Part 7. B3G and 4G Systems

Transcription

1 Part 7. B3G and 4G Systems p. 1

2 Roadmap HSDPA HSUPA HSPA+ LTE AIE IMT-Advanced (4G) p. 2

3 HSPA Standardization 3GPP Rel'99: does not manage the radio spectrum efficiently when dealing with bursty traffic Need for even better spectral efficiency, improved user experience and new services => High Speed Packet Access (HSPA) HSPA: High Speed Downlink Packet Access (HSDPA) + High Speed Uplink Packet Access (HSUPA) Source: H. Holma and A. Toskala, HSDPA/HSUP A for UMTS, JohnWiley and Sons, LTD.. p. 3

4 HSPA Deployment Source: H. Holma and A. Toskala, HSDPA/HSUP A for UMTS, JohnWiley and Sons, LTD.. Based on WCDMA network: either on the same carrier (f1) or using another carrier (f2) Why using another carrier: a high capacity and high bit rate solution HSPA and WCDMA share all the network elements in the core network and the radio network. Upgrade from WCDMA to HSPA: no core network impacts, new software package, some new pieces of hardware in the BS and RNC to support the higher data rates and capacity Upgrading cost: very low compared with building a new standalone data network p. 4

5 Commercial HSPA Network Korea: May 2006, SK Telecom, the world's first commercial HSDPA service, data rate 1.8Mbps Hong Kong: June 2006, SmarTone-Vodafone, HSDPA service at 1.8Mbps; Sept. 2006, enhanced 3.6Mbps HSDPA full-coverage network; 2008: support 14.4Mbps downloading (HSDPA) and 2Mbps uploading (HSUPA) SmarTone: Mobile Broadband, provides high speed access to Internet with your PC or Laptop USB modem for desktops and laptops Express card for laptops p. 5

6 HSDPA - High Speed Downlink Packet Access p. 6

7 Introduction HSDPA is a UMTS packet air interface (add-on solution on top of 3GPP R99/R4 architecture) that allows up to 3.6 Mbps peak data rate for a Category 6 Mobile per user with a classical Rake receiver and up to 14.4 Mbps peak data rate for a Category 10 mobile per user with advanced receiver solutions. HSDPA: offers significantly higher data capacity (at least twice per cell) and data-user speed, lower latency (70ms round trip delay), fully backward compatible with Rel'99 (WCDMA) A new downlink shared transport channel (HS-DSCH) with shorter frame size (2ms) A fast link adaptation controlled by the Node B (BTS): dynamic adaptive modulation and coding A fast scheduler A fast physical layer retransmission and transmission combining Source: Nortel, HSDPA and beyond, White paper. p. 7

8 New Channels (1) New channel types: HS-DSCH (Downlink Shared Channel), HS- SCCH (Shared Control Channel), HS-DPCCH (Dedicated Physical Control Channel) HS-DSCH: High Speed Downlink Shared Channel shared by all users of a sector by a number of SF 16 codes and time within each 2 ms TTI, up to 15 parallel code channels can be used for the HS-DSCH: may all be assigned to one user, or may be split among several users no more power control, HS-DSCH is transmitted at a constant power the modulation, the coding and the number of codes are changed to adapt to the variations of radio conditions difference between HS-DSCH and DSCH in WCDMA: the scheduling of HS-DSCH is done at the Node B (BS) rather than the RNC Source: Nortel, HSDPA and beyond, White paper. p. 8

9 New Channels (2) Comparison of fundamental properties of the DCH and HS-DSCH Features Channel coding Modulation Variable spreading factor Fast power control Adaptive modulation and coding Multi-code operation Physical layer retransmission BTS-based scheduling and link adaptation DCH (WCDMA) Convolutional or Turbo QPSK No and SF=4~512 Yes No Yes No, only at RLC layer No HS-DSCH (HSDPA) Only Turbo QPSK and 16QAM No and SF=16 No Yes Yes, extended Yes, and also at RLC layer Yes p. 9 Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD..

10 New Channels (3) Source: Nortel, HSDPA and beyond, White paper. p. 10

11 New Channels (4) New functions p. 11 HS-DSCH channel coding chain Source: H. Holma and A. Toskala, HSDPA/HSUP A for UMTS, JohnWiley and Sons, LTD..

