Wireless Networking: Spread Spectrum Transmission, Radio System Components, and Mixer Types

This article discusses the need for spread spectrum transmission and the types of spread spectrum transmission. It also covers the components of radio system and the types of mixer. The article provides a detailed explanation of Direct-Sequence Spread Spectrum, Chirp-Spread Spectrum, and Frequency-Hopping Spread Spectrum. It also explains the elements of radio transmitter and radio receiver. The article concludes with a definition of mixer and its types.

Running head: WIRELESS NETWORKING
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Name of Student-
Name of University-
Author’s Note-

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Question 1
Signals that are wireless conventional generally has some frequency, that are specified by
megahertz and by gigahertz. These frequencies do not change with respect to time. The digits of
radio frequency remain same all the time (Chen & Hashemi, 2014). The frequency is always kept
same at all the time in a signal, which is conventional wireless. As a result of this, the bandwidth
of the signal are kept in a certain limit and therefore, the signals can be located easily by some
other person who want to intrude the signal and retrieve all the data on that network.
Need for spread spectrum transmission
With the conventional wireless communication, there are certain problems that arise with
the frequency of bandwidths. The signal that has a constant frequency is automatically subjected
to some catastrophic interference. This catastrophic interference occurs when another signal of
almost similar frequency is transmitted very near to the transmitted signal (Cai, 2015). The
catastrophic interference that occurs can be of two types- deliberate catastrophic or an accidental
catastrophic interference. Second most problem that arise with constant frequency is those
signals can be easily intercepted and so, constant signals are not at all appropriate for
applications that are to keep confidential data in between the transmitting party (source) or the
receiving party (destination).
So, to overcome these problem that arise from conventional constant frequencies, spread
spectrum transmission is used. The signals that are transmitted over the network are varied so
that there is no change of catastrophic interference or intercepted signals. The transmission is

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basically varied over a large segment of spectrum that has electromagnetic radiation. There are
specific mathematical functions for varying the signals of spectrum that are transmitted.
Types of spread spectrum transmission
There are commonly three types of spread spectrum transmission- Direct-Sequence
Spread Spectrum, Chirp-Spread Spectrum, and Frequency-Hopping Spread Spectrum.
Direct-Sequence Spread Spectrum- The most common type of spread spectrum that is
used widely is the Direct-Sequence Spread Spectrum. By multiplying radio frequency carrier and
pseudo noise, the process of Direct-Sequence is acheived. There is binary code known as the PN-
Code that is produced at very high frequency compared to the data that is sent for transmission.
Since, there is a high frequency, the signal is followed by large bandwidth. The data that is send
through Direct-Sequence Spread Spectrum transmission is multiplied with some noise that is
known as pseudorandom code (Edwards & Steer, 2016). The PN-Code is basically modulated on
information signal. The pseudorandom code that is generated in noise consists of number ranging
from 1 and -1. Higher frequency of signals can be achieved on multiplying the PN-Code with the
original data leading to spreading of energy.
Chirp-Spread Spectrum- The Chirp-Spread Spectrum is usually a technique that includes
using the linear frequency chirp pulse that are modulated for encoding the information. A chirp
can be technically defined as sinusoidal signal in which the frequency of the signal decreases or
increases over a span of time. The complete bandwidth that is allocated to the Chirp-Spread
Spectrum is used for the transmission of signal and makes the signal a stringer one against any
kind of interference or signals (Koda et al., 2016). The signal of data that is transmitted, spreads
over wide range of frequency band through Chirp-Spread data spectrum transmission. The

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transmission of Chirp-Spread Spectrum is resistant to the multi-path fading. Pseudo-random
codes are not used in this type of transmission. This spectrum transmission depends on the chirp
nature pulse that is considered to be a linear one. The Doppler Effect is also protected by this
transmission method. CSS techniques are used recently for the purpose of wireless
communication so that there does not exist any type of jamming or any interference in the signal.
Frequency-Hopping Spread Spectrum- In Frequency-Hopping Spread Spectrum
transmission, a transmitter is generally hopped in between the frequencies that are available. This
is done according to some predefined algorithm or some programs that is created randomly or
was pre-planned. The Transmitter or the receiver are synchronized together with same frequency.
A small part of the data is basically transmitted over a narrowband at some frequency. Therefore,
hopping the frequency is capable over the transmitter over the given bandwidth for multiple
times in a second (Tang & Pan, 2016). This hopping transmits a particular frequency of signal
over a certain time period and then hops to some other frequency and transmits again.
Question 2
Different components used for radio system
There are basically two types of components that are available- a receiver and a
transmitter.
Radio Transmitters- Several elements are present in a radio transmitter that works
together for generating the radio waves containing useful data or information including digital
data, video, or audio (Diemer, Wheeler & Nocera, 2014). The elements of radio transmitter are:

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 Power Supply: Power provides the system with necessary electricity so that the
transmitter can operate on the signals.
 Oscillator: The oscillator creates current alternatively at some frequency by which the
transmitter will transmit the signal (SMITH et al., 2017). Sine waves are basically
generated that are referred to as the carrier wave.
 Amplifier: The amplifier helps in modulating the carrier wave so that the power of the
transmitter increases. Increasing the strength of the amplifier, the broadcasting power of
the signal becomes strong.
 Modulator: Modulator generally adds information to carrier wave. Modulator follows
two ways of adding information (Manugian, Van Bonn & Harvey, 2015). First is the
amplitude modulation that decreases or increases the intensity of carrier wave, and
second is the frequency modulation that decreases or increases the frequency of the
carrier wave.
 Antenna: The antenna finally amplifies the original signal to the radio wave.
Figure 1: Elements of Radio Transmitter

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Radio Receivers- Radio Receiver works opposite to that of the radio transmitter. An
antenna is used to capture the radio waves, those waves are then processes to the desired
frequency of the vibrating signals. The receivers extracts audio signals added to the waves, helps
to amplify the audio signals and then plays the signal on speaker.
 Antenna: Helps in capturing the radio waves (Hoang et al., 2016). The antenna consists
of a wire that are when exposed to the radio waves, a small amount of alternating current
is induced in the antenna by the waves of signals.
 RF amplifier: This is a sensitive amplifier, which generally amplifies the radio
frequency signals that are weak, from the antenna and forwards the signal to tuner for
further processing.
 Tuner: Tuner is a circuit that extracts the signals of some frequency from mixers of
signals that are of different frequencies. All frequencies of a=radio waves are captured by
the antenna and are send to RF amplifier for amplification of the signals.
 Detector: The detector is responsible for separating the information that comes from
carrier wave (Magno et al., 2014). This is generally done by a diode, which helps to
rectify signal of alternating current. This process is followed by amplitude modulation
signals. For frequency modulation signals, the detection is done in a complicated way.
 Audio Amplifier: The audio amplifier helps to amplify all the weak signals coming from
detector. The amplification of the signals are basically done using a simple circuit
consisting of transistor amplifier. This finally transmits the signal on the speaker and
helps in making the signal audible.

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Figure 2: Elements of Radio Receiver
Definition of Mixer
A mixers is basically a component that has three ports and perform the task of converting
the frequency. The functionality of mixer varies for different types of application that includes
the military radar, cellular base stations, satellite communications (SatCom) and many more
applications. Both upconversion of frequency and downconversion of frequency is done by
mixer.
Generally, there are three types of mixer- analog mixer, digital mixer, and powered
mixer.
1) Analog Mixer: The work of analog mixers is to adjust volumes and the tones of all the audio
input signals. The top panel of analog mixers has most of the faders and the knobs for controlling
the signals. The analog mixer that are operating is basically a intuitive process.

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Figure 3: Analog Mixers
2) Digital Mixers: The digital mixer basically takes the audio signals as an input and then
adjusts the volume and the tone of the digital signal with the processing technology (Torrieri,
2015). Different types of tones that are generally not possible by the analog mixers can be done
by digital processing mixers. The position of knobs and faders can be stored by the digital mixer
and the positions can be recalled at any time. Different types of knobs and faders are performed
by the digital mixers to keep the unit compact even increasing the number of channels.
Figure 4: Digital Mixers

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3) Powered Mixers: These types of mixer are basically analog mixer that has built-in power
amplifier (Prince, Sheela & Anjana, 2017). Sounds are directly played with mixers that have
connection with the speaker. Powered mixtures are used where there is a connection of same
equipment to tune the power. With tuning the power, the operation becomes convenient and
simplified.
Figure 5: Powered Mixer

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Question 3:

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References
Cai, W. (2015). 2.4 GHz heterodyne receiver for healthcare application (Doctoral dissertation,
UC Irvine).
Chen, R., & Hashemi, H. (2014). A 0.5-to-3 GHz software-defined radio receiver using discrete-
time RF signal processing. IEEE Journal of Solid-State Circuits, 49(5), 1097-1111.
Diemer, K. M., Wheeler, H. E., & Nocera, J. J. (2014). Retention rates of glue-attached radio-
transmitters on two small bird species with contrasting life histories. The Wilson Journal
of Ornithology, 126(1), 39-46.
Edwards, T. C., & Steer, M. B. (2016). Foundations for microstrip circuit design. John Wiley &
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Hoang, S., Pantellini, F., Harvey, C. C., Lacombe, C., Mangeney, A., Meyer-Vernet, N., ... &
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Koda, J., Barrett, J., Hasegawa, T., Hayashi, M., Shafto, G., Slechta, J., & Metchev, S. (2016). A
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Magno, M., Marinkovic, S., Srbinovski, B., & Popovici, E. M. (2014). Wake-up radio receiver
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