Device and method for cellular synchronization assisted location estimation

A device and method for determining the location of a cellular device, such as a mobile cell phone, utilizing a Timing Advance (TA) issued by one or more cellular base stations, such as an LTE or LTE-A enhanced NodeB (eNB), to the cellular device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to devices and methods for locating a network device, such as cellular device, in a cellular network. More particularly, the invention relates to devices and methods for locating the position of a network device communicating on an orthogonal frequency division multiplexing (OFDM) network, such as a Long Term Evolution or Long Term Evolution-Advanced (LTE/LTE-A) network.

2. Description of the Related Art

Long Term Evolution (LTE) is a high speed wireless technology for providing communication services to mobile cellular devices. The LTE access network is a network of base stations, termed evolved NodeBs (eNBs). The current LTE network positioning architecture utilizes a network-centric positioning scheme termed the LTE Positioning Protocol (LPP). LPP currently supports three positioning methods: assisted-global navigation satellite system (A-GNSS), observed time difference of arrival (OTDOA), and enhanced-cell identification (E-CID).

With the widespread adoption of the Global Positioning System (GPS) and related systems, A-GNSS has been one choice for mobile positioning. A-GNSS, while reasonably accurate, suffers from power-hungry implementations and requires additional specific hardware in the mobile device. Further, A-GNSS suffers from a vulnerability to severe multipath channels, such as those found in metropolitan canyons and indoor environments.

OTDOA requires the use of specific time-frequency resources in each frame in order to transmit a positioning reference signal from several adjacent eNBs in LTE. The time difference is then recorded by the user equipment (UE) and transmitted back to the network for analysis. As the resulting systems of hyperbolic equations are usually inconsistent, an approximation technique must be used to form a position estimate. OTDOA also suffers in urban and indoor environments where non-line of sight (NLOS) and multipath environments channels dominate.

The E-CID option was developed as part of the LPP in answer to the multipath problem. In E-CID the network requests the UE make certain signal measurements, e.g., signal strength, channel quality, cell ID, etc., and send them back to the network for analysis. The network then compares the current signal measurements and matches them with previously made measurements stored in a network database. While this radio fingerprinting method has achieved relative success and is more robust in multipath environments, this method suffers from high up front database creation costs, database maintenance costs, and is limited by each individual UE's measurement capabilities. Thus, each LPP positioning method suffers from particular flaws, but the common problem is that each method builds on the existing infrastructure and requires additional valuable bandwidth to provide a UE its location.

SUMMARY OF THE INVENTION

Embodiments in accordance with the invention include a device and method for cellular synchronization assisted location estimation of a cellular device for use with LTE/LTE-A compliant networks. The device and method utilize an existing network timing management signal, termed the timing advance (TA), together with uplink transmissions from a cellular device to provide a position estimate of the cellular device. Embodiments in accordance with the invention mitigate many of the weaknesses noted in current LTE/LTE-A cellular positioning technologies while providing a comparable level of accuracy. The method requires no additional network infrastructure, no additional network bandwidth or cooperation, and is power frugal. The method can be used as a complimentary positioning technology as well as to locate a cellular device by a third party device. The method can be implemented without a cooperative network and is passive, in that a third party device utilizing the method does not need to identify itself to the network or the cellular device.

In accordance with one embodiment, a method for cellular synchronization assisted location estimation of a target device in a cellular service area by a sensor device includes: obtaining a location of the sensor device; obtaining a location of an evolved NodeB (eNB) in an LTE/LTE-A network; establishing downlink synchronization with the eNB; determining a downlink frame timing of the eNB; monitoring transmissions sent from the eNB for a timing advance (TA) sent from the eNB to a target device; obtaining the TA transmitted by the eNB to the target device; determining an annulus, TTA, around the eNB based on the TA; determining an uplink frame burst time for the target device; obtaining an uplink frame sent by the target device to the eNB; determining a distance, d, from the sensor device to the target device; determining a circle, Tcircle, around said sensor device at the distance, d, from the sensor device to the target device; determining a refined locus, Tl, based on an intersection of the annulus, TTA, and the circle, Tcircle; and determining a location of the target device in the refined locus.

