Technologies for controlling discontinuous reception operation

Abstract

The disclosure relates to methods for improving the DRX operation of a UE by introducing an additional DRX wake-up cycle, which runs in parallel to the short and/or long DRX cycle. The DRX wake-up cycle defines time intervals after which the UE starts monitoring the PDCCH for a wake-up duration of time; the UE does not perform any other operation during the wake-up duration apart from monitoring the PDCCH. The time intervals of the wake-up cycle between the wake-up durations are preferably shorter than the one of the DRX long cycle, and may have the same or a shorter length than the ones of the DRX short cycle. The wake-up duration may be as long as the on-duration of the DRX short/long cycle, or may be preferably much shorter, such as only one or a few subframes.

Claims

1. An integrated circuit configured to control operation of a base station, the integrated circuit comprising: control circuitry, which, in operation, configures, for a mobile terminal in communication with the base station, a short discontinuous reception (DRX) cycle and a DRX short cycle timer according to a first configuration that defines the short DRX cycle, and a long DRX cycle according to a second configuration that defines the long DRX cycle; and transmission circuitry, which, in operation: controls transmission, to the mobile terminal, of a first DRX command medium access control (MAC) control element to cause the mobile terminal to start the DRX short cycle timer using the short DRX cycle and to start the long DRX cycle after the DRX short cycle timer expires, and controls transmission, to the mobile terminal, of a second DRX command MAC control element, which is different from the first DRX MAC control element, to cause the mobile terminal to stop the DRX short cycle timer and to start the long DRX cycle.

2. The integrated circuit according to claim 1, wherein the transmission circuitry, in operation, controls transmission of the second DRX command MAC control element when the base station expects an end of downlink data for the mobile terminal.

3. The integrated circuit according to claim 2, comprising: reception circuitry, which, in operation, receives an indication of the end of the downlink data from the mobile terminal.

4. The integrated circuit according to claim 1, wherein the transmission circuitry, in operation: controls transmission, to the mobile terminal, of a third configuration that defines an additional DRX cycle and is to cause the mobile terminal to start using the additional DRX cycle in parallel to using the short DRX cycle or the long DRX cycle, and controls transmission, to the mobile terminal, of a downlink control channel for messages destined to the mobile terminal for a defined duration of time.

5. The integrated circuit according to claim 1, wherein the control circuitry, in operation: configures the mobile terminal to repeat using the long DRX cycle until a scheduling message is transmitted from the base station.

6. The integrated circuit according to claim 1, wherein the transmission circuitry, in operation: controls transmission, to the mobile terminal, of a physical downlink control channel (PDCCH) by discontinuously using the short DRX cycle and the long DRX cycle.

7. An integrated circuit configured to control a process executed by a base station, the controlled process comprising: configuring, for a mobile terminal in communication with the base station, a short discontinuous reception (DRX) cycle and a DRX short cycle timer according to a first configuration that defines the short DRX cycle, and a long DRX cycle according to a second configuration that defines the long DRX cycle, transmitting, to the mobile terminal, a first DRX command medium access control (MAC) control element, to cause the mobile terminal to start the DRX short cycle timer using the short DRX cycle and to start the long DRX cycle after the DRX short cycle timer expires, and transmitting, to the mobile terminal, a second DRX command MAC control element, which is different from the first DRX MAC control element, to cause the mobile terminal to stop the DRX short cycle timer and to start the long DRX cycle.

8. The integrated circuit according to claim 7, wherein the controlled process comprises: transmitting the second DRX command MAC control element when the base station expects an end of downlink data for the mobile terminal.

9. The integrated circuit according to claim 8, wherein the controlled process comprises: receiving an indication of the end of the downlink data from the mobile terminal.

10. The integrated circuit according to claim 7, wherein the controlled process comprises: transmitting, to the mobile terminal, a third configuration, which defines an additional DRX cycle and is to cause the mobile terminal to start using the additional DRX cycle in parallel to using the short DRX cycle or the long DRX cycle, and transmitting, to the mobile terminal, a downlink control channel for messages destined to the mobile terminal for a defined duration of time.

11. The integrated circuit according to claim 7, wherein the controlled process comprises: configuring the mobile terminal to repeat using the long DRX cycle until a scheduling message is transmitted from the base station.

12. The integrated circuit according to claim 7, wherein the controlled process comprises: transmitting, to the mobile terminal, a physical downlink control channel (PDCCH) by discontinuously using the short DRX cycle and the long DRX cycle.

13. One or more non-transitory, computer-readable storage media (NTCRM) having instructions that, when executed by one or more processors, cause a base station to: transmit configuration information to a mobile terminal to configure a short discontinuous reception (DRX) cycle, a DRX short cycle timer, and a long DRX cycle; transmit, to the mobile terminal, a first DRX command medium access control (MAC) control element to cause the mobile terminal to start the DRX short cycle timer using the short DRX cycle and to start the long DRX cycle after the DRX short cycle timer expires; and transmit, to the mobile terminal, a second DRX command MAC control element, which is different from the first DRX MAC control element, to cause the mobile terminal to stop the DRX short cycle timer and to start the long DRX cycle.

14. The one or more NTCRM of claim 13, wherein the instructions, when executed, further cause the base station to transmit the second DRX command MAC control element when the base station expects an end of downlink data for the mobile terminal.

15. The one or more NTCRM of claim 14, wherein the instructions, when executed, further cause the base station to: receive an indication of the end of the downlink data from the mobile terminal.

16. The one or more NTCRM of claim 13, wherein the configuration information is first configuration information and the instructions, when executed, further cause the base station to: transmit, to the mobile terminal, second configuration information that defines an additional DRX cycle and is to cause the mobile terminal to start using the additional DRX cycle in parallel to using the short DRX cycle or the long DRX cycle; and transmit, to the mobile terminal, a downlink control channel for messages destined to the mobile terminal for a defined duration of time.

17. The one or more NTCRM of claim 13, wherein the configuration information is to configure the mobile terminal to repeat using the long DRX cycle until a scheduling message is transmitted from the base station.

18. The one or more NTCRM of claim 13, wherein the instructions, when executed, further cause the base station to: transmit a physical downlink control channel (PDCCH) by discontinuously using the short DRX cycle and the long DRX cycle.

