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5/22/2018 EDGE Overview
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EDGE Overview
5/22/2018 EDGE Overview
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EDGE = Enhanced Data Rates for GSM (or Global) Evolution
Enhancement results from introduction of new modulation (8-PSK)+ channel coding schemes
ECSD (Enhanced Circuit Switched Data): circuit switched channels/ services EGPRS (Enhanced GPRS): packet switched channels/ services
New modulation triples the nominal bit rates
Update of the GSM Standard towards 3rd generation
networks/mobiles
What is EDGE?
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EDGE and 3G
The IMT-2000 3rdgenerationrequirements arefulfilled with EDGEtechnology, excluding2 Mbit/s indoorrequirement
Operators who do notget/want 3G-license
(UMTS/WCDMA) canprovide 3G-services
Gradual networkupdate with relativelow investments oninfrastructure
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New modulation: 8-PSK
(0,0,1)
(1,0,1)
(d(3k),d(3k+1),d(3k+2))=
(0,0,0) (0,1,0)
(0,1,1)
(1,1,1)
(1,1,0)
(1,0,0)
8-PSK (Phase Shift Keying) hasbeen selected as the new
modulation added in EDGE
Non-constant envelopehighrequirements for linearity of thepower amplifier
Because of amplifier non-linearities, a 2-4 dB powerdecrease (back-off) is typically
needed
3 bits per symbol Symbol rate and burst length
identical to those of GMSK
EDGE GSMModulation 8-PSK, 3bit/sym GMSK, 1 bit/sym
Symbol rate 270.833 ksps 270.833 ksps
Payload/burst 342 bits 114 bits
Gross rate/time slot 68.4 kbps 22.8 kbps
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8-PSK Tx Power Reduction compared to GMSK Tx
GMSK
8PSK
Time
Envelope (amplitude)
Time
Envelope (amplitude)
Peak to Average of 3,2 dB
Pin
Pout
Back Off= 2 dB
Compression point
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EDGE in GSM/GPRS network
8-PSK coverage
EDGE capable TRX,GSM compatible
GMSK coverage
A-bis
BTS
BTS
MSC
Gn
GGSN
EDGE capableterminal,
GSM compatible
More capacity in interfacesto support higher data usage
GbBSC
A
SGSN
EDGE functionality in
the network elements
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EDGE vs GPRS
EDGE Benefits
EGPRS link level performance
EGPRS vs GPRS bitrates
Coverage comparison
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EDGE vs GPRSBenefits
EGPRS is the same as GPRS but with an enhanced radio interface (EDGE)
Same GPRS architecture and protocols Same mobility management Similar Radio Resource Management as GPRS
But... Enhanced RLC/MAC protocol:
Longer RLC windows
Enhanced re-transmission mechanism Incremental Redundancy
Retransmissions can be performed in different MCS from the original Better Link performance New requirements are needed in the Abis and Gb interfaces
Higher bitrates do not fit into Abis 16kbps channels throughputs
The Dynamic Abis Pool is a shared extra Abis resource for EGPRSchannels and TRXs
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EGPRS link level performance
EGPRS - TU3 noFH
0
10
20
30
40
50
60
0 5 10 15 20 25 30
CIR [dB]
Through
putperTSL
(Kbps)
MCS1 to MCS9
No IR
IR
EGPRS - TU3 noFH
0.001
0.010
0.100
1.000
0 5 10 15 20 25 30
CIR [dB]
BLER
MCS1 to MCS-9
Link Adaptation will select the (M)CS that maximizes SE whileachieving the user QoS requirements
Link Adaptation takes into account IR
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GPRS & EGPRS Coding Schemes
coding
scheme
modulation RLC blks /
radio blk
FEC
code rate
user bits /
20 ms
bit rate
(bps)CS-1 1 0.45 160 8,000
CS-2 1 0.65 240 12,000
CS-3 1 0.75 288 14,400
GPRS
CS-4 1 n/a 400 20,000
MCS-1 1 0.53 176 8,800
MCS-2 1 0.66 224 11,200
MCS-3 1 0.85 296 14,800
MCS-4
GMSK
1 1.00 352 17,600
MCS-5 1 0.38 448 22,400
MCS-6 1 0.49 592 29,600
MCS-7 2 0.76 448+448 44,800MCS-8 2 0.92 544+544 54,400
EGPRS
MCS-9
8-PSK
2 1.00 592+592 59,200
TS 03.64 Bit rate excluding RLC/MAC headers
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0
10
20
30
40
50
60
1 2 3 4 5 6 7 8 9 10 11
Pathloss distance [km]
DLThrough
putperTSL[Kbps]
EGPRS
GPRS CS1-2
GPRS CS1-4
Path loss [dB]120.8 132.1 138.8 143.5 147.1 150.1 152.6 154.8 156.7 158.4 160.0
EGPRS coverage compared with GPRS
L= 40(1-4x10-hb)Log10(R) -18Log10(hb) + 21Log10(f) + 80 dB.
