What exactly is UWB? What will it bring to us?
Editor’s note: This article is from WeChat public account “Fresh Jujube Classroom” (ID: xzclasscom) , the author Xiaozaojun. The original title “Black Technology for New iPhone: Uncovering UWB Technology”
On September 11, Apple’s fall conference was held at the Jobs Theatre. A series of new products represented by the iPhone 11 unveiled the mysterious veil and met with the “fruit powder”.
The characteristics and parameters of the new iPhone, I believe that everyone has already understood through the introduction of major media. However, there is a detail, I don’t know if you have noticed – the full range of new iPhones released this time, all equipped with U1 chips supporting ultra-wideband (UWB) technology.
According to official publicity, this new technology will significantly enhance the spatial awareness of Apple’s mobile phone.
So what is the problem, what does spatial awareness mean? What can the U1 chip do? What is the black technology of UWB ultra-wideband technology? All of these, will lead a new round of smart device application innovation?
Through this article, the author will reveal the answers to these questions for you.
What is spatial awareness?
The so-called spatial perception ability is the ability to sense orientation. More directly, it is the ability to locate.
According to Apple’s introduction, the new iPhone with U1 chip further enhances the positioning function of the mobile phone, not only can sense the location of its mobile phone, but also the location of other mobile phones around.
When using AirDrop (a function of wireless sharing files provided by Apple devices), based on U1 chipFor spatial awareness, simply point your iPhone to someone else’s iPhone and the system will prioritize (the closer you are, the higher the priority), allowing you to share files faster.
To put it bluntly, with the positioning ability of U1, iPhone11 can achieve the application effect of “getting closer to me and getting the first response”.
Speaking of positioning, I believe everyone is familiar with it. We often use apps such as Gold Maps or Baidu Maps, which have positioning and navigation services.
The location service helps us to grasp the location information, indicate the direction, increase our sense of security and control, and bring great convenience to our work and life.
So, what is the difference between UWB technology and the positioning technology we use today?
The positioning technology we use today mainly includes satellite positioning and base station positioning.
Satellite positioning is a technology that uses artificial earth satellites for point measurement. It is also the most widely used and most popular positioning technology. Its characteristics are outstanding, that is, high precision, high speed and low cost of use.
The well-known US Global Positioning System (GPS), China’s Beidou (BDS), Europe’s Galileo (Galileo), Russia’s GLONASS (GLONASS) are all satellite positioning systems.
The principle of base station positioning is similar to radar. Radar positioning Everyone knows that it is to transmit radar waves and perform spatial position estimation based on the reflection of the target.
If the base station is located, the base station is equivalent to a “radar”.
Usually, in a city, a cell phone will be under the signal coverage of multiple base stations. The mobile phone “measures” the downlink pilot signals of different base stations, and obtains the signal TOA (arrival time) or TDOA (time difference of arrival) of each base station. According to this measurement result, combined with the coordinates of the base station, the coordinate value of the mobile phone can be calculated.
Draw a picture and see it at a glance:
All of these positioning methods have an obvious disadvantage, that is, they cannot penetrate the building and cannot achieve indoor positioning.
Satellite positioning requires the receiver to receive enough satellite signals. When entering the room, or when there is occlusion, the satellite signal is very weak and cannot be effectively positioned.
The above picture shows the GPS positioning signal received by the mobile phone outdoors. The following picture shows the GPS positioning signal received by the mobile phone indoors
As can be seen from the diagram, when the number of satellites found is reduced, the positioning error increases from 10 meters to 66 meters.
On the one hand, satellite and base station positioning technology cannot meet the needs of indoor positioning. On the other hand, there are more and more business scenarios for indoor positioning. For example, underground garage navigation, shopping malls looking for shops and goods, and even children’s loss, there is an urgent need for indoor positioning.
In demandIn the context of continued rise, a series of techniques have been developed that attempt to provide positioning capabilities using other types of anchor nodes. This includes technologies such as Wi-Fi, Bluetooth, and UWB.
