WO2021156659A1

WO2021156659A1 - Apparatus and method for cyclic prefix-based time and/or frequency correction

Info

Publication number: WO2021156659A1
Application number: PCT/IB2020/058538
Authority: WO
Inventors: Jian Gu; Yuanye WANG; Ping Hou
Original assignee: Zeku Inc.
Priority date: 2020-02-07
Filing date: 2020-09-15
Publication date: 2021-08-12
Also published as: CN115176446A; CN115176446B

Abstract

Embodiments of apparatus and method for cyclic prefix (CP)-based time and frequency correction are disclosed. In an example, a symbol including a CP and a payload is received. The CP is detected, and an auto-correlation of the CP and the payload is performed. At least one of a time or a frequency of the received symbol is adjusted based on a result of the auto-correction.

Description

APPARATUS AND METHOD FOR CYCLIC PREFIX-BASED TIME AND/OR FREQUENCY

CORRECTION

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/971,608 filed February 07, 2020, entitled “POWER SAVING METHOD FOR CP-OFDM BASED SIGNAL WITH DISCONTINUOUS RECEPTION,” which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Embodiments of the present disclosure relate to apparatus and method for wireless communication. [0003] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Orthogonal frequency division multiplexing (OFDM) is one of the most widely used and adopted digital multi-carrier modulation methods and has been used extensively for cellular communications, such as 4th-generation (4G) Long Term Evolution (LTE) and 5th-generation (5G) New Radio (NR). One version of OFDM, for example, used in 4G LTE, is cyclic prefix OFDM (CP-OFDM), which has a waveform format that is designed to overcome the inter-symbol interference (ISI) resulting from delays and reflections.

[0004] Discontinuous reception (DRX) mode is a method used in mobile communication to conserve the battery of the mobile device. The periodic repetitions of “sleep mode and wake-up mode” would greatly reduce the power consumption of the user equipment (UE) for receiving data from the network.

SUMMARY

[0005] Embodiments of apparatus and method for wireless communication with cyclic prefix (CP)-based time and frequency correction are disclosed herein.

[0006] In one example, an apparatus includes at least one processor and memory storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to receive a symbol including a CP and a payload. The instructions, when executed by the at least one processor, also cause the apparatus to detect the CP and perform an auto-correlation of the CP and the payload. The instructions, when executed by the at least one processor, further cause the apparatus to adjust at least one of time or a frequency of the received symbol based on a result of the auto-correction.

[0007] In another example, a baseband chip includes an interface and a time and frequency correction circuit operatively coupled to the interface is disclosed. The interface is configured to receive the OFDM symbol including a CP and a payload. The time and frequency correction circuit is configured to detect the CP and perform an auto-correlation of the CP and the payload. The time and frequency correction circuit is also configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto correction.

[0008] In further another example, an apparatus for wireless communication includes a data processing module and a time and frequency correction module is disclosed. The data processing module is configured to receive an OFDM symbol including a CP and a payload. The time and frequency correction module is configured to detect the CP and perform an auto-correlation of the CP and the payload. The time and frequency correction module is also configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction. The data processing module is further configured to process the OFDM symbol based on the adjusted time or frequency.

[0009] In still another example, a method for time and/or frequency correction is disclosed. A symbol including a CP and a payload is received. The CP is detected and an auto-correlation of the CP and the payload is performed. At least one of a time or a frequency of the received symbol is adjusted based on a result of the auto-correction.

[0010] In yet another example, a non-transitory computer-readable medium encoded with instructions that, when executed by at least one processor of a terminal device, perform a process is disclosed. The process includes receiving a symbol including a CP and a payload. The process also includes detecting the CP and performing an auto-correlation of the CP and the payload. The process further includes adjusting at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

[0011] In also another example, a device for time and/or frequency correction includes a receiving module, a detecting module, an auto-correlation module and a time or a frequency correction module is disclosed. The receiving module is configured to receive the OFDM symbol comprising a cyclic prefix (CP) and a payload. The detecting module is configured to detect the CP. The auto-correlation module is configured to perform an auto-correlation of the CP and the payload. The time or a frequency correction module is configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the pertinent art to make and use the present disclosure.

[0013] FIG. 1 illustrates an exemplary wireless network, according to some embodiments of the present disclosure.

[0014] FIG. 2 illustrates a detailed block diagram of an exemplary wireless communication system with CP- based time and frequency correction, according to some embodiments of the present disclosure.

[0015] FIG. 3A illustrates a schematic diagram of an exemplary CP adding process applied to a stream of OFDM symbols, in the wireless communication system in FIG. 2, according to some embodiments of the present disclosure.

[0016] FIG. 3B illustrates an auto-correlation result of a CP and a payload in the time domain, in the wireless communication system in FIG. 2, according to some embodiments of the present disclosure.

[0017] FIG. 4 illustrates timing diagrams of exemplary time and frequency corrections performed upon wake- up of receiving device, in the wireless communication system in FIG. 2, according to some embodiments of the present disclosure.

[0018] FIGs. 5A and 5B illustrate block diagrams of an exemplary apparatus including a host chip, a radio frequency (RF) chip, and a baseband chip implementing the wireless communication system in FIG. 2 in software and hardware, respectively, according to some embodiments of the present disclosure.

[0019] FIG. 6 illustrates a flow chart of an exemplary method for CP-based time and frequency correction, according to some embodiments of the present disclosure.

[0020] FIG. 7 illustrates a flow chart of an exemplary method for auto-correlation for the CP-based time and frequency correction method in FIG. 6, according to some embodiments of the present disclosure.

[0021] FIG. 8 illustrates a flow chart of another exemplary method for CP-based time and frequency correction, according to some embodiments of the present disclosure.

[0022] FIG. 9 illustrates a block diagram of an exemplary receiving device, according to some embodiments of the present disclosure.

[0023] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

DETAILED DESCRIPTION

[0024] Although specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present disclosure. It will be apparent to a person skilled in the pertinent art that the present disclosure can also be employed in a variety of other applications.

[0025] It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “some embodiments,” “certain embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of a person skilled in the pertinent art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. [0026] In general, terminology may be understood at least in part from usage in context. For example, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures or characteristics in a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context.

[0027] Various aspects of wireless communication systems will now be described with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, units, components, circuits, steps, operations, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, firmware, computer software, or any combination thereof. Whether such elements are implemented as hardware, firmware, or software depends upon the particular application and design constraints imposed on the overall system.

[0028] The techniques described herein may be used for various wireless communication networks, such as code division multiple access (CDMA) system, time division multiple access (TDMA) system, frequency division multiple access (FDMA) system, orthogonal frequency division multiple access (OFDMA) system, single -carrier frequency division multiple access (SC-FDMA) system, and other networks, including but not limited to 4G LTE, and 5G NR cellular networks. The terms “network” and “system” are often used interchangeably. The techniques described herein may be used for the wireless networks mentioned above, as well as other wireless networks.

[0029] Discontinuous reception (DRX) is a method used in mobile communication to conserve the battery of the mobile device. The periodic repetitions of “sleep mode and wake-up mode” would greatly reduce the power consumption of the user equipment (UE) for receiving data from the network. To reduce the power consumed by a UE, the UE stops listening on a channel and stays in a sleep mode (i.e., idle mode) for a period of time and wakes up for an interval. During the sleep (e.g., the period for being in sleep mode), the main clock (e.g., the high-resolution clock source and part of the processor associated with the clock) for the UE to ensure synchronization is turned off. Thus, a time and/or frequency drift may happen meanwhile because of the sleep.

[0030] To perform the time and frequency correction (i.e., synchronization) after wake-up from the sleep mode, in conventional discontinuous reception (DRX) technologies, extra wake-up time is needed for receiving reference signal(s) based on which the time and frequency correction is performed.

