WO2023104291A1

WO2023104291A1 - Sidelink connection set up assistance

Info

Publication number: WO2023104291A1
Application number: PCT/EP2021/084547
Authority: WO
Inventors: Gang ZOU; Andres Reial; Henrik Sjöland
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2023-06-15

Abstract

Disclosed herein is a method of a first wireless communication device for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device. The first wireless communication device comprising a first transceiver arrangement and a second transceiver arrangement. The method comprises detecting by the first transceiver arrangement operating at a first power level, one or more discovery signals from the second device; assisting, by the first receiver arrangement, side link connection set up to the second wireless communication device by performing one or more sidelink assist operations based on the one or more discovery signals; waking up, by the first transceiver arrangement, the second transceiver arrangement, wherein the second transceiver arrangement when awake is operating at a second power level, wherein operation at the first power level requires less power than operation at the second power level;relaying, by the first transceiver arrangement an outcome of the one or more sidelink assist operations to the second wireless receiver arrangement; and setting up, by the second transceiver arrangement, a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operations. Also disclosed herein is an apparatus, a computer program product and a method for transmitting a discovery signal.

Description

SIDELINK CONNECTION SET UP ASSISTANCE

Technical Field

The present invention relates generally to the field of device to device (D2D) communication. More particularly, it relates to sidelink connection set up assistance in a D2D communication scenario.

Background

Device-to-Device (D2D) communication typically establishes a sidelink between a pair of user equipment (UEs, it should be noted that the term "UE" may be used interchangeably with the term "device" or "wireless communication device" in this disclosure) so that the UEs can communicate directly between each other without involving a central unit such as e.g. a base station. For new and future communication systems employing e.g. 5G and 6G, it is becoming more and more important to lower communication latency and increase network capacity. One way of achieving this is by allowing D2D communication through sidelink connections between devices operating within a network. When utilizing a sidelink, traditional uplink and downlink communication through e.g. a base station is omitted.

To initiate D2D sidelink communication, a peer discovery is typically performed by a communication device to discover a peer device which typically broadcasts certain discovery signals (DS) to e.g. make its presence known. In order to guarantee the D2D performance, the peer discovery mechanism should preferably meet certain requirements pertaining to e.g. device power efficiency and low latency.

In the existing technology (for example, 3GPP LTE / NR sidelink spec. Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation, Release 15), the latency to set up the D2D sidelink is high, and the device power consumption is not optimized. This may risk impacting the operation time of the devices. Therefore, there is a need to optimize the peer discovery and connection set up process to improve on power efficiency and time latency in D2D communication scenarios. Thus, there is a need for a method and apparatus for enabling an energy and latency efficient sidelink connection set up.

Summary

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. It is an object of some embodiments to obviate or mitigate at least some of the above disadvantages and to provide methods, apparatuses and computer program products for establishing an efficient device to device sidelink connection.

According to a first aspect this is achieved by a method of a first wireless communication device for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device. The first wireless communication device comprises a first transceiver arrangement and a second transceiver arrangement. The method comprises detecting by the first transceiver arrangement operating at a first power level, one or more discovery signals from the second device. The method also comprises performing, by the first transceiver arrangement, one or more sidelink assist operations based on the one or more discovery signals and waking up, by the first transceiver arrangement, the second transceiver arrangement. The second transceiver arrangement, when awake, is operating at a second power level, wherein operation at the first power level requires less power than operation at the second power level. The method also comprises relaying, by the first transceiver arrangement an outcome of the one or more sidelink assist operations to the second wireless transceiver arrangement and setting up, by the second transceiver arrangement, a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operations.

In some embodiments, the first transceiver arrangement operates according to an always on principle and the second transceiver arrangement operates according to a sleep mode principle. Or, in some embodiments, the first transceiver arrangement operates according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep.

In some embodiments, the first transceiver arrangement is a low power receiver comprising at least one antenna element.

In some embodiments, the method further comprises detecting, by the first transceiver arrangement, the one or more discovery signals as a narrowband signal by using a time domain correlation.

In some embodiments, the one or more discovery signals comprise one or more of a primary sidelink synchronization signal, PSSS, a secondary sidelink synchronization signal, SSSS, a sidelink radio frequency beam tracking signal, a physical sidelink broad cast channel, PSBCH, a device to device wake up signal.

In some embodiments, performing one or more sidelink assist operations comprises performing, by the first transceiver arrangement, a radio frequency power estimation based on the one or more discovery signals and performing the step of setting up, by the second receiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operations comprises performing, by the second transceiver arrangement, automatic gain control, AGC, based on the radio frequency power estimation.

In some embodiments, performing one or more sidelink assist operations comprises obtaining, by the first transceiver arrangement, synchronization information from the one or more discovery signals and the step of setting up, by the second transceiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operations comprises performing, by the second transceiver arrangement, automatic frequency correction, AFC, based on the synchronization information.

In some embodiments, the method further comprises performing by the first transceiver arrangement synchronization to the second wireless communication device based on the obtained synchronization information.

In some embodiments, performing one or more sidelink assist operations comprises decoding, by the first transceiver arrangement, a sidelink beam index associated with the one or more discovery signals and relaying the decoded beam index to the second tranceiver arrangement.

In some embodiments, the first transceiver arrangement comprises more than one antenna elements and performing one or more sidelink assist operation comprises performing beam matching, by the first transceiver arrangement, by determining an angle of arrival of at least one beam comprising the one or more discovery signals and relaying to the second transceiver arrangement an indication of a preferred beam based on the determined angle of arrival.

In some embodiments, the method further comprises reporting, to a network node operating in a wireless communication network, a low power discovery signal reception capability during a connection establishment to the network node.

In some embodiments, the method further comprises receiving from the network node information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink reception range.

A second aspect is a computer program product comprising a non-transitory computer readable medium. The non-transitory computer readable medium has stored there on a computer program comprising program instructions. The computer program is configured to be loadable into a data-processing unit, comprising a processor and a memory associated with or integral to the data- processing unit. When loaded into the data-processing unit, the computer program is configured to be stored in the memory, wherein the computer program, when loaded into and run by the processor is configured to cause the processor to execute method steps according to any of the methods described according to the first aspect.

A third aspect is an apparatus of a first wireless communication device for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device. The apparatus comprises a first transceiver arrangement configured to operate at a first power level and a second transceiver arrangement configured to operate at a second power level when awake. Operation at the first power level requires less power than operation at the second power level. The apparatus further comprises a controlling circuitry. The controlling circuitry is configured to cause the first transceiver arrangement to detect one or more discovery signals from the second device; perform one or more sidelink assist operations based on the one or more discovery signals, wake up the second transceiver arrangement and relay an outcome of the one or more sidelink assist operation to the second wireless transceiver arrangement. The controlling circuitry is configured to cause the second transceiver arrangement to set up a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operation.

In some embodiments, the first transceiver arrangement is configured to operate according to an always on principle, and the second transceiver arrangement is configured to operate according to a sleep mode principle. I some embodiments, the first transceiver arrangement is configured to operate according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep.

In some embodiments, the controlling circuitry is further configured to cause the first transceiver arrangement to detect the one or more discovery signals as a narrowband signal by using a time domain correlation.

In some embodiments, the controlling circuitry is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to perform a radio frequency power estimation based on the one or more discovery signals. The controlling circuitry is configured to cause the second transceiver arrangement to perform setting up the sidelink connection based on the outcome of the one or more sidelink assist operation by being configured to cause the second transceiver arrangement to perform automatic gain control, AGC, based on the radio frequency power estimation.

