WO2023019584A1

WO2023019584A1 - Methods, devices and computer storage media for communication

Info

Publication number: WO2023019584A1
Application number: PCT/CN2021/113889
Authority: WO
Inventors: Lin Liang; Gang Wang
Original assignee: Nec Corporation
Priority date: 2021-08-20
Filing date: 2021-08-20
Publication date: 2023-02-23

Abstract

A method comprises receiving, at a second device and from a first device, a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of the second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and performing the uplink transmission based on the precoding indication. In this way, the UL performance can be increased without overhead increment in both codebook based precoding scenario and non-codebook based precoding scenario.

Description

METHODS, DEVICES AND COMPUTER STORAGE MEDIA FOR COMMUNICATION

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to methods, devices and computer storage media for uplink (UL) frequency selective precoding.

BACKGROUND

For the channel condition and environment which has large delay spread, the channel response in frequency domain may vary between largely separated Resource Block (RB) . Due to the various channel response, different RBs may have different optimized precoding matrices.

SUMMARY

In general, example embodiments of the present disclosure provide methods, devices and computer storage media for uplink frequency selective precoding.

In a first aspect, there is provided a method. The method comprises generating, at a first device, a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and transmitting the precoding indication to the second device.

In a second aspect, there is provided a method. The method comprises receiving, at a second device and from a first device, a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of the second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and performing the uplink transmission based on the precoding indication.

In a third aspect, there is provided a method. The method comprises transmitting, from a first device and to a second device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a sounding reference signal, SRS, transmission of the second device; or a data transmission to be transmitted from the second device; in accordance with a determination that the SRS transmission is received, generating, based on the received SRS transmission, a SRS resource indicator for scheduling a data transmission to be transmitted from the second device, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference; and transmitting the SRS resource indicator to the second device.

In a fourth aspect, there is provided a method. The method comprises receiving, at a second device and from a first device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a sounding reference signal, SRS, transmission of the second device; or a data transmission to be transmitted from the second device; performing the SRS transmission based on the grouping indication, a same precoding matrix being used for respective resource blocks within each of the one or more precoding resource block groups based on downlink non zero power channel state information; and receiving, from the first device, the SRS resource indicator for scheduling a data transmission to be transmitted from the second device generated by the first device based on the SRS transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.

In a fifth aspect, there is provided a first device. The first device comprises a processor and a memory. The memory is coupled to the processor and stores instructions thereon. The instructions, when executed by the processor, cause the first device to perform the method according to the first aspect of the present disclosure.

In a sixth aspect, there is provided a second device. The second device comprises a processor and a memory. The memory is coupled to the processor and stores instructions thereon. The instructions, when executed by the processor, cause the second device to perform the method according to the second aspect of the present disclosure.

In a seventh aspect, there is provided a first device. The first device comprises a processor and a memory. The memory is coupled to the processor and stores instructions thereon. The instructions, when executed by the processor, cause the first device to perform the method according to the third aspect of the present disclosure.

In an eighth aspect, there is provided a second device. The second device comprises a processor and a memory. The memory is coupled to the processor and stores instructions thereon. The instructions, when executed by the processor, cause the second device to perform the method according to the fourth aspect of the present disclosure.

In a ninth aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor, cause the at least one processor to perform the method according to any of the first aspect, the second aspect the third aspect and the fourth aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

FIG. 1 shows an example communication network in which embodiments of the present disclosure can be implemented;

FIG. 2 shows a signaling chart illustrating a process of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 3 shows a diagram of an example of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 4 shows a signaling chart illustrating a process of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 5 shows a diagram of an example of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 6 shows a flowchart of an example method of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 7 shows a flowchart of an example method of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 8 shows a flowchart of an example method of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 9 shows a flowchart of an example method of uplink frequency selective precoding in accordance with some embodiments of the present disclosure;

FIG. 10 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish functionalities of various elements. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. 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” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as fifth generation (5G) systems, Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) new radio (NR) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR Next Generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

Although functionalities described herein can be performed, in various example embodiments, in a fixed and/or a wireless network node, in other example embodiments, functionalities may be implemented in a user equipment apparatus (such as a cell phone or tablet computer or laptop computer or desktop computer or mobile IoT device or fixed IoT device) . This user equipment apparatus can, for example, be furnished with corresponding capabilities as described in connection with the fixed and/or the wireless network node (s) , as appropriate. The user equipment apparatus may be the user equipment and/or or a control device, such as a chipset or processor, configured to control the user equipment when installed therein. Examples of such functionalities include the bootstrapping server function and/or the home subscriber server, which may be implemented in the user equipment apparatus by providing the user equipment apparatus with software configured to cause the user equipment apparatus to perform from the point of view of these functions/nodes.