[0031] For example, in 4G and LTE scenarios, when the UE wakes up from the sleep mode, it turns on the RF module before the Paging Occasion (PO) or on-duration when the modulated symbol corresponding to original data is received (e.g., before the PO when the UE was in radio resource control (RRC)-idle mode, or before the on-duration when the UE was in RRC -connected mode). In some embodiments, the time and frequency correction is performed based on cell specific reference signal(s) (CRS(s)), and the extra wake-up duration is one or several LTE/4G subframes for receiving the CRS. Using the CRS-based algorithms, the UE can perform channel estimation based on the CRS, and the time and frequency correction can be performed based on the channel estimation.

[0032] In some other embodiments, if the time and/or frequency drift is higher than what the CRS can track, a primary synchronization signal (PSS), a secondary synchronization signal (SSS) based cell search may be performed. Accordingly, extra wake-up (e.g., before the time slot of PO or on-duration) may be needed for reception of the PSS/SSS.

[0033] For another example, in 5G scenarios, the time and frequency correction may be performed based on synchronization signal blocks (SSBs). The SSB has a duration of 4 symbols and may not be aligned with the PO or on-duration. Accordingly, the UE may need to perform extra wake-up to receive SSB in order to correct the time and frequency error based on SSB. All of the above extra wake-up times cause extra UE power consumption for performing time and frequency correction.

[0034] Various embodiments in accordance with the present disclosure provide systems and methods for time and frequency correction based on the CP of the received symbol. The CP of the symbol may be an exact copy of the last portion (e.g., for a predetermined length such as 16 samples, 128 samples, etc.) of the symbol, copied to the front of the signal. The CP is designed to overcome the inter-symbol interference (ISI) resulting from delays and reflections (e.g., multipath interference). The time and frequency correction may be performed based on detecting the CP of the symbol and performing an auto-correlation of the CP and the payload of the symbol. As a result, no extra wake-up is needed for time and frequency correction, and the power consumption of the UE can be reduced desirably.

[0035] The time or the frequency of the symbol is adjusted based on the peak(s) of the auto-correlation. Because the CP is the copy of the last portion of the symbol (e.g., the last portion of the payload), ideally, the highest peak of the auto-correlation in the time domain between the CP and the payload can provide information about a time error (e.g., indicates the end position of the symbol with a drift), and a phase of the peak in the frequency domain can provide information about a frequency error. Based on detecting the end position of the symbol, the time and frequency correction can be performed for the symbol. In some embodiments, the time and frequency drift of the symbol can be corrected according to the communication protocol used for transmitting the symbol. For example, the time and frequency drift of the symbol can be corrected based on a time and frequency of the symbol indicated by the result of the auto-correlation, according to a sampling frequency predetermined (e.g., predetermined based on the communication protocol) for demodulating the symbol.

[0036] In some embodiments, because of the interferences, such as the inter-symbol interference (ISI) and the multipath interference, more than one peaks above a threshold (e.g., set to make sure the peak is not caused by some random similarities within the payload of the symbol) may be detected in the correlation. For example, because of the multipath issues, one or more delayed copies of the symbol may be received, and a peak may show up where the end of the delayed copies is. In some embodiments, because the delayed copies are received with a delay because of the long transmission path, the earliest peak above the threshold may be selected for positioning the end of the symbol. In some other embodiments, because the delayed copies are reflected by surrounding objects, the peaks indicating the end of the delayed copies may be weaker (e.g., have a smaller amplitude in the auto-correlation result) comparing to the peak indicating the end of the received symbol. Thus, the strongest peak (e.g., the highest peak in the auto-correlation result) may be selected for positioning the end of the symbol.

[0037] In some embodiments, the length of the CP (e.g., the bits or the time span) may not be enough to cover the influence caused by ISI. For example, a time span of the more than one peaks above the threshold is longer than the time span of the CP (e.g., the time span between the first peak and the last peak of the more than one peaks is longer than the time span of the CP). In some embodiments, the received symbol may be converted to a number of copies according to the number of peaks above the threshold that is at least apart from each other by the time span of the CP. The time and frequency correction (e.g., performing correlation for the CP and the payload of each copy) may be performed on each copy of the symbol, respectively, and each copy may be processed (e.g., converted from the time domain to the frequency domain, demodulate each copy, etc.) respectively based on the adjusted time or frequency of that copy. The output of the demodulation process may be selected from the processed copies based on a metric (e.g., quality of the copy such as a signal- to-noise ratio (SNR)) of each of the processed copies.

[0038] In some embodiments, when no valid CP is detected, or no peak above the threshold can be detected (e.g., because of the quality of the received symbol is not good), the symbol may be processed without the time and frequency correction being performed (e.g., with the default timing), or with an alternative method for performing the time and frequency correction (e.g., using one of the reference signal-based the time and frequency correction methods in conventional DRX technologies).

[0039] In some embodiments, the condition of the received symbol may also be used for determining activities for the subsequent wake-up, such as the time and frequency correction method to be performed, and/or a starting time point of the subsequent wake-up (e.g., if an extra wake-up is needed for receiving the reference signal(s)).

[0040] FIG. 1 illustrates an exemplary wireless network 100, in which certain aspects of the present disclosure may be implemented, according to some embodiments of the present disclosure. As shown in FIG. 1, wireless network 100 may include a network of nodes, such as a UE 102, an access node 104, and a core network element 106. User equipment 102 may be any terminal device, such as a mobile phone, a desktop computer, a laptop computer, a tablet, a vehicle computer, a gaming console, a printer, a positioning device, a wearable electronic device, a smart sensor, or any other device capable of receiving, processing, and transmitting information, such as any member of a vehicle to everything (V2X) network, a cluster network, a smart grid node, or an Internet-of-Things (IoT) node. It is understood that user equipment 102 is illustrated as a mobile phone simply by way of illustration and not by way of limitation.

[0041] Access node 104 may be a device that communicates with UE 102, such as a wireless access point, a base station (BS), a Node B, an enhanced Node B (eNodeB or eNB), a next-generation NodeB (gNodeB or gNB), a cluster master node, or the like. Access node 104 may have a wired connection to UE 102, a wireless connection to UE 102, or any combination thereof. Access node 104 may be connected to UE 102 by multiple connections, and UE 102 may be connected to other access nodes in addition to access node 104. Access node 104 may also be connected to other UEs. It is understood that access node 104 is illustrated by a radio tower by way of illustration and not by way of limitation.

[0042] Core network element 106 may serve access node 104 and user equipment 102 to provide core network services. Examples of core network element 106 may include a home subscriber server (HSS), a mobility management entity (MME), a serving gateway (SGW), or a packet data network gateway (PGW). These are examples of core network elements of an evolved packet core (EPC) system, which is a core network for the LTE system. Other core network elements may be used in LTE and in other communication systems. In some embodiments, core network element 106 includes an access and mobility management function (AMF) device, a session management function (SMF) device, or a user plane function (UPF) device, of a core network for the NR system. It is understood that core network element 106 is shown as a set of rack mounted servers by way of illustration and not by way of limitation.

[0043] Core network element 106 may connect with a large network, such as the Internet 108, or another Internet Protocol (IP) network, to communicate packet data over any distance. In this way, data from user equipment 102 may be communicated to other user equipment connected to other access points, including, for example, a computer 110 connected to Internet 108, for example, using a wired connection or a wireless connection, or to a tablet 112 wirelessly connected to Internet 108 via a router 114. Thus, computer 110 and tablet 112 provide additional examples of possible user equipment, and router 114 provides an example of another possible access node.

[0044] A generic example of a rack-mounted server is provided as an illustration of core network element 106. However, there may be multiple elements in the core network including database servers, such as a database 116, and security and authentication servers, such as an authentication server 118. Database 116 may, for example, manage data related to user subscription to network services. A home location register (HLR) is an example of a standardized database of subscriber information for a cellular network. Likewise, authentication server 118 may handle authentication of users, sessions, and so on. In the NR system, an authentication server function (AUSF) device may be the specific entity to perform user equipment authentication. In some embodiments, a single server rack may handle multiple such functions, such that the connections between core network element 106, authentication server 118, and database 116, may be local connections within a single rack.

