Data Services in GSM Data transmission in GSM with only 9.6 kBit/s • Advanced channel coding allows 14.4 kBit/s • Still not enough for Internet access or even multimedia applications Thus: UMTS as “3G network”: Integration of data and voice in one network • But: new network infrastructure, new software, new devices, … • Development of other enhancements of GSM as interim solutions “2.5G networks” as interim solution • HSCSD as software solution • GPRS as hardware solution • EDGE as 3G solution in a 2G network
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Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
38Chapter 3.4: Mobile Networks
Data Services in GSM
Data transmission in GSM with only 9.6 kBit/s• Advanced channel coding allows 14.4 kBit/s
• Still not enough for Internet access or even multimedia applications
Thus: UMTS as “3G network”: Integration of data and voice in one network• But: new network infrastructure, new software, new devices, …
• Development of other enhancements of GSM as interim solutions
“2.5G networks” as interim solution• HSCSD as software solution
• GPRS as hardware solution• EDGE as 3G solution in a 2G network
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
39Chapter 3.4: Mobile Networks
HSCSD
HSCSD (High-Speed Circuit Switched Data)• Put together several time slots for one AIUR (Air Interface User Rate, up to 57.6
kBit/s with 4 Slots of 14.4 kBit/s)• Symmetrical (2 time channels each for up- and downlink) and asymmetrical (3 + 1
channels) communication are supported
• Mainly software update for the realization of the putting together• Advantage: fast availability, continuous quality, simple
• Disadvantage: connection-oriented, 4 channels are blocked the whole time, signaling for several channels necessary
� Needed infrastructure: GSN (GPRS Support Nodes) - GGSN and SGSN- GGSN (Gateway GSN): translation between GPRS und PDN (Packet Data
Network)- SGSN (Serving GSN): support of the MS (location, accounting, security)- GR (GPRS Register): Management of user addresses
GPRS (General Packet Radio Service)
• Packet-oriented transmission, usable also for multicast• Usage of up to 8 time slots of a TDMA frame on demand
• Usage of time slots only when data are available for sending (e.g. 50 kBit/s with short usage of 4 slots)
• Advantage: step towards UMTS, flexible
• Disadvantage: expensive because some new infrastructure is needed to handle the new transmission mechanism, wireless transmission becomes a bottleneck for high traffic amount
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
41Chapter 3.4: Mobile Networks
GPRS – Infrastructure Components
HLRGR VLR
PSTNISDNMSC GMSC
4
4
4 NSS
RSS
GPRS
EIRAUC
OSS
BSC
PCU
SGSNPDNGGSN
AUC: Authentication CenterBSC: Base Station ControllerEIR: Equipment Identity RegisterGMSC: Gateway Mobile Switching CenterHLR: Home Location RegisterMSC: Mobile Switching CenterVLR: Visitor Location Register
GGSN: Gateway GPRS Support NodeGR: GPRS RegisterPCU: Packet Control UnitSGSN: Serving GPRS Support Node
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
42Chapter 3.4: Mobile Networks
GPRS Data Rates [kBit/s]
171,2149,8128,410785,664,242,821,4CS-4
124,8109,293,67862,446,831,215,6CS-3
107,293,880,46753,640,226,813,4CS-2
72,463,3554,345,2536,227,1518,29,05CS-1
8 time slots
7 time slots
6 time slots
5 time slots
4 time slots
3 time slots
2 time slots
1 time slot
(error-)coding
CS-1 to CS-4: decreasing error protection
• Dynamic choice of coding
• Basing on measurements of signal quality (and the needed QoS)
• The user is assigned the highest possible data rate
Position
Data rate
CS-4
CS
-3
CS
-2
CS-1
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
43Chapter 3.4: Mobile Networks
Advantages of GPRS
“Always connected”• Long duration for connection establishment are eliminated
• Transmission of data on demand• Accounting by data volume, not by
connection duration
• Robust connection� Coding of data bases
on current signal quality
� Even the BSS checks the data correctness and initiates – if necessary – a transmission repeat
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
44Chapter 3.4: Mobile Networks
EDGE
EDGE (Enhanced Data Rates for GSM Evolution)
• Up to 384 kBit/s by enhanced modulation (8PSK instead of GMSK)• Transmission repeat:
Change of coding to adapt to the current channel quality
• Is build upon the existing GSM/GPRS system:
� New transceiver are needed (hardware upgrade in the BSS)
� Software-Upgrade BSS und BSC� New devices (8PSK)
� No changes in the core network!� Cheap alternative to UMTS?
