Reference signals with different resource densities

Abstract

A method of wireless communication includes transmitting an indication of N regions in a resource grid defined by transmission resources in a frequency domain and / or time resources in a time domain from a first communication device to a second communication device, and communicating a reference signal between the first communication device and the second communication device according to density information. Here, each of the N regions has a corresponding resource density indicating a density of time-frequency resources configured for reference signal transmission, and N is an integer greater than 1.

Description

Technical Field

[0001] This document relates to systems, devices, and techniques for wireless communication.

Background Art

[0002] Currently, efforts are underway to define a next-generation wireless communication network that provides various techniques for enhancing deployment flexibility, supporting a large number of devices and services, and efficiently utilizing bandwidth.

Summary of the Invention

Means for Solving the Problems

[0003] Various methods and apparatuses for achieving different reference signal densities in a wireless communication system are described.

[0004] In one exemplary aspect, a method of wireless communication is disclosed. The method includes transmitting an indication of N regions within a resource grid defined by transmission resources in the frequency domain and / or time resources in the time domain from a first communication device to a second communication device, and communicating a reference signal between the first communication device and the second communication device according to density information. Here, each of the N regions has a corresponding resource density indicating the density of time-frequency resources configured for reference signal transmission, and N is an integer greater than 1.

[0005] In another exemplary aspect, a method of wireless communication is disclosed. The method includes receiving, by a second communication device from a first communication device, an indication of N regions within a resource grid defined by transmission resources in a frequency domain and / or time resources in a time domain, and communicating a reference signal between the first communication device and the second communication device according to density information. Here, each of the N regions has a corresponding resource density indicating a density of time-frequency resources configured for reference signal transmission, and N is an integer greater than 1.

[0006] In yet another exemplary aspect, a wireless communication device including a processor is disclosed. The processor is configured to implement the methods described herein.

[0007] In other exemplary aspects, the various techniques described herein may be embodied as processor-executable code and stored in a computer-readable program medium.

[0008] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the specification text and drawings, as well as from the claims.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0022] The section headings in this document are used only to improve readability and do not limit the disclosed embodiments and the scope of the technology of each section to that section only. Further, some embodiments are described in relation to the 3rd Generation Partnership Project (3GPP (registered trademark)) New Radio (NR) standard ("5G") for ease of understanding, and the described technology may be implemented in different wireless systems implementing protocols other than the 5G protocol.

[0023] In existing NR systems, various reference signals, such as DM-RS (Demodulation reference signals), CSI-RS (Channel State Information Reference Signal), and SRS (Sounding Reference Signal), are defined to measure interference in wireless communication. A typical reference signal is a signal whose characteristics are predefined so that the receiver of the reference signal knows what to expect. Existing reference signals are typically configured to have the same frequency density across the frequency domain. For example, the frequency density can be measured with respect to the number of subcarriers or resource blocks allocated to the reference signal per unit of frequency.

[0024] However, in scenarios with different interferences across the frequency domain, such as sub-band full-duplex and dynamic time-division duplexing (TDD), constructing a reference signal with the same frequency density across the entire frequency bandwidth may cause undesirable resource overhead. For example, in a frequency spectrum with strong or dynamic interference, it may be better to have a high frequency density assigned to reference signal transmission so that, for example, that portion of the frequency spectrum can be characterized and calibrated more accurately and quickly. Conversely, in a frequency spectrum region with low and stable interference, it may be more appropriate to have a low frequency density of the reference signal in order to save transmission resources for other transmissions such as data transmission. Similar problems exist in the time domain when the interference varies across the time domain. However, today's systems are unable to recognize such a need, and as a result, do not provide a way in which a wireless communication system can configure and use reference signal transmissions with various resource densities, such as time density or frequency density.

[0025] This document discloses, among other things, various techniques that can be used by embodiments to construct and use reference signals with different frequency or time resource densities.

[0026] 1. Initial Discussion

[0027] In wireless communication, it is necessary to filter the signal before transmission through the medium so that the transmitted signal power can be restricted within the desired frequency range. Ideally, there should be no leakage signal outside the desired frequency range after filtering. However, due to limitations in technology and implementation complexity, typically, there exists non-zero signal power, sometimes called a leakage signal, outside the desired frequency range. FIG. 1 shows an example of a typical output signal after the filtering process. In FIG. 1, the horizontal axis represents frequency and the vertical axis represents signal power. In the case of a desired signal with a center frequency of f and a bandwidth B, the leakage signals within the bandwidth B adjacent to the desired signal (i.e., f - 3B / 2 to f - B / 2 and f + B / 2 to f + 3B / 2) are stronger than the leakage signals with a bandwidth B that are further away from the desired signal (e.g., from f - 5B / 2 to f - 3B / 2 and from f + 3B / 2 to f + 5B / 2). On the other hand, the leakage signals within the bandwidth B adjacent to the desired signal are more dynamic. The leakage signals interfere with the desired signal within the frequency resources of f - 5B / 2 to f - B / 2 and f + B / 2 to f + 5B / 2. This is also known as a "roll-off filter".

[0028] To help demodulate the desired signal and ensure optimal operation of the channel between the transmitter and the receiver, the receiver typically measures interference. A reference signal is transmitted to aid in interference measurement. However, reference signal transmission takes bandwidth away from other traffic such as user data. Thus, reference signal transmission is typically only performed at some frequencies and some time opportunities, and the channel estimates obtained by receiving the reference signal at these times or frequencies are interpolated to obtain channel estimates over the entire target frequency band and the entire period. The receiver can measure interference more accurately and thus demodulate the desired signal more accurately if the reference signals are transmitted frequently in the time domain or transmitted close to each other in the frequency domain. However, transmitting more reference signals results in more resource overhead. To address this situation, the transmitter can transmit more reference signals in frequency resources with strong dynamic interference (e.g., f - 3B / 2 to f - B / 2 and f + B / 2 to f + 3B / 2), and transmit fewer reference signals in frequency resources with low stable interference (e.g., f - 5B / 2 to f - 3B / 2 and f + 3B / 2 to f + 5B / 2).

[0029] In some embodiments, the available transmission resources can be defined over a grid o in the time domain and the frequency domain using, for example, the orthogonal frequency division multiple access (OFDMA) scheme defined by 3GPP® for long term evolution or NR technology. In such a system, the transmitter transmits a reference signal to the receiver with one or more resource elements. Each resource element is uniquely identified by an index in the frequency domain and an index in the time domain, and the index in the time domain refers to the symbol position in the time domain relative to some reference point.

[0030] The reference signal has different frequency densities across the frequency domain. The receiver measures the reference signal to assist in demodulating the desired signal or to monitor the interference situation.

[0031] In various embodiments, the techniques described herein may be implemented in a transmitter-receiver configuration such as the following.

[0032] The transmitter is a base station and the receiver is a UE (user equipment). In this case, the reference signal is used for the UE to demodulate the DL (downlink) signal.

[0033] The transmitter is a UE and the receiver is a base station. In this case, the reference signal is used for the base station to demodulate the UL (uplink) signal.

[0034] The transmitter is a base station and the receiver is also a base station. In this case, the reference signal is used for interference measurement between base stations.

[0035] The transmitter is a UE and the receiver is also a UE. In this case, the reference signal is used for interference measurement between UEs.

