01-Handout-1.pdf

IT1718 History of Communication Communication - the process of exchanging information or intelligence. WHEN WHERE/WHO WHAT...

IT1718 History of Communication Communication - the process of exchanging information or intelligence. WHEN WHERE/WHO WHAT 1876 Alexander Bell Invention of telephone 1887 Heinrich Hertz Discovery of radio waves 1948 BELL Laboratories Invention of transistor 1973–1976 Metcalfe Ethernet and first LANs 1975 United States First personal computers 1977 United States First use of fiber-optic cable 1982 United States TCP/IP protocol adopted 1995 United States Global Positioning System deployed 1997 United States First Wireless LANs 2009 Worldwide First 100 Gb/s fiber optical networks Table 1.1 Historical Milestone of Electronic Communication Block Diagram of Communication Systems Figure 1.1 Communication Systems Block Diagram Retrieved from: Frenzel L., Principles of Electronic Communication Systems, Page 4  Transmitter converts the electrical signal to a suitable signal for transmission over a medium.  Channel or Medium is the material in which electronic signal is sent.  Receiver accepts the transmitted signal from the medium and convert it back to a form understandable by human.  Undesired current or voltages that occur in a circuit are called Noise.  Circuits that can transmit and receive signals are called Transceivers. Modulation and Communication Theories Types of Electronic Communication  One-way communication is called Simplex; it can send information in one direction only.  Full Duplex is a two-way communication system where both parties can talk and listen simultaneously.  Half Duplex is also a two-way communication system, but applies alternating direction. Analog Communication Figure 1.5 Analog Communication Block Diagram Retrieved from: Madhow U., Introduction to Communication Systems, Page 16  Information Source is the information or intelligence to be sent.  Message Signal is the information or intelligence in electrical form. 01 Handout 1 *Property of STI Page 1 of 4  IT1718  Modulator transforms the message signal into transmitted signal.  Signals that are suitable for transmission are called Transmitted Signal.  Channel/Medium is the pathway of signals.  Demodulator converts the signal back to a form understandable by human.  Information Consumer is the recipient of information or intelligence. Digital Communication Figure 1.6 Digital Communication Block Diagram Retrieved from: Madhow U., Introduction to Communication Systems, Page 17  Information Source is the information or intelligence to be sent.  Source Encoder converts the message signal into a sequence of bits.  Information Bit is a basic unit of data/message used in digital communications.  Channel Encoder adds redundancy to facilitate error recovery after transmission.  Modulator maps the coded bits to be sent to the channel.  Channel/Medium is the pathway of signals.  Demodulator performs signal processing; produces bit estimates to be feed to the channel decoder.  Channel decoder processes the imperfect bit estimates from the demodulator.  Source Decoder processes the estimated information bits to obtain an estimate of the message.  Information Consumer is the recipient of information or intelligence. Modulation  Modulation is an electronic method for transmitting information from a place to another.  It is the process by which an information or intelligence is modified by the Carrier.  Carrier is a high-frequency signal, usually a sine-wave generated by an oscillator.  Original information or intelligence are called Baseband Signals.  Baseband Transmission is the process of putting the baseband signal directly into a medium. Figure 1.7 Digital Communication Block Diagram Retrieved from: Frenzel L., Principles of Electronic Communication Systems, Page 9 01 Handout 1 *Property of STI Page 2 of 4  IT1718  Information or intelligence is sent upon the carrier.  