TECHNICAL FIELD

The present disclosure relates to a client device (STA) using a wake-up packet (WUP) for channel selection decision and an access point device (AP) transmitting such wake-up packet. The disclosure further relates to a method and a device for wake-up signal based channel selection, in particular for client devices, access-point devices and/or machine- type communication devices of wireless communication networks, for example according to the 802.1 1 ax WiFi standard or according to the 3GPP LTE (Long Term Evolution) standard.

BACKGROUND

Commonly the operation in wireless network starts with a network search where stations (STAs) are scanning known frequency bands to find an existing network to associate with. The specific working frequency is called a Channel and the search process is a part of the channel selection procedure.

Channel selection can be a very long procedure (especially during initial association) that requires a number of trials and iterations, till the relevant network is obtained. In many cases, like an loT (Internet of Things) network, the power resources of a station are limited. Thus an initial network search can be crucial for total power consumption budget. In order to minimize it, the next generation of wireless networks introduce a wake-up packet (WUP) transmitted by the Access Point (AP). This signal allows a STA to stay in a very low power consumption mode until it is triggered by a WUP and needs to switch to a regular mode for data exchange with an AP. Currently most of STAs perform an initial network search by active or passive techniques, where they sense the network or transmit a trial signal to determine if there is an AP that can accept the STA. Most of the designs involve a lot of data that should be sent in order to find a relevant network that is available for association of a new STA. Due to the absence of prior knowledge on network status (the exact frequency and availability) in worst scenario a STA can scan all the available bands before a relevant network is found. WUP is to be introduced for next generation networks where many STAs have power consumption constraints (e.g. loT STAs). WUP is specially designed to be decoded by a very simple receiver which does not require high power consumption blocks (like exact frequency in RF, digital processing and etc.). Current discussions regarding WUP format are mostly focusing on a trigger that can be recognized by the STA in order to switch to normal operating mode. This allows a STA to stay in a very low power operational mode as long as no data is required to be sent or received. This also allows a STA to perform an initial scan in a low power mode before the association procedure is initialized.

The main problem of both existing methods and the new discussed WUP based techniques is an absence of prior knowledge regarding the network. Even if a STA operates in a regular power mode, where all the functionalities are switched on, it cannot predict where an AP is located in frequency (which channel is being used by the AP) and which APs are available for association. In lower power mode this knowledge is even more limited because the information that is provided by the WUP is relevant for wake up decision only. Thus in most cases the only technique to find an AP is by scanning all the available frequencies and/or transmitting probe packets on each frequency that can be potentially a relevant one.

In Figures 1 and 2 two examples of initial channel selection are depicted. Figure 1 illustrates the regular channel scan 100. The STA is scanning a network to find a broadcasted signal 102 or trying to transmit at every frequency until the relevant response is received. Assuming the broadcast signal 102 contains enough information to decide on the association, STA starts association 106 after first broadcast signal is detected. All the process is performed in regular power mode which leads to a high power consumption.

Figure 2 illustrates the channel scan using WUP 200. Assuming WUP can be used for the initial scan, Figure 2 depicts an example of channel selection procedure. A STA starts scanning 201 from some frequency. Upon detecting WUP 202 a primary modem is switched on 203, however STA cannot predict if there will be a trigger for association data 204. After timeout 205 STA switches 206 to the next channel and performs the same procedure 207, 208, 209, 210. It can easily be understood that in the worst case a very long period of time could be wasted before the relevant channel is found 212. Moreover, during at least part of this period the STA is working in regular power mode which significantly increases the power consumption.

The main point of both examples is that current existing procedure and possible future procedure including WUP can be very inefficient and lead to a very high overhead of time and power.

SUMMARY It is the object of the invention to improve the channel selection procedure in wireless communication networks, in particular in order to save time and/or power.

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

The idea presented in this disclosure presents an efficient reuse of WUP for minimization of time required to complete the channel selection procedure.