[0036] 2. Examples of Different Regions with Different Resource Densities

[0037] In a sub-band full-duplex system, the base station can transmit and receive simultaneously. FIG. 2 shows an example of a sub-band full-duplex system on the base station side. FIG. 2 shows an example of a two-dimensional resource grid where the horizontal axis represents time (in slot units) and the vertical axis represents the frequency domain. A similar visual rendering method is also used for FIGS. 3 to 6, and additional reference signal resources are indicated by diagonal hatching lines. The area allocated for uplink transmission is indicated by horizontal hatching lines, and the area allocated for downlink transmission is indicated by vertical hatching lines. In this example, the bandwidth of the uplink frequency resources in slots 1 / 2 / 3 is approximately twice that of the downlink. In slots 1 / 2 / 3, there is a guard band between the downlink resources and the uplink resources. The guard band can be several RBs (resource blocks) or can be zero RBs. Between slots 1, 2, and 3, the base station needs to transmit and receive simultaneously. However, in slot 0, only downlink resources are allocated, so the base station only needs to transmit. Similarly, in slot 4, only uplink resources are allocated, so the base station only needs to receive.

[0038] The transmission signal has a much higher power than the received signal from the base station side. Since the leakage signal from the transmission signal enters the received signal, there can be interference from the downlink to the uplink. Due to the "roll-off filter", the interference from the downlink to the uplink can be stronger and more dynamic in the area closer to the downlink resources, i.e., the first area. Also, the interference can decrease and become flat in the second area. Therefore, the reference signal in the first area can have a higher frequency density across the frequency domain, and the reference signal in the second area can have a lower frequency density.

[0039] Figure 3 shows another example of a sub-band full-duplex system on the base station side. The downlink resources are configured on both sides of the uplink resources. In this example, the bandwidth of the uplink frequency resources in slots 1 / 2 / 3 is approximately three times the bandwidth for the downlink on each side. Due to the "roll-off filter", the interference from the downlink to the uplink can be stronger and more dynamic in the areas closer to the downlink resources, i.e., the first area and the third area. Also, the interference can decrease and become flat in the second area. Therefore, the reference signals in the first area and the third area can have a higher frequency density across the frequency domain, and the reference signals in the second area can have a lower frequency density.

[0040] Figure 4 shows an example of a sub-band full-duplex system on the UE side. UE#1 and UE#2 operate on the same carrier, for example, both operating at 2.6 GHz with a 60 MHz bandwidth. The UEs operate in half-duplex mode, which means that the UEs cannot transmit and receive simultaneously. In slots 1 / 2 / 3, UE#1 is receiving the downlink and UE#2 is transmitting the uplink. Similarly, the transmission signal of UE#2 has a much higher power than the received signal of UE#1. If UE#1 is physically located close to UE#2, there can be interference from the uplink to the downlink due to the leakage signal from the transmission signal of UE#2 entering the received signal of UE#1.

[0041] In this example, the bandwidth of the downlink frequency resources in slots 1 / 2 / 3 is approximately twice the bandwidth for the uplink. Due to the "roll-off filter", the interference from the uplink to the downlink can be stronger and more dynamic in the area closer to the uplink resources, i.e., the first area. The interference can decrease and become flat in the second area. Therefore, the reference signal in the first area can have a higher frequency density across the frequency domain, and the reference signal in the second area can have a lower frequency density.

[0042] FIG. 5 is another example of a sub-band full-duplex system on the UE side. The UE can transmit and receive simultaneously in slots 1 / 2 / 3. Similarly, the transmission signal has much higher power than the reception signal. Since the leakage signal from the transmission signal enters the reception signal, there may be interference from the uplink to the downlink. Due to the "roll-off filter", the interference from the uplink to the downlink can be stronger and more dynamic in the area closer to the uplink resource, i.e., the first area. The interference can decrease and become flat in the second area. Therefore, the reference signal in the first area can have a higher frequency density across the frequency domain, and the reference signal in the second area can have a lower frequency density.

[0043] Here, only an example of sub-band full-duplex is described, but when the characteristics of interference (e.g., intensity and rate of change) are different across different frequency resources, reference signals with different frequency densities can be applied to any scenario. For example, a full-duplex system, a dynamic TDD system, a TDD system with different slot formats between cells, a cell with co-channel or adjacent-channel interference.

[0044] Here, only two or three areas are described as examples, but the number of areas can be more than three. In practice, the number of areas should be determined by the interference and the implementation algorithm. For example, if the characteristics of interference are clearly different among four areas, four areas can be configured.

[0045] The base station configures N areas and indicates them to the UE or the base station, and each area is associated with one frequency density regarding the reference signal. N is an integer greater than 1. When the area is configured for the downlink, the base station transmits a reference signal with the corresponding frequency density associated with each area. When the area is configured for the uplink, the UE transmits a reference signal with the corresponding frequency density associated with each area.

[0046] Each area can be determined by frequency domain resources (or frequency resources for simplicity) and time domain resources. The frequency domain resources of an area can be determined by one of the following options.

[0047] Option 1. The base station configures the frequency resources associated with each area. Each area can have one or more RBs or PRGs (resource block groups).

[0048] Option 2. The base station configures the number of areas. The base station and / or the UE determine the frequency resources of each area based on the number of downlink or uplink areas and the total number of RBs / PRGs. For example, if the total number of uplink RBs is 90 RBs and the number of areas is 3, each area includes 30 RBs. If the total number of RBs is not divisible by the number of areas, specific rules can be used to determine the number of RBs for each area. For example, the first (or last) area can have fewer RBs, and all other areas can have the same number of RBs. If the total number of RBs for the uplink is 86 RBs and the number of areas is 3, the first area and the second area

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[0049] The time domain resources of an area can be determined by one of the following options.

[0050] Option 1. The base station does not configure any time-domain resources for each area. In this case, all slots / symbols are associated with each area. For example, if two areas are configured for uplink, all uplink slots / symbols are associated with these two areas.

[0051] Option 2. The base station does not configure any time-domain resources for each area. In this case, for a sub-band full-duplex system, all slots / symbols in which the base station or the UE can transmit and receive simultaneously are associated with each area. Taking Figure 2 as an example, if the base station does not configure time-domain resources for the first area and the second area, it means that all three slots (slot 1, slot 2, and slot 3) are associated with the first area and the second area. This is because the base station can transmit and receive simultaneously in these three slots.

[0052] Option 3. The base station configures time-domain resources for the area. The time-domain resources can be configured in units of frames, sub-frames, slots, sub-slots, symbols, seconds, or milliseconds. Taking the figure as an example, slot 2 is configured as the time-domain resource for the first area and the second area.

[0053] The frequency density regarding the reference signal indicates the density of the reference signal in the frequency domain. The frequency density of each area can be determined by one of the following options.

[0054] Option 1. The base station configures the frequency density associated with each area. Taking FIG. 2 as an example, the base station can configure the frequency density for the first area as "4", which means there are 4 REs transmitting the reference signal for each RB. The base station can configure the frequency density for the second area as "2", which means there are only 2 REs transmitting the reference signal for each RB. Here, the densities "4" and "2" are merely exemplary values. As long as the base station and the UE can have the same understanding, the base station can use other values / parameters to indicate the density.

[0055] Option 2. The base station configures the frequency density associated with the reference area and also configures other scaling factors for other areas. Taking FIG. 2 as an example, the base station can configure the frequency density for the first area as "4" and configure the scaling factor for the second area as "1 / 2". Therefore, it can be derived that the frequency density for the second area is "2".

[0056] Option 3. The frequency density for each area is defined in this specification.

[0057] Option 4. The frequency density for each area is indicated or updated by MAC-CE.

