• Cellular networks provide wireless connectivity through a system of interconnected base stations (cell towers) that divide geographic areas into hexagonal coverage zones called cells
• Each cell is served by a base station that communicates with mobile devices using radio frequencies, enabling voice, data, and messaging services
• Networks are designed with frequency reuse patterns - the same frequencies can be reused in non-adjacent cells to maximize spectrum efficiency without interference

Network Architecture

• Mobile Station (MS): The end-user device (smartphone, tablet, cellular modem)
• Base Transceiver Station (BTS): Radio equipment that communicates directly with mobile devices within a cell
• Base Station Controller (BSC): Manages multiple BTS units and handles handoffs between cells
• Mobile Switching Center (MSC): Core network element that routes calls and connects to public switched telephone network (PSTN)
• Home Location Register (HLR): Database storing subscriber information and current location
• Visitor Location Register (VLR): Temporary database for roaming subscribers

Cellular Generations Comparison

Frequency Bands and Spectrum

• Low Band (600-900 MHz): Excellent coverage and building penetration but limited capacity
• Mid Band (1-6 GHz): Balance of coverage and capacity - most commonly used for LTE
• High Band/mmWave (24-100 GHz): Ultra-high speeds but very limited range (few hundred meters)
• Networks use Licensed spectrum allocated by regulatory bodies (FCC in US) to prevent interference
• Carriers often aggregate multiple frequency bands simultaneously to increase throughput

Cellular Network Integration with Enterprise

• Small Cells: Low-power base stations deployed indoors or in dense urban areas to improve coverage
• Distributed Antenna Systems (DAS): Network of antennas connected to common source to provide coverage in large buildings
• Private LTE/5G: Enterprise-owned cellular networks using licensed or unlicensed spectrum for industrial applications
• Cellular Backhaul: Connection between cell towers and core network, often using fiber optic cables or microwave links

Handoff and Mobility Management

• Soft Handoff: Mobile device maintains connection to multiple base stations during transition (CDMA networks)
• Hard Handoff: Connection broken with one base station before establishing with another (GSM networks)
• Location updates track subscriber movement between cells to ensure proper call routing
• Roaming agreements allow subscribers to use services when traveling outside home network coverage

Vocabulary

• IMEI: International Mobile Equipment Identity - unique identifier for mobile devices
• SIM: Subscriber Identity Module - card containing subscriber authentication information
• MIMO: Multiple-Input Multiple-Output - antenna technology using multiple antennas to increase data rates
• Beamforming: Directional signal transmission technique that focuses radio energy toward specific users
• Network Slicing: 5G feature allowing creation of multiple virtual networks on shared infrastructure
• eMBB: Enhanced Mobile Broadband - 5G use case focused on high-speed data services
• URLLC: Ultra-Reliable Low-Latency Communications - 5G use case for mission-critical applications

Notes

• Cellular networks complement Wi-Fi by providing wide-area mobility - enterprises often use both technologies together
• Signal strength decreases with distance and obstacles - indoor coverage typically requires small cells or DAS
• Cellular modems in enterprise equipment (routers, IoT devices) provide backup connectivity when primary links fail
• 5G introduces network slicing allowing carriers to create dedicated virtual networks with guaranteed performance characteristics
• Battery life in cellular devices is heavily impacted by signal strength - weak signals force higher transmission power
• Consider cellular as primary WAN connection for remote sites where fiber/cable isn’t available, but monitor data usage costs carefully