01_nokia gprs radio resource management
TRANSCRIPT
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 1/33
NTC Version: draft © Nokia Telecommunications Oy
1 (33)
Nokia GPRS Radio ResourceManagement
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 2/33
Contents
NTC Version: draft © Nokia Telecommunications Oy
2 (33)
The information in this document is subject to change without notice and describes only the productdefined in the introduction of this documentation. This document is intended for the use of NokiaTelecommunications' customers only for the purposes of the agreement under which the document issubmitted, and no part of it may be reproduced or transmitted in any form or means without the priorwritten permission of Nokia Telecommunications. The document has been prepared to be used byprofessional and properly trained personnel, and the customer assumes full responsibility when usingit. Nokia Telecommunications welcomes customer comments as part of the process of continuousdevelopment and improvement of the documentation.
The information or statements given in this document concerning the suitability, capacity, orperformance of the mentioned hardware or software products cannot be considered binding but shallbe defined in the agreement made between Nokia Telecommunications and the customer. However,Nokia Telecommunications has made all reasonable efforts to ensure that the instructions contained inthe document are adequate and free of material errors and omissions. Nokia Telecommunications will,if necessary, explain issues which may not be covered by the document.
Nokia Telecommunications' liability for any errors in the document is limited to the documentarycorrection of errors. Nokia Telecommunications WILL NOT BE RESPONSIBLE IN ANY EVENT FORERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL(INCLUDING MONETARY LOSSES), that might arise from the use of this document or the informationin it.
This document and the product it describes are considered protected by copyright according to theapplicable laws.
NOKIA logo is a registered trademark of Nokia Corporation.
Other product names mentioned in this document may be trademarks of their respective companies,and they are mentioned for identification purposes only.
Copyright © Nokia Telecommunications Oy 1999. All rights reserved.
No. of
Pages
34
Edited by/Translator
Ashley Colley
Jari Malinen
Author
11.8.99
Arto Kangas
Approved by
22.9.1999
Reko Juntto
Previous issue
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 3/33
Contents
NTC Version: draft © Nokia Telecommunications Oy
3 (33)
Contents
1 General 41.1 Document revision history 4
2 Sharing Capacity between Circuit Switched and PacketSwitched 52.1 Territory Method 52.1.2 Parameters for Territory management 62.2 Territory Upgrade and Downgrade 72.2.1 Reasons for starting the upgrade procedure 72.2.2 Intra cell handover of CS call due to GPRS Territory
Upgrade 72.2.3 GPRS territory downgrade 82.2.4 Free TS for CS calls 82.3 Effect on existing features 9
3 PS Channel Allocation 123.2 PS Channel allocation principles 123.3 Scheduling 133.4 GPRS Territory Upgrade / Downgrade Request 143.5 GPRS MS Class 153.5.1 MS multislot class 16
4 GPRS Air Interface Channels 19
5 GPRS Uplink 225.1 Uplink TBF establishment 225.2 Medium Access (MAC) modes 245.3 Uplink data transfer (acknowledged mode) 24
6 GPRS Downlink 266.1 PS Paging 266.2 Downlink TBF establishment 266.3 Downlink Data transfer 27
7 Power Control 297.1 Uplink Power Control 297.2 Downlink power control 29
8 Coding Scheme Selection 31
9 Cell Selection and Re-selection 33
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 4/33
General
NTC Version: draft © Nokia Telecommunications Oy
4 (33)
1 General
This document does not belong to Nokia official customer documentation. This
document is made only to give some answers to frequently asked questionsregarding the GPRS radio resourse management principles and Nokia GPRS
BSS implementation. The GPRS development and further specification work is
ongoing both in ETSI standardisation and in Nokia R&D. This documentdescribes the current understanding of the issues as it is basis. Further changes
for subjects mentioned here are possible. The final customer documentation will
be available once the Nokia GPRS system and products implemention isfinalized. Nokia undertakes rights to make changes, corrections to subjects
described here if necessary.
Note, Items shown in italics are not supported in the 1 st
Nokia GPRS release
Responsible person: Ashley Colley / Jari Malinen
Status: 1.0
Confidentiality: Nokia Customer Confidential.
1.1 Document revision history
Version Date Author Comments
0.1 11.8.99 AKa/Aco Conversion from .ppt
0.2 31.8.99 JMa Editing
1.0 22.09.99 RJu First approval
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 5/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
5 (33)
2 Sharing Capacity between CircuitSwitched and Packet Switched
2.1 Territory Method
In Nokia solution for each cell separate territories for circuit switched andpacket switched connections can be defined, this is shown in the figure below.
The border between the territories can move dynamically based on the load of
circuit switched and packet switched traffic.
• Circuit Switched traffic has priority
• In each cell Circuit Switched & Packet Switched territories are defined
• Territories consist of consecutive timeslots
TRX 1
TRX 2
CCCH TS TS TS TS TS TS TS
TS TS TS TS TS TS TSTS
DedicatedGPRS
Capacity
CircuitSwitched
Territory
PacketSwitchedTerritory
Territory border movesD y n a m i c a l l y based onCircuit Switched traffic load
C i r c u i t S w i t c h e d c a p a c i t y n o t a f f e c t e d
b y i n t r o d u c i n g G P R S
DefaultGPRS
Capacity
AdditionalGPRS
Capacity
Figure 1 The Territory Method
This method of defining separate territories maximises the availability of
comsecutive multislots being available in both PS and CS territories (compared
to the alternative of randomly mixing CS and PS calls together).
