Patent Publication Number: US-2022217640-A1

Title: Method and apparatus for low power transmission using backscattering

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 16/786,340, filed Feb. 2, 2020, the contents of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to low power transmission using backscattering. 
     BACKGROUND 
     Mobile communication devices are increasingly ubiquitous. One feature that tends to define mobile communication devices is a rechargeable battery. It is a common feature of modern life that people go to great lengths to achieve longer battery life. From the device designer&#39;s perspective, one approach to achieve longer battery life involves increasing the capacity of the battery for a given mobile communication device. Another approach involves a power saving approach, wherein the rate of use of the power available from the battery is, in some way, reduced. The power saving approach may be regarded as more critical for low cost devices, such as different types of sensors with built-in communications. 
     SUMMARY 
     Aspects of the present application relate to mobile communication devices having active device components integrated with passive device components and, more particularly, to operation of the passive device components to backscatter a received forward signal. It is assumed that the passive device components will consume less power than the active device components would have consumed while the passive device components perform various functions that would have been performed by the active device components. Conveniently, overall power consumption can be reduced while maintaining, or even enhancing, mobile communication device operation. 
     According to an aspect of the present disclosure, there is provided a method of operating an electronic device. The method includes receiving, by the electronic device, a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal, and transmitting, by the electronic device, a second RF signal, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal. Additionally, aspects of the present application provide an electronic device for carrying out this method and a computer-readable medium containing instructions for causing a processor in an electronic device to carry out this method. 
     According to another aspect of the present disclosure, there is provided a method of obtaining information about an electronic device. The method includes transmitting a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal, and receiving, from an electronic device, a second RF signal, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal. The method optionally comprises processing the backscatter signal to obtain information about the electronic device. Additionally, aspects of the present application provide a network device for carrying out this method and a computer-readable medium containing instructions for causing a processor in a network device to carry out this method. 
     According to a further aspect of the present disclosure, there is provided a network device such as a base station or a transmission and reception point (TRP). The network device includes a memory storing instructions and a processor caused, by executing the instructions, to transmit a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal and receive, from an electronic device, a second RF signal, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal. 
     According to a still further aspect of the present disclosure, there is provided a computer-readable medium on which is stored instructions for a processor in a combination transmission point and reception point. The instructions, when executed by the processor, cause the processor to transmit a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal and receive, from an electronic device, a second RF signal, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal. 
     According to an even further aspect of the present disclosure, there is provided a system. The system includes a base station, a transmission point and a reception point. The transmission point transmits a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal. The reception point receives from an electronic device, a second RF signal, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal, and transmits to the base station the second RF signal. The base station processes the second RF signal to obtain information about the electronic device. 
     In the above aspects, the forward signal may have specific autocorrelation properties. In the above aspects, a network device may associate a cross-correlation value with each time shift value among a plurality of time shift values, the cross-correlation value obtained between the backscatter signal and the forward signal shifted by each time shift value. In the above aspects, a network device may determine a particular time shift value associated with a greatest cross-correlation value among the plurality of cross-correlation values. In the above aspects, a network device may process the particular time shift value to obtain the information about the electronic device. Processing the particular time shift value may comprise: obtaining a value for a relative time difference; and converting the relative time difference to an indication of a position for the electronic device. Processing the particular time shift value may comprise: obtaining indications of boundaries for the contiguous subset of the sub-signals received over the defined duration; and analyzing the boundaries to obtain an indication of a timing for the electronic device. 
     According to aspects of the present disclosure, there is provided a method. The method includes receiving, by the electronic device, a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal, receiving, by the electronic device, signaling indicating a configuration parameter defining a second RF signal, generating, by the electronic device, the second RF signal from the first RF signal without decoding the plurality of sub-signals, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal and transmitting, by the electronic device, the second RF signal. 
     According to aspects of the present disclosure, there is provided a electronic device. The electronic device includes a memory storing instructions and a processor. The processor is caused, by executing the instructions, to receive a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal, receive signaling indicating a configuration parameter defining a second RF signal, generate the second RF signal from the first RF signal without decoding the plurality of sub-signals, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal and transmit the second RF signal. 
     According to aspects of the present disclosure, there is provided a computer-readable medium on which is stored instructions for a processor in an electronic device, the instructions, when executed by the processor, causing the processor to receive a first radio frequency (RF) signal, the first RF signal including a time-domain plurality of sub-signals, each sub-signal comprising an RF-upconverted baseband signal, receive signaling indicating a configuration parameter defining a second RF signal, generate the second RF signal from the first RF signal without decoding the plurality of sub-signals, the second RF signal being a time-domain function of a contiguous subset of the time-domain plurality of sub-signals in the first RF signal and transmit the second RF signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present embodiments, and the advantages thereof, reference is now made, by way of example, to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates, in a schematic diagram, a communication system in which embodiments of the disclosure may occur, the communication system includes example electronic devices and an example base station; 
         FIG. 2  illustrates, as a block diagram, an example electronic device of  FIG. 1 , according to aspects of the present disclosure; 
         FIG. 3  illustrates, as a block diagram, the example base station of  FIG. 1 , according to aspects of the present disclosure; 
         FIG. 4A  illustrates a pair of operation modes for the electronic devices of  FIG. 1  in accordance with aspects of the present application; 
         FIG. 4B  illustrates a state diagram including three Radio Resource Control states and labelled transitions between the states in the context of the operation modes of  FIG. 4A  in accordance with aspects of the present application; 
         FIG. 4C  illustrates a state diagram including three Radio Resource Control states and labelled transitions between the states in the context of the operation modes of  FIG. 4A , as an alternative to the illustration of  FIG. 4B  in accordance with aspects of the present application; 
         FIG. 5A  illustrates, in a flow diagram, a simplified version of the communication system of  FIG. 1 , the flow extends between an electronic device, a transmission point and a reception point in accordance with aspects of the present application; 
         FIG. 5B  illustrates, in a flow diagram, a simplified version of the communication system of  FIG. 1 , the flow extends between an electronic device, a transmission point, a reception point and a base station in accordance with aspects of the present application; 
         FIG. 5C  illustrates, in a flow diagram, a simplified version of the communication system of  FIG. 1 , the flow extends between an electronic device, a transmission point, a reception point and a base station in accordance with aspects of the present application; 
         FIG. 6  illustrates a forward signal and a corresponding backscatter signal, according to aspects of the present disclosure; 
         FIG. 7  illustrates example steps in a method of processing, at the reception point of  FIG. 5A , the received backscatter signal, according to aspects of the present disclosure; 
         FIG. 8  illustrates example steps in a method of processing, at the reception point of  FIG. 5A , a time shift value associated with a greatest cross-correlation value to obtain information about the electronic device of  FIG. 5A , according to aspects of the present disclosure; 
         FIG. 9  illustrates example steps in a method of processing, at the reception point of  FIG. 5A , a time shift value associated with a greatest cross-correlation value to obtain information about the electronic device of  FIG. 5A , according to aspects of the present disclosure; 
         FIG. 10  illustrates a plurality of identity slots corresponding to the plurality of electronic devices of  FIG. 1 , according to aspects of the present disclosure; 
         FIG. 11  illustrates example steps in a method of processing a backscatter signal that includes data; 
         FIG. 12  illustrates example steps in a method of processing the received backscatter signal for channel state information acquisition, according to aspects of the present disclosure; 
         FIG. 13  illustrates example steps in a method, carried out at the electronic device of  FIG. 2 , to switch between the active device components and the passive device components according to aspects of the present disclosure; 
         FIG. 14  illustrates example steps in a method, carried out at the electronic device of  FIG. 2 , to switch between the passive device components and the active device components according to aspects of the present disclosure; 
         FIG. 15  illustrates example steps in a method of implementing a switch between operation modes, according to aspects of the present disclosure; and 
         FIG. 16  a temporal view of operation of the electronic device of  FIG. 2  according to aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     For illustrative purposes, specific example embodiments will now be explained in greater detail in conjunction with the figures. 
       FIGS. 1, 2 and 3  illustrate examples of networks and devices that could implement any or all aspects of the present disclosure. 
