WO2020216441A1

WO2020216441A1 - Method and arrangements for managing multicast and unicast transmissions

Info

Publication number: WO2020216441A1
Application number: PCT/EP2019/060465
Authority: WO
Inventors: Zexian Li; Vinh Van Phan; Ling Yu
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2019-04-24
Filing date: 2019-04-24
Publication date: 2020-10-29

Abstract

Network node of a wireless communication system is configured to schedule one or more targeted transmissions to one or more receiving nodes to take place in a data packet. These receiving nodes form a subgroup of less than all receiving nodes. Contents of an indicator field in a control message to said receiving nodes indicates the scheduling and one or more intended recipients of said targeted transmissions, which comprise a targeted multicast transmission to said subgroup and/or a unicast transmission to an individual receiving node. The indicator field comprises at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to said subgroup or a common multicast transmission to all receiving nodes, and a second indicator indicative of said one or more intended recipients.

Description

METHOD AND ARRANGEMENTS FOR MANAGING MULTICAST AND UNICAST TRANSMISSIONS

FIELD OF THE INVENTION

The invention relates to the technical field of scheduling transmissions in a wireless communication system in which a transmitting node may need to make multicast and/or unicast transmissions to a number of receiving nodes. In par ticular the invention relates to a way in which various combi nations of multicast and unicast transmissions are announced to the receiving nodes.

BACKGROUND OF THE INVENTION

Versatile wireless communication systems, such as the one that is being specified as the fifth generation (5G) sys tem, will be expected to offer a wide range of specialized communications. One particular area of application will be in dustrial internet of things (IIoT), where 5G communications can be used to control complicated processes in real time. The processes may involve aspects such as motion control, mobile robots, massive sensor networks, remote access, maintenance and so on. Strict requirements will be placed concerning both reliability and latency of communications, with the obvious aim of achieving as error-free communications with as short delays as possible. The acronym URLLC has been coined to des ignate such communications, coming from Ultra-Reliable and Low Latency Communications.

Figs, la and lb illustrate four steps that can be performed cyclically in an example of an industrial process. The devices that are illustrated are a motion controller 101, a plurality of actuators 102, and a plurality of sensors 103. Each actuator 102 is shown schematically to comprise a wire less transceiver 104, an internal buffer 105, and an actuator interface 106. Each sensor 103 is shown schematically to com prise a wireless transceiver 104, an internal buffer 105, and a sensor head 107. In the first step the motion controller 101 sends set points to all actuators 102. In the second step the actua tors take these set points and put them into their respective internal buffers 105. In the third step all sensors 103 trans mit their current actual values, read from their internal buffers 105 respectively, to the motion controller 101. The fourth step takes place at a well-defined instant of the cur rent time cycle, commonly referred to as the "common sampling point". It comprises the actuators 102 retrieving their latest set points from the internal buffer and acting accordingly, as well as the sensors 103 determining the current state of the process and storing the value thus acquired to their internal buffer 105.

The cycle time of these four steps may be in the or der of a millisecond, and there can be dozens of devices (ac tuators 102 and sensors 103) involved. This puts some serious challenges to the wireless interface.

Transmissions types that the motion controller 101 (or other network node transmitting in the downlink direction) utilizes may comprise multicast and unicast transmissions. A multicast transmission is a common transmission targeted to a number of receiving nodes simultaneously, while a unicast transmission is targeted to only one receiving node. Transmis sions may be arranged in transport blocks, so that a multicast transmission may comprise a transport block addressed to a plurality of receiving nodes simultaneously, and unicast transmissions can be made by addressing a separate, appropri ately addressed transport block to each receiving node that is to receive individual data.

Due to the tight time schedule, the reception capa bility of a receiving node (which is typically a simpler de vice than the motion controller for cost reasons) may not be sufficient to receive two transport blocks simultaneously, one conveying a multicast transmission and the other a unicast transmission. This may create a problem in a situation in which the motion controller would need to augment some common data, transmitted as multicast, with individually addressed data to at least some of the same nodes. Another problem of the known multicast transmis sions is the relatively static nature of groups to which such multicasts are to be transmitted. If a message was meant to only a temporarily defined subset of a predefined group, also those members of the group who are not in that subset consume energy in receiving the multicast, while only at some higher layer protocol they find out that there was actually no need for them to receive that transmission even in the first place.

SUMMARY

An objective of the invention is to present methods and arrangements that enable flexible handling of multicast and unicast transmissions, also with temporarily defined sub sets of multicast-receiving nodes. Another objective of the invention is to enable transmissions of both multicast and unicast type to receiving nodes of a wireless communication system even under tight constraints regarding time and relia bility. A further objective of the invention is to enable re ceiving nodes of a wireless communication system to save power by avoiding the processing of unnecessary transmissions. Yet another objective of the invention is to reduce the signaling overhead that is needed in making multicast and unicast trans missions in a wireless communication system.

These and further advantageous objectives are achieved with methods and devices the characterizing features of which are listed in the respective independent claims ap pended to this text. Features of advantageous embodiments are presented in depending claims.