19. One or more non-transitory, computer-readable storage media (NTCRM) having instructions that, when executed by one or more processors, cause a mobile terminal to: configure a short discontinuous reception (DRX) cycle and a DRX short cycle timer according to a first configuration; configure a long DRX cycle according to a second configuration, the long DRX cycle to be used after expiration of the DRX short cycle timer; start, based on a receipt of a first DRX command medium access control (MAC) control element from a base station, the DRX short cycle timer and the short DRX cycle; and in response to receiving, from the base station, a second DRX command MAC control element, which is different from the first DRX MAC control element, stop the DRX short cycle timer and start using the long DRX cycle.

20. The one or more NTCRM of claim 19, wherein the instructions, when executed, further cause the mobile terminal to: transmit, to the base station, an expected end of downlink data.

21. The one or more NTCRM of claim 19, wherein the instructions, when executed, further cause the mobile terminal to: receive a third configuration that defines an additional DRX cycle from the base station; start using the additional DRX cycle in parallel to using the short or long DRX cycle; and monitor a downlink control channel for messages destined to the mobile terminal for a defined duration of time.

22. The one or more NTCRM of claim 19, wherein the instructions, when executed, further cause the mobile terminal to: repeatedly use the long DRX cycle until a scheduling message is received from the base station.

23. The one or more NTCRM of claim 19, wherein the instructions, when executed, further cause the mobile terminal to: monitor a physical downlink control channel (PDCCH) by discontinuously using the short DRX cycle and the long DRX cycle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) In the following the disclosure is described in more detail in reference to the attached figures and drawings. Similar or corresponding details in the figures are marked with the same reference numerals.

(2) FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

(3) FIG. 2 shows an exemplary overview of the overall E-UTRAN architecture of 3GPP LTE,

(4) FIG. 3 shows exemplary subframe boundaries on a downlink component carrier as defined for 3GPP LTE (Release 8/9),

(5) FIG. 4 shows an exemplary downlink resource grid of a downlink slot as defined for 3GPP LTE (Release 8/9),

(6) FIGS. 5 & 6 show the 3GPP LTE-A (Release 10) Layer 2 structure with activated carrier aggregation for the downlink and uplink, respectively,

(7) FIG. 7 shows a state diagram for a mobile terminal and in particular the states RRC_CONNECTED and RRC_IDLE and the functions to be performed by the mobile terminal in these states,

(8) FIG. 8 illustrates the DRX operation of a mobile terminal, and in particular the DRX opportunity, on-duration, according to the short and long DRX cycle,

(9) FIGS. 9 & 10 illustrate the tradeoff between the battery saving opportunities given to the UE by the DRX operation and the response time to scheduling by the base station,

(10) FIG. 11 illustrates the DRX operation of a mobile terminal including the additional DRX wake-up cycle according to one embodiment of the disclosure,

(11) FIG. 12 illustrates the parallel operation of the DRX wake-up cycle and the DRX long cycle, and the corresponding response times in case downlink data arrives at the base station for the mobile terminal,

(12) FIG. 13 illustrates a DRX long cycle of 2560 subframes and a DRX wake-up cycle of 160 subframes and depicts the gain in response time that can be achieved by the parallel DRX wake-up cycle,

(13) FIG. 14 illustrates the DRX operation in the PCell and SCell according to another embodiment of the disclosure, where the DRX wake-up cycle is only operated on PCell but not on SCell,

(14) FIG. 15 illustrates the DRX operation in the PCell and SCell and in particular the wake-up time of the SCell when receiving a PDDCH on the PCell,

(15) FIG. 16 illustrates the DRX operation according to another embodiment of the disclosure, including a wake-up duration enable timer,

(16) FIG. 17 illustrates the DRX operation according to another embodiment of the disclosure, including a wake-up duration prohibition timer,

(17) FIG. 18 illustrates the DRX operation according to another embodiment of the disclosure, where paging occasions of the mobile terminal are used to get a paging with a particular wake-up RNTI for wake-up opportunities, and

(18) FIG. 19 illustrates the DRX operation according to another embodiment of the disclosure, where the SPS assignments are used to monitor the PDSCH for a transport block.

DETAILED DESCRIPTION

(19) The following paragraphs will describe various embodiments of the disclosure. For exemplary purposes only, most of the embodiments are outlined in relation to a radio access scheme according to 3GPP LTE (Release 8/9) and LTE-A (Release 10/11) mobile communication systems, partly discussed in the Technical Background section above. It should be noted that the disclosure may be advantageously used for example in a mobile communication system such as 3GPP LTE-A (Release 10/11) communication systems as described in the Technical Background section above, but the disclosure is not limited to its use in this particular exemplary communication networks.

(20) The term “active” and “becoming active” used in the claims and in the description refers to the operation of the mobile terminal in the discontinuous reception mode, where the mobile terminal wakes up and becomes active for an on-duration of time, so as to, e.g., perform and report measurements and monitor the PDCCH. As such, the expression is equivalent to the one used in the standardization of LTE of the UE “entering Active Time”.

(21) One aspect of the disclosure is to improve the DRX operation of the mobile terminal with regard to the response time and battery consumption opportunity provided for the mobile terminal. To said end, the disclosure introduces an additional DRX cycle (in the following called DRX wake-up cycle), which runs in parallel to the DRX short and/or long cycle.

(22) FIG. 11 illustrates the DRX wake-up cycle, in parallel to the DRX long cycle, according to one embodiment of the disclosure, and will be used exemplary to explain the concepts behind the disclosure. FIG. 11 is to be regarded as only exemplary and thus shall restrict the scope of protection of the disclosure to this particular embodiment.

(23) The disclosure allows maintaining the UE operation for the DRX short cycle and DRX long cycle unchanged compared to the standard. The DRX wake-up cycle introduced by this disclosure runs in parallel to the DRX short and/or long cycle.

(24) As apparent from FIG. 11, the DRX wake-up cycle runs in parallel with only the DRX long cycle, and not the DRX short cycle. Correspondingly, the operation of the mobile terminal according to the DRX wake-up cycle is thus started at basically the same time as the one for the DRX long cycle, namely upon expiry of the Short DRX cycle Timer. Alternatively, the DRX wake-up cycle may start with a predetermined time offset compared to the DRX long cycle (not shown).

