Sleep estimator for cellular telephones

A method for waking up user equipment in a cellular network includes waking up a receiver module at a predetermined wakeup time to receive a transmitted paging signal, when awake, determining prevailing conditions for receiving paging signals, and skipping at least a next possible wakeup time if at least one of the prevailing conditions exceeds an associated threshold level. A user equipment for use on a mobile communications network includes a reception quality determiner to determine at least one of a reception quality of a received signal and a radio frequency (RF) level of the signal, a paging indication processor to process received paging signals, a system message handler to determine a level of activity for a cellular network, and a conditional wakeup mechanism that is configured to set a next wakeup for the user equipment time responsively to an input from at least one of the reception quality determiner and the system message handler.

FIELD

The present invention relates to wireless communication generally and to low power operation of wireless user equipment in particular.

BACKGROUND

Cellular systems typically employ paging and/or control channels over which a base station may periodically communicate various information to the user equipment (UE) or mobile units, even when the user equipment is in an idle mode (i.e. not currently engaged in a call). For example, a base station may transmit paging indication signals at regular intervals and the user equipment must be configured to receive and analyze these signals in order to receive an incoming call when required.

In order to conserve energy and lengthen battery life, user equipment may be set to enter an idle, or standby, mode when not actively engaged in a call. During standby operation, the user equipment may generally be off, but must partially “wakeup” in time to receive and then analyze paging indication signals. During the wakeup period, various other signals may also be received and analyzed. The analysis may involve, for instance, decoding the paging indication signal from a serving cell and performing measurements on signals transmitted by the serving cell or by neighbor cells, as required, for example, in order for the network to make handoff, or UE to make cell reselection, decisions. The UE will be in deep sleep for the rest of the time.

The power consumption of the user equipment (UE) while in standby mode may be optimized by efficiently monitoring the paging channel. The periodicity and/or duration of wakeup to receive paging information, as well as optimization of power consumption during the wakeup periods, can significantly impact UE performance.

Network configuration, for instance, may impact UE power consumption and performance. Networks may adjust the intervals at which paging signals may be transmitted, which may necessitate a matching adjustment of UE wakeup intervals. This effectively trades off system performance against UE power consumption. In GSM networks for example, paging intervals are measured in terms of MultiFRraMes (MFRM). A MFRM lasts approximately 235 msec. Paging intervals for telephony may typically range between MFRM2 (470 msec) and MFRM9 (2.1 sec). Longer intervals may result in improved UE standby power performance. However the reduced power consumption may result in reduced UE performance (e.g. longer time to identify an incoming call); notably, when paging intervals are missed, as may occur in poor reception conditions or when the network is heavily loaded, further performance degradation, e.g. missed calls, may be experienced. Consequently, in many networks shorter intervals between paging indication signals (thus higher standby power consumption), such as MFRM2/4, and repetitive transmission of paging indication signals have been given preference in an effort to improve system service.

SUMMARY

There is provided, in accordance with an embodiment, a method for waking up user equipment in a cellular network, including waking up a receiver module at a predetermined wakeup time to receive a transmitted paging signal, when awake, determining prevailing conditions for receiving paging signals, and skipping at least a next possible wakeup time if at least one of the prevailing conditions exceeds an associated threshold level.

Further, in accordance with an embodiment, determining the prevailing conditions includes at least one of determining reception quality of received signals, determining radio frequency (RF) level, and determining network activity.

Moreover, in accordance with an embodiment, the skipping includes skipping more than one wakeup time.

Additionally, in accordance with an embodiment, determining network activity comprises determining a level of paging activity.

Further, in accordance with an embodiment, the method also includes performing while awake at least some neighbor cell measurements that were to be performed during a skipped wakeup time period so as to maintain a target number of neighbor cell measurements.

There is also provided, in accordance with an embodiment, a user equipment for use on a mobile communications network, including a reception quality determiner to determine at least one of a reception quality of a received signal and a radio frequency (RF) level of the signal, a paging indication processor to process received paging signals, a system message handler to determine a level of activity for a cellular network, and a conditional wakeup mechanism configured to set a next wakeup for the user equipment time responsively to an input from at least one of the reception quality determiner and the system message handler.

Further, in accordance with an embodiment, the conditional wakeup mechanism is configured to cause the UE to periodically skip waking up for at least one or more possible wakeup time.

Still further, in accordance with an embodiment, the system message handler comprises a paging activity determiner to determine a level of paging activity.

