User equipment, user equipment method, and base station device

Abstract

To provide a method for communication by user equipment and a base station, associated with a communication process in a wireless communication system based on a short TTI.SOLUTION: A method includes receiving an uplink demodulation reference signal (DMRS) from user equipment in uplink transmission time intervals (TTIs) of uplink sub-frames supporting two or more uplink TTIs. At least one uplink TTI supported by the uplink sub-frames is configured to transmit only uplink control information and / or uplink data without the uplink DMRS.SELECTED DRAWING: Figure 7A

Description

[Technical field]

[0001] The present disclosure relates generally to wireless communications, and more particularly to a method and apparatus for demodulation reference signal (DMRS) transmission based on reduced Transmission Time Intervals (TTI) in a communication system. [Background technology]

[0002] This section is intended to provide background for the various embodiments of the inventions described in this disclosure. The description herein may include concepts that could be pursued, but not necessarily those that have been previously conceived or pursued. Thus, unless otherwise indicated herein, what is described in this section is not prior art to the description and / or claims of this disclosure, and is not admitted to be prior art by virtue of its inclusion in this section.

[0003] The long-term evolution (LTE) system, launched by the third generation partnership project (3GPP), is currently considered as a new air interface and radio network architecture that provides high data rates, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) and communicates with multiple mobile stations referred to as user equipment (UEs). The radio protocol stack of the E-UTRAN is given including a radio resource control layer (RRC), a packet data convergence protocol layer (PDCP), a radio link control layer (RLC), a media access control layer (MAC), and a physical layer (PHY).

[0004] In a 3GPP radio access network (RAN) LTE system, a node may be a combination of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly referred to as an evolved Node B, enhanced Node B, eNodeB, or eNB) and a Radio Network Controller (RNC), which communicates with wireless devices known as user equipment (UE). A downlink (DL) transmission may be a communication from a node (e.g., an eNodeB) to a wireless device (e.g., a UE), and an uplink (UL) transmission may be a communication from a wireless device to a node.

[0005] In LTE, data can be transmitted from the UE to the eNodeB via a physical uplink shared channel (PUSCH). The PUSCH carries scheduled data traffic and possible control signaling. The PUSCH can be carried in subframes of a radio frame. Furthermore, data can be transmitted from the eNodeB to the UE via a physical downlink shared channel (PDSCH). The PDSCH is also carried in 1 ms subframes and is downlink scheduled over the respective TTI. The UE can send acknowledgement (ACK) / non-acknowledgement (NACK) feedback to the base station via a physical uplink control channel (PUCCH), which can be used to carry uplink control information. Conventionally, a 1 millisecond (ms) subframe containing 14 symbols can only allow a 1 ms TTI, which is the smallest time unit for scheduling DL and UL transmissions.

[0006] Demodulation Reference Signals (DMRS) are used in Time Division Duplexing (TDD) and / or Frequency Division Duplexing (FDD) wireless communication systems to determine the quality of downlink and uplink channels.

[0007] According to the current 3GPP specification, the DMRS signal is currently composed of PUCCH / PUSCH / PDSCH channels. Figures 1A-1C show schematic diagrams of an example pattern of DMRS in a PUCCH, PUSCH, PDSCH configuration in an existing LTE system. In every TTI supporting 14 symbols, multiple symbols need to be allocated for DMRS transmission.

[0008] At the 3GPP RAN#67 meeting, a study item on “Study of LTE latency reduction techniques” was approved. For RAN1, TTI reduction and processing time reduction should be considered and documented from at least the following perspectives: · Study feasibility and performance of TTI lengths between 0.5 ms and one OFDM symbol, considering the impact on reference signals and physical layer control signals; Backward compatibility must be maintained, thus allowing normal operation of pre-Rel 13 UE on the same carrier.

[0009] Nevertheless, the study concluded that "by shortening the TTI length, the network can schedule the UE faster and shorten the round trip time (RTT). Reducing the RTT increases TCP throughput. Reducing the TTI length can also increase system capacity for small data transmissions."

[0010] Therefore, there is a need to provide a solution for DMRS communication based on short TTI in wireless communication systems. Summary of the Invention

[0011] From the viewpoint of latency reduction technology, the number of symbols in one TTI is reduced, so that when a DMRS signal is introduced in each TTI, the DMRS overhead must be considered, especially for short TTIs containing one or two symbols. Furthermore, especially for short TTIs in continuous scheduling or high frequency, the channel condition may not change much. In that sense, some DMRS may not be needed when demodulating control information or data.

[0012] To address the above problems, one or more method and apparatus embodiments of the present disclosure aim to provide a solution for DMRS communication based on shortened TTI. Other features and advantages of the present disclosure will be understood from the following description of specific embodiments, taken in conjunction with the accompanying drawings illustrating the principles of the present disclosure.

[0013] According to a first aspect of the present disclosure, there is provided a method for communication by a base station operating in a wireless communication system, the method including receiving an uplink demodulation reference signal (DMRS) in an uplink subframe supporting two or more uplink transmission time intervals (TTIs), at least one uplink TTI supported by the uplink subframe configured to transmit only uplink control information and / or uplink data without uplink DMRS.

[0014] According to a second aspect of the present disclosure, there is provided a method for communication by a base station operating in a wireless communication system, the method including transmitting a downlink DMRS to a user equipment in a downlink TTI of a downlink subframe supporting two or more TTIs, where at least one downlink TTI supported by the downlink subframe is configured to transmit only downlink control information and / or downlink data without a downlink DMRS.

[0015] According to a third aspect of the present disclosure, there is provided a method for communication by a user equipment operating in a wireless communication system, the method including transmitting an uplink demodulation reference signal (DMRS) to a base station in an uplink TTI of an uplink subframe supporting two or more uplink transmission time intervals (TTIs), where at least one uplink TTI supported by the uplink subframe is configured to transmit only uplink control information and / or uplink data without uplink DMRS.

[0016] According to a fourth aspect of the present disclosure, there is provided a method for communication by a user equipment operating in a wireless communication system, the method including receiving a downlink DMRS from a base station in a downlink TTI of a downlink subframe supporting two or more downlink TTIs, at least one downlink TTI after the downlink TTI in which the downlink DMRS is received is configured not to transmit any downlink DMRS.

[0017] According to a further aspect of the present disclosure, there is provided a base station, comprising a transmitter and a receiver configured to perform the functions set out above in the first and second aspects of the present disclosure.

[0018] According to a further aspect of the present disclosure, there is provided a user equipment, comprising a transmitter and a receiver configured to perform the functions set out above in the third and fourth aspects of the present disclosure.

[0019] According to a further aspect of the present disclosure, there is provided a base station, comprising: processing means configured to perform a method for base station communication according to any of the various embodiments of the present disclosure.

