Wake up method for a user equipment

Abstract

A method of operating a user equipment (100) comprising a main radio (120) which is configured to operate in an idle mode and in an operating mode and a wake up radio (110) which is configured to transmit a trigger signal to main radio (120) for triggering operating mode.

Description

[0001] WAKE UP METHOD FOR A USER EQUIPMENT

[0002] TECHNICAL FIELD

[0003] Invention relates to a method of operating a user equipment for wake up and synchronization, said user equipment comprising a main radio which is configured to operate in an idle mode and in an operating mode and a wake up radio which is configured to transmit a trigger signal to main radio for triggering operating mode. Invention also relates to the user equipment, a method of an access point and the access point.

[0004] PRIOR ART

[0005] Present 5G User Equipment (UE) demonstrates high power consumption, requiring frequent recharging, particularly within a few hours for smartphones and just days for resource-limited sensors. This challenge is particularly significant for devices with small batteries or those lacking convenient access to charging facilities, such as wearables and remote sensors. While prolonged periods of Discontinuous Reception (eDRX) can provide certain power-saving benefits, the associated latency drawbacks pose significant challenges for time-sensitive applications like fire detection and industrial automation.

[0006] 3GPP Rel-18 seeks to overcome existing limitations by introducing an innovative ultra-low power wake-up mechanism. Departing from the conventional continuous polling approach, this new paradigm enables User Equipment (UE) to enter a deep sleep state and be awakened by a dedicated "Wake-Up Signal" (WUS) transmitted by the network. This transformative solution involves the use of a separate, ultra-low power Wake-Up Receiver (WUR) distinct from the main radio that consumes substantial data. Essentially, it employs a sentinel to safeguard the device's valuable energy reserves.

[0007] The design of the Wake-Up Signal (WUS) itself holds great significance, influencing both power consumption and the reliable detection capabilities of the compact Wake-Up Receiver (WUR). The primary goal is to develop optimal WUS / WUR solutions customized for power-sensitive UEs, including loT sensors and wearables, yielding substantial benefits beyond the powersaving methods introduced in Rel-15 / 16 / 17. Importantly, this initiative extends its impact beyond these specific use cases, encompassing potential applications in areas such as XR glasses and smart homes.

[0008] The integration of the WuS frame with the legacy 5G NR is a challenging task as discussed in

[0001] , mainly due trade off between accuracy and complexity. As the 3GPP standards continues to evelove towards release

[0019] a more concrete establishemnet of the OFDM based WuS is proposed which arises the problem of synchronization of the low complex WuRs.

[0009] EP3389317A1 EFFICIENT PREAMBLE DESIGN AND MODULATION SCHEMES FOR WAKE-UP PACKETS IN WLAN WITH WAKE-UP RADIO RECEIVERS proposes a sequence in the WuS to indicate information used for packet detection, automatic gain control and / or time / frequency synchronization. The sequence embedding information is selected from a poll of pre-defined sequence the detection of a specified sequence relates to specific signature control information.

[0010] US2018049130A1 SYNCHRONIZATION FOR WAKE-UP RADIO discloses method that uses a low-power WuR to wake-up periodically the WLAN radio accourding to a timining synchronization function (TSF) timer and a integrated processing circuitry by decoding a signal from the master node or access point. The signal has the TSF value associated with the TSF timer of the access point to synchronize the local timer of the WLAN radio within its range based on a counter of octets.

[0011] WO2018156199A1 LOW POWER WAKE-UP RADIO BEACON SIGNALING proposes a signaling method for wake-up radio beacons where an access point can ascertain timing details for transmitting WuS beacons and forward this timing data to a user device. Then, the access point can dispatch low-power wake-up radio beacons to the user device according to the provided timing information, and the user device can receive these beacons in accordance with the timing details.

[0012] US1 1343772B2 proposes a method, where a WUR receives a first WUS then check its validity, if it belongs to the serving cell the WUR measure its power. If the power is above a certain level, the WUR receives a secondary WUS which may contain other information / payload. This payload is extracted using a synchronization signal included in the first WUS. The first WUS may include cell information in addition to the synchronization signal, both may used for channel sensing. EP3737163A1 proposes a method for time-frequency synchronization using a physical signal used by a module to synchronize a base-station and a device in idle mode in case of downlink transmission.

