Patent ID: 12191895

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

DETAILED DESCRIPTION

FIG.1is a schematic diagram illustrating broadcast operations performed in a Bluetooth wireless communication system. The wireless communication system1includes Bluetooth devices11and13. The Bluetooth device11is a broadcaster, and the Bluetooth device13is a scanner.

During the broadcast operation, the Bluetooth device11(broadcaster) transmits radio waves to the Bluetooth device13(scanner), wherein the radio waves are originated from a broadcast signal bcS carrying broadcast information BD. The broadcaster splits and encapsulates the broadcast information BD as broadcast packets, and the broadcast packets are transmitted in a unit of intervals. The interval may represent a time slot in BR/EDR or a time interval in LE. For the sake of illustration, a duration of a broadcast operation lasts for four continuous intervals T1, T2, T3, and T4 is illustrated example, as shown inFIG.2. However, the length of the duration of the broadcast operation is not limited.

Bluetooth standard utilizes adaptive frequency hopping (hereinafter, AFH) for data transmission. Bluetooth standard divides frequency bands into smaller radio frequency (hereinafter, RF) channels and rapidly hops between the RF channels when transmitting the broadcast packets.

FIG.2is a schematic diagram illustrating that the RF channels utilized as broadcast channels in different intervals bCh(T1), bCh(T2), bCh(T3), bCh(T4) are randomly selected for transmitting broadcast packets. The horizontal axis represents RF channels rfCh_1 to rfCH_X defined in Bluetooth standard. X=79 for BR/EDR applications and X=40 for LE applications.

Please note that not all the RF channels can be utilized for broadcast operation, and the selection of the broadcast channels needs to follow the Bluetooth standard. In the specification, the RF channels being utilized for transmitting broadcast packets are defined as the broadcast channel(s).

Thus, the RF channel being selected for transmitting the broadcast packet BD(T1) in interval T1 is defined as a broadcast channel bCh(T1). The RF channel being selected for transmitting the broadcast packet BD(T2) in interval T2 is defined as a broadcast channel bCh(T2). The RF channel being selected for transmitting the broadcast packet BD(T3) in interval T3 is defined as a broadcast channel bCh(T3). The RF channel being selected for transmitting the broadcast packet BD(T4) in interval T4 is defined as a broadcast channel bCh(T4).

From intervals T1 to T4, the broadcaster sequentially broadcasts the broadcast packets BD(T1), BD(T2), BD(T3), and BD(T4) over the broadcast channels bCh(T1), bCh(T2), bCh(T3) and bCh(T4). The broadcast channels bCh(T1), bCh(T2), bCh(T3), and bCh(T4) are freely selected by the broadcaster. On the other hand, the scanner sequentially scans whether there are broadcast packets that can be found in the broadcast channels.

FIG.3is a schematic diagram illustrating that some of the broadcast packets are disturbed. Three figures are shown inFIG.3. In these figures, the vertical axis represents the broadcast channels being selected during the broadcast operation, and the horizontal axis represents the interval (T). The broadcast channels being selected during the broadcast operation are arranged in the order of frequencies and numbered in ascending order.

The upper part in the dotted frame redraws and summarizes the relationship of the broadcast packets in intervals T1 to T4 inFIG.2. Please refer toFIG.2and the topmost figure inFIG.3together. As the broadcast channel being selected for transmitting the broadcast packet BD(T1) corresponds to the lowest frequency, it is defined as a broadcast channel bCh1. As the broadcast channel being selected for transmitting the broadcast packets BD(T2) and BD(T4) corresponds to the highest frequency, it is defined as a broadcast channel bCh3. As the broadcast channel bCh(T3) being selected or transmitting the broadcast packet BD(T3) corresponds to a middle frequency, it is defined as a broadcast channel bCh2.

The middle part in the dotted frame represents the distribution of interference20in the air. The existence and the distribution of interference20are unknown to the broadcaster and the scanner, and interference20might cover several selected broadcast channels at different intervals.