The GPRS territory is a set of consecutive TS, excluding:
• TS that are not capable of full rate traffic (BCCH, SDCCH, HR)
• blocked TS
• TSL 0 when Base Band Frequency Hopping is used
• T HSCSD connection
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 6/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
6 (33)
2.1.2 Parameters for Territory management
The following are the operator configurable parameters for territory
management:
• GPRSenabled (BTS-level)
• GPRSenabledTRX (TRX-level)
• DedicatedGPRScapacity (BTS-level)
• DefaultGPRScapacity (BTS-level)
• PreferBCCHfreqGPRS (BTS-level)
• TerritoryUpdateGuardTimeGPRS (BSC-level)
GPRS territory parameters can be changed when the cell GPRS capability is set
off by GPRSenabled parameter or when the cell is locked.
PS TCH reservation is done in two phases. First the CS RRM allocates theTCHs which the PCU may use. Abis switching through GSWB to PCU is made
to those TCHs. PCU and CCU make the frame synchronization right after the
switch. PS RRM makes the actual PS channel allocation to PS connections using
the TCHs determined by the CS RRM.
Dedicated GPRS capacity
Part of the TCHs can be reserved totally for GPRS. These TCHs are blocked for
CS.
Default GPRS capacity
The default GPRS capacity is always allocated to GPRS territory when allowedby the CS load. The CS RRM initiates upgrading and downgrading of these
TCHs. These TCHs are allocated to GPRS territory whether there is any GPRS
traffic or not.
Additional GPRS capacity
When the default GPRS capacity is allocated to GPRS territory the PS RRM can
ask for additional TCHs. The PS RRM initiates upgrade requests for theadditional resources. The CS RRM controls the reservation of the additional
TCHs based on the CS load. GPRS territory downgrade of TCHs allocated as
additional GPRS capacity can be initiated by CS or PS RRM.
Location of GPRS Territory (TRX)
The location of the GPRS territory within each cell is determined by:
• parameter PreferBCCHfreqGPRS
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 7/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
7 (33)
• TSL Configuration
• SDCCH TSL < HR TSL < DR TSL < FR TSL
• Resource situation
• multislot HSCSD calls < busy TS < idle TSL
2.2 Territory Upgrade and Downgrade
2.2.1 Reasons for starting the upgradeprocedure
Upgrade of the GPRS territory (ie. increasing the number of TS available for
GPRS traffic) may be started for the following reasons:
• GPRS is set enabled in a BTS (BTS parameter GPRSenabled)
• GPRS-TRX is created => default GPRS capacity increases
• GPRS-TRX is deblocked, e.g. the first GPRS-TRX in a BTS
• TSL inside the GPRS territory is deblocked
• CS call is released, ie. CS load decreases
• PS RRM requests additional GPRS capacity
2.2.2 Intra cell handover of CS call due to GPRSTerritory Upgrade
GPRS territory upgrade is dependent on the CS load. If the CS load, GPRSdemand and parameter settings demand that a GPRS territory upgrade procedure
is started any CS call(s) in the TSL(s) to be included in the new GPRS territory
are handed over to other TS in the same cell. This is shown in the figure below:
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 8/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
8 (33)
B = BCCH TSL
S = SDCCH TSL
C = CSW call
DefaultGPRScapacity = 20%
DedicatedGPRScapacity = 10%
FreeTSLsforCSW = 3
= GSM territory
= GPRS territory
B C C C C C C
S
C
C C
C
C d d D D D
C C C C
C C C
C
GPRS territory upgrade
Figure 2 Intra cell handover to CS call to GPRS TerritoryUpgrade
2.2.3 GPRS territory downgrade
A GPRS territory downgrade is initiated due to increase of CS load. PCU can
initiate GPRS resource downgrade to additional GPRS resources.
2.2.4 Free TS for CS calls
Some TS are kept free for incoming CS calls. This is to avoid:
• delays in allocating TS to CS calls
• continuous GPRS territory upgrade and downgrade, which also disturbs PStraffic (ie. To provide some hysterysis)
The amount of TS kept free depends on the cell size, this is shown in the table
below:
Free TSLs
TRXs downgrade upgrade
1 1 1
2 1 2
3 1 2
4 2 3
5 2 4
6 2 4
7 2 4
8 3 5
9 3 5
10 3 6
11 3 6
12 3 6
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 9/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
9 (33)
Table 1 Free TS for CS calls
The numberr of free TS has been set such that:
For downgrade:
• - 95 % probability that there is no need for new downgrade procedure duringthe previous downgrade.
For upgrade:
• - 95 % probability that there will be no downgrade needed in four seconds
after the upgrade.
2.3 Effect on existing features
Introducing GPRS resources in a BTS has effect on existing features that are
based on load of circuit switched (CS) traffic. In general, resources that cannotbe used for CS calls, i.e. dedicated GPRS TS, must be totally excluded from the
available resources in various CS resources management features. However,
default GPRS resources are included in decisions since they may be allocated
for CS traffic when necessary. This gives rise to the following:
• Number of working resources for CS features = working resources in BTS -
dedicated GPRS resources
• Number of idle resources for CS features = idle CS resources + GPRS
resources - dedicated GPRS resources• Number of occupied resources for CS features = occupied CS resources.
The following lists various features and notes the impact of GPRS on each.
Interference band recommendation
TCHs in the GPRS territory are allocated to CS calls only when there are no free
TS elsewhere in the cell. Interference band recommendation is used to
allocations done in CS territory.
Frequency Hopping
TSL 0 not used for GPRS in Base Band Hopping.
Optimization Of The MS Power Level In Handovers
Power optimization is not done when reserving TCHs for CS connection from
GPRS territory.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 10/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
10 (33)
Intelligent Underlay Overlay
Super-reuse frequencies are not supported for GPRS.
Forced Handover For O&M Reason
If there are GPRS-TS in the TRX to be blocked, the BSC moves those TS to the
CS territory and starts a downgrade procedure immediately. The BSC
downgrades all of the TS in the TRX regardless of which territory they belongto. If the TRX to be blocked does not include GPRS-TS, the BSC does not
change the territories.
