BSSPAR1: Chapter 12
(E)GPRS
1
© Nokia Siemens Networks
Course Objectives
•
•
•
•
Give an overview of CS and MCS coding schemes
Explain parameters required for enabling GPRS/EDGE
Explain how cell reselection is done in EGPRS
Explain the parameter for EGPRS resource allocation and the
setting of CS and PS territory parameters
• Describe parameters controlling link adaptation in GPRS and
EDGE
• Explain how power control is done in EGPRS and the
parameters controlling it
• Describe parameters for TBF release delay
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System Principles
Network elements and interfaces
Protocols
Air interface and logical channels
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(E)GPRS Network Infrastructure
MS
MSC
BSC
BTS
PSTN
SS7
Network
SMS-GMSC
SGSN
HLR/AuC
Nokia
Security GW
SGSN
Nokia
Security GW
EIR
CG
Router
Nokia IP650
sec GW
STM-1
Router
LAN
SWITC
H
Router
GPRS IP
Backbone
Network
Router
STM-1
MODEM
POOL FOR DIALUP
SGSN
Internet
Nokia
Security GW
SGSN
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Nokia IP650
sec GW
Nokia IP650 Corporate 1
Intranet
sec GW
Nokia
Security GW
MODEM
POOL FOR DIALUP
LIG
GGSN
GGSN
Router
DNS
Corporate 2
Intranet
(E)GPRS Network Elements and Primary Functions
SGSN
• Mobility Management
• MS Authentication
• Ciphering
• Interaction with
VLR/HLR
• Charging and statistics
• GTP tunnelling to
other GSNs
Border Gateway
• Interconnects
different GPRS
operators' backbones
GGSN
GTP tunnelling to
other GSNs
Secure interfaces
to external
networks
Charging &
statistics
IP address
management
Charging Gateway
CDR consolidation
Forwarding CDR
information to
• Enables GPRS roaming billing center
• Standard Nokia IP
router family
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Domain Name Server
• Translates IP host names to IP
addresses
• Makes IP network configuration
easier
• In GPRS backbone SGSN uses DNS
to get GGSN and SGSN IP
addresses
• Two DNS servers in the backbone
to provide redundancy
Legal Interception Gateway
• Enables authorities to intercept
subscriber data and signaling
• Chasing criminal activity
• Operator personnel has very
limited access to LI functionality
• LI is required when launching the
GPRS service
NSN - Fully ETSI Compliant Interfaces
SMS-GMSC
SMS-IWMSC
E
SM-SC
C
Gd
HLR
MSC/VLR
D
Gs
A
TE
MT
R
BSS
Um
Gc
Gr
Gb
Gi
GGSN
SGSN
Gn
Gn
EIR
Gp
Gf
SGSN
GGSN
Other PLMN
Signaling Interface
Signaling and Data Transfer Interface
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PDN
TE
Bursts on the Air Interface – Mapping RLC blocks
RLC Blocks
RLC/MAC Blocks
1 TDMA frame = 4.615 ms
= BURST PERIOD
0
70
TDMA Bursts
70
70
7
Note: Amount of RLC
blocks per radio block
depends on used
(modulation) coding
scheme (M)CS
4 x TDMA Frames = 4 Bursts = 1 Radio block = 1-2 RLC block(s)
0 1 2 3 4 5 6 7 8 9 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
B0(0..3)
B1(4..7)
B2 (8..11)
P
T
C
C
H
B3(13..16)
B4(17..20)
B5(21..24)
I
D
L
E
B6(26..29)
52 TDMA Frames (240 ms)
B7(30..33)
B8(34..37)
P
T
C
C
H
B9(39..42)
12 x RLC/MAC Blocks = 1 x 52 PDCH MultiFrame = 240 ms
12 radio Blocks / 0.240 s = 50 RLC/MAC Blocks / s
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B10(43..46)
B11(47..50)
I
D
L
E
(E)GPRS Logical Channels
GPRS Air Interface Logical Channels
CCCH
Common Control Channels
PCH
AGCH
RACH
Paging CH Access Grant CH Random Access CH
Existing GSM Channels
DCH
Dedicated Channels
PACCH
Packet Associated
Control CH
PDTCH
Packet Data TCH
NEW GPRS Channels
No new EGPRS parameters related to logical channels! AGCH PCH
setting affect both GSM voice and data.
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State and Mobility Management and TBF
establishment
GPRS Attach / Detach
RA / LA Update
PDP Context Activation
TBF establishment
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(E)GPRS Mobile States
NSN SGSN parameters
The relation of Mobile states:
GPRS
Attach/ Detach
MSRT, DET
READY
Timer Expiry
RDY
Idle
MS location
not known.
Subscriber is not
reachable by the
GPRS NW.
•
•
•
•
•
•
10
STANDBY
Timer Expiry
STBY
Standby
MS location known to
SGSN level.
MS is capable of receiving
Point-to-Multipoint data
and being paged for
Point-to-Point data
Ready State Timer (RDY) – Default: 44 seconds
STANDBY state timer (STBY) – Default: 44 seconds
Periodic update timer (PER) = default 54 minutes
Force to Standby (FTS) – Default: N
Detach timer (DET) – Default: 00 hours – 00 minutes
MS Reachable Timer (MSRT) – Default: 120 minutes
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Ready
Packet
TX/RX
MS location known to
cell level.
MS is transmitting or has
just been transmitting.
MS is capable of receiving
Point-to-Point data and
Point-to-Multipoint data.