(25) According to another embodiment not depicted in FIG. 11, the DRX wake-up cycle may start at the same time as the one for the DRX short cycle, i.e., upon expiry of the Inactivity Timer or when receiving a corresponding MAC CE from the base station. In addition, a time offset can be implemented compared to the DRX short cycle, which the mobile terminal waits before starting operating according the DRX wake-up cycle too. A corresponding offset parameter for starting the DRX wake-up cycle may be called wake-upDRX-CycleStartOffset and can assume any particular number of subframes, e.g., between 0 and the actual cycle length of the DRX wake-up cycle.

(26) According to a further embodiment not depicted in FIG. 11, the DRX wake-up cycle may start at the same time as the one for the DRX short cycle, i.e., upon expiry of the Inactivity Timer or when receiving a corresponding MAC CE from the base station and end again after the expiry of the Short DRX Cycle timer. In addition, as described above, a time offset can be implemented compared to the DRX short cycle, which the mobile terminal waits before starting operating according the DRX wake-up cycle too.

(27) According to another embodiment not depicted in FIG. 11, the DRX wake-up cycle may start at the same time as the one for the DRX short cycle only upon reception of a corresponding MAC CE from the base station, i.e., only when the mobile terminal entered DRX short cycle commanded from eNodeB. The usage of the DRX wake-up cycle will end again after the expiry of the Short DRX Cycle timer.

(28) With reference to FIG. 11, the DRX wake-up cycle and the DRX long cycle simultaneously start with the expiry of the Short DRX Cycle Timer. After a time interval defined for the DRX wake-up cycle, the mobile terminal starts monitoring the control regions for one subframe for PDCCH-s destined to itself, which means for PDCCHs masked with one of the RNTIs assigned to the mobile terminal. Correspondingly, the mobile terminal powers the necessary radio parts and performs various blind decoding attempts to check whether any message (any DCI format) is present for itself in this one subframe within the monitored control region. It should be noted that the mobile terminal only performs the monitoring of the control region of the subframe for PDCCHs without performing any other operation.

(29) If the mobile terminal does not find any message, it continues in the DRX mode and waits during the time interval of the DRX wake-up cycle until it again starts monitoring for the PDCCH for the wake-up duration of one subframe. This is repeatedly performed by the mobile terminal until the mobile terminal enters into Active Time, because it detects a PDCCH message destined to itself during the on-duration of the DRX short/long cycle or during the wake-up duration of the DRX wake-up cycle.

(30) It should be also noted that the behavior of the mobile terminal when it receives a PDCCH message during the wake-up duration of the DRX wake-up cycle is the same as its behavior when it receives a PDCCH message during the on-duration of the DRX short/long cycle. In both cases, the mobile terminal becomes active, i.e., enters Active Time in the next subframe (when the previous subframe was a wake-up duration) or stays in Active time (if the previous subframe was a DRX on-duration), e.g., according to the message received in the PDCCH.

(31) As apparent from FIG. 11, the time intervals between the wake-up opportunities provided in the DRX wake-up cycle are much shorter than the time intervals between the on-durations of the DRX long cycle. Though this is not strictly necessary, the DRX wake-up cycle should be shorter than the DRX long cycle to provide the advantage of improving the response time compared to only operating according to the DRX long cycle.

(32) In one embodiment of the disclosure, the DRX wake-up cycle interval (i.e., the interval between the wake-up durations) can be the same as the one configured for the DRX short cycle. Correspondingly, in this case the DRX wake-up cycle would reuse the parameter shortDRX-cycle defined for the DRX short cycle. Alternatively, a separate parameter may of course be defined for the DRX wake-up cycle, for example a wake-upDRX-cycle parameter which can assume any particular number of subframes, e.g., between 2 and 640 subframes in 16 steps, as with the shortDRX-cycle.

(33) Similarly, the wake-up duration of the DRX wake-up cycle might be as long as the on-duration of the DRX short/long cycle, thus being also configured by the onDurationTimer parameter. Though a long wake-up duration allows the base station more flexibility in transmitting the PDCCH message to the mobile terminal, the battery consumption is increased with every subframe for which the mobile terminal monitors the PDCCH, which has an impact on the battery due to the comparatively short DRX wake-up cycle. Thus, alternatively and more advantageously, the wake-up duration of the DRX wake-up cycle should be much shorter (e.g., one subframe) and could be configured by a separate parameter, e.g., called wake-upDurationTimer, which can assume a low number of subframes such as between 1 and 8 subframes in 8 steps.

(34) The measurement and reporting requirements (e.g., intra-frequency, inter-frequency, inter-RAT, CQI reporting) are still depending on the length of the intervals of the DRX long cycle as explained in detail in the Background Section; the measurement and reporting requirements are not depending or influenced by the DRX wake-up cycle of the disclosure. Correspondingly, while the mobile terminal has the opportunity of waking-up more often, it does not need to perform measurements or reporting so often. The mobile terminal performs the necessary measurements during the DRX opportunities given by the Long DRX cycle depending on UE implementation; e.g., intra-frequency measurements during the on-duration, for inter-frequency measurements in one of the DRX opportunities the mobile terminal powers up its RF part, retunes the RF part to the corresponding frequency and performs the inter-frequency measurements.

(35) The behavior of the mobile terminal during the wake-up duration is different from the one during the on-duration. While the mobile terminal during the on-duration is considered to be active, i.e., be in active time, the mobile terminal during the wake-up duration is not as such active; it merely powers up the necessary parts to monitor the downlink control region for PDCCHs addressed to its assigned RNTIs, this procedure including the blind decoding of the various DCI formats. During the wake-up duration, the mobile terminal does not have to perform any reporting of CSI or other measurements; it thus only monitors for the PDCCHs.