       FIG. 1  illustrates an example communication system  100 . In general, the system  100  enables multiple wireless or wired elements to communicate data and other content. The purpose of the system  100  may be to provide content (voice, data, video, text) via broadcast, narrowcast, user device to user device, etc. The system  100  may operate efficiently by sharing resources, such as bandwidth. 
     In this example, the communication system  100  includes a first electronic device (ED)  110 A, a second ED  110 B and a third ED  110 C (individually or collectively  110 ), a first radio access network (RAN)  120 A and a second RAN  120 B (individually or collectively  120 ), a core network  130 , a public switched telephone network (PSTN)  140 , the Internet  150  and other networks  160 . Although certain numbers of these components or elements are shown in  FIG. 1 , any reasonable number of these components or elements may be included in the communication system  100 . 
     The EDs  110  are configured to operate, communicate, or both, in the communication system  100 . For example, the EDs  110  are configured to transmit, receive, or both via wireless communication channels. Each ED  110  represents any suitable end user device for wireless operation and may include such devices (or may be referred to) as a user equipment/device (UE), wireless transmit/receive unit (WTRU), mobile station, mobile subscriber unit, cellular telephone, station (STA), machine type communication device (MTC), Internet of Things (IoT) device, personal digital assistant (PDA), smartphone, laptop, computer, touchpad, wireless sensor, or consumer electronics device. 
     In  FIG. 1 , the first RAN  120 A includes a first base station  170 A and the second RAN includes a second base station  170 B (individually or collectively  170 ). Each base station  170  is configured to wirelessly interface with one or more of the EDs  110  to enable access to any other base station  170 , the core network  130 , the PSTN  140 , the internet  150  and/or the other networks  160 . For example, the base stations  170  may include (or be) one or more of several well-known devices, such as a base transceiver station (BTS), a Node-B (NodeB), an evolved NodeB (eNodeB), a Home eNodeB, a gNodeB, a transmission and receive point (TRP), a site controller, an access point (AP) or a wireless router. Any ED  110  may be alternatively or additionally be configured to interface, access or communicate with any other base station  170 , the internet  150 , the core network  130 , the PSTN  140 , the other networks  160  or any combination of the preceding. The communication system  100  may include RANs, such as the RAN  120 B, wherein the corresponding base station  170 B accesses the core network  130  via the internet  150 , as shown. 
     The EDs  110  and the base stations  170  are examples of communication equipment that can be configured to implement some or all of the functionality and/or embodiments described herein. In the embodiment shown in  FIG. 1 , the first base station  170 A forms part of the first RAN  120 A, which may include other base stations (not shown), base station controller(s) (BSC, not shown), radio network controller(s) (RNC, not shown), relay nodes (not shown), elements (not shown) and/or devices (not shown). Any base station  170  may be a single element, as shown, or multiple elements, distributed in the corresponding RAN  120 , or otherwise. Also, the second base station  170 B forms part of the second RAN  120 B, which may include other base stations, elements and/or devices. Each base station  170  transmits and/or receives wireless signals within a particular geographic region or area, sometimes referred to as a “cell” or “coverage area.” A cell may be further divided into cell sectors and a base station  170  may, for example, employ multiple transceivers to provide service to multiple sectors. In some embodiments, there may be established pico or femto cells where the radio access technology supports such. In some embodiments, multiple transceivers could be used for each cell, for example using multiple-input multiple-output (MIMO) technology. The number of RANs  120  shown is exemplary only. Any number of RANs may be contemplated when devising the communication system  100 . 
     The base stations  170  communicate with one or more of the EDs  110  over one or more air interfaces  190  using wireless communication links, e.g., radio frequency (RF) wireless communication links, microwave wireless communication links, infrared (IR) wireless communication links, visible light (VL) communications links, etc. The air interfaces  190  may utilize any suitable radio access technology. For example, the communication system  100  may implement one or more orthogonal or non-orthogonal channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA) or single-carrier FDMA (SC-FDMA) in the air interfaces  190 . 
     A base station  170  may implement Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access (UTRA) to establish the air interface  190  using wideband CDMA (WCDMA). In doing so, the base station  170  may implement protocols such as High Speed Packet Access (HSPA), Evolved HPSA (HSPA+) optionally including High Speed Downlink Packet Access (HSDPA), High Speed Packet Uplink Access (HSUPA) or both. Alternatively, a base station  170  may establish the air interface  190  with Evolved UTMS Terrestrial Radio Access (E-UTRA) using LTE, LTE-A, LTE-B and/or 5G New Radio (NR). It is contemplated that the communication system  100  may use multiple channel access functionality, including such schemes as described above. Other radio technologies for implementing air interfaces include IEEE 802.11, 802.15, 802.16, CDMA2000, CDMA2000 1×, CDMA2000 EV-DO, IS-2000, IS-95, IS-856, GSM, EDGE and GERAN. Of course, other multiple access schemes and wireless protocols may be utilized. 
     The RANs  120  are in communication with the core network  130  to provide the EDs  110  with various services such as voice communication services, data communication services and other communication services. The RANs  120  and/or the core network  130  may be in direct or indirect communication with one or more other RANs (not shown), which may or may not be directly served by the core network  130  and may or may not employ the same radio access technology as the first RAN  120 A, the second RAN  120 B or both. The core network  130  may also serve as a gateway access between (i) the RANs  120  or EDs  110  or both, and (ii) other networks (such as the PSTN  140 , the Internet  150  and the other networks  160 ). 
     The EDs  110  may communicate with one another over one or more sidelink (SL) air interfaces  180  using wireless communication links, e.g., radio frequency (RF) wireless communication links, microwave wireless communication links, infrared (IR) wireless communication links, visible light (VL) communications links, etc. The SL air interfaces  180  may utilize any suitable radio access technology and may be substantially similar to the air interfaces  190  over which the EDs  110  communication with one or more of the base stations  170  or they may be substantially different. For example, the communication system  100  may implement one or more channel access methods, such as CDMA, TDMA, FDMA, OFDMA or SC-FDMA in the SL air interfaces  180 . In some embodiments, the SL air interfaces  180  may be, at least in part, implemented over unlicensed spectrum. 
     Some or all of the EDs  110  may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies and/or protocols. Instead of wireless communication (or in addition thereto), the EDs  110  may communicate via wired communication channels to a service provider or a switch (not shown) and to the Internet  150 . The PSTN  140  may include circuit switched telephone networks for providing plain old telephone service (POTS). The Internet  150  may include a network of computers and subnets (intranets) or both and incorporate protocols, such as internet protocol (IP), transmission control protocol (TCP) and user datagram protocol (UDP). The EDs  110  may be multimode devices capable of operation according to multiple radio access technologies and incorporate multiple transceivers necessary to support multiple radio access technologies. 
       FIG. 2  illustrates example components that may implement the methods and teachings according to the present disclosure. In particular,  FIG. 2  illustrates an example ED  110 . These components could be used in the communication system  100  or in any other suitable system. 
     As shown in  FIG. 2 , the ED  110  includes at least one processor or processing unit  200 . The processing unit  200  implements various processing operations of the ED  110 . For example, the processing unit  200  could perform signal coding, bit scrambling, data processing, power control, input/output processing, or any other functionality, thereby enabling the ED  110  to operate in the communication system  100 . The processing unit  200  may also be configured to implement some or all of the functionality and/or embodiments described in more detail herein. Each processing unit  200  includes any suitable processing or computing device configured to perform one or more operations. Each processing unit  200  could, for example, include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array or an application specific integrated circuit. 
     The ED  110  also includes at least one transceiver  202 . The transceiver  202  includes an RF circuit  210  that is configured to modulate data or other content for transmission by at least one antenna  204 . The transceiver  202  is also configured to demodulate data or other content received by the at least one antenna  204 . Each transceiver  202  includes any suitable structure for generating signals for wireless or wired transmission and/or processing signals received wirelessly or by wire. Each antenna among the at least one antenna  204  includes any suitable structure for transmitting and/or receiving wireless or wired signals. One or multiple transceivers  202  could be used in the ED  110 . One or multiple antennas  204  could be used in the ED  110 . Although shown as a single functional unit, a transceiver  202  could also be implemented using at least one transmitter and at least one separate receiver. 
     The RF circuit  210  is illustrated as including a set of active device components  211  connected to one of the antennas  204 . In addition, the RF circuit  210  is illustrated as including a set of passive device components  212  connected to an associated one of the antennas  204 . 
     The term “passive,” as used herein in the phrase “passive device components,” bears clarification. In a typical discussion of electronic components, the term “passive” is given to those electronic components that lack an ability to control electric current by means of another electrical signal. Examples of passive electronic components are capacitors, resistors, inductors, transformers and some diodes. In contrast, the term “active” is given to those electronic components that can control the flow of electricity by means of another electrical signal. Some examples of active electronic components are transistors, vacuum tubes and silicon-controlled rectifiers. 
     In a discussion of electronic components in the present application, the term “passive” is given to those electronic components that lack a requirement for conversion to baseband when receiving or transmitting signals. In contrast, the term “active” is given to those electronic components that employ conversion to baseband when receiving or transmitting. In other words, the “passive” circuits of the present application may, in some examples, consist of only those electronic components that lack an ability to control electric current by means of another electrical signal, and in some other examples, may further comprise those electronic components that can control the flow of electricity by means of another electrical signal. Conveniently, passive device components  212  are configured to perform their functions in the RF domain in contrast to the active device components  211 , which are configured to perform their functions in the baseband domain. As a consequence, the power consumption level of the passive device components  212  is very low relative to the power consumption level of the active device components  211 . 
