Methods, devices, and computer program for scheduling triggering of ambient power (AMP) stations

Abstract

A communication method for a wireless network comprising an access point, AP, and at least one ambient power, AMP, station, STA. After the AP obtained a charging parameter of the at least one AMP STA, the AP triggers the at least one AMP STA for data transmission based on the obtained parameter.

Description

[0001] METHODS, DEVICES, AND COMPUTER PROGRAM FOR SCHEDULING TRIGGERING OF AMBIENT POWER (AMP) STATIONS

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure generally relates to wireless communications and more specifically to wireless communications in a network involving AMbient Power (AMP) stations (STAs).

[0004] BACKGROUND OF THE DISCLOSURE

[0005] The 802.11 family of standards adopted by the Institute of Electrical and Electronics Engineers (IEEE) provides a great number of mechanisms for wireless communications between stations (STAs). As an example, it provides wireless communication mechanisms for Internet of Things (loT) devices.

[0006] The legacy loT devices are usually powered by batteries which have a limited lifespan, thus affecting the user experience in a negative way. The increase of loT networks and loT devices has pushed the limits of maintenance expenditure, including both labour and battery costs, to a whole new level.

[0007] Some use cases requiring maintenance-free, ultra-low complexity, very small size, and very long life cycle cannot be addressed by the existing IEEE 802.11 based WLAN loT technologies (WLAN standing for Wireless Local Area Network).

[0008] In this context, in January 2023, IEEE has approved the formation of the AMbient Power Study Group (AMP SG) during an IEEE 802.11 Interim meeting. The initial scope of the AMP SG is to investigate MAC and PHY capabilities to enable 802.11 WLAN support of ultra-low complexity and ultra-low power consumption (e.g., less than 1 mW) devices powered by ambient power source, and reuse existing 802.11 features as much as possible, with a target start of the Task Group (TG) in 2024.

[0009] The ambient power communication studied in the AMP SG is a technology which enables battery-free communication, the main motivation being to achieve maintenance- free devices. The operation of such technologies relies on the energy harvested from a variety of sources including Radio Frequency (RF) energy, solar energy, thermal energy, piezoelectric energy, etc., so that the conventional batteries are useless and can be removed.

[0010] Regarding RF energy harvesting, some contributions discussed in the AMP SG points out that a dedicated AMP RF power signal may be necessary to allow RF energy harvesting by an AMP STA. Indeed, to enable RF harvesting, the RF signal reception level must be greater than or equal to a minimum threshold required by an RF harvesting circuit of an AMP STA. This threshold level is typically around -15 / -20dBm which is much higher than the RF signal reception level usually observed in an 802.11 WLAN for data reception. The AMP RF power signal could be a continuous wave or a narrow band signal. It could be generated by the AMP Access Point (AP) or by a dedicated station called AMP Assisting STA.

[0011] An AMP WLAN generally comprises an AMP Access Point (AP), one or more AMP Stations (STAs), and optional one or more AMP Assisting STAs.

[0012] In such a network, the AMP STAs are low power, low cost, and battery-free devices that are energized through ambient energies such as RF energy, solar / light energy, temperature energy, piezoelectric energy, and the like. Some examples of requirements discussed in the AMP SG for AMP STAs are directed to a peak device power consumption of 1 mW, a maximum payload size of 256 bits, and a peak data rate of 51 Kbps (Kilobits per second).

[0013] The AMP STAs may carry out three functions that are sensor data transmission, (indoor) positioning, and identification and may be categorized by their energy harvesting type, their energy storage capability, and their transmission mode. In addition, it is observed that the AMP SG defines two types of AMP loT devices, the AMP-Only loT devices and the AMP-Assisted loT devices:

[0014] - an AMP-Only loT device features with ultra-low complexity, ultra-low power consumption, a very small form factor, and no battery (i.e., such devices do not use conventional battery). Since it may not need power storage or may need only limited power storage (e.g., a capacitor), an AMP-Only loT STA can have no power storage or small power storage (e.g., a capacitor). It can harvest energy from RF waves or from another ambient energy source and it can transmit data by using a backscattering mechanism or by using an active ultra-low power transmitter;

[0015] - an AMP-Assisted loT device features high capabilities similar to those of a legacy 802.11 device. In particular, it can reuse the current PHY design but with enhanced MAC features to adapt to a specific ambient power. It can have a higher storage capability than an AMP-only loT Device. An AMP-Assisted loT device can harvest energy from RF waves or from another ambient energy source. It has a higher power storage than an AMP-Only loT device, which makes it possible to transmit data by using an active transmitter. Regarding the AMP-Only loT STAs featuring power storage, the operation is characterized by a duty cycle made of a power charging phase and a working phase.

[0016] During the power charging phase, the AMP STA harvests an ambient energy to charge its Power Storage unit (e.g., a capacitor). An AMP STA can harvest energy at any time, independently of any data exchange with an AP, the only condition being the availability of the ambient energy of interest. The charging time is typically of the order of a few tens of milliseconds.

[0017] During the working phase, once the Power Storage unit of the AMP STA has reached a required charge level, the AMP STA is able to receive a frame from an AP and to transmit a response frame to the AP. Once this frame exchange has occurred, the AMP STA may be totally discharged. The time period of this working phase is typically of the order of a few milliseconds.

[0018] It is observed that an AMP-Only loT STA featuring power storage may not be able to carry out the steps of a legacy EDCA mechanism to access the communication medium (EDCA standing for Enhanced Distributed Channel Access). The reason is that the time last to sense the medium is unpredictable and may consumed an important amount of the harvested energy. As a result, while gaining the medium access, the AMP STA may not be able to transmit any frame, its Power Storage unit being at a low level of charge.

[0019] Therefore, there is a need for improving communications in AMP WLANs, in particular for improving communication medium access of AMP-Only loT STAs featuring power storage.

[0020] SUMMARY OF THE DISCLOSURE

[0021] It is a broad aspect of the present disclosure to provide methods, devices, and computer programs to manage properly the communication in the AMP WLAN. According to particular aspects, the present disclosure provides a method, a device, and a computer program for an AMP AP to schedule efficiently the triggering of AMP-Only loT STAs featuring power storage.

[0022] According to a first aspect, it is provided a communication method for a wireless network comprising an access point, AP, and at least one ambient power, AMP, station, STA, the method comprising, in the AP: obtaining a charging parameter of the at least one AMP STA; and triggering the at least one AMP STA for data transmission based on the obtained parameter. Accordingly, the present disclosure makes it possible to optimize the overall power consumption in the AMP WLAN. It also makes it possible for the AMP AP to optimize the duration and / or level of an AMP RF Power signal needed by AMP STAs using RF power harvesting to access a communication medium. It also permits to the AMP AP to trigger the AMP STAs at the right time (while being at a sufficient level of charge), thus mitigating the number of unsuccessful / wasted transmissions.

[0023] According to some embodiments, the communication method further comprises determining a time period for the at least one AMP STA to reach a given level of charge, based on the charging parameter, wherein the triggering for data transmission is done based on the time period for the at least one AMP STA to reach a given level of charge.

[0024] Still according to some embodiments, the given level of charge is a charging level required for the at least one AMP STA to receive and process a request for data transmission and to transmit the data, the triggering for data transmission being carried out so that data transmission occurs at or after a time at which the at least one AMP STA reaches the given level of charge.

[0025] Still according to some embodiments, the given level of charge is determined based on a percentage of a time period needed for the at least one AMP STA to be fully charged.

[0026] Still according to some embodiments, the communication method further comprises emitting and / or triggering an emission of a power signal for charging the at least one AMP STA.

[0027] Still according to some embodiments, the communication method further comprises determining a time period and / or a power level of the power signal, based on the obtained parameter.

[0028] Still according to some embodiments, the obtaining comprises obtaining characteristics of a power storage unit of the at least one AMP STA and / or obtaining current charging characteristics of the power storage unit.

[0029] Still according to some embodiments, the communication method further comprises receiving data and current charging characteristics of the power storage unit in response to the triggering.

[0030] Still according to some embodiments, the obtaining is carried out for a plurality of AMP STAs, the method further comprising triggering the plurality of AMP STAs by sending a trigger frame containing a sequence scheduling the AMP STAs to transmit data. Still according to some embodiments, the triggering the plurality of AMP STAs is carried out once each AMP STA of the plurality of AMP STAs reaches a given level of charge.

[0031] Still according to some embodiments, the triggering the plurality of AMP STAs is carried out after a first AMP STA of the plurality of AMP STAs reaches a given level of charge.

[0032] Still according to some embodiments, the communication method further comprises determining the sequence, based on an obtained charging parameter of each AMP STA of the plurality of AMP STAs.

[0033] According to a second aspect, it is provided a communication method for a wireless network comprising an access point, AP, and at least one ambient power, AMP, station, STA, the method comprising, in the at least one AMP STA, transmitting a charging parameter of the at least one AMP STA to the AP.

[0034] Accordingly, the present disclosure makes it possible to optimize the overall power consumption in the AMP WLAN. It also makes it possible for the AMP AP to optimize the duration and / or level of an AMP RF Power signal needed by AMP STAs using RF power harvesting to access a communication medium. It also permits to the AMP AP to trigger the AMP STAs at the right time (while being at a sufficient level of charge), thus mitigating the number of unsuccessful / wasted transmissions.

[0035] According to some embodiments, the charging parameter comprises characteristics of a power storage unit of the at least one AMP STA.

[0036] Still according to some embodiments, the communication method further comprises receiving, from the AP, a request for data transmission and determining, from the request, a time at which data are to be transmitted, current charging parameter of the at least one AMP STA being transmitted along with the data at the time at which data are to be transmitted, the current charging parameter comprising current charging characteristics of a power storage unit of the at least one AMP STA.

[0037] Still according to some embodiments, the communication method further comprises entering within a power save mode, during a period of time determined based on the time at which data are to be transmitted.