In some embodiments, the controlling circuitry is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to obtain synchronization information from the one or more device to device specific reference signal. The controlling circuitry is configured to cause the second transceiver arrangement to perform setting up the sidelink connection based on the outcome of the one or more sidelink assist operations by being configured to cause the second receiver arrangement to perform automatic frequency correction, AFC, based on the synchronization information.

In some embodiments, the controlling circuitry is further configured to cause the first transceiver arrangement to perform synchronization to the second wireless communication device based on the obtained synchronization information.

In some embodiments, the controlling circuitry is configured to cause the first transceiver arrangement to perform the one or more sidelink assist operation by being configured to cause the first transceiver arrangement to decode a sidelink beam index associated with the one or more other device to device specific reference signal and relay the decoded beam index to the second transceiver arrangement.

In some embodiments, the first transceiver arrangement comprises more than one antenna elements, and wherein the controlling circuitry is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to perform beam matching by determining an angle of arrival of at least one beam comprising the one or more discovery signals and relay to the second transceiver arrangement an indication of a preferred beam based on the determined angle of arrival.

In some embodiments, the controlling circuitry is further configured to cause reporting, to a network node operating in a wireless communication network of, a low power discovery signal reception capability during a connection establishment to the network node.

In some embodiments, the controlling circuitry is further configured to cause reception, from the network node, of information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink reception range.

A fourth aspect is a wireless communication device comprising the apparatus according to the second aspect.

A fight aspect is a method for initiating a device to device sidelink connection by a first wireless communication device to a second wireless communication device. The method comprises determining that the second wireless communication device comprises a first transceiver arrangement operating at a first power level, and a second transceiver arrangement operating, when awake, at a second power level. The first power level is less than the second power level. The method further comprises transmitting at least one discovery signal according to a signal configuration which allows detection of the at least one discovery signal by the first transceiver arrangement.

In some embodiments, the signal configuration that allows detection and decoding of the at least one device to device specific reference signal by the first transceiver arrangement comprises transmitting the discovery signal as a narrowband signal. In some embodiments, the signal configuration that allows detection and decoding of the at least one device to device specific reference signal by the first transceiver arrangement comprises modulating the discovery signal with a low order modulation.

In some embodiments, the method further comprises receiving a response from the second wireless communication device based on the transmitted discovery signal and setting up the sidelink connection between the first wireless communication device and the second wireless communication device.

In some embodiments, any of the above mentioned aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the above aspects.

An advantage of some embodiments is that a power efficient sidelink connection set up with low latency is enabled.

Brief Description of the Drawings

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings, in which:

Fig. 1 is a flowchart illustrating example method steps according to some embodiments;

Fig. 2 is a schematic drawing illustrating an example network scenario according to some embodiments;

Fig. 3 is a flowchart illustrating example method steps according to some embodiments;

Fig. 4 is a block diagram illustrating an example apparatus according to some embodiments; and

Fig. 5 is a block diagram illustrating an example computer product according to some embodiments.

Detailed Description

In the following, embodiments will be described where power efficient and low latency sidelink connection set up between two wireless devices is enabled.

A wireless communication device is typically equipped with some sort of transceiver arrangement. Such an arrangement may e.g. comprise a separate receiver and transmitter or a combined receiver and transmitter. The transceiver arrangement may further comprise an antenna array comprising one or more antenna elements. The transceiver is typically a power consuming entity, and one way to mitigate the power consumption for a wireless device is to allow the transceiver to operate in different modes. Typical modes are active, idle and (deep) sleep. In active mode the transceiver typically sends, receives and monitors incoming and outgoing signals, i.e. the device communicates with its surroundings. In idle mode, the transceiver is awake and consumes power but does not perform any communication operations. In sleep mode, the transceiver may typically be viewed as being "shut off".

Although the sleep mode is power efficient it may negatively impact communication latency, since prior to any communication the transceiver typically needs to be woken up, and following the wake up, it typically performs one or more operations in order to set up a communication connection to either a base station or another device. These operations may typically be both power consuming and add to latency.

The peer discovery in device to device (D2D) communication enables devices to discover the presence of other devices in their neighborhood. One of the chronic concerns about peer discovery is the energy efficiency of the process. One solution is using D2D peer discovery signal (DS) to dedicate small time-slots for the purpose of peer discovery. Various signals may function as discovery signals. The discovery signals may e.g. be device to device specific reference signals (hence the terms discovery signal and device to device specific reference signal may be used interchangeably in this disclosure). Such device to device specific reference signals can e.g. be the D2D sidelink synchronization signals (the terms D2D and sidelink may be used interchangeably in this disclosure). For example, 3GPP LTE sidelink provides synchronization signals (SSs) for one user equipment (UE) to another UE directly without any intervention of the network. There are two types of SS in the sidelink, a primary sidelink SS (PSSS) and a secondary sidelink SS (SSSS). By detecting PSSS and SSSS, the neighbor UE can acquire the carrier frequency offset (CFO), subframe and symbol timings, and sidelink identity of the source UE. Other examples of discovery signals may be device to device specific wake up signals.

Long term evolution (LTE) sidelink channels are designed using single carrier frequency division multiple access (SC-FDMA) waveforms for transmission over the uplink spectrum. Typically, a subframe is configured for sidelink synchronization under a normal cyclic prefix (CP) operation, where a maximum number of sidelink (NSS) subcarriers around the center frequency are utilized for synchronization and signaling. The PSSS and SSSS symbols constructed using (Nd) subcarriers are transmitted twice within the same subframe. The PSSS is transmitted in the central 62 resource elements of two adjacent SC- FDMA symbols in a synchronization subframe. The same sequence of 62 complex values is repeated in each of the symbols, The SSSS is transmitted in the central 62 resource elements of two adjacent SC- FDMA symbols in a synchronization subframe. The same sequence of 62 complex values is repeated in each of the symbols.

The synchronization in new radio (NR) Sidelink is very similar to the one used in LTE, though the signal structure is different.

However, although the discovery signals enhance energy efficiency, latency which may typically occur when one of the devices about to engage in D2D communication is in deep sleep may present a problem. Typically, when in deep sleep, the receiver part is not active and cannot detect the discovery signals and thus the device does not become aware that someone wants to engage in D2D communication. The receiver thus needs to be taken to active mode during a fraction of the time and then there is a trade-off between power consumption and latency. The more time spent in active mode, the more likely the discovery signal will be detected quickly, but the larger the power consumption becomes.

In some embodiments, by adding a so-called low power receiver (LPR) to the existing main transceiver arrangement of a wireless device, the power consumption of the main transceiver as well as potential communication latency may be reduced. A low power receiver typically uses a simple antenna arrangement comprising a low number of antenna elements (e.g. less than 20 antenna elements) with limited functionalities compared to a main transceiver, including potentially lower reception quality and related front end relaxations that save power.

Since the LPR operates at such low power, it can e.g. always be on without having an overly large impact on the overall power consumption of the device. Since the LPR is typically always on (or at least have long active periods compared to the main receiver), it may in some embodiments assist the main transceiver when the main transceiver is in idle or sleep mode to monitor for discovery signals and hence relieve the main transceiver of this process. In some embodiments the LPR may operate in a duty cycle (i.e. it may alternate between active and sleep mode), but the duty cycle may be larger than the duty cycle of the main receiver for the same power consumption. This would allow for reduced latency while not resulting in a major increase of power consumption. However, in embodiments where low latency is critical (such as e.g. in URLL scenarios) allowing the LPR to operate according to an always on principle may typically result in the least amount of latency for sidelink connections, while still maintaining an acceptable power consumption. In some embodiments, reduced power consumption may be of more importance than minimum latency, and in such embodiments, it may hence be beneficial to allow the LPR to operate according to a duty cycle.