     In accordance with aspects of the present application, the processing unit  200  of the electronic device  110  may cause the passive device components  212  to perform certain functions known to be performed by the active device components  211 , thereby reducing overall power consumption. Indeed, the amount by which the overall power consumption is expected to be reduced is roughly the power consumption associated with the active device components  211  performing the certain functions. 
     The ED  110  further includes one or more input/output devices  206  or interfaces (such as a wired interface to the Internet  150 ). The input/output devices  206  permit interaction with a user or other devices in the network. Each input/output device  206  includes any suitable structure for providing information to, or receiving information from, a user, such as a speaker, a microphone, a keypad, a keyboard, a display or a touch screen, including network interface communications. 
     In addition, the ED  110  includes at least one memory  208 . The memory  208  stores instructions and data used, generated or collected by the ED  110 . For example, the memory  208  could store software instructions or modules configured to implement some or all of the functionality and/or embodiments described herein and that are executed by the processing unit  200 . Each memory  208  includes any suitable volatile and/or non-volatile storage and retrieval device. Any suitable type of memory may be used, such as a random access memory (RAM), a read only memory (ROM), a hard disk, an optical disc, a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card and the like. 
     As illustrated in  FIG. 3 , the base station  170  includes at least one processing unit  350 , at least one transmitter  352 , at least one receiver  354 , one or more antennas  356 , at least one memory  358  and one or more input/output devices or interfaces  366 . A transceiver (not shown) may be used instead of the transmitter  352  and receiver  354 . A scheduler  353  may be coupled to the processing unit  350 . The scheduler  353  may be included within, or operated separately from, the base station  170 . The processing unit  350  implements various processing operations of the base station  170 , such as signal coding, bit scrambling, data processing, power control, input/output processing or any other functionality. The processing unit  350  can also be configured to implement some or all of the functionality and/or embodiments described in more detail above. Each processing unit  350  includes any suitable processing or computing device configured to perform one or more operations. Each processing unit  350  could, for example, include a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array or an application specific integrated circuit. 
     Each transmitter  352  includes any suitable structure for generating signals for wireless or wired transmission to one or more EDs  110  or other devices. Each receiver  354  includes any suitable structure for processing signals received wirelessly or by wire from one or more EDs  110  or other devices. Although shown as separate components, at least one transmitter  352  and at least one receiver  354  could be combined into a transceiver. Each antenna  356  includes any suitable structure for transmitting and/or receiving wireless or wired signals. Although a common antenna  356  is shown here as being coupled to both the transmitter  352  and the receiver  354 , one or more antennas  356  could be coupled to the transmitter  352  and one or more separate antennas  356  could be coupled to the receiver  354 . Each memory  358  includes any suitable volatile and/or non-volatile storage and retrieval device(s) such as those described above in connection to the ED  110 . The memory  358  stores instructions and data used, generated or collected by the base station  170 . For example, the memory  358  could store software instructions or modules configured to implement some or all of the functionality and/or embodiments described above and that are executed by the processing unit  350 . 
     Each input/output device  366  permits interaction with a user or other devices in the network. Each input/output device  366  includes any suitable structure for providing information to or receiving/providing information from a user, including network interface communications. 
     Additional details regarding the ED  110  and the base stations  170  are known to those of skill in the art. As such, these details are omitted here for clarity. 
     Different mechanisms for reducing the rate of power use have been studied by people involved in the known 3rd Generation Partnership Project (3GPP). Such mechanisms include strategies that aim to reduce an “active” time of mobile communication devices. 
     An ED  110  can operate in a variety of modes in order to trade off certain features for more or less device power consumption and/or network resource consumption. Two example modes are illustrated in  FIG. 4A  along with an indication of a transition between the modes. In particular,  FIG. 4A  illustrates a normal power consumption operation mode  402  and a low power consumption operation mode  404 . 
     The functionalities that can be enabled using backscattering communications, when the ED  110  is in the low power consumption operation mode  404 , include: allowing a network entity to track a relative position for the ED  110 ; allowing the network entity to maintain a timing reference for the ED  110 ; allowing the network entity to identify the ED  110 ; and allowing the network entity to get some other information about the ED  110 , including preamble and data. Conveniently, an approach wherein backscattering communications is used for allowing the network entity to track relative device position, maintain timing references and identify devices, may be seen as particularly suitable for extremely low cost Internet-of-Things (IoT) devices. 
     In 3GPP New Radio (NR), each UE may operate in one of several modes known as Radio Resource Control (RRC) states. Accordingly, a UE (such as the ED  110 ) may operate in one of the following three RRC states, illustrated in  FIG. 4B : an RRC_IDLE state  408 ; an RRC_CONNECTED state  410 ; and an RRC_INACTIVE state  406 . In other documentation, these states may be referenced as “modes”, for example, “RRC_IDLE mode.” When the ED  110  is in the RRC_CONNECTED state  410 , the ED  110  may be considered to have been connected to the network as a result of a connection establishment procedure  424 . When the ED  110  has transitioned to the RRC_IDLE state  408 , say, by way of a release procedure  442  or by way of a release procedure  462 , the ED  110  is not connected to the network, but the network knows that the ED  110  is present in the network. By switching to the RRC_INACTIVE state  406  by way of a release with suspend procedure  446 , the ED  110  helps conserve network resources and local power (thereby lengthening, for example, perceived battery life of the ED  110 ). The RRC_INACTIVE state  406  may be useful, for example, in those instances when the ED  110  is not communicating with the network. When an ED  110  is in the RRC_INACTIVE state  406 , the ED  110  is also helping to conserve network resources and local power. However, when the ED  110  is in the RRC_INACTIVE state  406 , the network and the ED  110  both store at least some configuration information to, thereby, allow the ED  110  to reconnect to the network, by way of a resume procedure  464 , more rapidly than the ED  110  would be able to reconnect, by way of the connection establishment procedure  424 , in the case wherein the ED  110  is in the RRC_IDLE state  408 . The storage of at least some configuration information when the ED  110  is in the RRC_INACTIVE state  406  is one aspect that distinguishes the RRC_INACTIVE state  406  from the RRC_IDLE state  408 . Notably, the acronym RRC is a reference to the known Radio Resource Control protocol. 
       FIG. 4B  illustrates the normal power consumption operation mode  402  and the low power consumption operation mode  404  introduced in  FIG. 4A . In the configuration illustrated in  FIG. 4B , the normal power consumption operation mode  402  includes the RRC_CONNECTED state  410  and the low power consumption operation mode  404  includes the RRC_IDLE state  408  and the RRC_INACTIVE state  406 . Accordingly, one way to reduce an “active” time of mobile communication devices, in the 3GPP NR context, is to reduce a time that the ED  110  spends in the RRC_CONNECTED state  410 . 
       FIG. 4C  illustrates the normal power consumption operation mode  402  and the low power consumption operation mode  404  introduced in  FIG. 4A . In the configuration illustrated in  FIG. 4C , the normal power consumption operation mode  402  includes the RRC_CONNECTED state  410  and the low power consumption operation mode  404  includes the RRC_CONNECTED state  410 , the RRC_IDLE state  408  and the RRC_INACTIVE state  406 . Accordingly, the task of reducing an “active” time of mobile communication devices, in the 3GPP NR context, is more complex than simply reducing a time that the ED  110  spends in the RRC_CONNECTED state  410 . 
     To reduce the power consumption by the electronic devices  110  in the communication system  100  of  FIG. 1 , aspects of the present application relate to the use of the passive device components  212  in the electronic devices  110  to carry out tasks often carried out by the active device components  211 . The passive device components  212  are configured to perform specific functions typically performed by the active device components  211 , thereby allowing the active device components  211  to remain powered off for longer periods. The expected result of allowing the active device components  211  to remain powered off for longer periods is that power consumption at the ED  110  will be reduced. 
     The passive device components  212  may perform the specific functions using so-called backscattering communications. A well-known example of a backscattering communication application is known as radio frequency identification (RFID). 
       FIG. 5A  illustrates a flow diagram  500 A suitable for reviewing aspects of the present application. The flow diagram  500 A may be considered to be a simplified version of the communication system  100  of  FIG. 1  in that  FIG. 5A  includes one of the electronic devices  110  from  FIG. 1 , a transmission point  502 , a reception point  512  (which may also be called a “reader”) and one of the base stations  170  from  FIG. 1 . As illustrated in  FIG. 5A , the reception point  512  and the transmission point  502  are separate devices, located apart from one another. Notably, the reception point  512  and the transmission point  502  may be part of a single device, such as one of the base stations  170 . Furthermore, the reception point  512  and the transmission point  502  may be co-located, but distinct from one of the base stations  170 . In an instance wherein the reception point  512  is located away from the base station  170 , the reception point  512  may maintain a communication channel with the base station  170 . The communication channel between the reception point  512  and the base station  170  may be wired or wireless. In other aspects of the present application, the reception point  512  may maintain a communication channel with a network node that is not the base station  170 . 
