WO2023014372A1

WO2023014372A1 - Method for pdcch power saving in 5g discontinuous reception

Info

Publication number: WO2023014372A1
Application number: PCT/US2021/044966
Authority: WO
Inventors: Jian Gu
Original assignee: Zeku, Inc.
Priority date: 2021-08-06
Filing date: 2021-08-06
Publication date: 2023-02-09

Abstract

In various embodiments, a method for obtaining control information by user equipment (UE) is provided. In this method, the UE receives, from an access point, a first number of symbols at a first time in a transmission period. The first number of symbols carrying control information for UE accessing the access point. The UE then decodes the first number of symbols and determines whether the first number of symbols carries control information for the UE. When the UE determines that the first number of symbols carries control information instructing the UE to perform data transmission at a second time in the transmission period, the UE enters into a sleep mode until the second time in the transmission period. In those embodiments, the reception of the second number of symbols by the UE is in parallel with the decoding of the first number of symbols by the particular UE.

Description

METHOD FOR PDCCH POWER SAVING IN 5G DISCONTINUOUS RECEPTION

BACKGROUND

[0001] In wireless transmission, cells are typically deployed to cover a wide area. Wireless transmission within a cell is typically facilitated by one or more base stations within the cell. Typically, at a given point of time, user equipment (such as mobile phones) within the cell communicates with other devices through base station(s) in the cell. Distribution of user equipment (UE) locations is typically not uniform within the cell. For example, certain user equipment may be located very close to the base station(s), while other UE may be located a bit far away from the base station(s).

[0002] The base station(s) in the cell typically transmits a PDSCH (Physical Downlink Shared Channel, physical downlink shared channel) and a corresponding PDCCH (Physical Downlink Control Channel) to user equipment according to a schedule for resource allocation. The PDSCH is typically used to carry data information. The PDCCH is a downlink channel that allows the base station to control a UE during data communications in the PDSCH. The PDCCH typically carries control information about a particular PDSCH, such as resource allocation information, modulation and coding information. For example, if the UE has data in the PDSCH, it needs to know where the data is located. The PDCCH will tell the UE that the data it is looking for is located at this location on PDSCH. This means that if the UE is unable to decode PDCCH then the UE cannot read the PDSCH in that subframe and consistent decoding failures of PDCCH.

SUMMARY

[0003] Various embodiments provide a technique in which a terminal device kicks off control information reception after only a portion of control symbols have been received by the terminal device. In this technique, the terminal device does not wait until all control symbols have been received and then starts decoding the control symbols to obtain control information. This technique involves an early start of control information reception by the terminal device and can help the terminal device to save power. For example, in some embodiments, the terminal device can go to sleep mode once control information is obtained from the portion of the control symbols received.

[0004] In various embodiments, a method for obtaining control information by user equipment (UE) is provided. In this method, the UE receives, from an access point, a first number of symbols at a first time in a transmission period. The first number of symbols carrying control information for UE accessing the access point. The UE then decodes the first number of symbols and determines whether the first number of symbols carries control information for the UE. When the UE determines that the first number of symbols carries control information instructing the UE to perform data transmission at a second time in the transmission period, the UE enters into a sleep mode until the second time in the transmission period. In those embodiments, the reception of the second number of symbols by the UE is in parallel with the decoding of the first number of symbols by the particular UE.

[0005] In some embodiments, the decoding of the first number of symbols by the UE is started after the channel condition has been determined exceeding the threshold. In those embodiments, when it is determined that the channel condition has not exceeded the threshold, the UE continues receiving symbols from the access point according to an indication from the access point, where the indication indicates a total number of symbols to be received, and the total number is greater than the first number. The total number of symbols are received by the UE at a second time in the transmission period, where the second time is later than the first time.

[0006] In some embodiments, the method further includes: decoding, by the UE, the total number of symbols at the second time; determining, by the UE, whether the total number of symbols carries the control information for the UE; when determining that the total number of symbols carries the control information instructing the UE to perform data transmission at the second time in the transmission period, performing, by the UE, the data transmission at the second time; and when determining that the total number of symbols does not carry the control information instructing the UE to perform data transmission in the transmission period, entering, by the UE, into the sleep mode.

[0007] In various embodiments, the particular UE decodes the firs number of symbols only after the channel quality is determined to exceed a threshold. In those embodiments, the UE determines the channel quality includes: determining a correlation between different parts of a cyclic prefix (CP) in a signal received by the UE from the access point in the transmission period; and determines the channel quality based on the correlation.

[0008] Other examples, embodiments, implementations, benefits, and motivations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0010] FIG. 1 illustrates one example control symbol reception by a UE in a power saving mode.

[0011] FIG. 2 illustrates one example of a control information reception method performed by a

UE in accordance with the present disclosure.

[0012] FIG. 3 illustrates an example timing-graph to illustrate the method shown in FIG. 2.

[0013] FIG. 4A illustrates an example method implemented by a UE in accordance with the disclosure.

[0014] FIG. 4B illustrates another example method implemented by a UE in accordance with the disclosure.

[0015] FIG. 5 shows a timing-graph that illustrates one example implementation of method shown in FIG. 4.

