WO2020062104A1

WO2020062104A1 - Extension of signatures for multiple access technology

Info

Publication number: WO2020062104A1
Application number: PCT/CN2018/108490
Authority: WO
Inventors: Emad Farag; Yuantao Zhang; Dan Park
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2018-09-28
Filing date: 2018-09-28
Publication date: 2020-04-02
Also published as: CN112889229A; CN112889229B

Abstract

Embodiments of the present disclosure provide methods, devices and computer readable media for communication. In a method implemented at a terminal device, the terminal device determines a first number of time slots for data transmission to be performed by the terminal device. The terminal device determines a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number. The terminal device performs the data transmission in the first number of time slots using the determined signature pattern. The embodiments of the present disclosure can support a large multiple access capacity without a full collision over a plurality of time slots.

Description

EXTENSION OF SIGNATURES FOR MULTIPLE ACCESS TECHNOLOGY

FIELD

Embodiments of the present disclosure generally relate to wireless communication, and in particular, to extension of signatures for multiple access technology, for example, non-orthogonal multiple access (NOMA) technology.

BACKGROUND

Non-orthogonal multiple access (NOMA) is an ongoing study item in 3GPP release 16. In the NOMA, multiple terminal devices share the same time frequency resource using non-orthogonal signatures. The use of non-orthogonal signatures increases the available number of signatures, hence more terminal devices can be supported, but also introduces multiple access interference (MAI) , which necessitates the use of advanced receivers to separate the terminal devices and achieve good performance. The NOMA can be used with grant-free and grant-based transmission. In case of grant free-transmission, a terminal device can be configured a signature, or it can randomly select from a pool of signatures.

However, the number of available signatures in conventional multiple access schemes is usually still limited compared to the potentially huge number of terminal devices, particularly in the NOMA schemes, which means that these multiple access schemes may have a limited capacity and/or high collision rate, and thus have poor performance if the number of terminal devices is large.

SUMMARY

In general, example embodiments of the present disclosure provide methods, devices and computer readable media for communication, in particular, for extension of signatures in a multiple access system.

In a first aspect, there is provided a method implemented at a terminal device. The method comprises determining a first number of time slots for data transmission to be performed by the terminal device. The method also comprises determining a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number. The method further comprises performing the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially.

In a second aspect, there is provided a method implemented at a network device. The method comprises receiving data transmission from a terminal device in a first number of time slots. The method also comprises determining a signature pattern from the data transmission, the determined signature pattern being from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number. The method further comprises separating the data transmission by the terminal device from further data transmission by a further terminal device, using the determined signature pattern.

In a third aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory storing computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the terminal device to determine a first number of time slots for data transmission to be performed by the terminal device. The at least one memory and the computer program code are also configured to, with the at least one processor, cause the terminal device to determine a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number. The at least one memory and the computer program code are further configured to, with the at least one processor, cause the terminal device to perform the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially.

In a fourth aspect, there is provided a network device. The network device comprises at least one processor and at least one memory storing computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the network device to receive data transmission from a terminal device in a first number of time slots. The at least one memory and the computer program code are also configured to, with the at least one processor, cause the network device to determine a signature pattern from the data transmission, the determined signature pattern being from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number. The at least one memory and the computer program code are further configured to, with the at least one processor, cause the network device to separate the data transmission by the terminal device from further data transmission by a further terminal device, using the determined signature pattern.

In a fifth aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor of a device, cause the device to carry out the method according to the first aspect.

In a sixth aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor of a device, cause the device to carry out the method according to the second 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 is a schematic diagram of a communication environment in which embodiments of the present disclosure can be implemented;

Fig. 2 shows a flowchart of an example method in accordance with some embodiments of the present disclosure;

Fig. 3 is a schematic diagram illustrating dynamic multi-slot data transmission by a terminal device in accordance with some embodiments of the present disclosure;

Fig. 4 is a schematic diagram illustrating that terminal devices may transmit with non-aligned starting time slots in accordance with some embodiments of the present disclosure;

Fig. 5 is a graph illustrating probability of collision as a function of the number of signatures in a signature pattern in accordance with some embodiments of the present disclosure;

Fig. 6 shows a flowchart of an example method in accordance with some other embodiments of the present disclosure; and

Fig. 7 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 elements.

DETAILED DESCRIPTION OF EMBODIMENTS

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 limitations 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.

As used herein, the term “network device” or “base station” (BS) refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an Evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio head (RH) , a remote radio head (RRH) , a low power node such as a femto node, a pico node, and the like. For the purpose of discussion, in the following, some embodiments will be described with reference to eNB or gNB as examples of the network device.

As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. For the purpose of discussion, in the following, some embodiments will be described with reference to UEs as examples of terminal devices and the terms “terminal device” and “user equipment” (UE) may be used interchangeably in the context of the present disclosure.

