WO2019019173A1

WO2019019173A1 - Transmission and reception of demodulation reference signal

Info

Publication number: WO2019019173A1
Application number: PCT/CN2017/094967
Authority: WO
Inventors: Yu Xin; Yi Wu; Luanjian BIAN
Original assignee: Zte Corporation
Priority date: 2017-07-28
Filing date: 2017-07-28
Publication date: 2019-01-31
Also published as: CN110710286A

Abstract

Reducing reference signal overhead is an effective technique for improving the spectral efficiency of wireless communication. In some embodiments, a base station may select between and transmit to a mobile station a legacy resource pattern for reference signals and a new resource pattern for reduced reference signals. The exemplary new resource patterns can reduce the resource elements overhead used for reference signals.

Description

TRANSMISSION AND RECEPTION OF DEMODULATION REFERENCE SIGNAL

TECHNICAL FIELD

This document is directed generally to wireless communications.

BACKGROUND

Mobile telecommunication technologies are moving the world toward an increasingly connected and networked society. In comparison with the existing wireless networks, next generation systems and wireless communication techniques will need to support a much wider range of use-case characteristics and provide a more complex and sophisticated range of access requirements and flexibilities.

SUMMARY

This document relates to methods, systems, and devices for transmission and reception of reference signals such as demodulation reference signal (DMRS) , using flexible transmission resources.

In one exemplary aspect, a wireless communication method is disclosed. The wireless communication method comprises transmitting an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern, determining a second resource pattern representing time and frequency resources for a subsequent transmission of the reference signal, communicating the second resource pattern for the subsequent transmission of the reference signal to one or more mobile stations, and transmitting the subsequent transmission of the reference signal using the time and frequency resources corresponding to the second resource pattern.

In another exemplary aspect, a wireless communication method is disclosed. The wireless communication method includes receiving, by a mobile station, an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern, receiving, by the mobile station, information related to a second resource pattern representing time and frequency resources for a subsequent reception of the reference signal, and receiving, by the mobile station, the subsequent reception of the reference signal using the time and frequency resources corresponding to the second resource pattern.

In yet another exemplary aspect, a wireless communication base station is disclosed. The wireless communication base station comprises a memory that stores instructions for operations of the base station, and a processor in communication with the memory operable to execute instructions to cause the base station to transmit an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern, determine a second resource pattern representing time and frequency resources for a subsequent transmission of the reference signal, communicate the second resource pattern for the subsequent transmission of the reference signal to one or more mobile stations, and transmit the subsequent transmission of the reference signal using the time and frequency resources corresponding to the second resource pattern.

In yet another exemplary aspect, a wireless communication mobile station is disclosed. The wireless communication mobile station comprises a memory that stores instructions for operations of the mobile station, and a processor that is in communication with the memory and operable to execute the instructions to cause the mobile station to receive an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern, receive information related to a second resource pattern representing time and frequency resources for a subsequent reception of the reference signal, and receive the subsequent reception of the reference signal using the time and frequency resources corresponding to the second resource pattern.

In yet another exemplary aspect, the above-described methods are embodied in the form of processor-executable code and stored in a computer-readable program medium.

In yet another exemplary embodiment, a device that is configured or operable to perform the above-described methods is disclosed.

The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a base station communicating a resource pattern with DMRS signals to one or more mobile stations.

FIGS. 2A-2C show downlink DMRS patterns employed by current Long Term Evolution (LTE) standard.

FIGS. 3A-3G show exemplary DMRS overhead reduction patterns.

FIG. 4 shows a block diagram for an exemplary wireless communication base station for transmission of the legacy DL DMRS patterns and the reduced DL DMRS patterns.

FIG. 5 shows an exemplary flow chart for a base station for using resource pattern with legacy and reduced DMRS signals.

FIG. 6 shows a block diagram for an exemplary wireless communication mobile station for reception of the legacy DL DMRS patterns and the reduced DL DMRS patterns.

FIG. 7 shows an exemplary flow chart for a wireless communication mobile station for using a resource pattern with legacy and reduced DMRS signals.

