HK1226235B - Method and arrangement for adapting power of reference signals - Google Patents

Description

Method and apparatus for adjusting the power of a reference signal

Technical Field

The present disclosure relates to the field of telecommunications. More particularly, the present disclosure relates to a method and apparatus for adapting the power of resource elements of a demodulation reference signal in a radio network node.

Background Art

The Third Generation Partnership Project (3GPP) is responsible for the standardization of the Universal Mobile Telecommunications Service (UMTS) system and Long Term Evolution (LTE). LTE is a technology for enabling high-speed packet-based communications that can achieve high data rates in both the downlink and uplink, and is considered the next generation mobile communications system to the UMTS system. The 3GPP work on LTE is also known as the Evolved Universal Terrestrial Access Network (E-UTRAN). The LTE system is capable of providing a peak rate of 300 Mbps, such as a radio network latency of 5 ms or less, significantly increased spectrum efficiency, and a network architecture designed to simplify network operation, reduce costs, etc. In order to support high data rates, LTE allows for a system bandwidth of up to 20 MHz. LTE is also capable of operating in different frequency bands and can operate in at least frequency division duplex (FDD) and time division duplex (TDD). The modulation technique or transmission scheme used in LTE is called orthogonal frequency division multiplexing (OFDM).

For next generation mobile communication systems, such as International Mobile Telecommunications Advanced (IMT-Advanced) and/or LTE-Advanced (which is an evolution of LTE), support for bandwidths up to 100 MHz has been discussed. LTE-Advanced can be considered a future discovery version of the LTE standard, and since it is an evolution of LTE, backward compatibility is important so that LTE-Advanced can be deployed in the spectrum already occupied by LTE. In LTE and LTE-Advanced radio base stations, called eNBs or eNodeBs (where e stands for evolution), multiple antennas with precoding/beamforming techniques can be employed to provide high data rates to user equipment. LTE and LTE-Advanced are therefore examples of Multiple Input Multiple Output (MIMO) radio systems. Another example of a MIMO radio system is the Worldwide Interoperability for Microwave Access (WiMAX) system.

In known LTE systems, such as LTE Release 8 or 9 (Rel 8 or 9), so-called user equipment-specific reference signals (RSs) are specified for single-layer beamforming. Single-layer beamforming implies rank-1 transmission, also known as rank-1 transmission. As an example, the reference signal is provided for channel quality measurement purposes to enable channel demodulation. Two-layer beamforming can also be used. Two-layer beamforming can be referred to as rank-2 transmission, or rank-2 transmission.

In the case of rank 1 or 2 transmissions for the known LTE systems mentioned above, it has been decided to use the same or equal transmit power for reference signal resource elements (RS REs) and data resource elements (data REs). Therefore, when a user equipment (UE) receives the transmission, the user equipment processes and assumes the same transmit power for RS REs and data resource elements (data REs). Therefore, the UE can apply the same power processing to the demodulation reference signal resource elements (DM-RS REs) and data REs for each layer. Since the same power processing is used for all layers, there is no need for control signaling related to power normalization to indicate to the UE which power level has been used.

In LTE-Advanced, it has been proposed to use advanced antenna configurations, such as 8x8 high-order MIMO, to support up to rank 8 transmission or rank 8 transmission. In addition, up to 8 user equipment-specific reference signals, called demodulation RS or DM-RS, have been introduced for the purpose of channel demodulation.

FIG1 shows a resource element structure of two resource blocks used in OFDM transmission in an LTE-Advanced system. The first resource block is indicated by a dotted rectangle. The vertical axis indicates time/symbol in the time domain, and the horizontal axis indicates frequency, e.g., subcarrier. DM-RS resource elements are indicated by C1 and C2 as described below. The empty boxes in FIG1 may include, for example, symbols for data, control, or other items. Referring to FIG1 , according to LTE-Advanced, some characteristics of a DM-RS with a normal cyclic prefix (CP) are described below:

• Same RS position, i.e. in the last two symbols in the time domain and in frequency domain subcarrier numbers 1, 2, 6, 7, 11 and 12 in each resource block.

RS overhead of 12 RE per layer, see 12 indicators for C1 and C2 respectively.

• Up to two CDM groups (Code Division Multiplexing) Frequency Division Multiplexing (FDM) as shown by C1 and C2.

• For rank 3-8 transmissions, two CDM groups indicated by C1 and C2 are used, and for ranks 1-2, only one CDM group (group 1 indicated by C1) is used.

