2 simple methods to find broken in the set of ibeacons

2 simple methods to find broken in the set of ibeacons Akylbek Mnazhatdinov Kazakh British Technical University, Almaty, Kazakhstan amnazhatdinov@gmail.com Ibeacon. Working principle. What is iBeacon? Ibeacon utilizes Bluetooth technology which allows Mobile Apps (running on both iOS and Android devices) to listen for signals from beacons in the physical world and react accordingly. In essence, iBeacon technology allows Mobile Apps to understand their position on a micro-local scale, and deliver hyper-contextual content to users based on location. The underlying communication technology is Bluetooth Low Energy. [3] What is Bluetooth Low Energy (BLE)? Bluetooth Low Energy is a wireless personal area network technology used for transmitting data over short distances. As the name implies, it's designed for low energy consumption and cost, while maintaining a communication range similar to that of its predecessor, Classic Bluetooth. [2] How is BLE different from Regular Bluetooth? - Power Consumption: Bluetooth LE, as the name hints, has low energy requirements. It can last up to 3 years on a single coin cell battery. - Lower Cost: BLE is 60-80% cheaper than traditional Bluetooth. - Application: BLE is ideal for simple applications requiring small periodic transfers of data. Classic Bluetooth is preferred for more complex applications requiring consistent communication and more data throughput. How does iBeacon use BLE communication? With iBeacon, Apple has standardized the format for BLE Advertising. Under this format, an advertising packet consists of four main pieces of information[1].UUID: This is a 16 byte string used to differentiate a large group of related beacons. For example, if Adidas company maintained a network of beacons in a chain of clothes stores, all Adidas beacons would share the same UUID. This allows Adidas' dedicated smartphone app to know which beacon advertisements come from Adidas-owned beacons. Major: This is a 2 byte string used to distinguish a smaller subset of beacons within the larger group. For example, if Adidas had four beacons in a particular clothes store, all four would have the same Major. This allows Adidas to know exactly which store its customer is in. Minor: This is a 2 byte string meant to identify individual beacons. Keeping with the Adidas example, a beacon at the front of the store would have its own unique Minor. This allows Adidas' dedicated app to know exactly where the customer is in the store. Tx Power: This is used to determine proximity (distance) from the beacon. How does this work? TX power is defined as the strength of the signal exactly 1 meter from the device. This has to be calibrated and hardcoded in advance. Devices can then use this as a baseline to give a rough distance estimate. Example: A beacon broadcasts the following packet UUID: 1122334455667 Major: 2 Minor: 1 A device receiving this packet would understand it's from the Adidas Beacon (UUID) in the Target on 2-nd Street (Major) at the front of the store (Minor).

Figure 1: Working principle of Ibeacon Ibeacon problem. Determination of broken beacon Main problems of beacon The advertising interval is the second important parameter for the radio module. This defines how frequently radio signals are broadcast. Beacons can be thought of as tiny lighthouses, intermittently flashing information into the surrounding area. The more frequent the ashes, the greater the chance a receiver will see them. Of course, beacons can be set to broadcast all the time, but that requires a lot of energy and dramatically reduces the battery life. This table (Figure 3) indicates typical beacon life expectations for new CR2450 battery depending on power and advertising interval settings. As you see on Figure 3, battery life durations of beacons are different and depend on some parameters. This information on the table is only expected and is not static. As we mentioned above, beacon's range is affected by many obstacles such as walls, furniture or people. This may be cause of lowing battery very fast. And we can see that the main problem of beacon is its battery. The corpus of beacon is plastic and it is fragile. That is another problem. If people accidentally touch it, it may be broken. Also temperature and pressurecondition can affect to beacon.There are many crashing causes, and defining process of broken beacon is problematic. For example, medium type stores need 2000-5000 beacons to cover all products. They will crash at different time, so we cannot predict specific date of crashing or lowing the battery of beacon.