The bottommost figure inFIG.3is a combination of the two figures in the dotted frame. It shows that interference20affects the broadcast operation. In interval T1, the broadcast packet BD(T1) can be successfully received at the selected broadcast channel bCh1(T1). However, interference20overlaps the broadcast channel bCh2 in intervals T2 and T3, and the broadcast packets BD(T2) and BD(T3) being transmitted in intervals T2 and T3 are damaged. Thus, the scanner cannot receive the broadcast packets BD(T2) and BD(T3). In interval T4, the broadcast packet BD(T4) can be successfully received at the selected broadcast channel bCh3. This implies that not all broadcast packets can be successfully received by the scanner.

To prevent broadcast packets from being disturbed in the environment, the present disclosure proposes a mechanism to create several replicas (copies) of the broadcast packets BD(T1), BD(T2), BD(T3), and BD(T4). Moreover, the replicas of each of the broadcast packets BD(T1), BD(T2), BD(T3), and BD(T4) are individually and concurrently transmitted at different broadcast channels. A variable M is utilized to represent the number of replicas of broadcast packets, and M is a positive integer greater than 1 (M>1).

Instead of selecting only one broadcast channel in each interval, the broadcaster, according to the embodiment of the present disclosure, selects M broadcast channels in each interval. In some embodiments, M broadcast channels are simultaneously selected in at least one interval. The broadcast channels bCh1 to bChM are selected based on the BR/EDR and/or LE specifications. Moreover, the broadcast channels being concurrently selected in the same interval are not necessary to be continuous RF channels.

At the M-selected broadcast channel bCh1 to bChM, the M replicas of the broadcast packets are simultaneously and individually transmitted. As there are M replicas of the broadcast packets in the air, the scanner has a better chance of successfully receiving any of the M replicas of the broadcast packets. Of course, the type of broadcast packet provided is merely an example and can be any type of packet for communication via Bluetooth, and the aspects herein are not limited by such example.

FIG.4is a schematic diagram illustrating that broadcast packets are duplicated, and the replicas of broadcast packets are combined for transmission. The broadcast packet BD(T1) corresponding to interval T1 has M=3 replicas. The content of the replicas of the broadcast packet BD(T1) is substantially identical to each other. The three replicas of the broadcast packet BD(T1) are defined as an original broadcast packet oBD(T1) and two mirrored broadcast packets m1BD(T1) and m2BD(T1).

Similarly, the broadcast packets BD(T2), BD(T3), and BD(T4) corresponding to intervals T2, T3, and T4 are duplicated with M=3 replicas. The original broadcast packet, such as oBD(T1), oBD(T2), oBD(T3), and oBD(T4), are shown with solid frames. The two mirrored broadcast packets other than the original broadcast packet, such as broadcast packets m1BD(T1) and m2BD(T1) in interval T1, broadcast packets m1BD(T2) and m2BD(T2) in interval T2, broadcast packets m1BD(T3) and m2BD(T3) in interval T3, and broadcast packets m1BD(T4) and m2BD(T4) in interval T4, are shown with dotted frames.

The broadcast signal bcS corresponds to the M replicas of broadcast packets to be sent from a broadcaster to a scanner in each interval.FIG.5is a schematic diagram illustrating an exemplary scheduling procedure in which those replicas of broadcast packets are transmitted simultaneously in each interval T1 to T4.

Please refer toFIGS.3and5together. For the sake of illustration, the original broadcast packets oBD(T1), oBD(T2), oBD(T3), and oBD(T4) inFIG.5are transmitted through broadcast channels identical to those inFIG.3. On the other hand, the mirrored broadcast packets m1BD(T1), m2BD(T1), m1BD(T2), m2BD(T2), m1BD(T3), m2BD(T3), m1BD(T4) and m2BD(T4) are transmitted through the broadcast channels different from those inFIG.3.

For example, the broadcast channel bCh1 in interval T1 (represented as bCh1(T1)) is utilized to transmit the original broadcast packet oBD(T1), the broadcast channel bCh2 in interval T1 (represented as bCh2(T1)) is utilized to transmit the mirrored broadcast packet m2BD(T1), and the broadcast channel bCh3 in interval T1 (represented as bCh3(T1)) is utilized to transmit the mirrored broadcast packet m1BD(T1). Illustrations related to the broadcast channels (bCh1, bCh2, and bCh3) in intervals T1 to T4 (bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), bCh3(T1) to bCh3(T4)), original/mirrored broadcast packets oBD(T1) to oBD(T4), m1BD(T1) to m1BD(T4), and m2BD(T1) to m2BD(T4), and intervals T1 to T4 are omitted but summarized in Table 1.

