3G New Data Services for GSM HSCSD GPRS 3G UMTS IMT2000 UMTS - - PowerPoint PPT Presentation

CMPE 477

Evolution of GSM in to 2.5G and 3G

New Data Services for GSM

HSCSD GPRS

3G – UMTS

IMT2000 UMTS Architecture UTRAN Architecture

CMPE 477 – Wireless and Mobile Networks

Data services in GSM I

Data transmission standardized with only 9.6 kbit/s

 advanced coding allows 14,4 kbit/s  not enough for Internet and multimedia applications

HSCSD (High-Speed Circuit Switched Data)

 mainly software update  bundling of several time-slots to get higher AIUR (Air

Interface User Rate) (e.g., 57.6 kbit/s using 4 slots, 14.4 each)

 advantage: ready to use, constant quality, simple  disadvantage: channels blocked for voice transmission

AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.4 4.8 1 9.6 2 1 14.4 3 1 19.2 4 2 28.8 3 2 38.4 4 43.2 3 57.6 4

Data services in GSM II

GPRS (General Packet Radio Service)

 Avoids the problems of HSCSD by packet switching  Network providers charge on volume rather than duration  One to 8 slots can be allocated per frame, no fixed assignment but

• n demand

 Maximum rate 171.2kbps but …

 Available data rate depends on the current cell load: using free (idle)

slots only if data packets ready to send

 Transfer rate depends on the capabilities of the MS, also the

maximum number of slots per frame is limited

 Typical Class 10 device achieves a receiving rate of 53.6kbps and a

sending rate of 26.8kbps

 All GPRS services can be used in parallel to conventional GSM

services

advantage: one step towards UMTS, more flexible disadvantage: more investment needed (new hardware)

GPRS network elements

GSN (GPRS Support Nodes): GGSN and SGSN (Routers)

 GGSN (Gateway GSN)

 interworking unit between GPRS and PDN (Packet Data

Networks; IP, X25)

 Performs address conversion, tunnels data  Connected to IP networks

 SGSN (Serving GSN)

 supports the MS (location, billing, security-ciphering)  the delivery of data packets from and to the mobile

stations within its geographical service area

 GR (GPRS Register also called Gateway Location Register)

 user addresses, part of HLR, current SGSN, current VLR

GPRS architecture and interfaces

MS BSS GGSN SGSN MSC Um EIR HLR/ GR VLR PDN Gb Gn Gi SGSN Gn

Towards 3G: UMTS and IMT-2000

Proposals for IMT-2000 (International Mobile Telecommunications)

 UWC-136, cdma2000, WP-CDMA  UMTS (Universal Mobile Telecommunications System) from ETSI

(European Proposal)

UMTS

 UTRA (was: UMTS, now: Universal Terrestrial Radio Access): the

radio interface

 requirements

 min. 144 kbit/s rural (goal: 384 kbit/s)  min. 384 kbit/s suburban (goal: 512 kbit/s)  up to 2 Mbit/s urban  Should be compatible with GSM, IP and ISDN-based networks

IMT-2000 family

IMT-DS

(Direct Spread)

UTRA FDD (W-CDMA) 3GPP IMT-TC

(Time Code)

UTRA TDD (TD-CDMA); TD-SCDMA 3GPP IMT-MC

(Multi Carrier)

cdma2000 3GPP2 IMT-SC

(Single Carrier)

UWC-136 (EDGE) UWCC/3GPP IMT-FT

(Freq. Time)

DECT ETSI GSM (MAP) ANSI-41 (IS-634) IP-Network IMT-2000 Core Network ITU-T IMT-2000 (3G) Radio Access ITU-R Interface for Internetworking Flexible assignment of Core Network and Radio Access Initial UMTS (R99 w/ FDD)

As a single standard could not be found, the ITU standardized five groups of 3G Radio Access Technologies

Enhancements of GSM

EDGE (Enhanced Data rates for GSM Evolution) – 2.75G:

 GSM up to 384 kbit/s, using the same 200kHz wide carrier

and the same frequencies

 Uses enhanced modulation techniques, 8PSK instead of

GMSK

CAMEL (Customized Application for Mobile Enhanced Logic)

 VHE (virtual Home Environment) for visiting subscribers  services to be offered when a subscriber is roaming, like, for

instance, no-prefix dialing

 QoS Aspects, several migration aspects …

UMTS architecture (Release 99)

UTRAN UE CN Iu Uu

UTRAN (UTRA Network)

 Cell level mobility  Radio Network Subsystem (RNS)  Encapsulation of all radio specific tasks (handover,

resource management, etc.)

