METHOD AND DEVICE TO COMMUNICATE THE ENERGY AVAILABILITY OF A PROCESSING SYSTEM BASED ON INTERMITTENT_ MICROARCHITECTURES,_ WITHOUT

ELECTRICITY CONSUMPTION

The present invention refers to a method and a device for allowing transmitting apparatuses to know the energetic state of receiving apparatuses, the energetic state being communicated by the receiving apparatuses without any energy consumption . Backscatter is a particular telecommunication technique that exploits the physical phenomenon of diffuse reflection. Due to it, it is possible to establish a communication bridge between two or more devices (which constitute a wireless network) with practically no energy consumption. This is because nodes and sensors of the network do not emit any signal, but merely reflect the waves, already present in the atmosphere, emitted by other devices . Practical applications of this physical principle to the world of high tech are known. For some time, for example, experiments have been conducted in the field of passive Wi-Fi backscatter, a technology designed to reduce (also in this case) the energy consumption of routers and devices.

Other examples of backscatter are passive RFID tags and experimental research using radio waves of a TV signal. In research contexts such as Wireless Sensors

Network (WSN) and Internet of Things (IoT), radio frequency backscatter is becoming an attractive technology due to its ultra-low power consumption requirement. In this way it is possible to draw energy from the environment avoiding having to rely on the distribution network or the use of batteries so that, in many cases, it is not even necessary to wire the network nodes or the need to recharge the batteries.

A very low energy consumption means that, for this application, a large-scale production of electricity is not necessary, with consequent savings on primary energy sources (oil, coal, etc.). The energy source for the harvesters is in fact present as an environmental background. For example, there are temperature gradients due to the operation of a combustion engine and, in urban areas, there is a large amount of electromagnetic energy in the environment due to radio and television broadcasting.

Recent advances in microelectronics have led to the development of battery-free sensors that operate on the basis of ambient energy alone.

Modern battery-less platforms collect energy from various environmental sources (e.g. solar, RF radio frequency, bacterial species) and store the collected energy in capacitors. The capacitors are designed to conserve a marginal amount of energy and to power a microcontroller, and other peripherals such as sensors, radios, and communication interfaces.

On one hand, these peripherals frequently drain the capacitor. On the other hand, environmental energy sources are sporadic and supply energy in a discontinuous way. Therefore, devices without batteries work intermittently, that is, they are characterized by frequent charging and discharging cycles due to data acquisition/processing/transmission and rest.

The introduction of energy storage systems from the ambient RF electromagnetic field further improves backscatter communication capabilities. Therefore, devices without batteries can benefit from backscatter communication as their energy availability is very low and every small amount of energy must be carefully managed.

However, in backscatter telecommunication technology, battery-less nodes powered by energy taken from the environment and stored in capacitors suffer from frequent interruptions in operation.

Avoiding the possibility of a power outage during data transmission and reception is still an open and real challenge.

Due to the energy constraints of battery-less systems, data communication via active radio-based technologies is costly in terms of energy. The RF backscatter communication, implemented by traditional RFID devices, allows a near zero power communication for one of the two devices, eliminating the electronic components with high energy consumption present in traditional active radio systems (for example, RF amplifiers to generate the carrier). Therefore, radio frequency backscatter is a great choice for battery-less devices considering their marginal power budgets.

In case of traditional RF backscatter, the nodes transmit by modulating the reflection of the RF signal generated by a dedicated reader.

Backscatter transmission requires several orders of magnitude less energy than transmission with active radios. However, transient powered battery-less devices operate intermittently and are not always available for data transceivers. Without coordination between nodes, the result of the transmission of data packets between these devices is always random and subject to a significant amount of errors. For a proper communication, the energy stored on both sides of the data communication channel (transmitter and receiver) must be sufficient to carry out the transmission and reception of packets. A coordination mechanism is therefore needed to ensure package delivery and eliminate wasted energy.