     In overview, and in view of a flow diagram  500 A illustrated in  FIG. 5A , the transmission point  502  transmits (step  522 ) a radio frequency signal  600 FS (a so-called “forward signal”) on a forward channel. The forward signal  600 FS may comprise a plurality of sub-signals (e.g., a-symbols). The ED  110  receives (step  526 ) the forward signal  600 FS, forms (step  528 ) a radio frequency backscatter signal and transmits (step  530 ) the backscatter signal  600 BS over a back channel. At the ED  110 , the forming (step  528 ) of the backscatter signal  600 BS may involve use of the passive device components  212  of the ED  110 . The backscatter signal  600 BS may be defined as a time-restricted (e.g., restricted to a single p-slot) set of contiguous sub-signals among the plurality of sub-signals included in the forward signal  600 FS. The ED  110  may transmit (step  530 ) the backscatter signal  600 BS over a defined duration (e.g., a p-slot). The operation of transmitting (step  530 ) the radio frequency backscatter signal may occur subsequent to the operation of forming (step  528 ) the backscatter signal  600 BS through modification of the forward signal  600 FS in the RF domain performed under control of the processing unit  200 . In some embodiments, this modification is implemented by applying amplitude and/or phase changes on the forward signal  600 FS through adjusting the impedance in the passive device components  212  of the RF circuit  210  (see  FIG. 2 ). In some embodiments, the modification may also include not reflecting the forward signal  600 FS over one p-symbol or a plurality of p-symbols. In some embodiments, the backscatter signal  600 BS is merely a reflection of the forward signal  600 FS over one p-symbol or a plurality of p-symbols. That is, the passive device components  212  need not necessarily modify the forward signal  600 FS to form the backscatter signal  600 BS. Instead, the passive device components  212  may merely time-limit transmission of the backscatter signal  600 BS. 
     Subsequent to the transmission (step  530 ) of the backscatter signal  600 BS by the ED  110 , the reception point  512  receives (step  534 ) the backscatter signal  600 BS over the back channel. The reception point  512  processes (step  538 ) the backscatter signal  600 BS to obtain information. 
     In other aspects of the present application, and in view of a flow diagram  500 B illustrated in  FIG. 5B , the reception point  512  may transmit (step  536 ), over a communication channel, the received backscatter signal  600 BS to the base station  170  and the base station  170  may perform at least a part of the processing (step  538 BS) of the backscatter signal  600 BS. 
     In some embodiments, and in view of a flow diagram  500 C illustrated in  FIG. 5C , the reception point  512  may perform some processing (step  535 ) on the backscatter signal  600 BS and transmit (step  537 ), over the communication channel, a partly processed backscatter signal  600 BSP to the base station  170 , thereby allowing the base station  170  to perform some further processing (step  539 ). 
     When designing the forward signal  600 FS, consideration is given to resource allocation. The primary resources that are available for allocation are time resources and frequency resources. Determining a manner in which to allocate these resources may be considered to depend on the application, that is, the desired functionality of the backscatter signal. 
     In one example application, the desired functionality of the backscatter signal is to allow the reception point  512  to accurately determine a position for the ED  110 . For this application, it is preferred to design the forward signal  600 FS to have a wide frequency bandwidth. It may also be preferred that time resources are narrowly allocated to allow more granularity in the time domain processing. 
     In another example application, wherein the ED  110  is in a location with limited coverage, it is preferred to design the forward signal  600 FS to have a narrow frequency bandwidth and allocate relatively large time slots. 
     One aspect of the forward signal design is the waveform design. Examples of waveforms include single-carrier, multi-carrier, ultra-wide band (UWB) pulse, Frequency-Modulated Continuous Wave (FMCW), or the like. Multi-carrier waveforms include cyclic prefix (CP)-OFDM and single-carrier (SC)-FDMA. 
     Waveform design for the forward signal  600 FS may depend on the required performance metric. For example, if very accurate timing acquisition and positioning for ED  110  is required, waveforms with fine timing granularity and good autocorrelation in time domain are preferable. Examples include single-carrier and UWB pulse waveforms. Good autocorrelation means delta-like autocorrelation function R(τ) which has a peak at τ=0 and very low values for other values of τ. 
     In some embodiments, the waveform design may also depend on whether or not the forward signal  600 FS contains any data for any ED (ED  110  or any other ED in the range of the forward signal  600 FS). In the case wherein the forward signal  600 FS contains data, waveforms allowing more efficient modulating and demodulating the data are preferable. Examples of waveforms that allow for efficient modulating and demodulating of the data include CP-OFDM and SC-FDMA. 
     In some other embodiments, other metrics like power efficiency of the transmitter may be considered in the forward signal waveform design. In this case, the waveforms with a low peak-to-average-power ratio (low-PAPR) property would be preferred. Examples of low-PAPR waveforms include single carrier waveforms and SC-FDMA. 
     A forward signal  600 FS may be said to have a frame structure. As such, forward signal design may be referenced as frame structure design. Two “levels” of frame structure design are considered herein. 
     A first level of the frame structure may be called “passive slots” or “p-slots.” Passive slots are arranged to have a time granularity that allows for signal processing and backscatter signal transmission to be carried out by the passive device components. 
     A second level of the frame structure may be called “active slots,” “active symbols,” “a-slots” or “a-symbols.” Within each p-slot, there can be multiple a-slots carrying regular transmission, perhaps for consumption by other, more active, devices. Each a-slot can contain multiple a-symbols. Such a frame structure design should be familiar from 3GPP NR. A “regular” transmission may be one or more baseband signals that have been upconverted to RF for transmission over an air interface. In other words, first a baseband signal is generated. Next, the baseband signal is upconverted in the frequency domain by multiplying by a sinusoidal signal with a carrier frequency. Notably, the backscattering operation in the present disclosure occurs entirely in the RF domain. That is, the passive device components  212  do not convert a received signal to the baseband domain. Accordingly, the passive device components  212  have no access to the information encoded in signals in the baseband domain. 
     In a manner consistent with design of other signals, the designing of forward signals includes consideration of generally configuring numerology, which may include specifically configuring sub-carrier spacing. Indeed, appropriately configuring numerology for the forward signal  600 FS allows the reception point  512 , the intended receiver of the backscatter signal, to obtain information by processing the backscatter signal. Notably, even though multiple a-slots carrying information may be found within a p-slot, the passive device components of the ED  110  are not configured to obtain any of the information transmitted in the a-slots. That is, the ED  110  operating in accordance with aspects of the present application may be seen to eschew baseband processing of the a-slots and analog to digital conversion. It follows that the ED  110  only transmits (step  530 ) information to the reception point  512  by backscattering a signal received from the transmission point  502 . Configuration parameters that define the duration of a p-slot, the duration of an a-slot and the numerology of the forward signal  600 FS may be provided to the transmission point  502  by an entity in the environment  100  of  FIG. 1 . The configuration parameters of the forward signal  600 FS may also be provided to the ED  110  by an entity in the environment  100  of  FIG. 1 . 
     In typical operation, a base station  170  communicates with an ED  110  that is operating in the RRC_CONNECTED state  410 . Perhaps responsive to a received instruction from the base station  170 , the ED  110  may use active components to generate a transmission, such as a Sounding Reference Signal transmission or a Preamble transmission. Upon receipt of the transmission, the base station  170  is expected to be able to acquire information related to identity, timing and positioning for the ED  110 . However, it may be considered difficult to obtain the same information for the ED  110  when the ED  110  is not in the RRC_CONNECTED state  410 . 
     In operation according to the aspects of the present application that relate to enhancing the ability of the reception point  512  to acquire information related to identity, timing and positioning when the ED  110  is not operating in the normal power consumption operation mode  402 , the transmission point  502  transmits a forward signal  600 FS that has been designed to facilitate obtaining such information by the reception point  512 . 
     According to aspects of the present application, the forward signal  600 FS may be designed to use a waveform and numerology that features fine granularity in the time domain.  FIG. 6  illustrates a forward signal  600 FS and a corresponding backscatter signal  600 BS. The forward signal  600 FS includes a plurality of transmitted a-slots  602 A,  602 B,  602 C,  602 D,  602 E,  602 F,  602 G,  602 H,  602 I,  602 J,  602 K,  602 L and  602 M (individually or collectively  602 ). The backscatter signal  600 BS includes a time-restricted set of the contiguous a-slots  602  in the forward signal  600 FS. Indeed, in the example of  FIG. 6 , the backscatter signal  600 BS includes only a-slots  602 C,  602 D,  602 E,  602 F,  602 G,  602 H and  602 I. In a beneficial method of operation, the ED  110  transmits the backscatter signal  600 BS without awareness of the a-slots incorporated therein. 
     The ED  110  transmits (step  530 ,  FIG. 5A ) backscattering transmission while the ED  110  is not in the normal power consumption operation mode  402 . The backscattering transmission is based on p-slot timing that is specific to the ED  110 . For example,  FIG. 6  illustrates an ED p-slot  606  that starts at the beginning of a-slot  602 C and ends at the end of a-slot  602 I. The boundaries of the ED p-slot  606  may be defined based on the last frame synchronization information that the ED  110  obtained while the ED  110  was in the RRC_CONNECTED state  410 . 
     According to aspects of the present application, the reception point  512  can obtain timing and positioning information for the ED  110  based on receiving (step  534 ) the backscatter signal  600 BS in the context of a record of the specific forward signal  600 FS. 
     Notably, in  FIG. 6 , the backscatter signal  600 BS does not include all of the a-slots  602  that are in the forward signal  600 FS. In aspects of the present application, the ED  110  does not transmit (step  530 ) the backscatter signal  600 BS continuously. Instead, the ED  110  transmits (step  530 ) the backscatter signal  600 BS following a sometimes-on and sometimes-off pattern. The ED p-slot  606  of the backscatter signal  600 BS corresponds to the passive device components  212  of the ED  110  initially being controlled by the processing unit  200  to be OFF, then being controlled by the processing unit  200  to be ON and transmitting a-slots  602 C through  602 I and then being controlled by the processing unit  200  to turn OFF. 
       FIG. 7  illustrates example steps in a method of processing (step  538 R,  FIG. 5A ) the received backscatter signal at the reception point  512 . The method of  FIG. 7  commences with the reception point  512  determining (step  702 ) the ED p-slot  606  of the backscatter signal  600 BS. That is, the reception point  512  determines (step  702 ) the boundaries of the ED p-slot  606 . Determining (step  702 ) the boundaries of the ED p-slot  606  can be performed by examining the transition time between ON and OFF patterns. In some embodiments, it is also possible to determine (step  702 ) the boundaries of the ED p-slot  606  by examining the phase transition time between the normalized received backscatter signal over all a-symbols defined as 
     
