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Channel Switching

Channel Switching. Channel Switching. Capability Optimizes the utilization of radio resources, by switching UE’s to the most suitable transport channel based on traffic volume (throughput), radio resources availability, radio conditions and mobility.

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Channel Switching

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  1. Channel Switching Channel Switching Capability • Optimizes the utilization of radio resources, by switching UE’s 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). Impacting features • Admission Control • Congestion Control • Soft Handover

  2. Switch to dedicated Switch to common TTime-out Release dedicated channel Packet Packet Packet Channel Switching Channel type switching User 1 DATA Common Channel (Cell_FACH) Dedicated Channel (Cell_DCH)

  3. Channel Switching Channel rate switching Up-switche.g. 64 128 384 Kbps Down-switche.g. 384 128 64 Kbps Bit rate Distance from RBS or Load in the cell Distance from RBS or Load in the cell

  4. Channel Switching Overview of trigger mechanisms Channel SwitchingAlgorithms Down/up switch based on coverage and user activity Congestion Control Admission Control ChannelSwitching Down-switch from dedicated to common channel to resolve congestion Down-switch from one dedicated channel to another, e.g. from 64/384 to 64/128 to free up radio resources 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

  5. 1. Common to Dedicated 2b 2a 2. Dedicated to dedicated Single RAB 2b 2a 3 3. Dedicated to common 1 4. Common to Idle Mode 4 Channel Switching Single RAB State Transitions Connected Mode Dedicated Channel (Cell_DCH) Cell_DCH 64/384 kbps UL/DL Cell_DCH 64/128 kbps UL/DL Cell_DCH 64/64 kbps UL/DL Common Channel (Cell_FACH) RACH/FACH(max. 32 kbps) Idle Mode

  6. Connected Mode Dedicated Channel(Cell_DCH) Cell_DCH64/384 kbps UL/DL Cell_DCH64/128 kbps UL/DL Cell_DCH 64/64 kbps UL/DL Common Channel(Cell_FACH) RACH/FACH Channel Switching Idle Mode 1. Common to Dedicated Evaluation cont’ 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. UL RLCbuffer load Up-switch X ulRlcBufUpswitch [256 bytes] A request is sent to Admission Control to perform an up-switch from Cell_FACH to Cell_DCH 64/64 kbps or DL RLCbuffer load Up-switch X dlRlcBufUpswitch [512 bytes]

  7. Connected Mode Dedicated Channel(Cell_DCH) Cell_DCH64/384 kbps UL/DL Cell_DCH64/128 kbps UL/DL DL TX code power < [Power Alarm Threshold] – reportHysteresis while the timer is running, the down-switch request is cancelled. DL TX code power > [Power Alarm Threshold] – reportHysteresis and timer coverageTimer expires. The down-switch is executed. Cell_DCH 64/64 kbps UL/DL Common Channel(Cell_FACH) RACH/FACH Channel Switching Idle Mode 2a. Dedicated to Dedicated Coverage triggered Down-Switch Evaluation cont’ Monitors if a switch to a lower rate radio bearer is required due to coverage. DL TX code power > [Power Alarm Threshold], defined as Max Code Power – downswitchPwrMargin. A down-switch to Cell_DCH with lower bitrate is requested. Timer coverageTimer starts. Pcode

  8. Connected Mode Dedicated Channel(Cell_DCH) Cell_DCH64/384 kbps UL/DL Cell_DCH64/128 kbps UL/DL Cell_DCH 64/64 kbps UL/DL Common Channel(Cell_FACH) RACH/FACH Channel Switching Idle Mode 2b. Dedicated to Dedicated Up-Switch Evaluation Monitors if the throughput becomes close to the max user bandwidth and switch to the next higher bitrate radio bearer is required. 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 Power – downswitchPwrMargin – Estimated Power Increase – upswitchPwrMargin. Timer upswitchTimer starts. Pcode DL throughput is < 90 % of max. possible bitrate on current radio bearer OR the DL code power becomes >= [Power up-switch threshold] while the upswitchTimer is still running. The timer stops and no up-switch is executed. [2.9 dB for up-switch from 64-to-128 kbps] [4.7 dB for up-switch from 128-to-384 kbps] DL throughput is > 90 % of max. possible bitrate of current RB AND the DL code power is< [Power up-switch threshold] when timer upswitchTimer expires. The up-switch request is sent Admission Control.

