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4 TMN CARRIER AGGREGATION One of the principal features of the technology that comes under the LTE-A umbrella has been the increasing expansion of carrier aggregation. Carrier aggregation increases the available bandwidth to a cell by enabling cells to combine an operator's various spectrum holdings into one. LTE-A has moved from two to up to five component carriers, while 4.5G moves carrier aggregation beyond five component carriers to a target of up to 32 component carriers. The driver for this is the need for operators to provide increased throughputs to users for mobile broadband use cases, driven mostly by the delivery of higher bit rate video codecs across the network, and the increasing consumption of mobile video. Just as an example, three Component Carrier Aggregation – which enables the aggregation of 60 MHz of LTE spectrum, allied with 256 Quadrature Amplitude Modulation (QAM) and 4x4 Multiple Input Multiple Output (MIMO) – which doubles the number of unique data streams being transmitted to the user's smartphone - can support a LTE peak data rate of 1 Gbps over the downlink. The number of commercial LTE-Advanced (LTE-A) carrier aggregation launches continues to increase. Operators are evolving their LTE-A networks with Category (Cat) 4, 6, 9 and 11 implementations and Cat 16 devices, which support 1 Gbps data speeds, are expected in the second half of 2016. LTE UNLICENSED Related to carrier aggregation is the ability to add carriers from within unlicensed spectrum - known as Licensed Assisted Access (LAA). LAA enables licensed spectrum small cells to take advantage of spectrum opportunities of unlicensed spectrum in the 5GHz band. WLAN operating in the 5GHz band nowadays already supports 80MHz in the field and 160MHz is to follow in Wave 2 deployment of IEEE 802.11ac. There are also other frequency bands, such as 3.5 GHz, where aggregation of more than one carrier on the same band is possible, in addition to the bands already widely in use for LTE. This drive to take advantage of unlicensed spectrum bands is directly relevant for small cells designers because small cells will be necessary for the efficient operation of LAA. The tight scheduling required for LAA, which involves very fast channel selection decisions to be made so that there is no interference between WiFi and cellular access points, will mandate the presence of small cells very close to the user. As small cells underpin LAA, it seems very likely that small cells will be required to support increasing combinations of carrier aggregation, in unlicensed and licensed bands. NEW IOT STANDARDS (NB-IOT, EC-GSM) One of the most strategically important additions to the LTE-A standards has been the adoption of standards to enable low power Machine-to-Machine and Internet of Things (IoT) connectivity on cellular networks. This work was actually accelerated in response to the commercialisation of a number of non-cellular based network technologies designed to provide connectivity for lower power devices. These LPWA rivals, such as SigFox, LoRa, Weightless and Ingenu (OnRAMp) are proprietary rivals to the cellular networks. As such 3GPP contributors accelerated specification of technology that would allow low power operation of machine-type communications within cellular networks. As operators look to introduce technology to support a number of IoT use cases, the role of small cells may not be immediately obvious, but there are two main areas where small cells will be critical enablers. These are where very low latencies are required, and where support is required for very high device densities. Indeed, it's possible that a class of small cell may be developed specifically to meet IoT requirements. SPECTRAL EFFICIENCY ENHANCEMENTS Other enhancements within R13 include increasing interference (eICIC) CoMP etc. These technologies take advantage of a shift in network architecture to enable a centralised function - presiding as a controller over a number of small cells - to control interference management and coordination across a cluster of small cells. Higher order modulation (256 QAM) and MIMO (4x4 MIMO) that allows for multiple simultaneous channels to connect to and from a device, will also impact on small cell designs. 3 TOWARDS 5G While 4.5 introduces to small cells a range of technologies that are intended to increase throughputs, and to introduce some support for low power IoT use cases, it is with 5G that the real flowering of small cell capabilities will be seen. Although there is a lot of debate about what 5G really means, 5G use cases can really be defined as any use case that cannot be met by technologies on the LTE-A progression path. These include providing high throughputs up to 10- SMALL CELL EVOLUTION

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