[0045] As described below in detail, in some embodiments, wireless communication can be established between any suitable nodes in wireless network 100, such as between UE 102 and access node 104, and between UE 102 and core network element 106 for sending and receiving data (e.g., OFDM symbol(s)). A transmitting node may generate the OFDM symbol(s) (e.g., performing mapping, serial to parallel, inverse Fast Fourier transform (IFFT), CP adding, parallel to serial, etc.) and transmit the symbol to a receiving device (e.g., a UE). When the receiving device wakes up from the sleep mode and receives the symbol, the receiver may detect the CP, perform an auto-correlation of the CP and the payload of the symbol, and adjust at least one of a time or a frequency of the symbol based on a result of the auto-correction.

[0046] Each node of wireless network 100 in FIG. 1 that is suitable for DRX may be considered a receiving device. More detail regarding the possible implementation of a receiving device is provided by way of example in the description of a receiving device 900 in FIG. 9. Receiving device 900 may be configured as user equipment 102, access node 104, or core network element 106 in FIG. 1. Similarly, receiving device 900 may also be configured as computer 110, router 114, tablet 112, database 116, or authentication server 118 in FIG. 1. As shown in FIG. 9, receiving device 900 may include a processor 902, a memory 904, and a transceiver 906. These components are shown as connected to one another by a bus, but other connection types are also permitted. When receiving device 900 is user equipment 102, additional components may also be included, such as a user interface (UI), sensors, and the like. Similarly, receiving device 900 may be implemented as a blade in a server system when receiving device 900 is configured as core network element 106. Other implementations are also possible.

[0047] Transceiver 906 may include any suitable device for sending and/or receiving data. Receiving device 900 may include one or more transceivers, although only one transceiver 906 is shown for simplicity of illustration. An antenna 908 is shown as a possible communication mechanism for receiving device 900. If the communication is MIMO, multiple antennas and/or arrays of antennas may be utilized for. Additionally, examples of receiving device 900 may communicate using wired techniques rather than (or in addition to) wireless techniques. For example, access node 104 may communicate wirelessly to user equipment 102 and may communicate by a wired connection (for example, by optical or coaxial cable) to core network element 106. Other communication hardware, such as a network interface card (NIC), may be included as well. [0048] As shown in FIG. 9, receiving device 900 may include processor 902. Although only one processor is shown, it is understood that multiple processors can be included. Processor 902 may include microprocessors, microcontrollers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field- programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout the present disclosure. Processor 902 may be a hardware device having one or more processing cores. Processor 902 may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Software can include computer instructions written in an interpreted language, a compiled language, or machine code. Other techniques for instructing hardware are also permitted under the broad category of software.

[0049] As shown in FIG. 9, receiving device 900 may also include memory 904. Although only one memory is shown, it is understood that multiple memories can be included. Memory 904 can broadly include both memory and storage. For example, memory 904 may include random-access memory (RAM), read-only memory (ROM), static RAM (SRAM), dynamic RAM (DRAM), ferro-electric RAM (FRAM), electrically erasable programmable ROM (EEPROM), CD-ROM or other optical disk storage, hard disk drive (HDD), such as magnetic disk storage or other magnetic storage devices, Flash drive, solid-state drive (SSD), or any other medium that can be used to carry or store desired program code in the form of instructions that can be accessed and executed by processor 902. Broadly, memory 904 may be embodied by any computer-readable medium, such as a non-transitory computer-readable medium.

[0050] Processor 902, memory 904, and transceiver 906 may be implemented in various forms in receiving device 900 for performing wireless communication with CP-based time and frequency correction functions. In some embodiments, processor 902, memory 904, and transceiver 906 of receiving device 900 are implemented (e.g., integrated) on one or more system-on-chips (SoCs). In one example, processor 902 and memory 904 may be integrated on an application processor (AP) SoC (sometimes known as a “host,” referred to herein as a “host chip”) that handles application processing in an operating system environment, including generating raw data to be transmitted. In another example, processor 902 and memory 904 may be integrated on a baseband processor (BP) SoC (sometimes known as a modem, referred to herein as a “baseband chip”) that converts the raw data, e.g., from the host chip, to signals that can be used to modulate the carrier frequency for transmission, and vice versa, which can run a real-time operating system (RTOS). In still another example, processor 902 and transceiver 906 (and memory 904 in some cases) may be integrated on an RF SoC (sometimes known as a transceiver, referred to herein as a “RF chip”) that transmits and receives RF signals with antenna 908. It is understood that in some examples, some or all of the host chip, baseband chip, and RF chip may be integrated as a single SoC. For example, a baseband chip and an RF chip may be integrated in a single SoC that manages all the radio functions for cellular communication.

[0051] Various aspects of the present disclosure related to time and frequency correction may be implemented as software and/or firmware elements executed by a generic processor in a baseband chip (e.g., a baseband processor). It is understood that in some examples, one or more of the software and/or firmware elements may be replaced by dedicated hardware components in the baseband chip, including integrated circuits (ICs), such as application-specific integrated circuits (ASICs). Mapping to the wireless communication (e.g., 4G, LTE, 5G, etc.) layer architecture, the implementation of the present disclosure may be at Layer 1, e.g., the physical (PHY) layer.

[0052] FIG. 2 illustrates a detailed block diagram of an exemplary wireless communication system 200 with CP-based time and frequency correction, according to some embodiments of the present disclosure. Wireless communication system 200 may be used between suitable nodes in wireless network 100. As shown in FIG. 2, wireless communication system 200 may include a transmitting device 201 and a receiving device 202. For example, transmitting device 201 may be an example of user equipment 102, access node 104, or core network element 106, and receiving device 202 may be an example of user equipment 102 or core network element 106 of wireless network 100 in FIG. 1. Wireless communication system 200 may be used for saving the power consumption of receiving device 202 and increase the accuracy of wireless communication by providing better synchronization performance. Both transmitting device 201 and receiving device 202 may include a processor, a memory, and a transceiver, which may be examples of processor 902, memory 904, and transceiver 906 described above in detail, respectively, with respect to FIG. 9.

[0053] As shown in FIG. 2, transmitting device 201 may process the original data (e.g., process the input data through various function stages of data modulation, mapping, IFFT, CP adding, etc.) and may transmit the processed data (e.g., the OFDM symbols) to receiving device 202. Receiving device 202 may receive the symbol, perform the time and frequency correction and detect the original data (e.g., the decoded bits) through reverse processes, such as demodulation, de -mapping, CP removal, FFT, etc.

[0054] As shown in FIG. 2, transmitting device 201 may include a data mapping module 210, an OFDM modulation module 220, and a CP adding module 230 for processing the original data to be transmitted.

[0055] For example, data mapping module 210 may apply a mapper (e.g., quadrature phase shift keying (QPSK)) to group information bits of the original data into symbols. In OFDM modulation module 220, an IFFT (e.g., when the number of sub-carriers is 2") or an inverse discrete Fourier Transform (IDFT) may be applied to the symbol to keep the sub-carrier remaining orthogonal. CP adding module 230 may add the CP to the symbol by taking and coping the last portion with a predetermined length (e.g., the number of bits) of the symbol, to the front of the symbol. For example, FIG. 3A illustrates a schematic diagram of an exemplary CP adding process applied to a symbol stream 302 of OFDM symbols 304, according to some embodiments of the present disclosure.

[0056] As illustrated in FIG. 3A, each OFDM symbol 304 may include a payload 306 carrying data and a CP 308 at the beginning of OFDM symbol 304. In some embodiments, the last portion of payload 306 is inserted at the beginning of payload 306 of OFDM symbol 304 as CP 308. In some embodiments, CP 308 may serve as a guard interval preventing ISI between successive OFDM symbols 304.