[0020] According to a further aspect of the present disclosure there is provided a user equipment comprising: processing means configured to perform a method for communication by a user equipment according to any of the various embodiments of the present disclosure. [Brief description of the drawings]

[0021] The inventive features which are believed to be characteristic of the invention are set forth in the appended claims. However, the invention, its modes of implementation, other objects, features and advantages will be better understood from the following detailed description of illustrative embodiments, which should be read in conjunction with the accompanying drawings, in which:

[0022] [Figure 1A] FIG. 1A illustrates generally an example DMRS pattern configured with a PUCCH for a wireless communication system. [Figure 1B] FIG. 1B illustrates generally an example DMRS pattern consisting of a PUSCH for a wireless communication system. [Figure 1C] FIG. 1C illustrates generally an example DMRS pattern comprised of a PDSCH for a wireless communication system.

[0023] [Figure 2A] FIG. 2A is a diagram that illustrates a schematic diagram of an example DMRS structure applicable to multiple short TTIs according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B is a diagram illustrating a schematic of an example DMRS structure applicable to multiple short TTIs according to an embodiment of the present disclosure.

[0024] [Figure 3A] FIG. 3A is a diagram illustrating an example DMRS structure having candidate DMRS positions and fixed DMRS positions, in accordance with one or more embodiments of the present disclosure. [Figure 3B] FIG. 3B is a diagram illustrating an example DMRS structure having candidate DMRS positions and fixed DMRS positions, in accordance with one or more embodiments of the present disclosure.

[0025] [Figure 4A] FIG. 4A is a diagram illustrating a schematic of an example DMRS structure suitable for one symbol-based TTI in accordance with one or more embodiments of the present disclosure. [Figure 4B] FIG. 4B is a diagram illustrating a schematic diagram of an example DMRS structure suitable for one symbol-based TTI in accordance with one or more embodiments of the present disclosure. [Figure 4C] FIG. 4C is a diagram that illustrates a schematic diagram of an example DMRS structure suitable for one symbol-based TTI in accordance with one or more embodiments of the present disclosure.

[0026] [Diagram 5] FIG. 5 is a diagram that illustrates a schematic of a method for communication by a base station in accordance with one or more embodiments of the present disclosure.

[0027] [Figure 6] FIG. 6 is a diagram that illustrates a schematic of a method for communication by a user device in accordance with one or more embodiments of the present disclosure.

[0028] [Figure 7A] FIG. 7A is a diagram illustrating example UL and DL subframes having an uplink DMRS, in accordance with one or more embodiments of the present disclosure. [Figure 7B] FIG. 7B is a diagram illustrating example UL and DL subframes having an uplink DMRS, in accordance with one or more embodiments of the present disclosure. [Figure 7C]FIG. 7C is a diagram illustrating example UL and DL subframes having an uplink DMRS, in accordance with one or more embodiments of the present disclosure.

[0029] [Figure 8] FIG. 8 is a diagram illustrating example UL and DL subframes having an uplink DMRS according to a further embodiment of the present disclosure.

[0030] [Figure 9] FIG. 9 is a diagram that illustrates a schematic diagram of an example scheme for demodulating a PUCCH channel based on an uplink DMRS in accordance with one or more embodiments of the present disclosure.

[0031] [Figure 10A] FIG. 10A is a diagram illustrating example UL and DL subframes having an uplink DMRS in accordance with one or more embodiments of the present disclosure. [Figure 10B] FIG. 10B is a diagram illustrating example UL and DL subframes having an uplink DMRS in accordance with one or more embodiments of the present disclosure. [Figure 10C] FIG. 10C is a diagram illustrating example UL and DL subframes having an uplink DMRS in accordance with one or more embodiments of the present disclosure.

[0032] [Figure 11] FIG. 11 is a diagram that illustrates a schematic of a method for communication by a base station in accordance with one or more further embodiments of the present disclosure.

[0033] [Figure 12] FIG. 12 is a diagram that illustrates a schematic diagram of a method for communication by a user equipment according to one or more further embodiments of the present disclosure.

[0034] [Figure 13A]FIG. 13A is a diagram that illustrates example UL and DL subframes having a downlink DMRS in accordance with one or more further embodiments of the present disclosure. [Figure 13B] FIG. 13B is a diagram that illustrates example UL and DL subframes having a downlink DMRS in accordance with one or more further embodiments of the present disclosure.

[0035] [Figure 14] FIG. 14 is a block diagram that illustrates a schematic of a base station in accordance with one or more further embodiments of the present disclosure.

[0036] [Figure 15] FIG. 15 is a block diagram that illustrates a schematic of a user device according to one or more further embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following description, many specific details are set forth in order to provide a more comprehensive understanding of the present disclosure. However, it is apparent to those skilled in the art that the implementation of the present invention may not have these details. Furthermore, it should be understood that the present invention is not limited to the specific embodiments introduced herein. On the contrary, any combination of the following features and elements may be considered to implement and practice the present invention, regardless of whether they include different embodiments. For example, for illustrative purposes, the following is described in the context of a 5G cellular communication system, but those skilled in the art will recognize that one or more embodiments of the present disclosure may also be applied to various other types of cellular communication systems. Therefore, the following aspects, features, embodiments, and advantages are for illustrative purposes only and should not be construed as elements or limitations of the appended claims unless expressly specified in the claims.

[0038] User equipment (UE) may comprise or be implemented as or known as an access terminal, subscriber station, subscriber unit, mobile station, remote station, remote terminal, user terminal, user agent, user device, user station, or some other terminology.

[0039] In some implementations, a user equipment may include a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a personal digital assistant (PDA), a handheld device with wireless connectivity capabilities, a station (STA), or some other suitable processing device connected with a wireless modem. Thus, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or a smartphone), a computer (e.g., a laptop), a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a global positioning system device, or any other suitable device configured to communicate via a wireless or wired modem. In some aspects, a node is a wireless node. Such a wireless node may provide connectivity for or to, for example, a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

[0040] A base station (BS) may include a NodeB, a radio network controller (RNC), an eNodeB (eNB), a base station controller (BSC), a base transceiver station (BTS), a transceiver function (TF), a wireless router, a wireless transceiver, a basic service set (BSS), an extended service set (ESS), a radio base station (RBS), or some other terminology. Alternatively, a base station (BS) may be implemented or known as a NodeB, a radio network controller (RNC), an eNodeB (eNB), a base station controller (BSC), a base transceiver station (BTS), a transceiver function (TF), a wireless router, a wireless transceiver, a basic service set (BSS), an extended service set (ESS), a radio base station (RBS), or some other terminology.

