Investigation of the Performance of Wired and Wireless Communication Systems

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The respective S21 in figure 1.4 (b) shows us that there is clear change in the magnitude gain of the signal from 0.2dB to 10dB and also the reduction of noise could be seen as compared to the previous results because the plot of the signal is more clear and understandable. This is because of the removal of all other frequencies except 710-850 MHz.

Study of wireless communication link with results, analysis and discussion:

The communication done when the medium or channel of communication (transmission and reception) is air and no any other thing is used as medium or channel is called wireless communication. From this definition it clears now that wireless communication depends upon air as a channel of communication. As for communication through air we would need antennas for transmitting and receiving the signal for which we arranged two monopoles antennas of the kind as shown in figure 2.0 which we connected to the network analyzer one at transmitting port and other at receiving port with the help of cables similarly as wired connections to the network analyzer.

This antenna shown in the figure 2.0 has power 10W and gain 3.4dBi at 1200 MHz frequency. So, these are the specifications of the used antenna. To get the Transmission coefficient (S21) for the wireless link we placed the antennas first close to each other with no gap in between and took

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the results in the form of the following figure 2.1 in which the frequency range of the network analyzer was set according to the specification of antennas which is 100 MHz to 880 MHz

From the results we can see that the peak of the signal’s gain plot with no distance between the antennas is approximately or near to zero but there is some attenuation. Then we slightly started to increase the distance between the antennas at the increment of 10 cm up to 2.0 m with the help of measuring tap as in figure 2.2 to avoid wrong measurements in the experiments. Thus, recorded the results at each stage similarly as before with the help of print function in network analyzer.

With the increase in distance between the antennas we noticed that there is increase in loss of power also in the transmission coefficients recorded at each stage. As in the given figures we can see some of the results achieved at different distances at the increment of 10 cm till 2 m respectively between the antennas.

From this we see that there is a clear loss in the gain of the transmitted signal with the increase in the distance between the transmitter and receiver. We cannot display all the results at the same time so plotted the loss versus separation between antennas with the help of matlab to pursue a clear understanding.

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Now in order to check both the direct and indirect path responses of the wireless communication link we placed a metal obstacle in the path of the transmission we set the antennas to the obstacle in such a configuration to make isosceles triangle and the two antennas were exactly pointing towards each other through which we recorded the results in the form of plots which are obviously transmission coefficients (S21) for the indirect path as shown in the figure 2.4 and marked the three peak values in the plot with the marker button in the network analyzer.[pic 6]

Figure 2.4

From the figure 2.4 we can see that the gain is decreased as compared to the first one with no separation in antennas now it is about -20 dB at three peaks of the S21 of the signal. In normal day to day life in wireless communication there is dependence of loss and gain because of reflection and diffraction due to different kind of objects in the way of transmitted signal which weakens the power of transmitted signal as every object has its properties like refractive index, permittivity etc.

Conclusion:

By doing the experiment practically we concluded from it that if we compare the wired communication with the wireless communication there is more loss in the transmission in wireless communication but depends upon the terrain and different conditions as temperature, distance, mobility and obstacles in the way of the transmission and the power of antenna which completely affects the transmission coefficient of the signal but we can improve the wireless communication by installing more powerful antennas and other apparatus used which increases the expanses. And the wired is better way of communicating but it also depends upon some certain conditions of the terrain where there is less possibility to communicate through wire because of wear and tear of the terrain such as if mountainous or hilly area and water etc. But there is complexity and loss due to long wires and joints in the wires if communicating with large distances.

References

[1]LATHI, B.P. (1998) “Modern Digital and Analogue Communications Systems (3rdEdition)”, New York, and Oxford: Oxford University Press.

[2] NATIONAL INSTRUMENTS. “Elements of an Electrical Communications System”, [online] Available from: http://zone.ni.com/devzone/cda/ph/p/id/82 [Accessed: 17th January, 2014]