• Orthogonal Cover Codes (OCC) spanning the time domain only.

Therefore, for high-order MIMO according to LTE-Advanced, up to 8 DM-RSs will be transmitted in combination with up to rank 8 transmission. As shown in Figure 1, two CDM groups C1, C2 will be applied when the transmission layers exceed two, that is, for ranks 3-8, the transmission layers will be distributed into two CDM groups C1, C2. Rank 1-2 transmission of LTE-Advanced can reuse the rank 1-2 transmission of the known LTE system mentioned above. Therefore, the power utilization scheme of LTE-Advanced for ranks 1-2 is different from the power utilization scheme of the known LTE system mentioned above for ranks 1-2. Therefore, for consistency reasons, it may have been proposed to extend the power utilization scheme to also include LTE-Advanced ranks 3-8. In such cases, the DM-RS REs will require different power treatment compared to the data REs. However, as mentioned above, the UE adopts the same transmission power. Therefore, this can, for example, lead to inaccurate channel estimation and low power efficiency.

Summary of the Invention

One object is how to provide a power utilization scheme for reference elements in the downlink which improves the performance in a telecommunication system.

According to one aspect, the object can be achieved by a method in a radio network node for adjusting the transmission power of resource elements of a demodulation reference signal, referred to as "reference elements." The radio network node is configured for multiple-input multiple-output transmission, referred to as "MIMO transmission," to a user equipment. The MIMO transmission includes at least three layers, each layer being allocated to a resource block of the MIMO transmission. The resource block includes subcarriers. Two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers. A first subcarrier of the resource block carries data elements for the at least three layers. The first subcarrier is different from the two consecutive subcarriers. The radio network node adjusts the transmission power of the at least three reference elements so that the average transmission power of the at least three reference elements over the two consecutive subcarriers is equal to the transmission power of the first subcarrier for the data elements for the at least three layers. In addition, the radio network node transmits the at least three reference elements to the user equipment using the adjusted transmission power.

According to another aspect, the object can be achieved by a device in a radio network node for adjusting the transmission power of resource elements of a demodulation reference signal, referred to as "reference elements." The radio network node is configured for multiple-input multiple-output transmission, referred to as "MIMO transmission," to a user equipment. The MIMO transmission includes at least three layers, each layer being allocated to a resource block of the MIMO transmission. The resource block includes subcarriers. Two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers. A first subcarrier of the resource block carries data elements for the at least three layers. The first subcarrier is different from the two consecutive subcarriers. The device includes a processing circuit configured to adjust the transmission power of the at least three reference elements so that the average transmission power of the at least three reference elements over the two consecutive subcarriers is equal to the transmission power of the first subcarrier for the data elements of the at least three layers. In addition, the processing circuit is configured to transmit the at least three reference elements to the user equipment using the adjusted transmission power.

Therefore, in an embodiment disclosed herein, the radio network node adjusts the transmit power of the at least three reference elements such that the average transmit power over the two consecutive subcarriers of the at least three reference elements is equal to the transmit power for the first subcarrier of the data elements for the at least three layers. In this way, gaps (i.e., any existing gaps) between the transmit power of the reference elements and the data elements are averaged. The gaps may be represented by a transmit power difference between the transmit power of one of the two consecutive subcarriers and the transmit power of the first subcarrier. Due to the adjustment of the transmit power as specified above, a more efficient power utilization scheme is provided. The more efficient power utilization scheme exploits the gaps, i.e., the transmit power of the reference elements is adjusted, for example, to at least partially fill the gaps. As a result, the above-mentioned objects are achieved.

Further features of the embodiments and aspects, as well as advantages thereof, will become apparent when studying the appended claims and the following description.It will be understood that different features disclosed herein can be combined to form embodiments other than those described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments and aspects will become more fully understood from the accompanying drawings and the following detailed description, which are given by way of illustration only and thus are not intended to limit the scope of the present disclosure.

FIG1 shows a resource element structure used in OFDM transmission.

2A-2D illustrate power diagrams for rank 1 to 4 MIMO transmissions according to the prior art.

3 is a block diagram of a radio base station communicating with user equipment using MIMO transmissions.

FIG. 4 shows a schematic, exemplary combined signaling and flow diagram according to an embodiment of a method performed in the system of FIG. 3 .

