ELEC 6040 Mobile Radio Communications

Transcription

1 ELEC 6040 Mobile Radio Communications Lecturers: Dr. S. D. Ma and Dr. T. I. Yuk Date & Time: Wednesday: 7:00-9:30pm Place: CYC (Chow Yei Ching Building ) -B Notes can be obtained from: p. 1

2 Objective: To gain an understanding of mobile radio communications. Contents Introduction to Mobile Radio Communications Systems : Overview of mobile radio communications Overview of digital communication systems: Model of a digital communication system; a brief review of digital modulation, source coding and channel coding. Mobile radio propagation characteristics Error performance over radio links Multiple access methods An introduction to orthogonal frequency division multiplexing p. 2

3 Contents Mobile Radio Communications Engineering : Introduction to cellular systems Basic cellular system; performance criteria; cellular planning Elements of cellular systems design concept of frequency reuse; cell coverage; desired S/I from an omni-directional antenna; handoff mechanism; co-channel interference and power control; channel allocation schemes; cell splitting and traffic consideration. Mobile communication standards 2G and 2.5G systems 3G systems beyond 3G and 4G systems appreciation of GPRS, EDGE, IEEE a/b wireless LANs and HIPERLAN/2, Bluetooth, WiMax, LTE, etc. p. 3

4 References Theodore S. Rappaport, "Wireless Communications: Principles & Practice", 2/e, Prentice Hall, John G. Proakis, "Digital Communications", 4th ed., McGraw Hill, William C. Y. Lee, "Mobile Communications Design Fundamentals", John Wiley & Son, Inc Siegmund M. Redl et al. "An Introduction to GSM", Boston : Artech House, c1995. H. Holma and A. Toskala, "WCDMA for UMTS: Radio Access for Third Generation Mobile Communications", 3rd ed. Chichester : Wiley, c2004. H. Holma and A. Toskala, "HSDPA/HSUPA for UMTS: High Speed Radio Access for Mobile Communications" IEEE standards Journal and magazine articles as appropriate p. 4

5 Assessment Assignments: 30% Final Examination: 70% p. 5

6 Lecture Notes Part 1. Introduction Part 2. Cellular System Engineering Part 3. Multiple Access Methods Part 4. Communications over Wireless Channels Part 5. 2G and 2.5G Systems Part 6. 3G Systems Part 7. B3G and 4G systems p. 6

7 Part 1. Introduction p. 7

8 It All Started Like This First telephone call Alexander Bell, March 10, 1876 "Mr. Watson--come here -- I want to see you. 1897: Guglielmo Marconi firstly demonstrated radio's ability to provide continuous contact with ships sailing in the English channel. Beginning of 20th century: Short wave radio communications were used in marine secure operation systems. 1921: The first car mounted radio telephone p. 8

9 Going Further 1934 Municipal police radio systems in the US (AM) 1946 First commercial mobile radio-telephone service by Bell and AT&T in Saint Louis, USA. Half duplex (FM) 1968 AT&T proposed the cellular concept to the FCC 1973 First handheld cellular phone Motorola First cellular net Bahrein 1980 s 1G (1st generation mobile communication systems) Employed cellular technique for capacity enhancement Features: Used analog modulation (FM in majority), voice service Examples: E-TACS (UK), NMT (Northern European countries), AMPS (US), JTACS (Japan) Well-known names: AT&T, etc. p. 9

10 Historical Review on the Development of Mobile Radio Communications (3) 1990 s: 2G (2nd generation mobile communication systems) Motivation: Increase the capacity, use the frequency spectrum efficiently Technical Features: Digital modulation is used. DSP techniques (e.g., channel equalization, source coding, channel coding) are also used. Higher capacity than 1G (e.g., USDC versus AMPS: 3 times) Service: mainly voice, text message Political issues: Intense debate on whether CDMA or TDMA was better, during the first half of 1990 s. Examples: USDC (some parts of US; TDMA), IS-95 or cdmaone (some parts of US, Korea, HK, China, Japan s KDD, etc.; CDMA), GSM & DCS-1800/PCS (most part of the world; TDMA), GSM-1900 (some parts of US; TDMA), PDC & PHS (Japan s NTT DoCoMo; TDMA) Well-known names: Ericsson, Nokia, Qualcom, A. J. Viterbi p. 10