[0016] FIG. 6 illustrates one example method implemented by a UE, where the UE uses past valid SNRs (Signal-to-Noise Ratio) for determining whether to start control information obtaining operation for a particular transmission period.

[0017] FIG. 7 illustrates one example of a method implemented by a UE by which the UE estimates SNR based on CP (Cyclic Prefix) in one or more signals received.

[0018] FIG. 8 illustrates one example of an UE in accordance with the disclosure.

DETAILED DESCRIPTION

[0019] In some wireless communications systems, an access point is configured to control data transmission in both downlink and uplink directions. In this way, these systems can react to changing radio conditions of each accessing terminal device and optimize the overall throughput; ensure quality of service (QoS) for each accessing terminal device; deal with system overload situations; and/or any other factors. For example, LTE and 5^th generation (5G) networks are such systems that a base station is configured to schedule uplink and downlink communications for accessing UEs based on a number of factors.

[0020] Dynamic scheduling is a technique referring to an access point scheduling of communication resources for accessing terminal devices dynamically in each transmission period. Generally, in dynamic scheduling, for a given transmission period, resources allocated by the access point to transmit control information and data information can be different from other transmission periods. In each transmission period, a given accessing terminal device can first receive the control information, and then receive the data information according to the control information received in the transmission period. Two important factors in dynamic scheduling are channel conditions and the number of terminal devices to be scheduled in the transmission period. For example, when terminal devices request the access point to facilitate communications for these devices, resources are used to provide control information to these devices in a transmission period. The access point typically aggregates control information for scheduled UE in one chunk and transmits this chunk to the scheduled terminal devices in the transmission period to instruct them how to perform data transmission in this period. After receiving such a chunk of control information in the transmission period, the individual scheduled terminal devices may search the chunk for control information specifically for itself. Thus, the more terminal devices are to be scheduled by the access point in the transmission period, the more resources are needed to carry the aggregated control information, and vice versa.

[0021] Another factor that may impact the amount of resources used by the access point in the transmission period for carrying control information is channel conditions for the terminals. Due to various factors, terminal devices can have different channel conditions in the transmission period, meaning some may have better signal quality than others. For example, certain terminal devices may be very close to the access point, and thus have better channel conditions (over the air) with respect to the access point compared to terminal devices that are located far from the access point. When scheduling resources, in situations where more terminal devices requesting communication resources than the access point can handle, the access point may prioritize those terminal devices with better channel conditions to be scheduled. As another example, the access point may build certain redundancy in the control information to ensure all terminal devices may receive control information when there are fewer terminal devices request communication resources than it can handle.

PDCCH SCHEDULING

[0022] With dynamic scheduling having been generally described, further details are provided in this section with an example of PDCCH scheduling in the 5G technology. However, it should be understood that details provided in this section are merely for illustrating inventive concepts, motivations, and various embodiments in accordance with the present disclosure and thus are not intended to be limiting. For example, the present disclosure should not be construed to be limited only to 5G technology because this section provides details about PDCCH scheduling in the context of 5G technology. The inventive concepts, motivations, and embodiments described and illustrated herein are also applicable to any other wireless transmission technologies such as LTE/4G or WiMax as appropriate.

[0023] Information carried in the PDCCH is typically referred to as downlink control information (DCI). DCI typically contains scheduling information for downlink data channels and/or other control information of the one user equipment (UE), a group of UEs, all UEs in the cell. Downlink scheduling assignments may be sent, by a base station, to a UE to indicate to the UE parameters related to the formatting of a forthcoming transmission of downlink communication traffic packets by the base station on a PDSCH. For example, it may indicate the location(s) of the physical resource(s) to be used for that transmission. DCI messages may also convey other types of control information or provide specific instructions to the UE (e.g., power control commands, an order to perform a random access procedure, or a semi-persistent scheduling activation or deactivation). A separate DCI packet may be transmitted by the base station to the UE for each traffic packet/ sub-frame transmission.

[0024] In the 5G technology, the payload bits of each DCI carried in the PDCCH are typically scrambled by a scrambling sequence. The scrambling of the bits of a given DCI may involve generating complex- valued modulation symbols that are mapped to physical resources in units referred to as control channel elements (CCEs). Each CCE consists of six resource element groups (REGs), where a REG is defined as one physical resource block (PRB ) in one OFDM symbol which contains nine resource elements (REs) for the PDCCH payload and three demodulation reference signal (DMRS) REs. A PRB is a unit in frequency-domain resource allocation for channels/signals. For each DCI, 1, 2, 4, 8, or 16 CCEs can be allocated, where the number of CCEs for a DCI is denoted as aggregation level (AL). Based on the channel environment and available resources, the base station can adaptively choose a proper AL for a DCI to adjust the code rate.

[0025] A DCI with AL L is mapped to physical resources in a given a bandwidth part (BWP), where necessary parameters such as frequency and time domain resources, and scrambling sequence identity for the DMRS for the PDCCH are configured to a UE by means of control resource set (CORESET). A UE may be configured with up to three CORESETs on each of up to four BWPs in a cell. A DCI of AL L comprises L continuously numbered CCEs, and the CCEs are mapped on a number of REGs in a CORESET.