Routing Area
• Routing Areas are used for GPRS Mobility
Management
– A RA is a subset of one, and only one,
Location
Area (LA)
MSC/VLR
Location Area
– A RA is served by only one SGSN
– For simplicity, the LA and RA can be the same
• Routing area identification
– (RAI) = MCC+MNC+LAC+RAC
 Routing Areas are created in the BSS Radio
Network Configuration Database (BSDATA)
• NSN SGSN parameters related to RA:
– Periodic RA Update Timer (PRAU) – Default:
54 minutes
– RA Paging Area (RPA) – Default: 2
– RA Paging Repetition (RPR) – Default: 3.5
seconds
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Gs Interface
Routing
Area
(RA)
SGSN
Attach Procedure
• GPRS Attach procedure is used for the following two purposes:
– a normal GPRS Attach - attach the IMSI for GPRS services only
– a combined GPRS Attach - attach the IMSI for GPRS and non-GPRS services
(needs Gs interface)
• Attach procedure description
–
–
–
–
MS initiates by sending Attach Request
If network accepts, it sends Attach Accept
If network does not accept it sends Attach Rejected
MS can respond for Attach Accept message with Attach Complete (if P-TMSI
changes)
Attach
Request
Attach A
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ccept
Session Management - Establishing a PDP
Context
• PDP Context (Packet Data Protocol):
• Network level information which is used to bind a mobile station
(MS) to various PDP addresses and to unbind the mobile station
from these addresses after use
• PDP Context Activation
• Gets an IP address from the network
• Initiated by the MS
• Contains QoS and routing information enabling data transfer
between MS and GGSN
• PDP Context Activation and Deactivation should occur within 2
seconds
te
PDP Con
est
xt Requ
155.131
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.33.55
Temporary Block Flow
Temporary Block Flow (TBF):
• Physical connection where multiple mobile stations can share one or more traffic
channels – each MS has own TFI (Temporary Flow Indicator)
• The traffic channel is dedicated to one mobile station at a time (one mobile station
is transmitting or receiving at a time)
• Is a one-way session for packet data transfer between MS and BSC (PCU)
• Uses either uplink or downlink but not both (except for associated signaling)
• Can use one or more TSLs
Comparison with circuit-switched:
normally one connection uses both the uplink and the downlink timeslot(s) for traffic
In two-way data transfer:
uplink and downlink data are sent in separate TBFs - as below
Uplink TBF (+ PACCH for downlink TBF)
Downlink TBF (+ PACCH for uplink TBF)
PACCH (Packet Associated Control Channel): Similar to GSM CS SACCH
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BSC
PSW territory and multislot usage
(E)GPRS Territory
PSW Activation, Territory and Allocation
Free TSL Size
Configuration parameters
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(E)GPRS Territory
Introduction
• Territories consists of consecutive timeslots (starting from RTSL7)
• GPRS dedicated time slots (CDED) can be defined. Only (E)GPRS can
use them.
• PS territory TRX has to be defined by enabling the GTRX parameter
• Dedicated territory (CDEF) is subset of Default territory
• The Maximum GPRS capacity (CMAX) defined the total maximum size for
the (E)GPRS territory
Maximum
GPRS
Capacity (%)
Free time slots in Circuit
Switched territory
GTRX=Y
TS
TS
TS
TS
TS
TS
TS
TS
Dedicated GPRS
Capacity (%)
Additional GPRS
capacity
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Default GPRS Capacity
CDEF (%)
(E)GPRS Territory
Introduction
• Territory movement (upgrade and downgrade) are affected by
– PS traffic
 Nr of TBFs per Radio timeslot can get above the allowed threshold () and the
territory will be upgraded (if possible)
– CS traffic
 CS has priority over PS outside the dedicated territory and can downgrade
the territory
• The amount of timeslots for data will depend also on the
parameters
– CSU - Free TSL for CS Upgrade
– CSD - Free TSL for CS Downgrade
– Territory upgrade in interval of Territory Upgrade Guard Time (both for
upgrade and downgrade)
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(E)GPRS Territory
Introduction
TRX 1, GTRX=N
BCCH
TS
TS
TS
Maximum
GPRS
Capacity (%)
Additional GPRS
capacity
TRX 2, GTRX=Y
TS
TS
TS
TS
TS
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TS
TS
Circuit
Switched
Territory
Default GPRS capacity threshold
TS
Free time slots in Circuit
Switched territory
Territory upgrade in interval of
Territory Upgrade Guard Time.
Valid for upgrades / downgrades
due to (E)GPRS traffic.
TS
Circuit /
Packet
Switched
Dedicated GPRS Territory
TS
TS
TS
Capacity (%)
Default GPRS
Capacity (%)
Territory downgrade
forced by the Circuit
Switched traffic
PSW Activation, Territory and Allocation
Parameters
PSW Activation
BTS
GPRS Enabled (GENA)
EGPRS Enabled (EGENA)
GPRS Cell Barred (GBAR)
Not Allowed Access Classes (ACC)
TRX
GPRS Enabled TRX (GTRX)
Neighbour
Adjacent GPRS Enabled (AGENA)
Channel Allocation Parameters
SEG
Prefer BCCH frequency GPRS (BFG)
TRX priority in TCH allocation (TRP)
Free TSLs
BSC
Free TSL for CS Upgrade (CSU) Free
TSL for CS Downgrade (CSD)
Territory Settings
BTS
Default GPRS Capacity (CDEF)
Dedicated GPRS Capacity (CDED)
MAX GPRS Capacity (CMAX)
BSC
GPRS territory update guard time (GTUGT)
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Territory Setting Parameters – calculation method
• Dedicated GPRS Capacity
(CDED) – timeslots only for PS
(no CS)
• Default GPRS Capacity (CDEF)
- timeslots primarily for PS (CS
can overtake)
• MAX GPRS Capacity (CMAX) –
maximum territory size
Territory size (TSL) =
Rounddown (CDED/CDEF/CMAX(%) x FR capable TSLs, where GTRX=Y)
• CDED/CDEF/CMAX percentage is converted to TSL by multiplying it with all FR
traffic capable TSLs (FR/DR) of the cell where GTRX=Y.
• Signaling and HR TSLs of TRXs (where GTRX=Y) are not taken into account in
the calculation.
