WO2015000171A1

WO2015000171A1 - Signaling for uplink demodulation reference signal

Info

Publication number: WO2015000171A1
Application number: PCT/CN2013/078880
Authority: WO
Inventors: Erlin Zeng; Shuang TAN; Pengfei Sun; Haiming Wang
Original assignee: Broadcom Corporation
Priority date: 2013-07-05
Filing date: 2013-07-05
Publication date: 2015-01-08

Abstract

The present invention relates to methods, apparatuses and a computer program product for signaling for uplink demodulation reference signal. The invention includes causing reception of an uplink grant message at a user equipment, evaluating the uplink grant message, and determining, based on the result of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

Description

SI GNALI NG FOR UPLI NK DEMODULATI ON REFERENCE SI GNAL

Field of the invention The present invention relates to signaling for reduced uplink demodulation reference signal, and more particularly, relates to methods, apparatuses and a computer program product for signaling for uplink demodulation reference signal.

Background

The present invention relates to the uplink (UL) demodulation reference signal (DM RS) overhead reduction, which is in the scope of a study item for small cell enhancements for 3GPP (3^rd Generation Partnership Project) Release 12, as described in document [1].

Uplink DM RS reduction has been discussed in RAN1 #72bis meeting (cf. document [2]), and the following observations have been made and captured in the meeting minutes, which will be part of the technical report of the study item. The main methods considered for UL DM RS overhead reduction are:

reduction of number of DM RS symbols per subframe, and

reduction of number of subcarriers carrying DM RS.

Some gains are observed with only 1 DM RS symbol per subframe at high SINR (Signal to Interference plus Noise Ratio) and low UE mobility. Further, implementation issues also need to be considered.

For the main methods above, the first method is to drop one of the two DM RS symbols in a subframe, which theoretically reduce the RS overhead by 50%. The exact gain of the method has been evaluated and observed in 3GPP RAN1. The second method has different flavours, e.g., the overhead can be reduced by reducing the DM RS subcarriers from 12 to 6 in each Physical Resource Block (PRB), etc. Some embodiments of the invention focus on the first method, as the second method has larger specification impact and leads to increased PAPR (Peak-to- Average Power Ratio) if data and RS are multiplexed in the same OFDM (Orthogonal Frequency Division Multiplexing) symbol.

For the first method, there have been no discussions on the signaling mechanism to support such reduced DM RS. More specifically, signaling needs to be designed to indicate the DM RS pattern to the UE. Furthermore, in the legacy LTE uplink, OCC (Orthogonal Cover Code) is used to ensure orthogonality between spatial layers in case of SU- (Single User) or MU- (Multiple User) MIMO (Multiple Input Multiple Output). Therefore, signaling to support OCC with or without reduced DM RS needs to be considered as well.

Generally, there are two types of signaling, i.e., higher layer signaling or physical layer signaling. For the first type the configuration is semi-static, but doesn't require any changes to physical control channel such as the DCI design. For reduced DM RS pattern indication (especially method 1 listed above) and OCC allocation, it is beneficial to allow more flexibility via physical layer signaling mechanisms. For example, with method 1, as the DM RS symbol is only present in one of the two slots in a subframe, it is not possible to use frequency hopping for more robustness. Neither is it possible to multiplex two UEs via MU-MIMO.

On the other hand, in the legacy system, it is always possible to dynamically switch to fall back mode in PUSCH transmissions (i.e., from DCI format 4 to format 0) to use frequency hopping, or to dynamically switch between MU- and SU-MIMO based on eNB's scheduling decision. Therefore, if the DM RS reduction can be dynamically configured while no extra L1 overhead is introduced, it will bring eNB more choices to select the optimal operation mode, i.e. either reduce DM RS to increase single user's spectrum efficiency or not reduce DM RS to utilize frequency diversity or MU-MIMO.

With some embodiments of the invention, it is aimed at balancing the standardization effort and the flexibility of signaling design. References:

[1]: RP- 122032, New Study Item Proposal for Small Cell Enhancements for E- UTRA and E-UTRAN - Physical- layer Aspects

[2]: 3GPP RAN1 #72bis, RAN1 Chairman's Notes, 15th - 19th April, 2013

Summary of the invention In view of the above, it is an object of some embodiments of the present invention to provide a signaling mechanism to support reduction of number of uplink demodulation reference signal (UL DM RS) symbols per subframe.