Communication in the domain of intermittent battery-less devices requires a notion of coordination between nodes so that the transmitter knows in advance the possibility of receiving data from the receiver and only in case of positive verification it begins to transmit its data. In other words, it must be ensured that both nodes are simultaneously in a high-energy state before transmitting a packet.

Object of the present invention is at least partially overcoming the aforementioned drawbacks by providing a method and a device for measuring the energy availability of the receiver so as to evaluate whether the energy is sufficient to transmit/receive an entire packet.

The above and other objects, as will be explained below, are achieved through a method and a device as claimed in the respective independent claims.

The invention deals with a method and an electronic device, based on backscatter communication, to detect/communicate the energy state of transmitting/receiving devices in which the communication occurs without energy consumption by the receiving devices.

The device (1), which constitutes one of the nodes of a wireless network, is designed to communicate its energy state to the devices, and comprises: a first block (10), designed to withdraw energy from the environment, if necessary, to convert energy into electricity and to store energy to make it available for the operation of the device (1) as a signal (Vcap);

- a second self-modulating block (20), designed to encode information of the energy level and generate the modulation signal (Vmod) for a front-end backscatter (31); - a third block (30), capable of operating in the radiofrequency domain and transmitting the energy state to the other nodes, taking charge of the modulation signal (Vmod), and receiving information on the respective energy states from the nodes, reporting them via a signal (Vout); wherein:

* the first block (10) comprises:

- a harvester (11);

- a device (12) for storing collected electricity; * the second block (20) comprises:

- an analog device (21), connected directly to the signal (Vcap) coming from the first block (10), having the function of evaluating the amount of energy present in the storage device (12) and of communicating it to a logic combination circuit (24);

- a very low consumption timer (22), connected to the logic combination circuit (24), designed to enable an energy communication channel to transmit the energy level on board the device (1); a low frequency oscillator (23), designed to generate a modulation signal for transmission, the modulating being constituted by a sequence of pulses of duration correlated to the energetic state of the storage device (12) and modulated by a signal (Vinf) at the output of the logic combination circuit (24);

- the logic combination circuit (24) which, on the basis of information on the energy state received from the analog device (21) and the consent signal received from the timer (22), enables a communication channel of the on-board energy level by sending the signal (Vinf) to a logic gate <and> (25); - the logic gate <and> (25), designed to receive the first signal (Vinf) from the logic combination circuit (24) and a second signal from the oscillator (23), and to enable its transmission towards the front-end backscatter (31) when both signals are present simultaneously; * the third block (30) comprises: the front-end backscatter (31) designed to modulate the signal coming from the low frequency oscillator (23), using the signal (Vinf) generated by the logic combination circuit (24) and to transmit it to an antenna (13), which backscatters it to the other nodes of the network.

The front-end backscatter (31) is then connected to a Microcontroller Unit, MCU (32), to which it sends a signal (Vout), suitable for evaluating the energy state of the nodes from which it receives information, the Microcontroller Unit MCU being connected with the logic combination circuit, so as to possibly be designed to supervise the operations of the logic combination circuit (24).

The method for detecting/communicating the energy state of transmitting/receiving devices includes the following steps: - surveying the energy state of its own device

(1) and communicating the energy state to a logic combination circuit (24) and to similar nodes adjacent to the device (1); generating a signal to enable an energy communication channel to transmit the energy level of the device (1); generating a signal to enable an energy communication channel to transmit the energy level of the device, modulating being made up of a sequence of pulses of duration related to the energy state of the device;

- receiving through an antenna (13) any signal and bouncing the signal modulated with information of the energy state of the device (1). The communication method, called TRAP

(TRAnsiently-powered Protocol), for devices with transient power supply, and more generally devices that require guarantees on the possibility of reception, is based on information of the energy state of the nodes, transmitted by the proposed circuit on a dedicated backscatter channel. Using the energy status signal of a neighboring node, a transmitter node can initiate data transmission on the data transmission channel (other than the energy level sharing backscatter channel), using a radio dedicated to data transmission only, both active that passive.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims. It is understood that all attached claims form an integral part of the present description. Industrial applications

The proposed energy level sharing circuit can be integrated with modern battery-less Wireless Sensors Network (WSN) and Internet of Things (IoT) devices and the TRAP protocol can be used to enable communications for such devices in "green" IoT applications, from smart cities to smart buildings and smart agriculture.