UE (User Equipment) CN (Core Network)

 Inter system handover  Gateways to other networks

UMTS domains and interfaces I

User Equipment Domain

 Assigned to a single user in order to access UMTS services

Infrastructure Domain

 Shared among all users  Offers UMTS services to all accepted users

USIM Domain Mobile Equipment Domain Access Network Domain Serving Network Domain Transit Network Domain Home Network Domain Cu Uu Iu User Equipment Domain Zu Yu Core Network Domain Infrastructure Domain

UMTS domains and interfaces II Universal Subscriber Identity Module (USIM)

Functions for encryption and authentication of users Located on a SIM inserted into a mobile device,

stores all user related data Mobile Equipment Domain

Functions for radio transmission User interface for establishing/maintaining end-to-

end connections Access Network Domain

Access network dependent functions

UMTS domains and interfaces III Core Network Domain

Access network independent functions Serving Network Domain

 Network currently responsible for communication

Home Network Domain

 Location and access network independent functions

Transit Network Domain

 Necessary if the serving network cannot directly contact

the home network domain

Spreading and scrambling of user data

UMTS uses DS-CDMA Constant chipping rate of 3.84 Mchip/s Different user data rates supported via different spreading factors

 higher data rate: less chips per bit and vice versa

User separation via unique, orthogonal scrambling codes

 users are not separated via orthogonal spreading codes  much simpler management of codes: each station can use

the same orthogonal spreading codes

Spreading Data

The first step in a sender is spreading user data using

• rthogonal spreading codes.

This separates the different data streams of a sender. These codes are called orthogonal variable spreading factor (OVSF) codes.

• Doubles a chipping sequence X with and without

flipping the sign of the chips: X and –X

• The spreading factor sf=n become sf=2n

OVSF coding

1 1,1 1,-1 1,1,1,1 1,1,-1,-1 X X,X X,-X 1,-1,1,-1 1,-1,-1,1 1,-1,-1,1,1,-1,-1,1 1,-1,-1,1,-1,1,1,-1 1,-1,1,-1,1,-1,1,-1 1,-1,1,-1,-1,1,-1,1 1,1,-1,-1,1,1,-1,-1 1,1,-1,-1,-1,-1,1,1 1,1,1,1,1,1,1,1 1,1,1,1,-1,-1,-1,-1 SF=1 SF=2 SF=4 SF=8 SF=n SF=2n ... ... ... ...

Spreading and Scrambling of user Data

data1 data2 data3 scrambling code1 spr. code3 spr. code2 spr. code1 data4 data5 scrambling code2 spr. code4 spr. code1

sender1 sender2

OVSF spreads the data streams but the spreading codes chosen in the senders can be the same After spreading all chip streams are added and scrambled. Scrambling does not further spread the chip sequence but XORs chips based on a code In the FDD mode, this code is unique for each sender and separates all senders

In the TDD mode, the scrambling code is cell specific.

UMTS FDD frame structure

W-CDMA

• 1920-1980 MHz uplink
• 2110-2170 MHz downlink
• chipping rate:

3.840 Mchip/s

• spreading: UL: 4-256;

DL:4-512

1 2 12 13 14 ... Radio frame Pilot FBI TPC Time slot 666.7 µs 10 ms Data Data1 uplink DPDCH uplink DPCCH downlink DPCH TPC 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 Information TPC: Transmit Power Control TFCI: Transport Format Combination Indicator DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPCH: Dedicated Physical Channel

Slot structure NOT for user separation but synchronisation for periodic functions!