11 Historical Review on the Development of Mobile Radio Communications (4) Late 1990 s: 2.5G Why 2.5G? data service: the data rate of 2G is low new standard: a long time replacing 2G systems with 3G systems: huge amount of investment on 2G Solution: 2.5G, based on the existing 2G systems, increase the data rate Standards: GPRS (up to 114kbps; for GSM networks), EDGE (up to 384kbps; for GSM and DCS-1800/1900 networks), IS-95B (IS- 95 s data-transmission extension) Well-known names: i-mode, WAP (Wireless Application Protocol), Multimedia messaging service (MMS) p. 11

12 Historical Review on the Development of Mobile Radio Communications (5) 2000 s: 3G (3rd generation mobile communication systems) Feature 1: Initially intended to support multimedia communications; currently targeted to support Internet access, mobile TV, games etc Feature 2: Employs all sorts of capacity enhancement techniques: turbo codes (invented in 1993), multiuser detection (invented in 1986), transmit diversity (invented in ~1993), fast power control (invented in ~1993), smart antennas (long-known technique). Political issues: Initial attempt to unify all mobile radio communications into a single standard; not successful due to disagreements among major players Data-transmission rate: from 144kbps (vehicular environments) to 2Mbps (indoor environments) Approved standards: WCDMA, cdma2000, TD-SCDMA Market status: CDMA2000 first commercial service at Seoul in late 2000 and WCDMA in Tokyo in May 2001 Well-known names: NTT DoCoMo, Qualcom, Ericsson, Nokia, 3GPP, 3GPP2 p. 12

13 Frequency Allocation Standard Year of Intro. Multiple Access Frequency Band Modulation Channel Bandwidth NMT FDMA MHz FM 25kHz AMPS 1983 FDMA MHz FM 30kHz E-TACS 1985 FDMA 900 MHz FM 25kHz NMT FDMA MHz FM 12.5kHz JTACS 1988 FDMA MHz FM 25kHz NAMPS 1992 FDMA MHz FM 10kHz USDC 1991 TDMA MHz π/4-dqpsk 30kHz GSM 1990 TDMA MHz GMSK 200kHz DCS TDMA MHz GMSK 200kHz DCS TDMA GHz GMSK 200kHz IS CDMA MHz; GHz QPSK / BPSK 1.25MHz PACS 1994 TDMA / FDMA GHz π/4-dqpsk 300kHz PDC 1993 TDMA MHz π/4-dqpsk 25kHz PHS 1993 TDMA MHz π/4-dqpsk 300kHz DECT 1993 TDMA MHz GFSK 1.728MHz WCDMA CDMA GHz QPSK / BPSK 5MHz cdma2000 CDMA GHz QPSK / BPSK 5MHz p. 13

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17 Roadmap Data rate (Mbps) x000 p. 17 x00 x0 x.x Date rate requirement increases exponentially due to high desire of better user experience stage1: , File transfer, Web browse, Voice-over-ip, etc 1 Source: NTT DoCoMo stage2: On-line game, Video conference, Tele-Medicare, etc 2 stage3: HDTV, Virtual reality, etc Capacity bottle neck due to Rare radio resource Power limitation Impairments of wireless channel G 3.5G Year Big gap needed to be filled. Revolutionary technologies should be explored. Maximum Data Rate 2 Mbps 14 Mbps

18 Targets and Achievable Data Rate in Cellular Systems p. 18 Data rate (bit/second) 10 M 1 M 100 k 10 k 1 k 9.6 k GSM 2G & 2.5G 32 k PHS 3G & 3.5G Maximum value in specification 2 M GPRS 171 k EDGE 384 k W-CDMA 1X 144k cdma Peak data rate 14 M Average data rate 2 to 4 M HSPA+ DL:56 M UL:22M HSDPA (High-Speed Downlink Packet Access) High-rate data services in megabit/second class are possible using HSDPA Year