The term “circuitry” used herein may refer to hardware circuits and/or combinations of hardware circuits and software. For example, the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware. As a further example, the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (memories) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions. In a still further example, the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation. As used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.

FIG. 1 shows an example communication network 100 in which embodiments of the present disclosure can be implemented. The network 100 includes a network device 120 and terminal devices 110-1, 110-2…, 110-N served by the network device 120. The serving area of the network device 120 is called as a cell 102. Hereinafter, the terminal devices 110-1, 110-2…, 110-N may be collectively referred to as “UE 110” , “terminal device 110” or “second device 110” and the network device 120 may also be referred to “first device 120” or “gNB 120” .

It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The communication network 100 may include any suitable number of network devices and terminal devices adapted for implementing embodiments of the present disclosure.

In NR downlink (DL) , a UE assumes that the precoding is the same within a Physical RB (PRB) bundling which the PRB bundling size can be configured by Radio Resource Control (RRC) and is indicated by Downlink Control Information (DCI) format 1_1. Some rules are specified to determine PRB bundling size due to different frequency resources allocations.

No signal overhead for DL frequency selective precoding except for at most 1 bit field in DCI to indicate dynamic PRB bundling size. The precoding matrix is selected on each PRB bundling at network side by implementation and there is no need to be known by the UE, hence no indication to the UE about the Transmission Precoding Matrix Indication (TPMI) information.

However, for better radio resource control by network, the UL TPMI should be selected by network and indicate the TPMI determination to the UE. To save signaling overhead, only one wideband TPMI is indicated in DCI.

The UL frequency selective precoding may be one of candidate solutions to be study further in 3GPP, to further enhance UL capacity and link performance. The UL frequency selective precoding may improve link performance while increase signaling overhead as a result. The key point in studying the UL frequency selective precoding is the balance between the pros and cons.

The conventional UL precoding solutions may include codebook based precoding and non-codebook based precoding. In the codebook based transmission, frequency selective and frequency non-selective precoding in digital domain may be considered for a wide system bandwidth. The support for the frequency selective precoding is determined according to decision on NR waveform (s) .

As an option, in a UE-aided and BS-centric mechanism, the UE may recommend candidate UL precoders from a predefined codebook to BS based on DL RS measurement. In addition, the BS may determine the final precoder taken from the codebook.

As another option, in a UE-centric and BS-aided mechanism, the BS provides CSI (e.g. channel response, interference-related information) to the UE. In addition, the UE determines the final precoder based on the information from the BS.

In the non-codebook based transmission, it is possible that multiple PMIs may be signaled via a single DCI or multi-level DCI. For frequency selective precoding, the configuration of UL precoding granularity may need to be further discussed.

In the solution of the present invention, a mechanism of UL frequency selective precoding is proposed. The gNB may generate a precoding indication comprising at least one of first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a UE and the number of layers associated with the UE and second precoding information for each precoding resource block group in the one or more precoding resource block groups. The gNB may transmit the precoding indication to the UE.

In this way, the UL performance can be increased without overhead increment in both codebook based precoding scenario and non-codebook based precoding scenario.

Principle and implementations of the present disclosure will be described in detail below with reference to FIGs. 2-9.

Now the reference is made to FIG. 2, which illustrates a signaling chart of an example process 200 of uplink frequency selective precoding in accordance with some embodiments of the present disclosure. For the purpose of discussion, the process 200 will be described with reference to FIG. 1. The process 200 may involve the UE 110 and the gNB 120 as illustrated in FIG. 1.

For the UL frequency selective precoding, as shown in FIG. 2, the gNB 120 may configure 202 the resource blocks allocated for the UL transmission of the UE 110 into one or more precoding RB groups.

In some embodiments, the gNB 120 may configure the one or more precoding RB groups based on different UL resource allocation types.

