ICT 5305 Mobile Communications. Lecture - 6 April Dr. Hossen Asiful Mustafa

Transcription

1 ICT 5305 Mobile Communications Lecture - 6 April 2016 Dr. Hossen Asiful Mustafa

2 4 types of handover MS MS MS MS BTS BTS BTS BTS BSC BSC BSC MSC MSC

3 Handover decision receive level BTS old receive level BTS new HO_MARGIN MS MS BTS old BTS new

4 Handover procedure MS measurement report BTS old measurement result BSC old MSC BSC new BTS new HO decision HO required HO request HO command HO command HO command HO access Link establishment clear command clear command clear complete clear complete resource allocation ch. activation HO request ack ch. activation ack HO complete HO complete

5 Security in GSM Security services access control/authentication user SIM (Subscriber Identity Module): secret PIN (personal identification number) SIM network: challenge response method confidentiality voice and signaling encrypted on the wireless link (after successful authentication) anonymity temporary identity TMSI (Temporary Mobile Subscriber Identity) newly assigned at each new location update (LUP) encrypted transmission 3 algorithms specified in GSM A3 for authentication ( secret, open interface) A5 for encryption (standardized) A8 for key generation ( secret, open interface) secret : A3 and A8 available via the Internet network providers can (and do) use stronger mechanisms

6 GSM - authentication mobile network SIM K i RAND RAND RAND K i AC 128 bit 128 bit 128 bit 128 bit A3 SRES* 32 bit SRES A3 32 bit SIM MSC SRES* =? SRES SRES 32 bit SRES K i : individual subscriber authentication key SRES: signed response

7 GSM - key generation and encryption mobile network (BTS) MS with SIM K i RAND RAND RAND K i AC 128 bit 128 bit 128 bit 128 bit SIM A8 A8 cipher key K c 64 bit K c 64 bit BSS A5 data encrypted data SRES data A5 MS

8 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 ) advantage: ready to use, constant quality, simple disadvantage: channels blocked for voice transmission AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F

9 Data services in GSM II GPRS (General Packet Radio Service) packet switching using free slots only if data packets ready to send (e.g., 50 kbit/s using 4 slots temporarily) standardization 1998, introduction 2001 advantage: one step towards UMTS, more flexible disadvantage: more investment needed (new hardware) GPRS network elements GSN (GPRS Support Nodes): GGSN and SGSN GGSN (Gateway GSN) interworking unit between GPRS and PDN (Packet Data Network) SGSN (Serving GSN) supports the MS (location, billing, security) GR (GPRS Register) user addresses

10 GPRS quality of service Reliability class Lost SDU probability Duplicate SDU probability Out of sequence SDU probability Corrupt SDU probability Delay SDU size 128 byte SDU size 1024 byte class mean 95 percentile mean 95 percentile 1 < 0.5 s < 1.5 s < 2 s < 7 s 2 < 5 s < 25 s < 15 s < 75 s 3 < 50 s < 250 s < 75 s < 375 s 4 unspecified

11 GPRS user data rates in kbit/s Coding scheme 1 slot 2 slots 3 slots 4 slots 5 slots 6 slots 7 slots 8 slots CS CS CS CS

12 GPRS architecture and interfaces SGSN G n MS BSS SGSN GGSN PDN U m G b G n G i MSC HLR/ GR VLR EIR

13 GPRS protocol architecture MS U BSS m G SGSN b G GGSN n G i apps. IP/X.25 IP/X.25 SNDCP LLC SNDCP LLC GTP UDP/TCP GTP UDP/TCP RLC RLC BSSGP BSSGP IP IP MAC MAC FR FR L1/L2 L1/L2 radio radio

14 TETRA - Terrestrial Trunked Radio Trunked radio systems many different radio carriers assign single carrier for a short period to one user/group of users taxi service, fleet management, rescue teams interfaces to public networks, voice and data services very reliable, fast call setup, local operation TETRA - ETSI standard formerly: Trans European Trunked Radio point-to-point and point-to-multipoint encryption (end-to-end, air interface), authentication of devices, users and networks group call, broadcast, sub-second group-call setup ad-hoc ( direct mode ), relay and infrastructure networks call queuing with pre-emptive priorities

15 TETRA Contracts by Sector (percentage) Used in over 70 countries, more than 20 device manufacturers Industrial, 1 others, 6 PAMR, 6 Military, 6 Oil/Gas, 3 Public safety & security, 39 Government, 7 Utilities, 8 Transportation, 24

