tmo54048_gprs & egprs planning_b10
TRANSCRIPT
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E-GPRS RNP (Radio Network Planning) B10 Fundamentals
TMO54048
E-GPRS RNP (Radio NetworkPlanning) B10 Fundamentals
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Objectives
By the end of the course, participants know:
GPRS Session Management,
TBF Management, Location Management,
System Information Management,
Cell Selection and Re-selection,
Power Control and RLC Measurements,
Coding Scheme and Link Adaptation,
Radio Resources Re-allocation,
(E)GPRS Planning Principles,
(E)GPRS Network Planning,
Network Evolution Scenarios,
(E)GPRS QoS Enhancement Features, (E)GPRS with GSM Capacity Enhancement Features
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Objectives
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Table of Contents
Switch to notes view! Page
1 Basics 91.1 Service Overview GPRS 101.2 Service Overview EGPRS 11
1.3 Support of GPRS QoS classes 121.3.1 Radio Network Planning Impact 13
1.4 Dual Transfer Mode 141.4.1 Radio Network Planning Impact 15
1.5 (E)GPRS MS Multislot Classes 161.6 (E)GPRS General Architecture 171.7 Alcatel (E)GPRS Architecture 191.8 (E)GPRS Protocol Layers (Transmission Plane) 221.9 Alcatel (E)GPRS BSS Hardware support 231.10 Modulation Technique: 8-PSK only for EGPRS 241.11 8-PSK TRA Power Aspects 251.12 (E)GPRS Radio Blocks Structure 431.13 GPRS Channel Coding 451.14 EGPRS Channel Coding 48
1.15 Radio Link Adaptation Overview 531.16 Automatic ReQuest for repetition (ARQ) 541.17 Type-I ARQ mechanism 551.18 Type-I ARQ in GPRS 561.19 Type-I ARQ in EGPRS 571.20 (E)GPRS radio physical channel: PDCH Concept 611.21 (E)GPRS Multiframe 621.22 (E)GPRS Logical Channels 631.23 Master/Slave PDCH concept 651.24 Temporary Block Flow 661.25 Resources Sharing 681.26 MS multiplexing co-ordination 721.27 GPRS mobility management (GMM) states for MS 751.28 Radio Resource (RR) operating modes for MS 76
1.29 Attach procedure 771.30 PDP context activation 791.31 Location management 801.32 Routing Area 811.33 Network Mode of Operation (NMO) 821.34 TBF establishment 831.35 UL TBF establishment on CCCH, 1 phase access 841.35 UL TBF establishment on CCCH, 1 phase access 851.36 UL TBF establishment on CCCH, 2 phases access 861.37 DL TBF establishment on CCCH 881.38 System information broadcasting on BCCH 891.39 System information broadcasting on PBCCH 911.40 (E)GPRS Transmission Aspects 941.40 TRX Classes Concept 95
1.41 Two Abis Links per BTS 982 Features 99
2.1 Enhanced Packet Cell Reselection (R4 MSs) 1002.1.1 Radio Network Impact 101
2.2 Extended Uplink TBF Mode 1022.2 Radio Network Planning Impact 1032.3 Enhanced support of E-GPRS (EDGE) in uplink 105
2.3.1 Radio Network Planning Impact 1072.4 Counter Improvements for Release B9 108
2.4.1 Radio Network Planning Impact 112
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Table of Contents [cont.]
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2.5 Autonomous Packet Resource Allocation 1132.5.1 Radio Network Planning Impact 115
2.6 2G/3G Inter-working 116
2.6.1 Radio Network Planning Impact 1192.7 M-EGCH Statistical Multiplexing 120
2.7.1 Radio Network Planning Impact 1222.8 Dynamic Abis allocation 123
2.8.1 Radio Network Planning Impact 1242.9 Enhanced transmission resource management 1252.10 RMS_I1 Improvements 126
2.10.1 Radio Network Planning Impact 1272.11 RMS_I2 Improvements 128
2.11.1 Radio Network Planning Impact 1293 (E)GPRS Radio Algorithms 131
3.1 Cell Reselection Overview 1323.2 Cell reselection: NC0 mode, no PBCCH established 1363.3 Cell reselection: NC0 mode, PBCCH established 138
3.4 Cell reselection execution: NC0 in PTM 1453.5 Cell reselection: NC2 mode 1473.6 GPRS redirection 1583.7 GPRS Power Control: Overview 1603.8 GPRS Power Control: Measurements 1613.9 GPRS Power Control: Algorithm 1653.10 Link adaptation: DL GPRS Radio Link Control 1683.11 Link adaptation: UL GPRS Radio Link Control 1723.12 Link adaptation in EGPRS: New metrics 1753.13 Link adaptation: DL EGPRS Radio Link Control 1763.14 EGPRS Link Adaptation Decision 1783.15 TRX ranking/TRX transmission pool set-up 1793.16 TRX capability for PS traffic 1813.17 Radio Resource Allocation: Overview 182
3.18 Radio Resource Allocation: PDCH state 1833.19 TRX selection for EGPRS TBFs 1863.20 Radio Resource Allocation: EGPRS TBFs 1913.21 Radio Resource Allocation: TBF Re-allocation 1943.22 Radio Resource Allocation: Min_PDCH 1953.23 Radio Resource Allocation: Fast initial (E)GPRS access 196
4 General (E)GPRS planning principels 1974.1 Throughput Dependency -> Interference (and Level) 1984.2 Packet data throughput 1994.3 Reference performance point 2004.4 Saturation effect 2014.5 Cell area and throughput 2034.6 Throughput C/I 204
5 (E)GPRS Network introduction 207
5.1 GPRS network planning 2085.2 GPRS Greenfield planning 2095.3 GPRS traffic calculation and traffic analysis 2115.4 GPRS traffic calculationand PS traffic 2125.5 GPRS traffic calculation and user profile 2145.6 GPRS traffic calculation and market applications 2155.7 GPRS traffic calculation and user behavior 2165.8 Customer questionnaire 2175.9 Traffic Model (Example) 2195.10 User mapping 2205.11 Multi-Service 2215.12 QoS per User Application 2225.13 GPRS traffic calculation 2235.14 Exemplary results of the 3 traffic calculation methods 228
5.15 GPRS traffic calculation result 233
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Table of Contents [cont.]
Switch to notes view! Page
6 (E)GPRS Network design 2356.1 General 2366.2 Frequency planning 239
6.3 Throughput 2416.4 Link budget 2426.5 Interference analysis on BCCH frequencies 2456.6 Interference analysis on TCH frequencies 2466.7 TRX assignment to GPRS service 2476.8 GPRS Analysis 2486.9 LA and RA planning 2526.10 Quality of Service 262
7 Considerable features to react (E)GPRS target 2657.1 General 2667.1 Optimization campaign on parameters 2677.2 MPDCH 2687.3 Enhanced PDCH Adaptation & Fast pre-emption 2717.4 User multiplexing 272
7.5 PDCH Resource Multiplexing 2737.6 Radio (TBF) Resource Reallocation 2747.7 Coding Scheme Adaptation 2767.8 Cell Reselection 2777.8 GPRS Power Control 2797.8 Features on DL TBF establishment and release 280
7.8.1 Delayed DL TBF release 2817.8.2 Fast Downlink TBF re-establishment process 2837.8.3 Non-DRX feature 284
8 GPRS introduction into operational GSM network 2858.1 General 286
9 GSM Network enhancement features & GPRS 2939.1 Frequency Hopping 2949.2 -cell 296
9.3 Dual Band 2989.4 Concentric cell 301
10 E-GPRS 30310.1 E-GPRS main differences 304
11 GPRS traffic calculation example 30711.2 User and area distribution determination 31011.3 Traffic demand for CS traffic 31111.4 Traffic demand for packet traffic 31211.5 Network capacity calculation 31611.6 Traffic dimensioning 320
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1.1 Service Overview GPRS
GPRS General Packet Radio Service
GPRS is a GSM feature
It has been introduced to provide end-to-end packet-switched (PS)data transmission between MS users and fixed packet data networks
GPRS provides efficient utilization of the radio resources:
multislot operation
flexible sharing of radio resources between MS
resources are allocated only when data are transmitted
Charging is mainly based on data volume transmitted and not on theconnection time
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1.2 Service Overview EGPRS
EDGE Enhanced Data rates for GSM Evolution
ETSI standardized solution and can be introduced in two ways:
CS enhancement: Enhanced circuit-switched data or ECSD
PS enhancement for GPRS EGPRS
EGPRS relies on the introduction of8-PSK (Eight Phase Shift Keying)modulation technique:
Same qualities in terms of generating interference on an adjacentchannel as GMSK makes possible to integrate EDGE channels intoexisting frequency plan
8-PSK Symbol rate = GMSK Symbol rate, but one symbol represents now 3bits instead of 1 bit in GMSK increased data rates
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1.3 Support of GPRS QoS classes
Four QoS classes (or traffic classes) are defined:
The conversational class will be very likely dedicated to real-time
conversation. Speech and video conferencing tools are someexamples of such applications
The streaming class corresponds to a real-time stream and enforcesmainly constraints on jitter. Video streaming or PoC (Push to takover Celullar) are typical applications for the streaming traffic class.
