WO2018137516A1

WO2018137516A1 - Method and apparatus for transmitting signals

Info

Publication number: WO2018137516A1
Application number: PCT/CN2018/072892
Authority: WO
Inventors: Hua Xu
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2017-01-27
Filing date: 2018-01-16
Publication date: 2018-08-02
Also published as: TWI698142B; CN109845339B; TW201828755A; CN109845339A

Abstract

Methods and apparatus for transmitting signals are provided. In a 1-port DMRS design, two REs in a RE set are configured for DMRS and rest REs are configured for PDCCH. Alternatively, two REs in a RE set are configured for DMRS, two null REs are configured for power boosting, and the rest REs are configured for PDCCH.

Description

METHOD AND APPARATUS FOR TRANSMITTING SIGNALS

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/451,266, field on January 27, 2017, the disclosure of which is herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to the field of communication, and particularly to a method and apparatus for transmitting signals.

BACKGROUND

In long term evolution (LTE) release (Rel) -8, cell-specific reference signal (CRS) is used for physical downlink control channel (PDCCH) demodulation and number of CRS ports are cell-specific. In LTE Rel-11, 1-port demodulation reference signal (DMRS) is specified for localized enhanced PDCCH (EPDCCH) demodulation and 2-port DMRS is specified for distributed EPDCCH demodulation.

In a 5G new radio (NR) system, DMRS could be used for PDCCH decoding and a new NR PDCCH DMRS design is correspondingly required to accommodate requirements in 5G NR.

SUMMARY

In this innovation, DMRS are used for PDCCH decoding and some DMRS design such as 1-port and 2-port DMRS design is proposed for 5G NR PDCCH and user equipment (UE) -specific DMRS port configuration is proposed.

In one embodiment, techniques can include provide a method for transmitting signals in which 1-port DMRS for NR PDCCH could use two REs in a RE set for DMRS and rest for PDCCH.

In one embodiment, techniques can include provide a method for transmitting signals in which 1-port DMRS for NR PDCCH could use four REs in a RE set for DMRS and rest for PDCCH.

In one embodiment, techniques can include provide a method for transmitting signals in which two REs in a RE set can be configured for DMRS, two null REs can be configured in the RE set, and the rest REs in the RE set can be configured for PDCCH.

In one embodiment, techniques can include provide a method for transmitting singles in which 2-port DMRS for NR PDCCH could use four REs in a RE set for DMRS and rest for PDCCH.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be better understood from the following description taken in conjunction with the accompanying figures, in which:

FIG. 1 illustrates a wireless communication system.

FIG. 2 illustrates a terminal.

FIG. 3 illustrates a network device.

FIG. 4 illustrates a PDCCH CRS design for LTE.

FIG. 5 illustrates a PDCCH 1-port DMRS design for 5G NR according to an embodiment of the present disclosure.

FIG. 6 illustrates another PDCCH 1-port DMRS design for 5G NR according to an embodiment of the present disclosure.

FIG. 7 illustrates still another PDCCH 1-port DMRS design for 5G NR according to an embodiment of the present disclosure.

FIG. 8 illustrates still another PDCCH 1-port DMRS design for 5G NR according to an embodiment of the present disclosure.

FIG. 9 illustrates a PDCCH 2-port DMRS design for 5G NR according to an embodiment of the present disclosure.

FIG. 10 is a block diagram of an apparatus for transmitting signals according to an embodiment of the present disclosure.

FIG. 11 is a block diagram of an apparatus according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system according to the present disclosure. The wireless communication system may operate on a high frequency band, which includes but not limited to a long term evolution (LTE) system, a future evolved fifth generation (5G) system, a new radio (NR) system, and a machine to machine (M2M) system. The wireless communication system illustrated in FIG. 1 is merely illustrative of the technical solution of the present disclosure and is not intended to limit the scope thereof. It will be appreciated by those of ordinary skill in the art that with the evolution of the network architecture and the emergence of new business scenarios, technical solutions proposed herein can be equally applicable to similar technical problems.

As shown in FIG. 1, the wireless communication system 100 may include one or more network devices 101, one or more terminals 103, and a core network 111.

Network device 101 can be a base station, which can communicate with one or more terminals or base stations with terminal function. In a 5G NR system, the base station can be gNB. Terminal 103 may be distributed throughout the wireless communication system 100, either stationary or mobile. In some embodiments, terminal 103 may be a mobile device, a mobile station, a mobile unit, an M2M terminal, a wireless unit, a remote unit, a user agent, a mobile client and so on. Network device 101 can communicate with terminal 103 under the control of a controller which is not illustrated in the figure. In some embodiments, this controller can be part of core network 111 or can be integrated into network device 101. Network devices 101 may also communicate with each other directly or indirectly through a back-haul interface 107 such as an X2 interface. Network device 101 may be operable to transmit control information or user data to core network 111 through a back-haul interface 109 (e.g., S1 interface) . Terminal 103 can be located within the coverage of one or more cells 105.

