Lecture overview. UMTS concept UTRA FDD TDD

Transcription

1 Lecture overview 3G UMTS concept UTRA FDD TDD

2 3 rd Generation of Mobile Systems Goal to create a global system enabling global roaming International Mobile Telecommunications (IMT-2000) requirements: Throughput rates: Up to 2 Mb/s indoors and pedestrian throughput rate 384 kb/s for terminals moving with the speed 120 km/h and less in urban areas 144 kb/s in rural areas and fast moving vehicles Support global mobility Service independent of radio interface technology (multimode terminals must be used)

3 Seamless switching between fixed and wireless communications Support of circuit- and packet-switched services Support of multimedia and real-time services The implementation of system fulfilling these requirements responsibility of regional bodies: ETSI (European Telecommunications Standard Institute) Universal Mobile Telecommunication System (UMTS) and Wideband CDMA (WCDMA) T1P1 committee in USA multicarrier CDMA based on IS-95 ARBI (Association for Radio Industries and Business) in Japan TTA (Telecommunications Technology Association) in South Korea

4 Three different IMT-2000 standards were agreed upon: UTRA (UMTS Terrestrial Radio Access) wideband CDMA transmission with FDD and TDD modes and 5 MHz carrier spacing MC CDMA (Multicarrier CDMA) UWC136 (Universal Wireless Communications) based on convergence of IS-136 and GSM EDGE extension of TDMA Initially the UMTS system will use the GSM core network Interworking functions added to enable roaming and other services In longer perspective all IMT-2000 systems will work with IP core network

5 Spectrum Allocation MHz ITU IMT-2000 IMT 2000 MSS IMT 2000 MSS 1885 MHz 2025 MHz 2110 MHz 2170 MHz Europe GSM 1800 DECT UMTS MSS UMTS MSS 1880 MHz 1980 MHz 2170 MHz MHz Japan PHS IMT 2000 MSS IMT 2000 MSS MHz 2160 MHz USA PCS MSS Reserved MSS

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7 UMTS requirements: Concept of UMTS Operation in various types of environment rural to indoor, picoto macrocells, satellite link a supplement for underdeveloped and low density areas Choice of duplex transmission FDD or TDD transmission Wide service offer: voice, data, symmetric and asymmetric Cooperation with fixed networks e.g. ISDN offers basic access at 144 kb/s rate (two B plus D channel) High level of security (tele-banking, e-commerce) High quality Adaptive Multi Rate (AMR) speech coding with discontinuous transmission and comfort noise insertion 8 different bit rates ( kb/s) choice depends on network load, service level and current SNR

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9 UMTS Radio Access Network Architecture There are 3 main elements of architecture: User Equipment (UE): Mobile equipment radio terminal UMTS Subscriber Identity Module (USIM) smart card similar to SIM in GSM contains subscriber identity, authentication algorithms, encryption keys etc UMTS Terrestrial Radio Access Network (UTRAN) BS s called Node B channel coding, data interleaving rate matching, modulation etc. Radio Network Controllers (RNCs) manage radio resources assigned to them, participate in handovers, connected to single MSC/VLR for routing of circuit-switched and to single SGSN for packet-switched traffic

10 Core Network (CN) shared with GSM and GPRS: Home Location Register Mobile Switching Centre/Visitor Location Register Gateway MSC Serving GPRS Support Node Gateway GPRS Support Node Interfaces in UMTS have been defined in detail to allow different elements of system to be produced by different manufactures Uu Interface radio interface between terminals and BS Iub Interface between BS and RNC Iu Interface connects UTRAN with core network

11 Uu Iub Iu

12 UMTS Air Interface UMTS Terrestrial Radio Access (UTRA also known as Wideband CDMA) was defined by the 3 rd Generation Partnership Project (3GPP) It has 2 modes of operation differing in applications and air interface: Paired bands operate in FDD Unpaired use TDD mode

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14 Protocol Layers UMTS Air interface layer structure covers three lowest layers of OSI model: Layer 1 Physical Layer: Layer 2 Data link Layer (MAC & RLC) Medium Access layer Radio Link Control layer Layer 3 Network Layer Radio Resources Layer

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16 Physical layer: information transfer in form of transport channels Signal processing Channel coding Interleaving Spreading Synchronization etc. Mapping transport channels onto physical channels Data Link Protocol Layer consist of following sub-layeres: Medium Access Control (MAC) - Data transfer on logical channels Radio Link Control (RLC) ARQ algorithm, segmentation and assembly of user data, controls data blocks sequences and ensures avoiding block duplications Transport Format (TF) decision - possible mapping, encoding and interleaving for transmission