[0058] The following are some examples of frequency density. 1. The reference signal is transmitted on each RE of each RB within the area. 2. The reference signal is transmitted on each odd RE (or even RE) of each RB within the area. 3. The reference signal is transmitted on the 6th RE of odd RBs within the area. 4. The reference signal is transmitted on the 2nd RE and the 8th RE of every 6 RBs within the area, such as RBs with RB index m and m mod6 = 1, for example.

[0059] The transmitter transmits a reference signal with a specific frequency density, and the receiver determines the frequency resources of the reference signal based on the frequency density. Then, the receiver can measure the reference signal within the corresponding determined frequency resources.

[0060] If the frequency resources of the reference signal are entirely within one area, the reference frequency density is the frequency density associated with this area.

[0061] If the frequency resources of the reference signal span two or more areas, one of the following options can be applied.

[0062] Option 1. The frequency density of the related area is used for the frequency resources of the reference signal within the related area. Thus, there can be multiple frequency densities for one reference signal.

[0063] Option 2. The frequency density of the reference signal is determined by the frequency density associated with the area that overlaps with the lowest RB of the reference signal.

[0064] Option 3. The frequency density of the reference signal is determined by the frequency density associated with the area that overlaps with the highest RB of the reference signal.

[0065] Option 4. The frequency density of the reference signal is determined by the frequency density associated with the area with the lowest index that overlaps with the reference signal.

[0066] Option 5. The frequency density of the reference signal is determined by the frequency density associated with the area with the highest index that overlaps with the reference signal.

[0067] Option 6. The frequency density of the reference signal is determined by the frequency density associated with the area with the highest frequency that overlaps with the reference signal.

[0068] Option 7. The frequency density of the reference signal is determined by the frequency density associated with the area with the lowest frequency overlapping with the reference signal.

[0069] Taking FIG. 6 as an example, there are a total of 8 RBs in the frequency domain, which are divided into two areas, namely the first area and the second area. The reference signal is transmitted over 8 RBs. The frequency density of the first area is higher than that of the second area. In the first area, the reference signal is transmitted on all odd-numbered REs of the 4 RBs. In the second area, the reference is transmitted on the first RE, the fifth RE, and the ninth RE of all 4 RBs.

[0070] FIG. 7 is another example. Similarly, there are a total of 8 RBs in the frequency domain, which are divided into two areas, namely the first area and the second area. The reference signal is transmitted for each RE of all 4 RBs within the first area. The reference signal is transmitted for each RE of the even-numbered RBs within the second area.

[0071] The reference signal can be transmitted together with a data channel such as PDSCH and PUSCH, which can be similar to the existing DMRS for PDSCH and PUSCH. The resources for the reference signal are not available for the data channel. In other words, afterwards, when mapping the data channel to the REs, the data channel is not mapped to these REs used for the reference signal.

[0072] In this case, the reference signal is transmitted within the frequency resources of the data channel. The reference signal is transmitted in one or more symbols of the data channel. When the data channel is completely transmitted within one area, the frequency density of the reference signal is the frequency density associated with that area. When the data channel is transmitted over two or more areas, the frequency density of the relevant area is used for the frequency resources of the reference signal within the relevant area. Therefore, there can be multiple frequency densities for one reference signal.

[0073] Taking Fig. 8 as an example, there are a total of 8 RBs. Each RB has 12 REs. The lower 4 RBs are in the first area, and the remaining 4 RBs are in the second area. PUSCH is scheduled in the 6 lower RBs and transmitted in all 14 symbols in the time domain. The third symbol is used for the transmission of DMRS, and in the fourth symbol, a reference signal for interference measurement is transmitted. Since PUSCH is transmitted across two areas, the frequency density regarding the reference signal is different for each area. In the first area, the frequency density is higher, that is, the reference signal is transmitted in the odd REs of all 4 RBs. In the second area, in the 5th and 6th RBs, the reference is transmitted in the 1st RE, the 5th RE, and the 9th RE.

[0074] 3. Example of Dynamic Indication of Frequency Density

[0075] Method #1: Dynamic Indication of Frequency Density.

[0076] The base station configures N areas and indicates them to the UE, where N is an integer greater than 1. The DCI indicates the frequency density regarding the data channel.

[0077] When the data channel is completely transmitted within one area, the DCI indicates the corresponding frequency density for the reference signal transmitted together with the data channel. The frequency density can be directly transmitted by the DCI or configured by RRC signaling and indicated by the DCI. Also, the DCI can indicate that there is no reference signal transmitted together with the data channel when the interference is low or there is no interference. This can be determined by an interference threshold configured by RRC signaling, for example, an RSRP (Reference Signal Received Power) or RSSI (Received Signal Strength Indicator) threshold. When the interference is smaller than the threshold, the reference is not required. For example, when the RRC configures four frequency densities {4, 2, 1, 0}, "4", "2", or "1" means that there are 4 REs, 2 REs, or 1 RE respectively in each RB for the reference signal. "0" means that there is no reference signal transmitted together with the data channel.

[0078] When the data channel is transmitted over two or more areas, the DCI indicates the corresponding frequency density for the reference signal for each area. The RRC signaling configures the association between the index and the corresponding frequency density for each area. The DCI indicates the index, and thus the UE can determine the corresponding frequency density for each area.

[0079] Taking Figure 8 as an example, the RRC signaling configures the following association between the index and the corresponding frequency density for each area. Similarly, "0" means that there is no reference signal for the corresponding area. In Figure 8, the DCI indicates index 0 for the UE. Thus, the UE transmits the PUSCH according to the frequency density associated with index 0, that is, 6 for the first area and 3 for the second area. This is shown in Table 1. [Table 1] Method #2: Dynamic indication of area frequency resources and frequency density.

[0080] The DCI indicates the frequency resources and frequency density of the area related to the data channel. One of the following options can be used to indicate the frequency resources and frequency density of the area.

[0081] Option 1. The RRC signaling constitutes a first index associated with the frequency resource partition for each area and a second index associated with the frequency density. The DCI indicates the first index and the second index to the UE, and thus the UE can determine the frequency density regarding the corresponding frequency resources. The frequency resource partition for each area is constituted by one of the options of Embodiment 2.

[0082] For example, each area can be determined by the frequency domain resources (or frequency resources for simplicity) and the time domain resources. The frequency domain resources of the area can be determined by one of the following options.

[0083] Option 1. The base station constitutes the frequency resources associated with each area. Each area can have one or more RBs or PRGs (resource block groups).

[0084] Option 2. The base station constitutes the number of areas. The base station and / or the UE determine the frequency resources of each area based on the number of downlink or uplink areas and the total number of RBs / PRGs. For example, when the total number of uplink RBs is 90 RBs and the number of areas is 3, each area includes 30 RBs. When the total number of RBs is not divisible by the number of areas, a specific rule can be used to determine the number of RBs for each area. For example, the first (or last) area can have fewer RBs, and all other areas can have the same number of RBs. When the total number of RBs regarding the uplink is 86 RBs and the number of areas is 3, the first area and the second area

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[0085] Option 2. The RRC signaling constructs an index associated with the frequency resource partition for each area and the corresponding frequency density. The DCI indicates the index to the UE, and the UE can determine the frequency density for the corresponding frequency resource. The frequency resource partition for each area is configured by one of the options in Embodiment 2.

[0086] Taking Figure 8 as an example, as shown below, the RRC signaling constructs an index associated with the frequency resource partition for each area and the corresponding frequency density. In this example, the DCI indicates index 0 to the UE. Therefore, the frequency resource is divided into two areas, and the frequency resource for each area can be determined. For example, each area has the same number of RBs. Table 2 shows an example of the resource density in this case.