According to some example aspects of the present invention, there are provided methods, apparatuses and a computer program product for signaling for reduced uplink DM RS.

Various aspects of example embodiments of the present invention are set out in the appended claims.

According to an example aspect of the present invention, there is provided a method comprising:

causing reception of an uplink grant message at a user equipment, evaluating the uplink grant message, and

determining, based on the result of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

According to another example aspect of the present invention, there is provided a method comprising:

composing, at part of a network entity, an uplink grant message, configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and causing transmission of the uplink grant message to the user equipment.

According to another example aspect of the present invention, there is provided an apparatus comprising:

at least one processor,

and at least one memory including computer program code,

the at least one memory and the computer program code arranged to, with the at least one processor, cause the apparatus at least to perform:

causing reception of an uplink grant message,

evaluating the uplink grant message, and

at least one processor,

and at least one memory including computer program code,

composing, at part of a network entity, an uplink grant message, configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and

causing transmission of the uplink grant message to the user equipment.

means for causing reception of an uplink grant message,

means for evaluating the uplink grant message, and

means for determining, based on the result of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern. According to another example aspect of the present invention, there is provided an apparatus comprising:

means for composing an uplink grant message,

means for configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and

means for causing transmission of the uplink grant message to the user equipment. According to another example aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present invention), is arranged to cause the computer to carry out the method according to any one of the aforementioned method- related exemplary aspects of the present invention.

Such computer program product may comprise or be embodied as a (tangible) computer-readable (storage) medium or the like on which the computer- executable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof.

Advantageous further developments or modifications of the aforementioned example aspects of the present invention are set out in the dependent claims.

Brief Description of the Drawings

For a more complete understanding of example embodiments of the present invention, reference is now made to the following description taken in connection with the accompanying drawings in which:

Fig. 1 including Figs. 1 (a) and 1 (b) shows diagrams illustrating some examples of demodulation reference signal patterns; Fig. 2 is a flowchart illustrating an example of a method according to certain embodiments of the present invention;

Fig. 3 is a block diagram illustrating an example of an apparatus according to certain embodiments of the present invention;

Fig. 4 is a flowchart illustrating an example of another method according to certain embodiments of the present invention; Fig. 5 is a block diagram illustrating an example of another apparatus according to certain embodiments of the present invention.

Description of example embodiments Example aspects of the present invention will be described herein below. More specifically, example aspects of the present are described hereinafter with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied.

It is to be noted that the following description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain example network configurations and deployments. Namely, some embodiments of the invention are mainly described in relation to 3GPP specifications being used as non-limiting examples for certain example network configurations and deployments. In particular, a LTE/LTE- Advanced communication system is used as a non-limiting example for the applicability of thus described example embodiments. As such, the description of example embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the invention in any way. Rather, any other network configuration or system deployment, etc. may also be utilized as long as compliant with the features described herein. As indicated above, in the legacy system, it is possible for eNB to dynamically schedule different transmissions "modes" in the uplink, e.g., SU- or MU-MI MO, with or without frequency hopping, and it would be desirable if similar flexibility is achievable without increasing the overhead in Rel-12.

If the eNB determines that MU-MIMO can be used to boost the spectrum efficiency, it will schedule full DM RS pattern to the UE so that OCC is enabled. Further, if the eNB determines that frequency hopping should be used for a UE for robustness, it will schedule full DM RS pattern. Otherwise reduced pattern can be used to save overhead.

Certain embodiments of the present invention generally provide signaling designs to support reduction of number of DM RS symbols per subframe, and more particularly, introduces some physical layer signaling to inform the user equipment (UE) about the use of reduced DMRS pattern or normal, full DMRS pattern dynamically, namely via DCI format/content, RNTI, as described in detail in the following. In a first example aspect of the present invention, the UE determines whether reduced DM RS is used from the DCI (Downlink Control Information) format that it detects, or the RNTI (Radio Network Temporary Identifier) used to scramble the uplink grant. In a second example aspect of the present invention, the UE determines whether reduced DM RS is used from a redefined DCI field, e.g., certain state of the TPC (Transmit Power Control) command or cyclic shift for DM RS and OCC index.