17 Packet Data Convergence Protocol (PDCP) transmission and reception of networks Protocol Data Units (PDU) in acknowledged or unacknowledged or transparent RLC modes Broadcast/Multicast Control (BMC) broadcast and multicast transmission in transparent or unacknowledged mode Radio Resource Control (RRC) (Network Layer) broadcasting system information, radio resources handling, control of quality of service requests, measurements reports and control (slow power control) Communication between RRC and RLC/MAC is performed through logical channels, which are then mapped onto transport channels. Transport channels are then mapped onto physical channels

18 Channel types in UMTS Logical channels communication between MAC/RLC and RRC Control Channels (CCH) Broadcast Control Channel (BCCH) broadcast of system control information Paging Control Channel (PCCH) paging MS downlink Common Control Channel (CCCH) transfer control information (bidirectional) Dedicated Control Channels (DCCH) point-to-point, control information between network and MS during establishment of RRC connection Traffic Channels: Dedicated Traffic Channel (DTCH) point-to-point, transfer of data between user and network Common Traffic Channels (CTCH) point-to-multipoint, information for group of users

19 Logical channels are mapped by MAC onto Transport Channels: Dedicated Transport Channel (DTCH) point-to-point channel carrying both user data and higher level control data Common Transport Channels: Broadcast Channel (BCH) system- and cell-specific information at low bit rate, carries part of logical BCCH Forward Access Channel (FACH) downlink, another part of BCCH Paging Channel (PCH) Random Access Channel (RACH) uplink low rate channel Common Packet Channel (CPCH) optional uplink transport channel, transmission of bursty data, (true packet channel) Downlink Shared Channel (DSCH) associated with DTCH, optional transport channel shared by several users

20 After channel coding and interleaving several transport channels can be multiplexed together and the received data stream is assigned to the physical data channel

21 Physical channels: Dedicated Physical Channel Dedicated Physical Control Channel (DPCCH) pilot symbols for coherent detection, commands for fast power control, may include Transport Format Identifier (TFI) block containing applied TF Dedicated Physical Data Channel (DPDCH) Common Pilot Channel (CPICH)* general reference channel for received signal power ad quality, coverage of this channel defines coverage, fixed bit pattern Synchronisation Channel (SCH)* no spreading or scrambling,, cell search and timing synchronization

22 Primary & Secondary Common Control Physical Channels* broadcast system information, uses constant spreading factor of 256, assigned code no 1 allows the user to read information immediately after acquiring scrambling code, initiates an incoming call Acquisition Identification Channel (AICH)* indicates whether system can be accessed (response to access request from UE on PRACH) Paging Indicator Channel (PICH)* indicated incoming call using simple bit mask, simplifies idle mode of mobile station Physical Random Access Channel (PRACH)** Physical Common Packet Channel (PCPCH)**- packet transmission * Downlink only, ** Uplink only One DPCCH & up to 6 DPDCH - assigned to each connection

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24 UTRA FDD Mode In the physical layer of UTRA time is divided into 10-ms frames Each frame is divided into 15 slots µs long In FDD slot are time units in which the transmission of appropriate channel blocks takes place (not multiple access method) Each time slot carries 2560 chips (3.84 Mchip/s) Physical channel is determined by: carrier frequency, spreading sequence, applied signal component (in uplink inphase and quadrature components can carry different physical channels)

25 In uplink the binary stream of DPDCH is fed to the in-phase input, DPCCH to quadrature input of the transmitter If there is more than 1 DPDCH odd-numbered channels are transmitted using in-phase and even-numbered using quadrature component DPDCH transmits user data DPCCH pilot signal for channel estimation, TFI block (format of the DPDCH), Feedback Information for downlink diversity and Transmit Power Control Both data streams are spread using two different mutually orthogonal channelisation codes Due to different bit rates in both channels there could be power difference between both components. Therefore applied spreading matches the current data rate

26 Cell search: MS searchers for Primary Synchronisation Channel (SCH physical channel in form of 256-chip sentence common to all cells used in downlink). It allows for allocation of the starting point of the slots. MS chooses the cell with strongest signal Next MS acquire the frame synchronisation and find a code group used in secondary SCH. There are 64 possible secondary synchronisation code words applied in this channel each determines different code group Finding the scrambling code MS correlates received signal with all possible scrambling signals belonging to the given code group. After this the MS is able to read the primary common control channel, which holds system parameters sent on broadcast channel. Once in the network MS is allocated a paging group. It reads Paging Indicator Channel (PICH) for its paging indicator, stating that there is a message for it in the Common Control Channel