The devices and methods described herein may perform random access procedures. Random access (RA) is a procedure that allows client type communication devices to request from an access point (AP) type communication device resources for transmission by use of a resource request and by another procedure to initiate an association procedure with the AP. In other words, this mechanism is usually applied by the client devices that need to request the resources. The client devices can achieve an association with a specific AP. Currently, in the 802.1 1 ax standard, RA is applied immediately after a trigger frame (TF), which is transmitted by the AP. Thus the client devices wait for AP to trigger them (indicate the existence of a random access opportunity). A TF frame may be followed by several RA opportunities. Within each opportunity, clients can try to access the channel. For doing so they contend with each other.

The devices and methods described herein may be configured to communicate using MAC based RA. In this technique, the RA is transmitted as regular data, including payload, where each client allocates its transmission within a single resource unit (RU) as defined in 802.1 1 ax. A RU is defined as a set of continuous subcarriers, e.g. 26, over some period of time. The AP can decide to provide more than one RA frame triggered by a single TF. The specific frame and the RU within the frame can be chosen in a random way by each client type communication device. No distinguishing between the non- associated client type communication devices and associated client type communication devices is introduced and all the client type communication devices that try to transmit an RA, are allowed to choose any time/frequency resources allocated for the current RA opportunity. A random access block typically comprises a plurality of frequency subcarriers and a plurality of time slots. A frequency section comprises at least one such frequency subcarrier but typically a plurality of neighboring (the spacing between two neighboring frequency subcarriers depends on what is defined by the underlying communication system) frequency subcarriers.

The devices and methods described herein may be configured to communicate using PHY based RA. PHY based RA is transmitted as PHY signaling and does not include any higher layer (MAC or above) payload. Several communication techniques regarding PHY based RA, where the RA data is a simple PHY signaling that informs the AP that a specific client type communication device wants resources, are available. The RA data is thus very short and allows a higher number of client type communication devices to be allocated within a single RA frame. The devices described herein may be machine type communication devices. Machine

Type Communication (MTC or M2M) enables machines to communicate directly with one another, e.g. according to the requirements of the Internet of Things (loT). Machine to machine (M2M) refers to direct communication between devices using any

communications channel, including wired and wireless. Machine to machine

communication can include industrial instrumentation, enabling a sensor or meter to communicate the data it records (such as temperature, inventory level, etc.) to application software that can use it (for example, adjusting an industrial process based on temperature). The methods and devices described herein may be implemented in wireless

communication networks, in particular communication networks based on mobile communication standards such as LTE, in particular LTE-A and/or OFDM, as used in 4G and 5G networks, for example. The methods and devices described below may further be implemented in a base station (NodeB, eNodeB) or a mobile device (or mobile station or User Equipment (UE)). The described devices may include integrated circuits and/or passives and may be manufactured according to various technologies. For example, the circuits may be designed as logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, optical circuits, memory circuits and/or integrated passives. The devices described herein may be configured to transmit and/or receive radio signals. Radio signals may be or may include radio frequency signals radiated by a radio transmitting device (or radio transmitter or sender) with a radio carrier frequency lying in a range of about 3 kHz to 300 GHz. The frequency range may correspond to frequencies of alternating current electrical signals used to produce and detect radio waves.

The devices and methods described herein may be applied in OFDM and OFDMA systems. OFDM and OFDMA are schemes for encoding digital data on multiple carrier frequencies. A large number of closely spaced orthogonal sub-carrier signals may be used to carry data. Due to the orthogonality of the sub-carriers crosstalk between sub- carriers may be suppressed.

