Carrier aggregation, LTE-Hi surfaced to seize the commanding heights of LTE-A Evolution

China's LTE commercialization is approaching, and the industry's attention to the subsequent evolution of LTE has reached a new peak. Compared with 3G, LTE significantly improves the spectrum efficiency. However, the industry has not stopped. A few years ago, 3GPP began to research and develop the LTE-Advanced standard, and a series of technologies that can effectively improve the performance of existing LTE Networks emerged.

Among them, the two most important technologies are carrier aggregation and LTE-Hi. If carrier aggregation is a technology representative of the LTE-Advanced R10 version, LTE-Hi is the biggest highlight of the LTE-Advanced R12 version. Recently, a reporter from the communications industry news (Internet) interviewed several industry experts to unveil the secrets of these two hot technologies.

Application carrier aggregation is the trend of the times

For operators, spectrum is always the most scarce and valuable resource. Compared with 2G and 3G technology, one of the major advantages of LTE is that it can be flexibly deployed in different frequencies to achieve full spectrum resources. At present, nearly 40 frequencies in the 3GPP specification can be used for LTE. Operators can not only deploy LTE in new frequencies, but also deploy LTE in existing 2G and 3G frequencies. The best example is GSM1800 Refarming. 94 commercial LTE Networks have been deployed in the 1800Mhz band. While LTE provides band flexibility, operators also have to face the problem that the overall spectrum utilization is low because the spectrum is too scattered. To solve this problem, the carrier aggregation technology came into being.

According to Huawei's technical experts, the carrier aggregation technology is a representative Technology in the LTE-Advanced R10 standard. By aggregating multiple LTE member carriers to form a larger bandwidth, the peak rate of upstream and downstream rows and the edge rate of upstream and downstream rows are multiplied, and the cell capacity is multiplied. This technology can bring more powerful TD-LTE network transmission capability to TDD operators with rich spectrum resources.

As one of the important technologies of LTE-A, carrier aggregation can combine discrete spectrum resources to obtain the maximum spectrum utilization rate similar to continuous spectrum. For example, the Korean operator SKT has 10 mbps bandwidth in the 1.8G and 850M frequencies respectively. Without the carrier aggregation technology, the two frequencies can provide the maximum downlink rate of 75 Mbps respectively, using the carrier aggregation technology, it can provide a Mbps downstream speed with the same bandwidth for a 20 MHz system, which is twice the original maximum rate. Nokia network experts said that this not only improves the spectrum utilization, but also greatly increases the network capacity, helps operators effectively cope with the challenges of rapid growth of data traffic and simplifies network operations, in the future, LTE Networks will provide users with an excellent GB-level personalized data experience.

It can be seen that the emergence of carrier aggregation will have an important impact on the LTE network. Huawei experts said that in the future, carrier aggregation will play two important roles: on the one hand, it will provide users with high-speed bandwidth solutions, as mobile terminals and mobile data applications develop in big screen, high-definition, and 3D ways, users' demand for mobile data bandwidth is increasing day by day, carrier aggregation can provide users with downstream access bandwidth of up to 1 Gbps, meeting users' needs for high-speed data bandwidth in the future. On the other hand, when the operator's continuous spectrum resources are scarce, the ability of carrier aggregation to integrate multi-segment discontinuous bandwidth and multiple standards, in response to increasingly serious "Fragmentation" of wireless spectrum, it will also play an important role.

Initial LTE network construction demands are not urgent

So how should carriers in China grasp the deployment pace of LTE carrier aggregation technology? According to an expert, carrier aggregation is the focus of many operators on the future evolution of LTE technology, China Mobile in TD-LTE bidding requirements, carrier aggregation is as basic technology requirements equipment manufacturers support carrier aggregation technology, from the technical requirements of mobile bidding, we can see that carrier technology support is a key requirement for LTE network construction. At present, carriers can carry out research on all aspects of LTE-Advanced technology deployment, and make a good technical reserve. After the mature scale of carrier aggregation terminals is supported for commercial use, carrier aggregation is used for data hotspot areas first, to meet the user speed requirements and improve the overall user perception and network brand, With the popularization of terminals and the increase in user demand for data, the entire network is upgraded to support LTE-Advanced carrier aggregation.

Nokia network experts also said that in the initial phase of LTE network construction, network coverage should be solved first, and the demand for carrier aggregation technology, which mainly solves the capacity problem, is not urgent. In the middle of the Development of LTE Networks, with the increasing number of LTE users, you can enable intra-band carrier aggregation at 20 MHz + 20 MHz in the D band to increase the single-user rate to 300 Mbps. This has played an active role in marketing, attracting high-end users, and expanding new 4G businesses. In the mature stage of LTE network development, carrier aggregation between the F-band and the D-band can be considered to further increase the user's peak rate to more than 1 Gbps. However, considering the ratio of different time slots, the carrier aggregation between different base stations and different manufacturers has not been determined in the 3GPP specification, the specific implementation scenarios of carrier aggregation in the F and D frequencies must be determined based on the actual network deployment.

For fdd lte, its carrier aggregation technology is currently widely used in Japan, South Korea, North America and other countries. Samsung Galaxy and other terminals have supported 20 MHz carrier aggregation, therefore, the deployment time of fdd lte carrier aggregation can be advanced according to the commercial time of fdd lte in China.

At present, mainstream vendors have released corresponding solutions on the system side. The carrier can support the carrier aggregation function through software upgrade. However, it is still difficult to support LTE carrier aggregation on terminals. In particular, for the multi-carrier aggregation between BAND or LTE systems, terminals need to work with multiple RF Modules at the same time, or multiple operating systems at the same time, which requires high chip performance and power consumption. Haisi's experts said that there are more than 40 LTE spectrum distributed globally, and the challenge to achieve the aggregation of any two-way carrier in the spectrum is very great.

LTE-Hi is still in the R & D stage

Carrier aggregation is a representative Technology in the LTE-Advanced R10 standard, while LTE-Hi is the biggest highlight of the LTE-Advanced R12 standard. LTE-Hi is an enhanced version of SmallCell. It is a collection of new technologies and solutions for mobile communication networks towards mobile broadband networks. It is mainly used for hot spot and Indoor scenarios. It aims to use High-frequency segments (Higher frequency), with High bandwidth and High performance). At present, some technical points of LTE-Hi have been written into R12, which mainly improves the spectrum efficiency, operation efficiency, mobility and structure optimization.

Huawei experts said that the purpose of LTE-Hi is to meet the needs of higher air port capacity and better coordination with macro networks. At present, the 3GPP Standardization Organization is standardizing the enhancement of Small cells. The standardization content is mainly to introduce higher-order modulation, Community adaptive switch and rapid Community discovery, and inter-site empty port synchronization, and macro-site/small-site multi-stream aggregation.

Some technologies of LTE-Hi will be gradually applied to products with the development of the LTE SmallCell industry, and may form public network applications, local access applications, and other products for different application scenarios. Huawei experts said that LTE-Hi can provide higher capacity for small stations and better collaboration with macro stations to improve the experience of mobile users. Therefore, LTE-Hi is an inevitable trend of small stations. The time for the LTE-Hi standardization freeze was around September 2014, and it was quite appropriate for operators to start deployment in 2015.