TABLE 1intervalT1T2T3T4broadcastbCh1originalmirroredmirroredmirroredchannelsbroadcastbroadcastbroadcastbroadcastbeingpacketpacketpacketpacketconcurrentlyoBD(T1)m1BD(T2)m2BD(T3)m1BD(T4)selectedbCh2mirroredmirroredoriginalmirroredbroadcastbroadcastbroadcastbroadcastpacketpacketpacketpacketm2BD(T1)m2BD(T2)oBD(T3)m2BD(T4)bCh3mirroredoriginalmirroredoriginalbroadcastbroadcastbroadcastbroadcastpacketpacketpacketpacketm1BD(T1)oBD(T2)m1BD(T3)oBD(T4)

Please note that, inFIG.5, an RF channel corresponding to the same selected broadcast channel in different intervals may vary. Moreover, the broadcast channel labeled with the same numbering in different intervals is unnecessary to be the same RF channel. For example, the actual RF channel represented by the broadcast channel bCh1 corresponding to interval T1 (bCh1(T1)) can be different from the RF channel represented by the broadcast channel bCh1 corresponding to interval T2 (bCh1(T2)). That is, bCh1(T1)*bCh1(T2).

Depending on the version of the Bluetooth standard, the features of RF channels and which RF channels are available to be utilized for broadcasting are different. According to BR/EDR specification, 79 RF channels are defined, and each RF channel has a bandwidth of 1 MHz. Among the 79 RF channels defined in BR/EDR specification, either only odd RF channels or only even RF channels are utilized for broadcasting. According to LE specification, 40 RF channels are defined, and each RF channel has a bandwidth of 2 MHz. Among the 40 RF channels defined in LE specification, RF channels #37, #38, and #39 are utilized for broadcasting.

FIG.6is a schematic diagram illustrating that the channels utilized as broadcast channels bCh1, bCh2, and bCh3 in different intervals T1, T2, T3, and T4 for transmitting replica broadcast packets are randomly defined based on the Bluetooth BR/EDR scheme. InFIG.6, the vertical axis represents the amplitude of signals, and the horizontal axis represents RF channels defined in BR/EDR specification. Moreover, center frequencies corresponding to the broadcast channels bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4) are labeled with dotted vertical lines. Please note that mapping between the replicas of broadcast packets (including the original/mirrored broadcast packets), the broadcast channels bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4), and the intervals T1 to T4 in Table 1 andFIGS.5and6correspond to each other.

The topmost dotted frame corresponds to the distribution of the broadcast channels being selected in interval T1, represented as bCh1(T1), bCh2(T1), and bCh3(T1). The second dotted frame corresponds to the distribution of the broadcast channels being selected in interval T2, represented as bCh1(T2), bCh2(T2), and bCh3(T2). The third dotted frame corresponds to the distribution of the broadcast channels being selected in interval T3, represented as bCh1(T3), bCh2(T3), and bCh3(T3). The bottommost dotted frame corresponds to the distribution of the broadcast channels being selected in interval T4, represented as bCh1(T4), bCh2(T4), and bCh3(T4).

As shown inFIG.6, the broadcast channel bCh1 in interval T1 (that is, bCh1 (T1)) corresponds to a lower RF channel, and the RF channel corresponding to the broadcast channel bCh1 in interval T2 (that is, bCh1 (T2)) is shifted rightward (toward high frequency). Moreover, the broadcast channels bCh1 in intervals T3 and T4 (that is, bCh1 (T3) and bCh1(T4)) correspond to an RF channel between those in intervals T1 and T2. Similarly, an RF channel corresponding to each broadcast channel bCh1, bCh2, and bCh3 is changed with different intervals T1 to T4.

