TBO

1 © Nokia Siemens Networks

R8 Optimization

Telcel AMX, México


• Optimization algorithm is used to adapt PS DCH channel bit rate using radio bearer reconfigurations so that the bit rate meets the actual capacity requirement

• Channel can be even released if the utilization of the channel is low enough

• Optimization is based on throughput measurement of the channel

• Optimization is performed in both uplink and downlink.

• Throughput-based optimisation works in parallel with the inactivity timer. The NRT DCH has to be totally silent during the inactivity period until it is released.

100%

downgrade_threshold 1

downgrade_threshold 2

release_threshold

ave_throughput

send release request to PSsend downgrade request to PS

Optimized usage of BTS HW, Iub transmission and DL channelisation code

resources

Optimized usage of BTS HW, Iub transmission and DL channelisation code

resources

PS - Throughput based optimization

• Adapts the allocated DCH to the data bit rate

• Better utilization of radio, transport and HW resources

• Triggers transition to FACH when throughput is sufficiently low – without check of inactivity timers

• Applied also to HSDPA return channel (controlled with parameter)


PS - Throughput based optimization ExampleFigure below shows case where 85k UDP data stream is send and throughput based optimization is activated with default values. Blue line show PPP layer throughput, and red dotted line present DL bit rate currently allocated.

Yellow dots with the number are related to RB reconfiguration events, and explained below

1. Initial bit rate is allocated (64kbps)

2. UG to Maximum bit rate (384kbps)

3. Uplink is DG from 64 kbps (initial) to 8 kbps (7s) - DG is happening due the lower throughput measurement but DCHutilguardtime (6s) is delaying DG

4. DG DL 384 kbps to 256 kbps. This DG is based on upper throughput measurements. Upper downgrade threshold for 384 kbps is 256 kbps which happens around 7sec. after maximum was allocated.

5. DG DL 256 kbps to 128 kbps. This downgrade is also based on upper throughput measurements. Upper downgrade threshold for 256 kbps is 128 kbps. This happens around 7sec. after previous downgrade from 384 kbps to 256 kbps.

6. Release to CELL_FACH, this event is based on release throughput measurements


PS - Flexible Upgrade of NRT DCH data rate• Flexible upgrade of NRT DCH

data rate enables bit rate upgrades from all bit rate levels

• Upgrade is triggered if the traffic volume in the UE or RNC RLC buffer exceeds the defined threshold.

• Threshold can be defined separately for each bit rate in DL and in UL

High Throughput Measurement

• Unnecessary upgrades can be avoided with the high throughput measurement:

• Upgrade can be allowed only if the current DCH utilization is above threshold

time

time

time

Maximized end-user throughput and utilization of Maximized end-user throughput and utilization of radio, BTS HW and Iub transmission resourcesradio, BTS HW and Iub transmission resources

Maximized end-user throughput and utilization of Maximized end-user throughput and utilization of radio, BTS HW and Iub transmission resourcesradio, BTS HW and Iub transmission resources

DCH bit rate

Throughput / DCH bit rate

NRT DCH

Traffic volume

RLC buffer

Bit rate is upgraded

DCH utilization

Operator defined thresholds

• Flexible upgrade provides a mechanism to control the bit rate upgrades in order to avoid unnecessary ones.

• Throughput is checked along with capacity upgrade requests.

• Applied also to HSDPA return channel (controlled with parameter)


Throughput Based Optimization

• DCHUtilBelowDowngradeThr: This parameter defines together with the RNP parameters DCHUtilUpperDowngradeThr(BitRate) and DCHUtilLowerDowngradeThr(BitRate) the upper and lower downgrade thresholds for the upper and lower throughput measurements. The threshold below downgrade rate is defined as % down from upper/lower target downgrade bit rate.

The value is common for both "upper" and "lower" throughput measurements and for following NRT DCH bit rates: 32 kbps, 64 kbps, 128 kbps, 256 kbps, and 384 kbps.

Example: The allocated NRT DCH bit rate is 384 kbps and if the upper downgrade bit rate is 256 kbps, the lower downgrade bit rate is 64 kbps and the threshold below downgrade bit rate is 4%. So the downgrade upper threshold for the upper throughput measurement is (256 kbps - 256 kbps*4/100) ~246 kbps and the downgrade lower threshold for the lower throughput measurement is (64 kbps - 64 kbps*4/100) ~61 kbps.

• DCHUtilLowerAveWin (128, 256, 32, 384, 64): This parameter defines the lower sliding measurement window size for the NRT DCH. The lower throughput measurement measures the number of received/sent bits in UL/DL NRT DCH during the sliding measurement window period. The special value 0 of this parameter means that the lower throughput measurement is not actived for the NRT DCH.


Throughput Based Optimization

• DCHUtilLowerTimeToTrigger (128, 256, 32, 384, 64): This parameter defines the period of the time between timing of the lower throughput goes below the lower bit rate threshold and the timing of sending lower downgrade request for the NRT DCH.