The term “circuitry” used herein may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable) : (i) a combination of analog and/or digital hardware circuit (s) with software/firmware and (ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation. ”

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

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. The term “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as “best, ” “lowest, ” “highest, ” “minimum, ” “maximum, ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

Fig. 1 is a schematic diagram of a communication environment 100 in which embodiments of the present disclosure can be implemented. The communication environment 100 may comprise a network device 110, which provides wireless connections for a plurality of

terminal devices

120, 130, and 140 within its coverage. The

terminal devices

120, 130, and 140 may communicate with the network device 110 via wireless transmission channels 115, 125, and 135, respectively. Additionally, the

terminal devices

120, 130, and 140 may communicate with each other via device-to-device (D2D) links (not shown in Fig. 1) .

In some embodiments, the wireless transmission channels 115, 125, and 135 may be carried by a common physical channel, such as the physical uplink shared channel (PUSCH) as defined in 3GPP specifications. In this event, a multiple access scheme, such as the NOMA, may be employed by the

terminal devices

120, 130, and 140 for accessing the common physical channel. Ifthe NOMA scheme is utilized, the

terminal devices

120, 130, and 140 may transmit in same time frequency resources but use different signatures, so that the network device 110 as a receiving device may distinguish transmitted data from different terminal devices.

As indicated above, the signatures in the NOMA scheme are non-orthogonal to each other. As used herein, a signature might be, but not restricted to a spreading sequence, an interleaver pattern, a codebook, a DMRS pattern/sequence, or the like, depending on the details of the NOMA scheme. It should be noted that, although the present disclosure may be described below based mainly on the NOMA scheme, embodiments of the present disclosure may also be applicable to other possible multiple access schemes, such as FDMA, TDMA, CDMA, and SDMA schemes.

It is to be understood that the number of network devices and the number of terminal devices as shown in Fig. 1 are only for the purpose of illustration without suggesting any limitations. The communication environment 100 may include any suitable number of network devices and any suitable number of terminal devices adapted for implementing embodiments of the present disclosure. In addition, it would be appreciated that there may be various wireless communications as well as wireline communications (if needed) among these additional network devices and additional terminal devices.

The communications in the communication environment 100 may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Extended Coverage Global System for Mobile Internet of Things (EC-GSM-IoT) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , and the like.

Furthermore, the communications in the communication environment 100 may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, 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 fifth generation (5G) communication protocols.

By way of illustrative example, the various example implementations or techniques described herein may be applied to various terminal devices, such as machine type communication (MTC) terminal devices, enhanced machine type communication (eMTC) terminal devices, Internet of Things (IoT) terminal devices, and/or narrowband IoT terminal devices.

IoT may refer to an ever-growing group of objects that may have Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status, and may send a report to a server or other network device, for example, when an event occurs. Machine Type Communications (MTC, or Machine to Machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans.

Also, in an example implementation, a terminal device or UE may be a UE/terminal device with URLLC applications. A cell (or cells) may include a number of terminal devices connected to the cell, including terminal devices of different types or different categories, for example, including the categories ofMTC, NB-IoT, URLLC, or other UE category.

The various example implementations may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G, cmWave, and/or mmWave band networks, IoT, MTC, eMTC, URLLC, and the like, or any other wireless network or wireless technology. These example networks or technologies are provided only as illustrative examples, and the various example implementations may be applied to any wireless technology/wireless network.

Through a study of the conventional solutions of multiple access, the inventors find that the number of signatures provided by conventional multiple access schemes may be too less to support a large number of terminal devices. For example, a multiple access system with N terminal devices is considered, and M available signatures in one time slot, where a time slot may be defined as a time interval during which a terminal device can randomly select a signature and transmit data. In the case that the signatures are preconfigured and N＞M, each or some of the signatures may be assigned to more than one terminal device, that is, assigned to n terminal devices, where

Consider a Poisson distribution, where the average number of terminal devices transmitting in a time slot is λ, with λ being much smaller than 1. For simplicity, assuming

the probability that a terminal device does not transmit in a time slot is given by e ^-λ. The probability that a terminal device does not collide with another terminal device is derived in the case where a terminal device selects a signature, and the remaining n-1 terminal devices assigned to this signature do not transmit. This probability is given by (e ^-λ) ^n-1. Hence, the probability of collision is given by 1 - (e ^-λ) ^n-1. It can be seen that the probability of collision greatly increases as the number of terminal devices increases.

In addition, there are recently proposed some Radio Access Network 1 (RAN1) contributions for the configured grant in 3GPP release 15. The inventors note that the configured grant according to 3GPP release 15 considers repeated transmission to improve the reliability of transmission, but fails to utilize the repeated transmission to extend the limited number signatures for multiple access technology. In particular, traditional multiple access schemes do not have the feature of multiple access signature pattern over the repeated transmission.

In view of the above, embodiments of the present disclosure propose methods, devices and computer readable media for communication, in particular, for extension of signatures in a multiple access system. According to the embodiments of the present disclosure, a terminal device may perform data transmission over a plurality of time slots, and an individual signature may be used in each time slot. In this way, considering the plurality of time slots as a whole, available signature patterns may be created from various permutations of the individual signatures. Accordingly, the number of available signature patterns may be much greater than the number of individual signatures, so that the overall probability of transmission collision among terminal devices may be reduced. With the embodiments of the present disclosure, a large multiple access capacity can be supported without a full collision over a plurality of time slots. In the following, some embodiments according to the present disclosure will be detailed with reference to Figs. 2-7.