(36) In case the wake-up duration according to the DRX wake-up cycle falls on a subframe which is also part of the on-duration according to one of the other DRX short/long cycle (as in FIG. 11), the UE behavior follows the one of the DRX short/long cycle. In other words, when the wake-up duration and the on-duration fall together (or overlap for some subframes) the DRX wake-up duration is overwritten by the on-duration of the DRX short/long cycle. Basically, since the mobile terminal during every subframe of the on-duration monitors for PDCCHs (in the same way as it does during the wake-up duration), the functioning of the DRX wake-up cycle is not affected by this coincidence of on-duration and wake-up duration.

(37) FIG. 12 discloses one example of the different scheduling opportunities given by the DRX wake-up cycle and the DRX Long Cycle, for the case where downlink data for the mobile terminal arrives shortly after entering the DRX Long/wake-up Cycle. As can be appreciated from said FIG. 12, according to the present disclosure the base station can schedule the mobile terminal shortly after receiving the downlink data using the wake-up duration of the mobile terminal as an opportunity to transmit a PDCCH DCI format 1 for example. It is of course assumed that the base station is not hindered by any other operation (e.g., scheduling other mobile terminals) and can indeed exploit this wake-up opportunity given by the wake-up duration of one subframe.

(38) In contrast thereto, FIG. 12 alternatively (in dashed lines) depicts the case where the mobile terminal is scheduled using the on-duration of the DRX long cycle; the base station needs to wait for a longer time to be able to schedule the mobile terminal, and thus the response time for the mobile terminal is rather long.

(39) With reference to FIG. 13 a quantitative example is given to compare the functioning of the DRX wake-up cycle of one embodiment of the disclosure with the one of the DRX long cycle. In the example of FIG. 13 it is assumed that the DRX wake-up cycle starts at the same time and in parallel to the DRX long cycle. The DRX wake-up cycle is assumed to be 160 subframes, and the DRX long cycle is configured to be 2560 subframes; the on-duration is considered to be 4 ms (i.e., 4 subframes), and the wake-up duration is one subframe.

(40) As apparent from FIG. 13 data arrives shortly after the first wake-up duration of the mobile terminal, assumed one subframe after the end of the wake-up duration, which can be regarded as being the worst case for the DRX wake-up cycle. Correspondingly, the base station has to wait at least 159 subframes (ms) for the first wake-up opportunity given by the subsequent second wake-up duration. Regarding the DRX long cycle, the base station would have to wait 2399 subframes (2560−161 subframes) for the first opportunity to schedule the mobile terminal using the on-duration of the mobile terminal. Accordingly, this is reduction of the delay of 2240 ms, or put in other words, only 6.6% of the delay for the DRX Long cycle.

(41) In a second example downlink data arrives one subframe after the second-last wake-up duration, which is the example which yields a minimum gain of 160 ms as follows. According to the DRX wake-up cycle the downlink scheduling by the base station has to wait 159 ms; considering only DRX long cycle, the base station would have to wait 319 ms (160 ms+159 ms) to schedule the mobile terminal.

(42) As already explained above, the reduced response time comes at the cost of only marginal additional power consumption, and will be explained in the following according to the above example of FIG. 13. The worst case scenario with regard to the power consumption is that no data is received during the DRX cycle. The mobile terminal has to power up its RF part for 15 additional subframes to monitor the PDCCH. The DRX long cycle having 2560 ms and a 4 ms on duration, allows a power reduction of 99.84% (1−4/2560). In contrast to a mobile terminal also performing according to the DRX wake-up cycle, the power reduction is 99.25% (1−19/2560), thus experiencing a power saving loss of only ˜0.59%.

(43) The above considerations however only refer to the theoretical power consumption of the mobile terminal. In reality, the mobile terminals needs to power up the RF part first, and then power down the RF part after the wake-up duration (or on-duration for that matter). In other words, there is a pre- and post wake-up duration, which lengths are dependent on UE implementation. In one realistic implementation, the pre wake-up duration can be assumed to be 5 ms, and the post wake-up duration could be 3 ms. Therefore, the wake-up duration spans 9 ms in total (5 ms+1 ms+3 ms), and the on-duration spans 12 ms in total (5 ms+4 ms+3 ms). Considering these “realistic” power consumption durations, the power reduction provided by the DRX long cycle alone is 99.53%, and the one for a parallel DRX wake-up cycle is 94.26% (1−(15*9/2560+12/2560)). The DRX wake-up cycle thus yields a power saving loss of 5.26%.

(44) To further asses the advantage provided by the present disclosure, a comparison will be performed between the DRX wake-up cycle and a “short” DRX long cycle with regard to the measurement requirements that are to be fulfilled by the mobile terminal, and in particular only considering the intra and inter-frequency measurements. It is assumed that the DRX long cycle is 2560 ms long, and the DRX wake-up cycle runs in parallel. On the other hand it is assumed that the DRX long cycle is 160 subframes long, and the DRX wake-up cycle is not used. As explained before, the measurement and reporting requirements for the mobile terminal still follow the DRX long cycle, and are not influenced or changed by the DRX wake-up cycle which may run parallel to the DRX long cycle. No additional subframes for measurements are necessary regarding the DRX wake-up cycle.

(45) Depending on the implementation of the mobile terminal, the subframes of the on-duration can be used for intra-cell measurements; thus if the on-duration is more than 5 subframes, no additional subframes are needed for intra-frequency measurements. In the following, this is however not considered for exemplary purposes; the mobile terminal is assumed to perform the intra-frequency measurements on subframes outside the on-duration.

(46) When intra-frequency measurements and the corresponding neighbor cell identification are assumed to be performed in combination, the mobile terminal is required to spend power on four additional subframes every DRX cycle, assuming that the on-duration is at least one subframe and can be used for measurements.

(47) On the other hand, assuming that the previous DRX long cycle was 2560 ms long, if the DRX long cycle is reduced to 160 subframes, to allow the same response time as with a DRX wake-up cycle of 160 subframes (see above), the mobile terminal has to spend 16*4 subframes in 2.56 seconds for the intra-frequency measurements and cell identification. Thus, there is a difference of 60 subframes which are spent for intra-frequency measurements when reducing the DRX long cycle to 160 ms.

(48) With regard to inter-frequency measurements and corresponding cell identification, the mobile terminal is required to spend power on 6 additional subframes every 2.56 seconds, in case of a DRX long cycle of 2560 subframes.