19 Mobility Targets for Systems Beyond 3G High 3G Enhancement Enhanced 3G New mobile access 100 Mbps Systems beyond 3G. 1 Gbps Low New nomadic / Local area wireless access Peak useful data rate (Mb/s) p. 19 Extracted from ITU-R.1645

20 3.5G and LTE Beyond 3G (B3G) Existing 3G: uplink/downlink: 200/500kbps, much lower than expected Improving existing 3G systems to support data rates up to 10Mbps Mid-term evolution: WCDMA uplink/downlink: HSUPA/HSDPA, up to 5.76/14Mbps cdma2000 cdma2000 1xEV-DO Rel. 0 Rev A Rev B Commercial service: 2003: Verizon Wireless, CDMA2000 1xEV-DO, the United States 2003: KDDI, CDMA2000 1xEV-DO, Japan May 2006: SK Telecom, the world first HSDPA service, Korea Aug. 2006: NTT DoCoMo, HSDPA, Japan Sept. 2006: Smartone, HSDPA (3.6 Mbps), Hong Kong 3GPP LTE (long term evolution): using 4G technologies (MIMO, OFDMA, etc.) on 3G systems uplink/downlink: 170/320Mbps p. 20

21 4G Mobile Communications (1) Research ongoing: 4G 4G: replacing existing 3G systems Objectives: a fully IP-based integrated system; being capable of providing between 100 Mbit/s and 1 Gbit/s speeds both indoors and outdoors, with premium quality and high security. Feature 1: totally new broadband frequency spectrum is needed, 100M Feature 2: A mixture of different communication systems, including: broadcasting systems, cellular networks, wireless LANs (WLANs), wireless personal-area networks (WPANs), and fixed networks. Intersystem handover required. Billing among different operators more difficult. Feature 3: IP-based; packetized communications. Enabling technologies: MIMO, OFDM, space-time coding, smart antennas, channel-dependent scheduling, link adaptation, relaying Well-known names: NTT DoCoMo, Samsung, Nokia, Sony-Ericsson, Philips, Huawei, Northern European countries p. 21

22 Research target of 4G 4G Mobile Communications (2) 4G wireless network Cellular system Isolated-cell environment 3G: current data rate 14Mbps wide coverage full mobility 100Mbps 4G: target data rate local area coverage low mobility 1Gbps p. 22

23 Asymmetric data traffic 4G Mobile Communications (3) Typical service: watching HD movie in real time Uplink: light traffic, low data rate Relatively narrow bandwidth: 40MHz Downlink: heavy traffic high data rate sending orders video streams Broad bandwidth: 100MHz p. 23

24 4G Mobile Communications (4) Broadband wireless access Cellular system Same air interface Local area environment To reduce network cost All IP-based core network p. 24

25 HK Economic Journal June In 2007, NTT DoCoMo announced it achieved a maximum packet transmission rate of approximately 5Gbps in the downlink using 100MHz frequency bandwidth to a mobile station moving at 10km/h, the world's first 5Gbps packet transmission in 4G Field Experiment. p. 25

26 Wireless Networks 1G~4G WiMax, e IEEE p. 26

27 Wireless LAN (1) WLAN utilizes spread-spectrum/ofdm technology based on radio waves to enable communication between devices in a limited area gives users the mobility to move around within a local coverage area and still be connected to the network Different WLAN Standards various version of IEEE by vendors joined IEEE HIPERLAN 5GHz standard by researchers in ETSI (European Telecommunications Standards Institute) no strong vendor influence p. 27

28 Wireless LAN (2) IEEE a - 6~54 Mbps, in unlicensed 5-GHz radio band IEEE b - older, up to 11 Mbps, in 2.4 GHZ radio band p. 28 IEEE d to add support for "additional regulatory domains". This support includes the addition of a country information element to beacons, probe requests, and probe responses. IEEE e - QoS (quality of service) issue in LANs IEEE g - to increase the speed of b - 54 Mbps in 2.4 GHz band IEEE x - security and other class of service specifications. IEEE n - for very high-speed WLANs ( Mbps) over short distances. IEEE p - WAVE Wireless Access for the Vehicular Environment

