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P. P. Mahale
GSM n/w corporate offices
IP phone/PC
Intranet
GSM/BTS
Architecture
MSC
VLR
HLR
Gateway
Access
node
Service
node
Terminal mobility:
User mobility:
They communicate with each other using H.323 protocol
Service node: user mobility, controls calls, translate
addr, authentication
Access node: manage connection, mobility & radio
resources, related to core n/w & BTS nodes
GSM/BTS: wireless access for GSM MS in IP addr
Gateway: interface GSM on net & other n/w.
Terminal equipment: can be IP phone, PC
1) The H.323 Network:
packet based n/w
H.323 terminal
* optionally included
H.323 architecture
H.323
Gatekeeper
H.323
Gatew
ay
H.323
Multipoint
Control unit
MP*
MC*MP*
MC*
MC*
MP*
MC
ISDN
LAN
PSTN
Terminal:
Gateway
Gatekeeper
MCU(multipoint control unit):
MC( multipoint controller):
MP(multipoint processor):
2) The iGSM architecture:
GSM MAP & H.225 RAS (registration, admission & status)
GSM/PSTN/IP call setup & release
Every iGSM gatekeeper is assigned ISDN no.
It is recognized by HLR, also maintain DB.
We can connect iGSM gateways & gatekeeper.
MS
BTS/BSC
H.323 terminal
IP n/w
iGSM architecture
GSM
MSC
VLR
HLR
iGSM
gatew
ay
Gatekeeper
iGSm VLR
Describes registration, dereg & call delivery.
Database can be distributed among several gate
keepers.
MSISDN of the MS
Transport addr of H.323 terminal
Password of the iGSM subscriber
HLR addr (ISDN no)
IMSI of the MS
User profile, indicates service features & restrictions
Presence indication of iGSM
MS Registration
1
BTS/BSC
H.323 terminal
7
8 6 IP n/w
5 3 2
4 5 4
3 6
Movement from the GSM n/w to IP n/w
GSM
MSC
VLR
HLR
iGSM
gatew
ay
Gatekeeper
iGSm VLR
H.323 Gatekeeper Gateway HLR OLD VLR
term
2.RRQ(MSISDN, pwd)
3.IRQ( loc, IMSI, VLR, MSC)
3.MAP_UPDATE_LOC(IMSI, VLR, MSC)
4.MAP_INSERT_SUBSR_DATA(user profile)
4.IRR(INSSUBS DATA,user profile)
5.IRQ(inssubdataack) 7.MAP_CANCEL_LOC
8.MAP_CANCEL_LOC_ack
5.MAP_INSERT_SUB_DATA_ack
6.MAP_UPDATE_LOC_ack(HLR no)
6.IRR(updateLocAck, HLR no)
6.RCF
Message flow for iGSM registration
Gatekeeper H.323
HLR Gateway (old VLR) term
MAP_CANCEL_LOC(IMSI)
IRR(CanLoc, IMSI)
URQ
UCF
MAP_CANCEL_LOC_ack IACK(CanLocAck)
Message flow for iGSM deregistration
12 H.323 terminal
11
3 7 IP 10
2 8 n/w 9
6
2 5
GSM 3 4 2 3
1
originating
1
PSTN
HLR
GM
SC
s/w
iGSM
Gate
way
Gatekeeper
iGSM VLR
Ori GMSC HLR Gateway Gatekeeper H.323
s/w VLR term
1.IAM 2.MAP_SEND_ROUTING_INFO(MSISDN)
2.MAP_PROVIDE_ROAMING_NO(IMSI)
2.LRQ(RoamNo, IMSI)
3.LCF(RoamNoAck, MSRN)
3.MAP_PROVIDE_INFORMATION_NO_ack(MSRN)
3.MAP_SEND_ROUTING_INFO_ack(MSRN)
4. IAM 5. ARQ
6. ACF
7. Setup
8. Call Proceeding
9. ARQ
10. ACF
11. ACM 11. ACM 11. Altering
12. ANM 12. Connect
12. ANM
Conversation
GPRS functional group:
N/w access:
Standard point to point data transfer
Registration of MS
Authentication & authorization
Admission control which communicates with MS
Msg screening
Charging information collection
Packet routing & transfer function:
Route the data betwn Ms & destinations
Relay function used by BSS
Fwd packets betwn BSS & serving or gateway GSN
Routing.
Addr translation & mapping
Encapsulation & tunneling,
Compression & ciphering
Logical link management:
Communication channel betwn MS & GSM n/w
Logical link establishment
Logical link release
Radio resource management:
Allocates & maintenance radio communication path
Um mgmnt- radio resources allocated
Cell selection
Um-tranx- packet data transfer capability
Path management: maintains communication path
D
A Gs Gr Gc
Um Gb Gn Gi
Gn Gp
other GPRS n/w
---------- Signaling Interface
________ signaling and Data Transfer Interface
MSC/VLR
GGSNSGSN
GGSNSGSNBSSMS
HLR
PDN
In this architecture all respective system are modified.