In order to describe the invention in detail, the following terms, abbreviations and notations will be used:

STA: Station, also referred to as client device

AP: Access Point, also referred to as access point device

loT: Internet of Things

WUP: Wake-Up Packet

RA: Random Access

TF: Trigger Frame

TFR: Trigger Frame for RA

OFDM: Orthogonal Frequency Division Multiplexing

OFDMA: Orthogonal Frequency Division Multiple Access

UL: Uplink

DL: Downlink

PHY: Physical layer (device)

MAC: Medium Access Controller

According to a first aspect, the invention relates to a client device (STA) for

communicating with an access point device (AP), the STA comprising: a transceiver, configured to: receive a wake-up packet (WUP) indicating the STA to switch from a low power operation mode to a regular power operation mode, wherein the WUP comprises channel selection information for assisting the STA in a channel selection decision. By using such channel selection information, unnecessary trial of association can be prevented and the time required for completing an initial scan and association can be minimized. Using channel selection information allows prior knowledge to decide on association initialization. The STA can maximize the working period in low power mode during the initial scan and reduce the power consumption. Thus, the channel selection procedure can be improved saving time and power.

In a first possible implementation form of the STA according to the first aspect, the channel selection information comprises information of a frequency bandwidth supported by the AP for association with the STA.

Using the channel selection information to indicate information of a frequency bandwidth supported by the AP for association with the STA allows the STA to directly move its local oscillator frequency to the frequency bandwidth supported by the AP without searching the correct frequency bandwidth in a long searching procedure. Thus time and power can be saved.

In a second possible implementation form of the STA according to the first aspect as such or according to the first implementation form of the first aspect, the channel selection information comprises at least one of channel specification information, channel availability information and channel suggestion information.

When the channel selection information includes channel specification information, channel availability information and/or channel suggestion information, the current channel supported by the AP can be specified, its availability can be indicated or the STA can be directed to another channel supported by the AP. This accelerates the initialization procedure and hence saves time and resources.

In a third possible implementation form of the STA according to the second

implementation form of the first aspect, the channel specification information comprises at least one of: an indication whether a current communication channel of the AP is a Primary Channel or not, in particular a yes or no indication, a channel number of a current communication channel of the AP, and a location of the current communication channel of the AP relative to a predetermined communication channel, in particular relative to the Primary Channel.

Such information facilitates the channel selection procedure by indicating the STA whether a current communication channel of the AP is a Primary Channel or not, by indicating the STA a channel number of a current communication channel of the AP, and by indicating the STA a location of the current communication channel of the AP relative to a predetermined communication channel, e.g. relative to the Primary Channel. By using such information the STA can save time and power.

In a fourth possible implementation form of the STA according to any of the second or the third implementation forms of the first aspect, the channel availability information comprises information if the AP accepts a new STA for an association, in particular a yes or no indication.

When the STA knows if the AP accepts a new STA it can continue its channel selection procedure, otherwise it can interrupt the current channel selection procedure and start searching for another AP. This improves the channel initialization. In particular a yes or no indication is highly efficient saving time and bandwidth resources.

In a fifth possible implementation form of the STA according to any of the second to the fourth implementation forms of the first aspect, the channel suggestion information comprises information, in particular a channel number, on which communication channel the AP accepts a new STA for an association.

Such information helps the STA to find the correct channel on which the AP is available for an association, thereby saving time and power consumption.

In a sixth possible implementation form of the STA according to any of the second to the fifth implementation forms of the first aspect, the channel suggestion information comprises information, in particular a channel number, on which communication channel another AP accepts a new STA for an association. Such information helps the STA to quickly find another AP, in particular a channel on which another AP is available for an association, thereby saving time and power consumption.

According to a second aspect, the invention relates to an access point device (AP) for communicating with a client device (STA), the AP comprising: a transceiver, configured to: transmit a wake-up packet (WUP) indicating the STA to switch from a low power operation mode to a regular power operation mode, wherein the WUP comprises channel selection information for assisting the STA in a channel selection decision.

By using such channel selection information, unnecessary trial of association can be prevented and the time required for completing an initial scan and association can be minimized. Using channel selection information allows prior knowledge to decide on association initialization. The STA can maximize the working period in low power mode during the initial scan and reduce the power consumption. Thus, the channel selection procedure can be improved saving time and power.

In a first possible implementation form of the AP according to the second aspect, the channel selection information comprises information of a frequency bandwidth supported by the AP for association with the STA.