In some embodiments, when applied in D2D communication, the LPR keeps monitoring the surrounding radio frequency (RF) environment of the UE, for e.g. discovery signals (or other device to device specific reference signals) transmitted by a peer UE. When a D2D sidelink connection is required, and the LPR detects a potential peer device, it can wake the main transceiver in the UE and share its RF detection results with the main transceiver so that the UE can quickly find the peer UE and setup the D2D sidelink connection.

Fig. 1 illustrates a method 100 according to some embodiments.

The method 100 is of a first wireless communication device for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device. The first and second wireless communication devices may be configured to operate in a wireless communication network. In some embodiments, the first wireless communication device and the second wireless communication device operates in a same wireless communication network. In some embodiments, the first wireless communication device and the second wireless communication device operates in different wireless communication networks.

The first wireless communication device comprises a first transceiver arrangement and a second transceiver arrangement. In some embodiments, the second wireless communication device also comprise a first transceiver arrangement and a second transceiver arrangement, having the same functionalities as those of the first communication device.

In the method 100, steps 110-150 may be carried out by the first transceiver arrangement (1st TRX). The step 160 may be carried out by the second transceiver arrangement (2nd TRX). It should be noted that the second transceiver arrangement is capable of carrying out some of the steps 110-150 as well.

The method 100 starts in step 110 with detecting, by the first transceiver arrangement operating at a first power level, one or more discovery signals from the second device. The discovery signal may e.g. be transmitted by the second device. A discovery signal may e.g. be one or more of sidelink synchronization signals, sidelink radio frequency beam tracking signals and a wake up signal.

In optional step 121 (which step has been illustrated as being comprised in step 120, but which may take place prior to the step 120), the method 100 may comprise the first transceiver arrangement extracting information from the detected discovery signal. The first transceiver arrangement may e.g. extract one or more samples from the detected discovery signal. The first transceiver arrangement may further store in optional step 122 (which step has been illustrated as being comprised in step 120, but which may take place prior to or after the step 120) the extracted information and/or extracted one or more samples in e.g. a memory.

The method comprises the first transceiver arrangement assisting side link connection set up to the second wireless communication device by performing in step 120 one or more sidelink assist operations based on the one or more discovery signals. The sidelink assist operations may e.g. be performed based on the previously extracted and stored samples of the detected discovery signal.

Then in step 140, the method continues with waking up, by the first transceiver arrangement, the second transceiver arrangement. The second transceiver arrangement when awake is operating at a second power level. Operation at the first power level requires less power than operation at the second power level. When, in some embodiments, the first transceiver arrangement operates according to a duty cycle, the first power level is associated with an active state of the first transceiver arrangement.

Then, in step 150 the method comprises, relaying by the first transceiver arrangement an outcome of the one or more sidelink assist operations to the second transceiver arrangement.

In step 160, the method comprises setting up, by the second transceiver arrangement, a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operations. By storing (or by relaying directly) samples and/or the outcome of the one or more sidelink assist operations based on the detected one or more discovery signals and relaying those to the second transceiver arrangement when it has been woken up, the burden of device discovery and sidelink connection set up is lessened for the second, more power consuming, transceiver arrangement.

As noted previously, in some embodiments, the first transceiver arrangement may be a low power receiver (or possibly a low power transceiver since it is envisioned that the LPR may in some embodiments have transmitting abilities as well) which operates with limited functionality. Hence, in some embodiments, the first transceiver arrangement is a receiver arrangement. The second transceiver arrangement may be a regular transceiver operating with full functionality, and hence acts as the main transceiver arrangement of the wireless device. The first transceiver arrangement may in some embodiments operate according to an always on principle, or the first transceiver arrangement may operate according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep. The second transceiver arrangement may in some embodiments operate according to a sleep mode principle. By sleep mode principle it is meant that the second transceiver arrangement may, in times of inactivity, retreat into an idle mode, inactive mode, and/or sleep mode (although the terms are slightly different, they may be used interchangeably in this disclosure). In these modes the main transceiver typically requires less power and will typically not carry out any communication or monitor for reference signals and/or discovery signals. In sleep mode the second transceiver arrangement may additionally have shut off some of its components and functionalities.

In some embodiments, the second transceiver arrangement may further be configured to leave sleep mode at regular intervals to see whether there is communication intended for it. The second transceiver arrangement hence operates according to a duty cycle.

By always on principle, it is meant that the first transceiver arrangement is always on and does not revert into a sleep state/mode on regular basis.

However, some embodiments, the first transceiver arrangement operates according to a first duty cycle comprising an active time which at least partly overlaps with a time period during which the second transceiver arrangement is in sleep mode. Le. the first transceiver arrangement is awake for longer periods of time and/or more often than the second transceiver arrangement. The first transceiver arrangement may e.g. in some embodiments be configured to enter idle mode when the sidelink connection has been set up (and/or when the second transceiver arrangement is engaged in communication with another device or base station).

In some embodiments, the first transceiver arrangement operates according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep. Le. the first transceiver arrangement may be in an active state during a majority of the total time of one monitoring period. It should be noted that the first and second power level referred to above concerns the power required when the transceivers are awake and perform operations associated with connectivity and communication. Hence, when the second transceiver arrangement is in a sleep/inactive/idle mode it will require less power than the first transceiver arrangement, which operates according to the first power level in an always on fashion or according to a duty cycle where a large part of the time can be spent in the active state. However, when the second transceiver arrangement has been woken up, it typically operates according to the second power level, which is higher than both the first power level as well as any power required when being in sleep/inactive/idle mode. The difference in power between the first and second power level may vary but is typically two orders of magnitude or more.

As noted above, in some embodiments, the first transceiver arrangement is a low power receiver comprising at least one antenna element.

The first transceiver arrangement comprises in some embodiments a single antenna. In some embodiments, the first transceiver arrangement further comprises a narrow bandwidth RF receiver (or transceiver) and a signal detector featuring a time-domain correlator.

The first transceiver arrangement may hence typically be implemented with low power consumption so that it can be kept always-ON and running in the background for narrow bandwidth signal detection while the main second transceiver arrangement can be configured into sleep/low- power mode.

In some embodiments the first transceiver arrangement may be implemented with a duty cycle comprising an active state which applies for long periods of times (e.g. minutes, hours, days, weeks or even months) and a sleep state.

In some embodiment the first transceiver arrangement may be implemented with a duty cycle, wherein the duty cycle defines as a ratio between an active time and a total time during a monitoring period (or over time) when the second transceiver arrangement is in deep sleep. I.e. the duty cycle has a total time which is divided into active time and unactive time. Active time makes out a certain percentage of the total time, which percentage may vary and be dynamically set e.g. based on network conditions.

Furthermore, in some embodiments, the method 100 may further comprise detecting, by the first transceiver arrangement, the discovery signal as a narrowband signal by using a time domain correlation.

In some embodiments, a D2D Wakeup signal may be used as DS. E.g., in cases when its neighbor device is in deep sleep, a device may send out a wakeup signal (typically a narrow band signal with simple modulation technique, e.g. on-off keying (OOK)) to wake up the neighbor device so that a D2D sidelink can be setup.

