Patent Application
20110141878
Various embodiments relate generally to radio communications. More particularly, various embodiments relate to bundling concepts and enhanced channel selection methods in accordance with the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) Advanced (LTE-A) standardization that are also backwards compatible with bundled ACK/NACK handling, where each ACK/NACK of bundled ACK/NACKS is associated with one downlink packet when the amount of downlink resources is greater than the amount of uplink resources in accordance with the 3GPP LTE Release 8 standard.
This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The Universal Mobile Telecommunications System (UMTS) is a third generation (3G) mobile communication system which provides a variety of multimedia services. The UMTS Terrestrial Radio Access Network (UTRAN) is a part of a UMTS network which includes one or more radio network controllers (RNCs) and one or more nodes. The 3GPP is a collaboration of several independent standardization organizations that is focused on the development of globally applicable 3G mobile phone system specifications. The Technical Specification Group Radio Access Network (TSG RAN) is responsible for the definition of the functions, requirements and interfaces of the universal terrestrial radio access (UTRA) network in its two modes, frequency division duplex (FDD) and time division duplex (TDD). Evolved UTRAN (E-UTRAN), which is also known as LTE, provides new physical layer concepts and protocol architectures for UMTS.
LTE is currently part of a work item phase within the 3GPP that is planned to be ratified as a standard in 3GPP Release 8. One of the central elements of the system is a downlink control channel, which will carry all of the control information needed to assign resources for the downlink as well as the uplink data channels, where downlink and uplink conventionally refer to transmission paths to and from a mobile station and, for example, a base transceiver station. The elements for the control channel carrying allocation for the downlink channel, following the 3GPP 36.211 and 36.213 specifications, can comprise at least: a resource allocation map describing the allocation map for physical resource blocks (PRBs); a modulation scheme/technique; a transport block size or payload size; Hybrid Automatic Repeat-reQuest (H-ARQ) information; multiple-input multiple-output (MIMO) information; and/or a duration of assignment.
LTE supports both a frequency division duplex (FDD) communications mode and a time division duplex (TDD) communications mode. With regard to TDD, information/data/packets may be transmitted over, e.g., the bandwidth of a channel in time multiplexed intervals, referred to as transmission time intervals (TTIs). Due to time multiplexing between downlink and uplink in TDD operation, uplink may have limited resources/time whereas downlink may require a large amount of resources. Conventionally, each downlink packet (transmitted within a TTI) requires one uplink return channel to send back, e.g., an ACK/NACK for Hybrid Automatic Repeat Request (HARQ) operation. For example, in the latest Radio Access Network (RAN)1 decision, ACK/NACK bundling (i.e., an operation of AND over all ACK/NACKs) was accepted to decouple allocated downlink resources from the required uplink return channel capability. That is, a user equipment (UE) only/always sends a one bit (or two bit in case of MIMO) ACK/NACK in the uplink. As a consequence, the coverage/capacity of the uplink ACK/NACK is also decoupled from the required/allocated downlink resources.
In ACK/NACK bundling for the associated downlink transmissions, a UE and evolved node B (eNB) base transceiver station would both need to know how many packets have been transmitted in downlink and that need to be simultaneously (e.g., bundled or AND'ed) ACK/NACK'ed, i.e., sent acknowledgement/negative-acknowledgements. Signaling such information would create a constant signaling overhead for all allocations. Additionally, due to physical downlink control channel (PDCCH) detection errors, a “blind” common understanding between the eNB and the UE cannot be assumed.
Moreover, when a large number of ACK/NACKs for downlink packets are bundled in a bundle/bundling window (where the bundle/bundling window refers to, e.g., the downlink TTI/subframes whose ACK/NACK is to-be-bundled), PDCCH detection reliability, for example, can begin to dominate the link adaptation error target. Hence, a simple AND'ed operation for ACK/NACK bundling becomes unpractical and the eNB must reduce the scheduling flexibility with when, e.g., data packets can be transmitted, such as only allowing one downlink transmission per downlink scheduling window associated with one uplink feedback instance grant. For example, in a 9 downlink/1 uplink scenario, the UE will be reduced to 1/9 of the available system capacity. In an environment with few active users per cell, certain negative implications arise with regard to system performance.
