LTE-Advanced, or LTE-A, is not characterized by a single standard, technology or technology enhancement. Rather, LTE-A, as primarily established by the Third Generation Partnership Project (3GPP) Releases 10 and 11 (and further forthcoming Releases), comprises a series standards and technologies, features, techniques and capabilities. LTE-A targets overall network performance improvements focused on:
Delivering increased peak data rates
- Theoretical Downlink (DL): 3 Gbps/Uplink (UL):
- Theoretical Downlink (DL): 3 Gbps/Uplink (UL):
- 1.5 Gbps speeds using up to 100 MHz of spectrum. Comparable with theoretical rates for LTE of DL: 73 – 150 Mbps/UL: 36 – 75 Mbps using 10-20 MHz of spectrum
- Greater spectral efficiency, both in terms of capacity and coverage enhancements, with techniques that include:
- Carrier aggregation
- Advanced multi-antenna technologies,
- A variety of signaling enhancements,
- Support for heterogeneous networks,
- Network self-optimization features,
- Enhanced modulation and, interference techniques etc.
While Carrier Aggregation (CA) is the focus of current service provider LTE-A launches and trials, LTE-A involves a multifaceted array of techniques or sub-standards as categorized on a top level in Table 1, below.
In South Korea, SKT Telecom announced the launch of its LTE-A network in June 2013. It is based on CA combining two 10x10MHz carriers across FDD spectrum holdings in the 850 (Band 5) and 1800 MHz (Band 3) ranges. SKT has also outlined plans to introduce small cell interference cancellation technology (eICIC) in 2014. SKT claims a peak DL speed of 150Mbps on its LTE-A network.
Such peak rates are also touted by other service providers, notably in Europe, although these theoretical data rates are enabled by deployment of increased spectrum resources for the delivery of standard LTE services and they are not based on CA. For example, in the United Kingdom, EE has doubled its speed to a theoretical peak of 150Mbps by increasing its 1800MHz LTE network based on a 20x20MHz carrier. EE has announced that it is trialing LTE-A with CA using 1800MHz and 2.6GHz spectrum.
Also in South Korea, in July 2013, LG U+ unveiled its variant of LTE-A. The network is based on CA (two 10x10MHz: 850 MHz (Band 5), 2100 MHz) and claims the same peak speed of 150Mbps. Korea Telecom followed in September 2013, promising the same peak data rate as its competitors.
Service providers around the world are also accelerating LTE-A trial activities. However, these too are currently primarily focused on testing the CA component of the LTE-A. Examples include Telstra in Australia using 900 MHz and 180MHz spectrum holdings. Hong Kong’s CSL has trialed CA using 20MHz each in the FDD 1800MHz and 2600MHz bands and reaching a peak downlink rate of 300Mbps. Using CA with 800MHz and 1800MHz spectrum Lebanon Touch claimed trial LTE-A peak speed of 250Mbps. For its part, France’s SFR has trialed LTE-A with CA using 800MHz and 2600MHz paired spectrum reaching a download peak of 174Mbps. As an example of intra-band CA, Japan’s Softbank recently trialed LTE-A using 5 carriers of using TDD spectrum in the 3.5GHz band, achieving a peak download speed of 770Mbps. In China, China Mobile has trialed with TDD spectrum touting a downlink peak rate of 223mbps.
Other operators that have trialed LTE-A, or plan to do so, include Turkcell in Turkey, SMART in the Philippines, Japan’s DoCoMo and eAccess, Yota in Russia and VIVA in Kuwait. In the United States AT&T is looking to LTE-CA with 700MHz (Band 17) and AWS (Band 4) spectrum resources followed by CA with 700MHz and PCS (Band 2) spectrum. Verizon is expected to follow a CA path combining 700MHz (Band 13) with AWS spectrum. T-Mobile claims that its existing LTE network is ‘LTE-A Ready’, while Sprint’s LTE-A plans rest on the use of Clearwire’s 2600MHz TDD (Band 41) spectrum holdings.
While the current service provider focus is on LTE-A via CA, the ultimate shift to widespread LTE-A deployments will be iterative and evolutionary following 3GPP enhancements and service provider integration of multiple, often differing, techniques. As discussed, LTE-A is based on a wide range of techniques and options from which service providers will pick and choose, implementing different enhancements on an incremental basis. Some features, such as high order MIMO might take longer to be implemented because of the physical cell site modifications that are typically needed. LTE-A is the basis for service providers to optimize the use of spectrum resources to increase network capacity. However, the parallel unrelenting growth in bandwidth demand will continue to compromise actual service speeds experienced by end-users.
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