Since the DS may take various forms, it may further carry different types of information.

Hence, in some embodiments the first transceiver arrangement may take various actions depending on what type of signal the discovery signal is (as will be elaborated on below) and hence what type of signal it is configured to detect.

According to some embodiments herein, the first transceiver arrangement may detect and monitor discovery signals, and based on this, wake up the second transceiver arrangement. When the second transceiver arrangement wakes up it may receive information from the first transceiver arrangement pertaining to the detected discovery signals. This enables the second transceiver arrangement to conserve energy and reduce latency since it does not have to actively search for unknown discovery signals and/or reference signals as this has already been done by the first transceiver arrangement.

In some embodiments, the first transceiver arrangement may, in addition to monitoring and detecting discovery signals, also carry out simple computations (step 120 of the method 100) and/or assist operations on the detected signals (i.e. on the information comprised by the detected signals, which the first transceiver arrangement may extract) in order to further assist the second transceiver arrangement to set up a sidelink connection. This may in some embodiments be done prior to, or after, step 140, where the first transceiver arrangement wakes up the second transceiver arrangement. It may in some embodiments be done in combination with optional step 130 (which step will be elaborated on further below).

The operations may e.g. be assisting the second transceiver arrangement in performing radio frequency power estimation, calculating automatic gain control (AGC), automatic frequency correction (AFC), calculating beam index, perform beam coding, or perform synchronization to the second wireless communication device. The calculations and/or operations performed by the first transceiver arrangement may result in fairly coarse values. However, they may serve as valuable starting inputs from which the second transceiver arrangement may base its own more complex calculations and thus faster converge to accurate values and finish the set up of the sidelink connection. This in turn has the potential to reduce the operating time needed for the second transceiver arrangement which in turn may lower power consumption of the second transceiver arrangement, as well as reduce latency in the sidelink connection set up.

For example, typically when a UE wakes up from deep sleep, it should preferably perform automatic gain control (AGC) to tune its receiver gain so it can map the received range of signal levels at the UE antenna connector onto the dynamic range of the analog-to-digital converter (ADC). The first transceiver arrangement can keep monitoring discovery signals such as D2D reference signals and/or D2D wake up signals, estimating the power of the reference signals and/or wakeup signals. Once the second (main) transceiver arrangement wakes up, it can use the RF power estimation from the first transceiver arrangement to perform AGC, and/or to use the estimate from the first transceiver arrangement as initial AGC setting for first reception attempt. Hence, the step 120 comprising performing one or more sidelink assist operations may comprise performing, by the first transceiver arrangement, a radio frequency power estimation based on the discovery signal. After step 140, comprising waking up the second transceiver arrangement, the method continues in step 150 with relaying (by the first transceiver arrangement) the radio frequency power estimation to the second transceiver arrangement.

Then, performing the step 160 of setting up, by the second transceiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operation comprises performing, by the second transceiver arrangement, automatic gain control, AGC, based on the radio frequency power estimation (and setting up and/or finalize the sidelink connection to the second wireless communication device based at least in part on the performed AGC).

By continuously monitoring (e.g. detecting and decoding) discovery signals and/or sidelink reference signals, the first transceiver arrangement can always synchronize itself to the second wireless communication device. It can also share the synchronization info, e.g. estimated frequency offset with regards to a known signal or internal frequency reference in the UE, with the second transceiver arrangement. Once the second transceiver arrangement is woken up from sleep mode, it can perform automatic frequency correction (AFC) at a lower complexity and more quickly (than if it had not been assisted by the first transceiver arrangement). This may lead to a smoother set up and hence initiation of sidelink communication.

Thus, in some embodiments, performing (e.g. in step 120) one or more sidelink assist operation may comprise obtaining, by the first transceiver arrangement, synchronization information from the one or more discovery signals. Synchronization information may e.g. relate to time or frequency offset estimates.

The obtained synchronization information is relayed (e.g. in step 150) to the second transceiver arrangement.

Hence, the step 160 of setting up, by the second transceiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operation may comprise performing, by the second transceiver arrangement, automatic frequency correction, AFC, based on the synchronization information (and setting up the connection based on the AFC).

In some embodiments, the method may further comprise performing (e.g. in step 120) by the first transceiver arrangement synchronization to the second wireless communication device based on the obtained synchronization information. The synchronization performed by the first transceiver arrangement towards the second communication device may in some embodiments be performed independently of synchronization performed by the second transceiver arrangement. Hence, it is not required that the first transceiver arrangement, in order to perform synchronization, relays synchronization information to the second transceiver arrangement. Furthermore, the first transceiver arrangement can decode sidelink beam index in cases when the sidelink supports the transmission of discovery/reference signals with beam sweeping and with beam index encoded.

Hence, in some embodiments, performing (e.g. in step 120) one or more sidelink assist operations may comprise performing decoding, by the first transceiver arrangement, of a sidelink beam index associated with the discovery signal. The decoded beam index may then be relayed (e.g. in step 150) to the second transceiver arrangement.

Although a low power receiver, such as the first transceiver arrangement, may comprise a single antenna element, which typically results in low power consumption, it is envisioned that a low power receiver (and/or low power transceiver) according to some of the embodiments herein may comprise more than one antenna elements. If more than one antenna elements are allowed, slightly more complex computations or operations may be carried out by the first transceiver arrangement while still keeping its power consumption very low compared to the main transceiver.

For example, a quick beam match between the devices which are about to engage in a D2D sidelink can be made. For example, the first transceiver arrangement can be associated with multiple antenna elements (e.g. 2-16 antenna elements) in order to detect an angle of arrival (AoA) of swept beams of detected discovery signals and provide preferred receiver beam info to the second transceiver arrangement (which may then exchange the beam info with the second wireless device).

Hence, in some embodiments, the first transceiver arrangement comprises more than one, antenna elements, and performing (e.g. in step 120) one or more sidelink assist operation may comprise performing beam matching, by the first transceiver arrangement, by determining an angle of arrival (AoA) of at least one beam comprising the discovery signal and relaying (e.g. in step 150) to the second transceiver arrangement an indication of a preferred beam based on the determined angle of arrival. In some embodiments, the preferred beam is a receive beam. In some embodiments the preferred beam is a transmit beam.

In some embodiments, the method 100 may comprise optional step 130, where the first receiver arrangement checks whether the second receiver arrangement is in sleep mode or is awake. When it is determined that the second receiver arrangement is not in sleep mode (N-path out of 130) the method may continue with the first transceiver arrangement relaying (in step 150) an outcome of the performed one or more sidelink assist operation to the second transceiver arrangement and/or returning to step 110 where further detection of other discovery signals may be made.

Typically, if the second transceiver is awake, it may be assumed that it is already involved in communication or is currently setting up a connection (in such cases the first transceiver arrangement may in some embodiments revert into a sleeping state). In such cases it may not be beneficial from a power perspective to allow the first transceiver arrangement to perform operations or computations on the detected discovery signals (since it may be assumed that the needed computations are already taken care of by the second transceiver arrangement). Hence, although optional step 130 has been illustrated to follow step 120 in the method 100, in some embodiments, optional step 130 may be incorporated into step 120. The first transceiver arrangement may hence check, prior to making any extensive operations, if the second transceiver arrangement is awake or not.

