Field of the Invention

The present invention relates to Short Range Device as defined by the Electronic Communications Committee and to Low Power Wide Area Network and the Internet of Things as defined by the International Telecommunication Union.

Background of the Invention

The internet of things (loT) is a type of communication network in which sensors communicate with a backend infrastructure to optimize the efficiency of city or business operations for example. loT application can rely on a class of wireless systems under the generic name of low power wide area network (LPWAN), that operates under the regulation for short range devices (SRD) and are particularly well suited for devices that need to send only a few bytes messages per day. The LPWAN technologies may be proprietary or open standards and are designed to address massive loT applications, that is with a very large number of connected devices. The most popular use cases are in logistics, manufacturing, smart cities and home, utility or agriculture.

LPWAN uses a star topology architecture in which access points (AP) are deployed between the devices and the communication network and can use different communication technologies (3G,4G, Ethernet, Wi-Fi...) to backhaul the data to the LPWAN core network. When installed on high points and outdoor, LPWAN AP can cover up to tens of kilometers with thousands of devices within the service area of a BS. For deep indoor applications like gas or water metering, repeaters may be installed to extend the LPWAN coverage in-building. As LPWAN systems use generally license-exempt spectrum, mechanisms to ensure fair usage of the frequency resources are enforced through duty-cycle (1% or 10%), “listen before talk” or “frequency hopping” mechanism. Devices, access points and repeaters have to respect the limitations and therefore can only meet low throughput requirements. Popular examples of LPWAN in today’s world are Sigfox and LoRaWAN. Sigfox relies on ultra-narrow band (UNB) technology, where high selectivity filtering combined with narrower signal bandwidth (100 Hz) improves sensitivity threshold. Two modulation schemes are available 100bps and 600 bps and each uplink frame with a payload up to 12 bytes can be repeated up to 3 times on different frequency channel to improve the message success rate. Using the standard configuration (3 frame per message, 100bps, each device with a duty cycle of 1 % for example can send a maximum of 72 bytes per hour, and using high capacity configuration (no repetition, 600 bps) 1 296 bytes per hour, that 18 times more than the standard configuration.

LoRaWAN uses a chirp spread spectrum techniques (CSS) which reduce the sensitivity level below noise floor thanks to coding gain depending on the spreading factor. For a bandwidth of 125 kHz, with a spreading factor of 12, a device may send up to 438 bytes per hour at application layer, while the number increases to 14 455 bytes per hour for a spreading factor of 7.

Apart from low throughput network, the SRD ECC Rec. 70-03 also encapsulates different usage patterns including wideband data (WB) transmission to be provided by standards like Bluetooth, RFID, NFC, Wi-Fi or UWB. Both LPWAN and WB devices use very low power like LPWAN devices, but while LPWAN is optimized for long range low throughput communication (a few bytes over then of kilometers), WB is designed for short range high throughput communication (kilo/megabytes over a few meters) using license-exempt spectrum. WB radio networks are composed of access points to connect the devices to the WB core network using a supporting communication technology (Ethernet, xPON, 4G...). The WB AP coverage is in the range of 20 to 50 m indoor.

A short-range beacon (SRB) is a subclass of WB SRD, that broadcasts at regular intervals an advertisement frame, which includes one or several unique identifiers (UID). The UID and several bytes sent with it can be used to determine the SRB physical location, track customers, or trigger a location-based action on the device such as a check-in on social media or a push notification. A SRB is not attached, paired or controlled by the network infrastructure in nominal operations. The most common SRB on the market today relies on the Bluetooth low energy (BLE) standard.

BLE is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group (Bluetooth SIG) aimed at novel applications in the healthcare, fitness, beacons, security, and home entertainment industries. Compared to Classic Bluetooth, Bluetooth Low Energy provides considerably reduced power consumption and cost while maintaining a similar communication range. Supported by the vast majority of operating systems for smart phones and computers, BLE has gained a significant momentum for consumer applications but also in the industry. Bluetooth beacons are hardware transmitters - a class of Bluetooth low energy (LE) and SRB devices that broadcast their identifier to nearby portable electronic devices. The BLE beacon formats are following various standards, like iBeacon or Eddystone UID, defined by the industry leaders.