Table 2

[0087] Method #3: Other exemplary methods

[0088] The following method can also be used to indicate the frequency density.

[0089] Method 3-1: The DCI indicates the number of frequency densities. When the DCI indicates M as the number of frequency densities and M is an integer greater than 1, the frequency resources of the scheduled data channel are divided into M areas. For example, if the total number of RBs of the scheduled data is 90 RBs and the number of areas is 3, each area includes 30 RBs. When the total number of RBs cannot be divided evenly by the number of areas, the number of RBs for each area can be determined using a specific rule. For example, the first (or last) area can have fewer RBs, and all other areas can have the same number of RBs. When the total number of RBs related to the uplink is 86 RBs and the number of areas is 3, the first area and the second area have

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[0090] Method 3-2: The DCI indicates the number of frequency densities. When the DCI indicates M frequency densities and M is an integer greater than 1, the frequency resources of the scheduled data channel are divided into M areas.

[0091] 4. Examples of Time Domain Resources

[0092] The reference signal can be transmitted in one or more symbols within the scheduled data channel. The DMRS is used to measure the channel state. To facilitate PDSCH demodulation, the DMRS symbol or at least some of the DMRS symbols are in front of the scheduled PDSCH / PUSCH. In the case of type A PDSCH / PUSCH scheduling, the DMRS is usually in the 3rd or 4th symbol of the slot (counted from the 1st symbol). In the case of type B PDSCH / PUSCH scheduling, the DMRS is usually in the 1st symbol of the scheduled PDSCH / PUSCH.

[0093] The reference signal is used to measure interference and thus helps to demodulate the data channel. To facilitate the demodulation of the data channel (e.g., obtain the interference measurement result faster) and ensure the interference measurement accuracy, the reference signal is arranged adjacent to the DMRS using the following options.

[0094] Option 1: The reference signal is arranged in the symbol next to the DMRS. When two consecutive symbols are used as the DMRS, the reference signal is arranged in the symbol next to the last DMRS symbol.

[0095] Option 2: The reference signal is arranged in the symbol before the DMRS. When two consecutive symbols are used as the DMRS, the reference signal is arranged in the symbol before the first DMRS symbol.

[0096] The DMRS symbol can also be transmitted at the center or the end of the scheduled data channel according to the configuration. The reference signal can be configured in the symbol next to or before one or more DMRS symbols.

[0097] Taking Figure 8 as an example, only one symbol DMRS is transmitted, and the reference signal is transmitted in the symbol next to the DMRS.

[0098] Taking Figure 9 as an example, a total of four symbols are transmitted, and the four symbols are divided into two sets. The first set of DMRS symbols is in the front and occupies two consecutive symbols. The second set of DMRS symbols is at the end and also occupies two consecutive symbols in this case. In this example, the reference signal is transmitted in the symbol next to the last DMRS symbol of each set of DMRS symbols.

[0099] 5. Examples of Sequences Transmitted via the Reference Signal

[0100] The transmitter does not transmit any signal on these resources for the reference signal, and thus, the receiver can use it to measure the interference state.

[0101] Alternatively, the transmitter may transmit the following sequence via these resources for the reference signal.

[0102] Option 1. Pseudo-random sequence;

[0103] Option 2. Low PAPR (Peak-to-Average Power) sequence, such as Zadoff-Chu sequence;

[0104] Option 3. Reuse of the sequence for DMRS;

[0105] Option 4. Reuse of the sequence for SRS;

[0106] Option 5. Reuse of the sequence for CSI-RS.

[0107] 6. Examples of different time densities for the reference signal

[0108] Interference may vary between different symbols / slots. Taking Figure 2 as an example, there is interference from the downlink to the uplink on the base station side and interference from the uplink to the downlink on the UE side. Therefore, the interference in slot 0 or slot 4 is lower than that in slot 1, slot 2, or slot 3. Thus, the reference signal also has different time densities in the time domain. For example, in slot 0 and slot 4, the reference signal is transmitted with two symbols in each slot respectively. In slot 1, slot 2, and slot 3, the reference signal is transmitted with four symbols in each slot respectively.

[0109] Different methods can be applied to configure or indicate different time densities for the reference signal.

[0110] Method #1: The base station constructs different time domains and time densities associated with the time domains.

[0111] The time domain includes one or more symbols / slots and can be defined as a time domain pattern. For example, in FIG. 10, the first time domain pattern can be slot 0 and slot 4 in each period, and the period is 5 slots. The second time domain pattern can be slot 1, slot 2, and slot 3 in each period.

[0112] When the reference signal is transmitted in one time domain, the time density of the reference signal is determined by the time domain in which the reference signal is transmitted.

[0113] When the reference signal is transmitted over two or more time domains, the time density of the reference signal is determined by the following options.

[0114] Option 1. The time density of the reference signal is determined by the time domain in which the reference signal is transmitted.

[0115] Option 2. The time density of the reference signal is determined by the time domain that overlaps with the first symbol of the reference signal.

[0116] Option 3. The time density of the reference signal is determined by the time domain that overlaps with the last symbol of the reference signal.

[0117] Method #2: The base station indicates the time density regarding the reference signal via DCI or MAC-CE.

[0118] The RRC signaling constructs a set of configurations including an index for the UE and the corresponding time density associated with the index. The DCI or MAC-CE indicates the index for the UE. The UE determines the time density of the reference signal based on the indication. One of the indexes indicates that the reference signal is not transmitted.

[0119] For example, RRC signaling configures the following associations to the UE. Index 0 refers to a time density of "4", which means that the reference signal is transmitted in 4 symbols in each slot. There are many common solutions to determine which 4 symbols are used, e.g., the symbols constituted by RRC signaling, the first and second symbols of the scheduled data channel + the last and the second last symbols are used. Index 3 refers to a time density of 0, which means that the reference signal is not transmitted. Table 3 shows an example of such a configuration.

Table 3

[0120] DCI or MAC-CE can also indicate two or more time densities to the UE. If DCI schedules PDSCH / PUSCH with N - 1 repetitions (therefore, a total of N PDSCH / PUSCH transmissions), or if DCI schedules N PDSCH / PUSCH transmissions with different transport blocks, DCI indicates M time densities of PDSCH / PUSCH via the following options. N is an integer greater than 1. M is an integer greater than 1, and M is less than or equal to N. Typically, M is equal to 2.

[0121] Option 1. The reference signal transmitted together with the first

Fig.

Fig.

[0122] Option 2. The reference signal transmitted together with the PDSCH / PUSCH of the ((i mod M)+1)-th is transmitted at the time density of the ((i mod M)+1)-th indicated by the DCI. i is the PDSCH / PUSCH index starting from 0. For example, when the DCI schedules 4 PDSCH transmissions and indicates 2 time densities, the time density for the reference signal transmitted together with the first PDSCH (i.e., the PDSCH with index 0) is the first time density indicated by the DCI. Similarly, the time density for the reference signal transmitted together with the third PDSCH (i.e., the PDSCH with index 2) is the first time density indicated by the DCI. The time density for the reference signal transmitted together with the second PDSCH (i.e., the PDSCH with index 1) is the second time density indicated by the DCI. The time density for the reference signal transmitted together with the fourth PDSCH (i.e., the PDSCH with index 3) is the second time density indicated by the DCI.

[0123] 7. Examples of Different Frequency Densities for DMRS

[0124] Interference can be dynamic over the time domain. Taking Figure 2 as an example, in slot 0 and slot 4, the interference can be smaller compared to the interference in slots 1 / 2 / 3. Therefore, two DMRSs can be defined. The first DMRS is associated with one frequency density, and the second DMRS is associated with another frequency density. The DCI indicates the frequency density of the transmitted DMRS for the scheduled data channel.