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
45Chapter 3.4: Mobile Networks
UMTS und IMT-2000
Proposals for IMT-2000 (International Mobile Telecommunications) as world-wide standardized 3G communication system:
• UWC-136, cdma2000, WP-CDMA• UMTS (Universal Mobile Telecommunications System, ETSI)
UMTS• … bases on UTRA: Universal Terrestrial Radio Access
• Integration of different mobile, cordless and pager systems into only one radio access network supporting world-wide roaming
• Integration von voice, data, and multimedia data services
• Enhancement of GSM: higher data rates, enhanced service concept, global roaming• Data rates: 144 kBit/s up to 2 MBit/s
– min. 144 kBit/s rural (target: 384 kBit/s)– min. 384 kBit/s suburban (target: 512 kBit/s)– up to 2 MBit/s urban
• Compatibility to GSM, ATM, ISDN and IP
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
46Chapter 3.4: Mobile Networks
Frequencies for IMT-2000
IMT-2000
1850 1900 1950 2000 2050 2100 2150 2200 MHz
MSS↑ITU allocation IMT-2000
MSS↓
Europe
China
Japan
NorthAmerica
UTRAFDD ↑
UTRAFDD ↓
TDD
TDD
MSS↑
MSS↓
DECT
GSM1800
1850 1900 1950 2000 2050 2100 2150 2200 MHz
IMT-2000 MSS↑ IMT-2000
MSS↓
GSM1800
cdma2000W-CDMA
MSS↓
MSS↓
MSS↑
MSS↑
cdma2000W-CDMA
PHS
PCS rsv.
MSS: Mobile satellite servicesDECT: Digital Enhanced Cordless TelecommunicationsPHS: Personal Handyphone System PCS: Personal Communications Service (GSM1900)
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
47Chapter 3.4: Mobile Networks
IMT-2000 Family
IMT-DS(Direct Spread)
UTRA FDD(W-CDMA)
IMT-TC(Time Code)UTRA TDD(TD-CDMA);TD-SCDMA
IMT-MC(Multi Carrier)
cdma2000
IMT-SC(Single Carrier)
UWC-136(EDGE)
IMT-FT(Freq. Time)
DECT
GSMANSI-41(IS-634)
IP networkIMT-2000core networkITU-T
IMT-2000radio accessITU-R
Interface for networking
Flexible assignment of core network and radio access
• Complex power control (1500 power control cycles/s)
• Spreading factor: UL: 4-256; DL: 4-512
0 1 2 12 13 14...
Radio frame
Pilot FBI TPC
Time slot
666,7 µs
10 ms
Data
Data1
Uplink DPDCH
Uplink DPCCH
Downlink DPCHTPC TFCI Pilot
666,7 µs
666,7 µs
DPCCH DPDCH
2560 Chips, 10 Bits
2560 Chips, 10*2k Bits (k = 0...6)
TFCI
2560 Chips, 10*2k Bits (k = 0...7)
Data2
DPDCH DPCCH FBI: Feedback InformationTPC: Transmit Power ControlTFCI: Transport Format Combination IndicatorDPCCH: Dedicated Physical Control ChannelDPDCH: Dedicated Physical Data ChannelDPCH: Dedicated Physical Channel
Slot structure not for user separation but synchronization for periodic functions!
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
55Chapter 3.4: Mobile Networks
UMTS TDD Frame Structure
TD-CDMA• 2560 Chips per slot
• Spreading factor: 1-16• Symmetric or asymmetric slot assignment to UL/DL (min. 1 per direction)
• Tight synchronization needed• Simpler power control (100-800 power control cycles/s)
0 1 2 12 13 14...