(49) On the other hand, if the DRX long cycle is reduced to 160 subframes, the mobile terminal has to spend 16*6 subframes for inter-frequency measurements in 2.56 seconds. This implies 90 additional subframes.

(50) Therefore, only considering intra-frequency and inter-frequency measurement requirements, a short DRX long cycle of only 160 subframes would require 150 additional subframes to perform the necessary intra/inter-frequency measurements and cell identifications. This means a penalty of 5.86% (150/2560) for the power consumption of the mobile terminal, only due to complying with the increased measurement requirements. Put differently, the implementation of the DRX wake-up cycle according to one embodiment of the disclosure allows saving 150 subframes that would be necessary for performing the intra-frequency and inter-frequency measurements in case the DRX long cycle is configured to be 160 subframes. Therefore, instead of using 160 subframes, only 10 subframes are necessary when applying the DRX wake-up cycle of 160 subframes with a DRX long cycle of 2560 subframes; this means a power reduction for measurements of 93.75% (150 subframes/160 subframes).

(51) Further assuming an on-duration of 4 ms, and the pre and post wake-up duration of additional 8 ms per on-duration, in 2560 subframes the mobile terminal would have to use 1216 subframes for the on-duration and 150 subframes for the measurements. Thus, 342 subframes out of the 2560 subframes would be spent, and could not be used by the mobile terminal to save power. Thus, the DRX power saving is reduced to only 86.64% in this case.

(52) In truth, the power saving loss for complying with the requirements for measurements is higher, since the mobile terminal does not only have to perform the intra-frequency and inter-frequency measurements but other measurements as well, such as inter-RAT, CQI, SRS . . . .

(53) It should thus be noted that the requirements for cell measurements are greatly increased with a short DRX long cycle, which is avoided by the disclosure.

(54) Similar to the DRX configuration of the prior art, the DRX wake-up cycle can be configured for the mobile terminal also by the base station, e.g., using RRC messages using the configuration parameters already explained in above paragraphs. Thus, the eNodeB knows the DRX wake-up cycle of each mobile terminal and can thus use the scheduling opportunities provided by the corresponding wake-up duration subframe(s) to schedule the mobile terminal and/or transmit small data.

(55) One drawback of the embodiments of the disclosure is that the base station may not have current information on the channel quality available for the mobile terminal, thus making the scheduling by the base station less efficient since it cannot be based on the current channel state. Since the measurement and reporting requirements are linked to the DRX long cycle and not the DRX wake-up cycle, the mobile terminal correspondingly does neither measure nor report channel quality information to the base station as frequently as might be necessary. The base station has the opportunity to send downlink data to the mobile terminal, besides the corresponding PDCCH message for the downlink data, in the subframe of the wake-up duration. Since the base station does not know the channel state it can preferably use a conservative modulation and coding scheme to compensate for the missing channel quality information and to thus make sure that the downlink data is received correctly in the mobile terminal. Consequently, the base station can forward small amounts of downlink data with only a small delay to the mobile terminal, and this also in the absence of any channel quality information.

(56) Furthermore, the mobile terminal might be configured to measure the channel and to transmit channel quality information besides the uplink data to the base station, in case it gets a DCI format 0 message on the PDCCH. This is particularly useful since the base station otherwise lacks the information of the channel state as just explained above. The mobile terminal would thus perform the necessary measurements on the channel and would use the uplink grant assigned with the DCI format 0 message, to transmit the CQI to the base station. Of course, this depends also on whether the UE does have enough time for the channel measurements before the uplink grant is due.

(57) Variants

(58) As explained in the background section, several DCI formats are transmitted on the PDCCH, and the mobile terminal has to perform various blind decoding attempts to identify these PDCCH messages when monitoring for the PDCCHs. In the previous embodiments it is assumed that the mobile terminal monitors the PDCCH during the wake-up duration in the same way, as the mobile terminal does for the on-duration; namely, the UE monitors basically all DCI formats, one part in the common search space and the other part in the UE-specific search space as explained in detail in the background section.

(59) In the following embodiment of the disclosure, it is assumed that for the wake-up duration the mobile terminal shall monitor the PDCCH not for all kind of DCI formats, but only for a reduced set thereof. In other words, the mobile terminal monitors the PDCCH during the wake-up duration for only pre-determined messages destined to itself.

(60) In one exemplary embodiment of the disclosure, the DCI formats to be monitored is limited to only DCI formats 0, 1A, 3 and 3A. As apparent from the background section, these DCI formats have the same size (namely 42 bits), and thus the mobile terminal needs to perform the blind decoding for only one DCI size, which reduces the number of blind decoding attempts that the mobile terminal needs to perform. The DCI formats 0, 1A, 3 and 3A allow uplink and downlink scheduling as well as providing Transmit Power Control commands to the mobile terminal.

(61) Other restrictions with regard to the DCI formats are possible as well. For example, the mobile terminal might be configured to only monitor for one DCI format, e.g., for DCI format 0 thus limiting the mobile terminal to uplink assignments only, or for DCI format 1A, limiting the mobile terminal to downlink assignments only. This has the advantage that the mobile terminal needs to be readied only for one type of transmission which is known in advance.

(62) In addition or alternatively, the mobile terminal may ignore all DCI formats that do not contain a code point for indicating a CQI-only assignment. A code point for CQI-only tells the mobile terminal that it should perform channel measurements and report the CQI to the base station without informing the MAC layer of either reception or transmission of a transport block. The mobile terminal will use a control channel (PUCCH) for sending the CQI to the base station since no other uplink resource was provided to the mobile terminal Thus, the base station can specifically request a CQI from the mobile terminal, particularly in those cases where downlink data is to be transmitted to the mobile terminal and the base station wants to first learn the channel state before forwarding the data to the UE. However, the step of first requesting the UE to perform measurements and report the CQI introduces an additional delay of ˜6 ms-8 ms for forwarding the downlink data to the mobile terminal.

(63) However, this 6-8 ms delay corresponds roughly to the time necessary for an SCell to wake up. Thus, this delay may not be detrimental for those cases where the SCell is involved.