FIG. 2 illustrates a terminal 200. Terminal 200 may include one or more terminal processors 201, a memory 202, a communication interface 203, a bus 204, a receiver 205, a transmitter 206, a coupler 207, an antenna 208, a user interface 202, and an input and output device (such as a microphone, a keyboard, a display, and the like) . The processors 201, the communication interface 203, the receiver 205 and the transmitter 206 may be connected via bus 204 or other means. Communication interface 203 may be used for terminal 200 to communicate with other communication devices, such as network devices. Transmitter 206 may be used to transmit signals output from terminal processor 201, such as perform signal modulation. Input/output device 210 may be used to implement the interaction between terminal 200 and users/external environment. Memory 202 is coupled to terminal processor 201 for storing various software programs and/or instructions. Terminal processor 201 may be used to read and execute computer readable instructions such as those stored in memory 202.

FIG. 3 illustrates a network device 300. Network device 300 may be a gNB and include one or more network device processors 301, a memory 302, a communication interface 303, a transmitter 305, a receiver 306. These components may be connected via a bus 304 or other means. As illustrated in FIG. 3, the network device 300 may further include a coupler 307 and an antenna 308 connected to the coupler. Communication interface 303 may be used for network device 300 to communicate with other communication devices, such as a terminal device or other network device. Transmitter 305 may be used to transmit signals output from network device processor 301, such as perform signal modulation. Network device processor 301 can be responsible for wireless channel management, communication links establishment, and cell switching control for users within the control area. Network device processor 301 can also read and executed computer readable instructions such as those stored memory 302 which is coupled thereto.

Between the network device and the terminal, physical downlink control channel (PDCCH) is generally configured to carry scheduling and other control information, including transport format, resource allocation, uplink scheduling grant, power control, and uplink retransmission information. Physical downlink shared channel (PDSCH) as a downlink channel is generally configured to carry user data.

FIG. 4 illustrates a PDCCH cell-specific reference signal (CRS) design for LTE. As illustrated in FIG. 4, in LTE system, PDCCH is transmitted in the first several orthogonal frequency division multiplexing (OFDM) symbols span the whole system bandwidth at the beginning of a subframe. As can be seen from FIG. 4, PDCCH can occupy three symbols for example. One PRB can occupy twelve sub-carries in the frequency domain, and in one RE set, two REs can be configured for CRS port #0, and another two REs can be configured for CRS port #1.

CRS is used to demodulate the PDCCH, and 1-port CR, 2-port CRS and 4-port CRS are supported, where “port” refers to “antenna port” . In a LTE system, the CRS ports are cell-specific and therefore do not change on per UE basis. In LTE Rel-11, 1-port DMRS is specified for localized EPDCCH demodulation and 2-port DMRS is specified for distributed EPDCCH demodulation.

In a 5G NR system, DMRS could be used for PDCCH decoding and 1-port or 2-port DMRS could be supported. This application provides techniques, including 1-port and 2-port DMRS designs for 5G NR and UE-specific DMRS port configurations, which can accommodate requirements in a 5G NR system. Technical solutions of the embodiments described herein may be configured to transmit signals and the like.

As DMRS is adopted for PDCCH and could be embedded and transmitted in the PRB that carries PDCCH, the number of DMRS port could be UE-specific and configured on per UE basis semi-statically using higher layer signaling. For example, if a UE is at cell center and therefore may not need to transmit diversity to improve its PDCCH performance, the UE could be configured with 1-port DMRS and the exemplary DMRS design illustrated in any of FIG. 5 to FIG. 8 can be used for the PDCCH demodulation of the UE. For another UE, which is at cell edge and may need to use transmit diversity to improve its PDCCH performance/coverage, 2-port DMRS could be configured and the exemplary design in FIG. 9 could be used.

The “resources” referred herein refer to time-frequency resources, including time domain resources and frequency domain resources, usually in the form of resource elements (RE) , resource blocks (RB) , symbols, carrier (subcarrier) , transmission time interval (TTI) , and the like. The definition of concepts such as resource particles, resource blocks and the like may refer to the LTE standard but not limited to the LTE standard, and the definition of various resource forms may be vary in future communication standards, however, this does not affect the nature of the invention. Hereinafter, take physical resource block (PRB) and RE as examples for illustration. It should be noted that, terms and phrases used herein are intended to be exemplary rather than limiting in any way.