However, in some embodiments, it may be beneficial to allow the first transceiver arrangement to perform measurements/computations/operations on the detected discovery signals even though the second transceiver arrangement is awake. The first transceiver arrangement may thus provide additional input to the second transceiver arrangement, which may enhance robustness and also reduce latency when setting up connections or discovering peer devices located geographically close to the first wireless communication device. The first transceiver arrangement may also relieve the second transceiver arrangement from the discovery signal monitoring tasks and allow it to perform other tasks in parallel, possibly in other frequency bands; in such cases the second transceiver sleep principle may be viewed as not being active in the frequency region where the sidelink discovery signals are transmitted.

Furthermore, in some embodiments, the step 160, where a sidelink connection is set up, may further comprise transmitting by the second transceiver arrangement to the second wireless communication device, an indication of a transmit power to be used for communicating through the sidelink.

The transmit power to be used for communicating through the sidelink may be determined e.g. based on a power of the detected discovery signal and/or based on the outcome of the one or more assist operation described above.

E.g., if the discovery signal is detected by the first transceiver arrangement at high power, this may be an indication that the second wireless communication device could actually decrease transmit power and its transmissions would still be well received by the first wireless communication device. Likewise, if the discovery signal is barely detected or detected at low power, it may be an indication that the second wireless communication device needs to increase transmit power in order to be properly received by the first wireless communication device.

In some embodiments, the step 160 may further comprise transmitting by the second transceiver arrangement to the second wireless communication device an indication of a beam to be used for communicating through the sidelink.

Fig. 2 illustrates a network scenario according to some embodiments, where e.g. the method 100 is applicable.

Fig. 2 illustrates wireless communication network 200 comprising a network cell 201.

The wireless communication network 200 may be one or more of an LTE (long term evolution) network, a 5G radio access network, and a 6G radio access network. Network cell 201 is managed by network access node 210. Note that, in the description herein, reference may be made to the term "cell"; however, particularly with respect to 5G NR (new radio) concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

Network access node 210 may e.g. be a "radio access node" or "radio network node" or "radio access network node" or a "network node" which may be any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

Furthermore, two wireless communication devices are present in the network cell 201. A first wireless communication device 220, and a second wireless communication device 230. It should be noted that the network 200 may comprise more than, or less than, two wireless communication devices, Fig. 2 just illustrates an example scenario.

A wireless communication device as used herein may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (loT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless connection.

The first and second wireless communication devices 220, 230 may communicate traditionally with the network access node 210 as indicated by arrows 211 and 212. However, the first wireless communication device 220 and the second wireless communication device 230 may also communicate directly with each other through a sidelink connection, as indicated by arrow 213. The sidelink connection 213 may e.g. be set up according to the method 100 as described in conjunction with Fig. 1.

For example, both the first and second wireless communication devices may comprise a first transceiver arrangement and a second transceiver arrangement. The first transceiver arrangement may be configured to operate according to an always on principle (or with a duty cycle as previously described), and the second transceiver arrangement may be configured to operate according to a sleep mode principle (as previously described).

Device to device communication may benefit from assistance from the network access node 210. The network access node may e.g. gather (e.g. as part of connection procedure to the network) information from other communication devices present in the cell 201 pertaining to communication capabilities of the other communication devices. This information may then be shared (e.g. through broadcasting or through dedicated signaling) with all of the devices present in the cell served by the network access node, as well as with devices located geographically close but e.g. in a different cell served by a different network node.

Although Fig. 2 only shows as an example one network cell and two wireless devices comprised in this cell, it should be noted that the embodiments described herein are applicable also for wireless devices operating in different network cells but located within D2D sidelink connection range. Hence the network node 210 could collect information pertaining to D2D capability from devices in adjacent cells from neighboring network nodes and further share this information with the wireless devices in the network cell 201. The devices in adjacent cells may be located geographically close to, and be within D2D communication range of, the first and/or second wireless devices 220, 230. Similarly, a sidelink connection may be directly established between either of the first and the second wireless devices and one or more other wireless communication devices located within sidelink connection range but not necessarily within the same network cell.

Furthermore, in some embodiments, wireless communication devices capable of D2D communication and implemented with e.g. a low power receiver in addition to a main receiver and/or transceiver may report low-power DS reception capability to the network (e.g. to a serving base station), as part of connection establishment or as part of connected mode signaling, or upon a direct request. The capability report may include details about which signals, or signal configuration, can be received with reduced power consumption.

The network may provide info about the presence of LPR D2D-capable devices in the cell or in the neighborhood (i.e. within sidelink communication/connection range) to other devices, via broadcast or dedicated signaling. Other D2D devices may use that info to configure discovery signals or other reference signal transmissions that are suitable for detection by a LPR in peer devices.

Hence, in some embodiments, the method 100 may further comprise reporting, to a network node (possibly operating in the wireless communication network), a low power discovery signal reception capability. E.g. during a connection establishment to the network node.

In some embodiments, the method 100 may further (additionally and/or alternatively) comprise receiving from the network node information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink connection range.

In some embodiments, the method 100 may further (additionally and/or alternatively) comprise receiving from the network node information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a network cell associated with the network node.

In some embodiments, the method 100 may further (additionally and/or alternatively) comprise receiving from the network node information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception located within an adjacent network cell.

A sidelink connection range may e.g. be defined by an area within which sidelink signaling have reach. Typically, sidelinks can be maintained over smaller areas, and a device attempting sidelink connection with another device is probably within a 100 meters of the another device. However, the range may expand or decrease depending on other factors such as mobility, buildings, line of sight, environments etc.

Herein, focus has been made on the wireless communication device detecting and/or receiving device to device specific reference signals e.g. as discovery signals. However, embodiments are envisioned where the wireless communication device transmits discovery signals in order to initiate device to device communication through a sidelink.

Typically, the discovery signal should be sent out as a narrowband signal having a relatively simple modulation technique in order for the low power receiver to be able to detect them. Such a modulation technique may e.g. be on and off keying (OOK), binary phase shift keying (BPSK), frequency shift keying FSK, or similar.

Hence, some embodiments may comprise a method 300 (as illustrated by Fig. 3) for initiating a device to device sidelink connection by a first wireless communication device to a second wireless communication device. The method comprises in step 311 determining that the second wireless communication device comprises a first transceiver arrangement operating according to a first power level, and a second transceiver arrangement operating, when awake, according to a second power level. The first power level is less than the second power level. The method also comprises transmitting 312 at least one discovery signal according to a signal configuration which allows detection and decoding of the at least one discovery signal by the first transceiver arrangement.

A signal configuration that allows detection and decoding of the at least one discovery signal by the first transceiver arrangement may e.g. be transmitting the discovery signal as a narrowband signal and/or using a low order modulation.

A low order modulation may e.g. be OOK, BPSK, FSK or similar. In some embodiments, the method 300 further comprises step 313, receiving a response from the second wireless communication device based on the transmitted discovery signal(s). The method 300 may then continue in step 314 with setting up the sidelink connection between the first wireless communication device and the second wireless communication device (based at least in part on the received response).

The first wireless communication device may e.g. be any of the first and second wireless communication devices described in conjunction with any of the previous Figs. 1-2. Similarly, the second wireless communication device may be any of the first and second wireless communication devices described in conjunction with any of the previous Figs. 1-2.

Furthermore, the method may comprise in step 311 obtaining from a network node (e.g. the network node 210, described in conjunction with Fig. 2) an indication whether the second wireless communication device comprise a first transceiver arrangement operating at a first power level and a second transceiver arrangement operating, when awake, at a second power level, wherein the first power level is less than the second power level.