According to a first aspect there is provided a net work node of a wireless communication system for making trans missions to a plurality of receiving nodes of the wireless communication system. The network node is configured to sched ule one or more targeted transmissions to one or more receiv ing nodes of said plurality of receiving nodes to take place in a data packet, said one or more receiving nodes forming a subgroup of less than all of said plurality of receiving nodes. The network node is configured to indicate, with con tents of an indicator field in a control message to said re- ceiving nodes, the scheduling and one or more intended re cipients among said receiving nodes of said one or more tar geted transmissions. Said one or more targeted transmissions comprise a targeted multicast transmission to said subgroup, and/or a unicast transmission to an individual receiving node among said plurality of receiving nodes. Said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to said subgroup or a common multicast transmis sion to all of said plurality of receiving nodes, and a second indicator indicative of said one or more intended recipients.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that when scheduling a common multicast transmission in said data packet to all of said plurality of receiving nodes, a first or third value is selected for the first indicator, and when scheduling a targeted multicast transmission in said data packet to said subgroup, a second or fourth value is selected for the first indicator. This in volves the advantage that a simple and straightforward way ex ists to differentiate between the four cases that need to be differentiated.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that when scheduling in said data packet a targeted multicast transmission to said subgroup and no unicast transmissions, a first bitmap is selected as a value of said second indicator, bit values in said first bitmap identifying said one or more intended recipients of said tar geted multicast transmission. This involves the advantage that receiving nodes that are not to receive the targeted multicast transmission can avoid performing unnecessary receptions and thus save power.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that when scheduling in said data packet a common multicast transmission to all of said plurality of re ceiving nodes and one or more unicast transmissions to respec tive individual receiving nodes among said plurality of re- ceiving nodes, a second bitmap is selected as a value of said second indicator, bit values in said second bitmap identifying said respective individual receiving nodes. This involves the advantage that the "double" scheduling of both a common mul ticast and a unicast transmission can be announced to the ap propriate receiving nodes in a very efficient and concise way.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that when scheduling in said data packet a targeted multicast transmission to said subgroup and one or more unicast transmissions to respective individual receiving nodes among the receiving nodes that form said subgroup, third and fourth bitmaps are selected as a combined value of said second indicator, bit values in said third bitmap identifying said one or more intended recipients of said targeted mul ticast transmission and bit values in said fourth bitmap iden tifying said respective individual receiving nodes. This in volves the advantage that the "double" scheduling of both a targeted multicast and a unicast transmission can be announced to the appropriate receiving nodes in a very efficient and concise way.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that said fourth bitmap contains as many bits as there are active bit values in said third bitmap that iden tify said intended recipients of said targeted multicast transmission, with one-to-one relation between the bits in the fourth bitmap and active bit values in said third bitmap. Among said bits of the fourth bitmap there is an active bit value for each individual receiving node that is an intended recipient of a respective unicast transmission in the data packet. This involves the advantage that the double scheduling of both a targeted multicast and a unicast transmission can be announced to the appropriate receiving nodes in a very effi cient and concise way.

According to an embodiment of the first aspect the network node is configured to select said contents of said in dicator field so that said fourth bitmap contains as many bits as said third bitmap, and among said bits of the fourth bitmap there is an active bit value for each individual receiving node that is an intended recipient of a respective unicast transmission in the data packet. This involves the advantage that the "double" scheduling of both a targeted multicast and a unicast transmission can be announced to the appropriate re ceiving nodes in a very efficient and concise way.

According to an embodiment of the first aspect the network node is configured to select said one or more intended recipients of the one or more targeted transmissions on the basis of at least one of the following kinds of semi-static group activity information: mapping rule linking command type and respective intended recipients, mapping rule linking each specific command and respective intended recipients, mapping rule linking origin of a received command and respective in tended recipients, mapping rule linking a sequence of commands and respective intended recipients. This involves the ad vantage that semi-static group activity information can be de rived in a straightforward way with minimal additional signal ing between the relevant network nodes.

According to an embodiment of the first aspect the network node is configured to select said one or more intended recipients of the one or more targeted transmissions on the basis of at least dynamic group activity information that the network node received in a message triggering a transmission to said plurality of receiving nodes. This involves the ad vantage that dynamic group activity information can be derived in a straightforward way with minimal additional signaling be tween the relevant network nodes.

According to a second aspect there is provided a re ceiving node of a wireless communication system for receiving transmissions from a network node of the wireless communica tion system. The receiving node is configured to decode, from contents of an indicator field received in a control message from said network node, an indication of whether the receiving node is an intended recipient of one or more targeted trans missions scheduled in a data packet. Said one or more targeted transmissions comprise a targeted multicast transmission to a subgroup of less than all of a plurality of receiving nodes and/or a unicast transmission to the receiving node itself. Said contents of said indica- tor field comprise at least a first indicator indicative of whether said data packet con tains a targeted multicast transmission to a subgroup or a common multicast transmission to all of said plurality of re ceiving nodes, and a second indicator indicative of said one or more intended recipients.

According to an embodiment of the second aspect the receiving node is configured to decode a first or third value of said first indicator into an indication of a common mul ticast transmission to all of said plurality of receiving nodes being scheduled in said data packet, and a second or fourth value of said first indicator into an indication of a targeted multicast transmission to a subgroup being scheduled in said data packet. This involves the advantage that a simple and straightforward way exists to differentiate between the four cases that need to be differentiated.

According to an embodiment of the second aspect the receiving node is configured to decode a dedicated bit value in a first bitmap received as said second indicator into an indication of whether said receiving node is an intended re cipient of a targeted multicast transmission scheduled in said data packet. This involves the advantage that if the receiving node is not to receive the targeted multicast transmission it can avoid performing unnecessary reception activity and thus save power.

According to an embodiment of the second aspect the receiving node is configured to decode a dedicated bit value in a second bitmap received as said second indicator into an indication of whether said receiving node is an intended re cipient of a unicast transmission scheduled in said data pack et. This involves the advantage that the double scheduling of both a common multicast and a unicast transmission can be an nounced to the receiving node in a very efficient and concise way .

