WO2020087350A1

WO2020087350A1 - Method, device and computer readable medium for communications

Info

Publication number: WO2020087350A1
Application number: PCT/CN2018/113023
Authority: WO
Inventors: Huan Sun
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2018-10-31
Filing date: 2018-10-31
Publication date: 2020-05-07
Also published as: CN113056944A; CN113056944B

Abstract

Embodiments of the present disclosure relate to a method, device and computer readable medium for configuring measurement gap pattern. In example embodiments, the method comprises selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device; transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information, DCI associated with the second network device and information about decoding of the DCI; determining whether a 1ink between the first network device and the second network device is an ideal backhaul 1ink or a non-ideal backhaul link; and in response to the determination that the 1ink is the ideal backhaul 1ink, transmitting the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.

Description

METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR COMMUNICATIONS

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunications, and in particular, to a method, device and computer readable medium for communications.

BACKGROUND

In a Next Radio (NR) system, cooperative transmission schemes of multiple transmission and reception points (TRPs) are investigated to improve cell edge performance for a low frequency band as well as to provide high rank transmission for a high low frequency band in line of sight (LOS) dominant transmission scenarios. In order to trade off performance of the NR system, complexity and backhaul link requirements, non-coherent joint transmission scheme (NCJT) were proposed. However, details of downlink control channel transmission and downlink data channel transmission associated with NCJT still need to be discussed.

SUMMARY

In general, example embodiments of the present disclosure provide a method, device and computer readable medium for communications.

In a first aspect, a communication method implemented at a first network device is provided. The method comprises selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device. The method also comprises transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information (DCI) associated with the second network device and information about decoding of the DCI. The method also comprises determining whether a link between the first network device and the second network device is an ideal backhaul or a non-ideal backhaul. The method also comprises in response to the determination that the link is the ideal backhaul, transmitting the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.

In some example embodiments, selecting the second network device for the cooperative downlink transmission to the terminal device comprises: comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between the second network device and the terminal device, the second uplink channel being between a third network device and the terminal device; in response to the first quality being higher than the second quality, transmitting to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device; transmitting to the terminal device information about a pair of uplink beams associated with the first quality; receiving from the terminal device an indication of the third quality; and in response to a determination that the third quality exceeding a first threshold quality, transmitting to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.

In some example embodiments, transmitting the DCI comprises: transmitting the DCI in a predefined control region in a sub-frame.

In some example embodiments, transmitting the DCI in the predefined control region comprises: transmitting a further DCI associated with the frst network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.

In some example embodiments, a size of the predefned control region is pre-configured.

In some example embodiments, the method further comprises: obtaining from the terminal device quality of a channel between the first network device and the terminal device; comparing the quality of the channel with a second threshold quality; and determining a starting position of the second sub-region in the sub-frame based on the comparison.

In some example embodiments, determining the starting position of the second sub-region in the sub-frame comprises: in response to the quality of the channel exceeding the second threshold quality, determining the third symbol in the sub-frame as the starting position of the second sub-region; and in response to the quality of the channel being below the second threshold quality, determining the fourth syrnbol in the sub-frame as the starting position of the second sub-region.

In some example embodiments, transmitting the resource allocation indication comprises: transmitting the resource allocation indication indicating the starting position of the second sub-region.

In some example embodiments, transmitting the further DCI and the DCI comprises: encoding the further DCI and the DCI with a predetermined space-time block code to obtain a first encoded DCI and a second encoded DCI; and transmitting the first encoded DCI and the second encoded DCI.

In some example embodiments, the method further comprises: in response to the determination that the link is the non-ideal backhaul, transmitting, in a first sub-frame, to the terminal device a first indication that a downlink transmission from the second network device is to be initiated.

In some example embodiments, transmitting the first indication comprises: transmitting the first indication in a control region in the first sub-frame.

In some example embodiments, transmitting the first indication comprises: transmitting the first indication in a data region in the first sub-frame.

In some example embodiments, the method further comprises: in response to receiving a positive acknowledge indicating that the downlink transmission from the second network device is accepted, disabling the transmission of the first indication in a second sub-frame subsequent to the first sub-frame.

In some example embodiments, the method further comprises: in response to receiving a negative acknowledge indicating that the downlink transmission from the second network device is rejected, transmitting the first indication in a third sub-frame subsequent to the first sub-frame.

In a second aspect, a communication method implemented at a first network device is provided. The method comprises: comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between a second network device and a terminal device served by the first network device, the second uplink channel being between a third network device and the terminal device; in response to the first quality being higher than the second quality, transmitting to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device; transmitting to the terminal device information about a pair of uplink beams associated with the first quality; receiving from the terminal device an indication of the third quality; and in response to a determination that the third quality exceeding a first threshold quality, transmitting to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.

In a third aspect, a method implemented at a terminal device is provided. The method comprises: receiving, on a downlink data channel between a first network device and a terminal device, a resource allocation indication for downlink control information, DCI associated with a second network device and information about decoding of the DCI; and in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device and the terminal device, receiving the DCI on the first downlink control channel.

In some example embodiments, receiving the DCI comprises: receiving the DCI in a predefined control region in a sub-frame.

In some example embodiments, receiving the DCI in the predefined control region comprises: receiving a further DCI associated with the first network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.

In some example embodiments, a size of the predefined control region is pre-configured.

In some example embodiments, the method further comprises: transmitting, to the first network device, quality of a channel between the first network device and the terminal device for determination of a starting position of the second sub-region in the sub-frame.

In some example embodiments, receiving the resource allocation indication comprises: receiving the resource allocation indication indicating the starting position of the second sub-region.

In some example embodiments, the starting position of the second sub-region is the third symbol in the sub-frame.

In some example embodiments, the starting position of the second sub-region is the fourth symbol in the sub-frame.

In some example embodiments, receiving the further DCI and the DCI comprises: receiving a first encoded DCI and a second encoded DCI; and decoding the first encoded DCI and the second encoded DCI with a predetermined space-time block code to obtain the further DCI and the DCI.

In some example embodiments, the method further comprises: in response to a determination that the resource allocation indication indicates resources on a second downlink control channel between the second network device and the terminal device, receiving, in a first sub-frame, from the first network device a first indication that a downlink transmission from the second network device is to be initiated.

In some example embodiments, receiving the first indication comprises: receiving the first indication in a control region in the first sub-frame.

In some example embodiments, receiving the first indication comprises: receiving the first indication in a data region in the first sub-frame.

In some example embodiments, the method further comprises: in response to success of decoding of the first indication, determining whether the downlink transmission is acceptable; in response to the determination that the downlink transmission is acceptable, transmitting to the first network device a positive acknowledge indicating that the downlink transmission is accepted; and in response to the determination that the downlink transmission is unacceptable, transmitting to the first network device a negative acknowledge indicating that the downlink transmission is rejected.

In some example embodiments, the method further comprises: in response to transmitting the negative acknowledge indicating that the downlink transmission is rejected, receiving the first indication in a third sub-frame subsequent to the first sub-frame.

In some example embodiments, the method further comprises: transmitting a first uplink reference signal to the second network device for measurement of a first quality of a first uplink channel between the second network device and the terminal device; transmitting a second uplink reference signal to the third network device for measurement of a second quality of a second uplink channel between a third network device and the terminal device; in response to receiving from the first network device information about a pair of uplink beams associated with the first quality, performing measurement of a third quality of a downlink channel between the second network device and the terminal device; and transmitting an indication of the third quality to the first network device for decision of a cooperative downlink transmission from the first and second network devices to the terminal device.

