11.a.
Key Technological Advancements from 1G to 5G and Their Contributions:
• 1G (First Generation – Analog Communication):
o Introduced: Early 1980s
o Technology: Used analog signals for voice communication.
o Features: Basic voice calling was the only service provided.
o Limitations: Poor voice quality, low capacity, high power consumption, and no data services.
o Impact: It laid the foundation for mobile communication but suffered from frequent call drops and
security issues due to lack of encryption.
• 2G (Second Generation – Digital Communication):
o Introduced: Early 1990s
o Technology: Shifted from analog to digital signals, using GSM (Global System for Mobile
Communication).
o Features: Improved voice quality, enhanced security with encryption, and better call clarity.
o Data Services: Introduced SMS (Short Message Service) and MMS (Multimedia Messaging Service).
o Impact: Enabled international roaming and improved spectral efficiency. Digital technology made
communication more secure and stable.
• 3G (Third Generation – Mobile Broadband):
o Introduced: Early 2000s
o Technology: Used packet-switching technology for data transmission.
o Features: High-speed internet, video calling, and multimedia messaging.
o Data Rates: Up to 2 Mbps for stationary devices and 384 Kbps for mobile devices.
o Impact: Revolutionized mobile usage by enabling services like mobile TV, online gaming, and real-time
video streaming.
• 4G (Fourth Generation – High-Speed Data):
o Introduced: Late 2000s
o Technology: Based on LTE (Long-Term Evolution) and IP-based networks.
o Features: High-definition video streaming, online gaming, VoIP (Voice over IP), and advanced
multimedia services.
o Data Rates: Up to 1 Gbps for stationary users and 100 Mbps for mobile users.
o Impact: Reduced latency, improved download and upload speeds, and provided seamless connectivity
for high-bandwidth applications.
• 5G (Fifth Generation – Next-Gen Connectivity):
o Introduced: Late 2010s
o Technology: Uses advanced technologies like OFDMA, MIMO, and millimeter-wave frequencies.
o Features: Ultra-high-speed connectivity, extremely low latency (<1 ms), and massive device
connectivity.
o Applications: Supports IoT (Internet of Things), autonomous vehicles, smart cities, augmented reality
(AR), and virtual reality (VR).
1.b. How OFDMA Improves Efficiency and Performance in 5G Networks:
• Orthogonal Frequency Division Multiple Access (OFDMA):
o Concept: OFDMA is a multi-user version of the Orthogonal Frequency Division Multiplexing
(OFDM) technique, where multiple users can transmit data simultaneously over different
subcarriers.
o Frequency Division: Divides the frequency band into multiple narrowband subcarriers,
allowing several users to share the same channel without interference.
o Spectral Efficiency: Maximizes spectrum efficiency by reducing guard bands and enabling
tighter packing of subcarriers.
o Data Rates: Provides high data rates and low latency, crucial for real-time applications like
video conferencing and gaming.
o Multipath Fading: Offers robustness against multipath fading by transmitting data over
multiple parallel subcarriers, improving signal quality in challenging environments.
o Dynamic Resource Allocation: Dynamically assigns subcarriers based on user demand and
channel conditions, optimizing throughput and network performance.
o Scalability: Supports both high-bandwidth users and low-data-rate IoT devices, enhancing
network flexibility.
o 5G Enhancement: Supports massive connectivity and high-speed data transfer, enabling
advanced services like IoT, AR, VR, and autonomous systems with unprecedented efficiency
and reliability.
2 a …..Direct Sequence Spread Spectrum (DSSS):
• Approach: DSSS spreads the signal by multiplying the data signal with a high-frequency pseudo-random noise
code. This results in a wider bandwidth compared to the original signal.
• Signal Spreading: The entire bandwidth is used for the transmission of the data, which reduces interference and
increases resistance to jamming.
• Advantages:
o Better resistance to interference and noise.
o Enhanced security due to spreading code usage.
o Improved signal clarity with reduced chances of data loss.
• Applications: Wi-Fi (802.11b) and GPS systems.
Frequency Hopping Spread Spectrum (FHSS):
• Approach: FHSS rapidly changes the carrier frequency according to a pseudo-random sequence, jumping across
different frequency channels.
• Signal Spreading: The signal hops between different frequencies within a wide band, making it less susceptible to
narrowband interference.
• Advantages:
o High resistance to jamming and eavesdropping.
o Efficient use of available frequency spectrum.
o Less impact from interference on any single frequency.
Multiple Input Multiple Output (MIMO) Technology:
MIMO is an advanced wireless communication technology that uses multiple antennas at both the transmitter and receiver
ends to improve communication performance. It enhances data throughput, reliability, and efficiency without requiring
additional bandwidth or power.
Enhancement of Performance:
• Increased Data Rate: By sending multiple data streams simultaneously over different spatial paths, MIMO
increases the overall data transmission rate.