In accordance with one embodiment of the invention, a cellular device for cellular synchronization assisted location estimation of a target device in a cellular service area includes: an antenna for monitoring and receiving communications transmitted over a LTE/LTE-A network; and a processing component configured to perform a method for cellular synchronization assisted location estimation of a target device, the method including: obtaining a location of the sensor device; obtaining a location of an evolved NodeB (eNB) in an LTE/LTE-A network; establishing downlink synchronization with the eNB; determining a downlink frame timing of the eNB; monitoring transmissions sent from the eNB for a timing advance (TA) sent from the eNB to a target device; obtaining the TA transmitted by the eNB to the target device; determining an annulus, TTA, around the eNB based on the TA; determining an uplink frame burst time for the target device; obtaining an uplink frame sent by the target device to the eNB; determining a distance, d, from the sensor device to the target device; determining a circle, Tcircle, around said sensor device at the distance, d, from the sensor device to the target device; determining a refined locus, Tl, based on an intersection of the annulus, TTA, and the circle, Tcircle; and determining a location of the target device in the refined locus. In some embodiments, the cellular device includes a locator device communicatively coupled to the cellular device.

Embodiments in accordance with the invention are best understood by reference to the following detailed description when read in conjunction with the accompanying drawings

Embodiments in accordance with the invention are further described herein with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Broadly viewed, embodiments in accordance with the invention include a device and method for determining the location of a cellular device, such as a mobile cellular phone, utilizing a Timing Advance (TA) issued by an eNB, such as an LTE or LTE-A eNB, to the cellular device. In one embodiment, a sensor device, such as a cellular device capable of receiving LTE or LTE-A transmissions uses downlink synchronization to refine an area within an initial timing advance annular locus in which a target device, such as a second cellular device, may be located and determines the location of the target device within that area. Embodiments in accordance with the invention are further described with continuing reference to the figures. Herein descriptions made referring to LTE are also applicable to LTE-A.

LTE is a time-synchronized network. LTE uses orthogonal frequency division multiplexing (OFDM) as the vehicle for air interface communication. LTE facilitates higher data rates and requires tight time synchronization between user equipment (UE), such as a cellular device, and an eNB. A UE's uplink frames must arrive at the eNB at very precise intervals. As the UE's propagation delay to an eNB may change based on the UE's current position, LTE utilizes a timing advance parameter, TA, to align the UE's transmission time to that of the LTE network. An LTE network uses two forms of the TA to control user equipment transmissions during normal cellular operation.

The first form of the TA, herein termed a first TA, is issued upon initial entry of the UE into the network. To enter the network, a UE searches for a primary search signal (PSS) and secondary search signal (SSS) which are regularly broadcast from each network eNB. Upon acquisition of the PSS/SSS signal by the UE, the UE establishes downlink synchronization with the eNB. The uplink timing is then approximated by the UE and a random access preamble is transmitted from the UE to the eNB of the network.

Upon receipt of the random access preamble by the eNB, a random access response (RAR) message is transmitted to the user equipment. Within the RAR is an 11-bit first TA quantity, where TAε{0, 1, . . . , 1282}, which specifies for the UE, in absolute terms, when the UE should begin its uplink bursts.FIG. 1illustrates a representative drawing of a RAR message containing a first TA. Each bit represents a time interval of 16×TA×TS, where TSis the sampling frequency. A UE locates the RAR by monitoring the L1/L2 control region, i.e., the physical dedicated control channel (PDCCH), within a selected amount of time after the random access preamble is transmitted. The PDCCH identifies to the UE where on the physical downlink shared channel (PDSCH) the RAR is scheduled. Location of a RAR and a first TA by a UE on an LTE/LTE-A network is well known to those of skill in the art.

The second form of the TA, herein termed a second TA, utilized by the LTE network is a maintenance command used during normal operation after a UE has linked to the eNB, and allows the network to maintain timing alignment with the UE as the UE moves throughout the network. The second TA is sent as a Medium Access Control (MAC) control element (CE) in a MAC header. The second TA is a 6-bit relative quantity TA where TA ε{0, 1, . . . , 63}. The relative nature of this quantity means that a UE will advance or retard its uplink transmission timing from a current value by 16×(TA−31)×TSseconds in order to accommodate the dynamic propagation delay.FIG. 2illustrates a representative drawing of a MAC header including a second TA. Location of a MAC header and a second TA by a UE on an LTE/LTE-A network is well known to those of skill in the art.

