Wireless Network Analysis and Signal Strength Calculations

This homework assignment delves into the core concepts of wireless network analysis, beginning with definitions of signal strength, signal-to-noise ratio (SNR), and effective isotropic radiated power (EIRP). It explores the differences between dBi and dBd antenna gains and provides a sample calculation of SNR. The assignment then examines various wireless network topologies including Independent Basic Service Set (IBSS), Basic Service Set (BSS), and Extended Service Set (ESS). It explains the role of beacon frames and the practice of cloaking access points. Furthermore, it discusses the use of Kismet for detecting hidden wireless networks and methods for improving network performance, such as prioritizing access points. Finally, the assignment concludes with calculations of link loss, received signal power, and system operating margin, as well as an overview of technologies like MIMO and MCS index, and their impact on wireless network performance.

1.
(a)
(i). Signal Strength is the size of an electric field at a central point that is
positioned at a distance far from the radio wire that transmits the signals. In
telecommunication, signal strength is majorly defined to be the power output from the
transmitter that is being received by a reference antenna that is situated at a separation
away from the antenna that is transmitting the signals.
According to Budhrani (2015), Signal to Noise Ratio can be termed to be the
difference between a signal received and the background noise level in decibel form.
Wikipedia also defines SNR to be the ratio of the strength of a signal (can be electrical or
non-electrical signal) to the unwanted interference encountered during the propagation of
the same signal.
Decibel is used because it is a relative expression. Having a +/-3dB means it is a
doubling or halving of power. Moreover, dB is often used since the human sense has a
logarithmic response to increasing the dynamic range.
(ii) Effective Isotropic Radiated Power (EIRP) EIRP is defined to be the power sum
which a hypothetical isotropic radio wire or antenna for that matter would discharge
or transmit so as to create the pinnacle/peak power density realized toward the
direction of most extreme antenna gain.
Difference in Antenna gains specified in dBi and in dBd.
dBi: This is the antenna gain that is defined in relation to an isotropic radiator on
the other hand, dBd is the antenna gain in relation to a dipole antenna.

b)
(i) Signal strength = -46dBm
Noise level = -96dBm
Antenna gain = 5.2dBi
(i) Signal/Noise ratio?
1 dBm = -30 dB
P(dBm) = P(dB) +30
P(Signal) = -46 – 30 dB
P(Noise) = -96 – 30 dB
Signal to noise ratio = Signal Power/Noise Power
(SNR)dB = P(signal) dB – P(Noise) dB
= -76 + 126
= 46 dB
10log10 (SNR) = 46dB
Source: http://ieeexplore.ieee.org/abstract/document/4178493/

(ii) Received power= P(W) = 1W ⋅ 10(P(dBm) / 10) / 1000
= 1 * 10(46dBm/10)/1000
= 19.8107 W
=19.8107/1000
=0.0198107 μW
(iii) Noise level
1Watt = 30 dB
96*30 = 2880 W
= 2.88 nW
2.
(a)
IBSS is the Independent Basic Service Set that allows many devices or more than
two gadgets to send signals directly to each other without needing a central device. This
technique is usually called Ad hoc.
BSS is the Basic Service Set wireless topology that has a single central access
point and several remote or wireless clients. This topology is mainly used for the
connection of wireless clients into a wired network infrastructure.
ESS is the Extended Service Set that is consisting of many Basic Service Set
networks interconnected. It covers a wide area where clients can roam between different
access points.
The diagram below shows the logical design of both the Basic Service Set and the
Independent Basic Service Set topologies.

3.
(a). (i).
Beacon frames are utilized by stations that are in an Independent Basic Service Set
network and also by access points to communicate with all the other nodes in the network.
Basically, beacon frames are used to tell network devices that there is an Access Point that
transmits signals and that they can join the network using the access point.
Beacon frames are utilized for advertising the presence of an access point in a location,
its configurations, and its capabilities to the nearby client devices.
Beacon frames are also used for enabling power saving modes on devices.
In an ad hoc network, it is the stations that transmit the beacon frames.

(ii).
Access points are cloaked by configuring them not to broadcast their SSIDs.
Small businesses that cannot afford strong infrastructure services like 802.1x for
protection of their wireless networks would cloak their access points so that their network SSID
is not visible to the average wardriver or the business next door.
(b)
(i).
Kismet utilizes channel hoping to allow for detection of hidden wireless networks. That
is it listens to one channel, hops to another channel to listen again, and another channel e.t.c.
Kismet is able to detect a response by a client to a beacon frame and then it utilizes this response
by the client to a wireless access point. On Kali Linux or Backtrack, running sudo kismet will
begin a session to auto-detect the network card.
(ii)

Figure 1: Starting Kismet Source: techrepublic.com/

Figure 2: Sorting the channel list Source: techrepublic.com
(iii). On the station, you will have to go to advanced system preferences and then move
the wanted Access point to the top of the list. This will allow the station to associate with the
most wanted access point even when other stronger access points are within the range.
4.
(a)

(i)
Link loss(dB) = Antenna Gain at receiver + antenna gain at sender – Cable loss
= 24+24 -14
= 34dB
(ii)
Received signal power = Transmitted Power (dB) + Gains (dB) − Losses (dB)
= 54dBm
(iii)The estimated system operating margin is -66.2 dB when the operating frequency is
2400MH
(iv) Cisco 1300 bridges provide link speed of 54 Mbps
(iv)The link reliability is 20.00dBm
Source: https://link.springer.com/article/10.1023/A:1022821110023
(b)
(i). Multiple antennas increase the signal range since by utilizing beamforming, they
improve the strength of signals towards the target. This way, the signal to noise ratio is strong
enough to send and receive data at longer distances.
(ii). Multiple spatial streams increase speed since every path will carry unique data.
When you have a 3 by 3 system, it will thus use stream (3*3:1), streams(3*3:2), or
streams(3*3:3). This way every stream will add just as much bandwidth.

Higher speeds of wireless N and AC are only achieved by utilizing the 40 MHz wide
channels. The default channel width of 20MHz thus needs to be changed on the control panel to
auto 20/40MHz.
The Short guard interval intends to prevent signal loss from multipath effect since, in
wireless transmissions, radio frequency signal gets to the receiving antenna via two or more than
two paths. The avoidance of signal degradation by having short guard intervals thus increases the
wireless transmission speeds.
(iii).The MCS index for 3*3 MIMO system is 16. Its modulation technique is BPSK and
its link speed is 40 Mbps according to the MCS table.
References
Abbasi, M. A. (2011). Interoperability of wireless communication technologies in hybrid
networks: Evaluation of end-to-end interoperability issues and quality of service
requirements (Doctoral dissertation, Brunel University, School of Information Systems,
Computing and Mathematics). From: http://core.ac.uk/d337962.pdf
Budhrani, R., & Sridaran, R. (2015). Wireless Local Area Networks: Threats and Their
Discovery Using WLANs Scanning Tools. International Journal Of Advanced
Networking & Applications, 137-150. From:
https://www.researchgate.net/profile/R_Sridaran/publication/273776388_Wireless_Local
_Area_Networks_Threats_and_Their_Discovery_Using_WLANs_Scanning_Tools/
links/550d4e650cf27526109854c3/Wireless-Local-Area-Networks-Threats-and-Their-
Discovery-Using-WLANs-Scanning-Tools.pdf

Woo, A., & Culler, D. E. (2003). Evaluation of efficient link reliability estimators for low-power
wireless networks (pp. 1-20). Oakland, Calif, USA: Computer Science Division,
University of California. From: http://nma.berkeley.edu/ark:/28722/bk0005s493p