The present invention will be better described by a preferred embodiment, provided by way of non limiting example, with reference to the attached drawings, in which: - FIG. 1 shows a block diagram of a device according to the invention;

- FIG. 2 shows a block diagram of a variation of the device according to the invention.

Block diagram of the device With reference to FIG. 1, (1) designates a device according to the invention and based on backscatter communication, to detect the energy state of receiving devices, the energy state being communicated without energy consumption by the receiving devices. According to a preferred embodiment, the device (1) comprises:

- a first block (10), designed to take electricity from the environment and store it to make it available for the operation of the apparatus;

- a second self-modulating block (20), designed to encode information of the energy level (Vmod) for a front-end backscatter (31);

- a third block (30) designed to communicate the energy state to the other nodes and to receive from the nodes information on the respective energy states.

The first block (10) comprises a harvester (11) and a device (12) for storing the collected electrical energy, for example a capacitor.

The first block (10) implements through the harvester (11) a method by which energy is taken from the external environment (for example, solar energy, thermal energy, wind energy, electromagnetic radiation field energy, gradients of salinity and kinetic energy, also known as environmental energy) and is stored in the capacitor (12), which is connected to the second block (20), as a signal (Vcap).

The harvester (11) provides a very small amount of energy, suitable for low-power electronics.

The second block (20) includes: an analog device (21), which uses the signal (Vcap) coming from the first block (10), which has the function of evaluating the amount of energy present in the energy storage system (12) and of communicating it to a logic combination circuit (24); - a very low consumption timer (22), connected with the logic combination circuit (24) designed to enable an energy communication channel to transmit the energy level on board the device

(l); - a low frequency oscillator (23), designed to generate the modulation signal for transmission, modulating being constituted by a sequence of pulses of duration correlated to the energetic state of the storage system (12) and modulated by a signal (Vinf) at the output of a logic combination circuit (24);

- the logic combination circuit (24) which, on the basis of information on the energy state received from the analog device (21) and the consent signal received from the timer (22), enables a communication channel of the on board energy level by sending a signal (Vinf) to a logic gate <and> (25);

- the logic gate <and> (25) designed to receive a first signal (Vinf) from the logic combination circuit (24) and a second signal from the oscillator (23) and to enable their transmission towards the front-end backscatter (31) when both signals are present simultaneously;

The third block (30) includes: the front-end backscatter (31) designed to modulate the signal coming from the low frequency oscillator (23) using the signal (Vinf) generated by the logic combination circuit (24) and to transmit it to an antenna (13), which back-spreads it in backscatter to the other nodes of the network; in practice, the antenna (13) receives a signal (Vin) (modulated or not) which reflects modulated with the signal (Vinf) produced by the automodulator (20); the front-end backscatter (31) then sends a digital signal (Vout) to an MCU microcontroller (32); the MCU microcontroller (32) which receives the signal (Vout) and if the node has sufficient energy to perform an action, decodes the duration and frequency information of the pulse sequence, identifying the energy state of the neighboring nodes and communicates it to the logic combination circuit (24).

The logic gate (25) is advantageously connected in output also with the logic combination circuit (24) so as to control the communication towards the front-end backscatter (31).

Energy communication channel

To transmit and receive information on the energy state of the nodes, the front-end backscatter (31) generates an RF signal modulated by the reflection of the incident electromagnetic field and allows communication with almost zero energy consumption. In this case, the main technical problem, solved by the device (1) according to the invention, is the modulation of the RF signal to encode information on its energy state, without using components and circuits with high energy consumption.