Dynamic SDCCH allocation
Dynamic SDCCH is not allocated to the GPRS territory.
Preferred BCCH TRX
CS and PS can prefer either the same kind of TRXs or the opposite kind of
TRXs or prefer nothing at all.
TRX fault
When a TRX carrying TCHs becomes faulty the radio timeslots on the TRX are
blocked from use. The possible ongoing calls and also the call control resourcesin the BSC are released. TCHs belonging to a GPRS territory are downgraded
from GPRS use. The CS RRM determines the possibility of GPRS territory
upgrade to another TRX. When the number of dedicated and default GPRS
capacity TS is counted working and blocked TS are included to the total, thusthe amount that the CS RRM tries to allocate for the GPRS territory is not
changing in case of a TRX fault.
HSCSD vs GPRS
In principle CS traffic has priority over PS traffic. Multislot HSCSD is always
preferred to additional GPRS capacity TCHs.
If there has been defined default GPRS capacity in a cell (DefaultGPRScapacity
> 0) load limits for incoming HSCSD requests are calculated based on the
existing HSCSD parameters with the following changes:
-default GPRS capacity TCHs which are reserved for GPRS use are counted asoccupied TCHs
-UpperLimitCellLoadHSCSD as a criterion for interrupting multislot allocations(that is used together with MinHSCSDcapacityCell) is replaced with the new
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 11/33
Sharing Capacity between Circuit Switched and Packet Switched
NTC Version: draft © Nokia Telecommunications Oy
11 (33)
GPRS limit Free TSLs for CS if the latter is more restricting; thus the one is
used that limits multisot allocation earlier
In case DefaultGPRScapacity = 0 HSCSD load parameters are applied as
without GPRS.
If multislot allocation is denied transparent HSCSD requests are rejected andnon-transparent requests are served with 1 TSL as before.
If TSL amount in HSCSD allocation is not restricted T requests are servedpreferably in the CSW territory, and in the PSW territory only if necessary. If atransparent HSCSD call ends up in the GPRS territory RRMPRB does not later
try to move it elsewhere with the intra cell handover. Instead it tries to replacethe lost GPRS channels on the other side of the arrived HSCSD call. But this of
course only when the sufficient margin exists (Free TSLs for CS).
NT HSCSD requests are always served in the CS territory as long as there is at
least one TCH/F available. A normal HSCSD upgrade procedure is applied laterto fulfil the need of the NT request if the call starts with less channels thanneeded. In order for the NT call to get the needed TSL amount CS RRM
starts an intra cell handover for suitable single slot calls beside the NT
HSCSD call. At starting of the handover RRMPRB has to check that a singleslot call is able to move and that HSCSD upgrade is in general allowed.
An NT HSCSD call enters the GPRS territory only in case of congestion of theCS territory. If multislot allocation was originally defined allowed it will be
applied also within the GPRS territory to serve the NT request. If the cell load
goes later down so that GPRS upgrade becomes enabled the NT HSCSD call is
handed over to another location in the cell so that the GPRS territory can beextended.
If the HSCSD state in a cell has been defined restricted so that HSCSD
downgrade should be made as a new TCH request arrives it is made instead of
GPRS downgrade. If the cell HSCSD state does not require HSCSD downgradethen a GPRS downgrade for the possible additional TSLs is made if maintaining
of the margin Free TSLs for CS requires it. If no additionals exist actions depend
on HSCSD traffic amount: if there are HSCSD TCHs more thanMinHSCSDcapacityCell requires then an HSCSD downgrade is made rather
than a GPRS downgrade. If the minimum HSCSD capacity is not in use then a
GPRS downgrade is made to maintain the margin Free TSLs for CS.
GPRS territory upgrade can be done although minHSCSDcapacity is not in use
and there are pending HSCSD connections in the cell. Free TSLs for CS is thelimiting factor for GPRS territory upgrade.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 12/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
12 (33)
3 PS Channel Allocation
This section describes how the PS resources are allocated between different
GPRS users.
The figure below describes the uplink sheduling. Up to 7 GPRS connections canshare the resources of a single TS (this is shown on the vertical axis). The uplink
and downlink scheduling are independent, for downlink upto 9 GPRSconnections can share the resources of a single TS. In the figure below three 3
TS mobile connections are shown TFI1,TFI,2 and TFI3.
TFI1TFI1TFI1TFI2
TFI3TFI3TFI2
TFI3
DedicatedGPRS
Capacity
DefaultGPRS
Capacity
0 1 2 3 4 5 6 7
1
2
3
4
5
6
7
TSL
TFI2
Figure 3 PS Channel Allocation/Scheduling
Temporary Block Flow / Temporary Block Identifier
A Temporary Block Flow (TBF) is a physical connection used by the two RR
entities to support the unidirectional transfer of LLC PDUs on packet dataphysical channels. The TBF is allocated radio resources on one or more TCHs
and comprises a number of RLC/MAC blocks carrying one or more LLC PDUs.
A TBF is temporary and is maintained only for the duration of the data transfer.
TBF is identified by Temporary Flow Identity (TFI).
3.2 PS Channel allocation principles
Packet Switched channels are allocated acording to the following:
1. Downlink and uplink are separate resources
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 13/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
13 (33)
2. Multiple phones can share one TCH, but the TCH is dedicated to one MS
(TBF) at a time. That means that the TCH is reserved for multiple MSs, but oneMS is transmitting or receiving at a time. It is possible to allocate 7
simultaneous uplink MSs and 9 simultaneous downlink MSs on the same TCH.
3. Channels allocated to a TBF must be allocated from the same TRX
4. Those TCHs which give the maximum possible capacity for the TBF are
allocated for the TBF within the limits of the multislot class of the mobile. An
exception for the above are short closed ended TBFs. In these cases only one
channel is allocated.
