Lte Carrier Aggregation Band Combinations – 3GPP Releases 10 and 11

CA enables the sharing of spectrum across multiple spectrum channels (component carriers) and multiple bands. CA can be implemented with both FDD and TDD spectrum. It can be intra-band using spectrum in the same band that is either contiguous or non-contiguous. Or, CA can involve the combined use of inter-band of spectrum in different bands. While CA makes possible the combination of 5x20MHz carriers across 5 spectrum bands, current activity – both in standards bodies and from service providers – centers on CA with single band or dual band scenarios.

According to Third Generation Partnership Project (3GPP) Releases 10 and 11, there is an array of band combinations now specified for LTE-A CA as shown in Table I, below.

Table 1: Carrier Aggregation Band Combinations – 3GPP Releases 10 and 11

Source: 3GPP, 2013

There is a significant omission in the spectrum band combinations detailed in Table 1, namely, options for CA with the Asia Pacific (APT700) MHz band plan, which is now widely adopted across the Asia Pacific region and by a growing pool of service providers in Latin America. However, this issue, along with the addition of multiple CA band configurations are being addressed as part of the current 3GPP Release 12 agenda, as detailed in Table 2, below.

Table 2: Carrier Aggregation Band Combinations – 3GPP Release 12

Source: 3GPP, 2013

Candidate spectrum bands for CA vary by region, with service providers in the US primarily focusing on combining 700MHz spectrum in either Band 12, 13 or 17 with AWS spectrum. Canadian operators are expected to follow the same path once 700MHz (based on the US band plan) is awarded next year. Although not reflected in Table 2, 3GPP Release 12 also includes work items for CA 3-band implementations across the North American bands – 2, 4, 5, 13, 17 and 30. In the United States, Sprint will initially focus on CA within the 2600MHz TDD. In Canada, Rogers is also looking to CA with its AWS and 2600MHz spectrum holdings.

European CA activities are focused on different combinations of spectrum across the 800MHz, 1800MHz and 2600MHz FDD bands. 1800MHz combined with 2600MHz FDD spectrum is also of interest to operators in the Asia Pacific. Service providers in the region will also examine sharing with 700MHz as it is progressively released across the region. This is also the case for service providers in Latin America. 3GPP Release 12 includes a work item for CA in the 1800MHz band with the APT700MMhz band. As shown in Tables 1 and 2, 3GPP releases also account for country specific band allocations such as in Japan, China and South Korea.

The 3GPP CA work item lists are also devoid of options for TDD-CA, other than in single band mode. While CA combining both FDD and TDD spectrum will eventuate in the longer term, CA TDD deployments will initially focus on intra-band deployments. This is made possible as, unlike FDD spectrum licenses, service provider TDD holdings are generally based on larger bandwidth (MHz) allocations (i.e. 2x20MHz) capable of supporting LTE-A delivery.

Lte Carrier Aggregation Band Combinations – 3GPP Releases 10 and 11

CA enables the sharing of spectrum across multiple spectrum channels (component carriers) and multiple bands. CA can be implemented with both FDD and TDD spectrum. It can be intra-band using spectrum in the same band that is either contiguous or non-contiguous. Or, CA can involve the combined use of inter-band of spectrum in different bands. While CA makes possible the combination of 5x20MHz carriers across 5 spectrum bands, current activity – both in standards bodies and from service providers – centers on CA with single band or dual band scenarios.

According to Third Generation Partnership Project (3GPP) Releases 10 and 11, there is an array of band combinations now specified for LTE-A CA as shown in Table I, below.

Table 1: Carrier Aggregation Band Combinations – 3GPP Releases 10 and 11

Source: 3GPP, 2013

There is a significant omission in the spectrum band combinations detailed in Table 1, namely, options for CA with the Asia Pacific (APT700) MHz band plan, which is now widely adopted across the Asia Pacific region and by a growing pool of service providers in Latin America. However, this issue, along with the addition of multiple CA band configurations are being addressed as part of the current 3GPP Release 12 agenda, as detailed in Table 2, below.

Table 2: Carrier Aggregation Band Combinations – 3GPP Release 12

Source: 3GPP, 2013

Candidate spectrum bands for CA vary by region, with service providers in the US primarily focusing on combining 700MHz spectrum in either Band 12, 13 or 17 with AWS spectrum. Canadian operators are expected to follow the same path once 700MHz (based on the US band plan) is awarded next year. Although not reflected in Table 2, 3GPP Release 12 also includes work items for CA 3-band implementations across the North American bands – 2, 4, 5, 13, 17 and 30. In the United States, Sprint will initially focus on CA within the 2600MHz TDD. In Canada, Rogers is also looking to CA with its AWS and 2600MHz spectrum holdings.

European CA activities are focused on different combinations of spectrum across the 800MHz, 1800MHz and 2600MHz FDD bands. 1800MHz combined with 2600MHz FDD spectrum is also of interest to operators in the Asia Pacific. Service providers in the region will also examine sharing with 700MHz as it is progressively released across the region. This is also the case for service providers in Latin America. 3GPP Release 12 includes a work item for CA in the 1800MHz band with the APT700MMhz band. As shown in Tables 1 and 2, 3GPP releases also account for country specific band allocations such as in Japan, China and South Korea.

The 3GPP CA work item lists are also devoid of options for TDD-CA, other than in single band mode. While CA combining both FDD and TDD spectrum will eventuate in the longer term, CA TDD deployments will initially focus on intra-band deployments. This is made possible as, unlike FDD spectrum licenses, service provider TDD holdings are generally based on larger bandwidth (MHz) allocations (i.e. 2x20MHz) capable of supporting LTE-A delivery.

LTE-Advanced Carrier Aggregation Band Combinations

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):

• 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.

Source : Dianne Northfield, VP Research, Tolaga Research www.tolaga.com