Service GPRS support nod(SGSN):
----> GPRS equivalent to the MSC
Gateway GPRS support nodes(GGSN):
----> interworking with external packet switched
networks.
Gr & Gc follows the GSM mobile application part(MAP).
A, Gs, Gr, Gc & D are used for signaling, without
involving user data transmission in GSM.
Interface Um, Gb, Gn, Gp & Gi are used for both
signaling & transmission in GPRS.
In BSS Um & Gb use Logical link control(LLC) & packet data
units(PDU)
In SGSN Gb & Gn use Packet data protocol(PDP) & PDU’s
Three GPRS terms
-- Mobility Management
-- PDP context
-- QoS
IDLE-> MS is not attached to the GPRS mobility management
STANBY-> MS is attached to GPRS MM but not obtained
detailed location information
READY-> loc information for MS has been identified on cell
levels
In GPRS attach procedure both to MS & SGSN are moved to
ready.
PDP context stored in MS, HLR, SGSN & GGSN contains
mapping & routing information for packet transmission .
PDP context activation
-- MS known to GGSN
-- communication to external n/w is possible.
-- terminal supports several IP address
When MS is detached all PDP context are deactivated.
PDP context can be two states ACTIVE & INACTIVE.
Reliability class-- residual error rates for data loss, out of
sequence delivery, & corrupted data
Precedence class– three transmission policy
Delay class-- four delay level
Peak throughput– max data transmission rate
Mean throughput– avg data transmission rate
Mobile station:
Transceiver consist of 2 section:
RF front end:
--This section converts the GSM/TDMA signal baseband
signal in I/Q form
GPRS signaling & data codes:
--This section encodes/decodes signaling msg for
GSM/TDMA BSS
--Transcends data into packets conforming with GPRS
specifications
MS Modes:
Class A: MS can operate simultaneously packet & ckt
s/w services.
Class B: MS can operate either one at one time.
Class C: Ms can operate only packet s/w services
GPRS aware SIM are:
IMSI:
(P-TMSI) packet temporary mobile subscriber identity
Addr of routing area
Current ciphering key
BSC must get a packet control unit to
--set up, supervise & disconnect packet switching calls
--also support cell change, radio resource confi & ch
assignments
MSC/VLR, HLR & SMS center must be enhanced for
interworking with GPRS
MS must be equipped with GPRS
Paging & mobility management for GPRS
PCU & TRAU is equivalent for packet data service
SGSN(service GPRS support node):
It is equivalent to that of MSC/VLR
It provide ciphering, MM, routing msg, billing report
IMSI & MSISDN no.
MM state
Routing area identity & cell identity
New SGSN buffered packets should be forwarded
Authentication & ciphering parameters
PPF(paging proceed flag)
GGSN(Gateway GPRS support node):
GGSN is primarily provisioned by router
It supports sub addr, mapping addr, routing, counting
& tunneling packets.
It contain DHCP(dynamic host configuration
protocol) to allocates IP addr.
PDP type & PDP addr
Dynamic addr indication
Access point name & charging ID
It stores current SGSN addr & profile of the user in
its location register
HLR:
Shared DB with GSM
Is enhanced with GPRS sub data & routing info
It keeps user profile, current SGSN & PDP addr info
SGSN exchange info with HLR
VLR:
It is responsible for a group of location areas
It stores data of only those users area responsibility
IMSI & MSISDN
It contact SGSN to request loc info or paging of voice
calls
Um interface:
1. Radio channel structure:
Packet paging ch- pages MS for both ckt-s/w, packet data
service
Packet access grant ch(PAGCH)- used in packet transfer
establishment
Packet notification ch- used to send point to point
multipoint
Packet broadcast ctrl ch(PBCCH)- specify for packet data
Packet associate control ch(PACCH)- convey signaling info
Packet timing advance control ch in uplink direction
(PTCCH/U)- transmission of addr.
MS N/W
1. PRACH (packet ch req)
phase 1 2. PAGCH (packet immediate assign)
3. PACCH (pack resource req)
phase 2(optional) 4. PACCH (pack resource assign)
5. PDTCH (data block)
Uplink transfer 6. PDTCH (data block)
7. PDTCH (resource req)
Resource reallocation 8. PACCH (pack resource assignt)
9. PACCH (pack resource reassign ack)
Uplink transfer 10. PDTCH (data block)
11. PDTCH (last data block)
12. PACCH (final pack ack/nack)
Fig. GPRS uplink packet transfer
2. Um protocol layers:
It include RF layers, physical link layer, radio link ctrl/
medium access ctrl
PLL provides service for information transfer over
physical layer
RLC/MAC provides info transfer GPRS.
Retransmission, buffering & reassembly.
3. Enhance data rates for GSM evolution:
Enhanced data rate for GSM evolution(EDGE)
Enhanced GPRS(EGPRS) provides higher data rate.