The core of the circuit is divided into two main blocks: the second self-modulating block (20), designed to encode information of the energy level for the front-end of the backscatter;

- the third block (30) designed to communicate the energetic state to the other nodes and to receive from the nodes information on the respective energetic states.

The automatic backscatter modulation consists of a sequence of pulses created by the very low power and low frequency self-modulator (20). Furthermore, the use of the MCU microcontroller (32) is essential for decoding the received signals and deciding whether to initiate a communication capable of being successful, or to postpone it. Front-end backscatter The backscatter transmitter (31) mismatches the antenna (13) using different RF switches and matching impedances. A single RF MOSFET (not shown) is used as a switch to achieve simple modulations such as ON-OFF keying (OOK). When the switch, located in the front-end backscatter block (31), is open, the antenna (13) is coupled and absorbs the incoming RF signal without reflecting it. When the switch is closed, the antenna is mismatched and reflects the incoming RF signal. The modulation, that is the switching on and off of the switch, is controlled by the automodulator block (20) (Vmod signal). Energy status information can be decoded on the receiver side when the receiver node has enough power to perform the necessary computation and is interested in communicating data. The front-end backscatter circuit (31) of the receiver is specially designed as a demodulator for OOK modulations with reduced transmission frequency. This is possible by exploiting an envelope detector to perform frequency translation in the baseband by implementing a low-power and economical circuit. The envelope detector consists of a biased and finely matched Schottky diode to the RF input (Vin) and the antenna (13). The remaining circuitry aims to optimize the voltage variation of the low frequency demodulated signal by using a high-pass filter amplifier stage and a comparator for the final digital output signal (Vout). The digital signal is sent to the MCU (32) which, if the node has sufficient energy to perform an action, decodes the duration and frequency information of the pulse sequence, identifying the energy state of the neighboring nodes. Energy state coding Information on the energy level of the nodes is modulated in the form of a pulse sequence with OOK modulation. With this modulation scheme, it is possible to use different levers on which one can act to code information on the energy level and identify the nodes between them: the number of pulses or, equivalently, the duration of the pulse sequence and the OOK modulation frequency.

According to a preferred embodiment, four different durations of the pulse sequence are chosen to distinguish between four different energy levels. Furthermore, the signal is characterized by an OOK modulation frequency. Slightly different frequencies are used for each node so that different nodes can be distinguished. Finally, the repetition period of the pulse sequence determines how fast the network energy level information is updated. The self-modulator (20) then carries out the coding of the energy level information for the front-end of the backscatter (31) (Vmod). Communication protocol

The communication protocol called TRAP (TRAnsiently-powered Protocol) is based on the information of the energy level of the nodes provided by the energy communication channel (30). Based on this information, TRAP ensures that transmitting and receiving devices have sufficient power to perform communication and prevent packet loss due to power outages. Physical level

TRAP uses an illuminator that continuously emits the carrier waves necessary for the operation of the backscatter transceivers. In some scenarios, a dedicated illuminator may not be necessary, as it is possible to take advantage of signals already present in the environment (e.g. TV signals or Wi Fi signals).

The goal of the illuminator is not to charge the devices, however, the devices can use an RF energy storage to receive even small amounts of energy from the illuminator. The devices are assumed to operate intermittently, which means their operation is made up of frequent charge/discharge cycles and power outages then rest.

Each transient power node in the system has two radios and antennas: the first transceiver communicates the energy level of the nodes via a backscatter channel; the main transceiver (it is possible to use both active and passive radios) is used exclusively for data communication.

Separating the power communication channel from the data transmission channel prevents packet collision and allows simultaneous transmission of data and energy status between devices.

Protocol definition

Each transiently powered node transmits its energy state over the energy communication channel using radio backscatter. Considering information about the energy state of the neighbors, the devices begin transmitting data on another channel using their main radio.