[0125] In summary, M sets of DMRS can be defined, and each set of DMRS is associated with one frequency density. The DCI indicates one from the M sets of DMRS for the scheduled data channel. In other words, the DCI indicates one from the M frequency densities of the DMRS transmitted for the scheduled data channel.

[0126] For example, in this embodiment, the base station does not need to configure or indicate any area. The base station only indicates the corresponding frequency density to the receiver.

[0127] 8. Examples of reference signals transmitted overlapping with the guard period

[0128] In the case of a sub-band full-duplex system, one or more symbols are reserved to shift the communication direction. Taking Figure 10 as an example, in slot 1, the third and fourth symbols are reserved as GP (guard period) for the transition from downlink to uplink. Similarly, in slot 3, the eleventh and twelfth symbols are reserved as the guard period.

[0129] It should be noted that the reference signal here is not limited to the reference signal with different frequency densities. It can be any reference signal.

[0130] The base station and the UE do not transmit any signals during the guard period. Therefore, in a sub-band full-duplex system, a reference signal can be transmitted using a DL symbol overlapping with the guard period and a UL symbol overlapping with the guard period. Since the base station and the UE do not transmit any signals during the guard period, the reference signal transmitted by the DL symbol (or UL symbol) overlapping with the guard period can be protected with less interference.

[0131] The reference signal transmitted by the DL symbol overlapping with the guard period can be any of the following.

[0132] Option 1. DMRS. When the UE receives the DMRS in the DL symbol overlapping with the guard period, there is no other UE transmitting in the uplink.

[0133] Option 2. CSI-RS. When the UE or another base station receives the DMRS in the DL symbol overlapping with the guard period, there is no other UE transmitting in the uplink.

[0134] The reference signal transmitted by the UL symbol overlapping with the guard period can be any of the following.

[0135] Option 1. DMRS. When the base station receives the DMRS in the UL symbol overlapping with the guard period, there is no interference from its own downlink.

[0136] Option 2. SRS. When the base station receives the SRS in the UL symbol overlapping with the guard period, there is no interference from its own downlink.

[0137] The guard period can be configured as a flexible symbol, and thus, neither the base station nor the UE transmits any signal on the guard period.

[0138] Some preferred embodiments may incorporate the features of the following solutions.

[0139] Referring to Sections 1-6, some exemplary solutions implemented on the transmitter side may be as follows.

[0140] 1. Transmitting (1102) an indication of N regions within a resource grid defined by transmission resources in the frequency domain and / or time resources in the time domain from a first communication device to a second communication device, where each of the N regions has a corresponding resource density indicating the density of time-frequency resources configured for reference signal transmission, and N is an integer greater than 1, and communicating (1104) a reference signal between the first communication device and the second communication device according to the density information. (For example, the method 1100 depicted in FIG. 11A). Various configurations and examples of the regions (also referred to as "areas") are described with reference to FIGS. 2-10.

[0141] Referring to Section 2, some exemplary solutions may be as follows.

[0142] 2. Further comprising, for each of the N regions, configuring frequency resources in the frequency domain, wherein the frequency resources in the frequency domain are defined in units of resource blocks or resource block groups, the method of Solution 1.

[0143] 3. The method of Solution 1, wherein the density information signals the value of N.

[0144] 4. For the methods of Solutions 2 - 3, when the time resources are not indicated for a specific region, the resource density is interpreted as applicable to all time units of the specific region.

[0145] 5. For the methods of Solutions 2 - 3, when the time resources are not indicated for a specific region, all time units transmitted by the first communication device or the second communication device are interpreted as applicable to all time units of the specific region.

[0146] 6. Further comprising, for each of the N regions, configuring time resources in the time domain, wherein the time resources are defined for each region in units of transmission symbols or time slots, the method of Solutions 2 - 3.

[0147] 7. For any of the methods of Solutions 1 - 6, the resource density of the N regions is indicated using a scaling factor related to the resource density of the reference region.

[0148] 8. For any of the methods of Solutions 1 - 7, the resource density is indicated in a Medium Access Control (MAC) Control Element (CE).

[0149] 9. Further comprising transmitting a reference signal using transmission resources in one or more of the N regions, wherein in each region, the reference signal is transmitted using a density determined according to a rule, the method of any of Solutions 1 - 8.

[0150] 10. The method of Solution 9, wherein the rule defines using the resource density of each region for the reference signal.

[0151] 11. The method according to any one of Solutions 1 to 10, further comprising transmitting a reference signal by multiplexing with a data channel along a frequency domain and / or a time domain.

[0152] Referring to Section 3, some exemplary solutions may be as follows.

[0153] 12. The method of Solution 1, including transmitting an indication message indicating resources used for data channel transmission and reference signal transmission from a first communication device to a second communication device, such that when the data channel completely fits within a specific one of N regions, the indication message indicates the resource density of reference signal transmission for the specific region, or when the data channel occupies two or more of the N regions, the indication message indicates the resource density of the reference signal for the two or more regions, or when the reference signal is not transmitted on the data channel, the indication message indicates the absence of reference signal transmission.

[0154] 13. The method of Solution 12, where when it is determined that the estimated interference on the wireless channel between the first communication device and the second communication device is below a threshold, the indication message indicates the absence of reference signal transmission. The threshold may be a predefined number or may be specific to the embodiment.

[0155] 14. The method according to Solutions 12 to 13, where in one region, data channel transmission and reference signal transmission are configured such that the resources allocated for reference channel transmission are not available for data channel transmission.

[0156] 15. The method of Solution 14, where data channel transmission includes physical downlink shared channel (PDSCH) transmission or physical uplink shared channel (PUSCH) transmission.

[0157] 16. The method according to any one of Solutions 12 to 15, wherein the indication message is carried by downlink control information (DCI).

[0158] 17. The method according to any one of Solutions 12 to 16, wherein the indication indicates a configuration previously configured by a higher layer message.

[0159] 18. The method according to Solution 17, wherein the higher layer message is a radio resource control (RRC) message configuring N regions and / or resource density regarding N regions.

[0160] 19. The method according to Solution 12, wherein the indication message and the indication are communicated by a downlink control indicator (DCI) message.

[0161] Referring to Section 4, some exemplary solutions may be as follows.

[0162] 20. The method according to Solution 1, wherein the N regions are adjacent to DMRS transmission in the time domain.

[0163] 21. The method according to Solution 1, wherein the N regions are arranged in the symbol next to the last DMRS symbol.

[0164] 22. The method according to Solution 1, wherein the N regions are arranged in the symbol before adjacent to the first DMRS symbol.

[0165] Referring to Section 6, some exemplary solutions may be as follows.

[0166] 23. The method according to Solution 1, wherein the resource density corresponds to the density along the time domain.

[0167] 24. The N regions are composed of different time densities of the reference signal, and the method further includes transmitting the reference signal using transmission resources in one or more of the N regions. In each region, the reference signal is transmitted using a density determined according to a rule, which is the method of solution 23.

[0168] 25. The rule determines that when the reference signal uses the transmission resources of a single region among the N regions, the reference signal is transmitted using the time domain resource density associated with the single region, which is the method of solution 24.

[0169] 26. The rule determines that when the reference signal uses the transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using the time domain resource density associated with each of the plurality of regions when the reference signal is transmitted in that region, which is the method of solution 24.