DETAILED DESCRIPTION

The demand for improving spectral efficiency has been fueled by radio spectrum scarcity and a demand for high data rate service. Reducing reference signal overhead is an effective technique for improving the spectral efficiency of wireless communication. In a typical communication system, a receiver has a priori knowledge of time and frequency locations of reference signals. For example, in transmissions schemes based on orthogonal frequency division multiplexing (OFDM) , transmission resources are often specified using time slots and subcarriers, thus forming a time-frequency grid of available transmission resources called resource elements. In such systems, the time slots and subcarriers used for reference signal transmissions are described using resource patterns, which may for example be resource elements allocated to the reference signal in a two-dimensional arrangement of resource elements called physical resource block (PRB) . The PRB is a unit of resource allocation that may repeat over time dimension (time slots) and frequency dimension (subcarriers) available for transmission.

In current LTE specification, three different downlink (DL) demodulation reference signal (DMRS) patterns have been defined for a multiple-input, multiple output (MIMO) transmission mode (TM) 9/10 for different transmission ranks. Depending on the transmission rank, one DMRS pattern will be selected for a user equipment (UE) or a mobile station specific reference signal transmission. These three DMRS patterns are designed for general wireless links, and are not optimal for some scenarios, such as wireless stationary links in small cell scenario. Thus, in some embodiments, the DMRS density can be reduced in, for example, a wireless stationary links scenario.

The disclosed technology presents DMRS overhead reduction techniques which can be utilized, for example, in scenarios with sufficiently high signal-to-noise ratio (SNR) such as small cell deployments. In some embodiments, the presented reduced DMRS patterns can be applied to any similar stationary wireless links with relatively high SNR. Several new low-overhead DMRS patterns and supporting technology are disclosed in this patent document. In some embodiments, the reduced DMRS patterns can be tailored for LTE DL single user multiple-input, multiple-out (SU-MIMO) rank 3/4 in transmission mode (TM) 9/10. The reduced DMRS patterns provide several benefits. For example, compared with the legacy DMRS patterns, the disclosed new DMRS patterns can reduce the resource elements (REs) overhead, while keep the performance at the same or similar level. Thus, the LTE DL system efficiency can be improved by using the presented DMRS patterns.

FIG. 1 illustrates a base station 120 communicating a resource pattern with

DMRS signals

140a, 140b, to one or more mobile stations110a, 110b. The one or more

mobile stations

110a, 110b may also send channel related information to the base station. For example, the

mobile station

110a, 110b, may send a channel quality indicator (CQI) 130a, 130b to the base station. The CQI provides information to the base station regarding the communication channel quality between the base station and the mobile station. To support multi-layer demodulation, UE-specific DMRS are defined for TMs 9/10 transmission in current LTE specification.

FIGs. 2A-2C illustrate three different legacy DL DMRS patterns that have been defined for TM 9/10 under different transmission ranks under current LTE standard. FIGs. 2A-2C includes resource patterns for each physical resource block (PRB) . As shown in FIG. 2A, a PRB includes twelve subcarriers along the y-axis and seven OFDM symbols along the x-axis. Each intersection of an OFDM symbol and a subcarrier is known as a resource element. Twelve subcarriers comprise a resource block and seven OFDM symbols comprise a slot.

FIG. 2A shows that DMRS pattern port 7/8 with orthogonal cover code OCC2 is used for DL SU-MIMO rank 1/2 transmission. In FIG. 2A, the DMRS signal is transmitted in 12 REs per PRB, and OCC2 is applied to the two adjacent REs in time domain so that port 7/8 can share these 12 REs. Thus, the DMRS overhead is 6 REs per PRB per port for rank 1/2.

FIG. 2B shows a DMRS pattern using OCC2 for DL SU-MIMO rank 3/4 transmission. The DMRS signal occupies 24 REs per PRB. Among these 24 REs, 12 REs are shared by ports 7/8 using OCC2 and the other 12 REs are shared by ports 9/10 using OCC2. OCC2 is applied to 2 adjacent REs in time domain with a same way as rank 1/2 DMRS pattern. It can be found that the DMRS overhead is 6 REs per PRB per port for rank 3/4. Compared with the DMRS overhead of rank 1/2, as shown in FIG. 2A, the DMRS overhead doubles for rank 3/4 transmission shown in FIG. 2B.

FIG. 2C shows a DL SU-MIMO transmission with rank >4, where DMRS pattern using OCC4 is defined. The DMRS signal is transmitted in 24 REs per PRB, and OCC4 is applied to 4 REs on the subcarrier across two slots. More specifically, port 7/8/11/13 share 12 REs, and port 9/10/12/14 share another 12 REs. Thus, the DMRS overhead is 3 REs per PRB per port for rank >4.

