CSSR CDR (2).ppt

CSSR and CDR KPI
Ericsson solution for call establishment
securisation & inter RNC mobility

Workshop IUR - Inter RNC Mobility | Commercial in confidence | 2/2882-4/FCP 121 5525 Uen, Rev PA1 | 2010-12-10 | Page 2
Introduction
› CSSR and CDR are par of the top KPIs of a mobile
network
› Operators’ networks based on Ericsson solution all over
the world get best in class CSSR and CDR KPI values
› These KPIs values are obviously not only dependent of the
supported features but also of the engineering &
optimisation of the network
› Ericsson does support several key features to maximize
call extablishment success rate and does provide proper
inter RNC mobility solution to minimize CDR in mobility
› This package presents these solutions

Ericsson features to maximize CSSR
› Based on Ericsson experience in many networks in the world, the value of the CCSR
KPI can be in a range of [+97% to 99%] in a well optimized network.
› Since the CSSR formula is composed of 3KPIs a package of several features
supported by Ericsson improve SDCCH congestion, SDCCH drop and TCH
assignement success rate
› Even though « 2nd assignment request on TCH » feature can favorabily impact the
CSSR, Ericsson does not support this feature as Ericsson support already several
features that lead to reach best in class CSSR KPI values
› Formula recommended by E///:
CSSR=SDCCH seizure*(1-SDCCH drop)*TCH assignment success rate
– CSSR_Global=100*((CCALLS-CCONGS)/(CCALLS))*(1-(CNDROP/CMSESTAB))*
(TCASSALL/TASSALL) ).
Features Positif Impact
ACLC Reduce congestion on SDCCH based on Dynamic channel allocation
Immediate Assignment on TCH Allocate a TCH for signaling in case of no SDCCH resources
Interference Rejection Combining (IRC) Improve the SDCCH drop due to interference
Cell Load Sharing The feature will impact indirectly TCH assignment Success Rate, by reducing congestion on the
cell, more TCH slots will be available to be assigned in case of new attempt
Assignment to Other Cell (AB,AW) It improves efficiently the TCH assignment success rate

Example of CSSR comparison
› Ericsson has swapped NSN BTS in many countries in the world already and CSSR after
the swap reach best values
› Not that CSSR is very dependent of the engineering, of the features activated and of the
optimization of the network
CSSR
CSSR GSM
97,5
98
98,5
99
99,5
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1
ERICSSON NOKIA SIEMENS

TCH assignment mechanism in E///

TCH assignment mechanism in E///
TASSREQ et TALLOC definitions:
› TASSREQ: Supervises the Assignment and Change of Channel Mode procedures in the BSC
The timer TASSREQ Started:
– On reception of a 48.008 ASSIGNMENT REQUEST (ASS_REQ) message
Stopped when :
– A 48.008 ASSIGNMENT COMPLETE (ASS_COM) message is sent to the MSC
– A 48.008 ASSIGNMENT FAILURE (ASS_FAIL) message is sent to the MSC
– A 48.008 CLEAR REQUEST (CLEAR_REQ) message is sent to the MSC
– CLEAR COMMAND is received from MSC
› TALLOC:This timer sets the minimum time between attempts to allocate a TCH resource when the first attempt has
failed. At TCH congestion and transcoder congestion .

Adaptive Configuration of logical channels -ACLC
Introduction to the feature:
The purpose of the feature is to minimize the risk of SDCCH congestion by automatically
adapting the number of SDCCHs in a cell to the demand for such channels.
Advantages:
› Dynamic dimensioning of Logical Channel (SDCCH) on demand
› Reduced SDCCH congestion
› Increase in Network Capacity
› SDCCH dimensioning becomes less critical

Adaptive Configuration of logical channels -ACLC
1-SDCCH Increase 2-SDCCH decrease

Immediate assignment on TCH
S
B T T T T P P
Congestion
T
T T T T T T T
S
T T T T T T T
T
T T T T T T T
S
B T T T T P P
T
T T T T T T T
T T T T T T T
T
T T T T T T T
T
Assign TCH to an SDCCH
This feature allows signaling to be done on a Traffic Channel (TCH).