PRB: a PRB is time-and-frequency resource that occupies twelve subcarriers in the frequency domain and fourteen OFDM symbols (that is, two slots) in the time domain.

RE: a RE is a time-and-frequency resource that occupies one subcarrier in the frequency domain and one OFDM symbol in the time domain. One PRB consists of twelve REs.

In one implementation, the number of DMRS port for NR PDCCH could be configured on per UE basis semi-statically, that is, via a higher layer signaling. For example, DMRS port configuration for NR PDCCH could be configured in conjunction with DMRS port configuration for PDSCH or configured separately. In detail, the DMRS port configuration for downlink (DL) PDCCH could be configured in conjunction with DMRS configuration for data (transmitted in physical downlink shared channel, PDSCH) , or they could be configured separately. For example, both PDCCH and PDSCH could be configured with 1-port DMRS (even though the DMRS port index for PDCCH and PDSCH could be different with different DMRS pattern and density) . Alternatively, number of DMRS port for PDCCH could be configured as 1 port, while number of DMRS ports for PDSCH could be configured as 2-8 ports, and the present disclosure is not particularly limited.

Hereinafter, 1-port DMRS design and 2-port DMRS design for PDCCH will be described in detail.

1-port DMRS design for a 5G NR system

Implementation 1

FIG. 5 illustrates a 1-port DMRS design for PDCCH. In the example illustrated, two REs in a RE set are used for DMRS (blocks in dark color in FIG. 5, in the following, “RE for DMRS” for short) and rest ten REs are used for PDCCH (blocks in light color in FIG. 5, in the following, “RE for PDCCH” for short) . Correspondingly, in a method for transmitting signals, DMRS are transmitted with two REs in a RE set and PDCCH are transmitted with rest ten REs in the PRB. “RE set” refers to REs in a physical resource block per orthogonal frequency division multiplexing (OFDM) symbol.

Locations of the two REs for DMRS, in other words, number of REs for PDCCH between the two REs for DMRS, could be configured flexibly. As illustrated in FIG. 5, even number (that is, six) of REs for PDCCH are arranged between the two REs for DMRS, while in FIG. 6, odd number (that is, three) of REs for PDCCH are arranged between the two REs for DMRS. Any other similar configuration may be adapted and the present disclosure is not particularly limited herein. As an implementation, locations of REs for DMRS may consider DMRS density, gap for channel estimation, and the like. With channel response in mind, the REs for DMRS in a RE set (in other words, in a PRB) shall be distributed evenly or discretely across the PRB to obtain more accurate channel estimation results across the PRB.

Comparing with LTE CRS design as illustrated in FIG. 4, the 1-port DMRS design for PDCCH as illustrated in FIG. 5 or FIG. 6 may provide similar gap/density in frequency as that in LTE, and therefore shall provide similar channel estimation performance as that in LTE.

Implementation 2

FIG. 7 illustrates another 1-port DMRS design for PDCCH, where two null REs are created for power boosting in a RE set on the basis of the DMRS design of FIG. 5. Null RE refers to a RE that is not configured for DMRS or PDCCH. As illustrated in FIG. 7, the null RE (blank blocks in FIG. 7) can be adjacent to the RE for DMRS (blocks in dark color in FIG. 7) , for example, on the left or right side of the DMRS RE. In this situation, eight REs (blocks in light color in FIG. 7) are to be used for PDCCH. Correspondingly, in a method for transmitting signals, DMRS are transmitted with two REs in a RE set, two null REs are configured for power boosting, and PDCCH are transmitted with rest eight REs in the RE set.

Implementation 3

Alternatively, FIG. 8 illustrates another 1-port DMRS design for PDCCH in which four REs in a RE set can be used for DMRS and rest REs can be used for PDCCH. As illustrated in FIG. 8, these four REs in dark color in a PRB could all be used to carry this 1-port DMRS, thus can achieve the same effect of power boosting as FIG. 7. These four REs for DMRS can be separated into two pairs with each pair has two adjacent REs, so as to achieve multiplex as well as obtain diversity gain. An orthogonal cover code would be added to the top of reference signals transmitted on each pair of adjacent REs, therefore, it is possible mitigate the interference from DMRS from other cells assuming they use the same pairs of REs.

Compared with the design of FIG. 5 or FIG. 6, even such change of FIG. 7 or FIG. 8 reduce the number of REs for PDCCH from ten to eight in a RE set, it would allow power boosting (DMRS could borrow power from null REs or the adjacent RE) and hence improve channel estimation accuracy.