The DMRS patterns in FIGs. 2A-2C are designed for general scenarios. Scenario-specific parameters, such as SNR and moving speed, have not been considered in DMRS patterns design. For some scenarios, like small cell scenario, the wireless link between eNB and stationary UE may be featured by high SNR, low frequency-selective and low time-selective fading. In such scenarios, the task of channel estimation is less challenging, and the DMRS overhead can be reduced while keeping the channel estimation degradation to a minimum.

A benefit of DMRS overhead reduction is to exploit the possibility of assigning some of the REs that form the legacy DMRS patterns in TM 9/10 to, for example, PDSCH transmission. These extra PDSCH REs can be used either to increase the throughput or improve the block error rate performance. DMRS overhead reduction can be achieved by reducing DMRS density in the frequency domain, time domain, or in both the frequency and time domain.

As shown in FIGs. 2A-2C, the legacy DMRS overhead is 6 REs per PRB per port for rank 1/2 and rank 3/4, and the DMRS overhead is 3 REs per PRB per port for rank greater than 4. In some embodiments, the DMRS overhead reduction techniques may be employed for rank 3/4 transmission. For example, several new low-overhead DMRS patterns may be employed for LTE DL SU-MIMO rank 3/4 transmission.

FIGs. 3A-3B show exemplary DMRS overhead reduction patterns, where DMRS signal is transmitted in 8 REs per PRB, and OCC4 may be applied to 4 REs on the subcarrier across two slots. The resource pattern of FIGs. 3A and of FIG. 3B may allocate exactly two pairs of adjacent resource elements per physical resource block (PRB) for the reference signal, where an orthogonal cover code may be applied to the adjacent resource elements. Each of the two adjacent resource elements of FIG. 3A and of FIG. 3B may be associated with any one of

transmission port

7, 8, 11 or 13. Compared with the legacy DL DMRS pattern in FIG. 2B, the DMRS overhead is reduced by 66.7％for the DMRS pattern of FIGs. 3A and 3B. Some of the differences between patterns in FIGs. 3A and 3B are that the DMRS REs of FIG. 3A have backwards compatibility with mobile stations that may use the DMRS patterns of FIGs. 2A-2B. Unlike in FIG. 3A, the DMRS REs of FIG. 3B are evenly distributed within the PRBs. A benefit of having evenly distributed DMRS REs is that it allows for improved channel estimation.

FIGs. 3C-3G show several exemplary DMRS overhead reduction patterns, where DMRS signal is transmitted in 4 REs per PRB, and OCC4 may be applied to 4 REs for each of these five patterns. Compared with the legacy DL DMRS pattern in FIG. 2B, DMRS overhead is reduced by 83.3％for the five DMRS patterns in FIGs. 3C-3G. The resource pattern of FIG. 3C may allocate exactly two adjacent resource elements per physical resource block (PRB) for the reference signal, where an orthogonal cover code may be applied to the adjacent resource elements. The two adjacent resource elements of FIG. 3C may be associated with any one of

transmission port

7, 8, 11 or 13.

The resource patterns of FIG. 3D and of FIG. 3E include a resource pattern that corresponds to exactly two pairs of adjacent resource elements of a first physical resource block for the reference signal. The resource pattern may not include any resource elements of a second physical resource block for the reference signal, where the second physical resource block is adjacent to the first physical resource block. Thus, in some embodiments, the second physical resource block of FIGs. 3D and 3E excludes allocation of resource elements for the reference signal. For example, the second physical resource block in FIGs. 3D and 3E does not use or allocate any resource elements for the reference signal. A benefit of not using resource elements for reference signals is that those resource elements can be used for data transmission. Thus, more data can be transmitted from a base station to a mobile station in a physical resource block. An orthogonal cover code may be applied to the adjacent resource elements of the first physical resource block. Each of the two adjacent resource elements of FIG. 3D and of FIG. 3E may be associated with any one of

transmission port

7, 8, 11 or 13.

The resource patterns of FIGs. 3F and 3G may allocate only two resource elements per physical resource block (PRB) for the reference signal, where an orthogonal cover code may be applied to the two resource elements. Each of the two resource elements of FIG. 3F and of FIG. 3G are associated with any one of

port

7, 8, 11 or 13.