UTRA-FDD Channels

Dedicated Physical Data Channel (DPDCH): Conveys user or signaling data. Spreading factor varies between 4 and 256 Data rates: 960 kbps(spreading factor 4), 480, 240, 120, 60, 30, 15kbps (spreading factor 256) Dedicated Physical Control Channel (DPCCH): Conveys control data for the physical channel Constant spreading factor, 256. Dedicated Physical Channel (DPCH): Multiplexes user and control data Spreading factors between 4 and 512 Data rates 6, 24, 51, 90, 210, 432, 912, and 1872kbps

UTRA-FDD Medium Access

No collisions on the downlink: Only the Basestation sends Uplink: Nodes use slotted Aloha (15 random access slots) Access a slot by sending a preamble with the lowest transmission power If no acknowledgement is received, try another slot with the next transmission power level

UMTS TDD frame structure (burst type 2)

TD-CDMA

• 2560 chips per slot
• spreading: 1-16
• symmetric or asymmetric slot assignment to UL/DL (min. 1 per

direction)

• tight synchronisation needed
• simpler power control (100-800 power control cycles/s)

1 2 12 13 14 ... Radio frame Data 1104 chips Midample 256 chips Data 1104 chips Time slot 666.7 µs 10 ms Traffic burst GP GP: guard period 96 chips 2560 chips

UTRAN architecture

UTRAN comprises several RNSs Node B can support FDD or TDD or both RNC is responsible for handover decisions requiring signalingto the UE Cell offers FDD or TDD

RNC: Radio Network Controller RNS: 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

RNC functions

Admission control Congestion control Encryption/Decryption ATM Switching and Multiplexing Radio resource control Code allocation Handover control Management

B-node and User Equipment

B-Node

Power control to mitigate near-far effects Measuring connection qualities and signal strength Supports softer handover User equipment Power control, signal quality measurements, spreading, modulation, encryption and decryption, requesting services from the network Cooperates with RNC for handover

Core network: architecture

BTS Node B BSC

Abis

BTS BSS MSC Node B Node B RNC

Iub

Node B RNS Node B SGSN GGSN GMSC HLR VLR

IuPS IuCS Iu

CN EIR

Gn Gi PSTN

AuC GR

Core network

The Core Network (CN) and thus the Interface Iu, too, are separated into two logical domains:

 Circuit Switched Domain (CSD)

 Circuit switched service incl. signaling  Resource reservation at connection setup  GSM components (MSC, GMSC, VLR), IuCS

 Packet Switched Domain (PSD)

 GPRS components (SGSN, GGSN)  IuPS

Release 99 uses the GSM/GPRS network and adds a new radio access!

 Helps to save a lot of money …  Much faster deployment

Handover

Hard Handover: Similar to GSM, switching between different antennas or systems.

 Inter-frequency handover: Changing the carrier frequency  Inter-system handover: Handover to and from GSM or to

• ther IMT-2000 systems

Soft handover:

New mechanism in UMTS:

With hard handoff, a definite decision is made on whether to handoff or not With soft handoff, a conditional decision is made on whether to hand off

Available in the FDD mode

Soft handover

Multicasting of data via several physical channels UE can receive signals from up to three antennas which may belong to different node B’s Uplink

 simultaneous reception of UE data

at several Node Bs by splitting data

 Reconstruction of data at RNC

Downlink

 Simultaneous transmission of data

via different cells

 Different spreading codes in

different cells

CN Node B RNC Node B UE

Soft Handover, Intra RNC

RNS controlling the connection is called SRNS (Serving RNS) RNS offering additional resources (e.g., for soft handover) is called Drift RNS (DRNS) SRNC forwards data to its not B and to the DRNC SRNC combines both data streams and forwards to CN

SRNC UE DRNC

Iur

CN

Iu

Node B

Iub

Node B

Iub

Example handover types in UMTS/GSM

RNC1 UE1 RNC2

Iur

3G MSC1

Iu

Node B1

Iub

Node B2 Node B3 3G MSC2 BSC BTS 2G MSC3

A Abis

UE2 UE3 UE4

Intra Node-B, intra RNC (Softer Handover): Between the antennas of a B-node Inter Node-B, intra RNC: RNC1 supports soft handover by combining and splitting data Inter RNC: Internal or external inter-RNC Inter MSC: Hard handover MSC2 takes over Inter system: Hard handover from 3G UMTS network to 2G GSM.

Review Terms

HSCSD GPRS IMT-2000 UMTS EDGE CAMEL UTRA UTRAN OVSF code DS-CDMA UTRA-FDD UTRA-TDD Gateway GSN Serving GSN GPRS Register B-node RNC Hard Handover Soft Handover Softer Handover