The exemplary and non-limiting embodiments of this invention relate generally to wireless communications systems, devices, methods and computer program products, specifically for selectively depowering a mobile station's receiver(s) that receives a common channel without degrading QoS to the user on those common channels.
Following are some acronyms used throughout the text below:
The third generation partnership project (3GPP) defines enhanced performance requirements for MBMS (multimedia broadcast and multicast), which under current specifications is sent using a WCDMA system, based on a diversity receiver reference architecture. Common channels in WCDMA include PCCPCH for the UE to receive system information, PICH for it to receive paging indications while it is in an idle mode, AICH for use in conjunction with RACH, and the SCCPCH which is used for a number of purposes including paging, FACH and providing MBMS services (MTCH, MCCH). Thus, the traffic channel MTCH carrying the substantive multimedia/multicast content is mapped to or otherwise associated with the control channel SCCPCH of the overall WCDMA architecture. Currently, specifications are under development for enhanced MBMS performance based on a reference receiver employing receive diversity.
Even without such specifications, manufacturers of UEs employ multiple approaches for conserving battery power so as to extend talk and standby time for their equipment. This is seen to be particularly important when receiving high-volume content such as multimedia/multicast or digital video over extended periods of time. This disclosure addresses those power saving concerns, and is particularly advantageous when used in conjunction with a WCDMA system over which MBMS or other common channel services are sent and received.
According to one exemplary embodiment of the invention is a method that includes monitoring a common channel with a first receiver and a second receiver, determining a target quality for the common control channel, measuring from the first and second receivers a quality parameter for the common control channel, and comparing the measured quality parameter to the target quality. Either the first or the second receiver is switched to a reduced performance mode of operation in response to the comparing.
According to another exemplary embodiment of the invention is an apparatus that includes a first receiver, a second receiver, and a processor. The first receiver is adapted to monitor a common channel. The second receiver is also adapted to monitor the common control channel. The processor is adapted to measure a quality parameter for the common control channel via the first and second receivers, and to compare the measured quality parameter to a target quality for the common control channel. Responsive to the comparing, either the first or the second receiver is adapted to switch to a reduced performance mode of operation.
According to yet another exemplary embodiment of the invention is a computer readable memory embodying a program of machine-readable instructions executable by a digital data processor to perform actions directed toward switching a receiver to a reduced performance mode of operation. In this embodiment, the actions include monitoring a common channel with a first receiver and a second receiver, determining a target quality for the common control channel, and measuring from the first and second receivers a quality parameter for the common control channel. The actions further include comparing the measured quality parameter to the target quality, and responsive to the comparing, switching either the first or the second receiver to a reduced performance mode of operation.
According to still another exemplary embodiment of the invention is an apparatus that includes first and second receiving means for receiving a common control channel, measuring means for determining from the first and second receiving means a quality parameter for the common control channel, and comparing means for comparing the measured quality parameter to a target quality for the common control channel. The first or the second receiving means is responsive to the comparing means to switch to a reduced performance mode of operation. In a particular embodiment, the first receiving means is a first wireless receiver, the second receiving means is a second wireless receiver, and the common control channel is one that is associated with a multimedia broadcast and multicast service traffic channel. In this particular embodiment the measuring means and the comparing means are embodied as a processor coupled to a memory.
Exemplary embodiments of the present invention are detailed below with reference to the following drawing figures.
Related to MBMS, there has been interest in conserving power in a UE which has multiple receivers, by switching off one or more of its receive (RX)-diversity receivers when the UE operates under non-challenging radio propagation channel conditions. As a general principle it may be acceptable to do so (depending upon the implementation) because when the UE is receiving common channels (which are not power-controlled for specific users but broadcast to all users in the cell) its receiver performance does not have any impact to the overall WCDMA system performance. The same is not true for the case of dedicated channels where dedicated radio resources are allocated to the UE specifically. Additionally, related to common channels other than MBMS, a UE manufacturer may still choose to use receiver diversity, even though no enhanced performance requirement has been defined, based on a receive diversity reference receiver. Power saving opportunities are also of value in this scenario.
Below is described a method, apparatus and computer program embodied on a storage medium to opportunistically operate one (or more) of a UE's receivers in a reduced performance mode when receiving a common channel. The term reduced performance mode indicates a power-saving mode of the receiver, and includes depowering the entire receiver, depowering/deactivating one or more of the RAKE correlator fingers, or depowering/deactivating any number of other receiver components so that the receiver in the reduced performance mode consumes less power as compared to the receiver operating in its normal fully-operational mode. More particularly, embodiments of this invention manage that reduced performance mode so as to ensure that the quality of service on the common channel suffers no noticeable degradation to the user.
Reference is now made to
At least one of the programs 16 stored in the memory 14 is assumed to include program instructions that, when executed by the associated processor 12, enable the UE to operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail.