LTE-A will be an evolution of the LTE Release 8 system fulfilling the International Telecommunication Union Radiocommunication Sector (ITU-R) requirements for International Mobile Telecommunications-Advanced (IMT-Advanced) systems. A Study Item on LTE-A was approved by the 3GPP relating to backwards compatibility. Certain assumptions regarding backwards compatibility have been made including the assumption that a Release 8 E-UTRA terminal must be able to work in an Advanced E-UTRAN network, and that an advanced E-UTRA terminal should be able to operate in a Release 8 E-UTRAN network. Therefore, bundling concepts and enhanced channel selection methods applicable to LTE-A should also be backwards compatible with LTE Release 8.
Various embodiments allow for determining a type of a received transmission stream and receiving information to use either two ACK/NACK fields or a single ACK/NACK field for the received transmission stream in LTE Release 8 TDD mode. Upon receiving the information to use the two acknowledgement/negative-acknowledgement fields, it is determined whether to divide the transmission stream and send the two acknowledgement/negative-acknowledgement fields for the transmission stream. Dividing bundling windows into smaller subbundles for UEs with sufficient link quality aids in increasing PDCCH reliability while facilitating large data-rate transmissions to each user. Additionally, issues associated with “mixed new and retransmissions” are reduced in cases when a single downlink grant is sent per downlink TTI. Moreover, existing physical uplink control channels (PUCCHs) can be re-used while providing a different interpretation of the ACK/NACK bit in TDD communications mode scenarios when there are more downlink resources than uplink resources. Therefore, PUCCH transmission remains the same as in the FDD communications mode, but higher layer signaling is utilized to change the interpretation of the ACK/NACK bit.
In LTE-A TDD mode, various embodiments provide bundling within the time domain, within the frequency domain, and within a hybrid time-frequency domain. With such methods of bundling in a LTE-A TDD system, the number of ACK/NACKs on the PUCCH can be reduced to 4 or 5 instances. LTE Release 8 TDD mode can support up to 4 ACK/NACKs on the PUCCH. That is, “almost the same” number of ACK/NACKs can be supported on the PUCCH.
Furthermore, enhanced channel selection methods are also provided in support of the above-mentioned bundling methods in accordance with various embodiments. That is, the LTE Release 8 TDD mode method of channel selection is not used in LTE-A TDD mode. Instead, an enhanced TDD channel selection method which ensures backward compatibility with LTE Release 8 is used, where the enhanced TDD channel selection method takes into consideration, These and other advantages and features of various embodiments of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the several drawings described below.
Embodiments of the invention are described by referring to the attached drawings, in which:
Various embodiments described herein enable different “bundling” methods for downlink transmissions and provide different interpretations of the “ACK/NACK” bit in accordance with LTE Release 8. In accordance with various embodiments, the UE is configured so that it commonly acknowledges all downlink TTIs within a bundle so that if one packet is determined to be erroneous, all packets in that bundle will be retransmitted. Additionally, various embodiments are implemented by allowing an interpretation to be applied to the uplink ACK/NACK field such that the eNB is able to decide how to divide bundled downlink packets into smaller windows which allows for a reduced negative impact on PDCCH detection reliability and/or determine how to interpret, e.g., a two bit ACK/NACK. Such a decision(s) is signalled to the UE so that the UE can effectuate the appropriate mapping and subbundle split. It should be noted that various embodiments can be used with UE that have a sufficient uplink link budget to support ACK/NACK reporting for dual-layer transmission. It should also be noted that in the context of transmission streams, e.g., dual-layer transmission, the terms “stream” and “layers” are used interchangeably.