Carrier is fed to the modulator along with the baseband signal.  The intelligence signal will be converted as modulated carrier through high-frequency carrier oscillator and modulator.  The modulated carrier is amplified and sent to the antenna (or any other channel/medium) for transmission. Frequency ( f )  The number of cycles of a repetitive wave  Measured in cycles per second (cps) or in Hertz (Hz) Note: 1𝑐𝑝𝑠 = 1𝐻𝑧 𝟏  Given as: 𝒇= where: 𝑻 f = frequency (Hz) T = Period (seconds) Wavelength ( λ )  The distance of a wave occupied by one cycle  Usually expressed in meters or miles 𝒄  Given as: 𝛌=𝒇 where: c = speed of light f = frequency (Hz) Note: Speed of light is given as 3x108 m/s or 186,000mi/s Electromagnetic Spectrum Electromagnetic Spectrum is the total span of frequencies and wavelengths used in communication systems. It is divided into different section bands. Each band has a name and boundary, and is used for many communication applications. Each service or user must use an assigned frequency band to avoid interfering with other users who may be broadcasting at the same time. The allocation of the communication services within the overall spectrum is made by general worldwide agreement under the control of the International Telecommunications Union (ITU). NAME FREQUENCY (𝒇) WAVELENGTH (λ) USAGE Extremely low 30-300 Hz 107 - 106 m AC power line frequencies frequencies (ELFs) Voice frequency 300 - 3000Hz 106 – 105 m Normal range of human speech (VF) Very low 3–30 kHz 105 – 104 m Higher end of the human hearing (15- frequencies (VLFs) 20kHz), musical instruments, government and military communications Low frequencies 30–300 kHz 104 – 103 m Aeronautical and marine navigation (LFs) Medium 300 kHz–3 MHz 103 – 102 m AM radio broadcasting frequencies (MFs) High frequencies 3–30 MHz 102 – 101 m Amateur radio and CB communication (HFs) Ultrahigh 300 MHz–3 1 – 10-1 m UHF TV channels, land mobile frequencies (UHFs) GHz communication, cellular phone Microwave and 3GHz – 30GHz 10-1 – 10-2 m Microwave oven, satellite Superhigh communication, radar, WLAN frequencies (SHF) Extremely high 30GHz – 10-2 – 10-3 m Satellite communication, telephony, frequency (EHF) 300GHz computer data, short-haul cellular network, specialized radar 01 Handout 1 *Property of STI Page 3 of 4  IT1718 Bandwidth (BW)  Portion of electromagnetic spectrum occupied by a signal.  Determines the maximum speed of data pulses the medium can handle  Expressed in Hertz (Hz)  Is given as: 𝑩𝑾 = 𝒇 𝑈 – 𝒇 𝐿 where: f U = upper limit frequency f L = lower limit frequency Gain, Attenuation and Decibels  Gain (A) is the amplification of a signal.  Attenuation (A) refers to the loss of power of a signal.  Gain or Attenuation are both the ratio of the output to the input of a circuit or antenna. output  Given as: 𝑨 = input  For cascaded circuits, the total gain or attenuation (AT) is the product of all gain and attenuation factors. AT = (A 1 )(A2 )(A3 )…(A n )  Gain and Attenuation are unitless or in Decibels (dB)  Decibels (dB) is a unit of measurement of the human hearing response.  Formulas to convert a unitless gain or attenuation to decibels are: 𝑽out 𝒅𝑩 = 20𝑙𝑜𝑔 voltage gain or attenuation. 𝑽in 𝑰out 𝒅𝑩 = 20𝑙𝑜𝑔 current gain or attenuation 𝑰in 𝑷out 𝒅𝑩 = 10𝑙𝑜𝑔 power gain or attenuation 𝑷in Metric Unit Guide Prefix Symbol Multiplier Tera T 1012 Giga G 109 Mega M 106 Kilo k 103 Milli m 10-3 Micro μ 10-6 Nano n 10-9 Pico p 10-12 NOTE: Use the table above as guide for the units that will be used for the rest of the subject. References: Beasley, J. & Miller, G. (2014). Modern electronic communication, ninth edition. London: Pearson Education Limited Frenzel, L. (2016). Principles of communication systems. New York: McGraw-Hill Education Madhow, U. (2014). Introduction to communication systems. California: University of California, Santa Barbara 01 Handout 1 *Property of STI Page 4 of 4