       
         
           
             
               
                 s 
                 norm 
               
               ⁡ 
               
                 ( 
                 t 
                 ) 
               
             
             = 
             
               
                 
                   s 
                   
                     B 
                     ⁢ 
                     S 
                   
                 
                 ⁡ 
                 
                   ( 
                   t 
                   ) 
                 
               
               
                 
                   s 
                   
                     F 
                     ⁢ 
                     S 
                   
                 
                 ⁡ 
                 
                   ( 
                   t 
                   ) 
                 
               
             
           
         
       
     
     where S BS (t) denotes the backscatter signal  600 BS and S FS (t) denotes the forward signal  600 FS. Without regard for the manner of determining the boundaries, a term, t p , may be used to denote a time difference between the start of the ED p-slot  606  and the start of the TP p-slot  604 . The reception point  512  may then initialize (step  704 ) a time shift value. The value of the time shift value is determined by the required time granularity for the timing acquisition and/or positioning of the ED  110  and also the bandwidth of the forward signal  600 FS.  FIG. 6  illustrates an initial transmission point (TP) p-slot  604  that starts at the beginning of a-slot  602 A and ends at the end of a-slot  602 G. The reception point  512  may then time shift (step  706 ) the initial TP p-slot  604  of the forward signal  600 FS by the time shift value to result in a time-shifted TP p-slot (not shown). If the initialized time shift value is zero, then the time-shifted p-slot begins at a-slot  602 A. The reception point  512  may then determine (step  708 ) a value for a cross-correlation between the time-shifted TP p-slot and the ED p-slot  606  determined in step  702 . 
     The determining (step  708 ) is to be carried out for an intended range of time shift values. Accordingly, the reception point  512  determines (step  710 ) whether the intended range of time shift values have been considered. Upon determining (step  710 ) that the entirety of the intended range of time shift values have not yet been considered, the reception point  512  increments (step  712 ) the time shift value and returns to time shift (step  706 ) the initial TP p-slot  604  of the forward signal  600 FS by the incremented time shift value to result in a further time-shifted TP p-slot (not shown). If the time shift value equals the duration of each a-symbol and incremented time shift value is one, then the further time-shifted p-slot begins at a-slot  602 B. In general, the value of the time shift value is less than or equal to the duration of an a-symbol. 
     The reception point  512  may then determine (step  708 ) a value for a cross-correlation between the further time-shifted TP p-slot and the ED p-slot  706  determined in step  702 . Upon determining (step  710 ) that the entirety of the intended range of time shift values have not yet been considered, the reception point  512  increments (step  712 ) the time shift value and returns to time shift (step  706 ) the initial TP p-slot  604  of the forward signal  600 FS by the incremented time shift value to result in an even further time-shifted TP p-slot (not shown). If the incremented time shift value is two, then the even further time-shifted p-slot begins at a-slot  602 C. 
     Upon determining (step  710 ) that the entirety of the intended range of time shift values have been considered, the reception point  512  determines (step  714 ) the time shift value, τ, associated with the greatest cross-correlation value. The reception point  512  may then process (step  716 ) the time shift value, τ, associated with the greatest cross-correlation value to obtain information about the ED  110 , including the position of the ED  110  and the timing of ED  110 . 
       FIG. 8  illustrates example steps in a method of processing (step  716 ,  FIG. 7 ), at the reception point  512 , the time shift value, τ, associated with the greatest cross-correlation value to obtain information about the ED  110 . In the example of  FIG. 8 , the time shift value, associated with the greatest cross-correlation value may be used to obtain (step  802 ) a value for a distance between the transmission point  502 /reception point  512  and the ED  110  (assuming that the transmission point  502  and the reception point  512  are located in the same place). The distance, d, may be obtained (step  802 ) through use of the equation 
     
       
         
           
             d 
             = 
             
               
                 τ 
                 ⁢ 
                 c 
               
               2 
             
           
         
       
     
     where τ is the time shift value determined in step  714  and c is the speed of light. Upon obtaining (step  802 ) the value for the distance, the reception point  512  may record (step  804 ) the distance as an indication of the position for the ED  110 . The recording (step  804 ) of the indication of the position for the ED  110  may, for example, involve storing the indication of the position in a memory. If the reception point  512  is the base station  170  illustrated in  FIG. 3 , the indication of the position for the ED  110  may be stored in the memory  358 . 
       FIG. 9  illustrates example steps in a method of processing (step  716 ,  FIG. 7 ) the time shift value, associated with the greatest cross-correlation value to obtain information about the ED  110 . In the example of  FIG. 9 , the reception point  512  determines (step  902 ) a relative time difference term, t 0 . Determining (step  902 ) the relative time difference term, t 0 , may involve the time shift value, (see step  714 ), associated with the greatest cross-correlation value and the time difference, t p  (see step  702 ), between the start of the ED p-slot  606  and the start of the TP p-slot  604  in 
     
       
         
           
             
               
                 t 
                 0 
               
               = 
               
                 
                   t 
                   p 
                 
                 - 
                 
                   τ 
                   2 
                 
               
             
             . 
           
         
       
