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Questions: 1. Different technology of Wireless LAN like IEEE 802.11a, 802.11b, 802.11g, 802.11n, etc. has different merits. Research any 4 WLAN technologies in details and pay specific attention to how they are used as well their strengths and weakness. Provide an opinion regarding which WLAN 802.11 standard will become the dominant players in the future . 2. Compare and contrast the FHSS and DSSS in the area of wireless networking? 3. A local engineering group ask you to present your finding on different types of antennas used in wireless technologies. Research on 4 different types of antennas in details and pay specific attention to how they are used as well their strengths and weakness. Provide an opinion regarding which antenna types will become the dominant players in the future. Please submit power point slides in your answer. Answers: Answer 1 There are different technologies of Wireless LAN, such as IEEE 802.11a, 802.11b, 802.11g, 802.11n and so on. These wireless technologies have different merits and demerits. The different aspects of these wireless technology is discussed below- IEEE 802.11a Wireless IEE 802.11a operates in 5-GHZ frequency band. This band is also termed as UNII or Universal Networking Information Infrastructure band. UNII is divided into three parts, UNII-1, UNII-2 and UNII-3. UNII-1 is mainly used for indoor usage, where an antenna is fixed to the radio. UNII-2 on the other hand is used for both indoor and outdoor usage, with the help of either a fixed or a remote antenna; while UNII-3 is only used for outdoor. The maximum speed of 802.11a is 54 mbps and uses OFDM (orthogonal frequency division multiplexing) for modulation. IEEE 802.11a is therefore, mostly used in WIFI. It shows the use of orthogonal frequency division multiplexing. This standard of wireless technology was released in the year 1999 and has a bandwidth of 20MHZ. IEEE 802.11a makes use of single input and single output technologies of antenna. Outdoor frequency ranges to 5Km within an operating frequency of 3.7G. It is less prone to interference in comparison to 802.11b mainly because of a higher operating frequency (Chakraborty eta al., 2014). The strength is that the data rate in this standard is flexible and offers 12 non-overlapping channels. However, it is somewhat expensive that other standards, which is its major weakness IEEE 802.11b IEEE 802.11b was also released in 1999 and enables a propagation speed of 11 mbps. It operates in 2.4 GHz operating frequency with a bandwidth of 22MHz. It makes use of Direct Sequence spread spectrum (DSSS) modulation technique and employs SISO antenna technology, similar to IEEE 802.11a. This standard is prone to higher interference due to its frequency range, as the frequency range of 2.4 GHz is becoming over crowded with carriers. The indoor range of IEEE 802.11b is 35m while that of outdoor range is 140m (Yuan et al., 2013). The strength is that his technology is less expensive, but has a greater interference, which is one of the major weaknesses. IEEE 802.11g It is a combination of IEEE 802.11a and IEEE 802.11b and was released in 2003. It operates in 2.4GHz frequency with a bandwidth of 20MHZ used (Baldi et al., 2013). the maximum speed in 54mbps, which is its major advantage along with the fact that it is compatible with 802.11b. However, it has interference issues as well. IEEE 802.11n It was released in 2009 and uses multiple antennas in transmission and data receive. It employs OFDM modulation technique and supports multiple input and multiple output, which is a key strength of this standard. However, the only weakness is its cost of implementation (Lim, Kim Suh, 2012). Therefore, it can be said that IEEE 802.11n will become a dominant player in future. This is because of the speed and reliability of this standard. This standard provides better service in comparison to the other three standards discussed above. The speed is very high, however, the cost of implementation should be a bit less as it is a major roadblock in evaluation of this standard (Khanduri and Rattan, 2013). Answer 2: FHSS: Frequency Hopping Spread Spectrum Frequency Hopping Spread Spectrum or FHSS is a process by which radio signals are