CS 590/490 Wireless Networks Baseband Transmissions (1) A type of signal transmissions in which signals are directly inserted onto a signal transmission medium Transmission Medium Sender Receiver Transmission Data Digital Signals 1 1 Signals all same shape Wireless_01/001

CS 590/490 Wireless Networks Baseband Transmissions (1) A type of signal transmissions in which signals are directly inserted onto a signal transmission medium Sender Receiver Transmission Analog Signals Transmission Medium Signals all same shape Fundamentals/002

CS 590/490 Wireless Networks Baseband Transmissions (2) A type of signal transmissions in which signals are directly inserted onto a signal transmission medium (the shape of the signals are same at the sender, in the transmission medium and even at the receiver) A type of signal transmissions that can transmit a signal from single sender at a time Host A Host B Host C (Transmission Medium) Fundamentals/003

CS 590/490 Wireless Networks Baseband Transmissions (2) A type of signal transmissions in which signals are directly inserted onto a signal transmission medium (the shape of the signals are same at the sender, in the transmission medium and even at the receiver) A type of signal transmissions that can transmit a signal from single sender at a time 1 (Signals merged) (Transmission Medium) Host A Host B Host C 1 The receiver receives “01010101”, but can’t tell who sent which signals 1 Fundamentals/004

CS 590/490 Wireless Networks + Baseband Transmissions (2) A type of signal transmissions in which signals are directly inserted onto a signal transmission medium (the shape of the signals are same at the sender, in the transmission medium and even at the receiver) A type of signal transmissions that can transmit a signal from single sender at a time Host A (Signals merged) Host C + Host B The receiver will receive merged analog signals, which will sound like gibberish (Transmission Medium) Fundamentals/005

CS 590/490 Wireless Networks Baseband Transmissions (3) Two major problems in baseband transmissions  Only one signal transmitter at a time  Can’t achieve (high-speed)  (long distance) transmission Fundamentals/006

CS 590/490 Wireless Networks Baseband Transmissions (3) Two major problems in baseband transmissions  Only one signal transmitter at a time Wired networks = “transmission medium” is “cable” What if we need to support multiple simultaneous communication using the baseband transmission? A B C D E F G Cable A-F Cable B-C Install more cables! Cable E-F Cable A-D (not efficient, but it would work) Cable B-G Fundamentals/007

CS 590/490 Wireless Networks Baseband Transmissions (3) Two major problems in baseband transmissions  Only one signal transmitter at a time Wireless networks = “transmission medium” is “open air” If we have to use the baseband transmission, only one user can use the cell phone at a time We can’t install another transmission medium for this cell. Your cell phone company may have To build a tower for each active customer Fundamentals/008

CS 590/490 Wireless Networks ? Baseband Transmissions (3) We sacrifice long-distance signal transmissions Two major problems in baseband transmissions  Can’t achieve (high-speed)  (long distance) transmission Input (Sender) Output (Receiver) Transmission Shorter Cable Length skew & distortion Digital Signals ? Transmission Medium Cable Length Fundamentals/009

Time for one signal cycle CS 590/490 Wireless Networks Baseband Transmissions (3) We sacrifice Signal frequency (transmission speed) Two major problems in baseband transmissions  Can’t achieve (high-speed)  (long distance) transmission 1 skew & distortion ? Transmission Medium 1 The minimum signal pattern possible Time for one signal cycle = signal cycle time Signal cycle 2 # of signal cycles in one second Signal frequency (in Hz) Fundamentals/010

Baseband Transmissions (4) Summary of baseband transmissions

CS 590/490 Wireless Networks Broadband Transmissions (1) A type of signal transmissions in which signals are first modulated onto “carrier signals” and then modulated signals are inserted onto a signal transmission medium Data 1 Digital Signals Modulator Carrier Signal Carrier Signal De Modulator Modulated Signals Modulated Signals Transmission Medium Fundamentals/012

CS 590/490 Wireless Networks Broadband Transmissions (2) Carrier signal = sin curve analog signal defined by three parameters  A (Amplitude) Time +v -v Amplitude (volt or power) t  F (Frequency) = 1 second / t Fundamentals/013

CS 590/490 Wireless Networks Broadband Transmissions (2) Carrier signal = sin curve analog signal defined by three parameters 0 90 180 270 +v t/4 2t/4 3t/4 Amplitude (volt or power)  P (Phase) in degree (0  P  360 ) Time t -v Fundamentals/014

CS 590/490 Wireless Networks Broadband Transmissions (3) Why “carrier signal”?  Sin carrier signals are known to have no skew or distortion on the signal-shape (even for long distance transmission)  Each sin carrier signal has a specific frequency and two carriers with different frequency can be separated at a receiver Fundamentals/015

CS 590/490 Wireless Networks Broadband Transmissions (3) Why “carrier signal”?  Sin carrier signals are known to have no skew even for long distance transmission Input (Sender) Output (Receiver) Transmission Carrier signals with a specific frequency If there is no “noise” Distance =  P F A = decrease The only limiting factor for transmission distance = Transmission Power (W) = not affected = not affected Fundamentals/016

CS 590/490 Wireless Networks Broadband Transmissions (3) No “phase”, not “amplitude but “frequency” Why “carrier signal”?  Each sin carrier signal has a specific frequency and two carriers with different frequency can be separated at a receiver Senders Receivers 1 FDM De-Multiplexer FDM Multiplexer Transmission Medium 2 1  2 Fundamentals/017

CS 590/490 Wireless Networks Broadband Transmissions (4) Called “modulation” Why “carrier signal”? Sin analog carrier signal itself does not have any meaning We override our payload signals on top of the carrier signal Senders Receivers payload signals payload signals FDM Multiplexer De-Multiplexer Tx Medium carrier carrier modulated carrier DeModulator Modulator modulated carrier carrier payload signals Fundamentals/018

Host A Host C Host B Computer D Computer B Computer F Computer A Computer E Computer G Computer C