In accordance with one embodiment for use with a FDD UE, two methods of ACK/NACK reporting are utilized. For a FDD UE, there is generally a one-to-one mapping between downlink allocations and uplink ACK/NACK signaling. First, a single ACK/NACK report can be sent by the FDD UE in response to a single-layer transmission in the downlink. Second, a dual ACK/NACK report can be sent corresponding to a dual-stream transmission in the downlink, where each stream of the dual-transmission stream has its own ACK/NACK. That is, one symbol is able to carry ACK/NACK information for a single resource allocation. This resource allocation for FDD can be either a single-stream transmission as noted above, where, e.g., an ACK/NACK symbol will carry one information bit. Alternatively, for dual-stream transmission as noted above, the ACK/NACK symbol will carry the ACK/NACK information for both layers (using, e.g., a modulation similar to quadrature phase shift keying (QPSK)). It should be noted that this ACK/NACK reporting applies to uplink transmission on a PUCCH as well as a physical uplink shared channel (PUSCH). Furthermore, these ACK/NACK reporting methods for the FDD UE are automatically triggered by a downlink grant that informs the UE what transmission mode is active. In the case of the dual-layer transmission, for example, the eNB shifts to a QPSK mode to make room for the two individual ACK/NACKs.
Another embodiment may be utilized in conjunction with a LTE TDD UE that is configured for TTI bundling. In accordance with this embodiment, a layer higher than the physical layer with which physical downlink channels (e.g., PDCCH and PDSCH) are associated can be utilized to inform the LTE TDD UE whether it is to transmit two ACK/NACKS for a corresponding bundle. Such higher layers are, e.g., the Medium Access Control (MAC) layer, Radio Link Control (RLC) layer, etc. Alternatively, the LTE TDD UE can be informed via a downlink grant instead of through the higher layers described above.
In accordance with such an embodiment, the LTE TDD UE performs one of the following operations for each downlink bundling window of TTIs, where each downlink bundling window can include two or more TTIs depending on the particular downlink/uplink configuration. If a relevant downlink transmission comprises a single-stream transmission over all of the bundled TTIs, the LTE TDD UE divides the bundle into two smaller TTI bundles, e.g., subbundles. For each subbundle, one ACK/NACK is sent by the LTE TDD UE. For a dual-stream transmission over all of the bundled TTIs, the LTE TDD UE also divides the TTI bundle into two smaller TTI bundles but will send a joint ACK/NACK for each subbundle separately. Because a joint ACK/NACK is sent for both subbundles representative of each stream, if one stream fails both streams are retransmitted. Alternatively, for the dual-layer transmission over all of the bundled TTIs, the LTE TDD UE can maintain the entire bundling window in a singular format and send separate ACK/NACKs for each of the streams. Therefore, only one multi-stream needs to be transmitted and/or retransmitted.
It should be noted that for simplicity, an eNB can be configured so that it is not able to switch between single and dual-layer transmission within the same bundle. Alternatively, “combinations” of single and dual-layer transmissions can be specified separately indicating how a LTE TDD UE utilizes/exploits its two ACK/NACK bits. For example, all dual-layer allocations from an ACK/NACK perspective, can be mapped to a single-stream and then joint ACK/NACKs can be sent for each subbundle.
The LTE TDD UE is also able to send a single ACK/NACK per bundle in accordance with various embodiments. That is, an option exists for a single-layer transmission over all of the bundled TTIs, where the LTE TDD UE sends a joint ACK/NACK for all downlink subframes. A subframe can be thought of, e.g., as two consecutive slots, where 20 slots can make up a radio frame. Therefore, if there is a reception error of at least either the PDCCH or the PDSCH for a window, everything is retransmitted. If a transmission is a dual-layer transmission over all of the bundled TTIS, the LTE TDD UE sends a joint ACK/NACK for both streams so that if one layer fails, both streams are retransmitted.
As described above and in accordance with various embodiments, smaller bundle windows can be created for UEs with sufficient link quality, thus increasing PDCCH reliability while facilitating large data-rate transmissions to each user. Additionally, issues associated with “mixed new and retransmissions” are reduced in cases when a single downlink grant is sent for a TTI bundle. Moreover, existing PUCCHs can be re-used while providing a different interpretation of the ACK/NACK bit in TDD communications mode scenarios when there are more downlink resources than uplink resources. Therefore, PUCCH transmission remains the same as in the FDD communications mode, but higher layer signaling is utilized to change the interpretation of the ACK/NACK bit.
