Wireless Communications Principles and Practice - Chapter 1: Introduction to Wireless Communication Systems

Wireless Communications Principles and Practice Chapter 1: Introduction to Wireless Communication Systems Components of score and References • Components of score: - Counts: 10 % - Exercises: 20 % - Project: 30 % - The exam : 40 % • References: - Theodore S.Rappaport, Wireless Communications Principles and Practice, Prentice Hall P T R, USA, 1996 - Andrea Goldsmith, Wireless Communications, Cambridge University, Faculty of Electronics & Telecommunications UK, 2005 The contents • Introduction to Wireless Communication Systems • Modern Wireless Communication Systems • The Cellular Concept – System Design Fundamentals • Mobile Radio Propagation: Large-Scale Path Loss • Multiple Access Techniques for Wireless Communications • Wireless Networking • Wireless Systems and Standards • Modulation Techniques for Mobile Radio Concepts • What is Wireless Communications ? Wireless communication is the transfer of information over a distance without the use of electrical conductors or wires. • The range of wireless services Radio spectrum is used for a wide range of services. These can be broken into the following broad classes: - Broadcasting services: including short wave, AM and FM radio as well as terrestrial television; - Mobile communications of voice and data: including maritime and aeronautical mobile for communications between ships, airplanes and land; land mobile for communications between a fixed base station and moving sites such as a taxi fleet and paging services, and mobile communications either between mobile users and a fixed network or between mobile users, such as mobile telephone services; Concepts Concepts Concepts Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Một số loại sóng Concepts • The range of wireless services - Fixed Services: either point to point or point to multipoint services; - Satellite: used for broadcasting, telecommunications and internet, particularly over long distances; - Other Uses: including military, radio astronomy, meteorological and scientific uses. Concepts • What is frequency? The number of cycles per unit of time is called the frequency. For convenience, frequency is most often measured in cycles per second (cps) or the interchangeable Hertz (Hz) (60 cps = 60 Hz), 1000 Hz is often referred to as 1 kHz (kilohertz). • 1 kHz = 1000 Hz • 1 mHz = 1000 kHz • 1 GHz = 1000 mHz Concepts • What is Radio frequency? Radio frequency (RF) is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. • What is Frequency Band ? In telecommunication, a band - sometimes called a frequency band - is a specific range of frequencies in the radio frequency (RF) spectrum, which is divided among ranges from very low frequencies (vlf) to extremely high frequencies (ehf). Each band has a defined upper and lower frequency limit. Xin hỏi các dải băng tần dùng cho thông tin vệ tinh? E – Extremely, S – Super, M – Medium, H – High, V – Very, L - Low, U – Ultra, VF – Voice Fequency. Concepts • What is Bandwidth? Bandwidth (the width of a band of electromagnetic frequencies) , The amount of data that can be sent over a given network connection. Used to describe the "speed" of a connection between two devices. expressed in bits per second(bps) or bytes per second. Example A V.90 modem supports a maximum theoretical bandwidth of 56 Kbps. Fast Ethernet supports a theoretical maximum bandwidth of 100 Mbps. Concepts What is Channel ? In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel. A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second Concepts • What is analog ? An analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, analogous to anothvarying signal. er time • What is Digital ? Digital describes electronic technology that generates, stores, and processes data in terms of two states: positive and non-positive. Positive is expressed or represented by the number 1 and non-positive by the number 0. Thus, data transmitted or stored with digital technology is expressed as a string of 0's and 1's. 1. Evolution of Mobile Radio Communication • In 1895, Guglielmo Marconi opened the way for modern wireless communications by transmitting the three-dot Morse code for the letter ‘S’ over a distance of three kilometers using electromagnetic waves. • Wireless communications has developed into a key element of modern society. • Satellite transmission, radio and television broadcasting to the now ubiquitous mobile telephone, wireless communications has revolutionized the way societies function. The electronics boom Figure 1.1 The growth of mobile telephony as compared with other popular inventions of the 20th century. 2. Mobile radiotelephone in the U.S • In 1946, the first public mobile telephone service was introduced: cover distances of over 50 km, the early FM push – to – talk, used 120 kHz of RF bandwidth. • IMTS (Improved Mobile Telephone Service): full duplex • In 1960s : developed the theory and techniques of cellular radiotelephony and the late 1970 was available. 2. Mobile radiotelephone in the U.S 3. Mobile Radio System Around the World 3. Mobile Radio System Around the World 3. Mobile Radio System Around the World 4. Examples of Mobile Radio Systems 4. 1. Basic concepts • Frequency division duplexing, FDD: forward channel and reverse channel – Most of system because of simplicity • Time division duplexing, TDD: – indoor system only, because of delay • Personal Communication Service (PCS) 4. Examples of Mobile Radio Systems 4. 1. Basic concepts • Public switched telephone network (PSTN): The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by switching centers, thus allowing any telephone in the world to communicate with any other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones. 4. 1. Basic concepts Base Station Mobile Station 4.2 Paging Systems • Paging systems are communication systems that send brief messages to a subscriber. • Depending on the type of severice, the messages may be either a numeric message, an alphanumeric messages, or a voice message. • The simple paging system may cover a limited range of 2 km to 5km, or may even be confined to within individual building. • The Wide area paging systems can provide worldwide coverage, may be in side a building, driving on a highway, or llying in an airplane. 4.2 Paging Systems 4.2 Paging Systems 4.3. Cordless Telephone Systems • Cordless telephone systems are full duplex communication systems that use radio to connect a portable handset to a dedicated base station, which is then connected to a dedicated telephone line with a specific telephone number on the Public switched telephone network (PSTN). 4.3. Cordless Telephone Systems 4.4.Cellular Telephone Systems • A cellular telephone system provides a wireless connection to the PSTN for any user location within the radio range of system. • Cellular systems accommodate a large number of users over a large geographic area, within a limited frequency spectrum. 4.4.Cellular Telephone Systems A basic cellular system which consists of mobile stations, base station and a mobile switching center (MSC). 4.4.Cellular Telephone Systems • A sophisticated switching technique called a handoff a call to procceed uninterrupted when the user moves from one cell to another • The mobile station contains a transceiver, an antenna, and control circuitry, and may be mounted in a vehicle or used as a portable hand – held unit. • The base station consist of several transmitters and receivers which simultaneously handle full duplex communications and generally have towers which support several transmitting and receiving antennas. • The MSC coordinates the activities of all of the base stations and connects the entire cellular system to the PSTN. 4.4.Cellular Telephone Systems • Communication between the base station and the mobile is defined by a standard common air interface (CAI) that specifies four different channels. - Forward voice channel (FVC): using for voice transmission from the BS to Mobile. - Reverse voice channels (RVC): using for voice transmission from the Mobile to BS. Two Channels responsible for initiating mobile calls, often called Setup channels are: - Forward control channels (FCC); - Reverse control channels (RCC); 4.5 How a cellular Telephone Call is Made Figure 1.6 Timing diagram illustrating how a call to a mobile user initiated by a landline subscriber is established. Mobile identification number (MIN) Electronic serial number (ESN) 4.5 How a cellular Telephone Call is Made Figure 1.7 Timing diagram illustrating how a call initiated by a mobile is established. 4.6 Comparison of Common Mobile Radio Systems 4.6 Comparison of Common Mobile Radio Systems