Transmitting acknowledgment messages on preferred link in 5G carrier aggregation

This disclosure relates to methods and devices for transmitting acknowledgment messages on a preferred cell in a carrier aggregation scenario. A user equipment device (UE) establishes a connection with a primary cell and one or more secondary cells, and determines a preferred cell from among the primary cell and the one or more secondary cells based at least in part on one or more quality metrics. The UE may determine the preferred cell at least in part in response to determining that transmission power of the UE has been limited due to a specific absorption rate (SAR) backoff feature of the UE. The UE transmits a notification to a network indicating that the UE intends to transmit an acknowledgement message to the preferred cell, and transmits the acknowledgment message to the preferred cell.

TECHNICAL FIELD

The present application relates to wireless communication, including methods, systems, and apparatuses to transmit acknowledgment messages during a carrier aggregation scenario.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further, wireless communication technology has evolved from voice-only communications to also include the transmission of data, such as Internet and multimedia content.

Mobile electronic devices may take the form of smart phones or tablets that a user typically carries. Wearable devices (also referred to as accessory devices) are a newer form of mobile electronic device, one example being smart watches. Additionally, low-cost low-complexity wireless devices intended for stationary or nomadic deployment are also proliferating as part of the developing “Internet of Things”. In other words, there is an increasingly wide range of desired device complexities, capabilities, traffic patterns, and other characteristics. In general, it would be desirable to recognize and provide improved support for a broad range of desired wireless communication characteristics. For example, the design of wireless networks may increasingly include carrier aggregation (CA). During a CA communication session, a wireless device may be in communication with each of a primary cell (PCell) and one or more secondary cells (SCells). The introduction of multiple active cells may introduce complications for realizing effective communication. Therefore, improvements in the field are desired.

SUMMARY

Embodiments are presented herein of, inter alia, systems, apparatuses, and methods for transmitting acknowledgment messages on a preferred cell in a carrier aggregation (CA) scenario.

In some embodiments, a user equipment device (UE) establishes a connection with a primary cell and one or more secondary cells, and determines a preferred cell from among the primary cell and the one or more secondary cells based at least in part on one or more quality metrics. The UE may determine a preferred cell in response to detecting that a specific absorption rate (SAR) backoff procedure has been implemented by the device, whereby transmission power of the UE is throttled due to a grip state of the user, in some embodiments. The UE transmits a notification to a network indicating that the UE intends to transmit an acknowledgement message to the preferred cell, and transmits the acknowledgment message to the preferred cell.

In some embodiments, the UE may periodically monitor the one or more quality metrics to obtain one or more updated quality metrics. In these embodiments, the UE may dynamically redetermine the preferred cell from among the primary cell and the one or more secondary cells based at least in part on the one or more updated quality metrics.

The techniques described herein may be implemented in and/or used with a number of different types of devices, including but not limited to cellular phones, tablet computers, accessory and/or wearable computing devices, portable media players, cellular base stations and other cellular network infrastructure equipment, servers, and any of various other computing devices.

DETAILED DESCRIPTION

Acronyms

The following acronyms are used in the present disclosure.

3GPP: Third Generation Partnership Project

3GPP2: Third Generation Partnership Project 2

RAN: Radio Access Network

GSM: Global System for Mobile Communications

UMTS: Universal Mobile Telecommunications System

UTRAN: UMTS Terrestrial Radio Access Network or Universal Terrestrial Radio Access Network

UE: User Equipment

LTE: Long Term Evolution

NR: New Radio

E-UTRAN: Evolved UMTS Radio Access Network or Evolved Universal Radio Access Network

RRC: Radio Resource Control

RLC: Radio Link Control

MAC: Media Access Control

PDCP: Packet Data Convergence Protocol

RF: radio frequency

BS: base station

MME: Mobility Management Entity

AMF: Access Management Function

RAT: radio access technology

PLMN: public land mobile network

LAA: licensed assisted access

PDCCH: physical downlink control channel

PDSCH: physical downlink shared channel

PRB: physical resource block

DCI: downlink control information

RSRP: reference signal received power

Terms

FIG. 1illustrates an exemplary (and simplified) wireless communication system in which aspects of this disclosure may be implemented, according to some embodiments. For example, any or all of the wireless devices illustrated inFIG. 1may be configured for performing signal detection as described herein, e.g., according to one or more of the methods described herein. It is noted that the system ofFIG. 1is merely one example of a possible system, and embodiments may be implemented in any of various systems, as desired.