The interactive class corresponds to mainly to traditional Internetapplications like web browsing. Some differentiation can be donebetween two services by using the traffic handling priority attribute.
The background class is typically corresponding to Best Effortservices. Applications that make use of this class might be e-mail
downloading, SMS, or even ftp downloading.
PFC procedure
Packet Flow Context (PFC) is a concept introduced starting with R99 3GPP release to ensure that the BSS
is involved in the R99 QoS negotiation. The interest of PFC is to differentiate on the radio interface the
conversational and streaming traffics and to reserve resources for these traffics. Without the PFC, the
BSS only knows the R97/98 QoS parameters (correspond to the interactive and background R99 QoS
classes). It enables to perform admission control and QoS based resource allocation in the BSS.
R99 QoS is taken into account if the PFC (Packet Flow Context) procedures are supported by the MS, the
BSS and the SGSN. It allows the BSS B9 to handle streaming and interactive traffics and also to negotiate
the QoS parameters.
R97/98 QoS should be also taken into account (OP12) if PFC is not supported by the MS or the SGSN in
order to handle interactive traffics or some specific applications as PoC (Push over Cellular).
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1.3.1 Radio Network Planning Impact
QoS subfeatures are of great interest in traffic-driven networks(number of sites determined by the traffic to be carried, not by thecoverage per site). They will define the actual traffic shape in thecell by allocating, in a selective manner, resources for (CS and) PScalls. Here a traffic capacity gain is expected (higher traffic levelscan be handled with feature activated than without).
Radio interface impact
a) Support of PFC feature by RLC/MAC :
- PFC_FEATURE_MODE: this 1 bit field is a part of the R99 extensions in the GPRS_Cell_Options. It is broadcasted on
BCCH (SI13) or PBCCH (PSI1, PSI13 and PSI14) and indicates to the MSs if the network supports the PFC feature.
- The PFC impact on the one phase access: "If the PFC_FEATURE_MODE is set in the system information and if a PFC
exists for the LLC data to be transferred then the PFI shall be transmitted along with the TLLI of the mobile
station in the RLC extended header during contention resolution. The PFI is not used for contention resolution but
is included to indicate to the network which PFC shall initially be associated with the uplink TBF.
b) RLC/MAC/ messages impacts:
- PI bit (PFI indicator) is created, it indicates the presence of the optional PFI field:
0 PFI is not present
1 PFI is present if TI field indicates presence of TLLI
The PFI field indicates a PFI coded as it is defined in TS 44.018.
RLC/MAC messages impacted are:
Packet Resource Request : PFI field is added
(EGPRS) Packet DL ACK/NACK: PFI field is added (if a Channel Request Description is also present) UL (EGPRS) RLC data blocks : PFI field is added after the TLLI field (see 44.060 10.2.2 and 10.3a.2).
PFI is included in the following SM messages :
Activate_PDP_Context_Accept,
Activate_Secundary_PDP_Context_Accept,
Modify_PDP_Context_Request (sent by the network) and
Modify_PDP_Context_Accept (in case the request to modify is sent by the MS).
PFC_FEATURE_MODE is included in the MS_Network_Capability I.E. (which is sent in the Attach_Request and
RA_Update_Request GMM messages).
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1.4 Dual Transfer Mode
This feature allows a dual transfer mode capable MS to use a radioresource for CS traffic and simultaneously one or several radioresources for PS traffic.
Single slot operation DTM MSs are not supported in Alcatel BSSbecause the implementation of these MSs is difficult compared tothe throughput expected in PS services. Only multislot operationDTM MSs are supported.
In Alcatels implementation, the Gs interface is required to supportDTM to ensure CS paging co-ordination. It avoids the BSS to ensurethe paging co-ordination.
While in dual transfer mode, the BSS only allocates full rate PDCH tothe MS.
The dynamic Abis feature allows to simplify the radio resourceallocations. It avoids defining new TBF re-allocation triggers.
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1.4.1 Radio Network Planning Impact
Some restrictions towards BSS in deploying DTM exist. They arepresented below: Half rate
Support of half rate configurations (one single timeslot encompassing one half
rate circuit channel + one half rate packet channel) was not considered in thefirst implementation of DTM.
Inter-cell handovers The number of inter-cell handovers should be minimized for DTM calls, as an
inter-cell HO leads to the re-allocation of the packet session. Therefore,handover causes having a low priority should be inhibited for the time the MSis operating in DTM.
Intra-cell handovers The number of intra-cell handovers should be minimized for DTM calls, as an
intra-cell HO leads to the re-allocation of the packet session.
Hierarchical networks As (E)GPRS are preferentially offered in macro cells, the BSS shall ensure that
at least one PDCH can be used in micro cells to re-direct the MS towards the
macro cells. It means that the BSS shall allow a PDCH used by a MS operating inDTM mode to be shared by other (E)GPRS MS.
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1 Basic
1.5 (E)GPRS MS Multislot Classes
Multislot
Class1 2 3 4 5 6 7 8 9 10 1 1 12 1 3 14 1 5 1 6 1 7 18 1 9 20 2 1 22 2 3 2 4 2 5 26 2 7 28 2 9
RX Timeslots 1 2 2 3 2 3 3 4 3 4 4 4 3 4 5 6 7 8 6 6 6 6 6 8 8 8 8 8 8
TX Timeslots 1 1 2 1 2 2 3 1 2 2 3 4 3 4 5 6 7 8 2 3 4 4 6 2 3 4 4 6 8
Sum of
Timeslots2 3 4 4 4 4 4 5 5 5 5 5 n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.n.a.
EGPRS MS is characterized by two multislot classes: GPRS multislot class
EGPRS multislot class
Typically, EGPRS multislot class < GPRS multislot classE.g. the multislot class of the mobile can be 3 RXs + 2 TXs (class 6) in pure GPRSmode and 2 RXs + 1 TX (class 2) in pure EGPRS mode
Type 1: class 1-12, class 19-29 recognized as class 10
Type 2: class 13-18, allocation is limited to max. 5+5 timeslots
(check also P.323)
MS type
Type 1 are simplex MSs, i.e., without duplexer: they are not able to transmit and receive at the same time
Type 2 are duplex MSs, i.e., with duplexer: they are able to transmit and receive at the same time
Rx
The maximum number of received time slots that the MS can use per TDMA frame. The receive TS shall be
allocated within window of size Rx, but they do not need to be contiguous. For SIMPLEX MS, no transmitted TSs
shall occur between receive TS within a TDMA frame. This does not take into account the measurement window
(Mx).
Tx
The maximum number of transmitted time slots that the MS can use per TDMA frame. The transmitted TS shall
be allocated within the window of size Tx, but they do not need to be contiguous. For SIMPLEX MS, no received
TS shall occur between transmit TS within a TDMA frame.
SUM
The maximum number of transmitted and received time slots (without Mx) per TDMA frame.