If the UE determines that full DM RS is used, it shall follow the OCC allocation mechanism as in the legacy LTE uplink.

However, if the UE determines that reduced DM RS is used, it shall assume that OCC is disabled. Thus, the procedure can be roughly divided in two parts, namely, determination of DM RS pattern and determination of OCC allocations.

Determination of DM RS pattern

For PUSCH transmissions, the UE has to determine the proper DM RS pattern to generate and send. Otherwise, it is not possible for the network to have correct channel estimation and decoding. Fig. 1 shows examples of a subframe of a LTE radio frame, wherein the subframe consists of two consecutive slots 11 and 12, and each slot contains 7 symbols. Fig.1(a) shows an example where slot 11 includes a DM RS symbol 13 and slot 12 includes a DM RS symbol 14. Fig. 1(b) shows an example where only slot 15 includes a DM RS symbol 17 and slot 16 does not include a DM RS symbol.

In the following, it is assumed that there are two possible DM RS patterns, i.e.,

• full DM RS pattern, as in legacy LTE uplink including one DM RS symbol in each slot (as illustrated in Figure 1a), and

• reduced DM RS pattern, where only the symbol #3 in slot #0 is used as DM RS and slot #1 does not include DM RS (as illustrated in Figure 1b).

According to some embodiments of the invention, the UE determines whether reduced DM RS pattern or full DM RS pattern is used from the DCI format that it detects, or the RNTI used to scramble the uplink grant.

For dynamic scheduling, one possible way according to this example aspect is that

• if UE detects DCI format 0 for a UL grant, it shall assume full DM RS pattern, and

· if UE detects DCI format 4 for a UL grant, it shall assume reduced DM

RS pattern. If DCI format 0 is used, then it is possible to enable intra-subframe frequency hopping as the DM RS are present in both slots #0 and #1 in the subframe, as shown in Figure 1 (a) . In another example, the UE determines the DM RS pattern based on both RNTI used for scrambling the UL grant and higher layer configuration. More specifically, if UE detects UL grant scrambled by SPS- (Semi-Persistent Scheduling) RNTI, it will apply the DM RS pattern predefined by higher layer for this case. Thus, whether reduced DM RS or full DM RS is used is predefined by the higher layer in this case.

According to some embodiments of the invention, the UE determines whether reduced DM RS pattern or the full DM RS pattern is used from a redefined DCI field.

In Table 1 , there is shown an example of redefining one of the four TPC states as DM RS pattern indication. One possible ways of defining this new state (in the example the new state corresponds to the TPC state 3, which means the two TPC bits are set to 11 in the DCI format) is that

· if TPC state is 3, then full DM RS pattern is used, and

• otherwise, reduced DM RS pattern is used.

Table 1 shown in the following illustrates example of the redefined TPC field in DCI format 0/4.

The impact with some embodiments of the invention is that the field 3 as shown in Table 1 is inapplicable for power control. To alleviate this, eNB can use DCI format 3 or 3A to adjust the PUSCH power if needed. Another way to avoid such impact in the case of DCI format 0 is that if UE detects that the TPC state is 0, 1, or 2 in the DCI format it can reuse the frequency hopping field as an indication of TPC as well (e.g., if frequency hopping bits is 1 then the power offset is equal to 3dB, otherwise it follows the value of the original TPC field). It is noted that in Table 1 the TPC bits are interpreted as either DM RS pattern indication or an offset power to the PUSCH, but in practice it can be either DM RS pattern indication or an absolute power value to the PUSCH.

Another example uses the field of cyclic shift for DM RS and OCC index to dynamically indicate whether legacy DM RS or reduced DM RS should be used, as seen in Table 2. Among all the eight states, four of them indicate length-2 OCC with no zero element implying legacy DM RS used for the scheduled uplink transmission. The other four have one zero element in the OCC vector which indicates that reduced DMRS will be applied.

