Low power receiver with long sequence correlation

Abstract

A method, wireless devices (WDs) and low power receivers with long sequence correlation are disclosed. According to one aspect, a method in a low power receiver includes receiving from a radio node a signal having a repeating modulation pattern. The method also includes successively correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock of the main transceiver. The method also includes determining a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations. The method further includes adjusting the reference clock of the main transceiver based at least in part on the frequency offset.

Description

[0001] LOW POWER RECEIVER WITH LONG SEQUENCE CORRELATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications, and in particular, to low power receivers with long sequence correlation.

[0004] BACKGROUND

[0005] The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile wireless devices (WD), as well as communication between network nodes and between WDs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks.

[0006] To save power, a wireless device (e.g., 3GPP WD) is configured to go to an idle / inactive mode when there is no downlink (DL) or uplink (UL) data traffic to or from the WD. The WD is configured to wake up for a Discontinuous Reception (DRX) cycle to receive paging information transmitted from a radio node. For each wakeup, prior to paging reception, the WD performs frequency synchronization to correct the frequency drift of its clock system so that its local oscillator (LO) frequency is tuned to align with the carrier frequency transmitted from the radio node. The radio node may be a base station, an access point (AP) or another WD.

[0007] When waking up from an idle / inactive state, the NR WD performs frequency synchronization by using Synchronization Signal Block (SSB) signaling. A radio node transmits SSB with a certain bandwidth (BW) (e.g., 5G mmW SSB BW=29MHz) and a repetitive rate. A WD detects the reference signals, calculates a phase shift between two successive reference blocks to estimate frequency error, and adjusts its local Crystal Oscillator (XO) frequency or Phase-Locked Loop (PLL) frequency divider. The frequency synchronization process leads to energy consumption overhead and time latency. Specially, for a 5G mmW WD, the energy consumption overhead for frequency tracking may be very costly.

[0008] There is a need for a mmWave WD perform frequency synchronization with lower power consumption and shorter latency. SUMMARY

[0009] Some embodiments advantageously provide methods, systems, and apparatuses for low power receivers with long sequence correlation.

[0010] Some embodiments include a method to reduce the WD energy overhead for frequency synchronization, using a dedicated low power receiver performing coherent correlations of a long periodic modulation sequence for frequency tracking and / or correction. Application of some embodiments allows freedom of choice of modulations schemes.

[0011] A radio node continuously transmits a sequence with very narrow bandwidth (BW) and a periodic pattern with a known period (e.g., amplitude modulation such as On-Off Keying (OOK) modulation).

[0012] In some embodiments, a low power receiver generates a signal with a local oscillator (LO) frequency via a low-power free-running oscillator (e.g., ring oscillator), and performs frequency down-conversion to an uncertain intermediate frequency (IF). The frequency of the IF signal is uncertain as the oscillator is free-running, and hence the frequency synchronization may advantageously be based on the signal modulation pattern, rather than the frequency of the IF signal.

[0013] In some embodiments, the reference clock runs continuously and provides a clock edge for each period of the modulation when the frequencies are synchronized. The mm-wave and analog parts of the receiver may be duty cycled, but the reference clock and correlator clock run continuously in some embodiments, so that correlations may be performed and compared coherently with the transmitted waveform. High accuracy may be achieved for long and uninterrupted operation, and comparisons may be performed for correlations over shorter time intervals centered at different points in time.

[0014] When the RF parts are active, correlation may be performed over a window size equal to the modulation period. The length of each correlation may be made long enough so the correlation peak is clearly found. In some embodiments, the low power receiver starts with short correlations, and increases the correlation length as may be necessary. When the peak is found, longer correlations may also be performed around it to clearly resolve the location. The peak location may be compared to the clock edge generated at the rate of the modulation period.

[0015] By comparing the peak location between different measurements, the frequency error may be estimated by the movement of the peak and its direction, and the time between measurements. The reference clock, such as a crystal oscillator, may then be tuned to reduce the frequency drift. In some embodiments, after some iterations, the drift is minimized, and the frequency error between the clocks of the radio node and the WD is also minimized. Since during operation of the main receiver, all frequencies are related to the reference clocks, by using PLLs, the mm-wave frequencies of the carriers may match with high accuracy.

[0016] To save power, after the peak has been found and the drift has been minimized, subsequent correlations may be performed over a much smaller hypothesis window or search space around the expected peak location. This captures drift due to external variations in temperature, for example. By continuing to perform measurements, such errors may be tracked and minimized.

[0017] The power consumption may be very low, while performing the frequency correction. The reference clock and some digital logic clocked by the reference clock may be the only circuit parts that must be on for the entire measurement session, in some embodiments. The mm- wave and analog parts may be duty cycled, and no power-hungry PLL is needed.

[0018] The low power frequency correction circuits disclosed herein may be always-on or operate with higher duty cycle than the WD wakeup duty cycle. This means less energy consumption for frequency correction and lower time latency for WD wakeup.

[0019] Some embodiments may be applicable to configure a WD and a low power receiver of the WD to perform RF carrier frequency tracking and correction with very low energy consumption.

[0020] In some embodiments, power consumption for WD frequency synchronization is moved from the low power WD to the less power constrained radio node.

