Transcript Wireless communication

Wireless
communication
Emmanuel Gyebison
Transmission
 Signals must be converted into digital values, using a
circuit called ADC (Analog to Digital Converter), before
they can be manipulated by digital equipment.
 Whenever we need the analog signal back, the
opposite conversion is needed , which is done by a
circuit called Digital to Analog Converter(DAC).
ADC
 The ADC circuit takes samples from the analog signal
from time to time, this is called sample rate. Each
sample will be converted into a number, based on its
voltage level.
DAC
 During the digital to analog conversion, the numbers
will be converted again into voltages.
 An algorithm is used to fill in spaces between points.
Noise and Signal-to-noise
ratio(SNR)
 Noise is unwanted additions to signals.
 Noise is created by a number of things such as electronics,
vibrations, and electromagnetic interference.
 SNR is the level of desired single to the level of background
noise.
 Under certain SNR, we can do coding and advanced
modulation.
 Under certain environments, SNR can be increased, by
increasing the transmitting power.
BER
 Bit error rate(BER) is the number of received bits of bit
errors divided by the total number of transferred bits
during a studied time.
 To lower the BER different coding schemes are used
such as repeated code.
 Repeated code is when you send the same code
multiple times.
Modulating
 Modulation is the process of varying one or more
properties of a periodic waveform, this is done with a
carrier signal.
 A carrier signal is usually at a higher frequency than the
signal with the information. After the signal has been
modulated the carrier signal contains the original
signal.
Demodulation
 Demodulation is the act of extracting the original
information from the modulated carrier wave.
USRP Board
 The Universal Software Radio Peripheral (USRP),
uses a daughterboard and a motherboard
 a daughterboard, is used for analog operations
such as up/down-conversion, filtering, and other
signal conditioning.
 A motherboard provides the following : clock
generation and synchronization, FPGA, ADCs,
DACs, host processor interface, and power
regulation.
Using usrp and FFT
 With a code that was provided to me, I was able to get
a fast Fourier transform(FFT) graph of the Wi-Fi in this
building and of my home.
 The federal communication commission (FCC) can use
this process to monitor frequencies, because there is a
designated broadcasting frequency, so the FCC can
see if someone is broadcasting out of the designated
frequency.