In the type 0 UL resource allocation, the resource blocks allocated for the UL transmission of the UE 110 may be indicated by a set of RB groups (RBGs) . Hereinafter a RBG may also be referred to as a reference resource block group. In this case, the gNB 120 may determine the grouping size of a precoding resource block group and/or maximum number of precoding resource block groups based on the allocated reference resource block groups for the UL transmission.

For example, the grouping size of the precoding resource block group may be equal to a RBG size for resource allocation or the integer multiple of RBG size for resource allocation. If the grouping size of the precoding resource block group is equal to the RBG size for resource allocation, each of precoding resource block groups may correspond to each RBG.

As another option, if the grouping size of the precoding resource block group is equal to integer multiple of RBG size for resource allocation, the precoding resource block group n is the RBG group M*n, M*n+1, …, M*n+M-1, where M is configured integer.

In the type 1 UL resource allocation, the resource blocks allocated for the UL transmission of the UE 110 may be indicated by a Start and Length Indicator Value (SLIV) for contiguous resource allocation. In this case, the gNB 120 may determine the grouping size of a precoding resource block group and/or maximum number of precoding resource block groups based on respective start locations and lengths for the one or more precoding resource block groups in a bandwidth part (BWP) associated with the UL transmission.

That is, in a case where the gNB 120 configures one or more precoding resource block groups based on the type 1 UL resource allocation, the precoding resource block group may be start from a common RB 0. For the BWP associated with the UL transmission, the first and the last precoding resource block groups in the BWP may be different from other precoding resource block groups in the BWP.

The gNB 120 may generate a grouping indication associated with the configure one or more precoding resource block groups and transmit 204 the grouping indication to the UE 110, for example, via a RRC signaling.

For codebook based UL transmission, the gNB 120 may provide precoding information to the UE for the UL transmission. As an option, the gNB 120 may determine first precoding information and number of layers for all of configure one or more precoding resource block groups. As another option, the gNB 120 may determine second precoding information for each precoding resource block group in the one or more precoding resource block groups, since all of configure one or more precoding resource block groups may have the same number of layers. The gNB 120 may generate 206 a precoding indication for the UL transmission of the UE 110 comprising at least one of the first precoding information and number of layers for all of precoding resource block groups and second precoding information for each precoding resource block group.

In some embodiments, for the i-th group, the TPMI is n + k (i) , where n is TPMI indicated for all groups and k (i) is delta information indicated for the i-th group.

The delta information can be configured by RRC or specified based on at least TPMI n information for all precoding resource block groups and/or configured codebookSubset (either fullyAndPartialAndNonCoherent, partialAndNonCoherent, and nonCoherent) information. An example TPMI indication is listed as below:

Table 1: TPMI information

For example, when 4 ports is support, subgroup TMPI should have the same usage antenna port (i.e. not 0) as wideband indication, thus for example for 4 antenna port with rank 1 transmission, the TPMI bits length for nonCoherent, no indication for each group; for partialAndNonCoherent, 2 bits indication for each group; and for fullyAndPartialAndNonCoherent, 4 bits indication for each group.

For example, as a configured table shown as below, as different wideband indication may have different optimized subset.

Table 2: configured precoding indication

Indicated n	Subset of k
16	+1, -1, +3, +5
17	-1, +2, +6, +8

where k (i) for specific i (e.g., i=1) can be fixed value 0, hence no signaling is needed for such group.

After generating the precoding indication, as shown in FIG. 2, the gNB 120 may transmit 208 the precoding indication to the UE 110. The precoding indication can be transmitted via DCI. For example, the first precoding information and number of layers for all of precoding resource block groups can be indicated in a legacy DCI field.

The second precoding information for each precoding resource block group can be indicated in DCI together with the first precoding information and number of layers for all of precoding resource block groups with fixed size based on maximum number of groups in BWP, or in another DCI with variable size based on number of groups in allocated resources.

In some embodiments, if the frequency hopping is enabled, the codepoint for each precoding resource block group is reserved and wideband TMPI is used by the UE 110. Typically the bit for indicating the precoding matrix may be not reserved when the frequency hopping is enabled, because the UE 110 may not be aware of the accurate precoding information. In the solution as described above, the UE 110 may obtain the accurate precoding information from the gNB 120, thus the bit for the indication of the precoding matrix can be reserved when the frequency hopping is enabled by using the solution of the present disclosure.