16 TETRA Network Architecture TETRA infrastructure NMS switch PSTN, ISDN, Internet, PDN switch switch BS BS other TETRA networks BS AI: Air Interface BS: Base Station DMO: Direct Mode Operation ISI: Inter-System Interface NMS: Network Management System PEI: Peripheral Equipment Interface

17 TETRA Direct Mode I Direct Mode enables ad-hoc operation and is one of the most important differences to pure infrastructure-based networks such as GSM, cdma2000 or UMTS. network Individual Call Dual Watch alternating participation in Infrastructure and ad-hoc network Group Call Managed Direct Mode Authorizing mobile station

18 TETRA Direct Mode II An additional repeater may increase the transmission range (e.g. police car) network Direct Mode with Repeater Direct Mode with Gateway network Authorizing Repeater network Direct Mode with Repeater/Gateway Managed Repeater/Gateway

19 TETRA Technology Services Voice+Data (V+D) and Packet Data Optimized (PDO) Short data service (SDS) Frequencies Duplex: FDD, Modulation: DQPSK Europe (in MHz, not all available yet) UL / DL; UL / DL, UL / DL; UL / DL Other countries UL / DL; UL / DL, UL / DL

20 TDMA structure of the voice+data system hyperframe s multiframe frame ms CF 1.02 s Control Frame 0 slot ms

21 UMTS and IMT-2000 Proposals for IMT-2000 (International Mobile Telecommunications) UWC-136, cdma2000, WP-CDMA UMTS (Universal Mobile Telecommunications System) from ETSI UMTS UTRA (was: UMTS, now: Universal Terrestrial Radio Access) enhancements of GSM EDGE (Enhanced Data rates for GSM Evolution): GSM up to 384 kbit/s CAMEL (Customized Application for Mobile Enhanced Logic) VHE (virtual Home Environment) fits into GMM (Global Multimedia Mobility) initiative from ETSI 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

22 Frequencies for IMT-2000 ITU allocation (WRC 1992) MHz IMT-2000 MSS IMT-2000 MSS Europe GSM 1800 DE CT T D D UTRA FDD MSS T D D UTRA FDD MSS China GSM 1800 IMT-2000 MSS IMT-2000 MSS Japan cdma2000 PHS W-CDMA MSS cdma2000 W-CDMA MSS North America PCS MSS rsv. MSS MHz

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

24 UMTS architecture (Release 99 used here!) UTRAN (UTRA Network) Cell level mobility Radio Network Subsystem (RNS) Encapsulation of all radio specific tasks UE (User Equipment) U u I u UTRAN CN (Core Network) Inter system handover Location management if there is no dedicated connection between UE and UTRAN UE CN

25 UMTS FDD frame structure 10 ms µs µs Radio frame Time slot Pilot TFCI FBI TPC 2560 chips, 10 bits Data 2560 chips, 10*2 k bits (k = 0...6) uplink DPCCH uplink DPDCH W-CDMA MHz uplink MHz downlink chipping rate: Mchip/s soft handover QPSK complex power control (1500 power control cycles/s) spreading: UL: 4-256; DL: µs Data 1 DPDCH TPC TFCI Data 2 Pilot DPCCH DPDCH DPCCH 2560 chips, 10*2 k bits (k = 0...7) downlink DPCH Slot structure NOT for user separation but synchronization for periodic functions! 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

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

27 Admission control Congestion control System information broadcasting Radio channel encryption Handover SRNS moving Radio network configuration Channel quality measurements Macro diversity Radio carrier control Radio resource control Data transmission over the radio interface Outer loop power control (FDD and TDD) Channel coding Access control UTRAN functions

28 Core network: protocols VLR RNS MSC GSM-CS backbone GMSC PSTN/ ISDN HLR RNS Layer 3: IP Layer 2: ATM Layer 1: PDH, SDH, SONET UTRAN SGSN GGSN GPRS backbone (IP) SS 7 CN PDN (X.25), Internet (IP)

29 Core network: architecture BTS A bis BSS I u VLR BSC MSC GMSC PSTN Node BTS B I u CS AuC EIR HLR Node B I ub GR Node B RNC SGSN G n GGSN G i Node B RNS I u PS CN

30 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

31 UMTS protocol stacks (user plane) Circuit switched UE U u UTRAN I u CS 3G MSC apps. & protocols RLC MAC RLC MAC SAR AAL2 SAR AAL2 radio radio ATM ATM Packet switched UE U u UTRAN I u PS 3G apps. & protocols SGSN IP, PPP, IP tunnel PDCP RLC MAC radio PDCP GTP GTP GTP RLC UDP/IP UDP/IP UDP/IP MAC radio AAL5 ATM AAL5 ATM L2 L1 G n 3G GGSN IP, PPP, GTP UDP/IP L2 L1

