JP2014060738A - Method for transmitting reference signal, and communication network element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further cooperate over an overall cell from different sites to improve performance more than in-eNB cooperation, as well as to enable easy implementation.SOLUTION: A method for transmitting a reference signal from a first network element to a second network element in a communication network includes the steps of: transmitting a reference signal of a first type related to a first communication system, using a first frame resource; and transmitting a reference signal of a second type related to a second communication system using a second frame resource.

Description

  The invention relates in particular to the field of communication network elements and methods for transmitting data in a communication network having a cooperative antenna system. The invention further relates to a communication network system, a program element, and a computer readable medium.

  Today, mobile communication networks are widely used. These communication networks include a plurality of network cells, each of which has at least one base station used to transmit and receive signals from user equipment such as mobile phones or PDAs. Several different environments or systems are known, such as GERAN, UTRAN, LTE, E-UTRAN, WCDMA®, or WLAN. In order to ensure good performance and particularly efficient data transmission, all data, data signals or data packets are considered at the intended recipient and like a base station of a mobile communication network. It is necessary to ensure reception at the relay station.

It is known in the art that inter-cell and intra-cell interference is one problem that limits the performance of data transmission. Some form of cooperative antenna (COOPA) system has been proposed to reduce inter-cell interference. From theory, it has been found that fully coordinated cellular radio systems have significantly improved performance in terms of capacity and coverage compared to conventional systems. With these great improvements not possible with other technologies, it is known from theory that COOPA systems provide an upper bound for interference-limited cellular radio systems.
At the same time, especially in the case of FDD systems, perfect coordination may not be practical due to the need for channel state information (CSI) for many base stations (BS) and thus high feedback overhead. it is obvious. A further agenda is the large amount of data on the backbone network that can result in significant costs in terms of CAPEX and OPEX.

  In particular, since COOPA based on intra-eNode B (eNB) cooperation between adjacent sectors of a site can be implemented regardless of any backbone network, it can be expected as the most basic cooperation scheme. The same applies to the distributed antenna system (DAS) in which the antenna elements (AE) of each sector are spatially distributed. A Tx station (usually a remote radio head (RRH)) is connected to a baseband device at an eNB site via a fiber, but does not include a backbone network. While intra-eNB coordination can be more easily implemented, greater performance requires further coordination across the cell from different sites.

  However, the COOPA system requires accurate channel estimation that needs to be fed back to the eNB and uses it for precoding in the cooperation area (CA) at the eNB. This channel estimation can be a major challenge, especially due to inter-cell interference from many cells and sites within the mobile communication system. The poor common design can fundamentally limit the performance of any collaborative scheme that can be realized in the future, so an optimal common reference signal (CRS) design may be paramount.

  Thus, there may be a need for communication network elements, reference signal transmission methods, program elements, and computer-readable media that improve the performance of multi-channel estimation, particularly in cooperative antenna systems.

  This need can be met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

  According to an exemplary aspect of the present invention, a method for transmitting a reference signal from a first network element to a second network element in a communication network uses a first resource of a frame and the first communication system. Transmitting a first type of reference signal associated with, and transmitting a second type of reference signal associated with the second communication system using the second resource of the frame.

  In particular, the first communication system can be a cellular system such as a 3GPP LTE system. An example of a GPP LTE system may be a system according to the LTE Release 8 standard. The second communication system may also be a cellular system such as a so-called advanced release 8 communication system or an LTE Advanced communication system. Specifically, the first type and second type reference signals may be common reference signals and / or COOPA reference signals. The transmitted reference signal can be used to generate channel state information, i.e., to estimate the actual performance of the channel that may be required to implement the transmission of cooperative data.

  According to an exemplary aspect of the present invention, there is provided a communication network element for transmitting a reference signal, particularly for a cooperative communication network, which uses a first resource of a frame to A first transmission unit adapted to transmit a first type of reference signal associated with one communication system and a second resource associated with the second communication system using a second resource of the frame; A second transmission unit adapted to transmit a type of reference signal.

  Specifically, this network element can be one of network element groups consisting of an extended Node B (eNB), a user equipment, a base station, and a relay node. The first and second transmission units can be formed by a single unit or by different units such as one or more antennas and can operate under the control of the control unit. Note that a network element such as a base station can mainly receive information such as a priority matrix index (PMI) or a channel quality indicator (CQI), but can also provide some control information in the downlink.

  A communication network system including a plurality of communication network elements can also be provided, the plurality of communication network elements including at least two base stations and at least two user equipments, wherein the at least one communication network element includes A communication network element according to an exemplary aspect of the invention, wherein the plurality of communication network elements are adapted to perform coordinated transmission of data, particularly data packets.