After receiving the precoding indication and the grouping indication, the UE 110 may perform the precoding operation for the UL transmission based on the precoding indication and the grouping indication and transmit 210 the UL transmission to the gNB 120.

Now the reference is made to FIG. 3, which shows an example of precoding resource block groups.

As shown, the gNB 120 may allocate a set of resources 310 for the UL transmission of UE 110, which may include multiple resource blocks.

For the type 0 resource allocation, the gNB 120 may configure the precoding resource block groups based on the set of reference RBGs, namely RBG 301-308. For example, the set of resources 310 may be divided into multiple precoding resource block groups 311-315.

In the example of FIG. 2, the grouping size of the precoding resource block group is equal to or less than the RBG size for resource allocation. It is to be understood that the grouping size of the precoding resource block group may also be equal to integer multiple of RBG size for resource allocation, as described above. In this case, the RBs in each precoding resource block group of the multiple precoding resource block groups 311-315 may use a same precoding matrix or a same precoding pattern. The precoding matrix or the precoding pattern can be obtained by the UE 110 from the precoding indication which may comprise at least one of the first precoding information and number of layers for all of precoding resource block groups and second precoding information for each precoding resource block group.

For the type 1 resource allocation, the gNB 120 may configure the precoding resource block groups based on a BWP 321 associated with the UL transmission. The precoding resource block group may be start from a common RB 0. The SLIV (Start location S and the length L) may indicate a precoding resource block group in the BWP associated with the UL transmission. The RBs in each precoding resource block group may use a same precoding matrix or a same precoding pattern.

As described above, the UL transmission may be performed based on the non-codebook precoding mechanism. Now the reference is made to FIG. 4, which illustrates a signaling chart of an example process 400 of uplink frequency selective precoding in accordance with some embodiments of the present disclosure. For the purpose of discussion, the process 400 will be described with reference to FIG. 1. The process 400 may involve the UE 110 and the gNB 120 as illustrated in FIG. 1.

Similarly, for the UL frequency selective precoding, as shown in FIG. 4, the gNB 120 may configure 402 the resource blocks allocated for the Sounding reference signal (SRS) transmission and/or the UL transmission of the UE 110 into one or more precoding RB groups.

In some embodiments, the gNB 120 may configure the one or more precoding RB groups based on configured SRS transmission bands. For example, the gNB 120 may determine the group size and/or the maximum number of one or more precoding RB groups based on the set of subbands configured for the SRS transmission.

Then the gNB 120 may generate a grouping indication associated with the configure one or more precoding resource block groups and transmit 404 the grouping indication to the UE 110, for example, via a RRC signaling.

Based on the grouping indication, the UE 110 may determine 406 one or more precoding matrix or patterns for the SRS transmission by itself. Specifically, the UE 110 may determine and use the same precoding matrix for RBs within each precoding resource block group based on DL Non-Zero-Power (NZP) -Channel State Information (CSI) when transmits SRS.

In some embodiments, if the group size of the one or more precoding resource block groups is larger than or equal to a sub-band size of a set of SRS transmission sub-bands, the UE 110 may select a same precoding matrix for precoding resource block groups corresponding to a same transmission sub-band.

In some embodiments, if the group size of the one or more precoding resource block groups is smaller than a sub-band size of a set of transmission sub-bands, the UE 110 may select different precoding matrices for different precoding resource block groups in a transmission sub-band.

Then the UE 110 may transmit 408 the SRS to the gNB 120 based on the determined precoding matrix or precoding pattern.

After receiving the SRS transmission, the gNB 120 may generate 410 a SRS resource indicator for scheduling the subsequence data transmission on the Physical Uplink Shared Channel (PUSCH) to be transmitted from the UE 110. The SRS resource indicator may indicate the resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval. The time difference between the first time interval and the second time interval may be less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission may be less than a second threshold difference.

Specifically, in some embodiments, the SRS resource indicator may indicate that the resources for the data transmission in a physical resource block is associated with resources of a most recent SRS transmission in the same physical resource block.

In some embodiments, it is also possible that the SRS resource indicator may indicate that the resources for the data transmission in a first physical resource block is associated with resources of a most recent SRS transmission in a second physical resource block which is nearest with the first physical resource block.