Transmission of the energy state The transmission of the energy state includes the following operations:

- a random value is added to the fixed period to generate the effective transmission period, managed by the very low consumption timer (22), which differs minimally from device to device, so as to guarantee an activation and transmission time of information at different intervals; when the timer (22) is activated, an energy communication channel is enabled to transmit the energy level on board; frequency and duration of the OOK modulation characterize the transmitted pulse sequence. The length of the sequence indicates the energy level information and the frequency of the OOK modulation identifies the node. A short sequence indicates a low energy level, a longer sequence indicates a higher energy level.

Data transmission

Data transmission includes the following steps:

- the node checks if it has sufficient energy to perform an action and data transmission. Note that this check is already performed periodically to transmit its energy state on the energy state channel automatically through the automodulator (20);

- if the transmitter node has sufficient power to perform data transmission, it starts listening to the energy communication channel via the front-end backscatter receiver circuit (31);

- when the MCU (32) starts to receive pulses from a signal (Vout) (shown in FIG. 1), it decodes the received sequence by counting the pulses in order to determine information on the energy state and the frequency that identifies the node that has transmitted the signal;

- if the node that transmitted the signal on the energy communication channel has a high energy level (or at least sufficient for a correct data reception), the node that performs the decoding can decide to safely transmit data packets.

According to a preferred variation (la), shown in FIG. 2, the device according to the invention provides a self-demodulator module (40), inserted in the third block (30), connected in input with the front-end backscatter (30), from which it receives the signal (Vout), and in output with a user (41), to which it sends a signal (Vrec). The user (41) can be connected to the logic combination circuit (24), so as to be designed to possibly supervise the operations of the logic combination circuit (24).

The self-demodulator module (40) is designed to interpret the energy levels received from the adjacent nodes by processing the signal (Vout), coming from the front-end backscatter (31), and returning an information, called signal (Vrec), which indicates the energy state and the node that transmitted the energy state, the signal (Vrec) being available for any user (41). The functions of the self-demodulator (40) are as follows:

- receiving in input the signal (Vout) coming from the front-end backscatter (31); - collating the information bits on the energy state of the node;

- decoding the received signal;

- generating at the output a digital signal (Vrec) which includes information on the adjacent node which transmitted the energy level.

In this way, according to the variation, in the device (la), the MCU microcontroller (32) is no longer necessary for the decoding operations. The system thus becomes completely autonomous in all its operations, including the reception of the energy level from adjacent nodes, picked up by the antenna (13), which enables the system to operate autonomously. The device (la) according to the variation can therefore operate in a completely independent way from the system to which it connects, both in modulation and in demodulation, expanding the potential applications to all electronic devices that want to communicate and share the energy level automatically.

The device (la) according to the variation is therefore completely autonomous and self- sufficient, so that it can interface with any node of a network of devices without batteries. The application is not excluded even for devices equipped with batteries but allows optimizing the data communication process.

Given the self-sufficiency of the self demodulator (40), the block (41), which the signal (Vrec) reaches, can be of any electronic nature, not necessarily based on microcontroller architecture, although it can include in its components, an MCU.

Finally, the signal (Vout) reports a demodulated signal from the front-end backscatter (31), containing information on the energy state of the node transmitting energy information.

The signal (Vrec) is a digital signal that contains information on the energy state and the identification of the transmitting node. The signal (Vrec) produced by the self-demodulator. (40) and supplied as an output to the system, reaches the user (41), who receives information from the self demodulator (40) to know the energy state of adjacent nodes and decide whether to engage or postpone a secure communication of information. Final remarks

Battery-less wireless sensors in a network and powered directly by miniaturized energy collectors can only be of interest if communication between the network nodes takes place without wasting energy.

In devices that operate using transient power sources, efficient communications remain an open challenge. The transmitting nodes must be aware of possible unavailable receiving nodes in order to avoid packet losses (and precious energy collected from the environment) due to lack of energy on board the receiving node. Transmission via RF backscatter can be used to propagate the energy level almost free of charge, in terms of energy consumption, into the surrounding environment.

This innovation features an RF backscatter mechanism and a protocol that regulates communication between nodes, ensuring packet transmissions only if sufficient energy is stored in both transmitter and receiver.