[0057] Referring back to FIG. 2, the OFDM symbol may be transmitted to receiving device 202 through a channel (e.g., the communication link(s) between transmitting device 201 and receiving device 202). When receiving device 202 wakes up from the sleep mode, upon receiving the OFDM symbol, CP-based time and frequency correction module 240 may perform a time and frequency correction based on performing an auto correlation of the CP (e.g., CP 308) and the payload (e.g., payload 306) of the OFDM symbol (e.g., OFDM symbol 304).

[0058] For example, FIG. 4 illustrates timing diagrams of exemplary time and frequency corrections performed upon wake-up of receiving device 202, according to some embodiments of the present disclosure. As illustrated in FIGs. 4a)-4c), in conventional DRX technologies where conventional time and frequency correction schemes are performed, extra wake-up period (e.g., the wake-up in addition to PO or on-duration) in the DRX period (e.g., the time span from the beginning of a PO or on-duration to the beginning of a next PO or on-duration) is needed for receiving reference signal(s) (e.g., CRS, PSS/SSS, SSB, etc.) for performing time and frequency correction. As a result, extra power consumption is needed for the UE (e.g., receiving device 202) to adjust the time or frequency accordingly.

[0059] As shown in FIG. 4d), for the same DRX period, performing CP-based time and frequency correction would require no extra wake-up period, as the CP is aligned with the payload of the OFDM symbol. Thus, this can largely reduce the power consumption of receiving device 202. Moreover, comparing to other auto correlation based time and frequency detection, where the whole OFDM symbol is used for correlation, using the CP (e.g., with much less bits than bits of the whole OFDM symbol) to perform the correlation with the payload of the OFDM symbol (will be described in detail along with the description of FIG. 3B below) would further save a lot of computational resources for performing time and frequency correction.

[0060] Referring back to FIG. 2, CP-based time and frequency correction module 240 may include a CP detection unit 242, an auto-correlation unit 244, and a time and frequency correction unit 246. In some embodiments, CP detection unit 242 may detect the CP (e.g., CP 308 in FIG. 3A) upon receiving the OFDM symbol (e.g. OFDM symbol 304). Auto-correlation unit 224 may start to perform an auto-correlation for the CP (e.g., CP 308) and the payload (e.g., payload 306) when starting to receive the payload of the OFDM symbol (e.g., OFDM symbol 304). For example, FIG. 3B illustrates an auto-correlation result of CP 308 and payload 306 in the time domain, according to some embodiments of the present disclosure. In FIG. 3B, the “T” axis represents the time, and the “Amplitude” axis represents the amplitude of the auto-correlation result. T₀ represents the end time point for OFDM symbol 304. As illustrated in FIG. 3B, when the correlation window moves from the beginning of payload 306 to the end of payload 306, a peak above a threshold (e.g., set to avoid peaks caused by some random similarities within the portions of the OFDM symbol) may indicate the position of the end of OFDM symbol 304 because CP 308 is an exact copy of the last portion of payload 306. In some embodiments, multiple peaks in the auto-correlation result may be above the threshold. For example, because of the interferences, such as the ISI and the multipath interference, delayed copies of the symbol may be received. As the delayed copies of the symbol have weaker energy (e.g., being reflected and thus lost part of the energy), the peak with the highest amplitude (e.g., corresponding to the strongest received symbol) may be used to indicate the position of the end of OFDM symbol 304. [0061] Referring back to FIG. 2, based on the position of the end of the OFDM symbol, time and frequency correction unit 246 may adjust the time or frequency of the OFDM symbol to correct the time and/or frequency drift caused by being in the sleep mode accordingly.

[0062] In some embodiments, the OFDM symbol with the adjusted time or frequency may be transmitted to data processing module 250 for extracting the original data. For example, data processing module 250 may convert the adjusted OFDM symbol from the time domain to the frequency domain using fast Fourier transform (FFT), and may demodulate and de-map the symbol using channels such as physical downlink control channel (PDCCH) receiver and/or physical downlink shared channel (PDSCH) receiver based on the adjusted time or frequency. The original data (e.g., data input of transmitting device 201) may be the output of data processing module 250.

[0063] In some embodiments, because of the interferences, such as the ISI and the multipath interference, more than one peak that is above a threshold may be detected in the auto-correlation result. For example, because of the multipath interference, one or more delayed copies of the symbol may be received, and peak(s) may show up at the end of the delayed copies.

[0064] In some embodiments, if a time span between the peaks is no longer than the time span of the CP, time and frequency correction unit 246 may adjust the time or frequency of the received OFDM symbol based on an earliest or strongest peak above the threshold. For example, because the delayed copies are received at a delay because of the longer transmission distance, the earliest peak above the threshold may be selected for positioning the end of the symbol. For another example, because the delayed copies are reflected by surrounding objects, the peaks corresponding to the delayed copies may be weaker (e.g., have a smaller amplitude in the auto-correlation result) comparing to the peak indicating the end of the received symbol. Thus, the strongest (e.g., highest in the auto-correlation result) peak may be selected for positioning the end of the symbol.

[0065] In some embodiments, a time span of the more than one peaks above the threshold is longer than the time span of the CP. In some embodiments, the received symbol may be converted to a number of copies according to the number of peaks above the threshold that is at least apart from each other by the time span of the CP. The time and frequency correction may be performed on each copy, respectively (e.g., correlate the CP with each copy), and each copy may be processed (e.g., converted from the time domain to the frequency domain, being demodulated, etc.) respectively based on the adjusted time or frequency of that copy. The output of the demodulation process may be selected from the processed copies based on a metric (e.g., a quality of the copy such as a signal-to-noise ratio (SNR)) of each of the processed copies.

[0066] In some embodiments, if no valid CP is detected, the OFDM symbol may be processed without the time and frequency correction being performed (e.g., processed with the default timing), or with an adjusted time or frequency, determined by an alternative time and frequency correction method (e.g., using one of the reference signal-based the time and frequency correction methods in conventional DRX technologies). Accordingly, CP-based time and frequency correction performed in CP-based time and frequency correction module 240 (e.g., processes performed in an auto-correlation unit 244, and a time and frequency correction unit 246) will not be performed in this scenario. For one example, the OFDM symbol may be transmitted to data processing module 250 for further processing without an update of the time and frequency drift. In other embodiments, receiving device 202 may turn on the FFT function unit and associated PDCCH receiver in data processing module 250, and try to decode PDCCH and get PDCCH demodulation reference signal (DMRS) or CRS to perform the time and frequency correction.

[0067] In some embodiments, based on the received symbol, the time and frequency correction for the current wake-up may be used as a quality standard for determining activities for the subsequent wake-up, such as the time and frequency correction module to be used, and/or a starting time point of the subsequent wake-up. For example, receiving device 202 may further include an alternative time and frequency correction module 260, where an alternative time and frequency correction method (e.g., methods based on reference signal(s)) is performed. The time and frequency correction module selection process may be controlled by a control signal for the time and frequency correction module selection provided by a processor (e.g., processor 902) in conjunction with time and frequency correction scheme selection module 270 according to the scheme(s) disclosed above. For one example, if no CP correlation peak above the threshold can be detected (e.g., because of the quality of the received symbol is low) in the current wake-up, in a subsequent wake-up, alternative time and frequency correction module 260 may be selected for time and frequency correction, and an early wake-up (e.g., with extra wake-up for receiving the reference signal(s)) may also be instructed.

[0068] It is contemplated that the possible time and frequency correction modules for time and frequency correction, and the time and frequency correction module selection methods are not limited to those being disclosed herein. Any other suitable alternative time and frequency correction modules and time and frequency correction module selection methods may be applied by receiving device 202 for time and frequency correction. Nevertheless, based on the selected time and frequency correction module, the adjusted OFDM symbol may be transmitted to data processing module 250 for further processing based on the adjusted time or frequency.