     
     Upon determining step  902 ) the relative time difference, the reception point  512  may then record (step  904 ) the relative time difference as an indication of the timing for the ED  110 . The recording (step  904 ) of the indication of the timing for the ED  110  may, for example, involve storing the indication of the timing in a memory. If the reception point  512  is the base station  170  illustrated in  FIG. 3 , the indication of the timing for the ED  110  may be stored in the memory  358 . 
     In an environment, such as the communication system  100  of  FIG. 1 , wherein a plurality of EDs  110  are present, it is preferred that the reception point  512  be provided with a manner of distinguishing between backscatter signals received from distinct EDs  110 . 
     To such an end, in an aspect of the present application, each particular ED  110  may arrange respective ED-unique on/off patterns of backscatter transmissions to, thereby, indicate, to the reception point  512 , an identity for the particular ED  110 . A transmission frame may be defined as including K p-slots. Each particular ED  110  may arrange to transmit (step  530 ,  FIG. 5A ) a backscatter transmission during only a subset of L p-slots in the transmission frame. 
       FIG. 10  illustrates a first transmission frame  1000 A corresponding to the first ED  110 A of  FIG. 1 , a second transmission frame  1000 B corresponding to the second ED  1106  of  FIG. 1  and a third transmission frame  1000 C corresponding to the third ED  110 C of  FIG. 1 . Each of the example transmission frames  1000 A,  1006 ,  1000 C (collectively or individually  100 ) has a transmission frame length  1202  of K=12 p-slots and each of the example transmission frames  1200  indicates that backscatter transmission occurs in L=4 of the p-slots. The first transmission frame  1000 A indicates that the first ED  110 A performs backscatter transmission (is ON) in p-slots 1, 4, 8 and 12 and is OFF in p-slots 2, 3, 5, 6, 7, 9, 10 and 11. The second transmission frame  10006  indicates that the second ED  1106  performs backscatter transmission (is ON) in p-slots 2, 4, 9 and 11 and is OFF in p-slots 1, 3, 5, 6, 7, 8, 10 and 12. The third transmission frame  1000 C indicates that the third ED  110 C performs backscatter transmission (is ON) in p-slots 3, 5, 8 and 11 and is OFF in p-slots 1, 2, 4, 6, 7, 9, 10 and 12. 
     Each particular ON/OFF pattern can be associated with an identity of the ED  110  that is configured to perform backscatter transmission according to the particular ON/OFF pattern. Such an association may be seen to facilitate identification of the ED  110  by the reception point  512 . The association can be stored as a pre-defined dictionary or a look up table (LUT). The dictionary or LUT may only be known among the elements of the communication system  100  of  FIG. 1 . 
     In order to minimize the number of hypothesis for ON/OFF patterns, each ON/OFF pattern may be recorded with an association to a location for the corresponding ED  110 . 
     In other aspects of the present application, an ON/OFF pattern can act as preamble transmission, thereby facilitating tracking and discovery of the corresponding ED  110 . Detection of the identity of ED  110  based on the ON/OFF pattern may be considered to enable joint ED identification and detection of ED data provided by the ED  110 , which will be disclosed more fully hereinafter. 
     Configuring an ON/OFF pattern that is specific to an ED  110  may be seen to improve ED detection performance and complexity by allowing partial collision between p-slots arriving at a reception point  512  from distinct EDs  110 . For example, in the fourth p-slot, both the first ED  110 A and the second ED  1106  are performing backscatter transmission and the third ED  110 C is not performing backscatter transmission. 
     As disclosed up to this point, and illustrated in  FIG. 5A , the ED  110  may transmit (ON, step  530 ) a backscatter signal in a p-slot or not transmit (OFF) a backscatter signal in a p-slot. Conveniently, upon processing (step  538 R,  FIG. 5A ) the backscatter signal received in each transmission frame, the reception point  512  may obtain information about the ED  110 , such as timing, position and identity. 
     It is proposed herein to assist the reception point  512  to distinguish between successive p-slots in which backscatter signals are transmitted by the ED  110 . That is, rather than simply performing backscatter transmission (ON) or not performing backscatter transmission (OFF), the ED  110  may subject the forward signal to a time-domain function when forming a backscatter signal. 
     At the ED  110 , subjecting the forward signal to a time-domain function may involve use of passive components of the ED  110 . For one example, the processing unit  200  may arrange a change in an impedance value in the RF circuit  210  connected to the antenna  204  (see  FIG. 2 ). The result of subjecting the forward signal to a time-domain function may be mathematically presented as multiplying the received forward signal by a complex-valued symbol. 
     In the p-slot associated with an index, k, the i th  ED  110  may multiply the received forward signal  600 FS in p-slot k by a complex-valued symbol, s i (k). Notably, the symbol, s i (k), in p-slot k may be different from the symbol, s i (k+1), in p-slot k+1. Furthermore, it may not be assumed that value of the symbol, s i (k), is known by the reception point  512 . It has been discussed that the ED  110  may subject the forward signal to a time-domain function. Notably, the time-domain function may be defined over a transmission frame and may considered to include a plurality of symbols, s i (k). In the simple cases, the symbols, s i (k), can take on a value of either 0 or 1. In other cases, each symbol, s i (k), is complex-valued. 
     Upon receiving (step  526 ,  FIG. 5A ) the forward signal  600 FS comprising a plurality of sub-signals (e.g., a-symbols), the ED  110  may form (step  528 ) the backscatter signal  600 BS by multiplying the received forward signal  600 FS by the symbol, s i (k). The ED  110  subsequently transmits (step  530 ) the radio frequency backscatter signal  600 BS over a defined duration (e.g., a p-slot). 
     It may be considered that the transmission (step  530 ) of the backscatter signal  600 BS that has been formed (step  528 ) by multiplying the received forward signal  600 FS by the symbol, s i (k), is one example of obtaining a time-domain function of a sub-signal among the plurality of sub-signals (a-slots) included in the received forward signal  600 FS. In those cases wherein the ED  110  is consistently transmitting backscatter signals, the distinctness of each symbol, s i (k), may allow the reception point  512  to distinguish between successive p-slots in the received backscatter signal. 
     The information that the reception point  512  may obtain about the ED  110  is augmented through the addition of ED data to the backscatter signal transmitted in the p-slots. That is, rather than simply performing backscatter transmission (ON) or not performing backscatter transmission (OFF), the ED  110  may subject the forward signal to a time-domain function when forming a backscatter signal. 
     In addition to merely allowing the reception point  512  to distinguish between successive p-slots in the received backscatter signal, the transmission of a time-domain function of a sub-signal among the plurality of sub-signals included in the received forward signal  600 FS may allow the ED  110  to transmit, to the reception point  512 , data, hereinafter called “ED data.” 
     The baseband equivalent of each symbol, s i (k), transmitted by a particular ED  110  may be constrained to be in a “projection set” of symbols {α 1 , . . . , α p } (with some possible phase rotations) where P denotes a number of distinct symbols (projections) that are available as a result of appropriate impedance changes that the processing unit  200  may arrange in the passive device components  212  of the RF circuit  210  (see  FIG. 2 ). The projection set can be different from ED  110  to ED  110 . When the symbol, s i (k), is used to communicate ED data, the ED may be configured to transmit m bits b i =(b 0 , b 1 , . . . , b m- 1) over each p-slot. This corresponds to a modulation size of M=2 m . 
     It may be considered that designing a codebook for the backscatter signal is an exercise similar to the known exercise of designing a codebook for a Sparse Code Multiple Access (SCMA) communications system. SCMA is a known, multi-dimensional, codebook-based, non-orthogonal multiple access technique. 
     The backscatter signal codebook can be made specific to a particular ED  110  by employing a sparsity pattern that is specific to the particular ED  110  and/or employing a projection set of symbols {α 1 , . . . , α p } that is specific to the particular ED  110 . A specific projection set can be realized by including, in the RF circuit  210  ( FIG. 2 ), a radio frequency phase shifter (not shown) that is specific to the particular ED  110 . A specific projection set can also be realized by implementing a perturbation function that is specific to the particular ED  110 . 
     A first example projection set may be called a “binary projection set.” In a binary projection set, the symbols can take on values {α 1 , α 2 }={1, −1}. 
     One manner of designing multi-dimensional codebook involves use of a binary generation matrix (which should be familiar from use in binary block codes), i.e., {right arrow over (s)} i =(1−G i  ⊙b i ), where ⊙ denotes a multiplication in the binary domain and G i  is called a generator matrix and {right arrow over (s)} i  is the vector of symbols to be transmitted by the ED  110  in the backscatter signal during the transmission frame. The generator matrix, G i , can be specific to the ED  110  that implements the codebook. As will be understood, any binary code with good Hamming distance between the codewords can be used. Indeed, the Hamming distance in the binary domain may be seen to directly translate to a Euclidean distance in the symbol domain. 
     A second example projection set may be called a “tertiary projection set.” In a tertiary projection set, the symbols can take on values {α 1 , α 2 , α 3 }={1,0, −1}. 
     One manner of designing multi-dimensional codebook involves use of a binary generation matrix. A 2-bit transmission, the case where m=2, can be realized by superposition of two binary codewords with orthogonal sequences 
         {right arrow over (s)}   i   =f   i,1 (1−2 b   0 )+ f   i,2 (1−2 b   1 ), where  f   i,1   H   f   i,2 =0.
 
     An example with L=2 may be represented as: 
     
       
         
           
             
               
                 s 
                 → 
               
               i 
             
             = 
             
               
                 
                   [ 
                   
                     
                       
                         1 
                       
                     
                     
                       
                         1 
                       
                     
                   
                   ] 
                 
                 ⁢ 
                 
                   ( 
                   
                     1 
                     - 
                     
                       2 
                       ⁢ 
                       
                         b 
                         0 
                       
                     
                   
                   ) 
                 
               
               + 
               
                 
                   [ 
                   
                     
                       
                         1 
                       
                     
                     
                       
                         
                           - 
                           1 
                         
                       
                     
                   
                   ] 
                 
                 ⁢ 
                 
                   
                     ( 
                     
                       1 
                       - 
                       
                         2 
                         ⁢ 
                         
                           b 
                           1 
                         
                       
                     
                     ) 
                   
                   . 
                 
               
             
           
         
       
     
     The sequences f i,1  and f i,2  may be made specific to the ED  110  at which the sequences are employed. In some embodiments, on/off pattern generation is incorporated into the symbol sequence design by including “0” in the projection set of symbols {α 1 , . . . , α p }. In this case, the symbol sequence length represents the total number of p-slots instead of only the ON p-slots. 
     An example codebook, with K=4, may be represented as: 
     
       
         
           
             
               
                 s 
                 → 
               
               i 
             
             = 
             
               
                 
                   [ 
                   
                     
                       
                         1 
                       
                     
                     
                       
                         1 
                       
                     
                     