[0021] According to one aspect, a method is provided in a receiver configured to operate in a wireless device, WD, the WD having a main transceiver with a reference clock. The method includes receiving from a radio node a signal having a repeating modulation pattern. The method also includes successively correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock of the main transceiver. The method further includes determining a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations. The method also includes adjusting the reference clock of the main transceiver based at least in part on the frequency offset.

[0022] According to this aspect, in some embodiments, the successive correlation windows vary in duration from a modulation period of the repeating modulation pattern for a first correlation, a time between successive correlation windows being increased when the frequency offset decreases and being decreased when the frequency offset increases. In some embodiments, a time duration of a correlation window of the successive correlation windows decreases when a signal to noise ratio, SNR, of the received signal increases, the time duration of the correlation window not being less than a modulation period of the repeating modulation pattern. In some embodiments, the repeating modulation pattern is an amplitude modulation pattern. In some embodiments, a sampling rate in a correlation window of the successive correlation windows is selected to have a resolution that is higher than a chip period of the repeating modulation pattern. In some embodiments, the method includes adjusting durations of successive correlation windows until a correlation peak is resolved, followed by decreasing durations of successive correlations windows around the correlation peak as a signal to noise ratio, SNR, of the received signal increases. In some embodiments, the method includes operating the receiver while the main transceiver of the WD is in a low power state. In some embodiments, a duration of a correlation window is based at least in part a quality of the received signal. In some embodiments, a frequency of the reference clock of the main transceiver of the WD is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver of the WD is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the method includes mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating an envelope of the mixed signal with the reference pattern. In some embodiments, the method includes placing the receiver in an idle mode between successive correlations.

[0023] According to another aspect, a low power receiver configured to operate in a wireless device, WD, is provided. The WD has a main transceiver with a reference clock. The low power receiver includes a radio interface configured to receive from a radio node a signal having a repeating modulation pattern. The low power receiver also includes processing circuitry in communication with the radio interface and configured to: successively correlate the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock of the main transceiver; determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjust the reference clock of the main transceiver based at least in part on the frequency offset.

[0024] According to this aspect, in some embodiments, the successive correlation windows vary in duration from a modulation period of the repeating modulation pattern for a first correlation, a time between successive correlation windows being increased when the frequency offset decreases and being decreased when the frequency offset increases. In some embodiments, a time duration of a correlation window of the successive correlation windows decreases when a signal to noise ratio, SNR, of the received signal increases, the time duration of the correlation window not being less than a modulation period of the repeating modulation pattern. In some embodiments, the repeating modulation pattern is an amplitude modulation pattern. In some embodiments, a sampling rate in a correlation window of the successive correlation windows is selected to provide a resolution that is higher than a chip period of the repeating modulation pattern. In some embodiments, the processing circuitry is further configured to adjust durations of successive correlation windows until a correlation peak is resolved, and to then decrease durations of successive correlations windows around the correlation peak as a signal to noise ratio, SNR, of the received signal increases. In some embodiments, the processing circuitry is further configured to operate the receiver while the main transceiver of the WD is in a low power state. In some embodiments, a duration of a correlation window is based at least in part a quality of the received signal. In some embodiments, a frequency of the reference clock of the main transceiver of the WD is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver of the WD is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the processing circuitry is further configured to mix the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating an envelope of the mixed signal with the reference pattern. In some embodiments, the processing circuitry is further configured to place the receiver in an idle mode between successive correlations. According to yet another aspect, a method in a wireless device, WD, configured to communicate with a radio node is provided. The WD includes a main transceiver and a low power receiver. The method includes receiving by the receiver from the radio node a signal having a repeating modulation pattern. The method also includes successively correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by a reference clock of the main transceiver. The method also includes determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations. The method also includes adjusting a reference clock of the main transceiver based at least in part on the frequency offset.

[0025] According to this aspect, in some embodiments, the method includes operating the receiver while the main transceiver is in a low power state. In some embodiments, a frequency of the reference clock of the main transceiver of the WD is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver of the WD is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the method includes mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating the mixed signal with the reference pattern. In some embodiments, the method includes operating the receiver in an idle mode between successive correlations.

[0026] According to another aspect, a wireless device, WD, configured to communicate with a radio node is provided. The WD includes a main transceiver including a reference clock, and a receiver configured to: receive from the radio node a signal having a repeating modulation pattern; successively correlate the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock of the main transceiver; determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjust the reference clock of the main transceiver based at least in part on the frequency offset. According to this aspect, in some embodiments, the receiver is configured to operate while the main transceiver of the WD is in a low power state. In some embodiments, a frequency of the reference clock of the main transceiver of the WD is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver of the WD is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the WD includes a free-running oscillator configured to produce an oscillator signal and a mixer configured to mix the received signal with the oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating the mixed signal with the reference pattern. In some embodiments, the receiver is configured to operate in an idle mode between successive correlations.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0029] FIG. l is a schematic diagram of an example network architecture illustrating a communication system connected via an intermediate network to a host computer according to the principles in the present disclosure;

[0030] FIG. 2 is a block diagram of a host computer communicating via a network node with a wireless device over an at least partially wireless connection according to some embodiments of the present disclosure;

[0031] FIG. 3 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for executing a client application at a wireless device according to some embodiments of the present disclosure;

[0032] FIG. 4 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data at a wireless device according to some embodiments of the present disclosure; FIG. 5 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data from the wireless device at a host computer according to some embodiments of the present disclosure;

[0033] FIG. 6 is a flowchart illustrating example methods implemented in a communication system including a host computer, a network node and a wireless device for receiving user data at a host computer according to some embodiments of the present disclosure;

[0034] FIG. 7 is a flowchart of an example process in a receiver (a low power receiver) with long sequence correlation;

[0035] FIG. 8 is a flowchart of an example process in a wireless device with long sequence correlation;

[0036] FIG. 9 is a block diagram of three components of an example radio interface of a wireless device WD configured according to principles disclosed herein;

[0037] FIG. 10 is a block diagram of an example of a low power receiver constructed in accordance with principles disclosed herein; and

[0038] FIG. 11 is a flowchart of another example process in a WD for compensating for frequency drift.