The cost of redefining some states of the field is reducing the number of available cyclic shift and OCC for multi-user scheduling. However, it has been noticed that for the targeted small cell scenario, the number of UEs per cell is expected very low, and thus it is believed that the introduced restriction of multiuser scheduling has little impact in the practical system.

The procedure according to the this example aspect is as follows:

1) eNB decides that reduced DM RS may be used for a UE, and configures the UE to be in a mode where reduced DM RS may be used; 2) if configured, UE interprets the DCI format in the newly defined way. Otherwise legacy operation will be used.

Determination of OCC allocations

OCC is used to support orthogonality among the spatial layers in MIMO transmissions. For example, two OCC vectors such as OCC# 1 [+1 +1] and OCC #2 [+1 -1], if applied to the two DM RS symbols in a subframe, enables interference cancelation by combining the two symbols if the cyclic shift of the sequence is the same. By allocating OCC vectors to the same UE or different UEs, SU- or MU-MIMO can be supported.

From high level, in some embodiments of the invention, UE determines the OCC allocation based on the determination of the DM RS pattern in use. If UE determines that full DM RS is used, it shall follow the OCC allocation mechanism as in the legacy LTE uplink. While if UE determines that reduced DM RS is used, it shall assume OCC is disabled.

For some embodiments of the invention, as described above, the UE first determines the DM RS pattern. If reduced DM RS pattern is used then OCC is disabled as there is only one RS symbol in the subframe. Otherwise, UE determines OCC based on the DCI format, which is the same behavior as in the current LTE specification. For some embodiments of the invention, as described above, with the example in Table 1 the procedure of determining OCC is similar as according to the above described example aspect, and with the example in Table 2, the OCC is determined directly by using the Table 2. In summary, according to certain embodiments of the present invention, there is provided a signaling mechanism to support a reduction of number of UL DM RS symbols per subframe. In particular, there is proposed signaling to inform UE about the use of reduced DM RS or normal DM RS dynamically using DCI format, redefined DCI field, or RNTI . Then, the OCC allocation is determined based on the determination of the DM RS pattern in use (OCC enabled/disabled depending on normal/ reduced DM RS) . , I f UE determines that full DM RS is used, it shall follow the OCC allocation mechanism as in the legacy LTE uplink, while if UE determines that reduced DM RS is used, it shall assume OCC is disabled.

Thus, according to certain aspect of the present invention, a flexible, dynamic indication of the use of reduced DM RS or normal, full DM RS to the UE without an increase of overhead is enabled. Fig. 2 shows a principle flowchart of an example for a method according to certain embodiments of the present invention. That is, as shown in Fig. 2, this method for use in a user equipment or part of the user equipment (e.g. a modem) comprises, in a step S21, causing reception of an uplink grant message at a user equipment, evaluating the uplink grant message in a step S22, and determining, in a step S23, based on the result of the evaluation of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

According to certain aspects of the present invention, evaluating the uplink grant message includes evaluating a downlink control information format of the uplink grant message.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the control information format of the uplink grant message, that downlink control information format 0 is used for the uplink grant message, applying a full demodulation reference signal pattern. According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the control information format of the uplink grant message, that downlink control information format 4 is used for the uplink grant message, applying a reduced demodulation reference signal pattern.

According to certain aspects of the present invention, evaluating the uplink grant message includes evaluating a radio network temporary identifier used in the uplink grant message.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the radio network temporary identifier used in the uplink grant message, that the radio network temporary identifier is a semi-persistent scheduling radio network temporary identifier, applying the demodulation reference pattern as predefined by higher layer signaling.

According to certain aspects of the present invention, evaluating the uplink grant message includes evaluating a redefined transmit power control command field in a downlink control information format of the uplink grant message.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the redefined transmit power control command field in a downlink control information format of the uplink grant message, that transmit power control command field 3 is used in the downlink control information format of the uplink grant message, applying a full demodulation reference signal pattern.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the redefined transmit power control command field in a downlink control information format of the uplink grant message, that any one of transmit power control command field 0,1, and 2 is used in the downlink control information format of the uplink grant message, applying a reduced demodulation reference signal pattern. According to certain aspects of the present invention, evaluating the uplink grant message includes evaluating a field of cyclic shift for DM RS and OCC index in the downlink control information format of the uplink grant message.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the field of cyclic shift for DM RS and OCC index in the downlink control information format of the uplink grant message, that the orthogonal cover code vector includes a zero element, applying a reduced demodulation reference signal pattern.