[0170] 27. The rule determines that when the reference signal uses the transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using the time domain resource density corresponding to the time domain resource density of the first region including the first symbol used for the transmission of the reference signal, which is the method of solution 24.

[0171] 28. The time density is configured using different values in the radio resource control (RRC) message and an index indicated by the medium access control control element (MAC CE) or the downlink control information (DCI), which is the method of any one of solutions 23 to 27.

[0172] 29. One index indicates that the reference signal transmission is not performed, which is the method of solution 28.

[0173] 30. The reference signal includes a pseudo-random sequence or a low peak-to-average power ratio sequence, or the same sequence as the demodulation reference signal or the sounding reference signal or the channel state information reference signal, which is the method of any one of solutions 1 to 29.

[0174] 31. The reference signal is any one of the methods of Solutions 1 to 29, including zero-power transmission where no signal is transmitted.

[0175] Referring to Sections 1 to 6, some exemplary solutions implemented on the receiver side may be as follows.

[0176] 32. Receiving (1152) from a first communication device to a second communication device an indication of N regions within a resource grid defined by transmission resources in the frequency domain and / or time resources in the time domain, where each of the N regions has a corresponding resource density indicating the density of time-frequency resources configured for reference signal transmission, and N is an integer greater than 1, and communicating (1154) a reference signal between the first communication device and the second communication device according to the density information (e.g., the method 1150 depicted in FIG. 11B). Various configurations and examples of regions (also referred to as "areas") are described with reference to FIGS. 2 to 10.

[0177] Referring to Section 2, some exemplary solutions may be as follows.

[0178] 33. For each of the N regions, a frequency resource in the frequency domain is configured, and the frequency resource in the frequency domain is defined in units of resource blocks or resource block groups, the method of Solution 32.

[0179] 34. The method of Solution 32, where the density information signals the value of N.

[0180] 35. When time resources are not indicated for a particular region, the resource density is interpreted as applicable to all time units of the particular region, the method of Solutions 33 to 34.

[0181] 36. If the time resource is not indicated for a specific area, all time units transmitted by the first communication device or the second communication device are interpreted as applicable to all time units of the specific area, the methods of Solutions 33 - 34.

[0182] 37. For each of the N areas, a time resource in the time domain is configured, and the time resource is defined for each area in units of transmission symbols or time slots, the methods of Solutions 33 - 34.

[0183] 38. The resource density of the N areas is indicated using a scaling factor related to the resource density of the reference area, any of the methods of Solutions 32 - 37.

[0184] 39. The resource density is indicated in the Medium Access Control (MAC) Control Element (CE), any of the methods of Solutions 32 - 38.

[0185] 40. Further includes receiving a reference signal using transmission resources in one or more of the N areas, and in each area, the reference signal is transmitted using a density determined according to a rule, any of the methods of Solutions 32 - 39.

[0186] 41. The rule determines to use the resource density of each area for the reference signal, the method of Solution 40.

[0187] 42. Further includes receiving the reference signal by multiplexing with a data channel along the frequency domain and / or the time domain, any of the methods of Solutions 32 - 41.

[0188] Referring to Section 3, some exemplary solutions may be as follows.

[0189] 43. A method of solution 32, including receiving, by a second communication device from a first communication device, an indication message indicating resources used for data channel transmission and reference signal transmission, whereby, if the data channel completely fits within a specific one of N regions, the indication message indicates the resource density of reference signal transmission for the specific region, or if the data channel occupies two or more of the N regions, the indication message indicates the resource density of the reference signal for the two or more regions, or if the reference signal is not transmitted on the data channel, the indication message indicates the absence of reference signal transmission.

[0190] 44. A method of solution 43, wherein when it is determined that the estimated interference on a wireless channel between a first communication device and a second communication device is below a threshold, the indication message indicates the absence of reference signal transmission. The threshold may be a predefined number or may be specific to an embodiment.

[0191] 45. A method of solutions 43 - 44, wherein in one region, data channel transmission and reference signal transmission are configured such that the resources allocated for reference channel transmission are not available for data channel transmission.

[0192] 46. A method of solution 45, wherein data channel transmission includes physical downlink shared channel (PDSCH) transmission or physical uplink shared channel (PUSCH) transmission.

[0193] 47. A method of solutions 43 - 46, wherein the indication message is carried by downlink control information (DCI).

[0194] 48. A method of solutions 43 - 47, wherein the indication indicates a configuration previously configured by a higher layer message.

[0195] 49. The method of solution 48, wherein the upper layer message is a radio resource control (RRC) message that configures the resource density for N regions and / or N regions.

[0196] 50. The method of solution 43, wherein the indication message and the indication are communicated by a downlink control indicator (DCI) message.

[0197] Referring to Section 4, some exemplary solutions may be as follows.

[0198] 51. The method of solution 32, wherein the N regions are adjacent to DMRS transmission in the time domain.

[0199] 52. The method of solution 32, wherein the N regions are arranged in the symbol next to the last DMRS symbol.

[0200] 53. The method of solution 32, wherein the N regions are arranged in the symbol before adjacent to the first DMRS symbol.

[0201] Referring to Section 6, some exemplary solutions may be as follows.

[0202] 54. The method of solution 32, wherein the resource density corresponds to the density along the time domain.

[0203] 55. The method of solution 54, wherein the N regions are composed of different time densities of the reference signal, and the method further includes receiving the reference signal using the transmission resources in one or more of the N regions, and in each region, the reference signal is transmitted using the density determined according to the rule.

[0204] 56. The method of solution 55, wherein the rule defines that when the reference signal uses the transmission resources of a single region among the N regions, the reference signal is transmitted using the time domain resource density associated with the single region.

[0205] 57. The method of Solution 55, wherein the rule determines that when the reference signal uses the transmission resources of a plurality of regions out of N regions, the reference signal is transmitted using the time-domain resource density associated with each of the plurality of regions when the reference signal is transmitted in that region.

[0206] 58. The method of Solution 55, wherein the rule determines that when the reference signal uses the transmission resources of a plurality of regions out of N regions, the reference signal is transmitted using the time-domain resource density corresponding to the time-domain resource density of the first region including the first symbol used for the transmission of the reference signal.

[0207] 59. The method according to any one of Solutions 54 to 58, wherein the time density is configured using different values in a Radio Resource Control (RRC) message and an index indicated by a Medium Access Control Control Element (MAC CE) or Downlink Control Information (DCI).

[0208] 60. The method of Solution 59, wherein one index indicates that the reference signal transmission is not performed.

[0209] 61. The method according to any one of Solutions 32 to 60, wherein the reference signal includes a pseudo-random sequence or a low peak-to-average power ratio sequence, or the same sequence as a demodulation reference signal, a sounding reference signal, or a channel state information reference signal.

[0210] 62. The method according to any one of Solutions 32 to 60, wherein the reference signal includes zero-power transmission where the signal is not transmitted.

[0211] The above solutions may preferably be implemented as follows.

[0212] 63. The method according to any one of Solutions 1 to 62, wherein the first communication device corresponds to a base station and the second communication device corresponds to a user equipment.

[0213] 64. A method according to any one of Solutions 1 to 62, wherein the first communication device corresponds to a user equipment and the second communication device corresponds to a base station.

[0214] 65. A wireless communication device comprising a processor configured to implement the method according to any one of Solutions 1 to 64.

[0215] 66. A computer-readable medium storing processor-executable code, which, when executed by a processor, causes the processor to implement the method according to any one of Solutions 1 to 64.

