**Cellular Mobile Communication**
Cellular mobile communication is a wireless networking technology that enables seamless communication between mobile devices and network infrastructure. It allows users to stay connected while on the move, making it an essential part of modern telecommunications. One of its key characteristics is the mobility of the user equipment, which supports features like handover and automatic roaming across different cells within the same network. This type of service includes voice, data, and video transmission, all delivered through a network composed of components such as the base station subsystem and the mobile switching subsystem.
**Classification of Cellular Mobile Communication**
Cellular networks are typically categorized into three main types based on their coverage and application: macrocells, microcells, and picocells. Each has unique properties and serves different purposes in network design.
**1. Macrocell Technology**
Macrocells are large-area cells designed to provide wide coverage, often spanning from 1 km to 25 km in radius. They are used to cover large geographic areas and form the backbone of most cellular networks. However, they can have issues like "blind spots" — areas where signal strength is weak due to obstructions — and "hot spots," where high traffic density leads to congestion. To address these challenges, network operators often use repeaters or cell splitting. While effective, these solutions can sometimes reduce signal quality or increase costs. As user demand grows, macrocells may be subdivided into smaller cells, but this approach becomes less efficient as cell size decreases due to increased interference and higher deployment costs.
**2. Microcell Technology**
Microcells are smaller in scale, covering areas ranging from 30 meters to 300 meters. They operate at lower power levels and are easier to install, making them ideal for improving coverage in hard-to-reach locations like underground stations or dense urban areas. They also help increase capacity in high-traffic zones such as shopping malls or sports venues. When combined with macrocells, microcells create a multi-layered network structure that enhances both coverage and performance. Unlike macrocells, microcells are independent in terms of system configuration and do not share the same broadcast channels.
**Cellular Mobile Communication System**
A typical cellular mobile communication system consists of three major components: the Switched Network Subsystem (NSS), the Radio Base Station Subsystem (BSS), and the Mobile Station (MS). The NSS handles call routing and user data management, while the BSS manages wireless communication with the MS. The interface between the NSS and BSS is called the "A" interface, and the connection between the BSS and the MS is known as the "Um" interface.
In systems like GSM, open interfaces ensure compatibility across different manufacturers, allowing greater flexibility in network design. The GSM system block diagram shows how the MSC, VLR, HLR, AUC, and EIR make up the NSS, while the BSC and BTS form the BSS. The MS, consisting of the mobile terminal and SIM card, is the end-user device that connects to the network.
The system also includes additional services like the Short Message Service Center (SMSC) for messaging and a Voice Mailbox for handling missed calls. These features improve user experience and network efficiency.
**2.2 Switched Network Subsystem (NSS)**
The NSS is responsible for managing core network functions such as call setup, mobility management, and security. Key components include:
- **MSC (Mobile Switching Center):** Acts as the central control point for voice and data exchanges within its coverage area.
- **VLR (Visitor Location Register):** Stores temporary information about visiting users.
- **HLR (Home Location Register):** Keeps permanent records of user data and location.
- **AUC (Authentication Center):** Provides authentication and encryption parameters.
- **EIR (Equipment Identity Register):** Tracks and manages mobile devices to prevent unauthorized access.
**2.3 Wireless Base Station Subsystem (BSS)**
The BSS includes the Base Station Controller (BSC) and the Base Transceiver Station (BTS). The BSC manages multiple BTSs, controlling radio resources, power levels, and handovers. The BTS handles the actual wireless communication, converting signals between the network and the mobile device.
**2.4 Mobile Station (MS)**
The MS is the user's device, made up of the mobile terminal and the SIM card. The terminal processes voice and data, while the SIM card stores user credentials and ensures secure access to the network.
**2.5 Operation and Maintenance Subsystem (OMS)**
The OMS monitors and manages the entire network, ensuring optimal performance and quick fault detection. Although the Q3 interface is still under standardization, the OMS plays a crucial role in maintaining network reliability and efficiency.
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