Hereafter “the resources for the data transmission is associated with resources for the SRS transmission” may be understood as the resources for the data transmission in certain range associated with the resources for the SRS transmission may use a same precoding matrix with the SRS transmission.

After generating the SRS resource indicator, the gNB 120 may transmit 412 the SRS resource indicator to the UE 110, for example, via the DCI.

Now the reference is made to FIG. 5, which shows an example of uplink frequency selective precoding in accordance with some embodiments of the present disclosure. With reference to FIG. 5, the scenario of non-codebook based precoding may be better understood.

For the

SRS transmission

521 and 522, which may correspond to different SRS transmission subbands, the UE 110 may use a first precoding matrix for the SRS transmission 521 and a second precoding matrix for the SRS transmission 522. By receiving the

SRS transmission

521 and 522, the gNB 120 may be aware of the precoding matrix used by the UE 110 for the SRS transmission and therefore generate the SRS resource indicator for scheduling the subsequence data transmission 510.

For example, the SRS resource indicator may indicate that a portion of resources allocated for the data transmission uses a same precoding matrix with the SRS transmission performed on a SRS transmission subband which has an association with the portion of resources allocated for the data transmission in a time domain and/or a frequency domain. If a most recent SRS transmission is performed on a SRS transmission subband and the frequency range of the portion of resources allocated for the data transmission corresponds to the SRS transmission subband, this portion of resources may use a same precoding matrix with the SRS transmission performed on the SRS transmission.

Thus, after receiving the SRS resource indicator, for example, via DCI 511, the portion 501 of the data transmission 510 may use a same precoding matrix with the SRS transmission 522 while the portion 502 of the data transmission 510 may use a same precoding matrix with the SRS transmission 521.

Now the reference is made to FIG. 6, which illustrates a flowchart of an example method 600 in accordance with some embodiments of the present disclosure. The method 600 can be implemented at a first device 120 as shown in FIG. 1. It is to be understood that the method 600 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At 610, the first device may generate a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block.

In some embodiments, the first device may allocating resource blocks for the uplink transmission of the second device; divide the resource blocks into the one or more precoding resource block groups, each of the one or more precoding resource block groups having contiguous resource blocks; and transmit a grouping indication of the one or more precoding resource block groups to the second device.

In some embodiments, the first device may determine one or more precoding resource block allocation parameters comprising at least one of the following: grouping size, or maximum number of the precoding resource block groups; and divide the resource blocks into the one or more precoding resource block groups based on the one or more precoding resource block allocation parameters.

In some embodiments, the first device may determine the group size based on a reference group size of a reference resource block group for the resource blocks.

In some embodiments, the group size is equal to the reference group size of the reference resource block group.

In some embodiments, the group size is integer multiple of the reference group size of the reference resource block group.

In some embodiments, the first device may determine respective start locations and lengths for the one or more precoding resource block groups in a bandwidth part associated with the second device.

In some embodiments, the first device may determine a common transmission precoding matrix index for the one or more precoding resource block groups and an offset value for each precoding resource block group in the one or more precoding resource block groups; and generate the indication at least based on the common transmission precoding matrix index and the offset value.

At 620, the first device may transmit precoding indication to the second device.

In some embodiments, the first device may transmit the precoding indication via downlink control information.

Now the reference is made to FIG. 7, which illustrates a flowchart of an example method 700 in accordance with some embodiments of the present disclosure. The method 700 can be implemented at a second device 110 as shown in FIG. 1. It is to be understood that the method 700 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At 710, the second device receives a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block.

At 720, the second device performs the uplink transmission based on the precoding indication.

Now the reference is made to FIG. 8, which illustrates a flowchart of an example method 800 in accordance with some embodiments of the present disclosure. The method 800 can be implemented at a first device 120 as shown in FIG. 1. It is to be understood that the method 800 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At 810, the first device transmits a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a SRS transmission of the second device; or a data transmission to be transmitted from the second device.

At 820, in accordance a determination that the SRS transmission is received, the first device may generate, based on the received SRS transmission, a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.

At 830, the first device transmits the SRS resource indicator to the second device.

In some embodiments, the SRS resource indicator indicating the resources for the data transmission in a physical resource block is associated with resources for a most recent SRS transmission in the same physical resource block.