According to certain aspects of the present invention, the method further comprises, if it is determined, as a result of the evaluation of the field of cyclic shift for DM RS and OCC index in the downlink control information format of the uplink grant message, that the orthogonal cover code vector includes no zero element, applying a full demodulation reference signal pattern.

According to certain aspects of the present invention, the method further comprises, if the reduced demodulation reference signal pattern is applied, determining that orthogonal cover code is disabled.

According to certain aspects of the present invention, the full demodulation reference signal pattern comprises two reference signal symbols in one subframe. According to certain aspects of the present invention, the reduced demodulation reference signal pattern comprises one reference signal symbol in one subframe.

Fig. 3 shows a principle configuration of an example for an apparatus according to certain embodiments of the present invention. The apparatus 30, which may be a user equipment or part of a user equipment, comprises at least one processor 31 and at least one memory 32 including computer program code, which are connected by a bus 34 or the like. As indicated with a dashed line in Fig. 3, an interface 33 may optionally be connected to the bus 34 or the like, which may enable communication e.g. to/from a base station, a network entity, or the like. The at least one memory and the computer program code are arranged to, with the at least one processor, cause the user equipment at least to perform causing reception of an uplink grant message at a user equipment, evaluating the uplink grant message, and determining, based on the result of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

For further functions of the apparatus according to further example embodiments of the present invention, reference is made to the above description of methods according to certain embodiments of the present invention, as described in connection with Fig. 2.

One option for implementing this example for an apparatus according to certain versions of the present disclosure would be a component in a handset such as user equipment UE according to 3G or LTE/LTE-A or any future developed technology. For example, the user equipment may be a mobile phone, a personal digital assistant (PDA), a laptop computer, a tablet computer, or the like.

Fig.4 shows a principle flowchart of an example for another method according to certain embodiments of the present invention. That is, as shown in Fig. 4, this method for use in a network entity (e.g. base station or part of the base station) comprises, in a step S41, composing an uplink grant message, configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern in a step S42, and causing transmission of the uplink grant message to the user equipment in a step S43.

According to certain aspects of the present invention, configuring the uplink grant message includes selecting a downlink control information format of the uplink grant message that indicates to the user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern. According to certain aspects of the present invention, selecting a downlink control information format 0 of the uplink grant message indicates to the user equipment to apply a full demodulation reference signal pattern. According to certain aspects of the present invention, selecting a downlink control information format 4 of the uplink grant message indicates to the user equipment to apply a reduced demodulation reference signal pattern.

According to certain aspects of the present invention, configuring the uplink grant message includes selecting a radio network temporary identifier to be used in the uplink grant message.

According to certain aspects of the present invention, selecting a semi-persistent scheduling radio network temporary identifier as the radio network temporary identifier used in the uplink grant message indicates to the user equipment to apply the demodulation reference pattern as predefined by higher layer signaling.

According to certain aspects of the present invention, configuring the uplink grant message includes selecting a redefined transmit power control command field or a normal transmit power control command field in a downlink control information format of the uplink grant message.

According to certain aspects of the present invention, a redefined transmit power control command field in the downlink control information format of the uplink grant message indicates to the user equipment to apply a full demodulation reference signal pattern.

According to certain aspects of the present invention, a normal transmit power control command field in the downlink control information format of the uplink grant message indicates to the user equipment to apply a reduced demodulation reference signal pattern.

According to certain aspects of the present invention, configuring the uplink grant message includes configuring a field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message.

According to certain aspects of the present invention, if the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message indicates that the orthogonal cover code vector includes a zero element, it is indicated to the user equipment to apply a reduced demodulation reference signal pattern. According to certain aspects of the present invention, if the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message indicates that the orthogonal cover code vector includes no zero element, it is indicated to the user equipment to apply a full demodulation reference signal pattern.