• Improved Signal Quality: MIMO combats fading and interference by using multiple antennas to receive the same
signal from different paths, improving reception through diversity.
• Better Spectrum Efficiency: It maximizes the use of available bandwidth by transmitting multiple data streams at
the same frequency, increasing capacity without using more spectrum.
Key Advantages:
• Spatial Multiplexing: Increases data throughput by transmitting independent data streams on multiple antennas.
• Diversity Gain: Reduces signal fading by combining multiple received signals, enhancing reliability and reducing
error rates.
• Beamforming: Directs the signal towards the intended receiver, improving signal strength and minimizing
interference.
Applications in Modern Wireless Networks (including 5G):
• Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax) use MIMO to support high-speed internet connections.
• 4G LTE and 5G Networks leverage MIMO for faster, more reliable mobile communication with higher data
capacity.
• Massive MIMO in 5G uses a large number of antennas to serve multiple users simultaneously, dramatically
increasing network efficiency and coverage.
For question 3a:
Given:
• Cluster size: 7
• Total radio channels: 504
Step 1: Calculate the number of channels per cell:
Since a cluster consists of 7 cells, the total available channels (504) are distributed equally among them:
Channels per cell=5047=72\text{Channels per cell} = \frac{504}{7} = 72Channels per cell=7504=72
Step 2: Calculate the total capacity of the system:
The capacity of a cellular system is the total number of channels available:
System Capacity=Total number of channels=504\text{System Capacity} = \text{Total number of channels} =
504System Capacity=Total number of channels=504
Final Answer:
• Number of channels per cell: 72
• Total system capacity: 504
For question 3b:
Given:
• Total radio channels: 504
• Cluster size: 7
• Number of cells per cluster: 7
Step 1: Calculate the number of channels per cell:
Channels per cell=5047=72\text{Channels per cell} = \frac{504}{7} = 72Channels per cell=7504=72
Step 2: Calculate the capacity of the system:
In cellular systems, the system capacity is the total number of channels available across the entire system. Since the total
number of channels is already provided as 504, the system capacity remains:
System Capacity=504\text{System Capacity} = 504System Capacity=504
Final Answer:
• Number of channels per cell: 72
• Total system capacity: 504
GSM Architecture Overview:
The Global System for Mobile Communications (GSM) is a standard for digital cellular networks, and its architecture
consists of three main subsystems:
1. Mobile Station (MS):
o User Equipment: The physical device used by the subscriber, like a mobile phone.
o SIM Card: Stores subscriber information, including IMSI (International Mobile Subscriber Identity) and
encryption keys.
2. Base Station Subsystem (BSS):
o Base Transceiver Station (BTS): Handles the transmission and reception of signals to and from the
mobile station.
o Base Station Controller (BSC): Manages multiple BTSs, controls handovers, and allocates radio
resources.
3. Network and Switching Subsystem (NSS):
o Mobile Switching Center (MSC): The central component responsible for call setup, routing, and
mobility management.
o Home Location Register (HLR): Database containing permanent subscriber information and current
location.
o Visitor Location Register (VLR): Temporary database of subscribers currently active in a particular area.
o Authentication Center (AUC): Ensures secure user authentication.
o Equipment Identity Register (EIR): Tracks valid mobile devices based on their IMEI number.
How GSM Works:
• When a mobile device is powered on, it registers with the network via the BTS and BSC.
• The MSC manages call routing and handovers between cells.
• HLR and VLR keep track of the subscriber’s location and profile.
• AUC and EIR ensure security and validate devices.
Key Features:
• Digital voice and data transmission.
• International roaming support.
• SMS and basic data services.
LTE Architecture in Brief:
Long-Term Evolution (LTE) is a high-speed wireless communication standard designed for mobile devices and data
terminals. Its architecture is simpler and more efficient than earlier systems like GSM and 3G, with two main components:
1. User Equipment (UE):
o Mobile Device: The end-user’s smartphone, tablet, or modem.
o Subscriber Identity Module (SIM): Stores user identity and network credentials.
2. Evolved Universal Terrestrial Radio Access Network (E-UTRAN):
o eNodeB (eNB): The LTE base station, responsible for radio communication with the UE, managing radio
resources, and handling handovers. Unlike GSM’s BTS and BSC, LTE combines these functions in the
eNB.
3. Evolved Packet Core (EPC):
o Mobility Management Entity (MME): Handles user authentication, session management, and mobility
tracking.
o Serving Gateway (S-GW): Routes data packets and manages handovers within LTE networks.
o Packet Data Network Gateway (P-GW): Connects the LTE network to external data networks like the
internet.
How LTE Works:
• UE connects to the eNodeB for radio access.
• eNodeB communicates with the EPC for control and data transmission.
• MME manages user registration and mobility.
• S-GW and P-GW handle data routing and external network access.
Key Features:
• High-speed data transmission (up to 100 Mbps for downloads).
• Low latency and improved network efficiency.
• All-IP architecture for seamless voice and data services.