[0041] As mentioned above, in order to reduce latency, it is necessary to reduce the number of symbols in one UL / DL TTI. However, in existing LTE technology, DMRS is introduced for each TTI and occupies at least one symbol. The DMRS overhead consumes radio resources significantly in both time and frequency domains, especially under the condition that the short TTI contains one or two symbols. Furthermore, the channel condition may not change much between short TTIs, especially for continuous scheduling or at high frequencies. In that sense, configuring DMRS with various physical channels in each TTI may cause radio resource efficiency problems.

[0042] To solve the above problem, one or more method and apparatus embodiments of the present disclosure aim to provide a solution for DMRS communication based on a shortened TTI. In this solution, UL / DL DMRS can be transmitted independently from the transmission of the respective physical channels, such as the physical uplink shared channel (PUSCH), the physical uplink control channel (PUCCH), and the physical downlink shared channel (PDSCH). In other words, the transmission of the DMRS is controlled by a means separate from the means for controlling the transmission of the respective physical channels. According to various embodiments of the present disclosure, the DMRS may be triggered to be transmitted dynamically. According to additional or alternative embodiments of the present disclosure, the transmission of the DMRS is set in one or more periodic patterns, which may be configured by higher layer signaling. The means for independently controlling the DMRS transmission may be applied in any suitable combination manner. As a result, for example, some TTIs may be transmitted without DMRS in the short TTI, and some TTIs may be controlled to transmit additional DMRS in the candidate DMRS positions.

[0043] 2A and 2B are schematic diagrams illustrating an example DMRS structure applicable to multiple short TTIs according to an embodiment of the present disclosure. For the purpose of simplicity, it is assumed that the TTI described with reference to FIG. 2A and 2B includes two or more symbols.

[0044] FIG. 2A shows a subframe structure in which the DMRS can be controlled to be transmitted only in some TTIs, while in some other TTIs there is no DMRS transmission.

[0045] An exemplary structure of a TTI with DMRS transmission is illustrated in dashed block 201. In one example, the DMRS may occupy one or more symbols of a TTI, and the remaining symbols of the TTI can be used to transmit data or control information depending on the type of physical channel currently scheduled in the TTI. In another example, the DMRS may be sparse in the time and / or frequency domain, e.g., occupying a portion of the frequency resources of one or more symbols in a TTI. The remaining symbols of the TTI can be used to transmit data or control information depending on the particular type of physical channel currently scheduled in the TTI.

[0046] The dashed block 202 provides an example structure of a TTI without DMRS. When there is no DMRS transmission in a TTI, in one example, the DMRS positions may be reserved or left empty even if the remaining symbols of the TTI are occupied by data or control information. In this example, these predefined radio resources are dedicated for transmitting DMRS and cannot be used for transmitting data or control information. If no DMRS is actually transmitted in this TTI, it is more efficient if data or control information can use these radio resources for DMRS transmission. In that example, all symbols of the TTI can be allocated for data or control information transmission. It should be understood that the DMRS structure for short TTI may be designed in the manner of any suitable combination of the above resource reservation mode and resource sharing mode.

[0047] FIG. 2B shows a subframe structure in which additional DMRS transmissions may be activated in some TTIs than in other regular TTIs.

[0048] As shown in Figure 2B, candidate DMRS positions may be predefined in a TTI. If DMRS transmission is triggered or configured by higher layer signaling, one or more DMRS positions may be selected from these candidate DMRS positions based on the trigger information or higher layer signaling. For backward compatibility, the new DMRS structure may support the fixed DMRS positions specified in existing LTE (as described with reference to Figures 1A-1C). Besides the fixed DMRS positions, additional DMRS may be transmitted as needed if additional DMRS are triggered or configured by higher layer signaling.

[0049] 3A and 3B are diagrams illustrating an example DMRS structure having candidate DMRS positions and fixed DMRS positions, in accordance with one or more embodiments of the present disclosure.

[0050] In some implementations, one additional DMRS can be configured (triggered or periodically) if frequency offset estimation is required. Otherwise, only the original fixed DMRS is transmitted (the historical frequency offset can be reused). FIG. 3A is a subframe structure with a fixed DMRS position, such as a legacy DMRS position. As shown in FIG. 3A, one TTI consists of 4 symbols, and one symbol of the fixed DMRS is shared by two consecutive TTIs. Additional DMRS positions may be arranged in each TTI. DMRS transmission may be activated in some additional DMRS positions by a separate control means, such as triggering by a designated trigger or transmitting in a periodic manner configured by higher layer signaling. For example, as shown in FIG. 3B, the additional DMRS positions in the first TTI are configured to transmit DMRS. In the next TTI shown, the additional DMRS positions are configured to not transmit DMRS, so that DMRS is transmitted only in the fixed positions in these TTIs.

[0051] 4A-4C are schematic diagrams illustrating example DMRS structures suitable for one symbol-based TTI in accordance with one or more embodiments of the present disclosure.

[0052] If the DMRS consists of only one symbol in one TTI, the DMRS may be multiplexed with data or control information (e.g., PUSCH, PUSCH, PDSCH) in the same symbol. Figures 4A and 4B show two different multiplexing methods for DMRS and data / control information. In the example shown in Figure 4A, the 1-symbol-based TTI with DMRS multiplexed with data / control information may be structured differently from those symbols without DMRS. The 1-symbol-based TTI occupies more frequency resources than symbols without DMRS multiplexed. In the example of Figure 4B, the 1-symbol-based TTI with DMRS is alternatively possible.

[0053] Figure 4C shows another example in which the DMRS is transmitted in a symbol different from the physical channel (PUSCH / PUCCH / PDSCH). As shown in Figure 4C, the DMRS occupies all resources of one symbol-based TTI and may be transmitted before data or control information. There is no multiplexing between the data / control information and the DMRS in one symbol-based TTI.

[0054] More generally, in an L-symbol-based TTI, the number of DMRSs (K, K>=0) may be dynamically configured, e.g., by downlink control information (DCI) and / or semi-statically configured, e.g., by higher layer signaling. Then, LK symbols are configured for data / control information. Alternatively, in one TTI, DMRSs may be sparse and multiplexed with data / control information in the frequency domain. In some implementations, different TTIs or TTI groups may have independent numbers of DMRSs. For example, the TTI groups may be consecutive TTIs or periodic TTIs with different periodicities and / or offsets. Also, the TTI group size may be configured, e.g., dynamically indicated in DCI or semi-statically indicated by higher layer information. Also, the independent number of DMRSs may be dynamically configured by DCI and / or semi-statically configured by higher layer signaling. As mentioned above, DMRSs may be configured in several candidate positions. Additionally or alternatively, the newly triggered DMRS may have a different pattern than the configured pattern.