Using the channel selection information to indicate information of a frequency bandwidth supported by the AP for association with the STA allows the STA to directly move its local oscillator frequency to the frequency bandwidth supported by the AP without searching the correct frequency bandwidth in a long searching procedure. Thus time and power can be saved.

In a second possible implementation form of the AP according to the second aspect as such or according to the first implementation form of the second aspect, the channel selection information comprises at least one of channel specification information, channel availability information and channel suggestion information.

When the channel selection information includes channel specification information, channel availability information and/or channel suggestion information, the current channel supported by the AP can be specified, its availability can be indicated or the STA can be directed to another channel supported by the AP. This accelerates the initialization procedure and hence saves time and resources. In a third possible implementation form of the AP according to the second implementation form of the second aspect, the channel specification information comprises at least one of: an indication whether a current communication channel of the AP is a Primary Channel or not, in particular a yes or no indication, a channel number of a current communication channel of the AP, and a location of the current communication channel of the AP relative to a predetermined communication channel, in particular relative to the Primary Channel.

Such information facilitates the channel selection procedure by indicating the STA whether a current communication channel of the AP is a Primary Channel or not, by indicating the STA a channel number of a current communication channel of the AP, and by indicating the STA a location of the current communication channel of the AP relative to a predetermined communication channel, e.g. relative to the Primary Channel. By using such information the STA can save time and power.

In a fourth possible implementation form of the AP according to any of the second or the third implementation forms of the second aspect, the channel availability information comprises information if the AP accepts a new STA for an association, in particular a yes or no indication.

When the STA knows if the AP accepts a new STA it can continue its channel selection procedure, otherwise it can interrupt the current channel selection procedure and start searching for another AP. This improves the channel initialization.

In a fifth possible implementation form of the AP according to any of the second to the fourth implementation forms of the second aspect, the channel suggestion information comprises information, in particular a channel number, on which communication channel the AP accepts a new STA for an association.

Such information helps the STA to find the correct channel on which the AP is available for an association, thereby saving time and power consumption. In a sixth possible implementation form of the AP according to any of the second to the fifth implementation forms of the second aspect, the channel suggestion information comprises information, in particular a channel number, on which communication channel another AP accepts a new STA for an association.

Such information helps the STA to quickly find another AP, in particular a channel on which another AP is available for an association, thereby saving time and power consumption. According to a third aspect, the invention relates to a method for assisting a client device (STA) in a channel selection decision, the method comprising: receiving a wake-up packet (WUP), from an AP, indicating the STA to switch from a low power operation mode to a regular power operation mode, wherein the WUP comprises channel selection information for assisting the STA in a channel selection decision.

By using such channel selection information, unnecessary trial of association can be prevented and the time required for completing an initial scan and association can be minimized. Using channel selection information allows prior knowledge to decide on association initialization. The STA can maximize the working period in low power mode during the initial scan and reduce the power consumption. Thus, the channel selection procedure can be improved saving time and power.

BRIEF DESCRIPTION OF THE DRAWINGS Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a time diagram illustrating a regular channel scan 100 as performed by a STA;

Fig. 2 shows a time diagram illustrating a channel scan using a wake-up packet (WUP) 200 as performed by a STA;

Fig. 3 shows a schematic diagram illustrating an exemplary wake-up packet (WUP) 300 with Channel Selection Info 303 according to an implementation form; Fig. 4 shows a schematic time-frequency diagram illustrating a channel information example 400 according to an implementation form; Fig. 5 shows a schematic time-frequency diagram illustrating a channel availability example 500 according to an implementation form;

Fig. 6 shows a block diagram illustrating a STA 600 according to an implementation form; Fig. 7 shows a block diagram illustrating an AP 700 according to an implementation form; and

Fig. 8 shows a schematic diagram illustrating a method 800 for assisting a client device (STA) in a channel selection decision according to an implementation form.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

Fig. 3 shows a schematic diagram illustrating an exemplary wake-up packet (WUP) 300 with Channel Selection Info 303 according to an implementation form. This WUP 300, that is just an example for the structure of a wake-up packet, may include a section including a WUP preamble 301 , a section including WUP data 302, a section including channel selection information 303 and a section including an error correction code 304, e.g. a cyclic redundancy check over the whole packet 300 or over part of the packet 300. The section including the channel selection information 303 is information added to the WUP 300 that can assist a STA in the decision of channel selection. As mentioned earlier, the main problem is an absence of the prior knowledge regarding the network

status/availability. Thus very simple information is added that can prevent unnecessary trials and shorten the initial channel selection. One exemplary WUP format design is presented on Fig. 3.