According to an embodiment of the second aspect the receiving node is configured to decode a dedicated bit value in a third bitmap received as a part of said second indicator into an indication of whether said receiving node is an in tended recipient of a targeted multicast transmission sched- uled in said data packet, and - in response to thus finding that said receiving node is an intended recipient of a target ed multicast transmission scheduled in said data packet - a corresponding bit value in a fourth bitmap received as a part of said second indicator into an indication of whether said receiving node is additionally an intended recipient of a unicast transmission scheduled in said data packet. Said fourth bitmap may contain as many bits as there are active bit values in said third bitmap each identifying an intended re cipient of said targeted multicast transmission, with one-to- one relation between the bits in the fourth bitmap and active bit values in said third bitmap. Alternatively said fourth bitmap may contain as many bits as the third bitmap. Among said bits of the fourth bitmap there is an active bit value for each individual receiving node that is an intended recipi ent of a respective unicast transmission in the data packet. This involves the advantage that the double scheduling of both a targeted multicast and a unicast transmission can be an nounced to the receiving node in a very efficient and concise way .

According to a third aspect there is provided a meth od for indicating scheduling of transmissions from a network node of a wireless communication system to receiving nodes of said wireless communication system. The method comprises scheduling one or more targeted transmissions to one or more receiving nodes of said plurality of receiving nodes to take place in a data packet, said one or more receiving nodes form ing a subgroup of less than all of said plurality of receiving nodes, and indicating, with contents of an indicator field in a control message to said receiving nodes, the scheduling and one or more intended recipients among said receiving nodes of said one or more targeted transmissions. Said one or more tar geted transmissions comprise at least one of: a targeted mul ticast transmission to said subgroup, a unicast transmission to an individual receiving node among said plurality of re ceiving nodes. Said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to said sub group or a common multicast transmission to all of said plu- rality of receiving nodes, and a second indicator indicative of said one or more intended recipients.

According to a fourth aspect there is provided a method for receiving, in a receiving node of a wireless commu nication system, transmissions from a network node of said wireless communication system. The method comprises decoding, from contents of an indicator field received in a control mes sage from said network node, an indication of whether the re ceiving node is an intended recipient of one or more targeted transmissions scheduled in a data packet. Said one or more targeted transmissions comprise at least one of: a targeted multicast transmission to a subgroup of less than all of a plurality of receiving nodes, a unicast transmission to the receiving node itself. Said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to a subgroup or a common multicast transmission to all of said plurality of receiving nodes, and a second indicator indica tive of said one or more intended recipients.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to pro vide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the in vention and together with the description help to explain the principles of the invention. In the drawings:

Figure la illustrates two phases of a suggested mo tion control process,

Figure lb illustrates two other phases of the sug gested motion control process,

Figure 2a illustrates an example of the scheduling of a common multicast transmission only,

Figure 2b illustrates an example of the scheduling of a targeted multicast transmission only,

Figure 2c illustrates an example of the scheduling of a common multicast transmission and one or more unicast trans missions, Figure 2d illustrates an example of the scheduling of a targeted multicast transmission and one or more unicast transmissions ,

Figure 3 illustrates an example of a method,

Figure 4 illustrates an example of a method, and.

Figure 5 illustrates an example of one step of the method of fig. 3.

DETAILED DESCRIPTION

The general technical framework of the following de scription in terms of participating devices and their roles may be the same as above with reference to figs, la and lb. A network node 101 of a wireless communication system is provid ed for making transmissions to a plurality of receiving nodes of the wireless communication system. Examples of such receiv ing nodes are the actuators 102 and sensors 103 shown in the drawings. The network node 101 may be for example a motion controller, a process controller, a hub of a sensor network, a controller of a building automation system, a base station, an access point, or other kind of a device that may have to make relatively frequent transmissions to at least some of the re ceiving nodes. As an example of what is considered frequent is the repetition of data distribution and acquisition cycles at every 1 ms, but this should be considered as a general example only. It does have any restricting or limiting effect to the applicability of the methods and arrangements described below. Using the designation "receiving node" does not mean that any of these devices should be restricted to receiving only. The designation is used here only to illustrate that these devices are at the receiving end of those transmissions that are de scribed in more detail below. Examples of receiving nodes in clude but are not limited to sensors, slave nodes, User Equip ments (UEs) and other devices.

The network node 101 is configured to schedule one or more targeted transmissions to one or more of the receiving nodes. At least some of the targeted transmissions, the sched uling of which is meant here, can be described as taking place in the form of data packets. The term data packet is a general term that is not meant to be limited to e.g. some detailed meaning for which it is used in some particular telecommu nications standard. A data packet is just some well-defined amount of digital data that can be conveniently handled for the purpose of being transmitted by the network node 101.

Intended recipients among the receiving nodes can be described in terms of a group, one or more subgroups, or indi vidual receiving nodes. Here it is assumed that the arrange ment of a network node and the receiving nodes to which it makes scheduled transmissions is a relatively static entity as a whole, for example so that the receiving nodes are devices of an industrial process or a building and the network node is a corresponding controller. Thus the whole plurality of re ceiving nodes can be called a group. Among that group there may be subgroups that can be statically or dynamically de fined. A subgroup comprises two or more, but not all receiving nodes of the whole group, i.e. less than all of the plurality of receiving nodes that constitute the group.