5A-5D illustrate power diagrams for rank 1 to 4 MIMO transmissions according to an embodiment of the present disclosure.

Fig. 6 shows a schematic, exemplary block diagram of the arrangement in a radio base station.

DETAILED DESCRIPTION

The present disclosure generally relates to demodulation performance improvements for LTE-Advanced, where high-order MIMO is applied to support transmissions up to rank 8. The following detailed description is based on an exemplary Evolved Universal Terrestrial Radio Access (E-UTRA) system (also commonly referred to as the Long Term Evolution (LTE) of the widely deployed WCDMA system).

With reference to the background section, some observations regarding extending the power utilization scheme to include LTE-Advanced ranks 3-8 will be described in conjunction with Figures 2A-2D to facilitate understanding of the embodiments disclosed herein. As mentioned in the background section, it is recommended to allocate the same power to reference elements, such as DM-RS REs, and data resource elements for each layer.

2A-2D , the figures illustrate power utilization for LTE-Advanced rank 1-4 cases based on the recommendation to use the same power for reference elements and data resource elements. The rank 5-8 cases can be similarly extended. In the figures, the 12 subcarriers of the physical resource block (PRB) are shown along the horizontal axis. The power of the resource elements is indicated along the vertical axis. The reference numerals 1, 2, 3, and 4 enclosed by the boxes shown in the figures represent the number of the relevant layers. For example, "1" refers to layer 1, "2" refers to layer 2, and so on. As shown in FIG2A-2B , the rank 1-2 cases are provided for comparison purposes only. It can be observed that for LTE-Advanced ranks 1-2, reference elements such as DM-RS REs have the same power allocation as data REs. For ranks 1-2, only one CDM group is applied, see subcarriers 1, 6, and 11. However, for LTE-Advanced rank 3, unequal (or uneven) layer allocation is performed in two CDM groups, see subcarriers 1, 2, 6, 7, 11, and 12 of FIG2C . The layer allocation is unequal because the total transmit power allocated to the reference elements of each CDM group is different compared to the transmit power of the data elements. In addition, it has been observed that the power utilization on reference elements such as DM-RS REs is not always efficient for rank 3 and higher. Therefore, for LTE-Advanced rank 3, the power utilization is not efficiently distributed among the subcarriers, and ranks 5 and 7 can be extended similarly. As a further example, for rank 4, as shown in Figure 2D, different power treatments for reference elements and data elements are required. A disadvantage of the proposal shown in Figures 2C-2D may be that the power utilization for DM-RS REs is not efficient in the case of rank 3 or higher. In addition, if the power difference between reference elements and data elements is not taken into account, the channel estimation accuracy may be affected.

To improve the power utilization for DM-RS REs, embodiments herein use DM-RS power boosting. However, in some embodiments, it appears that control signaling overhead is required to indicate to the UE terminal that power normalization is performed for M-QAM (Multi-level Quadrature Amplitude Modulation) demodulation.

Throughout the following description, like reference numerals are used to refer to like elements, parts, items, or features, where applicable.

FIG3 is a block diagram of a radio network node 120 communicating with a user equipment 110 using MIMO transmission. The radio communication system 100 may include the user equipment 110 and a radio network node 120, such as a radio base station (RBS), an eNodeB (eNB), or the like. The arrow denoted "MIMO transmission" indicates that the radio network node 120 may be configured for multiple-input multiple-output transmission, also known as "MIMO transmission," to the user equipment 110. MIMO transmission includes at least three layers. Each layer may be allocated to a resource block for MIMO transmission. The resource block includes subcarriers, wherein two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers, and wherein a first subcarrier of the resource block carries data elements for the at least three layers. The first subcarrier is different from the two consecutive subcarriers. In an embodiment, the resource block includes two subcarriers intended for transmission of reference elements, such as the two consecutive subcarriers.

Figure 4 shows an exemplary combined signaling and flow diagram describing communication between a radio network node and a UE.In one embodiment of the method performed in the radio network node of Figure 3, the following steps may be performed.

210 The radio network node 120 adjusts the transmit power of the at least three reference elements so that the average transmit power of the at least three reference elements on the two consecutive subcarriers is equal to the transmit power for the first subcarrier of the data elements for the at least three layers.

220 The radio network node 120 transmits the at least three reference elements to the user equipment 110 using the adjusted transmission power.

In some embodiments, one or more of steps 230, 240, 250, 260, and 270 may be performed as follows.