The meaning of Ttb, Tra et Trb changes regarding MS types.
For SIMPLEX MS (type 1):
- Ttb is the minimum time (in time slot) necessary between the Rx and Tx windows.
- Tra is the minimum time between the last Tx window and the first Rx window of the next TDMA in order to
be able to open a measurement window.
- Trb is the same as Tra without opening a measurement window.
For DUPLEX MS (type 2):
- Ttb is the minimum time necessary between 2 Tx windows belonging to different frames.
- Tra is the minimum time necessary between 2 Rx windows belonging to different frames in order to be
able to open a measurement window.
- Trb is the same as Tra without opening a measurement window.
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1.6 (E)GPRS General Architecture
(E)GPRS defines a network architecture dedicated to packet servicedomain, with radio access, which allows service subscriber to sendand receive data in an end-to-end packet transfer mode
(E)GPRS uses the BSS architecture, but defines a fixed network(GPRS backbone) which is different from the NSS, and which linksthe BSS to PDNs (packet data networks). The BSS is used for bothcircuit-switched and (E)GPRS services
The BSS has 2 clients:
the MSC, for circuit-switched services (A interface)
the GPRS backbone network, for GPRS (Gb interface)
one or more 64 kbit/s channels on one or more 2 Mbit/s links
Gb interface: Layer 1 specified in GSM 08.14The protocol stack defined in the stage 2, GSM 03.60
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1.6 (E)GPRS General Architecture [cont.]
(E)GPRS general architecture
GbInterface
PDNGPRS
backbone
Gi
Packet Switched services domain
BSS
MSC/VLR PSTN
Circuit Switched services domain
AInterface
GPRS network = IP network
Note: Additional IP routers might be used to route the information between the GSNs (intra-PLMN
backbone network). All the elements connected to this backbone have private permanent IP addresses.
Signaling protocols:
MAP/TCAP/SCCP/MTP on Gr, Gd and Gc (through the SGSN for the latter),
GTP/UDP/IP on Gn, BSSAP+/SCCP/MTP on Gs,
GMM/SM/LLC on Gb/Um.
Gc: for Network-Requested PDP contexts Activation (the GGSN asks the HLR for SGSN Routing Information).
Gs: defines the Network Mode of Operation I. It allows to perform LA + RA combined Location Update, and
PS and CS Paging Coordination.
Gr: exchange of Subscription Information at Attachment Phase.
Additional interfaces:
Gf (to the EIR).
Gd to deliver the SMS to the mobiles via the GPRS network (SGSN option and subscriber feature).
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1.7 Alcatel (E)GPRS Architecture
Packet Control Unit (PCU) function is defined by the GSM standard: controls the (E)GPRS activity in a cell
handles RLC/MAC functions may be either implemented in the BTS, BSC or the SGSN
Alcatel choice: PCU implemented in a new network element, A 9135 MFS (Multi-BSS Fast
Packet Server)
smooth and cost effective introduction of the GPRS
The standard specifies that the PCU function shall be implemented in one of the 3 following entities:
BTS,
BSC,
after the BSC (in the SGSN for instance) The implementation of the PCU functions determines the position of the Gb interface. ALCATEL chose the
MFS integration in order to offer a faster implementation inside the BSS as well as an easier maintenance
and supervision.
MFS: Multi BSS Fast packet Server.
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1.7 Alcatel (E)GPRS Architecture [cont.]
Alcatel packet-switched service domain architecture:
BTS
Internet/
Intranet
SGSN GGSNMFSBSCFire-
wall
Other
PLMN
Packet domain
GnGbAterAbis
MS
Gi
Gp
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1.7 Alcatel (E)GPRS Architecture [cont.]
GPRS backbone is an IP network and is composed of routers:
Serving GPRS Support Node (SGSN), at the same hierarchical level as theMSC, which is linked to several BSSs. It keeps track of the individual MSslocation and performs security functions and access control
Gateway GPRS Support Node (GGSN), which is linked to one or severaldata networks, provides interworking with external packet-switchednetworks and is connected with SGSNs via an IP-based GPRS backbonenetwork
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1.8 (E)GPRS Protocol Layers (Transmission Plane)
NSNetwork ServiceGSM 08.16
RLCRadio Link Control
GSM 04.60
httpHypertext Transfer
Protocol
relay
MACMediumAccess
ControlGSM 04.60
LLCLogical Link Control
GSM 04.64
Physical
Link LayerL1bisLayer 1bisGSM 08.14
Um Abis / AterMS MFSBTS Gb SGSN
L1-GCHLayer 1 GPRS
Channel
L2-GCHLayer 2 GPRS
Channel
BSSGPBSS GPRS Protocol
GSM 08.18
UDPUser Datagram
ProtocolRFC 768
TCPTransmission Control
ProtocolRFC 793
or:
IPInternet Protocol
RFC 791
GTPGPRS Tunneling
ProtocolGSM 09.60
Gn GGSN
SNDCPSubnetworkDependent
ConvergenceProtocol
GSM 04.65
Ethernet
FR
Frame Relay
ATMAsynchronous
Transfer Mode
E1 (PCM30)G.703 / G.704
Gi
relay
relay
TCPTransmission Control
ProtocolRFC 793
RLCRadio Link Control
GSM 04.60
MACMediumAccess
ControlGSM 04.60
L1-GCHLayer 1 GPRS
Channel
L2-GCHLayer 2 GPRS
Channel
NSNetwork ServiceGSM 08.16
BSSGPBSS GPRS Protocol
GSM 08.18
LLCLogical Link Control
GSM 04.64
SNDCPSubnetworkDependent
ConvergenceProtocol
GSM 04.65
IPInternet Protocol
RFC 791
GTPGPRS Tunneling
ProtocolGSM 09.60
IPInternet Protocol
RFC 791
and/or:
or:
UDPUser Datagram
ProtocolRFC 768
TCPTransmission Control
ProtocolRFC 793
or:
Ethernet
FR
Frame Relay
ATMAsynchronous
Transfer Mode
E1 (PCM30)G.703 / G.704
IPInternet Protocol
RFC 791
and/or:
or:
Applicationexample
wwwWorld Wide Web
Physical
RF Layer
Physical
Link Layer
Physical
RF Layer
L1bisLayer 1bisGSM 08.14
For the exact purposes of the tracing, please refer to Introduction to GPRS & E-GPRS Quality of Service
Monitoring It can be said from this protocol stacks diagram that after allocation of a GCH by the BSC to
the MFS, the data carried over the GCH are transparent for the BSC.
The RLC function defines the procedures for segmentation and reassemble of LLC PDUs into RLC/MAC
blocks and, in RLC acknowledged mode of operation, for the Backward Error Correction (BEC) procedures
enabling the selective retransmission of unsuccessfully delivered RLC/MAC blocks. In RLC acknowledged
mode of operation, the RLC function preserves the order of higher layer PDUs provided to it. The RLC
function provides also link adaptation. In EGPRS in RLC acknowledged mode of operation, the RLC
function may provide Incremental Redundancy (IR).
The MAC function defines the procedures that enable multiple mobile stations to share a common
transmission medium, which may consist of several physical channels. The function may allow a mobile
station to use several physical channels in parallel, i.e., use several time slots within the TDMA frame.
For the mobile station originating access, the MAC function provides the procedures, including the
contention resolution procedures, for the arbitration between multiple mobile stations simultaneously
attempting to access the shared transmission medium. For the mobile station terminating access, the
MAC function provides the procedures for queuing and scheduling of access attempts.
