Patent Application
20140133319
1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to control of receiver diversity in a TD-SCDMA network.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). For example, China is pursuing TD-SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. HSPA is a collection of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing wideband protocols.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
A method of wireless communication is offered. The method includes comparing a performance metric to a threshold. The method also includes enabling or disabling an additional receive chain based at least in part on a result of the comparing.
An apparatus for wireless communication is offered. The apparatus includes means for comparing a performance metric to a threshold. The apparatus also includes means for enabling or disabling an additional receive chain based at least in part on a result of the comparing.
An apparatus for wireless communication is offered. The apparatus includes a memory and a processor(s) coupled to the memory. The processor(s) is configured to compare a performance metric to a threshold. The processor(s) is further configured to enable or disable an additional receive chain based at least in part on a result of the comparing.
A computer program product for wireless communication in a wireless network is offered. The computer program product includes non-transitory program code recorded thereon. The program code includes program code to compare a performance metric to a threshold. The program code also includes program code to enable or disable an additional receive chain based at least in part on a result of the comparing.
This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
Turning now to
The geographic region covered by the RNS 107 may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly referred to as a node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, two node Bs 108 are shown; however, the RNS 107 may include any number of wireless node Bs. The node Bs 108 provide wireless access points to a core network 104 for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. For illustrative purposes, three UEs 110 are shown in communication with the node Bs 108. The downlink (DL), also called the forward link, refers to the communication link from a node B to a UE, and the uplink (UL), also called the reverse link, refers to the communication link from a UE to a node B.
The core network 104, as shown, includes a GSM core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of core networks other than GSM networks.
In this example, the core network 104 supports circuit-switched services with a mobile switching center (MSC) 112 and a gateway MSC (GMSC) 114. One or more RNCs, such as the RNC 106, may be connected to the MSC 112. The MSC 112 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 112 also includes a visitor location register (VLR) (not shown) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 112. The GMSC 114 provides a gateway through the MSC 112 for the UE to access a circuit-switched network 116. The GMSC 114 includes a home location register (HLR) (not shown) containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 114 queries the HLR to determine the UE's location and forwards the call to the particular MSC serving that location.
The core network 104 also supports packet-data services with a serving GPRS support node (SGSN) 118 and a gateway GPRS support node (GGSN) 120. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard GSM circuit-switched data services. The GGSN 120 provides a connection for the RAN 102 to a packet-based network 122. The packet-based network 122 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 120 is to provide the UEs 110 with packet-based network connectivity. Data packets are transferred between the GGSN 120 and the UEs 110 through the SGSN 118, which performs primarily the same functions in the packet-based domain as the MSC 112 performs in the circuit-switched domain.
The UMTS air interface is a spread spectrum Direct-Sequence Code Division Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data over a much wider bandwidth through multiplication by a sequence of pseudorandom bits called chips. The TD-SCDMA standard is based on such direct sequence spread spectrum technology and additionally calls for a time division duplexing (TDD), rather than a frequency division duplexing (FDD) as used in many FDD mode UMTS/W-CDMA systems. TDD uses the same carrier frequency for both the uplink (UL) and downlink (DL) between a node B 108 and a UE 110, but divides uplink and downlink transmissions into different time slots in the carrier.
At the UE 350, a receiver 354 receives the downlink transmission through an antenna 352 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 354 is provided to a receive frame processor 360, which parses each frame, and provides the midamble 214 (
In the uplink, data from a data source 378 and control signals from the controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the node B 310 or from feedback contained in the midamble transmitted by the node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (
The uplink transmission is processed at the node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the antenna 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (
The controller/processors 340 and 390 may be used to direct the operation at the node B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the node B 310 and the UE 350, respectively. For example, the memory 392 of the UE 350 may store receive chain control module 391 which, when executed by the controller/processor 390, configures the UE 350. A scheduler/processor 346 at the node B 310 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.