Fig. 2 shows a flowchart of an example method 200 in accordance with some embodiments of the present disclosure. The method 200 can be implemented at a terminal device, such as the

terminal devices

120, 130, and 140 as shown in Fig. 1. For the purpose of discussion, the method 200 will be described with reference to Fig. 1 and described as being performed by the terminal device 120 without loss of generality. It is understood that the method 200 may also be carried out by the

terminal devices

130 and 140 as well as further terminal devices not shown in Fig. 1.

At block 210, the terminal device 120 determines a first number of time slots for data transmission to be performed by the terminal device 120. There may be various ways for the terminal device 120 to determine the first number of time slots. In some embodiments, the terminal device 120 may transmit to the network device 110 a measurement report, which may reflect a link quality from the terminal device 120 to the network device 110. The network device 110 may determine based on the measurement report the first number of time slots for the terminal device 120. In this way, the number of time slots for data transmission may be adjusted based on the link quality.

For example, if the measurement report indicates that the link quality is poor, the network device 110 may configure the first number to be a relatively large number, so that the terminal device 120 may perform the data transmission for several times in the first number of time slots to improve the reliability of the data transmission. On the other hand, if the link quality is good, the network device 110 may configure the first number to be a relatively small number to save transmission resources. After determining the first number based on the measurement report, the network device 110 may send the first number to the terminal device 120, which may receive the first number from the network device 110 accordingly.

In some other embodiments, the terminal device 120 may select the first number from a plurality of predetermined numbers. In other words, the first number may be dynamically determined by the terminal device 120 from the plurality of predetermined numbers. In this event, to assist the network device 110 as a receiving device in determining the number of time slots used by the terminal device 120 as a transmitting device, respective sets of DMRSs may be defined for the plurality of predetermined numbers of time slots. That is, each of the plurality of predetermined numbers of time slots is associated with a respective set of DMRSs. For example, ifthere are two possible values for the first number and the two values are associated with two sets of DMRSs respectively, then the terminal device 120 may toggle between the two sets of DMRSs when switching between the two possible values of the first number. This is further explained with reference to Fig. 3.

Fig. 3 is a schematic diagram 300 illustrating dynamic multi-slot data transmission by the terminal device 120 in accordance with some embodiments of the present disclosure. As shown in Fig. 3, the top line of blocks (such as block 305) represents time slots. There are two possible values for the first number, namely, the terminal device 120 may switch between three time slots and two time slots when perform several instances of data transmission. It is understood that the specific numbers (three and two) of time slots used herein are just an example, without suggesting any limitations on the present disclosure. In other embodiments, data transmission may use any other suitable amount of time slots.

In the shown example, the terminal device 120 performs four

data transmission instances

330, 340, 350, and 360 using three time slots, two time slots, three time slots, and two time slots, respectively. As shown, the data transmission using three time slots is associated with DMRS set 0 and the data transmission using two time slots is associated with DMRS set 1. In this way, at the network device 110 as a receiving device, detection of a new set of DMRSs signifies the start of new data transmission from the terminal device 120. It is appreciated that the above association between particular DMRS sets and particular number of time slots for data transmission is just an example, without suggesting any limitations on the present disclosure. In other embodiments, other appropriate associations with any DMRS sets and any number of time slots for data transmission are possible. The key point is toggling the DMRS set with each new transmission.

Referring back to Fig. 2, at block 220, the terminal device 120 determines a signature pattern from a plurality of candidate signature patterns. The signature pattern is to be used in performing the data transmission, so that the network device 110 may distinguish the data transmission from other data transmission by other data transmissions sharing the same time frequency resources. For this purpose, each candidate signature pattern comprises a sequence of signatures of a second number. In other words, a candidate signature pattern may be a plurality of signatures arranged in a particular order.

As described above, in some embodiments, a signature may comprise a spreading sequence, an interleaver pattern, a codebook, and a DMRS pattern or sequence, or the like. In some other embodiments, a signature may be any other appropriate means which enables a receiver, for example, the network device 110 as shown in Fig. 1, to separate the data transmission by the terminal device 120 from other data transmission by another terminal device, such as the

terminal devices

130 and 140.

In some embodiments, the second number of the signatures in a candidate signature pattern may be configured based on the number of terminal devices to use the candidate signature patterns (that is, the number of terminal devices sharing the same transmission resources) , an estimated traffic arrival rate of one of the terminal devices, or other possible parameters. The reason is that the larger the second number is, the more the available different signature patterns. In this way, the number of the available signature patterns may be adapted to the number and properties of the related terminal devices.