[0055] 5 is a diagram that illustrates a method 500 for communication by a base station according to one or more embodiments of the present disclosure. The method 500 of FIG. 5 describes a process of uplink DMRS transmission from the perspective of the base station. As shown in FIG. 5, in step S510, the base station receives an uplink DMRS from a user equipment in an uplink TTI of an uplink subframe. The uplink subframe supports two or more uplink TTIs.

[0056] The transmission of the uplink DMRS is controlled independently from the transmission of the uplink physical channel. At least one uplink TTI supported by an uplink subframe may be configured to transmit only uplink control information and / or uplink data without having an uplink DMRS. The uplink DMRS may adopt any suitable DMRS structure as described above with reference to Figures 1-4.

[0057] According to one or more embodiments of the present disclosure, the method 500 may further include a step (not shown) of transmitting an uplink DMRS trigger to the user equipment to enable transmission of the uplink DMRS in the uplink TTI of the uplink subframe. The uplink DMRS trigger may be carried in the downlink TTI of the downlink subframe supporting two or more downlink TTIs. As an example, the uplink DMRS trigger may be one or more bits to enable transmission and / or configuration of the corresponding DMRS. According to one or more embodiments of the present disclosure, the uplink DMRS trigger may include information on how to configure the uplink DMRS transmitted from the user equipment to the base station. As discussed with reference to FIGS. 2-4, several types of DMRS configuration information may be included in the trigger. As an example, the uplink DMRS trigger may include at least one of the following information, but is not limited to: the number of symbols occupied by the uplink DMRS; the uplink DMRS time to be triggered; resource allocation for the uplink DMRS; and candidate symbol positions to be occupied by the uplink DMRS in the uplink TTI.

[0058] According to one or more additional or alternative embodiments of the present disclosure, the uplink DMRS may be received from the user equipment periodically, for example, the uplink DMRS being controlled by higher layer signaling to be transmitted in a periodic manner.

[0059] 6 is a diagram illustrating a method for communication by a user equipment according to one or more embodiments of the present disclosure. The method 600 of FIG. 6 describes a process of uplink DMRS transmission from the perspective of the user equipment. As shown in FIG. 6, in step S610, the user equipment transmits an uplink DMRS to a base station in an uplink TTI of a UL subframe that supports two or more uplink TTIs.

[0060] The transmission of the uplink DMRS is controlled independently from the transmission of the uplink physical channel. At least one uplink TTI supported by an uplink subframe may be configured to transmit only uplink control information and / or uplink data without having an uplink DMRS. The DMRS may adopt any suitable DMRS structure as described with reference to Figures 1-4.

[0061] Similarly, according to one or more embodiments of the present disclosure, the method 600 may further include receiving an uplink DMRS trigger from the base station (not shown) to enable transmission of the uplink DMRS in an uplink TTI of the uplink subframe. The uplink DMRS trigger may be carried in a downlink TTI of a downlink subframe supporting two or more downlink TTIs. As an example, the uplink DMRS trigger may be one or more bits to enable transmission and / or configuration of the corresponding DMRS. According to one or more embodiments of the present disclosure, the uplink DMRS trigger may include information on how to configure the uplink DMRS transmitted from the user equipment to the base station. As described with reference to FIGS. 2-4, several types of DMRS configuration information may be included in the trigger. As an example, the trigger may indicate which candidate symbol position the uplink DMRS occupies in the uplink TTI. The user equipment may trigger transmission of the uplink DMRS according to the configuration information indicated in the received trigger.

[0062] According to one or more additions or alternatives to the present disclosure, the uplink DMRS may be received from the user equipment periodically, for example controlled to be transmitted in a periodic manner by higher layer signaling.

[0063] 7A-7C are diagrams illustrating schematic diagrams of example UL and DL subframes having an uplink DMRS in which the uplink DMRS is transmitted during an uplink data scheduling process, according to one or more embodiments of the present disclosure.

[0064] During the uplink data scheduling process, the base station may transmit the uplink DMRS to the user equipment by including it in the DCI for uplink data scheduling (i.e., UL grant). As an example, one or more bits may be added to the existing DCI format 0 and / or format 4 to indicate an uplink DMRS trigger. In that case, the downlink TTI is configured to schedule both the uplink data (PUSCH) and the triggered uplink DMRS.

[0065] As shown in FIG. 7A, the base station transmits DCI for uplink data scheduling (i.e., UL grant) in DL TTI_n. In response, the user equipment transmits uplink data transmission (i.e., PUSCH) in UL TTI_n+k, where k is an integer, which may be typically set to 4 in an FDD system, and may be predefined according to an uplink / downlink configuration in a TDD system. When detecting an uplink DMRS trigger included in the DCI received in DL TTI_n, the user equipment may transmit an uplink DMRS in UL TTI_n+k according to the DMRS configuration information included in the trigger. In this way, the uplink DMRS and PUSCH share the same UL TTI_n+k. As described in FIG. 2-4, the uplink DMRS and uplink data may be multiplexed in the frequency domain, and / or the uplink DMRS may occupy M symbols of UL TTI_n+k, and the remaining symbols of UL TTI_n+k may be used to transmit the scheduled uplink data. As a result, the PUSCH for UL TTI_n+k may be shortened to occupy (LM) symbols, or the PUSCH and DMRS may be staggered in the frequency domain as shown in Figures 4A or 4B.

[0066] If the channel condition changes slightly, the base station may decide not to trigger the transmission of the uplink DMRS, and the channel condition estimation can be obtained based on the previous DMRS. For example, in DL TTI_n+1, DL TTI_n+2, the DCI does not include the trigger. Therefore, the user equipment transmits scheduled uplink data in UL TTI_n+k+1, UL TTI_n+k+2, where the UL DMRS is not transmitted.

[0067] FIG. 7B shows another example for handling a situation where a base station schedules uplink data and triggers uplink DMRS in the same DL TTI. In this example, the uplink DMRS may be configured to be transmitted in advance. As shown in FIG. 7B, it may be predefined that when receiving an uplink DMRS trigger together with a DCI in DL TTI_n, the user equipment can transmit the triggered DMRS in UL TTI_n+k-1. Then, in UL TTI_n+k, the user equipment transmits the uplink data scheduled by the DCI. Here, n represents the TTI number of the downlink TTI in which the downlink control information for uplink data scheduling is transmitted, and k is a predefined integer representing a predefined number of TTIs for scheduling.

[0068] FIG. 7C shows yet another example for handling a situation where a base station schedules uplink data and triggers an uplink DMRS in the same DL TTI. In this example, the transmission of the scheduled uplink data may be delayed one TTI after the uplink DMRS is transmitted. As shown in FIG. 7C, it may be predefined that when receiving an uplink DMRS trigger with a DCI in DL TTI_n, the user equipment may transmit the triggered DMRS in UL TTI_n+k. Then, in UL TTI_n+k+1, the user equipment transmits the uplink data scheduled by the DCI. Here, n represents the TTI number of the downlink TTI in which the downlink control information for uplink data scheduling is transmitted, and k is a predefined integer representing a predefined number of TTIs for scheduling. In those TTIs without DMRS transmission, the base station may demodulate the received PUSCH with reference to the previously received uplink DMRS.