[0039] DETAILED DESCRIPTION

[0040] Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to low power receivers with long sequence correlation. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Like numbers refer to like elements throughout the description.

[0041] As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0042] In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

[0043] In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections.

[0044] The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

[0045] In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (WD) are used interchangeably. The WD herein may be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as wireless device (WD). The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and / or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device, etc.

[0046] Also, in some embodiments the generic term “radio network node” is used. It may be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell / multicast Coordination Entity (MCE), IAB node, relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH). The term “radio node” may refer to a network node and may refer to a WD.

[0047] Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and / or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

[0048] Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices.

[0049] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0050] Some embodiments provide low power receivers with long sequence correlation. As used herein, the term “low power receiver” refers to a receiver in a WD that is in addition to the main receiver of the WD and is configured with less processing power, fewer components and lower energy consumption than the main receiver. A low power receiver also performs fewer than all the functions performed by the main receiver.

[0051] Referring now to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 1 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and / or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.

[0052] Also, it is contemplated that a WD 22 may be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 may have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, WD 22 may be in communication with an eNB for LTEZE-UTRAN and a gNB for NR / NG-RAN. In addition to communication with a network node 16, a WD 22a may be configured to communicate with another WD 22b via of sidelink communications.

[0053] The communication system 10 may itself be connected to a host computer 24, which may be embodied in the hardware and / or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 24 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 26, 28 between the communication system 10 and the host computer 24 may extend directly from the core network 14 to the host computer 24 or may extend via an optional intermediate network 30. The intermediate network 30 may be one of, or a combination of more than one of, a public, private or hosted network. The intermediate network 30, if any, may be a backbone network or the Internet. In some embodiments, the intermediate network 30 may comprise two or more subnetworks (not shown). The communication system of FIG. 1 as a whole enables connectivity between one of the connected WDs 22a, 22b and the host computer 24. The connectivity may be described as an over-the-top (OTT) connection. The host computer 24 and the connected WDs 22a, 22b are configured to communicate data and / or signaling via the OTT connection, using the access network 12, the core network 14, any intermediate network 30 and possible further infrastructure (not shown) as intermediaries. The OTT connection may be transparent in the sense that at least some of the participating communication devices through which the OTT connection passes are unaware of routing of uplink and downlink communications. For example, a network node 16 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 24 to be forwarded (e.g., handed over) to a connected WD 22a. Similarly, the network node 16 need not be aware of the future routing of an outgoing uplink communication originating from the WD 22a towards the host computer 24. A wireless device 22 is configured to include a low power receiver 24 which is configured to determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations of the received signal with a reference pattern over successive correlations. Example implementations, in accordance with an embodiment, of the WD 22, network node 16 and host computer 24 discussed in the preceding paragraphs will now be described with reference to FIG. 2. In a communication system 10, a host computer 24 comprises hardware (HW) 38 including a communication interface 40 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 10. The host computer 24 further comprises processing circuitry 42, which may have storage and / or processing capabilities. The processing circuitry 42 may include a processor 44 and memory 46. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 42 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 44 may be configured to access (e.g., write to and / or read from) memory 46, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0054] Processing circuitry 42 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by host computer 24. Processor 44 corresponds to one or more processors 44 for performing host computer 24 functions described herein. The host computer 24 includes memory 46 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 48 and / or the host application 50 may include instructions that, when executed by the processor 44 and / or processing circuitry 42, causes the processor 44 and / or processing circuitry 42 to perform the processes described herein with respect to host computer 24. The instructions may be software associated with the host computer 24.

[0055] The software 48 may be executable by the processing circuitry 42. The software 48 includes a host application 50. The host application 50 may be operable to provide a service to a remote user, such as a WD 22 connecting via an OTT connection 52 terminating at the WD 22 and the host computer 24. In providing the service to the remote user, the host application 50 may provide user data which is transmitted using the OTT connection 52. The “user data” may be data and information described herein as implementing the described functionality. In one embodiment, the host computer 24 may be configured for providing control and functionality to a service provider and may be operated by the service provider or on behalf of the service provider. The processing circuitry 42 of the host computer 24 may enable the host computer 24 to observe, monitor, control, transmit to and / or receive from the network node 16 and or the wireless device 22.

[0056] The communication system 10 further includes a network node 16 provided in a communication system 10 and including hardware 58 enabling it to communicate with the host computer 24 and with the WD 22. The hardware 58 may include a communication interface 60 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 10, as well as a radio interface 62 for setting up and maintaining at least a wireless connection 64 with a WD 22 located in a coverage area 18 served by the network node 16. The radio interface 62 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The communication interface 60 may be configured to facilitate a connection 66 to the host computer 24. The connection 66 may be direct or it may pass through a core network 14 of the communication system 10 and / or through one or more intermediate networks 30 outside the communication system 10.