[0026] Through such aggregation, it thus is achievable for the base station to transmit in just a few PDCCH symbols to provide DCI messages to a number of UEs within the cell. In 5G, the base station typically can transmit 1, 2, or 3 PDCCH symbols to cover UEs in the cell. The number of PDCCH symbol for a given transmission by the base station is typically defined by the CORSETS parameters. PDCCH symbols are typically transmitted by the base station to the UE during a subframe. As mentioned, the amount of PDCCH symbols transmitted by the base station can go up to 3 depending on the number of UEs in the cell requesting resources and/or the signal qualities in the cell known to the base station. Typically, the base station takes a conservative approach in determining the number of PDCCH symbols are used to carry the PDCCH such that it ensures the UEs having the worst signal quality in the cell can also obtain and decode the PDCCH symbols.

[0027] For a given UE, to save power, a mode referred to as discontinuous reception (DRX) may be used. In DRX, the UE can place its receiver in a sleep mode, e.g., turning off its receiver at certain times. The base station uses knowledge of a UEs DRX pattern (e.g., sequence of wake-up intervals of the device) when determining times to transmit to a wireless device that is in a DRX mode. For example, the base station can determine a time in which the wireless device will be actively listening for a transmission. The activity cycle of a DRX pattern can vary as a function of an assigned radio connection state or sub-state.

[0028] With respect to PDCCH symbol reception in DRX mode, a UE is typically configured to deactivate its receiver in certain periods known as sleep mode. In the sleep mode, the UE does not listen for PDDCH symbols from the base station. At other periods known as non-DRX mode, the UE is typically configured to activate its receiver. In the non-DRX mode, the UE can listen for PDCCH symbols. FIG. 1 illustrates one example of PDCCH symbol reception by a UE in DRX mode. As can be seen in this example, the UE is in the sleep mode up to time tl. At time tl, the UE is scheduled to wake up. At time t2, the UE receives a first PDCCH symbol from the base station, and at time t3, the UE receives a second PDCCH symbol from the base station. In this transmission shown in FIG. 1, the number of PDCCH symbols is 2. Thus, after the second PDCCH symbol is received, the UE understands all PDCCH symbols have been received in this transmission and at time t4, the UE starts channel estimation, at time t5 the UE starts demodulation and at time t5 it starts decoding the PDCCH symbols to obtain DCI from the base station intended for the UE, if any. As shown in this example, because the UE does not find such a DCI after decoding the PDCCH symbols, it goes back to sleep mode.

[0029] However, the inventor(s) of this disclosure has an insight that in certain situations a given UE may not need to receive all the PDCCH symbols before the UE starts demodulating and decoding the PDCCH symbols. For example, in a situation when the base station transmits multiple PDCCH symbols to the UEs in the cell to ensure even UEs with worst signal receiving quality will also obtain the PDCCH information (e.g., DCI), there is redundancy in the PDCCH symbols. For instance, the base station may determine to transmit two PDCCH symbols such that the first and second PDCCH symbols send the same DCI in case certain UEs (especially the ones at the edge of the cell) may not receive the first PDCCH symbol correctly due to the poor signal quality (e.g., noise in the transmission of the PDCCH symbols to those UEs). For a situation like this, the inventor(s) of this disclosure realizes the UEs having good signal quality may not need to receive the second PDCCH symbol to obtain DCI. That is, those UEs may be able to demodulate and decode the first PDCCH symbol to obtain DCI due to good channel quality.

PARALLEL RECEPTION OF CONTROL INFORMATION IN A POWER SAVING MODE [0030] Thus, according to one aspect of the present of disclosure, a technique for UE to obtain control information, such as PDCCH information, is provided. In this technique, a given UE may dynamically determine whether to start decoding and obtaining control information after an amount of symbols have been received during a transmission period. This amount of symbols may be a portion of an entire amount symbols transmitted by an access point for one or more UEs to obtain control information. That is, in this technique, a given UE may not wait until all of such symbols have been received, and then start decoding and obtaining control information carried in those symbols. In this technique, the UE may start decoding and obtaining control information carried in those symbols after a portion of these symbols having been received by the UE. It should be understood although contexts of 5G is provided above for illustration, methods described below and herein are not intended to be limited to 5G. Other applicable wireless transmission technologies, such as LTE or WiMax, are also applicable.

[0031] FIG. 2 illustrates one example of a control information reception method 200 performed by a UE in accordance with the present disclosure. At 202, in this example method, the UE determines a channel quality for the UE has exceeded a threshold. The determined channel quality can reflect that the UE has a good communication channel with the access point for receiving signals from the access point. In a number of situations, the UE may determine such a channel condition exists. For example, as mentioned, the UE may be located close to the access point. As another example, the UE may be located in an area where the UE has a clear line of transmission path to the access point such that overall noise level on this path is low. Still as another example, the UE may be relatively static in terms of movement with respect to the access point. Other examples are contemplated.

[0032] In some embodiments, the threshold may be a predetermined value configured into the UE. For example, the threshold may be a predetermined value in a control information reception algorithm implemented by the UE. However, this is not necessary the only case. The threshold may be, in some embodiments, a dynamic value provided by the access point or adjusted by the UE based on a number of factors, such as overall channel conditions in the area covered by the access point, how congested this area is in terms of a number of UEs are in this area accessing the access point, a priority of the UE (which may change from time to time), and/or any other consideration.