2-port DMRS design for a 5G NR system

FIG. 9 illustrates an example for 2-port DMRS for PDCCH, where in a RE set, two pairs of REs (blocks in dark color in FIG. 9 and one pair of REs includes two adjacent REs) are used for DMRS, and the rest of eight REs are used for PDCCH.

For each pair of REs used for DMRS, frequency division multiplexing (FDM) /code-division multiplexing (CDM) could be applied to result in 2-port of DMRS. Again, the density and gap between each pair of REs takes channel estimation performance into considerations. Compared with the case of 1-port DMRS, in addition to DMRS density and gap for channel estimation, locations of REs for DMRS in this 2-port DMRS design may further take the convenience of applying transmit diversity such as space frequency block code (SFBC) into consideration. Based on this, there could be even number of REs for PDCCH between the two pairs REs for DMRS as illustrated in FIG. 9.

Similarly, the number of DMRS port for NR PDCCH could be configured on per UE basis semi-statically, that is, via a higher layer signaling or signal. It could be configured in conjunction with DMRS port configuration for PDSCH or configured separately.

Comparing with LTE CRS design as illustrated in FIG. 4, the 2-port DMRS design for PDCCH as illustrated in FIG. 9 may provide similar gap/density in frequency as that in LTE, and therefore shall provide similar channel estimation performance as that in LTE.

Unified design

The 1-port DMRS configuration as illustrated in FIG. 7 and FIG. 8 can lead to the same RE mapping as the 2-port DMRS configuration illustrated in FIG. 9, which may further result in that same number of REs can be configured for PDCCH in each PRB (also called REG (resource element group) or RE set for PDCCH) to facilitate a more unified design of PDCCH regardless of DMRS antenna ports. Said differently, eight REs will be configured for PDCCH regardless of 1-port DMRS or 2-port DMRS.

Apparatus

According to an embodiment of the present disclosure, there is provided an apparatus for transmitting signals. During implementation, such apparatus can make use of the above-mentioned DMRS design and can be configured to perform the method for transmitting signals.

FIG. 10 is a block diagram illustrating the apparatus for transmitting signals. As illustrated in FIG. 10, apparatus 40 may include a configuration unit 42 and a transmitting unit 44. Apparatus 40 can be arranged at gNB side and communicate with UEs. Configuration unit 42 can be a processor integrated with a resource configuration function. Transmitting unit 44 can be a transmitter, transceiver, antenna, wireless transmission equipment, and any other devices equipped with a transmission function.

In the process of transmitting signals, configuration unit 42 can be configured to configure resources for carrying DMRS, where the resources for carrying DMRS are two or four REs in a RE set for 1-port or 2-port DMRS. Configuration of resources can be made based on at least one selected from a group consisting of DMRS density, gap for channel estimation, and transmit diversity.

In more detail, for 1-port DMRS, the configured resources for DMRS can be two REs or four REs. In the case of two REs, these two REs can be distributed evenly or discretely across one PRB to obtain more accurate channel estimation results across the PRB; in the case of four REs, these four REs can be distributed as two pairs each of which has two adjacent REs. For 2-port DMRS, the configured resources for DMRS is four REs, and similarly, these four REs can be distributed as two pairs each of which has two adjacent REs to achieve multiplex and diversity gain.

As one implementation, configuration unit 42 can be further configured to configure two null REs for power boosting when the configured resources are two REs for 1-port DMRS. These two null REs can be each adjacent to one of the two REs for DMRS and can be separated by even number of REs for PDCCH. For details, please refer to the foregoing description and FIG. 7.

In the process of transmitting signals, transmitting unit 44 is can be configured to transmit DMRS on the resources configured by configuration unit 42.

Details of the foregoing method embodiments are also applicable to this apparatus embodiment and will not be repeated here.

Certain aspects of the embodiments described in the present disclosure may be provided as a computer program product, or software, that my include, for example, a computer-readable storage medium or a non-transitory machine-readable medium having stored thereon instructions, which may be used to program a computer system (or other electronic devices) or a processor to perform a process according to the present disclosure. A non-transitory machine-readable medium includes any mechanism for storing information in a form (e.g., software, processing application) readable by a machine (e.g., a computer) . The non-transitory machine-readable medium may take the form of, but is not limited to, a magnetic storage medium, optical storage medium (e.g., CD-ROM) , magneto-optical storage medium, read only memory (ROM) , random access memory (RAM) , erasable programmable memory, flash memory, and so on.

Based on this, FIG. 11 illustrated an apparatus 50 in which a processor 52 and one or more interfaces 56 coupled with processor 52 via a BUS 54 are arranged. The interface 56 can be a general purpose input/output (GPIO) interface for example.