The definition of a statically defined subgroup does not need to be completely static, for which reason there can be used also the term semi-statically defined subgroup. A statically or semi-statically defined subgroup consists of re ceiving nodes that can be listed in a predefined manner, so that there exists a predefined, known relationship between something that identifies the subgroup and the receiving nodes belonging to that subgroup. A dynamically defined subgroup is one that can be formed on the fly, based on some changing cri terion. As a simplified example if a group consists of a plu rality of temperature sensors installed at various locations of an industrial process, a (semi-) statically defined subgroup could consist of those sensors that are located around a par ticular process stage, and a dynamically defined subgroup could consist of those sensors that at a given instant of time have detected a temperature that is higher than some value of interest. More examples of how ( semi- ) statically and dynami cally defined subgroups can be formed are discussed later in this text.

One consequence of the conceptual difference between ( semi- ) statically and dynamically defined subgroups is that it is possible to predefine a subgroup identifier for each (semi- ) statically defined subgroup. Those receiving nodes that be long to a ( semi- ) statically defined subgroup may e.g. recog nize a multicast transmission to that subgroup by noting a subgroup identifier in the transmission. For dynamically de fined subgroups that is not feasible because of the (possibly very frequent) changes in which receiving nodes belong to the dynamically defined subgroup.

A targeted transmission means a transmission for which there is one or more intended recipients among the re ceiving nodes. A common multicast transmission to all receiv ing nodes in the group is not called here a targeted transmis sion; in other words, targeting means selecting one or more but not all of the receiving nodes as the intended recipients. The definitions of subgroup and targeting introduced above mean that there are two kinds of targeted transmissions: a targeted multicast transmission to a subgroup and a unicast transmission to an individual receiving node among the plural ity of receiving nodes that form the group. If the simultane ous occurrence of a targeted multicast transmission to a sub group and a unicast transmission to an individual receiving node is considered, it must be noted that said individual re ceiving node may also belong to the subgroup, but not neces sarily.

Figs. 2a to 2d describe four possible cases of a net work node of a wireless communication system making transmis sions 201, 202, 203, and 204 to a plurality of receiving nodes 211 to 220 of the wireless communication system. Fig. 2a il lustrates a case in which case the network node is configured to schedule a common multicast transmission in a data packet 201. The intended recipients of common multicast transmission are thus all receiving nodes 211 to 220 of the plurality, or group, of receiving nodes. In fig. 2b the network node is con figured to schedule a targeted multicast transmission to a subgroup of receiving nodes in the data packet 202. The sub group in this exemplary case consists of the first, third, fourth, seventh, ninth, and tenth receiving nodes 211, 213, 214, 217, 219, and 220. Neither the data packet 201 in fig. 2a nor the data packet 202 in fig. 2b contain any unicast trans missions . Fig. 2c illustrates a case in which the network node is configured to schedule a common multicast transmission and three unicast transmissions in the data packet 203. The unicast transmissions in this exemplary case go to the fourth, seventh, and tenth receiving nodes 214, 217, and 220. In fig. 2d the network node is configured to schedule a targeted mul ticast transmission to a subgroup of receiving nodes, as well as three unicast transmissions in the data packet 204. Also in this exemplary case the unicast transmissions go to the fourth, seventh, and tenth receiving nodes 214, 217, and 220.

The network node is configured to indicate, with con tents of an indicator field in a control message to the re ceiving nodes, the scheduling and one or more intended recipi ents among the receiving nodes of the one or more targeted transmissions. Examples of contents of such an indicator field are shown on the left of each data packet 201 to 204 in figs. 2a to 2d. In order to achieve certain advantages discussed in more detail below it is advantageous to make the contents of the indicator field comprise at least a first indicator and a second indicator. Of these the first indicator is indicative of whether the data packet in question contains a targeted multicast transmission to a subgroup or a common multicast transmission to all of the plurality of receiving nodes in the group. The second indicator is indicative of the one or more intended recipients for which there are targeted transmissions (if any) in the data packet in question.

It is not necessary to place the first and second in dicator fields in a common, continuous field. In this respect the reference to an "indicator field" should be construed in a general sense so that there are ways of conveying both the first and the second indicator to the knowledge of the receiv ing nodes. Similarly naming the indicators as "first" and "second" indicator does not place any restrictions to their mutual order in any message or data structure. These designa tions are used in this text only as a concise way of making unambiguous reference to the two indicators that are described here. The network node is configured to select the contents of the indicator field in a particular way to indicate, what kind of transmissions have been scheduled in the data packet. In the example of figs. 2a to 2d the first indi cator 205 consists of two bits, and can consequently have four values 00, 01, 10, or 11. Using the exemplary relations shown in figs. 2a and 2c, it can be seen that when scheduling a com mon multicast transmission in the data packet (see data pack ets 201 and 203), a first value (here: 00) or a third value (here: 10) is selected for the first indicator 205. Similarly using the exemplary relations shown in figs. 2b and 2d, it can be seen that when scheduling a targeted multicast transmission in the data packet (see data packets 202 and 204), a second value (here: 01) or a fourth value (here: 11) is selected for the first indicator 205. Here again, and also in the continua tion, numerical specifiers like "first", "second", and so on do not mean that the values or other concepts referred to should be selected in this order from some ordered list. The numerical specifiers are only used as a concise and unambigu ous way of referring to each of the individual values or con cepts. The first indicator can have more than four possible values, if more than two bits are allocated to the first iden tifier. If all possible values are not defined to have a par ticular meaning they can be reserved for possible other uses of the first indicator.

The value of the second indicator can be a null (emp ty) value as in fig. 2a, or it may consist of one or more bit strings. For reasons that will become clear in the following the bit strings, if used as values of the second indicator, may be called bitmaps. Saying that there are two or more bit strings (or bitmaps) does not mean that these must be explic itly separate; they may appear as predefined parts of what ap pears to be just one long bit string.