Radio Frame
Data1104 Chips
Midample256 Chips
Data1104 Chips
Time slot
666,7 µs
10 ms
Traffic burstGP
GP: guard period96 Chips2560 Chips
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
56Chapter 3.4: Mobile Networks
UTRAN Architecture
• UTRAN comprises several RNSs
• Node B can support both, FDD or TDD
• RNC is responsible for handover decisions requiring signaling to the UE
• Cell offers FDD or TDD
RNC: Radio Network ControllerRNS: Radio Network Subsystem
Node B
Node B
RNC
Iub
Node B
UE1
RNS
CN
Node B
Node B
RNC
Iub
Node B
RNS
Iur
Node B
UE2
UE3
Iu
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
57Chapter 3.4: Mobile Networks
UTRAN Functions
• Admission Control
• Congestion Control• System Information Broadcasting
• Radio Channel Encryption• Handover
• Radio Network Configuration• Channel Quality Measurements• Macro Diversity
• Radio Carrier Control• Radio Resource Control
• Data Transmission over the Radio Interface• Power Control
• Channel Coding• Access Control
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
58Chapter 3.4: Mobile Networks
Core Network: Protocols
MSC
RNS
SGSN GGSN
GMSC
HLR
VLR
RNS
Layer 1: PDH, SDH, SONET
Layer 2: ATM
Layer 3: IPGPRS Backbone (IP)
SS 7
GSM-CSBackbone
PSTN/ISDN
PDN (X.25),Internet (IP)
UTRAN CN RNS can be UMTS RNS or GSM BSS
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
59Chapter 3.4: Mobile Networks
Core Network
The Core Network and thus also the interface Iu are separated into two logical domains:
• Circuit Switched Domain (CSD)� Circuit switched service inclusive signaling
Release 99 uses the GSM/GPRS network and just adds a new radio access
• Lower costs, faster deployment• Not as flexible as newer releases 4, 5, 6 (change to IP based functions, …)
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
60Chapter 3.4: Mobile Networks
Support of Mobility: Macro Diversity
• A device can receive signals over 3 antennas in parallel
• Multicast of data via several physical channels
� Enables soft handover� only in FDD mode
• Uplink� Simultaneous reception of UE
data at several Node Bs
� Reconstruction of data at Node B, SRNC or DRNC
• Downlink
� Simultaneous transmission of data via different cells
� Different spreading codes in different cells
CNNode B RNC
Node BUE
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
61Chapter 3.4: Mobile Networks
Support of Mobility: Handover
• From and to other systems (e.g. UMTS to GSM)
� A must for the beginning when UMTS coverage is poor• RNS controlling the connection is called SRNS (Serving RNS)
• RNS offering additional resources (e.g.. for soft handover) is called DRNS (Drift RNS)
• End-to-end connections between UE and CN only via Iu at the SRNS
� Change of SRNS requires change of Iu� Initiated by SRNS
� Controlled by the RNC and CN
SRNC
UE
DRNC
Iur
CN
Iu
Node BIub
Node BIub
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
62Chapter 3.4: Mobile Networks
Example Handover Types in in UMTS/GSM
RNC1
UE1
RNC2
Iur
3G MSC1
Iu
Node B1
IubNode B2
Node B3 3G MSC2
BSCBTS 2G MSC3
AAbis
UE2
UE3
UE4
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
63Chapter 3.4: Mobile Networks
Cell Breathing
GSM• Device gets full power from the base station
• Number of connected devices has no influence on the cell size
UMTS• Cell size and capacity are tightly correlated• Capacity is determined at the Signal-to-Noise-Ratio
• Noise is increased by interference…� with other cells� with other participants
• Devices at the cell border are not able to increase their signal strength (power limitation) � for too high noise no communication is possible
• Restriction of simultaneous number of users necessary• Cell breathing makes cell planning complicated
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
64Chapter 3.4: Mobile Networks
Cell Breathing: Example
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
65Chapter 3.4: Mobile Networks
UMTS Services
Virtual Home Environment (VHE)• Enables access to personalized data independent of location, access
network, and device• Network operators may offer new services without changing the network• Service providers may offer services based on components which allow the
automatic adaptation to new networks and devices• Integration of existing IN services