  9. UL and DL throughput increases above threshold downswitchTimerThreshold before the timer expires. The timer stops and no down-switch occurs. Connected Mode Dedicated Channel(Cell_DCH) Cell_DCH64/384 kbps UL/DL Cell_DCH64/128 kbps UL/DL Cell_DCH 64/64 kbps UL/DL Common Channel(Cell_FACH) RACH/FACH Channel Switching Idle Mode 3. Dedicated to Common Evaluation Monitors if a switch from a Cell_DCH to Cell_FACH is required due to a decrease in transmitted user data. DownswitchTimer DownswitchTimer UL and DL throughput falls below threshold defined by parameter downswitchThreshold and timer downswitchTimer starts. The timer expires and a request is issued to down-switch from common to dedicated channel.

  10. Connected Mode Dedicated Channel(Cell_DCH) Cell_DCH64/384 kbps UL/DL Cell_DCH64/128 kbps UL/DL Cell_DCH 64/64 kbps UL/DL Common Channel(Cell_FACH) RACH/FACH Channel Switching Idle Mode 4. Common to Idle Evaluation Monitors if a switch from Cell_FACH to Idle mode is required due to a complete lack of user data transmission. If both the UL and DL throughput is zero for a duration specified by parameter inactivityTimer, a request is sent to the Connection Handling function and further to Core via Iu, to release the connection.

  11. Channel Switching Multi-RAB Down-switch Evaluation Monitors if a release (or downswitch) of PS I/B RAB shall be initiated due to lack of PS 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) or downswitchTimerSp (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/B RAB (or to dowswitch if multiRabSp0Available) . The timer starts again in case there is any throughput in UL or DL before the PS RAB is released.

  12. Channel Switching Multi-RAB Up-switch Evaluation Monitors if an upswitch from multi-RAB SP0 to multi-RAB SP64 shall be initiated due to data buffered in either RNC or UE. When the RLC buffer load in the uplink exceeds the threshold value set by the parameter ulRlcBufUpswitchMrab, a measurement report is sent from the UE. An upswitch request is issued 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 dlRlcBufUpswitchMrab. If the dlRlcBufUpswitchMrab parameter is set to 0, the MultiRAB Upswitch Evaluation algorithm is turned off, meaning that no upswitches from SP0 will occur, irrespective of the RLC buffer load.

  13. stand-alone interactive RAB speech + interactive RAB HS speech + 384/HS 384/HS DCH 64/384 speech + 64/HS 128/128 64/HS speech + 64/64 64/128 speech + 0/0 64/64 Low/No throughput Measurement for down Switch timer period PS RAB Establishment UL throughput- based upswitch FACH Channel Switching activity/inactivity-based switching UL and/or DL coverage-triggered downswitch (DL only) IDLE Low/No RLC buffer load for Inactivity timer period DL throughput- based upswitch choice based on UE- and cell-capability Future releases

  14. Channel Switching Parameters related to Channel Switching • dlRlcBufUpswitch,ulRlcBufUpswitch: 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). • downswitchPwrMargin: margin, in relation to maximum allowed code power, which indicates a high power usage(unit: 0.5 dB) • coverageTimer :Time during which the power is allowed to be high before a downswitch (DCH to DCH) is issued (unit: second) • reportHysteresis: Reporting hysteresis for the code power measurements in the node B (unit: 0.5 dB) • upswitchPwrMargin: upswitch (DCH to DCH) power margin (unit: 0.5 dB) • upswitchTimer: Time during which the bandwidth utilization is allowed to be high before an upswitch request is issued (unit: second) • downswitchThreshold: threshold for channel switching from dedicated channels to FACH/RACH (unit: kbps) • downswitchTimer: sets the time during which throughput has to be low in order to trigger a downswitch fro DCH to FACH (unit: decisecond) • downswitchTimerThreshold: timer threshold to achieve hysteresis for channel switching from dedicated channel to FACH/RACH (unit: kbps) • inactivityTimer: timer for sending of IU RELEASE REQUEST message to the CN for UE in common state (unit: minutes)

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