The base station102A may be a base transceiver station (BTS) or cell site, and may include hardware and/or software that enables wireless communication with the UEs106A through106N. The base station102A may also be equipped to communicate with a network100(e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities). Thus, the base station102A may facilitate communication among the user devices and/or between the user devices and the network100.

The communication area (or coverage area) of the base station may be referred to as a “cell.” The base station102A and the UEs106may be configured to communicate over the transmission medium using any of various radio access technologies (RATs), also referred to as wireless communication technologies, or telecommunication standards, such as GSM, UMTS (WCDMA, TD-SCDMA), LTE, LTE-Advanced (LTE-A), NR, 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), Wi-Fi, WiMAX etc.

Note that a UE106may be capable of communicating using multiple wireless communication standards. For example, a UE106might be configured to communicate using two or more of GSM, UMTS, CDMA2000, WiMAX, LTE, LTE-A, NR, WLAN, Bluetooth, one or more global navigational satellite systems (GNSS, e.g., GPS or GLONASS), one and/or more mobile television broadcasting standards (e.g., ATSC-M/H or DVB-H), etc. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

FIG. 2illustrates user equipment106(e.g., one of the devices106A through106N) in communication with a base station102(e.g., one of the base stations102A through102N), according to some embodiments. The UE106may be a device with cellular communication capability such as a mobile phone, a hand-held device, a wearable device, a computer or a tablet, or virtually any type of wireless device.

As noted above, the UE106may be configured to communicate using any of multiple RATs. For example, the UE106may be configured to communicate using two or more of GSM, CDMA2000, UMTS, LTE, LTE-A, NR, WLAN, or GNSS. Other combinations of wireless communication technologies are also possible.

The UE106and/or BS102may be configured to perform carrier aggregation (CA). For example, the BS102may use carriers using any combination of RATs to communicate with UE106. As one possibility, the UE106and BS102may employ licensed assisted access (LAA) techniques, and may thus aggregate licensed and unlicensed spectrum for communication. Carrier aggregation may employ a primary cell (PCell) and one or more secondary cells (SCells), which may be collocated within a single base station tower, or may be distributed over a first BS and one or more neighboring BSs, according to various embodiments.

FIG. 3—Block Diagram of a UE Device

FIG. 3illustrates one possible block diagram of a UE device106. As shown, the UE device106may include a system on chip (SOC)300, which may include portions for various purposes. For example, as shown, the SOC300may include processor(s)302which may execute program instructions for the UE device106, and display circuitry304which may perform graphics processing and provide display signals to the display360. The SOC300may also include motion sensing circuitry370which may detect motion of the UE106, for example using a gyroscope, accelerometer, and/or any of various other motion sensing components. The processor(s)302may also be coupled to memory management unit (MMU)340, which may be configured to receive addresses from the processor(s)302and translate those addresses to locations in memory (e.g., memory306, read only memory (ROM)350, flash memory310). The MMU340may be configured to perform memory protection and page table translation or set up. In some embodiments, the MMU340may be included as a portion of the processor(s)302.

As shown, the SOC300may be coupled to various other circuits of the UE106. For example, the UE106may include various types of memory (e.g., including NAND flash310), a connector interface320(e.g., for coupling to a computer system, dock, charging station, etc.), the display360, and wireless communication circuitry330(e.g., for LTE, LTE-A, NR, CDMA2000, Bluetooth, Wi-Fi, NFC, GPS, etc.).

The UE device106may include at least one antenna, and in some embodiments multiple antennas335aand335b(and/or further additional antennas), for performing wireless communication with base stations and/or other devices. For example, the UE device106may use antennas335aand335bto perform the wireless communication. As noted above, the UE device106may in some embodiments be configured to communicate wirelessly using a plurality of wireless communication standards or radio access technologies (RATs).

