What’s a private LTE? Easier than local 5G


What’s a private LTE?

Private LTE provides LTE service using an unlicensed band, such as Wi-Fi, which is a frequency that does not require a license. LTE (Long Term Evolution) is a technology used in 4G (4th generation mobile communication system) served by Docomo, KDDI, SoftBank, or Rakuten Mobile in Japan. In order to use this technology, it is standardized to use the frequencies specified in the standard organization 3GPP, and these frequencies are specified in each country as the frequencies that require a license.

Acquiring a frequency license requires a large number of technical documentation and other application materials, which is quite difficult, and in countries where a license must be purchased, a large amount of money is required to obtain a license. Therefore, using the required frequency of a normal license is a high hurdle and can only be used by a fairly limited number of operators.

On the other hand, in an unlicensed band that does not require a license, the use of frequency is freely available within the specified range, making it easier for many companies to use the frequency. Therefore, Wi-Fi and Bluetooth using unlicensed bands are widely used all over the world.

Private LTE can be as popular as Wi-Fi by using unlicensed bands as well, which is expected to expand many new use cases that are different from traditional Wi-Fi and LTE.

Benefits of using private LTE

Private LTE is available in the 5GHz unlicensed band which Wi-Fi is used. With Wi-Fi already quite popular all over the world, what’s the benefit of using LTE when communicating with unlicensed bands?

Benefits of using LTE include:

  • Ensuring security
  • Reliability
  • Efficiency
  • Better coverages
  • Cost
  • LTE features use

Wi-Fi has low deployment barriers and is very easy to deploy, but security is a concern. Security must be taken, especially on networks that do not authenticate on public Wi-Fi, and care must be taken when exchanging sensitive information. LTE, on the other hand, has a highly confidential authentication method using SIM, which provides stronger security.

If you use Wi-Fi, you may occasionally experience slow communication or, in some cases, communication disrupted. There are several causes, most of which are radio interference with other Wi-Fi.

LTE is supposed to analyze the radio wave status of the target area in advance, and adjust the base station to reach a certain radio wave in the area where it should be, and builds the area. As a result, it is possible to provide a high-quality and reliable environment in the area, enabling efficient data communication.

These days, Wi-Fi status check is also conducted when it is introduced in the offices or factories to secure the better quality. However, in the case of Wi-Fi, it is very easy to obtain access points, for example, new access points may be installed in surrounding houses and other offices, and radio waves from those access points will cause new interference and the quality in the office or the like will deteriorate.

In addition, since the Wi-Fi access point of the surrounding environment increases or decreases frequently, it is very difficult to maintain the good environment in the office each time according to it.  Modern Wi-Fi systems also allow you to change the channel used while monitoring the surrounding radio environment and change the direction and strength of the radio waves, but it is difficult to reduce all interference to zero.

In the case of LTE, because the deployment barrier is higher than Wi-Fi, it is not possible to easily add an access point, resulting in a situation where frequent radio interference due to such interference is not possible.

In addition, LTE technology is used in a variety of technologies to ensure that radio waves reach the edge of the area, thereby ensuring stable coverage. This means that Wi-Fi needs dozens of access points to secure an area, but changing to LTE can reduce it to a few, which can reduce deployment and running costs.

The advantage of using LTE is that you can take advantage of the features defined in LTE. For example, LTE has a broadcast function (eMBMS) in addition to normal data communications, which allows you to broadcast the necessary information for each area to the device. By using this feature, for example, by delivering lectures on university campuses in real time only to tablets and PCs of students on university campuses, students can freely take lectures anywhere on campus, and universities can also use them to deliver assignments.


There are several methods of private LTE

There are several private LTE methods, including LTE-U, LAA, sXGP, and Multifire, and each has its own characteristics and limitations.

LTE-U/LAA taught by 3GPP

LTE-U began to be discussed at 3GPP around 2010, which was discussed not only by telecommunications carriers, telecommunications equipment venters, device vendors, but also by companies in various industries such as Wi-Fi and OTT such as Google. However, while LTE-U technical specifications were discussed and validated in 3GPP, there were quite a few objections around the world, especially Wi-Fi alliances that mutually authenticate Wi-Fi because they had a significant impact on Wi-Fi using the same unlicensed bands as LTE-U.

In some countries, carriers started a service using LTE-U, but this prolonged discussion with the opposition has made it difficult to standardize on 3GPP. In this situation, Qualcomm in the U.S. developed a specification for LAA (Licensed Applied Access) as a new method based on LTE-U that used unlicensed bands to reduce the impact on Wi-Fi, and as a result, LAA was standardized in Release13. However, release13 LAA standardizes only downlinks, which are base station-to-device communications, and uplinks, which are device-to-base station communications, are standardized in Release14.

3GPP specifies the available frequency for each communication technology. The frequencies available in LAA are Band46 (5150 – 5925MHz) in the 5GHz band and Band48 (3550 MHz – 3700 MHz). Wi-Fi specifies that the frequency in the 5GHz band is 5250-5350, 5470-5725MHz, so you will assign frequencies in each country so that they do not actually overlap with this frequency.

Although LAA needs to be used to develop devices that can use LTE in the 5GHz band, 131 devices already support LAA.

According to a March 2020 report released by GSMA, 38 operators in 21 countries have invested in LAA, and nine operators in six of them are already in commercial service. In addition, 29 operators in 18 countries are doing trials, deployment plans, and so on.