Processor 52 may be configured to read and execute computer readable instructions. In one implementation, processor 52 may primarily include a controller, an operator, and a register, and the hardware architecture of processor 52 may be an application specific integrated circuits (ASIC) architecture, a microprocessor without interlocked piped stages (MIPS) architecture, an advanced RISC machine (ARM) architecture, or a network processor (NP) architecture.

Interface 56 can be configured to input data to be processed to processor 52 and/or output processing results of processor 52 to the outside. Interface 56 can be connected with one or more peripheral equipment such as a display (for example, LCD) , camera, RF module and so on.

In conjunction with technical solutions of the present disclosure, processor 52 can invoke, from a memory, programs with regard to the method for transmitting signals and perform instructions contained in the programs to achieve corresponding operations such as resources configuration. Interface 56 can be configured to output the result of resources configuration, whereby a transceiver can transmit signals on the resources configured.

By means of technical solutions described herein, a new NR PDCCH DMRS design can be provided to accommodate requirements in 5G NR.

While the present disclosure has been described with reference to various embodiments, it will be understood that these embodiments are illustrative and that the scope of the disclosure is not limited thereto. Variations, modifications, additions, and improvements are possible. Functionality may be separated or combined in procedures differently in various embodiments of the disclosure or described with different terminology.

Claims

A method for transmitting signals, comprising:

transmitting demodulation reference signal (DMRS) for physical downlink control channel (PDCCH) with two resource elements (REs) in a RE set, wherein the DMRS is 1-port DMRS, and the RE set is REs in a physical resource block per orthogonal frequency division multiplexing (OFDM) symbol.
The method of claim 1, further comprising:

configuring two null REs in the RE set.
The method of claim 2, wherein the two null REs are each adjacent to one of the two REs for DMRS.
The method of claim 3, wherein even number of REs for PDCCH are interposed between the two null REs.
The method of claim 2, further comprising:

transmitting PDCCH with rest REs in the RE set, wherein the rest REs comprise: REs in the RE set except the two REs for the DMRS and the two null REs.
The method of any of claims 1 to 5, wherein configuration of REs for DMRS is configured per user equipment (UE) basis.
The method of any of claims 1 to 5, wherein configuration of REs for DMRS is configured via a higher layer signaling.
The method of any of claims 1 to 5, wherein locations of the two REs for DMRS are determined based on at least one selected from a group consisting of DMRS density and gap for channel estimation.
The method of any of claims 1 to 5, wherein number of ports is configured per UE basis and configured via a higher layer signaling.
The method of claim 9, wherein the number of ports is configured in conjunction with DMRS port configuration for physical downlink shared channel (PDSCH) .
A method for transmitting signals, comprising:

transmitting demodulation reference signal (DMRS) for physical downlink control channel (PDCCH) with four resource elements (REs) in a RE set, the RE set being REs in a physical resource block per orthogonal frequency division multiplexing (OFDM) symbol.
The method of claim 11, wherein the four REs for DMRS are separated into two pairs of REs by even number of REs for PDCCH, and wherein each pair of REs has two adjacent REs.
The method of claim 11 or 12, wherein locations of the four REs for DMRS are determined based on at least one selected from a group consisting of DMRS density, gap for channel estimation, and transmit diversity.
The method of claim 11 or 12, wherein configuration of REs for DMRS is configured per user equipment (UE) basis and configured via a higher layer signaling.
The method of claim 11 or 12, wherein number of ports is configured per UE basis and configured via a higher layer signaling.
The method of claim 15, wherein the number of ports is configured in conjunction with DMRS port configuration for physical downlink shared channel (PDSCH) .
The method of any of claims 11 to 16, wherein the DMRS is 1-port DMRS.
The method of any of claims 11 to 16, wherein the DMRS is 2-port DMRS.
An apparatus for transmitting signals, comprising:

a configuration unit, configured to configure resources for carrying demodulation reference signal (DMRS) , wherein the resources for carrying DMRS are two or four resource elements (REs) in a RE set for 1-port or 2-port DMRS; and

a transmitting unit, configured to transmit DMRS on the configured resources.
The apparatus of claim 19, wherein the configuration unit is further configured to configure two null REs when the configured resources are two REs for 1-port DMRS.
The apparatus of claim 19, wherein the two null REs are each adjacent to one of the two REs for DMRS and are separated by even number of REs for PDCCH.
The apparatus of any of claims 19 to 21, wherein the configuration unit is configured to configure the resources based on at least one selected from a group consisting of DMRS density, gap for channel estimation, and transmit diversity.