As illustrated above, the broadcast channels bCh1, bCh2, and bCh3 selected for broadcast are freely determined in each interval T1 to T4, and their corresponding RF channels can be different in different intervals T1 to T4. In practical applications, an approach of pre-defining some of the RF channels and further selecting the broadcast channels from the predefined RF channels (for example, 5 of the 40 BR/EDR odd RF channels are pre-defined, and the M broadcast channels are selected from the 5 pre-defined RF channels) can be helpful to simplify the circuit design.

As Bluetooth LE specification already defines three primary broadcast channels (#37, #38, #39), mapping between a selected broadcast channel and an RF channel is not changed with different intervals. That is, the maximum value of M is three in the Bluetooth LE specification. Under the assumption that M=3, the broadcast channel bCh1 represents RF channel #37 in different intervals T1 to T4, the broadcast channel bCh2 represents RF channel #38 in different intervals T1 to T4, and the broadcast channel bCh3 represents RF channel #39 in different intervals T1 to T4.

FIG.7is a schematic diagram illustrating that the RF channels utilized as broadcast channels bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4) in different intervals T1, T2, T3, and T4 for transmitting replicas of the broadcast packets are kept unchanged based on Bluetooth LE scheme. InFIG.7, the vertical axis represents the amplitude of signals, and the horizontal axis represents the RF channels defined in Bluetooth LE. Similarly, the center frequencies corresponding to the broadcast channels bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4) are labeled with dotted vertical lines. Please note that the mapping between the replicas of the broadcast packets (including the original/mirrored broadcast packets), the broadcast channels bCh1(T1) to bCh(T4), bCh2(T2) to bCh(T2), and bCh3(T1) to bCh3(T3), and the intervals T1 to T4 in Table 1 andFIGS.5and7correspond to each other.

The dotted frames from top to down respectively correspond to the distribution of the broadcast channels bCh1(T1), bCh2(T1), and bCh3(T1) in interval T1, the broadcast channels bCh1(T2), bCh2(T2), and bCh3(T2) in interval T2, the broadcast channels bCh1(T3), bCh2(T3), and bCh3(T3) in interval T3, and the broadcast channels bCh1(T4), bCh2(T4), and bCh3(T4) in interval T4. UnlikeFIG.6, the mappings between the RF channels and the broadcast channels bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4) are consistent in different intervals T1, T2, T3, and T4 inFIG.7.

Although the RF channels available for broadcasting are different with different Bluetooth versions, the transmission method used for broadcasting data proposed in the specification can be applied to both Bluetooth standards.FIG.8demonstrates how the data transmission method provides better data quality.

FIG.8is a schematic diagram illustrating that at least one of the replicas of the broadcast packets can still be successfully transmitted to a receiver in each interval, although a transmission path where the broadcast packets are transmitted is disturbed. Please refer toFIGS.3,5, and8together. The upper figure and the lower figure in the dotted frame inFIG.8are respectively the same asFIG.5and the lower figure in the dotted frame inFIG.3. Details of these two parts are not repetitively described. The bottommost figure inFIG.8is a combination of the two figures in the dotted frame. This figure can be interpreted together with the examples inFIGS.6and7.

For the replicas of the broadcast packet BD(T1) in interval T1, the original broadcast packet oBD(T1) and the mirrored broadcast packets m1BD(T1) and m2BD(T1) can be successfully received because all the broadcast channels bCh1(T1), bCh2(T1), and bCh3(T1) in interval T1 are not disturbed.

For the replicas of the broadcast packet BD(T2) in interval T2, the mirrored broadcast packet m1BD(T2) can be successfully received at the broadcast channel bCh1(T2) because the broadcast channel bCh1 is not disturbed. On the other hand, the mirrored broadcast packet m2BD(T2) and the original broadcast packet oBD(T2) cannot be successfully received because the broadcast channels bCh2 and bCh3 are disturbed.

For the replicas of the broadcast packet BD(T3) in interval T3, the mirrored broadcast packets m2BD(T3) and m1BD(T3) can be successfully received through the broadcast channels bCh1 and bCh3 because the broadcast channels bCh3 and bCh1 are not disturbed. On the other hand, the original broadcast packet oBD(T3) cannot be successfully received because the broadcast channel bCh2 is disturbed.