In the case of fig. 2a there is only a common mul ticast transmission scheduled in the data packet 201, for which reason there is no particular information to be conveyed through any particular value of the second indicator 206. Con sequently, a null value is selected as the value of the second indicator 206.

Fig. 2b is an example of how, when scheduling in the data packet 202 a targeted multicast transmission to a sub group and no unicast transmissions, a first bitmap is selected as a value of the second indi- cator 206. Bit values in the first bitmap identify the one or more intended recipients of the targeted multicast transmission. Here the reason for call ing the bit string a bitmap becomes evident. There are as many bits in the first bitmap as there are receiving nodes in total in the group. Each bit corresponds to a particular receiving node, and the value of the bit indicates whether or not that receiving node is a member of the subgroup, i.e. an intended recipient of the targeted multicast transmission. In the exam ple of fig. 2b the intended recipients of the targeted mul ticast transmission are the first, third, fourth, seventh, ninth, and tenth receiving nodes 211, 213, 214, 217, 219, and 220, so the values of the first, third, fourth, seventh, ninth, and tenth bit in the first bitmap are set.

Fig. 2c is an example of how, when scheduling in the data packet 203 a common multicast transmission to all of the plurality of receiving nodes and one or more unicast transmis sions to respective individual nodes among said plurality of receiving nodes, a second bitmap is selected as a value of the second indicator 206. Bit values in the second bitmap identify the respective individual nodes that are the intended recipi ents of the unicast transmissions. In the example of fig. 2c the intended recipients of the unicast transmissions are the fourth, seventh, and tenth receiving nodes 214, 217, and 220, so the values of the fourth, seventh, and tenth bit in the second bitmap are set.

Fig. 2d is an example of how the value of the second indicator can be composed when scheduling in the data packet 204 a targeted multicast transmission to a subgroup and one or more unicast transmissions to respective individual nodes among the receiving nodes that form said subgroup. Here the value of the second indicator 206 consists of two bitmaps, re ferred to here as the third (upper) and fourth (lower) bitmap. The third and fourth bitmaps are selected as a combined value of the second indicator 206. Bit values in the third bitmap identify the one or more intended recipients of the targeted multicast transmission. Bit values in the fourth bitmap iden tify the respective individual nodes. The use of the bit values in the third (upper) bitmap in the embodiment of fig. 2d is similar to the use of the first bitmap above in the embodiment of fig. 2b. There are as many bits in the third bitmap as there are receiving nodes in total in the group. Each bit corresponds to a particular receiving node, and the value of the bit indicates whether or not that receiving node is a member of the subgroup, i.e. an intended recipient of the targeted multicast transmission. In the example of fig. 2d the intended recipients of the targeted multicast transmission are the first, third, fourth, seventh, ninth, and tenth receiving nodes 211, 213, 214, 217, 219, and

220, so the values of the first, third, fourth, seventh, ninth, and tenth bit in the first bitmap are set. In other words, an active bit value (here: "1") of the third bitmap is one that identifies a corresponding receiving node as an in tended recipient of the targeted multicast transmission.

The fourth (lower) bitmap contains as many bits as there are active bit values in the third (upper) bitmap. In this example there are six "l"s in the third (upper) bitmap, so there are six bits in the fourth (lower) bitmap. There is a one-to-one relation between the bits in the fourth (lower) bitmap and active bit values in the third (upper) bitmap.

Among the bits of the fourth bitmap there is an active bit value for each individual node that is an intended recipient of a respective unicast transmission in the data packet. In other words, since each active bit value in the third (upper) bitmap identifies the corresponding receiving node as an in tended recipient of the targeted multicast transmission, the corresponding bit in the fourth (lower) bitmap tells, whether such a receiving node is additionally an intended recipient of a unicast transmission scheduled in the same data packet.

As was pointed out above, in the example of fig. 2d the ordered list of the six intended recipients of the target ed multicast transmission is: "first, third, fourth, seventh, ninth, and tenth receiving node". As the third, fourth, and sixth bit values are active in the fourth (lower) bitmap, there are scheduled unicast transmissions to the third, fourth, and sixth member in said ordered list, i.e. the fourth, seventh, and tenth receiving node. As another example, though not explicitly shown in fig. 2d, the fourth (lower) bitmap may contain as many bits as the third (upper) bitmap. In this case, each active bit value in the third (upper) bitmap identifies the corresponding re ceiving node as an intended recipient of the targeted mul ticast transmission, and each active bit value in the fourth (lower) bitmap identifies the corresponding receiving node as an intended recipient of a unicast transmission.

Fig. 3 illustrates an example of a method that the network node of a wireless communication system may perform to indicate scheduling of transmissions from the network node to receiving nodes of said wireless communication system. As a part of the scheduling, selecting the one or more intended re cipients of one or more targeted transmissions may be based on static or semi-static group activity information as shown with the reference designator 301, and/or dynamic group activity information as shown with the reference designator 302.

There may be various kinds of static or semi-static group activity information. One example is a mapping rule that links a command type and respective intended recipients, so that commands of a particular type are always sent only to a certain subgroup of receiving nodes. Another example is a map ping rule that links each specific command and respective in tended recipients. A further example is a mapping rule that links the origin of a received command and respective intended recipients, so that commands that originate from a particular origin are always sent only to a certain subgroup of receiving nodes. Yet another example is a mapping rule that links a se quence of commands and respective intended recipients. The semi-static group activity information may be configured to the network node via operation and management (O&M) or another network node in service domain or provided to the network node by at least one of the receiving nodes.