• The product of CDED/CDEF/CMAX and FR capable TSLs (GTRX=Y) is
rounded down to a whole number
• Rounding up will take place only when CDED/CDEF/CMAX value > 0% and
rounding would result to 0.
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Territory setting parameters - example
Table below provides example
how same parameter setting
can result different territory
sizes with different GRTX/TRX
configurations
# of TRXs (GTRX=Y)
1
2
3
4
# of signaling RTSL (GTRX =Y)
1
2
2
3
CDED = 1%
1 RTSL
1 RTSL
1 RTSL
1 RTSL
CDEF = 30%
2 RTSL
4 RTSL
6 RTSL
8 RTSL
CMAX = 80%
5 RTSL
11 RTSL
17 RTSL
23 RTSL
Any setting 1…20% of CDEF with 1 TRX configuration (GTRX=1)
will result 1 TSL territory.
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Resource Allocation
PSW Activation and Territory - SEG
TRX priority in TCH allocation (TRP) - voice
–
•
–
•
Values
–
–
–
–
•
Prefer BCCH frequency GPRS (BFG) - data
TRP defines whether the BCCH TRX or other TRXs
are preferred in traffic channel allocation.
0 (No prioritization between TRXs, all TRXs are
treated equally in TCH allocation)
1 (Traffic channel is allocated primarily from the BCCH
TRX.)
2 (Traffic channel is allocated primarily from another
TRX than the BCCH TRX)
3 (Traffic channel is allocated primarily from the BCCH
TRX for the non-AMR users and for the AMR users
primarily beyond the BCCH TRX)
–
Values
–
–
–
•
Default
BFG defines whether the BCCH TRX or other TRXs
are preferred in GPRS channel allocation.
0 (no prioritization is determined between TRXs),
1 (GPRS channels are allocated primarily from the
BCCH TRX),
2 (GPRS channels are allocated primarily beyond the
BCCH TRX)
Default
–
No (0)
No Priority (0)
An example how to allocate voice primarily to nonBCCH and
data to BCCH (because of EGPRS capability of BCCH TRX):
BTS ID
BTS1
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TRX ID
TRX capability
TRX1 (BCCH)
EGPRS
TRX2
GPRS
TRX3
GPRS
TRP
BFG
2
1
Free TSL Size (after CS Upgrade and Downgrade)
When a downgrade or upgrade procedure is requested, then the CSD and
CSU parameters can reduce or increase the border between CSW and
PSW territories.
TSL number after CS downgrade
TRX number
free TSL for CS downgrade (%)
(CSD)
70
95
99
1
2
3
4
5
0
0
0
1
1
1
1
1
2
2
1
1
2
2
3
1
0
2
1
3
1
4
1
5
2
1
2
2
3
4
1
2
3
4
5
2
3
4
5
6
TSL number after CS upgrade
TRX number
free TSL for CS upgrade (sec)
(CSU)
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1
4
7
10
Abis Basic Concepts
PCM frame (E1)
One 64 kbit/s (8 bits) channel in PCM frame is
called timeslot (TSL)
One 16 kbit/s (2bits) channel timeslot is Sub-TSL
PCM frame has 32 (E1) or 26 (E1) TSLs
One Radio timeslot corresponds one 16 kbit/s
Sub-TSL (BCCH, TCH/F etc.) and one TRX takes
two TSLs from Abis
One TRX has dedicated TRXsig of 16, 32 or 64
kbit/s
One BCF has dedicated BCFsig (16 or 64 kbit/s)
for O&M
Q1-management needed if TRS management
under BSC
MCB/LCB required if loop topology is used
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0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
TCH 0
TCH 4
TCH 1
TCH 5
MCB
LCB
TCH 2
TCH 6
TCH 3
TCH 7
TRXsig
BCFsig
Q1-management
TRX1
(E)GPRS Dynamic Abis Pool
DAP Introduction
• Fixed resources for signaling and voice
• Dynamic Abis pool (DAP) for data
– Also named EDAP
– Predefined size 1-24 PCM TSL per DAP
–
–
–
–
–
–
–
25
(Typically used range from 4 to 8 TSL)
DAP can be shared by several TRXs in
the same BCF (and same E1/T1)
Max 20 TRXs per DAP
Max 1600 DAPs per BSC3i 2000
DAP + TRXsig + TCHs have to be in
same PCM
UL and DL DAP use is independent
DAP schedule rounds for each active
Radio Block
Different users/RTSLs can use same
DAP Sub-TSL
© Nokia Siemens Networks
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
MCB
LCB
TCH 0
TCH 4
TCH 0
TCH 4
TCH 0
TCH 4
TCH 1
TCH 5
TCH 1
TCH 5
TCH 1
TCH 5
TCH 2
TCH 6
TCH 2
TCH 6
TCH 2
TCH 6
TCH 3
TCH 7
TCH 3
TCH 7
TCH 3
TCH 7
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
EDAP
TRXsig1
TRXsig3
BCFsig
TRXsig2
Q1-management
TRX1
TRX2
TRX3
EGPRS
pool
Configuration setup
DAP configuration parameters
Transceiver (TRX) radio network object parameters
• dynamic abis pool ID (DAP)
– Used for indicating the dynamic Abis pool ID. This can be given only if the site
type is Nokia MetroSite, Nokia UltraSite or Nokia FlexiEDGE.
Dynamic Abis Pool (DAP) radio network object parameters
• BCSU ID (BCSU)
– This parameter identifies the base station signaling unit where the physical PCU
card is installed and which should be attached to the logical PCU object
• PCU index (PCU)
– This parameter identifies the packet control unit logical index of the physical
card.
• circuit (CRCT)
– The parameter defines the Abis interface ET-PCM number and the time slots
reserved from the ET-PCM for the dynamic Abis pool. The pool size is from 1 to
24 ET-PCM TSLs.
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Configuration setup
DAP configuration parameters
Dynamic Abis Pool (DAP) radio network object parameters (cont.)