For the replicas of the broadcast packet BD(T4) in interval T4, the mirrored broadcast packets m1BD(T1) and m2BD(T1) and the original broadcast packet oBD(T1) can be successfully received because all the broadcast channels bCh1, bCh2, and bCh3 in interval T4 are not disturbed.

Please refer toFIGS.3and8together. InFIG.3, none of the broadcast packets BD(T2) and BD(T3) is received in intervals T2 and T3. InFIG.8, the mirrored broadcast packet m1BD(T2) can still be received at the broadcast channel bCh1 in interval T2, and the mirrored broadcast packets m2BD(T3) and m1BD(T3) can still be received at the broadcast channels bCh1 and bCh3 in interval T3.

FIG.9is a block diagram illustrating the internal components of the Bluetooth device according to an embodiment of the present disclosure. A Bluetooth device7includes a function circuit70, a Bluetooth controller71, a transmitter73, a receiver75, a switch77, and an antenna79. The Bluetooth controller71is electrically connected to the function circuit70, the transmitter73, the receiver75, and the switch77. The function circuit70provides application functions such as mobile, earphones, speakers, and so forth. When function circuit70needs to activate the Bluetooth function, the function circuit70interacts with the Bluetooth controller71. Besides, the transmitter73may support single-mode (BR/EDR or LE) or dual-mode (BR/EDR and LE).

The switch77is electrically connected to the antenna79, and selectively electrically connected to the transmitter73and the receiver75. The Bluetooth controller71sends a switching control signal ctlS_sw to the switch77, to select which of the transmitter73and the receiver73is connected to the antenna79.

The receiver75receives an input signal inS and transforms it to an input bitstream rxBS. The Bluetooth controller71transmits some receiver-related control signals ctlS_rx to the receiver75. Details about the design and operations of the receiver75are not described.

The transmitter73includes a digital modulation module731, up-conversion modules7331,7333, and7335, summers735aand735c, an I-path digital-to-analog converter (hereinafter, DAC)737a, a Q-path DAC737c, and an RF circuit739. As illustrated above, the selected broadcast channels bCh1, bCh2, and bCh3 are dynamically changed in different intervals (bCh1(T1) to bCh1(T4), bCh2(T1) to bCh2(T4), and bCh3(T1) to bCh3(T4)). This implies that the Bluetooth controller71needs to control the operations of transmitter73in an interval-based manner. Therefore, the Bluetooth controller71should dynamically generate control signals to the components in the transmitter73. The Bluetooth controller71respectively transmits a modulation control signal ctlS_mod, up-conversion control signals ctlS_uc, digital-to-analog control signals ctlS_dac, and RF control signals ctlS_rf to the digital modulation module731, the up-conversion modules7331,7333and7335, the I-path DAC737a, the Q-path DAC737c, and the RF circuit739.

The digital modulation module731receives a transmission bitstream txBS from the Bluetooth controller71. The transmission bitstream txBS carries the broadcast information BD to be transmitted to the scanner. Based on the transmission bitstream txBS, the digital modulation module731performs a Gaussian frequency-shift keying (hereinafter, GFSK) modulation on an I-path carrier signal and a Q-path carrier signal to generate an I-path modulated signal modI and a Q-path modulated signal modQ accordingly. The I-path carrier signal and a Q-path carrier signal have a phase shift of 90°. The I-path modulated signal modI and the Q-path modulated signal modQ are transmitted to the up-conversion modules7331,7333, and7335.

InFIG.9, it is assumed that the up-conversion modules7331,7333, and7335, respectively, correspond to the broadcast channels bCh1, bCh2, and bCh3. The up-conversion module7331up-converts the I-path modulated signal modI and the Q-path modulated signal modQ to a pair of up-converted signals (including an I-path up-converted signal upI1 and a Q-path up-converted signal upQ1) corresponding to broadcast channel bCh1. The up-conversion module7333up-converts the I-path modulated signal modI and the Q-path modulated signal modQ to another pair of up-converted signals (including an I-path up-converted signal upI2 and a Q-path up-converted signal upQ2) corresponding to broadcast channel bCh2. The up-conversion module7335up-converts the I-path modulated signal modI and the Q-path modulated signal modQ to still another pair of up-converted signals (including an I-path up-converted signal upI3 and a Q-path up-converted signal upQ32) corresponding to broadcast channel bCh3.