[0013] W02024012350A1 proposes a method for synchronization which includes, where a network sends a first synchronization signal to the device to synchronize, after that the WUS is transmitted and a secondary synchronization signal is transmitted. Multiple synchronization signals can be transmitted as well.

[0014] WO2018075130A1 uses a low-power protocol circuitry for WUR, where the WUR triggers the main-radio on and is able as well to perform synchronization. Each synchronization signal is received using a slot-skipping schedule, the processor circuitry is configured to synchronize a clock of the wake-up receiver to a clock of the wake-up transmitter using at least one synchronization signal.

[0015] In case of devices using WuS and WuR, the MR is in sleep mode (idle) hence after each wakeup the receiver requires synchronization which is a burden in terms of complexity, spectral efficiency, and latency. The existing methods mainly do the following:

[0016] 1 - After the base-station (BS) transmits a WuS to the WuR to trigger the MR to wake-up, the WuR either needs synchronization to extract information of the WuS or uses simple correlation to trigger the MR to wake-up. The last one is problematic since the correlation method has a high of false alarm probability, does not allow embedding payload over the WuS and most importantly uses limited set of correlation symbols / preambles which is not suitable where a lot of devices are in the coverage area.

[0017] 2- In both cases the MR requires synchronization, conventionally after wake-up the MR waits for a synchronization signal from the BS, which effects the latency, spectral efficiency, and power consumption.

[0018] 3- If the WuR has primary synchronization it may transfer this information to the MR, however this primary synchronization transferred from the WuR is not enough since the offset between the MR and WuR is not compensated. If no synchronization signal is used at the WuR, the MR requires a synchronization signal transmitted from the base-station or access point / gateway, which causes a great overhead and latency. A user-end (UE) requires synchronization before establishing communication, this requirements in critical especially in UE using WuR for power efficiency. Without loss of generality, a device using WuR has its MR in sleep mode (IDLE) unless a trigger signal or interrupt from the WuR is initiated to turn the MR on for reception. The WuR triggers the MR only if the WuS is valid and intended to that specific UE, most common WuS uses correlationbased sequences to validate the wake-up trigger. Nevertheless, those sequences have a high probability of false alarm since the WuR might wake the MR unnecessarily and inaccurately from a different UE’s WuS. Additionally, those sequences (which have high correlation properties) are limited and the preambles corresponding to them cannot accommodate high number of devices in a specific coverage area. Hence, it is evident to append ID and / or payload in the WuS.

[0019] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0020] BRIEF DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0022] An object of the invention is to provide a method reducing the latency, power consumption and overhead while achieving fine synchronization.

[0023] Another object of the invention is to provide a method that increases accuracy of validation in wake-up radio.

[0024] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method of operating a user equipment comprising a main radio which is configured to operate in an idle mode and in an operating mode and a wake up radio which is configured to transmit a trigger signal to main radio for triggering operating mode. Accordingly, comprising the steps of:

[0025] - by WUR receiving a wake up signal (WUS) comprising at least a first validation symbol WuS#1 , a second validation symbol WuS#2 and at least a primary synchronization signal (PSS) symbol;

[0026] - by WUR realizing a correlation on the first validation symbol WuS#1 and determining whether to trigger the MR; - by WUR performing a primary synchronization using PSS symbol and determining a primary offset;

[0027] - extracting WuS#2 from WUS (300) and realizing validation on WuS#2.

[0028] - by WUR transmitting a trigger signal to MR;

[0029] - by MR executing an offset calibrating process, wherein the offset calibrating process includes transmitting a predetermined signal so that WuR determines a timing offset between the MR and the WuR;

[0030] - by WUR reporting determined timing offset and the primary offset;

[0031] - by the MR performing a fine synchronization using the primary offset and the timing offset and switching to operation mode. Thus, wake-up procedure and synchronization is realized without the need of an extra step of synchronization between access point MR. Overhead and latency is reduced.

[0032] A possible embodiment of the invention is characterized in that wherein the received WUS comprises a second synchronization signal (SSS) symbol; wherein WUR reports SSS to MR and MR performs fine synchronization using the primary offset, SSS and the timing offset and switches to operation mode. Thus, synchronization accuracy is increased.