12 New Channels (5) Why is bit scrambling needed? HSDPA: QPSK and 16QAM are used Source: H. Holma and A. Toskala, HSDPA/HSUP A for UMTS, JohnWiley and Sons, LTD.. to recover 16QAM symbols: phase and amplitude (power level) information is required bit scrambling is introduced to avoid having long sequences of '1s' or '0s'. Otherwise, the terminal would have difficulties with HS-DSCH power level estimation p. 12

13 New Channels (6) HS-SCCH: HSDPA Shared Control Channel enables the UE to identify which codes of the HS-DSCH contain its data HS-DPCCH: HSDPA Dedicated Physical Control Channel responsible of Uplink signaling provides Channel Quality Indicator (CQI), ACK and NACK CQI: reflects the signal to Interference Ratio (SIR) provides real time (every 2ms) knowledge of the radio conditions for each user. Based on CQI, BTS may change every 2ms the modulation, coding and the number of codes makes HSDPA match the exact throughput of the radio bandwidth available for each user higher average throughput and higher spectrum efficiency Source: Nortel, HSDPA and beyond, White paper. p. 13

14 New Channels (7) Dynamic behavior of HSDPA p. 14 Source: Nortel, HSDPA and beyond, White paper.

15 Fast Link Adaptation (1) Fast link adaptation at BS: Adaptive modulation and coding (AMC) (TTI: 2ms) Principle of AMC: change modulation and coding format in accordance with variations in the channel conditions which leads to a higher data rate for users in favorable positions and reduced interference Enables bursty traffic => higher average throughput, three to five times higher than that without HSDPA Reduces the interferences variation link adaptation based on variations in the mod./coding scheme instead of variations of the transmit power Source: Nortel, HSDPA and beyond, White paper. p. 15

16 Fast Link Adaptation (2) p. 16 Example of link adaptation Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD..

17 Fast Retransmission (1) Fast Retransmission: Hybrid Automatic Request 3GPP R'99: ARQ in RLC layer; HSDPA: ARQ in physical layer p. 17 Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD.. BTS retransmission handling

18 Fast Retransmission (2) HSDPA: Stop-and-Wait (SAW) => simplest Waiting for ACK from the receiver Retransmission due to timer expiry p. 18

19 Fast Retransmission (3) 3GPP R'99: Selective Repeat (SR) => most complex and most efficient p. 19

20 Fast Retransmission (4) HSDPA: Why SAW instead of SR? SR: complex, need high memory, sequence information, high signaling bandwidth SAW: simple, need less memory, no sequence information, less signaling bandwidth => suitable for UE Improved SAW: Dual-Channel SAW HSDPA: Retransmission combining: Two combining schemes Chase combining: BT resends the same packet Incremental redundancy: BT provides additional coding by sending the parity bits in the retransmission, requires more memory, used with high coding rate p. 20

21 Fast Retransmission (5) p. 21 Example of Chase combining Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD..

22 Fast Retransmission (6) p. 22 Example of Incremental Redundancy Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD..

23 Fast Scheduling (1) Fast scheduling: Placed in the Node B in order to quickly respond to the changes in channel conditions. L1: physical layer p. 23 Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD..

24 Fast Scheduling (2) Scheduling algorithm: A compromise between a Round Robin and a Max C/I scheduler will be used. TTI Received C/I for each user #1 #2 #3 Max C/I Scheduler Time p. 24

25 Fast Cell Selection Fast cell selection Soft handoff is impossible for HSDPA A hard handoff is used for HS-DSCH: the UE indicates the best cell which should serve it through uplink signaling While multiple cells may be members of the active set, only one of them transmits at any time, potentially decreasing interference and increasing system capacity Source: Nortel, HSDPA and beyond, White paper. p. 25

26 Terminal Capability Categories p. 26 Source: Nortel, HSDPA and beyond, White paper.

27 HSUPA - High Speed Uplink Packet Access p. 27

28 Introduction (1) Why HSUPA: a complement of HSDPA HSDPA: provide high speed (up to 14.4Mbps) data transmission in downlink, increase data usage => the uplink throughput should be increased accordingly HSUPA: also called as Enhanced DCH, defines a new radio interface for the Uplink communication. The overall goal is to improve the coverage and throughput as well as to reduce the delay of the uplink dedicated transport channels. Enhancement of HSUPA over 3GPP R'99 (3GPP Study) % improvement in UL capacity % reduction in end user packet call delay - Around 50% in user packet call throughput - max 5.76 Mbps (one UE/cell), typical about 2 Mbps (several UEs/cell) p. 28