The communication protocols used by SRB are low power communication protocols that allow the manufacturing of devices small in size while designed to last for years. Also, as the market has massively adopted these technologies, the price of the electronic components has dropped down extensively over the years. Handheld cellular devices supporting these protocols have also increased dramatically over the years. For these reasons, small SRB tags have become very popular in the Internet of Things domain, especially for automatic inventory and asset tracking applications. To be able to function correctly, loT applications using SRB rely on a dense infrastructure of either stationary or non-stationary gateways, typically one every tens of meters (max range of SRB), and - in case of stationary type - connected to a power outlet and using WiFi, cellular or wire line for backhauling the information to the Internet, or - in case of non-stationary - relying on the cellular phones to arrange for the backhauling. The latter, while affording low-cost coverage, relies on factors beyond the control of the service supplier to secure certain Service Levels, that is cellular phone users being willing to allow use of their device to 3 ^rd party service providers, as well as professional management of the implied enlarged cyber attack surface this offers to malicious radio users. In addition, coverage is a function of people’s movements, which follow different patterns than some of the main uses of loT (other than city infrastructure).

A battery-operated gateway (BGW) is an electronic device, which power supply consists of batteries (primary or rechargeable) that relays the information between electronic devices and a communication core network A BGW usually acts as a transparent node in the end to end communication, receiving, processing and transmitting the data while minimizing the information losses. The BGW may as well implement network operations methods to control the flow of information and optimize the efficiency of the resource usage. The BGW may also embed additional operation and maintenance functionalities such as geolocation to report its position to the network on a regular basis.

While SRB BGW exist on the market, they do not rely on LPWAN to backhaul the data to the Internet nor offer life duration of multiple years without changing the batteries. This is mainly due to the high throughput low latency nature of the SRD protocols that requires the gateway to receive and send data all the time, without the option to go into deep sleep mode to save on the batteries.

In the case of mesh network, each relay node can be considered as an SRB BGW, but does not backhaul information over a LPWAN hence only providing short range connectivity. The connectivity towards the core network is ensured via de sink/source node connected to the Internet.

It is an objective to disclose a battery-operated gateway to transmit data advertised by SRB over a LPWAN, that overcomes the shortcomings of existing solutions. It is a further objective to disclose a deep sleep strategy for the gateway to reduce the energy consumption. It is a further objective to disclose an algorithm that allows data from multiple SRD to be aggregated into a single LPWAN message to save on throughput. It is a further objective to demonstrate how such a system can operate in the industrial context of real time asset inventory and tracking without the need to have a single device connected to a power outlet or relying on a public cellular or wireline telecommunication network.

Disclosure of the Invention

The BGW acquires, processes and transmits over an LPWAN the information contained in the advertisement frames of a fleet of SRB locating in the vicinity of the gateway. The transmission of the SRB advertisement frame is uplink only and triggered by a timer T _ADV or an external event.

A generic advertisement frame format for the SRB shall be described as:

- Header (10.1 ), a few bytes to describe the payload size and type. It also includes the physical layer preamble.

- Unique identifier (UID) (10.2), typically the Medium access control (MAC - 6 bytes), composed of organisationally unique identifier (OUI - 3 bytes) and network interface specific (NIC - 3 bytes)

- Data, generally a few tens of bytes, composed of additional blocks of information of two kinds: identifier Block _I ^l _D (10.3) and data Block _D ^l _ata (10.4). The data blocks may contain for example temperate or battery level, while the identifier blocks may be organized hierarchically

- CRC (10.5) is a cyclic redundancy check (physical layer)

It is therefore essential for functioning of the Invention, that the BGW performs three sets of routines at regular interval or triggered by a sensing event. The first routine, named “data acquisition” (DAC), aims at acquiring and storing the SRB advertisement data, while the second one, named “data transmission” (DTR) aims at sending the aggregated data from the first routine over the LPWAN. The first routine usually runs several times before the second one. The third routine, named “geolocation” (GEO) aims at acquiring the BGW geographical location by using GPS, Wi-Fi or similar methods.