According to certain aspects of the present invention, the full demodulation reference signal pattern comprises two reference signal symbols in one subframe.

According to certain aspects of the present invention, the reduced demodulation reference signal pattern comprises one reference signal symbol in one subframe.

According to certain aspects of the present invention, the network entity comprises a base station. Fig. 5 shows a principle configuration of an example for an apparatus according to certain embodiments of the present invention. The apparatus 50, which may be a network entity (e.g. a base station or part of a base station), comprises at least one processor 51 and at least one memory 52 including computer program code, which are connected by a bus 54 or the like. As indicated with a dashed line in Fig. 5, an interface 53 may optionally be connected to the bus 54 or the like, which may enable communication e.g. to/from a base station, a network entity, user equipment or the like. The at least one memory and the computer program code are arranged to, with the at least one processor, cause the network entity at least to perform composing, at part of a network entity, an uplink grant message, configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and causing transmission of the uplink grant message to the user equipment.

For further functions of the apparatus according to further example embodiments of the present invention, reference is made to the above description of methods according to certain embodiments of the present invention, as described in connection with Fig. 4.

One option for implementing this example for an apparatus according to certain versions of the present disclosure would be a component in a base station according to 3G or LTFJLTE-A, e.g. NodeB or eNodeB (eNB), or any future developed technology.

In the foregoing example description of the apparatuses, i.e. the user equipment or the network entity (or part of the user equipment or part of the network entity), only the units that are relevant for understanding the principles of the invention have been described using functional blocks. The apparatus may comprise further units that are necessary for its respective operation as user equipment or part of the user equipment or network entity or part of the network entity (e.g. a base station or eNB), respectively. However, a description of these units is omitted in this specification. The arrangement of the functional blocks of the apparatus is not construed to limit the invention, and the functions may be performed by one block or further split into sub-blocks.

According to exemplarily embodiments of the present invention, a system may comprise any conceivable combination of the thus depicted devices/apparatuses and other network elements, which are arranged to cooperate as described above.

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any procedural step or functionality is suitable to be implemented as software or by hardware without changing the idea of the present invention. Such software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C+ + , C, and Assembler, as long as the functionality defined by the method steps is preserved. Such hardware may be hardware type independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components. A device/ apparatus may be represented by a semiconductor chip, a chipset, system in package (SIP), or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/ apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor. A device may be regarded as a device/ apparatus or as an assembly of more than one device/ apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example. Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person. Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof. The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above- described concepts of methodology and structural arrangement are applicable.

Even though the present invention and/or example embodiments are described above with reference to the examples according to the accompanying drawings, it is to be understood that they are not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

Abbreviations:

3GPP 3rd Generation Partnership Project

DCI Downlink Control Information

DM RS Demodulation Reference Signal

MIMO Multiple Input Multiple Output

MU Multiple User

OCC Orthogonal Cover Code

OFDM Orthogonal Frequency Division Multiplexing

PAPR Peak-to-Average Power Ratio

PUSCH Physical Uplink Shared Channel

RAN Radio Access Network

RNTI Radio Network Temporary Identifier

PRB Physical Resource Block SINR Signal to Interference plus Noise Ratio

SPS Semi-Persistent Scheduling

SU Single User

TPC Transmit Power Control

UL Uplink

Claims

WHAT I S CLAI MED I S:

1. A method, comprising:

determining, based on the result of the evaluation of the downlink control information format of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

2. The method according to claim 1, wherein

evaluating the uplink grant message includes

evaluating a downlink control information format of the uplink grant message.

3. The method according to claim 2, further comprising

if it is determined, as a result of the evaluation of the control information format of the uplink grant message, that downlink control information format 0 is used for the uplink grant message,

applying a full demodulation reference signal pattern.

4. The method according to claim 2, further comprising

if it is determined, as a result of the evaluation of the control information format of the uplink grant message, that downlink control information format 4 is used for the uplink grant message,

applying a reduced demodulation reference signal pattern.

5. The method according to claim 1, wherein

evaluating the uplink grant message includes

evaluating a radio network temporary identifier used in the uplink grant message.