The indication may e.g. be received from the network node as broadcasted signal, or as dedicated signaling obtained during a connection procedure to the network node for cellular communication.

In some embodiments, the method may comprise in step 311 detecting a discovery signal (e.g. by applying the method 100 previously described), by the first transceiver arrangement, from the second wireless communication device. When a discovery signal is detected by the first transceiver arrangement, the first wireless communication device may determine that the discovery signal originates from a wireless communication device capable of D2D communication.

In some embodiments, the first wireless communication device may act as a synchronization source and may transmit discovery signals in synchronization subframes. The synchronization subframes may be transmitted over an already established sidelink connection in order to assist during communication. Alternatively, or additionally, synchronization subframes may be transmitted in order to detect and/or assist in establishing a sidelink connection.

Hence, in some embodiments, the method 300 may comprise transmitting (and/or receiving) discovery signals prior to having determined whether there are devices eligible for D2D communication in e.g. the same cell as (or in otherwise close vicinity to) the first wireless communication device.

Fig. 4 illustrates an apparatus 400 according to some embodiments. The apparatus 400 is of a first wireless communication device (e.g. the wireless communication device 220 and/or 230 of Fig.2 and/or the first wireless communication device described in conjunction with any of the Figs 1-3) for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device (e.g. the wireless communication device 220 and/or 230 of Fig. 2 and/or the second wireless communication device described in conjunction with any of the Figs. 1-3). The first and second wireless communication devices being configured to operate in a wireless communication network (e.g. the wireless communication network 200 described in conjunction with Fig 2 and/or the wireless communication network described in conjunction with any if the previous Figs 1-3). The apparatus 400 may further be configured to carry out any of the methods 100 and 300 as described in conjunction with respective Figs. 1 and 3.

The apparatus 400 comprises a first transceiver arrangement (1^st TRX) 420 configured to operate at a first power level and a second transceiver arrangement (2^nd TRX) 430 configured to operate at a second power level when awake, wherein operation at the first power level requires less power than operation at the second power level, and a controlling circuitry (CNTR) 410. The controlling circuitry 410 is configured to cause the first transceiver arrangement 420 to detect one or more discovery signals from the second device.

The first transceiver arrangement 421 comprises in some embodiments a single antenna element. In some embodiments, the first transceiver arrangement comprises a narrow bandwidth RF receiver (or transceiver).

The controlling circuitry 410 is configured to cause the first transceiver arrangement 420 to assist side link connection set up to the second wireless communication device. The controlling circuitry 410 may e.g. be configured to cause the first transceiver arrangement 420 to perform one or more sidelink assist operations based on the discovery signal.

The controlling circuitry 410 is configured to cause the first transceiver arrangement to wake up the second transceiver arrangement.

The controlling circuitry 410 is configured to cause the first transceiver arrangement to relay an outcome of the one or more sidelink assist operation to the second wireless transceiver arrangement. Furthermore, the controlling circuitry is configured to cause the second transceiver arrangement to set up a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operation.

In some embodiments, the controlling circuitry 410 may comprise or be connectable to the first transceiver arrangement 420 and the second transceiver arrangement 430.

Furthermore, in some embodiments, the first transceiver arrangement 420 may comprise a detector module (detector) 421. The detector module may e.g. be a signal detector featuring a timedomain correlator (not shown).

The controlling circuitry may e.g. cause the first transceiver arrangement and/or the detector module to detect the one or more discovery signals.

Furthermore, in some embodiments the first transceiver arrangement is configured to operate according to an always on principle. Or, in some embodiment, the first transceiver arrangement is configured to operate according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep. The second transceiver arrangement is configured to operate according to a sleep mode principle

In some embodiments, the first transceiver arrangement is configured to operate according to a first duty cycle comprising an active time which at least partly overlaps with a time period during which the second transceiver arrangement is in sleep mode .

In some embodiments, the first transceiver arrangement is a low power receiver (or transceiver) comprising at least one antenna element.

In some embodiments, the first transceiver arrangement is a low power receiver (or transceiver) comprising more than one antenna elements.

In some embodiments the controlling circuitry is further configured to cause the first transceiver arrangement to (e.g. by causing the detector module to): detect the one or more discovery signals as a narrowband signal by using a time domain correlation.

In some embodiments, the one or more discovery signals may comprise one or more of a primary sidelink synchronization signal, PSSS, a secondary sidelink synchronization signal, SSSS, a sidelink radio frequency beam tracking signal, a physical sidelink broad cast channel signal, PSBCH, a device to device wake up signal.

The first transceiver arrangement may comprise a relay module (relay) 424 for relaying signals and/or information extracted from detected signals e.g. to the second transceiver arrangement 450.

The second transceiver arrangement 430 may comprise a connect module (connect) 432 for setting up and/or establishing a sidelink connection to another peer device (e.g. the second wireless communication device).

In some embodiments, the apparatus 400 further comprises a storage module (not shown).

The storage module may e.g. be a memory. The controlling circuitry 410 may e.g. in some embodiments be configured to store the one or more detected discovery signals. The controlling circuitry 410 may e.g. be configured to extract information and/or samples from the detected discovery signal, and store the extracted information/samples in the storage module for later use. The stored information/samples may e.g. be directly relayed to the second transceiver arrangement when it has woken up. In some embodiments, the stored extracted/information samples are used for performing the one or more sidelink assist operations (as further elaborated on below). The outcome of such operations may be stored in the storage module and then be relayed (e.g. by the relay module 424) to the second receiver arrangement.

To this end, the first receiver arrangement 420 may comprise a measuring unit (measure) 423 which may be caused (e.g. by the controlling circuitry 410) to extract information from the discovery signal, measure on said information and/or perform calculations based on said information. The controlling circuitry may further be configured to cause the second transceiver arrangement 430 to perform setting up the sidelink connection by being configured to cause the second transceiver arrangement to set up the sidelink connection (e.g. by causing the connect module 432) based on the outcome of the one or more sidelink assist operation.

In some embodiments, the controlling circuitry 410 is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to perform a radio frequency power estimation based on the one or more discovery signals (e.g by causing the measuring module 423). When the second transceiver arrangement 430 is awake, the controlling circuitry may be configured to cause the first transceiver arrangement 420 to relay the radio frequency power estimation to the second transceiver arrangement.

In some embodiments, the controlling circuitry is configured to cause the second transceiver arrangement to perform setting up the sidelink connection by being configured to cause the second transceiver arrangement to perform automatic gain control, AGC, based on the radio frequency power estimation.

In some embodiments, the controlling circuitry 410 is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to obtain synchronization information (e.g. by causing the measuring module 423) from the discovery signal.

In some embodiments, the controlling circuitry is further configured to cause the first transceiver arrangement to relay (e.g. by causing the relay module 424 to relay) the obtained synchronization information to the second transceiver arrangement.

Furthermore, in some embodiments the controlling circuitry is further configured to cause the second transceiver arrangement to perform setting up the sidelink connection by being configured to cause the second transceiver arrangement to perform automatic frequency correction, AFC, based on the synchronization information.

To this end, the second transceiver arrangement may comprise a measuring module 431 (which may be different from, or be the same as, the measuring module 423 associated with the first transceiver arrangement) for measuring and/or performing calculations based on received information from the first transceiver arrangement, as well as on signals and information gathered by the second transceiver arrangement from other devices or network nodes.

In some embodiments, the controlling circuitry 410 is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to decode a sidelink beam index associated with the discovery signal and relay the decoded beam index to the second transceiver arrangement.