27 Power Control realised in a open and closed loop Closed loop control is performed in each slot and the resulting decision on reduction/increase in power is transmitted using DPCCH Handover in UTRA: Soft handover all cells operate on the same frequency therefore MS can be connected to multiple BS simultaneously. Uplink signal is received by all BS s participating in handover and combined to perform macro-diversity. Softer handover when MS is connected to 2 sectors served by the same BS

28 Inter-frequency handover when BS s transmit on different frequency (e.g. if MS moves from pico- cell to micro-cell etc.). MS employing dual receiver can perform the space diversity, in single receiver a compressed mode is used with certain period BS transmits frame content in a shorter time (5 instead of 10 ms). Rest of the frame is used by MS for measurement at different carrier frequency. Reduction in frame length is achieved by code puncturing and changing FET Handover between FDD and TDD is possible if MS can operated in dual mode Handover between UTRA and GSM is called a intrer-system handover

29 UTRA TDD Mode Uses unpaired spectral bands Time can be asymmetrically divided between uplink and downlink - dynamic adjustment to current traffic. Symmetric/asymmetric with multiple switching Symmetric/asymmetric with single switching At least one slot has to be assigned in uplink and one in downlink in each frame Frame lasts 10 ms and is divided into 15 slots Physical channel is determined by carrier frequency, time slot within the frame and applied spreading sequence.

30 Time slot lasts 2560 chips, transmission in form of bursts Each burst has 2 data fields, mid-amble and ends with a guard time Transmitted data is spread in the data fields in 2 steps using channelisation code and a complex scrambling code Handover only hard handover by several types: TDD - TDD TDD - FDD WCDMA (TDD) - GSM

31 Establishing the radio connection Starts via a random access procedure using the PRACH channel - uplink, response to paging message or initiated by UE RRC Connection Request: establishing cause (to determine required QoS) Transmit UE identity Reports on initial channel measurements RRC Connection Setup assignment of dedicated control channel to the mobile station (frequency channel no., max. transmit power, scrambling code, spreading code) RRC Connection Setup Complete - UE can activate uplink DPCCH closed power control, confirmation of the connection setup

32 Three phases of connection establishment: Radio connection establishment Paging or initiated by random access procedure End of phase dedicated logical control channel exists to allow Node B and UE o converse Physical layer power control responsible for connection quality Connection between UE and core network (MSC or SN) identification of UE through authentication procedure (comparing subscriber data with HLR) Sequrity mechanisms established (data encryption) Connection between UE and requested party radio connection between parties established with desired QoS Separate phases allow network components to act independently. It minimises burden upon the rest of the network.

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34 Mobile Originated Call

35 Mobile Terminated Call

36 Evolution of 3G Systems 3G Partnership Project and 3G Partnership Project 2 work on enhancements to both 3G standards: WCDMA and CDMA 2000 The extension are: Evolution Data-Optimised (1xEV-DO) or High Rate Packet Data Data optimised evolution of CDMA 2000 by 3GPP2 2.4 Mb/s (Rev-0) and 3.1 Mb/s (Rev-A) peak downlink rates kb/s (Rev-0) and 1.8 Mb/s (Rev-A) in uplink Standardisation of EV-DO Rev B DL 4.9 Mb/s All in 1.25 MHz channel Initially in South Korea now being deployed

37 High-Speed Downlink Packet Access (HSDPA) Data optimised evolution of WCDMA by 3GPP 14 Mb/s peak downlink rates in 5 MHz channel High-Speed Uplink Packet Access (HSUPA) enhancement in uplink data rates HSDPA includes: Adaptive Modulation and Coding (AMC - QPSK and 16 QAM) Multi-code operation Hybrid Automatic Repeat Request (H-ARQ): FEC + ARQ De-centralised architecture scheduling moved from Radio Network Controller to Node-B reduced latency and enabled fast scheduling Reduction in frame length from 10 to 2 ms

38 Combination of HSDPA and HSUPA is known as High- Speed Packet Access (HSPA) Enhanced Uplink includes several new physical channels for support of high-speed data transmission for Enhanced Data Channel Roadmap of 3G enhancements: 1xEV-DO Rev 0 first deployed in South Korea and Japan in 2003 EV-DO Rev A in Korea and Japan in 2005 Commercial launch of HSDPA announced in December 2005 HSUPA/HSPA not expected until 2007/2008 Long term WCMDA evolution leading to UTRAN Long Term Evolution (3.99G or Evolved UMTS) standards expected in 2007 products probably available in 2009 or later

39 Summary 3G UMTS concept UTRA Protocol model UTRA Channels FDD TDD