TCH selection to TBF
The channel allocator determines the number of TCHs that are needed and
counts the best throughput for that amount of TCHs. Eg. (see above figure) TFI3
will have TS 3, 4 and 5 since it will have 1/1 + 1/1 + 1/2 (=2½) service as TS 4,5 and 6 would offer 1/1 + 1/2 + 1/2 (=2) service and TS 5, 6 and 7 would offer
1/2 + 1/2 + 1/2 (=1½) service.
When the load of TCH combinations is equal they are first compared first by the
capacity type (additional < default < dedicated) and then by the PACCH load.
PACCH load is the amount of TBFs using a certain TCH as PACCH.
PACCH
Packet Associated Control Channel (PACCH) conveys signaling informationrelated to a given MS. The signaling information includes e.g.
acknowledgements and power control information. The PACCH also carries
resource assignment and reassignment messages, comprising the assignment of
a capacity for TCH(s) and for further occurrences of PACCH. One PACCH isassociated to one or several TCHs that are concurrently assigned to one MS.
PACCH is bi-directional channel. It can be allocated both on the uplink and on
the downlink regardless on whether the corresponding TCH assignment is foruplink or downlink. Assigned TCHs are used for PACCH for the direction the
data is sent. For the opposite direction the MS multislot capability has to be
taken into account when allocating the PACCH.
3.3 Scheduling
In this scheme each TBF has the following parameters:
• A time when it should be served.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 14/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
14 (33)
• A time interval by which its serving time is increased each time the TBF
gets a turn.
In addition a virtual time is kept. In each TCH, the first TBF is selected which
has the lowest serving time. When it has been served, its serving time isincremented by its time interval. Virtual time is incremented by the same time
interval.
In release 1 this works as Round Robin (ie. equal level of service to all), but this
can be easily updated to provide QoS and priorities in future releases.
The scheduler is responsible for scheduling the following:
Downlink:
• scheduling of RLC/MAC control blocks (prioritized over data blocks)
• scheduling of RLC data blocks
• Relative Reserved Block Period (RRBP) for polling requests
• Dummy control blocks
• Idle PCU frames to BTS, when nothing else to send
Uplink:
• single block reservations (for Packet Resource Request messages in two
phase uplink access)
• Dynamic MAC mode with USF (Uplink State Flag)
• reservations for Packet Uplink Ack/Nack messages (ordered by RRBP)
• CCU Uplink decoding mode (normal / access / idle)
3.4 GPRS Territory Upgrade, DowngradeRequest
PS RRM may request more TCHs to GPRS territory when the Default GPRS
capacity is already allocated to GPRS territory. The PS RRM is also responsiblefor requesting downgrade of the additional GPRS capacity TCHs when there is
not need for them.The algorithm uses internal parameters X1, X2 and X3, these are not directly
user definable but are set by the user definable radio NW parameters described
previously.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 15/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
15 (33)
PS RRM requests new TCH(s) to the GPRS territory when the average number
of TBFs in TCHs in the GPRS territory is greater than X1. The target averagenumber of TBFs in TCHs (X2) in the GPRS territory determines the number of
TCHs that the PS RRM is requesting from CS RRM.
When the average number of TBFs in TCHs in the GPRS territory is less than
X3, the PS RRM will request GPRS territory downgrade. The target averagenumber of TBFs in TCHs (X2) in the GPRS territory determines the number of
TCHs that the PS RRM is requesting the CS RRM to downgrade.
3.5 GPRS MS Class
Different classes and types of GPRS terminal are specified, this is shown in the
figure below:
• Classes
• A simultaneous CS and PS
• B ready for both, one active at a t ime
• C either CS MS or PS MS
• TypesType 1, multislot classes 1-12, like HSCSD- max 4 downlink and 2 uplink
Type 2, multislot classes 13-18, simultaneous receive&transfer- max 8 downlink and 8 uplink
Type 1, multislot classes 19-29, enhancements for GPRS- max 6 downlink but only 2 uplink due to USF scheduling
Figure 4 GPRS Terminals
The purpose of the definition of the GPRS MS Classes is to enable the differentneeds of the various market segments to be satisfied by a number of MS types
with distinct capabilities.
CLASS A: Supports simultaneous attach, simultaneous activation, simultaneous
monitor, simultaneous invocation and simultaneous traffic.CLASS B: Simultaneous traffic shall is not supported. The mobile user canmake and/or receive calls on either of the two services sequentially but not
simultaneously. The selection of the appropriate service is performed
automatically, i.e. an active GPRS virtual connection is put on hold, if the user
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 16/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
16 (33)
accepts an incoming circuit switched call or establishes an outgoing circuit
switched call.
CLASS C: Supports only non-simultaneous attach. Alternate use only. If bothservices (GPRS and Circuit Switched) are supported then a Class C MS can
make and/or receive calls only from the manually or default selected service,
i.e., either GPRS or Circuit Switched service. The status of the service whichhas not been selected is detached i.e., not reachable.
3.5.1 MS multislot class
The MS multislot class determines the number of simultaneous downlink and
uplink TS. For details, see GSM05.02.