Receive Diversity Control in TD-SCDMA
In certain situations, a UE may specify more than one communication chain capable of performing wireless communication. A communication chain may include components for performing wireless communication such as, for example, an antenna, processor, software, etc. A UE that has multiple receive chains may be said to have receive diversity (R×D). If multiple receive chains are tuned to different networks (such as a TD-SCDMA network or a GSM network) such UEs may simultaneously communicate on multiple networks. If multiple receive chains are combined to communicate with one network, the UE may employ receive diversity to improve communication performance with the network. For example, employing receive diversity to communications with a single network may improve data throughput or reduce a communication block error rate (BLER) over single chain receive activity. Employing receive diversity in this manner, however, may also increase UE power consumption.
To improve UE performance, a receive diversity control method is offered to manage UE performance, including performance quality, power consumption, and other factors. To manage receive diversity, measurements of UE operation and channel conditions may be made. The measurements may be analyzed by a receive diversity controller, which may control receive antennas and activate/deactivate receive diversity as conditions change to improve overall UE performance. For example, when channel conditions permit satisfactory UE communications, such as communications that exceed a BLER threshold, the controller may determine that a single antenna operation will be sufficient in the current condition. In other circumstances, such as when channel conditions are sufficiently poor, a single antenna may not meet a desired BLER threshold. Therefore, multiple antennas may be activated to improve communication performance, although with higher power consumption due to activation of receive diversity.
For UEs operating in a TD-SCDMA network a receive diversity control system is described below. A TD-SCDMA UE may employ a receive diversity controller as illustrated in
As shown in
As shown in
In another aspect, a Short-term BLER 412 may be considered. A high short-term block error rate (BLER), or a large burst of frame errors, indicates a poor quality downlink. When the short-term BLER is detected to be high, receive diversity may be enabled in order to avoid a large burst of bad frames in a row.
A hand-off (HO) indicator 416 may also be received. In a baton handoff, after the UE receives a handover command from the Node-B, the UE first stops uplink transmission and switches to the new serving cell. As a result, for the downlink, there is no power control for a certain period of time during the handover. In addition, the handover state suggests that the UE is on a cell edge. Therefore, receive diversity may be enabled in a handover mode to decrease the call drop rate. In some cases, a hard handover may occur when the UE is at the cell edge. The hard handover may be less demanding of receive diversity because a hard handover starts with a random access procedure. Receive diversity may still be enabled to achieve improved cell edge performance.
Furthermore, a special burst quality (SBQ) 418 indicator may be considered. Special bursts are transmitted when there is no traffic in a DPCH channel. Both BLER filter 408 and outer-loop power control (OLPC) 406 may be maintained once special bursts are detected. Consequently, SIR_Target 410 and short-term BLER 412 are not updated on receiving special bursts. Alternatively, the special burst may be monitored to determine a quality to detect the current channel condition.
A received signal code power (RSCP) 420 may also be considered. The RSCP 420 may be measured based on a common pilot and indicates the path loss of the UE. When RSCP 420 is low, it indicates a bad reception condition. Receive diversity may be enabled when RSCP 420 is less than a threshold.
An Out-of-Sync (OOS) indicator 422 may also be received. Out-of-sync in CELL_DCH (connected mode) may be declared after 160 ms of bad reception. Receive diversity may be enabled when the UE is out_of_sync. This test complements the BLER tests by examining the consecutive CRC failures instead of the average. When there is radio link failure, a UE enters the cell search stage, which is similar to operations performed during acquisition (ACQ).
The finite state machine may also consider the decode status 424 of the high speed-shared control channel (HS-SCCH) and whether it is successfully decoded. If successfully decoded, receive diversity may be enabled.
The receive diversity (R×D) finite state machine 500 according to one aspect of the present disclosure is illustrated in
The state machine 500 may be updated based on the most recent statistics. A variety of conditions and timers may be defined to control the transition between states. The conditions and timers may be configured to turn on receive diversity based on the finite state machine considerations described above (for example based at least in part on BLER, RSCP, SIR_Target, etc.) and the ability of receive diversity to improve UE performance. The conditions and timers may also be configured to turn off receive diversity to conserve UE power when the performance improvements for receive diversity may be outweighed by the increased power consumption. By adjusting the conditions and timers and employing the state machine, the UE may achieve receive diversity dynamic switching, allowing the UE to enable and disable receive diversity operations on the fly as desired.