In a fourth aspect, a communication method implemented at a second network device is provided. The method comprises: measuring, at a second network device, a first quality of a first uplink channel between the second network device and a terminal device served by a first network device; transmitting to the first network device an indication of the first quality and information about a pair of uplink beams associated with the first quality; in response to receiving from the first network device an indication for initiating a measurement of quality of a downlink channel between the second network device and the terminal device, transmitting to the terminal device a downlink reference signal for the measurement; and receiving from the first network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device in response to the quality of the downlink channel exceeding a first threshold quality.

In some example embodiments, the method further comprises: in response to receiving from the terminal device a positive acknowledge indicating that a downlink transmission from the second network device is accepted, initiating the downlink transmission.

In a fifth aspect, a first network device is provided. The first network device comprises at least one processor and at least one memory including 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 carry out the method according to the first aspect.

In a sixth aspect, a first network device is provided. The first network device comprises at least one processor and at least one memory including 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 carry out the method according to the second aspect.

In a seventh aspect, a terminal device is provided. The terminal device comprises at least one processor and at least one memory including 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 carry out the method according to the third aspect.

In an eighth aspect, a second network device is provided. The second network device comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the second network device to carry out the method according to the fourth aspect.

In a ninth aspect, an apparatus for communication is provided. The apparatus comprises: means for selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device; means for transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information, DCI associated with the second network device and information about decoding of the DCI; means for determining whether a link between the first network device and the second network device is an ideal backhaul or a non-ideal backhaul; and means for transmitting, in response to the determination that the link is the ideal backhaul, the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.

In a tenth aspect, an apparatus for communication is provided. The apparatus comprises: means for comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between a second network device and a terminal device served by the first network device, the second uplink channel being between a third network device and the terminal device; means for transmitting, in response to the first quality being higher than the second quality, to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device; means for transmitting to the terminal device information about a pair of uplink beams associated with the first quality; means for receiving from the terminal device an indication of the third quality; and means for transmitting, in response to a determination that the third quality exceeding a first threshold quality, to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.

In an eleventh aspect, an apparatus for communication is provided. The apparatus comprises: means for receiving, on a downlink data channel between a first network device and a terminal device, a resource allocation indication for downlink control information, DCI associated with a second network device and information about decoding of the DCI; and means for receiving, in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device and the terminal device, the DCI on the first downlink control channel.

In a twelfth aspect, an apparatus for communication is provided. The apparatus comprises: means for measuring, at a second network device, a first quality of a first uplink channel between the second network device and a terminal device served by a first network device; means for transmitting to the first network device an indication of the first quality and information about a pair of uplink beams associated with the first quality; means for transmitting, in response to receiving from the first network device an indication for initiating a measurement of quality of a downlink channel between the second network device and the terminal device, to the terminal device a downlink reference signal for the measurement; and means for receiving from the first network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device in response to the quality of the downlink channel exceeding a first threshold quality.

In a thirteenth aspect, there is provided a computer-readable medium storing a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the first aspect.

In a fourteenth aspect, there is provided a computer-readable medium storing a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the second aspect.

In a fifteenth aspect, there is provided a computer-readable medium storing a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the third aspect.

In a sixteenth aspect, there is provided a computer-readable medium storing a computer program thereon. The computer program, when executed by a processor, causes the processor to carry out the method according to the fourth aspect.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

Fig. 2 is a flowchart of a communication method implemented at a first network device in accordance with some embodiments of the present disclosure;

Fig. 3 is a signalling chart of an example process for selecting a network device for a cooperative downlink transmission in accordance with some embodiments of the present disclosure;

Fig. 4 is a schematic diagram of example transmission of downlink control information in accordance with some embodiments of the present disclosure;

Fig. 5 is a schematic diagram of example transmission of downlink control information in accordance with some other embodiments of the present disclosure;

Fig. 6 is a schematic diagram of example transmission of downlink control information in accordance with still other embodiments of the present disclosure;

Fig. 7 is a schematic diagram of example transmission of downlink control information in accordance with yet other embodiments of the present disclosure;

Fig. 8 is a flowchart of a communication method implemented at a first network device in accordance with some other embodiments of the present disclosure;

Fig. 9 is a flowchart of a communication method implemented at a terminal device in accordance with some other embodiments of the present disclosure;

Fig. 10 is a flowchart of a communication method implemented at a second network device in accordance with some other embodiments of the present disclosure; and

Fig. 11 is a block diagram of a device that is suitable for implementing example embodiments of the present disclosure.

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

DETAILED DESCRIPTION

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

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

As used herein, the term “network device” refers to any suitable device at a network side of a communication network. The network device may include any suitable device in an access network of the communication network, for example, including a base station (BS) , a TRP, a relay, an access point (AP) , a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a gigabit NodeB (gNB) , a Remote Radio Module (RRU) , a radio header (RH) , a remote radio head (RRH) , a low power node such as a femto, a pico, and the like.

The network device may also include any suitable device in a core network, for example, including multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs) , Multi-cell/multicast Coordination Entities (MCEs) , Mobile Switching Centers (MSCs) and MMEs, Operation and Management (O&M) nodes, Operation Support System (OSS) nodes, Self-Organization Network (SON) nodes, positioning nodes, such as Enhanced Serving Mobile Location Centers (E-SMLCs) , and/or Mobile Data Terminals (MDTs) .

As used herein, the term “terminal device” refers to a device capable of, configured for, arranged for, and/or operable for communications with a network device or a further terminal device in a communication network. The communications may involve transmitting and/or receiving wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for conveying information over air. In some example embodiments, the terminal device may be configured to transmit and/or receive information without direct human interaction. For example, the terminal device may transmit information to the network device on predetermined schedules, when triggered by an internal or external event, or in response to requests from the network side.

Examples of the terminal device include, but are not limited to, user equipment (UE) such as smart phones, wireless-enabled tablet computers, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , and/or wireless customer-premises equipment (CPE) . For the purpose of discussion, in the following, some example embodiments will be described with reference to UEs as examples of the terminal devices, and the terms “terminal device” and “user equipment” (UE) may be used interchangeably in the context of the present disclosure.

As used herein, the term “cell” refers to an area covered by radio signals transmitted by a network device. The terminal device within the cell may be served by the network device and access the communication network via the network device.

As used herein, the term “circuitry” 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 (e.g., 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” . Other definitions, explicit and implicit, may be included below.

In Release 15, downlink NCJT was discussed to support two scenarios transmission. One of the two scenarios is multi-TRP downlink transmission with ideal backhaul link, and the other is multi-TRP downlink transmission with non-ideal backhaul link. Some agreements on principles of Physical Downlink Control Channel (PDCCH) transmission and Physical Downlink Shared Channel (PDSCH) transmission were achieved for supporting different cases. For example, a single PDCCH transmission scheme for ideal backhaul link was agreed. In the single PDCCH transmission scheme, a single PDSCH may be scheduled and separate layers are transmitted from separate TRPs. In addition, a multi-PDCCH transmission scheme for non-ideal backhaul was agreed. In the multi-PDCCH transmission scheme, each PDCCH schedules a respective PDSCH and each PDSCH is transmitted from a separate TRP.

However, it was not discussed in Release 15 how a cluster of cooperative TRPs is determined before cooperative PDCCH and PDSCH transmissions, especially for NR high band systems which require beam management. In addition, it was not discussed how to guarantee the robustness of the single PDCCH transmission or multi-PDCCH transmission in order to improve transmission efficiency and decoding complexity.