29 Introduction (2) new uplink transport channel SF=2~256 uplink Hybrid ARQ HSUPA Node B controlled scheduling multicode transmission New Features in HSUPA 10ms TTI (mandatory) 2ms TTI (optional) Note: HSUPA does not support adaptive modulation because it does not support any higher order modulation schemes. Reason: more complex modulation schemes require more energy per bit to be transmitted than simply going for multicode transmission using simple BPSK modulation. p. 29

30 New Channels E-DPDCH: E-DCH Dedicated Physical Data Channel E-DPCCH: E-DCH Dedicated Physical Control Channel E-HICH: E -DCH HARQ Acknowledgement Indicator Channel E-AGCH: E-DCH Absolute Grant Channel for scheduling control E-RGCH: E-DCH Relative Grant Channel Source: H. Holma and A. Toskala, HSDPA/HSUPA for UMTS, JohnWiley and Sons, LTD.. E-DCH p. 30

31 E-DCH 24 bits 0, 8, 12, 16, 24 bits p. 31

32 E-DPDCH (1) E-DPDCH: similar structure to DPDCH - support variable spreading factor, multi-code transmission, BPSK modulation, fast power control loop Difference between E-DPDCH and DPDCH - E-DPDCH supports fast physical layer HARQ, fast Node B based scheduling, spreading factor of 2 Physical channel bit rates for DPDCH and E-DPDCH p. 32

33 E-DPDCH (2) Difference between E-DPDCH and DPDCH (Con't) - E-DPDCH supports TTI of 2ms E-DPDCH frame structure p. 33

34 E-DPCCH (1) E-DPCCH and DPCCH - both deliver the information needed to decode corresponding data channel transmission - DPCCH also provides common information related to channel estimation and power control E-DPCCH - fixed spreading factor: (30,10) Reed-Muller coding, 10 information bits every 3 slots E-TFCI: 7 bits, E-DCH transport format combination indicator, telling the receiver the transport block size coded on the E-DPDCH RSN: 2bits, retransmission sequence number, initial transmission RSN=0, the first with RSN=1, the second with RSN=2, all subsequent RSN=3 Happy bit: 1 bit, whether the UE is content with the current data rate or relative power allowed to be used for E-DPDCHs p. 34

35 E-DPCCH (2) (30, 10) Reed Muller coding E-DPCCH frame structure p. 35

36 E-DPCCH (3) Why use two TTI lengths? - 2ms: potential delay benefit - 10ms: needed for range purpose to ensure cell edge operation. At the cell edge, signaling using a 2-ms period starts to consume a lot of transmission power, especially at the BTS end. HSDPA: the number of active users is relatively small. HSUPA: a large number of active users p. 36

37 Comparison Features Uplink DCH (WCDMA) E-DCH (HSUPA) HS-DSCH (HSDPA) Channel coding Convoultional (1/2 or 1/3) and Turbo (1/3) Turbo (1/3) Turbo Variable spreading factor Yes Yes No Fast power control Yes Yes No Adaptive modulation and coding No No Yes Multi-code operation Yes Yes Yes Physical layer retransmission No Yes Yes BTS-based scheduling No Yes Yes Soft handover Yes Yes No TTI length (ms) 80, 40, 20, 10 10, 2 2 p. 37

38 Fast HARQ Fast physical layer retransmission (Hybrid ARQ) - basic principle is the same as that for HSDPA - both Chase combining and Incremental Redundancy are permitted HARQ and soft handover - special for HSUPA, similar rules to those for uplink power control: single ACK from the active set => successful transmission HSUPA ARQ operation in soft handover p. 38

39 Fast Scheduling BTS based fast scheduling - scheduling is moved from RNC to Node B, small latency Principle different to HSDPA - HSDPA: one to many scheduling. All the cell power can be directed to a single user for a short period of time and reach very high data rates, then to another user - HSUPA: many to one scheduling. Users have their own power resource that cannot be shared. The shared source of uplink is the uplink noise rise, or the total received power seen in the Node B. Tasks for uplink scheduler - avoid overload - use as much of the uplink capacity as possible without the risk of the cell becoming overloaded p. 39

40 HSUPA Terminal Categories p. 40

41 Summary of HSPA HSDPA employs mainly four measures to increase the packet data rate: new channel HS-DSCH; fast link adaptation; fast scheduler; fast retransmission and combinations. HS-DSCH: comparison to DCH in WCDMA; new function blocks needed to generate signals on HS-DSCH. Advantages of fast link adaptation Fast retransmission: HARQ schemes employed in HSDPA; combining schemes Advantages of fast scheduler HSUPA: only BPSK supported, no adaptive modulation and coding Reason for E-DPCCH in HSUPA supporting two TTI lengths, 10ms and 2ms. p. 41