[0069] It is contemplated that wireless communication system 200 with CP-based time and frequency correction described above may be implemented either in software or hardware. For example, FIGs. 5A and 5B illustrate block diagrams of an exemplary apparatus 500 including a host chip, an RF chip, and a baseband chip implementing the wireless communication system 200 with CP-based time and frequency correction in FIG. 2 in software and hardware, respectively, according to some embodiments of the present disclosure. Apparatus 500 may be an example of any node of wireless network 100 in FIG. 1 suitable for DRX, such as user equipment 102 or a core network element 106. As shown in FIG. 5, apparatus 500 may include an RF chip 502, a baseband chip 504 (baseband chip 504A in FIG. 5A or baseband chip 504B in FIG. 5B), a host chip 506, and an antenna 510. In some embodiments, baseband chip 504 is implemented by processor 902 and memory 904, and RF chip 502 is implemented by processor 902, memory 904, and transceiver 906, as described above with respect to FIG. 9. Besides on-chip memory 512 (also known as “internal memory,” e.g., as registers, buffers, or caches) on each chip 502, 504, or 506, apparatus 500 may further include a system memory 508 (also known as the main memory) that can be shared by each chip 502, 504, or 506 through the main bus. Although baseband chip 504 is illustrated as a standalone SoC in FIGs. 5A and 5B, it is understood that in one example, baseband chip 504 and RF chip 502 may be integrated as one SoC; in another example, baseband chip 504 and host chip 506 may be integrated as one SoC; in still another example, baseband chip 504, RF chip 502, and host chip 506 may be integrated as one SoC, as described above.

[0070] In the uplink, host chip 506 may generate original data and send it to baseband chip 504 for encoding, modulation, mapping, and CP adding. Baseband chip 504 may access the original data from host chip 506 directly using an interface 514 or through system memory 508 and then perform the functions of modules 210, 220, and 230, as described above in detail with respect to FIG. 2. Baseband chip 504 then may pass the modulated signal (e.g., the OFDM symbol) to RF chip 502 through interface 514. A transmitter (Tx) 516 of RF chip 502 may convert the modulated signals in the digital form from baseband chip 504 into analog signals, i.e., RF signals, and transmit the RF signals through antenna 510 into the channel.

[0071] In the downlink, antenna 510 may receive the RF signals (e.g., the OFDM symbol) through the channel and pass the RF signals to a receiver (Rx) 518 of RF chip 502. RF chip 502 may perform any suitable front-end RF functions, such as filtering, down-conversion, or sample -rate conversion, and convert the RF signals into low-frequency digital signals (baseband signals) that can be processed by baseband chip 504. In the downlink, interface 514 of baseband chip 504 may receive the baseband signals, for example, the OFDM symbol. Baseband chip 504 then may perform the functions of modules 240, 250, 260, and 270, as described above in detail with respect to FIGs. 2, 3A, and 3B. The original data may be extracted by baseband chip 504 from the baseband signals and passed to host chip 506 through interface 514 or stored into system memory 508. [0072] In some embodiments, the time and frequency correction schemes disclosed herein (e.g., by CP-based time and frequency correction module 240, alternative time and frequency correction modules 260, or wireless communication system 200) may be implemented in software by baseband chip 504A in FIG. 5A having a baseband processor 520 executing the stored instructions, as illustrated in FIG. 5A. Baseband processor 520 may be a generic processor, such as a central processing unit or a DSP, not dedicated to time and frequency correction. That is, baseband processor 520 is also responsible for any other functions of baseband chip 504A and can be interrupted when performing time and frequency correction due to other processes with higher priorities. Each element in apparatus500 may be implemented as a software module executed by baseband processor 520 to perform the respective functions described above in detail.

[0073] In some other embodiments, the time and frequency correction schemes disclosed herein, for example, by CP-based time and frequency correction module 240, alternative time and frequency correction modules 260, or wireless communication system 200, may be implemented in hardware by baseband chip 504B in FIG. 5B having a dedicated time and frequency correction circuit 522, as illustrated in FIG. 5B. Time and frequency correction circuit 522 may include one or more ICs, such as ASICs, dedicated to implementing the time and frequency correction detection schemes disclosed herein. Each element in wireless communication system 200 may be implemented as a circuit to perform the respective functions described above in detail. One or more microcontrollers (not shown) in baseband chip 504B may be used to program and/or control the operations of time and frequency correction circuit 522. It is understood that in some examples, the time and frequency correction detection schemes disclosed herein may be implemented in a hybrid manner, e.g., in both hardware and software. For example, some elements in wireless communication system 200 may be implemented as a software module executed by baseband processor 520, while some elements in wireless communication system 200 may be implemented as circuits.

[0074] FIGs. 6 and 7 illustrate flow charts of an exemplary method 600 for wireless communication with CP- based time and frequency correction, FIG. 8 illustrates a flow chart of another exemplary method 800 for wireless communication with CP-based time and frequency correction, according to some embodiments of the present disclosure. Examples of the apparatus that can perform operations of methods 600 and 800 include, for example, apparatus depicted in FIGs. 2, 5A, and 5B or any other apparatus disclosed herein. It is understood that the operations shown in methods 600 and 800 are not exhaustive and that other operations can be performed as well before, after, or between any of the illustrated operations. Further, some of the operations may be performed simultaneously, or in a different order than shown in FIGs. 6, 7, and 8. FIGs. 6 and 7 will be described together, and FIG. 8 will be described in conjunction with FIGs. 6 and 7.

[0075] Referring to FIG. 6, method 600 starts at operation 602, in which a UE (e.g., receiving device 202) wakes up from a sleeping mode and an OFDM symbol (e.g., OFDM symbol 304) including a payload (e.g., payload 306) and a CP (e.g., CP 308) is received by the UE. In some embodiments, transceiver 906 in FIG. 9 may be configured to receive the OFDM symbol.

[0076] Method 600 proceeds to operation at 604, in which if the CP is detected is determined. If yes, method 600 proceeds to operations at 608, 610 and 612, in which an auto-correlation of the CP and the payload of the OFDM symbol is performed, the time and frequency correction is performed on peak(s) of the auto-correction, and the data is processed based on the time and frequency correction. As shown in FIG. 2, CP-based time and frequency correction module 240 of receiving device 202 may perform the auto-correlation and the time and frequency correction. Data processing module 250 of receiving device 202 may perform the data processing. The details of operations 608, 610, and 612 may be described with more detail in FIG. 7.

[0077] For example, as illustrated in FIG. 7, after performing the auto-correlation for the CP and the payload in operation at 608, in operation at 702, in which if more than one peak above a predetermined threshold is detected is determined. As shown in FIG. 2, CP-based time and frequency correction module 240 of receiving device 202 may perform the determination.

[0078] In some embodiments, if only one peak above the threshold is detected, method 600 proceeds to operation 610a, in which the time and frequency correction is performed based on the peak of the auto correlation. Method 600 then proceeds to operation 612a, in which the data (e.g., the received OFDM symbol) is processed based on the time and frequency correction. As shown in FIG. 2, data processing module 250 of receiving device 202 may perform the data processing.

[0079] Referring back to operation 702, if more than one peak above the threshold is detected, method 600 proceeds to operation at 704, in which if a time span between the more than one peak above the threshold is longer than the time span for the CP is determined. If the time span between the more than one peak above the threshold is no longer than the time span for the CP, method 600 proceeds to operation at 610b, in which the time and frequency correction is performed based on the earliest peak or strongest peak of the auto-correlation. Method 600 proceeds to operation 612a, in which the data is processed based on the time and frequency correction (e.g., the adjusted time or frequency).

[0080] Referring back to operation 704, if the time span between the more than one peak above the threshold is longer than the time span for the CP, method 600 proceeds to operation at 706, in which the received OFDM symbol is converted to copies according to the number of the peaks above the threshold that are at least apart from each other for the time span of the CP. For example, if m peaks are detected that are above the threshold and are at least apart from each other for the time span of the CP, the received OFDM symbol may be converted into m copies accordingly.