For example, a state machine condition Cond_RD_On may be computed to determine whether receive diversity should be turned on based on inputs to the state machine. Similarly, a state machine condition Cond_RD_Off may be computed to determine whether receive diversity should be turned off based on inputs to the state machine. Depending on different types of traffic, Cond_RD_On and Cond_RD_Off may be computed differently. A timer, timer 1 may indicate a floor of how long the UE should stay in the receive diversity off state under certain conditions. Another timer, timer 2 may indicate a floor of how long receive diversity should be on under certain conditions. These, and other, conditions, and timers may determine when the state machine should transition states or stay in a same state.
For example, as shown in
If timer 2 expires and the condition Cond_RD_Off is set, the UE may transition from RD_ON to RD_TRANS. Upon this transition, a third timer, timer 3, may be set to T3 and the closed loop power control (CLPC) set-point, SIR_Target, may be increased by Δsetpoint. The state RD_TRANS may ensure that the signal to interference plus noise ratio (SINR) is not degraded too much in switching abruptly from RD_ON to RD_OFF. The increase in SIR_Target may send several power-control UP commands to a Node-B before shutting down the diversity receive chain.
When a UE is in RD_TRANS, timer 3 decreases until it expires. If timer 3 expires, the state machine will transition to RD_OFF and deactivate one of the two receive chains. The first timer, timer 1, will be set to T1, and the CLPC setpoint may reset to the value before transiting to RD_TRANS. The deactivated receive chain may be a fixed chain always designated for receive diversity, or may be the weaker receive chain in terms of the dynamic signal strength. Other factors may also be considered when determining which receive chain to deactivate.
A fourth state, the non-traffic state, may also be incorporated into the finite state machine of
The conditions and state machine may be configured to favor single receive chain operation, thus conserving UE power when possible, and to activate receive diversity only when single receive chain operation provides undesirable operation. For example, if a single receive chain operation reaches a level where increased power to the single chain may not improve operation (or further power increases are not possible) and a performance metric, such as SIR, continues to grow until it hits an upper bound, then receive diversity may be enabled to improve performance. When channel conditions improve, receive diversity may be disabled to conserve power. For example, the UE may enable receive diversity where the target BLER cannot be achieved with single antenna, but may be achieved with receive diversity.
The SIR_Target may be also adjusted through an OLPC block driven by the packet CRC. If a CRC failure is received, the SIR_Target may be increased by Up_Stepsize. If a CRC pass is received, the SIR_Target may be decreased by Down_Stepsize. For example, for a target BLER of 1%, values may be set at Up_Stepsize=0.5 dB and Down_Stepsize=0.5/99 dB. In this case, the target BLER may be achieved if the SIR_Target trace may be maintained around a constant value without saturation. On the other hand, if the BLER target cannot be achieved, the SIR_Target will increase until being saturated. Note that Up_Stepsize and Down_Stepsize may change adaptively based on UE conditions. By adjusting the SIR_Target in this manner, the decision of whether to enable receive diversity by the UE can account for the channel conditions.
Because the SIR_Target value reflects whether the channel is in good condition and whether the transmit power gap is reached, SIR_Target thresholding may be applied in receive diversity control. Specifically the UE can turn on receive diversity when the SIR_Target is greater than a threshold and turn off receive diversity if the SIR_Target is less than the threshold. The value of the threshold determines the level of the SIR_Target, and therefore determines the tradeoff between receive diversity on time and Node-B transmit power. A larger threshold makes it more difficult to turn on receive diversity, and thus consume more Node-B transmit power.
A large threshold value may be preferred to ensure that receive diversity is turned on only if a single antenna is not enough to maintain the target BLER. If the target BLER can be achieved with a single antenna, despite a high transmit power and a high SIR_Target value, it may be desired to keep receive diversity off to save UE power.
The initial value of the SIR_Target should not be set too low, because otherwise, if the channel condition is bad, it may take a long time for the SIR_Target to reach the threshold. On the other hand, it is possible that when the channel conditions suddenly worsen, the SIR_Target may still be low, and a number of error packets may be received before the SIR_Target reaches the threshold. As a result, a burst of packet errors may occur during this transition period. A short-term BLER test may be applied to avoid consecutive packet errors during this period. The error burst can be further alleviated if the BLER threshold is set differently in RD_ON and RD_OFF states.
