Wireless Communication: Antenna and Access Techniques

This assignment delves into the realm of wireless communication, focusing on antennas and multiple access techniques. The first section categorizes antennas into directional (Yagi and horn antennas), semi-directional, and omni-directional (cellular antennas), discussing their strengths, weaknesses, and applications. The assignment highlights the Yagi antenna's high gain and directivity, the horn antenna's high-frequency capabilities, and the cellular antenna's omni-directional nature. The second section examines multiple access protocols, including CDMA and FDMA, explaining how these techniques enable multiple users to share communication channels. It contrasts CDMA, which uses unique codes for signal identification, with FDMA, which divides the channel by frequency. The assignment underscores the importance of these techniques in optimizing bandwidth and avoiding interference in wireless communication.

Running head: ASSIGNMENT
Assignment
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[Professor’s Name Here]
[Date Here]

ASSIGNMENT 2
Question 1
Type of antennas
Antennas: these are devices that propagate electromagnetic signals to or from electronic
circuits using either conducting wires or conducting apertures. These devices are usually at
the forefront of signal reception or end point of signal transmission. Furthermore, based on
their design structure and propagation pattern, antennas are usually classified into three major
categories; directional antennas, semi-directional antennas and Omni-directional antennas.
Now, directional antennas usually propagate signals in one specific direction which improves
their gain and directivity properties. Example Yagi Uda (Yagi) and Horn antenna. Semi-
directional antennas, on the other hand, have their transmissions restricted in certain
directions. Examples; patch and panel antennas. Finally, Omni-directional antennas that
propagate signals in all directions. Example cellular antennas (MIT, 2004).
a. Yagi antenna – serving either as a directional or semi-directional antenna, Yagi
antenna is one of the most common antenna used in the market having the ability to
propagate RF waves in specific direction facilitated by high gains. Applications;
Televisions set receivers.
Strengths
 High gains that facilitate long distance transmission.
 Good directivity because of the design that focuses signals in one specific
direction having a high gain.
 Simple to design and install, as they are made of simple metallic rods (radio-
electronics, 2017).

ASSIGNMENT 3
Weaknesses
 The gain is limited to 20dB.
b. Horn antenna – another good example of directional antennas but with higher gains
and directivity levels. Due to these attributes, horn antennas are used to propagate
electromagnetic signals with high frequencies i.e. UHF (Ultra-high frequencies
ranging from 300MHz to 3 GHz). In addition to this, horn antennas are designed with
a horn like structure where a significant aperture flares out at the end of the device.
Application, transmission of microwaves signals.
Strengths
 Horn antennas are designed with the attributes of gain and directivity in mind.
This outcome is facilitated by their aperture structure that improves their gains
tremendously.
 Secondly, horn antennas can operate with a wide range of frequencies and
bandwidth.
Weaknesses
 Requires extended lengths to operate effectively.
 Complex to design and install (Rouse, 2017).
c. Cellular antenna – the only Omni-directional antennas considered in this case, thus
has the ability to propagate RF signals in all directions. However, this ability limits its
gains and directivity outcomes (Carr, 2012). Nevertheless, it’s convenient for mobile
devices thus is used in portable gadgets such as phones, tablets and even vehicles.
Strengths

ASSIGNMENT 4
 For their size and design structure, cellular antennas have optimal boosting
capability.
 Secondly, they are able to operate in all directions.
Weaknesses
 Cellular antennas have minimal gains.
 Moreover, they have a short coverage distance.
Future prospect for medium and long-distance application
In this context (coverage distance) directional and sometimes semi-directional antennas
are the best for the job as they focus the signal being transmitted (received) to the
appropriate destination (source). Therefore, the future of wireless technology will rely on
the same devices to accomplish the goal of transmitting RF signals across medium sized
distances and beyond. However, these antennas maybe modified to fit the need for smart
systems where the structure and design of Omni-directional antennas maybe incorporated
(Carr, 2012).
Question 2
Multiple access protocols/techniques
Multiple access techniques provide the users with the ability to use common
communication channels to transmit their signals. These techniques help to optimise the
available bandwidth which helps in resources allocations. Therefore, regardless of the
technique adopted (CDMA or FDMA), the objective is always the same, that of sharing a
common radio spectrum (corps, 2000). Furthermore, the same technique will enable
users to share the capacity of communication channels while operating in different
locations. In addition to this, the operational structure of the said techniques is always

ASSIGNMENT 5
designed to avoid interferences, an outcome that designates the mode of transmission
used.
Type 1: CDMA (Code division multiple access) – In this technique, unique pseudo codes
are used to share the communication channel among the signals or users involved. In
terms of operation, these codes are used as unique identifiers for the signals found in the
communication channel, thus they act as identification tags. Now, these tags are usually
attached at the onset of communication before, the signals are propagated into the channel
being used. At the reception stage, the tags (codes) are again used to separate the signals
thus transforming the signals into unique components as initially transmitted. A good
example of this technique is the IS-95 standard, a CDMA standard that uses 64 Walsh
code to transmits multiple signals under a common channel (corps, 2000).
Type2: FDMA (Frequency division multiple access) – as the name suggests, FDMA uses
an array of frequency channels to transmit multiple signals on a common channel. Now,
to start the transmission process, the frequency channels chosen must be unique i.e. non-
overlapping to avoid signal interference either during transmission or at the reception
stage. However, unlike the codes of the CDMA, the reception can fail to know the
frequencies being used as the channel is usually segmented by the frequency channels
chosen. Example; the technique is used in GSM communication where a 25MHz
frequency channel is usually divided into 124 carrier sections.
CDMA FDMA
The frequency is common throughout the
transmission process irrespective of the
signals considered.
The communication channel is split into
different sections based on the frequency.

ASSIGNMENT 6
Users/signals are uniquely identified by
pseudo-codes.
There are no unique identifiers used to
signify the user/signals as unique channel
segments are used.
For effective communication, the
receivers must know the codes of the
transmitting devices.
This attribute is not necessary for FDMA.
For every signal transmitted, the receivers
will only detect the necessary code while
identifying the rest as noise
Reception of signals is based on the
frequency channels chosen.
- FDMA will use filtering to eliminate
interferences e.g. noise
The overall concept is based on unique
identification codes.
A narrow range of frequency band is used.
(Zahra, 2015)
References

ASSIGNMENT 7
Carr, J. (2012). Directional or Omnidirectional antenna? Joe Carr's Radio Tech-notes,
Retrieved 14 August, 2017, from: http://www.dxing.com/tnotes/tnote01.pdf.
corps, W. (2000). FDMA vs. TDMA vs. CDMA. Connecting Wireless, Retrieved 14 August,
2017, from: http://wirelessapplications.com/pdf/lf/FD_TD_CDMA.pdf.
MIT. (2004). Chapter 3: Antennas. MIT, Retrieved 17 August, 2017, from:
https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-661-
receivers-antennas-and-signals-spring-2003/readings/ch3new.pdf.
radio-electronics. (2017). Yagi Antenna / Yagi-Uda Antenna. Antennas and propagation,
Retrieved 14 August, 2017, from:
http://www.radio-electronics.com/info/antennas/yagi/yagi.php.
Rouse, M. (2017). Horn antenna. Research gate, Retrieved 17 August, 2017, from:
http://searchmobilecomputing.techtarget.com/definition/horn-antenna.
Zahra. (2015). FDMA-TDMA-CDMA. Multiple access techniques in wireless
communication, Retrieved 16 August, 2017, from:
https://www.slideshare.net/SammarKhan2/fdmatdmacdma.