In order to at least in part solve above and other potential problems, embodiments of the present disclosure provide a solution for determining a cluster of multiple network devices for cooperative downlink transmission. According to embodiments of the present disclosure, a first network device serving a terminal device pre-selects one of a second network device and a third network device which has better quality of an uplink channel. The first network device indicates the pre-selected network device to initiate a measurement of quality of a downlink channel to the terminal device. In mm, the first network device may decide, based on the quality of the downlink channel, whether to include the pre-selected network device into the cluster for cooperative downlink transmission.

With the embodiments of the present disclosure, only the pre-selected network device needs to initiate a measurement of quality of a downlink channel to the terminal device. The terminal device only needs to measure quality of the downlink channel related to the pre-selected network device. Thus, processing complexity and the overall processing time duration for the terminal device are reduced. Because the terminal device only needs to feedback the quality of the downlink channel related to the pre-selected network device, the uplink overhead is decreased.

In addition, embodiments of the present disclosure provide a solution for cooperative downlink control channel transmission. According to embodiments of the present disclosure, a serving network device transmits, on a downlink data channel, to a terminal device a resource allocation indication for DCI associated with the cooperative network device. In this way, decoding of the DCI associated with the cooperative network device is independent from decoding of the DCI associated with the serving network device. Accordingly, even if the decoding of the DCI associated with the serving network device fails, the decoding of the DCI associated with the cooperative network device will not be affected by the failure. Thus, downlink data transmission from the serving network device may be decoupled from downlink data transmission from the cooperative network device.

Fig. 1 shows an example communication network 100 in which example embodiments of the present disclosure can be implemented. The network 100 includes a first network device 110, a second network device 120, a third network device 130 and a terminal device 140. It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of network devices and terminal devices adapted for implementing example embodiments of the present disclosure.

The communications in the network 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 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.

The terminal device 140 is served by the first network device 110. The second network device 120 and the third network device 130 may be configured as candidate network device for a cooperative downlink transmission to the terminal device 140. In order to improve cell edge performance for a low frequency band or to provide high rank transmission for a high low frequency band, the first network device 110 may select one of the second and third network devices for the cooperative downlink transmission.

Principle and implementations of the present disclosure will be described in detail below with reference to Fig. 2, which shows a flowchart of an example method 200 in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 200 will be described with reference to Fig. 1. The method 200 may involve the first network device 110, the second network device 120 and the terminal device 140 in Fig. 1. For example, the method 200 can be implemented at the first network device 110 as shown in Fig. 1. It is to be understood that the method 200 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block 210, the first network device 110 selects the second network device 120 for a cooperative downlink transmission to the terminal device 140. In some embodiments, the first network device 110 may select the second network device 120 via a process 300 as shown in Fig. 3.

Fig. 3 is a signalling chart of an example process 300 for selecting a network device for a cooperative downlink transmission in accordance with some embodiments of the present disclosure. The process 300 may involve the first network device 110, the second network device 120, the third network device 130 and the terminal device 140 as shown in Fig. 1. It is to be understood that process 300 may include additional acts not shown and/or omit some acts as shown. The scope of the present disclosure is not limited in this respect.

In some embodiments, upon an event trigger, the first network device 110 may select one of the second network device 120 and the third network device 130 for the cooperative downlink transmission. Examples of the event may include, but are not limited to, quality of a channel between the first network device 110 being below a threshold quality, and increase of the traffic to the terminal device 140.

In some embodiments, upon order to select one of the second network device 120 and the third network device 130, the first network device 110 may transmit 3010 information about configuration of the terminal device 140 to the second network device 120, and transmit 3020 the information about configuration of the terminal device 140 to the third network device 130. Examples of the information about configuration of the terminal device 140 include but not limited to information about configuration of reference signals for the terminal device 140, and information about beams of the terminal device 140.

Upon the event trigger, the terminal device 140 transmits 3030 a first uplink reference signal to the second network device 120 for measurement of a first quality of a first uplink channel between the second network device 120 and the terminal device 140. The terminal device 140 transmits 3040 transmits a second uplink reference signal to the third network device 130 for measurement of a second quality of a second uplink channel between the third network device 130 and the terminal device 140.

Examples of the first and second uplink reference signals may include but not limited to sounding reference signals (SRS) . In some embodiments, the terminal device 140 may implement the transmissions of the first and second uplink reference signals in continuously Orthogonal Frequency Division Multiplexing (OFDM) symbols (for example, up to four OFDM symbols) by beam sweeping mode transmission.

The second network device 120 measures the first quality of the first uplink channel by detecting the first uplink reference signal from the terminal device 140. The third network device 130 measures the second quality of the second uplink channel by detecting the second uplink reference signal from the terminal device 140. In some embodiments, each of the second network device 120 and the third network device 130 may perform the measurement of the quality of the respective uplink channel by performing beam management procedure for uplink transmission with the terminal device 140.

The second network device 120 transmits 3050 to the first network device 110 an indication of the first quality and information about a pair of uplink beams associated with the first quality. The third network device 130 transmits 3060 to the first network device 110 an indication of the second quality and information about a pair of uplink beams associated with the second quality.

The first network device 110 compares 3070 the first quality of the first uplink channel with the second quality of the second uplink channel.

If the first quality being is higher than the second quality, the first network device 110 transmits to the second network device 120 an indication of initiating a measurement of a third quality of a downlink channel between the second network device 120 and the terminal device 140. If the second quality being is higher than the first quality, the first network device 110 transmits to the third network device 130 an indication of initiating a measurement of a four quality of a downlink channel between the third network device 130 and the terminal device 140. In this example process, it is assumed that the first quality being is higher than the second quality. Thus, the first network device 110 transmits 3080 to the second network device 120 the indication of initiating the measurement of the third quality of the downlink channel.

Where the first quality being is higher than the second quality, the first network device 110 transmits 3090 to the terminal device 140 information about a pair of uplink beams associated with the first quality. In some embodiments, the pair of uplink beams associated with the first quality may include an uplink transmission beam at the side of the terminal device 140 and an uplink reception beam at the side of the second network device 120. The terminal device 140 transmits the first uplink reference signal with the uplink transmission beam. The second network device 120 measures the first quality of the first uplink channel by receiving the first uplink reference signal with the uplink reception beam. In some embodiments, with the beam corresponding properties, the uplink reception beam at the side of the second network device 120 will be used as the transmission beam for downlink transmission from the second network device 120.

Upon receiving the indication of initiating the measurement of the third quality of the downlink channel, the second network device 120 transmits 3100 to the terminal device 140 a downlink reference signal for the measurement.

The terminal device 140 performs the measurement of the third quality of the downlink channel by detecting the downlink reference signal from the second network device 120. In some embodiments, the terminal device 140 may perform the measurement of the third quality of the downlink channel by performing beam management procedure for downlink transmission with the second network device 120.

The terminal device 140 transmits 3110 an indication of the third quality to the first network device 110 for decision of the cooperative downlink transmission from the first network device 110 and the second network device 120 to the terminal device 140.

Upon receiving the indication of the third quality of the downlink channel between the second network device 120 and the terminal device 140, the first network device 110 compares 3120 the third quality with a first threshold quality. In some embodiments, the first network device 110 may use quality of the downlink channel between the first network device 110 and the terminal device 140 as the threshold quality. In other embodiments, the first threshold quality may be predefined quality.

If it is determined that the third quality exceeds the first threshold quality, the first network device 110 transmits 3130 to the second network device 120 an indication that the second network device 120 is selected for the cooperative downlink transmission to the terminal device 140.