What is UWB
Wi-Fi and Bluetooth are familiar to everyone. So what is UWB?
UWB, is Ultra Wideband, ultra-wideband technology. It stems from the pulse communication technology that emerged in the 1960s.
The students who understand communication know that the general communication system uses a high-frequency carrier to modulate a narrow-band signal, and the actual occupied bandwidth of the communication signal is not high.
While UWB differs from traditional communication technologies in that it transmits and receives wireless transmissions with very narrow pulses of sub-nano or microsecond order. Since the pulse time width is extremely short, ultra-wideband in the spectrum can be realized: the bandwidth used is above 500 MHz.
FCC (Federal Communications Commission) allocated UWB a total of 7.5 GHz band from 3.1 to 10.6 GHz, and also imposed stricter limits on its radiated power than FCC Part 15.92, limiting it to the band -41.3 dBm. .
In short, this technology enables fast data transfer at low power levels with very large bandwidth and low transmit power.
Since the time width of the UWB pulse is extremely short, it is also possible to perform distance measurement using high-precision timing.
UWB has the following advantages over Wi-Fi and Bluetooth positioning technology:
1) Strong multi-path resistance and high positioning accuracy: The bandwidth determines the distance resolution of the signal in a multipath environment (proportional relationship). UWB has a wide bandwidth and strong multipath resolution. It can distinguish and eliminate the influence of most multipath interference signals, and obtain highly accurate positioning results. UWB can be superior in distance resolution to other traditional systems, and its accuracy can even reach Wi in complex environments.-100 times more than traditional systems such as -Fi and Bluetooth.
2) High time stamp accuracy: The bandwidth of the ultra-wideband pulse signal is in the order of nanoseconds. When the position is calculated by timing, the error introduced is usually less than a few centimeters.
3) Strong electromagnetic compatibility: UWB has low transmission power and wide signal bandwidth, which can be well concealed in other types of signals and environmental noise. Traditional receivers cannot recognize and receive, and must be consistent with the transmitting end. The spread code pulse sequence can be demodulated, so it will not cause interference to other communication services, and can also avoid interference from other communication devices.
4) High energy efficiency: UWB has an RF bandwidth of more than 500 MHz, which can provide a large spread spectrum gain, making the UWB communication system more energy efficient. This means that for battery-powered equipment, the system’s operating time can be greatly extended, or the same transmission power limit, coverage is much larger than the traditional technology. Typically in short-haul applications, UWB transmitters typically have a transmit power of less than 1 mW; in long-haul applications, an additional power amplifier is required to achieve a distance of 200 meters while achieving an airspeed of 6.8 Mbps.
Based on the above technical advantages, UWB can be used to form a high-precision indoor positioning system.
Comparison of UWB and other positioning technologies
At present, there are three commonly used UWB ranging methods, namely:
(1) TOF (Time of Flight): The distance measurement is realized by measuring the time when the UWB signal flies between the base station and the tag.
<2> (2) TDOA (Time Difference of Arrival): The UWB signal is used to perform positioning by the time difference of the tag reaching each base station.
(3) PDOA (Phase Difference Of Arrival): The orientation angle between the base station and the tag is measured using the angle of arrival phase.
Because of the length, we will introduce the algorithm principle of UWB in detail later.
UWB Industry Development
Before 2002, UWB was widely used for military purposes. In 2002, the FCC (Federal Communications Commission of the United States) imposed a strict restriction on the power of UWB as mentioned above before lifting the ban on UWB technology and allowing access to the civilian sector.
