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

CMPE 477 – Wireless and Mobile Networks 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

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 on demand advantage : one step towards UMTS, more flexible  Maximum rate 171.2kbps but … disadvantage : more investment needed (new hardware)  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

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 SGSN G n PDN BSS SGSN GGSN MS U m G b G n G i HLR/ MSC GR VLR EIR

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 As a single standard could not be found, the ITU standardized five groups of 3G Radio Access Technologies Interface for Internetworking IMT-2000 GSM ANSI-41 IP-Network Core Network (MAP) (IS-634) ITU-T Initial UMTS Flexible assignment of (R99 w/ FDD) Core Network and Radio Access IMT-TC IMT-DS IMT-MC IMT-SC IMT-FT (Time Code) (Direct Spread) (Multi Carrier) (Single Carrier) (Freq. Time) IMT-2000 (3G) UTRA TDD Radio Access UTRA FDD cdma2000 UWC-136 DECT (TD-CDMA); ITU-R (W-CDMA) (EDGE) TD-SCDMA 3GPP 3GPP2 UWCC/3GPP ETSI 3GPP

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 (UTRA Network)  Cell level mobility  Radio Network Subsystem (RNS)  Encapsulation of all radio specific tasks (handover, resource management, etc.) UE (User Equipment) UE UTRAN CN U u I u CN (Core Network)  Inter system handover  Gateways to other networks

UMTS domains and interfaces I Home Network Domain Z u C u U u I u Y u Mobile Access Serving Transit USIM Equipment Network Network Network Domain Domain Domain Domain Domain Core Network Domain User Equipment Domain Infrastructure Domain 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

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 orthogonal 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 ... 1,1,1,1,-1,-1,-1,-1 1,1 1,1,-1,-1,1,1,-1,-1 ... 1,1,-1,-1 X,X 1,1,-1,-1,-1,-1,1,1 1 X 1,-1,1,-1,1,-1,1,-1 X,-X ... 1,-1,1,-1 1,-1,1,-1,-1,1,-1,1 1,-1 SF=n SF=2n 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

Spreading and Scrambling of user Data 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 sender s In the TDD mode, the scrambling code is cell specific. data 1 data 2 data 3 data 4 data 5 spr. spr. spr. spr. spr. code 1 code 2 code 3 code 1 code 4 scrambling scrambling code 1 code 2 sender 1 sender 2

UMTS FDD frame structure W-CDMA • 1920-1980 MHz uplink Radio frame • 2110-2170 MHz downlink 0 1 2 ... 12 13 14 10 ms • chipping rate: 3.840 Mchip/s Time slot • spreading: UL: 4-256; Pilot TFCI FBI TPC 666.7 µs uplink DPCCH DL:4-512 2560 chips, 10 bits 666.7 µs Data uplink DPDCH FBI: Feedback Information TPC: Transmit Power Control 2560 chips, 10*2 k bits (k = 0...6) TFCI: Transport Format Combination Indicator Data 1 TPC TFCI Data 2 Pilot 666.7 µs downlink DPCH DPCCH: Dedicated Physical Control Channel DPDCH: Dedicated Physical Data Channel DPDCH DPCCH DPDCH DPCCH DPCH: Dedicated Physical Channel 2560 chips, 10*2 k bits (k = 0...7) 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) Radio frame 10 ms 0 1 2 ... 12 13 14 Time slot Data Midample Data 666.7 µs Traffic burst GP 1104 chips 256 chips 1104 chips GP: guard period 2560 chips 96 chips 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)

UTRAN architecture RNS RNC: Radio Network Controller RNS: Radio Network Subsystem I ub UE 1 Node B I u RNC CN UE 2 Node B Node B UTRAN comprises several RNSs Node B can support FDD or TDD or UE 3 both RNC is responsible for handover I ur decisions requiring signalingto Node B the UE I ub Cell offers FDD or TDD Node B RNC Node B Node B RNS

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