In some embodiments of the method in the radio network node 120, the adjusting of the transmit power may be performed by:

230 The radio network node 120 determines a transmit power for each of the at least three reference elements based on the number of layers of the MIMO transmission. The number of layers is at least three.

In some embodiments of the method in the radio network node 120, the first set of reference elements includes a first at least one reference element of the at least three reference elements, the first at least one reference element being allocated to a first subcarrier of the two consecutive subcarriers, and the second set of reference elements includes a second at least one reference element of the at least three reference elements, the second at least one reference element being allocated to a second subcarrier of the two consecutive subcarriers.

In some embodiments of the method in the radio network node 120, the first set of reference elements is included in a first code division multiplexed group and the second set of reference elements is included in a second code division multiplexed group.

In some embodiments of the method in the radio network node 120, the determining 230 may be performed by the following steps.

240 the radio network node 120 determines a first transmit power for each reference element of the first set of reference elements by adjusting the transmit power by a first factor R/(Floor(R/2)); and/or

250 The radio network node 120 determines a second transmit power for each reference element of the second set of reference elements by adjusting the transmit power by a second factor R/(Ceil(R/2)), where R is the transmit rank of the MIMO transmission.

This is illustrated in Figures 5A-5B, which show power diagrams for MIMO transmissions of ranks 3 and 4, respectively. Since the boosted power (i.e., the increased power used for the DM-RS REs) is associated with the rank value R, there is no need to introduce additional control signaling for indicating the values (or factors) X and Y to the UE terminal in this embodiment.

Next a description is provided explaining how steps 240 and 250 may be derived.

The precoder design in LTE-Advanced can be analyzed by looking at the following two cases:

Case 1: Constant modulus precoder, where each layer is transmitted from all antennas with a constant modulus weight vector. This allows the transmission power to be evenly divided by the transmission layer.

Case 2: Non-constant modulus precoder, where each layer can be transmitted from some or all antennas with a non-constant modulus weighting vector. In this way, the transmission layers of the MIMO transmission can have different transmission powers.

As a first example, when using a constant modulus precoder, it may be possible to achieve full transmit power utilization for CDM groups 1 and 2. A function (or formula) that can be used by a user equipment to determine the power used for reference elements such as DM-RS REs has been developed. In Figures 5A-5B, the basic concepts for rank 3 and rank 4 are shown. In the figure, it can be seen that the transmit power is evenly divided between the transmission layers (or layers for short).

Continuing with the first example, in the case of rank 3, layer 1 (in CDM group 1) has boosted the power on the DM-RS RE by a factor of 3/1 (or in other words, increased it by a factor of 3/1), while layer 2 or layer 3 (in CDM group 2) has boosted the power on the DM-RS RE by a factor of 3/2.

Additionally, also as part of the first example, in the case of rank 4, layer 1 or layer 2 (in CDM group 1) has increased the power on the DM-RS RE by a factor of 4/2, while layer 3 or layer 4 (in CDM group 2) has increased the power on the DM-RS RE by a factor of 4/2.

The first example can be extended to ranks 5-8, a detailed description of which is not set forth herein.

Based on the first example, a unified definition of the boosted power for ranks 3-8 may be developed according to some embodiments. In the embodiments herein, the unified definition may uniquely associate the transmit power with the rank. Given a known rank value R, the following formula may be proposed:

In CDM group 1, each layer increases the power on the DM-RS RE by a factor of X, where

X＝R/floor(R/2). (1)

In CDM group 2, each layer increases the power on the DM-RS RE by a factor of Y, where

Y＝R/ceil(R/2). (2)

The floor and ceiling functions map real numbers to the largest preceding integer or the smallest following integer, respectively.

As a second example, when using a non-constant modulus precoder, for example, in the case of open-loop transmission in TDD or non-codebook-based precoding based on EBB (Eigenbase Beamforming), the transmission layers may have different powers. Basically, similar power boosting on DM-RS REs can be performed.

For ranks 3-8, the transmission layers are distributed in either CDM group 1 or CDM group 2. In order to average out the power difference between reference and data elements, it is proposed to roughly double the transmission power.

According to a second example, in some embodiments of the method in the radio network node 120, the following operations may be performed for the regulation of the transmit power:

260 The radio network node 120 determines the transmit power for each reference element by adjusting the transmit power by a third factor of 2. This is illustrated in Figures 5C-5D which show power diagrams for MIMO transmissions of ranks 3 and 4, respectively.