Multislotclass
Maximum number of slots Minimum number of slots Type
Rx Tx Sum Tta Ttb Tra Trb
1 1 1 2 3 2 4 2 1
2 2 1 3 3 2 3 1 13 2 2 3 3 2 3 1 1
4 3 1 4 3 1 3 1 1
5 2 2 4 3 1 3 1 1
6 3 2 4 3 1 3 1 17 3 3 4 3 1 3 1 1
8 4 1 5 3 1 2 1 19 3 2 5 3 1 2 1 1
10 4 2 5 3 1 2 1 1
11 4 3 5 3 1 2 1 1
12 4 4 5 2 1 2 1 1
13 3 3 NA NA a) 3 a) 2
14 4 4 NA NA a) 3 a) 2
15 5 5 NA NA a) 3 a) 2
16 6 6 NA NA a) 2 a) 2
17 7 7 NA NA a) 1 0 2
18 8 8 NA NA 0 0 0 2
19 6 2 NA 3 b) 2 c) 1
20 6 3 NA 3 b) 2 c) 1
21 6 4 NA 3 b) 2 c) 122 6 4 NA 2 b) 2 c) 1
23 6 6 NA 2 b) 2 c) 1
24 8 2 NA 3 b) 2 c) 1
25 8 3 NA 3 b) 2 c) 1
26 8 4 NA 3 b) 2 c) 1
27 8 4 NA 2 b) 2 c) 1
28 8 6 NA 2 b) 2 c) 1
29 8 8 NA 2 b) 2 c) 1
Table 2 MS multislot class
Type 1 MS are not required to transmit and receive at the same time. Type 2 MSare required to be able to transmit and receive at the same time.
Rx describes the maximum number of receive timeslots that the MS can use per
TDMA frame. The receive TS need not be contiguous.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 17/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
17 (33)
Tx describes the maximum number of transmit timeslots that the MS can use per
TDMA frame. The transmit TS need not be contiguous.
Sum is the total number of uplink and downlink TS that can actually be used bythe MS per TDMA frame.
Tta relates to the time needed for the MS to perform adjacent cell signal levelmeasurement and get ready to transmit. For type 2 MS it is not applicable.
Ttb relates to the time needed for the MS to get ready to transmit. This minimum
requirement will only be used when adjacent cell power measurements are notrequired by the service selected.
Tra relates to the time needed for the MS to perform adjacent cell signal levelmeasurement and get ready to receive.
Trb relates to the time needed for the MS to get ready to receive. This minimum
requirement will only be used when adjacent cell power measurements are not
required by the service selected.Example: Multislot class 12
Maximum number of DL channels = 4, UL channels = 4, time needed toswitch from receiving to sending Ttb = 1, time needed to switch from
sending to receiving and to perform measurements Tra = 2.
There can be several channel configurations which conform with the above
restrictions. One example, where four downlink TCHs (x) are allocated fordata transfer and the place of the uplink PACCH (p) is determined:
DL x x x xtb ra ra
UL
Figure 6 Multislot class 12
Type 1, MS multislot classes 1 - 12
Multislot classes 1 - 18 were defined at the time when HSCSD was specified.
There the type 1 classes 1 - 12 enables maximum of four downlink or uplink TSand five as a sum of donwlink and uplink TS (see example). For HSCSD only
downlink biased asymmetry is possible, so 3+2 (downlink+uplink) and 4+1 arethe maximum configurations. In GPRS the asymmetry can be also uplink biased.
There the maximum number of uplink TS is dependent on the allocation method
(see uplink data transfer):
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 18/33
PS Channel Allocation
NTC Version: draft © Nokia Telecommunications Oy
18 (33)
• 2 with dynamic allocation
• 3 with extended dynamic allocation
• 4 with fixed allocation
Only dynamic allocation is supported in Nokia GPRS release 1. Data traffic is
very downlink biased and MS hardware implementation is more complex themore there are uplink channels.
Type 2, MS multislot classes 13 - 18
These types include separate radio parts for receiving and transmitting, so there
are no restrictions to have time to change frequencies during the datatransmission. From the network point of view up to eigth TS can be supported
for both downlink and uplink (regardless of the uplink allocation method) in
GPRS. These kind of MSs would be very high priced and may not be available
in the near future.
Type 1, MS multislot classes 19 - 29
These types were introduced with GPRS knowing the fact that there doesn'tneed to be transmission to both dowlink and uplink direction in every TDMA-
frame. Example in the figure (where is it) shows a six TSL downlink data
transmission. TDMA-frames where the MS sends an acknowledgement canhave only four DL TCH TS, but TDMA-frames where there is no uplink
signalling six TS can be used.
Nokia GPRS release one supports maximum of six downlink TS to these
multislot classes. In theory it could be eight, but there needs to be time for theMS to make neighbour cell measurements and if the eight TS were assigned to
an MS, the network should schedule also gaps for MSs neighbour cell
measurements and that would complicate the PCU implementation. Seven or
eigth TS MSs are not expected to be on market in the near future.
In the uplink direction same restrictions apply as for multislot classes 1 - 12.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 19/33
GPRS Air Interface Channels
NTC Version: draft © Nokia Telecommunications Oy
19 (33)
4 GPRS Air Interface Channels
The figure below shows the GPRS air interface data flow.
BH
FH
LLC layer
RLC/MAC layer
Physical layer
Information field FCS
Normal burst Normal burst Normal burst Normal burst
Info fieldBH BCSRLCblocks
LLC frame
Primaryblock
Followingblock
Info field BCS Info fieldBH BCS
FH = Frame HeaderFCS= Frame Check SequenceBH = Block HeaderBCS= Block Check Sequence
(When SDCCH coding is used, BCS corresponds to the Fire code)
Figure 7 Transmission and Reception Data Flow
LLC
Logical Link Control (LLC): This layer provides a highly reliable cipheredlogical link. LLC shall be independent of the underlying radio interface
protocols in order to allow introduction of alternative GPRS radio solutions withminimum changes to the NSS.
LLC frames are sent between MS and SGSN. LLC has its own ARQ
(retransmissions).
RLC
The Radio Link Control function provides a radio-solution-dependent reliable
link. RLC blocks are sent between MS and BSS (PCU). There are two RLC
modes: acknowledge and unacknowledge mode. The latter doesn't have
retransmission.
Downlink data transmission
PCU receives LLC frames from SGSN, segments them to RLC blocks and sendsRLC blocks to MS. In normal case LLC frame is buffered in PCU as long as it
has been sent to MS including retransmission.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 20/33
GPRS Air Interface Channels
NTC Version: draft © Nokia Telecommunications Oy
20 (33)
Uplink data transmission
The PCU receives RLC data blocks from MS, reassembles them to LLC frames.