[0033] Another possible embodiment of the invention is characterized in that wherein the received WUS comprises a second validation symbol WuS#2; after realizing correlation on first validation symbol WuS#1 , extracting WuS#2 from WUS and realizing validation on WuS#2. Thus, validation accuracy is increased. This reduces false wake up procedures, which causes energy consumption further.

[0034] Another possible embodiment of the invention is characterized in that wherein second validation symbol WuS#2 and the PSS symbol are in the same symbol.

[0035] Another possible embodiment of the invention is characterized in that wherein at least a guard symbol is provided between the PSS and the SSS. Thus, reducing interference.

[0036] Also the present invention relates to a user equipment comprising a main radio which is configured to operate in an idle mode and in an operating mode and a wake up radio which is configured to transmit a trigger signal to main radio for triggering operating mode characterized in that wherein the user equipment is configured to realize a method in one of the claims 1 -5. Another possible embodiment of the invention is characterized in that transmitting a wake up signal (WUS) comprising at least a first validation symbol WuS#1 , a second validation symbol WuS#2 and at least a primary synchronization signal (PSS) symbol.

[0037] Another possible embodiment of the invention is characterized in that wherein the transmitted WUS comprises a second synchronization signal (SSS) symbol.

[0038] Another possible embodiment of the invention is characterized in that the method according to one preceding claims characterized in that wherein second validation symbol WuS#2 and the PSS symbol are in the same symbol.

[0039] Another possible embodiment of the invention is characterized in that the method according to one preceding claims characterized in that wherein at least a guard symbol is provided between the PSS and the SSS.

[0040] Another possible embodiment of the invention is characterized in that an access point which is configured to realize a method in one of the claims 7 to 1 1

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a drawing illustrating top schematic view of the system.

[0043] Figure 2a is a drawing depicting proposed WuS frame.

[0044] Figure 2a is a drawing depicting alternative WuS frame.

[0045] Figure 3 is a drawing illustrating the time-line of the third embodiment of the subject matter method.

[0046] Figure 4 is a drawing illustrating the third embodiment of the subject matter method.

[0047] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0048] 100 User equipment

[0049] 110 WUR (Wake up radio) 120 MR (Main radio)

[0050] 200 Access point

[0051] 300 WUS (Wake up signal)

[0052] DETAILED DESCRIPTION OF THE INVENTION

[0053] In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

[0054] Referring to figure 1 , an access point (200) is in communication with a user equipment (100). User equipment (100) comprises at least a main radio (MR (120)) for realizing communication with the access point (200). User equipment (100) comprises a wake up radio (WUR (110)) for receiving a wake up signal (WUS (300)) form access point (200). MR (120) operates in an operation mode and an idle mode. WUR (1 10) triggers MR (120) to wake up- operate in operating mode- and MR (120) synchronizes itself to access point (200) in order to realize communication. Access point (200) may for instance be a base station. User equipment (100) may for instance be a mobile phone and other terminals that uses MR (120) and WUR (110) in order to communicate with the access point (200).

[0055] In a first embodiment of the invention access point (200) transmits a wake up signal (WUS (300)). Wake up signal (300) directed to certain user equipment (100). WUS (300) are known in the art and it consists of multiple symbols. WUS (300) in the present invention comprises at least a first validation symbol WuS#1 , a second validation symbol WuS#2 and at least a primary synchronization signal symbol (PSS).

[0056] WUR (1 10) receives WUS (300). WUR (110) realizes a correlation on WuS#1 for determining if the WUS (300) is sent for the user equipment (100). If it is determined that WUS (300) is sent for the user equipment (100), i.e. the correlation results with a validation, WUR (110) extracts WuR#2 and checks its validation. WUR (1 10) performs a primary synchronization using the PSS symbol and determines a primary offset. This offset defines offset between WUR (1 10) and the access point (200). Then WUR (110) transmits a trigger signal to MR (120) to indicate to operate in the operating mode.