Additionally, in accordance with an embodiment, the paging indication processor also includes a neighbor cell measurer to make neighbor cell measurements and to maintain an average number of the neighbor cell measurements when skipping possible wakeup times.

It is noted that where considered appropriate, reference numerals are repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION

Reference is now made toFIG. 1, which illustrates a user equipment (UE) device6that is operative on a cellular telecommunications network. UE6may include a sleep estimator8, which is configured to increase the battery life of the user equipment6. For brevity and in order to avoid obfuscating teachings of the present disclosure, various other elements typically found in a UE are omitted from this description. Although specifically described in the context of Global System for Mobile communications (GSM), analogous principles may be adapted to other suitable wireless and cellular communication standards including, for example, without limitation, Wideband CDMA, LTE, LTE-A and the like.

In accordance with an embodiment, estimator8may determine a next wakeup time for UE6in an adaptive manner in response to a reception quality of received signals and/or network conditions.

A cellular network may be designed so that a given base station may accommodate user equipment that can be located anywhere within a designated paging area served by the given base station. As such, the base station may be designed to handle the more demanding conditions in which user equipment may operate, such as high mobility within a cell or between cells, and location of the UE at or near cell boundaries. In various extreme conditions, user equipment may be unable to suitably process a given paging indication signal. Therefore, if only a single paging indication signal were to be transmitted, a UE may fail to wake up from an idle mode to receive an incoming call. Consequently, networks may be configured to transmit redundant paging indication signals at successive paging indication slots, thereby increasing the probability that a UE can adequately receive at least one of the paging indication signals.

However, the prevailing connectivity conditions for a significant portion of the daily operation of most UEs are typically much better than in such extreme conditions. Sleep estimator8may be configured to take advantage of this fact to further save power for UE6by adapting the length of an interval for wakeup to check paging indication signals in response to reception quality and/or network conditions.

In accordance with an embodiment, sleep estimator8comprises a conditional wakeup mechanism10which may receive data from a reception quality determiner12, a paging indication processor14and a system message handler16. As will be discussed hereinbelow, reception quality determiner12may determine reception quality in the general area of UE6; paging indication processor14may process paging indication signals; and system message handler16may monitor paging activity on the network.

Conditional wakeup mechanism10may change the wakeup schedule of UE6in response to a reception condition and/or a network load. Thus, for example, when reception quality is high and steady (e.g. as measured by reception quality determiner12) and/or if there is relatively low paging activity on the network (e.g. as determined by system message handler16which decodes and handles system messages), such as may occur at certain times in the day (e.g. night time) or in rural areas, or for any other reason, then the interval between wakeup from idle mode may be increased. For instance, conditional wake up mechanism10may instruct UE6not to wake up at every time slot, also referred to as a paging slot, in which a paging indication signal may be transmitted. Instead, mechanism10may instruct UE6to remain in idle mode for one or more time slots during which a paging indication signal may be transmitted. It is noted that in such a case, some paging indication signals, including paging indication signals intended for UE6, may not be received because UE6may not wake up to receive them.

It is noted that determinations as to reception quality may be made in accordance with the applicable standard in accordance with which a UE is operating. For instance, in accordance with GSM standards, reception quality determiner12may determine reception quality based on an error rate in received paging signals (including both those that may be directed to the current UE and/or those that may be directed to other UEs) from a serving base station. Other signals and measures of reception quality, whether based on paging indication signals or on other messages or symbols, depending on the applicable standard, may also be suitable for determining reception quality.

Some networks may be configured to use relatively small intervals between slots for sending paging indication signals during busy hours and relatively larger intervals for sending paging intervals during off peak hours, or vice versa. In accordance with an embodiment, UE6may be instructed to further lengthen the standby period between wake up periods during which paging indication signals may be received and analyzed, based on reception quality and/or network conditions. In other words, conditional wakeup mechanism10may increase the sleep time of UE6whenever the reception conditions and/or network conditions enable it to do so, by skipping at least one paging slot for the next scheduled wakeup time. It is noted that when one or more wakeup time slots are skipped, it may be necessary to conduct additional measurements while UE6is awake in order to maintain an average rate for neighbor cell measurements. Such measurements may be required by relevant standards or network requirements, e.g. for determining whether to hand off a UE from one cell to another.

Reference is now briefly made toFIG. 2, which is a timing diagram of the active and sleep time of user equipment6, constructed and operative in accordance with an embodiment. InFIG. 2, dashes20indicate paging slots according to a default timing schedule during which the network transmits paging signals to one or more of the UEs that it serves. At a paging slot corresponding to a default timing schedule, a UE may be expected to wake up, check for incoming calls and perform other functions such as performing measurements on incoming signals. Dotted lines26represent a period of continuation of the timing diagram without change.

