Packet-switched vs. Circuit-switched Data Transfer
C ircu it S wit ch in g
P acket S wit ch in g
Info
BB
AA
BB
AA
BB
AA
Info
BB
AA
BB
AA
EN/FAD 109 0015
Info
AA
038 13 - LZU 108 881 Rev B
Info
BB
AA
Figure 12 - 1
BB
GSM Advanced Cell Planning
GPRS Logical Architecture
Um
BSS
TE
MT
ISDN/
PSTN
BTS
Abis
A
BSC
MS
Traffic and signaling
GMSC
MSC/VLR
Gs
Gb
EN/FAD 109 0015
MSC
VLR
HLR
AUC
EIR
SGSN
GGSN
Um
A, Abis
Gx
Terminal Equipment
Mobile Terminal
Mobile Station
Base Station System
Base Transceiver Station
Base Station Controller
Gateway Mobile Services Switching
Center
Mobile Switching Center
Visitor Location Register
Home Location Register
Authentication Center
Equipment Identity Register
Serving GPRS Support Node
Gateway GPRS Support Node
Air Interface
Interfaces (GSM)
Interfaces (GPRS)
038 13 - LZU 108 881 Rev B
Gf
AUC
SGSN
Signaling
TE
MT
MS
BSS
BTS
BSC
GMSC
EIR
Gr
HLR
External
IP Network
(Internet)
Gn
IP-Backbone
Network
GGSN
External
IP Network
(Corporate
LAN)
Gi
Gp
Other
PLMN
Figure 12 - 2
External
X.25 Network
GSM Advanced Cell Planning
GPRS Protocols
Application
IP / X.25
IP / X.25
Relay
SNDCP
SNDCP
GTP
GTP
LLC
LLC
UDP /
TCP
UDP /
TCP
IP
IP
Relay
RLC
RLC
BSSGP
BSSGP
MAC
MAC
Network
Service
Network
Service
L2
L2
GSM RF
GSM RF
L1bis
L1bis
L1
L1
Um
BSS
Gn
SGSN
Gi
GGSN
EN/FAD 109 0015
MS
Gb
038 13 - LZU 108 881 Rev B
Figure 12 - 3
GSM Advanced Cell Planning
Multiframe structure
52 Multi-frame Structure
RLC/MAC blocks
Radio blocks
EN/FAD 109 0015
continuous timing advance
(PTCCH)
idle bursts
52 TDMA frames
038 13 - LZU 108 881 Rev B
2/ 038 13 - LZU 108 876 Uen Rev B
Figure 12 - 4
GSM Advanced
CellSystem
PlanningSurv
GPRS
Radio Block Structure
Header
+
Info
bits

Coding
bits
M bits in
456-M bits of coding
RLC/MAC block
Coding
Max no. of Final RLC
Info bits
Block
Radio
Block
456 bits in each
radio block
Max data rate
per TS (kbps)
Target C/I
(dB)
RLC
CS-1
160
8
~6
12
~9
14.4
~12
20
~17
Data
RLC
CS-2
240
CS-3
288
Data
EN/FAD 109 0015
RLC
Data
RLC
CS-4
038 13 - LZU 108 881 Rev B
400
Data
Figure 12 - 5
GSM Advanced Cell Planning
bit
Structure of
RLC/MAC Block
8
7
Payload Type
6
bit
5
4
RRBP
3
S/P
2
1
8
7
6
5
4
Payload Type
USF
2
Spare
1
R
Octet 1

Octet 1




Control Message Contents
3

Control Message Contents
Octet 22
Octet 22
Uplink Control Block
Downlink Control Block
Header
Data
Uplink Traffic Block
Downlink Traffic Block
bit
8
7
Payload Type
6
5
RRBP
bit
4
3
S/P
2
1
8
7
Payload Type
USF
6
5
4
Countdown Value
1
SI
R
FBI
Octet 1
Temporary Flow Identity (TFI)
TI
Octet 1
Block Sequence Number (BSN)
E
Octet 2
Block Sequence Number (BSN)
E
Octet 2
Octet 3