(64) In another embodiment of the disclosure the aggregation levels that the mobile terminal is to monitor for PDCCH is limited. As explained in the background section, the PDCCH format defines the number of CCEs that are used for transmitting the PDCCHs; either 1, 2, 4 or 8 CCEs may be used, e.g., depending on the channel conditions (8 CCEs is most robust, 1 CCE is least robust). However, when the PDCCH is transmitted using a low number of CCEs this forces the mobile terminal to perform a lot of blind decoding to scan the search space for the PDCCH message. Correspondingly, in order to limit the effort by the UE for blind decoding the PDCCH format to be monitored can be limited, e.g., to just PDCCH formats 2 and 3, meaning 4 and 8 CCEs are used only, or to just PDCCH format 3, meaning that messages with 8 CCEs are to be checked only.

(65) A further option to reduce the blind decoding attempts at the mobile terminal, is to limit the monitoring of the PDCCH to only the common search space or the mobile terminal specific search space.

(66) The above embodiments of limiting the monitoring of PDCCH, with regard to a reduced set of DCI formats, predetermined PDCCH formats and one of the search spaces, can be combined as well to further reduce the power spent by the UE on blind decoding.

(67) When introducing the DRX wake-up cycle, there will be several mobile terminals monitoring the PDCCH during a given subframe. In view of that the probability of false alarm in LTE is just found acceptable, reducing the blind decoding attempts according to one or a combination of the above embodiments helps reducing the false alarm rate further.

(68) For the following it is assumed that carrier aggregation is applied for the UE, such that it has a primary cell (PCell) and one or several secondary cells (SCell). The DRX operation according to the prior art is valid for the complete UE, thus for the PCell and any other (activated) SCell(s). Correspondingly, the UE would operate according to the DRX short/long cycle in each PCell, SCell separately and would monitor the PDCCH of the PCell and the one of each SCell according to the currently active DRX cycle.

(69) In one embodiment of the present disclosure, the operation of the DRX wake-up cycle can be the same in the PCell as in any of the SCells; this means that the mobile terminal not only performs the DRX wake-up cycle, according to one of the above described embodiments, in the PCell but also in each of the SCells.

(70) According to another embodiment of the disclosure, the UE may however be configured such that the DRX wake-up cycle is only performed in the PCell but not in any of the SCell(s); the DRX short/long cycle would still be applied for the SCell, however the DRX wake-up cycle operation not. In other words, during the DRX wake-up duration the mobile terminal only monitors the PDCCH on the PCell.

(71) This is illustrated using FIG. 14, which depicts the PCell and one SCell. As apparent therefrom, the operation of the DRX short/long cycle is the same on the PCell and the SCell and is not different from the operation according to the prior art. On the other hand, it can be appreciated from FIG. 14 that according to the present embodiment of the disclosure, the UE operates according to the DRX wake-up cycle only on the PCell, according to one of the previous embodiments of the disclosure; in this case for example, it starts the DRX wake-up cycle with the DRX long cycle and without any offset.

(72) This allows saving further power since the UE does not need to monitor for PDCCHs on the SCell. This makes especially sense in case the SCell is on another frequency (with interband aggregation) since the radio head (radio frequency part) of the mobile terminal can thus be turned off for the SCell.

(73) Cross-carrier scheduling allows the PDCCH of a component carrier to schedule resources on another component carrier. For this purpose a component carrier identification field is introduced in the respective DCI formats, called CIF. However, cross carrier scheduling might not be supported when the DRX wake-up cycle is only implemented in the PCell, since the SCell requires a wake-up period to be able to decode messages.

(74) This is depicted in FIG. 15, displaying the SCell wake-up time necessary after receiving a corresponding PDCCH message on the PCell. The SCell can be ready for scheduling after ˜8 ms (similar to the time necessary for activating a previously deactivated SCell).

(75) Therefore, in case a scheduling message for the SCell is received on the PDCCH on the PCell, the downlink data on the same subframe of the SCell cannot be decoded by the UE. In case an uplink scheduling message for the SCell is received on the PDCCH on the PCell, the UE might still not have enough time to wake-up the SCell in time to prepare and send the uplink data via the SCell.

(76) Correspondingly, in one embodiment of the disclosure the mobile terminal ignores cross scheduling messages, i.e., PDCCH messages with the carrier indicator pointing to one of the SCells.

(77) According to still another embodiment of the disclosure, the mobile terminal does not monitor the complete cell bandwidth of a cell when monitoring the PDCCH during the wake-up duration of the DRX wake-up cycle, but restricts the monitoring to only part of the cell bandwidth. Assuming that the cell has an frequency bandwidth of 5 MHz, it has been assumed before that the mobile terminal does also receive the cell over its complete bandwidth of 5 MHz, when monitoring for PDCCHs using all of the available 5 MHz. However, in order to further save battery power, the mobile terminal may only monitor part of the cell bandwidth, e.g., 1.4 MHz around the center frequency of the subband. Usually, the System Information is transmitted in the 1.4 MHz subband around the center frequency.

(78) The eNodeB of course needs to transmit messages to the mobile terminal in this reduced frequency subband of 1.4 MHz so that the mobile terminal is able to decode the messages when monitoring the PDCCH.

(79) Furthermore, when the frequency bandwidth is limited as explained above, the eNodeB might send an Active Bandwidth Indicator to the mobile terminal in this limited frequency bandwidth. When the mobile terminal detects the Active Bandwidth Indicator, it returns the reception bandwidth to the regular cell bandwidth of, e.g., 5 MHz. Therefore, in future occurrences of the wake-up durations of the DRX wake-up cycle, the UE monitors the complete frequency bandwidth. Alternatively, the Active Bandwidth Indicator can be understood by the UE as a trigger to enter Active Time.

(80) A further embodiment of the disclosure relates to limiting the occurrences of the DRX wake-up duration, as will be explained in more detail below. For example smartphones run several applications at the same time, while not actively using them. The applications receive keep-alive packets in order to maintain connectivity with the network. These keep-alive packets may arrive with a “combined” periodicity and a particular variance around this periodicity. The exact determination of the arrival of the keep-alive packets is difficult, and such a packet shall not be delayed until the next on duration of the DRX long cycle. Usually, the DRX long Cycle is configured such that the DRX on-durations are placed at the expected arrivals of the keep-alive packets.