[0057] In the embodiment shown, the hardware 58 of the network node 16 further includes processing circuitry 68. The processing circuitry 68 may include a processor 70 and a memory 72. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 68 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 70 may be configured to access (e.g., write to and / or read from) the memory 72, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0058] Thus, the network node 16 further has software 74 stored internally in, for example, memory 72, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 74 may be executable by the processing circuitry 68. The processing circuitry 68 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16. Processor 70 corresponds to one or more processors 70 for performing network node 16 functions described herein. The memory 72 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 74 may include instructions that, when executed by the processor 70 and / or processing circuitry 68, causes the processor 70 and / or processing circuitry 68 to perform the processes described herein with respect to network node 16.

[0059] The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 80 that may include a radio interface 82 configured to set up and maintain a wireless connection 64 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 82 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. In particular, the radio interface 82 may be configured to include a low power receiver 34 in addition to a main transceiver 36.

[0060] The hardware 80 of the WD 22 further includes processing circuitry 84. The processing circuitry 84 may include a processor 86 and memory 88. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 84 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 86 may be configured to access (e.g., write to and / or read from) memory 88, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0061] Thus, the WD 22 may further comprise software 90, which is stored in, for example, memory 88 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 90 may be executable by the processing circuitry 84. The software 90 may include a client application 92. The client application 92 may be operable to provide a service to a human or non-human user via the WD 22, with the support of the host computer 24. In the host computer 24, an executing host application 50 may communicate with the executing client application 92 via the OTT connection 52 terminating at the WD 22 and the host computer 24. In providing the service to the user, the client application 92 may receive request data from the host application 50 and provide user data in response to the request data. The OTT connection 52 may transfer both the request data and the user data. The client application 92 may interact with the user to generate the user data that it provides.

[0062] The processing circuitry 84 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by WD 22. The processor 86 corresponds to one or more processors 86 for performing WD 22 functions described herein. The WD 22 includes memory 88 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 90 and / or the client application 92 may include instructions that, when executed by the processor 86 and / or processing circuitry 84, causes the processor 86 and / or processing circuitry 84 to perform the processes described herein with respect to WD 22.

[0063] In some embodiments, the inner workings of the network node 16, WD 22, and host computer 24 may be as shown in FIG. 2 and independently, the surrounding network topology may be that of FIG. 1.

[0064] In FIG. 2, the OTT connection 52 has been drawn abstractly to illustrate the communication between the host computer 24 and the wireless device 22 via the network node 16, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the WD 22 or from the service provider operating the host computer 24, or both. While the OTT connection 52 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network). The wireless connection 64 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the WD 22 using the OTT connection 52, in which the wireless connection 64 may form the last segment. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc.

[0065] In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 52 between the host computer 24 and WD 22, in response to variations in the measurement results. The measurement procedure and / or the network functionality for reconfiguring the OTT connection 52 may be implemented in the software 48 of the host computer 24 or in the software 90 of the WD 22, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 52 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 48, 90 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 52 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the network node 16, and it may be unknown or imperceptible to the network node 16. Some such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary WD signaling facilitating the host computer’s 24 measurements of throughput, propagation times, latency and the like. In some embodiments, the measurements may be implemented in that the software 48, 90 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 52 while it monitors propagation times, errors, etc.

[0066] Thus, in some embodiments, the host computer 24 includes processing circuitry 42 configured to provide user data and a communication interface 40 that is configured to forward the user data to a cellular network for transmission to the WD 22. In some embodiments, the cellular network also includes the network node 16 with a radio interface 62. In some embodiments, the network node 16 is configured to, and / or the network node’s 16 processing circuitry 68 is configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / ending a transmission to the WD 22, and / or preparing / terminating / maintaining / supporting / ending in receipt of a transmission from the WD 22.

[0067] In some embodiments, the host computer 24 includes processing circuitry 42 and a communication interface 40 that is configured to a communication interface 40 configured to receive user data originating from a transmission from a WD 22 to a network node 16. In some embodiments, the WD 22 is configured to, and / or comprises a radio interface 82 and / or processing circuitry 84 configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / ending a transmission to the network node 16, and / or preparing / terminating / maintaining / supporting / ending in receipt of a transmission from the network node 16.

[0068] FIG. 3 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIGS. 1 and 2, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIG. 2. In a first step of the method, the host computer 24 provides user data (Block SI 00). In an optional substep of the first step, the host computer 24 provides the user data by executing a host application, such as, for example, the host application 50 (Block SI 02). In a second step, the host computer 24 initiates a transmission carrying the user data to the WD 22 (Block SI 04). In an optional third step, the network node 16 transmits to the WD 22 the user data which was carried in the transmission that the host computer 24 initiated, in accordance with the teachings of the embodiments described throughout this disclosure (Block SI 06). In an optional fourth step, the WD 22 executes a client application, such as, for example, the client application 92, associated with the host application 50 executed by the host computer 24 (Block SI 08).

[0069] FIG. 4 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 1, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 1 and 2. In a first step of the method, the host computer 24 provides user data (Block SI 10). In an optional substep (not shown) the host computer 24 provides the user data by executing a host application, such as, for example, the host application 50. In a second step, the host computer 24 initiates a transmission carrying the user data to the WD 22 (Block SI 12). The transmission may pass via the network node 16, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step, the WD 22 receives the user data carried in the transmission (Block SI 14).