Relationship between path-loss and distance given by Okumura-Hata based-formula:
Averagegain: 3.6
Averagegain: 2.3 Es/No=8.3 dB
Es/No=42.3 dB
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EDGE description
Modulation & Coding Schemes
EGPRS Channel Coding
EGPRS MCS families
Segmentation and ARQ
Retransmission mechanisms
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EGPRS Coding Schemes
Portion of data and coding varies in different coding schemes
the more coding the more errors can be corrected in the radio interface
data coding
Radio interface block (1392 bits in 8-PSK)
Scheme
Modulatio
n
Raw
data in
block
(bits)
Raw
data in
block
(octets) Family
Data rate
(kbit/s)
MCS-9 8-PSK 2x592 2x74 A 59.2
MCS-8 8-PSK 2x544 2x68 A 54.4
MCS-7 8-PSK 2x448 2x56 B 44.8
MCS-6 8-PSK 592 74 A 29.6
MCS-5 8-PSK 448 56 B 22.4MCS-4 GMSK 352 44 C 17.6
MCS-3 GMSK 296 37 A 14.8
MCS-2 GMSK 224 28 B 11.2
MCS-1 GMSK 176 22 C 8.8
PCUBTS
EGPRS
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EGPRS Modulation and Coding Schemes
EGPRS has nine basiccoding schemes, MCS-1...9.
In general, a higher codingscheme has higher codingrate, and consequently higherpeak throughput, but it alsotolerates less noise orinterference.
The figure shows throughput
vs. C/I of EGPRS codingschemes in TU50iFH, withoutincremental redundancy.
The basic unit of transmissionis radio block (= 4 bursts = 20ms on average), whichcontains one or two RLCblocks.
0
10
20
30
40
50
60
0 5 10 15 20 25 30
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
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EGPRS Channel Coding
EGPRS channel coding consists
of separate data and headercoding, as shown in the figurefor MCS-9 downlink.
Coding of data part: Data part includes user
data, two bits from RLC header, BCS(block check sequence)and tail bits.
Coded using 1/3 convolutional code.
Punctured with a selectable puncturingscheme (P1, P2 or P3). Two separate data parts for MCS-7...9.
Header part: Includes RLC/MAC header information
and information on the coding of thedata part (like used puncturingscheme).
Convolutional coding + puncturing.
USF
encoded USF P2 P3
P1 P2 P3
puncturing puncturing
puncturing
1st burst 2nd burst 3rd burst 4th burst
1/3 tailbiting
convolutional codingblock
coding
P1
header FBI+E data 2 BCS tail
1/3 convolutionalcoding
FBI+E data 1 BCS tail
1/3 convolutional
coding
mother code
mother code
protectedheader
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EGPRS MCS families
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+3octets34+3octets
MCS-3
MCS-6Family Apadding
MCS-8
34 octets 34 octets 34 octets34 octets
The MCSs are divided into different families A,B andC.
Each family has a different basicunit of payload: 37(and 34), 28 and 22 octets respectively.
Different code rates within a family are achieved bytransmitting a different number of payload unitswithin one Radio Block.
For families A and B, 1 or 2 or 4 payload units aretransmitted, for family C, only 1 or 2 payload unitsare transmitted
When 4 payload units are transmitted (MCS 7, MSC-8 and MCS-9), these are splitted into two separateRLC blocks (with separate sequence BSN numbersand BCS, Block Check Sequences)
The blocks are interleaved over two bursts only,
for MCS-8 and MCS-9. For MCS-7 the blocks are interleaved over four
bursts
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EGPRS Dynamic Abis
GSM/GPRS Abis description
New EGPRS requirements for Abis
Dynamic Abis description
Dynamic Abis pool management, features and limitations
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The GSM/GPRS Abis Interface (1/3)
The Abis interface is situated between the BSC and the Base Station sites
The Abis interface is also used for GPRS services.