Data acquisition (DAC) routine (triggered by a timer T _DAC or an external sensing event)

Wake up from deep sleep mode

Demodulate the SRB advertisement frames during a sniffing window of duration W _DAC

Measure the Received Signal Strength Indicator (RSSI) of each SRB advertisement frames Filter the frames data based on Header, UID, data blocks or RSSI user-defined criterion Store the filtered data into a memory register Fall back into deep sleep mode

For each beacon demodulated, the BGW stores, at least, in a memory register the UID of the SRB, the content payload, the RSSI and a timestamp. To filter the eligible SRB able to connect to the BGW, a whitelisting on SRB UID range may be implemented for example on a OUI to demodulate only the SRB from a specific manufacturer. If the identifier blocks are organized as customer identifier Block^ ^stomer and project identifier Block^ ^oject , it would be possible to filter only a given customer or project. The filtering options and codes may be configurable by downlink over the LPWAN to allow over the air update of the BGW configuration.

The demodulation or sniffing window of the DAC routine duration depends on the configuration of the advertisement beacon of the SRB, with the recommendation of the sniffing interval to be N times greater than the average advertisement interval.

Data transmission (DTR) routine (triggered by a timer T'DTR or an external sensing event)

- Wake up from deep sleep mode

- Flank the memory entries according to a configurable criterion (highest number of occurrences, highest Fl SSI, oldest timestamp...)

- Create the LPWAN frame payload by concatenating the data from the highest priority memory entries. Compression techniques like sending only a part of the UID or specific block of information may be applied.

- Transmit the LPWAN frame until successful, if the information is available

- Remove the transmitted entries sent from the memory register

Geolocation (GEO) routine (triggered by the end of the DTR)

- Each geolocation method is assigned a priority by configuration

- Starting by the highest priority geolocation method, acquire geolocation information. o If successful, send the information over the LPWAN and fall back to deep sleep mode o If not successful, use the next in line priority geolocation method to acquire location

- Fall back to deep sleep mode

The DAC and DTR routines are triggered by a timer or an external event (movement or light detected...). As the frequency bands used by the LPWAN are commonly ISM bands, the timer of the DTR routine must be set to respect the local regulations in terms of medium access control (duty cycle or listen before talk). In Europe, the timers for the DAC and DTR could be respectively set to 10 min and 60 min for example. The SRB advertisement interval is chosen significantly lower to meet the industry standard for connecting to handheld devices (primary connection for the SRB) and to save on energy for the BGW, allowing the BGW sniffing period to be relatively short.

Table A: Main system parameters, notations and typical values

The BGW can be configured using a downlink frame to update:

- the white listing parameters of the beacons

- the sniffing window W _DAC and duration of the beacon demodulation period T _DAC

- the behaviour of the low power wide area network transmission TDTR

- the geolocation parameters and priority preferences

The life duration of the BGW increases with the duration of the deep sleep mode for which the power consumption is the lowest. Also, the DAC, DTR and GEO parameters have a large impact and it is advised to adjust the parameters to the use cases. Several parameters should be considered but the environment (indoor or outdoor), the speed of movement and their density of the SRB are prime. If the SRB and BGW are located indoor, it is advised to prevent from using GNSS methods in the GEO routine as the success rate is likely to be low and energy consumption high. In this case, low energy method like “WiFi or BLE sniffing” are recommended. The BGW beacon acquisition interval T _DAC is quantifying the ability of the BGW to detect the presence of a SRB in its vicinity (20m or so). For slow moving SRB, for example attached to furniture in an office space and BGW fixed on the wall, an increase of the value T _DAC is unlikely to impact the detection capabilities of the system while saving on battery. The data transmission interval TDTR has an impact of the throughput of the BGW and geolocation accuracy. If the density of SRB in the vicinity of the BGW is large, it is advised to lower the TDTR to be able to relay more data to the LPWAN. As LPWAN uses generally license-except spectrum, the value will be limited to 10 min for example in Europe on the 868 MHz ISM band. To increase the throughput of the system and its ability to relay more information from the SRB onto the LPWAN, various strategies can be put in place while respecting the regulations. For Sigfox, higher modulation schemes and no frame repetition may be used while a lower spreading factor is providing more throughput with LoRaWAN. Both strategies lead to a decrease in the maximum transmission range by lowering down the available link budget.