[0081] Method 600 then proceeds to operation at 610c, in which time and frequency correction is performed for each copy, respectively. For example, auto-correlation unit 244 may correlate the CP with each copy, respectively, and time and frequency correlation unit 246 may adjust the time or frequency of each copy based on each correlation result, respectively.

[0082] Method 600 then proceeds to operation at 612c, in which each copy is processed based on the time and frequency correction of the copy for demodulating the OFDM symbol, and at least one of the demodulated original data may be selected based on a metric (e.g., a signal-to-noise ratio (SNR)) of the demodulated original data, as an output of data processing module 250 in receiving device 202. For example, data processing module 250 may demodulate each copy, respectively, and select the one with the best quality (e.g., the best SNR) as the output.

[0083] Referring back to operation in 604 in FIG. 6, if no valid CP is detected, in operation 606, the data may be processed with the default timing (e.g., without the time and/or frequency drift being corrected based on the CP). [0084] In operation 614, activities for a subsequent wake-up is determined. For example, a time and frequency correction method used for the subsequent wake-up may be determined based on the time and frequency correction results for the current wake-up. For example, if no valid CP was detected, an SNR of the received data is lower than a threshold, or the time or frequency drift is larger than a detection range of the CP- based time and frequency correction scheme disclosed herein, alternative time and frequency correction schemes (e.g., reference signal-based time and frequency correction schemes) may be selected for the subsequent wake-up. In some embodiments, a time point for the subsequent wake-up can also be determined (e.g., if an extra wake-up period is needed for receiving the reference signal) based on the selection of time and frequency correction scheme for the subsequent wake-up. As shown in FIG. 2, modules 240, 260, and 270 of receiving device 202 operate jointly may be configured to decide activities for the subsequent wake-up.

[0085] In operation 616, after processing the received data, the UE may enter the sleep mode again for reducing the power consumption.

[0086] FIG. 8 illustrates a flow chart of an exemplary method 800 for wireless communication with additional steps in addition to method 600, according to some embodiments of the present disclosure.

[0087] Referring to FIG. 8, method 800 starts at operation 802, in which a UE (e.g., receiving device 202) wakes up from a sleeping mode, and an OFDM symbol is received by the UE.

[0088] Method 800 proceeds to operation at 804, in which if the CP-based time and frequency correction is enabled is determined. For example, the UE may determine if the CP-based time and frequency correction is enabled based on instruction(s) from the last wake-up (e.g., instructions generated in operation 614 in method 600). For example, if one or more of the following: 1) no valid CP was detected, 2) no peak above the threshold is detected, 3) the SNR of the demodulated symbol (e.g., the output of data processing module 250) is too low, and 4) the time or frequency drift is larger than a detection range CP-based time and frequency correction scheme, was detected in the last wake-up, the UE may instruct not to enable the CP-based time and frequency correction for the current wake-up. If the CP-based time and frequency correction is not enabled, method 800 proceeds to operation at 806, in which the time and frequency correction is performed using alternative time and frequency correction (e.g., methods based on reference signals such as a PSS, an SSS, a CRS, or an SSB). As shown in FIG. 2, alternative time and frequency correction module 260 may perform the time and frequency correction based on at least one of the reference signals described above.

[0089] If the CP-based time and frequency correction is enabled, method 800 proceeds to operation 604, where CP-based time and frequency correction is performed similarly to what is described in FIGs. 6 and 7. The same operations will not be described for clarity and simplification.

[0090] In method 800, when the CP-based time and frequency correction is performed, different from what is performed in method 600, in operation 606’, when no valid CP is detected in the current wake-up in operation 604, the data may be process based on the time and frequency adjusted based on alternative time and frequency correction, generated in operation 806, in contrast with using a default time for processing the data. As shown in FIG. 2, data processing module 250 may demodulate the data based on the adjusted time.

[0091] In various aspects of the present disclosure, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as instructions or code on a non-transitory computer-readable medium. Computer- readable media includes computer storage media. Storage media may be any available media that can be accessed by a receiving device, such as receiving device 900 in FIG. 9. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, HDD, such as magnetic disk storage or other magnetic storage devices, Flash drive, SSD, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a processing system, such as a mobile device or a computer. Disk and disc, as used herein, includes CD, laser disc, optical disc, DVD, and floppy disk where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0092] According to one aspect of the present disclosure, an apparatus includes at least one processor and memory including storing instructions is disclosed. The instructions, when executed by the at least one processor, cause the apparatus to receive a symbol including a CP and a payload. The instructions, when executed by the at least one processor, also cause the apparatus to detect the CP and perform an auto correlation of the CP and the payload. The instructions, when executed by the at least one processor, further cause the apparatus to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

[0093] In some embodiments, execution of the instructions further causes the apparatus to convert the adjusted symbol from the time domain to the frequency domain. [0094] In some embodiments, execution of the instructions further causes the apparatus to demodulate the converted symbol based on the adjusted at least one of the time or the frequency.

[0095] In some embodiments, to detect one or more peaks of the auto-correlation are above a threshold, execution of the instructions further causes the apparatus to detect one or more peaks of the auto-correlation above a threshold.

[0096] In some embodiments, execution of the instructions further causes the apparatus to adjust at least one of the time or the frequency of the received symbol based on the one or more peaks.

[0097] In some embodiments, to adjust at least one of the time or the frequency of the received symbol, execution of the instructions further causes the apparatus to detect that a plurality of the peaks are above the predetermined threshold.

[0098] In some embodiments, execution of the instructions further causes the apparatus to determine if a time span of the plurality of peaks is longer than a time span of the CP.

[0099] In some embodiments, to adjust at least one of the time or the frequency of the received symbol, execution of the instructions further causes the apparatus to in response to the time span of the plurality of peaks not being longer than the time span of the CP, adjust at least one of the time or the frequency of the received symbol based on at least one of an earliest peak or a strongest peak of the plurality of peaks.

[0100] In some embodiments, to adjust at least one of the time or the frequency of the received symbol , execution of the instructions further causes the apparatus to in response to the time span of the plurality of peaks being longer than the time span of the CP, at least some peaks that are apart by at least the time span of the CP from the plurality of peaks.

[0101] In some embodiments, to adjust at least one of the time or the frequency of the received symbol, execution of the instructions further causes the apparatus to convert the received symbol into copies based on the selected peaks.

[0102] In some embodiments, execution of the instructions further causes the apparatus to adjust at least one of a time or a frequency of each of the plurality of copies of the symbol, respectively, convert each copy of the symbol from the time domain to the frequency domain, demodulate each of the converted copies of the symbol based on the respective adjusted at least one of the time or the frequency, and select at least one of the demodulated copies of the symbol based on a metric of the demodulated copies of the symbol.

[0103] In some embodiments, execution of the instructions further causes the apparatus to determine if a quality standard is met based on the received symbol, and adjust at least one of a time or a frequency of another symbol received in a next wake-up based on the determination.

[0104] In some embodiments, wherein the quality standard includes an SNR of the received symbol being above a threshold.

[0105] In some embodiments, wherein the quality standard includes at least one peak of the auto-correlation being above a threshold.

[0106] In some embodiments, execution of the instructions further causes the apparatus to in response to the quality standard being met, adjust at least one of a time or a frequency of another symbol based on a result of auto-correction of another CP and another payload of the another symbol received in the next wake-up.

[0107] In some embodiments, execution of the instructions further causes the apparatus to in response to the quality standard not being met, adjust the at least one of the time or the frequency of the another symbol based on a reference signal received in the next wake-up.

[0108] In some embodiments, the reference signal includes at least one of a PSS, an SSS, a CRS, or an SSB. [0109] In some embodiments, execution of the instructions further causes the apparatus to determine a time point for staring an immediately subsequent wake-up based on the received symbol.

[0110] In some embodiments, the received symbol is an OFDM symbol.