[0038] Still according to some embodiments, the communication method further comprises determining a time period for the at least one AMP STA to reach a given level of charge, wherein the given level of charge makes it possible to receive and process a next request for data transmission and to transmit data and a next current charging parameter and wherein the current charging parameter comprises the determined time period.

[0039] Still according to some embodiments, the communication method further comprises harvesting power from a power signal, the power signal being received during at least the determined time period; receiving the next request for data transmission; and transmit data and the next current charging parameter.

[0040] Still according to some embodiments, the communication method further comprises determining a current harvesting power amount, wherein the current charging parameter comprises the determined current harvesting power amount.

[0041] Again, the present disclosure makes it possible to optimize the overall power consumption in the AMP WLAN. It also makes it possible for the AMP AP to optimize the duration and / or level of an AMP RF Power signal needed by AMP STAs using RF power harvesting to access a communication medium. It also permits to the AMP AP to trigger the AMP STAs at the right time (while being at a sufficient level of charge), thus mitigating the number of unsuccessful / wasted transmissions.

[0042] According to a third aspect, it is provided a wireless communication device comprising at least one microprocessor configured to carry out the methods described above. The advantages of this device are similar to those of the methods described above.

[0043] At least parts of the methods according to the disclosure may be computer implemented. Accordingly, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system". Furthermore, the present disclosure may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

[0044] Since the present disclosure can be implemented in software, the present disclosure can be embodied as computer readable code for provision to a programmable apparatus on any suitable carrier medium. A tangible, non-transitory carrier medium may comprise a storage medium such as a floppy disk, a CD-ROM, a hard disk drive, a magnetic tape device or a solid-state memory device and the like. A transient carrier medium may include a signal such as an electrical signal, an electronic signal, an optical signal, an acoustic signal, a magnetic signal or an electromagnetic signal, e.g. a microwave or RF signal.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Embodiments of the disclosure will now be described, by way of example only, and with reference to the following drawings in which:

[0047] Figure 1a illustrates a first example of an AMbient power network environment involving AMP communication between an AMP AP and an AMP STA energized through RF energy harvesting, in which some embodiments of the present disclosure may be implemented;

[0048] Figure 1b illustrates a second example of an AMbient power network environment involving AMP communication between an AMP AP and an AMP STA energized through solar energy harvesting, in which some embodiments of the present disclosure may be implemented;

[0049] Figure 2a illustrates an example of a format of an AMP Capabilities element to be provided by an AMP STA to an AMP AP, according to some embodiments of the disclosure;

[0050] Figure 2b illustrates an example of a format of an AMP Capabilities Information field of an AMP Capabilities element to be provided by an AMP STA to an AMP AP, according to some embodiments of the disclosure;

[0051] Figure 3a illustrates an example of a format of an AMP In-Operation parameters Element to be provided by an AMP STA to an AMP AP, when the AMP STA is used, according to some embodiments of the disclosure;

[0052] Figure 3b illustrates an example of a format of an AMP In-Operation parameters Information field of an AMP In-Operation parameters Element to be provided by an AMP STA to an AMP AP, according to some embodiments of the disclosure;

[0053] Figure 4 illustrates an example of an AMP discovery and association sequence between an AMP AP and an AMP STA, the AMP STA being energized through RF energy harvesting, according to some embodiments of the disclosure;

[0054] Figure 5 illustrates an example of a format of an AMP Trigger frame to be sent by an AMP AP to trigger one or more AMP STAs, according to some embodiments of the disclosure;

[0055] Figure 6a illustrates an example of steps carried out by an AMP AP to make it possible to obtain Capabilities and In-Operation parameters from one or more AMP STA, according to some embodiments of the disclosure; Figure 6b illustrates an example of steps carried out by an AMP STA to make it possible for an AMP AP to obtain its Capabilities and In-Operation parameters and its data, according to some embodiments of the disclosure;

[0056] Figure 7a, 7b, and 7c illustrate a first example of a scheduling sequence of AMP STAs, managed by an AMP AP, according to some embodiments of the disclosure;

[0057] Figure 8a, 8b, and 8c illustrate a second example of a scheduling sequence of AMP STAs, managed by an AMP AP, according to some embodiments of the disclosure;

[0058] Figure 9a shows a schematic representation of an AMP AP wireless communication device in accordance with some embodiments of the present disclosure; and

[0059] Figure 9b shows a schematic representation of an AMP STA wireless communication device in accordance with some embodiments of the present disclosure.

[0060] DETAILED DESCRIPTION OF EMBODIMENTS

[0061] According to some embodiments of the disclosure, charging parameters are used by an Access Point (AP) to trigger AMP stations (STAs) for data transmission. Such an AP, having features for managing efficiently AMP STAs, may be referred to as an AMP AP. To that end, some items of information regarding the power storage capabilities of an AMP STA, for example an AMP-only loT STA, are stored in or obtained by the AMP STA, to be sent to an AMP AP so that the AMP AP has knowledge about such capabilities. During operation, measurements relating to the power storage, referred to as In-Operation parameters, are obtained and transmitted to the AMP AP, making it possible for the AMP AP to estimate charging levels of AMP STAs and thus, to manage the communication medium access as a function of the charging state of the AMP STAs.

[0062] Accordingly, during a discovery and association phase, the AMP AP may obtain the Capabilities and In-Operation parameters of the AMP STAs and during operation, the AMP AP may obtain the updated In-Operation parameters of the AMP STAs. Therefore, the AMP AP may process the received Capabilities and In-Operation parameters to manage the scheduling of AMP STAs by: determining the duration (or time period) and / or the level of the AMP RF Power signal that is to be used for energizing the AMP STAs (in the case of RF Energy Harvesting), determining the scheduling sequence of all the AMP STAs (i.e. , the AMP STAs using all the types of energy harvesting), and triggering a scheduling scheme to energize the AMP STAs through the AMP RF Power Signal (in the case of RF energy harvesting) and then, to receive data from each AMP STA, for example sensor data, using dedicated AMP Trigger frames.

[0063] Ambient power wireless local area network

[0064] Figure 1a illustrates a first example of an AMbient power network environment involving AMP communication between an AMP AP and an AMP STA energized through RF energy harvesting, in which embodiments of the present disclosure may be implemented.

[0065] As illustrated, AMP WLAN 100 comprises an AMP AP referenced 110, an AMP STA referenced 111 , and an optional AMP Assisting STA 112. For the sake of illustration, AMP AP 100 and optional AMP Assisting STA 112 may be wall powered devices, that is to say devices for which there are no power supply issues. Still for the sake of illustration, AMP STA 111 may be an AMP-Only loT device with a RF harvesting circuit and a Power Storage unit. In addition, AMP STA 111 embeds an ultra-low power receiver and an ultralow power transmitter. In a variant, AMP STA 111 embeds a backscattering circuit, wherein the received RF signal is reflected back to the direction from which it came (thanks to a backscattering modulator, the AMP STA may modify the received RF signal to include data to be transmitted). It is noted that in some AMP SG contributions, backscattering is used with a Low Noise Amplifier (LNA), that is added to increase the level of the reflected / transmitted signal.

[0066] According to the example illustrated in Fig. 1a, the RF power waves used to energize AMP STA 111 may be provided by AMP AP 110, for example using either the Sub-1GHz (S1G) frequency band or the 2.4GHz frequency band. The frequency band used for the RF power transfer may be the same or not as the frequency band used for data communication. As illustrated, AMP AP 110 generates an AMP RF Power signal referenced 120, to energize AMP STA 111. The AMP RF Power signal could be a continuous wave or a narrow band signal. It should comply with regulation requirements, for example in terms of maximum power transmission, maximum duration of one transmission, etc. In addition or in a variant, AMP AP 110 may signal to the optional AMP Assisting STA 112, for example using frame 122, that it has to generate an AMP RF power signal, referenced 121 , to energize AMP STA 111. The use of the optional AMP Assisting STA 112 for generating AMP RF Power signal 121 may be necessary in some circumstances, for example if the distance between AMP AP 110 and AMP STA 111 is too far to enable RF power harvesting, from the AMP RF Power signal 120, within AMP STA 111. It is pointed out here that according to some embodiments, AMP AP 110 controls the generation of the AM P RF Power signal and so, it may control the energizing status of AMP STA 111.

[0067] After AMP STA 111 is energized, AMP AP 110 may communicate directly with AMP STA 111 through AMP DownLink (DL) data communication path 123 and AMP UpLink (UL) data communication path 124. For the sake of illustration, AMP DL 123 and AMP UL 124 data communication paths may use either the Sub-1GHz (S1G) frequency band or the 2.4GHz frequency band. To enable AMP WLAN 100 to achieve an ultra-low power consumption and an ultra-low complexity, simple modulation and code schemes should be used within AMP DL 123 and AMP UL 124 data communication paths. For example, On-Off Keying (OOK) or Frequency-Shift Keying (FSK) modulation mechanisms could be used for both AMP DL 123 and AMP UL 124 data communication paths.

[0068] It is noted that for the sake of illustration, AMP WLAN 100 comprises only one AMP STA (AMP STA 111) and one optional AMP Assisting STA (optional AMP Assisting STA 112). However, it should be understood that a higher number of AMP STAs, for example similar to AMP STA 111 , and / or a higher number of AMP Assisting STAs, for example similar to AMP Assisting STA 112 maybe contemplated in AMP WLAN 100. As an example, several hundreds of AMP STAs similar to AMP STA 111 and several tens of AMP Assisting STAs similar to AMP Assisting STA 112 may be contemplated.

[0069] Figure 1b illustrates a second example of an AMbient power network environment involving AMP communication between an AMP AP and an AMP STA energized through solar energy harvesting, in which embodiments of the present disclosure may be implemented.