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1 Basics
1.9 Alcatel (E)GPRS BSS Hardware support
BTS: Support of EGPRS (EDGE) in all BTS A9100 EVOLIUM Evolutionequipped with TRA transceiver:
G1 MK2 and G2 with DRFU: GPRS only, CS-1 and CS-2 only
A9100 EVOLIUM (G3): GPRS only, CS 1-4
A9100 EVOLIUM Evolution (G4): (E)GPRS, CS 1-4, MCS 1-9
micro BTS: support of EDGE in micro BTS A9110-E Micro BTS A9110 (M4M): GPRS only, CS 1-4
Micro A9110-E (M5M): (E)GPRS, CS 1-4, MCS 1-9
BSC A9120 (G2)
MFS A9135
TC A9125 (Transcoder) G2 and G2.5
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1 Basics
1.10 Modulation Technique: 8-PSK only for EGPRS
Q
I
010
011
100
101
111
110
001
000
Q
I
111
110
001
000 100
101
010
011
I
Q110
100
000
010
101
001
011
111
t
Q
I
010
011
100
101
111
110
001
000
Q
I
010
011
100
101
111
110
001
000
Q
I
111
110
001
000 100
101
010
011
Q
I
111
110
001
000 100
101
010
011
I
Q110
100
000
010
101
001
011
111
I
Q110
100
000
010
101
001
011
111
t
Q
I
Q
IdB
(147 bits)
PN
0
-20
8-PSK = Phase Shift Keying
8-PSK is not a constant envelope modulation. Part of the informationis conveyed by the amplitude of the carrier which varies over time
An 8PSK signal carries three bits per modulated symbol over the radiopath which allows to tripled the data transmission rates
GMSK = the Gaussian Minimum Shift Keying belongs to a subset of phase modulations
8-PSK = 8-state Phase Shift Keying
8-PSK is not a constant envelope modulation. Part of the information is conveyed by the amplitude
of the carrier which varies over time. An 8-PSK signal carries three bits per modulated symbol over the radio path, which allows to triple
the data transmission rates.
Modulation gross bit rate
The normal burst is divided into 156.35 symbol periods. A normal burst has a duration of 3/5.2seconds (577 s). (3GPP TS 05.02).
For GMSK modulation, a symbol is equivalent to a bit (3GPP TS 05.04)
A GMSK burst is composed of 156.35 bits (6 tail bits + 26 training sequence bits + 116 encrypted bits+ 8.25 guard period (bits))
Modulation gross bit rate = (156.35 bits) / (3/5.2 seconds) = 270 Kbit/s
For 8-PSK modulation, one symbol corresponds to three bits (3GPP TS 05.04).
An 8-PSK burst is composed of 156.35 x 3 = 468.75 bits (18 tail bits + 78 training sequence bits + 348encrypted bits + 24.75 guard period (bits)).
Modulation gross bit rate = (468.75 bits) / (3/5.2 seconds) = 810 Kbit/s
Amplitude variesconstantCarrier envelope
EGPRSGPRS / EGPRSPacket radio service
810 Kbit/s270 Kbit/sGross bit rate per
carrier
200 KHz200 KHzChannel spacing
Phase modulationFrequency modulationModulation type
8-PSKGMSK
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1 Basics
1.11 8-PSK TRA Power Aspects
TRA GMSK output power 8-PSK output power
900 MP 45 W / 46.5 dBm 15 W / 41.8 dBm
900 HP 60 W / 47.8 dBm 25 W / 44 dBm
1800 MP 35 W / 45.4 dBm 12 W / 40.8 dBm
1800 MP 60 W / 47.8 dBm 25 W / 44 dBm
900 EDGE+ 45 W / 46.5 dBm 30 W / 44.8 dBm
1800 EDGE+ 35 W / 45.4 dBm 30W / 44.8 dBm
Nominal output power (PN) of the transmitter represents theaverage power during the active burst
GMSK average power is identical to GMSK peak power
8-PSK peak power is equal to GMSK peak power but the 8-PSK averagepower is lower than the peak power
8-PSK power < GMSK power
the difference is called average power decrease (APD) or powerback off
G3 TREs are not able to handle the 8-PSK modulation. Only G4 TREs (also called TRA) are EDGE capable.
The TRA sensitivity is as follows :
GMSK : - 111 dBm. 8-PSK : - 108 dBm for MCS5, - 99 dBm for MCS9.
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1 Basics
1.11 8-PSK TRA Power Aspects [cont.]
Unbalanced BTS configuration
Case 1: BS_TXPWR_MAX=0
Case 2: BS_TXPWR_MAX0
APD, takes into account theBS_TXPWR_MAX and consequently theEffective GMSK Sector Power
Always 8 PSK pwr GMSK pwr
APD = 0 if 8 PSK pwr > GMSK pwr
Used by Link Adaptation process
8-PSK Delta power ( 8-PSK) considersonly the GMSK sector power without theBS_TXPWR_MAX
8-PSK 3 dB indicates that is a highpower TRE
GMSK POWER
8-PSK POWER
ATTENUATIONBS_TXPWR_MAX
8-PSK
APD
GMSK LEVELING
LEGEND
OUTPUT PWR
@ BTS ant.
connector
SECTORGMSK
8-PSK TRE 1
8-PSK TRE 2
HP TRE 1 MP TRE 1 HP TRE 1 MP TRE 2
-8PSK= APD
-8PSK= APD APD = 0
Case 1 Case 2
APD: Average Power Decrease
The back-off between average GMSK and 8-PSK output power comes from physics since 8-PSK is a non
constant envelope modulation unlike GMSK.
As a consequence power amplifiers can not be used at their maximum power. This results in a differencebetween mean output powers for GMSK and 8-PSK modulations.
Output power handling
The BTS sets all the TRE which transmit GMSK output powers at the same level which is the minimum
value among the maximum TRE output power in a sector and in a given band.
On a TRE, the maximum GMSK output power is higher than the maximum 8-PSK output power.
An O&M parameter (BS_TXPWR_MAX) allows a static power reduction of the maximum GMSK output
power of the sector.
The TRE transmit power in 8-PSK shall not exceed the GMSK transmit power in the sector.
The BTS determines for each TRE, the difference between the 8-PSK output power of the TRE and the
GMSK output power of the sector (8-PSK delta power).
According to the 8-PSK delta power value, a TRE is called High Power or Medium Power.
When a GCH channel is activated, the BTS sends the 8-PSK delta power to the MFS.
Together with BS_TXPWR_MAX (static power reduction), the 8-PSK delta power allows the MFS to
determine:
- a possible attenuation (BS_TX_PWR) for the 8-PSK DL RLC block emission, in order not to exceed the
GMSK power of the sector (for GMSK DL RLC block, the attenuation is BS_TXPWR_MAX).
- an Average Power Decrease which is the difference between the 8-PSK output power and the GMSK
output power after having taken into account BS_TXPWR_MAX. The Average Power Decrease is takeninto account in the link adaptation tables.
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1 Basics
1.11 8-PSK TRA Power Aspects [cont.]
Example: GSM 900, a mix BTS sector configuration is considered:
ANc combined with 4 TRA (TRAs = EGPRS capable TRE): TRE 1 (BCCH): 60W GMSK (25W in 8-PSK)
TRE 2..4: 45W GMSK (15W in 8-PSK)
BS_TXPWR_MAX = 2 dB;
RESULTS:
1st step: Output power at BTS antenna connector (after combiner andduplexer stage):
TRE 1 GMSK = 43.4 dBm; 8-PSK = 39.6 dBm
TRE 2..4 GMSK = 42.1 dBm; 8-PSK = 37.4 dBm
2nd step: LEVELING (BTS automatic GMSK power balancing):
TRE 1..4 GMSK = 42.1 dBm (Sector GMSK power)
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1 Basics
1.11 8-PSK TRA Power Aspects [cont.]
