Quiz 3: Wcdma For Umts Hspa Evolution And Lte: Chapter 3 Introduction To Wcdma

1. WCDMA has a frequency reuse of 1 between different cells. This means that the same frequencies can be reused in neighboring cells.

True

False

WCDMA (Wideband Code Division Multiple Access) indeed has a frequency reuse of 1 between different cells. This means that the same frequencies can be reused in neighboring cells. This is possible because WCDMA uses a spread spectrum technique where each user is assigned a unique code, allowing multiple users to share the same frequency band simultaneously. By reusing frequencies in neighboring cells, WCDMA maximizes spectrum efficiency and enables efficient use of available resources.

Explanation

WCDMA (Wideband Code Division Multiple Access) indeed has a frequency reuse of 1 between different cells. This means that the same frequencies can be reused in neighboring cells. This is possible because WCDMA uses a spread spectrum technique where each user is assigned a unique code, allowing multiple users to share the same frequency band simultaneously. By reusing frequencies in neighboring cells, WCDMA maximizes spectrum efficiency and enables efficient use of available resources.

2.

The multiplexing mode shown in the figure is TDD

The multiplexing mode shown in the figure is FDD

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Explanation

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3.

This image refers to soft handover

This image refers to softer handover

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Explanation

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4. Multipath diversity occurs when the time difference between different paths is larger than the duration of a chip (0.26 micro seconds = 1/3.84 MHz).

True

False

Multipath diversity occurs when the time difference between different paths is larger than the duration of a chip. This means that the signals from multiple paths arrive at the receiver at different times, allowing for better signal reception and reducing the effects of interference. Therefore, the statement is true.

Explanation

Multipath diversity occurs when the time difference between different paths is larger than the duration of a chip. This means that the signals from multiple paths arrive at the receiver at different times, allowing for better signal reception and reducing the effects of interference. Therefore, the statement is true.

5.

This image refers to soft handover

This image refers to softer handover

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Explanation

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6.

The multiplexing mode shown in the figure is TDD

The multiplexing mode shown in the figure is FDD

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Explanation

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7. Multipath diversity could be useful in 3G wireless mobile communications.

True

False

Multipath diversity refers to the phenomenon where a wireless signal reaches the receiver through multiple paths, each with a different propagation delay and attenuation. In 3G wireless mobile communications, multipath diversity can be beneficial because it helps mitigate the negative effects of fading and interference. By receiving multiple copies of the signal, the receiver can combine them to improve the overall signal quality and increase the reliability of the communication. Therefore, multipath diversity is indeed useful in 3G wireless mobile communications.

Explanation

Multipath diversity refers to the phenomenon where a wireless signal reaches the receiver through multiple paths, each with a different propagation delay and attenuation. In 3G wireless mobile communications, multipath diversity can be beneficial because it helps mitigate the negative effects of fading and interference. By receiving multiple copies of the signal, the receiver can combine them to improve the overall signal quality and increase the reliability of the communication. Therefore, multipath diversity is indeed useful in 3G wireless mobile communications.

8. During softer handover only one power control loop per connection is active.

True

False

During a softer handover, which is a type of handover in cellular networks, only one power control loop per connection is active. This means that the power level of the signal being transmitted and received is adjusted based on the quality of the connection. This allows for better management of the network resources and ensures that the signal strength is optimized for each connection. Therefore, the statement "During softer handover only one power control loop per connection is active" is true.

Explanation

During a softer handover, which is a type of handover in cellular networks, only one power control loop per connection is active. This means that the power level of the signal being transmitted and received is adjusted based on the quality of the connection. This allows for better management of the network resources and ensures that the signal strength is optimized for each connection. Therefore, the statement "During softer handover only one power control loop per connection is active" is true.

9. The duration for WCDMA frame is

10 ms

20 ms

100 ms

200 ms

The duration for WCDMA frame is 10 ms. WCDMA, or Wideband Code Division Multiple Access, is a mobile communication technology that uses code division multiple access for transmitting data. The frame duration refers to the time it takes for one complete cycle of data transmission. In the case of WCDMA, this duration is 10 ms, meaning that the data is transmitted in intervals of 10 ms. This allows for efficient and reliable communication between mobile devices.

Explanation

The duration for WCDMA frame is 10 ms. WCDMA, or Wideband Code Division Multiple Access, is a mobile communication technology that uses code division multiple access for transmitting data. The frame duration refers to the time it takes for one complete cycle of data transmission. In the case of WCDMA, this duration is 10 ms, meaning that the data is transmitted in intervals of 10 ms. This allows for efficient and reliable communication between mobile devices.

10. During soft handover two power control loops per connection are active

True

False

During soft handover, two power control loops per connection are active to ensure seamless transition between different base stations. This allows for better signal quality and improved call reliability. By having two power control loops, the mobile device can adjust its transmit power independently for each base station, optimizing the signal strength and minimizing interference. This helps to maintain a stable and consistent connection during the handover process. Therefore, the statement is true.

Explanation

During soft handover, two power control loops per connection are active to ensure seamless transition between different base stations. This allows for better signal quality and improved call reliability. By having two power control loops, the mobile device can adjust its transmit power independently for each base station, optimizing the signal strength and minimizing interference. This helps to maintain a stable and consistent connection during the handover process. Therefore, the statement is true.

11. Fast fading occurs when the path difference between two received signals is half wavelength approximately (7 cm at 2 GHz).

True

False

Fast fading occurs when the path difference between two received signals is half wavelength approximately (7 cm at 2 GHz). This is because when the path difference is half wavelength, the signals combine constructively and result in a stronger signal. Fast fading is a phenomenon in which the received signal strength fluctuates rapidly due to changes in the channel caused by factors such as multipath interference.