Current (as of release 11), the MAC CE further incorporates a 2 bit timing advance group (TAG) ID field. In a heterogeneous network (HetNet), in which multiple secondary eNBs, also termed secondary cells (SCells), are configured in addition to a primary eNB, also termed primary cell (PCell), the TAG ID located in the TAG ID field identifies to the UE which eNB sent the TA. This allows timing management from multiple groups of eNBs in physically different locations.

Because of the discrete nature of the TA, the spatial resolution is of particular interest. Each TA bit is interpreted as 16×TSseconds, where TS≈32.5 ns and is defined as the inverse of the product of the subcarrier spacing and Fast Fourier Transform size. If the speed of light, c, is used as the propagation speed, the spatial resolution, Sres, can be determined using

sres=c2⁢(16×Ts)
to be 78.125 meters (the extra factor of ½ is included to account for two way propagation delay). This implies that because max {TA}=1282, the maximum supportable cell size, i.e., eNB coverage area, is 100 km.

Both the first TA and the second TA are transmitted in the clear, i.e., unencrypted. The first TA which is located in the RAR is sent before a security key is negotiated with a UE and sent in the clear. The second TA is sent as a MAC CE in the MAC header which is below the Packet Data Convergence Protocol (PDCP) sublayer, which is responsible for encryption, and is thus also sent in the clear. Therefore, a UE with the ability to monitor LTE/LTE-A communications that is within range of an eNB can observe the transmissions of the first TA and the second TA.

As a plurality of users are typically simultaneously connected to a given eNB, each TA has a cell-radio network temporary identifier (C-RNTI) which serves as a temporary software address issued by the network to each UE. The C-RNTI is initially associated with a UE during network access negotiation and issued via the RAR. Second TAs are associated with a specific C-RNTI via downlink scheduling assignments made via the Physical Downlink Control Channel (PDCCH) found in the L1/L2 control region of each subframe. Because the L1/L2 control region of each subframe needs to be decoded by each UE, it is sent in the clear. Thus as further described herein a third party UE can use the information in the PDCCH to find the resource on which a transport block for a particular UE is located. The corresponding transport block could then be searched for a TA CE. As further described herein in order to initially associate a C-RNTI with a UE, a third party UE must observe a UE access the network in order to initially associate a C-RNTI with a UE.

As positioning can be of a continuous nature, and as the time to first fix (TTFF) is a reasonable quality of service metric, the frequency at which TAs are issued is of interest. This frequency is upper-bounded by a timeAlignmentTimer parameter which can be configured to assume values {500, 750, 1280, 1920, 2560, 5120, 10240, ∞}. The timeAlignmentTimervalues correspond to the maximum number of subframes which may pass without a TA update for the user equipment to still consider itself time aligned with the eNB. Because each subframe is 1 ms in duration, the timeAlignmentTimer values may be interpreted in milliseconds. Assuming a network implementation does not choose an infinite value, it can be assumed a TA is issued with an interval of no more than ˜10 s. In practice, the number of TAs issued will be much more frequently, usually on the order of several times per second.

FIG. 3illustrates a process flow diagram of a method for cellular synchronization assisted location estimation of a target cellular device by a sensor device in accordance with one embodiment of the invention. Referring now toFIGS. 1-5together, in one embodiment, a location aware sensor device402, such as shown inFIG. 4, is introduced into the cellular service area of a network eNB404, such as an eNB providing communication on an LTE/LTE-A network. In one embodiment, sensor device402is a cellular device capable of monitoring and receiving transmissions on the network sent from one or more eNBs404. In the current embodiment, sensor device402is implemented as a third party sensor device. In some embodiments, sensor device402can be implemented as an existing network picocell. In other embodiments, sensor device402can be implemented as a recruited peer device.

In operation302sensor device402, also termed herein a first device, obtains its current location and obtains the location of eNB404, also termed herein a base station. The location of sensor device402and/or the location of eNB404may be preloaded on sensor device402, directly loaded on sensor device402, sent to sensor device402over a communication link, or determined by sensor device402utilizing a locator device, such as GPS device connected to or in communication with sensor device402.