• new first time slot (NFT)
– This parameter defines the new first time slot.
• new last time slot (NLT)
– This parameter defines the new last time slot.
• Network Service Entity Identifier (NSEI)
• packet service entity identifier (PSEI)
– This parameter identifies the Packet Service Entity object in the BSC (PSE). The Packet
Service Entity Identifier (PSEI) is used in the BSS to determine Packet Control Pool
(PCP).
• pool identification (ID)
– This parameter identifies the Pool id of the ACP object.
• pool size (SIZE)
– This parameter defines the Pool size.
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TSL utilization
Acknowledgement Request
Pre-emptive transmission
BS_CV_MAX
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Acknowledgement Request
Acknowledgement Request
•
•
•
•
•
•
•
•
GPRS Uplink Penalty (default: 3)
GPRS Uplink Threshold (default: 22)
GPRS Downlink Penalty (default: 2)
GPRS Downlink Threshold (default: 16)
EGPRS Uplink Penalty (default: 1)
EGPRS Uplink Threshold (default: 25)
EGPRS Downlink Penalty (default: 1)
EGPRS Downlink Threshold (default: 25)
PRFILE PCU Telecom Parameters
Parameter 046: 0047 - 0054
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• Functionality of EGPRS DL requests:
– These parameters are used by the RLC
ACK algorithm to determine how
frequently the PCU polls the mobile
station having a TBF in EGPRS mode.
– The PCU has a counter, which is
incremented by one whenever an RLC
data block is transmitted for the first time
– The counter is incremented by (1 +
EGPRS_DOWNLINK_PENALTY)
whenever a negatively acknowledged
RLC data block is retransmitted.
– The mobile station is polled when the
counter exceeds the threshold value of
EGPRS_DOWNLINK_THRESHOLD.
Acknowledgement Request - retransmission
Penalty
RLC data block retransmission
Time
New RLC data Block
MS
RLC data block with poll
Packet Downlink ACK/NACK
GPRS Uplink Penalty = 3
GPRS Uplink Threshold = 18
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Bitmap (64 Blocks)
Increment
3
3
3
Counter
Total
3
6
9
1
1
1
1
1
10
11
12
13
14
1
1
1
1
15
16
17
18
PCU
Acknowledgement Request – no response
Penalty
RLC data transmission
Time
USF
Counter
Total
1
3
1
1
3
1
4
5
6
9
1
1
21
22
1
23
MS
Packet Uplink ACK/NACK
Packet Control ACK/NACK
31
Increment
© Nokia Siemens Networks
PCU
BS_CV_MAX
• The BS_CV_MAX functionality contains the following items:
– Transmission and acknowledgement
 MS is not expecting to receive NACK for the transmitted block until
(max(BS_CV_MAX,1) – 1) in RLC/MAC block period (20ms).
 So the NACK in the PACKET UPLINK ACK/NACK message will be ignored, if
the round trip time is less than (max(BS_CV_MAX,1) – 1).
 If the BS_CV_MAX is e.g. 9, than the RTT will be (9-1)*20ms ->160ms
– BS_CV_MAX is also impacting T3200 (MS timer), N3104 (MS timer)
and Countdown procedure
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BS_CV_MAX
BSS
BS_CV_Max
Time
MS
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Nack message
transmitted
TBF release and RTT
TBF Release Delay
TBF Release Delay Extended
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TBF Release Delay
• If there is not any RLC/MAC block received, the TBF will not be released
immediately, but it can be kept alive for a given time period.
• There are two modifiable parameters related to Delayed TBF feature
among PRFILE parameters:
– DL_TBF_RELEASE_DELAY (0,1-5sec, def 1s) Parameter 46:0067
 Adjust the delay in downlink TBF release.
 During DL delay period the possibly following uplink TBF can be established faster and
frequent releases and re-establishments of downlink TBF can be avoided
– UL_TBF_RELEASE_DELAY (0,1-3sec, def 0,5s) Parameter 46:0068
 This parameter is used to adjust the delay in uplink TBF release.
 During UL delay period following downlink TBF can be established faster.
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UL TBF Release with Extended UL TBF Mode
(EUTM)
• EUTM is Rel4 feature - MS support required.
• If EUTM is activated (MML: ZWOA,PRFILE) and MS supports it the UL
TBF Release parameter is ignored.
• UL_TBF_REL_DELAY_EXT
– This parameter defines the uplink TBF release delay time for mobile stations supporting
the Extended UL TBF Mode.
– Default value: 1000D
– Allowed values: 300D - 3000D, Increments: 100
• UL_TBF_SCHED_RATE_EXT
– This parameter defines how often a USF is scheduled for the MS during the inactivity
period in Extended UL TBF Mode. Parameter value unit is 20 ms (block period). Eg. value
5 means 100 ms (5 block periods).
– Default value: 5D
– Allowed values: 2D - 50D, Increments: 1
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UL TBF Release with Extended UL TBF mode
MS does not continue TBF
MS
Short description:
BSC / PCU
•
Countdown procedure is ongoing.
EUTM supporting mobile is allowed
to recalculate CV during procedure, if
it gets more data to send. PCU
notices this by monitoring Block
Sequence Number (BSN) and
Countdown value (CV) sent by MS.
•
After receiving CV=0 block PCU starts
UL extended state. It sends Packet
Uplink Ack/Nack message to MS with
no Final Ack Indicator (FAI) on, but
acknowledging all received blocks.
•
During UL extended state PCU
schedules USFs for MS according
adjustable scheduling rate
parameter. If MS has no new data to
send it sends UL dummy control
blocks on its sending turn.
•
When UL extended state ends,
according adjustable release delay
parameter, PCU sends Packet Uplink
Ack/Nack message to MS with Final
Ack Indicator (FAI) on.