The wireless communication circuitry330may include Wi-Fi Logic332, a Cellular Modem334, and Bluetooth Logic336. The Wi-Fi Logic332is for enabling the UE device106to perform Wi-Fi communications on an 802.11 network. The Bluetooth Logic336is for enabling the UE device106to perform Bluetooth communications. The cellular modem334may be a lower power cellular modem capable of performing cellular communication according to one or more cellular communication technologies (e.g., LTE, 5G NR, GSM, etc.).

As described herein, UE106may include hardware and software components for implementing embodiments of this disclosure. For example, one or more components of the wireless communication circuitry330(e.g., cellular modem334) of the UE device106may be configured to implement part or all of the methods described herein, e.g., by a processor executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium), a processor configured as an FPGA (Field Programmable Gate Array), and/or using dedicated hardware components, which may include an ASIC (Application Specific Integrated Circuit).

FIG. 4—Block Diagram of a Base Station (BS)

The base station102may include at least one antenna434, and possibly multiple antennas. The antenna(s)434may be configured to operate as a wireless transceiver and may be further configured to communicate with UE devices106via radio430(or multiple radios430). The antenna(s)434communicates with the radio430via communication chain432. Communication chain432may be a receive chain, a transmit chain or both. The radio430may be configured to communicate via various wireless communication standards, including, but not limited to, LTE, LTE-A, NR, GSM, UMTS, CDMA2000, Wi-Fi, etc.

The base station102may be configured to communicate wirelessly using multiple wireless communication standards. In some instances, the base station102may include multiple radios, which may enable the base station102to communicate according to multiple wireless communication technologies. For example, as one possibility, the base station102may include an LTE radio for performing communication according to LTE as well as a Wi-Fi radio for performing communication according to Wi-Fi. In such a case, the base station102may be capable of operating as both an LTE base station and a Wi-Fi access point. As another possibility, the base station102may include a multi-mode radio which is capable of performing communications according to any of multiple wireless communication technologies (e.g., LTE and Wi-Fi, LTE and UMTS, LTE and CDMA2000, LTE and 5G NR, UMTS and GSM, etc.). The BS102may provide one or more cells of one or more communication technologies and/or one or more public land mobile networks (PLMNs). The BS102may provide multiple cells which may be organized, grouped, or configured as one or more cell sets, according to some embodiments. One or more cell sets that are provided by BS102may also include cells provided by one or more additional base stations, according to some embodiments.

The BS102may be an eNodeB (eNB) or gNodeB (gNB), according to various embodiments.

Carrier Aggregation

5G New Radio (NR) and LTE, as well as other wireless networks, may include carrier aggregation (CA), enabling a user equipment device (UE) such as the UE106to communicate with multiple cells on separate bandwidths to increase overall throughput. CA techniques may allow for increased throughput or performance by efficiently using the spectrum/frequency resources available to a network. CA techniques may be used entirely in licensed spectrum, entirely in unlicensed spectrum, or in a mixture of licensed and unlicensed spectrum. For example, licensed assisted access (LAA) cells may be increasingly common. Note that an LAA cell may aggregate licensed and unlicensed spectrum of a radio access network, e.g., at a media access control level, among various possibilities. For example, an LAA cell (e.g., a special type of secondary cell or SCell) may operate in an unlicensed band and may be assisted by an LTE cell (e.g., a primary cell or PCell) that may operate in a licensed band.

In general, a UE may establish a connection with the network through the PCell, and may subsequently establish a secondary connection with one or more SCells to increase throughput. The PCell and the one or more SCells may be collocated, or they may be instantiated as separate base stations, according to various embodiments. The PCell and the one or more SCells may operate according to the same RAT (e.g., 5G NR) or different RATs, according to various embodiments.

Different UEs may have different capabilities with regard to CA. For example, some UEs may be able to perform CA with certain combinations of frequency ranges, but not with other combinations of frequency ranges. Similarly, different cells, different regions, or different networks may use various combinations of frequency ranges for CA. For example, a given PLMN may have licenses to use different frequency ranges in one region than another.