[0070] According to the illustrated example, AMP WLAN 100’ is similar to AMP WLAN 100 described in reference to Figure 1a, except that AMP STA 111 is replaced by AMP STA 113 that is an AMP-Only loT device comprising a solar harvesting circuit and a Power Storage unit. Since AMP AP 110’ is similar to AMP AP 110 and AMP DL 123’ and AMP UL 124’ data communication paths are similar to AMP DL 123 and AMP UL 124 data communication paths, respectively, they are not described again in reference de Figure 1 b.

[0071] For the sake of illustration, AMP STA 113 is an AMP-Only loT device with a solar harvesting circuit and a Power Storage unit, that embeds also an ultra-low power receiver and an ultra-low power transmitter. In a variant, AMP STA 113 embeds a backscattering circuit.

[0072] In AMP WLAN 100’, the solar power used to energize AMP STA 113 is provided by the sun, referenced 114, through solar radiation 125. It is observed here that AMP AP 110’ has no control over solar radiation 125 and so, it has also no control on the energizing status of AMP STA 113.

[0073] It is noted that for the sake of illustration, AMP WLAN 100’ comprises only one AMP STA (AMP STA 113). However, it should be understood that a higher number of AMP STAs similar to the AMP STA 113 maybe contemplated in AMP WLAN 100’. As an example, several hundreds of AMP STAs similar to the AMP STA 113 may be contemplated.

[0074] Although not represented, other variants of AMP WLAN may be contemplated. For example, an AMP WLAN may gather some AMP STAs similar to AMP STA 111 described in reference to Figure 1a and some AMP STAs similar to AMP STA 113 described in reference to Figure 1b. In another variant, the AMP WLAN may gather some AMP STAs similar to AMP STA 111 described in reference to Figure 1a, some AMP STAs similar to the AMP STA 113 described in reference to Figure 1b, and also some other AMP STAs energized through other types of ambient energy such as light, heat, vibrations, etc.

[0075] Element format

[0076] As described above, some power storage capabilities of an AMP station, for example an AMP-only loT STA, are sent to an AMP AP so that the AMP AP has knowledge about such capabilities. During operation, measurements relating to these power storage capabilities (denoted In-Operation parameters) are obtained and transmitted to the AMP AP, making it possible for the AMP AP to manage the communication medium access. The power storage capabilities and the In-operation parameters are transmitted as elements embedded in frames, called AMP capabilities elements and AMP In-Operation parameters elements, respectively.

[0077] Figure 2a illustrates an example of a format of an AMP Capabilities element referenced 200, to be provided by an AMP STA to an AMP AP. According to some embodiments of the disclosure, an AMP STA declares that it is an AMP STA by transmitting, in a frame, an AMP Capabilities element, such as AMP Capabilities element 200, to an AMP AP.

[0078] According to the illustrated example, AMP Capabilities element 200 is identified by the values of an Element ID field referenced 210 and of an Element ID Extension field referenced 230. The Element ID field 210 may be set to the value 255 for indicating that the Element ID Extension field 230 is present. The length of the Element ID field 210 may be one Byte. The Element ID Extension field 230 can be set to any value between 136-255. For example, it may be set to the value 136. The length of the Element ID Extension field 230 may be one Byte.

[0079] Length field 220 indicates the number of bytes in element 200, excluding the Element ID field 210 and Length field 220. As illustrated, Length field 220 may be set to the value 7 (1 Byte for the Element ID Extension 230 and 6 Bytes for the AMP Capabilities Information field 240). The Length of the Length field 220 may be one Byte.

[0080] The format of the AMP Capabilities Information field 240 and the items of information contained in the AMP Capabilities field 240 are described by reference to Figure 2b.

[0081] Figure 2b illustrates an example of a format of the AMP Capabilities Information field 240 of the AMP Capabilities element 200 in Figure 2a, to be provided by an AMP STA to an AMP AP, according to embodiments of the disclosure.

[0082] According to the illustrated example, the AMP Capabilities Information field 240 comprises the AMP Device I Dentifier (ID) subfield 241 that permits to uniquely identifies the AMP STA within the AMP WLAN of the AMP AP. The size of the AMP Device ID subfield 241 may be 12 bits, thus permitting up to 4 096 AMP STAs in an AMP WLAN. The value of the AMP Device ID subfield 241 can be set in factory or on-site by a human, for example in a configuration step prior to the setup of the AMP STAs within the AMP WLAN.

[0083] In a variant, the value AMP Device ID subfield 241 could be assigned by the AMP AP during a discovery / association procedure with the AMP STA. In such a case, the AMP Device ID subfield 241 may be placed in a MAC header field of an AMP frame (MAC standing for Media Access Control), instead of being placed in the AMP Capabilities Information field 240.

[0084] The AMP Device Type subfield 242 indicates the type of the AMP STA. According to a particular indexing scheme, the value of AMP Device Type subfield 242 is set to

[0085] - 0 if the AMP STA is an AMP-Only loT device, - 1 if the AMP STA is an AMP-Assisted loT device, and to

[0086] - 2 if the AMP STA is an AMP Assisting STA.

[0087] The value 3 is reserved.

[0088] Other indexing schemes may be contemplated for the AMP Device Type subfield 242. According to this example, the size of the AMP Device Type subfield 242 is two bits.

[0089] The Energy Harvesting Type subfield 243 indicates the type of energy harvesting used by the AMP STA. According to a particular indexing scheme, the value of Energy Harvesting Type subfield 243 is set to

[0090] - 0 if the AMP STA uses RF energy harvesting and to

[0091] - 1 if the AMP STA uses another ambient energy harvesting.

[0092] Other indexing schemes may be contemplated for this Energy Harvesting Type subfield 243. According to this example, the size of the Energy Harvesting Type subfield 243 is one bit. According to some embodiments, the RF energy harvesting type is distinguished from the other ambient energy harvesting types because the RF energy is an ambient energy that can be controlled by the AMP AP.

[0093] The Transmission Mode subfield 244 indicates the type of transmission used by the AMP STA. According to a particular indexing scheme, the value of Transmission Mode subfield 244 is set to

[0094] - 0 if the AMP STA uses a backscattering mechanism for data transmission, or to

[0095] - 1 if the AMP STA uses an active transmitter for data transmission.

[0096] Other indexing schemes may be contemplated for the Transmission Mode subfield 244. According to this example, the size of the Transmission Mode subfield 244 is one bit.

[0097] The Supported Frequency band for communication subfield 245 indicates the frequency band(s) supported by the AMP STA for DL / LIL data communication. According to a particular indexing scheme, the value of Supported Frequency band for communication subfield 245 is set to

[0098] - 0 if the AMP STA supports the Sub-1GHz (S1G) frequency band for DL / LIL data communication,

[0099] - 1 if the AMP STA supports the 2.4GHz frequency band for DL / LIL data communication, and to

[0100] - 2 if the AMP STA supports the Sub-1 GHz (S1G) and the 2.4GHz frequency bands for DL / LIL data communication. Other indexing schemes may be contemplated for the Supported Frequency band for communication subfield 245. According to this example, the size of the Supported Frequency band for communication subfield 245 is 2 bits.

[0101] The Supported Frequency band for RF Harvesting subfield 246 indicates the frequency band(s) supported by the AMP STA for RF energy harvesting. According to a particular indexing scheme, the value of Supported Frequency band for RF Harvesting subfield 246 is set to

[0102] - 0 if the AMP STA supports the Sub-1GHz (S1G) frequency band for RF harvesting, - 1 if the AMP STA supports the 2.4GHz frequency band for RF harvesting, and to

[0103] - 2 if the AMP STA supports the Sub-1 GHz (S1G) and the 2.4GHz frequency bands for RF harvesting.

[0104] Other indexing values may be contemplated for this Supported Frequency band for RF Harvesting subfield 246. According to this example, the size of the Supported Frequency band for RF Harvesting subfield 246 is two bits. When the Energy Harvesting Type subfield 243 is set to 1 , indicating that the AMP STA uses another ambient energy harvesting, the Supported Frequency band for RF Harvesting subfield 246 may not be present.

[0105] The Power Storage Availability subfield 247 indicates whether the AMP STA embeds a Power Storage unit such as a capacitor. According to a particular indexing scheme, the value of Power Storage Availability subfield 247 is set to

[0106] - 0 if the AMP STA does not embed a Power Storage unit and to

[0107] - 1 if the AMP STA embeds a Power Storage unit.

[0108] Other indexing schemes may be contemplated for the Power Storage Availability subfield 247. According to this example, the size of the Power Storage Availability subfield 247 is one bit.

[0109] The Minimum RF harvesting Power (Pppmin) subfield 248 indicates the minimum AMP RF Power signal reception level required by the RF harvesting circuit of the AMP STA to enable RF energy harvesting.

[0110] The Minimum RF harvesting Power (PRpmin) subfield 248 may contain a signed integer representing a value in dBm. This value can be seen as a threshold: when the level of the received AMP RF Power signal is above or equal to this threshold, the RF harvesting circuit of the AMP STA is able to perform energy harvesting and to charge the Power Storage unit and when the level of the received AMP RF Power signal is below this threshold, the RF harvesting circuit of the AMP STA is not able to perform energy harvesting and so, not able to charge the Power Storage unit. This RF harvesting circuit's characteristic may be due to the use of diodes to perform its operation. Another important RF harvesting circuit's characteristic to point out is its Power Conversion Efficiency (PCE) that may vary depending on the level of the received AMP RF power signal. Indeed, for such a circuit, the PCE improves when the received AMP RF Power Signal level increases. This PCE variation has a direct impact on the charging time of the Power Storage unit of the AMP STA.

[0111] According to this example, the size of the Minimum RF harvesting Power (PRpmin) subfield 248 is eight bits. When the Energy Harvesting Type subfield 243 is set to 1 , indicating that the AMP STA uses another ambient energy harvesting, the Minimum RF harvesting Power (PRpmin) subfield 248 may not be present.

