Energy-autonomous optical wireless communication system

Abstract

An optical wireless communication receiver (100 / 600) comprising: one or more harvesting solar cells (112) configured to convert light into electrical energy; one or more communication solar cells (122) configured to convert light into electrical signals with information embedded; a rechargeable battery (130) configured to store electrical energy generated by the one or more harvesting solar cells (112); a communication module (150) configured to decode the electrical signals generated by the one or more communication solar cells (122) and extract the information; a first switch (114) configured to connect the one or more harvesting solar cells (112) to the rechargeable battery (130) to achieve a first harvesting state, and to the communication module (150) to achieve a second communication state; a second switch (124) configured to connect the one or more communication solar cells (122) to the communication module (150) to achieve a first communication state, and to the rechargeable battery (130) to achieve a second harvesting state; and a microprocessor (140) configured to control the first switch (114) and the second switch (124).

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 023,454, filed May 12, 2020, entitled “FULLY ENERGY-AUTONOMOUSOPTICAL WIRELESS COMMUNICATION SYSTEM USING SWITCHABLE HYBRID PHOTORECEIVER”, the entire disclosure of which is incorporated herein by reference. background Technical Field

[0004] The embodiments of the subject matter disclosed herein generally relate to a system and method for exchanging data using light waves, and more specifically, to an energy-autonomous optical wireless communication system. Background Technology

[0006] Fifth-generation (5G) networks and beyond, as crucial communication infrastructure, face unprecedented opportunities and challenges. Several goals have been defined for 5G networks, such as data rates up to 10 Gbit / s, power consumption reduction of nearly 90%, improved network availability and reliability, and support for connectivity between millions of Internet of Things (IoT) devices.

[0007] To meet data traffic demands, millimeter-wave massive multiple-input multiple-output (MIMO) systems have become a highly attractive driver. However, a key challenge is the high power consumption resulting from densely deployed base stations, which could not only hinder the implementation of millimeter-wave MIMO systems but also exacerbate the energy crisis and global environmental degradation. Furthermore, millimeter-wave communication utilizing the 30 GHz to 300 GHz spectrum may generate strong electromagnetic radiation over short distances, posing unknown health risks to humans.

[0008] In this context, Optical Wireless Communication (OWC) technology should significantly alleviate the heavy burden on radio frequency spectrum by utilizing the abundant ~30PHz spectrum resources. Furthermore, OWC technology offers advantages such as high bandwidth, low latency, low cost, small size, low power consumption, and strong resistance to electromagnetic interference, demonstrating promising application prospects in 5G networks and beyond. For example, combined with innovative technologies such as big data, cloud computing, and artificial intelligence, OWC can be widely applied in wearable devices, smart homes, and intelligent transportation systems.

[0009] In recent years, solar cells with dual functions of energy harvesting and data acquisition have proven to be an attractive alternative to commonly used detectors such as PIN diodes and avalanche photodiodes to alleviate energy problems. Furthermore, as photovoltaic solar cells permeate every corner of our lives, they hold immense potential for supporting massive data traffic and connectivity of large-scale IoT devices in the future. However, using the same type of solar cell for both energy harvesting and data communication has proven inefficient for at least one of these functions.

[0010] Therefore, existing 5G systems are limited by their energy consumption and the amount of data they can transmit. Thanks to advancements in information, power electronics, and intelligent management, the Energy Internet in Industry 3.0 enables the efficient transmission and sharing of electricity, characterized by millions of distributed renewable energy devices. The significant progress of the Energy Internet lays a solid foundation for the Energy Internet of Things in Industry 4.0 and will undoubtedly benefit the innovation of the upcoming Industry 5.0 standards. With the progress of the industrial revolution, renewable solar energy has been developed to address the global energy crisis and environmental degradation, while meeting people's energy-related needs in daily life. As is well known, photovoltaic (PV) solar cells are the core component that converts solar energy into electricity using the PV effect. In the past few years, the development of photovoltaic solar cells has rapidly evolved from first-generation silicon (Si) wafer-based solar cells and second-generation thin-film solar cells to third-generation solar cells based on newly developed light-absorbing materials. First-generation silicon wafer-based solar cells, characterized by high stability, high efficiency, and low cost, have been widely used in global solar infrastructure. Due to the unique advantages of second-generation thin-film solar cells, such as high transparency, flexibility, and light absorption coefficient, their market penetration has also increased significantly. With advancements in materials, third-generation solar cells based on novel materials (such as dye-sensitized, organic, and perovskite solar cells) have emerged and achieved breakthroughs in photoelectric conversion efficiency (PCE). However, much work remains to overcome implementation hurdles related to stability, material growth, and manufacturing costs of third-generation solar cells, while accelerating their commercialization in the market.

[0011] Solar cells have shown great promise for simultaneous energy harvesting and signal detection in fifth-generation OWC networks and other networks [1-8]. By relying on the photoelectric effect to convert light signals into electrical signals without any external power source, solar cells can save more energy and are more environmentally friendly than traditional PIN diodes, avalanche photodiodes, and photomultiplier tubes. Furthermore, with the addition of external communication circuitry, solar cells, widely used in solar infrastructure and various emerging solar devices (e.g., wearable devices, autonomous vehicles, and drones), can perform the dual functions of energy harvesting and signal detection, which can facilitate the rapid development of future self-powered Internet of Things (IoT). In particular, due to the power shortage in marine environments, solar cells, which can be used as detectors for simultaneous signal detection and efficient energy harvesting, have significant application prospects in marine equipment.

[0012] Therefore, there is a need to develop an efficient autonomous optical wireless communication system, especially one that can also operate underwater. Summary of the Invention

[0013] According to one embodiment, an optical wireless communication receiver is provided, comprising: one or more collecting solar cells configured to convert light into electrical energy; one or more communicating solar cells configured to convert light into electrical signals embedded with information; a rechargeable battery configured to store the electrical energy generated by the one or more collecting solar cells; a communication module configured to decode the electrical signals generated by the one or more communicating solar cells and extract the information; a first switch configured to connect the one or more collecting solar cells to the rechargeable battery to achieve a first collecting state and to the communication module to achieve a second communicating state; a second switch configured to connect the one or more communicating solar cells to the communication module to achieve the first communicating state and to the rechargeable battery to achieve the second collecting state; and a microprocessor configured to control the first switch and the second switch.