[0069] It should be understood by those skilled in the art that similar schemes as described with reference to Figures 7A-7C may also be applied to these embodiments in which the periodic uplink DMRS is semi-statically configured by higher layer signaling to resolve issues caused by collisions between uplink DMRS and uplink data (e.g., PUSCH) transmissions.

[0070] In some embodiments, the uplink DMRS trigger may be received separately from the DCI for uplink data scheduling, i.e., the uplink DMRS trigger may be transmitted separately in a TTI where there is no DCI for uplink scheduling.

[0071] 8 is a schematic diagram of exemplary UL and DL subframes with uplink DMRS according to a further embodiment of the present disclosure, where an uplink DMRS trigger is transmitted separately in DL TTI_n. As shown in FIG. 8, in such an embodiment, the triggered uplink DMRS does not collide with scheduled uplink data. For example, in response to a trigger received in DL TTI_n, the user equipment may transmit an uplink DMRS in UL TTI_n+k. And in response to a DCI for uplink data scheduling received in DL TTI_n+1, the user equipment may transmit scheduled uplink data in UL TTI_n+k+1.

[0072] In implementation, if the user equipment needs PUSCH transmission, after the schedule request, the base station may trigger uplink DMRS by sending an uplink DMRS trigger in a separate TTI. The uplink DMRS trigger may include a resource allocation region. Since the user equipment may refer to the resource allocation region of the uplink DMRS trigger to perform subsequent uplink data transmission, after the DMRS trigger, the base station can schedule PUSCH by sending a compact DCI for uplink data scheduling.

[0073] During the downlink data scheduling process, the uplink DMRS may be required to demodulate an uplink control channel (e.g., PUCCH). Thus, according to one or more embodiments of the present disclosure, the base station may transmit the uplink DMRS to the user equipment as needed to trigger the transmission of the uplink DMRS. Additionally or alternatively, the uplink DMRS may be controlled to be transmitted in a periodic manner, for example, by higher layer signaling, to meet the requirement of PUCCH demodulation.

[0074] 9 is a diagram that illustrates an example scheme for demodulating a PUCCH channel based on an uplink DMRS in accordance with one or more embodiments of the present disclosure. As illustrated in FIG. 9, the uplink DMRS is transmitted independently of the PUCCH. For example, the periodicity and / or offset of the uplink DMRS and the PUCCH (including CQI / PMI / RI) may be different. In another example, the uplink DMRS may be triggered by the base station, e.g., in DCI information, so that the uplink DMRS is aperiodic.

[0075] Since the PUCCH is modulated with the same ZC sequence or transformed similarly to the uplink DMRS, after demodulating the PUCCH information, the remaining sequence can be used as a demodulation reference signal for channel estimation and provide a reference for the next subsequent PUCCH and / or uplink data. That is, the physical uplink control channel may be demodulated based on the uplink DMRS. And one or more subsequent physical uplink control channels may be demodulated based on the previously received uplink DMRS and / or the demodulated physical uplink control channel.

[0076] 10A-10C are diagrams illustrating example UL and DL subframes having an uplink DMRS according to one or more embodiments of the present disclosure, in which the uplink DMRS is transmitted during a downlink data scheduling process.

[0077] In the downlink data scheduling process, the user equipment needs to send ACK / NACK feedback information to the base station in the PUCCH. Since the ACK / NACK feedback information is related to the downlink data scheduling, both the user equipment and the base station know in which UL TTI the ACK / NACK feedback information is sent. If the base station needs the uplink DMRS from the user equipment to demodulate the ACK / NACK feedback information, the base station may trigger the transmission of the uplink DMRS by sending a downlink DMRS trigger, or may configure a periodic uplink DMRS by semi-static radio resource control (RRC) signaling.

[0078] According to one or more embodiments of the present disclosure, transmission of an uplink DMRS may be triggered by an uplink DMRS trigger. The base station may transmit the uplink DMRS trigger together with a DCI for downlink data scheduling (i.e., DL schedule) in a downlink TTI. As an example, one or more bits may be added to an existing DCI for downlink data scheduling to represent the uplink DMRS trigger. In that case, the downlink TTI is configured to schedule both the downlink data (PDSCH) and the triggered uplink DMRS.

[0079] As shown in FIG. 10A, the base station transmits DCI for downlink data scheduling (i.e., DL grant) in DL TTI_n. In response, the user equipment transmits ACK / NACK feedback for downlink data scheduling (in PUCCH) in UL TTI_n+k, where k is an integer and may be typically set as 4 in an FDD system, or may be predefined according to an uplink / downlink configuration in a TDD system. When detecting an uplink DMRS trigger included in the DCI received in DL TTI_n, the user equipment may transmit an uplink DMRS in UL TTI_n+k according to the DMRS configuration information included in the trigger. In this way, the uplink DMRS and the ACK / NACK feedback information share the same UL TTI_n+k. As described in FIGS. 2-4, the uplink DMRS and the ACK / NACK feedback information may be multiplexed in the frequency domain, and / or the uplink DMRS occupies M symbols of the UL TTI_n+k, and the remaining symbols of the UL TTI_n+k are used to transmit the ACK / NACK feedback information. As a result, the PUCCH in UL TTI_n+k may be shortened to occupy (LM) symbols, or the PUCCH and DMRS may be staggered in the frequency domain as shown in Figures 4A or 4B.

[0080] If there is no need to estimate the channel state, the base station may decide not to trigger the transmission of the uplink DMRS. For example, in DL TTI_n+1, DL TTI_n+2, the trigger is not included in the DCI. Therefore, the user equipment transmits scheduled ACK / NACK feedback information in UL TTI_n+k+1, UL TTI_n+k+2, where no UL DMRS is transmitted. In these TTIs without DMRS transmission, the base station may demodulate the received ACK / NACK feedback information with reference to the previously received uplink DMRS.

[0081] FIG. 10B illustrates another example for handling a situation in which a base station schedules downlink data and triggers uplink DMRS in the same DL TTI. In this example, the uplink DMRS may be configured to be transmitted in advance. As shown in FIG. 10B, it may be predefined that when receiving an uplink DMRS trigger together with a DCI for downlink scheduling in DL TTI_n, the user equipment can transmit the triggered DMRS in UL TTI_n+k-1. Then, in UL TTI_n+k, the user equipment transmits ACK / NACK feedback information for downlink data scheduling. Here, n represents the TTI number of the downlink TTI in which downlink control information for downlink data scheduling is transmitted, and k is a predefined integer representing a predefined number of TTIs for scheduling.

