Transcript of EDCH UL OLPC_FNI_RNCLevel_West.ppt
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* | EDCH UL OLPC | September 2013
Agenda
Introduction
Fast decrease mechanism
Agenda
Introduction
Fast decrease mechanism
Introduction
PS traffic has increased over the past years. User need for high
uplink throughput has pushed a lot of operators to request for
HSUPA.
HSUPA uses an uplink enhanced dedicated channel (E-DCH) on which it
employs link adaptation methods similar to those employed by
High-Speed Downlink Packet Access HSDPA, namely:
shorter Transmission Time Interval enabling faster link
adaptation;
HARQ (hybrid ARQ) with incremental redundancy making
retransmissions more effective.
Similarly to HSDPA, HSUPA uses a packet scheduler, but it operates
on a request-grant principle where the UEs request a permission to
send data and the scheduler decides when and how many UEs will be
allowed to do so.
A request for transmission contains data about the state of the
transmission buffer and the queue at the UE and its available power
margin. However, unlike HSDPA, uplink transmissions are not
orthogonal to each other
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Introduction
At the Physical Layer, HSUPA introduces new channels E-AGCH
(Absolute Grant Channel), E-RGCH (Relative Grant Channel), F-DPCH
(Fractional-DPCH), E-HICH (E-DCH Hybrid ARQ Indicator Channel),
E-DPCCH (E-DCH Dedicated Physical Control Channel) and E-DPDCH
(E-DCH Dedicated Physical Data Channel).
E-DPDCH is used to carry the E-DCH Transport Channel; and E-DPCCH
is used to carry the control information associated with the
E-DCH.
In order to maintain Ue call from being dropped, power control on
channels is performed.
The objective of power control is to maintain service SIR almost
equal to SIR target defined for each service.
The objective of the following feature is to decrease UL EDCH SIR
for non active users, therefore enhancing Ue battery lifetime and
enhancing a little UL RSSI.
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Agenda
Introduction
Fast decrease mechanism
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Outer loop power control principle
The general principle of UL OLPC for E-DCH with Alcatel-Lucent
implementation is summarized in the figure below.
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Outer loop power control principle
The UL OLPC algorithm takes into account the link quality of each
UL transport channel established (of DCH and/or E-DCH type) for the
considered user, so that finally the link quality of each UL
transport channel fulfills a target link quality specified
separately for each channel. This algorithm is often referred to as
“multiple reference transport Channel UL OLPC algorithm”.
Regarding the DCH transport channels, for each channel, a target
BLER is set to a value tunable by the customer, and the BLER is
monitored by an UL OLPC Machine dedicated to this channel. The BLER
of each DCH is derived by the RNC based on the CRC Indicator (CRCI)
of the selected UL DCH data frame (the NodeB computes a CRCI for
each transport block it receives from the air interface and sends
it to the RNC through Iub-FP. In addition, several data frames
transporting the same user data can be sent by the different NodeBs
having a link with the mobile; hence the CRCI retained by the RNC
is the CRCI carried by the UL DCH data frame selected by the
RNC).
A Partial UL SIR Target is derived each TTI (TTI period depends on
the DCH channel considered) by the UL OLPC Machine of each DCH
channel, so that BLER on a DCH channel would converge toward its
target BLER if this Partial UL SIR Target were applied as the UL
SIR Target.
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Outer loop power control principle
The main difference with respect to UL OLPC for DCH transport
channels is that, for the E-DCH channel, the quantity monitored is
not the BLER but the number of HARQ retransmissions instead, and
the link quality target is not a target BLER but a target average
number of HARQ retransmissions. This is possible since the
information concerning the number of HARQ retransmissions (for each
MAC-e PDU correctly received or at HARQ failure detection) is sent
by the NodeB to the RNC through Iub FP, via the N of HARQ
Retransmissions IE enclosed in E-DCH UL Data Frames.