[0014] According to another embodiment, a method for harvesting energy and transmitting data is provided, the method comprising: receiving light at one or more harvesting solar cells and converting the light into electrical energy; storing the electrical energy in a rechargeable battery; receiving light at one or more communication solar cells and converting the light into an electrical signal embedded with information; and decoding the electrical signal generated by the one or more communication solar cells and extracting the information at a communication module. The one or more harvesting solar cells, the rechargeable battery, the one or more communication solar cells, and the communication module are part of a single optical wireless communication receiver, and the storage and decoding steps are performed simultaneously.

[0015] According to another embodiment, an optical communication and energy harvesting system is provided, the system comprising: a transmitter configured to generate a light beam encoding data; and an optical wireless communication receiver configured to simultaneously use the light beam to generate electrical energy and extract the encoded data. The optical wireless communication receiver includes: one or more harvesting solar cells configured to convert the light beam into electrical energy, and one or more communication solar cells configured to convert the light beam into an electrical signal embedded with data. Attached Figure Description

[0016] To gain a more complete understanding of the invention, reference is now made to the following description in conjunction with the accompanying drawings, wherein:

[0017] Figure 1A This is a schematic diagram of an energy-autonomous optical wireless communication receiver with hybrid solar cells;

[0018] Figure 1B , Figure 1C , Figure 1D , Figure 1E and Figure 1F A schematic diagram of an energy-optical wireless communication receiver with different switching schemes is shown;

[0019] Figure 2A and Figure 2B Various geometric configurations of hybrid solar cells are shown;

[0020] Figure 3 The current density of a-Si thin-film solar cells under different power densities is shown;

[0021] Figure 4 The illuminance distribution of a white laser at a distance of 20m is shown;

[0022] Figure 5 The constellation diagram of a 1 Mb / s 4-orthogonal amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal is shown at a transmission distance of 20 m;

[0023] Figure 6 This is a schematic diagram of another energy-autonomous optical wireless communication receiver with a hybrid solar cell;

[0024] Figure 7 This is a schematic diagram of an optical wireless communication system using an energy-autonomous optical wireless communication receiver with hybrid solar cells;

[0025] Figure 8 The frequency response of the energy-autonomous optical wireless communication receiver, measured on a 20m air channel before and after hardware equalization, is shown.

[0026] Figure 9This shows the relationship between bit error rate and data rate over a 20m air channel;

[0027] Figure 10A , Figure 10B and Figure 10C The waveform, spectrum, and constellation diagram of a 1.2 Mbit / s OFDM signal at a distance of 30 meters are shown.

[0028] Figure 11 The bit error rate of a 1.2 Mbit / s 4-QAM OFDM signal is shown when the amplifier gain is reduced;

[0029] Figure 12 The measured solar irradiance, the power collected by the solar cells, and the power consumed by the energy-autonomous optical wireless communication receiver are shown.

[0030] Figure 13 The solar spectrum measured at the solar cell collection point is shown;

[0031] Figure 14 A screen showing an energy-efficient autonomous optical wireless communication receiver displays various parameters;

[0032] Figure 15 The bit error rate of the 1.2 Mbit / s OFDM signal received for different subcarriers after transmission through a 15 m air channel is shown.

[0033] Figure 16 The absorption, scattering, and attenuation coefficients of water are shown in the diagram, in which an energy-autonomous optical wireless communication receiver is deployed and tested.

[0034] Figure 17 The bit error rate of the 1.2 Mbit / s OFDM signal received for different subcarriers after transmission through a 2m turbid water channel is shown.

[0035] Figure 18 The results obtained for the energy-autonomous optical wireless communication receiver in laboratory test benches and various field tests are shown; and

[0036] Figure 19 This is a flowchart of a method for simultaneously collecting energy and transmitting data using an energy-autonomous optical wireless communication receiver. Detailed Implementation

[0037] The following description of the embodiments refers to the accompanying drawings. The same reference numerals in different drawings denote the same or similar elements. The following detailed description does not limit the invention. Rather, the scope of the invention is defined by the appended claims. For simplicity, the following embodiments are discussed for an energy-autonomous OWC system using two different types of solar cells to achieve energy harvesting and signal communication. However, the embodiments discussed below are not limited to only two types of solar cells or are limited to the dual functions of energy harvesting and signal communication.

[0038] Throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0039] According to one embodiment, a fully energy-autonomous hybrid solar cell receiver is provided for various application scenarios. In this embodiment, the hybrid solar cell receiver simultaneously utilizes a monocrystalline Si solar panel with high PCE for efficient energy harvesting and a thin-film amorphous Si (a-Si) solar panel with high light absorption coefficient for low-intensity light signal detection. In this document, a large PCE is considered to be greater than 10%, or even greater than 20%. In this document, a high light absorption coefficient of the solar cell is considered to be 10-1 per centimeter. 6 Up to 10 2 (Depending on the wavelength of the incident light). Compared to existing systems [1-7] that use only one type of solar cell for both energy harvesting and signal detection, the proposed novel hybrid solar cell receiver can fully utilize different types of solar cells to independently improve energy harvesting and the system's communication performance.

[0040] More specifically, Figure 1A One embodiment is shown in which a hybrid solar cell receiver 100 includes at least two types of solar cells: a first solar module 110, which includes one or more collecting solar cells 112 with high PCE; and a second solar module 120, which includes one or more communication solar cells 122 with high light absorption coefficients. In one application, the plurality of collecting solar cells are made of different materials from the plurality of communication solar cells. In this application or another application, the plurality of collecting solar cells are most sensitive to a first wavelength, and the plurality of communication solar cells are most sensitive to a second wavelength different from the first wavelength. For example, the first wavelength may be in the visible wavelength range, while the second wavelength may be in the ultraviolet wavelength range.

[0041] The first solar module 110 is electrically connected to the rechargeable battery 130 via a first switch 114. The first switch 114 may be an electronic switch, implemented, for example, using solid-state electronic devices such as integrated circuits or transistors, and is electronically controlled by a microcontroller unit (MCU) 140. The first switch 114 may be configured to have only two states: (1) a first collection state, in which the first solar module 110 is directly electrically connected to the rechargeable battery 130 (or the electronic device 116 associated with the battery 130), for the purpose of converting incident light into electrical energy and storing that energy; and (2) a second communication state, in which the first solar module is directly electrically connected to an amplifier 152, which is part of a communication module 150, for the purpose of feeding data-encoded light to the communication module for data retrieval. In one application, the amplifier 152 may be a transimpedance amplifier (TIA).

