LTE Architecture Part 1: Goals of 4g & evolution from 2G and 3G

LTE Delivers Much Faster Mobile Internet: Goals, Flexibility, and Throughput LTE, short for Long‑Term Evolution, targets a much faster mobile internet experience. Core requirements set peak downlink around 100 Mb/s over 20 MHz, sub‑100 ms idle‑to‑active transition, and flexible channel bandwidths from 1.25 to 20 MHz to fit diverse spectrum allocations. In 20 MHz, theoretical application‑layer rates depend on MIMO configuration—about 150 Mb/s with 4x4 and 300 Mb/s with 8x8—while LTE‑Advanced aggregates carriers to 40 or up to 100 MHz (five 20‑MHz carriers) reaching as high as 1.5 Gb/s. Real‑world averages vary widely, with places like Korea and Singapore around 35–40 Mb/s and many other regions closer to 5–10 Mb/s, yet coverage is now widespread globally.

From GSM to LTE‑Advanced: Expanding Bandwidth and Evolving Radio Techniques The path to LTE began with GSM in 1991, a mostly voice system using 200 kHz channels, followed by 1995’s packet‑switched GPRS core for basic data. UMTS arrived in 2002 with 5 MHz carriers and about 2 Mb/s data, then HSPA combined two 5‑MHz channels (10 MHz) to reach roughly 14.4 Mb/s and saw deployment by 2008. Initial LTE deployments around 2010 expanded to 20 MHz and about 150 Mb/s, and by 2012 LTE‑Advanced introduced carrier aggregation—two carriers (40 MHz) delivering roughly 300 Mb/s. Scaling to wider bands required moving from CDMA, which struggled beyond 5–10 MHz, to OFDM, while multi‑antenna MIMO became essential for the high data rates.