The efficiency of communication is a critical requirement in any society, community, or organization. Different technologies have been applied to achieve this specific objective. Digital Subscriber Line (DSL) is a communication technology that carries both voice signals and digital data based on the assumption that digital data does not need changes between analog and digital forms (FitzGerald et al., 2020). Several new technologies have been developed to facilitate DSL, some of which have become successful while others have failed. Arguably, a comparison between different DLS technologies reveals that each has its strengths and weaknesses, which means that combining them can improve communication.
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Discrete Multitone Technology (DMT) is a multicarrier modulation technology that transmits signals over multiple low-rate orthogonal subcarriers. The bandwidth of DMT can overlap because of its orthogonal nature and exists in the sin(x)/x formation (Bai et al., 2017). One of the significant advantages of DMT is that it provides toughness against channel dispersion, which allows easy phase and channel equalization and resolves channel dispersion-caused intersymbol interference (Bai et al., 2017). Nevertheless, DMT suffers from crosstalk interference, high peak-average power ratio, and high sensitivity to offset frequency and phase noise.
Carrierless amplitude phase (CAP) modulation technology combines two filtered signals to generate a quadrature amplitude modulation. In DSL communications, CAP is used to divide the available frequency spectrum into three distinct bands. The first band that ranges from 0 to 4 kHz is allocated for POTs transmissions (Ridzuan et al., 2018). The second ranges from 25 to 160 kHz and is allocated for upstream data traffic, while the third band ranging from 240 kHz to 1.5 MHz is assigned to downstream traffic (Ridzuan et al., 2018). This technology helps in building up fewer complexes, flexible and cost-effective transmission systems for both in-home network and optical access systems. In addition, CAP does not rely on local oscillators when generating carriers. However, it needs multiple electronic circuits and readily adjusts to noise conditions. Also, CAP is not applicable in current standards such as G.Fast and VDSL2 using DMT modulation.
The Multiple Virtual Line (MVL) is a DSL technology that connects users using the existing home cables over large distances. In DSL communications, MVL transforms one copper wire loop into multiple virtual lines with the ability to support multiple services simultaneously and independently (Chang, 2017). In DSL communications, MVL is virtually immune to line interference. Also, MVL coexists with other services and does not interfere with them. But MVL is less compatible with DMT and other DSL consortium members. Indeed, this is a problem because DMT is the line code expected to carry most DSL technologies into the residential mainstream.
Echo cancellation technology is used in DSL communication to improve voice quality by preventing the creation and capture of echo. The technique filters echo produced by acoustic means and any echo from electrical reflections and impedance mismatches (FitzGerald et al., 2020). The approach is easily applicable in existing copper wire lines and reduces communication interference by all forms of echo. However, it must be used along with other methods and highly depends on the existing lines, making it difficult to extend to the subscriber mainstream.
Based on this analysis, it is evident that all four approaches have their inherent capabilities, shortfalls, and weaknesses. DMT is effective in reducing interference, but unlike CAP, it is costly. While CAP is the most cost-effective method on the list, it needs many gadgets on the user-end and is prone to noise interference. While MVL is immune to noise, it is less compatible with most DSL technologies. On its part, Echo cancellation is easily applicable and reduces echo interference, but it cannot be used alone in most cases.
In conclusion, this comparison reveals no single method that does not have shortfalls and weaknesses. Instead, different situations determine the best method to apply. Therefore, applying multiple methods simultaneously can significantly improve DSL communication.
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Bai, T., Zhang, H., Zhang, R., Yang, L. L., Al Rawi, A. F., Zhang, J., & Hanzo, L. (2017). Discrete multi-tone digital subscriber loop performance in the face of impulsive noise. IEEE Access, 5, 10478-10495. Web.
Chang, F. (2017). Datacenter connectivity technologies: Principles and practice. River Publishers.
FitzGerald, J., Dennis, A., & Durcikova, A. (2020). Business data communications and networking. John Wiley & Sons.
Ridzuan, N. M., Abdullah, M. F. L., Othman, M. B., & Jaafar, M. B. (2018). A Carrierless Amplitude Phase (CAP) modulation format: Perspective and prospect in optical transmission system. International Journal of Electrical & Computer Engineering, 8(1), 585-595. Web.