[0112] The Maximum Charging Time (Tchargingmax) subfield 249 indicates the maximum time period for charging the Power Storage unit of the AMP STA, for example in units of 1ms or 10ms.

[0113] According to some embodiments, the maximum time period for charging the Power Storage unit corresponds to the time period needed to reach a sufficient level of charge of the Power Storage unit. It may correspond, for example, to a percentage of charge of the Power Storage unit such as 80% or 90%. Associating the maximum time for charging the Power Storage unit with a sufficient level of charge of the Power Storage unit may be efficient, in particular for some Power Storage unit technologies for which the time needed for charging the last 20% or 10% of the Power Storage unit, to reach a charge of 100%, may be very long in comparison to the first 80% or 90% of charge.

[0114] For any type of ambient energy harvesting, this maximum time may be obtained when the ambient energy harvesting circuit operates at its worst PCE, meaning that the received ambient energy (RF, solar, light, vibration, etc.) is considered equal to the threshold level that permit the ambient energy harvesting circuit to harvest energy. For the case of RF energy harvesting, the maximum time to charge the Power Storage unit of the AMP STA is obtained when the received AMP RF Power signal level is equal to PRFmin, as indicated in the Minimum RF harvesting Power subfield 248 described above.

[0115] More generally, the time to charge the Power Storage unit of the AMP STA is a function of the capacity of the Power Storage unit (e.g. the capacitance value in case of a capacitor) and the Power Conversion Efficiency (PCE) of the ambient energy harvesting circuit obtained for a given reception level of ambient energy.

[0116] According to this example, the size of Maximum Charging Time (Tchargingmax) subfield 249 is 16 bits. When the Power Storage Availability subfield 247 is set to 0, indicating that the AMP STA does not embed any Power Storage unit, the Maximum Charging Time (Tchargingmax) subfield 249 may not be present.

[0117] The Reserved subfield 250 corresponds to the reserved bits not assigned. For example, the size of the Reserved subfield 250 may be 3 bits.

[0118] Figure 3a illustrates an example of a format of an AMP In-Operation parameters element 300, to be provided by an AMP STA to an AMP AP, when the AMP STA is used. According to embodiments of the disclosure, an AMP STA signals its In-Operation parameters by transmitting an AMP In-Operation parameters element, such as AMP InOperation parameters element 300, in a frame, to an AMP AP.

[0119] According to the illustrated example, AMP In-Operation parameters element 300 is identified by the values of an Element ID field referenced 310 and of an Element ID Extension field referenced 330. The Element ID field 310 may be set to the value 255 for indicating that the Element ID Extension field 330 is present. The length of the Element ID field 310 may be one Byte. The Element ID Extension field 330 can be set to a value between 136-255. For the sake of illustration, it may be set to the value 137. The length of the Element ID Extension field 330 may be one Byte.

[0120] The Length field 320 indicates the number of Bytes in the element 300, excluding Element ID field 310 and Length field 320. According to the illustrated example, Length field 320 is set to the value 6 (1 Byte for the Element ID Extension field 330 and 5 Bytes for the AMP In-Operation Parameter Information field 340). The Length of the Length field 320 is 1 Byte.

[0121] The format of the AMP In-Operation Parameter Information field 340 and the items of information contained in the AMP In-Operation Parameter Information field 340 are described by reference to Figure 3b.

[0122] Figure 3b illustrates an example of a format of the AMP In-Operation parameters Information field 340 of the AMP In-Operation parameters Element 300 illustrated in Figure 3a, to be provided by an AMP STA to an AMP AP, according to embodiments of the disclosure.

[0123] As illustrated, the AMP In-Operation parameters Information field 340 comprises an AMP Device IDentifier (ID) subfield, referenced 24T, that permits to uniquely identifies the AMP STA within the AMP WLAN. It is similar to AMP Device ID subfield

[0124] 241 in Figure 2b. Subfield 241 ’, permitting to uniquely identifies the AMP STA within the AMP WLAN of the AMP AP, should be present in all the frames sent by the AMP STA to the AMP AP. In a variant, the AMP Device ID may be carried in the MAC header field of an AMP frame.

[0125] The Current RF harvesting Power (PRFeurrent) subfield 342 indicates a power reception level of the AMP RF Power signal actually received by the RF harvesting circuit of the AMP STA, enabling RF energy harvesting. According to some embodiments, the Current RF harvesting Power (PRFeurrent) subfield 342 contains a signed integer representing a value in dBm. The value of the Current RF harvesting Power (PRFeurrent) subfield 342 is equal or higher than the value indicated in Minimum RF harvesting Power (PRFmin) subfield 248 described previously in reference to Figure 2b. The knowledge of both PRFeurrent and PRFmin values, in addition to the knowledge of the current path loss for the AMP RF Power Signal, make it possible for the AMP AP to tune the transmission level of the AMP RF Power Signal, the purpose being to optimize the power consumption and to mitigate the possible interference create by the AMP RF Power Signal.

[0126] It should be highlighted here that the tuning of the transmission level of the AMP RF Power signal impacts directly the current charging time of the Power Storage unit of the AMP STA.

[0127] According to this example, the size of the Current RF harvesting Power (PRFeurrent) subfield 342 is 8 bits. If the AMP STA has signalled an Energy Harvesting Type subfield 243 set to 1 , indicating that the AMP STA uses another ambient energy harvesting, the Current RF harvesting Power (PRFeurrent) subfield 342 may not be present.

[0128] The Current Charging Time (Tchargingcurrent) subfield 343 indicates the current time period needed for charging the Power Storage unit of the AMP STA, for example in units of 1ms or 10ms. Like the Maximum Charging Time (Tchargingmax) subfield 249 described by reference to Figure 2b, the current time period for charging the Power Storage unit may correspond to the current charging time period needed to reach a sufficient level of charge of the Power Storage unit. It may correspond, for example, to a percentage of charge of the Power Storage unit such as 80% or 90%. According to other embodiments, the current time period for charging the Power Storage unit may correspond to the current charging time period needed to reach full charge of the Power Storage unit. In such embodiments, the AMP AP may determine on its own whether to wait for a full charge of the Power Storage unit for triggering communication, for example to reduce a risk of communication failure (in particular in the case where the AMP STA should wait after receiving a trigger frame to transmit data), or to wait for a partial charge, for example a partial charge making it possible for the AMP STA to receive and process a request for data transmission and to transmit the data and the current charging parameter.

[0129] For any type of ambient energy harvesting, this current charging time period directly depends on the current level of ambient energy (RF, solar, light, vibration, etc.), received by the AMP STA, that is used to harvest energy. For the case of RF energy harvesting, the current time period for charging the Power Storage unit of the AMP STA directly depends on the received AMP RF Power signal level (i.e., Pppcurrent, that is indicated in the Current RF harvesting Power subfield 342, as described above).

[0130] It is noted that the current level of ambient energy (RF, Solar, Light, Vibration, etc.) may be measured by the AMP STA. As an example, such a measurement may be done by the AMP STA once its Power Storage unit reaches a sufficient level of charge. As another example, several measurements may be done by the AMP STA once its Power Storage unit reaches a sufficient level of charge and an averaging is computed to obtain the current level of ambient energy.

[0131] This measured level is used by the AMP STA to determine its current charging time period. This determination may be performed by the AMP STA knowing the capacity of its Power Storage unit (e.g. the capacitance value in the case of a capacitor) and the PCE of its ambient energy harvesting circuit corresponding to this measured current level of ambient energy.

[0132] According to the illustrated example, the size of Current Charging Time (TchargingCurrent) subfield 343 is 16 bits. When the AMP STA has signalled a Power Storage Availability subfield 247 set to 0, indicating that the AMP STA does not embed a Power Storage unit, the Current Charging Time (TchargingCurrent) subfield 343 may not be present.

[0133] According to some embodiments, the Reserved subfield 344 corresponds to the reserved bits that are not yet assigned. For example, the size of the Reserved subfield 344 may be 4 bits.

[0134] AMP discovery and association

[0135] Figure 4 illustrates an example of an AMP discovery and association sequence between an AMP AP and an AMP STA, the AMP STA being energized through RF energy harvesting, according to some embodiments of the disclosure. It is noted that the AMP discovery and association sequence 400 illustrated in Figure 4 is provided solely for the sake of illustration. Other approaches for AMP discovery and association sequence between an AMP STA and an AMP AP could be contemplated, the aims being to provide a way for an AMP STA to transmit its AMP Capabilities and preferably also its AMP In-Operation parameters to the AMP AP.

[0136] The various charging statuses of the AMP STA all along the sequence are represented with the following elements:

[0137] - element 440 is representative of the “AMP STA discharged” status,

[0138] - element 441 is representative of the “AMP STA charging” status, and

[0139] - element 442 is representative of the “AMP STA charged” status.

[0140] The AMP discovery and association sequence 400 is initiated at time TO. To that end, the AMP AP (e.g,, AMP AP 110) generates an AMP RF Power signal 410 (e.g., AMP RF Power signal 120) to energize the AMP STA (e.g., AMP STA 111). The AMP RF Power signal generation lasts up to time T8.

[0141] At this stage and according to this example, the time period during which the AMP RF Power signal is active is set to a maximum value by the AMP AP. For example, this maximum time period may be specified by the regulation or issued from standard specifications (e.g., Maximum Time to charge the farthest AMP STA with the slowest charging time).

[0142] It is noted that before time TO, the AMP STA may be in a discharged state and considered as such by the AMP AP. From time TO, the AMP STA enters in a charging state.

[0143] At time T1 , the AMP STA is charged. Accordingly, it enters in the charged state. At this stage, the AMP AP has no information making it possible for the AMP AP to estimate that the AMP STA is charged.

