Wireless Digital Communications Assignment: Standards and Technologies

This assignment solution delves into the core concepts of wireless digital communications. It begins by comparing and contrasting the physical layers of the 802.11a and 802.11b standards, highlighting their differences in frequency bands, data rates, and modulation techniques. The solution then explains how the 802.11i standard facilitates client authentication, ensuring secure connections to wireless networks. Furthermore, it explores the use of Virtual Private Networks (VPNs) for establishing secure communication channels over public networks. The assignment also examines WMAN technologies, specifically WiMAX and Wi-Fi, and their suitability for business applications like ZeeTech. Finally, the solution analyzes Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Global System for Mobile Communications (GSM) technologies, comparing their strengths and weaknesses in the context of wireless communication systems.

Running head: WIRELESS DIGITAL COMMUNICATIONS 1
Question 1
The 802.11 standard
802.11 refers to a wireless technology specification created by Institute of Electrical and
Electronics Engineers (IEEE) involving two network layers including media access control
and physical layer. 802.11 is used for executing wireless communication networks in the
frequency bands including 900 MHz, 2.4, 3.6, 5, and 60 GHz (IEEE, 2017). Some of the most
widely used 802.11 standards include 802.11b and 802.11a. Below is a comparison of their
physical layers.
Comparison and contrast of physical layers for 802.11b and 802.11a standards
i) The 802.11 a physical Layer
The physical layer of 802.11a identifies the receiving and transmission frames belonging to
this standard. The 802.11a technology physical layer uses Orthogonal Frequency Division
Multiplexing (OFDM) technique to be able to sustain and maintain the operation of
approximately 50Mbps data transfer rates in 5GHz frequency band. The 802.11a physical
layer uses convergence procedure (PLCP) to transform 802.11 frames to be broadcasted into
a protocol data unit (PPDU) which has several fields such as PLCP preamble, rate, parity,
reserved length, tail, service, physical layer service data unit (PSDU) and pad bits. OFDM
distributes data signals transversely into 48 different channels inside a 20MHz channel to
offer broadcasts of between 6Mbps to 54Mbps. Under transmission, the 802.11a decodes data
signals into analog formats with frequencies equivalent to channels selected by users.
ii) The 802.11b physical Layer

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The physical layer of the 802.11b technology utilizes Direct Sequence Spread Spectrum
technique developed in the 2.4GHz frequency band in order to facilitate over 10 Mbps
transmission data rates. Its physical layer contains both Physical Media Dependency (PMD)
and Physical Layer Convergence Procedures (PLCP) layers. Physical Layer Convergence
Procedure prepares for the transmission of 802.11 frames and guides the physical medium to
transmit, change and receive data signals. Like 802.11 a, the PLCP in 802.11b takes
every802.11 data frames from the source device and forms a protocol data unit (PPDU) with
fields including service, sync, length, Start Frame Delimiter, Frame Check Sequence, signal
and Physical Layer Service Data Unit. Table 1 below shows a summary of their physical
layer similarities and differences.
802.11 a 802. 11b
Transmit data at 5 GHz frequency Transmit data at 2.4 GHz frequency
Can transmit over 50 Mbps of data Can transmit about 10 Mbps of data
Physical layer uses OFDM (Orthogonal
Frequency Division Multiplexing
modulation procedure
Physical uses direct sequence spread
spectrum modulation procedure
PPDU fields include Preamble, rate, parity,
reserved length, tail, service, Physical Layer
Service Data Unit (PSDU) and pad bits
PPDU fields include fields sync, Start
Frame Delimiter, signal, service, length,
Frame Check Sequence and Physical Layer
Service Data Unit
Table 1: Comparative study between 802.11a and 802.11b physical layers
Question 2

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a) How 802.11i allows for a client device to be authenticated against an
authentication server
802.11i is a wireless communication standard for local area network LANs). It
facilitates enhanced encryption for computer systems that use standards such as
802.11b, 802.11a, and 802.11g. The 802.11i technique requires strong
encryption protocols including innovative encryption algorithms such as AES and
Sequential key integrity protocols such as TKIP (Rouse M. , 802.11i, 2006). Client
authentication process starts when a client machine tries to connect to a wireless local
area network through a proxy machine. The authenticating device accepts the
invitation and generates a virtual connection with the client and the server machine
(Burns, 2003). The authentication server then tasks the client machine to verify itself
and sends its identifications to identify itself to the client which checks the server
details and also verify itself to the server. The 802.11i standard ensures that
authentication for the client machine is checked in a 4-way handshake before a
connection occurs between server and the client device. When the client machine is
acknowledged by the server, the proxy changes the virtual connection to an actual
port with the client changing the connection status to an approved state which allows
full network access.
b) Using virtual private network(VPN) to establish encrypted secure
communications channel between two points on a public network
A Virtual Private Network (VPN) is a dedicated link to link network across a public
connection (Microsoft, 2017). A virtual private network (VPN) spreads over
an isolated network over an open network, and facilitates data transmission for users
across the Internet as if the dedicated devices were connected directly to a reserved
network. It therefore manages the capability, management and security of a private
network over a public network. To achieve encrypted secure communications