[0042] The second switch 124 can also be configured to have only two states: (1) a first communication state, in which the second solar module 120 is directly electrically connected to the communication module 150, and the purpose of this state is to convert the incident light into an electrical signal that retains the encoded data and provide the electrical signal to the communication module for data extraction; and (2) a second collection state, in which the second solar module 120 is directly electrically connected to the battery 130 to convert the incident light into electrical energy and store the electrical energy in the battery, regardless of the encoded data. The battery 130 can be any type of known rechargeable battery. The battery 130 is electrically connected to all other electronic components of the receiver 100 via corresponding electrical links 130A to 130D to provide electrical energy. The second switch 124 can be an electronic switch, for example implemented with solid-state electronic devices such as integrated circuits or transistors, which is electronically controlled by the microcontroller unit 140.

[0043] In addition to amplifier 152, communication module 150 also includes filter 154, another amplifier 156, and analog-to-digital converter 158. In this configuration, TIA 152 converts the photocurrent generated by the harvesting solar cell 112 with a high PCE or the communication solar cell 122 with a high light absorption coefficient into a voltage signal 153. Filter 154 removes noise from the voltage signal 153 to generate a denoised voltage signal 155, and amplifier 156 amplifies the denoised voltage signal 155 to improve the signal-to-noise ratio of the received optical signal 121, thereby generating an analog signal 157. A / D converter 158 digitizes the analog signal 157 to generate a digital signal 159, which can be further processed, for example at processor 140, to extract the data encoded into the incident optical signal 121. Receiver 100 shown in the figure can be part of a router, computer, smart device, sensor, drone, aircraft, underwater vehicle, land-based vehicle, etc., for providing data communication and energy harvesting.

[0044] MCU 140 is configured to monitor the power of rechargeable battery 130 via link 142 and control an optional display screen 151 to display desired parameters of receiver 100 in real time, such as the output voltage and current of the high-PCE collecting solar cell 112, the voltage and current consumed by rechargeable battery 130, and the remaining capacity of rechargeable battery 130. Rechargeable batteries 130 are used to store energy collected by the high-PCE collecting solar cell 112 or the high-light absorption coefficient communication solar cell 122, and they fully power TIA 152, filter 154, amplifier 156, A / D converter 158, MCU 140, and display screen 151 (if present), making the receiver energy autonomous. This means that in this embodiment, receiver 100 has no other energy source besides the energy generated by the solar cells and stored in battery 130.

[0045] The high-PCE harvesting solar cell 112 is primarily used for energy harvesting, which helps to shorten the charging time of the rechargeable battery. Therefore, the first switch 114 is mainly kept in the first harvesting state. However, if the high-PCE harvesting solar cell 112 has high bandwidth, it can also be used for high-speed OWC. If this is the case, the MCU 140 instructs the first switch 114 to change its state from the first harvesting state to the aforementioned second communication state, that is, to directly connect the harvesting solar cell 112 to the communication module 150.

[0046] For example, MCU 140 is configured to detect that digital signal 159 (or any other signal used in communication module 150, see link 144 to module 150) contains instructions, commands, or data indicating that communication message 121 received at the second solar module 120 requires high-speed or high-quality data transmission. This might be the case when a movie is being transmitted and the data packet requires high priority. The opposite is true when an email transmission is being performed and is considered low priority. Based on this information, and knowing the possible data transmission speed and / or quality through the second solar module 120, MCU 140 can determine the speed and / or quality of the supplementary transmission by switching the first switch 114 from a first collection state to a second communication state, such that signal 111 from the first solar module 110 is also used for communication purposes instead of for energy collection. To achieve this change, MCU 140 is electrically connected to the first switch 114 via electrical connector 115. As will be discussed later, MCU 140 is similarly connected to the second switch 124 via electrical connector 125. In this scenario, both the first solar module 110 and the second solar module 120 feed their received data 111 and 121 to the communication module 150 for communication processing only. At this time, the entire receiver 100 operates based on the energy already stored in the battery 130. MCU 140 automatically switches the first switch from a first collection state to a second communication state, based entirely on the data stored in the received signal 121 and the capabilities of the second solar module 120, without manual intervention, or when the measured data rate through the communication module is less than a given threshold. In one application, this change can be generated using a time factor; for example, if the current time at MCU 140 is between dusk and dawn, the first collection state of the first switch 114 automatically changes to the second communication state, regardless of the data embedded in the received signal 121, because there is no solar energy to collect. This situation changes if another light source is used instead of the sun for collection. MCU 140 can utilize other factors to determine when to change the state of the first switch.

[0047] Similar to the dual objectives of the collecting solar cell 112, the communication solar cell 122, with its high light absorption coefficient, can not only function as a detector to achieve reliable and energy-efficient OWC via the communication module 150, but also be used for energy harvesting under low-light conditions because it has a higher response to low light. This means that the MCU 140 can be connected to the light sensor 146, which is located next to or above the first solar module 110, and the light sensor 146 provides information about the light intensity next to the first solar module. When the received light intensity signal has a value below a given threshold, the MCU 140 can be configured to determine that not enough light reaches the collecting solar cell 112, and therefore, the MCU 140 activates the second switch 124 via the dedicated electronic connector 125, changing the switch from a first communication state to a second harvesting state, in which the communication solar cell 122 acts as an energy harvesting battery, and all electrical energy converted from the received light energy is sent to the battery 130. This means that in this case, all solar cells 112 and 122 are only used to harvest energy and charge the battery 130. This also means that no light communication occurs during this phase. For example, when the MCU determines that the power level of battery 130 is below a certain threshold (e.g., 10%), the MCU 140 can switch the second switch 124 from the first communication state to the second collection state. Other values ​​can be used. This means that whenever the MCU determines that battery 130 has insufficient resources and the light intensity at the collection solar cell 112, as measured by sensor 146, is also low, the MCU decides that the communication solar cell 122 needs to assist the collection solar cell 112 in charging battery 130. It is important to note that since receiver 100 is energy autonomous, ensuring the proper functioning and charging of battery 130 is one of the MCU's key objectives. Therefore, the collection solar cell 112 with a high PCE and the communication solar cell 122 with a high light absorption coefficient constitute a switchable light receiver, which can be switched according to a possible application scenario, as discussed now.

