Introduction: GSM is a second-generation (2G) cellular technology that was introduced in the 1980s. It's a digital mobile telephony system that replaced the older analog systems.
Multiple Access: GSM uses Time Division Multiple Access (TDMA) for its radio interface. This means that multiple users share the same frequency channel, but they are assigned different time slots within that channel. Each time slot is 577 microseconds long, and in a typical GSM frame, there are 8 time slots, which means 8 different conversations or data sessions can occur simultaneously on one frequency channel.
Network Components:
Base Transceiver Station (BTS): Responsible for transmitting and receiving radio signals to/from mobile phones within its coverage area.
Base Station Controller (BSC): Manages multiple BTSs. It handles tasks like call setup, handovers, and allocating radio resources.
Mobile Switching Center (MSC): Connects the GSM network to the Public Switched Telephone Network (PSTN). It's responsible for call switching, mobility management, and other core functions.
Home Location Register (HLR) & Visitor Location Register (VLR): HLR stores subscriber information, while VLR holds data about subscribers currently in the coverage area of a particular MSC.
Frequency Bands: GSM operates in various frequency bands, including the 900 MHz and 1800 MHz bands, depending on the geographical region.
Services: Apart from voice calls, GSM supports services like SMS (Short Message Service), data transmission (GPRS, EDGE), and supplementary services like call waiting, call forwarding, etc.
LTE (Long-Term Evolution):
Introduction: LTE is a fourth-generation (4G) wireless communication standard that was developed to provide higher data rates, lower latency, and improved spectral efficiency compared to its predecessors like GSM.
Multiple Access: LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink (from base station to user device) and Single-Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink (from user device to base station). OFDMA allows multiple users to share the same frequency resources by dividing the spectrum into multiple orthogonal sub-carriers.
Network Components:
Evolved NodeB (eNodeB): Equivalent to the BTS in GSM, eNodeB is the base station in the LTE network responsible for radio transmission and reception.
Mobility Management Entity (MME): Similar to the MSC in GSM, MME handles tasks related to subscriber mobility, security, and bearer management.
System Architecture Evolution (SAE): This is the core network architecture of LTE, also known as Evolved Packet Core (EPC). It includes components like Serving Gateway (SGW), Packet Data Network Gateway (PGW), and more, which handle tasks like routing, packet switching, and IP address allocation.
Frequency Bands: LTE operates in various frequency bands, including both licensed bands (like 700 MHz, 1800 MHz, 2600 MHz) and unlicensed bands (like 2.4 GHz and 5 GHz).
Advanced Features: LTE offers features like MIMO (Multiple Input Multiple Output) for enhancing data rates and coverage, Carrier Aggregation for combining multiple LTE carriers to increase bandwidth, and VoLTE (Voice over LTE) for voice calls over the LTE network.