[0144] At time T2, the AMP AP transmits an AMP Discovery frame 420. At this stage, the AMP AP performs an AMP Discovery frame transmission trial, considering that the time period defined by times TO and T2 makes it possible for the AMP RF Power signal 410 to energize an AMP STA surrounding the AMP AP, that is candidate to join its AMP WLAN.

[0145] AMP Discovery frame 420 sent by the AMP AP is expected to trigger a response frame from an AMP STA located in the vicinity of the AMP AP. The AMP Discovery frame 420 permits to the AMP AP to win access to the medium and to obtain a Transmission Opportunity (TXOP) that covers the transmission of the expected response frame from the AMP STA. After the reception of the AMP Discovery frame 420, for example a Short InterFrame Space (SIFS) time after the end of the reception of the AMP Discovery frame 420, the AMP STA transmits a response frame to the AMP AP. For example, the AMP STA transmits an AMP Association request frame, referenced 430. According to some embodiments of the disclosure, this response frame transmitted by the AMP STA to the AMP AP carries an AMP Capabilities element (e.g., AMP Capabilities element 200, in Figure 2a) and an In-Operation parameters element (e.g., In-Operation parameters element 300 in Figure 3a), as described above in reference to Figures 2a, 2b, 3a, and 3b.

[0146] At time T3, once the transmission of the response frame 430 is completed, the AMP STA enters in the discharged state 440 and is considered as such by the AMP AP.

[0147] From time T4, the AMP STA enters in a charging state 441. It is to be noted that the time period defined by times T3 and T4, wherein the AMP STA is in the discharged state 440, is represented for illustration purpose only in Figure 4, in order to ease understanding. Indeed, since the AMP RF Power signal 410 is still generated, the time period defined by times T3 and T4 may be much shorter than represented in Figure 4.

[0148] At time T5, the AMP AP transmits an AMP Association Response frame 421 to the AM P ST A, considering that the AM P STA is now in a charged state 442. At this stage, since the AMP AP has received the AMP Capabilities and the AMP In-Operation parameters from the AMP STA, the AMP AP is able to estimate more accurately the time needed for the AMP-STA to be charged and thus, to determine that the time period defined by times T4 and T5 is enough for the AMP RF Power signal 410 to energize the AMP STA.

[0149] The AMP Association Response frame 421 sent by the AMP AP is expected to trigger an acknowledgement frame from the AMP STA. The AMP Association Response frame 421 makes it possible for the AMP AP to win access to the medium and to obtain a Transmission Opportunity (TXOP) that covers the transmission of the expected acknowledgment frame from the AMP STA. The AMP Association Response frame 421 sent by the AMP AP is a response to the AMP Association Request frame 430 sent previously by the AMP STA, it makes it possible for the AMP AP to inform the AMP STA that it is now discovered and associated with the AMP AP within its AMP WLAN.

[0150] After the reception of the AMP Association Response frame 421 , for example a Short InterFrame Space (SIFS) time after the end of the reception of the AMP Association Response frame 421 , the AMP STA transmits an acknowledgement frame 431 to the AMP AP. At time T6, once the transmission of the acknowledgement frame 431 is completed, the AMP STA enters in the discharged state 440 and is considered as such by the AMP AP.

[0151] From time T7, the AMP STA enters in a charging state 441.

[0152] At time T8, the AMP AP stops the generation of the AMP RF Power Signal generation, considering that the AMP STA is now in a charged state 442. At this time, the AMP discovery and association sequence 400 for the AMP STA is completed.

[0153] For the sake of illustration, the AMP discovery and association sequence 400 has been described on the assumption that the AMP RF Power signal 410 is generated by the AMP AP. However, it is noted that a similar sequence could be contemplated while considering that the AMP RF Power signal 410 (e.g., AMP RF Power signal 121 described in reference to the Figure 1a) is generated by an AMP Assisting STA (e.g., AMP Assisting STA 112 described in reference to Figure 1a). In such a case, the AMP AP may transmit a frame (e.g., frame 122 in Figure 1a) to the AMP Assisting STA to indicate that it should generate an AMP RF power signal. As an example, the frame 122 may carry some fields / subfields to indicate the start time to generate the AMP RF power signal, the duration of the AMP RF power signal, and the power level of the AMP RF power signal. Transmitting several AMP RF power signals, for example one from an AMP AP and one or more other ones from one or more AMP Assisting STAs may also be contemplated.

[0154] The AMP AP could also manage successive AMP discovery and association sequences. For example, it could manage a first sequence where the AMP AP generates an AMP RF Power signal and then several other sequences where an AMP Assisting STA similar to the AMP Assisting STA 112 in Figure 1a generates an AMP RF Power signal similar to the AMP RF Power signal 121. The management of such successive sequences makes it possible for the AMP AP to identify, for each discovered and associated AMP STAs, which device is the more efficient to provide RF energy (i.e. , the AMP AP or an AMP Assisting STA). This identification makes it possible for the AMP AP to tune the duration / level of each AMP RF Power signal independently.

[0155] As a subsequent sequence to complete the discovery and association sequence, the AMP AP could manage a specific discovery and association sequence where the AMP AP and some or all the AMP Assisting STAs (e.g., AMP Assisting STAs similar to the AMP assisting STAs 112 in Figure 1a) generate their own AMP RF Power signal simultaneously. This could permit to discover and associate some remaining AMP STAs that need summed AMP RF power signals to reach a sufficient level of charge of their Power Storage unit.

[0156] While the AMP discovery and association sequence 400 has been described considering an AMP STA energized through RF energy harvesting, as described in reference to Figure 1a, this sequence may be adapted to consider AMP STAs energized from other types of energy, for example through solar energy (e.g., AMP STA 113 in Figure 1b). In such a case, the generation of an AMP RF Power signal is not needed. For example, as an alternative, a virtual generation of an AMP Ambient power signal could be considered in order to provide timing boundaries for AMP AP and initiate the sequence.

[0157] Likewise, while the AMP discovery and association sequence 400 is directed to a single AMP STA for the sake of clarity, a similar sequence may be carried out for discovering and associating several AMP STAs, for example several AMP STAs similar to AMP STA 111 and / or AMP STA 113 in Figures 1a and 1 b, respectively.

[0158] Trigger frame format

[0159] Figure 5 illustrates an example of a format of an AMP Trigger frame to be sent by an AMP AP to trigger one or more AMP STAs, according to some embodiments of the disclosure.

[0160] The format example of the AMP Trigger frame 500 is based on some assumptions:

[0161] - an AMP triggering sequence is launched through an AMP scheduling scheme and makes it possible for the AMP AP to trigger all AMP STAs or a set of AMP STAs discovered and associated in the AMP WLAN. For the sake of illustration, several hundreds of AMP STAs may be triggered by the AMP AP in an AMP triggering sequence,

[0162] - the AMP AP transmits several AMP Trigger frames in an AMP triggering sequence, wherein an AMP Trigger frame can trigger one AMP STA or several AMP STAs. All Trigger frames transmitted by the AMP AP in a triggering sequence use the same triggering configuration (e.g., all the trigger frames of the triggering sequence trigger one AMP STA, all the trigger frames of the triggering sequence trigger ten (or any number) AMP STAs, etc.), - the AMP AP triggers the AMP STAs, in an AMP triggering sequence, based on their AMP STA ID, in increasing order and considering no numbering gap (if some AMP STA ID numbering gaps exist, the AMP STAs have to parse the User Info field(s) of the AMP Trigger frame).

[0163] The new AMP Trigger frame format illustrated in Figure 5 aims at providing items of information intended to the AMP STA(s) triggered by a trigger frame and also items of information intended to the AMP STA(s) not triggered by the trigger frame, but triggered in the on-going triggering sequence. This new AMP Trigger frame format signals to an AMP STA its triggering position and / or time within the AMP triggering sequence. This makes it possible, for example, for the AMP STA to manage a power saving mode while waiting for its transmission position and / or time and so, to avoid wasting its harvested power which could be damageable for the rest of the triggering sequence. Upon receiving an AMP Trigger frame 500 triggering it, an AMP STA transmits an AMP Response frame carrying its Sensor data and In-Operation parameters element (e.g., In-Operation parameters element 300 in Figure 3a).

[0164] AMP Trigger frame 500 allocates resources for and solicits one or more AMP Response frame(s) transmission(s) from AMP STA(s). AMP Trigger frame 500 also carries other information required by the responding AMP STA to send an AMP Response frame.

[0165] As illustrated, AMP Trigger frame 500 comprises a plurality of fields, among which some or all of the following:

[0166] - the frame control field 510, that indicates, as a whole, that AMP Trigger frame 500 is a control frame,

[0167] - the duration field 520, that represents a time value set by the AMP AP, that may correspond to the remaining duration of the on-going triggering sequence. This time value allows the receivers of the AMP Trigger frame 500 to set their Network Allocation Vector (NAV) which is an indication of the duration that a station should prevent from accessing the medium. It may be set to a time in unit of ps,

[0168] - the RA field 530, that may be set to the address of the AMP STA identified by the AMP STA ID subfield 561 of the User Info field 560a if there is only one User Info field 560a in the User Info list 560. Otherwise, if there are more than one User Info field 560a in the User Info list 560, the RA field 530 may be set to the broadcast address, - the TA field 540, that may be set to the address of the AMP AP, i.e., the station transmitting the AMP Trigger Frame 500.,

[0169] - the common info field 550 (describes hereafter),

[0170] - the user info list field 560, that contains one or more User Info field(s) 560a. The User Info field 560a is further described hereafter,

[0171] - the padding field 570, that is optionally present in the AMP T rigger frame to extend the frame length to give the recipient AMP STA(s) enough time to prepare a response for transmission a SIFS after the AMP Trigger frame is received, and

[0172] - the FCS field 580, that contains a 32-bit CRC.