When the LLC frame is ready it is sent to SGSN and released from PCU buffer.However, the LLC frames have to be sent to SGSN in the order they are
received from the MS.
MS BSS SGSN
CHANNEL REQUEST
IMMEDIATE ASSIGNMENT
PACKET RESOURCE REQUEST
PACKET UPLINK ASSIGNMENT
(OPTIONAL)
(OPTIONAL)
RACH
AGCH
PACCH
PACCH
Figure 8 Packet Data Transfer:Uplink
Common Control Channel signalling
Common control channel signalling is used for the following:
Paging
• SGSN initiates, paging area is BSS, Location Area, Routing Area or Cell
• Special case is a CS page on PACCH when MS is in GPRS transfer state
Uplink TBF setup
• single block access on two phase uplink access
• one phase access, where only 1 TCH is reserved
Downlink TBF setup
PACCH usage
The PACCH is used for the following functions:
• Uplink two phase access
• Establishment of other side (uplink or downlink) TBF when other side exists
• Packet Uplink ACK/NACK
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 21/33
GPRS Air Interface Channels
NTC Version: draft © Nokia Telecommunications Oy
21 (33)
• Packet Downlink ACK/NACK
• Packet Polling procedure to obtain initial Timing Advance value during
downlink TBF establishment
• Radio resource re-assignment
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 22/33
GPRS Uplink
NTC Version: draft © Nokia Telecommunications Oy
22 (33)
5 GPRS Uplink
5.1 Uplink TBF establishment
When the MS wants to send data or upper layer signaling messages to the
network, it requests establishment of an uplink TBF. If the MS is initially in the
packet idle mode, the request is sent via the CCCH channel. The establishment
is carried out either as one phase access, or two phase access depending on theneeds for the data transfer. If the MS is already in the packet transfer mode i.e. it
has a downlink TBF, the request can be sent using the PACCH channel assigned
to the downlink TBF. This may be needed eg. for upper layer
acknowledgements.
One phase access
In one phase access the MS sends the network CHANNEL REQUEST message
with establishment cause 'one phase access'. PCU can allocate one TCH for such
request, which is told to MS in IMMEDIATE ASSIGNMENT message. TFI and
USF values are told in the message. MS sends its TLLI in the first data blocksand the one phase access is finalized when the PCU sends PACKET UPLINK
ACK/NACK message to the MS containing the TLLI (contention resolution).
Note that contention resolution in one phase access is not included to signaling
figures.
If there are no TCHs to give for the MS, IMMEDIATE ASSIGMENT REJECT
message is sent to MS. One phase access is guarded by a timer in PCU.
Two phase access
In two phase access the MS sends the PCU CHANNEL REQUEST message
with establishment cause 'single block access'. PCU allocates one TCH for that
request and also schedules a certain frame number for that block. The TCH andthe frame number are told to MS in IMMEDIATE ASSIGNMENT message.
MS uses the allocated block to send the PCU more accurate request with
message PACKET RESOURCE REQUEST.
If there are no TCHs to give for the MS, IMMEDIATE ASSIGMENT REJECT
message is sent to MS.
The actual configuration for uplink TBF is made by the information received in
PACKET RESOURCE REQUEST message. The TCH configuration, USF
value for each TCH and TFI are told to MS in PACKET UPLINKASSIGNMENT message sent in PACCH. The PACCH is sent in the same TSL
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 23/33
GPRS Uplink
NTC Version: draft © Nokia Telecommunications Oy
23 (33)
as was used in first phase, but assigned TCHs may be elsewhere. The two phase
access is finalized when the first block on the assigned TCHs is received.
In two phase access the contention resolution procedure is done in a way thatMS sends its TLLI in the PACKET RESOURCE REQUEST message and the
PCU includes that in the PACKET UPLINK ASSIGNMENT message.
The channel allocation in the second phase of the two phase access is
independent of the first phase and if there are no TCHs to give for the MS,
PACKET ACCESS REJECT message is sent to MS. Second part of the two
phase access is also quarded with a timer.
Uplink TBF establishment when downlink TBF exists
During a downlink TBF the MS can request resources for an uplink TBF by
including Channel Request Description IE in the PACKET DOWNLINK
ACK/NACK message. If there is no need to change the downlink TCHconfiguration PACKET UPLINK ASSIGNMENT message is used to tell the
uplink TCH configuration, USF values for each TCH and TFI to the MS. If thedownlink TCH configuration is changed PACKET TIMESLOT
RECONFIGURE message is used to tell the MS both the uplink and downlink TCH configurations, USF values for the uplink TCHs and uplink and downlink
TFIs. The procedure is ready when first block on the assigned uplink TCHs is
received.
This procedure is guarded by a timer. If PACKET UPLINK ASSIGNMENTfails, the uplink TBF is released. If the PACKET TIMESLOT RECONFIGURE
fails, both downlink and uplink TBFs are released.
MS BSS SGSN
DATA BLOCK
DATA BLOCK
PACKET UPLINK ACK/NACK
DATA BLOCK
DATA BLOCK (last)
PACKET UPLINK ASSIGNMENT
PACKET UPLINK ACK/NACK
PACKET CONTROL ACK
LLC PDU
PDTCH
PDTCH
PDTCH
PDTCH
PACCH
PACCH
PACCH
PACCH
Figure 9 Packet Data Transfer:Uplink
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 24/33
GPRS Uplink
NTC Version: draft © Nokia Telecommunications Oy
24 (33)
5.2 Medium Access (MAC) modes
The PCU can assign multiple MSs to the same uplink TCHs. ETSIspecifications allow the scheduling of uplink transmission turns to be done by
three different MAC modes: dynamic allocation, extended dynamic allocation
and fixed allocation. Nokia GPRS release 1 will support only dynamicallocation.