In some embodiments, the SRS resource indicator indicating the resources for the data transmission in a first physical resource block is associated with resources for a most recent SRS transmission in a second physical resource block which is nearest with the first physical resource block.

In some embodiments, the first device may allocate resource blocks for the uplink transmission of the second device; and divide the resource blocks into the one or more precoding resource block groups, each of the one or more resource block groups having contiguous resource blocks.

In some embodiments, the first device may divide the resource blocks into the one or more resource block groups based on a set of transmission sub-bands associated with the SRS transmission.

Now the reference is made to FIG. 9, which illustrates a flowchart of an example method 900 in accordance with some embodiments of the present disclosure. The method 900 can be implemented at a second device 110 as shown in FIG. 1. It is to be understood that the method 900 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At 910, the second device receives a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a SRS transmission of the second device; or a data transmission to be transmitted from the second device.

At 920, the second device performs the SRS transmission based on the grouping indication, a same precoding matrix being used for respective resource blocks within each of the one or more precoding resource block groups based on downlink non zero power channel state information.

At 930, the second device receives a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.

In some embodiments, in accordance with a determination that a group size of the one or more precoding resource block groups is larger than or equal to a sub-band size of a set of transmission sub-bands, the second device may select a same precoding matrix for precoding resource block groups corresponding to a same transmission sub-band.

In some embodiments, in accordance with a determination that a group size of the one or more precoding resource block groups is smaller than a sub-band size of a set of transmission sub-bands, the second device may select different precoding matrices for different precoding resource block groups in a transmission sub-band.

Details for channel access in millimeter wave bands according to the present disclosure have been described with reference to FIGs. 2-9. Now an example implementation of the first device 120 will be discussed below. In some embodiments, the first device 120 comprises circuitry configured to: generate, at a first device, a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and transmit the precoding indication to the second device.

In some embodiments, the first device 120 comprises circuitry configured to allocate resource blocks for the uplink transmission of the second device; divide the resource blocks into the one or more precoding resource block groups, each of the one or more precoding resource block groups having contiguous resource blocks; and transmit a grouping indication of the one or more precoding resource block groups to the second device.

In some embodiments, the first device 120 comprises circuitry configured to determine one or more precoding resource block allocation parameters comprising at least one of the following: grouping size, or maximum number of the precoding resource block groups; and divide the resource blocks into the one or more precoding resource block groups based on the one or more precoding resource block allocation parameters.

In some embodiments, the first device 120 comprises circuitry configured to determine the group size based on a reference group size of a reference resource block group for the resource blocks.

In some embodiments, the first device 120 comprises circuitry configured to determine respective start locations and lengths for the one or more precoding resource block groups in a bandwidth part associated with the second device.

In some embodiments, the first device 120 comprises circuitry configured to determine a common transmission precoding matrix index for the one or more precoding resource block groups and an offset value for each precoding resource block group in the one or more precoding resource block groups; and generate the indication at least based on the common transmission precoding matrix index and the offset value.

In some embodiments, the first device 120 comprises circuitry configured to transmit the precoding indication via downlink control information.

Now an example implementation of the second device 110 will be discussed below. In some embodiments, the second device 110 comprises circuitry configured to: receive a precoding indication comprising at least one of the following: first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block and perform the uplink transmission based on the precoding indication.

Now an example implementation of the first device 120 will be discussed below. In some embodiments, the first device 120 comprises circuitry configured to: transmit a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a SRS transmission of the second device; or a data transmission to be transmitted from the second device; in accordance a determination that the SRS transmission is received, the first device may generate, based on the received SRS transmission, a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference and transmit the SRS resource indicator to the second device.

In some embodiments, the first device 120 comprises circuitry configured to allocate resource blocks for the uplink transmission of the second device; and divide the resource blocks into the one or more precoding resource block groups, each of the one or more resource block groups having contiguous resource blocks.

In some embodiments, the first device 120 comprises circuitry configured to divide the resource blocks into the one or more resource block groups based on a set of transmission sub-bands associated with the SRS transmission.

Now an example implementation of the second device 110 will be discussed below. In some embodiments, the second device 110 comprises circuitry configured to: receive a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following: a SRS transmission of the second device; or a data transmission to be transmitted from the second device; perform the SRS transmission based on the grouping indication, a same precoding matrix being used for respective resource blocks within each of the one or more precoding resource block groups based on downlink non zero power channel state information and receive a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.