In general, the various embodiments of the UE 10 can include, but are not limited to, mobile stations, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
The embodiments of this invention may be implemented by computer software executable by the processor 12 of the UE 10, or by hardware, or by a combination of software and hardware. In some embodiments, signaling specific to the invention is sent from the BS 24 or the RNC 28 to the UE 10. For those embodiments, the appropriate software program 16B, 16C to effect that signaling is embodied in the respective memory 14B, 14C and executable by the DP 12B, 12C.
The memory 14 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processor 12 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
Respecting power conservation at the UE 10, one difficulty in arriving at a particular solution in WCDMA is determining in what circumstances it would be acceptable to consider entering a reduced performance mode. Different applications typically have different quality of service requirements (e.g. BLER or radio link control RLC SDU error rate) and the desired quality of service for a particular application is not generally known by the UE 10 Further, direct quality of service measurements can only be made rather slowly (e.g., typically, BLER measurement might take seconds or tens of seconds, since it is averaged over multiple blocks and infrequent transmissions will extend the averaging period). In a fading and dynamically changing mobile environment, the UE 10 might need to enter or leave a reduced performance mode quite rapidly in order to give significant power saving benefits while still not impacting the perceived performance of the UE 10, so waiting a few seconds for an accurate BLER measurement would tend to eliminate much of the potential power savings that might otherwise occur.
To this end the inventors introduce the concept of a target quality for reception of a common channel. The target quality may be signaled to the UE 10 from the network 30 (e.g., UTRAN, E-UTRAN, GSM) or may be derived by other means. The target quality concept is similar to the quality of service currently used for some dedicated channels in other wireless systems, but to the inventor's knowledge is not used on common channels. Broadly, when the UE 10 is receiving the common channels with better than the quality target, it may enter the reduced performance mode. In the reduced performance mode, the UE 10 is allowed to make any kind performance reductions provided that the performance still remains better than the signaled quality target. If the measured quality of the received common channel becomes worse than the signaled quality target, then the UE 10 should use all available means to receive the channel of interest to meet or exceed the quality target. Because the MTCH is associated with the SCCPCH, the MBMS content that a user views on the display 46 and/or hears over the speaker 48 arrives over a common control physical channel. A quality target enables the UE 10 to operate its receiver for the SCCPCH in a manner that uses less power than if it were continuously in full operational mode, yet the user's experience through the interfaces 46, 48 are not degraded in a noticeable manner. In embodiments where the quality target is sent from the network 30, some additional signaling may be required from the network 30 (e.g., UTRAN, E-UTRAN, GSM) to the UE 10 to enable that additional signaling (e.g., one or several additional bits to indicate target BLER, RLC SDU error rate target, etc.).
Two approaches are described for comparing a measured quality parameter against a quality target. Recall that in some instances, the quality parameter is of one type (e.g., BLER, typically a longer term average measure) and the measured parameter is of another type (e.g., signal to interference ratio (SIR), typically a short term measure). The measured quality parameter is compared against threshold, which may be the quality target or (in the case where they are of different type) a value representative of the quality parameter. As an example of different quality parameter types, BLER is a measure on blocks and is measured after decoding the transport blocks; SIR is a measure on bits and is measured after despreading the received signal. The RLC SDU error rate is measured at a processing level even before despreading. The threshold is selected so as to ensure the quality target is met. For clarity of explanation, the below description simply describes the quality parameter and the measured parameter, but the described target quality may be replaced by some value representative of the signaled/stored target quality so as to ensure comparison of parameters of like types (e.g., SIR to SIR). Thresholds are adapted to ensure that the quality target is met and the UE is appropriately switched between full and reduced operating modes when the measured quality parameter is compared against the threshold. In the description below, the measured quality parameter is denoted generically as Q, regardless of whether that measured quality parameter is BLER, SIR, etc.
An overview of the process is shown in
First is described an embodiment where the measured quality parameter is directly compared against a threshold. The current receiver quality measurement, Q, could simply be compared to an absolute threshold. The threshold is adapted by the UE 10 in a similar way to how target SIR is adapted by outer loop power control when receiving a dedicated channel. It is shown below that the UE 10 may measure both Q for comparison against the threshold and the parameter used for the target threshold (where they differ) in order to adapt the threshold.
Hysteresis can be used, with separate thresholds for entering and leaving reduced performance mode to avoid too frequent switching between the modes.
A decision is made whether or not the UE 10 should be in a reduced performance mode. In the context of the description below, the measured quality Q may be understood to be the total received signal quality estimate measured using all receiver resources (for example, with both receiver branches in the case of receiver diversity), or may be an estimate of the quality in reduced mode, measured using the reduced receiver resources (for example, using only a single receiver branch in a case of receiver diversity). For example, using different thresholds for entering and leaving the reduced performance modes:
Then the thresholds are adapted based on the UE's other measurement of the parameter given by the target quality.