3rd step: 8-PSK Delta computation
TRE 1 = 42.1 39.6 = 2.5 dBm < 3 dBm recognized as HP TRE
TRE 2..4 = 42.1 37.4 = 4.7 dBm recognized as MP TREs
4th
step: static attenuation (only on GMSK power) TRE 1..4 GMSK = 42.1 2 = 40.1 dBm (Effective GMSK Sector Power)
5th step: GMSK power 8-PSK power ? YES, since 40.1 dBm 39.6 dBm 37.4 dBm no reduction of 8-PSK
power
6th step: APD computation
APD TRE 1 (BCCH) = 40.1 39.6 = 0.5 dBm
APD TRE 2..4 = 40.1 37.4 = 2.7 dBm
3GPP 05.08 constraint on the transmitted power of BCCH frequency: BCCHfrequency shall usually be transmitted at a constant level. A tolerance has beenintroduced with 8-PSK: a fluctuation ofup to 2 dB is allowed If APD isgreater than 2 dB, a static power attenuation should be applied or EGPRS capabilityshould not be activated on the BCCH TRE
Radio Network Planning Impact
Frequency hopping is not recommended for E-GPRS (MCS-1 to MCS-9) Therefore, the system is allocating
a higher priority for the packet-switched traffic for non-hopping TRX in a cell. In addition, the non-
hopping TRX may benefit from a special radio planning with higher reuse cluster size, in order to ensure
higher C/I conditions and offer better throughputs, both for GPRS and EDGE. APD should be considered inthe A9155 planning tool for the throughput estimation (based on interference calculation per pixel
approach) and also to determine the 8-PSK coverage. The IR gain should also be considered in the
throughput estimation. 3 dB can be taken for the average IR gain. PS_PREF_BCCH_TRX is a flag at celllevel which indicates whether the operator wishes to allocate packet on the BCCH TRX with highest
priority. Actually, is recommended to activate GPRS/EDGE traffic on the BCCH TRX due to its high RCS.
However the activation of EDGE on the BCCH TRX should be performed cautiously. 3GPP Rec. 05.08 has
defined a constraint on the transmitted power of BCCH frequency. This frequency shall usually be
transmitted at a constant level. A tolerance has been introduced with 8-PSK: a fluctuation of up to 2 dB
is allowed. Depending on the configuration in the BTS, it may happen that the difference between GMSK
and 8-PSK power on the BCCH TRX is greater than 2dB. A possible solution for this constraint, in case of a
BTS (e.g. ANc combined) equipped only with MP TRX (most of the cases) is presented below: The BCCH
MP TRX will be replaced by a HP TRX (to take also advantage from 8-PSK 25W power and
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Reminder : limitation of B8 Release
The BTS is levelling the output power of each TRE on a sector basis.
The level of output power, on a frequency band basis, is adapted to the lower TRE
output in the sector after coupling(s).
For example, if a sector is configured with a TRGM (35W) and a TRAG (45W), the
output power of the sector is automatically levelled to 35W.
1 Basics
Unbalancing TRX Output Power per BTS sector
Introduction (1 / 3)
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Reminder : coupling stage
Antenna coupling is the stage which handles
combining functions as well interface withthe antennas.
Antenna Network Combiner (ANc) performs
these functions for up to 4 TRXs.
As shown in the figure, if the
by-pass function is used (up to 2 TRX),
the TRE signal doesnt suffer the 3dB
attenuation.
For configurations of higher capacity (more
than 4 TRX), a combiner stage can be added
(ANY)
1 Basics
Unbalancing TRX Output Power per BTS sector
S plitter S plitterW BC
TR X 1
TX RX n RX d
TR X 2
TX RX n RX d
S plitter S plitterW BC
TR X 3
TX RX n RX d
TR X 4
TX RX n RX d
TXA R XA R XdivA R Xd ivBR XBT XB
S plitter S plitterW BC
TR X 1
TX RX n RX d
TR X 2
TX RX n RX d
S plitter S plitterW BC
TR X 3
TX RX n RX d
TR X 4
TX RX n RX d
S plitterS plitter S plitterS plitterW BCW BC
TR X 1
TX RX n RX d
TR X 1
TX RX n RX d
TR X 2
TX RX n RX d
TR X 2
TX RX n RX d
S plitterS plitter S plitterS plitterW BCW BC
TR X 3
TX RX n RX d
TR X 3
TX RX n RX d
TR X 4
TX RX n RX d
TR X 4
TX RX n RX d
TXA R XA R XdivA R Xd ivBR XBT XB
Antenna ATXA - RXA -RXdivB
SplitterWBC
TRX 1
TX RXnR Xd
TRX 2
TXRXnRXd
Splitter
Splitter
LNA
Duplexer
FilterFilter
Splitter Splitter WBC
Antenna BTXB-RXB -RXdivA
Duplexer
FilterFilter
Splitter
LNA
-1 dB
-3 dB
By-pass By-pass
Introduction (2 / 3)
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Reminder : coupling stage
As the lowest TRE output power definesthe final one on the sector, in case of
un-symetric configuration, the more
coupled stage influences the less one.
This is shown on the example here,
when adding a 3rd TRX (the by-pass
function is removed on both sides)
The 3dB loss impacts all TRX
of the cell
1 Basics
Unbalancing TRX Output Power per BTS sector
Antenna ATXA -RXA - RXdivB
SplitterWBC
TRX 1TXRXnRXd
TRX 2TXRXnRXd
Splitter
Splitter
LNA
Duplexer
FilterFilter
Splitter Splitter WBC
Antenna BTXB- RXB - RXdivA
Duplexer
FilterFilter
Splitter
LNA
TRX 3TXRXnRXd
Introduction (3 / 3)
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Two options available in B9: As of before : Balanced Configuration One single output power for all TRX in the same band
New Alternative : Unbalanced Configuration
Goal of the new Unbalanced Configuration: Benefit of higher output power for coverage gap/ better indoor penetration Benefit of the higher power provided by latest TRX versions
Principle : 2 output power levels in the cell Based on the concentric cell principle The cell is declared as a concentric cell
Automatic mapping ofTRE of highest power in the outer zone
1 Basics
Unbalancing TRX Output Power per BTS sector
Description of the new feature
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Unbalanced TRX Output Power in B9
The principle of the feature is to define a specific concentric cell in which the outputpower balancing is performed on a zone basis instead of sector basis.
When the feature is activated, the BSS system ensures that the more powerful TREs aremapped on TRX configured on the outer zone, and the less powerful ones, on the TRXconfigured on the inner zone.
Pre-requisitesThe cell is of type concentric mono-band
The cell is not shared
BenefitsAllows a smooth introduction of High Power GMSK (e-g better coverage, without
replacing all TREsUpgrade of 2 TRXs / cell in by-pass mode towards 3 TRXs w/o impact on coverage and
w/o need of Low Loss Configuration (higher CAPEX)
1 Basics
Unbalancing TRX Output Power per BTS sector
Description of the new feature (1 / 3)
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Specificities of concentric cells
A concentric cell is a cell made of two virtual zones : one Inner and one Outer A group of TREs transmits with higher power (Outer Zone), while the other group transmits with
lower power (Inner Zone). All the TREs work on the same band and cover the same cell.
There is only one BCCH, and it must be managed by the group of TREs of higher power in order to
guarantee the coverage of both zones.
1 Basics
Unbalancing TRX Output Power per BTS sector
Description of the new feature (2 / 3)
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Feature activation Activated at OMC through a new parameter: EN-Unbalanced-Output-Power
When activated, it introduces a new kind of concentric cell. In this cell, thebalancing of the output power will be performed on a zone basis.
The existing current mechanism is kept if the feature not activated.
Algorithm & System impacts The BTS informs the BSC, for each TRE, about the GMSK and 8PSK output power
(after coupling).
The BTS informs the OMC through HW audit about the output power of each TRE forGMSK and 8PSK modulation
When the feature is activated, the BSC maps on the HP TRE the TRX configured by
the operator on the outer zone and on the others the TRX of the inner zone. The information of unbalanced output power activated is transmitted to the BTS by
CDM at sector level. For each TRE, the output power computed by the BSC afterTRX/RSL mapping is also transmitted to the BTS by CDM.