Data block with CV = 1
UL TBF extended state
Data block with CV = 0
PACKET UL ACK/NACK (FAI=0,
Polling=NO)
Schedule USF turn for MS
UL dummy control
block
UL TBF Schedule Rate Ext
Schedule USF turn for MS
UL dummy control
block
Schedule USF turn for MS
UL dummy control
block
PACKET UL ACK/NACK (FAI=1,
Polling=YES)
PACKET CONTROL ACK
37
EUTM delay timer starts
© Nokia Siemens Networks
EUTM delay timer expires
UL TBF terminated
UL TBF Release with Extended UL TBF mode
MS continues data transfer on TBF
Short description:
MS
•
Countdown procedure is
ongoing. After receiving CV=0
block PCU starts UL extended
state. It sends Packet Uplink
Ack/Nack message to MS with
no Final Ack Indicator (FAI) on,
but acknowledging all received
blocks.
•
During UL extended state PCU
schedules USFs for MS
according adjustable
scheduling rate parameter. If
MS has no new data to send it
sends UL dummy control
blocks on its sending turn.
•
When MS gets new data to
send during extended state, it
sends UL data block with new
BSN, and also new CV value
when needed. Due BSN PCU
knows that new UL LLC is to be
sent by MS, and UL TBF
continues as normally.
BSC / PCU
UL TBF extended state
Data block with CV = 0
PACKET UL ACK/NACK (FAI=0,
Polling=NO)
UL dummy control
block
UL TBF Schedule Rate Ext
Schedule USF turn for MS
Data block with new BSN and CV
Data block
38
EUTM delay timer starts
Schedule USF turn for MS
© Nokia Siemens Networks
EUTM delay timer stopped,
TBF continues
Link Adaptations
GPRS Link Adaptation (CS1-2)
EGPRS Link Adaptation
39
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
GPRS Coding Schemes
Data Rate
(kbit/s)
NSN GPRS
PCU
CS1
181
9.05
CS2
268
13.4
NSN GPRS
PCU2
CS3
312
15.6
CS4
428
21.4
• CS1 & CS2 – Implemented in all NSN BTS without
HW change
• CS1 & CS4 – S11.5 (with PCU2) and UltraSite BTS
SW CX4.1 CD1 (Talk does not support CS3 and CS4)
40
© Nokia Siemens Networks
Error
Correction
Payload (bits)
per RLC block
Data
Coding
Scheme
More Data
=
Less Error
Correction
GPRS Link Adaptation Algorithm (CS1-2)
Introduction with PCU1
• The coding scheme will change based on BLER Thresholds.
• The BLER thresholds are defined by simulations and change from hopping to non hopping
networks
CS1 & CS2 Crosspoint
The crosspoint is defined by the following formula:
RLC/MAC throughput
(kbps)
8.0 kbps * (1 - BLER_CP_CS1) = 12 kbps * (1 - BLER_CP_CS2) ,
where:
–
–
–
–
–
8.0 kbps is the theoretical maximum bit rate for CS-1
12.0 kbps is the theoretical maximum bit rate for CS-2
BLER_CP_CS1 is the block error rate at the crosspoint when
CS-1 is used
BLER_CP_CS2 is the block error rate at the crosspoint when
CS-2 is used
Averaging is based on 10 RLC/MAC blocks
The parameters on the following slides
correspond to the BLER_CP_CS1.
41
© Nokia Siemens Networks
X
C/I (dB)
GPRS Link Adaptation Algorithm (CS1-2)
Parameters with PCU1
• GPRS Coding Scheme No Hopping (COD)
– The selection of Coding Scheme in RLC Acknowledged mode is indicated (frequency
hopping is not used).
 Range:
Link Adaptation used (0),
CS-1 used (1),
CS-2 used (2).
 Default: CS-2 used (2)
• DL BLER Crosspoint for CS Selection Non Hopping (DLB)
– The RLC BLER (block error rate percentage) for CS-1 channel coding is indicated.
– At this point CS-1 and CS-2 give the same effective bit rate and Coding Scheme selection
criteria in RLC Acknowledged mode for downlink TBFs changes.
– The parameter is meaningful only if link adaptation is used in case of no frequency
hopping.
 Range: 0...100 %, step 1 % . Default: 90%
• UL BLER Crosspoint for CS Selection Non Hopping (ULB)
– Same as above but for UL
 Range: 0...100 %, step 1 % . Default: 90%
42
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Parameters with PCU1
• GPRS Coding Scheme Hopping (CODH)
– The selection of Coding Scheme in RLC Acknowledged mode is indicated
(frequency hopping is used).
 Range: Link Adaptation used (0), CS-1 used (1), CS-2 used (2).
 Default: Link Adaptation used (0)
• DL BLER Crosspoint for CS Selection Hopping (DLBH)
– The RLC BLER (block error rate percentage) for CS-1 channel coding is
indicated.
– At this point CS-1 and CS-2 give the same effective bit rate and Coding
Scheme selection criteria in RLC Acknowledged mode for downlink TBFs
changes.
– The parameter is meaningful only if Link Adaptation and Frequency Hopping
are used.
 Range: 0...100 %, step 1 % . Default: 20%
• UL BLER Crosspoint for CS Selection Hopping (ULBH)
– Same as above but for UL.
 Range: 0...100 %, step 1 % . Default: 24%
43
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Parameters with PCU1
Calculation of the cross point of CS1 and CS2 is based on the following
formula: 8.0 kbps * (1 - BLER_CP_CS1) = 12 kbps * (1 - BLER_CP_CS2)
The below examples shows the relation CS1 and CS2 from BLER point of
view:
• COD (set to 2) with default DLB (set to 90%)
– 8.0 kbps * (1 - BLER_CP_CS1(DLB: 90%)) = 12 kbps * (1 - BLER_CP_CS2(calculated: 94,4%))
 CS1 will be selected instead of CS2 if CS2 has worse BLER than 94.4 %
• CODH (set to 2) with default DLBH (set to 20%)
– 8.0 kbps * (1 - BLER_CP_CS1(DLB: 20%)) = 12 kbps * (1 - BLER_CP_CS2(calculated: 46,6%))
 CS1 will be selected instead of CS2 if CS2 has worse BLER than 46.6 %
Remark: When the LA algorithm is used, the initial CS value at the beginning of a TBF is CS-2.