[0216] FIG. 12 is a block diagram of an exemplary embodiment of a wireless communication device 1200. Methods 1100 and 1150 may be implemented by device 1200. In some embodiments, for example, when implementing method 1100, device 1200 may be a first communication device such as a base station or a network device of a wireless network, and the second communication device may be a UE. In some embodiments, for example, when implementing method 1150, device 1200 may be a second communication device such as a UE. Device 1200 includes one or more processors for transmitting and receiving wireless signals, such as processor electronics 1210, transceiver circuitry 1215, and one or more antennas 1220. Device 1200 may include a memory 1205 that may be used to store data and instructions used by processor electronics 1210. Also, device 1200 may include a further network interface to one or more core networks or further equipment of a network operator. This further network interface, not explicitly shown in FIG. 12, may be wired (e.g., fiber or Ethernet (registered trademark)) or wireless.

[0217] FIG. 13 depicts an example of a wireless communication system 1300 in which the various techniques described herein may be implemented. The system 1300 includes a base station 1302 that may have a communication connection with a core network (1312) and a wireless communication medium 1304 to communicate with one or more user devices 1306. The user devices 1306 may be, for example, smartphones, tablets, machine-to-machine communication devices, Internet of Things (IoT) devices, and the like.

[0218] It can be appreciated that techniques for achieving different reference signal resource densities in the time and / or frequency domain are implemented. In one advantageous aspect, the disclosed techniques may be used by a transmitter (e.g., a base station) to schedule a denser resource grid of reference signals in a time-frequency region where there is a higher likelihood of interference, e.g., a time-frequency region where uplink and downlink transmissions occupy adjacent or proximate time slots of subcarriers. It can be further appreciated by those skilled in the art that the disclosed techniques may be used to reserve a particular resource element as a zero-power transmission resource (e.g., a reference signal transmission that does not include signal transmission). Additionally, embodiments may be able to divide all available time-frequency resources into a plurality of regions (also referred to herein as areas), and the resource density may be defined for each region. Data and reference signal transmissions may fall entirely within a single region or may occupy multiple regions, thereby providing a flexible resource density arrangement.

[0219] The disclosed embodiments and other embodiments, modules, and functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware that includes the structures disclosed in this document and their structural equivalents, or in a combination of one or more of them. The disclosed embodiments and other embodiments can be implemented as one or more computer program products, i.e., as one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter that provides a machine-readable propagated signal, or a combination of one or more of them. The term “data processing apparatus” includes, by way of example, all apparatus, devices, and machines for processing data, including programmable processors, computers, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the relevant computer program, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a mechanically generated electrical, optical, or electromagnetic signal, generated to encode information for transmission to an appropriate receiver device.

[0220] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, as a stand-alone program or including modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. The program can be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), a single file dedicated to the program in question, or multiple cooperating files (e.g., files that hold one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer, or on multiple computers located at one site, or on multiple computers distributed across multiple sites and interconnected by a communication network.

[0221] The processes and logical flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating input data to produce output. These processes and logical flows can also be performed by, for example, a special purpose logic circuit such as an FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and the apparatus can also be implemented as a special purpose logic circuit.

[0222] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, as well as any one or more processors of any kind of digital computer. In general, a processor receives instructions and data from, or both, read only memory or random access memory. Essential elements of a computer are a processor for executing instructions, and one or more memory devices for storing instructions and data. In general, a computer also includes, or is operatively coupled to receive from, or transfer data to, or both, one or more mass storage devices for storing data, such as magnetic, magneto-optical disks, or optical disks. However, a computer need not have such devices. Computer-readable media suitable for storing computer program instructions and data include, by way of example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks, including any form of non-volatile memory, media, and memory devices. The processor and memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0223] This document contains many details, but these should not be construed as limitations on the scope of the invention described in the claims or on the scope of inventions that may be described in the claims. Rather, they should be construed as descriptions of features specific to particular embodiments. The particular features described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented separately, or in any suitable partial combination, in multiple embodiments. Further, features may be described above as acting in a particular combination and may initially be claimed as such, but one or more features from the claimed combination may, in some cases, be excised from the combination, and the claimed combination may be directed to a partial combination or a variation of a partial combination. Similarly, each operation is depicted in the drawings in a particular order, but this should not be understood as requiring that such operations be performed in the particular order shown, or in a sequential order, or that all of the operations shown be performed, in order to achieve a desirable result.

[0224] Only a few examples and embodiments are disclosed. Based on the disclosed content, variations, modifications, and enhancements can be made to the described examples, embodiments, and other embodiments.

Claims

1. A method of wireless communication, comprising: transmitting, from a first communication device to a second communication device, an indication of N regions within a resource grid defined by transmission resources in a frequency domain and / or time resources in a time domain, wherein each of the N regions has a corresponding resource density indicating a density of time-frequency resources configured for reference signal transmission, wherein N is an integer greater than 1, and communicating a reference signal between the first communication device and the second communication device according to density information. The method according to claim 1, further comprising:

2. For each of the N regions, further comprising configuring frequency resources in the frequency domain, wherein the frequency resources in the frequency domain are defined in units of resource blocks or resource block groups. The method according to claim 1.

3. The method according to claim 1, wherein the density information signals a value of N.

4. The method according to claims 2 to 3, wherein when the time resources are not indicated for a particular region, the resource density is interpreted as applicable to all time units of the particular region.

5. The method according to claims 2 to 3, wherein when the time resources are not indicated for a particular region, all time units transmitted by the first communication device or the second communication device are interpreted as applicable to all time units of the particular region.

6. For each of the N regions, further comprising configuring time resources in the time domain, wherein the time resources are defined for each region in units of transmission symbols or time slots. The method according to claims 2 to 3.

7. The method according to any one of claims 1 to 6, wherein the resource density of the N regions is indicated using a scaling factor with respect to the resource density of a reference region.

8. The method according to any one of claims 1 to 7, wherein the resource density is indicated in a medium access control (MAC) control element (CE).

9. The method according to any one of claims 1 to 8, further comprising transmitting a reference signal using transmission resources in one or more of the N regions, wherein in each region, the reference signal is transmitted using a density determined according to a rule. The method according to any one of claims 1 to 8.

10. The method according to claim 9, wherein the rule defines using the resource density of each region with respect to the reference signal.

11. Transmitting a reference signal by multiplexing with a data channel along the frequency domain and / or the time domain The method according to any one of claims 1 to 10, further comprising.

12. Transmitting an indication message of resources used for data channel transmission and reference signal transmission from the first communication device to the second communication device, whereby when the data channel completely falls within a specific one of the N regions, the indication message indicates the resource density of the reference signal transmission for the specific region, or when the data channel occupies two or more of the N regions, the indication message indicates the resource density of the reference signal for the two or more regions, or when the reference signal is not transmitted on the data channel, the indication message indicates the absence of reference signal transmission. The method according to claim 1.

13. The method according to claim 12, wherein when it is determined that the estimated interference on the wireless channel between the first communication device and the second communication device is below a threshold, the indication message indicates the absence of reference signal transmission.

14. The method according to claims 12 to 13, wherein in one region, the data channel transmission and the reference signal transmission are configured such that the resources allocated for the reference channel transmission are not available for the data channel transmission.

15. The method according to claim 14, wherein the data channel transmission includes physical downlink shared channel (PDSCH) transmission or physical uplink shared channel (PUSCH) transmission.

16. The method according to any one of claims 12 to 15, wherein the indication message is carried by downlink control information (DCI).

17. The method according to any one of claims 12 to 16, wherein the indication indicates a configuration previously configured by a higher layer message.