[0082] FIG. 10C illustrates yet another example for handling a situation where a base station schedules downlink data and triggers an uplink DMRS in the same DL TTI. In this example, the transmission of corresponding ACK / NACK feedback information for downlink data scheduling may be delayed one TTI after the uplink DMRS is transmitted. As shown in FIG. 10C, it may be predefined that when receiving an uplink DMRS together with downlink data in DL TTI_n, the user equipment may first transmit the triggered DMRS in UL TTI_n+k. Then, in UL TTI_n+k+1, the user equipment transmits ACK / NACK feedback information for the downlink data, where n represents the TTI number of the downlink TTI in which the downlink control information for downlink data scheduling is transmitted, and k is a predefined integer representing a predefined number of TTIs for scheduling.

[0083] Here, it should be understood by those skilled in the art that in order to solve the problem caused by collision between the transmission of uplink DMRS and ACK / NACK feedback information (i.e., PUCCH), a similar scheme to that described with reference to Figures 10A to 10C may be applied to these embodiments in which the periodic uplink DMRS is semi-statically configured by higher layer signaling.

[0084] According to other embodiments of the present disclosure, the uplink DMRS trigger may not be carried in the DCI for downlink data scheduling. The base station may use a separate DL TTI to transmit the uplink DMRS trigger. In such an embodiment, the triggered uplink DMRS may not collide with the ACK / NACK feedback information for the downlink data scheduling. For example, in response to a trigger received in DL TTI_n, the user equipment may transmit the uplink DMRS in UL TTI_n+k. And in response to the downlink data received in DL TTI_n+1, the user equipment may transmit the scheduled uplink data in UL TTI_n+k+1.

[0085] 11 is a diagram that illustrates a method 1100 for communication by a base station according to one or more further embodiments of the present disclosure in the downlink case. The method 1100 of FIG. 11 describes a process of downlink DMRS transmission from the perspective of the base station. As shown in FIG. 11, in step S1110, the base station transmits a downlink DMRS to a user equipment in a downlink TTI of a downlink subframe. The downlink subframe supports two or more downlink TTIs.

[0086] 12 is a diagram that illustrates a schematic of a method for communication by a user equipment according to one or more further embodiments of the present disclosure. Method 1200 of FIG. 12 describes a process of downlink DMRS transmission from the perspective of a user equipment. As shown in FIG. 12, in step S1210, the user equipment receives an uplink demodulation reference signal (DMRS) from a base station in an uplink transmission time interval (TTI) of an uplink subframe that supports two or more TTIs.

[0087] The transmission of the downlink DMRS is controlled independently from the transmission of the downlink physical channel (e.g., PDSCH, etc.). In this way, it is possible that some downlink TTIs supported by a downlink subframe may be configured to transmit only downlink control information and / or downlink data without having a downlink DMRS. The downlink DMRS may adopt any suitable DMRS structure, such as those described with reference to Figures 1-4.

[0088] According to one or more embodiments of the present disclosure, a downlink DMRS trigger for enabling transmission of a downlink DMRS may be transmitted from a base station to a user equipment. As an example, the downlink DMRS trigger may be one or more bits for enabling transmission and / or configuration of a corresponding DMRS. As described with reference to FIGS. 2-4, several types of DMRS configuration information may be included in the trigger. As an example, the downlink DMRS trigger may include information indicating at least one of the following items, but is not limited to: the number of symbols occupied by the downlink DMRS; the time of the triggered downlink DMRS; the resource allocation for the downlink DMRS; and the candidate symbol positions that the downlink DMRS occupies in the downlink TTI.

[0089] 13A-13B are diagrams illustrating example UL and DL subframes having a downlink DMRS according to one or more further embodiments of the present disclosure, where the downlink DMRS is enabled by a downlink DMRS trigger.

[0090] According to one or more embodiments of the present disclosure, a downlink DMRS trigger for enabling transmission of the downlink DMRS may be transmitted together with the DCI for downlink data scheduling in the same downlink TTI. As shown in FIG. 13A, in DL TTI_n, the user equipment may transmit the downlink DMRS to the user equipment by including the downlink DMRS in the DCI for downlink data scheduling. In some implementations, at least a portion of the downlink DMRS may be sparse-multiplexed with the downlink data in the downlink TTI of the downlink subframe. Additionally or alternatively, the downlink DMRS may occupy one or more symbols of the downlink TTI, and the remaining symbols may be used for downlink data transmission. Since the user equipment may demodulate the downlink data transmitted in the downlink TTI_n+1 based on the previously received downlink DMRS, in the next downlink TTI_n+1, the base station may determine not to trigger transmission of the downlink DMRS.

[0091] According to additional or alternative embodiments, a downlink DMRS trigger for enabling transmission of a downlink DMRS may be transmitted separately from a DCI for downlink data scheduling. As shown in FIG. 13B, in a downlink TTI_n, a DMRS trigger is transmitted to indicate downlink DMRS configuration information to a user equipment. In the same TTI_n, the base station transmits a downlink DMRS according to the configuration information included in the downlink DMRS trigger. According to some implementations, since the user equipment may refer to the resource allocation region of the downlink DMRS trigger to perform a subsequent downlink data transmission, the base station may schedule a PDSCH in at least one subsequent TTI by transmitting a compact DCI for downlink data scheduling, taking into account the resource allocation information included in the downlink DMRS trigger.

[0092] To communicate the downlink DMRS independently of scheduling a physical downlink data channel (e.g., PDSCH), according to one or more additional or alternative embodiments of the present disclosure, the downlink DMRS may be transmitted from the base station to the user equipment periodically. The downlink DMRS may be controlled to be transmitted in a periodic manner, for example, by higher layer signaling.

[0093] FIG. 14 is a block diagram that illustrates a schematic of a base station in accordance with one or more further embodiments of the present disclosure.

[0094] As shown in Figure 14, a base station 1400 is configured to communicate with one or more user devices based on a downlink and uplink subframe structure having a short TTI. The base station 1400 comprises a transmitter 1410 and a receiver 1420. The base station 600 may also comprise a suitable radio frequency transceiver (not shown in Figure 14) that may be selectively coupled to one or more antennas (not shown in Figure 14) used to transmit signals to and receive signals from the one or more user devices.

[0095] The base station 1400 includes a processor 141, which may include one or more microprocessors or microcontrollers as well as other digital hardware, which may include digital signal processors (DSPs), dedicated digital logic, etc. The processor 141 may be configured to execute program code stored in a memory (not shown in FIG. 14), which may include one or more types of memory, such as read-only memory (ROM), random access memory, cache memory, flash memory devices, optical storage devices, etc. The program code stored in the memory includes program instructions for implementing one or more telecommunications and / or data communication protocols, and instructions for implementing one or more techniques described herein in some embodiments. In some implementations, the processor 141 may be used to cause the transmitter 1410 and the receiver 1420 to perform corresponding functions according to one or more embodiments of the present disclosure.