In order to meet the aforementioned backwards compatibility requirements, carrier aggregation is being considered as a method to extend bandwidth in a LTE-A system, where channel aggregation can be viewed as a multi-carrier extension of LTE Release 8. From an uplink/downlink control signaling point of view, the most straightforward multi-carrier concept involves copying the existing LTE Release 8 control plane (e.g., PDCCH, PUCCH, etc) to each “chunk.” This concept may be referred to as a N×PDCCH structure in LTE-A. Studies have shown that for UEs having resource allocation in multiple chunks, “per chunk” HARQ is more efficient.
In a LTE-A system and from a PUCCH coverage point of view, single-carrier transmission is desirable whenever possible (to minimize the cubic metric (CM) of the uplink signals). One high-level rule has been proposed to minimize CM properties when ACK/NACKs should be transmitted on the PUCCH in a LTE-A system with a N×PDCCH structure, where if no simultaneous PUSCH is available, uplink control signals are transmitted via a single chunk instead of multiple chunks (i.e., N×DL).
Additionally, to maintain backwards compatibility with LTE Release 8, the method of ACK/NACK multiplexing on the PUCCH in LTE Release 8 TDD (i.e., channel selection on the PUCCH format 1a/1b) should also be extended to LTE-A TDD to support the transmission of ACK/NACK on the PUCCH as described above in accordance with various embodiments.
However, although per chunk HARQ creates good performance in LTE-A systems with a N×PDCCH structure, more control signaling is required. For example, there should be ACK/NACK feedback/reporting for the transmission in each chunk per subframe. In LTE-A TDD mode, there could be 1, 2, 3, 4, or 9 downlink subframes associated with a single uplink subframe. Therefore, assuming a UE reception bandwidth is set as 5 chunks and spatial bundling has been adopted (as in LTE Release 8), the number of ACK/NACK bits to be transmitted in the uplink subframe may be 5, 10, 15, 20 and 45. Supporting such a dynamic range of numbers of ACK/NACKs on the PUCCH is not desirable both from a channel resource limitation perspective and an ACK/NACK detection performance point of view.
In LTE Release 8 TDD mode, the mapping between the states of multiple ACK/NACKs and the ACK/NACK channel derived from downlink subframes (as well as the constellation point derived from the QPSK constellation) has been defined to support ACK/NACK multiplexing on the PUCCH. However, it should be noted that, in LTE-A TDD mode, multiple chunks may be allocated within one subframe, whereas the LTE Release 8 TDD mode is unconcerned with such allocations. Hence such channel selection methods cannot be adopted in the LTE-A TDD mode directly because an ambiguity between the channel selection and frequency/chunk domain exists, which adversely affects efficient ACK/NAKs transmission on the PUCCH in LTE-A TDD mode. Studies have shown that for UEs having resource allocation in multiple chunks, “per chunk” HARQ is more efficient. Hence, various embodiments operative in a LTE-A TDD mode focus on ACK/NAK transmission on the PUCCH with a N×PDCCH structure.
To enable efficient ACK/NACK transmission on the PUCCH in LTE-A TDD mode with a N×PDCCH structure, further bundling over the subframe/chunk domain is provided in accordance with various embodiments to keep the number of ACK/NACK feedbacks at a reasonable level. Such bundling over the subframe/chunk domain is performed instead of/in addition to the bundled ACK/NACK reporting described in earlier embodiments for each downlink bundling window of TTIs/subbundle in LTE Release 8 TDD mode. Additionally, various embodiments provide support for efficient ACK/NACK transmission on the PUCCH in LTE-A TDD mode.
Thus, various embodiments provide bundling within the time domain, within the frequency domain, and within a hybrid time-frequency domain. With such methods of bundling in a LTE-A TDD system, the number of ACK/NACKs on the PUCCH can be reduced to 4 or 5 instances. LTE Release 8 TDD mode can support up to 4 ACK/NACKs on the PUCCH. That is, “almost the same” number of ACK/NACKs can be supported on the PUCCH. However, it should be noted that in LTE-A TDD mode, these “almost the same” results are based on the bundling methods described herein which ensure backwards compatibility with LTE Release 8 TDD mode, although such methods need not be used in LTE Release 8 TDD mode.