44
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Parameters with PCU1
• DL adaptation probability threshold (DLA)
– The allowed probability (%) is defined for the system to make a wrong decision
in downlink adaptation.
 Range: 0...50 %, step 1 %
 Default: 20%
• UL adaptation probability threshold (ULA)
– The allowed probability (%) is defined for the system to make a wrong decision
in uplink adaptation.
 Range: 0...50 %, step 1 %
 Default: 10%
45
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Introduction with PCU2
• A new Link Adaptation algorithm is introduced with PCU2, which replaces
the previous GPRS LA algorithm implemented on PCU1 and covers the
following coding schemes:
– CS-1 and CS-2 if CS-3 and CS-4 support is disabled in the territory in question
– CS-1, CS-2, CS-3, and CS-4 if CS-3 and CS-4 support is enabled (BSSPAR2)
• PCU2 uses two 2-dim tables for the LA operation (Acks/Nacks and DL/UL
separately)
– The values in the tables are initially based on the simulations
– Fixed values used if adaptive LA algorithm (ALA)= ‘N’
– If ALA = ‘Y’, the table is updated based on RXQual measurements
– LA algorithm defines the optimal CS based on the updated values
Coding Scheme
RXQ
46
© Nokia Siemens Networks
Updated based on
RXQuality
measurements
GPRS Link Adaptation Algorithm (CS1-2)
Parameters
• coding schemes CS3 and CS4 enabled (CS34)
– With this parameter the operator can define whether the Coding
Schemes CS-3 and CS-4 capability is enabled in the BTS.
 Range: Coding schemes CS3 and CS4 are disabled (N) (0), Coding schemes
CS3 and CS4 are enabled (Y) (1). Default: Adaptive LA algorithm is enabled
(Y) (0)
 More information is available in BSSPAR2
• adaptive LA algorithm (ALA)
– With this parameter the operator can define if the used GPRS Link
Adaptation algorithm is adaptive or not.
 Range: Adaptive LA algorithm is enabled (Y) (0), Adaptive LA algorithm is
disabled (N) (1). Default: Adaptive LA algorithm is enabled (Y) (0)
47
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Parameters
• DL Coding Scheme in Acknowledged Mode (DCSA)
• UL Coding Scheme in Acknowledged Mode (UCSA)
– Defines the initial CS in acknowledge mode in downlink/uplink direction.
 Range: CS1 (0), CS2 (1), CS3 (2), CS4 (3), LA with initial CS1 (4), LA with
initial CS2 (5), LA with initial CS3 (6), LA with initial CS4 (7).
 Default: CS2 (1)
 More information is available in BSSPAR2
Remark: The parameter values 2,3,6 and 7 are valid only for Nokia MetroSite, Nokia
UltraSite and Nokia Flexi EDGE
48
© Nokia Siemens Networks
GPRS Link Adaptation Algorithm (CS1-2)
Parameters
• DL Coding Scheme in Unacknowledged Mode (DCSU)
• UL Coding Scheme in Unacknowledged Mode (UCSU)
– Define the initial CS in unacknowledged mode downlink/uplink
direction.
 Range: CS1 (0), CS2 (1), CS3 (2), CS4 (3), LA with initial CS1 (4), LA with
initial CS2 (5), LA with initial CS3 (6), LA with initial CS4 (7).
 Default: CS2 (1)
 More information is available in BSSPAR2
Remark: The parameter values 2,3,6 and 7 are valid only for Nokia MetroSite, Nokia
UltraSite and Nokia Flexi EDGE
49
© Nokia Siemens Networks
EGPRS Link Adaptation
Introduction
• Link Adaptation
– The task of the LA algorithm is to
select the optimal MCS for each
radio condition to maximize
RLC/MAC data rate, so the LA
algorithm is used to adapt to
situations where signal strength and
/ or C/I level is pure and changing
within time
– Normally, LA adapts to path loss
and shadowing but not fast fading.
IR is better suited to compensate
fast fading
50
© Nokia Siemens Networks
• Incremental Redundancy
– The retransmission process is
based on Incremental Redundancy
– LA must take into account if IR
combining is performed at the
receiver.
– LA must take into account the effect
of finite IR memory.
Coding Schemes in EGPRS
Scheme Code rate
Raw Data
Header Modulation RLC blocks
within one
per Radio
Code rate
Radio Block
Block
(20ms)
Tail
HCS Data rate
payload
kb/s
MCS-9
1.0
0.36
2
2x592
A
MCS-8
0.92
0.36
2
2x544
A
MCS-7
0.76
0.36
2
2x448
B
44.8
MCS-6
0.49
1/3
1
592
544+48
A
29.6
27.2
MCS-5
0.37
1/3
1
448
B
MCS-4
1.0
0.53
1
352
C
17.6
MCS-3
0.80
0.53
1
296
272+24
A
14.8
13.6
8PSK
GMSK
2x12
59.2
2x6
54.4
8
12
6
22.4
MCS-2
0.66
0.53
1
224
B
11.2
MCS-1
0.53
0.53
1
176
C
8.8
NOTE:
51
Family BCS
the italic captions indicate the padding.
© Nokia Siemens Networks
EGPRS MCS Families
• The MCSs are divided into different families A, B
and C
• Each family has a different basic unit of payload:
37 (and 34), 28 and 22 octets respectively.
• Different code rates within a family are achieved
by transmitting a different number of payload units
within one Radio Block.