[0033] At 204, the UE receives a first number of symbols carrying control information. The control information may be transmitted by the access point to one or more UEs including the UE. However, this is not necessarily the only case. As will be described later, embodiment in accordance with the disclosure, in situations where the first number of symbols do not contain control information for the UE, the UE is still configured to decode and demodulate theose symbols. In those situations, as will be illustrated later, the UE is configured to either continue to receive the symbols or go to sleep mode if no control information is found in the first number of symbols.

[0034] In some embodiments, the first number is a value indicating a minimum number of symbols the UE should receive before it can start decoding the received symbols for the control information. In some implementations, this number may be a preconfigured number - for example 1 symbol. In some implementations, this number may be a dynamic number determined by the access point and/or the UE. For example, in LTE and 5G, a base station may determine the number of PDCCH symbols to be used in a subframe for the DCI messages based on the aggregation level mentioned above. In that example, there is a correspondence between the number of PDCCH symbols in the subframe and the aggregation level, and thus the number of PDCCH symbols for the UE to obtain the control information can change from subframe to subframe depending on the aggregation level. Typically, higher aggregation level needs at least two PDCCH symbols, while lower aggregation level may just need one PDCCH symbol. As mentioned above, the base station may add one more PDCCH symbol to this minimum number of PDCCH symbols based on overall channel conditions in the cell. In some embodiments, this is a design choice of base station scheduling algorithm. It should be understood that although LTE/5G is used here, they are not intended to be limiting the example method illustrated and described in FIG. 2. Instead, they are just for illustrating the concept of first number of symbols to be received by the UE at 204. As mentioned, such a number depends on the scheduling in an applicable wireless technology - such that it may be a predetermined value or a dynamic value.

[0035] In some implementations, the first number may be provided to the UE in advance before the UE starts receiving the first number of symbols. For example, another control information may be provided to the UE from time to time indicating such a number. In those implementations, the UE thus know how many symbols (first number) it needs to receive before it can obtain control information using those symbols. However, this is not necessarily the only case. As mentioned, in some implementations, the UE may determine what the first number should be. For example, the UE may determine based on a number of factors, such as channel condition with the access point, a priority of the communication to be performed by the UE, and/or any other factors, the value of the first number. In those implementations, the UE may be configured to ignore what the access point informs to the UE about the first number. For instance, the access point may inform the UE in advance that the first number is 2, but the UE may nevertheless determine the first number should be 1.

[0036] At 206, the UE starts control information reception after the first number of symbols having been received. Control information reception at 206 may involve decoding the first number of symbols and obtain the control information for the UE based on the resolved first number of symbols. For example, in the case of 5G described above, this may involve the UE starts channel estimation, demodulating the first number of symbols and decoding the demodulated first number of symbols to obtain DCI for the UE. In implementations, the UE may start such control information reception at the same time or more or less the same time when the first number of symbols having been received.

[0037] At 208, the UE enters into a sleep mode after the UE does not obtain the control information from the first number of symbols. As mentioned above, this may involve the UE deactivating its transceiver for a period of time. As used herein, a sleep mode may be referred to a light sleep or a deep sleep mode. Deep sleep means main clock of the UE is turned off. Light sleep means main clock of the UE is on but major part of the UE is turned off.

[0038] FIG. 3 illustrates an example timing-graph to illustrate the method shown in FIG. 2. As can be seen, the UE sleeps until time tl in the transmission period, and wakes up to monitor transmission from the access point. At time t2, the UE starts receiving from the access point the first number of symbols carrying control information. At time t3, the UE completes receiving the first number of symbols and starts obtaining control information by decoding the first number of symbols. By comparison, in other control information reception techniques, at time t3, the UE would continue to receive a second number of symbols carrying the control information - for example such as the one shown and illustrated in FIG. 1. At time t4, the UE successfully obtains the control information and enters into the sleep mode until time t5. By comparison, in other control information reception techniques, at time t4, after the UE completes obtaining the 2^nd number of symbols, the UE understands all of the symbols carrying the control information having been received from the access point, the UE then starts obtaining the control information. This is shown in the dotted line timing graph in FIG. 3 for reference.

[0039] Thus, the method described and illustrated in FIG. 2 is advantageous over other UE control information reception methods because between t4 and t5 the UE can enter into the sleep mode to save power. A key for this advantage is that the UE kicks off the control information obtaining operations in method 200 after only a portion of the symbols (e.g., first number) carrying control information having been received from the access point, instead of having to receive the second number of symbols. This allows the UE to enter into the sleep mode in time t4 to t5 because it has already obtained the control information from the first number of symbols.