RLC data
EN/FAD 109 0015
2
Temporary Flow Identity (TFI)
Octet 3


Octet
N
038 13 - LZU 108 881 Rev B
3
Figure 12 - 6

RLC data

Octet
N
GSM Advanced Cell Planning
Common Resource Pool
- PDCH carrying PCCCH
- PDCH not carrying PCCCH
BCCH
Carrier
Frequencies
BTS
01 2 34 5 67
-
BSC
CCCH, TCH or free time slot
TS
Common Resource Pool
PDCH
TCH
EN/FAD 109 0015
TS - Time Slot, BTS - Base Transceiver Station, BSC - Base Station Controller
BCCH - Broadcast channel, CCCH - Common control channel, PDCH - Packed data
channel, PCCCH - Packet common control channel
038 13 - LZU 108 881 Rev B
Figure 12 - 7
GSM Advanced Cell Planning
Channel Reservation
Channel Reservation Strategy
TBF
TBF
PSET1
TBF
limit
PSET2
MS5
MS4
MS3
MS3
MS5
MS2
MS2
MS2
MS3
MS1
MS1
MS1
MS1
MS6
PDCHs
MS6
MS6
PDCHs
D 109 0015 EN/FAD 109 0015
to GPRS idle list
• Fill up fixed channels first
• When no channels left under TBF-limit choose next PSET
• Unused channels goes to GPRS Idle list where they stay for 5 minutes before
they are given back to CS
038 13 - LZU 108 881 Rev B
Figure 12 - 8
GSM Advanced Cell Planning
GPRS MM states of MS and SGSN
IDLE
GPRS Attach
STANDBY timer
expiry
GPRS Detach
EN/FAD 109 0015
GPRS Detach
or
Cancel Location
GPRS Attach
STANDBY timer expiry
or
Cancel Location
READY
READY timer expiry
or
Force to STANDBY
038 13 - LZU 108 881 Rev B
IDLE
READY
READY timer expiry
or
Force to STANDBY
or
Abnormal RLC condition
LLC PDU
transmission
LLC PDU
reception
STANDBY
STANDBY
MM State Model of MS
MM State Model of SGSN
Figure 12 - 9
GSM Advanced Cell Planning
Network Operation Modes, Gs present (I) and nonpresent
(II Operational
and III) Modes
Network
MSC/
VLR
I
BSC
Gs
SGSN
II & III
MSC/
VLR
EN/FAD 109 0015
EN/FAD 109 0015
BSC
SGSN
• combined Location Area and
Routing Area update
• combined paging
• longer sleep periods for MS
• smaller paging load
MS is only paged within
Routing Area
• separate Location Area and
Routing Area update
• MS needs to listen to two types
of paging channels
• MS is paged in Location Area
GPRS System Survey
1/ 038 13 - LZU 108 876 Uen Rev B
038 13 - LZU 108 881 Rev B
Figure 12 - 10
GSM Advanced Cell Planning
MS on
PCCCH
BSS
Establishment of
an uplink TBF
MS on one or more PDTCHs
Concurrent Uplink
and Downlink TBFs
MS
Establishment of
a downlink TBF
Release of the
uplink TBF.
Establishment of
an uplink TBF
Release of the uplink TBF.
MS on
PCCCH
Release of the Downlink TBF.
EN/FAD 109 0015
EN/FAD 109 0015
MS on one or
more PDTCHs
Establishment of
a downlink TBF
038 13 - LZU 108 881 Rev B



Release of the
downlink TBF.
Etc.
Figure 12 - 11
GSM Advanced Cell Planning
MS
BSS
MS camps
on PCCCH
Downlink Transfer to
Attached MS in
Ready Mode
MS nurses a TBF on one
or more PDTCHs
Establishment of a TBF
Assignment of resources etc.
Transfer of one or more RLC
data blocks downlink, and the
associated control signalling
uplink and downlink.
MS camps
on PCCCH
Release of the TBF.
EN/FAD 109 0015
MS on
PDTCH
Establishment of a TBF
Assignment of resources etc.



038 13 - LZU 108 881 Rev B
09 0015
Etc.
Figure 12 - 12
GSM Advanced Cell Planning
Cell Re-selections rather than Handover
1
2
3
?
Data
Data
Cell
update
SGSN
Flush
Data
SGSN
EN/FAD 109 0015
SGSN
BSC/
PCU
BSC/
PCU
BSC/
PCU
038 13 - LZU 108 881 Rev B
Figure 12 - 13
GSM Advanced Cell Planning
Coding throughput, TU 50, ideal FH
Throughput per channel
CS-1
CS-2
CS-3
20
CS-4
10
EN/FAD 109 0015
0
0
5
10
15
20
25
30
C/I [dB]
038 13 - LZU 108 881 Rev B
Figure 12 - 14
GSM Advanced Cell Planning