Similarly, there may be various kinds of dynamic group activity information. Knowledge about which receiving nodes should be selected dynamically as the intended recipi ents of a targeted multicast transmission may exist in the network node itself, for example in the form of accumulated measurements of signal strength and/or success ratio in recep- tion from previously received uplink transmissions from the receiving nodes. Knowledge about which receiving nodes should be selected dynamically as the intended recipients of a tar geted multicast transmission may additionally or alternatively exist in servers or other devices deeper (i.e. further from the radio interface) in the network than the network node that is making the transmissions to the receiving nodes. In such cases the network node may receive dynamic group activity in formation in a message that triggers a transmission to the plurality of network nodes; in other words there may come a message that conveys to the network node a command to transmit something and also a list of the receiving nodes to which that something should be transmitted. Such a message may come for example from an individual device, like an application server, a motion controller, a sensor, or other kind of other device, either from deeper in the network or from the direction of wirelessly communicating nodes.

Step 303 in fig. 3 represents scheduling one or more targeted transmissions to one or more receiving nodes of the plurality of receiving nodes. The scheduled targeted transmis sions are to take place in a data packet, and said one or more receiving nodes form a subgroup of less than all of said plu rality of receiving nodes. In practice there may well come cases where no multicast but only unicast transmissions are scheduled in a data packet, which has not been described above with reference to figs. 2a to 2d, but the task of indicating the intended recipients can in such cases be handled with pre viously known ways it is not considered in more detail here.

Step 304 in fig. 3 represents composing the contents of, i.e. selecting the values to be used in, control infor mation fields through which the decided scheduling will be an nounced to the receiving nodes. The purpose of the actions performed in step 304 is to indicate, with contents of an in dicator field in a control message to said receiving nodes, the scheduling and one or more intended recipients among said receiving nodes of said one or more targeted transmissions. As has been described above, if there are one or more targeted transmissions they may comprise a targeted multicast transmis sion to a subgroup and/or one or more unicast transmissions to one or more individual receiv- ing nodes among the receiving nodes in the group.

The contents of the indicator field to be composed at step 304 comprise at least a first indicator indicative of whether said data packet contains a targeted multicast trans mission to a subgroup or a common multicast transmission to all of the plurality of receiving nodes. The contents comprise also a second indicator indicative of the one or more intended recipients of targeted transmissions.

Fig. 5 shows a more detailed example of what step 304 may contain. Step 501 represents checking, whether there is a common multicast transmission to be scheduled for the whole group of receiving nodes. A positive finding at step 501 means that either the case of fig. 2a or the case of fig. 2c is in question. In order to differentiate between the two, step 502 represents checking, whether there are one or more additional unicast transmissions to any selected receiving nodes to be scheduled in the same data packet. A negative finding at step 502 means that it is the case of fig. 2a, in which case a first value (here: "00") is selected for the first indicator and a null value is selected for the second indicator, i.e. no bitmap is included as a second indicator, as represented by step 503. A positive finding at step 502 means that it is the case of fig. 2c, in which case a third value (here: "10") is selected for the first indicator. A second bitmap (using the same numerical designators as above with reference to figs. 2a to 2d) is selected as the second indicator, so that bit values in the second bitmap identify the respective individual nodes that are to receive the unicast transmissions. The two last- mentioned actions are represented by step 504 in fig. 5.

A negative finding at step 501 means that either the case of 2b or the case of fig. 2d is in question, or then it may be that there are only unicast transmissions to be sched uled. Step 505 represents checking, whether there is a target ed multicast transmission to be scheduled. A negative finding here means exiting the method of fig. 5, because the schedul ing and indicating of only unicast transmissions can be made through known means. A positive finding at step 505 is fol lowed by an additional check represented by step 506, to find our whether there are unicast messages to receiving nodes that are also to receive the targeted multicast transmission.

A negative finding at step 506 means that it is the case of fig. 2b, in which case a second value (here: "01") is selected for the first indicator, and a first bitmap is se lected as the second indicator, represented by step 507 in fig. 5. Bit values in the first bitmap identify the one or more intended recipients of the targeted multicast transmis sion.

A positive finding at step 506 means that it is the case of fig. 2d, leading to what is represented as step 508 in fig. 5. A fourth value (here: "11") is selected for the first indicator. Third and fourth bitmaps are selected as the com bined value of the second indicator. Bit values in the third bitmap identify the one or more intended recipients of the targeted multicast transmission. Bit values in the fourth bit map identify the respective individual nodes, for which unicast transmissions are scheduled in the data packet. The fourth bitmap contains as many bits as there are active bit values in the third bitmap, with one-to-one relation between the bits in the fourth bitmap and active bit values in the third bitmap. Among the bits of the fourth bitmap there is an active bit value for each individual node that is an intended recipient of a respective unicast transmission in the data packet .

Referring back to fig. 3, step 305 in fig. 3 repre sents composing the control message in which the scheduling information is to be conveyed to the receiving nodes, and 306 represents transmitting the control message. For the purposes of the method and devices described here it is not important, what mechanisms are used in steps 305 and 306, and on which channel and in which physical form the control message is transmitted. As a non-limiting example, the control message may comprise a DCI block (Downlink Control Information) and it may be transmitted on a PDCCH (Physical Downlink Control Chan nel) .

Fig. 4 illustrates an example of a method that the receiving node of a wireless communication system may perform to receive transmissions from a network node of the wireless communication system. In many aspects the method is the mir ror image of the method of fig. 3, and its purpose is to es tablish information in the receiving node about whether or not there are common multicast, targeted multicast, and/or unicast transmissions coming in a data packet that the receiving node should receive.