[0040] As mentioned, method 200 is advantageous compared to other control reception methods, for example, when the UE has a good channel condition with the access point and can obtain control information only from a portion of symbols carrying control information. In some embodiments, the inventor(s) of the present disclosure has come up another way efficiently receiving control information for UE by taking into consideration that the UE may not always obtain the control information from a portion of the symbols even if it has a good condition with the access point. For example, the access point may have an overload situation and schedules communication resources in the transmission period based on UE priorities, where the UE at issue is not scheduled due to its relatively low priority. In that example, the UE thus may still have to receive the second number of symbols to ensure that indeed that it is not scheduled by the access point to perform data transmission in this transmission period. FIG. 4A illustrates an example method of 400 implemented by a UE that can address this situation.

[0041] Operations 402 and 404 are the same or substantially the same as operations 202 and 204 described and illustrated herein. Please refer to those operations for details.

[0042] At 405, a determination by the UE is made regarding whether a channel condition is below a threshold. As mentioned herein, different UEs within the cell controlled by the access point may have different channel conditions. The access point may aggregate the control information for the UEs in the current transmission period based on the worst channel condition(s) for the UEs in the current transmissions period. In various implementation, the access point builds into the aggregated control information some redundancy to ensure that even the UEs with worse channel conditions would still receive the aggregated control information. However, for each individual UE, its channel condition can be different from those of others in the cell. For instance, for a UE that has a good channel condition, it may not need to receive all of the aggregated control information, which has some redundancy, before it can starts obtaining control information specifically for itself sent by the access point (if any). Thus, in accordance with the present disclosure, the UE can determine a channel condition for itself - whether it is below or above a threshold channel condition. Example ways of such a determination by the UE at 405 are described below in the section “CHANNEL QUALITY DETERMINATION BY THE UE”.

[0043] As can be seen, if the UE determines that its channel condition is not below a threshold, the process goes to 406 to start obtaining control information specifically for itself sent by the access point in this transmission period. At 406, the UE has received the first number of symbols carrying the aggregated control information, and the UE starts control information reception operations to obtain control information specifically for itself by decoding the first number of symbols. Then, the UE determines whether control information specifically for the UE has been obtained from the first number of symbols..

[0044] At 410, where the UE determines the control information was not received by decoding the first number of symbols. In that case, UE understands that it is not scheduled by the access point in the current transmission period by the access point and thus, the UE enters into a sleep mode as described above in association with operation 208.

[0045] Referring back to 405. At 405, when the UE determines that its channel condition is below than a threshold, this indicates to the UE that it should still receive a second number of symbols carrying the aggregated control information before it can start obtaining control information specifically for itself sent by the access point (if any). In that case, the process proceeds to 408. It should be understood the second number of symbols may or may not represent the remaining of all of the symbols carrying the aggregated control information. For example, if the total number of symbols used by the access point to carry the aggregated control information is 2 for the current transmission period, the first number of symbol can be 1 and the second number of symbol can also be 1. However, this is not necessarily the only case. There can be situations where the access point use more than 2 symbols to carry the aggregated control information - for example 3. For instance, the first number can be 1 and the second number can also be 1. It should be understood, how first number and second number of symbols are determined may be a design choice and thus is not limited by the present disclosure. It is contemplated that in various implementations, the first number may be a minimum amount of symbols for the UE to obtain control information specifically for itself sent by the access point, and the second number may or may not be the remaining number of symbols. [0046] At 408, the UE receives the second number of symbols carrying the control information from the access point. As can be seen, the sequence of 408 and 412 is similar to the sequence of 404 and 405, and thus please refer to the description above for 404 and 405 for description of the sequence 408 and 412.

[0047] As can be seen, when the UE obtains control information at 406, the UE can enter into the sleep mode until the time when it needs to perform data transmission according to the control information. In some implementations, this means the UE can stop receiving the rest of symbols carrying the control information from the access point and/or stops obtaining control information from the remaining control symbols, thus saving power.

[0048] At 412, when the UE has not obtained the control information and has finishing receiving the second number of symbols, the UE once again determines whether control information can be obtained from the symbols received thus far, e.g., the first number plus the second number of symbols. There may be a few situations after 412 as determined by the UE. One is that the UE has obtained the control information by decoding the first and second number of symbols and thus may enter into the sleep mode if there is still a bit of time left until it needs to perform data transmission according to the control information. Another situation is that the UE does not obtain the control information by decoding the first and second number of symbols, but also understands all symbols carrying the control information have been received from the access point for the transmission period - for example according to a priori received indication indicating that the total number of symbols carrying control information in the transmission period is the first number plus the second number. In that situation, the UE can determine that there is no control information specifically for the UE in the transmission period and UE is not scheduled to perform data transmission in this period. Thus the UE may also enter into the sleep mode when that is determined. There is yet another situation where the UE understands there are more symbols carrying control information to be received from the access point, for example, a third number of symbols. In that situation, the UE can continue receiving the third number of symbols in parallel with the determination being made at 412. This cycle can continue similarly until all of the symbols carrying the control information having been received by the UE.