In some embodiments, the second number is equal to the first number of the time slots for performing the data transmission, which means that there is a one-to-one mapping between the individual signatures in one signature pattern and the individual time slots for the data transmission. As a simple example for demonstration purposes, consider a set of three available signatures, which is represented by {A, B, C} . The data transmission is performed over β time slots. That is, the first number is represented by β, and it is assumed that the second number is equal to the first number β=3. Then, the set of all possible signature patterns across the three time slots is {AAA, AAB, AAC, ABA, ABB, ABC, ACA, ACB, ACC, BAA, BAB, BAC, BBA, BBB, BBC, BCA, BCB, BCC, CAA, CAB, CAC, CBA, CBB, CBC, CCA, CCB, CCC} .

In other words, there are 27 available signature patterns in total. In case that all the 27 available signature patterns are taken as candidate signature patterns, if two terminal devices select two different signature patterns, the minimum number of signatures in corresponding positions that are different is one. For example, ifterminal device 120 selects the signature pattern “AAA, ” and the terminal device 130 selects the signature pattern “AAB, ” only the signature in the third position is different. This could negatively impacts the quality of the data communication, as the signatures of the two terminal devices collide in two time slots.

In order to improve the quality of the data communication, a subset of the 27 signature patterns can be selected as the candidate signature patterns, such that any two different signature patterns from this subset differ in more than one corresponding position. In other words, the available signature patterns are limited so as to maximize the number of slots in which signatures are different between any two signature patterns, when the signature patterns are used to perform data transmission.

For example, such a subset may be {ABC, BCA, CAB} , and when two terminal devices select different signature patterns from this subset, all three positions have different signatures. In this way, when such a subset is used to perform data transmission, a different signature can be used in each time slot for each specific terminal device. However, with this example subset, the available number of signature patterns is three, which is equal to the available number of signatures. Thus, there is no increase in the cardinality of the signature pattern subset.

As an intermediate option, a subset of signature patterns may be selected from all the 27 signature patterns as the candidate signature patterns, such that any two signature patterns in the subset differ in at least two corresponding positions. An example of such kind of subsets may be {ABA, BCA, CAA, ACB, BAB, CBB, AAC, BBC, CCC} . It can be seen that any two elements in this subset differ by at least two positions. An alternative possible subset may be {AAA, BBB, CCC, ABC, BCA, CAB, ACB, BAC, CBA} . In this manner, the number of available signature patterns has increased from three to nine.

It is appreciated that the specific numbers of available signatures, the time slots, and the number of signatures in one signature pattern are merely examples, without suggesting any limitations as to the scope of the disclosure. In other embodiments, any other suitable numbers of available signatures, the time slots, and the number of signatures in one signature pattern may be employed.

More generally, one example is presented here to illustrate how to determine the candidate signature patterns from all the possible signature patterns formed by the available signatures. Let “M” be the number of available signatures, where M is assumed to be a prime number, and let “β” be the number of signatures in one signature pattern, such that β ≤ M. A subset of signature patterns as the candidate signature patterns can be constructed such that any two signature patterns in the subset have at most “t” corresponding positions that have the same signature. As an example, the parameter “t” may be two, that is, any two of the candidate signature patterns have at most two same signatures in corresponding positions. With this value, a balance may be achieved between the number of signature patterns and the probability of collision of signatures in the signature patterns.

Without loss of generality, for a signature pattern g, where g = 0 ... M ^t+1 -1, the signature used in a time slot “i” may be given by the below equation, where s = 0 ... β -1, the sign “Permut () ” represents the permutation function, and the sign “%” represents the modulus operator.

Table 1 as below shows how the size of the subset of signature patterns as discussed above changes with the number of available signatures and the value of “t. ”

Table 1

The candidate signature patterns generated according to the above approach may be preconfigured in the terminal device 120, for example, stored in a memory of the terminal device 120. In this event, in determining a signature pattern from the candidate signature patterns for performing the data transmission, the terminal device 120 may select the signature pattern from the candidate signature patterns based on an identifier of the terminal device 120, a slot number of one of the first number of time slots, and/or other possible parameters.

The identifier of the terminal device 120 can be a configured identification (ID) by the communication network, an ID that is randomly selected by the terminal device 120, or a pre-assigned ID to the terminal device 120 (for example, the International Mobile Subscriber Identity, IMSI) , or a combination thereof. In this way, the signature pattern may be determined by a terminal device itself, and thus saving communication resources between the terminal device 120 and the network device 110.

As another option, the candidate signature patterns may be stored in the network device 110 rather than the terminal device 120. In this case, the network device 110 may configure a signature pattern for the terminal device 120. This applies mostly for Radio Resource Control (RRC) connected terminal devices. In other words, in determining a signature pattern, the terminal device 120 may receive an indication of a signature pattern from the network device 110, which signature pattern is selected by the network device 110 for the terminal device 120 from the candidate signature patterns. In this way, the terminal device 120 does not need to store the candidate signature patterns and does not need to perform operations for determining the signature pattern, and thus the requirement on the terminal device 120 may be lowered.