[0111] In some embodiments, at least one of the time or the frequency has a drift caused by the apparatus being in a sleep mode, prior to receiving the symbol.

[0112] In some embodiments, at least one of the time or the frequency of the received symbol is adjusted based on an end of the received symbol, indicated by the result of the auto-correction.

[0113] In some embodiments, at least one of the time or the frequency of the received symbol is adjusted based on a time and frequency of the symbol indicated by the result of the auto-correlation, according to a sampling frequency for demodulating the received signal.

[0114] According to another aspect of the present disclosure, a baseband chip includes an interface and a time and frequency correction circuit operatively coupled to the interface is disclosed. The interface is configured to receive the OFDM symbol including a CP and a payload. The time and frequency correction circuit is configured to detect the CP and perform an auto-correlation of the CP and the payload. The time and frequency correction circuit is also configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

[0115] In some embodiments, the baseband chip further includes a data processing circuit configured to convert the adjusted symbol from the time domain to the frequency domain, and demodulate the converted symbol based on the adjusted at least one of the time or the frequency.

[0116] In some embodiments, the time and frequency correction circuit is an ASIC.

[0117] According to yet another aspect of the present disclosure, a method for time and/or frequency correction is disclosed. A symbol including a CP and a payload is received. The CP is detected, and an auto correlation of the CP and the payload is performed. At least one of a time or a frequency of the received symbol is adjusted based on a result of the auto-correction.

[0118] In some embodiments, to adjust at least one of the time or the frequency of the received symbol, one or more peaks of the auto-correlation above a threshold are detected, and at least one of the timing or the frequency of the received symbol is adjusted based on the one or more peaks.

[0119] In some embodiments, the adjusted symbol is converted from the time domain to the frequency domain.

[0120] In some embodiments, the converted symbol is demodulated based on the at least one of the adjusted time or the frequency.

[0121] In some embodiments, a plurality of the peaks above the threshold are detected, and if a time span of the plurality of peaks are longer than a time span of the CP is determined.

[0122] In some embodiments, in response to the time span of the plurality of peaks not being longer than a time span of the CP, at least one of the time or the frequency of the received symbol is adjusted based on at least one of an earliest peak or a strongest peak of the plurality of peaks.

[0123] In some embodiments, in response to the time span of the plurality of peaks being longer than the time span of the CP, at least some peaks that are apart at least by the time span of the CP are selected from the plurality of peaks, and the received symbol is converted into a plurality of copies based on the selected peaks. [0124] In some embodiments, at least one of the time or the frequency of each copy of the symbol is adjusted, respectively, and each copy of the symbol is converted from the time domain to the frequency domain based on the respective adjusted at least one of the time or frequency.

[0125] In some embodiments, each of the converted copies of the symbol is demodulated based on the adjusted at least one of the time or the frequency, and at least one of the demodulated copies of the symbol is selected based on a metric of the demodulated copies of the symbol.

[0126] In some embodiments, if a quality standard is met is determined based on the received symbol, and at least one of a time or a frequency of another symbol received in a next wake-up is adjusted based on the determination.

[0127] In some embodiments, the quality standard includes an SNR of the symbol received being above a threshold.

[0128] In some embodiments, the quality standard includes at least one peak of the auto-correlation being above a threshold.

[0129] In some embodiments, in response to the quality standard being met, at least one of a time or a frequency of another symbol is adjusted based on a result of an auto-correction of another CP and another payload of the another symbol received in the next wake-up.

[0130] In some embodiments, in response to the quality standard not being met, at least one of the time or the frequency of the another symbol is adjusted based on a reference signal received in the next wake-up.

[0131] In some embodiments, the reference symbol includes at least one of a PSS, an SSS, a CRS, or an SSB. [0132] In some embodiments, a time point for staring the immediately subsequent wake-up is determined based on the received symbol.

[0133] In some embodiments, the received symbol is an OFDM symbol.

[0134] In some embodiments, at least one of the time or the frequency has a drift caused by the baseband chip being in a sleep mode, prior to receiving the symbol.

[0135] In some embodiments, at least one of the time or the frequency of the received symbol is adjusted based on an end of the received symbol, indicated by the result of the auto-correction.

[0136] In some embodiments, at least one of the time or the frequency of the received symbol is adjusted based on a time and frequency of the symbol indicated by the result of the auto-correlation, according to a sampling frequency for demodulating the received signal.

[0137] According to further another aspect of the disclosure, a non-transitory computer-readable medium encoded with instructions that, when executed by at least one processor of a terminal device, perform a process is disclosed. The process includes receiving a symbol including a CP and a payload. The process also includes detecting the CP and performing an auto-correlation of the CP and the payload. The process further includes adjusting at least one of a time or a frequency of the received symbol based on a result of the auto correction.

[0138] According to another aspect of the present disclosure, a device for time and/or frequency correction includes a receiving module, a detecting module, an auto-correlation module and a time or a frequency correction module is disclosed. The receiving module is configured to receive the OFDM symbol comprising a cyclic prefix (CP) and a payload. The detecting module is configured to detect the CP. The auto-correlation module is configured to perform an auto-correlation of the CP and the payload. The time or a frequency correction module is configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

[0139] The foregoing description of the specific embodiments will so reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0140] Embodiments of the present disclosure have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0141] The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0142] Various functional blocks, modules, and steps are disclosed above. The particular arrangements provided are illustrative and without limitation. Accordingly, the functional blocks, modules, and steps may be re-ordered or combined in different ways than in the examples provided above. Likewise, certain embodiments include only a subset of the functional blocks, modules, and steps, and any such subset is permitted.

[0143] The breadth and scope of the present disclosure should not be limited by any of the above -described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for wireless communication, comprising: at least one processor; and memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive a symbol comprising a cyclic prefix (CP) and a payload; detect the CP; perform an auto-correlation of the CP and the payload; and adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

2. The apparatus of claim 1, wherein execution of the instructions further causes the apparatus to: convert the symbol from the time domain to the frequency domain; and demodulate the converted symbol based on the adjusted at least one of the time or the frequency.

3. The apparatus of claim 1 or 2, wherein execution of the instructions further causes the apparatus to: detect one or more peaks of the auto-correlation above a threshold, wherein to adjust at least one of a time or a frequency of the received symbol, execution of the instructions causes the apparatus to: adjust at least one of the time or the frequency of the received symbol based on the one or more peaks.

4. The apparatus of claim 3, wherein to detect one or more peaks of the auto-correlation above a threshold execution of the instructions causes the apparatus to: detect that a plurality of peaks are above the threshold, wherein execution of the instructions causes the apparatus to: determine if a time span of the plurality of peaks is longer than a time span of the CP; wherein to adjust at least one of the time or the frequency of the received symbol based on the one or more peaks of the auto-correction execution of the instructions causes the apparatus to: adjust at least one of the time or the frequency of the received symbol based on the plurality of the peaks according to the determination.

5. The apparatus of claim 4, wherein to adjust at least one of the time or the frequency of the received symbol based on the plurality of peaks according to the determination, execution of the instructions causes the apparatus to: in response to the time span of the plurality of peaks not being longer than the time span of the CP, adjust at least one of the time or the frequency of the received symbol based on at least one of an earliest peak or a strongest peak of the plurality of peaks.

6. The apparatus of claim 4, wherein to adjust at least one of the time or the frequency of the received symbol based on the plurality of peaks according to the determination, execution of the instructions further causes the apparatus to: in response to the time span of the plurality of peak being longer than the time span of the CP, select at least some peaks that are apart by at least the time span of the CP from the plurality of peaks; and convert the received symbol into a plurality of copies based on the selected peaks; and adjusting at least one of the time or the frequency of each of the plurality of copies of the symbol, respectively.