[0049] FIG. 4B illustrates another example method 450 implemented by the UE for receiving the control information in accordance with the disclosure. As can be seen method 450 is similar to method 400 except that at step 406 when the UE determines that the control information has not been received, the UE is configured in method 450 to continue receive the second number of symbols. In implementation, operation(s) carried out by the UE to receive the control information in this method can be performed in parallel with the UE receiving the second number of symbols. For example, as illustration, after the UE receives the first number of symbols, it starts resolving for the control information using the first number of symbols. Until the UE successfully obtained control information, the UE is configured to continue to receive the second number of symbols. If the UE successfully obtains the control information from the first number of symbols, it then can enter into the sleep mode at 410, which can include setting an interrupt on receiving the second number of symbols (because the control information has already been received). In situations where the UE does not obtain the control information from the first number of symbols, the UE may have already entirely or partially received the second number of symbols and may be ready to obtain the control from the first and second number symbols together. In this way, efficiency of UE obtaining the control information is improved when the UE does not obtain the control from the first number of symbols.

[0050] FIG. 5 shows a timing-graph that illustrates one example implementation of method 400 shown in FIG. 4. As can be see, in this implementation, the UE is configured to receive the second number of symbols, the third number of symbols, and so on at the same time slots it would otherwise receive those in other control reception methods such as the one shown in FIG. 1. However, here, as shown, the UE is configured to kick off the control information obtaining operations (e.g., channel estimation, demodulation, decoding and/or any other operations) after the first number of symbols are received, after the second number symbols are received and so on, in parallel with the rest of symbols carrying the control information are still being received. As mentioned above, the UE, in this implementation, is configured to enter into the sleep after the control information is obtained by the UE and stops receiving and/or decoding the rest of symbols that are still in progress being transmitted and/or received. For example, after the UE obtains the control information at t4, it can enter the sleep mode until time tx when the control information instructs it to perform data transmission, and stops receiving the rest of symbols.

CHANNEL QUALITY DETERMINATION BY THE UE

[0051] As mentioned above, in various embodiments, the UE determines a channel quality for a transmission period and determines whether to kick off control information obtaining operations after a first number of symbols are received. The inventor(s) have come up a number of ways for the UE to determine the channel quality for such a purpose. In this section, details are provided.

Channel quality estimation through signal-to-noise ratio (SNR)

[0052] SNR is a measure used in telecommunication to compare the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, SNR= Psignai/Pnoise, where P is average power. A ratio higher than 1 : 1 (greater than 0 dB) indicates more signal than noise. However, one challenge for the UE to determine SNR for the purpose of kicking off control information obtaining when only a portion of the symbols carrying control information are received is that when the UE is not scheduled by the access point in a given transmission period, the SNR derived from the signal received by the UE in the transmission period may indicate a poor channel condition. However, as mentioned, the UE, until it receives and decodes all symbols carrying the control information, may not know that it is not scheduled by the access point in this transmission period. Thus, solely relying on the UE determining SNR in a channel estimation manner may result in the UE not kicking off control information obtaining operations when it actually has a good channel condition but is not scheduled by the access point in the transmission period.

Past SNR method

[0053] To address this issue, the inventor(s) of the present disclosure has come up a solution where the UE keeps track of its historical SNR for early start of control information obtaining operations. For example, in some embodiments, the UE is configured to store known valid SNRs and use these SNRs to determine whether to start control information obtaining operations after a portion of the symbols carrying the control information having been received. FIG. 6 illustrates one example method 600 implemented by a UE, where the UE uses past valid SNRs for determining whether to start control information obtaining operation for a particular transmission period. Method 600 shown in FIG. 6 is one embodiment of operation 202 shown in FIG. 2.

[0054] At 602, the UE is configured to obtain a valid SNR when the UE is scheduled to perform data transmission by the access point. For example, at a given transmission period, the UE is scheduled by the access point and thus can determine the valid SNR based on the signals received from the access point during that period. Such a SNR may include SNR measured over PDCCH, PBCH, SSS, PDSCH, and/or any other channels depending on an applicable wireless communication technology in accordance with the disclosure.

[0055] At 604, the UE is configured to store the valid SNR determined at 602 in a repository. The repository is configured to store such valid SNRs obtained by the UE at different transmission periods. For example, in some implementations, the repository may be memory of the UE.

[0056] At 606, for the particular transmission period where the UE is to determine, in advance, whether to kick off control information obtaining after a portion of the symbols carrying control information are received, the UE is configured to determine a movement of the UE. This movement may indicate a relative position and/or distance for the UE at that period with respect to a reference point or reference points. For example, the reference point may be the access point, or an average position/di stance of the UE over a time period. Various ways of determining such a movement can be used at 606. A motivation for 606 is to determine whether the prior obtained valid SNRs are good indication for the UE to use for the purpose mentioned above. For example, if the UE has moved quite a bit when determined at the particular transmission period, the channel quality of the UE with respect to the access point may have also changed quite a bit, and thus the historical valid SNRs obtained by the UE may not be, at least, solely relied upon for the purpose mentioned above. On the other hand, if the UE has not moved much or has not moved at all, the historical SNRs can be a good indicator for the UE to use to determine whether to kick off the control information obtaining after a portion of the symbols carrying control information are received.

[0057] At 608, for the particular transmission period, the UE is configured to determine whether to start the control information obtaining based on the movement determined at 606 and/or the historical SNRs stored at 604. In some embodiments, an average SNR is obtained at 608 from the repository. In some embodiments, a predicted SNR is obtained based on the SNRs in the repository and the movement determined at 606. In some embodiments, one or more selected SNRs are obtained from the repository at 606, for example one or more most recent SNRs obtained by the UE. Other examples are contemplated.