Arrows22indicate paging messages, referred to as paging indication signals, that are sent to a given UE6. At any periodic time slot indicated by dashes20, paging indication signals may be sent to a current given UE6, or to any other UE that is served by a base station. As seen inFIG. 2, four paging indication signals that are directed to a given UE6are shown for each of call events28and30. UE6may need to sufficiently wake up during each time slot20to receive one or more of signals22, and then fully wake up to receive an incoming call where required. It is noted that paging signals22sent to other UEs (not shown) may also be received at UE6; however, UE6should not wake up fully to receive a call in response to these other signals. Each of the paging indication signals22is transmitted during a paging slot20. It is noted that this is an example only and that the network may be configured to transmit a lesser or greater quantity of paging indication signals22during successive slots20.

Curve18ofFIG. 2corresponds to the activity of conditional wakeup mechanism10, where the lower level of curve18indicates a low power operation (“standby” or “idle” mode). The middle level indicates wakeup activity during which UE6wakes up to check whether it has received a paging indication signal22and performs other activities such as, for example, performing measurements to ascertain reception quality on received signals. A higher power level23indicates that UE6has entered into a call mode during which it engages in a received call.

In the example seen, user equipment6initially partially wakes up during each slot in which a paging indication signal may be transmitted. While partially awake, UE6may perform various measurements on received signals to ascertain a quality of reception of signals received from the serving base station, and may perform measurements on other received signals as required by relevant communication standards and network protocols. Additionally, while awake, conditional wakeup mechanism10may receive additional information about network load and other network system information that may be relied up to decide whether to continue waking up at every slot20, or rather to skip at least some slots20.

As seen inFIG. 2, a paging indication signal22signaling that UE6is to receive an incoming call may be transmitted in four successive time slots20. Consequently, if UE wakes up during each slot20, it may receive one of the transmitted paging indication signals22at any one of the four slots in which a signal22may have been sent.

Conditional wakeup mechanism10may periodically determine that reception conditions are sufficiently good and/or that network conditions are such that wake up for one or more paging slots20may be skipped. An example of the results of such a determination may be seen after the paging slot20indicated by arrow24. In other words, after such determination UE6may remain in idle mode during selected paging slots20. Consequently, in the period following arrow24, even though UE6may remain in standby mode during one or more paging slots20, because of favorable reception conditions and/or other suitable network conditions UE6is able to nevertheless receive at least one of the paging indication signals22despite having skipped wakeup at some of slots20. It is noted that the timing diagram shown inFIG. 2is only one example of many possible timing diagrams. In actual operation, more or less time may pass between changes of wakeup strategy as determined by conditional wakeup mechanism10.

It is noted that conditional wakeup mechanism10may be configured to skip one, two, or more paging slots20, depending on the quality of reception and the volume of network activity. Similarly, conditional wakeup mechanism10may be responsive to network level changes relating to the periodicity at which paging signals22are sent. For example, at times when network volume is reduced, or in locations where network volume is low, conditional wakeup mechanism10may be configured to avoid skipping slots20, or vice versa. In such cases, as long as reception is relatively good, it may be possible to remain in standby during some of paging slots20, and still have sufficient opportunity to receive one or more paging signals22. For these purposes, good reception may be defined, for example, as exceeding a threshold measure for a reception quality such as BER, BLER, RSSI, RSRP and the like. Conditional wakeup mechanism10may be thus configured to cause UE6to skip waking up for one out of every two paging slots20, to skip waking up for one out of every three paging slots20, to skip waking up for two out of every three paging slots20or for any other suitable combination of wakeup and skipping of wakeup at paging slots. The skipping of wakeup will result in an increase in time spent by UE6in standby mode, and will have the effect of reducing power demands as compared to when UE6is configured to wake up for every paging slot20. The conditions under which paging slots can be skipped, and the number of paging slots to be skipped, may, for example, all be configured at an operator or other level.

In best case conditions, during quiet network periods and/or when UE6is relatively stationary (i.e. when UE6does not move around within or between cells) with good reception conditions, power consumption may be significantly reduced, although there may be some increase in the paging delay due to the skipped paging slots. When reception conditions are relatively good, which may be the case, for example, for many hours during non-peak times and/or in rural areas, the standby power consumption may still be significantly reduced, while giving a small and bounded average and peak paging delay. However, in poor or marginal reception conditions and/or when the paging channel is highly active, little or no benefit may be realized from skipping slots20. Accordingly, there may be little or no change in power performance or in paging delay under such conditions.