                       
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     In this case, the on/off pattern depends not only on the identity of the ED  110 , but also on the input bit sequence. 
       FIG. 11  illustrates a method, for carrying out at the reception point  512 , of processing (step  538 R,  FIG. 5A ) the backscatter signal  600 BS that includes ED data. While  FIG. 7  illustrates processing the backscatter signal  600 BS to obtain information, such as position ( FIG. 8 ) and relative time difference ( FIG. 9 ), from p-slot borders,  FIG. 11  is specific to obtaining data that the ED  110  has included in the backscatter signal  600 BS using methods discussed hereinbefore. 
     The reception point  512  normalizes (step  1102 ) the received backscatter signal by dividing the received backscatter signal by the forward signal, thereby obtaining a normalized backscatter signal. The normalized backscatter signal may be considered to be representative of s i (k), k=1, . . . , K. The reception point  512  may then process (step  1104 ) the normalized backscatter signal to obtain the ED data represented by the symbol sequence s i (k), k=1, . . . , K. The reception point  512  may then record (step  1106 ) the ED data. 
     It has been disclosed hereinbefore that the symbol, s i (k), may be different from p-slot k to p-slot k+1. It has been discussed herein that the symbol, s i (k), may carry ED data. In an aspect of the present application, the symbol, s i (k), may be identical in each of the L p-slots among the K p-slots. This repetition of data may be understood to provide what is known as “coding gain.” 
     The forward signal may be designed to facilitate aggregate channel state information (CSI) estimation by the reception point  512 . The term “aggregate channel” may be understood to include the forward channel from the transmission point  502  to the ED  110  and the back channel from the ED  110  to the reception point  512 . Improvements in CSI estimation by the reception point  512  may be considered to be useful for allowing the reception point  512  to better decode the ED data over the p-slots. 
     The transmission (step  522 ,  FIG. 5A ) of the radio frequency forward signal  600 FS may be optimized for CSI acquisition. For CSI acquisition, frequency granularity may be considered more important than time granularity, since the aggregate channel may be considered to be more static over time than over frequency. 
     It follows that a multi-carrier design for the forward signal  600 FS is preferable. 
     In addition to the resource allocation aspects of the forward signal design, consideration may also be applied to a sequence design for the forward signal  600 FS. The sequence in a forward signal may include one or more of a positioning reference signal (PRS), a demodulated reference signal (DMRS), another reference signal and data. 
       FIG. 12  illustrates example steps in a method of processing (step  538 R,  FIG. 5A ), at the reception point  512 , the received backscatter signal  600 BS for CSI acquisition. The method of  FIG. 12  commences with the reception point  512  recognizing (step  1202 ) the ED p-slot of the backscatter signal  600 BS. That is, the reception point  512  determines the boundaries of the ED p-slot. The reception point  512  may then normalize (step  1204 ) the received backscatter signal  600 BS by dividing the received backscatter signal  600 BS by the forward signal  600 FS to, thereby, obtain a normalized backscatter signal. The normalized backscatter signal may be considered to be representative of the product of the aggregate channel (H) and s i (k). Therefore, if s i (k) is known or somehow can be obtained from the backscatter signal  600 BS, the normalized backscatter signal can be further divided by s i (k), k=1, . . . , K, over each corresponding p-slot from which the aggregate channel can be estimated (step  1206 ). 
     In some embodiments, when the knowledge of s i (k), k=1, . . . , K, is not available at the reception point  512 , the ED  110  can be instructed to transmit some “reference p-slots” over which s i (k) is known. In some embodiments, the ED  110  does not multiply the forward signal  600 FS in the reference p-slots and, hence, s i (k)=1 in those p-slots. This facilitates the estimation of aggregate channel over the reference p-slots and, if the channel does not change much over different p-slots, this helps determining s i (k) over other p-slots, which gives more accurate estimation of the aggregate channel. In some embodiments, the process of estimating the aggregate channel and s i (k), k=1, . . . , K, can be done in an iterative fashion. 
     In some embodiments, the step of normalizing (step  1204 ) the backscatter signal may not be performed. In this case, the reception point  512  performs removing the symbols s i (k), k=1, . . . , K from the backscatter signal based on the methods described above. After the symbols s i (k), k=1, . . . , K have been removed (step  1206 ) from the received backscatter signal, the result may be called a “raw” signal. It may be shown that the raw signal can act as a reference signal for CSI estimation (step  1208 ). It may also be shown that the raw signal can act as a radar signal for range estimation (step  1210 ). Notably, the CSI estimation (step  1208 ) and the range estimation (step  1210 ) may be carried out simultaneously. 
     Since the CSI estimation (step  1208 ) does not change over from one p-slot during which the ED  110  transmits the backscatter signal to another p-slot during which the ED  110  transmits the backscatter signal, the CSI estimation (step  1208 ) can be further improved by averaging over all L p-slots (among the total of K p-slots) during which the ED  110  transmits the backscatter signal. 
     Notably, when, according to aspects of the present application, the ED  110  transmits the backscatter signal that includes ED data, the ED  110  merely performs the transmitting responsive to receiving the forward signal. It follows that a malicious combination of the transmission point  502  and the reception point  512  could gain access to the ED data by sending a forward signal and reading the backscatter signal. 
     Accordingly, further aspects of the present application relate to configuration of the elements of the environment so that only the appropriate reception point  512  may have access to the ED data. It is proposed herein to arrange that the ED  110  perturbs the backscatter signal with a perturbation pattern for each transmission p-slot. The perturbation pattern may, in one example, be built-in to each ED  110 . The ED  110  may provide the perturbation pattern to the reception point  512  once, e.g., through a secure link. When deemed necessary, the transmission point  502  may reconfigure the ED  110  with a new perturbation pattern. In some embodiments, the perturbation pattern may be determined and configured by the network and provided to the ED  110  when the ED  110  accesses the network through a secure link. The transmission point  502  would also update the reception point  512  with the new perturbation pattern. 
     The perturbation may be represented as s i (k)=f i,k (u i (k)), where u i (k) denotes an ED-data-carrying symbol to be transmitted by the i th  ED  110  over the kth p-slot, f i,k (⋅) denotes the perturbation function, which depends on the identity of the i th  ED  110  and the index, k, of the p-slot, and s i (k) is the resultant transmitted symbol. That is, s i (k) is the symbol used by the ED  110  to alter the forward signal to form (step  528 ,  FIG. 5A ) the backscatter signal  600 BS. 
     One example of a perturbation function is a phase shift, which may be represented as s i (k)=u i (k)e jϕ     i,k   . This perturbation function can be embedded into a definition of a constellation or codebook that is specific to the ED  110  and can be realized by impedance matching. 
     As a consequence of the use of the perturbation function, a malicious version of the reception point  512 , without access to the codebook, would be unlikely to be able to quickly decode the received s i (k) to determine u i (k). It is understood that, theoretically, the malicious version of the reception point  512  may eventually decode the backscatter signal in a particular p-slot by testing multiple hypothesis phase shifts. It is further proposed that the feasibility of such a decoding approach may be rendered relatively low by causing the malicious version of the reception point  512  to have to test a very large number of hypothesis phase shifts. 
     In addition to the resource allocation aspects of the forward signal design, consideration may also be applied to a sequence design for the forward signal. The sequence in a forward signal may include one or more of a Positioning Reference Signal (PRS), a Demodulation Reference Signal (DMRS), another reference signal and data. 
     In a case wherein the transmission point  502 , at the origin of the forward signal, and the reception point  512 , the receiver of the backscatter signal, are part of the same node, the forward signal may be designed to contain data for specific EDs  110 . The data in the forward signal may be intended for all of the EDs  110 , in which case the data may be considered to be broadcast. The data in the forward signal may be intended for a specific subset of the EDs  110 , in which case the data may be considered to be groupcast. The data in the forward signal may be intended for a specific one of the EDs  110 , in which case the data may be considered to be unicast. 
     That is, just as the ED  110  may form (step  528 ,  FIG. 5 ) a backscatter signal  600 BS modulated with ED data for consumption by the reception point  512 , the transmission point  502  may form the forward signal modulated with data designated for consumption by specific EDs  110  before transmitting (step  522 ,  FIG. 5A ) the forward signal  600 FS. As will be understood, the specific EDs  110  designated for reception of the data from the transmission point  502  may be distinct from the EDs  110  that are configured for performing backscatter communications. 
     Throughout this application, various configuration parameters for the manner in which the ED  110  acts to backscatter, or acts to not backscatter, a forward signal have been discussed. For a given ED  110 , the configuration parameters may include a p-slot duration, an ON/OFF pattern, a backscatter codebook and a perturbation function, among other configuration parameters. Additionally, the configuration parameters may include the forward signal parameters including bandwidth, waveform, numerology, and a-slot duration. In some embodiments, a-slot duration can be obtained from numerology. In some embodiments, the configuration parameters may include the relation of p-slot and a-slot, for example how many a-slots are in each p-slot. In some embodiments, the configuration parameters may also include the index of the “reference p-slots” used for channel estimation at the reception point  512 . The configuration parameters that define the backscattering by the ED  110  may be provided to the ED  110  by an entity in the environment  100  of  FIG. 1  in the form of signaling. The signaling method may include dynamic signaling, such as layer one (L1) signaling, or semi-static signaling, for example, using a layer higher than L1, such as RRC or media access control (MAC) control element (MAC-CE). The configuration parameters of the backscattering may also be provided to the reception point  512  by an entity in the environment  100  of  FIG. 1 . If the reception point  512  is a network entity, the signaling method may include X2 or Xn signaling. If the reception point  512  is another ED  110 , the signaling method may include dynamic signaling, such as L1 signaling, or semi-static signaling, for example, using a higher layer, such as RRC or MAC-CE. Alternatively, in view of the ED  110  being configured to have an identity, selected configuration parameters may be determined by the ED  110  though use of a function. For example, by subjecting the identity of the ED  110  to a specific function, the ED  110  may determine an ON/OFF pattern. In this case, the parameters of the specific function may be provided to the ED  110  through signaling in the form of dynamic signaling, such as L1 signaling, or semi-static signaling, for example, using a higher layer, such as RRC or MAC-CE. 