(81) While the UE can assist the eNodeB to adapt the DRX long cycle with statistics information regarding the keep-alive packets arrival, it would be advantageous to also allow for the variance of the keep-alive packets. The active time of the UE and the DRX short cycle are not enough since they can take only care of packets arriving when a first packet was received in the on-duration during the DRX long cycle.

(82) According to another embodiment of the disclosure, the DRX wake-up cycle is thus configured such that the UE operates according to the DRX wake-up cycle for only a limited amount of time; the occurrences of the wake-up duration of the DRX wake-up cycle are thus reduced.

(83) According to one implementation of this embodiment, a wake-up duration enable timer is started when the DRX wake-up cycle starts. The UE monitors the PDCCH for the wake-up duration according to the time intervals given by the DRX wake-up cycle only when the wake-up duration enable timer is running. When the wake-up duration enable timer expires, the UE does not monitor the PDCCH even if it would according to the DRX wake-up cycle. The wake-up duration enable timer is reset every time the UE exists the Active Time of the on-duration of the DRX long cycle. This allows to only have occurrences of the DRX wake-up duration for a limited amount of time after the on-durations of the DRX long cycle.

(84) This will be explained with reference to FIG. 16, which illustrates the wake-up duration enable timer running after the end of the on-duration of the DRX long cycle. As in previous embodiments of the disclosure, the DRX wake-up cycle is assumed to start at the same time as the DRX long cycle. With start of the DRX wake-up cycle the wake-up duration enable timer is started too for the first time. The UE operates according to the DRX wake-up cycle as explained before, as long as the wake-up duration enable timer is still running. Correspondingly, every time the wake-up duration of the DRX wake-up cycle is imminent (i.e., the mobile terminal is due to monitor the PDCCH), the UE first checks the wake-up duration enable timer as to whether same is still running or whether it has already expired. The mobile terminal only monitors the PDCCH for the wake-up duration of time (as explained in previous embodiments) in case the wake-up duration enable timer is still running, i.e., has not yet expired. Otherwise, the UE will not monitor the PDCCH for the wake-up duration even if it would have to according to the DRX wake-up cycle. In FIG. 16 this yields that the mobile terminal only performs the PDCCH monitoring for two occurrences (instead of four) after the on-duration of the DRX long cycle.

(85) Thus, in case keep-alive packets unexpectedly arrive after the expected time (during the on-duration), the DRX wake-up cycle allows further scheduling opportunities for the base station to forward the keep-alive packets to the mobile terminal. At the same time, the mobile terminal does not have to monitor the PDCCH for all wake-up opportunities of the wake-up duration, which saves further power.

(86) Alternatively or in combination with the above, instead of having wake-up duration occurrences limited to only after the on-durations of the DRX long cycle, another embodiment allows to limit the wake-up duration occurrences to only before the on-durations of the DRX long cycle. Correspondingly, instead (or in addition) to the wake-up duration enable timer, a wake-up duration prohibition timer is implemented in the UE such that the UE only monitors the PDCCH for the wake-up duration of time according to the DRX wake-up cycle, when the wake-up duration prohibition timer is not running.

(87) This is illustrated in FIG. 17, where only two occurrences of the wake-up durations are depicted before the on-durations; the mobile terminal actually monitors the PDCCH only two times, since the first two wake-up opportunities are not used due to the running wake-up duration prohibition timer. In correspondence to the wake-up duration enable timer before, the wake-up duration prohibition timer is reset upon expiry of the on-duration of the DRX long cycle, upon exiting Active Time.

(88) By using one or both of the timers explained above, it is possible to flexibly configure the DRX wake-up cycle so as to adapt to the circumstances and needs of the mobile terminal and at the same time to avoid waste of battery power for wake-up durations where no downlink packet is to be received.

Further Embodiments

(89) In further embodiments, the mobile terminal monitors the PDCCH during the paging occasions while being in DRX of RRC_CONNECTED state, as will be explained below.

(90) In the current specification, the UE can monitor paging occasions also when being in the RRC_CONNECTED state, in order to be informed about System Information changes. The paging occasions occur more frequently than the on-durations in a DRX long cycle.

(91) According to a further embodiment, the UE being in DRX long cycle may monitor the PDCCH for messages during the paging occasions. For said purpose a wake-up RNTI (WU-RNTI) is introduced, such that when a PDCCH message is scrambled with the WU-RNTI, this would instruct the UE to wake-up. As with the P-RNTI, there is only WU-RNTI for the mobile terminal in the system.

(92) The paging and the wake-up mechanism is thus separated, which avoids unnecessary reception of the paging or wake-up message.

(93) In the wake-up message transmitted in the paging occasion, a wakeUpRecordList is added, similar to the normal paging message. The UE being in the DRX long cycle reads this wakeUpRecordList, and if it find its identity (C-RNTI), it wakes up from DRX.

(94) This is illustrated in FIG. 18, illustrating various paging occasions, one of which is used by the eNodeB to transmit a PDCCH message using the WU-RNTI, after downlink data arrives for the UE. Correspondingly, the UE monitors the PDCCH for this message, decodes same and due to the WU-RNTI learns that it shall wake-up. After a defined time of subframes after the paging occurrence, the UE returns to Active Time and could, e.g., be scheduled. This gap is necessary to provide time for the paging message reception; at least 4 subframes; may also allow for 8 subframes, similar to the SCell activation. In this time the mobile terminal can receive the wake-up message from the eNodeB, which CRC is scrambled now with the C-RNTI of the mobile terminal. At the beginning of the procedure it is not possible for the mobile terminal to receive a data transmission, only the wake-up message.

(95) The mobile terminal can thus be woken up by the eNodeB earlier than if only using the DRX long cycle. The exemplary difference is depicted in FIG. 18 using dashed lines. Furthermore, by reusing the paging mechanism the mobile terminal only needs to blindly decode one RNTI (besides the searching for the System Information change).