1 Basics
Unbalancing TRX Output Power per BTS sector
Description of the new feature (3 / 3)
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1 Basics
Unbalanced TRX Output Power
TRE M P (4 5W) TRE H P (6 0W)
At an tenn a connector 46,5 47,8
Not combined 45,5 46,8
Combined 42,1 43,4
Type o f TRE
Output power in dBm, in GMSK (900 MHz)
ANB
MPHP
60W
Outer zone Inner zone
Without newfeature
With newfeature
Without new feature With new feature
45,5 46,8 45,5-BS_TXPWR_MAX_INNER
45,5
Example 1 :2 TRE not combined1 Medium Power TRX+ 1 High Power TRX
Example 1 :2 TRE not combined1 Medium Power TRX+ 1 High Power TRX
Examples of configurations (1 / 3)
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1 Basics
Unbalanced TRX Output Power
TRE M P (4 5W) TRE H P (6 0W)
At an tenn a connector 46,5 47,8
Not combined 45,5 46,8
Combined 42,1 43,4
Type o f TRE
Output power in dBm, in GMSK (900 MHz)
Example 2 :
3 Trx in mixed mode:2 TRX MP (46,5 dBm)1 TRX HP (47,8 dBm) inByPass
Example 2 :
3 Trx in mixed mode:2 TRX MP (46,5 dBm)1 TRX HP (47,8 dBm) inByPass
Outer zone Inner zone
Without newfeature
With newfeature
Without new feature With new feature
42,1 46,8 42,1-BS_TXPWR_MAX_INNER
42,1
ANC
MP MP HP
BP
Examples of configurations (2 / 3)
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1 Basics
Unbalanced TRX Output Power
TRE M P (4 5W) TRE H P (6 0W)
At an tenn a connector 46,5 47,8
Not combined 45,5 46,8
Combined 42,1 43,4
Type o f TRE
Output power in dBm, in GMSK (900 MHz)
Example 3 :3 Trx in combined mode:2 TRX HP (47,8 dBm),1 TRX MP (46,5 dBm)
Example 3 :3 Trx in combined mode:2 TRX HP (47,8 dBm),1 TRX MP (46,5 dBm)
Outer zone Inner zone
Without newfeature
With newfeature
Without new feature With new feature
42,1 43,4 42,1-BS_TXPWR_MAX_INNER
42,1
ANC
HP HP MP
Examples of configurations (3 / 3)
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1 Basics
Unbalanced TRX Output Power
HMI name Definition Sub-system
Instance OMC-R access
Range / Defvalue
Recommended rule
EN-Unbalanced-Output-Power
This parameter activates the featureUnbalanced output power on the cell
BSC Cell CAE/Changeable
0-1
Def:0
When the flag is activated;it is recommended to setthe TPM parameter to 0 forall TRX of the outer zone.
Innerzone-Output-Power
This parameter defines the BTS outputpower on the inner zone for aconcentric cell wtih the UnbalancedTRX output power feature activated
BSC Cell CAE/Displayed
0-255
Def:255
Mandatory rule:
This parameter is displayedand meaningfull only if theEn-Unbalanced-Output-Power is set to True
Outerzone-Output-Power
This parameter defines the BTS output
power on the outer zone for a
concentric cell with the,UnbalancedTRX output power feature activated
BSC Cell CAE/Displayed
0-255
Def:255
Mandatory rule:
This parameter is displayedand meaningfull only if theEn-Unbalanced-Output-Power is set to True
TRE-8psk-Capability
This parameter gives the 8PSK powerlevel that a TRE is capable to emit
BSC TRE CAE/Displayed
0-255
Def:255
TRE-GMSK-Capability
This parameter gives the GMSK powerlevel that a TRE is capable to emit
BSC TRE CAE/Displayed
0-255
Def:255
Logical parameters
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Unbalanced TRX Output Power
OMC-R parameters view (at cell level)
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Unbalanced TRX Output Power
Impact on Counter RMSPw3 (MAX_POWER_PER_TRX)
Counter definition: Maximum GMSK TRX power level applied at the BTSantenna output connector in dBm. The power takes into account thedifferent losses (cables, internal combiners) and the internal/ externallevelling but it does not take into account the BS-TXPWR-MAX, attenuationrequired by the OMC_R.
Impact of the feature: If the feature is activated, the counter shall be set,by the BTS, to the power required by the BSC for the corresponding TRE.(TRE on which the TRX is mapped).
Counters & Indicators impact
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Impact on RNO indicators
Creation of 2 new indicators in B9, calculated per TRX from the counters RMSPw3 andRMS20. RMS20 provides the band (GMS or DCS) of the TRX.The 2 indicators are expressed in Watts, and defined as follows:
RMS_DL_Power_max_TRX_900:if RMS20= 6 or 2 or 0 (GSM850 or E-GSM or P-GSM)then RMS_DL_Power_max_TRX_900 = log(RMSPW3)else RMS_DL_Power_max_TRX_900 = "0"
RMS_DL_Power_max_TRX_1800:if RMS20= 1 or 3 (DCS1800 or DCS1900)then RMS_DL_Power_max_TRX_1800 = log(RMSPW3)else RMS_DL_Power_max_TRX_1800 = "0"
Both are consolidated at cell level by performing the sum on all TRX.
1 Basics
Unbalanced TRX Output Power
Counters & Indicators impact
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1.12 (E)GPRS Radio Blocks Structure
In order to be transmitted over the air interface, the LLC data issegmented at RLC layer into packets, called (E)GPRS radio blocks
Radio block characteristics: a block is the smallest data unit assigned to an user
one radio block is always entirely assigned to one user; inside a blockthere is no multiplexing of different users possible
the whole information belonging to one radio block is transmitted uponchannel coding, in a certain timeslot over 4 consecutive TDMA frames
the data amount carried in one (E)GPRS radio block is: 456 bits in GPRS (GMSK modulation)
464 bits in EGPRS (GMSK modulation)
1392 bits in EGPRS (8-PSK modulation)
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EGPRS Radio Block (data transfer)
RLC/MAC header: control fields which are different for uplink and downlink directions
RLC Data Field: LLC PDUs bytes; contains one or two RLC data blocks Block Check Sequence (BCS): for error detection of the data part
Header Check Sequence (HCS): for error detection of the header part
1 Basics
1.12 (E)GPRS Radio Blocks Structure [cont.]
GPRS Radio Block (data transfer)
MAC header: control fields which are different for uplink and downlink directions
RLC header: control fields which are different for uplink and downlink directions
RLC Data Block: bytes from one or more LLC PDUs Block Check Sequence (BCS): used for error detection
MAC header RLC data blockRLC header BCS
BCSHCSRLC/MAC header RLC data block 1 RLC data block 2only MCS-7/8/9
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1.13 GPRS Channel Coding
Channel coding provides error detection and error correction Essential for managing the impairments on the air interface
Data rates in GPRS on the air interface
The netto data rates on the air interface depend on the channel codingprocedure
For (E)GPRS, different channel coding levels are applied depending onthe actual radio conditions
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1.13 GPRS Channel Coding [cont.]
Four different coding schemes, CS-1 to CS-4, are defined for theGPRS Radio Blocks carrying RLC data, and are applied dependingfrom the actual radio conditions
The first step of the channel coding procedure is to add a BlockCheck Sequence (BCS) for error detection
For CS-1 to CS-3, the second step consists of pre-coding USF(except for CS-1), adding four tail bits and a half rateconvolutional coding for error correction that is punctured to givethe desired coding rate
For CS-4 there is no coding for error correction
The most protected mode is CS-1 which is therefore always used forGPRS signaling (even for EGPRS)
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1.13 GPRS Channel Coding [cont.]
Scheme Modulationschemes
Coding schemes
for RLC data block
Coderate
Maximum data rateper TS (RLC payload)
[kbps]
CS-4 GMSK No coding 1.00 20.0
CS-3 GMSK Half rate convolutionalcoding, punctured
0.75 14.4
CS-2 GMSK Half rate convolutionalcoding, punctured
0.66 12.0
CS-1 GMSK Half rate convolutionalcoding
0.50 8.0
8
12
14.4
CS-1
CS-2
CS-3
CS-420
GMSKmodulat ion
Header + Protection
Maximum User Payload [kbps]
USF BCS
rate 1/2 convolutional coding
456 bits
puncturing
Interleaving of GPRS Radio Block over 4consecutive TDMAs (4 PDCH)
GPRS RADIO BLOCK
Release B8
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1.14 EGPRS Channel Coding
Nine different coding schemes are defined: MCS-1 to MCS-9
First step of the EGPRS coding procedure, is to add a Block Check
Sequence (BCS) to each RLC data block, for error detection Second step consists of adding six tail bits (TB) and a 1/3 rate
convolutional coding for error correction that is punctured to givethe desired coding rate
The Pi (puncturing schemes) for each MCS correspond to differentpuncturing schemes achieving the same coding rate
Puncturing is a technique of removing bits in predetermined locations of thedata block after the block has been channel coded
MCS-9, MCS-8, MCS-7, MCS-4, MCS-3: are possible P1, P2, and P3
MCS-6, MCS-5, MCS-2, MCS-1: P1 and P2 are possible
The puncturing process consists of transmitting only some of the coded bits obtained after the rate 1/3
convolutional coding. Depending on the considered puncturing scheme, different coded bits are transmitted.