[0070] FIG. 5 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 1, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 1 and 2. In an optional first step of the method, the WD 22 receives input data provided by the host computer 24 (Block SI 16). In an optional substep of the first step, the WD 22 executes the client application 92, which provides the user data in reaction to the received input data provided by the host computer 24 (Block SI 18). Additionally or alternatively, in an optional second step, the WD 22 provides user data (Block S120). In an optional substep of the second step, the WD provides the user data by executing a client application, such as, for example, client application 92 (Block S122). In providing the user data, the executed client application 92 may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the WD 22 may initiate, in an optional third substep, transmission of the user data to the host computer 24 (Block S124). In a fourth step of the method, the host computer 24 receives the user data transmitted from the WD 22, in accordance with the teachings of the embodiments described throughout this disclosure (Block S126).

[0071] FIG. 6 is a flowchart illustrating an example method implemented in a communication system, such as, for example, the communication system of FIG. 1, in accordance with one embodiment. The communication system may include a host computer 24, a network node 16 and a WD 22, which may be those described with reference to FIGS. 1 and 2. In an optional first step of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 16 receives user data from the WD 22 (Block S128). In an optional second step, the network node 16 initiates transmission of the received user data to the host computer 24 (Block S130). In a third step, the host computer 24 receives the user data carried in the transmission initiated by the network node 16 (Block SI 32).

[0072] FIG. 7 is a flowchart of an example process in a low power receiver 34 with long sequence correlation. One or more blocks described herein may be performed by one or more elements of WD 22 such as by one or more of processing circuitry 84, radio interface 82, baseband circuitry 106 (including correlator 108) and / or communication interface 60. Low power receiver 34 is configured to receive from a radio node a signal having a repeating modulation pattern (Block SI 34). The process also includes successively correlate the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock of the main transceiver 36 (Block SI 36). The method further includes determining a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations (Block S138). The method also includes adjusting the reference clock of the main transceiver 36 based at least in part on the frequency offset (Block S140).

[0073] According to this aspect, in some embodiments, the successive correlation windows vary in duration from a modulation period of the repeating modulation pattern for a first correlation, a time between successive correlation windows being increased when the frequency offset decreases and being decreased when the frequency offset increases. In some embodiments, a time duration of a correlation window of the successive correlation windows decreases when a signal to noise ratio, SNR, of the received signal increases, the time duration of the correlation window not being less than a modulation period of the repeating modulation pattern. In some embodiments, the repeating modulation pattern is an amplitude modulation pattern. In some embodiments, a sampling rate in a correlation window of the successive correlation windows is selected to have a resolution that is higher than a chip period of the repeating modulation pattern. In some embodiments, the method includes adjusting durations of successive correlation windows until a correlation peak is resolved, followed by decreasing durations of successive correlations windows around the correlation peak as a signal to noise ratio, SNR, of the received signal increases. In some embodiments, the method includes operating the receiver while the main transceiver 36 of the WD 22 is in a low power state. In some embodiments, a duration of a correlation window is based at least in part a quality of the received signal. In some embodiments, a frequency of the reference clock of the main transceiver 36 of the WD 22 is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver 36 of the WD 22 is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the method includes mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating an envelope of the mixed signal with the reference pattern. In some embodiments, the method includes placing the receiver in an idle mode between successive correlations.

[0074] FIG. 8 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 84 (including the low power receiver 34), processor 86, radio interface 82 and / or communication interface 60. Wireless device 22 such as via processing circuitry 84 and / or processor 86 and / or radio interface 82 is configured to receive by the receiver from the radio node a signal having a repeating modulation pattern (Block S142). The method also includes successively correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by a reference clock of the main transceiver 36 (Block S144). The method also includes determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations (Block S146). The method also includes adjusting a reference clock of the main transceiver 36 based at least in part on the frequency offset (Block S148).

[0075] According to this aspect, in some embodiments, the method includes operating the receiver while the main transceiver 36 is in a low power state. In some embodiments, a frequency of the reference clock of the main transceiver 36 of the WD 22 is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock of the main transceiver 36 of the WD 22 is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between the first peak and the second peak. In some embodiments, an amount of one of an increase and a decrease in the frequency of the reference clock is based at least in part on a time between successive correlation windows of the successive correlation windows. In some embodiments, the method includes mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating the mixed signal with the reference pattern. In some embodiments, the method includes operating the receiver in an idle mode between successive correlations.

[0076] Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for low power receivers with long sequence correlation.

[0077] Some embodiments address a scenario where a radio node continuously transmits a periodic sequence with very narrow BW (50kHz-500kHz) with amplitude modulation such as On-Off Keying modulation. The low power receiver 34 of the WD 22 receives the periodic sequence and performs frequency tracking using the received sequence.

[0078] Note that although embodiments are described herein in the context of synchronization between the WD 22 and the network node, the principles disclosed herein are applicable to synchronization between WDs 22 via sidelink communications, where, for example, one wireless device 22a sends out a narrowband signal so ultra-low power devices of WDs in the vicinity can synchronize to it.