[0048] like Figure 1B As shown, when communication is not required, sunlight intensity is greater than a few μW / cm². 2 Furthermore, the light from the communication light source is much greater than a few μW / cm². 2 At that time, both high-PCE solar cells for energy harvesting and high-light-absorption solar cells for communication were used to harvest energy from sunlight and other light sources. Note that the system discussed herein is capable of using one light source (e.g., the sun) for energy harvesting purposes and another light source (e.g., a laser) for communication purposes. Therefore, Figure 1AIncident beam 111 in the figure can be sunlight, while incident beam 121 in the same figure can be a laser beam. In one application, both beams 111 and 121 are generated by the same light source, such as a laser device. A laser device is just one example. Those skilled in the art will understand that a laser device can be replaced by any light-emitting device. Furthermore, the wavelength ranges of the two incident beams 111 and 121 can be different, for example, visible light for beam 111 and UV or IR light for beam 121. In one application, both beams 111 and 122 are received by each of solar cells 110 and 120, but the solar cells can be configured to process only one or both of the beams.

[0049] like Figure 1C As shown, when communication is not required, sunlight is weak (approximately a few μW / cm²). 2 Furthermore, the light from the communication light source is weak (approximately a few μW / cm²). 2 When a communication solar cell with a high light absorption coefficient is used, it is used to harvest energy from sunlight and communication light sources.

[0050] like Figure 1B As shown, when communication is not required, sunlight is much stronger than approximately a few μW / cm². 2 And the light from the light source is weak (approximately a few μW / cm²). 2 When solar cells are used to collect energy from sunlight, communication solar cells with high light absorption coefficients are used to collect energy from sunlight and light sources.

[0051] like Figure 1B As shown, when communication is not required, sunlight is weak (approximately a few μW / cm²). 2 Furthermore, the light from the light source is much greater than a few μW / cm². 2 At that time, solar cells with high PCE are used to harvest energy from communication light sources, and communication solar cells with high light absorption coefficients are used to harvest energy from both sunlight and communication light sources.

[0052] like Figure 1D As shown, when the energy available for communication is sufficient (i.e., the stored energy exceeds the power requirements of the communication circuit) and communication is needed, sunlight is much stronger than a few μW / cm². 2 Furthermore, the light from the communication light source is much greater than a few μW / cm². 2 At the same time, communication solar cells with high light absorption coefficients are used to harvest energy from sunlight and communication light sources, while harvesting solar cells with high PCE are used to simultaneously perform signal detection and harvest energy from sunlight and light sources.

[0053] like Figure 1E As shown, when there is sufficient energy for communication and communication is required, sunlight is weak (approximately a few μW / cm²). 2Furthermore, the light from the communication light source is weak (approximately μW / cm²). 2 When a communication solar cell with a high light absorption coefficient is used, it is used to simultaneously detect signals and harvest energy from sunlight and communication light sources.

[0054] like Figure 1F As shown, when there is sufficient energy for communication and communication is required, sunlight is much stronger than a few μW / cm². 2 And the light from the light source is weak (approximately a few μW / cm²). 2 In this context, high PCE-based solar cells are used to harvest energy from sunlight, while high light absorption coefficient-based communication solar cells are used to simultaneously perform signal detection and harvest energy from both sunlight and communication light sources.

[0055] like Figure 1D As shown, when there is sufficient energy for communication and communication is required, sunlight is weak (approximately a few μW / cm²). 2 Furthermore, the light from the communication light source is much greater than a few μW / cm². 2 At the same time, communication solar cells with high light absorption coefficients are used to harvest energy from sunlight, and harvesting solar cells with high light absorption coefficients (PCE) are used to simultaneously perform signal detection and harvest energy from the light source.

[0056] like Figure 1B As shown, when the energy available for communication is insufficient (i.e., the stored energy is less than the power requirements of the communication circuit), and communication is still needed, sunlight has a power density much greater than approximately a few μW / cm². 2 Furthermore, the light from the communication light source is much greater than a few μW / cm². 2 At that time, both high-PCE solar cells for energy collection and high-light-absorption solar cells for communication are used to harvest energy from sunlight and communication light sources. For example... Figure 1D As shown, when there is sufficient energy for communication, a communication solar cell with a high light absorption coefficient is used to harvest energy from sunlight and communication light sources, and a harvesting solar cell with a high PCE is used to simultaneously perform signal detection and harvest energy from sunlight and communication light sources.

[0057] like Figure 1C As shown, when there is insufficient energy for communication but communication is required, sunlight is weak (approximately a few μW / cm²). 2 Furthermore, the light from the communication light source is weak (approximately a few μW / cm²). 2 In this context, communication solar cells with high light absorption coefficients are used to harvest energy from sunlight and communication light sources. For example... Figure 1E As shown, when there is sufficient energy for communication, a communication solar cell with a high light absorption coefficient can be used to simultaneously perform signal detection and harvest energy from both sunlight and communication light sources.

[0058] like Figure 1BAs shown, when the energy available for communication is insufficient, and communication is still required, sunlight has a power density far exceeding a few μW / cm². 2 And the light from the light source is weak (approximately a few μW / cm²). 2 In this context, high-PCE solar cells are used to harvest energy from sunlight, and high-light-absorption-coefficient communication solar cells are used to harvest energy from both sunlight and communication light sources. For example... Figure 1F As shown, when there is sufficient energy for communication, a harvesting solar cell with a high PCE is used to harvest energy from sunlight, and a communication solar cell with a high light absorption coefficient is used to simultaneously perform signal detection and harvest energy from both sunlight and communication light sources.

[0059] like Figure 1B As shown, when there is insufficient energy for communication but communication is required, sunlight is weak (approximately a few μW / cm²). 2 Furthermore, the light from the communication light source is intense, exceeding several μW / cm². 2 At that time, solar cells with high PCE are used to harvest energy from communication light sources, and communication solar cells with high light absorption coefficients are used to harvest energy from both sunlight and communication light sources. For example... Figure 1D As shown, when there is sufficient energy for communication, a communication solar cell with a high light absorption coefficient is used to harvest energy from sunlight, and a harvesting solar cell with a high light PCE is used to simultaneously perform signal detection and harvest energy from the communication light source.