Therefore, when the receiver receives two versions of the same RLC block sent with two different puncturing
schemes, it obtains additional information leading to an increased decoding probability.
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1.14 EGPRS Channel Coding [cont.]
MCSs are divided into 4 different families: A, A, B and C Each family has a different basic payload unit:
37 bytes: family A
34 bytes: family A (padding)
28 bytes: family B
22 bytes: family C
When switching to MCS-3 or MCS-6 from MCS-8, 3 or 6 padding bytes, areadded to the data bytes
Within a family different throughputs are achieved by transmitting adifferent number of basic payload units within one block
impact on retransmission Offset the GPRS disadvantage on retransmission
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1.14 EGPRS Channel Coding [cont.]
8.8
11.2
14.8
11.2 x 2 = 22.4
14.8 x 2 = 29.6
11.2 x 4 = 44.8
padding (MCS-3/6) 54.4
14.8 x 4 = 59.2
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
8.8 x 2 = 17.6
GMSK
8-PSK
Header + Protection
Maximum User Payload [kbit/s]
37 octets 37 octets 37 octets37 octets
MCS-3
MCS-6
Family A
MCS-9
28 octets 28 octets 28 octets28 octets
MCS-2
MCS-5
MCS-7
Family B
22 octets22 octets
MCS-1
MCS-4
Family C
34 +3 octets34 +3 octets
MCS-3
MCS-6Family Apadding
MCS-8
34 octets 34 octets 34 octets34 octets
The main GPRS imperfections are linked to:
the design of the GPRS coding schemes which were designed independently from the others with
their own data unit.
the fact that once the information contained in an radio block has been transmitted with a certainCS, it is not possible via the Automatic ReQuest for repetition (ARQ) mechanism to retransmit with
another CS.
- This could lead to the release of the TBF and to the establishment of a new one in order to
transmit the LLC frame.
EGPRS coding schemes have been designed to offset this problem. Four MCS families have been created
with for each of them a basic unit of payload.
This allows the re-segmentation of the RLC data blocks when changing of modulation and coding
schemes (within the same family).
- Example: if one MCS-6 radio block has not been received correctly by the receiver and if radio
conditions have degraded in the meantime, it is possible to re-send the same information in two
radio blocks with MCS-3 (more protection).
The level of protection applied (MCS usage) in case of retransmissions is in line with the radio
conditions.
The different code rates within a family are achieved by transmitting a different number of payload units
within one radio block. When 4 payload units are transmitted, these are split into 2 separate RLC blocks
(i.e., with separate sequence numbers).
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1.14 EGPRS Channel Coding [cont.]
MCS-9 basic payload unit = 37 bytes = 296 bits
MCS-9 RLC data block = 2 x basic payload unit =2* 296 bits = 592 bits
MCS-9 RLC payload throughput= 592 bits / 10 ms = 59.2 Kbps
USF HCSRLC/MAC
header E FBIRLC Data Block
= 592 bits BCS TB E FBIRLC Data Block =
592 bits BCS TB
36 bits
3 bits
135 bits 1836 bits 1836 bits
SB=8 36 bits 124 bits 612 bits 612 bits 612 bits 612 bits 612 bits 612 bits
puncturingpuncturing
P3P1 P2 P1 P2 P3
45 bits 612 bits 612 bits
1392 bits
Rate 1/3 convolutional coding Rate 1/3 convolutional coding
puncturing
Interleaving of the EGPRS Radio Block over 4 consecutive TDMAs
EGPRS MCS-9 RADIO BLOCK
MCS-9 Example:
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1.14 EGPRS Channel Coding [cont.]
Scheme Modulationschemes
Coding schemesfor RLC data block
Coderate
Maximum data rate per TS (RLCpayload)
[kbps]
MCS-9 8PSK 1/3 rate convolutional
coding, punctured
1.00 59.2
MCS-8 8PSK 1/3 rate convolutional
coding, punctured
0.92 54.4
MCS-7 8PSK 1/3 rate convolutionalcoding, punctured
0.76 44.8
MCS-6 8PSK 1/3 rate convolutionalcoding, punctured
0.49 29.6
MCS-5 8PSK 1/3 rate convolutional
coding, punctured
0.37 22.4
MCS-4 GMSK 1/3 rate convolutionalcoding, punctured
1.00 17.6
MCS-3 GMSK 1/3 rate convolutionalcoding, punctured
0.80 14.8
MCS-2 GMSK 1/3 rate convolutional
coding, punctured
0.66 11.2
MCS-1 GMSK 1/3 rate convolutionalcoding, punctured
0.53 8.8
Uplinktransfer
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1.15 Radio Link Adaptation Overview
(M)CS schemes are dynamically selected based on the quality of theradio channel, in order to maximize the throughput
Two different mechanisms exists for GPRS and EGPRS: CS Adaptation in case ofGPRS TBF mode and
Link Adaptation (LA) in case ofEGPRS TBF mode
Selection of the most suitable (M)CS is based on measurementsreported by the MS for the downlink path and by the BTS for theuplink path
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1.16 Automatic ReQuest for repetition (ARQ)
In the ARQmethod, when the receiver detects the presence oferrors in a received RLC block, it requests and receives a re-transmission of the same RLC block from the transmitter
The retransmission can be performed using:
Type-I ARQmechanism. This applies for both GPRS and EGPRS mode
Type-II hybrid ARQmechanism, also called Incremental Redundancy (IR).This applies only for DL EGPRS mode
IR is optional for the BTS, but is mandatory for the EGPRS MS (3GPPrequirement)
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1.17 Type-I ARQ mechanism
In the selective type-I ARQmechanism, the receiver discards theerroneous blocks, and indicates in the acknowledgement messagesthe reference of these erroneous blocks for their retransmission.Then, the sending side has to retransmit the erroneous data RLCblocks
MS
Uplink RLC data block B1 / PDTCH (1)
MFS
Packet UplinkAck/Nack /PACCH (3)
Uplink RLC data block B2 / PDTCH (2)
Uplink RLC data block B2 / PDTCH (4)
Uplink RLC data block B3 / PDTCH (5)
The Block 2 has been
unsuccessfully received
MS retransmits the uplinkRLC data block B2
With the type 1 ARQ mechanism, the decoding of a re-transmitted RLC block does not use the previously
transmitted versions (not correctly received) of this RLC block. The decoding of a RLC data block is only
based on the current transmission.
The type 1 ARQ mechanism is always used for the GPRS and in uplink for the EGPRS (B8 release case).
In EGPRS, only type I ARQ applies in uplink (B8 release case). The network implicitly sets the type I mode
by ordering the MS to use a specific MCS and setting the resegment bit to 1 in the Packet UL Ack/Nack
message (resegment bit = 1 indicates to the MS that the retransmitted RLC data block shall be resegmented
according to the commanded MCS (next lowest MCS in the same MCS family than the one used for the initial
block)).