In operation304sensor device402establishes downlink synchronization with eNB404. For example, sensor device402receives a primary synchronization signal/secondary synchronization signal (PSS/SSS) transmitted from eNB404and synchronizes to eNB404. The downlink synchronization is achieved passively, without identification of sensor device402to eNB404. Downlink synchronization with a network, such as an LTE or LTE-A network is well known by those of skill in the art and not further detailed herein.

In operation306, sensor device402determines the downlink frame timing at eNB404. For example, sensor device402calculates the propagation delay between itself and eNB404using

Δ⁢⁢t=dc,
where Δt is the time difference between sensor device402's observed frame boundaries and eNB404's sent frame boundaries, where d is the distance sensor device402is located from eNB404, and c is the speed of light, e.g., speed of light in a vacuum, 2.99792458×108m/s (approximately 3.00×108m/s). The downlink frame timing at eNB404is then determined using the propagation delay. Determination of propagation delay and downlink frame timing in a network such as an LTE or LTE-A network is well known by those of skill in the art and not further detailed herein.

In operation308sensor device402passively monitors MAC headers sent from eNB404for TAs issued to target device406.

In operation310, when sensor device402detects a TA transmitted by eNB404to target device406, sensor device402records the TA.

In operation312, an annulus410, herein also referred to as an annular locus410, is determined. In one embodiment, annulus410is described by the TA and bounds an area of possible locations of target device406from eNB404. Due largely to the discrete nature of a TA, a single measurement from an eNB will reduce the possible locations of target device406to an annulus of fixed width with eNB404as the center. In one embodiment, annulus410, TTA, is an annulus of width 78.125 meters, the center of which is the eNB404location.

TTA=A′\A″ where {A′:|p|≦aβ+β/2} and {A″:|p|<aβ−β/2} where β is the spatial resolution of TA, aεis the TA value issued by the eNB, and pεis the set of positions in the cellular service area.

In an LTE network, the distance from the location of eNB404to the middle of annulus410, TTA, is calculated as:

where a ε[0, . . . , 1282] is the integer timing advance value found in the MAC control element sent from eNB404, c is the speed of light, 15,000 corresponds to the subcarrier spacing, and 2048 is the FFT size.

In operation314, sensor device402estimates the uplink frame burst time from target device406to eNB404. In one embodiment, the uplink frame transmission timing is determined using the equation:

where ttxis the calculated frame transmission time, tfbis the eNB304frame boundary time, a is the integer timing advance value found in the MAC control element sent from eNB404.

In operation316sensor device402passively monitors the network for transmission of an uplink frame from target device406to eNB404, and on receipt of the transmission of an uplink frame from target device406to eNB404, records the uplink time.

In operation318sensor device402determines the distance from target device406to itself, i.e., sensor device402, based on the propagation delay between when target device406sent the uplink frame to eNB404and when sensor device402detected the transmission of the uplink frame. In one embodiment the distance from target device406to sensor device402is calculated using

d=Δ⁢⁢tc,
where d is the distance between sensor device402and target device406, Δt is the time difference from when target device406sent the uplink frame and when sensor device402receives, e.g., records, the uplink frame sent from target device406, and c is the speed of light, e.g., speed of light in a vacuum, 2.99792458×108m/s (approximately 3.00×108m/s).

In operation320, a circle408, Tcircle, of distance, d (calculated in operation318) around sensor device402is determined. Tcircledefines possible locations around sensor device402on which target device406should lie.

In one embodiment, circle408is calculated as:{Tcircle:|p|=d} where d is given as in operation318.

In operation322, a refined locus of possible locations of target device406is determined. As target device406is estimated to lie somewhere in annulus410, TTA, and on circle408, Tcircle, an intersection of annulus410, TTA, and on circle408, Tcircle, is determined to be a refined locus Tl. In one embodiment the refined locus, Tl, of target device406from eNB404is calculated using:
Tl=TTA∩TCircle
where Tlis the refined locus obtained from performing the intersection of annulus410, TTAand circle408, Tcircle.

In some embodiments where there is only one serving eNB, Tlmay be a disjoint set. In one embodiment, the disjoint set is resolved to one set using an ambiguity resolution technique. Ambiguity resolution techniques are well known to those of skill in the art. In the event the ambiguity cannot be resolved, the method has significantly reduced the locus size in which the target device406may be located to the disjoint sets.

In embodiments in which multiple eNBs and thus multiple annuli are available to sensor device402, the locus Tlis calculated using:

where TTASiis the TA issued from the ith SCell.