The number of the up-conversion modules7331,7333, and7335is equal to the number of the selected broadcast channels (M) supported by the broadcaster. The specification assumes that the number of the selected broadcast channels is three (M=3). In practical application, M can be other positive integers, as long as it is smaller than or equivalent to the number of broadcast channels defined in Bluetooth specification. Therefore, the maximum number of up-conversion modules is 40 for Bluetooth BR/EDR applications or 3 for Bluetooth LE applications.

The I-path up-converted signals upI1, upI2, and upI3 are transmitted to the I-path summer735a, and the Q-path up-converted signals upQ1, upQ2, and upQ3 are transmitted to the Q-path summer735c. Then, the I-path summer735asums the I-path up-converted signals upI1, upI2, and upI3 to generate an I-path summer output sumI to the I-path DAC737a. Similarly, the Q-path summer735csums the Q-path up-converted signals upQ1, upQ2, and upQ3 and generates a Q-path summer output sumQ to the Q-path DAC737c.

Then, the I-path DAC737aconverts the I-path summer output sumI to an I-path baseband signal bbI, and the Q-path DAC737cconverts the Q-path summer output sumQ to a Q-path baseband signal bbQ. The I-path baseband signal bbI and the Q-path baseband signal bbQ are transmitted to the RF circuit739to generate an output signal outS. For broadcast operations, the output signal outS is directly utilized as the broadcast signal bcS. Then, the antenna79radiates radio waves in the air based on the output signal outS.

FIG.10is a block diagram illustrating the internal components of the transmitter73according to an embodiment of the present disclosure. The internal components of the up-conversion modules7331,7333, and7335, and the RF circuit739are further illustrated.

Each of the up-conversion modules7331,7333, and7335includes an up-converter corresponding to an I-path, and an up-converter corresponding to a Q-path. In the up-conversion module7331, the I-path up-converter7331aup-converts the I-path modulated signal modI to an I-path up-converted signal upI1, and the Q-path up-converter7331cup-converts the Q-path modulated signal modQ to a Q-path up-converted signal upQ1. In the up-conversion module7333, the I-path up-converter7333aup-converts the I-path modulated signal modI to an I-path up-converted signal upI2, and the Q-path up-converter7333cup-converts the Q-path modulated signal modQ to a Q-path up-converted signal upQ2. In the up-conversion module7335, the I-path up-converter7335aup-converts the I-path modulated signal modI to an I-path up-converted signal upI3, and the Q-path up-converter7335cup-converts the Q-path modulated signal modQ to a Q-path up-converted signal upQ3.

The RF circuit739includes an I-path filter7391a, a Q-path filter7391c, a mixer circuit7393, and a power amplifier7395(hereinafter, PA). The I-path filter7391areceives the I-path baseband signal bbI from the I-path DAC737a, and the Q-path filter7391creceives the Q-path baseband signal bbQ from the Q-path DAC737c. The I-path filter7391afilters the I-path baseband signal bbI and generates an I-path filtered signal fltI, while the Q-path filter7391cfilters the Q-path baseband signal bbQ and generates a Q-path filtered signal fltQ.

The mixer circuit7393mixes the I-path filtered signal fltI with the Q-path filtered signal fltQ, and generates a mixed baseband signal mxS accordingly. The PA7395generates the output signal outS by increasing the signal power of the mixed baseband signal mxS.

InFIGS.9and10, the components showing with dotted screen tone are implemented in digital circuits. It can be noticed that the modulation and the up-conversion are performed by digital circuits. Although the present disclosure adopts more selected broadcast channels for broadcast operation, the circuit complexity is not increased, and the area cost increases insignificantly because the modulation and the up-conversion are implemented with digital circuits.

By transmitting replicas of the broadcast packets through multiple selected channels, the success rate for the scanner to receive broadcast packets is enhanced because some of the broadcast channels might not be disturbed. For some Bluetooth applications, such as headphones, music can be played without interruption caused by packet loss.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.