Channel Switching

5/23/2018 Channel Switching

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



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



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



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



Single RAB State Transitions

Channel Switching

Idle Mode

RACH/FACH

(max. 32 kbps)

Common Channel (Cell_FACH)

Cell_DCH 64/64 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



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



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.



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]



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



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



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.


12/14

RAN Feature Presentation Jul 27, 2005 12

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.


13/14


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


14/14


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)

Channel Switching

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