In operation324, a location of target device406is determined. In one embodiment, the position estimate, {circumflex over (p)}, i.e., the location, of target device406is determined as a point that is the centroid of Tl. In one embodiment, the position estimate of target device406is determined using:

where {circumflex over (p)} is the position estimate, p=(x,y) is any point in T=Tcircle∩Tl, and pc=(xc,yc) such that pcis the center of mass of T. In the event that {circumflex over (p)} is not unique, the position estimate is randomly chosen, with uniform likelihood, from among the set of points described by minp∥p−pc∥. In embodiments in which Tlis a disjoint set and an ambiguity cannot be resolved, operation324can be performed on each set to arrive at position estimates.

FIG. 5illustrates a block diagram of a cellular device500, such as target device402, including method300for cellular synchronization assisted location estimation in accordance with one embodiment of the invention. InFIG. 5, device500includes a computer processing unit (CPU)502, a memory504, a network interface506, and an antenna508for monitoring and receiving communications transmitted over a network, such as an LTE/LTE-A network. In some embodiments device500can also transmit to a network via antenna508, such as to an LTE/LTE-A network. In some embodiments, device500is communicatively coupled to a locator device510, such as Global Position System (GPS) device for receiving location information associated with device500as well as other devices, such as an eNB associated with an LTE/LTE-A network. In various embodiments device500can further include one or more I/O interfaces512to allow inputs from an input device, such as locator device510, a keyboard, or other input device, and to allow outputs from device500. In the present embodiment, cellular synchronization assisted location estimation method300is stored in memory504. In other embodiments, cellular synchronization assisted location estimation method300can be stored on another computer system, such as a server system, and accessed by device500over a network.

In some embodiments, such as in a HetNet environment in which multiple eNBs are present, another embodiment of the method for cellular synchronization assisted location estimation can be used with further minimization of the locus due to the presence of multiple timing advances issued by multiple eNBs. Referring now toFIG. 6, in one embodiment at least two serving eNBs602,604, i.e., a secondary serving cell (SCell) and a primary serving cell (PCell), are in physically separate locations. In the current embodiment, while physically disperse SCells (also termed picocells or femtocells) are not a general requirement for heterogeneous networks, SCells are not collocated. This embodiment can be utilized for advanced target devices, such as a target device606, enabled for carrier aggregation. In the present embodiment, multiple TAGs are used for the SCell(s)602and PCell604and are located within the structure of a TA CE, such as that shown inFIG. 2.

When each SCell is configured with its own TAG, a sensor device608, similar to sensor device402, monitors transmissions for all TAGs, TTASi, associated with the C-RNTI of target device606, and determines an annulus610for target device606around SCell602and an annulus612for target device606around PCell604. The intersection of the resulting annuli is the area within which target device606is located and is determined using:

Tl=⋂i⁢TTASi⋂TTAP
where i spans the set of SCells configured to target device606and Siis the ith SCell.

As earlier described with reference to operation322of method300, the locus of possible locations of target device606can then be minimized by further intersecting the area with a circle614, Tcircle(determined in operation318). More particularly, in this embodiment, the distance from target device606to sensor device608is based on the propagation delay between when target device606sends an the uplink frame to either SCell602or PCell604and when sensor device608detects the transmission of the uplink frame. The distance from target device606to sensor device608is calculated using

d=Δ⁢⁢tc,
where d is the distance between sensor device608and target device606, Δt is the time difference from when target device606sends the uplink frame and when sensor device608receives, e.g., records, the uplink frame sent from target device606, and c is the speed of light, e.g., speed of light in a vacuum, 2.99792458×108m/s (approximately 3.00×108m/s).

With circle614, Tcircle, determined, the locus of possible locations of target device606can be refined using:

In the present embodiment, illustrated inFIG. 6, only one SCell, SCell602, is configured. In other embodiments, in which all SCells are configured to use a common TAG, the locus of possible locations, Tl, is determined using:

In this embodiment, in which only one TAG is used for all of the SCells, the shape of

⋃i⁢TTASi
from the perspective of sensor device608is non-circular. As sensor device608does not know which of the picocells602,604is closest to target device606, sensor device608must calculate an annulus assuming each of the picocells602,604is closest. This results in the observed TA being placed around each serving picocell602,604with each being just as likely to contain target device606.