In 2007, the IEEE standardized the UWB technology in the 802.15.4a standard. After nearly a decade of development, UWB standards are constantly improving. When it comes to UWB’s industry chain, you have to mention Decawave. Decawave is currently the only UWB positioning chip manufacturer that supports IEEE 802.15.4. They offer low-cost chips for sale at retail prices of a few dollars. The chip model is DW1000, which complies with the IEEE 802.15.4-2011 UWB standard protocol (under ideal conditions, the maximum measurable range is 300m). DW1000 chip After Apple’s product launch, DEVRAN, a positioning manufacturer based on the Decawave chip DW1000, issued two tweets, claiming that its suite supports interoperability with the iPhone 11, and Decawave also forwarded the tweet. This shows that Apple U1 has great potential to support IEEE 802.15.4. Other vendors engaged in UWB technology research include Ubisense and BeSpoon. These vendors use their own UWB solutions, usually in the form of a module kit, but none of them support IEEE.802.15.4. To achieve better spatial awareness, you need to apply ecological support. In order to build the entire application ecosystem, different manufacturers need to achieve interoperability and compatibility. It is foreseeable that all future manufacturers’ equipment will likely support the IEEE 802.15.4 standard. In order to objectively judge different indoor positioning technologies, several international organizations have been actively organizing indoor positioning competitions. The current three high-profile indoor positioning competitions in the world include: 1) Microsoft Indoor Localization Competition (MILC) 2) PerfLoc (Performance Evaluation of Smart-phone Indoor Localization Apps) conducted by the National Institute of Standards and Technology (NIST) 3) International Indoor Positioning and Indoor Navigation Conference (IPIN) Indoor Positioning Competition: IPIN competition Microsoft’s MILC competition is recognized as the best stage for judging high-precision indoor positioning technology. The following is a list of the top three achievements in the MILC competition based on the infrastructure group: It can be seen that since 2015, UWB’s advantages have gradually emerged, and it has become the most promising technology in high-precision positioning technology. At the same time, Decawave’s DW1000 is also the mainstream choice in specific positioning solutions. Of the 8 award-winning UWB teams, 7 use the DW1000. The 2018 game uses a very high-performance laser SLAM to build a map (left) and based on this real-time output of the real position trajectory (right), which serves as the basis for the evaluation of the game The venue is in the Palace of Porto Stock Exchange in Portugal. The site environment is very complicated For the first time in 2018, the dynamic accuracy was evaluated. The venue was very complicated and the results were highly oriented. In this event, the Anthony Rowe team from Carnegie Mellon University in the United States is worth mentioning. This team is the leader in the field of indoor positioning, three times into the top three, and in 2018 won the first place and tied for second place. CMU Anthony Rowe Team More importantly, in 2018, the team’s first technical route was UWB+ Augmented Reality (AR), while the iPhone 11 Pro became the first mobile phone to support both AR and UWB. This is enough to prove that the team has strong technical insight. In addition, Nanjing Aiyi Electronic Technology Co., Ltd. from China is also worthy of attention. They are an emerging team. They entered the UWB market one year later and participated in the 2018 competition, achieving a second place. This is the best result of the domestic team in the competition so far. The above picture shows the real-time trajectory output of the Nanjing Aiwei team during the competition. It can be seen that except for a small part of the area, most of the areas output highly accurate positioning coordinates. Blue is the real-time trajectory of the laser SLAM, and the green point is the trajectory of the love team output., red is the vector error. The above picture is a comparison of the average positioning error of each team. The average positioning error of the Aiwei team is 0.4 meters, and several traditional strong teams, such as RaceLogic and Russian Research Institute, also use UWB technology, but only achieve results of nearly 1 meter or even worse, which fully illustrates the 2018 The difficulty of the game is great. All in all, this new iPhone’s comprehensive support for UWB is an invaluable opportunity for large-scale commercial promotion of UWB technology. This will also accelerate the development and maturity of the UWB upstream and downstream industry chain. With the advent of 5G, we are accelerating towards the era of Internet of Everything, and more and more IoT devices and applications will emerge. UWB technology can be closely integrated with these IoT scenarios according to its own characteristics, providing users with a better service experience. Including smart home, augmented reality, mobile payment, care tracking, geological exploration, indoor navigation, will be the use of UWB technology, has a very broad development prospects. According to the forecast of relevant institutions, UWB technology will occupy 30%~40% market share in the indoor positioning market in the future, and the market size will reach US$16.4 billion in 2022. The future of UWB, let us wait and see! 
UWB positioning effect
Conclusion