In another embodiment, the UE 10 measures a quality parameter on each UE receiver branch independently (provided both branches/receivers are powered on). These are denoted QRX1 and QRX2, which refer to the measured quality parameter at a particular receiver 34, 40 regardless of whether either or both of them is coupled to one or more antennas 20a, 20b. The UE then compares QRX1 and QRX2. If most of the useful receive signal is on only one antenna then this indicates that the performance benefit of using dual receivers is small at that moment in time. Thus:
In the above, K1 and K2 are constants which control how aggressively the UE attempts to save power. If only a small contribution of the overall Q comes from a particular receiver branch then it can be switched off relatively safely. The K factors for the two paths could be different to introduce a bias towards one path if it was known a-priori as likely to be of better reception quality. Constant K1 and K2 can also be adapted using the signaled BLER target in a similar way to the thresholds adapted as detailed above. If the actual UE performance is considerably better than the signaled quality target, then K can be reduced to make the switching algorithm more aggressive. If the actual performance is worse than the signaled quality target then K is increased to make the algorithm less aggressive.
Generalized process steps for adapting the thresholds are seen at
Having decided to switch one of the receivers off, the UE 10 also is described an algorithm to decide to switch it back on again. This is a more difficult problem because once a particular path has been switched off, the UE no longer has actual knowledge of the quality metric QRX1 or QRX2 for that path and therefore cannot determine if it has started to make a useful contribution to the overall quality (in fact, the combined quality is not known anymore). This is the cause of step 4A, which could be triggered in at least two possible ways, either as separate methods or in conjunction. Historic information can be used as a basis for switching the 2nd receiver back on, meaning that if the quality of the remaining path becomes significantly poorer than it was historically then both receivers are re-enabled. Alternatively, both receivers could just be switched back on periodically for a brief period to see if conditions have changed. The decision to re-enable a receiver from reduced performance to full operational mode for the purpose of taking measurements with both receivers could be scheduled or based on quality of the receiver that remains in the full operational mode (an actual quality measurement). In case of scheduled measurements the quality of the first/full mode branch could still be used as an additional “emergency” trigger for re-enabling the second/reduced mode receiver especially if the measurement interval is rather long (e.g. when the signaled quality target is hardly met or not met at all). Since some quality measurements can be made quite rapidly (e.g., from impulse response measurements), switching both receivers to full operating mode might only be needed for a brief period to verify that the other path/receiver isn't offering improved performance compared to the one which has been in use.
The above embodiments may represent distinct and separate approaches. Alternatively, they may be combined to yield a singular device, method, and embodied computer program product that takes some aspects of both embodiments described above, or that uses different of the various aspects under different circumstances of the measured parameter and received data rate.
Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a method, apparatus and computer program product(s) to operate a user equipment by monitoring a channel with a first and a second receiver of the same UE, where the channel is a common channel preferably a common control channel. A target quality is determined for that channel, which may be signaled to the UE or pre-stored in its memory. The UE then determines/measures a quality parameter for the channel, and compares the measured quality to the target quality. As seen above, the comparison may be between the measured quality parameter and a value representative of the quality parameter. Various embodiments to implement this comparison are shown, such as an absolute threshold, a comparative contribution of each receiver, etc. Responsive to the comparing, one of the receivers is then operated in a reduced performance mode, for which several examples are disclosed. The subject receiver may be switched from full operating mode to reduced performance, or from reduced performance mode to full, and in an implementation the comparison for switching in one direction uses a different threshold than the comparison for switching in the other direction. Embodiments further enable the dynamic adjusting of those thresholds based on measured conditions in the channel that more directly relate the threshold to the target quality. In some embodiments, when switching from reduced performance to full operating mode, the receiver in the reduced performance mode may be temporarily switched to full performance mode in order to take the measurement of quality parameter, and if the comparison is not favorable, that receiver may remain in the full operating mode. In an embodiment, the quality target and measured quality are for a common control channel with which a traffic channel is associated or otherwise mapped.
Further, the exemplary embodiments of this invention provide a method, apparatus and computer program product(s) to operate a network node, such as a BS or RNC, so as to signal/send to a UE a target quality that the UE is to maintain for a common channel. In an embodiment, this quality target relates to a common control channel with which a traffic channel is associated or otherwise mapped.
Another exemplary embodiment provides a method, apparatus and computer program product(s) to operate a UE to dynamically adjust a threshold, where the threshold is for switching a receiver between a full and a reduced operating mode. A common control channel is measured by both first and second receivers of the UE. That measurement is directly compared to a quality target. If the quality target is not met, then the threshold is adjusted. In an embodiment, the threshold and the quality target are of different types, the former being an instantaneous value and the latter being an average.
In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, or as signaling formats, or by using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
Programs, such as those provided by Synopsys, Inc. of Mountain View, Calif. and Cadence Design, of San Jose, Calif. automatically route conductors and locate components on a semiconductor chip using well-established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or “fab” for fabrication.
Various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications of the exemplary embodiments of this invention will still fall within the scope of the non-limiting embodiments of this invention.
Furthermore, some of the features of the various non-limiting embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not limitations thereof.
This application claims priority to Provisional U.S. Patent Application No. 60/837,906, filed on Aug. 14, 2006, the contents of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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60837906 | Aug 2006 | US |