Cyclic Prefix (CP) Based SNR method

[0058] Another method come up by the inventor(s) of the present disclosure is to use CP correlation in a received signal to estimate SNR for the purpose of determining whether to start receiving control information after a portion of symbols carrying control information having been received. This method may be applied to wireless communication technologies where CP is employed for control symbol generation, such as LTE or 5G. As mentioned above, the SNR obtained by the UE from channel estimation may not be reliably used by the UE for the purpose mentioned above. That is, when the UE is not scheduled, the SNR obtained from channel estimation would be poor but that’s mainly due to the signals received by the UE are not intended for the UE in the transmission period. The inventor(s) of the present disclosure realizes that SNR may be estimated based on the CP correlation in the signals received for the purpose mentioned above. That is, it is unnecessarily for the UE to know whether SNR is good enough for it to perform data transmission but rather for the UE to estimate how good is the channel condition based on the signals received even if the signals are not intended for the UE. [0059] FIG. 7 illustrates one example of a method 700 implemented by a UE by which the UE estimates SNR based on the CP in one or more signals received. Method 700 is one embodiment of operation 202 shown in FIG. 2.

[0060] At 702, a signal is received by the UE, for example in a channel. Specifics of this channel are not limited in the disclosure. As mentioned this channel may include a number of applicable channels so long as there is a CP in the signal transmitted through this channel. In some embodiments, a power of this signal is expressed by the following formula: y = h ®s +n

, where y denotes the signal, h denotes the channel, s denotes a signal transmitted by the access point, and n denotes noise. ® is a convolution sign in this formula.

[0061] At 704, a correlation between a CP in the signal received at 702 and a duplicated part of the CP in the signal is determined for a number of time points. In various embodiments, the determination at 704 involves calculating the correlation in the time domain. That is, at 704, it is determined how related the CP received at a given time point is to the CP received in a time point previous to the given time point. In some embodiments, the determination at 704 is expressed by the following formula: k =y_ky_k+N

, where Rk denotes the correlation at time k, yk denotes the signal power received at time k, and (yk+N)* denotes the conjugate of the duplicated part of the CP received at time k and N is a length of the CP.

[0062] At 706, an average of the correlations obtained at 704 is determined. In various embodiments, the determination at 706 is expressed by the following formula:

, wherein k=0 is the starting point of a sample CP portion in the signal, and L is equal to or smaller than a length of the CP.

[0063] At 708, a noise power N is determined by the UE. In various embodiments, the determination at 708 is expressed by the following formula:

As can be seen, N determined at 708 can reflect a standard deviation of the correlations from the average correlation S at the individual time points. This deviation may reflect a noise level of the UE with respect to the channel condition to the access point.

[0064] At 710, a SNR is determined. In various embodiments, the determination at 710 is expressed by the following formula:

SOME RESULTS

[0065] In this section, some results in accordance with some embodiments are provided. In one embodiments, using the technique(s) described and illustrated herein for early start of control information obtaining, when number of PDCCH symbol is 2, the coding rate of 1 symbol, PDCCH is 44/54=0.81, for AL =1, as long as SNR is good, UE can decode the PDCCH symbol after the first PDCCH symbol of the two is received. In one embodiment, when number of PDCCH symbol is 3, the coding rate of 1 symbol, PDCCH is 44*3/(4*54)=0.61, for AL=4, as long as SNR is good and AL=1 and 2 is not configured in SearchSpace for P-RNTI, UE can decode PDCCH after the first PDCCH symbol is received. In another embodiment, when number of PDCCH symbol is 3, the coding rate of s, PDCCH is 44*3/(4*54)=0.61, for AL=2, as long as SNR is good and AL=1 is not configured in SearchSpace for P-RNTI, UE can decode PDCCH after 2 PDCCH symbols have been received.

[0066] FIG. 8 illustrates one example of an UE 100 in accordance with the disclosure. The UE illustrated in FIG. 8 may be used to implement various methods and techniques described and illustrated herein. A shown, the UE 100 includes a transceiver 110 configured to receive and send information to an access point and/or to one or more other UEs. The UE 100 includes a processor 120 configured to perform various information processing for the UE 100 including the ones described and illustrated herein. The UE 100 may include any other components not shown in this example.

[0067] All or some of the foregoing embodiments may be implemented by using software, hardware, firmware, or any combination thereof. When software is used to implement the embodiments, all or some of the embodiments may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the procedure or the functions according to various embodiments in accordance with the present disclosure are all or partially generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in the computer-readable storage medium or may be transmitted from a computer- readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a storage disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid-state drive Solid State Disk (SSD)), or the like.

[0068] Having described several example configurations, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of steps may be undertaken before, during, or after the above elements are considered.

Claims

WHAT IS CLAIMED IS:

1. A method for obtaining control information comprising: receiving, by a particular user equipment (UE), from an access point, a first number of symbols at a first time in a transmission period, the first number of symbols carrying control information for one or more UEs accessing the access point; decoding, by the particular UE, the first number of symbols; determining, by the particular UE, that the first number of symbols does not carry control information for the particular UE; and after determining that the first number of symbols does not carry control information for the particular UE, entering, by the particular UE, into a sleep mode.