[0060] although Figure 1A The diagram shows the collecting solar cell 112 forming the first solar module 110 and the communication solar cell 122 forming the second solar module 120 placed separately. However, in one embodiment, the two types of cells can be combined in a single panel 102 or placed adjacent to each other, as shown. Figure 2A As shown in the figure. In the embodiment shown, communication solar cells 122 are inserted between the collecting solar cells 112 along both the X and Y axes. However, in one embodiment, cells 112 and 122 may be inserted along only a single axis. Although individual cells 112 and 122 are inserted, their electrical connections are configured such that the collecting solar cells 112 are electrically connected only to themselves and the communication solar cells 122 are electrically connected only to themselves, as shown in the figure. Figure 1A As shown. In other words, in this embodiment, there is no collecting solar cell electrically connected to the communication solar cell; that is, these cells are only in mechanical contact with each other and not in electrical contact. Other modes can be used to distribute cells 112 and 122 in a single solar panel 102. In one application, the distribution of cells 112 and 122 is non-uniform, for example, random.

[0061] The patterned distribution of cells 112 and 122 has the following advantages. If OWC is implemented for the communication solar cell 122, the light beam needs to be aligned with the light receiver so that the light signal is received by the solar cell. This alignment requirement is a serious problem for existing devices. However, this alignment problem is greatly alleviated when multiple communication solar cells are used and distributed over a larger area, because when the solar cells are distributed across the entire panel 102, the incident light beam may hit at least one of the communication solar cells 122.

[0062] The size of the communication solar cell 122 affects the speed of optical communication that can be achieved using the communication module 150. For example, if the area of ​​each solar cell 122 is approximately 1 cm²... 2 Up to 100cm 2 The maximum data transmission speed is in the range of Mbit / s. However, if the area of ​​each solar cell 122 is less than 1 cm², the maximum data transmission speed is within the range of Mbit / s. 2 Therefore, this configuration can achieve speeds of approximately Gbit / s. As long as the total area of ​​the collecting solar cells exceeds a given number, the area of ​​a single collecting solar cell 112 is irrelevant to energy harvesting. In one application, each of the collecting solar cells 112 may have a size L, one or more of the communication solar cells 122A may have the same size L, one or more of the other communication solar cells 122B may have a smaller size L1, and one or more of the other communication solar cells 122C may have an even smaller size L2, such as... Figure 2B As shown. In this embodiment, L1 and L2 are factors of L. In one embodiment, for a given module 102, only one of the communication solar cells 122A, 122B, or 122C can be used. However, in another embodiment, depending on the desired application, any combination of cells 122A to 122C or other smaller cells can be used.

[0063] The inventors have implemented a communication solar cell 122 using amorphous silicon (a-Si) thin-film solar cells with high light absorption coefficients. The current density of the a-Si thin-film solar cell was measured at different power intensities. Figure 3 As shown, a-Si thin-film solar cells at 10 -1 mW / cm 2 It has a minimum possible illuminance of 2.6 μA / cm. 2 High current density. Furthermore, a-Si thin-film solar cells exhibit a sufficiently low current density, approximately 3.2 nA / cm². 2The dark current density is 300, which results in a sufficiently large separation between the dark current and bright current for the detection of low-intensity light signals. Assuming a good linear dynamic response, the a-Si thin-film solar cell is expected to be able to detect 1 μW / cm². 2 Low-intensity light signals.

[0064] Using these solar cells, a system comprising a white laser as the optical communication beam source and an a-Si thin-film solar cell as the optical receiver for cell 122 was employed to further investigate the performance of a-Si thin-film solar cells in low-intensity optical signal detection. In the experiment, a distance of 20 m and a wavelength of 1385 cm⁻¹ were measured. 2 Illuminance distribution within an area, such as Figure 4 As shown, the area of ​​the light spot at a distance of 20m is much larger than the area of ​​the a-Si thin-film solar cell (36cm²). 2 The average illuminance of the a-Si thin-film solar cell is only 79.95 lx. Under these conditions, a 1 Mbit / s 4-orthogonal amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal was achieved using only a system bandwidth of 290 kHz. The bit error rate is 1.642 × 10⁻⁶. -3 The corresponding constellation chart is as follows Figure 5 As shown, the constellation diagram converges well. These results demonstrate that a-Si thin-film solar cells exhibit good robustness in low-intensity light signal detection. Furthermore, according to... Figure 4 It can be inferred that a data rate of 1 Mbit / s can still be achieved within an illumination area of ​​approximately 9 cm in radius at a distance of 20 m. This implies that white lasers and systems based on a-Si thin-film solar cells have great potential in alleviating link alignment problems.

[0065] In another embodiment, such as Figure 1A The receiver 100 shown has been modified to implement amplifier 156 as a programmable gain amplifier (PGA) and add demodulation unit 620 for demodulating digitized signal 159 and extracting embedded information, such as... Figure 6 The receiver 600 is shown in the diagram. Compared to using an amplifier with a fixed gain, the proposed scheme can automatically adjust the gain based on the remaining power to optimize communication performance. To test the communication performance, the inventors conducted experiments on a laboratory test bench of the system 700, which includes the receiver 600 and the transmitter 702, as shown in the diagram. Figure 7As shown, using a modified receiver 600 and a white light laser 710 for transmitter 702 (note that laser 710 is supported by electronics 711 that encodes data into beam 720), the inventors achieved illumination transmission at distances of 20m and 30m, and visible light communication (VLC) at data rates of 1.6 Mbit / s and 1.2 Mbit / s, respectively. Electronics 711 may include an arbitrary waveform generator (AWG) 712 configured to transmit a four-quadrature amplitude modulation (4-QAM) OFDM signal. After transmission via amplifier (AMP) 714 and attenuator (ATT) 716, the signal is superimposed on white light laser 710 via bias T (bias-T) 718. In this embodiment, white light laser 710 with a bias current of 670mA is used for simultaneous illumination and communication.

[0066] To investigate the performance of System 700 in simultaneous energy harvesting and VLC, field tests were conducted on a photovoltaic solar cell test bench. Energy autonomy was achieved using solar cell module 110 under direct sunlight. An OFDM signal with a data rate of 1.2 Mbit / s was obtained on an air channel 720 at a distance of 15 m. This demonstrates that System 600 exhibits good performance in energy harvesting, low-intensity light signal detection, and immunity to background noise. The inventors also investigated the communication performance of System 600 in a more challenging environment: namely, underwater in the turbid waters of the Red Sea, a 2 m transmission distance was successfully achieved at a data rate of 1.2 Mbit / s without precise link alignment. This implies that receiver 100 or 600 can be used in underwater mobile sensor networks. For this experiment, solar module 120 had a length of 6 cm and a width of 6 cm. It could detect signals as weak as 1 μW / cm². 2 The light source is beneficial for achieving long-distance VLC.