After receiving a control message from the network node, as represented by step 401 in fig. 4, the receiving node starts decoding, from contents of an indicator field received in the control message, an indication of whether the receiving node is an intended recipient of one or more targeted trans missions scheduled in a data packet. As has been explained above, the one or more targeted transmissions may comprise a targeted multicast transmission to a subgroup of less than all of a plurality of receiving nodes and/or a unicast transmis sion to the receiving node itself. As has also been explained above, the contents of the indicator field comprise at least a first indicator indicative of whether said data packet con tains a targeted multicast transmission to a subgroup or a common multicast transmission to all of said plurality of re ceiving nodes, and a second indicator indicative of the one or more intended recipients of the targeted transmissions, if any .

Step 402 represents checking, whether there is a com mon multicast transmission scheduled in the data packet to all of the plurality (= group) of receiving nodes. This would cor respond to either fig. 2a or 2c, so the receiving node is con figured to decode a first (here: "00") or a third (here: "10") value of the first indicator into an indication of such a scheduled common multicast transmission. A negative finding at step 402 means that it may be the case of fig. 2b or 2d in stead, so the receiving node is configured to decode a second (here: "01") or fourth (here: "11") value of said first indi cator into an indication of a targeted multicast transmission to a subgroup being scheduled in said data packet. This is represented by step 403 in fig. 4. If it is the case of fig. 2b, the receiving node is configured to decode a dedicated bit value in a first bitmap received as said second indicator into an indication of whether said receiving node is an intended recipient of the targeted mul- ticast transmission scheduled in said data packet. The receiving node knows which bit in the first bitmap is its dedicated bit, because it has been previ ously informed of this for example in a unicast message or be cause the mutual order of receiving nodes as an ordered list has been established otherwise.

A negative finding at step 403 may mean that either there is nothing to be received or that there is only a sched uled unicast transmission to be received. The differentiation between these two possibilities is represented by step 404 in fig. 4, with the obvious consequences represented by steps 405 and 406 respectively.

If a positive finding was made at either step 402 or 403, the receiving node must still check whether also a unicast transmission is scheduled to the receiving node in question in the data packet. This checking is represented by step 407 in fig. 4. If step 407 was preceded by a positive finding at step 402, the receiving node is configured to first check whether it was the first or third value of the first in dicator that caused the positive finding. If it was the first, the receiving node knows for certain that there is only the multicast transmission to be received, as represented by step 408. If it was the third, the receiving node is configured to decode a dedicated bit value in a second bitmap received as said second indicator into an indication of whether said re ceiving node is an intended recipient of a unicast transmis sion scheduled in said data packet.

Step 407 may have been preceded by a positive finding at step 403 instead. The possibility of it being the case of fig. 2b was already discussed above. If the first indicator has the fourth value (here: "11"), the finding "I'm targeted" at step 403 already included decoding a dedicated bit value in a third bitmap received as a part of the second indicator into an indication of the receiving node being an intended recipi ent of a targeted multicast transmission scheduled in said da ta packet. In that case step 407 comprises decoding a corre sponding bit value in a fourth bitmap received as a part of said second indicator into an indication of whether said re ceiving node is additionally an intended recipient of a unicast transmission scheduled in said data packet. As has been described above said fourth bitmap contains as many bits as there are active bit values in the third bitmap. Each such active bit value in the third bitmap identifies an intended recipient of the targeted multicast transmission. There is a one-to-one relation between the bits in the fourth bitmap and active bit values in said third bitmap. If among said bits of the fourth bitmap there is an active bit value for the receiv ing node in question, it knows that it is an intended recipi ent of a respective unicast transmission scheduled in the data packet .

A negative finding at step 407 leads to receiving the multicast transmission only, as represented by step 408 in fig. 4. A positive finding at step 407 leads to receiving both the multicast transmission and the unicast transmission, as represented by step 409. Concerning steps 408 and 409, it may be noted that regardless whether a targeted receiving node has unicast data coming to it or not, as long as the unicast and multicast data are multiplexed to be transmitted simultaneous ly (i.e. in the same transport block), the receiving node needs to receive the whole transport block anyway. But based on the indication, the receiving node knows whether the unicast or multicast is targeted to it or not.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the in vention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

Claims

1. Network node of a wireless communication system for making transmissions to a plurality of receiving nodes of the wireless communication system, wherein the network node is configured to:

- schedule one or more targeted transmissions to one or more receiving nodes of said plurality of receiving nodes to take place in a data packet, said one or more receiving nodes form ing a subgroup of less than all of said plurality of receiving nodes, and

- indicate, with contents of an indicator field in a control message to said receiving nodes, the scheduling and one or more intended recipients among said receiving nodes of said one or more targeted transmissions;

wherein said one or more targeted transmissions comprise at least one of: a targeted multicast transmission to said sub group, a unicast transmission to an individual receiving node among said plurality of receiving nodes,

and wherein said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to said subgroup or a common multicast transmission to all of said plurality of receiving nodes, and a second indicator indicative of said one or more intended recipients.

2. A network node according to claim 1, configured to select said contents of said indicator field so that

- when scheduling a common multicast transmission in said data packet to all of said plurality of receiving nodes, a first or third value is selected for the first indicator, and

- when scheduling a targeted multicast transmission in said data packet to said subgroup, a second or fourth value is se lected for the first indicator.

3. A network node according to claim 2, configured to select said contents of said indicator field so that

- when scheduling in said data packet a targeted multicast transmission to said subgroup and no unicast transmissions, a first bitmap is selected as a value of said second indicator, bit values in said first bit- map identifying said one or more intended recipients of said targeted multicast transmis sion.