It should be understood that the process 300 for selecting a network device for a cooperative downlink transmission is described by way of example. In some embodiments, the first network device 110 may employ any known process for selecting the cooperative network device. The scope of the present disclosure is not limited in this regard. For example, the terminal device 140 may perform a beam management procedure with the second network device 120 to determine quality of the uplink channel, a pair of uplink beam, and quality of the downlink channel. Subsequently, the terminal device 140 may perform a beam management procedure with the third network device 130 to measure quality of the uplink channel, a pair of uplink beam, and quality of the downlink channel. Then, the terminal device 140 feedbacks to the first network device 110 the quality of the downlink channel related to the second network device 120 and the quality of the downlink channel related to the third network device 130. Thus, the first network device 110 compares the both qualities with a threshold so as to select one of the second and third network devices for the cooperative downlink transmission.

With the process 300 for selecting the cooperative network device, the first network device 110 pre-selects (at 3070) one of the second and third network devices which has better quality of the uplink channel. Accordingly, only the pre-selected network device (for example, the second network device 120) needs to initiate a measurement of quality of a downlink channel to the terminal device 140. The terminal device 140 only needs to measure (at 3100) quality of the downlink channel related to the pre-selected network device. Thus, processing complexity and the overall processing time duration for the terminal device 140 are reduced. Because the terminal device 140 only needs to feedback (at 3110) the quality of the downlink channel related to the pre-selected network device, the uplink overhead is decreased.

Referring back to Fig. 2, upon selecting the second network device 120 for the cooperative downlink transmission, at 220, the first network device 110 transmits, on a downlink data channel, to the terminal device 140 a resource allocation indication for DCI associated with the second network device 120 and information about decoding of the DCI. For the purpose of discussion, the DCI associated with the second network device 120 is referred to as second DCI or DCI#2. Similarly, DCI associated with the first network device 110 is referred to as first DCI or DCI#1.

In some embodiments, the first network device 110 may transmit, via radio resource control (RRC) signaling or medium access control (MAC) control element (CE) , the resource allocation indication for the second DCI and information about decoding of the second DCI.

In accordance with the present disclosure, because the resource allocation indication for the second DCI is transmitted on a downlink data channel instead of a downlink control channel, decoding of the second DCI is independent from decoding of the first DCI. Accordingly, even if the decoding of the first DCI fails, the decoding of the second DCI will not be affected by the failure. Thus, downlink data transmission from the first network device 110 may be decoupled from downlink data transmission from the second network device 120. In addition, because decoding of the second DCI is independent from decoding of the first DCI, there is no time delay for decoding of the first DCI and the second DCI. Thus, decoding of the downlink data transmissions from the first network device 110 and from the second network device 120 are accelerated.

At block 230, the first network device 110 determines whether a link between the first network device 110 and the second network device 120 is an ideal backhaul link.

If it is determined that the link is the ideal backhaul link, at 240, the first network device 110 transmits the DCI to the terminal device 140 at least on a first downlink control channel between the first network device 110 and the terminal device 140.

Hereinafter, transmission of the first DCI and second DCI in case of the ideal backhaul link will be described with reference to Figs. 4 and 5.

Fig. 4 is a schematic diagram of example DCI transmission in accordance with some embodiments of the present disclosure. As shown, a sub-frame 400 comprises a control region 410, a data region 420 and an uplink (UL) region 430.

The data region 420 is configured to carry downlink data. The UL region 430 is configured to carry UL feedback from the terminal device 140.

The control region 410 is configured to carry downlink control information. The control region 410 comprises a sub-region 411 and a sub-region 412. In some embodiments, the sub-region 412 is subsequent to the sub-region 411.

The sub-region 411 is predefined for transmission of DCI#1 associated with the first network device 110. The sub-region 412 is predefined for transmission of DCI#2 associated with the second network device 120.

Sizes of the sub-region 411 and the sub-region 412 may be pre-configured. In some embodiments, the size of the sub-region 411 may be pre-configured as two or three Orthogonal Frequency Division Multiplexing (OFDM) symbols. The first network device 110 may determine whether to employ the two OFDM symbols or the three OFDM symbols based on comparison of quality of a channel between the first network device 110 and the the terminal device 140 with a second threshold quality. In other words, a starting position of the sub-region 412 in the sub-frame 410 may be determined based on the comparison of the quality of the channel with the second threshold quality.

For example, if it is determined that the quality of the channel exceeds the second threshold quality, the first network device 110 may determine to employ the two OFDM symbols for transmission of DCI#1. Thus, the third OFDM symbol in the sub-frame 410 is determined as the starting position of the sub-region 412. On the other hand, if it is determined that the quality of the channel is below the second threshold quality, the first network device 110 may determine to employ the three OFDM symbols for transmission of DCI#1. Thus, the fourth symbol in the sub-frame 410 is determined as the starting position of the sub-region 412.

In some embodiments, the size of the sub-region 412 may be pre-configured based on the number of terminal devices that are supported by the first network device 110 for concurrent cooperative downlink transmissions. For example, if the number of terminal devices is equal to one or two, the size of the sub-region 412 may be pre-configured one OFDM symbol. If the number of terminal devices is greater than two, the size of the sub-region 412 may be pre-configured more OFDM symbols.

In some embodiments, the resource allocation indication for DCI#2 may indicate the starting position of the sub-region 412.

In some embodiments, the first network device 110 and the second network device 120 may perform joint transmissions of DCI#1 and DCI#2 encoded with a predetermined space-time block code (STBC) , as will described with reference to Fig. 5.

Fig. 5 is a schematic diagram of example transmission of encoded DCI in accordance with some other embodiments of the present disclosure. As shown, the first network device 110 encodes the DCI#1 and DCI#2 with a predetermined STBC to obtain a first encoded DCI and a second encoded DCI. The DCI#1 may be represented by S1, the first encoded DCI may be the same as DCI#1 and represented by S1. The DCI#2 may be represented by S2, the second encoded DCI may be an inversion of a conjugate transpose of S2 and represented by -S2*, where *represents a conjugate transpose. The first network device 110 transmits the first encoded DCI (i.e., S1) in the sub-region 411 and the second encoded DCI (i.e., -S2*) in the sub-region 412.

A sub-frame 500 for the second network device 120 comprises a control region 510, a data region 520 and a UL region 530. The data region 520 is configured to carry downlink data. The UL region 530 is configured to carry UL feedback from the terminal device 140. The control region 510 is configured to carry downlink control information. The control region 510 comprises a sub-region 511 and a sub-region 512. In some embodiments, the sub-region 512 is subsequent to the sub-region 511.

The second network device 120 encodes the DCI#1 and DCI#2 with the predetermined STBC to obtain a third encoded DCI and a fourth encoded DCI. The DCI#1 may be represented by S 1, the third encoded DCI may be a conjugate transpose of DCI#1 and represented by S1*, where *represents a conjugate transpose. The DCI#2 may be represented by S2, the fourth encoded DCI may be the same as DCI#2 and represented by S2. At the same time when the first network device 110 transmits S1 in the sub-region 411 and -S2*in the sub-region 412, the second network device 120 transmits the third encoded DCI (i.e., S2) in the sub-region 511 and the fourth encoded DCI (i.e., S1*) in the sub-region 512.

Upon receiving the first, second, third and fourth encoded DCI, the terminal device 140 decodes them to obtain the DCI#1 and DCI#2. With the joint transmissions of DCI#1 and DCI#2 encoded with the predetermined STBC, decoding performance of DCI#1 and DCI#2 is improved.

It should be understood that the process of joint transmissions of DCI#1 and DCI#2 encoded with STBC are applicable to both the low frequency band transmission and the high low frequency band transmission. In the case of the high low frequency band transmission, a wideband beam will be used for DCI#1 and DCI#2 from each of the first and second network devices, and a narrow band beam is used for downlink data from each of the first and second network devices. Not only the beamforming gain can be achieved but also the STBC coding gain can be obtained. This can provide more robust transmission of DCI to guarantee multi-PDSCH decoding more successfully at the side of the terminal device 140 with low complexity.