In a further embodiment, the method for cellular synchronization assisted location estimation can be used while a PCell handover is initiated. During normal operation in an LTE/LTE-A network, the network may determine it is advantageous to hand responsibility for primary service over to a different eNB other than the one currently serving the UE. In this case, a sensor device can obtain TAs sent from originating eNBs participating in the handover. Referring now toFIG. 7, in one embodiment two annuli702,704determined by a sensor device710, such as a device similar to sensor device402, from TAs sent from originating eNBs,706,708, respectively, intersect to form an area of possible locations of a target device712. As earlier shown with reference toFIGS. 4 and 6, and method300, the area of possible locations of target device712in the annuli overlap can be minimized by further intersecting the annuli intersection with a circle714, determined as earlier detailed in method300, and determining a position estimate on the resulting locus Tl, as also earlier detailed in method300.

FIGS. 8-10illustrate simulation results of locating a target device both with and without cellular synchronization assisted location estimation. The illustrated results were obtained via Monte Carlo simulation over the course of 1000 trials per curve. In all cases error is defined as the distance from the estimated target location to the actual target location in a Euclidean sense. Parameters for the simulations are represented in Table 1.

Referring now toFIG. 8, the performances of attempts to locate a target with only one observed TA from a PCell with and without cellular synchronization assisted location estimation are presented via a cumulative distribution function (CDF). In a first curve, identified as “Raw TA Annulus,” when only one TA is available and cellular synchronization assisted location estimation is not used, the estimated target location is selected from a set of guesses uniformly distributed throughout the annulus. The low performance in this technique can be explained by the high degree of uncertainty offered by a large locus. Small errors are representative of scenarios when the TA quantity is small, i.e., a UE is physically close to the eNB, or in an unlikely scenario where the estimated position is chosen very near to the actual target location. Large errors are accounted for by large TA values, i.e., a UE is near or on the cell boundary, and when the estimated position is chosen on the opposite side of the annulus as the actual target device location. The first curve exhibits a near uniform appearance with a slight non-uniformity accounted for by the irregular shape of the locus.

In contrast to the first curve, a second curve, identified as “Refined TA Annulus,” illustrates the performance improvements realized through utilization of cellular synchronization assisted location estimation. The second curve exhibits a more exponential distribution, shifting a majority of errors to much lower values. In this simulation, the application of cellular synchronization assisted location estimation results in a 254 meter improvement in the circular error probable (CEP) 70% metric.

Referring now toFIG. 9the results of locating a UE configured for carrier aggregation in an LTE-A release 11+ heterogeneous deployments are illustrated where each SCell is assigned a unique TAG and cellular synchronization assisted location estimation is utilized as described with reference to a HetNet environment in which multiple eNBs are present. InFIG. 9, the estimated location is the center of Tlresulting from

Tl=⋂i⁢TTASi⋂TTAP⋂TCircle
as earlier described with reference to method300. The utilization of cellular synchronization assisted location estimation gives the error distribution a more exponential form. In these simulations the CEP 70% ranges from 32 meters with one SCell configured to 14 meters with four SCells configured. As evidenced inFIG. 9, more configured SCells result in better accuracy.

Referring now toFIG. 10, simulation results of a handover scenario with and without cellular synchronization assisted location estimation are shown. This type of scenario can be realized in legacy networks with legacy UEs. In addition to initial cell association, the handover provides the unique link between the arbitrary C-RNTI and the UE which a passive device, such as a sensor device, will need in order to identify the correct TA. Also, the initial TA is issued to the UE from the target cell thus establishing a baseline upon which all further TAs are given. The intersecting rings from both eNBs provide additional location based information not normally available. In this scenario, the locus of possible target device locations is defined as the intersection of TAs from the target eNB and the source eNB. As illustrated in the first curve, identified as “Handover,” the CEP 70% is 200 meters without the utilization of cellular synchronization assisted location estimation. In the second curve, identified as “Refined Handover,” the CEP 70% is 41 meters with utilization of cellular synchronization assisted location estimation—a significant improvement.

This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification or not, may be implemented by one of skill in the art in view of this disclosure. In particular those of skill in the art can recognize that the operations of method300are not limited to the order presented and other orders can be utilized.