch to
the next higher bitrate radio bearer is required.
Idle Mode
RACH/FACH
Common Channel
(Cell_FACH)
Cell_DCH
64/64 kbps UL/DL
Cell_DCH
64/128 kbps UL/DL
Cell_DCH
64/384 kbps UL/DL
Dedicated Channel
(Cell_DCH)
Connected Mode
DL throughput is > 90 % of max. possible bitrate on current radio bearer
AND the DL code power is < [Power up-switch threshold]
reportHysteresis, where the [Power up-switch threshold] is defined as Max
Code Powerdownswi tchPwrMarginEstimated Power Increase
upswi tchPwrMargin. Timer upswi tchTimerstarts.
Pcode
DL throughput is < 90 % of
max. possible bitrate oncurrent radio bearer OR
the DL code power
becomes >= [Power up-
switch threshold] while the
upswi tchTimeris still
running. The timer stops
and no up-switch is
executed.
DL throughput is > 90 % of max. possible bitrate of current RB AND the DL code power is
< [Power up-switch threshold] when timer upswi tchTimerexpires. The up-switch request is sent Admission Control.
[2.9 dB for u p-switc h from 64-to-128 kbps]
[4.7 dB for u p-switc h from 128-to-384 kbps]
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3. Dedicated to Common Evaluation
Channel Switching
Monitors if a switch from a Cell_DCH to Cell_FACH is required due to a decrease
in transmitted user data.
UL and DL throughput falls below
threshold defined by parameter
downswitchThresholdand
timer downswitchTimerstarts.
UL and DL throughput increases
above threshold
downswitchTimerThreshold
before the timer expires. The
timer stops and no down-switch
occurs.
The timer expires and a request
is issued to down-switch from
common to dedicated channel.
DownswitchTimerDownswitchTimer
Idle Mode
RACH/FACH
Common Channel
(Cell_FACH)
Cell_DCH
64/64 kbps UL/DL
Cell_DCH
64/128 kbps UL/DL
Cell_DCH
64/384 kbps UL/DL
Dedicated Channel
(Cell_DCH)
Connected Mode
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4. Common to Idle Evaluation
Channel Switching
If both the UL and DL throughput is zero for a durationspecified by parameter inact iv i tyTimer, a request is
sent to the Connection Handling function and further to
Core via Iu, to release the connection.
Monitors if a switch from Cell_FACH to Idle mode is required due to a complete
lack of user data transmission.
Idle Mode
RACH/FACH
Common Channel
(Cell_FACH)
Cell_DCH
64/64 kbps UL/DL
Cell_DCH
64/128 kbps UL/DL
Cell_DCH64/384 kbps UL/DL
Dedicated Channel
(Cell_DCH)
Connected Mode
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Multi-RAB Down-switch Evaluation
Channel Switching
Monitors if a release (or downswitch) of PS I/B RAB shall be initiated due to lack ofPS data throughput (zero), resulting in a single speech 12.2 kbps (or speech + PS
0/0) or CS64 RAB.
The SRNC measures the throughput in UL and DL every 500 ms.
When the throughput is zero in both UL and DL, timer
downswitchTimerUp(for CS64+PS8/8) ordownswitchTimerSp(for speech+PS64/64) starts. If there is any
throughput in UL or DL while the timer is running, the timer is
stopped.
When the timer expires, a request is sent to release the PS I/BRAB (or to dowswitch if mult iRabSp0Avai lable) . The timer
starts again in case there is any throughput in UL or DL before
the PS RAB is released.
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Multi-RAB Up-switch Evaluation
Channel Switching
Monitors if an upswitch from multi-RAB SP0 to multi-RAB SP64 shall be initiateddue to data buffered in either RNC or UE.
When the RLC buffer load in the uplink exceeds the threshold
value set by the parameter ulRlcBufUpswi tchMrab, a
measurement report is sent from the UE. An upswitch request isissued upon reception of the measurement report. A request is
also issued when the RLC buffer load in the RNC exceeds the
threshold value set by the parameter dlRlcBufUpswi tchMrab.
If the dlRlcBufUpswi tchMrabparameter is set to 0, theMultiRAB Upswitch Evaluation algorithm is turned off, meaning
that no upswitches from SP0 will occur, irrespective of the RLC
buffer load.
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Future releases
Channel Switching
activity/inactivity-based
switching UL and/or DL
DL throughput-
based upswitch
UL throughput-
based upswitch
coverage-triggered
downswitch (DL only)
choice based on UE-
and cell-capability
IDLE
FACH
DCH
HS384/HS
64/384
64/HS
64/128
64/64
128/128
stand-alone interactive RAB
speech
+ 0/0
speech
+ 64/64
speech
+ 64/HS
speech
+ 384/HS
speech + interactive
RAB
PS RAB Establishment
Low/No RLC buffer load for
Inactivity timer period
Low/No throughput
Measurement for down
Switch timer period
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RAN Feature Presentation Jul 27, 2005 14
Parameters related to Channel Switching
Channel Switching
dlRlcBufUpswi tch,ulRlcBufUpswi tch: downlink/uplink threshold for channel switching from
FACH/RACH to a dedicated channel (unit: bytes)
dlMaxPower:maximum power on the downlink for a specific RAB. The power is relative to
the primary CPICH power. (unit: 0.1 dB).
downswi tchPwrMargin: margin, in relation to maximum allowed code power, which
indicates a high power usage(unit: 0.5 dB)cov erageTimer :Time during which the power is allowed to be high before a downswitch
(DCH to DCH) is issued (unit: second)repor tHysteresis : Reporting hysteresis for the code power measurements in the node B
(unit: 0.5 dB)
upswi tchPwrMargin: upswitch (DCH to DCH) power margin (unit: 0.5 dB)
upswi tchTimer: Time during which the bandwidth utilization is allowed to be high before an
upswitch request is issued (unit: second)
downswi tchThreshold: threshold for channel switching from dedicated channels to
FACH/RACH (unit: kbps)downswi tchTimer: sets the time during which throughput has to be low in order to trigger a
downswitch fro DCH to FACH (unit: decisecond)
downswi tchTimerThreshold: timer threshold to achieve hysteresis for channel switching
from dedicated channel to FACH/RACH (unit: kbps)
inact iv i tyTimer: timer for sending of IU RELEASE REQUEST message to the CN for UE in
common state (unit: minutes)