The channel selection information 303 added to the WUP 300 may include one or more of the following information: Channel specification information, Channel availability information, and Channel suggestion information. Then, AP can set the information according to network status. STA can use the information to decide regarding association procedure initialization with higher probability to complete it (within a relatively short time). The disclosed method can provide important information for assisting STAs with respect to the decision on channel selection and therefore shorten the time required to complete an initial scan and association procedure.

Fig. 4 shows a schematic time-frequency diagram illustrating a channel information example 400 according to an implementation form. The time-frequency diagram illustrates the full 2.4/5G band 510 and a section thereof indicating the supported bandwidth (BW) 51 1 . This supported BW 51 1 includes the primary channel 501 , e.g. having the channel number 0, a detected channel 502, e.g. having the channel number 4 and further channels up to a channel number 8.

If a STA can understand which AP transmitted the WUP, what channel it is currently using and if it is possible to start the association with it, then the STA can decide when to stop the initial scan. Thus basic indication can be provided with a very small overhead within the WUP to create this understanding.

It is assumed that in low power mode the STA has some inaccuracy in frequency due to limited RF capabilities. Thus, information is provided on current channel. This information can be for example (as depicted in Fig. 4): Indication on Primary Channel 501 ('NOT Primary' in the example); Absolute channel number 502 ('4' in the example); Location of current channel 502 relative to some predefined point (e.g. '+4' relative to Primary Channel 501 ). Fig. 5 shows a schematic time-frequency diagram illustrating a channel availability example 500 according to an implementation form. The time-frequency diagram illustrates the full 2.4/5G band 510 and a section thereof indicating the supported bandwidth (BW) 51 1 . This supported BW 51 1 includes the primary channel 501 , e.g. having the channel number 0, a detected channel 502, e.g. having the channel number 4 and further channels available for association 503, e.g. channels up to a channel number 8.

For maximizing the probability that a STA can successfully complete the association procedure, the main question is whether it is possible for the AP to accept a new STA to the network. It can be provided by a simple YES/NO indication (in the channel availability information). If NO is indicated, STA will continue scanning without trying to send AP an association data.

If an AP is not available for association on the specific channel 502 but can accept a new STA on another channel 503 supported by this AP, it can indicate where to search for the available channel (by using channel suggestion information, see Fig. 5). For example, the AP can indicate to the STA that the current channel 502 is number 4, and the STA should associate on channel number 8.

For Channel Selection Procedure based on WUP info, the updated procedure can for example include the following steps: Scan channels till WUP is received; Decode the provided information; Check the availability for the association; If association is allowed start association on this channel; If association is not allowed, check if there is another channel available (e.g. suggested channel); If yes switch to the indicated channel; If no continue on scanning; If no availability for the association: continue on scanning.

Fig. 6 shows a block diagram illustrating a STA 600 according to an implementation form. The STA 600 may be used for communicating with an access point device (AP), e.g. an AP 700 as described below with respect to Fig. 7. The STA 600 includes a transceiver 601 . The transceiver 601 is configured to receive a wake-up packet (WUP), e.g. a WUP 300 as described above with respect to Fig. 3. The WUP 300 indicates the STA 600 to switch from a low power operation mode to a regular power operation mode. The WUP 300 includes channel selection information 303 for assisting the STA 600 in a channel selection decision.