18. The method according to claim 17, wherein the upper layer message is a radio resource control (RRC) message that constitutes the N regions and / or the resource density related to the N regions.

19. The method according to claim 12, wherein the indication message and the indication are communicated by a downlink control indicator (DCI) message.

20. The method according to claim 1, wherein the N regions are adjacent to DMRS transmission in the time domain.

21. The method according to claim 1, wherein the N regions are arranged in the symbol next to the last DMRS symbol.

22. The method according to claim 1, wherein the N regions are arranged in the symbol before the symbol adjacent to the first DMRS symbol.

23. The method according to claim 1, wherein the resource density corresponds to the density along the time domain.

24. The N regions are composed of different time densities of reference signals, and the method further includes: transmitting a reference signal using transmission resources in one or more of the N regions, and in each region, the reference signal is transmitted using a density determined according to a rule. The method according to claim 23.

25. The method according to claim 24, wherein the rule determines that when the reference signal uses the transmission resources of a single region among the N regions, the reference signal is transmitted using the time domain resource density associated with the single region.

26. The method according to claim 24, wherein the rule determines that when the reference signal uses the transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using the time domain resource density associated with each of the plurality of regions when the reference signal is transmitted in that region.

27. The method according to claim 24, wherein the rule determines that when the reference signal uses the transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using a time domain resource density corresponding to the time domain resource density of the first region including the first symbol used for the transmission of the reference signal.

28. The method according to any one of claims 23 to 27, wherein the time density represents different values in a radio resource control (RRC) message and is configured using an index indicated by a media access control control element (MAC CE) or downlink control information (DCI).

29. The method according to claim 28, wherein one index indicates that no reference signal transmission is performed.

30. The method according to any one of claims 1 to 29, wherein the reference signal includes a pseudo-random sequence or a low peak-to-average power ratio sequence, or the same sequence as a demodulation reference signal, a sounding reference signal, or a channel state information reference signal.

31. The method according to any one of claims 1 to 29, wherein the reference signal includes zero-power transmission where no signal is transmitted.

32. A method of wireless communication, comprising: receiving, by a second communication device from a first communication device, an indication of N regions in a resource grid defined by transmission resources in a frequency domain and / or time resources in a time domain, each of the N regions having a corresponding resource density indicating a density of time-frequency resources configured for reference signal transmission, wherein N is an integer greater than 1, and communicating the reference signal between the first communication device and the second communication device according to the density information. A method comprising.

33. The method according to claim 32, wherein for each of the N regions, frequency resources in the frequency domain are configured, and the frequency resources in the frequency domain are defined in units of resource blocks or resource block groups.

34. The method according to claim 32, wherein the density information signals a value of N.

35. The method according to claims 33 to 34, wherein when the time resource is not indicated for a particular region, the resource density is interpreted as applicable to all time units of the particular region.

36. The method according to claims 33 to 34, wherein when the time resource is not indicated for a particular region, all time units transmitted by the first communication device or the second communication device are interpreted as applicable to all time units of the particular region.

37. For each of the N regions, time resources in the time domain are configured, and the time resources are defined for each region in units of transmission symbols or time slots, according to the method of claims 33 to 34.

38. The resource density of the N regions is indicated using a scaling factor related to the resource density of a reference region, according to the method of any one of claims 32 to 37.

39. The resource density is indicated in a medium access control (MAC) control element (CE), according to the method of any one of claims 32 to 38.

40. Further including receiving a reference signal using transmission resources in one or more of the N regions, and in each region, the reference signal is transmitted using a density determined according to a rule. The method of any one of claims 32 to 39.

41. The rule determines using the resource density of each region with respect to the reference signal, according to the method of claim 40.

42. Receiving a reference signal by multiplexing with a data channel along the frequency domain and / or the time domain. Further included, according to the method of any one of claims 32 to 41.

43. Including receiving, by the second communication device from the first communication device, an indication message indicating resources used for data channel transmission and reference signal transmission, whereby when the data channel completely falls within a specific one of the N regions, the indication message indicates the resource density of the reference signal transmission for the specific region, or when the data channel occupies two or more of the N regions, the indication message indicates the resource density of the reference signal for the two or more regions, or when the reference signal is not transmitted on the data channel, the indication message indicates the absence of reference signal transmission. The method of claim 32.

44. When it is determined that the estimated interference on the wireless channel between the first communication device and the second communication device is below a threshold, the indication message indicates the absence of reference signal transmission, according to the method of claim 43.

45. The method according to claims 43 to 44, wherein in one area, the data channel transmission and the reference signal transmission are configured such that resources allocated for the reference channel transmission are not available for the data channel transmission.

46. The method according to claim 45, wherein the data channel transmission includes physical downlink shared channel (PDSCH) transmission or physical uplink shared channel (PUSCH) transmission.

47. The method according to any one of claims 43 to 46, wherein the indication message is carried by downlink control information (DCI).

48. The method according to any one of claims 43 to 47, wherein the indication indicates a configuration previously configured by a higher layer message.

49. The method according to claim 48, wherein the higher layer message is a radio resource control (RRC) message that configures the N regions and / or the resource density related to the N regions.

50. The method according to claim 43, wherein the indication message and the indication are communicated by a downlink control indicator (DCI) message.

51. The method according to claim 32, wherein the N regions are adjacent to DMRS transmission in the time domain.

52. The method according to claim 32, wherein the N regions are arranged in the symbol next to the last DMRS symbol.

53. The method according to claim 32, wherein the N regions are arranged in the symbol preceding the first DMRS symbol.

54. The method according to claim 32, wherein the resource density corresponds to the density along the time domain.

55. The N regions are configured with different time densities of reference signals, and the method further includes: receiving a reference signal using transmission resources in one or more of the N regions, wherein in each region, the reference signal is transmitted using a density determined according to a rule. The method according to claim 54.

56. The method according to claim 55, wherein the rule defines that when the reference signal uses the transmission resources of a single region among the N regions, the reference signal is transmitted using the time domain resource density associated with the single region.

57. The method according to claim 55, wherein the rule determines that when the reference signal uses transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using a time-domain resource density associated with each of the plurality of regions when the reference signal is transmitted in that region.

58. The method according to claim 55, wherein the rule determines that when the reference signal uses transmission resources of a plurality of regions among the N regions, the reference signal is transmitted using a time-domain resource density corresponding to the time-domain resource density of a first region including a first symbol used for the transmission of the reference signal.

59. The method according to any one of claims 54 to 58, wherein the time density represents different values in a radio resource control (RRC) message and is configured using an index indicated by a medium access control control element (MAC CE) or downlink control information (DCI).

60. The method according to claim 59, wherein one index indicates that no reference signal transmission is performed.

61. The method according to any one of claims 32 to 60, wherein the reference signal includes a pseudo-random sequence or a low peak-to-average power ratio sequence, or the same sequence as a demodulation reference signal, a sounding reference signal, or a channel state information reference signal.

62. The method according to any one of claims 32 to 60, wherein the reference signal includes zero-power transmission where no signal is transmitted.

63. The method according to any one of claims 1 to 62, wherein the first communication device corresponds to a base station and the second communication device corresponds to a user equipment.

64. The method according to any one of claims 1 to 62, wherein the first communication device corresponds to a user equipment and the second communication device corresponds to a base station.

65. A wireless communication device comprising a processor configured to implement the method according to any one of claims 1 to 64.

66. A computer-readable medium storing processor-executable code, wherein the code causes the processor to implement the method according to any one of claims 1 to 64 when executed by the processor.

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