In a traditional GSM/GPRS system, each TRX channel is mapped statically to AbisPCM timeslots
AbisBSC
SGSNBTS
Um Gb
PCU
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New Requirements for EGPRS
In the air interface, higher rates are achieved through the use 8-PSK. Achievabletransmission rates are in the order of 59.2 Kbit/s per Radio Timeslot (RTSL)
Higher data rates dont fit in 16 kbit/s A-bis channels 32, 48, 64 or 80 kbit/s Abis links are needed Fixed Abis allocation of such links would be expensive and would lack flexibility
The Dynamic Abis Pool is a shared extra Abis resource for EGPRS channels andTRXs
The Dynamic Abis functionality allocates Abis transmission capacity to cells when
needed instead of reserving full fixed transmission link per TRX
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Dynamic Abis (1/3)
PCU frame types PCU data frame
Used when TRX not in EDGEmodeOnly able to carry CS1 and CS2
PCU master data frameUsed when TRX is in EDGE modeCarries CS1 or MCS1 on its ownand CS2-4 and MCS2-9 with thehelp of slave frame(s)
Includes pointers to the slaveframes PCU slave data frame
Carries additional data that doesnot fit in PCU master data frames
MCS-1 M
M
M
M
M
M
M
M
M
S
S
S
CS-4
CS-3
CS-2
CS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
S
S
S
S
S
S
S
S
S
MM
M
M
S
S
S
S
S
S
S
S
CS-2CS-1
D
D
non-EDGE TRX
EDGE TRX
D
M
S
PCU data frame
PCU master data frame
PCU slave data frame
+
+
+
+
+
+
+
+
+
+
+
retrans M
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Dynamic Abis (2/3)
Fixed channels and EDAP For each GPRS radio timeslot on each
EDGE TRX, one fixed 16-kbps channelis allocated on the Abis for the transferof PCU master data frames
PCU slave data frames are allocated ina common pool, the EDAP (EDGEDynamic Abis Pool)
We are still going to make a staticallocation of 16 kbit/s per TCH, (used for
voice or data) In a PSD call, this sub-TSL is called amaster Abis channel, and if required, thesystem can allocate up to 4 extra slave
Abis sub-TSLs for same master fromdynamic pool
TS Bits used in timeslots
1 2 3 4 5 6 7 8
1
23
4
5
67
8
9
10
11
1213
14
15
16
1718
19
20
21
222324
Master
Slave
Reserved
Dynamic Abis Pool
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Dynamic Abis (3/3)
Dynamic Abis pointers Each downlink PCU master data frame
includes a pointer to downlink slaveframes on the same block period, and apointer to uplink slave frames on thenext block period
M M
S S S
S S S S
downlink PCMframes during
one block period
uplink PCMframes during
next block period
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Transmission Requirements for EGPRS MCS
Abis PCM allocation (fixed + pool)Coding Scheme Bit rate (bps)
CS-1 8,000
CS-2 12,000
CS-3 14,400
CS-4 20,000
MCS-1 8,800
MCS-2 11,200
MCS-3 14,800
MCS-4 17,600
MCS-5 22,400
MCS-6 29,600
MCS-7 44,800
MCS-8 54,400MCS-9 59,200
Slave Groups
CS-2 requires one Abis slave channel when the GPRS TBF is in EGPRS territory
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Incremental Redundancy
Incremental Redundancy description
Incremental Redundancy performance
Incremental Redundancy gains
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Incremental Redundancy (1)
IR is a physical layer performance enhancement for the acknowledged RLC modeof EGPRS
The basis for Incremental Redundancy (IR) is in the selective-reject-ARQ protocol of
the RLC layer. The ARQ protocol takes care of requesting and retransmittingincorrectly received blocks
By using the Backward Error Correction (BEC) procedures the selectiveretransmission of unsuccessfully delivered RLC/MAC blocks is obtained
IR improves the reception of retransmissions by combining the information in theoriginal transmission (which failed) with the received additional information, thereby
increasing the probability of correct reception The most important standardised feature of Incremental Redundancy is that MS has
mandatory IR combining in its receiver. IR has also been taken into account in thedesign of the coding schemes and block formats
Incremental Redundancy is suported by NOKIA. IR is set by default in NOKIAconfiguration
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Incremental Redundancy (2)
The figure shows an example of IR transmission and combining with differentpuncturing schemes for different transmission. The shown case corresponds to MCS-
4 or MCS-9, where the basic code rate is 1/1.