32 Support of mobility: macro diversity Multicasting of data via several physical channels Enables soft handover FDD mode only UE Node B Uplink simultaneous reception of UE data at several Node Bs Reconstruction of data at Node B, SRNC or DRNC Node B RNC CN Downlink Simultaneous transmission of data via different cells Different spreading codes in different cells

33 Support of mobility: handover From and to other systems (e.g., UMTS to GSM) This is a must as UMTS coverage is/was poor in the beginning RNS controlling the connection is called SRNS (Serving RNS) RNS offering additional resources (e.g., for soft handover) is called Drift RNS (DRNS) End-to-end connections between UE and CN only via Iu at the SRNS Change of SRNS requires change of Iu Initiated by the SRNS Controlled by the RNC and CN Node B SRNC CN UE I ub I ur I u Node B DRNC I ub

34 Example handover types in UMTS/GSM UE 1 Node B 1 RNC 1 3G MSC 1 UE 2 Node B 2 I ub I ur I u UE 3 Node B 3 RNC 2 3G MSC 2 UE 4 BTS BSC 2G MSC 3 A bis A

35 Breathing Cells GSM Mobile device gets exclusive signal from the base station Number of devices in a cell does not influence cell size UMTS Cell size is closely correlated to the cell capacity Signal-to-nose ratio determines cell capacity Noise is generated by interference from other cells other users of the same cell Interference increases noise level Devices at the edge of a cell cannot further increase their output power (max. power limit) and thus drop out of the cell no more communication possible Limitation of the max. number of users within a cell required Cell breathing complicates network planning

36 Breathing Cells: Example

37 Some current UMTS enhancements HSDPA (High-Speed Downlink Packet Access) initially up to 10 Mbit/s for the downlink, later > 20 Mbit/s using MIMO- (Multiple Input Multiple Output-) antennas can use 16-QAM instead of QPSK (ideally > 13 Mbit/s) user rates e.g. 3.6 or 7.2 Mbit/s HSUPA (High-Speed Uplink Packet Access) initially up to 5 Mbit/s for the uplink user rates e.g Mbit/s HSPA+ (Evolved HSPA) Rel-7/Rel-8/Rel-9/ Downlink 28/42/84/> 100 Mbit/s Uplink 11/23/>23 Mbit/s 2x2 MIMO, 64 QAM Dual-/Multi-Carrier HSPA (DC-/MC-HSPA Connect 2 (Rel-8/9) or more carriers (Rel-11) e.g. of two cells offering up to 672 Mbit/s (4x4 MIMO)

38 Long Term Evolution (LTE) Initiated in 2004 by NTT DoCoMo, focus on enhancing the Universal Terrestrial Radio Access (UTRA) and optimizing 3GPP s radio access architecture Targets: Downlink 100 Mbit/s, uplink 50 Mbit/s, RTT<10ms 2007: E UTRA progressed from the feasibility study stage to the first issue of approved Technical Specifications 2008: stable for commercial implementation 2009: first public LTE service available (Stockholm and Oslo) 2010: LTE starts in Germany LTE is not 4G sometimes called 3.9G Does not fulfill all requirements for IMT advanced

39 Key LTE features Simplified network architecture compared to GSM/UMTS Flat IP-based network replacing the GPRS core, optimized for the IP-Multimedia Subsystem (IMS), no more circuit switching Network should be in parts self-organizing Scheme for soft frequency reuse between cells Inner part uses all subbands with less power Outer part uses pre-served subbands with higher power Much higher data throughput supported by multiple antennas Much higher flexibility in terms of spectrum, bandwidth, data rates Much lower RTT good for interactive traffic and gaming Smooth transition from W-CDMA/HSPA, TD-SCDMA and cdma2000 1x EV-DO but completely different radio! Large step towards 4G IMT advanced See for all specs, tables, figures etc.!

40 LTE advanced GSM UMTS - LTE LTE advanced as candidate for IMT-advanced Worldwide functionality & roaming Compatibility of services Interworking with other radio access systems Enhanced peak data rates to support advanced services and applications (100 Mbit/s for high and 1 Gbit/s for low mobility) 3GPP will be contributing to the ITU-R towards the development of IMT-Advanced via its proposal for LTE-Advanced. Relay Nodes to increase coverage 100 MHz bandwidth (5x LTE with 20 MHz)