To handle different scenarios, such as transmission of various numbers of layers, it is proposed to predefine a set, for example, Z = {1, 2}, for each CDM group or for each of the two CDM groups. This means that each layer in each CDM group or the two CDM groups has its DM-RS RE power boosted by a factor of Z, where Z takes the appropriate value of 1 or 2 depending on the transmission rank.

In some embodiments of the method in the radio network node 120, the following operations may be performed:

270 The radio network node 120 sends a message to the user equipment 110 specifying the adjusted transmit power.

In some embodiments of the method in radio network node 120, the message includes information about the values of the first, second, and/or third factors. For example, the message may specify a value of Z to be applied to the reference element. In other words, the higher layer configuration message may indicate to UE 110 which value of Z to use.

In some embodiments, different types of precoders can be supported, including constant modulus precoders and non-constant modulus precoders. Therefore, to improve robustness, some embodiments use higher-layer configuration to indicate different power allocation schemes to the user equipment. In this way, the user equipment 110 can understand (i.e., receive relevant information) what power allocation scheme is applied by the radio network node 120, such as the eNB side, in any of the above embodiments.

Referring now to FIG. 6 , a schematic, illustrative block diagram of an apparatus 800 in a radio network node 120 for adjusting the transmit power of resource elements of a demodulation reference signal, referred to as "reference elements," is shown. The radio network node 120 may include the apparatus 800. The radio network node 120 is configured for multiple-input, multiple-output (MIMO) transmission, referred to as "MIMO transmission," to the user equipment 110. The MIMO transmission includes at least three layers, each layer being allocated to a resource block of the MIMO transmission. A resource block includes subcarriers. Two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers. A first subcarrier of the resource block carries data elements for the at least three layers. The first subcarrier is different from the two consecutive subcarriers. The apparatus 800 may include processing circuitry 820 configured to adjust the transmit power of the at least three reference elements such that an average transmit power of the at least three reference elements over the two consecutive subcarriers is equal to the transmit power of the data elements for the at least three layers for the first subcarrier. Additionally, the processing circuit 820 may be further configured to transmit the at least three reference elements using the adjusted transmit power to the user equipment 110. The processing circuit 820 may be a processing unit, a processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like.

Additionally, in some embodiments, the apparatus 800 may comprise a memory 830, shown as a dashed line, for storing software to be executed by, for example, the processing circuit 820. The software may comprise instructions enabling the processor to perform the method in the radio network node 120 described above.

In some embodiments, the device 800 may further include a transmitter 840 and a receiver 810 as shown in dashed lines.

In some embodiments of the apparatus 800 in the radio network node 120, the processing unit 820 may be further configured to determine the transmit power of each of the at least three reference elements based on a number of layers of the MIMO transmission. The number of layers is at least three.

In some embodiments of the apparatus 800 in the radio network node 120, the first set of reference elements includes a first at least one reference element of the at least three reference elements. The first at least one reference element is allocated to a first subcarrier of the two consecutive subcarriers. The second set of reference elements includes a second at least one reference element of the at least three reference elements. The second at least one reference element is allocated to a second subcarrier of the two consecutive subcarriers.

In some embodiments of the apparatus 800 in the radio network node 120, the first set of reference elements is included in a first code division multiplexing group and the second set of reference elements is included in a second code division multiplexing group.

In some embodiments of the apparatus 800 in the radio network node 120, the processing unit 820 may be further configured to determine a first transmit power for each reference element of the first set of reference elements by adjusting the transmit power by a first factor R/Floor (R/2). Additionally or alternatively, the processing unit 820 may be further configured to determine a second transmit power for each reference element of the second set of reference elements by adjusting the transmit power by a second factor R/ceil (R/2). R is a transmit rank of the MIMO transmission.

In some embodiments of the apparatus 800 in the radio network node 120, the processing unit 820 may be further configured to determine the transmit power of each reference element by adjusting the transmit power by a third factor of two.

In some embodiments of the apparatus 800 in the radio network node 120 , the transmitter 840 may be configured to send a message to the user equipment 110 specifying the adjusted transmit power.

In some embodiments of the apparatus 800 in the radio network node 120, the message may comprise information on the values of the first, second and/or third factors.