• For families A and B, 1 or 2 or 4 payload units are
transmitted, for family C, only 1 or 2 payload units
are transmitted
• When 4 payload units are transmitted (MCS 7,
MSC-8 and MCS-9), these are splitted into two
separate RLC blocks (with separate sequence BSN
numbers and BCS, Block Check Sequences)
• The blocks are interleaved over two bursts only,
for MCS-8 and MCS-9.
• For MCS-7 the blocks are interleaved over four
bursts
MCS-3
Family A
37 octets
37 octets
© Nokia Siemens Networks
37 octets
MCS-9
MCS-3
34+3 octets 34+3 octets
Family A
padding
MCS-6
34 octets
34 octets
34 octets
34 octets
MCS-8
MCS-2
Family B
28 octets
28 octets
28 octets
MCS-5
MCS-7
MCS-1
Family C
22 octets
22 octets
MCS-4
52
37 octets
MCS-6
28 octets
EGPRS Link Adaptation
Parameters
• EGPRS Link Adaptation Enabled (ELA)
– The EGPRS link adaptation can be enabled /
disabled on cell level.
– If disabled the system uses the MCS value
defined by initial MCS for acknowledged
mode or initial MCS for unacknowledged
mode parameters or a lower MCS.
 Range: EGPRS link adaptation is disabled (0),
enabled for RLC acknowledged mode (1),
enabled for RLC acknowledged and
unacknowledged (2) .
 Default: enabled for RLC acknowledged and
unacknowledged (2)
RLC/MAC throughput
(kbps)
60
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
LA
50
40
30
20
10
0
0
5
10
15
C/I (dB)
53
© Nokia Siemens Networks
20
25
30
EGPRS Link Adaptation
Parameters
• Initial MCS for Acknowledged Mode (MCA)
– Modulation and Coding Scheme (MCS) used at the beginning of a TBF for
acknowledged mode. The parameter is used in EGPRS link adaptation.
 Range: 1...9, step 1. Default: 6
• Initial MCS for Unacknowledged Mode (MCU)
– MCS used at the beginning of a TBF for unacknowledged mode. The parameter
is used in EGPRS link adaptation
 Range: 1...9, step 1. Default: 5
• Remark
– PCU1 uses always initial MCS value read from user parameter for new
established TBF.
– PCU2 uses last used MCS of previous TBF as initial MCS for new TBF in
situation when opposite direction of TBF has been active from last TBF release
to new TBF establishment (so the MS context has stayed stored in PCU2
memory), and if no BTS re-selection was done for opposite direction of TBF.
54
© Nokia Siemens Networks
EGPRS Link Adaptation
Parameters - SEG
• Maximum BLER in Acknowledged Mode (BLA)
– This parameter indicates the maximum block error rate of first transmission in
acknowledged mode. The parameter is used in EGPRS link adaptation.
 Range: 10...100 %, step 1 %. Default: 90%
• Maximum BLER in Unacknowledged Mode (BLU)
– With this parameter you indicate the maximum block error rate in
unacknowledged mode. The parameter is used in EGPRS link adaptation.
 Range: 10...100 %, step 1 %. Default: 10%
• Remark:
– The BLA 90% means that the coding scheme selection is done by LA algorithm,
if the BLER is less than 90%.
– If the BLER is higher than 90%, then the decision of LA will be ignored and
MCS will be downgraded
55
© Nokia Siemens Networks
EGPRS Link Adaptation
Parameters - SEG
• MBG and MBP parameters adjusts the MCS and modulation preferences.
• Mean BEP Offset GMSK (MBG)
– This is the offset added to reported GMSK mean BEP values before BEP table
lookups.
– The value applies to both uplink and downlink directions.
 Range: -31...31, step 1. Default: 0
• Mean BEP Offset 8PSK (MBP)
– This is the offset added to reported 8PSK mean BEP values before BEP table
lookups.
– The value applies to both uplink and downlink directions.
 Range: -31...31, step 1. Default: 0
56
© Nokia Siemens Networks
EGPRS Link Adaptation
Parameters
• The matrix shows an example how the MCSs are selected based on
GMSK_CV_BEP and GMSK_MEAN_BEP figures.
– More tables are available from NED/NOLS
• MBG can be used to move the selection decision information to both directions to
have more robust or less robust CS decision for the same GMSK_CV_BEP and
MBG with positive values
GMSK_MEAN_BEP figures.
GMSK_CV_BEP
GMSK_MEAN_BEP
0
1
2
3
4
5
6
7
0-3
4
5
6
7-9
10-19
20-31
1
1
2
2
3
3
4
1
1
2
2
3
3
4
1
1
2
2
3
3
4
1
1
1
2
3
3
4
1
1
1
2
2
3
4
1
1
1
2
2
3
4
1
1
1
1
2
3
4
1
1
1
1
2
2
4
MBG with negative values
57
© Nokia Siemens Networks
Remark: the values in the matrix are an example.
EGPRS Link Adaptation
Functionality
•Example of coding schemes modification by the LA algorithm in various radio
Coding Scheme (MCS)
environment during drive tests in Helsinki
9
20
Used MCS
C/I
Averaged C/I
8
7
18
16
14
6
12
5
10
4
8
3
6
2
4
1
2
0
0
0
50
100
Time (s)
58
© Nokia Siemens Networks
150
CI (dB)
Multiplexing
59
© Nokia Siemens Networks
Multiplexing
TSL sharing
The max amount of TBFs per TSL can be limited by the
following parameters:
• Maximum Number of DL TBF (MNDL)
– This parameter defines the maximum number of TBFs that a radio time
slot can have in a GPRS territory, in the downlink direction.
 Range: 1...9, step 1. Default: 9
• Maximum Number of UL TBF (MNUL)
– This parameter defines the maximum number of TBFs that a radio time
slot can have in a GPRS territory, in the uplink direction.
