EUL SCHEDULAR

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WCDMA

Eul Scheduler

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

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The uplink resources managed by the EUL scheduler are:• The air interface (Uu) interference load• The RBS hardware consumption as measured in Channel Elements (CEs)

E-DPDCH carries user data (scheduled and non-scheduled;ex RRC signalling);

E-DPCCH carries control information (ex: “happy bit” - signals to the EUL scheduler whether the UE is happy with the current scheduled rate, or if it requires an increase.)

.E-AGCH - Absolute Grant Channel. An absolute grant (AG) is sent by the EUL scheduler to a terminal to

give the user an absolute rate allocation expressed as an E-DPDCH/DPCCH amplitude ratio. It is only sent from the EUL scheduler in the serving cell. The more E-AGCH channels that are configured per cell, the more AGs that can be sent in parallel in the same 10 ms period.The AG contains the following:• The E-RNTI (identification) of the terminal the grant is targeting;• The maximum amplitude ratio the terminal is allowed to use;

E-RGCH - Relative Grant Channel carries relative grants to a single terminal or to a group of terminals. If the EUL scheduler detects overload, it can send a DOWN command, indicating to an E-DCH user to reduce its rate with a predefined step. The command is sent to one or many users that have a non-serving link in the cell.

EUL Scheduler


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EUL Scheduler

The scheduler operates on cell level for the air interface interference load. The EUL scheduler itself is responsible for allocation of the available base station pooled hardware resources and the allocation of UL air interface load consumption on the cell level towards E-DCH users.


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EUL Scheduler

1) It is assigned an initial minimum hardware allocation and a scheduled grant of zero kbps

2) UE request more rate (“happy bit”)3) UE is assigned to a minimum hardware allocated

= 32kbps4) UE request more rate (“happy bit”)5) EUL scheduler checks all resources6) EUL scheduler assigne UE to eulTargetRate7) UE request more rate (“happy bit”)8) The increase in the scheduled rate with the

maximum step size at each consecutive scheduling action continues until there are no more resources to schedule, or the UE signals that it is “happy”, or the grant reaches the maximum value that it is allowed for the user (MBR).

9) At the point when the UE has finished sending and there is no more datacoming from the terminal the scheduled grant is eventually reduced (back)to zero kbps. However, the minimum hardware allocation is kept until theconnection is released.


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ReschedulingIt is performed by a decrease in

rate for one E-DCH user to accommodate an increase in the rate for another E-DCH user.

An inactive user with a high scheduled rate is reduced to a scheduled rate corresponding to the minimum hardware allocation level and released resources can then be allocated to other users.

An inactive user with a scheduled rate already corresponding to the minimum hardware allocation is after another short period given a scheduled rate of zero kbps.

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eulTargetRate = 128 eulLowRate = 32 eulMaxAllowedSchRate = 3968(435 sites) and 4480(19

sites) Obs.: With the current value of 10msTTi the maximum

rate is 1448kbps.

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User Priority Handling

The internal priority for a user is determined by:

1. Granted rate for that user and

2. The Scheduling Weight eulSchedulingWeight .

A lower rate means a higher internal priority. A lower Scheduling Weight means a lower internal priority

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Overload HandlingIf overload occurs (i.e. Uu or HW),

the EUL scheduler then chooses:1) The E-DCH users with the lowest

priority in the resources 2) Reduces the Uu rates and/or the

hardware consumption rates3) If necessary more users are

selected in the reverse priority order (the lowest priority first).

4) Tries to reduce to low rate eulLowRate.

5) If necessary it reduces users down to zero rate

6) A cell may have both serving and non-serving users downgraded

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UL Uu Load EstimatorProvides the EUL scheduler with information so that UL

interference can be kept within limits.

Two types of headroom are estimated:• “Own cell interference” .The maximum own cell

interference tolerated is eulMaxOwnLoad. If the own cell interference is above this level, the headroom reported to the EUL scheduler is zero.

• “Coverage” estimate. The purpose with this estimate is to dynamically allow as much EUL throughput as possible without compromising the planned cell coverage. The maximum total interference tolerated is eulMaxRotCoverage.

The load is converted according to the formula:

L =1 - 10-B_IUL/10

BIUL = noise rise in dB L = load

Ex: 3 dB noise rise corresponds to 50% of the pole capacity8 dB noise rise corresponds to 86% of the pole capacity.

eulMaxOwnUuLoad =80 (8dB) eulMaxRotCoverage = 100 (10dB).

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EUL SCHEDULAR