[0173] The Common Info field 550 of the AMP Trigger frame 500 includes some or all of the following subfields:

[0174] - the T rigger T ype subfield 551 , that identifies the AM P T rigger frame variant, it can be set to a value between 8 and 15. For example, it is set to the value 8,

[0175] - the UL Length subfield 552, that indicates the total time period allocated to the AMP STAs addressed by the AMP Trigger frame 500 within the TXOP obtained by the AMP AP. It may be expressed in unit of 16ps. The UL Length subfield 552 may be used by an AMP STA not addressed by the AMP T rigger frame 500 to determine its triggering position and / or time within the triggering sequence without the need of parsing the Allocation Duration subfield(s) 562 of User Info field(s) 560a,

[0176] - the More TF subfield 553, that indicates whether a subsequent AMP Trigger frame 500 is scheduled for transmission,

[0177] - the Current Trigger Frame (TF) AMP STA ID Start subfield 554, that indicates the value of the AMP STA ID of the first AMP STA triggered by the AMP Trigger frame 500. According to some embodiments, the User Info field 560a of this first AMP STA triggered is placed at the first position in the User Info List field 560. This Current Trigger Frame (TF) AMP STA ID Start subfield 554 may be used by an AMP STA to determine whether it is concerned by the on-going triggering sequence, without the need of parsing the AMP STA ID subfield(s) 561 of User Info field(s) 560a. For example, if the value of the AMP STA ID of an AMP STA is less than the value indicated in the Current Trigger Frame (TF) AMP STA ID Start subfield 554, this means that the AMP STA has already been triggered in the ongoing triggering sequence or that the AMP STA is not concerned by the on-going triggering sequence, - the Current T rigger Frame (TF) AMP STAs number subfield 555, that indicates the number of AMP STAs triggered by the AMP Trigger frame 500 and so, that indicates the number of User Info fields 560a in the User Info List 560. The Current Trigger Frame (TF) AMP STA number subfield 555 and the Current Trigger Frame (TF) AMP STA ID Start subfield 554 may be used by an AMP STA to determine whether it is concerned by the on-going triggering sequence, without the need for parsing the AMP STA ID subfield(s) 561 of User Info field(s) 560a. For example, if the value of the AMP STA ID of an AMP STA is greater than or equal to the value indicated in the Current Trigger Frame (TF) AMP STA ID Start subfield 554 and less than the sum of the values indicated in the Current Trigger Frame (TF) AMP STA ID Start subfield 554 and in the Current Trigger Frame (TF) AMP STA number subfield 555, this means that the AMP STA is concerned by the on-going triggering sequence and addressed by the received AMP Trigger frame 500,

[0178] - the Current Triggering Sequence AMP STA ID Stop subfield 556, that indicates the value of the AMP STA ID of the last AMP STA triggered by the on-going triggering sequence. This Current Triggering Sequence AMP STA ID Stop subfield 556, together with the Current Trigger Frame (TF) AMP STA number subfield 555 and the Current Trigger Frame (TF) AMP STA ID Start subfield 554, may be used by an AMP STA to determine whether or not it is concerned by the on-going triggering sequence without the need for parsing the AMP STA ID subfield(s) 561 of User Info field(s) 560a. For example, if the value of the AMP STA ID of an AMP STA is greater than or equal to the sum of the values indicated in the Current Trigger Frame (TF) AMP STA ID Start subfield 554 and in the Current Trigger Frame (TF) AMP STA number subfield 555 and less than or equal to the value indicated in the Current Triggering Sequence AMP STA ID Stop subfield 556, this means that the AMP STA is concerned by the on-going triggering sequence but not addressed by the received AMP Trigger frame 500. In this case, the AMP STA may estimate its coming triggering position and / or time within the on-going triggering sequence based on the information provided in the described subfields of the Common Info field 550,

[0179] - the Next Triggering Sequence subfield 557, that indicates the starting time of the next triggering sequence. It may be expressed in second. For an AMP STA that has determined, based on the subfields of the Common Info field 550 described previously, that it is not concerned by the on-going triggering sequence, this Next Triggering Sequence subfield 557 indicates the starting time of the next triggering sequence planned by the AMP AP. This makes it possible for the AMP STA to manage a power saving mode up to this next triggering sequence and so, to avoid wasting its harvested power which could be damageable for the next triggering sequence, and

[0180] - the Reserved subfield 558, that corresponds to the reserved bits not assigned.

[0181] The User Info field 560a of the AMP Trigger frame 500 may include some or all of the following subfields:

[0182] - the AMP STA ID subfield 561 , that is set to the value of the AMP STA ID belonging to the AMP STA to which the User Info field 560a is intended,

[0183] - the Allocation Duration subfield 562, that indicates the time period allocated to the AMP STA within the TXOP obtained by the AMP AP 110, for example in units of 16ps, and

[0184] - the Reserved subfield 563 corresponds to the reserved bits not assigned.

[0185] Steps for exchanging Capabilities and In-Operation parameters between an AMP AP and AMP STAs

[0186] Figure 6a illustrates an example of steps carried out by an AMP AP to make it possible to obtain Capabilities and In-Operation parameters from one or more AMP STAs, according to some embodiments of the disclosure.

[0187] At step 600, the AMP AP starts a discovery and association procedure in order to discover AMP STAs and to associate the discovered AMP STAs (or some of them) with the AMP AP. For the sake of illustration, the AMP AP may start the discovery and association sequence by using the discovery and association sequence 400 described in reference to Figure 4.

[0188] Next, at step 601 , the AMP AP obtains and processes the AMP Capabilities and In-Operation parameters that are received from the discovered AMP STAs. For example, the AMP AP may obtain the AMP Capabilities and In-Operation parameters from AMP STAs by transmitting an AMP Discovery frame (e.g., AMP Discovery frame 420 in Figure 4) triggering a response frame (e.g., the AMP Association Request frame 430 in Figure 4) from AMP STAs.

[0189] Next, at step 602, the AMP AP computes the AMP RF Power signal duration and / or level and an AMP STAs scheduling sequence based on the AMP Capabilities and the In-Operation parameters received from AMP STAs. For example, the AMP AP may compute the AMP RF Power signal duration and the AMP STAs scheduling sequence described in reference to Figures 7a, 7b, and 7c or to Figures 8a, 8b, and 8c.

[0190] Next, during step 603, the AMP AP launches a scheduling scheme to schedule the triggering of AMP STAs in order to collect, for example, sensor data. The launched scheduling scheme may comprise generating the AMP RF Power signal and then, transmitting one or several AMP Trigger frames. For example, the AMP AP may launch the scheduling scheme described in reference to Figures 7a, 7b, and 7c or to Figures 8a, 8b, and 8c.

[0191] Next, at step 604, the AMP AP receives the data from the AMP STAs. For example, the AMP AP may receive sensor data. It may also receive the In-Operation parameters in an AMP Response frame sent by the AMP STAs.

[0192] Figure 6b illustrates an example of steps carried out by an AMP STA to make it possible for an AMP AP to obtain its Capabilities and In-Operation parameters and its data, according to some embodiments of the disclosure.

[0193] At step 650, the AMP STA (e.g., AMP STA 111 or 113 in Figure 1a or 1b, respectively) checks whether its internal Power Storage unit has reached a charging level 0 that makes it possible to handle DL and / or UL data communication with the AMP AP (e.g., AMP AP 110 in Figure 1a or 1b). For example, the AMP STA may check whether its Power Storage unit has reached a charging level greater than or equal to 80% or 90%. If the Power Storage unit has not reached a charging level greater than or equal to 80% or 90%, the algorithm loops to step 650. On the contrary, if the Power Storage unit has reached a charging level greater than or equal to 80% or 90%, the algorithm continues at step 651.

[0194] At step 651 , the AMP STA listens for an AMP frame to be received from an AMP AP. The algorithm loops on step 651 until an AMP frame is received. On the contrary, if an AMP frame is received, the algorithm continues at step 652.

[0195] At step 652, the AMP STA checks whether the received AMP frame is an AMP Discovery frame. If the received AMP frame is an AMP Discovery frame, the algorithm continues at step 657. On the contrary, if the received AMP frame is not an AMP Discovery frame, the algorithm continues at step 653.

[0196] At step 657, the AMP STA transmits an AMP Response frame, in response to the received AMP Discovery frame. The AMP Response frame carries the AMP Capabilities element (e.g., AMP Capabilities element 200 in Figure 2) and the AMP In-Operation parameters element (e.g., AMP In-Operation parameters element 300 in Figure 3). It is transmitted (by the AMP STA) to the AMP AP. Once step 657 is done, the algorithm loops to step 650.

[0197] At step 653, the AMP STA checks whether the received AMP frame is an AMP Trigger frame. If the received AMP frame is not an AMP Trigger frame, the algorithm continues at step 650. If the received AMP frame is an AMP Trigger frame, the algorithm continues at step 654.

[0198] At step 654, the AMP STA processes the received AMP Trigger frame to obtain its AMP Response frame transmission position and / or timing within the triggering sequence. Next, the algorithm continues at step 655.

[0199] At step 655, the AMP STA checks whether the obtained AMP Response frame transmission position and / or timing is reached. As illustrated, the algorithm loops on step 655 until the obtained AMP Response frame transmission position and / or timing is reached. When the obtained AMP Response frame transmission position and / or timing is reached, the algorithm continues at step 656. According to some embodiments, the AMP STA manages a power saving mode during step 655 to avoid wasting power which could be damageable for the rest of the triggering sequence.

[0200] At step 656, the AMP STA transmits its AMP Response frame to the AMP AP. The AMP Response frame carries data, for example its sensor data, and / or the InOperation parameters element (e.g., In-Operation Parameter element 300 in Figure 3). Once step 656 is done, the algorithm loops to step 650.

[0201] Figure 7a, 7b, and 7c illustrate a first example of a scheduling sequence of AMP STAs, managed by an AMP AP, according to some embodiments of the disclosure.