4. A network node according to claim 2 or 3, config ured to select said contents of said indicator field so that

- when scheduling in said data packet a common multicast transmission to all of said plurality of receiving nodes and one or more unicast transmissions to respective individual re ceiving nodes among said plurality of receiving nodes, a sec ond bitmap is selected as a value of said second indicator, bit values in said second bitmap identifying said respective individual receiving nodes.

5. A network node according to any of claims 2 to 4, configured to select said contents of said indicator field so that

- when scheduling in said data packet a targeted multicast transmission to said subgroup and one or more unicast trans missions to respective individual receiving nodes among the receiving nodes that form said subgroup, third and fourth bit maps are selected as a combined value of said second indica tor, bit values in said third bitmap identifying said one or more intended recipients of said targeted multicast transmis sion and bit values in said fourth bitmap identifying said re spective individual receiving nodes.

6. A network node according to claim 5, configured to select said contents of said indicator field so that

- said fourth bitmap contains as many bits as there are active bit values in said third bitmap that identify said intended recipients of said targeted multicast transmission, with one- to-one relation between the bits in the fourth bitmap and ac tive bit values in said third bitmap,

- among said bits of the fourth bitmap there is an active bit value for each individual receiving node that is an intended recipient of a respective unicast transmission in the data packet .

7. A network node according to claim 5, configured to select said contents of said indicator field so that - said fourth bitmap contains as many bits as said third bitmap,

8. A network node according to any of the preceding claims, configured to select said one or more intended recipi ents of the one or more targeted transmissions on the basis of at least one of the following kinds of semi-static group ac tivity information:

- mapping rule linking command type and respective intended recipients ,

- mapping rule linking each specific command and respective intended recipients,

- mapping rule linking origin of a received command and re spective intended recipients,

- mapping rule linking a sequence of commands and respective intended recipients.

9. A network node according to any of the preceding claims, configured to select said one or more intended recipi ents of the one or more targeted transmissions on the basis of at least one of the following kinds of dynamic group activity information :

- dynamic group activity information that the network node re ceived in a message triggering a transmission to said plurali ty of receiving nodes.

10. A receiving node of a wireless communication sys tem for receiving transmissions from a network node of the wireless communication system, wherein the receiving node is configured to:

- decode, from contents of an indicator field received in a control message from said network node, an indication of whether the receiving node is an intended recipient of one or more targeted transmissions scheduled in a data packet;

wherein said one or more targeted transmissions comprise at least one of: a targeted multicast transmission to a subgroup of less than all of a plurali- ty of receiving nodes, a unicast transmission to the receiving node itself,

and wherein said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to a subgroup or a common multicast transmission to all of said plurality of re ceiving nodes, and a second indicator indicative of said one or more intended recipients.

11. A receiving node according to claim 10, config ured to decode

- a first or third value of said first indicator into an indi cation of a common multicast transmission to all of said plu rality of receiving nodes being scheduled in said data packet, and

- a second or fourth value of said first indicator into an in dication of a targeted multicast transmission to a subgroup being scheduled in said data packet.

12. A receiving node according to claim 11, config ured to decode

- a dedicated bit value in a first bitmap received as said second indicator into an indication of whether said receiving node is an intended recipient of a targeted multicast trans mission scheduled in said data packet.

13. A receiving node according to claim 11 or 12, configured to decode a dedicated bit value in a second bitmap received as said second indicator into an indication of wheth er said receiving node is an intended recipient of a unicast transmission scheduled in said data packet.

14. A receiving node according to any of claims 11 to 13, configured to decode a dedicated bit value in a third bit map received as a part of said second indicator into an indi cation of whether said receiving node is an intended recipient of a targeted multicast transmission scheduled in said data packet, and - in response to thus finding that said receiving node is an intended recipient of a targeted multicast trans mission scheduled in said data packet - a corresponding bit value in a fourth bitmap received as a part of said second in- dicator into an indication of whether said receiving node is additionally an intended recipient of a unicast transmission scheduled in said data packet,

wherein said fourth bitmap contains either as many bits as there are active bit values in said third bitmap each identi fying an intended recipient of said targeted multicast trans mission, with one-to-one relation between the bits in the fourth bitmap and active bit values in said third bitmap, or as many bits as said third bitmap,

and wherein among said bits of the fourth bitmap there is an active bit value for each individual receiving node that is an intended recipient of a respective unicast transmission in the data packet.

15. A method for indicating scheduling of transmis sions from a network node of a wireless communication system to receiving nodes of said wireless communication system, the method comprising:

- scheduling one or more targeted transmissions to one or more receiving nodes of said plurality of receiving nodes to take place in a data packet, said one or more receiving nodes form ing a subgroup of less than all of said plurality of receiving nodes, and

- indicating, with contents of an indicator field in a control message to said receiving nodes, the scheduling and one or more intended recipients among said receiving nodes of said one or more targeted transmissions;

16. A method for receiving, in a receiving node of a wireless communication system, transmissions from a network node of said wireless communi- cation system, the method com prising :

- decoding, from contents of an indicator field received in a control message from said network node, an indication of whether the receiving node is an intended recipient of one or more targeted transmissions scheduled in a data packet;

wherein said one or more targeted transmissions comprise at least one of: a targeted multicast transmission to a subgroup of less than all of a plurality of receiving nodes, a unicast transmission to the receiving node itself,

and wherein said contents of said indicator field comprise at least a first indicator indicative of whether said data packet contains a targeted multicast transmission to a subgroup or a common multicast transmission to all of said plurality of re- ceiving nodes, and a second indicator indicative of said one or more intended recipients.