4G

Lore & Background

The earliest deployed technologies marketed as 4G were Long-Term Evolution (LTE), developed by the 3GPP group, and Mobile Worldwide Interoperability for Microwave Access (Mobile WiMAX), based on IEEE specifications. These provided significant enhancements over previous 3G and 2G. In November 2008, the International Telecommunication Union-Radio communications sector (ITU-R) specified a set of requirements for 4G standards, named the International Mobile Telecommunications Advanced (IMT-Advanced) specification, setting peak speed requirements for 4G service at 100 megabits per second for high mobility communication and 1 gigabit per second for low mobility communication.

Since the first-release versions of Mobile WiMAX and LTE support much less than 1 Gbit/s peak bit rate, they are not fully IMT-Advanced compliant, but are often branded 4G by service providers. On December 6, 2010, ITU-R recognized that these two technologies, as well as other beyond-3G technologies that do not fulfill the IMT-Advanced requirements, could nevertheless be considered 4G, provided they represent forerunners to IMT-Advanced compliant versions and a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed. Both the original LTE and WiMAX standards had previously sometimes been referred to as 3.9G/3.95G. The ITU's new definition for 4G also included Evolved High Speed Packet Access (HSPA+).

Mobile WiMAX Release 2 (also known as WirelessMAN-Advanced or IEEE 802.16m) and LTE Advanced (LTE-A) are IMT-Advanced compliant backwards compatible versions of the above two systems, standardized during the spring 2011, and promising speeds in the order of 1 Gbit/s. In January 2012, the ITU backtracked on its previous definition for 4G, claiming that Mobile WiMAX 2 and LTE Advanced are true 4G while their predecessors are transitional 3G-4G. As opposed to earlier generations, a 4G system does not support traditional circuit-switched telephony service, but instead relies on all-Internet Protocol based communication such as IP telephony. The spread spectrum radio technology used in 3G systems is abandoned in all 4G candidate systems and replaced by OFDMA multi-carrier transmission and other frequency-domain equalization schemes, making it possible to transfer very high bit rates despite extensive multi-path radio propagation. The peak bit rate is further improved by smart antenna arrays for multiple-input multiple-output (MIMO) communications.

Reader's Guide

4G represents a fundamental shift in mobile communications, moving from circuit-switched voice to all-IP packet-switched networks. This change eliminated the traditional telephony service in favor of IP telephony, enabling ultra-broadband mobile access. The ITU-R's IMT-Advanced specification set ambitious peak speed requirements of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility, though early deployments of LTE and Mobile WiMAX fell short of these targets. This led to a period of confusion, with some carriers branding pre-4G technologies as 4G, while others reserved the label for fully compliant versions like LTE Advanced and WiMAX 2. The ITU-R eventually recognized both categories as 4G under certain conditions, acknowledging the substantial performance improvements over 3G.

The technical underpinnings of 4G abandoned the spread spectrum radio used in 3G in favor of OFDMA multi-carrier transmission and frequency-domain equalization, which allowed very high bit rates even in environments with extensive multi-path radio propagation. Smart antenna arrays for MIMO communications further improved peak bit rates. The introduction of 4G enabled data-intensive applications such as high-definition media streaming and the expansion of Internet of Things (IoT) applications. The legacy of 4G is that it set the stage for all-IP mobile networks, with scalable channel bandwidths of 5–20 MHz (optionally up to 40 MHz) and high spectral efficiency targets. The confusion over what constitutes a generation—whether based on ITU compliance, non-backward-compatible technology, or marketing—remains a notable aspect of 4G's history.

Did You Know?

• The ITU-R specified IMT-Advanced requirements for 4G in November 2008, setting peak speeds of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility.
• First-release LTE and Mobile WiMAX were sometimes referred to as 3.9G or 3.95G because they did not fully meet IMT-Advanced requirements.
• On December 6, 2010, ITU-R recognized that technologies not fully IMT-Advanced compliant could still be considered 4G if they represented forerunners to compliant versions.