Spectrum efficiency is also higher
MS measured downlink perfo sends to BSS
BSS measures uplink MSC’s
BSS sends uplink MSC cmd to MS
Gb interface:
Allowing many users to multiplexed over same resource
Resource allocation when data actually delivered
It include LLC, base station, n/w service layer.
LLC is convey information betn MS & SGSN.
To maintain a sequential order of frames
Flow control
Format & operational errors, recovery of transmission
Maintain by MS moves bet cell
Provide GPRSMM(GMM)
Includes authentication & transport
1. N/W service:
NS layers delivers encapsulated packets
SGSN & BSS connects frame relay link.
It supports n/w service virtual links(NS-VLs)
The path is called as NS-VC
Blocking when NS-VC not available
Unblocking when path is available
Resetting, a new NS-VC is set-up
Testing to check end to end connection
2. BSS GPRS protocol:
Provides QoS & routing info to transmit used data
SGSN communicates multiple BSS, corresponding one
BSSGP is work
It uses DL-UNITDATA to deliver from SGSN to BSS
It uses UL-UNITDATA to deliver from BSS to SGSN
PDU is delivered from SGSN to BSS
PDU contain MS radio access capability, QoS profile.
GMM provides PAGING, SUSPEND & RESUMd
BSSGP supported FLOW CONTROL
Downlink buffer is not transfer to MS
Gn & Gp interface:
Uses GPRS tunneling protocol (GTP)
Tunnels user data signaling msg to GSN’s
Gn i/f GSN within the same GPRS n/w
Gp i/f GSN within the different GPRS n/w
Supported by TCP for connection oriented transmission
Supported by UDP for connectionless transmission
Tunnel is two way, point to point.
Band signaling separated from data tunnels.
GTP tunnel management:
It creates, update & delete tunnels.
Create_PDP_context_request send to GGSN with DNS.
New entry allows route & charge packet
TCP & UDP transport user data
Send update msg to modify packet
Redistributed for load balancing.
GTP mobility management:
Support GPRS attach, routing area update, activate PDP
Send identification to new SGSN.
SGSN_context_req send to old SGSN obtain MM
After receive SGSN send response msg
after receiving send ack
Gs Interface:
It connects to DB in MSC/VLR & SGSN
Not involve user data transmission
BSSAP+functionality of Gs i/f
Loc info IMSI & GPRS attach
Paging, suspend, resume & loc update proc
VLR send GPRS_paging to SGSN
New paging msg send back to VLR
Uses suspend msg to block GPRS
If MS unknown send suspend_failure
Send Resume msg to activate GPRS
Resume_ack
GPRS_loc_update_req
Loc update reject & accept
Gi Interface:
PSDN & PDP work thr GPRS
These are interworking entities
PSDN uses X.25 & X.75
PDN uses IP & PPP
It is dynamically assigned by GPRS
GPRS work with GGSN via IPV4 & IPV6
GPRS maintain a firewall restrict the IP appln
GPRS & GGSN manages the DNS
GPRS may transparently access internet
DNS send identification instead of MS
GPRS nontransparent access intranet via ISP
Ms must authenticate intranet using security
Either provide a Ipsec for confidentiality
1. GPRS attach & detach procedure:
1.1 Attach req
1.2 Identfn_req
1.2 Identfn_responce
1.3 Attach Accept
Attach message flow
MSNew
SGSN
Old
SGSN
GGS
NHLR
VLRBSS
RA/LA update
2.1 MAP_cancel_loc
2.2 Detach_req
2.3 Delete_PDP_context_req
2.3 Delete_PDP_context_resp
2.4 GPRS_attach_ind
2.5 Detach Accept
2.6 MAP_cancel_loc_ack
Detach message flow
MSSGS
N
GGS
NHLR
VLRBSS
2. PDP context procedure:
1.1 Active PDP context req
1.2 create PDP context req
1.2 create PDP context res
1.3 Active PDP context accept
PDP context activation message flow
MS SGSN GGSNBSS
2.1 Update PDP context req
2.1 Update PDP context res
2.2 Modify PDP context req
2.2 Modify PDP context res
PDP context update message flow
MS SGSN GGSNBSS
3.1 Delete PDP context req
3.1 Delete PDP context res
3.2 Deactivate PDP context req
3.2 Deactivate PDP context res
PDP context deactivate message flow
MS SGSN GGSNBSS
1. The combine RA/LA update procedure:
1. Routing area update req
2. SGSN_context_req
2. SGSN_context_res
2. SGSN_context_ack
(pack fwding)
3. Update PDP context req
3. Update PDP context res
4. Map_update_loc
4. Map_cancel_loc
4. Map_cancel_loc_ack
4. Map_insert_sub_data
4. Map_insert_sub_data_ack
4. map_update_loc_ack
5. GPRS_loc_updating_req
MSNew
SGSN
Old
SGSN
GGS
NHLRNew
VLRBSS