The short-term BLER may be measured via an infinite impulse response (IIR) filter driven by CRC. The short term BLER may be represented by
BLER(n)=(1−α)·BLER(n−1)+α·
where CRC(n)=0 if frame-n has a CRC failure and CRC(n)=1 if frame-n has a CRC pass. The BLER tests may be defined as
in RD_OFF state, and
in RD_ON state. ThBLER
In RD_OFF state, BLER_Hi_t is tested to see if BLER is too high to turn on receive diversity. The threshold ThBLER
In RD_ON state, BLER_Lo_t is tested to see if BLER is low enough to turn off receive diversity. A different BLER threshold, ThBLER
Based on an average BLER of each transport channel of a CCTrCH, the outer-loop power control module updates the SIR target of a CCTrCH. The same maximum SIR_Target may be considered in the SIR_Target test with the following thresholding operation.
where ThSIR is the set SIR threshold. Here the test may be over all CCTrCH targets. If there is no CCTrCH, SIR_t=false. The SIR_Target test may be updated every 20 ms, even in high speed (HS) mode, according to one configuration.
The parameter SBQ_Ave may be defined as the average of the special burst quality (SBQ) over a time period of DSBQ. The parameter SBQ_Ave may take special burst discontinuous transmission (DTX) into account. The SBQ test is the result of a thresholding operation, i.e.,
SBQ—t=SB_Detected&&(SBQ—Ave<ThSBQ)
where the test result (SBQ_t) is true when a special burst is detected (SB_Detected=true) and also the average of the special burst quality (SBQ_Ave) is below a threshold value (ThSBQ).
Regarding the RSCP, the following test may be defined
RSCP—t=RSCP<ThRSCP
where ThRSCP is the set RSCP threshold and RSCP is the actual received signal code power.
Using these values, the state machine conditions Cond_RD_On and Cond_RD_Off, may be computed as below:
where HO_t is true when a handoff occurs, OOS_t is true when the UE is out of synchronization.
The apparatus includes a processing system 714 coupled to a transceiver 730. The transceiver 730 is coupled to one or more antennas 720. The transceiver 730 enables communicating with various other apparatus over a transmission medium. The processing system 714 includes a processor 722 coupled to a computer-readable medium 726. The processor 722 is responsible for general processing, including the execution of software stored on the computer-readable medium 726. The software, when executed by the processor 722, causes the processing system 714 to perform the various functions described for any particular apparatus. The computer-readable medium 726 may also be used for storing data that is manipulated by the processor 722 when executing software.
The processing system 714 includes a comparing module 702 for comparing a performance metric to a threshold. The processing system 714 includes an enabling/disabling module 704 for enabling or disabling an additional receive chain based at least in part on a result of the comparing. The modules may be software modules running in the processor 722, resident/stored in the computer readable medium 726, one or more hardware modules coupled to the processor 722, or some combination thereof. The processing system 714 may be a component of the UE 350 and may include the memory 392, and/or the controller/processor 390.
In one configuration, an apparatus such as a UE is configured for wireless communication including means for comparing and means for enabling/disabling. In one aspect, the above means may be the antennas 352, the receiver 354, the receive processor 370, the controller/processor 390, the memory 392, receive chain control module 391, comparing module 702, enabling/disabling module 704, and/or the processing system 714 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.
Several aspects of a telecommunications system has been presented with reference to TD-SCDMA systems. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W-CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.
Several processors have been described in connection with various apparatuses and methods. These processors may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software will depend upon the particular application and overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with a microprocessor, microcontroller, digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gated logic, discrete hardware circuits, and other suitable processing components configured to perform the various functions described throughout this disclosure. The functionality of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with software being executed by a microprocessor, microcontroller, DSP, or other suitable platform.
Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. A computer-readable medium may include, by way of example, memory such as a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disc (CD), digital versatile disc (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, or a removable disk. Although memory is shown separate from the processors in the various aspects presented throughout this disclosure, the memory may be internal to the processors (e.g., cache or register).
Computer-readable media may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.
It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.
The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
