Multiple Access Techniques In Wireless-Free-Samples for Students

Questions: 1.Provide an Opinion regarding which antenna types will become the dominant players in the future of medium- and long-distance Wireless link. 2.Compare and Contrast the Multiplexing techniques CDMA and FDMA in the area of Wireless Networking? Answers: 1.Antennas devices that are used in wireless communication as propagation components for radio frequency signals. These devices will convert the electric signals into electromagnetic waves and vice versa which facilitate communication through the radio spectrum where no physical mediums are used. Moreover, antennas can be classified based on their propagation designs which depict certain patterns as highlighted by their signals lobes (NRAO, 2010). Types of antennas: Omni-directional antennas these antennas transfer or receive signals in all directions without any form of restriction. Semi-directional antennas propagate signals in multiple directions, however, they are limited or restricted in certain directions. Directional antennas one direction antennas, which means they can only ferry signals in specific directions (Rouse, 2017). Common examples: Yagi Uda (Yagi) antenna an example of directional antennas, the Yagi antenna is popularly used in broadcasting where it acts as a reception tool for television sets. Its affiliated with long distance application, an attribute caused by its design structure. Strengths It has a high sense of directivity which concentrate signals in one direction. High gains due to the attribute above. Its a simple device made of metallic rods. Weaknesses The high gain stated above is limited to its size (proportional). Secondly, the gain only reaches 20dB. Horn antenna another directional antenna that is characterised with very high gains. This antenna consists of a pyramid-like structure that flares out toward its extreme end. This structure increases its signal reception and transmission areas which favour its gains. Its commonly used with ultra-high signals e.g. microwave signals (Radio-electronics, 2017). Strengths As stated above, it exhibits very high gains due to its flare like structure. Secondly, its a directional antenna that has high levels of directivity. Weaknesses It's sometimes complex to implement and install. Similar to other directional antennas, its gains are limited to its size(Carr, 2012). Cellular antenna an example of an Omni-directional antenna, this antenna is characterised with mobile communication where its size facilitates its integration into small devices such as smartphones, tablets and other portable devices. The cellular antenna may transfer signals in all directions, however, its lack of directivity limits its gains (Carr, 2012). Strengths It has an optimal amplifying capability. Secondly, its an efficient device that has a convenient structure for mobile communication. Weaknesses Directivity is extremely limited in the device. Secondly, it has limited gains which result in small coverage distance (Cisco, 2007). Medium and long distance coverage Considering the devices that are currently used in this application, the directional antennas seems to hold a strong footing in the future application of long distance wireless communication. For medium and long distance coverage, the user requires high levels of directivity in order to focus the signals in specific directions. This operation method makes the process efficient as minimal resources are spent in the propagation of signals. Future technologies will try to optimise on the available resources such as power and cost, an outcome that is easily facilitated by directional antennas such as horn and Yagi Uda. 2.Multiplexing this is a telecommunication technique that combines multiple signals into one common element that is transferred via a single communication channel. This technique is vital to wireless communication as it facilitates the sharing of the radio spectrum, a communication medium that has limited operational space. In all, multiplexing will optimise the resource available especially the bandwidth. Nevertheless, the technique should also ensure that signal interference does not happen which constitutes the different multiplexing techniques as designated by their operation methods (TECH, 2011). The multiplexing techniques: Code division multiple access (CDMA): one of the many techniques used to support the multiplexing process in communication. CDMA uses pseudo-codes (unique codes) to share the channel of communication. Moreover, in this technique, the signals are assigned a unique set of codes which are used to identify them to both the transmitter and receiver. Characteristics of CDMA Unlike other multiplexing techniques, signals in CDMA use the entire bandwidth available during communication i.e. no space allocation. CDMA is associated with the propagation of both video and data signals. Devices having the same codes can communicate with each other. Codes are the defining factor of the technique(Zahra, 2015). Frequency division multiple access (FDMA): In comparison to CDMA, FDMA uses frequency and not codes to propagate multiple signals in single channels. Furthermore, the technique uses a number of sub-band frequencies to assign space within the radio spectrum. Therefore, the users are allocated bandwidth and do not use the entire radio spectrum. Characteristics The technique allocates space based on the number of signals and their bandwidth requirement. Its commonly characterised with idle channels as it does not re-assign frequency bands. To avoid signal interference, filters are used. Frequency is the defining component of the technique (Zahra, 2015) A comparison of the two techniques CDMA FDMA The technique uses codes to identify and separate the propagated signals. Frequency bands divide the radio spectrum (channel) into the sections needed for communication. In CDMA, signals use the entire bandwidth without any form of restriction or allocation. Signals are restricted by their frequency bands as allocated at the start of communication. No idle time, the entire spectrum is used by all the signals. Associated with idle time, when certain bands are not in use. Used for both video and data communication. Voice signals are commonly used with this technique (corps, 2000). References Carr, J. (2012). Directional or Omnidirectional antenna? Joe Carr's Radio Tech-notes, Retrieved 14 August, 2017, from: https://www.dxing.com/tnotes/tnote01.pdf. Cisco. (2007). Omni Antenna vs. Directional Antenna. WLAN, Retrieved 19 August, 2017, from: https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/82068-omni-vs-direct.html. NRAO. (2010). Antenna Fundamentals. Antenna Fundamentals, Retrieved 19 August, 2017, from: https://www.cv.nrao.edu/course/astr534/PDFnewfiles/AntennaTheory.pdf. Radio-electronics. (2017). Microwave Horn Antenna. Antennas and propagation, Retrieved 19 August, 2017, from: www.radio-electronics.com/info/antennas/horn_antenna/horn_antenna.php. Rouse, M. (2017). Horn antenna. Research gate, Retrieved 17 August, 2017, from: https://searchmobilecomputing.techtarget.com/definition/horn-antenna. TECH, M. C. (2011). Multiple access techniques for wireless communications. wireless mobile communication , Retrieved 19 August, 2017, from: https://www.slideshare.net/HILDA519/multiple-access-techniques-for-wireless-communications. Zahra. (2015). FDMA-TDMA-CDMA. Multiple access techniques in wireless communication, Retrieved 16 August, 2017, from: https://www.slideshare.net/SammarKhan2/fdmatdmacdma.