[0079] FIG. 9 shows an example of low power receiver 34 and a main transceiver 36 of a WD 22. A reference clock 94, such as a crystal oscillator is shared between the low power receiver 34 and the main transceiver 36. The low power receiver 34 is configured to control the reference clock 94, according to principles disclosed herein.

[0080] FIG. 10 is block diagram of an example of a low power receiver 34 configured according to principles disclosed herein. A clock of the main transceiver 36 is driven from the output of a crystal oscillator (XO) 94, which also serves as system clock for the low power receiver baseband.

[0081] The low power receiver 34 estimates frequency drift of the reference clock 94 versus the modulation frequency of the RF carrier which is transmitted from a radio node such as the network node 16 or another wireless device 22. The low power receiver 34 generates a control signal to tune the frequency of the reference clock 94 so that frequency drift of the reference clock 94 may be reduced.

[0082] In some embodiments, the low power receiver 34 may be always-on or operate with a high duty cycle. It is also possible to duty-cycle the analog parts of the low power receiver 34, which consumes most of the power, while keeping most of the frequency error detection performance. This leads to less energy overhead for frequency correction and lower time latency for WD wakeup.

[0083] The example low power receiver of FIG. 10 is configured to perform long sequence correlation to achieve RF carrier frequency tracking and correction.

[0084] As shown in FIG. 10, a radio front end 95 includes an antenna 96, a mixer 98, and a free- running oscillator 100 to generate a local oscillator frequency that is mixed in the mixer 98 with a signal received by the antenna 96 to produce an IF or baseband signal. The local oscillator (LO) 100 may be implemented with an LC-tuned ring oscillator to achieve low power consumption. The IF / baseband signal from the mixer 98 is input to an envelope detector circuit 102 which extracts the OOK sequence contained in the received signal. For simplicity, IF and envelope amplifiers and filters are not shown in the figure. There is also circuitry preceding the mixer 98, such as impedance matching circuitry and amplifiers. Following the envelope detector circuit 102 (and suitable amplification and filtering), a sampling circuit 104, such as a clocked comparator circuit, compares the OOK sequence to a threshold to produce digital samples to the processing circuitry 106. It is noted that processing circuity 106 can be included as part of or separate from processing circuitry 84.

[0085] The processing circuitry 106 may include a processor and memory. In addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor may be configured to access (e.g., write to and / or read from) memory, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). The functions herein attributed to the processing circuitry 106 may be performed by a combination of a processor configured to execute computer instructions and / or application specific hardware.

[0086] A correlator 108 of the processing circuitry 106 correlates the digital OOK signal with the same OOK sequence as the transmitted one from the radio node with a different cyclic time shift hypothesis. This same sequence is generated locally by the sequence generator 110. The correlation window has the same size as the period of the modulation or an integer number of such periods, and a resolution higher than the chip period of the modulation, in some embodiments. The cyclic time shift hypotheses may span a range of one period of the modulation, also with a resolution higher than the chip period of the modulation. As an example, if the modulation has a period of 64 chips and a chip rate of 200kHz, the chip period would be 5ps and the modulation period would be 64*5ps=320us. An oscillator control 112 may be employed to detect a peak in a hypothesis window of size 320ps and with a resolution of 2.5ps. The clock rate could be 400kHz, which would be an oversampling of the modulation by a factor of 2. The correlation peak may have a fixed location with respect to a clock edge of a clock derived from the reference clock 94, by for example, a frequency divider, to have the same rate as the modulation period, when the frequencies of the references are matched at the radio interface of the WD 22 and the network node 16 or another WD 22. An example reference clock frequency is 10MHz which may be divided by a frequency divider of 50*64=3200.

[0087] By performing repeated measurements and comparing the correlation peak location between measurements, the processing circuitry 106 of the low power receiver 34 may derive the frequency offset. For instance, if the location of the peak has moved from bin 34 to bin 38 in the example above, in two measurements 100ms apart, this corresponds to 4*2.5ps=10ps clock drift in 100ms, which is lOOps / s =100ppm. The estimated clock drift and its sign (direction of movement of the peak) may be used to calculate a correction to the frequency of the reference clock 94 to reduce the frequency offset. This correction may be sent from the comparator 112 to the reference clock 94 as a digital control signal or as a voltage control signal received from a digital to analog converter (DAC), for example, after a few iterations the error may be largely suppressed. The measurements may nevertheless continue in order to counteract frequency drift due to external changes, such as temperature shifts.

[0088] The components that that may need to be on all the time are the reference clock 94 and a frequency divider of the processing circuitry 106 to generate the correlation window reference clock edge. Other more power consuming parts may be duty-cycled.

[0089] Power may also be saved in the correlator 108 by reducing the correlation hypothesis window when the frequency drift has been minimized. Also, the length of the correlation may be adjusted, to save power in all parts not having to operate longer than necessary. The correlation time may then be increased until the peak is resolved with sufficient quality, after which the correlation may stop or be suspended

[0090] FIG. 11 is a flowchart of another example method according to principles disclosed herein. According to the example of FIG. 11, a local sequence is generated (Block SI 50), the local oscillator 100 is enabled (Block SI 52), the low power receiver 34 is enabled (Block SI 54), and a received signal sequence is sampled (Block SI 56). The local sequence is correlated with the sampled signal sequence (Block SI 58). The location of the peak of the correlation is compared to a location of a correlation peak obtained from a previous measurement (Block SI 60). This may be performed to determine which sequence delay results in a highest correlation. If the correlation peak location is the same as obtained from the previous measurement (Block SI 62), the process may continue by disabling one or more of the LO 100, mixer 98, and processing circuitry 106, for a certain duration (Block SI 64). After the duration, the process may continue at Block SI 52. If the correlation peak location is not the same as the previously measured peak location, a frequency drift of the reference clock 94 is estimated by the processing circuitry 106 (Block SI 66). If the peak location is later than the previously measured location (Block SI 68) then the reference clock frequency is increased (Block SI 70). Otherwise, the reference clock frequency is decreased (Block SI 72).

