Challenges of Wireless Communications

Transcription

1 Marconi/WINLAB celebration, Sept. 30, 1999 Challenges of Wireless Communications Fumiyuki Adachi Wireless Laboratories NTT Mobile Communications Network, Inc. Outline 1. Bridging the Expanse of Mobile Multimedia 2. Trends in Wireless Access Technology 3. Global 3G CDMA 4. Beyond Global 3G NTT DoCoMo/FA/

2 Growth of Mobile Communications in Japan Penetration rate of mobile communications surpassed 40% point and is expected to overtake fixed telephone within a year Number of fixed telephone lines has declined to 58million (its peak was 61 million in 1997) Number of users Million PHS Cellular Aug ,262,000 (40.5%) 5.698m m Mar PDC July 1995 Start of PHS NTT DoCoMo/FA/ Year 2 20,9m 7 m Dec ,739, m 5.98 m Dec ,990,000 (35.5%) 39.0m

3 Weight and Talk Time of Mobile Phones Increased utilization efficiency of portable phones is an important factor of gaining popularity of mobile phones Weight (g) Vehicle-mounted Shoulder-type Analog PDC Year (a) Mobile phone weight Source: K. Honma et al., Mobile terminal NTT DoCoMo/FA/ technologies, Proc. IEICE, Feb Talk time (min) Year (b) Talk time

4 Time Taken to arrive at 10% (house hold) Point The rate at which mobile radio and Internet communications services have proliferated throughout our society is striking In the fixed networks, voice conversation was a long-time dominant service, but the introduction of Internet communication services is significantly changing our society Telephone Fax Mobile commun. Personal computer Internet Year Source: Communications White Paper, MPT, 1999 NTT DoCoMo/FA/

5 Evolution to Wireless Multimedia Society A combination of mobile communications, personal computers, and Internet services will drive our society to evolve into a wireless multimedia society Ultimate goal is to communicate any information with anyone, at any time, from anywhere Recently, mobile communications services are shifting their focus from only voice conversation to Internet connections in line with the increasing popularity of Internet communications in fixed networks Mobile Communications Computer Internet NTT DoCoMo/FA/

6 Multimedia-type i-mode service Over PDC-Packet Networks The first step toward bridging the expanse from today s society to wireless multimedia society is seen in a new Internet access service called i-mode service IP IP Internet IP TCP/IP HTTP Leased line Server PDC-P Network PDC/PDC-P Voice PDC-P: PDC Packet (9.6kbps) IP: Information Provider PDC Network NTT DoCoMo/FA/

7 Contents of i-mode service i-mode service provides ing, web access, various types of on-line services as well as voice conversation Transactions Daily information Mobile banking Reservations for Weather flights,accommodations News Town info. Stock prices Stock trading etc. etc. ing Web access Data base Restaurant guide Town page Dictionary Train transfer info. Cooking recipes etc. Voice Entertainment Karaoke Network game Movie listings Fortune-telling etc. NTT DoCoMo/FA/

8 Rapid Growth of i-mode service Rapid growth: one million users in Aug after its introduction in Feb Accelerating the popularity of i-mode services is the increasing number of IP sites (positive feedback): over 1400 in 8 Aug Feb.99 Apr. June 8 Aug. (a) Number of users (x1000) NTT DoCoMo/FA/ Apr. May June July 8 Aug. (b) Number of IP sites

9 Preparing for Wireless Multimedia Society Major services will shift from voice to multimedia services over Internet indicated by i-mode, but with much faster transfer rate and much better representation Fixed networks Internet traffic will exceed voice traffic in 2001 and 22% of mobile users will use multimedia services in 2000 Multimedia services (Internet/ISDN) Increased capacity (consistent growth of markets) 3G System (IMT-2000) Global standard (worldwide travelers, economy of global scale) NTT DoCoMo/FA/

