Traditional Wireless Mobile Communication

The cellular device has evolved significantly and become an integral part of everyone's life as a portable communication device. Most people now have access to mobile technology that uses the Global System for Mobile Communication (GSM), which represents traditional wireless mobile communication. The first mobile phones used radio waves for communication, with cellular technology comprising cells and base stations that divide coverage areas into smaller cells for frequency reuse.

The traditional analog system was designed to transmit voice signals in analog form rather than digital format. The Motorola DynaTAC 8000X, introduced commercially in the 1980s, was the first wireless mobile phone with a distinctive brick-like design.

Evolution from Analog to Digital Systems

Analog systems transmitted voice signals in analog form but had significant disadvantages. Digital Signal Processing (DSP) chips were later developed as microprocessors for mobile communication baseband design and lower layer protocols, though they were costly to install and maintain.

Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) were proposed for fully digital systems to reduce setup costs and improve efficiency. To standardize mobile communication and avoid confusion between CDMA and TDMA, GSM was agreed upon as the global standard, which is essentially a form of TDMA.

Advantages of GSM over Analog Systems

• Enhanced data transmission Traffic-free data transmission with improved signaling capabilities

• Lower interference Reduced noise and interference levels compared to analog systems

• Increased capacity Digital systems handle more simultaneous calls and users

• Better integration Combines transmission and switching functions more efficiently

GSM System Architecture

The GSM system is divided into three main subsystems, each performing specific functions:

Mobile Station (MS)

The Mobile Station includes all user equipment such as the mobile phone, SIM (Subscriber Identity Module), and communication software. Its primary components are:

• SIM Card Removable memory circuit storing user information and authentication protocols

• Mobile Termination Handles error detection/correction, radio transmission, and encoding/decoding

• Terminal Equipment The actual mobile device that connects to the mobile station

• Terminal Adapter Provides interface access to Mobile Termination functions

Base Station Subsystem (BSS)

The BSS manages radio network functions and consists of two main components:

Base Station Controller (BSC) Acts as an intermediate element between Base Transceiver Stations and telecommunication networks. It controls radio network functions, manages handovers, monitors radio resource quality and allocation, and handles incoming/outgoing calls from mobile stations.

Base Transceiver Station (BTS) Controls and monitors the air interface, handling radio communication between mobile stations and the network. Each BTS serves a specific cell and performs functions including:

• Call processing and management

• Data encryption and decryption for secure transmission

• Speech processing (analog-to-digital and digital-to-analog conversion)

• Channel coding for error protection

• Signal modulation and demodulation

Operation and Support System (OSS)

The OSS manages network operations and maintenance through the Operation Maintenance Centre. It provides cost-effective support for local, regional, and centralized operations. Key functions include:

• Call management Handling incoming and outgoing calls

• Mobility management Managing subscriber movement across the network

• Subscriber data management Maintaining user information, billing, and service plans

• Call switching Managing calls between cellular networks and Public Switched Telephone Networks (PSTN)

The OSS is divided into two main divisions: Database (storing subscriber and network information) and Switches (managing call routing and connections).

Key Differences from Wired Communication

Unlike traditional wired communication with fixed locations, wireless mobile communication must address subscriber mobility using radio wave transmission. The primary challenge is locating subscribers, identifying their service requirements, and maintaining connectivity as they move between cells.

Conclusion

Traditional wireless mobile communication evolved from analog systems to digital GSM standards, providing improved capacity, security, and global compatibility. The three-tier GSM architecture (MS, BSS, OSS) enables efficient mobile communication by managing user equipment, radio networks, and system operations while addressing the unique challenges of subscriber mobility.