Basic Cellular System

Introduction

The Basic Cellular System is a fundamental concept in cellular mobile communication. It plays a crucial role in providing wireless communication services to a large number of users. This topic covers the performance criteria, uniqueness of the mobile radio environment, and the operation of cellular systems.

Importance of Basic Cellular System

The Basic Cellular System is essential for enabling wireless communication over long distances. It allows users to make calls, send messages, and access the internet using their mobile devices. Without the Basic Cellular System, mobile communication would be limited to short-range communication.

Fundamentals of Basic Cellular System

The Basic Cellular System operates by dividing a geographical area into smaller regions called cells. Each cell is served by a base station, which communicates with mobile devices within its coverage area. The cells are designed to overlap, ensuring continuous coverage throughout the service area.

Performance Criteria

Performance criteria are used to evaluate the effectiveness and efficiency of cellular systems. The key performance criteria in cellular systems are:

1. Coverage: The extent of the geographical area covered by the cellular network. It determines the availability of service to users.
2. Capacity: The maximum number of simultaneous users that can be supported by the cellular network. It determines the system's ability to handle high traffic loads.
3. Quality of Service (QoS): The level of service provided to users in terms of call quality, data transfer rates, and reliability.
4. Mobility Management: The ability of the cellular system to handle user mobility, including handovers between cells.
5. Handover: The process of transferring an ongoing call from one cell to another as the user moves.

Mobile Radio Environment

The mobile radio environment is unique due to various factors that affect wireless communication. These factors include propagation characteristics, interference, fading, and shadowing.

Uniqueness of Mobile Radio Environment

1. Propagation Characteristics: The way radio waves propagate in the mobile radio environment, including signal attenuation, diffraction, and reflection.
2. Interference: The presence of unwanted signals that can degrade the quality of wireless communication.
3. Fading: The fluctuation of signal strength due to multipath propagation and other environmental factors.
4. Shadowing: The blocking or weakening of signals by obstacles such as buildings, trees, or terrain.

Factors Affecting Mobile Radio Environment

1. Distance from Base Station: The signal strength decreases as the distance between the mobile device and the base station increases.
2. Obstacles: Buildings, trees, and other obstacles can block or weaken the signals, leading to reduced coverage.
3. Weather Conditions: Weather conditions such as rain, fog, or snow can affect signal propagation and cause signal degradation.
4. Frequency Band: Different frequency bands have different propagation characteristics and are affected differently by obstacles and interference.

Operation of Cellular Systems

The operation of cellular systems involves the interaction of various components and procedures.

Basic Architecture of Cellular Systems

1. Base Station: The base station is responsible for transmitting and receiving signals to and from mobile devices within its coverage area.
2. Mobile Station: The mobile station refers to the user's mobile device, such as a smartphone or tablet.
3. Mobile Switching Center (MSC): The MSC is the central hub that connects the cellular network to the public switched telephone network (PSTN) or other networks.
4. Home Location Register (HLR): The HLR is a database that stores subscriber information, including the current location of the mobile device.
5. Visitor Location Register (VLR): The VLR is a database that stores temporary information about roaming subscribers.

Call Setup Procedure in Cellular Systems

The call setup procedure in cellular systems involves several steps:

1. Registration: When a mobile device is powered on or enters a new cell, it registers with the network by sending its identification information.
2. Paging: When a call is initiated for a specific mobile device, the network sends a paging message to locate the device.
3. Channel Assignment: Once the mobile device is located, a dedicated channel is assigned for the call.
4. Call Establishment: The call is established by connecting the calling and called parties through the assigned channels.
5. Call Termination: When the call is completed, the channels are released, and the mobile device returns to idle mode.

Frequency Reuse in Cellular Systems

To maximize the capacity and efficiency of cellular systems, frequency reuse techniques are employed:

1. Frequency Planning: The allocation of different frequency bands to different cells to minimize interference.
2. Cell Splitting: When a cell becomes congested, it can be split into smaller cells to increase capacity.
3. Cell Sectoring: Dividing a cell into sectors to increase capacity and reduce interference.
4. Interference Management: Techniques such as power control and adaptive modulation are used to mitigate interference and improve system performance.

Advantages and Disadvantages of Basic Cellular System

Advantages

1. Increased Capacity: The use of cellular systems allows for a higher number of simultaneous users compared to traditional point-to-point communication systems.
2. Improved Coverage: Cellular systems provide wider coverage, allowing users to stay connected over larger geographical areas.
3. Better Call Quality: The use of cellular systems ensures better call quality and reduced call drops compared to other communication systems.
4. Efficient Spectrum Utilization: Cellular systems employ frequency reuse techniques to efficiently utilize the available spectrum.

Disadvantages

1. High Infrastructure Cost: Setting up and maintaining cellular infrastructure requires significant investment.
2. Interference Issues: Interference from other devices or environmental factors can affect the performance of cellular systems.
3. Limited Battery Life for Mobile Devices: Continuous use of cellular services can drain the battery life of mobile devices quickly.

Summary

The Basic Cellular System is a fundamental concept in cellular mobile communication. It involves dividing a geographical area into smaller cells served by base stations. The performance criteria of cellular systems include coverage, capacity, quality of service, mobility management, and handover. The mobile radio environment is unique due to factors such as propagation characteristics, interference, fading, and shadowing. The operation of cellular systems involves components like base stations, mobile stations, MSC, HLR, and VLR. The call setup procedure includes registration, paging, channel assignment, call establishment, and call termination. Frequency reuse techniques like frequency planning, cell splitting, cell sectoring, and interference management are used in cellular systems. The advantages of the Basic Cellular System include increased capacity, improved coverage, better call quality, and efficient spectrum utilization. However, there are also disadvantages such as high infrastructure cost, interference issues, and limited battery life for mobile devices.

Analogy

Imagine a city divided into multiple neighborhoods, each with its own neighborhood watch. The neighborhood watch members communicate with each other using walkie-talkies. The city is the coverage area, and each neighborhood is a cell. The walkie-talkies represent the base stations and mobile devices. The neighborhood watch members can move freely within their neighborhood without losing communication. When they move to another neighborhood, they hand over the communication to the corresponding neighborhood watch. This division and handover process ensure continuous communication throughout the city, just like the Basic Cellular System.