4G Technical understanding

In March 2008, the International Telecommunications 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 (Mbit/s) for high mobility communication (such as from trains and cars) and 1 gigabit per second (Gbit/s) for low mobility communication (such as pedestrians and stationary users).

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".

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,^{[citation needed]} and promising speeds in the order of 1 Gbit/s. Services are expected in 2013.

As opposed to earlier generations, a 4G system does not support traditional circuit-switched telephony service, but all-Internet Protocol (IP) based communication such as IP telephony. As seen below, 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 (FDE) schemes, making it possible to transfer very high bit rates despite extensive multi-path radio propagation (echoes). The peak bit rate is further improved by smart antenna arrays for multiple-input multiple-output (MIMO) communications.

The term "generation" used to name successive evolutions of radio networks in general is arbitrary. There are several interpretations, and no official definition has been made despite the consensus behind ITU-R's labels. From ITU-R's point of view, 4G is equivalent to IMT-Advanced which has specific performance requirements as explained below. According to operators, a generation of network refers to the deployment of a new non-backward-compatible technology. The end user expects the next generation of network to provide better performance and connectivity than the previous generation. Meanwhile, GSM, UMTS and LTE networks coexist; and end-users will only receive the benefit of the new generation architecture when they simultaneously: use an access device compatible with the new infrastructure, are within range of the new infrastructure, and pay the provider for access to that new infrastructure.