Referring back to Fig. 2, ifit is determined at block 230 that the link is a non-ideal backhaul link, at 250, the first network device 110 transmits, in a first sub-frame, to the terminal device 140 a first indication that a downlink transmission from the second network device 120 is to be initiated.

In some embodiments, the first network device 110 may transmit the first indication in a control region in the first sub-frame. Alternatively, if the control region is too crowed and has no enough resource for transmission of the first indication, the first network device 110 may transmit the first indication in a data region in the first sub-frame to guarantee the decoding performance for the first indication.

Hereinafter, example transmission of the first indication in the control region will be described with reference to Figs. 6 and 7.

Fig. 6 is a schematic diagram of example transmission of the first indication in accordance with some embodiments of the present disclosure. In the example as shown in Fig. 6, the first network device 110 transmits, in a control region in a first sub-frame, a first indication that a downlink transmission from the second network device 120 is to be initiated. The terminal device 140 transmits to the first network device 110 and the second network device 120 a positive acknowledge indicating that the downlink transmission is acceptable. Upon receiving the positive acknowledge, the first network device 110 disables the transmission of the first indication in a control region of a second sub-frame subsequent to the first sub-frame.

As shown, a set 600 of sub-frames for the first network device 110 comprises a sub-frame 610 and a sub-frame 620 subsequent to the sub-frame 610.

The sub-frame 610 comprises a control region 611, a data region 612 and a UL region 613. The sub-frame 620 comprises a control region 621, a data region 622 and a UL region 623. The

control region

611 and 621 are configured to carry DCI associated with the first network device 110. The

data regions

612 and 622 are configured to carry downlink data from the first network device 110. The

UL regions

613 and 623 are configured to carry UL feedbacks from the terminal device 140.

Similarly, a set 605 of sub-frames for the second network device 120 comprises a sub-frame 630 and a sub-frame 640 subsequent to the sub-frame 630.

The sub-frame 630 comprises a control region 631, a data region 632 and a UL region 633. The sub-frame 640 comprises a control region 641, a data region 642 and a UL region 643. The

control regions

631 and 641 are configured to carry DCI associated with the first network device 110. The

data regions

632 and 642 are configured to carry downlink data from the second network device 120. The

UL regions

633 and 643 are configured to carry UL feedbacks from the terminal device 140.

As shown in Fig. 6, the first network device 110 transmits, in the control region 611 in the sub-frame 610, a first indication 6111 that a downlink transmission from the second network device 120 is to be initiated.

Upon receiving the first indication 6111, the terminal device 140 decodes the first indication 6111. If decoding of the first indication 6111 succeeds, the terminal device 140 may determine whether the downlink transmission from the second network device 120 is acceptable. If it is determined that the downlink transmission is acceptable, the terminal device 140 transmits to the first network device 110 a positive acknowledge indicating that the downlink transmission is acceptable. In the example as shown in Fig. 6, the terminal device 140 transmits to the first network device 110 the positive acknowledge in the UL region 613 and the positive acknowledge is represented as “A” .

In addition, if it is determined that the downlink transmission is acceptable, the terminal device 140 also transmits to the second network device 120 the positive acknowledge indicating that the downlink transmission is acceptable. In the example as shown in Fig. 6, the terminal device 140 transmits to the second network device 120 the positive acknowledge in the UL region 633.

Upon receiving the positive acknowledge, the second network device 120 includes DCI#2 into the control region 641 of the sub-frame 640 and downlink data into the data region 642 so as to initiate the downlink transmission to the terminal device 140.

Moreover, if the first network device 110 receives the positive acknowledge, the first network device 110 disables the transmission of the first indication 6111 in the control region 621 of the sub-frame 620 subsequent to the sub-frame 610.

In some embodiments, if the same type of traffic and different data layers of the traffic will be transmitted from the first network device 110 and the second network device 120, the first network device 110 may transmit in the control region 611 of the sub-frame 610 an indication 6112 for an order of decoding of the data channel associated with the first network device 110 and the data channel associated with the second network device 120. For example, the indication 6112 may indicate that the data channel associated with the first network device 110 is to be first decoded so as to improve the accuracy of decoding of the data channels.

Fig. 7 is a schematic diagram of example transmission of the first indication in accordance with some other embodiments of the present disclosure. In the example as shown in Fig. 7, the first network device 110 transmits, in the control region in the first sub-frame, the first indication that the downlink transmission from the second network device 120 is to be initiated. The terminal device 140 transmits to the first network device 110 and the second network device 120 a negative acknowledge indicating that the downlink transmission is rejected. Upon receiving the negative acknowledge, the first network device 110 transmits the first indication in a control region of a third sub-frame subsequent to the first sub-frame.

As shown, a set 700 of sub-frames for the first network device 110 comprises a sub-frame 710 and a sub-frame 720 subsequent to the sub-frame 710.

The sub-frame 710 comprises a control region 711, a data region 712 and a UL region 713. The sub-frame 720 comprises a control region 721, a data region 722 and a UL region 723. The

control region

711 and 721 are configured to carry DCI associated with the first network device 110. The

data regions

712 and 722 are configured to carry downlink data from the first network device 110. The

UL regions

713 and 723 are configured to carry UL feedbacks from the terminal device 140.

Similarly, a set 705 of sub-frames for the second network device 120 comprises a sub-frame 730 and a sub-frame 740 subsequent to the sub-frame 730.

The sub-frame 730 comprises a control region 731, a data region 732 and a UL region 733. The sub-frame 740 comprises a control region 741, a data region 742 and a UL region 743. The

control regions

731 and 741 are configured to carry DCI associated with the first network device 110. The

data regions

732 and 742 are configured to carry downlink data from the second network device 120. The

UL regions

733 and 743 are configured to carry UL feedbacks from the terminal device 140.

Similar to the example as shown in Fig. 6, in the example as shown Fig. 7, the first network device 110 transmits, in the control region 711 in the sub-frame 710, the first indication 6111 that the downlink transmission from the second network device 120 is to be initiated.

Upon receiving the first indication 6111, the terminal device 140 decodes the first indication 6111. If decoding of the first indication 6111 succeeds, the terminal device 140 may determine whether the downlink transmission from the second network device 120 is acceptable. In some embodiments, the terminal device 140 may determine, based on capability of the terminal device 140, whether to accept or reject the downlink transmission. In other words, the terminal device 140 may control the receiving of the cooperative transmission from the first and second network devices or the receiving of a single transmission from the first network device.

If it is determined that the downlink transmission from the second network device 120 is unacceptable, the terminal device 140 transmits to the first network device 110 a negative acknowledge indicating that the downlink transmission is rejected. In the example as shown in Fig. 7, the terminal device 140 transmits to the first network device 110 the negative acknowledge in the UL region 713 and the negative acknowledge is represented as “N” .

In addition, if it is determined that the downlink transmission is unacceptable, the terminal device 140 also transmits to the second network device 120 the negative acknowledge indicating that the downlink transmission is rejected. In the example as shown in Fig. 7, the terminal device 140 transmits to the second network device 120 the negative acknowledge in the UL region 733.

Upon receiving the negative acknowledge, the second network device 120 does not include DCI#2 into the control region 741 of the sub-frame 740 or downlink data into the data region 742. In this case, the terminal device 140 will not perform blind decoding of DCI#2. Thus, the power consumption of the terminal device 140 can be saved and the processing complexity of the terminal device 140 can be reduced.