One of the differences between the five patters in FIGs. 3C-3G is the distribution of DMRS REs within PRB. Depending on the channel condition, the base station, such as the eNB, can select or determine the most appropriate pattern. For instance, the base station can determine the frequency and time variations in the channel between the mobile station and the base station by receiving either the sounding reference signal (SRS) or the channel quality indicator (CQI) from the mobile station. The DMRS pattern of FIG. 3C is more suitable for the channel with relatively lower variation in the frequency domain. Further, the DMRS patterns of FIGs. 3D and 3E are more suitable for the channels with relatively lower variation in the time domain. For the channel with variation in both the time and frequency domains, DMRS patterns of FIGs. 3F and 3G should be used. The DMRS REs of patterns of FIGs. 3D and 3F have backwards compatibility with legacy DMRS patterns, while the DMRS REs of patterns of FIGs. 3E and 3G are evenly distributed within the PRBs.

In some embodiments, the DMRS overhead reduction patterns as shown in FIGs. 3A-3G may be applied to other scenarios, for example, for rank 1/2 or rank greater than 4 transmission in TM 9/10, if the base station or the mobile station determines that the channel conditions are good.

FIG. 4 shows a block diagram for an exemplary wireless communication base station 400 for transmission of both the legacy DL DMRS patterns and the reduced DL DMRS patterns. The wireless communication base station comprises a memory 405 that stores instructions for operations of the base station, and one or more processors 415 in communication with the memory 405 operable to execute instructions to cause the base station to perform several exemplary operations.

For example, a reference signal generation module 425 may generates a reference signal, such as DMRS, using the time and frequency resources corresponding to a resource pattern. The reference signal generation module 425 may generate an initial transmission of a DMRS for a first resource pattern that may be a legacy pattern as described in FIGs. 2A-2C. The reference signal generation module 425 may also generate subsequent transmission of DMRS for a second resource pattern that may be one of the reduced DMRS patterns as described in FIGs. 3A-3G. The transmitter 415 of the base station transmits the initial and subsequent transmission of the reference signals using the time and frequency resources corresponding to a selected or determined resource pattern.

The reference signal selection module 430 selects or determines a resource pattern representing time and frequency resources for transmission of the reference signal. The reference signal selection module 430 may select between a first resource pattern corresponding to a legacy pattern, and a second resource pattern corresponding to one of the exemplary reduced DMRS patterns. For example, an eNB may select and inform a UE which DMRS pattern will be used.

The reference signal communication module 435 may communicate the information indicative of the reduced DMRS pattern to one or more mobile stations. For example, if channel condition changes, an eNB may switch between a legacy and a reduced DMRS patterns in the middle of communications. Thus, the reference signal communication module 435 communicates the information indicative a second resource pattern, such as one of the reduced DMRS patterns, for the subsequent transmission of the reference signal to the one or more mobile devices.

The reference signal communication module 435 transmits a signal to the UE to inform the UE of the switch for subsequent transmissions. In LTE, this can be implemented in two ways. The first signaling method is to use DCI so that DMRS pattern can be switched dynamically on a sub-frame basis. The main advantage of dynamic switching is that the suitable DMRS pattern can be setup quickly as the channel condition changes. Larger DCI overhead may be the price paid for this rapid response. In some embodiments, the information indicative of the reduced DMRS pattern may be communicated to the one or more mobile station by transmitting the second resource pattern using downlink control information (DCI) .

The other signaling method is to introduce a new bit filed in the RRC signaling. The eNB reconfigures DMRS pattern through a RRC signaling if judged necessary, e.g., when the channel condition becomes bad. With this semi-static switching method, the signaling overhead can be reduced greatly. Thus, in some embodiments, the information indicative of the reduced DMRS pattern may be communicated to the one or more mobile station by transmitting the second resource pattern using a radio resource control message. In some embodiments, DMRS overhead reduction is used under wireless stationary links where channel variation is assumed to be small. In such embodiments, a semi-static DMRS pattern switching through RRC signaling may be preferred.

The channel quality module 440 allows the base station to monitor channel conditions. For example, as shown in FIG. 1, the channel quality module 440 of the base station may receive, using the receiver 420, a channel quality indicator (CQI) value from one or more mobile stations. Based on the CQI value, the channel quality module 440 may instruct the reference signal selection module 430 to either select the legacy DMRS pattern or one of the exemplary reduced DMRS patterns. For example, when the CQI value indicates that the modulation order is a higher modulation order, such as 256 QAM, 512 QAM or 1024 QAM, or higher, the channel quality module 440 may instruct the reference signal selection module 430 to select or determine one of the exemplary reduced DMRS patterns.