10 IMT-2000 Deployment and Capability It is expected to be deployed worldwide starting around Technical target: information rates of up to 2 Mbps, same quality as fixed networks, use of 2-GHz bands IMT-2000 probably better represents Internet Mobile Telecommunications in the years of 2000 s IMT-2000 Network Indoor 2000Mbps Pedestrian 384kbps Vehicular 144kbps NTT DoCoMo/FA/

11 Evolution Path to Wireless Multimedia Society To realize IMT-2000, a new wideband wireless access technique incorporating as many recent technological achievements as possible is necessary Service type Voice Multimedia Narrowband Era ~ 1G Analog AMPS TACS NTT 2.4kbps 2G ~ Digital IS95 IS136 GSM PDC 64kbps IMT-2000 (Internet Mobile Telecommunications) 2000kbps Year NTT DoCoMo/FA/ ~ Wideband Era 3G

12 Harmonization Solution to Global 3G 8 out of 10 proposals submitted to the ITU in July 1998 were based on DS-CDMA TIA: cdma2000 Japan:ARIB started its selection process for a wireless access technique in 1995 and chose W-CDMA in 1997 ETSI: UTRA (W-CDMA for FDD and TD/CDMA for TDD) Intensive harmonization studies are currently under way to establish a global 3G standard Core Network G3G CDMA NNI Evolved GSM Evolved ANSI-41 Direct Spread 3.84Mcps Multi-carrier 3.68Mcps TDD FDD NTT DoCoMo/FA/

13 R&D Plan for IMT-2000 Target year of commercial deployment is Mar Research phase (transmission up to 2Mbps, voice/video) Design &Implementation Field test 1 W-CDMA air interface Field test 2 Revised W-CDMA Interference canceller, Adaptive antenna array System -test phase RFC RFP Design/ manufacture Field test W-CDMA air interface Control functions (L2/L3) Commercial system development phase NTT DoCoMo/FA/

14 System Test 3 sites Akasaka, Aoyama, Mita, Chiyoda YRP 4 sites Tokyo NTT DoCoMo/FA/

15 Migration Path Toward IMT-2000 Overlay of IMT-2000 with PDC PDC PDC/IMT dual mode dual band IMT-2000 terminal PDC-TDMA PDC RAN W-CDMA IMT-2000 RAN GSM evolved RAN-CN I/F (Proprietary) PDC CN IMT-2000 CN Mobility Management: GSM evolved MAP Service Control: INAP (CAMEL) IWF GSM evolved NNI Service area of IMT-2000 system (IMT-2000 RANIMT-2000 CN) will be overlayed with that of existing PDC system (PDC RAN PDC CN). IMT-2000 CN connects and inter-works with PDC through IWF (inter-working function). Initially, IMT2000-PDC dual mode terminal as well as IMT-2000 single mode terminal will be introduced. NTT DoCoMo/FA/

16 Advanced Transceivers In a multimedia W-CDMA communications system, link capacity is predominantly limited by high rate users producing severe multi-access interference (MAI) Two promising advanced receivers - Interference canceling (IC) receiver Multi-stage successive IC receiver: Interference subtraction is performed successively for different users in the order of decreasing power, thereby improving SIR for low rate users - Adaptive antenna array receive/transmit diversity Beam is directed toward the desired user while reducing interference particularly from high rate users NTT DoCoMo/FA/

17 Multi-stage IC Receiver Structure Interference subtraction is performed successively for different users in the order of decreasing power Received signal r(t) D - D - Channel ranking CEIGU User #1 CEIGU User #2 Ranking information D D - - CEIGU CEIGU to next stage User#1 data User#2 data r(t) (j) r k-1 iif j = 0 and k = 0 (j-1) s k D D CEIGU user #k - (j) r k (j) s k D - CEIGU User #K D - - CEIGU User#K data k = 0, l, s (-1) k = 0 2,.., K -1 for each j- th stage Iterative multi-stage IC receiver 1st stage 2nd stage CEIGU: channel estimation and NTT DoCoMo/FA/ interference replica generation unit 17

