5G

09 January 2025 12:07 AM

(2marks)
1) Family of 3G and 4G Wireless Standards with Data Rates
• 3G:
○ WCDMA: Up to 2 Mbps
○ HSPA: Up to 14 Mbps (downlink), 5.8 Mbps (uplink)
○ EV-DO: Up to 3.1 Mbps (downlink), 1.8 Mbps (uplink)
• 4G:
○ LTE: Up to 100 Mbps (downlink), 50 Mbps (uplink)
○ WiMAX: Up to 75 Mbps
2) Define Multi-Carrier Modulation
• A technique where data is transmitted using multiple carrier frequencies, such as in OFDM.
• It helps in combating inter-symbol interference and enhances spectral efficiency.
3) Comparison of BER for Wireline and Wireless Communication Systems
• Wireline: Low BER due to stable channels and minimal noise.
• Wireless: Higher BER due to fading, interference, and mobility issues.
4) Advantage of MMSE Receiver over ZF Receiver
• MMSE minimizes both noise and interference, offering better performance in noisy environments.
• ZF cancels interference but amplifies noise, leading to poorer performance at low SNR.
5) Advantages of Space-Time Coding Techniques
• Improves reliability by transmitting redundant data across multiple antennas.
• Enhances diversity gain and increases data rates in MIMO systems.
6) Challenges for Existing 4G Cellular Technology
• Insufficient bandwidth for massive IoT connections.
• High latency compared to 5G.
• Limited support for high-mobility scenarios.
7) OFDM Transmitter Schematic with IFFT
• Consists of a serial-to-parallel converter, modulator, IFFT block, parallel-to-serial converter, and cyclic prefix
addition.
8) Pseudo Inverse Matrix in ZF Receiver
• A pseudo-inverse matrix is used to find the least-squares solution when the channel matrix is non-invertible.
• It helps in reconstructing transmitted signals by minimizing error.
9) Advantages of Using mmWave Technology for 5G
• High data rates due to larger bandwidth.
• Lower latency and better support for dense networks.
• Enables ultra-reliable low-latency communication (URLLC).
10) Services and Features of Different Generations of Cellular Networks
• 1G: Voice-only service, analog technology.
• 2G: SMS, digital voice, low-speed data (up to 64 kbps).
• 3G: Mobile internet, video calls, data rates up to 2 Mbps.
• 4G: High-speed internet, HD streaming, VoIP, data rates up to 100 Mbps.
• 5G: Ultra-high-speed internet, IoT connectivity, URLLC, data rates up to 10 Gbps.

1) Family of 3G and 4G Wireless Standards with Data Rate

• 3G Standards:
○ WCDMA: Up to 2 Mbps
HSPA: 14 Mbps (DL), 5.8 Mbps (UL)

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 ○ HSPA: 14 Mbps (DL), 5.8 Mbps (UL)
○ CDMA2000: 2.4 Mbps
• 4G Standards:
○ LTE: 100 Mbps (DL), 50 Mbps (UL)
○ WiMAX: 75 Mbps
○ LTE-Advanced: 1 Gbps (DL), 500 Mbps (UL)

2) How Cyclic Prefix Helps Remove Inter-Symbol Interference

• Cyclic prefix acts as a guard interval by repeating the last part of the OFDM symbol at the start.
• It absorbs delayed versions of the symbol, preventing overlapping and inter-symbol interference in multipath
channels.

5) Difference Between Alamouti Code and V-BLAST in MIMO

Alamouti Code V-BLAST

Provides diversity gain Provides multiplexing gain
Uses 2 transmit antennas Can use multiple antennas
Simple decoding (orthogonal design) Complex decoding (SIC needed)
Suitable for low data rates Suitable for high data rates

6) Challenges for 5G Mobile Communications

• High cost of infrastructure deployment.
• High susceptibility to interference at mmWave frequencies.
• Limited range and penetration issues of mmWave.
• Energy consumption in dense networks.

7) PAPR for OFDM

• PAPR (Peak-to-Average Power Ratio) represents the ratio of the peak power to the average power of an OFDM
signal.
• High PAPR is problematic as it requires expensive power amplifiers with a large linear range.

8) BER for Wireline and Wireless Communication Systems

• Wireline: Low BER due to a stable channel and fewer distortions.
• Wireless: Higher BER due to fading, interference, and mobility issues. BER depends on modulation, channel
coding, and SNR.

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9) Brief on NOMA Technology
• NOMA (Non-Orthogonal Multiple Access) allows multiple users to share the same time and frequency
resources.
• Differentiates users by power levels and uses successive interference cancellation (SIC) for decoding.
• Provides better spectral efficiency and supports massive connectivity.

10) Concept of Deep Fading

• Deep fading refers to a situation where the signal amplitude drops significantly due to destructive interference
from multipath propagation.
• It results in temporary loss of signal and higher BER, requiring diversity techniques or channel coding to mitigate.