7. The apparatus of claim 6, wherein execution of the instructions causes the apparatus to: convert each copy of the symbol from the time domain to the frequency domain; demodulate each of the converted copies of the symbol based on the respective adjusted at least one of the time or the frequency; and select at least one of the demodulated copies of the symbol based on a metric of the demodulated copies of the symbol.

8. The apparatus of any one of claims 3-7, wherein execution of the instructions causes the apparatus to: determine if a quality standard is met based on the received symbol; and adjust at least one of a time or a frequency of another symbol received in a next wake-up based on the determination.

9. The apparatus of claim 8, wherein the quality standard comprises at least one of a signal-to- noise ratio (SNR) of the received symbol being above a threshold or at least one peak of the auto-correlation being above a threshold.

10. The apparatus of any one of claims 8-9, wherein to adjust at least one of the time or the frequency of another symbol received in the next wake-up execution of the instructions causes the apparatus to: in response to the quality standard being met, adjust the at least one of the time or the frequency of the another symbol based on a result of auto-correction of another CP and another payload of the another symbol received in the next wake-up.

11. The apparatus of any one of claims 8-9, wherein to adjust at least one of the time or the frequency of another symbol received in the next wake-up, execution of the instructions causes the apparatus to: in response to the quality standard not being met, adjust the at least one of the time or the frequency of the another symbol based on a reference signal received in the next wake-up.

12. The apparatus of claim 11, wherein the reference signal comprises at least one of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a common reference signal (CRS), or a synchronization signal block (SSB).

13. The apparatus of any one of claims 1-12, wherein execution of the instructions further causes the apparatus to: determine a time point for staring an immediately subsequent wake-up based on the received symbol.

14. The apparatus of claim 13, wherein to determine the time point for staring the immediately subsequent wake-up, execution of the instructions further causes the apparatus to: determining whether a quality standard is met; in determination that the quality standard is met, waking up at a time point of starting to receive the symbol; and in determination that the quality standard is not met, waking up at a time point prior to the time point of starting to receive the symbol, for receiving a reference signal used for time and frequency correction.

15. The apparatus of any one of claims 1-14, wherein to determine the time point for staring the immediately subsequent wake-up, execution of the instructions causes the apparatus to: adjust at least one of the time or the frequency of the received symbol based on a time and frequency of the symbol indicated by the result of the auto-correlation, according to a sampling frequency for demodulating the received signal.

16. The apparatus of any one of claims 1-15, wherein at least one of the time or the frequency has a drift caused by the apparatus being in a sleep mode, prior to receiving the symbol.

17. A baseband chip, comprising: an interface configured to receive an orthogonal frequency division multiplexing (OFDM) symbol; and a time and frequency correction circuit operatively coupled to the interface and configured to: receive the OFDM symbol comprising a cyclic prefix (CP) and a payload; detect the CP; perform an auto-correlation of the CP and the payload; and adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.

18. The baseband chip of claim 17, further comprising a data processing circuit configured to: convert the symbol from the time domain to the frequency domain; and demodulate the converted symbol based on the adjusted at least one of the time or the frequency.

19. The baseband chip of claim 17 or 18, wherein the time and frequency correction circuit is an application-specific integrated circuit (ASIC).

20. A method for time and/or frequency correction, comprising: receiving a symbol comprising a cyclic prefix (CP) and a payload; detecting the CP; performing an auto-correlation of the CP and the payload; and adjusting at least one of a time or a frequency of the received symbol based on a result of the auto correction.

21. The method of claim 20, further comprising: converting the adjusted symbol from the time domain to the frequency domain; and demodulating the converted symbol based on the adjusted at least one of the time or the frequency.

22. The method of claim 20 or 21, further comprising: detecting one or more peaks of the auto-correlation above a threshold, wherein adjusting at least one of the time or the frequency of the received symbol comprises: adjusting at least one of the time or the frequency of the received symbol based on the one or more peaks of the auto-correction.

23. The method of claim 22, wherein detecting one or more peaks of the auto-correlation above a threshold comprises: detecting that a plurality of the peaks are above the threshold, wherein the method further comprises: determining if a time span of the plurality of peaks is longer than a time span of the CP; wherein adjusting at least one of the time or the frequency of the received symbol based on the one or more peaks of the auto-correction comprises: adjusting at least one of the time or the frequency of the received symbol based on the plurality of the peaks according to the determination.

24. The method of claim 23, wherein adjusting at least one of the time or the frequency of the received symbol based on the plurality of peaks according to the determination comprises: in response to the time span of the plurality of peaks not being longer than the time span of the CP, adjusting at least one of the time or the frequency of the received symbol based on at least one of an earliest peak or a strongest peak of the plurality of peaks.

25. The method of claim 23, wherein adjusting at least one of the time or the frequency of the received symbol based on the plurality of peaks according to the determination comprises: in response to the time span of the plurality of peaks being longer than the time span of the CP, selecting at least two peaks that are apart at least by the time span of the CP from the plurality of peaks, converting the received symbol into a plurality of copies based on the selected peaks; and adjusting at least one of the time or the frequency of each of the plurality of copies of the symbol, respectively.

26. The method of claim 25, the method comprising: converting each adjusted copy of the symbol from the time domain to the frequency domain; demodulating each of the converted copies of the symbol based on the respective adjusted at least one of the time or the frequency; and selecting at least one of the demodulated copies of the symbol based on a metric of the demodulated copies of the symbol.

27. The method of any one of claims 22-26, further comprising: determining if a quality standard is met based on the received symbol; and adjusting at least one of a time or a frequency of another symbol received in a next wake-up based on the determination.

28. The method of claim 27, wherein the quality standard comprises a signal-to-noise ratio (SNR) of the received symbol being above a threshold, or at least one peak of the auto-correlation being above the threshold.

29. The method of any one of claims 27-28, wherein adjusting at least one of the time or the frequency of another symbol received in the next wake-up further comprises: in response to the quality standard being met, adjusting at least one of the time or the frequency of the another symbol based on a result of auto-correction of another CP and another payload of the another symbol received in the next wake-up.

30. The method of any one of claims 27-28, wherein adjusting at least one of the time or the frequency of another symbol received in the next wake-up further comprises: in response to the quality standard not being met, adjusting at least one of the time or the frequency of the another symbol based on a reference signal received in the next wake-up.

31. The method of claim 30, wherein the reference signal comprises at least one of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a common reference signal (CRS), or a synchronization signal block (SSB).

32. The method of any one of claims 20-31, further comprising: determining a time point for staring an immediately subsequent wake-up based on a quality of the received symbol.

33. The method of claim 32, wherein determining a time point for staring the immediately subsequent wake-up further comprises: determining whether a quality standard is met; in determination that the quality standard is met, waking baseband chip up at a time point of starting to receive the symbol; and in determination that the quality standard is not met, waking up at a time point prior to the time point of starting to receive the symbol, for receiving a reference signal used for time and frequency correction.

34. The method of any one of claims 20-33, wherein at least one of the time or the frequency has a drift caused by the baseband chip being in a sleep mode, prior to receiving the symbol.

35. The method of any one of claims 20-34, wherein adjusting at least one of the time or the frequency of the received symbol comprises: adjusting at least one of the time or the frequency of the received symbol based on a time and frequency of the symbol indicated by the result of the auto-correlation, according to a sampling frequency for demodulating the received signal.

36. A non-transitory computer-readable medium encoded with instructions that, when executed by at least one processor of an apparatus, perform a process comprising: receiving a symbol comprising a cyclic prefix (CP) and a payload; detecting the CP; performing an auto-correlation of the CP and the payload; and adjusting at least one of a time or a frequency of the received symbol based on a result of the auto correction.

37. A device for time and/or frequency correction, comprising: a receiving module configured to receive the OFDM symbol comprising a cyclic prefix (CP) and a payload; a detecting module configured to detect the CP; an auto-correlation module configured to perform an auto-correlation of the CP and the payload; and a time or a frequency correction module configured to adjust at least one of a time or a frequency of the received symbol based on a result of the auto-correction.