Bn303 Wireless Networks And Security- Assessment Answers

Answer:

Antennas are the means of coupling a transmitter to a medium. An antenna is an electromagnetic radiator that creates an electromagnetic field that travels out of the antenna towards the receiving antenna. In the receiving antenna, the electromagnetic wave is converted into electrical signals.  There are different types of antennas such as Yagi horn and cellular antennas. The comparison among the three antennas are elaborated below (Stutzman & Thiele, 2012) -

1.1. Yagi

Yagi is a commonly used directional antenna, which uses several elements to form a directional array. This antenna is commonly used in communication where the frequency is above 10 MHZ. The Amateur radio and the citizens band radio operators generally use this type of antenna. This type of antenna is a basic form of antenna generally with a narrow bandwidth. Yagi antenna are sometimes designed to operate on multiple bands as well (Sun et al., 2013).

The strength of Yagi antennas are listed below-

1) It is a directional antenna with a 50 to 70 degree beam width. Since the focus is in one direction only, yagi antenna, they put out relatively higher gain in relation to the multidirectional antennas, making them ideal for receiving lower strengths signals.

2) The high gain enables the yagi antennas to work in relatively good range.

3) The design of the Yagi antennas filers out almost all the noise associated with the signal coming from opposite direction. Thus, yagi is a good choice for telecommunication.

4) The yagi antennas are easier to mount on vertical towers due to its structure. This gives th yagi an additional benefit.

5) The cost of yagi antenna is generally less than an LP antenna.  

The weaknesses of Yagi antenna are as follows-

1) Bandwidth of yagi antenna is limited and thus the gain is also limited to 6-9 dB unless there is more than one antenna.

2) The performance of yagi antenna degrades, as the user move away from the frequency range Yagi is designed for. This is particularly because yagis are based on resonant elements and thus off resonant operations results in increase of SWR.

1.2 Horn

A horn is a type of antenna that consists of a metal wave guard shaped like a horn, which is used to direct radio waves in a beam. This type of antennas is widely used at UHF frequencies above 300 MHz. Horn antenna is generally used in transmission and reception of microwave signals. It is termed as horn because of its flared appearance. The axis of the horn is used for maximum radiation (Cai et al., 2014).

The strength-

1) Offers greater directivity

2) Has narrow bandwidth

3) Capable of avoiding standing waves

 Weakness

1) The flare angle decides the directivity of the antenna

2) The angle and the flare are needed to be very small.

1.3 Cellular Antennas 

Cellular antennas are generally used in communication services. Every cell phone contains at least one radio antenna to transmit radio signal (Zhao, Ying & He, 2015).

Strength

1) Frequency reuse in cellular antenna allows a number of user to work on same frequency.

2) The range of cellular antennas is generally high

3) Offers increasing security

Weaknesses

1) More expensive than other antennas

2) More complicated than traditional antennas

3) Location is needed to be considered.

From the above discussion, it can be concluded that cellular network is and will dominate among the other network as it enables a long distance wireless link and frequency reuse. Moreover, it offers the highest range of bandwidth as the bandwidth increases from the frequency reuse. It provides additional security, as the signals are not radiated in all the directions.

2.1 CDMA and FDMA in wireless networking

CDMA or code division multiple access is a protocol, generally used in 2G and 3G wireless communications. It is a form of multiplexing that allows a number of signals to occupy a same transmission channel, which in turn optimizes the use of bandwidth available.

FDMA or frequency division multiple access on other hand divides the allocated bandwidth for wireless cellular communication into 30 different channels. These channels carry a voice conversation or carry a digital data. FDMA is a basic technology in analog advanced mobile service. Unlike CDMA, in FDMA, each channel can be used or assigned to only one user at a time.

CDMA channel is generally 1.23 MHz wide and uses soft handoff procedures that minimizes the occasion of signal breakup. FDMA however is a physical layer technique that transmits low bandwidth channels through the channels of high bandwidth. FDMA segments the frequency band into different disjoint sub bands, while CDMA spread the spectrum using different orthogonal codes.

Both CDMA and FDMA have an uninterrupted frequency in the terminal.  However, in FDMA every terminal has an uninterrupted frequency of its own, while in CDMA, all the terminals are capable of being active simultaneously and stay uninterrupted as well.