Furthermore, enhanced channel selection methods are also provided in support of the above-mentioned bundling methods. That is, the LTE Release 8 TDD mode method of channel selection is not used in LTE-A TDD mode. Instead, an enhanced TDD channel selection method which ensures backward compatibility with LTE Release 8 is used, where the enhanced TDD channel selection method takes into consideration, the multi-carrier aspects of LTE-A.
In accordance with one embodiment, chunk bundling (i.e., time domain bundling) is performed. That is, ACK/NACK bundling is performed over the entire bandwidth or UE reception bandwidth within one subframe. Each subframe (downlink TTI) generates one ACK/NACK feedback, and the number of ACK/NACK feedbacks is based on the number of associated downlink subframes. When each subframe generates only one ACK/NACK feedback, the number of ACK/NACKs within the entire “scheduling window” is reduced to the number of associated downlink subframes. It should be noted that most if not all of the embodiments described above can be “re-used” because through the use of “chunk bundling,” a multi-carrier case in LTE-A TDD mode becomes a single-carrier case, such as that described above and supported by LTE Release 8 TDD mode.
In accordance with another embodiment, subframe bundling (i.e., frequency domain bundling) is provided. For subframe bundling, ACK/NACK bundling is performed over an entire “scheduling window” within one allocated chunk, where the number of ACK/NACK feedbacks is based on the number of chunks within the whole bandwidth or UE reception bandwidth. That is, within a UE reception bandwidth, each chunk over the entire “scheduling window” only generates one ACK/NAK feedback/report. Therefore, subframe bundling effectively turns a multi-subframe case to a single-subframe case. Moreover, if a “chunk” in LTE-A TDD mode is considered to be a “subframe” in LTE Release 8 TDD mode, various embodiments described above for handling bundling (via ACK/NACK reporting for single-layer and dual-layer transmissions over all bundled TTIs/subframes) can be re-used in LTE-A TDD mode.
In accordance with yet another embodiment, block bundling (i.e., hybrid time-frequency domain bundling) is provided. ACK/NAK bundling over both subframe and chunk domains is performed. One PRB/block consists of several subframes and chunks, and generates one ACK/NACK feedback. The number of ACK/NACKs is based on the number of blocks. This method of block bundling can be considered to be a general case of “chunk bundling” and “subframe bundling.”
In LTE-A TDD mode, to enable efficient ACK/NAK feedback on the PUCCH, channel selection should be derived from both downlink subframes and UE reception bandwidth as described above. Furthermore, constellation point selection can re-use the mapping specified in LTE Release 8 TDD mode. Generally, the selected ACK/NACK channel is denoted as (h(i,j), Q(k)), where i refers to the selected downlink subframe/or control channel element (CCE) number, j refers to a single chunk number used to transmit ACK/NACKs, and k refers to a selected constellation point. For LTE A TDD mode, enhanced channel selection methods corresponding to different ACK/NACK bundling methods are as follows.
In accordance with one embodiment, channels for chunk bundling of ACK/NACK feedback (subframe number i, constellation point number k) are selected based on the mapping specified in LTE Release 8 TDD mode. The chunk number j is selected based on the following methods, including but not limited to, a certain position chunk (e.g., the first or last allocated/detected chunk) within subframe i, or channel status.
In accordance with another embodiment, channels for subframe bundling (chunk number j, constellation point number k) are selected based on the mapping in LTE Release 8 TDD mode, and subframe number i is selected based on a certain position subframe (e.g., the first or last allocated/detected subframe) within chunk j. It should be noted that if a UE reception bandwidth is set to 5 chunks, up to 5 ACK/NACK feedbacks will be generated while the channel selection method supports multiple ACK/NACK feedbacks up to 4. In such a case, more than one CCE per chunk-specific PDCCH can be allocated so that more than one PUCCH ACK/NACK resources are available per chunk. Alternatively, all constellation points in both slots of one PUCCH subframe may be utilized for different ACK/NACK information instead of repeating/hopping the same ACK/NACK in 2 slots of one PUCCH subframe. Alternatively still, some many-to-one mappings of 5-bit ACK/NACK to 20 states (i.e., a type of sub-bundling or ACK/NACK compression between pure multiplexing and pure bundling) can be made to fit into 20 PUCCH ACK/NACK constellation points available from a 5 chunk-specific PDCCH, each having a single dedicated PUCCH ACK/NACK channel and each channel having 4 constellation points, i.e., QPSK modulation.