[0067] To achieve energy balance, a monocrystalline silicon solar panel 110 is used for energy harvesting and is implemented as two off-the-shelf, series-connected monocrystalline silicon solar cells to provide 156cm² energy. 2The total effective area is 13 cm long and 12 cm wide. Energy collected by the monocrystalline silicon solar panel 110 is stored in two cells. When communicating using the thin-film a-Si solar module 120, the generated photocurrent is first converted to voltage using a TIA 152 and then sent to a low-pass filter (LPF) 154 to remove noise, which improves the signal-to-noise ratio (SNR) of the received signal. Note that a microcontroller unit 140 is used to monitor the cell power in real time. The voltage gain of the PGA 156 automatically changes according to the cell power, which saves energy and helps enhance communication performance by increasing the signal amplitude. Finally, the output signal 159 is captured by a mixed-signal oscilloscope (MSO) and demodulated offline. A display screen 151 is used to display some parameters of the system 600 in real time. Since all components consume only a small amount of power, the total power consumption of the system 600 is only about 500 mW.

[0068] For the experiments on the laboratory test bench, the frequency response of the system was first measured in a 20m air channel. Through hardware pre-equalization, the -3dB bandwidth of System 600 and VLC System 700 based on white laser was increased from 290kHz[1] to 348kHz, such as Figure 8 As shown. Next, the inventors investigated the maximum data rate achievable over a 20m air channel when the PGA has its maximum gain (74dB). The relationship between bit error rate (BER) and data rate is as follows. Figure 9 As shown, the insets are constellation diagrams for 4-QAM OFDM signals at data rates of 1 Mbit / s and 1.6 Mbit / s, respectively. Note that symbols transmitted at different time intervals were recorded, and the average BER was calculated to improve the reliability of the experiments. Therefore, the different shades in the constellation diagrams represent symbols transmitted at different time intervals. The results show that the maximum achievable data rate is 1.6 Mbit / s, and the BER is 1.814 × 10⁻⁶. -3 Below 3.8×10 -3 Forward error correction (FEC) limits.

[0069] The inventors also investigated the maximum data rate supported by the maximum gain (74dB) of the PGA at a greater distance of 30m. The BERs of OFDM signals at 1 Mbit / s, 1.2 Mbit / s, and 1.4 Mbit / s were 2.257 × 10⁻⁶. -3 2.131×10 -3 and 6.450×10 -3 Therefore, the maximum data rate at 30m is 1.2 Mbit / s. The corresponding waveform, spectrum, and constellation diagram are as follows: Figure 10A , Figure 10B and Figure 10C As shown. From Figure 10AThe waveform shown indicates that, over a 30m air channel, the average peak-to-peak amplitude of the 1.2 Mbit / s OFDM signal amplified by the PGA on the receiver side is as high as 160.9 mV, which provides a relatively high signal-to-noise ratio. Figure 10B The spectrum shown also indicates that the SNR is high enough to support signal transmission at 600 kHz (i.e., 1.2 Mbit / s).

[0070] Considering that the gain in the PGA decreases as battery power in the receiving circuit is consumed, the inventors investigated the impact of PGA gain on communication performance. The gain in the PGA at different battery levels is shown on a display screen (not shown), where V... sun and I sun These represent the output voltage and current of the monocrystalline silicon solar panel, respectively. Therefore, V sun and I sun The product of V and y is the power extracted from sunlight. b and I b These represent the total voltage and total current consumed by the two types of batteries, respectively. Power represents the power consumed by the system at 600V, which is expressed in V. b and I b The product of the two. Gain refers to the gain generated by the PGA. The remaining capacity of both batteries is also displayed on display 151. Note that as power is consumed, the PGA gain gradually decreases from 73dB to 69dB. Figure 11 As shown, when the PGA gain decreases from 73dB to 69dB, the BER of the 1.2Mbit / s 4-QAM OFDM signal remains within a very small range (approximately 10). -4 The signal fluctuates, but remains below the FEC limit. The inset shows the constellation of a 1.2 Mbit / s 4-QAM OFDM signal with good convergence when the PGA gain is 69 dB. This means that even though the PGA gain decreases to 69 dB as the battery level drops, it is still high enough to provide a high SNR and thus support 1.2 Mbit / s data transmission over 20 m.

[0071] In the field test, the inventors first measured the solar irradiance, the power collected by the monocrystalline silicon solar panel 110, and the power consumed by the receiver circuit at different times, such as... Figure 12As shown, solar irradiance increases between 9:00 AM and 12:00 PM and decreases between 12:00 PM and 5:00 PM. The collected and consumed power fluctuates within a small range at different times, but the total collected power is always greater than the consumed power. This indicates that the receiver 600 is energy autonomous. Excess collected energy is stored in the battery for backup. In one application, the collected power can be further increased by using an autonomous solar tracking system, and the consumed power can be further reduced by using a wake-up strategy, which helps to shorten the battery charging time.

[0072] Next, the inventors demonstrated the superiority of the white light laser 710 and receiver 600 in realizing long-distance VLC systems under strong background sunlight. Figure 13 The solar spectrum measured during the field test is shown. The measured solar illuminance was 75080.28 lx. Recorded parameters for the system 600 used for simultaneous energy harvesting and VLC under bright sunlight are shown below. Figure 14 As shown. On the display screen, V sun and I sun The voltages are 10.31V and 150mA, respectively. Therefore, the power harvested from sunlight is 1.5465W. b and I b The voltages are 7.85V and 64.6mA, respectively. Therefore, the power consumption of System 600 is 0.51W. Under specific conditions, the gain is 72dB, and a 4-QAM OFDM signal of 1.2Mbit / s is obtained after transmission over a 15m air channel. Figure 15 The BER of a 1.2 Mbit / s OFDM signal received for different subcarriers is shown. The higher BER in the low-frequency region is attributed to strong optical background noise. However, the total BER is 1.624 × 10⁻⁶. -4 This is below the FEC limit. The corresponding constellation diagram is as follows: Figure 15 As shown in the illustration, the convergence is good. This indicates that the receiver 600 has good performance in terms of background noise immunity and low-intensity light signal detection in long-distance VLC under strong sunlight.