In some embodiments, the second device 110 comprises circuitry configured to: in accordance with a determination that a group size of the one or more precoding resource block groups is larger than or equal to a sub-band size of a set of transmission sub-bands, the second device may select a same precoding matrix for precoding resource block groups corresponding to a same transmission sub-band.

In some embodiments, the second device 110 comprises circuitry configured to: in accordance with a determination that a group size of the one or more precoding resource block groups is smaller than a sub-band size of a set of transmission sub-bands, the second device may select different precoding matrices for different precoding resource block groups in a transmission sub-band.

FIG. 10 is a simplified block diagram of a device 1000 that is suitable for implementing embodiments of the present disclosure. The device 1000 can be considered as a further example implementation of the first device 120 or the second 110 as shown in FIG. 1. Accordingly, the device 1000 can be implemented at or as at least a part of the first device 120 or the second 110.

As shown, the device 1000 includes a processor 1010, a memory 1020 coupled to the processor 1010, a suitable transmitter (TX) and receiver (RX) 1040 coupled to the processor 1010, and a communication interface coupled to the TX/RX 1040. The memory 1010 stores at least a part of a program 1030. The TX/RX 1040 is for bidirectional communications. The TX/RX 1040 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and a terminal device.

The program 1030 is assumed to include program instructions that, when executed by the associated processor 1010, enable the device 1000 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGs. 2 to 9. The embodiments herein may be implemented by computer software executable by the processor 1010 of the device 1000, or by hardware, or by a combination of software and hardware. The processor 1010 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1010 and memory 1020 may form processing means 1050 adapted to implement various embodiments of the present disclosure.

The memory 1020 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1020 is shown in the device 1000, there may be several physically distinct memory modules in the device 1000. The processor 1010 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to FIGs. 2-5. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrations operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separation embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A method comprising:

generating, at a first device, a precoding indication comprising at least one of the following:

first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or

second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and

transmitting the precoding indication to the second device.
The method of claim 1, further comprising:

allocating resource blocks for the uplink transmission of the second device;

dividing the resource blocks into the one or more precoding resource block groups, each of the one or more precoding resource block groups having contiguous resource blocks; and

transmitting a grouping indication of the one or more precoding resource block groups to the second device.
The method of claim 2, wherein dividing the resource blocks into the one or more precoding resource block groups comprises:

determining one or more precoding resource block allocation parameters comprising at least one of the following:

grouping size, or

maximum number of the precoding resource block groups; and

dividing the resource blocks into the one or more precoding resource block groups based on the one or more precoding resource block allocation parameters.
The method of claim 3, wherein determining the group size comprises:

determining the group size based on a reference group size of a reference resource block group for the resource blocks.
The method of claim 4, wherein the group size is equal to the reference group size of the reference resource block group.
The method of claim 4, wherein the group size is integer multiple of the reference group size of the reference resource block group.
The method of claim 3, wherein determining the group size comprises:

determining respective start locations and lengths for the one or more precoding resource block groups in a bandwidth part associated with the second device.
The method of claim 1, wherein generating the indication comprises:

determining a common transmission precoding matrix index for the one or more precoding resource block groups and an offset value for each precoding resource block group in the one or more precoding resource block groups; and

generating the indication at least based on the common transmission precoding matrix index and the offset value.
The method of claim 1, wherein transmitting the precoding indication comprises:

transmitting the precoding indication via downlink control information.
The method of any of claims 1-9, wherein the first device comprises a network device and the second device comprises a terminal device.
A method comprising:

receiving, at a second device and from a first device, a precoding indication comprising at least one of the following:

first precoding information for one or more precoding resource block groups allocated for an uplink transmission of the second device and the number of layers associated with the second device, or

second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and

performing the uplink transmission based on the precoding indication.
The method of claim 11, wherein the first device comprises a network device and the second device comprises a terminal device.
A method comprising:

transmitting, from a first device and to a second device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following:

a sounding reference signal, SRS, transmission of the second device; or

a data transmission to be transmitted from the second device;

in accordance with a determination that the SRS transmission is received, generating, based on the received SRS transmission, a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference; and

