lecture 1

EE359Wireless

Communications

Engr Asad Riaz

Outline

Introduction to Wireless Communication

The propagation channelModulation techniques Channel coding and EqualizationCellular concepts and site planningA complete overview of GSM network.CDMA overview

Wireless Communication

Aim

To communicate information from one user or a selected group of users irrespective of the information or user location and motion.

Wireless History

First Mobile Radio Telephone 1924

Wireless History

1867 - Maxwell predicts existence of electromagnetic (EM) waves

1887 - Hertz proves existence of EM waves; first spark transmitter generates a spark in a receiver several meters away

1896 - Marconi demonstrates wireless telegraph to English telegraph office

Wireless History

1897 - ``The Birth of Radio'' - Marconi awarded patent for wireless telegraph

1897 - First ``Marconi station'' established on Needles island to communicate with English coast

1898 - Marconi awarded English patent no. 7777 for tuned communication

1898 - Wireless telegraphic connection between England and France established

Wireless History

1901 - Marconi successfully transmits radio signal across Atlantic Ocean from Cornwall to Newfoundland

1902 - First bidirectional communication across Atlantic

1909 - Marconi awarded Nobel prize for physics

Wireless History

1914 - First voice over radio transmission 1920s - Mobile receivers installed in police

cars in Detroit 1930s - Mobile transmitters developed;

radio equipment occupied most of police car trunk

1935 - Frequency modulation (FM) demonstrated by Armstrong

1940s - Majority of police systems converted to FM

Wireless History

Birth of Mobile Telephony 1946 - First interconnection of mobile users to public

switched telephone network (PSTN) 1949 - FCC recognizes mobile radio as new class of service 1940s - Number of mobile users > 50K 1950s - Number of mobile users > 500K 1960s - Number of mobile users > 1.4M 1960s - Improved Mobile Telephone Service (IMTS)

introduced; supports full-duplex, auto dial, auto trunking 1976 - Bell Mobile Phone has 543 pay customers using 12

channels in the New York City area; waiting list is 3700 people; service is poor due to blocking

Wireless History

Cellular Mobile Telephony 1979 - NTT/Japan deploys first cellular communication

system 1983 - Advanced Mobile Phone System (AMPS) deployed

in US in 900 MHz band: supports 666 duplex channels 1989 - Groupe Spècial Mobile defines European digital

cellular standard, GSM 1991 - US Digital Cellular phone system introduced 1993 - IS-95 code-division multiple-access (CDMA)

spread- spectrum digital cellular system deployed in US 1994 - GSM system deployed in US, relabeled ``Global

System for Mobile Communications''

Wireless history

PCS and Beyond 1995 - FCC auctions off frequencies in

Personal Communications System (PCS) band at 1.8 GHz for mobile telephony

1997 - Number of cellular telephone users in U.S. > 50M

2000 - Third generation cellular system standards? Bluetooth standards?

Electromagnetic Waves

According to the wave equations, a time-varying(oscillating) electric field generates a magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave. Electromagnetic radiation is generally described as a self-propagating wave in space with electric and magnetic components.

Electromagnetic Waves

Electromagnetic Waves

These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other. Electromagnetic radiation is classified into types according to the frequency of the wave: these types include, in order of increasing frequency, radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. In some technical contexts the entire range is referred to as just 'light'. EM radiation carries energy and momentum, which may be imparted when it interacts with matter.

Electromagnetic Spectrum

Radio waves are a form of electromagnetic radiation, created whenever a charged object (in normal radio transmission, an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to three hundred gigahertz, although commercially important uses of radio use only a small part of this spectrum

Electromagnetic Spectrum

The Cellular Concept

Basic Principles

Frequency Reuse

Cell Splitting

First proposed by D.

H. Ring at Bell Laboratories in 1947

The Cellular Concept

Solves spectral congestion and user capacity problems. Splitting one high power transmitter (large cell) into many low power transmitters (small cells). Each base station is assigned a different group of channels and nearby BS are assigned different frequencies

Cellular Systems:Reuse channels to maximize

capacity Geographic region divided into cells Frequencies/timeslots/codes reused at spatially-separated locations. Co-channel interference between same color cells. Base stations/MTSOs coordinate handoff and control functions Shrinking cell size increases capacity, as well as networking burden

BASESTATION

MTSO

Cellular Systems:Reuse channels to maximize

capacity

The concept of cellular radio can be used to explain the differing receptions at various locations.

An area to be supplied with radio service is divided into cells. Each of these cells is assigned a range of frequencies (f1 - f6) and they each have corresponding radio base stations. The group of frequencies can be reused in other cells bearing in mind that it is not reused in adjacent cells as that will cause co-channel interference. Co-channel interference results when frequencies are reused in adjacent neighbouring cells. A reuse distance, D is calculated as D=R√3N

where R is the cell radius and N is the number of cells per cluster. cells may vary in radius in the ranges (1 km to 30 km). The shape of the cells can be hexagonal, circular or some other undefined irregular shapes. The boundaries of the cells can also overlap between adjacent cells.

Cellular - Implementation

Cellular - Implementation

In the 900 MHz band the uplink frequency band is 890-915 MHz, and the downlink frequency band is 935-960 MHz. This 25 MHz bandwidth is subdivided into 124 carrier frequency channels, each spaced 200 kHz apart. Time division multiplexing is used to allow eight full-rate or sixteen half-rate speech channels per radio frequency channel. There are eight radio timeslots (giving eight burst periods) grouped into what is called a TDMA frame. Half rate channels use alternate frames in the same timeslot. The channel data rate is 270.833 kbit/s, and the frame duration is 4.615 ms

Cellular Phone Networks

Cellular Phone Networks

The EIR (Equipment Identity Register) is often integrated to the HLR. The EIR keeps a list of mobile phones (identified by their IMEI) which are to be banned from the network or monitored. This is designed to allow tracking of stolen mobile phones. In theory all data about all stolen mobile phones should be distributed to all EIRs in the world through a Central EIR. It is clear, however, that there are some countries where this is not in operation. The EIR data does not have to change in real time, which means that this function can be less distributed than the function of the HLR

World Telecom Statistics

Crossover has happened in May 2002!

World Cellular Subscribers by Technology

as of June 20062.41 Billion Cellular Customers Worldwide

GSM/UMTS Totals 82.3%

GSM Growth - 1993 to June 2006

Exciting Developments

Internet and laptop use exploding2G/3G wireless LANs growing rapidlyHuge cell phone popularity worldwideEmerging systems such as Bluetooth,

UWB, Zigbee, and WiMAX opening new doors

Military and security wireless needsImportant interdisciplinary applications