[0073] The inventors also investigated the underwater communication performance of receiver 600. Note that the transmitter and receiver were not perfectly aligned due to uneven terrain. Furthermore, since the underwater field trial was primarily designed to test communication performance, the monocrystalline silicon solar panels used for energy harvesting were not connected to system 600. However, system 600 can be deployed in surface or shallow waters where sunlight can reach, enabling simultaneous energy harvesting and VLC. It can also be mounted on an autonomous underwater vehicle (AUV), allowing it to recharge in surface or shallow water after completing its mission in deep water. Therefore, it will play a significant role in future self-powered underwater IoT, significantly alleviating underwater energy shortages.

[0074] Figure 16 The absorption coefficient (a), scattering coefficient (b), and attenuation coefficient (c) of water, measured by an AC-S spectral absorption and attenuation sensor at different wavelengths λ, are displayed. Based on these values, the water type at the port is optically complex, such as in coastal areas, primarily composed of inorganic suspended particles, such as sediment. Various suspended particles are suspended between the transmitter and receiver. In these cases, a transmission distance of 2 m was still achieved at a data rate of 1.2 Mbit / s without strict link alignment. Figure 17 The BER of a 1.2 Mbit / s OFDM signal received across all subcarriers is shown. Some random noise is noticeable in the spectrum. However, the average BER is 6.125 × 10⁻⁶. -4 This is below the FEC limit. The corresponding constellation diagram is as follows: Figure 17 As shown in the illustration, convergence is good. This indicates that the receiver 600, with its large detection area, support for low-intensity light signal detection, and resistance to background noise, exhibits good robustness in turbid water. Furthermore, given these advantages, the system 600 can be used in future underwater mobile sensor networks to alleviate the stringent requirements for pointing, acquisition, and tracking.

[0075] Hybrid solar cell receivers 100 or 600, comprising at least two types of solar cells, have been described for simultaneous high-efficiency energy harvesting and low-intensity light signal detection. Results obtained from laboratory test benches (onshore) and various field tests (onshore and at sea) are listed below. Figure 18 Table 1 shows that, using hardware pre-equalization technology and OFDM on a laboratory test bench, the -3dB bandwidth of receiver 600 was increased from 290kHz to 340kHz, and the achievable data rate at a distance of 20m was increased from 1Mbit / s to 1.6Mbit / s. Furthermore, due to the high absorption efficiency of the thin-film a-Si solar cell, illumination and VLC over a distance of 30m were achieved at a data rate of 1.2Mbit / s. On an outdoor solar cell test bench, system 600 performed well in terms of background noise immunity, attributed to the PGA and filter design in the hardware, the gap design in the OFDM, and the selection of low-noise components. Energy autonomy was achieved under bright sunlight, and a transmission distance of 15 meters was achieved at a data rate of 1.2Mbit / s. In a more challenging field test underwater (at a local port), an OFDM signal of 1.2Mbit / s was obtained over a 2-meter transmission distance without strict link alignment, demonstrating the good robustness of receiver 600 with a large detection area. Given the above, energy-autonomous solar cell receivers, which have the advantages of efficient energy harvesting, low-intensity light signal detection, and resistance to background noise, have wide applications in IoT and underwater mobile sensor networks.

[0076] Now about Figure 19 A method for simultaneously performing energy harvesting and data communication is discussed. The method includes: step 1900 of receiving light at multiple harvesting solar cells and converting the light into electrical energy; step 1902 of storing the electrical energy in a rechargeable battery; step 1904 of receiving light at multiple communication solar cells and converting the light into electrical signals embedded with information; and step 1906 of decoding the electrical signals generated by the multiple communication solar cells and extracting the information at a communication module. The multiple harvesting solar cells, the rechargeable battery, the multiple communication solar cells, and the communication module are part of a single optical wireless communication receiver, and the storage and decoding steps are performed simultaneously.

[0077] The method may further include: changing a first collection state of a first switch that electrically connects the plurality of collecting solar cells to the rechargeable battery to a second communication state, thereby electrically connecting the plurality of collecting solar cells to the communication module; and / or changing a first communication state of a second switch that electrically connects the plurality of communication solar cells to the communication module to a second collection state, thereby electrically connecting the plurality of communication solar cells to the rechargeable battery. The method may further include: measuring the data rate in the communication module using a microprocessor and changing the first switch from the first collection state to the second communication state when the rate is below a given speed threshold; and / or measuring the power level of the rechargeable battery and changing the second switch from the first communication state to the second collection state when the power level is below a power threshold. In one application, the plurality of collecting solar cells are staggered with the plurality of communication solar cells along two mutually perpendicular axes. The plurality of collecting solar cells are most sensitive to a first wavelength, and the plurality of communication solar cells are most sensitive to a second wavelength different from the first wavelength.

[0078] The disclosed embodiments provide an energy-autonomous optical wireless communication system using a switchable hybrid optical receiver. It should be understood that this description is not intended to limit the invention. Rather, the embodiments are intended to cover alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. Furthermore, numerous specific details are set forth in the detailed description of the embodiments to provide a full understanding of the claimed invention. However, those skilled in the art will understand that various embodiments can be practiced without these specific details.

[0079] Although the features and elements of this embodiment are described in specific combinations in the embodiments, each feature or element may be used alone without using other features and elements of the embodiments, or may be used in combination with other features or elements disclosed herein.

[0080] This written description uses examples of the disclosed subject matter to enable those skilled in the art to practice the same methods, including manufacturing and using any device or system and performing any combined methods. The patentable scope of the subject matter is defined by the claims and may include other examples as may be conceived by those skilled in the art. Such other examples are intended to fall within the scope of the claims.

[0081] References

[0082] The entire contents of all publications listed herein are incorporated herein by reference.

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[0085] [3] M. Kong, B. Sun, R. Sarwar, J. Shen, Y. Chen, F. Qu, J. Han, J. Chen, H. Qin, and J. Xu, Underwater wireless optical communication using alens-free solar panel receiver, Optics Communications, vol. 426, pp. 94–98, 2018.