[0091] In the estimation of the frequency drift of the reference clock 94, wrap around may be compensated for by subtracting a modulation period from the difference between two consecutive peak locations when the difference is larger than half a modulation period, and adding a modulation period when the difference is less than half a modulation period. Simulation Results

[0092] Simulations show that the frequency drift causes the correlation peak to move between measurements, and that the movement direction depends on the sign of the frequency error, as expected. In the simulations, the correlation peak moved by 20 samples, corresponding to 40ps (2ps per sample). This movement occurred in 0.4s (1000 frames, each frame with a duration of 20 / 50kHz=0.4ms). This corresponds to lOOppm (40ps / 0.4s=100e-6), which corresponds to the frequency error imposed on the receiver reference oscillator in the simulation. The calculations set forth above have been verified.

[0093] Some embodiments may include one or more of the following:

[0094] A method for a device (WD) using a low power receiver to achieve RF carrier frequency tracking / correction by performing coherent correlations of a long periodic modulation sequence, wherein

[0095] 1. A radio node continuously transmits a periodic narrow-bandwidth reference sequence with OOK modulation.

[0096] 2. The WD comprises a main transceiver and the low power receiver. The reference clock of the main transceiver is from the output of a crystal oscillator (XO) which also serves as system clock for the low power receiver baseband.

[0097] 3. The low power receiver includes, a. a low power free-running oscillator generates the local carrier frequency (LO) which is fed to a down-conversion mixer. b. a baseband circuit includes a correlator that correlates the received OOK sequence with the local -generated sequence or locally delayed versions of the sequence. c. the baseband circuit also includes a circuit that generates a clock signal with the same period time as the modulation.

[0098] 4. The correlation delay hypothesis window is related to the clock signal in 3c. The correlation peak location in the window is monitored between repeated measurements, and the frequency drift is estimated.

[0099] 5. The frequency drift estimate is used to adjust the XO.

[0100] 6. The correlation in 4 may be extended in length until the correlation peak may be clearly resolved.

[0101] 7. The correlation delay hypothesis window in 4 may be reduced in size when the drift has been minimized.

[0102] 8. The mm-wave and analog parts may be in idle-mode between measurements

[0103] As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0104] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0105] These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0106] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0107] It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0108] Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0109] Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

[0110] Abbreviations that may be used in the preceding description include:

[0111] Abbreviation Explanation

[0112] AP Access Point

[0113] BW Bandwidth

[0114] DL Downlink

[0115] DRX Discontinuous Reception

[0116] IF Intermediate Frequency

[0117] LO Local Oscillator mmW Millimeter-Wave

[0118] OOK On-Off Keying

[0119] NR Next generation radio

[0120] SSB Synchronization Signal Block

[0121] UE User Equipment

[0122] UL Uplink

[0123] VCO Voltage Control Oscillator

[0124] XO Crystal Oscillator

[0125] WD Wireless Device

[0126] It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

CLAIMS:

1. A method in a receiver (34) configured to operate in a wireless device, WD (22), the WD (22) having a main transceiver (36) with a reference clock (94), the method comprising: receiving (S134) from a radio node (16, 22) a signal having a repeating modulation pattern; successively (SI 36) correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock (94) of the main transceiver (36); determining (SI 38) a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjusting (S140) the reference clock (94) of the main transceiver (36) based at least in part on the frequency offset.

2. The method of Claim 1, wherein the successive correlation windows vary in duration from a modulation period of the repeating modulation pattern for a first correlation, a time between successive correlation windows being increased when the frequency offset decreases and being decreased when the frequency offset increases.

3. The method of Claim 1, wherein a time duration of a correlation window of the successive correlation windows decreases when a signal to noise ratio, SNR, of the received signal increases, the time duration of the correlation window not being less than a modulation period of the repeating modulation pattern.

4. The method of any of Claims 1-3, wherein the repeating modulation pattern is an amplitude modulation pattern.

5. The method of any of Claims 1-4, wherein a sampling rate in a correlation window of the successive correlation windows is selected to have a resolution that is higher than a chip period of the repeating modulation pattern.

6. The method of any of Claims 1-5, further comprising adjusting durations of successive correlation windows until a correlation peak is resolved, followed by decreasingdurations of successive correlations windows as a signal to noise ratio, SNR, of the received signal increases.

7. The method of any of Claims 1-6, further comprising operating the receiver (34) while the main transceiver (36) of the WD (22) is in a low power state.

8. The method of any of Claims 1-7, wherein a duration of a correlation window is based at least in part a quality of the received signal.9 The method of any of Claims 1-8, wherein a frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation.

10. The method of Claim 9, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time difference between the first peak and the second peak.

11. The method of any of Claims 9 and 10, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between successive correlation windows of the successive correlation windows.