[0096] According to an embodiment of one aspect of the present disclosure, the receiver 1420 is configured to receive an uplink DMRS from a user equipment in an uplink TTI of an uplink subframe supporting two or more uplink TTIs, where at least one uplink TTI supported by the uplink subframe is configured to transmit only uplink control information and / or uplink data without an uplink DMRS.

[0097] According to one or more embodiments of this aspect of the disclosure, the transmitter 1510 may be configured to transmit an uplink DMRS trigger to the user equipment to enable transmission of the uplink DMRS in an uplink TTI of an uplink subframe. The uplink DMRS trigger may be carried in a downlink TTI of a downlink subframe supporting two or more downlink TTIs. In some embodiments, the uplink DMRS trigger may include information indicating at least one of the following: the number of symbols the uplink DMRS occupies; the time of the triggered uplink DMRS; the resource allocation for the uplink DMRS; and the candidate symbol positions the uplink DMRS occupies in the uplink TTI.

[0098] According to one or more embodiments of this aspect of the disclosure, the uplink DMRS trigger may be included in the downlink control information for uplink data scheduling, or alternatively, the uplink DMRS trigger may be received separately from the downlink control information for uplink data scheduling.

[0099] According to one or more embodiments of this aspect of the disclosure, the uplink DMRS may be received periodically from the user equipment.

[0100] In some embodiments of this aspect of the disclosure, the receiver 1420 may be further configured to receive uplink data scheduled in uplink TTI n+k at which the uplink DMRS is received; or may be further configured to receive uplink data scheduled in uplink TTI n+k immediately following uplink TTI n+k-1 at which the uplink DMRS is received; or may be further configured to receive uplink data scheduled in uplink TTI n+k+1 immediately following uplink TTI n+k at which the uplink DMRS is received, where n represents a TTI number of a downlink TTI at which downlink control information for uplink data scheduling is transmitted and k represents a predefined number of TTIs for uplink scheduling.

[0101] According to one or more embodiments of this aspect of the disclosure, the physical uplink control channel may be demodulated based on the uplink DMRS, and in some embodiments, a further physical uplink control channel may be demodulated based on the uplink DMRS and / or the demodulated physical uplink control information.

[0102] According to one or more embodiments of this aspect of the disclosure, the transmitter 1410 may be configured to transmit an uplink DMRS trigger included in downlink control information for downlink data scheduling.

[0103] According to one or more embodiments of this aspect of the disclosure, the receiver 1420 may be further configured to receive acknowledgement (ACK) / non-acknowledgement (NACK) feedback information for downlink data scheduling in uplink TTI n+k at which the uplink DMRS is received; or may be further configured to receive ACK / NACK feedback information for downlink data scheduling in uplink TTI n+k immediately after uplink TTI n+k-1 at which the uplink DMRS is received; or may be further configured to receive ACK / NACK feedback information for downlink data scheduling in uplink TTI n+k+1 immediately after uplink TTI n+k at which the uplink DMRS is received, where n represents a TTI number of the downlink TTI at which downlink data for the downlink data scheduling is transmitted, and k represents a predefined number of TTIs for downlink scheduling.

[0104] According to one or more embodiments of this aspect of the disclosure, the transmitter 1410 may be configured to transmit the uplink DMRS trigger separately from downlink control information for downlink data scheduling.

[0105] According to an embodiment of another aspect of the present disclosure, the transmitter 1410 may be configured to transmit a downlink DMRS to a user equipment in a downlink TTI of a downlink subframe supporting two or more downlink TTIs, where at least one downlink TTI supported by the downlink subframe is configured to transmit only downlink control information and / or downlink data without having a downlink DMRS.

[0106] According to embodiments of this aspect of the disclosure, the transmitter 1410 may be configured to transmit a downlink DMRS trigger to enable transmission of the downlink DMRS included in downlink control information for downlink data scheduling. In some embodiments, the transmitter 1410 may be further configured to transmit at least a portion of the downlink DMRS sparse-multiplexed with the downlink data in a downlink TTI of a downlink subframe.

[0107] According to an alternative embodiment of this aspect of the disclosure, the transmitter 1410 may be configured to transmit a downlink DMRS trigger to enable transmission of the downlink DMRS separately from downlink control information for downlink data scheduling.

[0108] According to an embodiment of this aspect of the disclosure, the downlink DMRS trigger may include information indicating at least one of the following: the number of symbols occupied by the downlink DMRS; the time of the triggered downlink DMRS; the resource allocation for the downlink DMRS; and the candidate symbol positions that the downlink DMRS occupies in the uplink TTI.

[0109] According to an embodiment of this aspect of the disclosure, the transmitter 1410 may be configured to periodically transmit a downlink DMRS to a user equipment.

[0110] FIG. 15 is a block diagram that illustrates a schematic of a user device in accordance with one or more embodiments of the present disclosure.

[0111] As shown in Fig. 15, user equipment 1500 is configured to communicate with a base station based on a downlink and uplink subframe structure having a short TTI. User equipment 1500 includes a receiver 1510 and a transmitter 1520. User equipment 1500 may also include a number of suitable radio frequency transceivers (not shown in Fig. 15) that may be operatively coupled to one or more antennas (not shown in Fig. 15) used to transmit signals to and receive signals from other wireless nodes, such as a NodeB, eNodeB, or WiFi AP.

[0112] The user device 1500 includes a processor 151, which may include one or more microprocessors or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), dedicated digital logic, and the like. The processor 151 may be configured to execute program code stored in a memory (not shown in FIG. 15), which may include one or several types of memory, such as a read-only memory (ROM), a random access memory, a cache memory, a flash memory device, an optical storage device, and the like. The program code stored in the memory includes program instructions for implementing one or more telecommunications and / or data communication protocols, and in some embodiments, instructions for implementing one or more techniques described herein. In some implementations, the processor 151 may be used to cause the receiver 1510 and the transmitter 1520 to perform corresponding functions in accordance with one or more embodiments of the present disclosure.

[0113] According to an embodiment of one aspect of the present disclosure, the transmitter 1420 is configured to transmit an uplink DMRS to the base station in an uplink TTI of an uplink subframe supporting two or more uplink TTIs, where at least one uplink TTI supported by the uplink subframe is configured to transmit only uplink control information and / or uplink data without an uplink DMRS.