[0057] MR (120) executes an offset calibrating process, wherein the offset calibrating process includes transmitting a predetermined signal so that WuR (1 10) determines a timing offset between the MR (120) and the WUR (1 10). Offset calibrating process may be over the air pre distortion (OTAP) process. OTAP process is well-known in the art. Timing offset defines the offset between the MR and the WUR (110). Said predetermined signal is known on both MR (120) and WUR (110) side. The term known indicates that the signal is pre-recorded on both sides and they are programmed to use it in OTAP process. WUR (1 10) then reports timing offset and the primary offset to MR (120). MR (120), performs a fine synchronization using the primary offset and the timing offset, and starts operating in operation mode.

[0058] In a second embodiment of the invention, access point (200) transmits a wake up signal (WUS (300)). WUS (300) in the second embodiment of the invention comprises at least a first validation symbol WuS#1 and at least a primary synchronization signal (PSS) symbol and a second synchronization signal (SSS) symbol. WUR (1 10) receives WUS (300). WUR (110) realizes a correlation on WuS#1 for determining if the WUS (300) is sent for the user equipment (100). If it is determined that WUS (300) is sent for the user equipment (100), i.e. the correlation results with a validation, WUR (1 10) performs a primary synchronization using the PSS symbol and determines a primary offset. Then WUR (1 10) transmits a trigger signal to MR (120) to indicate to operate in the operating mode.

[0059] MR (120) executes an over-the-air pre-distortion (OTAP) process, wherein the OTAP process includes transmitting a predetermined signal so that WUR (1 10) determines a timing offset between the MR (120) and the WUR (110). WUR (1 10) then reports timing offset, SSS symbol and the primary offset to MR (120). MR (120), performs a fine synchronization using the primary offset, SSS symbol and the timing offset, and starts operating in operation mode. Since offset (primary offset) between access point (200) and the WUR (1 10) is known and also the offset (timing offset) between is known, MR (120) can synchronize itself with the access point (200) since it can calculate total offset between MR (120) and the access point (200). SSS symbol increases accuracy of the synchronization.

[0060] MR (120) executes an over-the-air pre-distortion (OTAP) process, wherein the OTAP process includes transmitting a predetermined signal so that WuR (1 10) determines a timing offset between the MR (120) and the WuR (1 10). WUR (1 10) then reports timing offset, and the primary offset to MR (120). MR (120), performs a fine synchronization using the primary offset, and the timing offset, and starts operating in operation mode. Since offset (primary offset) between access point (200) and the WUR (1 10) is known and also the offset (timing offset) between is known, MR (120) can synchronize itself with the access point (200) since it can calculate total offset between MR (120) and the access point (200). This method reduces the rate of false wake-up actions.

[0061] In a third embodiment, referring to figure 3 and 4, access point (200) transmits a wake up signal (WUS (300)). WUS (300) in the second embodiment of the invention comprises at least a first validation symbol WuS#1 and at least a primary synchronization signal (PSS) symbol, SSS symbol and a second validation symbol WuS#2. WUR (1 10) receives WUS (300). WUR (110) realizes a correlation on WuS#1 for determining if the WUS (300) is sent for the user equipment (100). WUR (1 10) extracts WuR#2 and checks its validation. If it is determined that WUS (300) is sent for the user equipment (100), i.e. the correlation results with a validation and WuS#2 is validated, WUR (110) performs a primary synchronization using the PSS symbol and determines a primary offset. Then WUR (110) transmits a trigger signal to MR (120) to indicate to operate in the operating mode.

[0062] MR (120) executes an over-the-air pre-distortion (OTAP) process, wherein the OTAP process includes transmitting a predetermined signal so that WuR (1 10) determines a timing offset between the MR (120) and the WuR (110). WUR (1 10) then reports timing offset, SSS symbol and the primary offset to MR (120). MR (120), performs a fine synchronization using the primary offset, SSS symbol and the timing offset, and starts operating in operation mode. This method greatly reduces rate of false wake-up actions, increases accuracy of synchronization. Referring to figure 2a, PSS and WuS#2 may be provided in the same symbol. Referring to figure 2b, PSS and WuS#2 may be provided in different symbols. A guard may be provided between SSS symbol and the PSS symbol for preventing interference. Guard specifically may be provided between WuS#2 and the SSS symbol. This guard will not allow interference between the WuS (300) frame and the transmitted signal of the MR (120) and permit the WuR (110) to report the offset to the MR (120) since the latency is minimum and the signal in known to both ends.

