Global LTE development has entered the fast lane. According to relevant statistics, the number of LTE users worldwide reached 238 million in 2013, an increase of 190% compared with the 82 million at the end of 2012. The speed is quite amazing. In 2014, the global LTE development will usher in a new wave. On the one hand, the US, South Korea, Japan and other markets continue to lead, on the other hand, the comprehensive promotion of China's LTE commercial, will bring the source of power to the development of LTE. At the same time, with the advancement of the market, LTE technology is also rapidly maturing, and related products are constantly emerging. It is particularly worth mentioning that the development of LTE's evolutionary technology LTE-Advanced is also progressing in an orderly manner, and carrier aggregation technology is expected to achieve commercial scale in 2014.
LTE-Advanced (LTE-A for short) is a further evolved version of LTE technology that enables higher peak rates and system capacity. It should be noted that LTE-A is not an independent technology, but is a carrier aggregation (Carrier AggregaTIon, CA) defined in the 3GPP R10-R12 version standard, high-order MIMO (downstream TM9, uplink TM2), and enhanced inter-cell. A set of enhancements consisting of a series of enhanced features such as interference coordination (eICIC), coordinated multipoint (CoMP), relay, and small cell enhancement (Small Cell). Therefore, the industry can selectively implement the development of various LTE-A technology options step by step, without having to be in one step.
When the industry chooses to prioritize the development of LTE-A technology, it mainly considers two factors: the operator's needs and implementation complexity. Starting from these two factors, the global industry has determined that the first LTE-A technology will be carrier aggregation, and the remaining high-end MIMO, eICIC, Small Cell, CoMP, Relay and other technologies will gradually be industrialized in the next few years. And scale deployment.
Carrier Aggregation Leads LTE-A Technology Deployment
The carrier aggregation technology is a technology for aggregating multiple carriers together in order to increase the peak rate of the LTE system, and the technical complexity depends on the number of "component carriers" of the aggregation and the distribution of these carriers. If the component carriers are continuously distributed, called continuous carrier CA, the implementation complexity of the radio is relatively low; if the component carriers are not continuously distributed, it is called non-continuous carrier CA, and the radio frequency implementation complexity is relatively high; if the component carriers are distributed in one In the frequency band, called intra-band CA, the implementation complexity of radio frequency is relatively low. If the component carriers are distributed in different frequency bands, called inter-band CA, the radio frequency implementation complexity is relative. Higher.
Carrier aggregation has become the fastest growing LTE-A technology, first of all due to the needs of operators. Due to the explosive growth of mobile Internet services, international operators as the "access pipeline" of the mobile Internet, on the one hand, must expand the capacity of the pipeline, on the other hand, they must claim to the user that they have a "peak rate advantage." Therefore, operators that have deployed LTE countries in the world are involuntarily involved in “peak rate competitionâ€. In the fastest growing LTE-A Korea, three operators have started commercial deployment of carrier aggregation in 2013 to strengthen Its "technical lead" advantage. Three other carriers in the world are deploying carrier aggregation networks, and 21 have plans or are experimenting. In August 2013, Softbank Japan demonstrated five TD-LTE systems using five 20MHz CA and 44 MIMO at 3.5GHz, with a peak rate of over 700Mbps. At the Mobile World Congress (MWC 2014) in Barcelona in February 2014, Nokia (NSN) demonstrated a LTE FDD system demonstration using six 20MHz carrier aggregation and 88 MIMO with a peak rate of 2.6Gbps.
However, these are just demonstrations based on concept prototypes and do not represent the progress of real product development. At present, most mainstream system equipment vendors have implemented the 2 carrier downlink in-band CA defined by the R10 version, thereby doubling the downlink peak rate. Leading vendors have begun to support a larger number of carriers and cross-band CAs. At MWC 2014, Huawei demonstrated an LTE FDD system with three carriers, a total of 50MHz cross-band CA and 44 MIMO, with a peak rate of 460Mbps. The remaining mainstream system manufacturers are expected to support the downlink cross-band CA of 3 carriers in 2014.
Of course, carrier aggregation, like other wireless communication technologies, requires complete "end-to-end" development from the network to the terminal to achieve true industrialization. Since the development bottleneck of an emerging technology is often on the terminal side rather than the network side, the actual commercial time of the CA technology will also depend on the development progress of the terminal side. In the 3GPP standard, a terminal supporting 2 carrier CA and 300 Mbps peak rate is defined as a "Level 6" (Cat6) terminal. Therefore, whether carrier aggregation technology can be widely used depends on the degree of support of the international terminal and chip industry for Cat6 terminals. As of January 2014, of the 1,371 LTE terminals that were released, only two were announced as Cat6 terminals. Fortunately, at MWC 2014, Qualcomm (80.55, 0.41, 0.51%) has demonstrated its Cat6 terminal chip platform based on 20nm advanced semiconductor technology and is expected to be commercially available in the third quarter of 2014. For CAs with more than two carriers and cross-bands, there is no clear and reliable roadmap for terminal chip manufacturers. Since the uplink CA was standardized in the 3GPP R12 version, it is not possible to clearly determine its R&D and industrialization schedule in the near future.