In some embodiments, the second number of the signatures in a signature pattern is greater than the first number of time slots for data transmission. This means that the length of a signature pattern can be determined assuming that the data transmission is performed in the second number of time slots, but the terminal device 120 actually uses fewer (the first number of) time slots than the second number of time slots for the data transmission. As an example, referring again to Fig. 3, the

signature patterns

310 and 320 each include four signatures and thus can span four time slots. That is, in Fig. 3, the second number of the signature in a signature pattern is four, which is greater than the first number (three or two) of time slots for data transmission instances 330-360.

In addition, for the last data transmission instance 360 in Fig. 3, the network device 110 can rely on DTX detection of DMRSs in the first time slot with no DMRSs. The terminal device 120 can send a respective set of DMRSs with no data for one time slot, and the network device 110 may use DTX detection for data. Alternatively, the terminal device 120 may send a special signature pattern on data that the network device 110 can detect.

In case that the second number is greater than the first number, the candidate signature patterns may be determined based on the first number. Specifically, the signatures or the signature patterns may be partitioned depending on the first number. For example, for single slot transmission (the first number=1) , the terminal device 120 may use first M ₁ signatures. For double slot transmission (the first number=2) , the terminal device 120 may use next M ₂ signatures to create M ₂ signature patterns, where any two signature patterns differ in two corresponding positions. For three-slot transmission (the first number=3) , the terminal device 120 may use next M ₃ signatures to give (M ₃) ² signature patterns, where any two signature patterns differ in at least two corresponding positions. For an even larger value of the first number, a large amount of partially overlapping signature patterns can be generated. In this way, not many signatures would be needed for a large value of the first number.

Referring back to Fig. 2, at block 230, the terminal device 120 performs the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially. For example, if three time slots are used for the data transmission and the determined signature pattern is “ABC, ” the terminal device 120 may use the signature “A” in the first time slot, use the signature “B” in the second time slot, and the signature “C” in the third time slot, when performing the data transmission.

If the second number of the signatures in the determined signature pattern is greater than the first number of time slots for the data transmission. The terminal device 120 may use consecutive signatures of the second number from the second number of the signatures. For example, if three time slots are used for the data transmission and the determined signature pattern is “ABCCA, ” the terminal device 120 may use the first three signatures to perform the data transmission, and the remaining signatures “CA” may be used for next data transmission. This may be case of

signature patterns

310 and 320 shown in Fig. 3. In some other embodiments, the terminal device 120 may use other consecutive three signatures to perform the data transmission.

It is appreciated that the specific numbers and the specific signature patterns are merely examples, without suggesting any limitations as to the scope of the disclosure. In other embodiments, any other suitable numbers and any other signature patterns may be employed.

To support terminal devices with different starting slot index numbers and/or different number of time slots for data transmission, there may be a common starting time slot where all the signature patterns start. For this purpose, in some embodiments, the terminal device 120 may initiate the detennined signature pattern before the first number of time slots for data transmission, such that the determined signature pattern starts at a time slot with a predetermined slot number. The reason may be that the data transmission may be started in any time slot, for example. In this way, all signature patterns may start at a same time slot, regardless of when the terminal device 120 starts the data transmission. This is further described with reference to Fig. 4.

Fig. 4 is a schematic diagram 400 illustrating that the terminal devices 120-140 may transmit with non-aligned starting time slots in accordance with some embodiments of the present disclosure. As an example, the subset of signature patterns {ABA, BCA, CAA, ACB, BAB, CBB, AAC, BBC, CCC} is considered. As shown in Fig. 4, the terminal device 120 use the signature pattern “ABA, ” the terminal device 130 use a signature pattern “ACB, ” and the terminal device 140 use a signature pattern “CBB. ”

The terminal device 120 performs four data transmission instances 122, 124, 126, and 128 and starts data transmission at the first time slot. The terminal device 130 performs three data transmission instances 132, 134, and 136 and starts data transmission at the second time slot. The terminal device 140 performs three data transmission instances 142, 144, and 146 and starts data transmission at the third time slot. It is noted that each of the

terminal device

120, 130, and 140 uses the same signature pattern for subsequent transmission instances. In other embodiments, it is also possible to have each terminal device use a different sequence for subsequent transmission instances.

Regarding the timing of the data transmission over the first number of time slots, there may be two options. As a first option, in some embodiments, the terminal device 120 may initiate the data transmission in a time slot with a predetermined slot number. That is, data transmission over the first number of time slots may be synchronized to start at the same slot boundary for all terminal devices. For example, if the time slots available for uplink transmission are numbered consecutively using an index number “p. ” A β-slot data transmission may start at time slot p, such that p is an integer multiple of β. This option introduces additional latency as the data transmission would have to wait till a time slot p which is multiple of β.

As a second option, in some other embodiments, data transmission over β time slots may be allowed to start at any time slot and span β time slots. In this event, the signature used in slot m is given by the equation below, where m = n, n + 1, ... n + β -1, the sign “Permut () ” represents the permutation function, and the sign “%” represents the modulus operator.

In this case, despite the terminal devices starting at different time slots, the signature pattern is determined based on the absolute slot number m, which allows the co-existence of terminal devices with unique signature patterns starting in different time slots. It should be noted that the second option, while reducing the latency, increases the computation complexity at a receiver (for example, the network device 110) , as it may require multiple hypothesis testing with different starting time slots.