2. The method of claim 1, further comprising: receiving, by the particular UE, from the access point, an indication of a total number of symbols carrying control information for the one or more UEs to be received prior to the first time in the transmission period, wherein the total number is greater than the first number.

3. The method of claim 1, further comprising: receiving, by the particular UE, from the access point, a second number of symbols after the first number of symbols having been received, the second number of symbols being received before the second time in the transmission period, and carrying control information for the one or more UEs.

4. The method of claim 3, wherein the reception of the second number of symbols by the particular UE is in parallel with the decoding of the first number of symbols by the particular UE.

5. The method of claim 1, further comprising: determining, by the particular UE, that a channel condition has exceeded a threshold at the first time in the transmission period; and, wherein the decoding of the first number of symbols by the particular UE is started after the channel condition has been determined exceeding the threshold.

6. The method of claim 5, wherein in response to determining that the channel condition has not exceeded the threshold by the particular UE, continuing, by the particular UE, receiving symbols from the access point according to an indication from the access point, wherein the indication indicates a total number of symbols to be received by the one or more UEs, and the total number is greater than the first number.

7. The method of claim 6, wherein the total number of symbols are received by the particular UE at a second time in the transmission period, the second time being later than the first time, and wherein the method further comprises: decoding, by the particular UE, the total number of symbols at the second time; determining, by the particular UE, that the total number of symbols carries the control information for the particular UE; in response to determining that the total number of symbols carries the control information for the particular UE instructing the particular UE to perform data transmission at the second time in the transmission period, performing, by the particular UE, the data transmission at the second time.

8. The method of claim 7, the method further comprises: in response to determining that the total number of symbols does not carry the control information for the particular UE instructing the particular UE to perform data transmission in the transmission period, entering, by the particular UE, into the sleep mode.

8. The method of claim 1, further comprising determining, by the particular UE, a channel quality; and wherein the particular UE decodes the first number of symbols only after the channel quality is determined to exceed a threshold.

9 . The method of claim 8, wherein determining, by the particular UE, the channel quality comprises: obtaining a valid signal-to-noise ratio (SNR) when the UE is scheduled by the access point in a different transmission period; and determining the channel quality based on the valid SNR.

10. The method of claim 8, wherein determining, by the particular UE, the channel quality comprises: determining a correlation between different parts of a cyclic prefix (CP) in a signal received by the particular UE from the access point in the transmission period; and determining the channel quality based on the correlation.

11. A device configured to obtain control information comprising: a transceiver and a processor, wherein the transceiver is configured to receive from an access point, a first number of symbols at a first time in a transmission period, the first number of symbols carrying control information for one or more devices accessing the access point, and wherein the processor is configured to decode the first number of symbols; determine that the first number of symbols does not carry control information for the device; and after determining that the first number of symbols does not carries control information for the device, performing data transmission at a second time in the transmission period and entering into a sleep mode until the second time in the transmission period.

12. The device of claim 11, wherein the transceiver is further configured to: receive, from the access point, an indication of a total number of symbols carrying control information for the one or more devices to be received prior to the first time in the transmission period, wherein the total number is greater than the first number.

13. The device of claim 11, wherein the transceiver is further configured to: receive, from the access point, a second number of symbols after the first number of symbols having been received, the second number of symbols being received before the second time in the transmission period, and carrying control information for the one or more devices.

14. The device of claim 13, wherein the reception of the second number of symbols is in parallel with the decoding of the first number of symbols.

15. The device of claim 11, wherein the processor is further configured to: determine whether a channel condition has exceeded a threshold at the first time in the transmission period; and, wherein the decoding of the first number of symbols is started after the channel condition has been determined exceeding the threshold.

16. The device of claim 15, wherein when it is determined that the channel condition has not exceeded the threshold, the processor is configured to continue receiving symbols from the access point according to an indication from the access point, wherein the indication indicates a total number of symbols to be received by the one or more devices, and the total number is greater than the first number.

17. The device of claim 16, wherein the total number of symbols are received at a second time in the transmission period, the second time being later than the first time, and wherein the processor is further configured to: decode the total number of symbols at the second time; determine whether the total number of symbols carries the control information for the device; when determining that the total number of symbols carries the control information for the device instructing the device to perform data transmission at the second time in the transmission period, perform the data transmission at the second time; and when determining that the total number of symbols does not carry the control information for the device instructing the device to perform data transmission in the transmission period, entering into the sleep mode.

18. The device of claim 11, wherein the processor is further configured to determine a channel quality; and wherein the decoding of the firs number of symbols is performed only after the channel quality is determined to exceed a threshold.

19. The device of claim 18, wherein determining the channel quality comprises: obtaining a valid signal-to-noise ratio (SNR) when the device is scheduled by the access point in a different transmission period; and determining the channel quality based on the valid SNR.

20. The device of claim 18, wherein determining the channel quality comprises: determining a correlation between different parts of a cyclic prefix (CP) in a signal received by the device from the access point in the transmission period; and determining the channel quality based on the correlation.

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