Mobilne Telekomunikacije Ispit (Test 1)

The class of algorithms that are highly efficient for calculating discrete Fourier transform is called Fast Fourier Transform (FFT). This algorithm is commonly denoted as FFT or fft. It is widely used in various fields such as signal processing, image processing, and data compression due to its ability to quickly compute the Fourier transform of a sequence or signal.

Increasing the number of terms in the finite Fourier series improves the approximation of the original signal.

The sum in a physical system is often characterized as a Gaussov sum, which refers to the Gaussian distribution or the normal distribution. This distribution is commonly used to describe the probability distribution of a continuous random variable. It is symmetric and bell-shaped, with the majority of values clustering around the mean. The term "Gausov sum" is likely a variation of the term "Gauss sum," which is used to describe the summation of a series of numbers following a specific pattern.

If a cluster contains 100 channels and uses a frequency reuse factor of 4, then each cell contains 25 channels. This is because with a frequency reuse factor of 4, the available channels are divided into groups of 4 and each group is assigned to a different cell. Therefore, each cell will have 1/4th of the total number of channels, which is 25.

The dipole antenna is the type of antenna that has the least directivity. This means that it radiates and receives signals equally in all directions. Unlike the yagi and monopol antennas, which are more directional and focus their energy in a specific direction, the dipole antenna is omnidirectional. It is commonly used in applications where a wide coverage area is desired, such as in broadcast radio and television.

As the mobile is moving with a velocity of 30m/s, there will be a Doppler shift in the frequency of the carrier wave. The Doppler shift formula is given by Δf/fc = v/c, where Δf is the change in frequency, fc is the carrier frequency, v is the velocity of the mobile, and c is the speed of light. Substituting the given values, we can calculate the change in frequency to be 600Hz. Therefore, the maximum frequency that the mobile receives is fc + 600Hz.

The correct answer is "Ako je trajanje simbola mnogo manje od koheretnog vremenskog intervala kanala impulsni odziv kanala se brzo menja u odnosu na promene signala u osnovnom opsegu." This statement is incorrect because if the symbol duration is much smaller than the coherent time interval of the channel, the channel's impulse response changes slowly compared to the signal variations in the baseband.

The correct answer is "pravougaonika" (rectangle). A uniform distribution on an interval means that all values within the interval have an equal probability of occurring. Graphically, this can be represented by a rectangle, where the height of the rectangle represents the probability density function and the width represents the interval. Since all values within the interval have the same probability, the height of the rectangle remains constant. Therefore, the shape of a uniform distribution on an interval is that of a rectangle.

Ravan fading occurs when the duration of symbols is large compared to the standard deviation of the delay of multiple signal paths. This means that if the symbols are transmitted for a longer duration and there is a significant difference in the delay of the multiple signal paths, ravan fading will occur. The speed of the user's movement is not a factor in ravan fading.

The correct answer is "if the number of cells in the cluster decreases." This means that as the number of cells in the cluster decreases, the system capacity increases. This can be explained by the fact that with fewer cells in the cluster, there is less interference and congestion, allowing for better utilization of resources and increased capacity.

The correct answer is 40dBm because the power in dBm is calculated by taking the logarithm (base 10) of the power in milliwatts and multiplying it by 10. In this case, since the power is given as 10W, we need to convert it to milliwatts by multiplying it by 1000 (1W = 1000mW). Taking the logarithm of 10,000 (10W * 1000mW/W) gives us 4, and multiplying it by 10 gives us 40dBm.

If the factor of multiple repetition of frequency is 13, it means that the frequency is repeated 13 times. In order to have the closest neighboring cells, we need to consider the cells that have the same frequency. Since the factor is 13, the closest neighboring cells would be the 6 cells that have the same frequency, as they are the closest in terms of the repetition factor. Therefore, the correct answer is 6.

The correct answer is "Iznosi najvise 1Mbps" because if the minimum duration of a symbol is 1*10-6s, it means that the maximum number of symbols that can be transmitted in one second is 1/1*10-6, which is equal to 1,000,000 symbols. Since the symbol rate is equal to the data rate in this case, the maximum data rate that can be achieved is 1Mbps.