Specific Absorption Rate (SAR) Backoff

In some embodiment, a UE may be configured to implement a specific absorption rate (SAR) backoff feature, wherein the UE may be configured to detect a grip orientation of the UE and/or detect the proximity of the UE to a user's hand and/or ear. When the UE is sufficiently close to a particular body part of the user (e.g., when the UE is placed against a user's ear), the SAR backoff feature may limit a transmission (Tx) power of the UE for one or more frequency ranges, to prevent excessive radiation exposure to the user and/or to comply with applicable laws and regulations. For example, a UE that supports millimeter wave (mmWave) or higher frequency transmissions may be configured to limit its Tx power for these frequencies in certain user grip conditions, to satisfy SAR limits and/or regulations. SAR limits may be tiered, in some embodiments, where a first Tx power limit is set while the device is being held in hand, and a second (e.g., more strict) Tx power limit is set while the device is held against a user's head. Further, in some embodiments, the Tx limits imposed by SAR regulations may vary depending on frequency. For example, higher frequency transmissions (e.g., above 30 GHz) such as those anticipated to be utilized by 5G NR may be subject to stricter transmission power limits during certain grip orientations than lower frequencies, as the higher frequencies may potentially pose a greater health risk to the user.

In these embodiments, even though the radio frequency (RF) link conditions may be symmetric with respect to uplink (UL) and downlink (DL), while the UE is limited by SAR backoff the link may become asymmetric (e.g., because Tx power is limited). The limits imposed on Tx power may adversely affect reception by the network of acknowledgment/negative acknowledgment (ACK/NACK) messaging sent by the UE. Accordingly, higher retransmission rates for DL communications from the network may occur if ACK/NACK messages do not reach the network, as the network may unnecessarily retransmit packets that were successfully received by the UE (e.g., if the network failed to receive an ACK message). This may be particularly undesirable when a UE is receiving a high volume of DL data while the UE is Tx limited (e.g., through a SAR backoff protocol or for another reason), potentially resulting in network congestion and excess expenditure of radio resources.

In a carrier aggregation (CA) scenario, a UE may be in communication with a primary cell (PCell) and one or more secondary cells (SCells). While the connection with the PCell may be of sufficiently high quality for successful ACK/NACK reception during normal transmission scenarios, this may not necessarily be the case when the UE is utilizing limited transmission power. To address these and other concerns, embodiments herein describe methods and devices to detect a preferred cell for ACK/NACK transmissions, and to transmit ACK/NACK messages on the preferred cell.

FIG. 5is a flowchart diagram illustrating a method for dynamically transmitting ACK/NACK messages on a preferred cell, according to some embodiments. Embodiments of the method ofFIG. 5may increase the likelihood that ACK/NACK messages are successfully received by the network, according to some embodiments. In various embodiments, some of the elements of the method shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired.

Aspects of the method ofFIG. 5may be implemented by a wireless device, such as the UE(s)106, in communication with one or more base stations (e.g., BS102) as illustrated in and described with respect to the Figures, or more generally in conjunction with any of the computer systems or devices shown in the Figures, among other circuitry, systems, devices, elements, or components shown in the Figures, among other devices, as desired. For example, one or more processors (or processing elements) of the UE (e.g., processor(s)302, baseband processor(s), processor(s) associated with communication circuitry (e.g.,330), etc., among various possibilities) may cause the UE to perform some or all of the illustrated method elements. Similarly, processor(s)404, baseband processor(s), processor(s) associated with communication circuitry (e.g.,430,432), etc., among various possibilities) may cause the BS to perform some or all of the illustrated method elements. The techniques ofFIG. 5may be applied to various RRC messages that employ ACK/NACK messaging, among various possibilities. As shown, the method may operate as follows.

At502, the UE may connect to a network that employs carrier aggregation in the downlink (DL). The network carrier may configure and activate up to N cells, each of which transmits information to the UE through a separate carrier aggregation frequency band on the DL

At504, the UE may receive DL communications on all activated CA bands. Each activated CA band may be associated with an activated cell, which may be a PCell or an SCell, for example. The UE may establish a connection with one PCell and one or more SCells, for example.