BGW throughput

The throughput of the BGW is defined as the uplink throughput between the BGW and the LPWAN. As described in the DAC and DRT routines, the advertisement frame of a SRB is processed and compressed by the BGW and transmitted as a block of size S _SRB , each SRB being allocated the same number of bytes. Therefore, it is convenient to express the BGW throughput in block per day to reflect the number of SRB that can be bridged to the LPWAN. The results are presented in Tab. B and Tab. C:

Table B: BGW throughput with respect to the SRB block size and data transmission interval (100 bps modulation)

(0 Assumptions: Sigfox LPWAN, 2 bytes out of the 12 bytes uplink frame are used for in-band signalling (20.2)(20.3), 100 bps modulation, 3 frames per message.

Table C: BGW throughput with respect to the SRB block size and data transmission interval (600 bps modulation) ⁽²⁾ Assumptions: Sigfox LPWAN, 2 bytes out of the 12 bytes uplink frame are used for in-band signalling (20.2)(20.3), 600 bps modulation, 3 frames per message.

Using the typical values in Tab. A, the BGW throughput is of 120 SRB blocks per day for 100 bps modulation.

Battery life duration

The battery life duration of the BGW depends on a large number of factors ranging from 6 months to 15 years for the range of values considered in Tab. D. The following battery monitoring and operations are available: the BGW battery level (20.3) is sent on the LPWAN on a regular basis as in-band signalling, facilitating its monitoring the configuration parameters may be updated by a downlink LPWAN message to optimize the batterie consumption the BGW is designed in such a way that the batteries can be replaced

Table D: Battery life duration

Assumptions:

General. Sigfox LPWAN, EU regulations, 100 bps modulation, 3 frames per message, 1 downlink configuration per day

DAG. BLE beacon, W _DAC at 5 sec

DTR. 12 bytes frame size

GEO. Wi-Fi sniffing first, 10 % if failed Wi-Fi sniffing, GPS cold start at 30 sec

Battery, capacity 5 400 mAh, voltage 3.6 V, efficiency 70%

The DAC and DTR routines shall alternatively triggered based on a sensing event, like a movement being detected. While the DTR routine has to follow the frequency band regulation (every 20 min for example), there is no regulation for the DAC routine and therefore the battery life duration cannot be predicted. To maximise the life time of the BGW, it is recommended to implement a data acquisition interval in any case to avoid a quick drainage of the battery. Such a policy could be, for example, “run the DAC routine every 10 min while a movement is detected and every 1 hour if not”.

Brief description of the drawings

Figure 1. is a system overview showing the invention, the battery-operated gateway, relaying information from the short-range beacons towards the low power wide area network.

Figure 2. is showing the block diagram of the battery-operated gateway (2).

Figure 3. is showing the state machine diagram of the battery-operated gateway (2). Figure 4. is describing the frame format transmitted by the SRB (1 ) and the BGW (2).

Figure 5. is describing events in chronological order for the SRB (1) and the BGW (2).

Best mode for carrying out the invention

The BGW can be implemented using the references in Tab. E Table E: Gateway hardware configuration

Industrial applicability

The invention aims at facilitating the deployment a low-cost battery powered network infrastructure to connect the short-range beacons to any cloud applications. The following use cases may be applicable:

Asset inventory. In office space management, SRB as a small footprint device may be attached to virtually any assets and for example to furniture. The installation of BGW is offices would allow automatic inventory of the furniture in a given area without having to manually count or scan each piece of furniture at regular intervals.

Asset tracking. In logistics, returnable industrial packages play a major role in making the economy more circular by replacing one-time packaging. The SRBs may be attached to plastic pallets for example and installation of BGW in transportation trucks and docking areas provides visibility of the journey of the plastic pallets.

Sub-metering. In utility, the BWG can be used to aggregate the consumption measurements and alerts of individual meters without having to equip each meter with a long-range metering sensor.