In summary, the basic configuration of CA technology is eager to complete industrialization in 2014 and achieve initial scale deployment. Finally, it should be noted that the application of CA technology is not necessarily concentrated in the traditional LTE core frequency band such as 2.6 GHz. Recently, the international allocation of 3.5 GHz spectrum is accelerated. Because the bandwidth resources in this band are relatively more abundant, it is more operational. The deployment of the CA provides conditions, and may also become the frequency band for the next phase of CA application requirements. However, in recent years, the 3.5GHz frequency band is not the focus of R&D of manufacturers, especially the terminal chip manufacturers. Therefore, the slow progress of CA industrialization in this frequency band is more serious, and the gap between the demand and operators is more prominent.
China's TD-LTE-A technology test results show up
In order to promote the industrialization of TD-LTE-A technology research and development, under the unified leadership of the TD-LTE working group of the Ministry of Industry and Information Technology, China began to organize TD-LTE-A technology trials in the second half of 2013, mainly for the 3GPP R10 version. The introduced LTE-A enhancement technologies, including CA, high-order MIMO (downstream TM9, uplink TM2) and eICIC, are tested.
The TD-LTE working group will develop 25 technical specifications, and two of them have been completed, and another nine have been developed. The first round of LTE-A system equipment test was launched in September 2013. The test content includes: CA - verification of the relevant functions, performance and RF indicators of the 20MHz+20MHz continuous carrier CA in the 2.6GHz band; downlink TM9 - right The function and performance of TM9 (currently required to support single-user dual-stream transmission) based on codebook and non-codebook implementation are verified; uplink TM2--authentication of uplink dual-stream MIMO function is optional test content.
By the end of 2013, three system vendors had basically completed this round of testing, and one vendor completed the CA part of the test. In the test, the support level of the relevant test instrument to TD-LTE-A has also been verified: in the CA aspect, the terminal simulator and channel emulator have met the test requirements; in the high-order MIMO, the terminal emulator cannot support the real 8 antenna ports, currently only based on the 2 antenna port mode for preliminary test verification.
A variety of LTE-A technologies are developing steadily
Among other LTE-A technical features, the fastest progress in research and development is downlink high-order MIMO, that is, transmission mode 9 (TM9). However, the number of terminal antennas is still limited to two antennas for a long time. Even if the base station development of 4~8 streams is completed, the end-to-end industrialization cannot be realized. Therefore, mainstream system vendors still only support dual-stream TM9 transmission (including single Terminal dual-stream single-user MIMO and dual-terminal single-stream multi-user MIMO), TM9's "high-order MIMO" advantage has not been fully utilized. Therefore, although mainstream chip manufacturers expect to support TM9 in the first half of 2014 (the terminal chip will theoretically support the reception of 4~8 streams of TM9 signals, data card and mobile phone design will be difficult to support MIMO signal reception of more than 2 streams in the short term. ), but the operator's deployment requirements for this technology are not clear. Moreover, considering that the international base station has a lot of antennas with a large number of antennas, such as Softbank and China Mobile, most FDD LTE operators have many difficulties in increasing the number of base station antennas to more than four. It may bring about a substantial increase in the cost of network construction. Therefore, although the development progress of the basic TM9 technology does not lag behind carrier aggregation, it is difficult to achieve scale deployment in 2014, and it is difficult to truly complete industrialization.
For uplink high-order MIMO technology, TM2 needs to increase the number of uplink RF transmission modules, which is more complicated than the complexity and terminal cost caused by downlink MIMO. In addition, LTE operators are currently paying attention to the improvement of downlink data rate, and have not paid much attention to uplink enhancement. Most mainstream terminal chip manufacturers have no clear research and development schedule, so it is expected that this technology will not be industrialized soon.
The eICIC technology is an enhanced interference suppression technology developed for heterogeneous network (HetNet) deployment scenarios, which can improve the anti-interference performance of increasingly LTE micro cells, indoor coverage, and home base stations. eICIC can be implemented through software upgrades. There are no additional requirements for base stations and terminal hardware. This technology can be supported by the network side and terminal side in the first half of 2014 and the second half of 2014 respectively. The deployment progress of this technology depends more on the choice of operators. If some operators pay attention to LTE micro-area deployment and cascading networking, it may require early implementation of this technology. eICIC may be industrialized and deployed in 2014. .
Other LTE-A technologies in the pre-research phase include CoMP, Relay, etc. Due to the controversy in performance gains in actual networks, the complexity and cost of product upgrades, most vendors, especially terminal chip vendors, have not yet A clear development schedule is not expected to be industrialized in the near future. As a recent emerging LTE enhancement technology, Small Cell has received extensive attention from the industry, but the standardization of this technology has not yet been completed, and the real Small Cell industrialization is difficult to achieve in the near future.
It should be noted that some companies regard VoLTE as an LTE-A technology, but from the perspective of the 3GPP standard, VoLTE is not in the LTE-A standard.
Conclusion:
LTE and LTE-A have become important technical means for many international operators to expand network capacity for the development of mobile Internet. Although the development of LTE is still uneven in the international arena, the development of LTE in European countries has just started. However, in the United States, South Korea, Japan and other countries, LTE-developed operators have begun to deploy LTE-A technology to strengthen their technological advantages. In 2014, carrier aggregation is expected to be the first LTE-A technology to complete industrialization and begin scale deployment. In the next few years, some of the R10~R12 LTE-A technologies will gradually be applied, and the performance of mobile communication systems will continue to improve until the arrival of 5G.
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