Wireless Communication Instructor: Jin Wang Department of Electrical & Electronics Engineering

2 Jin Wang Subject Outline Introduction to Cellular Mobile Communications Radio Propagation : Large Scale Effects  Path loss prediction models  Shadowing Radio Propagation : Small Scale Effects  Multi-path models : Rayleigh, Rician  Doppler effect, power spectra and signal correlation  Coherence time and bandwidth, flat and selective fading channel Modulation Techniques  Constant envelope and phase modulation  QPSK, π /4 QPSK, FSK, GMSK

3 Jin Wang Subject Outline Equalization, Diversity and Coding Techniques  Linear and non-linear equalization  Selection, equal-gain and maximal ratio combining  Interleaving and convolution coding Multiple Access Techniques  FDMA, TDMA, CDMA, SDMA  Packet radio and random access Cellular System Concepts  Frequency reuse  Channel assignment and control  Cellular traffic  Cellular coverage  System expansion techniques

4 Jin Wang Subject Outline CDMA Cellular Systems  Power Control and Interference  Multi-user Detection  Capacity and Enhancement More Advanced Topics (if time allows)  Orthogonal Frequency Division Mulitplexing (OFDM)  Multi-carrier CDMA System Speech Coding Fundamentals of quantization, PCM, Vocoder Brief Overview of System Standards GSM, IS-95, IMT2000

5 Jin Wang References Theodore S. Rappaport, Wireless Communications: Principles & Practice, Prentice-Hall, 2nd Edition. Jon W Mark, Weihua Zhuang, Wireless Communications and Networking, Prentice Hall. Simon R. Saunders, Antennas and Propagation for Wireless Communication Systems, Wiley. William C. Y. Lee, Mobile Communications Engineering, McGraw- Hill. J. D. Parsons, The mobile radio propagation channel, Wiley, 2nd Edition. Michel Daoud Yacoub, Foundations of Mobile Radio Engineering, CRC Press. William C. Jakes, Microwave Mobile Communications, IEEE Press.

6 Jin Wang Wireless Communications Satellite TV Cordless phone Cellular phone Wireless LAN, WIFI Wireless MAN, WIMAX Bluetooth Ultra Wide Band Wireless Laser Microwave GPS Ad hoc/Sensor Networks

7 Jin Wang Europe Standards GSM CT2 Dect

8 Jin Wang Japan Standards

9 Jin Wang North American Major Standards PCS GSM Coreless FDMA TDMA CDMA Modulation  FM  QPSK  GMSK  BPSK  QAM

10 Jin Wang Basic concepts Simplex, half-duplex, and full duplex Frequency division duplexing, FDD  Most of system because of simplicity Time division duplexing, TDD:  indoor system only, because of delay Different from FDMA and TDMA

11 Jin Wang Basic concepts

12 Jin Wang Pager System

13 Jin Wang Cordless phone Virtually all telephones now sold in the US use the 900 MHz, 2.4 GHz, or 5.8 GHz bands. There is no specific requirement for any particular transmission mode on 900, 2.4, and 5.8, but in practice virtually all 900 MHz phones are inexpensive, bare-bones analog models; digital features such as DSSS and FHSS are generally only available on the higher frequencies.DSSSFHSS The recently allocated 1.9 GHz band is used by the popular DECT phone standard from EuropeDECT

14 Jin Wang Mobile

15 Jin Wang Base Station

16 Jin Wang Introduction The target for mobile communications is to provide communications for anyone, from anywhere, at any time. A demanding task. Technological challenges include:  Time–varying, hostile communication channel.  Location and tracking complexities due to mobility.  Efficient use of scarce resources such as frequency spectrum ⇒ cellular structure. The amount of interference generated is critical.  Power restrictions due to health issues.

17 Jin Wang Introduction The exponential growth of mobile subscribers worldwide is due to the decreasing service charges and diminishing hardware costs. The continuous development of the enabling technologies is the key.

18 Jin Wang Introduction RF technologies (such as improved frequency stability in electronics)

19 Jin Wang Introduction  IC design (size)  Battery technology (weight and size)  Higher order modulation is made possible due to the use of more sophisticated advanced digital signal processing techniques.  Speech coding techniques – reduces the required bandwidth per channel.

20 Jin Wang Cellular system Example :  Consider a system allocated total bandwidth of 12.5MHz and each voice channel requires a 10kHz slot. We can only support 12.5MHz/10kHz or 1250 simultaneous conversations.  Supposing the penetration rate in Singapore is 10%, for a population of 3M+, this is equivalent to 300k users. What happen if 1% of the users making call at the same time? Channels need to be in someway reused or shared?

21 Jin Wang Cellular system What can we do?  Frequency bands are reused at different locations. With this, higher user capacity in the same frequency spectrum can be achieved.  Technical challenge: interference issue, location tracking, etc., needs to be overcome.

22 Jin Wang Cellular system

23 Jin Wang Cellular system Each cell has a base station (BS), providing the radio interface to the mobile station (MS). A sophisticated switching technique called a handover enables a call to proceed uninterrupted across cell boundaries. All the BS’s are connected to a mobile switching center (MSC) which is responsible for connection users to the public switched telephone network (PSTN). Control channels transmit and receive data messages that carry call initiation and service requests, and are monitored by mobiles when they do not have a call in progress. ~5% of total available channels.

24 Jin Wang Cellular system Communication between the BS and the mobiles is defined by a standard common air interface that specifies 4 different physical channels  Forward (Downlink) voice/data channel : BS to MS  Reverse (Uplink) voice/data channel : MS to BS  Forward (Downlink) control channel : BS to MS  Reverse (Uplink) control channel : MS to BS A MS contains a transceiver, an antenna and control circuitry. A BS consists of several transmitters and receivers.

25 Jin Wang 1G 2G Distributions

26 Jin Wang 2G Standard

27 Jin Wang 2G to 3G evolution

28 Jin Wang