29 IEEE / IEEE b Approved & standardized 1997 (IEEE ) early 2000 (IEEE b) Major market players Intersil, Agere, etc. Rates 1Mbps, 2Mbps (IEEE ) 5.5Mbps, 11Mbps (IEEE b) Carrier frequency 2.4GHz (unlicensed ISM band) [NA for infrared] Transmission techniques Source of external interference Direct-sequence spread spectrum ( & b) Frequency-hopped spread spectrum (802.11) Infrared (802.11) Bluetooth TM devices Microwave ovens European counterpart HIPERLAN/1 (no commercial products!) IEEE g Up to 54 Mbps adopt a technique in b p. 29

30 IEEE a Approved & end of 1999 standardized Major market players Atheros, Intersil, etc. Rates 6Mbps 54Mbps Carrier frequency 5.2GHz (unlicensed band called UNII) Transmission techniques Source of external interference OFDM (orthogonal frequency division multiplexing) other IEEE a access points or mobile stations no other known interference up to now European counterpart HIPERLAN/2 (standard published) Japanese counterpart MMAC (published) p. 30

31 Summary of IEEE a/b WLANs and HIPERLAN/2 HIPERLAN/2 is better than IEEE a in QoS support and security. Source: J. De Vriendt, P. Lainé, C. Lerouge and X. Xu, Mobile network evolution: a revolution on the move, IEEE Communications Magazine, pp , Apr p. 31

32 WiMax IEEE (2001) - point to multi-point broadband wireless transmission in the GHz band, using single carrier physical standard IEEE a - for 2 ~ 11 GHz, adding OFDM/OFDMA IEEE d (IEEE ) fixed WiMax (supersedes the earlier amendments) IEEE e - mobile WiMax, OFDM and MIMO techniques, full mobility support WiMax is very different from WiFi WiMax: over many kilometers, stronger encryption, less interference WiFi: short range (10's of meters), WEP/WPA encryption, suffer from interference p. 32

33 Bluetooth an industrial specification for wireless personal area networks (PANs). provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles via a secure, globally unlicensed short-range radio frequency proposed by Ericsson named after Harald Bluetooth, a king of Denmark and Norway in 10th century, known for his unification of previously warring tribes Bluetooth: intended to unify different technologies like computers and mobile phones. technical information: 2.4G ISM band, low power consumption, short range (<100m) low-cost transceiver, data rate (<1Mbps) p. 33

34 Typical Applications Wireless control of and communication between a cell phone and a hand free headset Wireless control of a games console Nintendo's Wii and Sony's PlayStation 3 Wireless communications with PC input and output devices mouse, keyboard and printer a Bluetooth mobile phone headset Apple wireless keyboard and mouse p. 34

35 Other Wireless Network: WSN (1) WSN (Wireless Sensor Network) A wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations Standards: ZigBee, WirelessHART, ISA100, etc., all based on IEEE ) p. 35

36 Other Wireless Network: WSN (2) WSN (Wireless Sensor Network) originally motivated by military applications such as battlefield surveillance civilian applications: environment and habitat monitoring, healthcare applications, home automation, and traffic control the size of a sensor environment and habitat monitoring p. 36

37 Future Wireless World Laptop Computer Accessories PDA Vehicle Handset Home Appliance Mobile Phone Wireless Access Network p. 37

38 Important Technologies Important technologies for the flourish of mobile communications Cellular concepts: the ability to provide mobile radio communications to an entire population detailed illustration in Part 2 Digital communications: digital techniques such as source coding, channel coding, digital modulation... capacity improvement over analog systems: USDC three times AMPS p. 38