Moreover, if the first network device 110 receives the negative acknowledge, the first network device 110 transmits the first indication 6111 in the control region 721 of the sub-frame 720 subsequent to the sub-frame 710.

Accordingly, upon receiving the first indication 6111 in the control region 721, the terminal device 140 may transmit the positive or negative acknowledge (A/N) to the first network device 110 in the UL region 723, and to the second network device 120 in the UL region 743.

Fig. 8 is a flowchart of a communication method 800 in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described with reference to Fig. 1. The method 800 may involve the first network device 110, the second network device 120 and the terminal device 140 in Fig. 1. For example, the method 800 can be implemented at the first network device 110 as shown in Fig. 1. It is to be understood that the method 800 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block 810, the first network device 110 compares a first quality of a first uplink channel with a second quality of a second uplink channel. The first uplink channel is between the second network device 120 and the terminal device 140 served by the first network device 110, the second uplink channel is between the third network device 130 and the terminal device 140.

At block 820, in response to the first quality being higher than the second quality, the first network device 110 transmits to the second network device 120 an indication of initiating a measurement of a third quality of a downlink channel between the second network device 120 and the terminal device 140.

At block 830, the first network device 110 transmits to the terminal device 140 information about a pair ofuplink beams associated with the first quality.

At block 840, the first network device 110 receives from the terminal device 140 an indication of the third quality.

At block 850, in response to the third quality exceeding a first threshold quality, the first network device 110 transmits to the second network device 120 an indication that the second network device 120 is selected for a cooperative downlink transmission to the terminal device 140.

Fig. 9 is a flowchart of a communication method 900 in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described with reference to Fig. 1. The method 900 may involve the first network device 110, the second network device 120 and the terminal device 140 in Fig. 1. For example, the method 900 can be implemented at the terminal device 140 as shown in Fig. 1. It is to be understood that the method 900 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block 910, the terminal device 140 receives, on a downlink data channel between the first network device 110 and the terminal device 140, a resource allocation indication for downlink control information, DCI associated with a second network device 120 and information about decoding of the DCI.

At block 920, in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device 110 and the terminal device 140, the terminal device 140 receives the DCI on the first downlink control channel.

In some example embodiments, the method 900 further comprises: transmitting, to the first network device, quality of a channel between the first network device and the terminal device for determination of a starting position of the second sub-region in the sub-frame.

In some example embodiments, the method 900 further comprises: in response to a determination that the resource allocation indication indicates resources on a second downlink control channel between the second network device and the terminal device, receiving, in a first sub-frame, from the first network device a first indication that a downlink transmission from the second network device is to be initiated.

In some example embodiments, the method 900 further comprises: in response to success of decoding of the first indication, determining whether the downlink transmission is acceptable; in response to the determination that the downlink transmission is acceptable, transmitting to the first network device a positive acknowledge indicating that the downlink transmission is accepted; and in response to the determination that the downlink transmission is unacceptable, transmitting to the first network device a negative acknowledge indicating that the downlink transmission is rejected.

In some example embodiments, the method 900 further comprises: in response to transmitting the negative acknowledge indicating that the downlink transmission is rejected, receiving the first indication in a third sub-frame subsequent to the first sub-frame.

In some example embodiments, the method 900 further comprises: transmitting a first uplink reference signal to the second network device for measurement of a first quality of a first uplink channel between the second network device and the terminal device; transmitting a second uplink reference signal to the third network device for measurement of a second quality of a second uplink channel between a third network device and the terminal device; in response to receiving from the first network device information about a pair of uplink beams associated with the first quality, performing measurement of a third quality of a downlink channel between the second network device and the terminal device; and transmitting an indication of the third quality to the first network device for decision of a cooperative downlink transmission from the first and second network devices to the terminal device.

Fig. 10 is a flowchart of a communication method 1000 in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described with reference to Fig. 1. The method 1000 may involve the first network device 110, the second network device 120 and the terminal device 140 in Fig. 1. For example, the method 1000 can be implemented at the second network device 120 as shown in Fig. 1. It is to be understood that the method 1000 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block 1010, the second network device 120 measures a first quality of a first uplink channel between the second network device 120 and the terminal device 140 served by the first network device 110.

At block 1020, the second network device 120 transmits to the first network device 110 an indication of the first quality and information about a pair of uplink beams associated with the first quality.

At block 1030, in response to receiving from the first network device 110 an indication for initiating a measurement of quality of a downlink channel between the second network device 120 and the terminal device 140, the second network device 120 transmits to the terminal device 140 a downlink reference signal for the measurement.

At block 1040, the second network device 120 receives from the first network device 110 an indication that the second network device 120 is selected for a cooperative downlink transmission to the terminal device 140 in response to the quality of the downlink channel exceeding a first threshold quality.

In some example embodiments, the method 1000 further comprises: in response to receiving from the terminal device 140 a positive acknowledge indicating that a downlink transmission from the second network device 120 is accepted, initiating the downlink transmission.

In some embodiments, an apparatus capable of performing the method 200 (for example, the first network device 110) may comprise means for performing the respective steps of the method 200. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises means for selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device; means for transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information, DCI associated with the second network device and information about decoding of the DCI; means for determining whether a link between the first network device and the second network device is an ideal backhaul or a non-ideal backhaul; and means for transmitting, in response to the determination that the link is the ideal backhaul, the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.

In some embodiments, the means for selecting the second network device for the cooperative downlink transmission to the terminal device comprises: means for comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between the second network device and the terminal device, the second uplink channel being between a third network device and the terminal device; means for transmitting, in response to the first quality being higher than the second quality, to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device; means for transmitting to the terminal device information about a pair ofuplink beams associated with the first quality; means for receiving from the terminal device an indication of the third quality; and means for transmitting, in response to a determination that the third quality exceeding a first threshold quality, to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.

In some embodiments, the means for transmitting the DCI comprises: means for transmitting the DCI in a predefined control region in a sub-frame.

In some embodiments, the means for transmitting the DCI in the predefined control region comprises: means for transmitting a further DCI associated with the first network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.

In some embodiments, a size of the predefined control region is pre-configured.

In some embodiments, the apparatus further comprises: means for obtaining from the terminal device quality of a channel between the first network device and the terminal device; means for comparing the quality of the channel with a second threshold quality; and means for determining a starting position of the second sub-region in the sub-frame based on the comparison.

In some embodiments, the means for determining the starting position of the second sub-region in the sub-frame comprises: means for determining, in response to the quality of the channel exceeding the second threshold quality, the third symbol in the sub-frame as the starting position of the second sub-region; and means for determining, in response to the quality of the channel being below the second threshold quality, the fourth symbol in the sub-frame as the starting position of the second sub-region.

In some embodiments, the means for transmitting the resource allocation indication comprises: means for transmitting the resource allocation indication indicating the starting position of the second sub-region.

In some embodiments, the means for transmitting the further DCI and the DCI comprises: means for encoding the further DCI and the DCI with a predetermined space-time block code to obtain a first encoded DCI and a second encoded DCI; and means for transmitting the first encoded DCI and the second encoded DCI.

In some embodiments, the apparatus further comprises: means for transmitting, in a first sub-frame, in response to the determination that the link is the non-ideal backhaul, to the terminal device a first indication that a downlink transmission from the second network device is to be initiated.

In some embodiments, the means for transmitting the first indication comprises: means for transmitting the first indication in a control region in the first sub-frame.

In some embodiments, the means for transmitting the first indication comprises: means for transmitting the first indication in a data region in the first sub-frame.

In some embodiments, the apparatus further comprises: means for disabling the transmission of the first indication in a second sub-frame subsequent to the first sub-frame in response to receiving a positive acknowledge indicating that the downlink transmission from the second network device is accepted.