This document proposes the use of DM-RS power boosting for UE-specific reference signals (DM-RSs) in LTE-Advanced, such as LTE Rel-10. In some embodiments, this is achieved without the need for explicit dynamic control signaling, while improving transmit power utilization for reference elements. It should be noted that the increased power of the reference elements is not borrowed from or derived from the data REs, but rather is an effect of the improved power utilization scheme. Furthermore, L1 control signaling overhead is not increased because the UE knows which scheme to use by observing the rank of the MIMO transmission, eliminating the need for explicit dynamic control signaling.

In some embodiments disclosed herein, a uniform power boosting scheme is used. The uniform power boosting scheme determines the power offset between data REs and RM-RS REs as a function of the number of layers, or equivalently, the transmission rank, or equivalently, the number of antenna ports used.

Briefly, in some embodiments, the power offset between data resource elements and reference signal resource elements (DM-RS REs) is determined as a function of the number of layers, or equivalently the transmission rank, or equivalently the number of antenna ports used.

In the above description, for the purpose of explanation rather than limitation, specific details such as specific techniques and applications are set forth in order to provide a thorough understanding of the embodiments disclosed herein. In other cases, detailed descriptions of well-known methods and devices are omitted to avoid obscuring the description of the embodiments with unnecessary details.

It will be apparent that the embodiments can be varied in a variety of ways. Such variations should not be considered as departing from the scope of this disclosure. All such modifications as will be apparent to those skilled in the art are intended to be included within the scope of the appended claims.

In one embodiment, a method for adjusting the transmit power of a reference signal in a multiple-input multiple-output telecommunication system is provided, characterized by adjusting the transmit power of resource elements carrying reference signaling to be approximately equal to the transmit power of resource elements used to carry data.

In one embodiment, at least two code division multiplexing groups are used for transmission.

In one embodiment, each code division multiplexing group includes four layers.

In one embodiment, first and second code division multiplexing groups, each group including four layers, constituting a rank 8 transmission scheme, are used.

In one embodiment, the power of the first code division multiplexing group is increased by R/(Floor(R/2)) times, and the power of the second code division multiplexing group is increased by R/(Ceil(R/2)) times, where R is the rank used for transmission or the number of layers used.

In one embodiment, the power of resource elements used to carry reference signaling for rank 1 and 2 transmissions is not boosted, and the power of resource elements used to carry reference signaling for ranks 3 to 8 is doubled.

In one embodiment, the method comprises defining a set of values defining a power boost to be used for each code division multiplexing group.

In one embodiment, the method comprises sending a message to the user equipment to indicate which value or values to use for power boosting of resource elements carrying reference signalling.

In one embodiment, the method comprises sending a message to the user equipment to indicate a resource element power boosting scheme to be used by the radio base station to boost the transmit power of resource elements carrying reference signaling.

In one embodiment, there is provided a radio base station configured to perform a method according to any embodiment described herein.

In one embodiment, a user equipment is provided comprising a receiver module configured to adjust the receiver module in dependence on an indication of resource element power boosting according to any embodiment disclosed herein for boosting transmit power of resource elements carrying reference signaling.

In one embodiment, the indication is selected from the group of indications, the group of indications comprising: use of a rank transmission scheme with an order higher than 2, a message received from a radio base station indicating a resource element power boost value, a message received from a radio base station indicating a resource element power boost scheme.

Claims (20)