42 3GPP Long Term Evolution (LTE) and System Architecture Evolution p. 42

43 Introduction With HSPA, UTRA will remain highly competitive for several years Threat from WiMAX to cellular systems WiMAX provides high speed wireless data services: up to 20Mbps Advantage of WiMAX: high speed, low cost to construct, various services including voice over IP, video, multimedia transmission, etc. Vendor strategy: Leading 3G vendors backing LTE, vendors that are not 3G leaders using WiMAX as an end around WiMAX: big threat to 3G Current 3GPP standards should be further developed to maintain the competitiveness of 3G in long term future Peak DL Throughput Peak UL Throughput Average DL Throughput Average UL Throughput WiMAX 20.1Mbps 5.0Mbps 2.3Mbps 2.2Mbps HSPA 3.6Mbps 2.3Mbps 2Mbps 700kbps p. 43

44 3GPP LTE and SAE LTE focuses on enhancement of the Universal Terrestrial Radio Access (UTRA) optimization of the UTRAN architecture SAE focuses on enhancement of Packet Switched technology to cope with rapid growth in IP traffic higher data rates lower latency packet optimized system through fully IP network simplified network architecture distributed control p. 44

45 Targets of LTE (1) 3GPP has concluded a set of targets and requirements for LTE Peak data rates exceeding 100 Mbps for the downlink direction and 50 Mbps for the uplink direction Mean user throughput improved by factors 2 and 3 for uplink and downlink respectively Cell-edge user throughput improved by a factor 2 for uplink and downlink Uplink and downlink spectrum efficiency improved by factors 2 and 3 respectively Significantly reduced control-plane latency Reduced cost for operator and end user Spectrum flexibility, enabling deployment in many different spectrum allocations p. 45

46 Targets of LTE (2) p. 46

47 New Technologies for LTE The reference system of LTE is a basic WCDMA system new radio transmission technologies are needed Downlink: OFDM with frequency domain adaptation OFDM supports varying spectrum allocations, ranging from 1.4MHz to 20MHz OFDM is suitable for broadcast services Channel-based adaptation in frequency domain Uplink: Single carrier FDMA with dynamic bandwidth to satisfy the requirement for uplink transmission: power-efficient userterminal transmission to maximize coverage the base station assigns a unique time-frequency interval to the terminal for the transmission of user data Channel-based adaptation in frequency domain Multi-Antenna solutions to increase data rates, improve coverage and capacity p. 47

48 Further Agreement on LTE Currently no more macro diversity no soft handover required Security Control Plane: Ciphering and Integrity provided by enhanced Node B (BTS), RLC and MAC provided directly in the enhanced Node B User plane: Ciphering and integrity in the enhanced Access Gateway functionality p. 48

49 4G Scenarios People s Expectation on 4G Mobile Communications High-data-rate transmission: up to 100Mbps and 1Gbps for macro and hot spot areas High mobility A wide coverage area and seamless roaming among different systems 4G will be a mixture of different communication systems, such as cellular systems, wireless LANs, personal communication systems, etc. Higher capacity and lower cost per bit Expected to be at least 10 times of that of 3G in capacity Wireless QoS control Features of 4G New mobile access scheme New spectrum for 4G with broader band, e.g., 100MHz Key 4G technologies LTE uses 4G technologies on 3G systems, key 4G technologies similar to LTE: OFDM, Multiple Antenna p. 49

50 Layered Architecture of 4G Digital audio/video broadcasting (DAB, DVB), Satellite comm. Distribution Layer GSM, 3G, 4G-cellular Cellular Layer Hot-Spot Layer WLANs p. 50 Personal Network Layer Fixed (Wired) Layer Bluetooth, DECT Handover

51 Summary HSDPA employs mainly four measures to increase the packet data rate: new channel HS-DSCH; fast link adaptation; fast scheduler; fast retransmission and combinations. HS-DSCH: comparison between HS-DSCH and DCH in WCDMA; new function blocks needed to generate signals on HS-DSCH. Fast link adaptation: principle of AMC; advantages of fast link adaptation Fast retransmission: HARQ schemes employed in HSDPA; combining schemes Advantages of fast scheduler HSUPA: only BPSK supported, no adaptive modulation and coding Reason for E-DPCCH in HSUPA supporting two TTI lengths, 10ms and 2ms. p. 51