In some embodiments, in performing the data transmission, the terminal device 120 may repeatedly perform the data transmission in the first number of time slots. This is done to advantageously increase the reliability of grant-free transmission. If repeated data transmission over multiple time slots (let’s assume β time slots) is considered, this repetition has two effects on the collision of signatures. The first effect is that the probability of no transmission, across the β time slots may be decreased, according to the term e ^-βλ in the probability equation.

The second effect is that as the number of time slots for data transmission increase, the number of available signatures increases. For simplicity, it is assumed that this increase is linear, even though the increase can be greater than linear which gives better results. Hence, the number of signatures per time slot is inversely proportional to β. The probability of collision considering β time slots is given by 1 - (e ^-βλ) ^n/β-1.

Fig. 5 is a graph 500 illustrating probability of collision as a function of the number of signatures in a signature pattern in accordance with some embodiments of the present disclosure. The line 510 in Fig. 5 shows how the probability of collision changes with the second number (in this case it equals to the first number β) . In this specific example shown in Fig. 5, the average number of terminal devices transmitting in a time slot, which is represented with λ, is assumed to be 0.01, and the number of terminal devices allocated with a same signature, which is represented with n, is assumed to be 10.

It can be seen that as the number of time slots being aggregated for a single data transmission instance increases, the probability of collision decreases. The rationale is that there are fewer terminal devices assigned to each signature, which reduces the likelihood that two terminal devices collide on the same signature.

In the above, it is described that how the signature pattern used by the terminal device 120 for performing data transmission is determined. In addition to the signature pattern proposed herein, there may be a DMRS or preamble pattern available for the terminal device 120 to use in performing data transmission. In general, the DMRS or preamble is used for channel estimation and identification of a terminal device. There are different options for the association of the signatures or the signature patterns with the DMRS/preambles.

As a first option, in some embodiments, the terminal device 120 may associate each signature with a unique demodulation reference signal (DMRS) or preamble. That is, there is a one-to-one mapping between the signature and the DMRS/preamble. In this option, when there is a collision on a signature in a time slot, there is also a collision on the DMRS/preamble in the same time slot. If one of the colliding terminal devices (for example, terminal device 120) is decodable, thanks to transmission on other time slot (s) that do not collide, the signal from the terminal device 120 can be reconstructed (assuming that the channel is sufficiently stationary over the β time slots for data transmission) and thus can be cancelled in the colliding time slot from the DMRS/preamble and data signal for the benefit of other colliding terminal devices, for example, the

terminal devices

130 and 140.

As a second option, in some embodiments, the terminal device 120 may associate each candidate signature pattern with a unique DMRS or preamble. In other words, there is a one-to-one mapping between the signature pattern and the DMRS/preamble. In this option, each signature pattern has its unique DMRS/preamble. This has the advantage that the channel estimation and detection for each terminal device can be done independent of whether some signatures collide in some time slots. On the other hand, this requires a significant increase in the number of unique preambles/DMRS ports.

As a third option, in some other embodiments, the terminal device 120 may associate a group of candidate signature patterns from the plurality of candidate signature patterns with a same DMRS or preamble. This is a hybrid solution of the first and second options, such that groups of signature patterns are associated with the same DMRS/preamble.

Fig. 6 shows a flowchart of an example method 600 in accordance with some other embodiments of the present disclosure. The method 600 can be implemented at a network device, such as the network device 110 as shown in Fig. 1. For the purpose of discussion, the method 600 will be described with reference to Fig. 1 and described as being performed by the network device 110. It is understood that the method 600 may also be carried out by other network devices not shown in Fig. 1.

At block 610, the network device 110 receives data transmission from a terminal device 120 in a first number of time slots.

At block 620, the network device 110 determines a signature pattern from the data transmission. The determined signature pattern is from a plurality of candidate signature patterns. Each candidate signature pattern comprises a sequence of signatures of a second number. The second number is greater than or equal to the first number.

At block 630, the network device 110 separates the data transmission by the terminal device 120 from further data transmission by a further terminal device 130, using the determined signature pattern.

In some embodiments, as mentioned above, the network device 110 may determine the signature pattern for the terminal device 120. For this purpose, the network device 110 may select, for the terminal device 120, the signature pattern from the plurality of candidate signature patterns. Then, the network device 110 may transmit an indication of the signature pattern to the terminal device 120 for performing the data transmission.

In some embodiments, as mentioned above, the network device 110 may determine the first number of time slots for the data transmission by the terminal device 120. In this event, the network device 110 may receive a measurement report from the terminal device 120, determine the first number based on the measurement report, and transmit the first number to the network device 120.

In some embodiments, an apparatus for performing the method 200 (for example, the

terminal devices

120, 130, and 140) may comprise respective means for performing the corresponding steps in the method 200. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises: means for determining a first number of time slots for data transmission to be performed by the terminal device; means for determining a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and means for performing the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially.

