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Solution: Wireless Networks Assignment

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Discuss the usage of a virtual private network in establishing an encrypted secure communications channel between two points on a public network

Answer 1:

Data travelling through private networks is considered to be more susceptible to interceptions, as such connection do not use appropriate security standards. When Virtual Private Network is used, a private tunnel is established within the public network between sender and receiver. Virtual Private Network connection allow users to work at home or at any other location in secure manner using routing infrastructure given by public internetworks like internet. From the perspective of user, Virtual Private Network is a point-to-point connection that is maintained between the corporate server and user’s computer. VPN can be used for creating secure connection to protect traffic which flows between the trusted and controlled endpoints. However, still certain risks arise while providing access to VPN partners. A Virtual Private Connection can encrypt data when it is transferred over the public network (IBM, 2018). Through VPN, type of data can also be restricted that flows across the VPN connection, this in return will help in providing a measure of network level security. However, Virtual private network does not operate in same manner as firewall does for regulating the traffic into as well as out of the system. There are various types of VPN that are established for securing communication between two points on public network:

PPP (Point-Point Tunneling protocol): PPP is a protocol of OSI layer and is a dial up in which multi-protocol is used for connecting to the user with internet.

IPsec (Internet Protocol Security): IPsec is used for securing data transfer at the OSI layer and it provides data integrity, encryption and authentication services.

Question 2:

Discuss the three different multiple access technologies used with 2G: time division multiple access (TDMA), code division multiple access (CDMA), and global system for mobile communications (GSM).

Answer 2:

TDMA: Time Division Multiple Access is a technology employed in digital cellular telephone communications and divides the cellular channels into three different slots so that amount of data being carried can be increased. An out-link control is required for operating Time Division Multiple Access as this will helps in controlling all the remote sites in which some control information is stored. However, Time Division Multiple Access provides non-continuous transmission that makes hand-off simpler and shares single carrier frequency with more than one users. But at the same time it also creates interferences at frequency which is directly associated with the time slot length.

CDMA: Code-Division Multiple Access is considered as one of the protocol used in both 2nd Generation as well as 3rd Generation wireless communication. CDMS is type of multiplexing, in which various signals are allowed to occupy a single transmission channel and optimize the use of available bandwidth. Analog to Digital Conversion is used by CDMA in combination with the spread spectrum technology. Initially, the audio signal sin CDMA are digitized into binary elements, then the frequency of the transmitted signals is made to change as per the code. Thus, it can be intercepted by the receiver only whose frequency is programmed with the similar code.

GSM: Global System for Mobile Communications is a second generation standard for mobile networks which operates on three different carrier frequencies. 1800MHz, 1900MHz and 900MHz. GSM system Due to GSM standard, GPRS (General Packet Radio Service) and EDGE (Enhanced Data Rates for GSM Evolution) came into existence and being a cellular network, GSM uses cells for providing wireless communication to subscribers present in the vicinity of these cells. Various benefits are provided by GSM such as international roaming, low cost mobile set as well as base stations, compatibility with Integrated Services Digital Network-ISDN (Agarwal, 2018).

Question 3:

Please explain what is the tens and threes rule? If a transmitter generates a 10 dBm signal and is connected to an amplifier and then to an antenna with two cables. The gain of the amplifier is 10 dB. Each cable is with a loss of 3 dB, whose connector has a loss of 1 dB each end. Please estimate the signal level at the input of the antenna in dBm and milliwatts?

According to the rule of 10s and 3s:

  • The power presented in milliwatts (mW) is doubled, for each and every gain of 3dB.
  • The power presented in milliwatts (mW) is halved, for each and every loss of 3dB.
  • The power presented in milliwatts (mW) is multiplied by 10, for each and every gain of 10dB.
  • The power presented in milliwatts (mW) is divided by 10, for each and every loss of 10dB.

Signal loss for 2 connectors = 2 * 1dBm = +2dBm

Signal loss for the cable = +3dBm

Total Loss = 2dBm + 3dBm = +5dBm

Therefore, signal level at the input of the antenna = +10dBm - 5dBm = +5dBm

Hence, 3.16 milliwatts

 Question 4:

What are the four components of WLAN? Explain and discuss two of them in details.

The main four components of WLAN include access points, network interface cards, extension points, and directional antennae which are discussed below: 

  1. Access points act as the main radio transmitter in the wireless LAN that translate the network traffic into the radio signals and further transmit that signal to the wireless enabled computers. It can also be connected with the wired network with the use of cables that can allow the wireless enable devices to access the wired devices.
  2. Network interface cards are installed within the wireless enabled computers that is responsible for picking up the signal from a particular base station and convert that signal into the computer understandable form. It also enables the computers to directly communicate on peer-to-peer devices in which they are installed (IDC, 2018). Printers and files can be shared with the use of NICs in which there is not any need of access points.
  3. Extension points or the wireless relays are considered as similar to access points. It is responsible to extend the wireless network range by relaying the signals from the wireless devices.
  4. Directional antennae are built into most of the access points which are not well designed. The addition of one antenna is responsible to increase the improve the range of the wireless LAN. The antennas are of different designs each of which is designed for particular use. Some of the antennas are responsible for producing the focused directional signals.

Question 5:

What happens as a cellular phone user moves around within a particular cell and into another cell?

A mobile phone is considered as electronic device which is used for the mobile telecommunication s over the cellular network consist of specialized base stations also known as cell sites. When the cellular phone user moves from one cell area to another cell area, then the commands automatically send by the system to the mobile phone as well as cell site in order to keep the link with stronger signal and switching on to the new frequency. This is because a cell phone mainly offers the full duplex communication and also transfer a link when the cellular phone user moves around within a particular cell and into another cell. Cellular phone is mainly use for the purpose of voice communication (Miller, 2018). Along with the standard voice function, the new generation mobile phones mainly support number of additional services such as email, packet switching, gaming, Bluetooth, text messaging etc.

Question 6:

What is multipath distortion? If the radio system has been detected to have multipath distortion, please propose two solutions to minimize effect of multipath distortion with reasons.

Multipath distortion is the form of RF interference which occurs when the radio signal is having more than one path present between the transmitter and receiver. Multipath distortion occurs in the cells which have metallic and other RF reflective surfaces like coated glass, furniture, walls etc. when an object is reflected off an RF signal, number of wave fronts are created. As a result, number of new and duplicate wave fronts are reached to the receiver. Multiple propagation mainly occurs when from source to destination, number of different paths are taken by RF signal. Multipath can also be defined as the combination of duplicate and original wave fronts.

If the radio system has been detected to have multipath distortion, following steps can be considered in order to minimize the effect of multipath distortion:

  1. The use of dual antennas can be considered in order to minimize the effect of multipath distortion. The reason behind is number of access points are reinforced with the dual antennas. When the antenna is deployed manually, there should be the difference of 5 inches.
  2. The second way to reduce the effect of multipath distortion is to insert or deploy antennas mainly in the widely opened areas. By doing so, there should not be any distortion in the signal while signal is transforming one point to another point (Ali, 2018).

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