transmitting the SRS resource indicator to the second device.
The method of Claim 13, wherein the SRS resource indicator indicating the resources for the data transmission in a physical resource block is associated with resources for a most recent SRS transmission in the same physical resource block.
The method of Claim 13, wherein the SRS resource indicator indicating the resources for the data transmission in a first physical resource block is associated with resources for a most recent SRS transmission in a second physical resource block which is nearest with the first physical resource block.
The method of Claim 13, further comprising:

allocating resource blocks for the uplink transmission of the second device; and

dividing the resource blocks into the one or more precoding resource block groups, each of the one or more precoding resource block groups having contiguous resource blocks.
The method of claim 16, wherein dividing the resource blocks into the one or more precoding resource block groups comprises:

dividing the resource blocks into the one or more resource block groups based on a set of transmission sub-bands associated with the SRS transmission.
The method of claim 13, wherein the first device comprises a network device and the second device comprises a terminal device.
A method comprising:

receiving, at a second device and from a first device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following:

a sounding reference signal, SRS, transmission of the second device; or

a data transmission to be transmitted from the second device;

performing the SRS transmission based on the grouping indication, a same precoding matrix being used for respective resource blocks within each of the one or more precoding resource block groups based on downlink non zero power channel state information; and

receiving, from the first device, the SRS resource indicator for scheduling the data transmission generated by the first device based on the SRS transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.
The method of claim 19, the SRS resource indicator indicating the resources for the data transmission in a physical resource block is associated with resources for a most recent SRS transmission in the same physical resource block.
The method of Claim 19, wherein the SRS resource indicator indicating the resources for the data transmission in a first physical resource block is associated with resources of a most recent SRS transmission in a second physical resource block which is nearest with the first physical resource block.
The method of Claim 19, wherein performing the SRS transmission comprises:

in accordance with a determination that a group size of the one or more precoding resource block groups is larger than or equal to a sub-band size of a set of transmission sub-bands, selecting a same precoding matrix for precoding resource block groups corresponding to a same transmission sub-band.
The method of Claim 19, wherein performing the SRS transmission comprises:

in accordance with a determination that a group size of the one or more precoding resource block groups is smaller than a sub-band size of a set of transmission sub-bands, selecting different precoding matrices for different precoding resource block groups in a transmission sub-band.
The method of claim 19, wherein the first device comprises a network device and the second device comprises a terminal device.
A first device, comprising:

a processor configured to:

generate, at a first device, a precoding indication comprising at least one of the following:

first precoding information for one or more precoding resource block groups allocated for an uplink transmission of a second device and the number of layers associated with the second device, or

second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and

transmit the precoding indication to the second device.
A second device, comprising:

a processor configured to:

receive, at a second device and from a first device, a precoding indication comprising at least one of the following:

first precoding information for one or more precoding resource block groups allocated for an uplink transmission of the second device and the number of layers associated with the second device, or

second precoding information for each precoding resource block group in the one or more precoding resource block groups, wherein the precoding resource block group includes at least one resource block; and

perform the uplink transmission based on the precoding indication.
A first device, comprising:

a processor configured to:

transmit, from a first device and to a second device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following:

a sounding reference signal, SRS, transmission of the second device; or

a data transmission to be transmitted from the second device;

in accordance with a determination that the SRS transmission is received, generate, based on the received SRS transmission, a SRS resource indicator for scheduling the data transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference; and

transmit the SRS resource indicator to the second device.
A second device, comprising:

a processor configured to:

receive, at a second device and from a first device, a grouping indication of one or more precoding resource block groups allocated for an uplink transmission including at least one of the following:

a sounding reference signal, SRS, transmission of the second device; or

a data transmission to be transmitted from the second device;

perform the SRS transmission based on the grouping indication, a same precoding matrix being used for respective resource blocks within each of the one or more precoding resource block groups based on downlink non zero power channel state information; and

receive, from the first device, the SRS resource indicator for scheduling the data transmission generated by the first device based on the SRS transmission, the SRS resource indicator indicating resources for the data transmission in a first time interval is associated with resources for the SRS transmission in a second time interval, the time difference between the first time interval and the second time interval being less than a first threshold difference and the frequency difference between the resources for the data transmission and the resources for the SRS transmission being less than a second threshold difference.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 1-10, the method of any of claims 11-12, the method of any of claims 13-18 or the method of any of claims 19-24.