[0063] In the method, OFDM waveform may be adapted as wake-up signal. Other waveforms may be used such as OTFS, OCDM, AFDM, etc. as long as they comprise mentioned features.

[0064] Similar to 5G NR adopted frame, the WuS (300) frame may use a primary synchronization signal (PSS) and secondary synchronization signal (SSS) at the second and fifth symbols, respectively. The WuS (300) incorporates a high correlation sequence at the first symbol WuS#1 used for time-correlation to perform first verification of the validity of the WuS (300) intended for that specific UE. Then if the sequence is valid, the WuR (110) leverages the PSS on the second symbol to perform primary synchronization and extract WuS (300) ID and / or payload. The WuS (300) ID / payload are simple and not complex (low-order modulation for example) the PSS is sufficient.

[0065] The proposed method may use correlation sequences such as Zad-off chu. Method may use other correlation sequences as long as it has high correlation properties. As a WuS#1 as a first stage check and information / payload WuS#2 embedded into the WuS (300) to get double verification of the intended WuS (300) to avoid false wake-up interrupts, this can be seen as a two-stage wake-up verification mechanism.

[0066] The proposed method uses a specific design of the WuS (300) frame without great modifications from the existing 5G frame to use for both MR (120) and WuR (1 10) synchronization using only the WuS (300) while achieving minimum latency, overhead and complexity.

[0067] Mentioned predetermined signal is a low power signal.

[0068] The transmission between device internal components considered that it does not exceed 20 micro-seconds, thus the latency caused by it, is not an issue.

[0069] The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

Claims

CLAIMS1. A method of operating a user equipment (100) comprising a main radio (120) which is configured to operate in an idle mode and in an operating mode and a wake up radio (110) which is configured to transmit a trigger signal to main radio (120) for triggering operating mode characterized in that comprising the steps of:- by WUR (1 10) receiving a wake up signal (WUS (300)) comprising at least a first validation symbol WuS#1 , a second validation symbol WuS#2 and at least a primary synchronization signal (PSS) symbol;- by WUR (1 10) realizing a correlation on the first validation symbol WuS#1 and determining whether to trigger the MR (120);- extracting WuS#2 from WUS (300) and realizing validation on WuS#2. by WUR (1 10) performing a primary synchronization using PSS symbol and determining a primary offset;- by WUR (1 10) transmitting a trigger signal to MR (120);- by MR (120) executing an offset calibrating process, wherein the offset calibrating process includes transmitting a predetermined signal so that WuR (110) determines a timing offset between the MR (120) and the WuR (110);- by WUR (1 10) reporting determined timing offset and the primary offset; by the MR (120) performing a fine synchronization using the primary offset and the timing offset and switching to operation mode.

2. The method according to claim 1 , characterized in that wherein the received WUS (300) comprises a second synchronization signal (SSS) symbol; wherein WUR (110) reports SSS to MR (120) and MR (120) performs fine synchronization using the primary offset, SSS and the timing offset and switches to operation mode.

3. The method according to one preceding claims characterized in that wherein second validation symbol WuS#2 and the PSS symbol are in the same symbol.

4. The method according to one preceding claims characterized in that wherein at least a guard symbol is provided between the PSS and the SSS.

5. The method according to one preceding claims characterized in that the offset calibrating process is over the air pre distortion (OTAP) process.

6. A user equipment (100) comprising a main radio (120) which is configured to operate in an idle mode and in an operating mode and a wake up radio (1 10) which is configured to transmit a trigger signal to main radio (120) for triggering operating mode characterized in that wherein the user equipment (100) is configured to realize a method in one of the claims 1 -5.

7. A method of operating an access point (200) characterized in that transmitting a wake up signal (WUS (300)) comprising at least a first validation symbol WuS#1 , a second validation symbol WuS#2 and at least a primary synchronization signal (PSS) symbol.

8. The method according to one of the claims 7 characterized in that wherein the transmitted WUS (300) comprises a second synchronization signal (SSS) symbol.

9. The method according to one of the claims 6 to 8 claims characterized in that wherein second validation symbol WuS#2 and the PSS symbol are in the same symbol.

10. The method according to one of the of the claims 6 to 9 characterized in that wherein at least a guard symbol is provided between the PSS and the SSS.

11. An access point (200) which is configured to realize a method in one of the claims 6 to 10.

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