Due to the skipped paging slots and the resultant skipping of at least some of the paging indication signals, paging indication processor14may change its measurement scenario for performing measurements on neighboring cells, one of its main functions. The network may typically set a requirement for an average rate of measurements on signals from neighboring cells, which may not be possible to achieve when skipping slots for receiving paging indication signals. Accordingly, when paging slots are to be skipped, conditional wakeup mechanism10may indicate to paging indication processor14that it needs to increase the number of measurements performed on signals transmitted by neighboring cells, thereby to maintain a required average rate of neighbor cell measurements. It is noted that, in some user equipment, the functionality for measuring neighboring cells may not be included in paging indication processor14, but rather may be provided either separately or as part of a bundle of functionality offered by a different utility.

Reference is now made toFIG. 3, which illustrates, in flow chart format, operation of paging indication processor14and conditional wakeup mechanism10. In step30, paging indication processor14may receive and decode paging indication signals that are transmitted on a network. Processor14may determine whether one of the paging indication signals is intended for the current UE. At block32, if yes, UE6may perform call establishment procedures.

It is noted that any and all signals received by UE6may be processed in step30. For example, in accordance with some cellular communication standards, paging indication signals and reference symbols may be transmitted on a control channel. Accordingly, determination of reception quality may not be based solely on the received paging indication signal. Paging indication signals may not be sent at every slot, but only when the network indicates that a given UE6should wake up and receive a call. Step30may also include the receipt by processor14(and/or any other suitable functionalities installed on UE6) of other signals that may be indicative of reception quality.

If, at block32, a determination is made that none of the received paging signals are intended to wakeup the present UE6, processor14may then typically determine (step34) neighbor cell information, such as, for example, BCCH and RSSI (RXLEV) measurements, as well as reselection criteria, access parameters, and any other information that may be gleaned from the paging indicating signal and other signals that UE6receives while awake.

Based on the result from step34, at step36, a determination may be made as to whether the cell needs to be changed. If the cell needs to be changed, then UE6may perform cell reselection procedures.

If cell reselection is not required, flow continues to step38, where conditional wakeup mechanism10may evaluate the prevailing conditions to determine the schedule for the next wakeup time. Reception quality, as received from reception quality determiner12, may be processed (step40) to check for high reception quality conditions. High reception quality may, for example, be defined as a block error rate (BLER) of less than 1%.

RF (radio frequency) level, as received from reception quality determiner12, may also be processed (step42) to check for a condition of good RF. For example, a threshold for good RF may be defined as −85 dBm.

Other measures of reception quality may be utilized. Each type of cellular network may have its own measures of reception quality, depending on the way signals are transmitted. The reception quality measures may be set accordingly.

Network activity, as received from system message handler16, may also be processed (step44) to check for a condition of low activity. For example, a threshold for low network activity may be defined as one paging message every three minutes. It is noted that network activity may include activity by other UEs6in the same area. Accordingly, the paging signals tracked in order to determine network activity may include signals that are directed to other UEs6as well.

Conditional wakeup mechanism10may then determine how many, if any, paging slots20to skip before the next wakeup time for UE6. In accordance with an embodiment, if any of the conditions are met in steps40,42and44, the next paging20may be skipped. If no favorable conditions have been detected (i.e. reception quality is not sufficiently high, RF level is not sufficiently good and/or network activity is not sufficiently low), then conditional wakeup mechanism10may schedule the next wakeup time for the next paging slot20. It is noted that the determination formula presented hereinabove is merely illustrative; any suitable algorithm based on the conditions as input to conditional wakeup mechanism10may be used to determine the number of paging slots20to be skipped, if any.

It is also noted that the definitions for favorable conditions may be implemented as configurable settings which may be changed, for example, according to the technology in the associated mobile network.

Embodiments of the present invention may include apparatus for performing the operations herein. This apparatus may be specially constructed for the desired purposes, or it may comprise general-purpose computer hardware selectively activated or reconfigured by a computer program stored in memories associated with the computer. Such a computer program may be stored in a computer readable storage medium. In addition, embodiments of the present invention are not described with reference to any particular programming language. It is noted that a variety of programming languages may be used to implement the teachings of the invention as described herein.

While certain features of embodiments of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will be apparent to those of ordinary skill in the art. It is, therefore, to be noted that the appended claims are intended to cover all such modifications and changes.