In some embodiments, the first transceiver arrangement comprises more than one elements. Furthermore, in some embodiments the controlling circuitry 410 is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by performing beam matching by determining an angle of arrival of at least one beam comprising the discovery signal and relay to the second transceiver arrangement an indication of a preferred beam based on the determined angle of arrival.

In some embodiments, the preferred beam may be a receive beam. In some embodiments the preferred beam may be a transmit beam.

In some embodiments, the controlling circuitry is further configured to cause reporting, to a network node operating in the wireless communication network, of a low power device to device specific reference signal reception capability during a connection establishment to the network node.

In some embodiments, the controlling circuitry is further configured to cause reception, from the network node, of information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink connection range.

In some embodiments, the controlling circuitry 410 is further configured to cause determination of that the second wireless communication device comprises a first transceiver arrangement operating at a first power level, and a second transceiver arrangement operating at a second power level when awake. The first power level is less than the second power level. When it is determined that the second wireless communication device comprises a first transceiver arrangement operating at a first power level, and a second transceiver arrangement operating at a second power level, the controlling circuitry is further configured to cause transmission of at least one discovery signal according to a signal configuration which allows detection and decoding of the at least one discovery signal by the first transceiver arrangement comprised in the second wireless communication device.

A signal configuration that allows detection and decoding of the at least one discovery signal by the first transceiver arrangement may e.g. be transmitting the discovery signal as a narrowband signal. Furthermore, in some embodiments, the signal configuration may further comprise using a low order modulation such as OOK, BFSK, FSK.

In some embodiments, the apparatus 400 may further comprise additional components not shown in Fig. 4. Such components may e.g. be signal generators, modulators, amplifiers, filters etc. which may assist in communication between devices.

Furthermore, the controlling circuitry 410 may be further configured to cause obtaining from a network node an indication whether the second wireless communication device comprise a first transceiver arrangement operating at a first power level and a second transceiver arrangement operating at a second power level when awake, wherein the first power level is less than the second power level.

The indication may e.g. be received from the network node as broadcasted signal, or as dedicated signaling. Dedicated signaling may in some embodiments be obtained during a connection procedure to the network node for cellular communication. Alternatively, or additionally, dedicating signaling may in some embodiments be obtained as a response upon a direct request from the wireless device.

In some embodiments, the controlling circuitry 410 may further be configured to cause reception of a response from the second wireless communication device based on the transmitted discovery signal(s).

In some embodiments, the controlling circuitry 410 may be configured to cause setting up of the sidelink connection between the first wireless communication device and the second wireless communication device.

Hence, in some embodiments, the controlling circuitry 410 may be configured to cause transmission of discovery signals prior to having determined whether there are devices eligible for D2D communication in e.g. the same cell as the first wireless communication device.

The apparatus 400 may be comprised in a wireless communication device. The apparatus 400 may e.g. be comprised in any of the first and/or second wireless communication devices previously described in conjunction with any of the Figs. 1-3. The apparatus 400 may further be configured to carry out method steps according to any of the methods 100 and/or 300 described in conjunction with any of the respective Figs. 1, and 3.

Fig. 5 illustrates a computer program product comprising a non-transitory computer readable medium 500, wherein the non-transitory computer readable medium 500 has stored there on a computer program comprising program instructions. The computer program is configured to be loadable into a data-processing unit 510, comprising a processor (PROC) 520 and a memory (MEM) 530 associated with or integral to the data-processing unit. When loaded into the data-processing unit 510, the computer program is configured to be stored in the memory 530, wherein the computer program, when loaded into and run by the processor 520 is configured to cause the processor to execute method steps according to any of the methods described in conjunction with the figures 1 and 3

The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. They may be performed by general-purpose circuits associated with or integral to a communication device, such as digital signal processors (DSP), central processing units (CPU), coprocessor units, field-programmable gate arrays (FPGA) or other programmable hardware, or by specialized circuits such as for example application-specific integrated circuits (ASIC). All such forms are contemplated to be within the scope of this disclosure.

Embodiments may appear within an electronic apparatus (such as a wireless communication device) comprising circuitry/logic or performing methods according to any of the embodiments. The electronic apparatus may, for example, be a portable or handheld mobile radio communication equipment, a mobile radio terminal, a mobile telephone, a base station, a base station controller, a pager, a communicator, an electronic organizer, a smartphone, a computer, a notebook, a USB-stick, a plug-in card, an embedded drive, or a mobile gaming device.

According to some embodiments, a computer program product comprises a computer readable medium such as, for example, a diskette or a CD-ROM. The computer readable medium may have stored thereon a computer program comprising program instructions. The computer program may be loadable into a data-processing unit, which may, for example, be comprised in a mobile terminal. When loaded into the data-processing unit, the computer program may be stored in a memory associated with or integral to the data-processing unit. According to some embodiments, the computer program may, when loaded into and run by the data-processing unit, cause the data-processing unit to execute method steps according to, for example, the methods shown in any of the Figures lands.

Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims. For example, the method embodiments described herein describes example methods through method steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence.

In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. In the same manner, functional blocks that are described herein as being implemented as two or more units may be implemented as a single unit without departing from the scope of the claims.

Hence, it should be understood that the details of the described embodiments are merely for illustrative purpose and by no means limiting. Instead, all variations that fall within the range of the claims are intended to be embraced therein.

Claims

1. A method (100) of a first wireless communication device for establishing a device to device, D2D, sidelink connection between the first wireless communication device and a second wireless communication device, the first wireless communication device comprising a first transceiver arrangement and a second transceiver arrangement, the method comprising:

Detecting (110) by the first transceiver arrangement operating at a first power level, one or more discovery signals from the second device;

Performing (120), by the first transceiver arrangement, one or more sidelink assist operations based on the one or more discovery signals; waking up (140), by the first transceiver arrangement, the second transceiver arrangement, wherein the second transceiver arrangement when awake is operating at a second power level, wherein operation at the first power level requires less power than operation at the second power level; relaying (150), by the first transceiver arrangement an outcome of the one or more sidelink assist operations to the second wireless transceiver arrangement; and setting up (160), by the second transceiver arrangement, a sidelink connection between the first and second communication device based on the outcome of the one or more sidelink assist operations.

2. The method according to claim 1, wherein the first transceiver arrangement operates according to an always on principle, and wherein the second transceiver arrangement operates according to a sleep mode principle, or wherein the first transceiver arrangement operates according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep.

3. The method according to any of the previous claims, wherein the first transceiver arrangement is a low power receiver comprising at least one antenna element.

4. The method according to any of the previous claims, further comprising

Detecting (110), by the first transceiver arrangement, the one or more discovery signals as a narrowband signal by using a time domain correlation.

5. The method according to any of the previous claims 1-4, wherein the one or more discovery signals comprise one or more of a primary sidelink synchronization signal, PSSS, a secondary sidelink

26 synchronization signal, SSSS, a sidelink radio frequency beam tracking signal, a physical sidelink broad cast channel, PSBCH, a device to device wake up signal.

6. The method according to any of the previous claims 1-5, wherein performing (120) one or more sidelink assist operations comprises: performing, by the first transceiver arrangement, a radio frequency power estimation based on the one or more discovery signals; and wherein performing the step of setting up, by the second receiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operations comprises performing, by the second transceiver arrangement, automatic gain control, AGC, based on the radio frequency power estimation.