Explanation

Fast fading occurs when the path difference between two received signals is half wavelength approximately (7 cm at 2 GHz). This is because when the path difference is half wavelength, the signals combine constructively and result in a stronger signal. Fast fading is a phenomenon in which the received signal strength fluctuates rapidly due to changes in the channel caused by factors such as multipath interference.

12. The processing gain is equal to the spreading factor

True

False

The processing gain refers to the increase in signal power achieved by spreading the signal over a wider bandwidth. It is directly proportional to the spreading factor, which is the ratio of the chip rate to the data rate. Therefore, if the processing gain is equal to the spreading factor, it means that the signal power is increased by the same amount as the ratio of chip rate to data rate. Thus, the statement is true.

Explanation

The processing gain refers to the increase in signal power achieved by spreading the signal over a wider bandwidth. It is directly proportional to the spreading factor, which is the ratio of the chip rate to the data rate. Therefore, if the processing gain is equal to the spreading factor, it means that the signal power is increased by the same amount as the ratio of chip rate to data rate. Thus, the statement is true.

13. The target Signal to Interference Ratio (SIR) is determined in the

Base station

Radio network controller

The target Signal to Interference Ratio (SIR) is determined in the radio network controller. The radio network controller is responsible for managing and controlling the overall operation of the base station. It is in charge of allocating radio resources, optimizing network performance, and making decisions regarding power control and interference management. Therefore, it is logical that the target SIR, which is a crucial parameter for maintaining good signal quality and minimizing interference, would be determined at the radio network controller level.

Explanation

The target Signal to Interference Ratio (SIR) is determined in the radio network controller. The radio network controller is responsible for managing and controlling the overall operation of the base station. It is in charge of allocating radio resources, optimizing network performance, and making decisions regarding power control and interference management. Therefore, it is logical that the target SIR, which is a crucial parameter for maintaining good signal quality and minimizing interference, would be determined at the radio network controller level.

14. Tight and fast power control is very important for WCDMA, especially in the

Uplink

Downlink

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Explanation

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15. A base station mainly uses --------------------- to control the output power of mobiles.

Open loop power control

Closed loop power control

A base station mainly uses closed loop power control to control the output power of mobiles. Closed loop power control is a feedback mechanism that continuously monitors the received signal strength from the mobiles and adjusts the transmit power accordingly. This ensures that the mobiles are operating at an optimal power level, minimizing interference and maximizing network capacity. Open loop power control, on the other hand, does not take into account the received signal strength and relies on fixed power settings. Closed loop power control is more efficient and adaptive in managing power levels in a cellular network.

Explanation

A base station mainly uses closed loop power control to control the output power of mobiles. Closed loop power control is a feedback mechanism that continuously monitors the received signal strength from the mobiles and adjusts the transmit power accordingly. This ensures that the mobiles are operating at an optimal power level, minimizing interference and maximizing network capacity. Open loop power control, on the other hand, does not take into account the received signal strength and relies on fixed power settings. Closed loop power control is more efficient and adaptive in managing power levels in a cellular network.

16.

For this DS-CDMA, the spreading factor is 1

For this DS-CDMA, the spreading factor is 2

For this DS-CDMA, the spreading factor is 4

For this DS-CDMA, the spreading factor is 8

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Explanation

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17. In an uplink fading channel, the mobile output power propotions --------------------- to the base station received power (SIR).

Directly

Inversely

In an uplink fading channel, the mobile output power is inversely proportional to the base station received power (SIR). This means that as the base station received power increases, the mobile output power decreases, and vice versa. This relationship is due to the fading effects in the channel, where the signal strength fluctuates. As the received power increases, the mobile device needs to reduce its output power to maintain a constant SIR.

Explanation

In an uplink fading channel, the mobile output power is inversely proportional to the base station received power (SIR). This means that as the base station received power increases, the mobile output power decreases, and vice versa. This relationship is due to the fading effects in the channel, where the signal strength fluctuates. As the received power increases, the mobile device needs to reduce its output power to maintain a constant SIR.

18. Fast fading could be useful in 3G wireless mobile communications.

True

False

Fast fading refers to the rapid fluctuations in the strength of a wireless signal due to factors such as multipath interference and signal blockage. In 3G wireless mobile communications, fast fading can be detrimental as it can cause frequent signal dropouts and reduced signal quality. Therefore, fast fading is not useful in 3G wireless mobile communications.

Explanation

Fast fading refers to the rapid fluctuations in the strength of a wireless signal due to factors such as multipath interference and signal blockage. In 3G wireless mobile communications, fast fading can be detrimental as it can cause frequent signal dropouts and reduced signal quality. Therefore, fast fading is not useful in 3G wireless mobile communications.

19. Fast fading can be removed with the aid of

Strong coding

Pilot symbols

Retransmission protocols

Time diversity

Pilot symbols can help remove fast fading. In wireless communication, fast fading occurs due to rapid changes in signal strength caused by obstacles or interference. Pilot symbols are known reference signals that are inserted into the transmitted signal. These symbols are used at the receiver to estimate the channel conditions and compensate for the fading effects. By using pilot symbols, the receiver can accurately reconstruct the transmitted signal, even in the presence of fast fading, improving the overall reliability and quality of the communication link.

Explanation

Pilot symbols can help remove fast fading. In wireless communication, fast fading occurs due to rapid changes in signal strength caused by obstacles or interference. Pilot symbols are known reference signals that are inserted into the transmitted signal. These symbols are used at the receiver to estimate the channel conditions and compensate for the fading effects. By using pilot symbols, the receiver can accurately reconstruct the transmitted signal, even in the presence of fast fading, improving the overall reliability and quality of the communication link.