Unit 1: Introduction to Wireless Communication System

GTU Course Code: 3171608 | Detailed Notes & Study Resources

1. Evolution of Mobile Communications (1G to 5G)

Mobile communication has undergone radical technical transformations roughly every decade, shifting from analog voice signals to ultra-high-speed, low-latency digital networks:

• 1G (1st Generation - 1980s): Analog cellular technology based on Frequency Division Multiple Access (FDMA). Examples include AMPS (Advanced Mobile Phone System) and TACS. It suffered from low traffic capacity, poor voice quality, no data support, zero call encryption, and high susceptibility to crosstalk.
• 2G (2nd Generation - 1990s): The digital revolution in mobile networks. Introduced digital voice, SMS, and encrypted channels using GSM (Time Division Multiple Access - TDMA) and IS-95 (Code Division Multiple Access - CDMA).
  • 2.5G (GPRS): Introduced packet-switched data (up to 115 kbps).
  • 2.75G (EDGE): Enhanced data rates using 8-PSK modulation (up to 384 kbps).
• 3G (3rd Generation - 2000s): Enabled mobile broadband, web browsing, and video calls. Built on Wideband CDMA (W-CDMA / UMTS) and CDMA2000. Provided data rates ranging from 384 kbps up to 2 Mbps.
• 4G LTE (4th Generation - 2010s): Pure All-IP packet-switched network architecture utilizing Orthogonal Frequency Division Multiple Access (OFDMA) for downlink and SC-FDMA for uplink. Enabled HD video streaming and low latency (<50 ms) with peak rates of 100 Mbps to 1 Gbps (LTE-Advanced).
• 5G NR (5th Generation - Present): Operates on sub-6 GHz and millimeter-wave (mmWave) bands. Uses Massive MIMO and beamforming to support three main use cases: Enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communication (URLLC), and Massive Machine Type Communication (mMTC).

🔗 GeeksforGeeks Tutorial: Read Full Article on Generations of Wireless Communication (1G - 5G)

2. Types & Comparison of Common Wireless Systems

Wireless networks differ based on operational coverage, network architecture, and subscriber mobility requirements:

System Type	Coverage Range	Data Rate	Mobility	Key Technology
Paging Systems	Wide Area (~10-50 km)	Very Low (Bps)	One-Way / Low	Simulcast RF Transmitters
Cellular Systems	Nationwide / Global	Mbps to Gbps	High (Vehicular)	Frequency Reuse, GSM/LTE/5G
WLAN (Wi-Fi)	Local (~100 meters)	Up to 9.6 Gbps	Pedestrian / Indoor	IEEE 802.11, OFDM, CSMA/CA
WLL (Fixed Wireless)	Last Mile (~5-10 km)	Moderate to High	Fixed / Stationary	Direct Microwave / CDMA-WLL
PAN (Bluetooth)	Personal Area (< 10 m)	1 to 3 Mbps	Short-Range Devices	IEEE 802.15.1, FHSS

🔗 GeeksforGeeks Tutorial: Detailed Comparison: Cellular Networks vs Wi-Fi Networks

3. 2G Cellular Standards: GSM Architecture & Channels

GSM (Global System for Mobile Communications) is the world's most widely adopted 2G standard[cite: 1]. It uses a hybrid combination of **FDMA** and **TDMA** over 200 kHz radio carrier channels.

Architecture Subsystems:

1. Mobile Station (MS): Consists of the physical Mobile Equipment (ME) and the Subscriber Identity Module (SIM) card containing IMSI and authentication keys.
2. Base Station Subsystem (BSS):
   • Base Transceiver Station (BTS): Contains radio transceivers, handles channel encryption/decryption and signal modulation.
   • Base Station Controller (BSC): Manages radio resources, frequency allocation, and inter-cell handovers for multiple BTSs.
3. Network & Switching Subsystem (NSS):
   • MSC (Mobile Switching Center): Central call routing engine connecting cellular calls to PSTN/ISDN.
   • HLR (Home Location Register): Permanent subscriber database storing user profile and current location info.
   • VLR (Visitor Location Register): Temporary database holding subscriber info currently roaming within the MSC area.
   • AuC (Authentication Center): Stores secret keys for SIM validation.
   • EIR (Equipment Identity Register): Tracks stolen or blacklisted handset IMEI numbers.

🔗 GeeksforGeeks Tutorial 1: GSM System Architecture Explained

🔗 GeeksforGeeks Tutorial 2: How Call Routing and GSM Handshake Works

4. Wireless Local Loop (WLL) Architecture

Wireless Local Loop (WLL), also referred to as Fixed Wireless Access (FWA), replaces traditional copper wires connecting subscribers to the local telephone central office exchange with a wireless radio link.

Core Elements of a WLL System:

• PSTN Central Office: The main telephone switching center.
• WANU (Wireless Access Network Unit): Installed at the central exchange. Integrates the Access Manager (AM), Home Location Register (HLR), transceiver modules, and WLL controllers to manage wireless channels.
• WASU (Wireless Access Subscriber Unit): Installed at the customer's home/office premises. It converts wireless RF signals into standard RJ-11 analog signals for telephones, fax machines, or modems.

Advantages of WLL:

• Rapid, low-cost deployment in difficult topographies (mountains, rural areas) where trenching copper wires is cost-prohibitive.
• Highly scalable and easy to expand capacity without physical wire replacement.

🔗 GeeksforGeeks Tutorial: Wireless Local Loop (WLL) System Architecture & Working

5. Wireless Local Area Networks (WLAN / IEEE 802.11)

A WLAN provides high-speed wireless connectivity over short ranges using unlicensed Industrial, Scientific, and Medical (ISM) radio bands (2.4 GHz, 5 GHz, 6 GHz).

WLAN Architectural Components:

• Stations (STA): End-user wireless devices (laptops, phones, IoT devices).
• Access Point (AP): The central hub connecting wireless devices to the wired Ethernet backbone.
• Basic Service Set (BSS): A single Access Point managing a group of associated stations.
• Extended Service Set (ESS): Two or more interconnected BSSs forming a unified large-scale network with seamless roaming.

Operating Modes:

1. Infrastructure Mode: Devices communicate through a centralized Access Point (Standard home/office setup).
2. Ad-Hoc Mode (IBSS): Peer-to-peer connection where stations communicate directly without any central Access Point.

🔗 GeeksforGeeks Tutorial 1: WLAN Architecture and 802.11 Standards

🔗 GeeksforGeeks Tutorial 2: Understanding Differences Between WLAN and Wi-Fi

6. Bluetooth & Personal Area Networks (PAN)

Bluetooth (IEEE 802.15.1) is an ad-hoc, low-power, short-range wireless communication standard operating in the 2.4 GHz ISM band. To prevent signal interference, Bluetooth employs Frequency Hopping Spread Spectrum (FHSS), hopping across 79 channels at 1600 hops per second.

Bluetooth Network Topologies:

• Piconet: An ad-hoc network consisting of 1 Master device and up to 7 active Slave devices. The Master controls transmission clock timing and channel access for all Slaves.
• Scatternet: Formed by interconnecting multiple Piconets. A device can act as a Slave in one Piconet and a Master in another, bridging data across Piconets.

🔗 GeeksforGeeks Tutorial: Personal Area Networks (PAN) & Bluetooth Architecture