Dynamic allocation
In the assignment message the MS is given an USF value for each assignedTCH. the MS monitors the downlink RLC blocks on the TCHs it has been
assigned. Whenever the MS finds the USF value in the downlink RLC block, it
may send an uplink RLC block in the corresponding uplink frame. The
scheduling of RLC data block in each TSL is independent of other TS.
5.3 Uplink data transfer (acknowledgedmode)
RLC data blocks are collected to PCUs buffer. PCU has a receive window for 64
RLC blocks. That is the maximum number of unacknowledged RLC blocks. To
make the RLC data flow fluent the acknowledgements should be sent morefrequently. PCU can schedule the MS to send further RLC data blocks along
with the acknowledgement procedure.
PCU can sent PACKET UPLINK ACK/NACK message to MS whenever itwants. This however requires usage of downlink PACCH and is not reasonableto sent them too often. PACKET UPLINK ACK/NACK message includes a
bitmap which tells the correctly received blocks relative to the last correctly
received block (details can be found from GSM04.60). PACKET UPLINKACK/NACK message can be used for other purposes too, eg. to change coding
scheme and that also effects to the frequency of the acknowledgements.
PCU has a counter to control the MSs ability to sent RLC blocks in the frames it
has been assigned by USF values. Counter is reset always when the MS uses theframe it has been scheduled. If the counter reaches its maximum value the
uplink TBF is released.
PCU can change the uplink TCH configuration whenever it wants by sending
the MS PACKET UPLINK ASSIGNMENT or PACKET TIMESLOT
RECONFIGURE message. Reasons for reallocation are:
• GPRS territory downgrade
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 25/33
GPRS Uplink
NTC Version: draft © Nokia Telecommunications Oy
25 (33)
• downlink TBF establishment
• MSs change of requirements
If the reallocation is impossible for example in the case of GPRS territory
downgrade the PCU may release a TBF by PDCH RELEASE message.
Normal uplink TBF release is done by a countdown procedure. There the MScounts down the last RLC data blocks (15 or less) with the last last block numbered 0. There may be still some retransmission. When all the RLC data
blocks have been received correctly the PCU sends the LLC frame to SGSN and
a PACKET UPLINK ACK/NACK message with final ack indicator to MS. MSresponds to that with PACKET CONTROL ACK message and the TBF can be
released.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 26/33
GPRS Downlink
NTC Version: draft © Nokia Telecommunications Oy
26 (33)
6 GPRS Downlink
6.1 PS Paging
The PCU forwards the paging to the correct CCCH(s). The MS's paging
response is as any other uplink data transmission. MS sends some LLC frame to
SGSN and cell id is included in the message towards the SGSN. This is shown
in the figure below.
MS BSS SGSN
Packet Paging Request
Packet Paging Request
CHANNEL REQUEST
IMMEDIATE ASSIGNMENT
DATA BLOCK (last)
PACKET UPLINK ACK/NACK
PACKET CONTROL ACK
LLC PDU
PDTCH
PACCH
PACCH
PCH
RACH
AGCH
Figure 10 GPRS Paging
6.2 Downlink TBF establishment
Once the SGSN knows the MS location it can send LLC frames to correct PCU.SGSN tells the cell id in every message where it sends the LLC frame. PCU
allocates TCHs for the TBF. Assigned TCH and TFI are told to MS in
IMMEDIATE ASSIGNMENT message. Only one TCH can be assigned in theIMMEDIATE ASSIGNMENT. The actual allocation for multislot is done in the
beginning but it is told to MS by reallocation message.
When the MS is ready, the PCU sends a control message to the MS and requests
acknowledgement from the MS. This is done in order to determine the initialTiming Advance for the MS. If the channel configuration reserved for the DL
TBF consists only of one channel already assigned to the MS, the control
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 27/33
GPRS Downlink
NTC Version: draft © Nokia Telecommunications Oy
27 (33)
message sent is PACKET POLLING REQUEST. If the resources allocated form
a multislot configuration a PACKET DOWNLINK ASSIGNMENT message issent, and the whole configuration is given to the MS. The Timing Advance
value measured by BTS is included in PACKET POWER CONTROL/TIMING
ADVANCE message sent to MS.
In the case the are no radio resources for new TBF, the LLC frame is discardedand DISCARD message is sent to SGSN. Assignment procedure is guarded withtwo timers, one for resending the IMMEDIATE ASSIGNMENT message and
one for aborting the establishment.
Downlink TBF establishment when Uplink TBF exists
This follows the same principles as uplink TBF establishment when downlink
TBF exists.
6.3 Downlink Data transfer
MS BSS SGSN
PACKET DOWNLINK ASSIGNMENT
LLC PDU
IMMEDIATE ASSIGNMENT
Four access bursts
DATA BLOCK
PACKET DOWNLINK ASSIGNMENT
DATA BLOCK (polling, final)
PACKET DOWNLINK ACK/NACK
PDTCH
PDTCH
PDTCH
PDTCH
PACCH
PACCH
PACCH
AGCH
PACKET POWER CONTROL/TIMING ADVANCE
Figure 11 Packet Data Transfer:Downlink
The MS recognizes the RLC blocks sent to it by the TFI, which is included in
every RLC block header.
The PCU has 64 block transmit window, that is the maximum number of
unacknowledged RLC blocks. The PCU can ask whenever the MS to send an
DOWNLINK ACK/NACK message by setting polling flag to RLC data block header. PCU can sent further RLC data blocks along with the acknowledgement
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 28/33
GPRS Downlink
NTC Version: draft © Nokia Telecommunications Oy
28 (33)
procedure. Due to Abis transmission delays the fluent polling mechanism is
important especially in downlink data transfer.