[0202] For the sake of illustration, it is assumed that the AMP AP has discovered five AMP STAs (denoted AMP STA1 to AMP STA5), for example five AMP STAs similar to AMP STA 111 described in reference to Figure 1a (i.e., AMP STAs using RF energy harvesting), and is associated with these AMP STAs, for example using a Discovery and Association procedure similar to the Discovery and Association procedure 400 described in reference to Figure 4. The number of five AMP STAs illustrated in Figures 7a, 7b, and 75c is only for illustration purpose and ease of understanding. A higher number of AMP STAs may be contemplated for such a scheduling scheme. Likewise, the AMP STAs associated with the AMP AP may comprise AMP STAs similar to the AMP STA 113 illustrated in Figure 1 b (i.e. AMP STAs using solar energy harvesting). The AMP STAs associated with the AMP AP may comprise AMP STAs featuring the same ambient energy harvesting or may be a mix of AMP STAs featuring distinct ambient energy harvesting.

[0203] It is noted that the timing values considered for the duration of the AMP RF Power Signal, for the charging time of the Power Storage units of AMP STAs, and for the duration of the triggering frame exchange for each of the AMP STAs, in the example illustrated in Figure 7a, 7b, and 7c are chosen for illustration purpose. Other timing values may be contemplated.

[0204] For the scheduling scheme illustrated in Figures 7a, 7b, and 7c, it is assumed that the AMP AP has received In-Operation parameters elements (e.g., In-Operation parameters elements 300 described in reference to Figure 3) from AMP STAs1 to AMP STA5 with the following current timing charge values (Tchargingcurrent):

[0205] - for AMP STA1 , Tchargingcurrent = 20ms,

[0206] - for AMP STA2, Tchargingcurrent = 30ms,

[0207] - for AMP STA3, Tchargingcurrent = 50ms,

[0208] - for AMP STA4, Tchargingcurrent = 50ms, and

[0209] - for AMP STA5, Tchargingcurrent = 100ms.

[0210] In addition, it is assumed that the triggering frame exchange between the AMP AP and each AMP STA, referenced 721 , 722, 723, 724, and 725, respectively, lasts around 2ms. The triggering frame exchange gathers the duration of the AMP Trigger frame sent by the AMP AP, a SIFS time, and the time period needed by an AMP STA to send the AMP Trigger frame response.

[0211] According to the scheduling scheme illustrated in Figure 7a, 7b, and 7c, the AMP AP starts the scheduling of triggering the five AMP STAs (AMP STA1 to AMP STA5) once all the AMP STA are charged.

[0212] Figure 7a illustrates the AMP RF Power signal generated by the AMP AP, referenced 700, to energize AMP STA1 to AMP STA5, being assumed that the AMP AP has obtained and processed the AMP Capabilties and In-Operation parameters elements from each of the AMP STA1 to AMP STA5, especially it has obtained and processed the current timing charge value (Tchargingcurrent) from each of the AMP STA1 to AMP STA5. Based on the received Tchargingcurrent values, the AMP AP computes the time period of the AMP RF Power signal that is needed to energize the AMP STAs and then to trigger all of the AMP STA1 to AMP STA5. According to the illustrated example, the AMP RF Power signal is generated during about 120ms (the AMP AP has computed this time period from the maximum Tchargingcurrent of 100ms obtained from the AMP STA5, plus a margin of 20ms).

[0213] In a variant, the AMP AP could also use the current RF harvesting power (PRFeurrent), the minimum RF harvesting power (Pppmin), and the maximum charging time (Tchargingmax) received from each of the AMP STA1 to AMP STA5 to compute both the level and the duration of the AMP RF Power signal 700.

[0214] Figure 7b illustrates the charging signals 711 to 715 corresponding to the charging levels of the Power Storage units of the AMP STA1 to AMP STA5, respectively. For the sake of illustration, it is assumed that the charging of the Power Storage units of the AMP STAs is linear. Considering the charging signals 711 to 715, the AMP AP is able to estimate the timing of charge of each of the AMP STA1 to AMP STA5 and thus, when to perform DL / LIL data communication. As illustrated, when the RF Power is stopped, at time 150ms, all of the AMP STA1 to AMP STA5 are charged.

[0215] Figure 7c illustrates the scheduling of the triggering 721 to 725 of the AMP STA1 to AMP STA5, respectively, by the AMP AP. According to this example, the AMP AP schedules the triggering of the AMP STA1 to AMP STA5 based on their current charging time value (Tchargingcurrent), in increasing order. As a result, the AMP AP schedules firstly the triggering 721 of AMP STA1 with Tchargingcurrent = 20ms, secondly the triggering 722 of AMP STA2 with Tchargingcurrent = 30ms, thirdly the triggering 723 of AMP STA3 with Tchargingcurrent = 50ms, fourthly the triggering 724 of AMP STA4 with Tchargingcurrent = 50ms, and fifthly the triggering 725 of AMP STA5 with Tchargingcurrent = 100ms.

[0216] As illustrated, once an AMP STA has been triggered, its charging signal (711 , 712, 713, 714, or 715), corresponding to the charging level of its Power Storage unit, falls to zero, corresponding to the discharged state.

[0217] The AMP AP may schedule the triggering of AMP STA1 to AMP STA5 using an AMP Trigger frame (e.g., AMP Trigger frame 500 described by reference to Figure 5) indicating the triggering position for each AMP STA in the current triggering sequence. This makes it possible for an AMP STA to enter in power save mode while waiting for its turn in the triggering sequence.

[0218] The scheduling scheme described in Figures 7a, 7b, and 7c makes it possible for the AMP AP to schedule efficiently the triggering of AMP STAs (i.e. of AMP-Only loT STAs featuring Power Storage) and, for example, to retrieve sensor data of all the AMP STAs within the AMP WLAN. The scheduling sequence described in reference to Figures 7a, 7b, and 7c may be restart periodically by the AMP AP. According to the example illustrated in Figures 7a, 7b, and 7c, the AM P RF Power signal 700 is generated by the AMP AP. According to another example, a similar scheduling scheme could be contemplated where the AMP RF Power signal is generated by AMP Assisting STA (e.g., AMP RF Power signal 121 in Figure 1a, that is generated by AMP Assisting STA 112), based on a specific frame (e.g., frame 122 in Figure 1a) received from the AMP AP. As yet another example, a similar scheduling scheme could be contemplated where the AMP RF Power signal 700 and one or several AMP RF Power signal(s) similar to the AMP RF Power signal 121 in Figure 1a are generated simultaneously or successively, respectively, by the AM P AP and by one or several AM P Assisting STA(s) similar to the AMP Assisting STA 112 in Figure 1a.

[0219] According to the examples provided herein above, all AMP RF Power signals are generated based on the computation of duration and / or level carried out by the AMP AP using the Capabilities and In-Operation parameters received from the AMP STA(s).

[0220] Figure 8a, 8b, and 8c illustrate a second example of a scheduling sequence of AMP STAs, managed by an AMP AP, according to some embodiments of the disclosure.

[0221] For the sake of clarity, the same assumptions are made here as in Figures 7a, 7b, and 7c.

[0222] In the scheduling scheme illustrated in Figure 8a, 8b, and 8c, the AMP AP starts the scheduling of triggering an AMP STA (AMPS STA1 , AMPS STA2, AMPS STA3, AMPS STA4, and AMP STA5) once it is charged. This second scheduling scheme may be seen as an optimization of the first scheduling scheme described in reference to Figures 7a, 7b, and 7c.

[0223] Figure 8a illustrates the AMP RF Power signal generated by the AMP AP, referenced 800, to energize AMP STA1 to AMP STA5, being assumed that the AMP AP has obtained and processed the AMP Capabilties and In-Operation parameters elements from each of the AMP STA1 to AMP STA5, especially it has obtained and processed the current timing charge value (Tchargingcurrent) from each of the AMP STA1 to AMP STA5. Based on the received Tchargingcurrent values, the AMP AP has computed the time period of the AMP RF Power signal that is needed to energize and then schedule the triggering of each of the AMP STA1 to AMP STA5 once it is charged. According to the illustrated example, the AMP RF Power signal is generated during about 120ms (the AMP AP has computed this time period from the maximum Tchargingcurrent of 100ms obtained from the AMP STA5, plus a margin of 20ms). Figure 8b illustrates the charging signals 811 to 815 corresponding to the charging levels of the Power Storage units of the AMP STA1 to AMP STA5, respectively. For the sake of illustration, it is assumed that the charging of the Power Storage units of the AMP STAs is linear. Considering the charging signals 811 to 815, the AMP AP is able to estimate the timing of charge of each of the AMP STA1 to AMP STA5 and thus, when to perform DL / LIL data communication. This makes it possible for the AMP AP to schedule the triggering of an AMP STA once it is charged. As illustrated, when the AMP RF Power signal is stopped, at time 150ms, AMP STA1 to AMP STA5 have been triggered and their charging levels are not the same: while AMP STA1 to AMP STA4 are fully re-charged, AMP STA5 is only partially re-charged.

[0224] Figure 8c illustrates the scheduling of the triggering 821 to 825 of AMP STA1 to AMP STA5, respectively, by the AMP AP. According to this example, the AMP AP schedules the triggering of AMP STA1 to AMP STA5 based on their current charging time value (Tchargingcurrent), in increasing order, right after they reach their charged state.

[0225] As a result, the AMP AP schedules firstly the triggering 821 of AMP STA1 with Tchargingcurrent = 20ms, secondly the triggering 822 of AMP STA2 with Tchargingcurrent = 30ms, thirdly the triggering 823 of AMP STA3 with Tchargingcurrent = 50ms, fourthly the triggering 824 of AMP STA4 with Tchargingcurrent = 50ms, and fifthly the triggering 825 of AMP STA5 with Tchargingcurrent = 100ms.