     Aspects of the present application may be seen to have advantages in the area of sensor nodes operating according to 5G networking protocols. Such sensor nodes (sometimes “tags”) may be considered to include very low-cost devices that have limited battery power. Despite limited battery power, the sensor nodes are regularly called upon to actively communicate with a central network component to report a result of some sensing. Sensor nodes operating in accordance with aspects of the present application may be seen to only transmit information to a reception point  512  by backscattering a signal received from a transmitter. Conveniently, the sensor nodes need not necessarily perform baseband processing or analog to digital conversion. 
       FIG. 13  illustrates example steps in a method, carried out by the processor  200  of the electronic device  110 , to switch between the active device components  211  and the passive device components  212 . The context for the method of  FIG. 13  may be considered to begin with the electronic device  110  operating in the normal power consumption operation mode  402  (see  FIGS. 4A, 4B and 4C ). Upon determining that, responsive to an instruction received (step  1302 ) from the base station  170 , the electronic device  110  is to transition itself into the low power consumption operation mode  404 . 
     Responsive to detecting (step  1302 ) the initiation, the processor  200  optionally deactivates (step  1204 ) the active device components  211  and causes (step  1306 ) the passive device components  212  to commence backscattering, where the backscattering assists in the performance of the certain functions previously performed by the active device components  211 . The certain functions, as discussed hereinbefore, may relate to facilitating of tracking the electronic device  110 , facilitating timing maintenance, facilitating identification of the electronic device  110 , facilitating preamble transmission, facilitating determination of a position for the electronic device  110  and facilitating channel measurements. 
     In some aspects of the present application, the electronic device  110  implicitly receives (step  1302 ) an instruction to cause (step  1306 ) the passive device components  212  to commence backscattering when the electronic device  110  detects initiation of the release procedure  442  or the release with suspend procedure  446  (see  FIGS. 4B and 4C ). In some aspects of the present application, the electronic device  110  explicitly receives (step  1302 ) an instruction via signaling to cause (step  1306 ) the passive device components  212  to commence backscattering. 
     As noted hereinbefore and illustrated, in  FIG. 13 , through the use of dashed lines, the deactivation (step  1304 ) of the active device components  211  is optional. That is, it is possible to cause (step  1306 ) the passive device components  212  to be activated without turning off the active device components  211 . It is also possible to cause (step  1306 ) the passive device components  212  to be activated without the electronic device  110  transitioning itself into the RRC_INACTIVE state  406 . In the scheme illustrated in  FIG. 4B , it may be considered that only the active device components  211  are active when the electronic device  110  is operating in the RRC_CONNECTED state  410  (in the normal power consumption operation mode  402 ) and only the passive device components  212  are active when the electronic device  110  is operating in the RRC_IDLE state  408  (in the low power consumption operation mode  404 ). 
     A signaling mechanism that allows a network entity to cause the ED  110  to enter into the low power consumption operation mode  404  may be periodic or aperiodic (on-demand based). For periodic transmission of the signaling, the network entity may be expected to provide, to the electronic device  110 , an indication of a starting time for the signaling, a period (a duration for the time between transmissions) as well as a duration for the signaling. For aperiodic transmission of the signaling, may be expected to provide, to the electronic device  110 , an indication of a starting time reference (e.g., a time slot in a transmission frame or an absolute timing point in a transmission frame) for the signaling and a duration for the signaling. It follows that the network entity may also use signaling to cause the electronic device  110  to enter into the normal power consumption operation mode  402 . 
       FIG. 14  illustrates example steps in a method, carried out by the processor  200  of the electronic device  110 , to switch between the passive device components  212  and the active device components  211 . The context for the method of  FIG. 14  may be considered to begin with the electronic device  110  operating in the low power consumption operation mode  404  (see  FIG. 4A ). Upon determining that, responsive to an instruction received (step  1402 ) from the base station  170 , the electronic device  110  is to transition itself into the normal power consumption operation mode  402 . That is, in the context of the scheme of  FIG. 4B , the electronic device  110  detects (step  1402 ) initiation of the resume procedure  464  or the establish procedure  424 . Responsive to detecting (step  1402 ) the initiation, the processor  200  optionally activates (step  1404 ) the active device components  211  and causes (step  1406 ) the passive device components  212  to cease backscattering. 
     It has been discussed that the receiving (step  1302 ,  1402 ) of an instruction from the base station  170  may involve detecting initiation of the release procedure  442 , the release with suspend procedure  446 , the resume procedure  464  or the establish procedure  424 . It should also be clear that, outside of the various state-to-state transition procedures ( 424 ,  442 ,  446 ,  462 ,  464 ) illustrated in  FIG. 4B , an entity of the environment  100  ( FIG. 1 ) that is not necessarily the base station  170 , may use a signaling mechanism to directly instruct the ED  110  to switch between the normal power consumption operation mode  402  and the low power consumption operation mode  404 , that is, to cause the passive device components  212  to commence (step  1306 ) or cease (step  1406 ) backscattering. The signaling method may include dynamic signaling, such as L1 signaling, or semi-static signaling, for example using a higher layer such as RRC or MAC-CE. 
     Indeed, such a signaling mechanism from a network entity in the environment  100  of  FIG. 1  to the ED  110  may be one of many signaling mechanisms. As an example, the signaling method may include dynamic signaling, such as L1 signaling, or semi-static signaling, for example, using a higher layer such as RRC or MAC-CE. 
     A signaling mechanism that allows the network entity to control the ED  110  to cause the passive device components  212  to commence (step  1306 ) or cease (step  1406 ) backscattering may be periodic or aperiodic (on-demand based). For periodic transmission of the signaling, the network entity may be expected to provide, to the ED  110 , an indication of a starting time for the signaling, a period (a duration for the time between transmissions) as well as a duration for the signaling. For aperiodic transmission of the signaling, may be expected to provide, to the ED  110 , an indication of a starting time reference (e.g., a time slot in a transmission frame or an absolute timing point in a transmission frame) for the signaling and a duration for the signaling. 
     To this point, the ED  110  has been discussed as being one of three distinct states, based on RRC signaling: the RRC_CONNECTED state  410 ; the RRC_INACTIVE state  406 ; and the RRC_IDLE state  408  (see  FIG. 46 ). In future, different states may be defined for the ED  110 . It should be clear that, the passive device components  212  may operate in accordance with aspects of the present application in whatever state the ED  110  is operating. 
     In other aspects of the present application, a switch between the normal power consumption mode  402  and the low power consumption mode  404  may be initiated by the electronic device  110 . In accordance with aspects of the present application represented by example steps in a method illustrated in  FIG. 15 , the electronic device  110  may be configured to transmit (step  1502 ) signaling to a network entity to indicate that the electronic device  110  will imminently perform a switch between the normal power consumption mode  402  and the low power consumption mode  402 . In one instance, the electronic device  110  does not wait for permission, from the network entity, before performing (step  1506 ) the mode switch. In another instance, the electronic device  110  waits to receive (step  1504 ) permission, from the network entity, before performing (step  1506 ) the mode switch. 
       FIG. 16  illustrates a temporal view  1600  of operation of the electronic device  110 , including a time period  1602  during which the electronic device  110  is operating in the normal power consumption mode  402 . The temporal view  1600  also includes a time period  1604  during which the electronic device  110  is operating in the low power consumption mode  404 . The temporal view  1600  further includes an indication  1606  of a moment at which there is mode switch signaling. In one example, the indication  1606  relates to the electronic device  110  transmitting signaling to a network entity to indicate that the electronic device  110  will imminently perform a switch between the normal power consumption mode  402  and the low power consumption mode  404 . In another example, the indication  1606  relates to the electronic device  110  receiving signaling, from a network entity, to instruct the electronic device  110  to perform a switch between the normal power consumption mode  402  and the low power consumption mode  404 . 
     Notably, without regard to whether the mode switch signaling is received (steps  1302 ,  1402 ) or transmitted (step  1502 ), the mode switch signaling may contain additional information beyond an instruction (steps  1302 ,  1402 ) or an indication (step  1502 ). The additional information may relate to the functions (or, perhaps, a single function) that are to be performed, by the electronic device  110 , when in the low power consumption mode  404 . 
     It should be appreciated that one or more steps of the embodiment methods provided herein may be performed by corresponding units or modules. For example, data may be transmitted by a transmitting unit or a transmitting module. Data may be received by a receiving unit or a receiving module. Data may be processed by a processing unit or a processing module. The respective units/modules may be hardware, software, or a combination thereof. For instance, one or more of the units/modules may be an integrated circuit, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs). It will be appreciated that where the modules are software, they may be retrieved by a processor, in whole or part as needed, individually or together for processing, in single or multiple instances as required, and that the modules themselves may include instructions for further deployment and instantiation. 
     Although a combination of features is shown in the illustrated embodiments, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system or method designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
     The embodiments set forth herein represent information sufficient to practice the claimed subject matter and illustrate ways of practicing such subject matter. Upon reading the following description in light of the accompanying figures, those of skill in the art will understand the concepts of the claimed subject matter and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
     Moreover, it will be appreciated that any module, component, or device disclosed herein that executes instructions may include, or otherwise have access to, a non-transitory computer/processor readable storage medium or media for storage of information, such as computer/processor readable instructions, data structures, program modules and/or other data. A non-exhaustive list of examples of non-transitory computer/processor readable storage media includes magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, optical disks such as compact disc read-only memory (CD-ROM), digital video discs or digital versatile discs (i.e., DVDs), Blu-ray Disc™, or other optical storage, volatile and non-volatile, removable and non-removable media implemented in any method or technology, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology. Any such non-transitory computer/processor storage media may be part of a device or accessible or connectable thereto. Computer/processor readable/executable instructions to implement an application or module described herein may be stored or otherwise held by such non-transitory computer/processor readable storage media. 
     Although this disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the disclosure, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.