The EIRP (Effective Isotropic Radiated Power) is calculated by adding the transmit power (in dBW) to the gain of the transmitting antenna (in dBi). In this case, the transmit power is 10W (or 10dBW) and the gain of the transmitting antenna is 10dBi. Adding these values together, we get 10dBW + 10dBi = 20dBW. Therefore, the EIRP is 20dBW.

The question asks for the Effective Radiated Power (ERP) in the case of a half-wave dipole antenna, given that the transmitter power is 10W and the gain of the transmitting antenna is 10dBi. The ERP can be calculated by adding the transmitter power to the gain of the antenna. In this case, the gain is given in decibels relative to an isotropic radiator (dBi), so we need to convert it to a linear scale. 10dBi is equivalent to a gain of 10^(10/10) = 10 times. Therefore, the ERP is 10W + 10W = 20W. However, the answer choices provided do not match this result, so the correct answer cannot be determined.

When a vehicle is moving perpendicular to the direction of the emitted wave, the Doppler shift is equal to zero. This means that there is no change in the frequency of the wave as observed by the receiver on the vehicle. This occurs because the vehicle's motion is neither towards nor away from the transmitter, resulting in no apparent change in frequency.

The amplitude spectrum of a cosine and sine function with the same frequency and amplitude will look the same because the only difference between the two functions is a phase shift of 90 degrees. The amplitude spectrum represents the magnitude of each frequency component in the signal, and since the frequency and amplitude are the same for both functions, their amplitude spectra will be identical.

The explanation for the given correct answer is that the distribution of a large number of random variables is being described as Gaussian, also known as the normal distribution. The repetition of "Gausovoj raspodeli, gausovoj raspodeli, GAUSOVOJ RASPODELI" emphasizes that the random variables are following a Gaussian distribution.

Polu-dupleks komunikacija podrazumeva da se predaja i prijem podataka vrše preko istog kanala, ali ne istovremeno. To znači da se jedan uređaj može koristiti za slanje podataka dok drugi uređaj istovremeno prima podatke, ali ne mogu istovremeno oba uređaja slati i primati podatke.

The correct answer is "kontinualnih i preiodicnih signala" which means "continuous and periodic signals" in English. The Fourier series is used to analyze signals that are continuous and periodic in nature. It breaks down these signals into their individual frequency components, allowing for a better understanding of their spectral characteristics. This analysis is commonly used in fields such as telecommunications, audio processing, and image analysis.

The correct answer is "Rejlijevom raspodelom". The Rayleigh distribution is commonly used to describe the amplitude of a signal that is transmitted through a multipath fading channel. In this type of channel, the signal takes multiple paths to reach the receiver, resulting in constructive and destructive interference. The Rayleigh distribution models the random variations in the amplitude of the received signal, which is caused by the different path lengths and phase shifts.

The correct answer is 1/1.1µs. The average delay time can be determined by taking the reciprocal of the given value, which in this case is 1/1.1µs. This means that on average, there is a delay of 1.1µs between the input and the output.

The wavelength of an antenna can be calculated by dividing the speed of light by the frequency of the antenna. In this case, the frequency is given as 3GHz (3 billion Hz). By using the formula wavelength = speed of light / frequency, we can find the wavelength. The speed of light is approximately 3 x 10^8 meters per second. Dividing this by 3 x 10^9 Hz gives us a wavelength of 0.1 meters, which is equivalent to 0.1m. Therefore, the correct answer is 0.1m.

The correct answer is "diskretnih signala". The Discrete Fourier Transform (DFT) is used to analyze the frequency components of discrete signals. It transforms a sequence of discrete data points into its equivalent representation in the frequency domain. This allows for the identification of specific frequencies present in the signal and is commonly used in fields such as telecommunications, audio processing, and image analysis.