• DCHUtilMeasGuardTime: This parameter defines the period of time during which downgrading the allocated DCH bit rate of the NRT RB is denied due to throughput measurements. Guard timer is started if a bit rate other than DCH 0/0 kbps is allocated for the NRT RB. Guard timer is restarted when the NRT DCH bit rate is downgraded or upgraded.

• DCHUtilUpperAveWin (128, 256, 32, 384, 64): This parameter defines the upper sliding measurement window size for the NRT DCH. The upper throughput measurement measures the number of received/sent bits in UL/DL NRT DCH during the sliding measurement window period. The special value 0 of this parameter means that lower throughput measurement is not actived for the NRT DCH.

• DCHUtilUpperTimeToTrigger (128, 256, 32, 384, 64): This parameter defines the period of the time between timing of the upper throughput goes below the upper bit rate threshold and the timing of sending upper downgrade request for the NRT DCH.


Flexible Upgrade

• DCHUtilHighAveWin: This parameter defines the sliding measurement window size for the high throughput measurement in uplink and downlink NRT dedicated channels. The high throughput mesurement measures the number of received/sent bits in UL/DL NRT DCH during the sliding measurement window period. The measurement window size is common for all NRT DCH data rates. The special value 0 means that high throughput measurement is not active.

• Time to Trigger for the high throughput measurement is respectively 0.2 s, which means that the measured bit rate over 1.2 s needs to be greater than the high throughput threshold before the NRT DCH data rate can be upgraded. Zero (0) means high throughput measurement is inactive

• DCHUtilHighBelowNRTDataRateThr: This parameter defines the threshold for the high throughput measurement.

The threshold below the NRT DCH data rate is defined as % down from the NRT DCH data rate.

The value is common for all NRT DCH data rates.

Example: The allocated NRT DCH data rate is 128 kbps and the threshold below the NRT DCH data rate is 4%. So the threshold for the high throughput measurement is (128 kbps - 128 kbps*4/100) ~123 kbps.


Throughput Based Optimization / Flexible UpgradeMO

ClassParameter Name Abbreviated Name Modification RNC VJZR1 RNC CASR1 Recommendation Comments

RNCThreshold below the downgrade bit rate DCHUtilBelowDowngradeThr On-line 6 6 4%

This recommendation aims to speed up bit rate downgrade once utilization is below defined threshold. Combined with others TBO parameters brings a better DCH utilization (higher throughput per

Radio Bearer) and therefore reduces CE consumption.

RNCWindow size for the high throughput measurement DCHUtilHighAveWin On-Line 100 (1000 ms) 100 (1000 ms) 500 ms

Related to High Throughput Measurements. It means that the measured bit rate over DCHUtilHighTimeToTrigger +

DCHUtilHighAveWin needs to be greater than the high throughput threshold before the NRT DCH data rate can be upgraded.

RNCThreshold below the NRT DCH

data rate DCHUtilHighBelowNRTDataRateThr On-line 6 6 4%

Related to High Throughput Measurements. This recommendation aims to retard bit rate upgrade once utilization is below defined

threshold.

RNCLower measurement window size for NRT DCH of 128 kbps DCHUtilLowerAveWin128 On-Line 200 (2000 ms) 200 (2000 ms) 1000 ms


RNCLower measurement window

size for NRT DCH of 32 kbps DCHUtilLowerAveWin32 On-Line 200 (2000 ms) 200 (2000 ms) 1000 ms


RNCLower measurement window

size for NRT DCH of 64 kbps DCHUtilLowerAveWin64 On-Line 200 (2000 ms) 200 (2000 ms) 1000 ms

RNCLower time to trigger for the

NRT DCH of 128 kbps DCHUtilLowerTimeToTrigger128 On-Line 140 (1400 ms) 140 (1400 ms) 800ms









RNCGuard time for throughput

measurement DCHUtilMeasGuardTime On-Line 6 6 2s

If TimeToTrigger and AveWin are reduced as recommended above, then DCHUtilMeasGuardTime should be reduced to avoid being a

bottleneck.

RNCUpper measurement window size for NRT DCH of 128 kbps DCHUtilUpperAveWin128 On-Line 200 (2000 ms) 200 (2000 ms) 1000ms


RNCUpper measurement window

size for NRT DCH of 32 kbps DCHUtilUpperAveWin32 On-Line 200 (2000 ms) 200 (2000 ms) 1000ms


RNCUpper measurement window

size for NRT DCH of 64 kbps DCHUtilUpperAveWin64 On-Line 200 (2000 ms) 200 (2000 ms) 1000ms

RNCUpper time to trigger for the

NRT DCH of 128 kbps DCHUtilUpperTimeToTrigger128 On-Line 400 (4000 ms) 400 (4000 ms) 2000ms









It's related to Throughput Based Optimization (TBO) feature. This recommendation aims to speed up bit rate downgrade once

utilization is below defined threshold. Combined with others TBO parameters brings a better DCH utilization (higher throughput per


Actual Value

It's related to Throughput Based Optimization (TBO) feature. This recommendation aims to speed up bit rate downgrade once

utilization is below defined threshold. Combined with others TBO parameters brings a better DCH utilization (higher throughput per


New Value

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