Mobile and Wireless Communication (Essay Sample)

Mobile and Wireless Communication
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Question 1
The diagram shown is a representation of protocols to send uni-cast packets. It uses the basics of Distributed Foundation Wireless Media Access Control (DFWMAC). The mechanisms used here are Request to Send (RTS) and Clear to Send (CTS). From the diagram, data transmission by other nodes has to seek authentication with RTS (request to send). It is then relayed to CTS (clear to send). When the transmission is successful, the terminal frame node confirms with the ACK (Acknowledgement) frame to tell the sender that the message relay has been a success. The NAV (Network Allocation Vector), acts like a guard to other nodes by informing them the amount of time that other channels would wish to spend. Short Inter-Frame Spacing (SIFS) is utilized as a small time waiting period for other frames like CTS, RTS, ACK and DATA. DIFS (Distributed Inter-Frame Space) allows transmission from CTS and RTS if the data destination system is idle, otherwise it is postponed until a DIFS period when the current data is transmitted.
Question 2
A wireless networking involves the use of computer networks for wireless network connection. The most basic features of wireless networking can be described as;
High capacity load balancing to reduce congestion in users
Scalable, that is expansion as demand increases without necessarily overhauling the whole system
Role based access control to assign role the wireless based devices depending its authentication.
Web content filtering
Mobile device management
A wireless networking can be compared to wire networking in that wireless devices require power source to operate. Wireless networkings suffer from signal loss and fading in dead spots, in this case on areas without reception. On the other hand, wireless networking has from multipath distortion because of wave reflection to other antennas. This is common with radio waves which get reflected in case they come across an obstacle. More over there is the problem of shared airwaves due to limited spectrum.
A wireless network loses privacy whenever it enters the air and so it is prone to errors and data loss. The argument behind this is that this type of networking uses waves to transmit data from source to destination; hence the waves can be reflected to some other receivers once they are reflected by an obstacle. This means that data does not get to the desired destination (loss) and gets to the wrong hands (privacy). This is unlike wired networking which requires coupling very close to the wire to intercept the signals.
Question 3
Basestations are sometimes described as fixed hosts which are used to connect several mobile hosts or systems. Basestations cover some fixed and specific distances known as cell which can communicate to the mobile host if is within some specific fixed distances. The basics under which a base station works on mobile/cellular or fixed networking is the same; the signals pass between the base station and the subscriber because both of them emit radio frequency waves which are used for communication.
Question 5
The relationship between time domain, frequency domain and phase domain
Any electromagnetic signal can be represented in frequency, phase and time domain. The frequency of a signal is the number of cycles per second (number of periods per second). Time domain is a representation of how amplitude of a signal varies on a given time, while phase domain is described as the difference between where the signal starts and its initial point. Two signals S1 (t) and S2 (t) can be represented by the equation;
S1 (t) - 5sin (2pi106 t -pi/4)
S2 (t) – 4sin (2pi 104 t + pi/4)
The time domain can be represented as


The frequency domain is a representation of how amplitude varies with frequency. Under this domain the variable parameter are frequency and amplitude. Phase domain is a representation of how amplitude varies with phase. Under this domain the variables are time and frequency.
Question 6
For B to get a route to J a Route Request (RREQ) packet for transmission has to be created. In this case, every packet from B to J will contain addresses; J’s IP address, SEQ#, B’s address, SEQ#, hopcount=0. A RREQ message will be send from node B to its neighboring nodes; Q, C, D, F) with broadcast id .
Question 9
Multipath propagation of signals takes place all directions and angles. Since the signals do not take place in a specific path when they leave or enter the trans...