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

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

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 (Transmission Medium) CS 590/490 Wireless Networks Fundamentals/003 Host A Host B Host C

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 (Signals merged) The receiver receives “ ”, but can’t tell who sent which signals CS 590/490 Wireless Networks Fundamentals/004 (Transmission Medium) Host A Host B Host C

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 (Transmission Medium) The receiver will receive merged analog signals, which will sound like gibberish + CS 590/490 Wireless Networks Fundamentals/005 Baseband Transmissions (2) Host A Host B Host C (Signals merged)

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

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

Two major problems in baseband transmissions  Only one signal transmitter at a time CS 590/490 Wireless Networks Fundamentals/008 Baseband Transmissions (3) 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 Wireless networks = “transmission medium” is “open air”

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

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

Baseband Transmissions (4) Summary of baseband transmissions: CS 590/490 Wireless Networks Fundamentals/011 A type of signal transmissions in which signals are directly inserted onto the transmission medium A type of signal transmissions that can transmit a signal from single sender at a time Two major problems in baseband transmissions  Since only one sender at a time, it is not an efficient for wireless signal transmissions  Can’t achieve (high-speed)  (long distance) transmission Wired signal transmissions Either:(a) high-speed short distance transmissions (b) low-speed long distance transmissions Baseband signals are susceptible to signal skews and distortions during during transmission (i.e. during propagation in the transmission medium Cost-effective and high-speed since no additional hardware and processing is required

Baseband Transmissions (4) CS 590/490 Wireless Networks  Since only one sender at a time, it is not an efficient for wireless signal transmissions  Can’t achieve (high-speed)  (long distance) transmission Wired signal transmissions Either:(a) high-speed short distance transmissions (b) low-speed long distance transmissions PC Motherboard Memory Modules Memory Bus Processor Graphic subsystem Internal Bus High-speed Short-distance Baseband transmissions Fundamentals/012

Baseband Transmissions (4) CS 590/490 Wireless Networks  Since only one sender at a time, it is not an efficient for wireless signal transmissions  Can’t achieve (high-speed)  (long distance) transmission Wired signal transmissions Either:(a) high-speed short distance transmissions (b) low-speed long distance transmissions PC Motherboard Memory Modules Memory Bus Processor Graphic subsystem Internal Bus keyboard Mouse Printer Slower I/O devices Low-speed Long-distance Baseband transmissions High-speed Short-distance Baseband transmissions Fundamentals/013

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 Digital Signals Modulator Modulated Signals Modulated Signals De Modulator Transmission Medium Carrier Signal CS 590/490 Wireless Networks Fundamentals/014 Broadband Transmissions (1) Data

Carrier signal= sin curve analog signal defined by three parameters Time 0 +v -v Amplitude (volt or power) t  A (Amplitude)  F (Frequency) = 1 second / t CS 590/490 Wireless Networks Fundamentals/015 Broadband Transmissions (2)

Carrier signal= sin curve analog signal defined by three parameters Time 0 +v -v Amplitude (volt or power) t t/4 2t/43t/4 CS 590/490 Wireless Networks Fundamentals/016 Broadband Transmissions (2) 90  00 180  270   P (Phase) in degree (0   P  360  )

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 Broadband Transmissions (3) CS 590/490 Wireless Networks Fundamentals/017

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 Distance =  = not affected = decrease P F A The only limiting factor for transmission distance = Transmission Power (W) If there is no “noise” Broadband Transmissions (3) CS 590/490 Wireless Networks Fundamentals/018

Why “carrier signal”?  Each sin carrier signal has a specific frequency and two carriers with different frequency can be separated at a receiver Transmission Medium Senders FDM Multiplexer FDM De-Multiplexer Receivers Broadband Transmissions (3) CS 590/490 Wireless Networks Fundamentals/019 No “phase”, not “amplitude but “frequency” 11 22 1  21  2

modulated carrier Why “carrier signal”? Sin analog carrier signal itself does not have any meaning Senders Receivers We override our payload signals on top of the carrier signal Called “modulation” FDM Multiplexer FDM De-Multiplexer Tx Medium carrier modulated carrier payload signals payload signals payload signals payload signals Modulator DeModulator Broadband Transmissions (4) CS 590/490 Wireless Networks Fundamentals/020