IRC
› The purpose of Interference Rejection Combining (IRC) is to improve
performance on the uplink in radio environments limited by interference.
› IRC minimizes the disturbance from an interferer by combining the signal received on
diverse antennas and suppressing the interfering signal.
› From an operator point of view, IRC can be used to increase capacity in a radio network
limited in the uplink, improve speech quality, and increase data throughput in the uplink.
› From a subscriber point of view, IRC gives improved speech quality, fewer dropped calls,
and increased data throughput due to fewer re-transmissions.

Cell Load Sharing
Introduction:
The feature is designed to distribute the traffic load between neighbouring cells at heavy
traffic load. This is achieved by moving established connections in a congested cell to
neighbouring cells that have enough idle resources , thereby reducing the high load peaks in
the cell.
MSs near cell border
Remark: The feature will impact indirectly and positively the TCH assignment
Success Rate, as by reducing congestion on the cell, more TCH slots will be
available to be assigned in case of new attempt

CLS-Parameter setting
Nominal cell
border
Maximum
CLS region
100% IDLE TCH 100% IDLE TCH
Incoming
traffic Outgoing
traffic
CLSLEVEL
CLSACC
Thresholds for Cell Load Sharing Triggered Handovers

Cell A Cell B
TCH
SDCC
H
TCH
Assignment to Other Cell
The ASSOC feature operates at call set-up, during which a TCH is to be
assigned. (ASSOC = a handover from the SDCCH in originating cell
directly to a TCH, in target cell.)
The target cell is either ranked better than the serving cell in the locating
evaluations (AB), or worse (AW), .

SRNS re-location
› The CN is changed to the RNC that controls the cells constituting the active set
› There are two variants of this mobility, the first one called “Core Network Hard
Handover” (CNHHO), or “SRNS re-location, UE involved”, and the other one called
“SRNC/DRNC mobility followed by SRNS re-location”, or “SRNS re-location, UE
not involved”, which requires the Iur connection
› Ericsson implements the “Hard Handover via the Core Network”, also referred to
as “SRNS relocation, UE involved”

Example of CDR comparison
› Ericsson has swapped NSN Node B in many countries in the world already
and CDR after the swap reach best values
› Not that CDR is very dependent of the engineering, of the features activated
and of the optimization of the network
Caídas 2G Voz
0,6
0,7
0,8
0,9
1
1,1
1,2
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1
ERICSSON NOKIA SIEMENS
CDR

SRNS re-location
› Estimates of the execution time for SRNS Relocation indicate that an SRNS
Relocation takes about 5 sec to execute. During this time neither update of the
active set nor channel rate switch may be performed (the radio connection with a
UE must remain unchanged)
› Radio resource management algorithms such as soft handover and channel
switching will be severely affected during this time
› The delay in the ASU procedure will cause a user moving into the next cell to
increase its power and thereby both increase its own resource utilization
NO ASU during SRNCS
Relocation (5sec)
DRNC
SRNC
IUR (in case of SRNS relocation,
UE not involved)
It has been estimated that a delay
of the handover decisions by 400
ms causes an increase of the
mean downlink power around
50% - 60%

iur vs srns relocation
IUR HOT TOPICS
› Transmission usage
– Ability to perform AAL2 switching minimizes the need for over-dimensioning of IUR
links;
– The increased UTRAN transmission (UP and CP) caused by IUR links compared to
SRNS re-location (UE involved) is calculated to be:
› between 5% - 8% in DL; between 5% - 12% in UL
› Inter-PLMN connections
– Ericsson includes the CNHHO feature in order to maintain standard accounting for
the inter-operator connections, even though post-processing of CDR’s could solve
the accounting issue in case of Iur;
› Congestion & Admission control
– 3GPP standards support congestion control algorithm over the Iur
› Signalling delay
– Any delay caused by Iur is in the order of a few milliseconds
› Multi-RAB packet scheduling over the Iur
– Iur does not limit packet scheduling

iur vs srns relocation
SRNS RE-LOCATION HOT TOPICS
› Large capacity margins are required in the RNC border regions
– It’s not possible to optimize the radio connection during the SRNS re-location
procedure (which can take up to 2-5 seconds);
– It leads to loose capacity and to affect the quality of the connections
› More interfaces involved
– Ericsson believes that inter-operability in the SRNS re-location case is more complex
than in case of IUR
– SRNS re-location requires interoperability on Layer 3, while IUR requires
interoperability on layer 1 and 2 only
– If only one of the many messages through the different interfaces fails, the complete
SRNS re-location is terminated

CSSR CDR (2).ppt

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