6. The method according to claim 5, further comprising if it is determined, as a result of the evaluation of the radio network temporary identifier used in the uplink grant message, that the radio network temporary identifier is a semi-persistent scheduling radio network temporary identifier,

applying the demodulation reference pattern as predefined by higher layer signaling.

7. The method according to claim 1, wherein

evaluating the uplink grant message includes

evaluating a redefined transmit power control command field in a downlink control information format of the uplink grant message.

8. The method according to claim 7, further comprising

if it is determined, as a result of the evaluation of the redefined transmit power control command field in a downlink control information format of the uplink grant message, that transmit power control command field 3 is used in the downlink control information format of the uplink grant message,

applying a full demodulation reference signal pattern.

9. The method according to claim 7, further comprising

if it is determined, as a result of the evaluation of the redefined transmit power control command field in a downlink control information format of the uplink grant message, that any one of transmit power control command field 0,1, and 2 is used in the downlink control information format of the uplink grant message,

applying a reduced demodulation reference signal pattern.

10. The method according to claim 9, further comprising

reusing a frequency hopping field in the uplink grant message as an indication of transmit power control.

11. The method according to claim 10, further comprising

if the frequency hopping bit in the uplink grant message is set to 1, setting a predetermined power offset.

12. The method according to claim 1, wherein

evaluating the uplink grant message includes

evaluating a field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message.

13. The method according to claim 12, further comprising

if it is determined, as a result of the evaluation of the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message, that the orthogonal cover code vector includes a zero element,

applying a reduced demodulation reference signal pattern.

14. The method according to claim 12, further comprising

if it is determined, as a result of the evaluation of the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message, that the orthogonal cover code vector includes no zero element,

applying a full demodulation reference signal pattern.

15. The method according to anyone of claims 1 to 14, further comprising

if the reduced demodulation reference signal pattern is applied,

determining that orthogonal cover code is disabled.

16. The method according to any one of claims 1 to 15, wherein

the full demodulation reference signal pattern comprises two reference signal symbols in one subframe.

17. The method according to any one of claims 1 to 16, wherein

the reduced demodulation reference signal pattern comprises one reference signal symbol in one subframe.

18. A method, comprising: composing, at part of a network entity, an uplink grant message, configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and

causing transmission of the uplink grant message to the user equipment.

19. The method according to claim 18, wherein

configuring the uplink grant message includes

selecting a downlink control information format of the uplink grant message that indicates to the user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

20. The method according to claim 19, wherein

selecting a downlink control information format 0 of the uplink grant message indicates to the user equipment to apply a full demodulation reference signal pattern.

21. The method according to claim 19, wherein

selecting a downlink control information format 4 of the uplink grant message indicates to the user equipment to apply a reduced demodulation reference signal pattern.

22. The method according to claim 18, wherein

configuring the uplink grant message includes

selecting a radio network temporary identifier to be used in the uplink grant message.

23. The method according to claim 22, wherein

selecting a semi-persistent scheduling radio network temporary identifier as the radio network temporary identifier used in the uplink grant message indicates to the user equipment to apply the demodulation reference pattern as predefined by higher layer signaling.

24. The method according to claim 18, wherein

configuring the uplink grant message includes

selecting a redefined transmit power control command field or a normal transmit power control command field in a downlink control information format of the uplink grant message.

25. The method according to claim 24, wherein

a redefined transmit power control command field in the downlink control information format of the uplink grant message indicates to the user equipment to apply a full demodulation reference signal pattern.

26. The method according to claim 24, wherein

a normal transmit power control command field in the downlink control information format of the uplink grant message indicates to the user equipment to apply a reduced demodulation reference signal pattern.

27. The method according to claim 18, wherein

configuring the uplink grant message includes

configuring a field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message.

28. The method according to claim 27, wherein

if the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message indicates that the orthogonal cover code vector includes a zero element it is indicated to the user equipment to apply a reduced demodulation reference signal pattern.

29. The method according to claim 27, wherein

if the field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message indicates that the orthogonal cover code vector includes no zero element it is indicated to the user equipment to apply a full demodulation reference signal pattern.