In accordance with still another embodiment, channels for block bundling: (block number h, constellation point number k) are selected based on the mapping in LTE Release 8 TDD mode. Subframe number i and chunk number j are selected based on either a certain position subframe and chunk (e.g., the first or last allocated/detected subframe/chunk) within block h or on channel status within block h.
For example, in LTE-A TDD mode, 4 downlink subframes may be associated with 1 uplink subframe, where the UE reception bandwidth is set to 3 chunks. Assuming chunk/subframe/block number and constellation point number (1,1) is selected according to ACK/NAK state and the mapping table as defined in LTE Release 8 TDD mode, exemplary implementations of the bundling methods described above in accordance with various embodiments are described with reference to
The ACK/NACK bundling methods of various embodiments described above control the number of ACK/NACK feedbacks by keeping them at a reasonable level. Additionally, an enhanced channel selection method utilized in accordance with the various bundling methods, which is based on time-frequency domain channel selection, takes the multi-carrier property of LTE-A TDD into account. Therefore, efficient ACK/NACK transmission on the PUCCH in LTE-A TDD is supported while remaining fully backwards compatible with bundling methods applicable to LTE Release 8 TDD.
For exemplification, the system 10 shown in
The exemplary communication devices of the system 10 may include, but are not limited to, an electronic device 12 in the form of a mobile telephone, a combination personal digital assistant (PDA) and mobile telephone 14, a PDA 16, an integrated messaging device (IMD) 18, a desktop computer 20, a notebook computer 22, etc. The communication devices may be stationary or mobile as when carried by an individual who is moving. The communication devices may also be located in a mode of transportation including, but not limited to, an automobile, a truck, a taxi, a bus, a train, a boat, an airplane, a bicycle, a motorcycle, etc. Some or all of the communication devices may send and receive calls and messages and communicate with service providers through a wireless connection 25 to a base station 24. The base station 24 may be connected to a network server 26 that allows communication between the mobile telephone network 11 and the Internet 28. The system 10 may include additional communication devices and communication devices of different types.
The communication devices may communicate using various transmission technologies including, but not limited to, Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Transmission Control Protocol/Internet Protocol (TCP/IP), Short Messaging Service (SMS), Multimedia Messaging Service (MMS), e-mail, Instant Messaging Service (IMS), Bluetooth, IEEE 802.11, etc. A communication device involved in implementing various embodiments of the present invention may communicate using various media including, but not limited to, radio, infrared, laser, cable connection, and the like.
Various embodiments described herein are described in the general context of method steps or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.
Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware may reside, for example, on a chipset, a mobile device, a desktop, a laptop or a server. Software and web implementations of various embodiments can be accomplished with standard programming techniques with rule-based logic and other logic to accomplish various database searching steps or processes, correlation steps or processes, comparison steps or processes and decision steps or processes. Various embodiments may also be fully or partially implemented within network elements or modules. It should be noted that the words “component” and “module,” as used herein and in the following claims, is intended to encompass implementations using one or more lines of software code, and/or hardware implementations, and/or equipment for receiving manual inputs.
Individual and specific structures described in the foregoing examples should be understood as constituting representative structure of means for performing specific functions described in the following the claims, although limitations in the claims should not be interpreted as constituting “means plus function” limitations in the event that the term “means” is not used therein. Additionally, the use of the term “step” in the foregoing description should not be used to construe any specific limitation in the claims as constituting a “step plus function” limitation. To the extent that individual references, including issued patents, patent applications, and non-patent publications, are described or otherwise mentioned herein, such references are not intended and should not be interpreted as the limiting the scope of the following claims.
The foregoing description of embodiments has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit embodiments of the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. The embodiments discussed herein were chosen and described in order to explain the principles and the nature of various embodiments and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2009/005075 | 3/25/2009 | WO | 00 | 2/28/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61039361 | Mar 2008 | US | |
| 61109143 | Oct 2008 | US |