39 Overview of Cellular Concepts (1) Early-day mobile radio communications: Objective: achieve a large coverage by using a single, high powered transmitter Macro-cell system: one central base station served all mobiles Advantage: large coverage: a thousand square miles Disadvantages: small number of supported users (capacity) impossible to reuse frequency high transmit power p. 39

40 Overview of Cellular Concepts (2) Cellular Mobile Systems: Introduced by AT&T during 1960 s. Made use of signal attenuation after traveling a certain distance; so that the same carrier frequency can be reused after a certain distance. Capacity is greatly increased. p. 40

41 Terminologies Used in Cellular Systems (1) Base Station (Access Point, Node B in WCDMA) A fixed station in a mobile radio system used for radio communication with mobile stations Mobile Station A station in the cellular radio service intended for use while in motion at unspecified locations Mobile Switching Center (MSC) Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connects the cellular base stations and the mobiles to the PSTN (Public switched telephone network) Roaming A MS which operates in a service area other than that from which service has been subscribed p. 41

42 Terminologies Used in Cellular Systems (2) Dual Band allowed to use different frequency bands, e.g., GSM900 and GSM1800 Dual Mode allowed to use different air interfaces, e.g., WCDMA and GSM Forward Channel downlink channel, BS MS Reversed Channel uplink channel, MS BS Control Channel radio channels used for transmission of call setup, call request, call initiation, or control purposes p. 42

43 Terminologies Used in Cellular Systems (3) Traffic Channel radio channels used for transmission of user voice or data Full Duplex Transmission (TX) and Receiving (RX) are allowed simultaneously, e.g., GSM, WCDMA Half Duplex TX or RX is allowed at any given time, e.g., police radio Simplex only one-way transmission, e.g., paging p. 43

44 Overview of Digital Communication Systems Analog Communication System 1G is an analog radio communication system with FM modulation p. 44

45 Digital Communication System Information Source Source Encoding Channel Encoding Modulation Transmitter Digital Domain Analog Waveform Physical Channel Receiver Information Sink Source Decoding Channel Decoding Demodulation p. 45

46 Elements of Digital Communication Systems (1) Information source: voice signals for 1G and 2G systems voice and/or video signals for 3G and B3G systems Internet data for 2.5G, 3G and B3G systems Source coding: To remove redundancy in source signals before transmission. Transmission efficiency is improved. Also known as data compression. Examples: code excited linear prediction (CELP), MPEG. p. 46

47 Elements of Digital Communication Systems (2) Channel coding: To add redundancy in the digital signal so that the signal can be recovered even in the presence of noise and interference. Transmission reliability is improved. Examples: repetition code, Reed-Solomon code, BCH code, convolutional code. Modulation and Demodulation: Modulation (demodulation) maps (retrieves) the digital information into (from) an analog waveform appropriate for transmission over the channel. Generally involve translating (recovering) the baseband digital information to (from) a bandpass analog signal at a carrier frequency that is very high compared to the baseband frequency. Examples: BPSK, QPSK, π/4-dqpsk, GMSK, OFDM p. 47

48 Elements of Digital Communication Systems (3) Communication channels: The physical medium used to send the signal from the transmitter to the receiver. Essential feature: the transmitted signal is corrupted in a random manner Examples: o Wireline channels o Fiber-optic channels o Wireless electromagnetic channels o Underwater acoustic channels o Storage channel p. 48

49 A Simple Example of Source Coding Original Picture (2M TIF file) Highly compressed picture (177k JPEG file) p. 49

50 Example of Channel Coding: Convolutional Code used for IS95 Forward Links + Coded symbols Data Forward link; rate = 1/2; constraint length = 9 + Coded symbols p. 50

51 Example of Channel Coding: Convolutional Code used for IS95 Reverse Links + Coded symbols Data + Coded symbols Reverse link; rate = 1/3; constraint length = 9 + Coded symbols p. 51

52 Example of Channel Coding: Coding Gains of the Convolutional Code used for IS95 Good for voice communications Good for video transmission p. 52 Source: CDMA Systems Engineering Handbook, pp

53 Examples of Digital Modulations Popular for mobile communications (IS-95, WCDMA) p. 53