Japan leading sXGP

Japan focuses on sXGP (Shared Extended Global Platform) as private LTE and is leading the world. sXGP is the latest PHS successor based on PHS technology, which became popular about 25 years ago in Japan, and both PHS and sXGP were developed in Japan. PHS was a proprietary technology, but one of its major characteristics is that sXGP has 100% compatibility with TD-LTE, which means sXGP fully supports TD-LTE.

Today, PHS is not popular and often seen in Japan, however why is sXGP gotten attention?

In Japan, PHS services were launched in 1995 and initially becoming quite popular as mobile communications with low tolls. However, after that, the shift to cellular and the number of PHS users began to decrease rapidly due to low cellular phone charges and terminals. Although PHS service are still served however it will be terminated by 2021 including the IoT use cases like vending machine management, elevator monitoring, etc.

On the other hand, PHS had high security and the sound quality of the call was very good compared to the cellular phone at the time, so it is often used as a digital cordless telephone (such as an extension phone), and PHS technology is still used, especially in hospitals and factories. Although the PHS services provided by carriers have been shrinking, PHS technology is still used in digital cordless market.

Therefore, sXGP is expected to be used continuously as digital cordless phones such as these extension phones and to further expand its use. sXGP fully supports TD-LTE, which means you can expect the same communication speed as LTE. In addition, because sXGP is positioned as a successor to PHS, unlicensed band 1.9GHz can be utilized and this is also one of the benefit.

sXGP is still available, however frequencies are very narrow at 10MHz at 1893.5-1906.1MHz currently.  The Ministry of Internal Affairs and Communications expects sXGP as private LTE technology and has a plan to expand the bandwidth for sXGP as follows.

Currently, sXGP only uses 5MHz, but this frequency allocation change allows the use of up to 40MHz width. This is expected to significantly improve the communication speed. This expansion also extends the target frequency to 1880-1920MHz, which is exactly the same frequency as Band39 in the 3GPP in Table 1. As a result, smartphones and modules that support Band39 released in various countries around the world can be utilized, and it is expected to spread at once.

Various use cases are being considered because sXGP is license-free, easy to deploy, and maximizes LTE’s technical benefits.

For example, in a hospital, it is not just a substitute for an extension phone, but by using high-speed communication with sXGP, data from various measuring instruments used by inpatients can be managed in the center in real time, so that the patient’s condition can always be checked. This makes it possible for doctors and nurses to reliably check the patient’s condition only when necessary, which increases efficiency.

In factories, sXPG may be utilized in factory production lines. In traditional production lines, each equipment was wired, and each product had to have its specific production line. If you prepare a dedicated line, products that depend on the season and season will be very inefficient in the line where the busy season and the quiet season are divided. It is possible to freely change the layout of the production line by providing an environment where each device in the production line can be wirelessly connected by sXGP instead of wired, and the layout of the production line can be changed freely, and production efficiency is increased by using equipment that was rarely used in the previously quiet season in another production line.

In this way, private LTE using sXGP in the 1.9GHz band is expected to be very easy to deploy because it is possible to use it without requiring a license application while using band39 of 3GPP, and many companies are already interested and have started selling solutions using sXGP.

Self-employed BWA using 2.5GHz

In Japan, in addition to private LTE using frequencies for 1.9GHz digital cordless, self-employed BWA using the 2.5GHz band is also being promoted as a private LTE.

In Japan, there is a broadband service “Regional BWA (Broadband Wireless Access)” that use the 2.5GHz band for the purpose of eliminating digital devices nationwide and developing locally. In 2008, BWA, commonly known as “Regional WiMAX,” provided wireless broadband services in rural areas by non-carriers such as local governments.

Self-employed BWA is private LTE services with 2.5GHz band which is assigned to regional BWA. Regional BWA is given a 20MHz in the2.5GHz band (2575 to 2595 MHz). As follows, regional BWA will use its own BWA in vacant areas because of the limited use of BWA.

Self-employed BWA uses 2.5GHz, the frequency at which the license is required, so you need to apply for a license as well as regional BWA, but the advantage of using a license band is that you can use a Badn38 (2570–2620MHz) compatible terminal that partially overlaps the frequency used by your own BWA.


Popular globally, MultiFire

In Japan, Private LTE using sXGP is the mainstream but MultiFire is attracting attention globally. MultiFire is 100% compatible with 3GPP LTE as well as sXGP, and aims to make LTE technology that is easy for anyone except carriers to deploy. Therefore, sXGP in Japan is used at only 1.9GHz (Band39), but MultiFire is aimed at use in any unlicensed band. Currently, in addition to 3GPP LAA as well as 5GHz usage, there are provisions such as Band39 for sXGP and 2.4GHz.

MultiFire is a technology developed by Qualcomm that is being promoted globally, and the members of the study are telecommunications infrastructure vendors, chipset vendors, and carriers from all over the world.


Private LTE Perspectives

Local 5G is getting a lot of attention these days, and private LTE is getting a lot of attention, too. With regard to local 5G, use cases that take advantage of the characteristics of 5G are expected, but 5G itself is a technology that has just started service in the world, and it is likely to take a little more time to spread base stations and terminals using this 5G technology.

On the other hand, private LTE is a technology that has been in use for more than a decade and is very stable, and there are many choices of devices that can be used. In Japan, Band39 can be utilized as unlicensed band for sXGP and this is big advantage while 28GHz was assigned for Local 5G and Sub6 band will be ready soon, however both of them requires license.

In Japan, Private LTE has very low deployment barriers and can be expected to be used in a variety of industries in the near future.