original data
1/3 coded data
1st xmission
2nd xmission
3rd xmission
1st decoding attempt
2nd decoding attempt
3rd decoding attempt
r = 1/3
r = 1/2
r = 1/1
r = 1/1
r = 1/1
r = 1/1
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Link Adaptation
Link Adaptation introduction
Link Adaptation algorithm
Bit Error Probability (Mean_BEP, CV_BEP)
Link Adaptation Procedure
I t d ti
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Introduction
In GSM Specification, there is full support for Bit Error Probability (BEP) based Link Adaptation(LA) algorithm
MS reports both mean and (normalized) standard deviation (std) of BEP values for thereceived radio blocks
Although mean BEP is clearly a dominant quantity in the selection procedure, stdBEP is found to be relevant for the strong coded MCSs
MS reports the network also if it has run out of IR memory The LA algorithm is based on these reports
The task of the LA algorithm is to select the optimal MCS for each radio condition to maximizechannel throughput
To maintain good throughput the goal for the LA algorithm is to adapt to situations wheresignal strength compared to interference level is changing within time
LA adapts to path loss and shadowing but not fast fading This corresponds to the "ideal LA"curves in link level simulations
Incremental Redundancy (IR) is better suited to compensate for fast fading
EGPRS LA is implemented in the Packet Control Unit (PCU)
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Resource Allocation Management
Multiple MS and Uplink Transmission
Multiple MS and Downlink Transmission
Radio Resource Operating Modes
EGPRS Territory Method
EGPRS Downgrades and Upgrades
Resource Allocation management from PCU
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Resource Allocation management from PCUMultiple Mobiles and Uplink Transmission
USF = 1
USF = 2
USF = 3
USF = 3
MSs
BTS
RLC Data Block
Mobile transmissions controlled by USF (Uplink State Flag) sent on DL
Mobile with correct USF will transmit in following block
Resource Allocation management from PCU
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Resource Allocation management from PCUMultiple Mobiles and Downlink Transmission
TFI2
TFI5
TFI3
TFI2
MSs
BTS
TFI value included in RLC block header - indicates with which TBF the
RLC block is associated
RLC Data Block
Resource Allocation management from PCU
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Resource Allocation management from PCU(E)GPRS territory method
RRM features optimally manage between circuit-switched and packet-
switched servicesTRX 1
Packet-switched TerritoryTRX 2
BCCH TCH TCH TCH TCH TCH TCH
TCHTCH P-TCH /
TCH
P-TCH /
TCH
P-TCH P-TCH
Circuit-switched TerritorySignalling
Circuit-switched Default (E)GPRS
Capacity
dedicated (E)GPRS(never filled with speech services)
P-TCH /
TCH
P-TCH /
TCH
PBCCH
Additional (E)GPRS
capacity
can be used for speech
Territory Border moves DYNAMICALLY based on CSW traffic load
Resource Allocation management from PCU
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gTerritory Upgrades and Downgrades
The need for additional GPRS channels is checked when a new TBF is establishedor an existing TBF is terminated.
The PCU will request additional channels, if a GPRS territory contains less channels than could be allocated to a mobile
according to its multislot class or if the average number of TBFs per TSL is more than 1.5 after the allocation of
the new TBF (average TBF/TSL>1.5). These additional channels will be requested only if all GPRS default channels
are already in the GPRS territory.
The number of additional channels the PCU will request is the greater of thefollowing two numbers:
The number of additional channels needed in the allocation according to theMS's multislot class (this criterion is used only when the GPRS territory containsfewer channels than the MS is capable of using), and
The number of additional channels needed for the average number of allocatedTBFs per TSL to be 1(average TBF/TSL=1).
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