1. A method in a user equipment, the user equipment including a receiver module configured to receive a multiple-input multiple-output (MIMO) transmission called a "reference element" from a radio network node, wherein the MIMO transmission includes at least three layers, each layer being allocated to a resource block of the MIMO transmission, wherein the resource block includes a subcarrier, wherein two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers, wherein a first subcarrier of the resource block carries data elements for the at least three layers, the first subcarrier being different from the two consecutive subcarriers, wherein the method includes: The at least three reference elements are received from the radio network node, wherein the transmission power of the at least three reference elements is adjusted by the radio network node using the transmission power such that the average transmission power of the at least three reference elements on two consecutive subcarriers is equal to the transmission power of the data elements for the first subcarrier used for the at least three layers; and The receiver module is adjusted according to the indication of the resource element power increase. 2. The method of claim 1, wherein the indication is selected from the group of indications including: the use of a rank transmission scheme with an order greater than 2, a message received from a radio network node indicating a power boost value for a resource element, and a message received from a radio network node indicating a power boost scheme for a resource element. 3. The method of any one of claims 1-2, wherein the transmission power of each of the at least three reference elements is determined based on the number of layers transmitted by the MIMO, wherein the number of layers is at least three. 4. The method of claim 3, wherein the first set of reference elements includes a first at least one reference element of the at least three reference elements, wherein the first at least one reference element is assigned to a first subcarrier of the two consecutive subcarriers, and the second set of reference elements includes a second at least one reference element of the at least three reference elements, wherein the second at least one reference element is assigned to a second subcarrier of the two consecutive subcarriers. 5. The method of claim 4, wherein the first set of reference elements is included in a first code division multiplexing group, and the second set of reference elements is included in a second code division multiplexing group. 6. The method of claim 4, wherein a first transmission power of each reference element of the first set of reference elements is determined by adjusting the transmission power according to a first factor R/(Floor(R/2)); and/or The second transmission power of each reference element in the second set of reference elements is determined by adjusting the transmission power according to a second factor R/(Ceil(R/2)), where R is the transmission rank of the MIMO transmission. 7. The method of any one of claims 1-2, wherein the transmission power of each reference element of the reference element is determined by adjusting the transmission power by a third factor of 2. 8. The method according to any one of claims 1-2, further comprising: Receive a message from the radio network node specifying the adjusted transmission power. 9. The method of claim 6, further comprising: Receive a message from the radio network node specifying the adjusted transmission power, wherein the message includes information relating to the values of the first factor and the second factor. 10. The method of claim 7, further comprising: Receive a message from the radio network node specifying the adjusted transmission power, wherein the message includes information relating to the value of the third factor. 11. A user equipment including a receiver module, The receiver module adjusts according to the instruction to increase the power of the resource element. The receiver module is configured to receive multiple-input multiple-output (MIMO) transmissions, referred to as "reference elements," from a radio network node. The MIMO transmissions comprise at least three layers, each layer being allocated a resource block of the MIMO transmission. Each resource block includes subcarriers. Two consecutive subcarriers of the resource block carry at least three reference elements for the at least three layers. A first subcarrier of the resource block carries data elements for the at least three layers, and this first subcarrier differs from the two consecutive subcarriers. The receiver module is further configured to receive the at least three reference elements from the radio network node, wherein the transmission power of the at least three reference elements is adjusted by the radio network node using the transmission power such that the average transmission power of the at least three reference elements on two consecutive subcarriers is equal to the transmission power of the data elements for the at least three layers on the first subcarrier. 12. The user equipment of claim 11, wherein the indication is selected from the group of indications including: the use of a rank transmission scheme with an order greater than 2, a message received from a radio network node indicating a power boost value for a resource element, and a message received from a radio network node indicating a power boost scheme for a resource element. 13. The user equipment as claimed in any one of claims 11-12, wherein the transmission power of each of the at least three reference elements is determined based on the number of layers of the MIMO transmission, wherein the number of layers is at least three. 14. The user equipment of claim 13, wherein the first set of reference elements includes a first at least one reference element of the at least three reference elements, wherein the first at least one reference element is assigned to a first subcarrier of the two consecutive subcarriers, and the second set of reference elements includes a second at least one reference element of the at least three reference elements, wherein the second at least one reference element is assigned to a second subcarrier of the two consecutive subcarriers. 15. The user equipment of claim 14, wherein the first set of reference elements is included in a first code division multiplexing group, and the second set of reference elements is included in a second code division multiplexing group. 16. The user equipment of claim 14, wherein the first transmission power of each reference element in the first set of reference elements is determined by adjusting the transmission power according to a first factor R/(Floor(R/2)); and/or The second transmission power of each reference element in the second set of reference elements is determined by adjusting the transmission power according to a second factor R/(Ceil(R/2)), where R is the transmission rank of the MIMO transmission. 17. The user equipment as claimed in any one of claims 11-12, wherein the transmission power of each reference element of the reference element is determined by adjusting the transmission power by a third factor of 2. 18. The user equipment as claimed in any one of claims 11-12, wherein the receiver module is further configured to receive from the radio network node a message specifying the adjusted transmission power. 19. The user equipment of claim 16, wherein the receiver module is further configured to receive from the radio network node a message specifying an adjusted transmission power, wherein the message includes information relating to the values of the first factor and the second factor. 20. The user equipment of claim 17, wherein the receiver module is further configured to receive from the radio network node a message specifying an adjusted transmission power, wherein the message includes information relating to the value of the third factor.