In some embodiments, the apparatus further comprises: means for transmitting the first indication in a third sub-frame subsequent to the first sub-frame in response to receiving a negative acknowledge indicating that the downlink transmission from the second network device is rejected.

In some embodiments, an apparatus capable of performing the method 800 (for example, the first network device 110) may comprise means for performing the respective steps of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between a second network device and a terminal device served by the first network device, the second uplink channel being between a third network device and the terminal device; means for transmitting, in response to the first quality being higher than the second quality, to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device; means for transmitting to the terminal device information about a pair of uplink beams associated with the first quality; means for receiving from the terminal device an indication of the third quality; and means for transmitting, in response to a determination that the third quality exceeding a first threshold quality, to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.

In some embodiments, an apparatus capable of performing the method 900 (for example, the terminal device 140) may comprise means for performing the respective steps of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for receiving, on a downlink data channel between a first network device and a terminal device, a resource allocation indication for downlink control information, DCI associated with a second network device and information about decoding of the DCI; and means for receiving, in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device and the terminal device, the DCI on the first downlink control channel.

In some embodiments, the means for receiving the DCI comprises: means for receiving the DCI in a predefined control region in a sub-frame.

In some embodiments, the means for receiving the DCI in the predefined control region comprises: means for receiving a further DCI associated with the first network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.

In some embodiments, a size of the predefined control region is pre-configured.

In some embodiments, the apparatus further comprises: means for transmitting, to the first network device, quality of a channel between the first network device and the terminal device for determination of a starting position of the second sub-region in the sub-frame.

In some embodiments, the means for receiving the resource allocation indication comprises: means for receiving the resource allocation indication indicating the starting position of the second sub-region.

In some embodiments, the starting position of the second sub-region is the third symbol in the sub-frame.

In some embodiments, the starting position of the second sub-region is the fourth symbol in the sub-frame.

In some embodiments, the means for receiving the further DCI and the DCI comprises: means for receiving a first encoded DCI and a second encoded DCI; and means for decoding the first encoded DCI and the second encoded DCI with a predetermined space-time block code to obtain the further DCI and the DCI.

In some embodiments, the apparatus further comprises: means for receiving, in a first sub-frame, from the first network device a first indication that a downlink transmission from the second network device is to be initiated in response to a determination that the resource allocation indication indicates resources on a second downlink control channel between the second network device and the terminal device.

In some embodiments, the means for receiving the first indication comprises: means for receiving the first indication in a control region in the first sub-frame.

In some embodiments, the means for receiving the first indication comprises: means for receiving the first indication in a data region in the first sub-frame.

In some embodiments, the apparatus further comprises: means for determining whether the downlink transmission is acceptable in response to success of decoding of the first indication; means for transmitting to the first network device a positive acknowledge indicating that the downlink transmission is accepted in response to the determination that the downlink transmission is acceptable; and means for transmitting to the first network device a negative acknowledge indicating that the downlink transmission is rejected in response to the determination that the downlink transmission is unacceptable.

In some embodiments, the apparatus further comprises: means for receiving the first indication in a third sub-frame subsequent to the first sub-frame in response to transmitting the negative acknowledge indicating that the downlink transmission is rejected.

In some embodiments, an apparatus capable of performing the method 800 (for example, the second network device 120) may comprise means for performing the respective steps of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for measuring, at a second network device, a first quality of a first uplink channel between the second network device and a terminal device served by a first network device; means for transmitting to the first network device an indication of the first quality and information about a pair of uplink beams associated with the first quality; means for transmitting, in response to receiving from the first network device an indication for initiating a measurement of quality of a downlink channel between the second network device and the terminal device, to the terminal device a downlink reference signal for the measurement; and means for receiving from the first network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device in response to the quality of the downlink channel exceeding a first threshold quality.

In some embodiments, the apparatus further comprises: means for initiating the downlink transmission in response to receiving from the terminal device a positive acknowledge indicating that a downlink transmission from the second network device is accepted.

Fig. 11 is a simplified block diagram of a device 1100 that is suitable for implementing embodiments of the present disclosure. The device 1100 can be considered as a further example implementation of the

network devices

110 and 120 as well as the terminal device 140 as shown in Fig. 1. Accordingly, the device 1100 can be implemented at or as at least a part of the

network device

110 or 120, or the terminal device 140.

As shown, the device 1100 includes a processor 1110, a memory 1120 coupled to the processor 1110, a suitable transmitter (TX) and receiver (RX) 1140 coupled to the processor 1110, and a communication interface coupled to the TX/RX 1140. The memory 1120 stores at least a part of a program 1130. The TX/RX 1140 is for bidirectional communications. The TX/RX 1140 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and UE.

The program 1130 is assumed to include program instructions that, when executed by the associated processor 1110, enable the device 1100 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Figs. 1 to 10. The embodiments herein may be implemented by computer software executable by the processor 1110 of the device 1100, or by hardware, or by a combination of software and hardware. The processor 1110 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1110 and memory 1120 may form processing means 1150 adapted to implement various embodiments of the present disclosure.

The memory 1120 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 1120 is shown in the device 1100, there may be several physically distinct memory modules in the device 1100. The processor 1110 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 1100 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally, various example 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 representations, it is to be understood that the block, apparatus, system, technique or method 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

methods

200, 800, 900, 1000 as described above with reference to Figs. 2, 8, 9 and 10. 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.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable media.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer 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 computer 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 implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of 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 languages 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 for communications, comprising:

selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device;

transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information, DCI associated with the second network device and information about decoding of the DCI;

determining whether a link between the first network device and the second network device is an ideal backhaul link or a non-ideal backhaul link; and

in response to the determination that the link is the ideal backhaul link, transmitting the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.
The method of Claim 1, wherein selecting the second network device for the cooperative downlink transmission to the terminal device comprises:

comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between the second network device and the terminal device, the second uplink channel being between a third network device and the terminal device;

in response to the first quality being higher than the second quality, transmitting to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device;

transmitting to the terminal device information about a pair of uplink beams associated with the first quality;

receiving from the terminal device an indication of the third quality; and

in response to a determination that the third quality exceeding a first threshold quality, transmitting to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.
The method of Claim 1, wherein transmitting the DCI comprises:

transmitting the DCI in a predefined control region in a sub-frame.
The method of Claim 3, wherein transmitting the DCI in the predefined control region comprises:

transmitting a further DCI associated with the first network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.
The method of Claim 4, wherein a size of the predefined control region is pre-configured.
The method of Claim 4, further comprising:

obtaining from the terminal device quality of a channel between the first network device and the terminal device;

comparing the quality of the channel with a second threshold quality; and

determining a starting position of the second sub-region in the sub-frame based on the comparison.
The method of Claim 6, wherein determining the starting position of the second sub-region in the sub-frame comprises:

in response to the quality of the channel exceeding the second threshold quality, determining the third symbol in the sub-frame as the starting position of the second sub-region; and

in response to the quality of the channel being below the second threshold quality, determining the fourth symbol in the sub-frame as the starting position of the second sub-region.
The method of Claim 6, wherein transmitting the resource allocation indication comprises:

transmitting the resource allocation indication indicating the starting position of the second sub-region.
The method of Claim 4, wherein transmitting the further DCI and the DCI comprises:

encoding the further DCI and the DCI with a predetermined space-time block code to obtain a first encoded DCI and a second encoded DCI; and

transmitting the first encoded DCI and the second encoded DCI.
The method of Claim 1, further comprising:

in response to the determination that the link is the non-ideal backhaul link, transmitting, in a first sub-frame, to the terminal device a first indication that a downlink transmission from the second network device is to be initiated.
The method of Claim 10, wherein transmitting the first indication comprises:

transmitting the first indication in a control region in the first sub-frame.
The method of Claim 10, wherein transmitting the first indication comprises:

transmitting the first indication in a data region in the first sub-frame.
The method of Claim 10, further comprising:

in response to receiving a positive acknowledge indicating that the downlink transmission from the second network device is accepted, disabling the transmission of the first indication in a second sub-frame subsequent to the first sub-frame.
The method of Claim 10, further comprising:

in response to receiving a negative acknowledge indicating that the downlink transmission from the second network device is rejected, transmitting the first indication in a third sub-frame subsequent to the first sub-frame.
A method for communications, comprising:

comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between a second network device and a terminal device served by the first network device, the second uplink channel being between a third network device and the terminal device;

in response to the first quality being higher than the second quality, transmitting to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device;

transmitting to the terminal device information about a pair of uplink beams associated with the first quality;

receiving from the terminal device an indication of the third quality; and

in response to a determination that the third quality exceeding a first threshold quality, transmitting to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.
A method for communications, comprising:

receiving, on a downlink data channel between a first network device and a terminal device, a resource allocation indication for downlink control information, DCI associated with a second network device and information about decoding of the DCI; and

in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device and the terminal device, receiving the DCI on the first downlink control channel.
The method of Claim 16, wherein receiving the DCI comprises:

receiving the DCI in a predefined control region in a sub-frame.
The method of Claim 17, wherein receiving the DCI in the predefined control region comprises:

receiving a further DCI associated with the first network device in a first sub-region of the predefined control region and the DCI in a second sub-region of the predefined control region, the second sub-region being subsequent to the first sub-region.
The method of Claim 18, wherein a size of the predefined control region is pre-configured.
The method of Claim 18, further comprising:

transmitting, to the first network device, quality of a channel between the first network device and the terminal device for determination of a starting position of the second sub-region in the sub-frame.
The method of Claim 20, wherein receiving the resource allocation indication comprises:

receiving the resource allocation indication indicating the starting position of the second sub-region.
The method of Claim 21, wherein the starting position of the second sub-region is the third symbol in the sub-frame.
The method of Claim 21, wherein the starting position of the second sub-region is the fourth symbol in the sub-frame.
The method of Claim 18, wherein receiving the further DCI and the DCI comprises:

receiving a first encoded DCI and a second encoded DCI; and

decoding the first encoded DCI and the second encoded DCI with a predetermined space-time block code to obtain the further DCI and the DCI.
The method of Claim 16, further comprising:

in response to a determination that the resource allocation indication indicates resources on a second downlink control channel between the second network device and the terminal device, receiving, in a first sub-frame, from the first network device a first indication that a downlink transmission from the second network device is to be initiated.
The method of Claim 25, wherein receiving the first indication comprises:

receiving the first indication in a control region in the first sub-frame.
The method of Claim 25, wherein receiving the first indication comprises:

receiving the first indication in a data region in the first sub-frame.
The method of Claim 25, further comprising:

in response to success of decoding of the first indication, determining whether the downlink transmission is acceptable;

in response to the determination that the downlink transmission is acceptable, transmitting to the first network device a positive acknowledge indicating that the downlink transmission is accepted; and

in response to the determination that the downlink transmission is unacceptable, transmitting to the first network device a negative acknowledge indicating that the downlink transmission is rejected.
The method of Claim 28, further comprising:

in response to transmitting the negative acknowledge indicating that the downlink transmission is rejected, receiving the first indication in a third sub-frame subsequent to the first sub-frame.
The method of Claim 16, further comprising:

transmitting a first uplink reference signal to the second network device for measurement of a first quality of a first uplink channel between the second network device and the terminal device;

transmitting a second uplink reference signal to the third network device for measurement of a second quality of a second uplink channel between the third network device and the terminal device;

in response to receiving from the first network device information about a pair of uplink beams associated with the first quality, performing measurement of a third quality of a downlink channel between the second network device and the terminal device; and

transmitting an indication of the third quality to the first network device for decision of a cooperative downlink transmission from the first and second network devices to the terminal device.
A method for communications, comprising:

measuring, at a second network device, a first quality of a first uplink channel between the second network device and a terminal device served by a first network device;

transmitting to the first network device an indication of the first quality and information about a pair of uplink beams associated with the first quality;

in response to receiving from the first network device an indication for initiating a measurement of quality of a downlink channel between the second network device and the terminal device, transmitting to the terminal device a downlink reference signal for the measurement; and

receiving from the first network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device in response to the quality of the downlink channel exceeding a first threshold quality.
The method of Claim 31, further comprising:

in response to receiving from the terminal device a positive acknowledge indicating that a downlink transmission from the second network device is accepted, initiating the downlink transmission.
A network device, comprising:

at least one processor; and

at least one memory including 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 perform the method of any of Claims 1 to 14.
A network device, comprising:

at least one processor; and

at least one memory including 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 perform the method of Claim 15.
A terminal device, comprising:

at least one processor; and

at least one memory including 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 perform the method of any of Claims 16 to 30.
A network device, comprising:

at least one processor; and

at least one memory including 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 perform the method of any of Claims 31 to 32.
An apparatus for communications, comprising:

means for selecting, at a first network device serving a terminal device, a second network device for a cooperative downlink transmission to the terminal device;

means for transmitting, on a downlink data channel, to the terminal device a resource allocation indication for downlink control information, DCI associated with the second network device and information about decoding of the DCI;

means for determining whether a link between the first network device and the second network device is an ideal backhaul or a non-ideal backhaul; and

means for transmitting, in response to the determination that the link is the ideal backhaul, the DCI to the terminal device at least on a first downlink control channel between the first network device and the terminal device.
An apparatus for communications, comprising:

means for comparing a first quality of a first uplink channel with a second quality of a second uplink channel, the first uplink channel being between a second network device and a terminal device served by the first network device, the second uplink channel being between a third network device and the terminal device;

means for transmitting, in response to the first quality being higher than the second quality, to the second network device an indication of initiating a measurement of a third quality of a downlink channel between the second network device and the terminal device;

means for transmitting to the terminal device information about a pair of uplink beams associated with the first quality;

means for receiving from the terminal device an indication of the third quality; and

means for transmitting, in response to a determination that the third quality exceeding a first threshold quality, to the second network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device.
An apparatus for communications, comprising:

means for receiving, on a downlink data channel between a first network device and a terminal device, a resource allocation indication for downlink control information, DCI associated with a second network device and information about decoding of the DCI; and

means for receiving, in response to a determination that the resource allocation indication indicates resources on a first downlink control channel between the first network device and the terminal device, the DCI on the first downlink control channel.
An apparatus for communications, comprising:

means for measuring, at a second network device, a first quality of a first uplink channel between the second network device and a terminal device served by a first network device;

means for transmitting to the first network device an indication of the first quality and information about a pair of uplink beams associated with the first quality;

means for transmitting, in response to receiving from the first network device an indication for initiating a measurement of quality of a downlink channel between the second network device and the terminal device, to the terminal device a downlink reference signal for the measurement; and

means for receiving from the first network device an indication that the second network device is selected for a cooperative downlink transmission to the terminal device in response to the quality of the downlink channel exceeding a first threshold quality.
A computer-readable medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method of any of Claims 1 to 14.
A computer-readable medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method of Claim 15.
A computer-readable medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method of any of Claims 16 to 30.
A computer-readable medium storing a computer program thereon, the computer program, when executed by a processor, causing the processor to carry out the method of any of Claims 31 to 32.