30. The method according to any one of claims 18 to 29, wherein

31. The method according to any one of claims 18 to 30, wherein

32. The method according to any one of claims 18 to 31, wherein

the network entity comprises a base station.

33. An apparatus, comprising:

at least one processor,

and at least one memory including computer program code,

causing reception of an uplink grant message,

evaluating the uplink grant message, and

34. The apparatus according to claim 33, wherein

evaluating the uplink grant message includes

evaluating a downlink control information format of the uplink grant message.

35. The apparatus according to claim 34, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform if it is determined, as a result of the evaluation of the control information format of the uplink grant message, that downlink control information format 0 is used for the uplink grant message,

applying a full demodulation reference signal pattern.

36. The apparatus according to claim 34, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

applying a reduced demodulation reference signal pattern.

37. The apparatus according to claim 33, wherein

evaluating the uplink grant message includes

38. The apparatus according to claim 37, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

if it is determined, as a result of the evaluation of the radio network temporary identifier used in the uplink grant message, that the radio network temporary identifier is a semi-persistent scheduling radio network temporary identifier,

39. The apparatus according to claim 33, wherein

evaluating the uplink grant message includes

40. The apparatus according to claim 39, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

applying a full demodulation reference signal pattern.

41. The apparatus according to claim 39, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

applying a reduced demodulation reference signal pattern.

42. The apparatus according to claim 41, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

43. The apparatus according to claim 42, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

44. The apparatus according to claim 33, wherein

evaluating the uplink grant message includes evaluating a field of cyclic shift for demodulation reference signal and orthogonal cover code index in the downlink control information format of the uplink grant message.

45. The apparatus according to claim 42, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

applying a reduced demodulation reference signal pattern.

46. The apparatus according to claim 42, wherein the at least one memory and the computer program code are further arranged to, with the at least one processor, cause the apparatus at least to perform

applying a full demodulation reference signal pattern.

47. The apparatus according to anyone of claims 33 to 46, further comprising if the reduced demodulation reference signal pattern is applied,

determining that orthogonal cover code is disabled.

48. The apparatus according to any one of claims 33 to 47, wherein

49. The apparatus according to any one of claims 33 to 48, wherein

50. The apparatus according to any one of claims 33 to 49, wherein the apparatus comprises a user equipment.

51. An apparatus, comprising:

at least one processor,

and at least one memory including computer program code,

composing an uplink grant message,

configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and

causing transmission of the uplink grant message to the user equipment.

52. The apparatus according to claim 51, wherein

configuring the uplink grant message includes

53. The apparatus according to claim 52, wherein

54. The apparatus according to claim 52, wherein

55. The apparatus according to claim 52, wherein

configuring the uplink grant message includes selecting a radio network temporary identifier to be used in the uplink grant message.

56. The apparatus according to claim 55, wherein

57. The apparatus according to claim 51, wherein

configuring the uplink grant message includes

58. The apparatus according to claim 57, wherein

59. The apparatus according to claim 57, wherein

60. The apparatus according to claim 51, wherein

configuring the uplink grant message includes

61. The apparatus according to claim 60, wherein

62. The apparatus according to claim 60, wherein

63. The apparatus according to any one of claims 51 to 62, wherein

64. The apparatus according to any one of claims 51 to 63, wherein

65. The apparatus according to any one of claims 51 to 64, wherein

the apparatus comprises a base station, NodeB or eNodeB.

66. An apparatus, comprising

means for causing reception of an uplink grant message,

means for evaluating the uplink grant message, and

means for determining, based on the result of the evaluation of the downlink control information format of the uplink grant message, whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern.

67. An apparatus, comprising:

means for composing an uplink grant message, means for configuring the uplink grant message so as to inform a user equipment whether to apply a full demodulation reference signal pattern or a reduced demodulation reference signal pattern, and

means for causing transmission of the uplink grant message to the user equipment.

68. A computer program product comprising computer-executable computer program code which, when the program is run on a computer, is arranged to cause the computer to carry out the method according to any one of claims 1 to 32.

69. The computer program product according to claim 68, embodied as a computer-readable storage medium.