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channels between two devices in a public network, a virtual private network client
uses tunneling protocols including Point to Point Tunneling Protocols, Secure Socket
Layers(SSL), Layer2 Tunneling protocols (L2TP) and IP security to ensure security
(Tarantola, 2013). Participating devices have a virtual dedicated point to point
connection between them. In a VPN network, a client device normally initiates a
virtual connection to a remote server via the Internet (Microsoft, 2017). The server
responds, authenticates the client, and transmits data between the VPN client and the
network.
Question 3
WMAN Technologies
A Wireless Metropolitan Area Network (WMAN) is a wireless technology based on 802.16
standard. WMAN are capable of extending data with transfer speeds of up to 10 Mbps
within distances of up to 10kms. WMAN are thus primarily used by for communications
corporations. Popular WMAX technologies include WiMax and Wi Fi. Table 1 summarizes
some differences between the WiMAX and Wi-Fi.
WiMAX Wi-Fi
Large network coverage Limited network coverage
Designed specifically for Metropolitan Area
Networks(MANs)
Designed to work with Local Area
Networks (LANs)
WiMAX offer high speed internet as a
broadband access which transfer data, voice,
video at very high speed
Offers short range of data transfer because
Wi-Fi can connect only in specified areas so
only file sharing may possible.
Table 2: WMAN technologies
WiMAX Technology for ZeeTech

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WiMAX technology will work very effectively for ZeeTech WiMAX offers high- speed
internet broadband access which transmits voice, data, and video at very high speeds (High-
tech, 2017). This will ensure that all data transmission for the company will function
smoothly. ZeeTech is therefore assured of efficient data transmission services. WiMAX
technology can reach speeds of up to 70 Mbps over a radius of many kilometer and supports
point to point or point to multipoint network connections. This will enable ZeeTech make
connections to the many distributed branches and offices. Since WiMAX is a wireless
technology, network installation is easy and implementation does not require a lot of
infrastructure compared to Wi-Fi and LANs. In terms of security, WiMAX uses triple DES
and AES which are secure data encryption algorithms. Company data will therefore be secure
on transmission over the Internet.
Question 4
Time Division Multiple Access (TDMA)
Time Division Multiple Access (TDMA) is a wireless communication system. TDMA
provides channel sharing minus signal interfering. TDMA allows many channel devices to
make use one bandwidth channel by allocating users separate time slots during transmission
(Techopedia, 2017). Channels users transfer data rapidly each one using its allotted time slot.
Strengths of TDMA
i) No channel interference from multiple transfers since TDMA separates users into
different time slots
ii) It is cheaper to convert analog to digital signals using TDMA technology
iii) TDMA is adaptable to both data and voice transmissions
Disadvantages of TDMA

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i) Users have access to preplanned transmission time slots in TDMA which could
result to disconnection in case of channel movement
ii) TDMA technology can result to multi-path signal distortion.
Code Division Multiple Access (CDMA)
CDMA is a wireless communication technique that makes use of spread- spectrum
procedures. Unlike TDMA, CDMA uses the entire channel bandwidth and hence does not
apportion frequency slots for users. Instead, each channel uses the entire channel spectrum
(Rouse, 2015). As a result, CDMA provides better capability for both data and voice
communications facilitating more users to make connections any time.
Strengths of CDMA
i) CDMA has high channel capacity and can accommodate multiple per frequency per
band
ii) Failure only occurs when device is far away from the base station and can therefore
be used in areas where GSM cannot be applicable
Disadvantages of CDMA
i) Can result to channel interference and pollution
ii) Lacks data roaming capabilities
iii) Limited support
iv) Technology is embedded on device and is therefore not easy to upgrade
Global System for Mobile Communications (GSM)
GSM is a universally recognized technology used for digital mobile communications
(Wheeler, 2017). It was developed to standardize cellular communication and operates on the
1900 MHz, 1800 MHz and 900 MHz frequencies. Global System for Mobile

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Communications transforms voice signals and converts into digital data prior forwarding
through the communication channel with other user data streams specific for each user.
Strengths of GSM
i) Extensive channel and device coverage
ii) No roaming charges
Disadvantages of GSM
i) Bandwidth congestion because users share channel bandwidth
ii) Results to electronic interference

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References
Burns, J. (2003, April 3). How 802.1x authentication works. Retrieved from Computer
World: https://www.computerworld.com/article/2581074/mobile-wireless/how-802-
1x-authentication-works.html
High-tech. (2017, September). WiMAX - 802.16 - Worldwide Interoperability for Microwave
Access. Retrieved from CCM: http://ccm.net/contents/808-wimax-802-16-worldwide-
interoperability-for-microwave-access
IEEE. (2017, September 23). IEEE standards association. Retrieved from IEEE:
https://standards.ieee.org/develop/policies/opman/sect8.html
Microsoft. (2017, September 22). Virtual Private Networking. Retrieved from Microsoft:
https://technet.microsoft.com/en-us/library/dd469653(v=ws.11).aspx
Rouse. (2015, July). Code-Division Multiple Access. Retrieved from Tech Target:
http://searchtelecom.techtarget.com/definition/CDMA
Rouse, M. (2006, June). 802.11i. Retrieved from Tech Target:
http://searchmobilecomputing.techtarget.com/definition/80211i
Rouse, M. (2015, July). CDMA (Code-Division Multiple Access). Retrieved from Tech
Target: http://searchtelecom.techtarget.com/definition/CDMA
Tarantola, A. (2013, March 3). VPNS: what they do and how they work. Retrieved from
gizmodo.com: https://gizmodo.com/5990192/vpns-what-they-do-how-they-work-and-
why-youre-dumb-for-not-using-one
Techopedia. (2017, September ). Time Division Multiple Access (TDMA). Retrieved from
Techopedia: https://www.techopedia.com/definition/5089/time-division-multiple-

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access-tdma
Wheeler, D. (2017, September). The Advantages and Disadvantages of GSM. Retrieved from
Techwalla: https://www.techwalla.com/articles/the-advantages-and-disadvantages-of-
gsm