18 Measured BER Performance with 3-stage IC (Laboratory Experiment) The BER performance improvement is almost saturated at 3-stage 10 0 b,k/n0 = Eb,1/N for k = 2, 3,...,K E Average BER Single user 1.024Mc/s, SF=16 2-path Rayleigh, f D T slot =0.05 (80Hz) Antenna diversity, Convolutional coding No fast TPC MF 3-stage Multi-stage IC Average E b /N 0 per antenna (db) NTT DoCoMo/FA/ K=16 K=13 K=9 K=5

19 Broadband Wireless Communications 1G Data rate 100M 10M 1M 100K High-speed wireless LAN Wireless LAN 4G broadband wireless commun. network IMT-2000 (3G W-CDMA) 10K Stationary Cordless Indoor PHS Quasistationary Quasistationary Pedestrian Vehicular Mobility 2G cellular (PDC) Outdoor NTT DoCoMo/FA/

20 What is 4G System? A major objective is to offer mobile users broadband multimedia services, which will soon be in full force in fixed networks based on next generation Internet technology Information transferred over the Internet will become increasingly rich, most of the information may contain high-quality still and moving images Other services may include Various e-commerce transactions Broadcasting services Support of Intelligent Transportation Systems (ITS) NTT DoCoMo/FA/

21 4G System Is A Broadband Wireless Packet System? Broadband wireless multiple access optimized for IP transfer Broadband packet access with peak rate of more than 2Mbps in a vehicular environment and 10-20Mbps in stationary-to-pedestrian environments Flexible resource allocation between up- and down-link Wireless IP network Intelligent IP data routing algorithm with mobility handling Pico-cell with fast handoff algorithm Inter-operation with 3G Software radio technology NTT DoCoMo/FA/

22 Technical Challenges Broadband propagation channel produces severer frequency selective fading - Robust broadband data modulation scheme is necessary Significant difference between forward and reverse link rates e.g. WEB site access and down load of a 259kB image data indicates up/down link rate ratio of 1:55 Asymmetric link Access to NASA Web site to retrieve a galaxy image of 259kB Amount of data transmitted Up-link: 5kB Down-link: 274MB Time=4min 15sec for PDC (8.6kbps throughput) Which wireless access, TDMA, DS-CDMA, or OFDM? It may be hybrid use of OFDM and DS-CDMA with TDD NTT DoCoMo/FA/

23 Technical Challenges (cont d) Power limitation Power f 2.6 Rate - Example: Transmit power with 64 kbps at 5GHz is 87 times larger than with 8kbps at 2GHz, or cell size must be reduced by about 3.7 times (pico cell) Power reduction and interference suppression techniques are important - Space-time processing (adaptive antenna array and coding) - Adaptive modulation - Packet interference cancellation NTT DoCoMo/FA/

24 Concept of 4G System 4G island covers high multimedia traffic area 4G island inter-operates with 3G network Flexible extension of 4G island Switching center 1-2km 4G 4G Satellite cell m 3G network Array beam feeder 4G island (clustered cell area) NTT DoCoMo/FA/

25 Conclusion G3G CDMA system - Target year is Flexible offer of wideband multimedia services in addition to basic service (voice/fax/voice-band data) - Up to 2Mbps transfer rates - Larger capacity and wider coverage than any other 2nd generation systems (GSM, PDC, IS95, etc) G3G CDMA can be enhanced by advanced wireless techniques, i.e. - Adaptive antenna array transceiver - Interference canceling receiver 4G system for rich multimedia communications services - Target year is around Broadband wireless packet access with peak rate of > 20Mbps - Significantly bandwidt/power efficient techniques necessary Space-time processing, packet interference cancellation - Inter-operation with 3G Software radio technology NTT DoCoMo/FA/

26 We will continuously face very difficult but interesting technical challenges in the coming years! Thank you! NTT DoCoMo/FA/