[0086] [4]H.Y.Wang,J.T.Wu,C.W.Chow,Y.Liu,C.H.Yeh,X.L.Liao,K.H.Lin,W.L.Wu,andY.Y.Chen,Using pre-distorted PAM-4 signal andparallel resistance circuit toenhance the passive solar cell based visible lightcommunication,OpticsCommunications,vol.407,pp.245–249,2018.

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Claims

1. An optical wireless communication receiver (100 / 600), comprising: One or more solar cells (112) are configured to convert light into electrical energy; One or more communication solar cells (122) are configured to convert light into electrical signals embedded with information; A rechargeable battery (130) is configured to store electrical energy generated by the one or more collecting solar cells (112); A communication module (150) is configured to decode electrical signals generated by the one or more communication solar cells (122) and extract the information; A first switch (114) is configured to connect one or more collecting solar cells (112) to the rechargeable battery (130) to achieve a first collecting state, and to connect to the communication module (150) to achieve a second communication state; A second switch (124) is configured to connect one or more communication solar cells (122) to the communication module (150) to achieve a first communication state, and to connect to the rechargeable battery (130) to achieve a second collection state; and The microprocessor (140) is configured to control the first switch (114) based solely on 1) data stored in an electrical signal embedded with the information, or 2) a measurement of the data rate of the communication module (150), and to control the second switch (124) based on the power level in the rechargeable battery (130).

2. The receiver of claim 1, wherein the one or more collecting solar cells are interleaved with the one or more communicating solar cells along a first axis.

3. The receiver of claim 1, wherein the receiver has no other power source.

4. The receiver of claim 1, wherein the area of ​​the solar cells in the one or more collecting solar cells is greater than the area of ​​the solar cells in the one or more communicating solar cells.

5. The receiver of claim 1, wherein the microprocessor is configured to instruct a first switch to change from a first collection state to a second communication state, such that when the collection solar cell acts as a communication solar cell, an electrical signal generated by the one or more collection solar cells is transmitted to the communication module.

6. The receiver of claim 5, wherein when the data communication speed is higher than a given threshold, the microprocessor instructs the first switch to change from a first collection state to a second communication state.

7. The receiver of claim 1, wherein the microprocessor is configured to instruct a second switch to change from a first communication state to a second collection state, such that an electrical signal generated by the one or more communication solar cells is added as electrical energy to the rechargeable battery.

8. The receiver of claim 7, wherein when the power level in the rechargeable battery is below a given threshold, the microprocessor instructs the second switch to change from a first communication state to a second collection state.

9. The receiver of claim 1, wherein the one or more collecting solar cells are made of a different material than the one or more communicating solar cells.

10. The receiver of claim 1, wherein the one or more collecting solar cells are most sensitive to a first wavelength, and the one or more communicating solar cells are most sensitive to a second wavelength different from the first wavelength.

11. A method for performing energy harvesting and data communication, the method comprising: Light is received at one or more solar cells (112) and converted into electrical energy; The electrical energy is stored in a rechargeable battery (130); Light is received at one or more communication solar cells (122) and converted into electrical signals embedded with information; The electrical signals generated by the one or more communication solar cells (122) are decoded and the information is extracted at the communication module (150); The one or more collecting solar cells (112) are connected to the rechargeable battery (130) at the first switch (114) to achieve a first collecting state, and connected to the communication module (150) to achieve a second communication state; One or more communication solar cells (122) are connected to the communication module (150) at the second switch (124) to achieve a first communication state, and connected to the rechargeable battery (130) to achieve a second collection state; as well as The first switch (114) is controlled at the microprocessor (140) based solely on 1) data stored in an electrical signal embedded with the information, or 2) a measurement of the data rate of the communication module (150), and the second switch (124) is controlled based on the power level in the rechargeable battery (130). Wherein, the one or more collecting solar cells, the rechargeable battery, the one or more communication solar cells, and the communication module are part of a single optical wireless communication receiver (100, 600), and The storage step and the decoding step are performed simultaneously.

12. The method of claim 11, further comprising: The first state of the first switch (114) that electrically connects one or more collecting solar cells (112) to the rechargeable battery (130) is changed to a second communication state, such that when the collecting solar cells act as communication solar cells, the first switch electrically connects one or more collecting solar cells (112) to the communication module (150).

13. The method of claim 12, further comprising: The first communication state of the second switch (124) that electrically connects one or more communication solar cells (122) to the communication module (150) is changed to a second collection state, such that the second switch electrically connects the communication solar cells to the rechargeable battery.

14. The method of claim 13, further comprising: The microprocessor (140) measures the speed of the data and, when the speed exceeds a given speed threshold, changes the first switch from a first collection state to a second communication state.

15. The method of claim 13, further comprising: The power level of the rechargeable battery is measured, and when the power level is below a power threshold, the second switch is changed from a first communication state to a second collection state.

16. The method of claim 11, wherein the one or more collecting solar cells are interleaved with the one or more communicating solar cells along two mutually perpendicular axes.

17. The method of claim 11, wherein the one or more collecting solar cells are most sensitive to a first wavelength, and the one or more communicating solar cells are most sensitive to a second wavelength different from the first wavelength.

18. An optical communication and energy harvesting system (700), comprising: The transmitter (702) is configured to generate a beam (720) that encodes data. and An optical wireless communication receiver (100 / 600) is configured to simultaneously use the light beam (720) to generate electrical energy and extract encoded data. The optical wireless communication receiver (100 / 600) includes: One or more collecting solar cells (112) are configured to convert the beam of light into electrical energy. One or more communication solar cells (122) are configured to convert a light beam into an electrical signal embedded with data. A rechargeable battery (130) is configured to store electrical energy generated by the one or more collecting solar cells (112); A communication module (150) is configured to decode electrical signals generated by the one or more communication solar cells (122) and extract the data; A first switch (114) is configured to connect one or more collecting solar cells (112) to the rechargeable battery (130) to achieve a first collecting state, and to connect to the communication module (150) to achieve a second communication state; A second switch (124) is configured to connect one or more communication solar cells (122) to the communication module (150) to achieve a first communication state, and to connect to the rechargeable battery (130) to achieve a second collection state; and The microprocessor (140) is configured to control the first switch (114) based solely on 1) data stored in an electrical signal embedded with information, or 2) a measurement of the data rate via the communication module (150), and to control the second switch (124) based on the power level in the rechargeable battery (130).

19. The system of claim 18, wherein the one or more collecting solar cells are interposed with the one or more communicating solar cells along two mutually perpendicular axes.

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