Naming, Identity, and the 2.75G Debate

Enhanced Data rates for GSM Evolution carries a mouthful of a name, and operators around the world have given it several aliases over the years. You will find it referred to as EGPRS, IMT Single Carrier, or Enhanced Data rates for Global Evolution, depending on who is doing the talking. The 3GPP standards body that governs it officially labels the technology "2.75G," a nod to the fact that it sits between the 2.5G GPRS layer it upgrades and the full 3G UMTS networks arriving at the same time. Yet the International Telecommunication Union takes a different view: within its IMT-2000 framework, EDGE is counted as a legitimate member of the 3G family. That classification quirk reflects a broader tension in the industry—whether a meaningful speed bump on existing infrastructure deserves the 3G badge or whether it is simply a very fast 2G. For subscribers the label mattered less than the experience: EDGE delivered data rates that felt a world away from plain GPRS while requiring none of the wholesale network overhauls that UMTS demanded.

Engineering a Threefold Leap

The engineering behind EDGE is where the technology earns its reputation. Rather than replacing the radio layer, it layers a more sophisticated modulation and coding stack on top of the existing GPRS foundation. The first four of its nine modulation-and-coding schemes rely on the familiar GMSK waveform, but schemes MCS-5 through MCS-9 switch to 8PSK, packing three bits into every carrier-phase transition and effectively tripling the gross throughput of a standard GSM channel. A rate-adaptation algorithm continuously tunes the active MCS to match the quality of the radio link, trading raw speed for robustness when conditions deteriorate. Perhaps the most consequential new mechanism is incremental redundancy: instead of simply retransmitting a corrupted packet, the transmitter sends additional parity information that the receiver combines with the original, raising the odds of a clean decode without a full round-trip. In packet mode the technology can sustain 236 kbit/s across four timeslots, with a theoretical ceiling of 473.6 kbit/s when all eight are allocated—roughly four times the traffic a plain GPRS link can carry. Crucially, none of this demands changes to the GSM core network; operators only need EDGE-capable transceivers and an upgraded base-station subsystem, and in many cases the upgrade is nothing more than flipping a software switch.

From Indianapolis to 147 Nations

The story of EDGE's global spread reads like a relay race that started in the American Midwest. On June 30, 2003, Cingular—now part of AT&T—lit up the first commercial EDGE service over Indianapolis, making the United States the proving ground for what would become a worldwide standard. Within a year, Rogers Wireless in Canada and DiGi in Malaysia's Klang Valley had followed, while TeliaSonera brought the technology to Finnish subscribers in April 2004. European adoption accelerated through 2005: Orange trialled the service in France, Bouygues Telecom completed a national rollout and explicitly chose EDGE over 3G because the deployment costs were far lower, and Telfort became the first Dutch carrier to go live. Orange then launched the UK's first EDGE network in February 2006. By the time the Global Mobile Suppliers Association tallied the numbers in 2008, EDGE services had been launched in 147 countries. The pattern was consistent: operators who already ran GSM and GPRS infrastructure could activate EDGE with minimal capital expenditure, making it an attractive middle path before the more expensive UMTS build-out was complete.

Evolved EDGE and the Bridge to What Came Next

EDGE did not stop at its original specification. The follow-on standard, often called Evolved EDGE or EDGE Evolution and sometimes tagged "2.875G," pushed the technology further along several axes at once. The Transmission Time Interval was halved from 20 milliseconds to 10, shaving latency in half. Peak bit-rates climbed to 1 Mbit/s and end-to-end latency dropped to around 80 milliseconds, achieved through dual-carrier operation, a higher symbol rate, and a jump to 32QAM and 16QAM modulation in place of the original 8PSK. Turbo codes replaced the older convolutional schemes to improve error correction. The result was a service that more than doubled the performance of classic EDGE while keeping the same fundamental GSM architecture. By the time Evolved EDGE matured, every major chip vendor supported the technology for both GSM and WCDMA/HSPA handsets, and in networks where the base-station hardware was already in place, the upgrade could be activated purely through software. In that sense, EDGE and its evolution served as the practical bridge that kept 2G networks competitive while the industry built the 3G and 4G infrastructure that would eventually supersede them.