If the PCU doesn't receive PACKET DOWNLINK ACK/NACK message whenit has polled, it increments a counter. After N consecutive unanswered pollings
the MS is considered lost and the downlink TBF is released, the LLC frame is
discarded from the PCU buffer and discard message is sent to SGSN.
PCU can change the downlink TCH configuration whenever it wants by sending
the MS PACKET DOWNLINK ASSIGNMENT or PACKET TIMESLOT
RECONFIGURE message. Reasons for reallocation are:
• GPRS territory downgrade
• uplink TBF establishment
• SGSN change of requirements
If the reallocation is impossible for example in the case of GPRS territory
downgrade the PCU may release a TBF by PDCH RELEASE message.The normal downlink TBF release is initiated by the PCU by setting a Final
Block Indicator FBI bit in the last RLC block header. There may be still some
retransmission. TBF can be released and the LLC frame removed from the PCUbuffer when the MS sends PACKET DOWNLINK ACK/NACK message with
Final Ack Indicator bit on.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 29/33
Power Control
NTC Version: draft © Nokia Telecommunications Oy
29 (33)
7 Power Control
7.1 Uplink Power Control
Nokia GPRS Release 1 supports uplink power control. It is used for optimising
the signal strength from MS to BTS.
• Uplink power control
PCH = min(Γ 0
− Γ CH - α∗(C + 48),PMAX)
0
5
1015
20
2530
35
- 4 5
- 5 0
- 5 5
- 6 0
- 6 5
- 7 0
- 7 5
- 8 0
- 8 5
- 9 0
- 9 5
- 1 0 0
- 1 0 5
- 1 1 0
Signal Strength (dBm)
M S O u t p
u t P o w e r
( d
B m )
gamma_ch = 30 alfa = 0.8
gamma_ch = 20, alfa = 0.3
Figure 12 Power control
Power Control parameters
Operator is given cell specific parameters α and Γ CH used in formula
• Γ CH, sets the minimum power level
• α, sets the slope for field streng effect to uplink power level
7.2 Downlink power control
The standardization of downlink power control is still ongoing.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 30/33
Power Control
NTC Version: draft © Nokia Telecommunications Oy
30 (33)
The downlink power control is a feature candidate for future releases (BSS10)
Power of each block needs to be sufficient for two MSs
• MS receiving the data
• MS receiving the USF flag
By the current ETSI specs the uplink MSs receiving the USFs in downlink direction are not reporting any measurements. Each new TBF is started with
maximum power. MSs Adaptive Gain Control:
• Dynamic downlink power control range 10 dB
• B0 of each multiframe must be sent with max power
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 31/33
Coding Scheme Selection
NTC Version: draft © Nokia Telecommunications Oy
31 (33)
8 Coding Scheme Selection
Nokia Simulations - polling interval = 18 blocks, non-frequency hopping)
• All Nokia BTS support GPRS without any modification (CS1 & CS2)
•8 Timeslot parallel connections supported
0
5
10
15
20
25
30
35
40
45
4 6 8 10 12 14 16 18 20 22 24
0
5
10
15
20
25
4 6 8 10 12 14 16 18 20 22 24
K b i t / s
C/I
CS-4
CS-3CS-2
CS-1
Network throughput - 1 Timeslot
Typical NW C/I
Minimum Average
C/I
Network throughput - 3 Timeslots
Typical NW C/I
Minimum AverageCS-2
CS-1
K b i t / s
Figure 13 GPRS Coding Schemes
Coding schemes
Stealing bits in the channel coding (for more information see GSM05.03) are
used to indicate the actual coding scheme (CS) which is used for each block
sent.
In downlink packet transfer the PCU selects the CS and the code word for the
selected CS is included in each sent RLC data block. If the CS is changed duringone TBF reservation, the new CS code word is included to the blocks.
In uplink data transfer the initial CS to be used is told to the MS in either theIMMEDIATE ASSIGNMENT or PACKET UPLINK ASSIGNMENT message.
The PCU can command the MS to change the CS by sending PACKET
UPLINK ACK/NACK message, which includes the Channel Coding Command
field.
In retransmission the same CS has to be used as in the initial block transmission.
Coding schemes CS-1 and CS-2 are supported in Nokia GPRS release 1.
GPRS radio link measurements
• Uplink RX_LEV and RX_QUAL in uplink transfer
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 32/33
Coding Scheme Selection
NTC Version: draft © Nokia Telecommunications Oy
32 (33)
• Downlink RX_LEV, RX_QUAL, SIGN_VAR and interference level in
downlink transfer
Uplink CS selection
CS change will be based on the BLER.
Downlink CS selection
CS change will be based on the BLER.
7/31/2019 01_Nokia GPRS Radio Resource Management
http://slidepdf.com/reader/full/01nokia-gprs-radio-resource-management 33/33
Cell Selection and Re-selection
9 Cell Selection and Re-selection
• MS selects the cell in standby state
• C1/C2
• MS reselects the cell in ready state (handover)
• C1/C2
• MS stops the transmission in the old cell
• MS reads system information messages in the new cell
• MS reports to the SGSN
• initiates uplink TBF (data, signalling or dummy) or
• makes routing area update
• If the target cell is in the same RA and handled by the same PCU the data isrerouted
• If the target cell is in different RA or PCU, the data is discarded
Figure 14 GPRS Cell Selection and Re-selection
Network Control Order
The network may request measurement reports from the MS and control its cell
re-selection. This is indicated by the parameter
NETWORK_CONTROL_ORDER:
• NC0, the MS performs autonomous cell re-selection.
• NC1, the MS sends measurement reports to the network, but performs still
autonomous cell re-selection.
• NC2, the MS sends measurement reports to the network and the network performs the cell re-selection.
The parameter values NC1 and NC2 only apply in Ready state. In Standby state,
the MS shall always use normal MS control independent of the ordered NC
mode.
NC0 method is supported in Nokia GPRS release 1