FIG. 5 shows an exemplary flow chart for operations performed by a base station to use the resource pattern with legacy and reduced DMRS signals. At the initial transmitting operation 502, the base station transmits an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern. The first resource pattern may be a legacy resource pattern that is known a priori to the receivers. At the determining operation 504, the base station selects or determines a second resource pattern representing time and frequency resources for a subsequent transmission of the reference signal. In some embodiments, the determining operation 504 may be performed before the initial transmitting operation 502. For example, before transmitting the initial transmission of the reference signal, the base station may select or determine a second resource pattern representing time and frequency resources for a subsequent transmission of the reference signal, such as one of the reduced DMRS patterns. Alternatively or additionally, the determining operation 504 may be performed after the initial transmission operation 502, based on a current operational condition of the wireless channel.

In the communicating operation 506, the base station communicates the second resource pattern for the subsequent transmission of the reference signal to one or more mobile stations. For example, when the base station sends a DCI to a mobile device as part of the communicating operation 506, the DCI may include a CQI indicating the modulation order of either 256 QAM or 1024 QAM. Upon receiving the modulation order information, the mobile station knows that a second resource pattern, such as one of the reduced DMRS patterns, will be used after an initial transmission of the reference signal according to a first resource pattern.

In some embodiments, the communicating operation 506 may be performed before the initial transmitting operation 502. For example, when the CQI sent by one of the mobile stations and received by the base station indicates that the modulation order is 1024 QAM, the communicating operation 506 may be performed before the initial transmitting operation 502 because the second resource pattern will be used after transmitting an initial transmission of a reference signal according to a first resource pattern.

At the subsequent transmitting operation 508, the base station transmits the subsequent transmission of the reference signal using the time and frequency resources corresponding to the second resource pattern to one or more mobile devices.

FIG. 6 shows a block diagram for an exemplary wireless communication mobile station 600 for reception of the legacy DL DMRS patterns and the reduced DL DMRS patterns. The wireless communication mobile station 600 comprises a memory 605 that stores instructions for operations of the mobile station 600, and one or more processors 610 that is in communication with the memory 605 and operable to execute the instructions to cause the mobile station to perform several exemplary operations.

For example, a reference signal reception module 625 may receive, using a receiver 620, a reference signal using the time and frequency resources corresponding to a resource pattern. The reference signal reception module may receive reference signals transmitted by the base station using either the legacy DMRS pattern described in FIGs. 2A-2C or one of the exemplary reduced DMRS patterns described in FIGs. 3A-3G. For example, the reference signal reception module 625 receives an initial transmission of a reference signal using the time and frequency resources corresponding to a first resource pattern.

The reference signal communication module 630 receives, using a receiver 620, information related to a resource pattern representing time and frequency resources for the initial or subsequent reception of reference signal. In some embodiments, after an initial transmission of the legacy DMRS patterns, the reference signal communication module 630 receives information from the base station that the base station may transmit reduced DMRS patterns for subsequent reception of the reference signal. In some embodiments, the reference signal communication module 630 receives information related to a selection of the second resource pattern by receiving information indicative of the second resource pattern from a radio resource control (RRC) message. In some embodiments, the reference signal communication module 630 receives information related to a selection of the second resource pattern by receiving information indicative of the second resource pattern from a downlink control information (DCI) .

The channel quality module 635 provides information about the channel to the base station. For example, the channel quality module 635 may transmit, using the transmitter 615, a channel quality indicator (CQI) value to the base station. Based on the CQI value, the base station may determine either select the legacy DMRS pattern or one of the exemplary reduced DMRS patterns and may communicate the selection of either pattern to the mobile station.

In some cases, DMRS overhead reduction may lead to degradation of channel estimation accuracy. This may degrade the system performance. Thus, a channel estimation module 640 may improve channel estimation using one of two ways. First, the channel estimation module 640 may improve channel estimation by using one of the exemplary reduced DMRS patterns with more REs used per PRB for DMRS transmission than one of the other reduced DMRS patterns. For example, by using the exemplary reduced DMRS pattern of FIG. 3B, the UE may receive DMRS signals in 8 REs per PRB, which while being lower than the legacy DMRS pattern, is not lower than, for example, the reduced DMRS pattern of FIG. 3G that only uses 2 RE per PRB for DMRS.