(96) Alternatively, instead of monitoring the paging occasion for the WU-RNTI the mobile terminal can monitor the paging occasion for a PDCCH message masked with another RNTI assigned directly to the mobile terminal. This allows for a faster procedure for waking up the mobile terminal as no further checks as described above have to be performed as the RNTI is already specific to the mobile terminal. This alternative comes with the drawback of increasing PDCCHs during the paging occasion.

(97) In another embodiment of the disclosure, the eNodeB configures the mobile terminal with persistent downlink assignments (SPS, semi-persistent scheduling), where the intervals is several times shorter than the DRX long cycle. SPS is activated during the Active Time. During DRX, the UE shall receive the PDSCH on configured assignments, and decodes the transport block of these configured assignments.

(98) In case the decoding of the transport block at the configured assignment fails, no HARQ operation is to be performed, and consequently, the mobile terminal does not wake up for re-transmissions (HARQ RTT not started). On the other hand, if the decoding of the transport block is successful, the mobile terminal returns to Active Time. It should be noted that a gap might become necessary to provide time for the transport block to be successfully decoded, before the UE can actually enter Active Time.

(99) The benefit of this embodiment is that it is implementation friendly since only changes to the SPS operation during DRX are required. However, there may be a delay between the configured assignment and the start of the Active Time. Also, additional signaling might be necessary, if SPS needs to be activated/deactivated before/after the DRX phase. Further, if SPS stay active during the Active Time, this would lead to a waste of downlink resources. FIG. 19 depicts the functioning of this embodiment of the disclosure.

(100) Mobile terminals, and in particular smartphones create traffic from multiple application being active in the mobile terminal at the same time. Such a mix of application creates data traffic which is hard to predict. This is especially true on the RAN level, where the downlink data arriving in the eNodeB cannot be correlated with a specific application. Furthermore, applications have different delay requirements.

(101) The network is in control of putting the mobile terminal in a state with more power saving (e.g., RRC_IDLE) or to keep the mobile terminal in active state. Correspondingly, the network has to weigh the mobile terminal's power consumption against the network's signaling load and basically has two choices. At the cost of higher signaling load for the state transition and an increased delay, the mobile terminal's power saving is enhanced. At the cost of higher power consumption in the mobile terminal, network refrains from state transmission and the corresponding signaling thus reducing the signaling overhead, and avoids the delay introduced by being in idle.

(102) Therefore, there is the problem that due to the unknown traffic pattern at network side, the mobile terminal is kept in active state longer than would be necessary; this is unnecessary from the mobile terminal's point of view, and wastes the mobile terminal's battery.

(103) As explained in the background section Fast Dormancy was introduced by Release 8 of LTE.

(104) One embodiment of the disclosure solves this problem differently. The UE indeed has knowledge of the applications it is running, and thus may conclude from the active application, the expected data reception/transmission behavior on RAN layer. Therefore, the UE may predict the downlink traffic pattern, it will be scheduled with from the eNodeB.

(105) The UE indicates the expected end of the downlink data to the eNodeB, in response to which the eNodeB may send a DRX MAC CE to the mobile terminal in order for the mobile terminal to enter the DRX mode. This avoids signaling overhead as the UE is kept in active state. A good power efficiency is achieved by the configuring the short and long DRX cycles appropriately. For example, the short DRX cycle may be configured to match the actual traffic, and the long DRX cycle may model the idle mode. The short and long DRX cycles may also be extended to cycle periods longer than currently allowed in the standardization (current 640 ms and 2560 ms, respectively), so as to achieve higher power efficiency.

(106) According to a further embodiment of the disclosure, the eNodeB may indicate to the UE to directly operate according to the Long DRX cycle without operating according the Short DRX cycle first, in order to further save batter power in the UE. This could be implemented for example by changing the MAC DRX CE to not only include the command for “go-to-sleep” but also the indication of “immediate transition from short to long DRX cycle”.

(107) The indication of the expected end of the downlink data to the eNodeB can be implemented according to one of the following.

(108) The indication could be done via RRC signaling, like in HSPA fast dormancy. Alternatively, a new MAC control element could be defined, using one of the currently reserved LCIDs; no payload is thus necessary for indicating the expected end of the downlink data. Or, the indication can be inserted into the Buffer Status Report (BSR).

(109) In the MAC header for the short and/or long BSR, one of the reserved bits is used to indicate that the UE expects the end of downlink data. In this case, the indication will only be sent if a BSR is triggered; thus, the triggering rule may need to be changed.

(110) A further alternative embodiment relates to sending the indication in the CQI report. When the UE is configured with periodic CQI reporting, the mobile terminal can set an “out of range” value, when reporting, e.g., the wideband CQI.

(111) Furthermore, in one embodiment the measurements on the activated SCells do not follow the DRX long cycle but the parameter measCycleSCell usually employed for deactivated SCells. The measCycleSCell is configurable to 160, 256, 320, 512, 640, 1024 and 1280 subframes. The UE is configured to measure once within 5 times the measCycleSCell. This allows further relaxed measurement requirements for the UE with further power saving.

(112) Hardware and Software Implementation of the Disclosure

(113) Another embodiment of the disclosure relates to the implementation of the above described various embodiments using hardware and software. In this connection the disclosure provides a user equipment (mobile terminal) and a eNodeB (base station). The user equipment is adapted to perform the methods described herein. Furthermore, the eNodeB comprises means that enable the eNodeB to evaluate the IPMI set quality of respective user equipments from the IPMI set quality information received from the user equipments and to consider the IPMI set quality of the different user equipments in the scheduling of the different user equipments by its scheduler.

(114) It is further recognized that the various embodiments of the disclosure may be implemented or performed using computing devices (processors). A computing device or processor may for example be general purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, etc. The various embodiments of the disclosure may also be performed or embodied by a combination of these devices.

(115) Further, the various embodiments of the disclosure may also be implemented by means of software modules, which are executed by a processor or directly in hardware. Also a combination of software modules and a hardware implementation may be possible. The software modules may be stored on any kind of computer readable storage media, for example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.

(116) It should be further noted that the individual features of the different embodiments of the disclosure may individually or in arbitrary combination be subject matter to another disclosure.

(117) It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present disclosure as shown in the specific embodiments without departing from the spirit or scope of the disclosure as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.