Figure 2: Broadcasting power

Determination of broken beacon. Linear trajectory method. As we mentioned above, normal distance for getting signal well is 3-5 meters. And most of stores try to keep this distance between two neighboring beacons. It allows to know the client's location and show appropriate information. If beacons are located in linear way, we can de ne broken beacon by "linear trajectory method". The linear trajectory method's working principle depends on client's path. First of all, we create service that will show map of the beacons (Figure 4). When client enter to range of the beacon, application installed on smartphone

Figure 4: Linear map of beacons will send request with UUID of beacon to the server, and server de ne which beacon got signal and where client is now. After getting the signal server service tracks it and draws trajectory of client (Figure 5)

Figure 5: The path of the client. The last signal was received from beacon 3 If the trajectory of client splits, system will track UUID of beacons which are located between the last and the previous beacon (Figure 6). As we see on Figure 6, trajectory of the device jumped from beacon 1 to beacon 4, it means that beacons 2 and 3 are broken.

System tracks only broken beacon's UUID. And there device causes may affect. For example, client may switched o the phone near the beacon 1 and turn it on near the beacon 4. In this situation system will insert to table 2-nd and 3-rd beacons. However, this is not problem. After each iteration, when system receives signal from device, it will retrieve data from the table of broken beacons, and compare with received UUID, if the table contains same UUID it will be removed Figure 6: The path of the client when some of the beacons crashed

"Three neighbors" method. We told about the "linear trajectory" method. And this is only for small markets which have only single gate. However, as we know, most of stores have more complex structure and the method mentioned above doesn't work there. Complex structure stores use more than 10000 beacons and locate them in matrix form. The matrix form of beacons can interact system with client continuously, and get user's current location. The matrix form contains big amount of beacons, accordingly finding broken beacon in this situation is not easy process. And "Three neighbors" method is very useful here.

In the matrix formed map distances between beacons b_ij to b_i+1j and b_ij to b_ij ₊₁ are same. This option will help us to find broken beacon. First of all, we must create monitoring map for beacons in the store like in linear trajectory method. In this type of map, system receives 3 or more signals simultaneously. For ex-ample, if client in the center of the store, there are may be 9 beacons that can get signal from device. In the matrix below client is on the beacon b₂₂ now. In this situation all other neighbors may receive signal. However, b₁₁, b₃₁, b₁₃ and b₃₃ are not in normal distance range, and we cannot confidently say that they always can get signal. Therefore, these neighbors are not important for us.

The "Three neighbors" method uses only 3 nearest beacons. If 3 beacons simultaneously get signal from the device, the 4-th nearest beacon that has same distance from all of them must get signal too. If the 4-th beacon doesn't get signal, we confidently can say that it is not working. For example, on Figure 7 if beacons b₁₂, b₂₁ and b₂₃ get signal, it means that the nearest beacon for device is beacon b₂₂. If b₂₂ doesn't get signal, we can say that it is not working and insert it to the table. There is a problem if 2 or more

Figure 7: Matrix formed map

Conclusion With an iBeacon network, any brand, retailer, app, or platform will be able to understand exactly where a customer is in the brick and mortar environment. This provides an opportunity to send customers highly contextual, hyper-local, meaningful messages and advertisements on their smartphones.[4] And there some problems occur. Beacons are fragile and we cannot predict battery life duration. Beacons may be crashed at different time, and main problem is to determine broken beacon in the large set of beacons. And we offer 2 methods to deal with this problem. First method called "linear trajectory" useful when beacons are located in linear way. It is generally small markets, small museums and etc. The second method is "Three neighbors" method. This method is useful for matrix formed map of beacons. It will help to determine broken beacon by using three neighbor working beacons. Of course, there are so many complex structure used in buildings. And in the most of them both of offered methods may not work. However, these two methods only start of our research. And I believe that deeply research will help us to develop more complex solution and these two methods will serve as a basis of it. References [1] http://blogs.aerohive.com/blog/the-wi- -security-blog/ibeacon-part-23a-how-does-it work. iBeacon: What is it? Aerohive Networks, 2014. [2] https://passkit.com/how-ibeacon works. Bluetooth Low Energy (BLE) Communication. PassKit, Inc, 2014. [3] https://www.passbeemedia.com/ibeacon/. iBeacon. Passbeemedia, 2014. [4] http://www.ibeacon.com/what-is-ibeacon-a-guide-to beacons/. iBeacon. 2014.