At506, the UE may measure one or more properties of each of the activated bands, and may determine a preferred uplink path from the plurality of activated bands. This step is described in greater detail inFIG. 6, which illustrates a variety of criteria which may be used to determine a preferred CA band, according to various embodiments. In some embodiments, measuring the one or more properties of the activated bands to determine the preferred uplink path may be performed in response to a determination that transmission power of the UE has been throttled as a result of implementation of a SAR backoff procedure, or another factor. While the PCell may have a sufficiently strong signal strength to successfully receive ACK/NACK messaging from the UE during a normal transmission scenario, this may not necessarily be the case when the transmission power of the UE is throttled as a result of SAR backoff or another reason. Accordingly, transmission of ACK/NACK messaging through a preferred link, as described in greater detail below, may increase the likelihood of their successful reception by the network, in some embodiments.

As illustrated,FIG. 6shows a plurality of RF measurements and other factors that may be used to identify a preferred cell for transmitting ACK/NACK messaging at602, according to various embodiments. The measurements and factors listed inFIG. 6may be used in various combinations, whereby different subsets of the listed quantities and measurements may be considered, as desired. The measurements and factors used to determine the preferred cell in any particular embodiment may be aggregated to determine an overall preferability score, and the preferred cell may be determined based on the preferability score. The aggregation may apply different weights to different factors considered, in some embodiments.

As illustrated, the UE may measure one or more quality metrics for all activated CA bands at604. For example, the UE may measure one or both of the reference signal received power (RSRP) at606and the signal-to-noise ratio (SNR) at608of the PCell and the one or more activated SCells. The measurements may be used to determine an uplink link budget for each of the activated cells, which may be different between the PCell and the one or more SCells, for example. The UE may consider a cell with a higher RSRP and/or SNR to be more preferable, for example.

The UE may further measure and/or determine one or more parameters associated with a SAR backoff feature currently activated on the UE device. For example, the UE may measure and/or determine one or more of an effective total radiated power (TRP) at610and/or equivalent isotropically radiated power (EIRP) allowed by the SAR backoff feature, a grip impact on the SAR implementation at612, an amount of thermal backoff at614, an overall antenna efficiency at618, and/or other SAR backoff parameters, according to various embodiments. The SAR backoff parameters may be utilized to determine a likelihood of successfully transmitting ACK/NACK messaging through each of the PCell and the one or more SCells given the SAR backoff restrictions, to assist in determining a preferred cell for ACK/NACK messaging.

Additionally or alternatively, the UE may measure one or more of an available bandwidth at620, a total bandwidth per CA band at622, and/or current network loading on each of the activated cells at624, in some embodiments. The UE may consider one or more of these quantities while determining a preferred cell. For example, the UE may prefer a cell with a higher available bandwidth, a higher total bandwidth, and/or lower current network loading over a cell with lower available bandwidth, lower total bandwidth, and/or higher current network loading.

Returning toFIG. 5, at508, the UE may determine whether the PCell is the preferred link for transmitting UL ACK/NACK messaging. If the PCell is the preferred UL link, at518the UE may transmit ACK/NACK messaging through the PCell. However, if the PCell is not the preferred link, the UE may determine that a particular SCell “x” is the preferred link at510.

The NW may typically configure the UE to send ACK/NACK on the Pcell. To override this default configuration, at512, and in response to determining that SCell “x” is the preferred cell, the UE may notify the NW using uplink control information (UCI) that the UE intends to transmit ACK/NACK messaging over SCell “x” rather than over the PCell. The network may thereby expect to receive ACK/NACK messaging over the indicated SCell. At514, the UE may then proceed to transmit ACK/NACK messaging over SCell “x”.

At516, the UE may monitor the activated links by periodically re-measuring the one or more properties of each of the activated bands, to dynamically redetermine which of the PCell or the one or more SCells is the current preferred UL link. In various embodiments, the UE may re-measure the one or more properties at a regular period (e.g., after a predetermined number of milliseconds), or it may re-measure the one or more properties based on an event trigger such as a determination that an ACK/NACK was unsuccessfully received, or another type of event trigger.

FIG. 7—Flowchart for Transmitting ACK/NACK Over Preferred Cell

FIG. 7is a flow chart diagram illustrating a method for transmitting acknowledgment messages over a preferred cell, according to some embodiments. Embodiments of the method ofFIG. 7may increase the likelihood of successfully transmitting ACK/NACK messages to a network, especially during a limited transmission power scenario, by transmitting them over a preferred cell, according to some embodiments. In various embodiments, some of the elements of the method shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired.