 Range: 1...7, step 1. Default: 7
60
© Nokia Siemens Networks
Multiplexing
DL TSLs in (E)GPRS/GPRS multiplexing
• In PCU2 USF Granularity 4 is used, meaning that 1 block carrying USF signaling to GPRS TBF
assigns transmission turn to GPRS TBF for 4 consecutive UL radio blocks.
• Originally 4 DL 8-PSK TSLs (TSL 4-7) were used, but now TSL 6 and 7 are GMSK modulated,
because of USF is pointed to GPRS MS
not tinin
UUSSFF44 neo
uusse
6
7
Radio Block 1
0
1
2
3
4
5
USF
USF
Radio Block 2
USF
USF
Radio Block 3
USF
USF
Radio Block 4
USF
USF
……
USF
USF
GMSK
• Originally 4 DL 8-PSK TSLs (TSL 4-7) were used, but now TSL6 and 7 are GMSK
modulated, because of USF is pointed to GPRS MS
0
in
UUSSFF44 in
uussee
Radio Block 1
2
3
4
5
6
7
USF
USF
USF
USF
GMSK
Radio Block 2
Radio Block 3
GMSK
Radio Block 4
……
61
1
© Nokia Siemens Networks
Multiplexing
Territory upgrade/downgrade
• The algorithm checks the need for re-allocation in given period defined by
TBF_LOAD_GUARD_THRSHLD, in order to separate TBFs.
– The Territory Upgrade/Downgrade procedure is performed with three parameters:
– X1: 1.5, X2: 1, X3: 0.5
– The PS RRM request an upgrade when the average number of TBF's per TSL in the PS territory is
greater than X1 (and Default territory is already allocated)
– The target average number of TBFs in the PS territory is defined by X2
– When the average number of TBF per TSL in the PS territory is less than X3, the PS RRM will request
a GPRS downgrade. (but only as far as the default boundary)
– PRFILE modifiable parameter (default=50; values 0-255)
• GPRS Territory Update Guard Timer (GTUGT, default: 5s)
– This parameter defines the time which must elapse between two subsequent territory updates.
• Example:
– The average number of TBF / TSL is 1.75 on the TRX below, so there will be a territory
upgrade request to achieve 1 TBF / TSL ratio
TSL0
signaling
62
© Nokia Siemens Networks
TSL1
TSL2
TSL3
TSL4
TSL5
TSL6
TSL7
TBF1
TBF1
TBF2
TBF1
TBF2
TBF1
TBF2
(E)GPRS Power Control
63
© Nokia Siemens Networks
Uplink Power Control
• UL Power control
– Reduces Interference in the NW
– Saves battery power
– Open loop power control – UL TX powers based on MS received signal level
(DL).
• No DL PC available yet
• UL PC Parameters
– Alpha: determines the slope by which the downlink RX_Level affects the MS
power
– Gamma : determines the minimum MS output power
– IFP : changes the averaging for the field strength values in idle mode
– TFP: changes the averaging for the field strength values in transfer mode
64
© Nokia Siemens Networks
Uplink Power Control
PC parameters for MS are transmitted on BCCH
Uplink Power Control
PCH = min(  CH - C + 48),PMAX)
35
 CH, sets the minimum power level
Range 0…62
Default 34 (GSM900) , 36 (GSM1800)
 , sets the slope for the uplink power
level
•
•
Range 0…10 equivalent 0.0….1.0
Default 7 (GSM900) , 8 (GSM1800)
30
Ms Output Power (dBm)
•
•
25
20
0,3
15
1
10
5
 C, received signal level
 0, 39(GSM900), 36 (GSM1800)
 PMAX, max MS power allowed in the cell
65
© Nokia Siemens Networks
Signal Strength (dBm)
-110
-108
-106
-104
-98
-102
-96
-100
-94
-92
-90
-88
-86
-84
-82
-80
-78
-76
-74
-72
-70
-68
-66
-64
-62
-60
-58
-56
-54
-52
-50
-48
0
Uplink Power Control
Averaging Parameters
Measurement
Mode
Mobile State
66
Packet Transfer Mode
Packet Idle Mode
Ready
Standby
Parameter
Range
Default
Packet Idle Mode Signal Strength Filter Period
0…25
9
Packet Transfer Mode Signal Strength Filter Period
0…25
13
© Nokia Siemens Networks
Uplink Power Control
Averaging Parameters
Packet Transfer / Idle Mode Signal
Strength Filter Period = 25
Packet Transfer / Idle Mode Signal
Strength Filter Period = 1
Mobile Output Power
Mobile Output Power
40
40
20
20
0
0
19 37 55 73 91 109 127 145 163 181 199 217 235 253 271 289 307 325 343 361 379 397 415 433 451
1
SS
P_IDLE
P_TRANSFER
Power
Power
1
-20
-20
-40
-40
-60
-60
-80
-80
67
© Nokia Siemens Networks
16 31 46 61 76 91 106 121 136 151 166 181 196 211 226 241 256 271 286 301 316 331 346 361 376 391 406 421 436 451
(E)GPRS Mobility
C1/C2
HYS
68
© Nokia Siemens Networks
(E)GPRS mobility
• Network Control Mode (NCM) defines how cell re-selection is performed:
– Network Control Mode = 0 (NC0): the MS will perform an autonomous cell reselection.
– Network Control Mode = 2 (NC2): the MS sends neighbors cell measurements to the
network and the network commands the MS to perform cell re-selection (Network
Controlled Cell Re-selection).
 NCM is modified with MML command ZEEM.
• The GSM idle mode functionality is used for (E)GPRS cell (re)-selection, if NC0 is
implemented.
– C1 and C2 parameter setup is taken into account in (E)GPRS cell selection and reselection process
• HYS parameter
– the HYS parameter is used for all the cell changes, if a TBF is ongoing
– In case of standby mode (TBF is not established), the HYS parameters is used on RA
border only
69
© Nokia Siemens Networks