Second, to overcome the possible performance degradation due to DMRS overhead reduction, in an exemplary embodiment, a channel estimation module 640 can use a decision directed (DD) channel estimation method to exploit information on the non-pilot symbols. The channel estimation module 640 may use DD channel estimation to treat reliably detected data symbols as pilot symbols and use them for channel estimation. A benefit of using DD channel estimation is that it is equivalent to increasing the density of DMRS signals, and thus improves the quality of channel estimation. In some implementations, the channel estimation module 640 determines that the mobile station has successfully demodulated data in a first PRB that includes legacy DMRS signals using the time and frequency resources corresponding to a first resource pattern. Subsequently, when a mobile station receives a second PRB with a reduced DMRS signals using the time and frequency resources corresponding to a second resource pattern, the channel estimation module 640 may estimate the channel by using the data symbols from resource elements of the first physical resource block (PRB) that includes the legacy DMRS signals corresponding first resource pattern. Thus, the data symbols of the first PRB can be used as DMRS for the second PRB.

FIG. 7 shows an exemplary flow chart for operations performed by a wireless communication mobile station to use a resource pattern with legacy and reduced DMRS signals. At the receiving initial transmission operation 702, the mobile station receives an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern. At the receiving information operation 704, the mobile station receives information related to a second resource pattern representing time and frequency resources for a subsequent reception of the reference signal. At the receiving subsequent transmission operation 706, the mobile station receives the subsequent reception of the reference signal using the time and frequency resources corresponding to the second resource pattern.

The term “exemplary” is used to mean “an example of” and, unless otherwise stated, does not imply an ideal or a preferred embodiment.

Some of the embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM) , Random Access Memory (RAM) , compact discs (CDs) , digital versatile discs (DVD) , etc. Therefore, the computer-readable media can include a non-transitory storage media. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-or processor-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

Some of the disclosed embodiments can be implemented as devices or modules using hardware circuits, software, or combinations thereof. For example, a hardware circuit implementation can include discrete analog and/or digital components that are, for example, integrated as part of a printed circuit board. Alternatively, or additionally, the disclosed components or modules can be implemented as an Application Specific Integrated Circuit (ASIC) and/or as a Field Programmable Gate Array (FPGA) device. Some implementations may additionally or alternatively include a digital signal processor (DSP) that is a specialized microprocessor with an architecture optimized for the operational needs of digital signal processing associated with the disclosed functionalities of this application. Similarly, the various components or sub-components within each module may be implemented in software, hardware or firmware. The connectivity between the modules and/or components within the modules may be provided using any one of the connectivity methods and media that is known in the art, including, but not limited to, communications over the Internet, wired, or wireless networks using the appropriate protocols.

While this document contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this disclosure.

Claims

A wireless communication method, comprising:

transmitting an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern；

determining a second resource pattern representing time and frequency resources for a subsequent transmission of the reference signal；

communicating the second resource pattern for the subsequent transmission of the reference signal to one or more mobile stations； and

transmitting the subsequent transmission of the reference signal using the time and frequency resources corresponding to the second resource pattern.
The method of claim 1, wherein the communicating step includes transmitting information indicative of the second resource pattern using a radio resource control (RRC) message.
The method of claim 1, wherein the communicating step includes transmitting information indicative of the second resource pattern using downlink control information (DCI) .
The method of claim 1, wherein the determining step is performed responsive to receiving a channel quality indicator (CQI) value.
The method of claim 4, wherein the channel quality indicator (CQI) value indicates a modulation order of any one of 256 Quadrature Amplitude Modulation (QAM) , 512 QAM, and 1024 QAM.
The method of claim 1, wherein the first resource pattern is a legacy demodulation reference signal (DMRS) pattern defined for a multiple-input, multiple-output (MIMO) transmission mode in a legacy communication network.
The method of claim 1, wherein the second resource pattern comprises two pairs of adjacent resource elements per physical resource block (PRB) for the reference signal, the method further including applying an orthogonal cover code to the adjacent resource elements.
The method of claim 7, wherein the two pairs of adjacent resource elements per PRB are exactly two pairs of adjacent resource elements per PRB for the reference signal.
The method of claim 1, wherein the second resource pattern comprises two adjacent resource elements per physical resource block (PRB) for the reference signal, the method further including applying an orthogonal cover code to the two adjacent resource elements.
The method of claim 9, wherein the two adjacent resource elements per PRB are exactly two adjacent resource elements per PRB for the reference signal.
The method of claim 1, wherein