The correct answer is "sporim fedingom" because the given information states that the duration of the coherent time interval is 0.001s, and the duration of the symbol is 10-6s. Slow fading refers to a situation where the channel conditions remain relatively constant over the duration of the coherent time interval, but may change significantly over longer periods of time. In this case, since the symbol duration is much smaller than the coherent time interval, it indicates that the channel conditions are expected to remain relatively constant over the symbol duration, thus exhibiting slow fading.

The correct answer is that the number of cells in the cluster does not affect the system capacity or the signal interference ratio. This means that increasing the number of cells in the cluster does not decrease the system capacity nor increase the signal interference ratio.

For dynamic channel allocation, it generally reduces the probability of call blocking. This means that by dynamically assigning channels, there is a higher chance that calls will be successfully connected without being blocked.

The correct answer is "kontinualnih i aperiodicnih signala" which translates to "continuous and aperiodic signals" in English. The Fourier transform is used to analyze signals in the frequency domain, and it is applicable to continuous signals (those that exist over a continuous range of time) as well as aperiodic signals (those that do not repeat in a regular pattern). This transform allows us to decompose a signal into its individual frequency components, providing valuable information about its spectral content.

Co-channel interference refers to the interference caused by multiple cells using the same frequency channel. When the number of cells in a cluster decreases, it means that there are fewer cells using the same frequency channel. As a result, the interference caused by co-channel interference also decreases. Therefore, the correct answer is "Ako broj celija u klasteru opada" which translates to "If the number of cells in the cluster decreases."

Sektorizacija se koristi kako bi se smanjila istokanalna interferencija. To znači da se delovi frekvencijskog spektra koji se koriste za prenos signala preklapaju u manjoj meri, što smanjuje smetnje i poboljšava kvalitet prenosa. Umanjenje istokanalne interferencije omogućava bolju komunikaciju i smanjuje mogućnost grešaka u prenosu podataka.

By controlling the power, the goal is to minimize the power emitted by the users. This means that the aim is to reduce the amount of power being transmitted by the users in order to achieve a more efficient and optimal use of resources. By minimizing the power emitted by the users, it helps in reducing interference, conserving energy, and improving overall system performance.

The correct answer is "zvonasti oblik, sa maksimumom za x jednako srednjoj vrednosti". This means that the shape of the Gaussian function is bell-shaped, and the maximum value of the function is located at the mean value of x.

Sports fading occurs when the duration of symbols is much shorter than the coherent time interval of the channel. This means that the symbols transmitted in the channel are not able to maintain their coherence due to the rapid changes in the channel. As a result, the received signal experiences fading, causing fluctuations in the signal strength. This phenomenon is particularly common in mobile communication systems where the channel conditions can vary rapidly.

If the frequency separation between two sinusoids is smaller than the coherent bandwidth of the channel (Vs), they will experience different channel effects. In other words, the channel will introduce different distortions or variations in amplitude and phase for each sinusoid. This is because the channel's influence on the signal depends on its frequency content, and if the sinusoids have different frequencies, they will be affected differently. Therefore, the statement that "Dve sinusoide sa frekvencijskim razmakom manjim od Vs (koheretnog opsega kanala) podlezu razlicitom uticaju kanala" is incorrect.

Brz feding nastaje kada je trajanje simbola veće od koherentnog vremenskog intervala kanala. This means that fast fading occurs when the duration of symbols is longer than the coherent time interval of the channel. In fast fading, the channel conditions change rapidly over time, causing significant fluctuations in the received signal strength. This can result in errors and degraded performance in wireless communication systems.

Buffer underrun typically occurs at very low transfer speeds. When the transfer speed is too slow, the buffer in the device being written to cannot be filled fast enough, causing the writing process to pause and resulting in a buffer underrun error. This error can be prevented by ensuring that the transfer speed is sufficient to keep the buffer consistently filled during the writing process.

Frequency selective fading occurs when the frequency range of the signal is larger than the coherent bandwidth of the channel. In other words, the signal experiences different levels of attenuation or distortion across different frequencies within the channel. This can result in variations in signal strength and quality, leading to potential communication errors or disruptions.