In FDMA, the signal is separated by filtering in the frequency domain, while in CDMA the signal is separated using code plus special receivers. Both FDMA and CDMA provide continuous transmission in wireless networking.

The cell capacity is however, limited in FDMA, while in CDMA there is no limit in the channel capacity, which offers additional benefits. Both CDMA and FDMA is robust and flexible which offers increasing advantages.

When FDMA channel is not in use, it sits idle and the bandwidth of the channel is also narrow, which is 30 kHz, much less in comparison with CDMA. CDMA offers certain benefits such as the receiver detects only the desired codeword while others appear as a noise. However, it becomes mandatory for the receivers to know the codeword. Transmitter is sending. In FDMA, tight filtering is generally needed to minimize the interference of noise.

CDMA offers additional security, as every user has a different pseudo codeword for communication, which remains orthogonal to the other users. This is needed because every user, uses same frequency in simultaneous transmission (Glisic & Leppänen, 2013).

In FDMA, the entire band of frequencies is generally divided into multiple RF channels or carriers. These carriers are allocated to different users. In CDMA, the entire bandwidth is shared among the different users. This is ascertained by assigning unique codes to different users (Straullu et al., 2015).

Wireless communication has nowadays become an integral part of everyone’s life as it allows the users to communicate from anywhere, even from remote places. The devices that are involved in wireless communication are mobile phone, GPS unit, satellite television and so on.Satellite communication is used to communicate with the radio signals directly via radio signals. It provides a powerful mode of broadcasting.

Wireless networking provides several benefits by connecting different devices wirelessly. Most prominent being the lesser equipments cost and hassle free installation of the system.WiMAX offers transmission of data at maximum speed. The cost of data, which is available using the WiMAX varies widely with the distance from its transmitter.  

Wi-Fi networks have limited range as it allows the users only to connect with the router, which is in close proximity. The Wifi network is necessarily be secured with passwords for ensuring security.Radio waves are generally used in Bluetooth communication and the range of transmission is generally 15-50 feet. The devices are needed to be paired at first in order to establish a Bluetooth connection.Cellular antenna provides highest range of bandwidth and is increasingly used in setting up communications.

References

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Bilotti, F., Di Palma, L., Ramaccia, D., & Toscano, A. (2012). Self-filtering low-noise horn antenna for satellite applications. IEEE Antennas and Wireless Propagation Letters, 11, 354-357.

Cai, Y., Qian, Z. P., Zhang, Y. S., Jin, J., & Cao, W. Q. (2014). Bandwidth enhancement of SIW horn antenna loaded with air-via perforated dielectric slab. IEEE antennas and wireless propagation letters, 13, 571-574.

Gagliardi, R. M. (2012). Satellite communications. Springer Science & Business Media.

Glisic, S. G., & Leppänen, P. A. (2013). Wireless communications: TDMA versus CDMA. Springer Science & Business Media.

Heydon, R. (2013). Bluetooth low energy: the developer's handbook. Prentice Hall.

Jiang, W., & Che, W. (2012). A novel UWB antenna with dual notched bands for WiMAX and WLAN applications. IEEE Antennas and Wireless Propagation Letters, 11, 293-296.

Kosaka, M. (2012). U.S. Patent No. 8,270,390. Washington, DC: U.S. Patent and Trademark Office.

Straullu, S., Savio, P., Chang, J., Ferrero, V., Nespola, A., Gaudino, R., & Abrate, S. (2015). Optimization of reflective FDMA-PON architecture to achieve 32 Gb/s Per upstream wavelength over 31 dB ODN loss. Journal of Lightwave Technology, 33(2), 474-480.

Stutzman, W. L., & Thiele, G. A. (2012). Antenna theory and design. John Wiley & Sons.

Sun, H., Guo, Y. X., He, M., & Zhong, Z. (2013). A dual-band rectenna using broadband yagi antenna array for ambient RF power harvesting. IEEE Antennas and Wireless Propagation Letters, 12, 918-921.

Zhao, K., Ying, Z., & He, S. (2015, May). Antenna designs of smart watch for cellular communications by using metal belt. In Antennas and Propagation (EuCAP), 2015 9th European Conference on (pp. 1-5). IEEE.