[0226] As illustrated, some AMP STAs are triggered while the AMP RF Power signal is still generated and thus, they can take advantage of the AMP RF Power signal to recharge totally or partially their Power Storage unit after their triggering.

[0227] The AMP AP schedules the triggering of AMP STA1 to AMP STA5 using an AMP Trigger frame indicating the triggering position for each of AMP STA1 to AMP STA5 in the triggering sequence. This makes it possible for an AMP STA to enter in a power save mode while waiting for its turn in the current or next triggering sequence. The AMP Trigger frame format may conform the one described by reference to Figure 5.

[0228] The scheduling scheme described in Figures 8a, 8b, and 8c makes it possible for the AMP AP to schedule efficiently the triggering of AMP STAs (i.e. , of AMP-Only loT STAs featuring Power Storage) and, for example, to retrieve sensor data from all the AMP STAs within the AMP WLAN. The scheduling sequence illustrated in Figures 8a, 8b, and 8c may be restart periodically by the AMP AP.

[0229] In the scheduling scheme illustrated in Figures 8a, 8b, and 8c, the AMP RF Power signal is generated by the AMP AP. As another example, a similar scheduling scheme could be contemplated where the AMP RF Power signal is generated by an AMP Assisting STA (e.g., AMP Assisting STA 112 in Figure 1a), based on a specific frame (e.g., frame 122 in Figure 1a) received from the AMP AP. As yet another example, a similar scheduling scheme could be contemplated where the AMP RF Power signal 800 and one or several AMP RF Power signal(s) similar to the AMP RF Power signal 121 in Figure 1a are generated simultaneously or successively, respectively, by the AMP AP and by one or several AMP Assisting STA(s) similar to the AMP Assisting STA 112 in Figure 1a.

[0230] According to the examples provided herein above, all AMP RF Power signals are generated based on the computation of duration and / or level carried out by the AMP AP using the Capabilities and In-Operation parameters received from the AMP STA(s).

[0231] Figure 9a shows a schematic representation of an AMP AP wireless communication device in accordance with some embodiments of the present disclosure.

[0232] The communication device 900, that may be the AMP AP described above, of an AMP wireless network, is configured to implement at least partially at least one of the embodiments of the present disclosure. The communication device 900 may be a device such as a micro-computer, a workstation, or a light portable device. The communication device 900 comprises a communication bus 913 to which may be connected: a central processing unit 901 , such as a processor, denoted CPU; a memory 903 for storing an executable code of methods or steps of the methods according to some embodiments of the disclosure as well as the registers adapted to record variables and parameters necessary for implementing the methods; at least one transmitter / receiver communication interfaces 902 connected to the wireless communication network, for example an AMP communication network operating in the Sub-1GHz (S1G) and / or 2.4GHz frequency band(s), via Tx / Rx antenna 904; and a RF power source 905 for generating radio frequency energy, via its antenna 906, towards AMP STAs wireless communication devices that may be energized through radio frequency energy.

[0233] According to some embodiments, the communication bus 913 provides communication and interoperability between the various elements included in the communication device 900 or connected to it. The representation of the bus is not limiting and in particular the central processing unit is operable to communicate instructions to any element of the communication device 900 directly or by means of another element of the communication device 900.

[0234] The executable code may be stored in a memory that may either be read only, a hard disk or on a removable digital medium such as for example a disk. According to an optional variant, the executable code of the programs can be received by means of the communication network, via the interface 902, in order to be stored in the memory of the communication device 900 before being executed.

[0235] In some embodiments, the communication device is a programmable apparatus which uses software to implement embodiments of the disclosure. Alternatively, some embodiments of the present disclosure may be implemented, totally or partially, in hardware (for example, in the form of an Application Specific Integrated Circuit or ASIC).

[0236] Figure 9b shows a schematic representation of an AMP STA wireless communication device in accordance with embodiments of the present disclosure.

[0237] The communication device 950, that may be one of the AMP STAs described above, of an AMP wireless network, is configured to implement at least partially at least one of the embodiments of the present disclosure. The communication device 950 may be a device such as a micro-computer, a workstation, or a light portable device. The communication device 950 comprises a communication bus 963 to which may be connected: a central processing unit 951 , such as a processor, denoted CPU; a memory 953 for storing an executable code of methods or steps of the methods according to some embodiments of the disclosure as well as the registers adapted to record variables and parameters necessary for implementing the methods; at least one transmitter / receiver communication interfaces 952 connected to the wireless communication network, for example an AMP communication network operating in the Sub-1GHz (S1G) and / or 2.4GHz frequency band(s), via Tx / Rx antenna 954; and a sensor 957 for measuring a value, such as a temperature or a humidity value, to be transmitted to another wireless communication device, for example the AMP AP device 900 in Figure 9a, through the interface 952.

[0238] According to some embodiments, the communication bus 963 provides communication and interoperability between the various elements included in the communication device 950 or connected to it. The representation of the bus is not limiting and in particular the central processing unit is operable to communicate instructions to any element of the communication device 950 directly or by means of another element of the communication device 950.

[0239] The communication device 950 further comprises an ambient energy sensing element 960 such as an antenna in case of RF energy or photovoltaic cells in case of solar or light energy connected to a power harvesting circuit 959 for harvesting ambient energy and charging the Power Storage unit 958. The Power Storage unit 958, for example a capacitor, is used to energize the communication device 950.

[0240] The executable code may be stored in a memory that may either be read only, a hard disk or on a removable digital medium such as for example a disk. According to an optional variant, the executable code of the programs can be received by means of the communication network, via the interface 952, in order to be stored in the memory of the communication device 950 before being executed.

[0241] In some embodiments, the device is a programmable apparatus which uses software to implement embodiments of the disclosure. Alternatively, some embodiments of the present disclosure may be implemented, totally or partially, in hardware (for example, in the form of an Application Specific Integrated Circuit or ASIC).

[0242] Although the present disclosure has been described hereinabove with reference to specific embodiments, the present disclosure is not limited to the specific embodiments, and modifications will be apparent to a skilled person in the art which lie within the scope of the present disclosure.

[0243] Many further modifications and variations will suggest themselves to those versed in the art upon referring to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the disclosure, that being determined solely by the appended claims. In particular the different features from different embodiments may be interchanged, where appropriate.

[0244] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

Claims

CLAIMS1. A communication method for a wireless network comprising an access point, AP, and at least one ambient power, AMP, station, STA, the method comprising, in the AP: obtaining a charging parameter of the at least one AMP STA; and triggering the at least one AMP STA for data transmission based on the obtained parameter.

2. The communication method of claim 1 , further comprising determining a time period for the at least one AMP STA to reach a given level of charge, based on the charging parameter, wherein the triggering for data transmission is done based on the time period for the at least one AMP STA to reach a given level of charge.

3. The communication method of claim 2, wherein the given level of charge is a charging level required for the at least one AMP STA to receive and process a request for data transmission and to transmit the data, the triggering for data transmission being carried out so that data transmission occurs at or after a time at which the at least one AMP STA reaches the given level of charge.

4. The communication method of claim 2 or 3, wherein the given level of charge is determined based on a percentage of a time period needed for the at least one AMP STA to be fully charged.

5. The communication method of any one of claims 1 to 4, further comprising emitting and / or triggering an emission of a power signal for charging the at least one AMP STA.

6. The communication method of claim 5, further comprising determining a time period and / or a power level of the power signal, based on the obtained parameter.

7. The communication method of any one of claims 1 to 6, wherein the obtaining comprises obtaining characteristics of a power storage unit of the at least one AMP STA and / or obtaining current charging characteristics of the power storage unit.

8. The communication method of claim 7, further comprising receiving data and current charging characteristics of the power storage unit in response to the triggering.

9. The communication method of any one of claims 1 to 8, wherein the obtaining is carried out for a plurality of AMP STAs, the method further comprising triggering the plurality of AMP STAs by sending a trigger frame containing a sequence scheduling the AMP STAs to transmit data.

10. The communication method of claim 9, wherein the triggering the plurality of AMP STAs is carried out once each AMP STA of the plurality of AMP STAs reaches a given level of charge.

11. The communication method of claim 9, wherein the triggering the plurality of AMP STAs is carried out after a first AMP STA of the plurality of AMP STAs reaches a given level of charge.

12. The communication method of any one of claims 9 to 11 , further comprising determining the sequence, based on an obtained charging parameter of each AMP STA of the plurality of AMP STAs.

13. A communication method for a wireless network comprising an access point, AP, and at least one ambient power, AMP, station, STA, the method comprising, in the at least one AMP STA, transmitting a charging parameter of the at least one AMP STA to the AP.

14. The communication method of claim 13, wherein the charging parameter comprises characteristics of a power storage unit of the at least one AMP STA.

15. The communication method of claim 14, further comprising receiving, from the AP, a request for data transmission and determining, from the request, a time at which data are to be transmitted, current charging parameter of the at least one AMP STA being transmitted along with the data at the time at which data are to be transmitted, the current charging parameter comprising current charging characteristics of a power storage unit of the at least one AMP STA.

16. The communication method of claim 15, further comprising entering within a power save mode, during a period of time determined based on the time at which data are to be transmitted.

17. The communication method of claim 15 or 16, further comprising determining a time period for the at least one AMP STA to reach a given level of charge, wherein the given level of charge makes it possible to receive and process a next request for data transmission and to transmit data and a next current charging parameter and wherein the current charging parameter comprises the determined time period.

18. The communication method of claim 17, further comprising harvesting power from a power signal, the power signal being received during at least the determined time period; receiving the next request for data transmission; and transmit data and the next current charging parameter.

19. The communication method of any one of claims 15 to 18, further comprising determining a current harvesting power amount, wherein the current charging parameter comprises the determined current harvesting power amount.

20. A wireless communication device comprising at least one microprocessor configured to carry out the method according to any one of claims 1 to 19.

21. A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a wireless device, causes the wireless device to perform the method according to any one of claims 1 to 19.

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