[0114] According to an embodiment of this aspect of the disclosure, the receiver 1500 is configured to receive an uplink DMRS trigger from a base station for enabling transmission of an uplink DMRS in an uplink TTI of an uplink subframe. The uplink DMRS trigger may be carried in a downlink TTI of a downlink subframe supporting two or more downlink TTIs. According to some embodiments, the uplink DMRS trigger may include information indicating at least one of the following: the number of symbols the uplink DMRS occupies; the time of the triggered uplink DMRS; the resource allocation for the uplink DMRS; and the candidate symbol positions the uplink DMRS occupies in the uplink TTI.

[0115] According to embodiments of this aspect of the disclosure, the receiver 1510 may be configured to receive the uplink DMRS trigger included in the downlink control information for uplink data scheduling. In some alternative embodiments, the receiver 1510 may be configured to receive the uplink DMRS trigger separately from the downlink control information for uplink data scheduling.

[0116] According to an embodiment of this aspect of the disclosure, the transmitter 1520 may be configured to periodically transmit the uplink DMRS to the base station.

[0117] In some embodiments of this aspect of the disclosure, the transmitter 1520 may be further configured to transmit the scheduled uplink data in uplink TTI n+k at which the uplink DMRS is received; or may be further configured to transmit the scheduled uplink data in uplink TTI n+k immediately following uplink TTI n+k-1 at which the uplink DMRS is received; or may be further configured to transmit the scheduled uplink data in uplink TTI n+k+1 immediately following uplink TTI n+k at which the uplink DMRS is received, where n represents the TTI number of the downlink TTI at which the downlink control information for uplink scheduling is transmitted and k represents a predefined number of TTIs for uplink scheduling.

[0118] According to one or more embodiments of this aspect of the disclosure, the user equipment 1500 may be configured to demodulate a physical uplink control channel based on the uplink DMRS. In some embodiments, the user equipment 1500 may be configured to demodulate a further physical uplink control channel based on the uplink DMRS and / or the demodulated uplink control channel.

[0119] According to one or more embodiments of this aspect of the disclosure, the receiver 1510 may be configured to receive an uplink DMRS trigger included in downlink control information for downlink data scheduling.

[0120] According to one or more embodiments of this aspect of the disclosure, the transmitter may be further configured to transmit ACK / NACK feedback information for downlink data scheduling in uplink TTI n+k at which the uplink DMRS is received; or may be further configured to transmit ACK / NACK feedback information for downlink data scheduling in uplink TTI n+k immediately following uplink TTI n+k-1 at which the uplink DMRS is received; or may be further configured to transmit ACK / NACK feedback information for downlink data scheduling in uplink TTI n+k+1 immediately following uplink TTI n+k at which the uplink DMRS is received, where n represents a TTI number of the downlink TTI at which downlink data for the downlink data scheduling is transmitted, and k represents a predefined number of TTIs for downlink scheduling.

[0121] According to one or more embodiments of this aspect of the disclosure, the receiver 1510 may be configured to receive the uplink DMRS trigger separately from downlink control information for downlink data scheduling.

[0122] According to an embodiment of another aspect of the present disclosure, the receiver 1510 is configured to receive a downlink DMRS from a base station in a downlink TTI of a downlink subframe supporting two or more downlink TTIs, and at least one downlink TTI after the downlink TTI in which the downlink DMRS is received is configured not to transmit any downlink DMRS.

[0123] According to embodiments of this aspect of the disclosure, the receiver 1510 may be configured to receive a downlink DMRS trigger to enable transmission of the downlink DMRS included in downlink control information for downlink data scheduling. In some embodiments, the receiver 1510 may be configured to receive at least a portion of the downlink DMRS sparse-multiplexed with the downlink data in a downlink TTI of a downlink subframe.

[0124] According to an embodiment of this aspect of the disclosure, the receiver 1510 may be configured to receive a downlink DMRS trigger to enable transmission of the downlink DMRS separately from downlink control information for downlink data scheduling.

[0125] According to an embodiment of this aspect of the present disclosure, the downlink DMRS trigger may include information indicating at least one of the following: the number of symbols occupied by the downlink DMRS; the time of the triggered downlink DMRS; the resource allocation for the downlink DMRS; and the candidate symbol positions that the downlink DMRS occupies in the uplink TTI.

[0126] According to an embodiment of this aspect of the disclosure, the receiver 1510 may be configured to periodically receive a downlink DMRS from a base station.

[0127] In general, various exemplary embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware and other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, although the disclosure is not limited thereto. Although various aspects of the exemplary embodiments of the disclosure are shown and described as block diagrams and signaling diagrams, it is understood that these blocks, devices, systems, techniques, or methods described in the disclosure may be implemented, by way of non-limiting examples, in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0128] As such, it should be understood that at least some aspects of exemplary embodiments of the present disclosure may be implemented with a variety of components such as integrated circuit chips and modules, etc. As is well known in the art, the design of integrated circuits is, for the most part, a highly automated process.

[0129] The present disclosure may also be embodied in a computer program product that includes all the features capable of performing the methods described herein, and that may perform the methods when loaded into a computer system.

[0130] Although the present disclosure has been particularly shown and described with reference to preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the spirit and scope of the present disclosure.

Claims

1. A receiving unit that receives a radio resource control signal including first information indicating information regarding the presence or absence of transmission of an additional demodulation reference signal (DMRS) for a physical uplink shared channel (PUSCH) from a base station device, The receiving unit receives, from the base station device, DCI (Downlink Control Information) including second information indicating a time interval; The processing unit determines a position of the additional DMRS to be transmitted in addition to a first DMRS for the PUSCH transmitted by the user equipment at a first position within the time interval, based on the first information and the second information. User equipment.

2. The processing unit determines a position and a number of the additional DMRSs to be transmitted by the user equipment within the time interval based on the first information and the second information. The user device of claim 1.

3. The first DMRS for the PUSCH is transmitted at a first position within the time interval regardless of the first information and the second information. The user device of claim 1.

4. The number of the first DMRS is one, and the position of the additional DMRS is after the first position. The user device of claim 1.

5. Receive a radio resource control signal including first information indicating information regarding the presence or absence of transmission of an additional demodulation reference signal (DMRS) for a physical uplink shared channel (PUSCH) from a base station device; receiving, from the base station device, downlink control information (DCI) including second information indicating a time interval; Based on the first information and the second information, a position of the additional DMRS to be transmitted in addition to a first DMRS for the PUSCH transmitted by the user equipment at a first position within the time interval is determined. A method for a user device.

6. A transmitter that transmits a radio resource control signal including first information indicating information regarding the presence or absence of transmission of an additional demodulation reference signal (DMRS) for a physical uplink shared channel (PUSCH) to a user equipment, The transmitter transmits, to the user equipment, DCI (Downlink Control Information) including second information indicating a time interval; The position of the additional DMRS to be transmitted in addition to the first DMRS for the PUSCH transmitted by the user equipment at the first position within the time interval is determined based on the first information and the second information. Base station equipment.

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