UNIT 1

11A)Using Mathematical expressions, model the wireless communication systems.

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11B) Derive the expression for the received signal y(t) in terms of multipath components

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11B)Explain about Constructive and Destructive Interference with example

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12A)Briefly discass about the multi-carrier transmission

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12B)Explain the MIMO OFDM transmitter and receiver blocks in detail

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12B)Discuss the advantages of adding cyclic prefix in OFDM

What is Cyclic Prefix in OFDM?

• A cyclic prefix (CP) is a repetition of the end portion of an OFDM symbol, added at the start of the symbol.
• It helps combat inter-symbol interference (ISI) caused by multipath propagation.
• The CP acts as a buffer zone, ensuring orthogonality between subcarriers in the presence of delays.
Advantages of Adding Cyclic Prefix
• Eliminates ISI: Prevents interference between successive symbols.
• Preserves Orthogonality: Maintains orthogonality of subcarriers by absorbing delay spread.
• Simplifies Equalization: Converts linear convolution into circular convolution, allowing frequency domain
equalization.
• Enhances Robustness: Makes OFDM resilient to multipath fading and time dispersion.
• Reduces Complexity: Enables simpler receiver designs.
• Improved Synchronization: Facilitates timing and frequency synchronization at the receiver.
• Scalability: Allows adaptation to varying channel conditions by adjusting CP length.
• Flexibility in Receiver Design: Reduces sensitivity to timing offsets and channel estimation errors.
• Energy Spread Management: Reduces inter-carrier interference (ICI) by accommodating channel-induced
delays.
• Interoperability: Enhances performance in diverse environments, such as urban areas with significant multipath
effects.
• Simplified Implementation: Makes FFT processing feasible by converting channel effects into a manageable
form.

14A)Derive the equation of estimated output for ZF MIMO receiver

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14B)Derive the equation of estimated outpat for MMSE MIMO receiver

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14B)Obtain the system model for 4x4 MIMO in vector form

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15A)Explain besraforming uring Alamotti Code with necessary expressions

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15B)Explain working of V BLAST MIMO receiver using necessary equations

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15B)Point the advantages using Space Time Coding techniques

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16A)What are the challenges for 5G mobile Communications

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16B)Describe briefly about NOMA Technology

16A)Explain the 2 Key mm wave and MIMO Technology that can be used for 5G communications

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16B)Discuss the different application for 50 wireless communication technology.

Applications of 5G Wireless Communication Technology:

• Enhanced Mobile Broadband (eMBB):
○ Ultra-fast internet for smartphones and tablets.
○ High-quality streaming (4K/8K videos, AR/VR experiences).
• Massive IoT (Internet of Things):
○ Connects billions of devices (smart homes, wearables, sensors).
○ Enables smart cities (traffic control, energy management).
• Ultra-Reliable Low-Latency Communication (URLLC):
○ Critical applications like remote surgery and autonomous vehicles.
○ Industrial automation with precise control and monitoring.
• Augmented and Virtual Reality (AR/VR):
○ Real-time gaming and immersive experiences.
○ Training simulations for education and industries.
• Smart Transportation:
○ Vehicle-to-everything (V2X) communication for safer roads.
○ Efficient public transport and traffic management.
• Healthcare:
○ Remote diagnostics and telemedicine.
○ Real-time monitoring with wearable medical devices.
• Entertainment and Media:
○ Enhanced live streaming and interactive experiences.
○ High-speed downloads and cloud gaming.
• Agriculture:
○ Smart farming with connected equipment and sensors.
○ Precision agriculture for better crop management.
• Energy and Utilities:
○ Smart grids and efficient energy distribution.
○ Real-time monitoring of power systems.
• Manufacturing:
○ Factory automation with robotic systems.
○ Predictive maintenance and IoT-enabled machines.

17A)Derive the mathcmatical model expression for Rayleigh Ending wireless channel

Rayleigh Fading Wireless Channel (Short Version)

1. Received Signal:

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 1. Received Signal:
r(t)=h(t)s(t)+n(t)r(t) = h(t) s(t) + n(t)r(t)=h(t)s(t)+n(t)
○ s(t)s(t)s(t): Transmitted signal
○ h(t) h(t)h(t): Fading coefficient (random)
○ n(t) n(t)n(t): Additive noise
2. Channel Coefficient h(t)h(t)h(t):
○ No direct line-of-sight (LOS), only multipath components.
○ ∣h(t)∣|h(t)|∣h(t)∣ follows a Rayleigh distribution (random amplitude variation).
○ ∣h(t)∣2|h(t)|^2∣h(t)∣2 (power) follows an exponential distribution.
3. Main Effect:
○ Received signal strength varies randomly due to multipath fading.
4. Doppler Effect:
○ Due to motion, the channel varies over time, causing frequency shifts.
5. Autocorrelation:
○ Describes how similar the channel is at different times, modeled using Jakes' model.