transmitted by rapid interchange or switching of the carriers among the different frequency channels. The radio signals are transmitted across numerous channels with the pseudorandom sequence. The sender and receiver know this sequence. It is defined in 2.4GHz band and is operated in round 79 frequencies that range from 2.402 GHz to 2.480 GHz (Torrieri, 2015). It is a robust technology and with very less issues of interference from noise and other environmental factors. It finds its usage on cellular or fixed broadband wireless access as in this cases, the use of DSSS is ractically impossible. Furthermore, in FHSS, the number of simultaneously active systems in a single geographic area is higher. Therefore, this technology is mainly used in designs that cover a large area. FHSS systems generally operate in narrow band signals that are mainly located around the different carrier frequencies. Like DSSS, F HSS also retransmits the lost packets until a proper acknowledgement is received across the channel, thus increasing the accuracy of data transfer (Zeng et al., 2012). DSSS: Direct Sequence Spread Spectrum Direct sequence spread spectrum is a transmission technology and is generally used in local area networks. The data signals in DSSS are coupled with an increased data rate sequence, dividing the entire data in different spreading ratios. DSSS is resistant to jamming, which is its major advantage. It furthermore has an advantage of sharing channels among multiple users. It is generally used for transmission of digital signals in order to resist the jamming attempts. A particular stream of information in DSSS is subdivided into a number of small pieces. Data signals at points of transmission are combined in a higher data bit rate sequence in DSSS. If any bits of data is damaged during the transmission, the original data can be easily recovered. The major differences between FHSS and DSSS are as follows (Swamy et al., 2013)- While transmission, FHSS changes the frequency while that of DSSS changes the phase FHSS is considerably easier to synchronize in comparison to DSSS DSS finds its use in positioning system whereas, FHSS is used in cellular or fixed broadband connections. DSS has a short latency time while the latency time in FHSS is higher. DSSS possess no dwell time, whereas the dwell time in FHSS is 400 microsecond DHSS generally has short indoor range and long outdoor range, while in FHSS both indoor and outdoor range is short. The overall data throughput is higher in DSSS in comparison to FHSS (Quyen, Yem Hoang, 2013). The constant processing gain in DSS corresponds to a better signal to noise ratio while in FHSS there is no processing gain. Answer 3: Different types of Antenna References Baldi, M., Bianchi, M., Maturo, N., Chiaraluce, F. (2013). A physical layer secured key distribution technique for IEEE 802.11 g wireless networks.IEEE wireless communications letters,2(2), 183-186.). Chakraborty, U., Kundu, A., Chowdhury, S. K., Bhattacharjee, A. K. (2014). Compact dual-band microstrip antenna for IEEE 802.11 a WLAN application.IEEE Antennas and Wireless Propagation Letters,13, 407-410 Khanduri, R. and Rattan, S.S., 2013. Performance comparison analysis between IEEE 802. 11a/b/g/n standards.International Journal of Computer Applications,78(1). Lim, W. S., Kim, D. W., Suh, Y. J. (2012). Design of efficient multicast protocol for IEEE 802.11 n WLANs and cross-layer optimization for scalable video streaming.IEEE Transactions on Mobile Computing,11(5), 780-792 Quyen, N. X., Yem, V. V., Hoang, T. M. (2013). A chaos-based direct-sequence/spread-spectrum communication scheme.). Swamy, M.K., Deepthi, M., Mounika, V. and Saranya, R.N., 2013. Performance analysis of DSSS and FHSS techniques over AWGN channel.Development (IJECIERD),3(2), pp.7-14. Torrieri, D. (2015).Principles of spread-spectrum communication systems. Springer. Yuan, W., Wang, X., Linnartz, J. P. M., Niemegeers, I. G. (2013). Coexistence performance of IEEE 802.15. 4 wireless sensor networks under IEEE 802.11 b/g interference.Wireless Personal Communications, 1-22. Zeng, X., Cai, H., Tang, X. and Yang, Y., 2012. A class of optimal frequency hopping sequences with new parameters.IEEE Transactions on Information Theory,58(7), pp.4899-4907.