the second resource pattern comprises two pairs of adjacent resource elements of a first physical resource block (PRB) for the reference signal, and

the method further including applying an orthogonal cover code to the adjacent resource elements of the first physical resource block.
The method of claim 11, wherein the two pairs of adjacent resource elements of the first PRB are exactly two pairs of adjacent resource elements of the first PRB for the reference signal.
The method of claim 11, wherein

the second resource pattern includes a second physical resource block (PRB) adjacent to the first physical resource block, and

the second PRB excludes allocation of resource elements for the reference signal.
The method of claim 1, wherein the second resource pattern comprises only two resource elements per physical resource block (PRB) for the reference signal, wherein an orthogonal cover code is applied to the two resource elements.
The method of claim 7, 9, 11, or 14, wherein the allocated resource elements are associated with any one of transmission port 7, 8, 11 or 13.
The method of claim 1, wherein the reference signal is a demodulation reference signal (DMRS) for use by a receiving device for channel estimation.
A wireless communication method, comprising:

receiving, by a mobile station, an initial transmission of a reference signal using time and frequency resources corresponding to a first resource pattern；

receiving, by the mobile station, information related to a second resource pattern representing time and frequency resources for a subsequent reception of the reference signal； and

receiving, by the mobile station, the subsequent reception of the reference signal using the time and frequency resources corresponding to the second resource pattern.
The method of claim 17, wherein the information related to the second resource pattern is received in response to the mobile station transmitting a channel quality indicator (CQI) value.
The method of claim 18, wherein the channel quality indicator (CQI) value indicates a modulation order of any one of 256 Quadrature Amplitude Modulation (QAM) , 512 QAM, and 1024 QAM.
The method of claim 17, wherein the receiving of the information related to a selection of the second resource pattern includes receiving information indicative of the second resource pattern from a radio resource control (RRC) message.
The method of claim 17, wherein the receiving of the information related to a selection of the second resource pattern includes receiving information indicative of the second resource pattern from a downlink control information (DCI) .
The method of claim 17, wherein the first resource pattern is a legacy demodulation reference signal (DMRS) pattern defined for a multiple-input, multiple-output (MIMO) transmission mode in a legacy communication network.
The method of claim 17, wherein the second resource pattern comprises two pairs of adjacent resource elements per physical resource block (PRB) for the reference signal, an orthogonal cover code applied to the adjacent resource elements.
The method of claim 23, wherein the two pairs of adjacent resource elements per PRB are exactly two pairs of adjacent resource elements per PRB for the reference signal.
The method of claim 17, wherein the second resource pattern comprises two adjacent resource elements per physical resource block (PRB) for the reference signal, an orthogonal cover code applied to the two adjacent resource elements.
The method of claim 25, wherein the two adjacent resource elements per PRB are exactly two adjacent resource elements per PRB for the reference signal.
The method of claim 17, wherein

the second resource pattern comprises two pairs of adjacent resource elements of the first physical resource block (PRB) for the reference signal, and

an orthogonal cover code applied to the adjacent resource elements of the first physical resource block.
The method of claim 27, wherein the two pairs of adjacent resource elements of the first PRB are exactly two pairs of adjacent resource elements of the first PRB for the reference signal.
The method of claim 27, wherein

the second resource pattern includes a second physical resource block (PRB) adjacent to the first physical resource block, and

the second PRB excludes allocation of resource elements for the reference signal.
The method of claim 17, wherein the second resource pattern comprises only two resource elements per physical resource block (PRB) for the reference signal, wherein an orthogonal cover code is applied to the two resource elements.
The method of claim 23, 25, 27, or 30, wherein the allocated resource elements are associated with any one of transmission port 7, 8, 11 or 13.
The method of claim 17, wherein the reference signal is a demodulation reference signal (DMRS) for use by a receiving device for channel estimation.
The method of claim 17, further comprising:

performing channel estimation using the received reference signal of the second resource pattern.
The method of claim 17, further comprising:

performing a decision directed channel estimation using data symbols from resources elements of a first physical resource block that includes the first resource pattern.
An apparatus for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements a method recited in any of claims 1 to 16.
A computer readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method recited in any of claims 1 to 16.
An apparatus for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements a method recited in any of claims 17 to 34.
A computer readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method recited in any of claims 17 to 34.