17B)Stiefly explain about OFDM-PAPR

17C)Compute the BER for BPSK conumunication over a multi- antina fading wireless channel with L-
mceive antenna at SNR=20 dB

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17A)List the services and features of different generations of cellular networks

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17B)Relate mulli carrier transmission system with What is the condition OFOM

17C)what is the condition for deep fading in terms of attenuation and SNR

18A)How MIMO systema achives significani luger data rates than traditional SISO

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18B) What are the different types of Space time codes used for MIMO Communication system

Types of Space-Time Codes Used for MIMO Communication Systems

1. Alamouti Code:
○ Simple and Efficient: The Alamouti code is a 2x1 space-time block code, which is one of the
simplest and most widely used for two transmit antennas.
○ Maximizes Diversity: Provides diversity gain and improves reliability in the presence of
fading.
2. Space-Time Block Codes (STBC):
○ Generalized Alamouti: These codes are designed for multiple transmit antennas and can
achieve both diversity and coding gains.
○ Higher Dimensions: Can work with more than two antennas, offering better performance
and robustness.
3. Space-Time Trellis Codes (STTC):
○ Trellis Structure: STTC combines trellis coding with space-time coding, providing higher
coding gains.
○ Complex Decoding: Requires more complex decoding algorithms but provides significant
performance improvements.
4. Vertical Bell Laboratories Layered Space-Time (VBLAST):
○ Layered Architecture: VBLAST uses multiple layers to transmit different data streams across
multiple antennas.
○ Performance: It can achieve high data rates and is good for systems with many transmit
antennas.
5. Orthogonal Space-Time Block Codes (OSTBC):
○ Orthogonality: These codes use orthogonal designs for space-time coding, which simplifies
decoding and reduces interference.
○ Robust: They provide robust performance under fading conditions and are used in systems
like 3G/4G.
6. Differential Space-Time Codes (DSTC):
○ No Channel State Information (CSI) Required: These codes don’t require the receiver to
know the exact channel conditions, making them useful in scenarios with limited channel

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 know the exact channel conditions, making them useful in scenarios with limited channel
feedback.
7. Golden Code:
○ High-Diversity Code: A special type of STBC that achieves full diversity and performs well in
terms of error rates.
○ Four Transmit Antennas: Primarily designed for systems with four transmit antennas.

18C)What are the advantages of mm Waves technology for 5G cellular communication

Advantages of mmWave Technology for 5G Cellular Communication

1. High Data Rates:
○ mmWave supports higher frequencies (30 GHz to 300 GHz), allowing much higher data
transfer rates than traditional cellular bands.
2. Increased Bandwidth:
○ The wide bandwidth available at mmWave frequencies enables more data to be transmitted
simultaneously, improving network capacity.
3. Low Latency:
○ mmWave supports low latency communication, which is crucial for applications like real-
time gaming, autonomous vehicles, and augmented reality.
4. Enhanced Capacity:
○ mmWave can handle a large number of users and devices simultaneously, supporting the
high demands of 5G networks.
5. Efficient Use of Spectrum:
○ With more available spectrum at higher frequencies, mmWave helps alleviate congestion in
the lower frequency bands.
6. Improved User Experience:
○ The higher frequencies allow for faster download and upload speeds, improving overall user
experience in 5G networks.
7. Supports Dense Urban Environments:
○ mmWave is ideal for urban environments where high user density and demand for
bandwidth are high.
8. Advanced Applications:
○ Enables emerging technologies like virtual reality (VR), 4K/8K video streaming, and smart
cities due to its high-speed, high-capacity nature.

18A)Compare MMSE receiver ant ZF receivers for MIMO receivers

18B) Explain the successive Interference Cancellation in V-Blast MIMO receivers

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18C) Explain the challenges of using mm Waves for 5G

Challenges of Using mmWaves for 5G

• Limited Range:
○ MmWaves have a shorter range compared to lower-frequency signals, requiring more base
stations for coverage.
• High Path Loss:
○ MmWave signals suffer from higher attenuation as they travel, leading to weaker signals
over distance.
• Blockage Sensitivity:
○ Obstructions (e.g., buildings, trees, walls) can easily block mmWave signals, reducing
reliability.
• Atmospheric Absorption:
○ MmWave frequencies are absorbed by rain, humidity, and oxygen, leading to further signal
degradation.
• Need for Line-of-Sight:
○ MmWave communication requires a clear line-of-sight between the transmitter and
receiver for optimal performance.
• Interference:
○ Higher frequency bands are more prone to interference from other devices, limiting the
efficient use of available spectrum.
• Energy Consumption:

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• Energy Consumption:
○ Transmitting in mmWave frequencies requires more power, leading to higher energy
consumption in devices and base stations.
• Device Size and Cost:
○ MmWave antennas require advanced technologies, increasing the cost and complexity of
devices and infrastructure.
• Challenges in Beamforming:
○ Accurate beamforming is crucial for mmWave systems, and it can be more complex and
difficult to implement due to the high frequency.

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