Carrier aggregation

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Carrier aggregation (English; abbreviation: CA) is a technology used in mobile communications to increase the data rate per user. Several individual frequency blocks ( carriers ) are assigned to a user . The maximum data rate per user increases by the number of frequency blocks. The overall data rate per cell is also increased through improved resource utilization. In addition, “load balancing” can be carried out, thus increasing the data rate for each individual in a busy radio cell.

use

UMTS / HSPA +

The channel bandwidth for UMTS / HSPA + is around 3.8 MHz with a channel spacing of 5 MHz. Carrier aggregation, which is part of the UMTS extension HSPA +, assigns two download channels to a user. In UMTS / HSPA +, carrier aggregation is also referred to as dual cell. 3GPP has standardized carrier aggregation for HSPA + for the uplink with up to two and for the downlink with up to four (four carrier HSDPA) individual channels.

LTE-Advanced

Since its introduction, LTE has supported various channel bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. With LTE-Advanced (from Release 10) any two channels can be assigned to a user. The difference between carrier aggregation of e.g. B. two 10 MHz channels and an original 20 MHz channel is that with carrier aggregation, the control information is completely available in each channel.

In the years around 2015, the so-called L-band was auctioned in the EU.As it is a former radio band, it has no upload frequency and can therefore only be used with carrier aggregation for LTE services. The first tests with this tape were carried out in Sanremo , Italy by the mobile operator Tim with a Kathrein antenna and an Ericsson base station. LTE Advanced with CA enables Gigabit LTE. This is also supported by higher modulations (256QAM) and 4x4 MIMO . In the current LTE releases (as of mid-2018), 5 bands (5CA) can be linked, resulting in a maximum of 100 MHz usable bandwidth. This means that theoretically up to 2 Gigabit / s are possible with MIMO and 256QAM. However, since no network operator in Germany has 100 MHz available for LTE (Telekom could theoretically provide 90 MHz with 5CA for band 3 + 3 + 7 + 32 + 20) and not all frequencies are set to 4x4 Mimo, the realistically achievable bandwidth is included approx. 1.2 gigabit / s.

Types of carrier aggregation

Different types of carrier aggregation.

The individual channels (component carrier) can be in different frequency bands (inter-band) or in the same frequency band next to each other (intra-band contiguous) or in the same frequency band with a frequency gap (intra-band non-contiguous).

LTE Advanced with German providers

The German Telekom is building a lot of band 3 + 3 LTE (20 + 10 MHz) from the 2CA. These locations are often already prepared for 4x4 MIMO and offer up to 600 Mbit / s throughput when 256QAM is activated. In cities with more than 100,000 inhabitants, Telekom mostly builds LTE with bands 3 + 3 + 7 (3CA), less often (bands 3 + 7 + 20). In some places LTE band 3 + 3 + 20 is possible, due to the different technology suppliers, this is not always possible. At locations that have not yet been converted to “Single RAN”, there is often band 3 + 7 (2CA) with up to 300 Mbit / s in large cities. 4CA has not yet been seen live in the Telekom network, but it should be possible with Band 32 (L-Band).

Vodafone often uses volume 20 + 7 in the 2CA when CA is available. Volume 3 is also used in some regions. This also results in a 50 MHz (band 3 + 7 + 20) bandwidth at 256QAM up to 500 Mbit / s (this expansion is not yet very widespread), in addition Vodafone has recently installed LTE on band 1. Vodafone is starting with the help of 3CA and 4CA connections in combination with 4x4 MIMO to prepare the network for gigabit speeds.

Telefonica (o2) has a different level of expansion depending on the region in Germany. Completely developed regions often offer 2CA (band 3 + 20 or B7 + B20 or less often B3 + B7) or 3CA (B3 + B7 + B20). Since September 2018, Telefonica has also started expanding LTE Band 1. This will be built in 2CA (B1 + B3) or 3CA (B1 + B3 + B20). 4CA should also be possible in the future (B1 + B3 + B7 + B20). Telefonica also activated 256QAM modulation on its network in September. The maximum speed can thus ideally be up to 600 Mbit / s, Telefonica currently only advertises with 225 Mbit / s.

Web links

Individual evidence

  1. ↑ Dahlman, Erik, 4G LTE / LTE-Advanced for Mobile Broadband , Elsevier, 2014.
  2. ↑ Deutsche Telekom AG: Deutsche Telekom: 4x4 MIMO - what the fourfold multi-antenna technology brings. Retrieved September 28, 2018 .
  3. ↑ Deutsche Telekom AG: Deutsche Telekom: 256QAM: That's behind the high-speed cellular technology. Retrieved September 28, 2018 .
  4. ↑ Deutsche Telekom AG: Deutsche Telekom: 3CA in Berlin: Three frequencies for more speed with mobile surfing. Retrieved September 28, 2018 .
  5. ↑ LTE: Vodafone offers 1 GBit / s in mobile communications in more cities - Golem.de . ( golem.de [accessed on September 28, 2018]).
  6. ↑ CellMapper: Cellular Tower and Signal Map. Retrieved September 28, 2018 .