7. The method according to any of the previous claims 1-6, wherein performing (120) one or more sidelink assist operations comprises: obtaining, by the first transceiver arrangement, synchronization information from the one or more discovery signals; and wherein the step of setting up (160), by the second transceiver arrangement, the sidelink connection based on the outcome of the one or more sidelink assist operations comprises: performing, by the second transceiver arrangement, automatic frequency correction, AFC, based on the synchronization information.

8. The method according to claim 7, further comprising

Performing (120) by the first transceiver arrangement synchronization to the second wireless communication device based on the obtained synchronization information.

9. The method according to any of the previous claims 1-8, wherein performing one or more sidelink assist operations comprises:

Decoding (120), by the first transceiver arrangement a sidelink beam index associated with the one or more discovery signals and relaying the decoded beam index to the second tranceiver arrangement.

10. The method according to any of the previous claims 1-9, wherein the first transceiver arrangement comprises more than one antenna elements, wherein performing (120) one or more sidelink assist operation comprises: performing beam matching, by the first transceiver arrangement, by determining an angle of arrival of at least one beam comprising the one or more discovery signals; and relaying (150) to the second transceiver arrangement an indication of a preferred beam based on the determined angle of arrival.

11. The method according to any of the previous claims 1-10, further comprising reporting, to a network node operating in a wireless communication network, a low power discovery signal reception capability during a connection establishment to the network node.

12. the method according to claim 11, further comprising receiving from the network node information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink reception range.

13. A computer program product comprising a non-transitory computer readable medium (500), wherein the non-transitory computer readable medium (500) has stored there on a computer program comprising program instructions, wherein the computer program is configured to be loadable into a data-processing unit (510), comprising a processor (520) and a memory (530) associated with or integral to the data-processing unit (510), wherein when loaded into the data-processing unit (510), the computer program is configured to be stored in the memory (530), wherein the computer program, when loaded into and run by the processor (520) is configured to cause the processor (520) to execute method steps according to any of the methods described in conjunction with the claims 1-12.

14. An apparatus (400) of a first wireless communication device (220, 230) for establishing a device to device, D2D, sidelink connection between the first wireless communication device (220, 230) and a second wireless communication device (220, 230), the apparatus comprising a first transceiver arrangement (420) configured to operate at a first power level and a second transceiver arrangement (430) configured to operate at a second power level when awake, wherein operation at the first power level requires less power than operation at the second power level, and a controlling circuitry (410), the controlling circuitry (410) being configured to cause the first transceiver arrangement (420) to: detect, one or more discovery signals from the second device (220, 230); performing one or more sidelink assist operations based on the one or more discovery signals; wake up the second transceiver arrangement (430); relay an outcome of the one or more sidelink assist operation to the second wireless transceiver arrangement (430); and wherein the controlling circuitry (410) is configured to cause the second transceiver arrangement (430) to set up a sidelink connection between the first and second communication device (220, 230) based on the outcome of the one or more sidelink assist operation.

15. The apparatus (400) according to claim 14, wherein the first transceiver arrangement (420) is configured to operate according to an always on principle, and wherein the second transceiver arrangement (430) is configured to operate according to a sleep mode principle or wherein the first transceiver arrangement (420) is configured to operate according to a duty cycle defined as a ratio between an active time and a total time during a monitoring period when the second transceiver arrangement is in deep sleep.

16. The apparatus (400) according to any of the previous claims 14-15, wherein the first transceiver arrangement (420) is a low power receiver comprising at least one antenna element.

17. The apparatus (400) according to any of the previous claims 14-16, wherein the controlling circuitry (401) is further configured to cause the first transceiver arrangement (420) to: detect the one or more discovery signals as a narrowband signal by using a time domain correlation.

18. The apparatus according to any of the claims 14-17, wherein the one or more discovery signals comprise one or more of a primary sidelink synchronization signal, PSSS, a secondary sidelink synchronization signal, SSSS, a sidelink radio frequency beam tracking signal, a physical sidelink broad cast channel, PSBCH, a device to device wake up signal.

19. The apparatus (400) according to any of the previous claims 14-18, wherein the controlling circuitry (410) is configured to cause the first transceiver arrangement (420) to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement (420) to: perform a radio frequency power estimation based on the one or more discovery signals; and wherein the controlling circuitry is configured to cause the second transceiver arrangement (430) to perform setting up the sidelink connection based on the outcome of the one or more sidelink assist operation by being configured to cause the second transceiver arrangement (430) to: perform automatic gain control, AGC, based on the radio frequency power estimation.

20. The apparatus (400) according to any of the previous claims 14-19 wherein the controlling circuitry (410) is configured to cause the first transceiver arrangement (420) to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to: obtain synchronization information from the one or more device to device specific reference signal; and wherein the controlling circuitry is configured to cause the second transceiver arrangement (430) to perform setting up the sidelink connection based on the outcome of the one or more sidelink 29 assist operations by being configured to cause the second receiver arrangement to: perform automatic frequency correction, AFC, based on the synchronization information.

21. The apparatus (400) according to claim 20, wherein the controlling circuitry (410) is further configured to cause the first transceiver arrangement (420) to perform synchronization to the second wireless communication device based on the obtained synchronization information.

22. The apparatus (400) according to any of the previous claims 14-21, wherein the controlling circuitry (410) is configured to cause the first transceiver arrangement (420) to perform the one or more sidelink assist operation by being configured to cause the first transceiver arrangement to: decode a sidelink beam index associated with the one or more other device to device specific reference signal and relay the decoded beam index to the second transceiver arrangement.

23. The apparatus (400) according to any of the previous claims 14-22, wherein the first transceiver arrangement (420) comprises more than one antenna elements, and wherein the controlling circuitry (410) is configured to cause the first transceiver arrangement to perform one or more sidelink assist operation by being configured to cause the first transceiver arrangement to: perform beam matching by determining an angle of arrival of at least one beam comprising the one or more discovery signals and relay to the second transceiver arrangement (430) an indication of a preferred beam based on the determined angle of arrival.

24. The apparatus (400) according to any of the previous claims 14-23, wherein the controlling circuitry (410) is further configured to cause reporting, to a network node operating in a wireless communication network of, a low power discovery signal reception capability during a connection establishment to the network node.

25. the apparatus (400) according to claim 24, wherein the controlling circuitry (410) is further configured to cause reception, from the network node, of information indicating the presence of one or more other wireless communication devices capable of low power discovery signal reception, within a sidelink reception range.

26. A wireless communication device (220, 230) comprising the apparatus (400) according to any of the claims 14-25.

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1. A method (300) for initiating a device to device sidelink connection by a first wireless communication device to a second wireless communication device, wherein the method comprises determining (311) that the second wireless communication device comprises a first transceiver arrangement operating at a first power level, and a second transceiver arrangement operating, when awake, at a second power level, wherein the first power level is less than the second power level; transmitting (312) at least one discovery signal according to a signal configuration which allows detection of the at least one discovery signal by the first transceiver arrangement.

28. The method according to claim 27, wherein the signal configuration that allows detection and decoding of the at least one device to device specific reference signal by the first transceiver arrangement comprises transmitting the discovery signal as a narrowband signal.

29. The method according to any of the previous claims 27-28, wherein the signal configuration that allows detection and decoding of the at least one device to device specific reference signal by the first transceiver arrangement comprises modulating the discovery signal with a low order modulation.

30. The method according to any of the previous claims 27-30, further comprising receiving (313) a response from the second wireless communication device based on the transmitted discovery signal; and setting up (314) the sidelink connection between the first wireless communication device and the second wireless communication device.

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