12. The method of any of Claims 1-11, further comprising mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating an envelope of the mixed signal with the reference pattern.

13. The method of any of Claims 1-12, further comprising placing the receiver (34) in an idle mode between successive correlations.

14. A receiver (34) configured to operate in a wireless device, WD (22), the WD (22) having a main transceiver (36) with a reference clock (94), the receiver (34) comprising:a radio front end (95) configured to receive from a radio node (16, 22) a signal having a repeating modulation pattern; and processing circuitry (106) in communication with the radio front end (95) and configured to: successively correlate the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock (94) of the main transceiver (36); determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjust the reference clock (94) of the main transceiver (36) based at least in part on the frequency offset.

15. The receiver (34) of Claim 14, wherein the successive correlation windows vary in duration from a modulation period of the repeating modulation pattern for a first correlation, a time between successive correlation windows being increased when the frequency offset decreases and being decreased when the frequency offset increases.

16. The receiver (34) of Claim 14, wherein a time duration of a correlation window of the successive correlation windows decreases when a signal to noise ratio, SNR, of the received signal increases, the time duration of the correlation window not being less than a modulation period of the repeating modulation pattern.

17. The receiver (34) of any of Claims 14-16, wherein the repeating modulation pattern is an amplitude modulation pattern.

18. The receiver (34) of any of Claims 14-17, wherein a sampling rate in a correlation window of the successive correlation windows is selected to provide a resolution that is higher than a chip period of the repeating modulation pattern.

19. The receiver (34) of any of Claims 14-18, wherein the processing circuitry (106) is further configured to adjust durations of successive correlation windows until a correlation peak is resolved, and to then decrease durations of successive correlations windows around the correlation peak as a signal to noise ratio, SNR, of the received signal increases.

20. The receiver (34) of any of Claims 14-19, wherein the processing circuitry (106) is further configured to operate the receiver (34) while the main transceiver (36) of the WD (22) is in a low power state.

21. The receiver (34) of any of Claims 14-20, wherein a duration of a correlation window is based at least in part a quality of the received signal.

22. The receiver (34) of any of Claims 14-21, wherein a frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation.

23. The receiver (34) of Claim 22, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between the first peak and the second peak.

24. The receiver (34) of any of Claims 22 and 23, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between successive correlation windows of the successive correlation windows.

25. The receiver (34) of any of Claims 14-24, wherein the processing circuitry (106) is further configured to mix the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating an envelope of the mixed signal with the reference pattern.

26. The receiver (34) of any of Claims 14-25, wherein the processing circuitry (106) is further configured to place the receiver (34) in an idle mode between successive correlations.

27. A method in a wireless device, WD (22), configured to communicate with a radio node (16, 22), the WD (22) comprising a main transceiver (36) and a receiver (34), the method comprising: receiving (S142) by the receiver (34) from the radio node (16, 22) a signal having a repeating modulation pattern; successively (S144) correlating the received signal with a reference pattern over successive correlation windows, each correlation being clocked by a reference clock (94) of the main transceiver (36); determine (SI 46) a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjusting (S148) a reference clock (94) of the main transceiver (36) based at least in part on the frequency offset.

28. The method of Claim 27, further comprising operating the receiver (34) while the main transceiver (36) is in a low power state.

29. The method of any of Claims 27 and 28, wherein a frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation.

30. The method of Claim 29, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between the first peak and the second peak.

31. The method of any of Claims 29 and 30, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between successive correlation windows of the successive correlation windows.

32. The method of any of Claims 27-31, further comprising mixing the received signal with a free-running oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating the mixed signal with the reference pattern.

33. The method of any of Claims 27-32, further comprising operating the receiver (34) in an idle mode between successive correlations.

34. A wireless device, WD (22), configured to communicate with a radio node (16, 22), the WD (22) comprising: a main transceiver (36) including a reference clock (94); and a receiver (34) configured to: receive from the radio node (16, 22) a signal having a repeating modulation pattern; successively correlate the received signal with a reference pattern over successive correlation windows, each correlation being clocked by the reference clock (94) of the main transceiver (36); determine a frequency offset based at least in part on a movement of a peak of the correlations over successive correlations; and adjust the reference clock (94) of the main transceiver (36) based at least in part on the frequency offset.

35. The WD (22) of Claim 34, wherein the receiver (34) is configured to operate while the main transceiver (36) of the WD (22) is in a low power state.

36. The WD (22) of any of Claims 34 and 35, wherein a frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is decreased when a first time of a first peak of a first correlation is later than a second time of a second peak of a previous correlation and the frequency of the reference clock (94) of the main transceiver (36) of the WD (22) is increased when the first time of the first peak of the first correlation is earlier than the second time of the second peak of the previous correlation.

37. The WD (22) of Claim 36, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between the first peak and the second peak.

38. The WD (22) of any of Claims 36 and 37, wherein an amount of one of an increase and a decrease in the frequency of the reference clock (94) is based at least in part on a time between successive correlation windows of the successive correlation windows.

39. The WD (22) of any of Claims 34-38, further comprising a free-running oscillator(100) configured to produce an oscillator signal and a mixer (98) configured to mix the received signal with the oscillator signal to produce a mixed signal at an intermediate frequency prior to correlating the mixed signal with the reference pattern.

40. The WD (22) of any of Claims 34-39, wherein the receiver (34) is configured to operate in an idle mode between successive correlations.

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