In some embodiments, the means for determining the signature pattern comprises: means for selecting the signature pattern from the plurality of candidate signature patterns based on at least one of the following: an identifier of the terminal device, and a slot number of one of the first number of time slots.

In some embodiments, the means for determining the signature pattern comprises: means for receiving an indication of the signature pattern from a network device in communication with the terminal device.

In some embodiments, any two of the plurality of candidate signature patterns have at most two same signatures in corresponding positions.

In some embodiments, the means for performing the data transmission comprises: means for initiating the determined signature pattern before the first number of time slots, such that the determined signature pattern starts at a time slot with a predetermined slot number.

In some embodiments, the second number is configured based on at least one of the following: the number of terminal devices to use the plurality of candidate signature patterns, and an estimated traffic arrival rate of one of the terminal devices.

In some embodiments, the apparatus further comprises at least one of the following: means for associating each of the second number of signatures with a unique demodulation reference signal (DMRS) or preamble; means for associating each candidate signature pattern with a unique DMRS or preamble; and means for associating a group of candidate signature patterns from the plurality of candidate signature patterns with a same DMRS or preamble.

In some embodiments, the means for performing the data transmission comprises: means for initiating the data transmission in a time slot with a predetermined slot number.

In some embodiments, the means for determining the first number of time slots comprises: means for transmitting a measurement report to a network device in communication with the terminal device; and means for receiving the first number from the network device.

In some embodiments, the means for determining the first number of time slots comprises: means for selecting the first number from a plurality of predetermined numbers, each of the plurality of predetermined numbers of time slots associated with a respective set of DMRSs.

In some embodiments, the plurality of candidate signature patterns are determined based on the first number.

In some embodiments, the means for performing the data transmission comprises: means for repeatedly performing the data transmission in the first number of time slots.

In some embodiments, each of the signatures comprises at least one of the following: a spreading sequence, an interleaver pattern, a codebook, and a DMRS pattern or sequence.

In some embodiments, an apparatus for performing the method 600 (for example, the network device 110) may comprise respective means for performing the corresponding steps in the method 600. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises: means for receiving data transmission from a terminal device in a first number of time slots; means for determining a signature pattern from the data transmission, the determined signature pattern being from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and means for separating the data transmission by the terminal device from further data transmission by a further terminal device, using the determined signature pattern.

In some embodiments, the apparatus further comprises: means for selecting, for the terminal device, the signature pattern from the plurality of candidate signature patterns; and means for transmitting an indication of the signature pattern to the terminal device for performing the data transmission.

In some embodiments, the apparatus further comprises: means for receiving a measurement report from the terminal device; means for determining the first number based on the measurement report; and means for transmitting the first number to the network device.

Fig. 7 is a simplified block diagram of a device 700 that is suitable for implementing embodiments of the present disclosure. The device 700 can be considered as a further example embodiment of the network device 110 and the

terminal devices

120, 130, and 140 as shown in Fig. 1. Accordingly, the device 700 can be implemented at or as at least a part of the network device 110 or the

terminal device

120, 130, and 140.

As shown, the device 700 includes a processor 710, a memory 720 coupled to the processor 710, a suitable transmitter (TX) and receiver (RX) 740 coupled to the processor 710, and a communication interface coupled to the TX/RX 740. The memory 720 stores at least a part of a program 730. The TX/RX 740 is for bidirectional communications. The TX/RX 740 has at least one antenna to facilitate communication. 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 730 is assumed to include program instructions that, when executed by the associated processor 710, enable the device 700 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Figs. 1 to 6. The embodiments herein may be implemented by computer software executable by the processor 710 of the device 700, or by hardware, or by a combination of software and hardware. The processor 710 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 710 and memory 720 may form processing means 750 adapted to implement various embodiments of the present disclosure.

The memory 720 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 720 is shown in the device 700, there may be several physically distinct memory modules in the device 700. The processor 710 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 700 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.

The components included in the apparatuses and/or devices of the present disclosure may be implemented in various manners, including software, hardware, firmware, or any combination thereof. In one embodiment, one or more units may be implemented using software and/or firmware, for example, machine-executable instructions stored on the storage medium. In addition to or instead of machine-executable instructions, parts or all of the units in the apparatuses and/or devices may be implemented, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs) , Application-specific Integrated Circuits (ASICs) , Application-specific Standard Products (ASSPs) , System-on-a-chip systems (SOCs) , Complex Programmable Logic Devices (CPLDs) , and the like.