Aspects of the method ofFIG. 7may be implemented by a wireless device, such as the UE(s)106, in communication with one or more base stations (e.g., BS102) as illustrated in and described with respect to the Figures, or more generally in conjunction with any of the computer systems or devices shown in the Figures, among other circuitry, systems, devices, elements, or components shown in the Figures, among other devices, as desired. For example, one or more processors (or processing elements) of the UE (e.g., processor(s)302, baseband processor(s), processor(s) associated with communication circuitry (e.g.,330), etc., among various possibilities) may cause the UE to perform some or all of the illustrated method elements. Similarly, processor(s)404, baseband processor(s), processor(s) associated with communication circuitry (e.g.,430,432), etc., among various possibilities) may cause the BS to perform some or all of the illustrated method elements. Note that while at least some elements of the method ofFIG. 7are described in a manner relating to the use of communication techniques and/or features associated with 3GPP specification documents, such description is not intended to be limiting to the disclosure, and aspects of the method ofFIG. 7may be used in any suitable wireless communication system, as desired. The techniques ofFIG. 7may be applied to ACK/NACK messaging associated with various types of RRC messages, among various possibilities. As shown, the method may operate as follows.

At702, a UE establishes a connection with a primary cell and one or more secondary cells. The primary cell and the one or more secondary cells may be configured to conduct coordinated DL communications with the UE according to a carrier aggregation (CA) protocol.

At704, a preferred cell is determined from among the primary cell and the one or more secondary cells based at least in part on one or more quality metrics. In some embodiments, the preferred cell may either be the primary cell or one of the one or more secondary cells. In some embodiments, determining the preferred cell and transmitting the notification are performed at least in part in response to determining that the UE is in a limited transmission power scenario. In some embodiments, the limited transmission power scenario may be a result of implementation of a specific absorption rate (SAR) backoff procedure that has been enabled on the UE. For example, the UE may be configured to limit its transmission power in one or more frequency bands when the UE detects that it is in a certain grip orientation (e.g., held in hand, held against head, etc.). In these embodiments, responsive to detecting the limitation(s) to transmission power, the UE may determine a preferred cell for transmission of acknowledgment messages in one of the frequency bands in which the UE is limiting its transmission power.

In some embodiments, the one or more quality metrics may include one or more of an effective total radiated power, grip impact, SAR backoff parameters, thermal backoff parameters, overall efficiency. In some embodiments, the one or more quality metrics may include a measured reference signal received power (RSRP) and/or a measured signal-to-noise ratio (SNR) of each of the primary cell and the on or more secondary cells. Alternatively or additionally, for each the primary cell and the one or more secondary cells, the one or more quality metrics may include an available bandwidth for the cell, a total bandwidth of the cell, and/or network loading on the cell. The UE may aggregate one or more of the measured and/or determined quality metrics to determine the preferred cell.

At706, a notification is transmitted to a network indicating that the UE intends to transmit an acknowledgement message to the preferred cell. For example, the UE may transmit a notification to the primary cell that a first one of the one or more secondary cells is the preferred cell, and that the UE intends to transmit acknowledgment messages to the first one of the one or more secondary cells.

At708, the acknowledgment message is transmitted to the preferred cell. Advantageously, the likelihood of successful reception by the network of the acknowledgment message may be improved by transmitting the message to the preferred cell, especially in a limited transmission power scenario such as during implementation of a SAR backoff feature.

In some embodiments, the UE may periodically monitor the one or more quality metrics to obtain one or more updated quality metrics. In these embodiments, the UE may dynamically redetermine the preferred cell from among the primary cell and the one or more secondary cells based at least in part on the one or more updated quality metrics. In other words, the UE may dynamically update its preferred cell determination to adapt to changing radio conditions, SAR backoff restrictions, and/or network loading on the primary cell and the one or more secondary cells.

In some embodiments, a network device (e.g., a BS102) may be configured to include a processor (or a set of processors) and a memory medium, where the memory medium stores program instructions, where the processor is configured to read and execute the program instructions from the memory medium, where the program instructions are executable to implement any of the various method embodiments described herein (or, any combination of the method embodiments described herein, or, any subset of any of the method embodiments described herein, or, any combination of such subsets). The network device may be realized in any of various forms.