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Agenda
Introduction
Fast decrease mechanism
Fast decrease mechanism
UA6 34249 introduces a “Fast Decrease” mechanism for Partial SIR
Target(s) related to MAC-d flow(s) carried on E-DCH. This mechanism
allows a faster convergence of the UL SIR Target when UE is in good
radio conditions. The principle of this mechanism is as
follows.
For the considered MAC-d flow carried on E-DCH, if more than
edchNrOfConsecutiveZeroHarqReTxThreshold MAC-es PDUs are received
at the RNC without any HARQ retransmission or HFI (HARQ Failure
Indication), then the “Fast Decrease” mechanism is triggered, i.e.
the Partial SIR Target related to this MAC-d flow is updated
according to a specific formula
Once the triggering condition for “Fast Decrease” mechanism has
been fulfilled, the Partial SIR Target of the considered MAC-d flow
is updated according to above specific formula at each consecutive
E-DCH Data Frame received without any HARQ retransmission or
HFI.
“Fast Decrease” mechanism is cancelled as soon as an E-DCH Data
Frame is received with at least one HARQ retransmission or with an
HFI, and the Partial SIR Target is then updated according to the
usual formula
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Agenda
Introduction
Fast decrease mechanism
Feature overview
The fast decrease mechanism didn’t take into account updating
inactive users UL SIR.
The improvement introduced by this feature is to make UL SIR
decrease rapidly also for non active users.
The introduction of a timer to manage the case where nothing is
received by RNC was the solution encountered to enhance the “Fast
Decrease” mechanism.
After expiring the above mentioned timer, a new “Fast Decrease”
mechanism is triggered so the SIR target is reduced to the
limit.
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Feature overview
The UL SIR Target values of all existing MAC-d flows shall be
preserved to their latest values from last activity period before
triggering the new “Fast Decrease” process.
Traffic inactivity must persist for a configurable period of time
before applying the fast decreased power.
This can be configured using the parameter
eDCHOlpcInactivityTimeThreshold.
The decrease of UL SIR Target due to inactivity is limited to an
optimum value so that it does not adversely impact the performance
of UL physical control channels. This can be configured using the
parameter eDCHOlpcInactivitySIRDecreaseLimit.
If Partial_UL_SIR_Target
>eDCHOlpcInactivitySIRDecreaseLimit:
Finally, the preserved UL SIR Target values of all existing MAC-d
flows shall berestored following detection of activity, i.e.
receipt of MAC-d PDUs at RNC on any MAC-d flow. Initial power
(saved right before fast decrease process) is reinstated as soon as
traffic resumes, on any of the RAB.
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Agenda
Introduction
Fast decrease mechanism
Activation strategy
eDCHOlpcInactivitySIRDecreaseLimit set to 4 db
eDCHOlpcInactivityTimeThreshold set to 500ms
Agenda
Introduction
Fast decrease mechanism
KPI results
No change in HARQ behavior was observed after feature
activation
121085 has NO obvious impact on HARQ retransmission when
eDCHOlpcInactivitySIRDecreaseLimit is 4 db.
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KPI results
Uplink traffic didn’t affect after feature activation, and so is
missing PDUs
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KPI results
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KPI results
Enhancement in SIR distribution, as number of samples with SIR
distribution less than 7 has decreased on the other hand number of
samples less than 5 has increased, so achieving 2 Db gain in UL
SIR
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KPI results
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KPI results
Number of EDCH active users didn’t affect after feature
activation
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Agenda
Introduction
Fast decrease mechanism
Conclusion
Feature has been tested successfully
Feature benefits has been proven.
Uplink SIR distribution has enhanced, saving 2 dB for Ues and
therefore enhancing power saving for mobiles
Main KPIs didn’t affect after feature activation
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Agenda
Introduction
Fast decrease mechanism
Future steps
Roll out on the whole western region network is expected
Tuning for eDCHOlpcInactivitySIRDecreaseLimit and
eDCHOlpcInactivityTimeThreshold in order to see impact on RNC level
(mainly SIR distribution)
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