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 any of Figs. 2 and 6. 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 illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific embodiment 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 separate 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 implemented at a terminal device, comprising:

determining a first number of time slots for data transmission to be performed by the terminal device;

determining a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and

performing the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially.
The method of claim 1, wherein determining the signature pattern comprises:

selecting the signature pattern from the plurality of candidate signature patterns based on at least one of the following: an identifier of the terminal device, and a slot number of one of the first number of time slots.
The method of claim 1, wherein determining the signature pattern comprises:

receiving an indication of the signature pattern from a network device in communication with the terminal device.
The method of claim 1, wherein any two of the plurality of candidate signature patterns have at most two same signatures in corresponding positions.
The method of claim 1, wherein performing the data transmission comprises:

initiating the determined signature pattern before the first number of time slots, such that the determined signature pattern starts at a time slot with a predetermined slot number.
The method of claim 1, wherein the second number is configured based on at least one of the following: the number of terminal devices to use the plurality of candidate signature patterns, and an estimated traffic arrival rate of one of the terminal devices.
The method of claim 1, further comprising at least one of the following:

associating each of the second number of signatures with a unique demodulation reference signal (DMRS) or preamble;

associating each candidate signature pattern with a unique DMRS or preamble; and

associating a group of candidate signature patterns from the plurality of candidate signature patterns with a same DMRS or preamble.
The method of claim 1, wherein performing the data transmission comprises:

initiating the data transmission in a time slot with a predetermined slot number.
The method of claim 1, wherein determining the first number of time slots comprises:

transmitting a measurement report to a network device in communication with the terminal device; and

receiving the first number from the network device.
The method of claim 1, wherein determining the first number of time slots comprises:

selecting the first number from a plurality of predetermined numbers, each of the plurality of predetermined numbers of time slots associated with a respective set of DMRSs.
The method of claim 1, wherein the plurality of candidate signature patterns are determined based on the first number.
The method of claim 1, wherein performing the data transmission comprises:

repeatedly performing the data transmission in the first number of time slots.
The method of claim 1, wherein each of the signatures comprises at least one of the following: a spreading sequence, an interleaver pattern, a codebook, and a DMRS pattern or sequence.
A method implemented at a network device, comprising:

receiving data transmission from a terminal device in a first number of time slots;

determining a signature pattern from the data transmission, the determined signature pattern being from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and

separating the data transmission by the terminal device from further data transmission by a further terminal device, using the determined signature pattern.
The method of claim 14, further comprising:

selecting, for the terminal device, the signature pattern from the plurality of candidate signature patterns; and

transmitting an indication of the signature pattern to the terminal device for performing the data transmission.
The method of claim 14, further comprising:

receiving a measurement report from the terminal device;

determining the first number based on the measurement report; and

transmitting the first number to the network device.
A terminal device, comprising:

at least one processor; and

at least one memory storing computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the terminal device to:

determine a first number of time slots for data transmission to be performed by the terminal device;

determine a signature pattern from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and

perform the data transmission in the first number of time slots using signatures of the first number in the determined signature pattern sequentially.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

select the signature pattern from the plurality of candidate signature patterns based on at least one of the following: an identifier of the terminal device, and a slot number of one of the first number of time slots.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

receive an indication of the signature pattern from a network device in communication with the terminal device.
The terminal device of claim 17, wherein any two of the plurality of candidate signature patterns have at most two same signatures in corresponding positions.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

initiate the determined signature pattern before the first number of time slots, such that the determined signature pattern starts at a time slot with a predetermined slot number.
The terminal device of claim 17, wherein the second number is configured based on at least one of the following: the number of terminal devices to use the plurality of candidate signature patterns, and an estimated traffic arrival rate of one of the terminal devices.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to at least one of the following:

associate each of the second number of signatures with a unique demodulation reference signal (DMRS) or preamble;

associate each candidate signature pattern with a unique DMRS or preamble; and

associate a group of candidate signature patterns from the plurality of candidate signature patterns with a same DMRS or preamble.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

initiate the data transmission in a time slot with a predetermined slot number.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

transmit a measurement report to a network device in communication with the terminal device; and

receive the first number from the network device.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

select the first number from a plurality of predetermined numbers, each of the plurality of predetermined numbers of time slots associated with a respective set of DMRSs.
The terminal device of claim 17, wherein the plurality of candidate signature patterns are determined based on the first number.
The terminal device of claim 17, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the terminal device to:

repeatedly perform the data transmission in the first number of time slots.
The terminal device of claim 17, wherein each of the signatures comprises at least one of the following: a spreading sequence, an interleaver pattern, a codebook, and a DMRS pattern or sequence.
A network device, comprising:

at least one processor; and

at least one memory storing computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the network device to:

receive data transmission from a terminal device in a first number of time slots;

determine a signature pattern from the data transmission, the determined signature pattern being from a plurality of candidate signature patterns, each candidate signature pattern comprising a sequence of signatures of a second number, the second number being greater than or equal to the first number; and

separate the data transmission by the terminal device from further data transmission by a further terminal device, using the determined signature pattern.
The network device of claim 30, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the network device to:

select, for the terminal device, the signature pattern from the plurality of candidate signature patterns; and

transmit an indication of the signature pattern to the terminal device for performing the data transmission.
The network device of claim 30, wherein the at least one memory and the computer program code further configured to, with the at least one processor, cause the network device to:

receive a measurement report from the terminal device;

determine the first number based on the measurement report; and

transmit the first number to the network device.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor of a device, causing the device to carry out the method according to any of claims 1 to 13.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor of a device, causing the device to carry out the method according to any of claims 14 to 16.