The channel selection information 303 may include information of a frequency bandwidth supported by the AP 700 for association with the STA 600, e.g. frequency bandwidth information 51 1 as described above with respect to Figures 4 and 5. The channel selection information 303 may include channel specification information, channel availability information and/or channel suggestion information.

The channel specification information may include an indication whether a current communication channel of the AP 700 is a Primary Channel or not, in particular a yes or no indication, e.g. as described above with respect to Figures 4 and 5. The channel specification information may include a channel number of a current communication channel of the AP 700, e.g. as described above with respect to Figures 4 and 5. The channel specification information may include a location of the current communication channel of the AP 700 relative to a predetermined communication channel, in particular relative to the Primary Channel, e.g. as described above with respect to Figures 4 and 5.

The channel availability information may include information if the AP 700 accepts a new STA 600 for an association, in particular a yes or no indication, e.g. as described above with respect to Figures 4 and 5.

The channel suggestion information may include information, in particular a channel number, on which communication channel the AP 700 accepts a new STA 600 for an association, e.g. as described above with respect to Figures 4 and 5. The channel suggestion information may include information, in particular a channel number, on which communication channel another AP accepts a new STA 600 for an association, e.g. as described above with respect to Figures 4 and 5.

Fig. 7 shows a block diagram illustrating an AP 700 according to an implementation form. The AP 700 may be used for communicating with a client device (STA), e.g. a STA 600 as described above with respect to Fig. 6. The AP 700 includes a transceiver 701. The transceiver 701 is configured to transmit a wake-up packet (WUP), e.g. a WUP 300 as described above with respect to Fig. 3, indicating the STA 600 to switch from a low power operation mode to a regular power operation mode. The WUP 300 includes channel selection information 303 for assisting the STA 600 in a channel selection decision, e.g. channel selection information 303 as described above with respect to Fig. 3.

The channel selection information 303 may include information of a frequency bandwidth supported by the AP 700 for association with the STA 600, e.g. frequency bandwidth information 51 1 as described above with respect to Figures 4 and 5.

The channel selection information 303 may include channel specification information, channel availability information and/or channel suggestion information. The channel specification information may include an indication whether a current communication channel of the AP 700 is a Primary Channel or not, in particular a yes or no indication, e.g. as described above with respect to Figures 4 and 5. The channel specification information may include a channel number of a current communication channel of the AP 700, e.g. as described above with respect to Figures 4 and 5. The channel specification information may include a location of the current communication channel of the AP 700 relative to a predetermined communication channel, in particular relative to the Primary Channel, e.g. as described above with respect to Figures 4 and 5.

The channel availability information may include information if the AP 700 accepts a new STA 600 for an association, in particular a yes or no indication, e.g. as described above with respect to Figures 4 and 5.

The channel suggestion information may include information, in particular a channel number, on which communication channel the AP 700 accepts a new STA 600 for an association, e.g. as described above with respect to Figures 4 and 5. The channel suggestion information may include information, in particular a channel number, on which communication channel another AP accepts a new STA 600 for an association, e.g. as described above with respect to Figures 4 and 5. Fig. 8 shows a schematic diagram illustrating a method 800 for assisting a client device (STA) in a channel selection decision according to an implementation form. The STA may be a STA 600 as described above with respect to Fig. 6. The method 800 includes:

receiving 801 a wake-up packet (WUP), e.g. a WUP 300 as described above with respect to Fig. 3, from an AP, e.g. an AP 700 as described above with respect to Fig. 7, indicating the STA 600 to switch from a low power operation mode to a regular power operation mode, wherein the WUP 300 comprises channel selection information for assisting the STA 600 in a channel selection decision, e.g. channel selection information 303 as described above with respect to Fig. 3 for assisting the STA 600 in a channel selection decision as described above with respect to Figures 4 and 5.

The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein, in particular the step of the method 800 described above. Such a computer program product may include a readable non-transitory storage medium storing program code thereon for use by a computer. The program code may perform the performing and computing steps described herein, in particular the method 800 described above. While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms "coupled" and "connected", along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be

appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.