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1.18 Type-I ARQ in GPRS
GPRS CSs are designed independently from the others with its own basicpayload unit size, so the family concept does not exists in GPRS
Before its transmission over the radio interface, the LLC frame is segmentedinto payload units according to CS that will be used to transmit the radioblock
In case of erroneous reception, the RLC data block can be retransmittedonly with the same CS (segmentation is not possible) If the radio conditions have changed and the coding rate is not appropriate tothem, the receiver will never be able to decode the retransmission of the RLCdata block. This will lead to the release of the TBF and the establishment of anew one in order to transmit the LLC frame
In order to avoid this problem, the choice of the CS on the network side has tobe made carefully. This often results in an non-optimized use of the radiointerface, leading to a reduction of network capacity compared with itstheoretical capacity
GPR
SDRAWBACK
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1.19 Type-I ARQ in EGPRS
MCSs have been designed to offset the GPRS disadvantage
MCS family concept is applied
In EGPRS, in case of retransmission request (type-I ARQ) for a RLC datablock, the same or a next lower MCS within the same family is used
The retransmission can be performed with or w/o RLC data segmentation (e.g.from MCS-9 to MCS-6 w/o, and MCS-6 to MCS-3 with segmentation)
When one RLC data block is retransmitted with a lower MCS, the coding rate isdecreased by two, but the redundancy transmitted is increased
That increases the capability to decode the radio block ! Retransmission operates in connection with the link adaptation
E.g. if the LA mechanism orders the usage of MCS-5 and the first transmission ofan erroneous RLC block was with MCS-6, the transmission will be performed withMCS-3. The blocks that are sent for the first time will be transmitted with thelast-ordered MCS
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1.19 Type-I ARQ in EGPRS [cont.]
Type-II ARQ(IR) is an efficient combination of 2 techniques: Automatic Repeat reQuest : in case of error detection in a received RLC block, a
re-transmission of the same RLC data block is requested
Forward Error Correction : adds redundant information to the user information atthe transmitter, the receiver uses the info to correct errors causes by radiodisturbances
In the IRmechanism: The information which is sent first results from an initial puncturing scheme
(PS1) applied to the encoded RLC data block
If an error is detected by the receiver: the received message is stored
selective retransmission of the RLC data block is requested
a second puncturing scheme (PS2) is applied to the same MCS, by the sender
the receiver decodes (combines) the resulting message together with the previouslyreceived message(s)
multiple retransmission can be requested until decoding succeeds
The type 2 ARQ mechanism or incremental redundancy (IR) is an ETSI function, mandatory for the EGPRS MS receiver
(downlink path) and optional for the BTS receiver (uplink path). In B8 release, the IR feature is only available on the
downlink path. It is important to notice that the IR feature is always running in the EDGE MS receiver (except in case
of MS memory shortage). The DL incremental redundancy is not used for the signaling blocks, the GPRS data blocks
and the data blocks in RLC unacknowledged mode. It is only used for the EGPRS data blocks in RLC acknowledgedmode.
In the type II ARQ mechanism (IR):
the first emission of a RLC data block is done using a first puncturing scheme (PS1),
in case of re-transmission of this RLC block, the transmitter uses the same MCS or a MCS of the same family
than the one used for the initial block. On the DL path, depending on the value of the parameter
EN_FULL_IR_DL, re-segmentation of the RLC block may be performed or not,
at the output of the demodulator, the receiver combines the information of soft bits corresponding to the first
transmission of the block and its different re-transmissions, thus increasing the decoding probability of the RLC
block.
Remark : according to the 04.60 (RLC/MAC layers) GSM recommendation, the soft-combining inside the MS
receiver is only performed between an :
- MCSx block and MCSx block (that is the same MCS is used for the re-transmission),
- MCS9 block and an MCS6 block (in that case the RLC data blocks carry the same number of payload units),
- MCS7 block and an MCS5 block (in that case the RLC data blocks carry the same number of payload units).
If the "MS OUT OF MEMORY" field is set by the mobile in the EGPRS Packet DL Ack/Nack message, the type I ARQ shall
apply in the MS receiver (ARQ without IR). This occurs when the memory for IR operation runs out in the MS (that is
when the memory of the MS is full due to the storage of the different versions of a RLC block not correctly decoded).
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1.19 Type-I ARQ in EGPRS [cont.]
puncturing
scheme 1
puncturing
scheme 2
Nack
MS BTS MFS
Data Block
Data Block
Data Block
Data Block
Data Block
Data Block
(1) The BSS sends a DL data blockusing the puncturing scheme P1 andMCS-6. B1 is not successfully
decoded by the MS. The MS storesthe received block
(2) The MS requests a selectiveretransmission of the erroneousblock, in the next EGPRS Packet DLAck/Nack
(3) The MS retransmits the DL datablock using a new puncturingscheme P2 and the same MCS-6.If the block header is correctlydecoded, the MS decodes the datamaking soft combination with theprevious transmission
In the puncturing scheme selection for re-transmission, 2 cases have to be considered:
if the selected MCS has not changed : if all the different punctured versions of the data block have been
sent, the procedure shall start over and PS1 shall be used, followed by PS2, then by PS3 (if available for
the considered MCS), so that the PS selection is cyclic,
if the selected MCS has changed : the PS to be used is indicated by the table below.
Previous MCS New MCS Previous PS New PS
PS1 or PS3 PS1MCS9 MCS6
PS2 PS2
PS1 PS3MCS6 MCS9
PS2 PS2
MCS7 MCS5 PS1, PS2 or PS3 PS1
MCS5 MCS7 PS1 or PS2 PS2
All other combinations Any PS1
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1.19 Type-I ARQ in EGPRS [cont.]
B9 release: the IR mechanism is implemented in uplink anddownlink
This mechanism is associated with link adaptation in order toprovide superior radio efficiency on the air interface
IR feature is always running in the EGPRS MS receivers, except whena memory shortage is reported by the MS the stored packets arediscarded and type-I ARQ is set !
Parameter for IR activation:
EN_FULL_IR_DL which enable or disable the RLC data segmentation forretransmissions
EN_FULL_IR_DL = disable; e.g. if MCS-5 is ordered by LA, and the firsttransmission was with MCS-6 then, the retransmission is performed with MCS-3(segmentation on the initial RLC data block, ARQ Type-I)
EN_FULL_IR_DL=enable; even if MCS-5 is ordered, the retransmission isperformed with MCS-6 (no segmentation, ARQ Type-II)
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1.20 (E)GPRS radio physical channel: PDCH Concept
Packet Data Channel (PDCH)
(E)GPRS radio access method = GSM TDMA (8 timeslots per carrier)
One PDCH represents a physical channel (1 timeslot) dedicated to packetdata traffic (GPRS/EDGE), over the radio interface
PDCH group
The available PDCHs are grouped into PDCH groups
One PDCH group contains consecutive timeslots (without TS holes)belonging to the same TRX, having the same radio configuration
possible to have hopping and non hopping PDCH groups in one cell
maximum number of PDCH groups/cell is equal to 16 (equal to maximumnumber of TRX / cell) 16 TRX/cell achieved with help of the B7 feature cell split over 2 BTSs, EVOLIUM BTS
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1.21 (E)GPRS Multiframe
12 radio blocks (B0 to B11) form a 52-(E)GPRS multiframe
The frames 25 and 51 are idle frames and the frames 12 and 38 areused for the PTCCH
One TDMA frame
= 8 TS (4,615 ms)
One PDCH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 47 48 49 50
One 52 -multiframe (240 ms)
Block B0 Block B1 Block B2 Block B3
16
TPTCCH Block B11
51
Xidle
0 1 2 3 4 5 6 7
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1.22 (E)GPRS Logical Channels
EGPRS is reusing the existing GPRS logical channels
Packet logical channels are mapped in one physical channel (PDCH)
using the technique of multiframing The sharing of the PDCH is done on blocks basis
PBCCH (Packet Broadcast Control Channel) used for broadcastingsystem information (SI)
PCCCH (Packet Common Control Channel) used to initiate packettransfer
PRACH (Packet Random Access Channel)
PPCH (Packet Paging Channel)
PAGCH (Packet Access Grant Channel)
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1.22 (E)GPRS Logical Channels [cont.]
PTCH (Packet Traffic Channel) used for user data transmission andits associated signaling
PDTCH (Packet Data Traffic Channel) used to carry user data (LLC PDUsegmented is RLC/MAC blocks)
PACCH (Packet As