  According to an exemplary aspect of the present invention, there is provided a program element adapted to control or implement a method according to an exemplary aspect of the present invention when executed by a processor.

  According to an exemplary aspect of the invention, a computer readable medium stores a computer program adapted to control or implement a method according to an exemplary aspect of the invention when executed by a processor.

  The term “resource” transmits data regardless of whether the data is payload data, reference data, control data, or the like of a communication network within a particular communication system. Means all kinds of abilities to do. For example, due to the fact that different resources are associated with different subframes and / or different frequencies of the same frame, they can be distinguished from each other, for example, two resources are associated with the same subframe but with different frequencies In other words, data transmitted by using two resources can be transmitted at different frequencies. In general, resources can be distinguished from each other by any suitable parameters such as frame number, subframe number, frequency band used, coding scheme, and the like.

  The method according to the exemplary aspect of the present invention can ensure the backward compatibility of the communication system related to the new standard, for example using two different types of reference signals and releasing one type The Release 8 standard can be combined with the LTE advanced standard by allowing it to be used in an 8 communication system or transmission scheme while allowing the other to be used in the advanced LTE standard. Each of the two reference signals can be a common reference signal, for example, common to all channels. Both types of reference signals can be clearly adapted to one standard, thus ensuring channel state estimation (CSI) accuracy is increased, which is taken as another important element of the COOPA system It can even facilitate Interference Rejection Coupling (IRC) that can be relied upon and can rely on quality CSI estimation.

  An example aspect can be found in providing a method for transmitting and receiving reference signals for a cooperative data transmission scheme, which provides backward compatibility with previous schemes and improves multi-cell channel estimation. Can be possible. As a basic concept, for multi-cell channel estimation, one subframe of a communication system frame or communication scheme frame, such as an LTE Release 8 radio frame, is completely or partially transmitted for transmission of an LTE advanced common reference signal (CRS). Can be set aside. Reducing data and CRS duplication from different cells, which can cause CRS interference floor due to data transmission due to inability to control data signal when using the method according to the exemplary aspects of the present invention. Can do.

  Next, further exemplary embodiments of the data transmission method will be described. However, these embodiments also apply to communication network elements, communication network systems, program elements, and computer readable media.

  According to another exemplary embodiment of the method, the first type of reference signal and the second type of reference signal are transmitted in different subframes.

  That is, the first resource and the second resource can be related to different subframes. For example, a first type of reference signal associated with Release 8 can be transmitted using resources defined by the Release 8 standard, while a second type of reference signal associated with an advanced Release 8 system or LTE Advance, etc. The reference signal can be transmitted only during a specific subframe such as the first subframe.

  According to another exemplary embodiment of the method, the first type of reference signal and the second type of reference signal are transmitted in a common subframe.

  In particular, the first type and the second type of reference signal can be transmitted only during a particular subframe, such as the first or any other suitable subframe, while in other subframes. Cannot transmit a reference signal. Of course, the reference signal can also be transmitted in two or more subframes. That is, even in a subframe that carries a second type of reference signal such as LTE advanced CRS, each network element such as eNB is configured with a reference grid defined by another standard such as LTE Release 8 standard, etc. A reference signal can be transmitted.

  According to another exemplary embodiment of the method, the first resource is associated with the first frequency band of the subframe.

  Of course, the second resource can also be associated with a specific frequency band, such as the first frequency band or other specific frequency band.

  According to another exemplary embodiment of the method, a first reference signal is transmitted using a first frequency band in a first frame, and a first reference signal is transmitted in a second frame. It is transmitted using another frequency band.

  That is, for each successive individual frame, a different frequency band can be allocated to transmit the reference signal. Specifically, the assignment of reference signals in the LTE advanced communication system can be changed. Of course, after changing the frequency band assignment a predetermined number of times, the frequency band assigned in the first frame can be used again. For example, a first frequency band can be used in the first frame, a second frequency band can be used in the second frame, and a third frequency band can be used in the third frame. However, in the fourth frame, the first frequency subband can be used again.

  According to another exemplary embodiment of the method, a first type and / or a second type of reference signal is generated by a Hadamard sequence.

  In particular, Hadamard sequences can be applied to CRSs in different cells of the communication network. By using Hadamard sequences, inter-cell crosstalk between reference signals from different cells can be reduced or minimized. For example, a subframe may carry a combination of LTE Release 8 CRS and LTE advanced reference signals in resources not occupied by LTE Release 8 reference signals. Furthermore, the allocation of resources used for transmission of reference signals such as the first type reference signal and / or the second type reference signal, the sequence already orthogonal with respect to a short sequence length, such as eNB or UE This can be done by assigning to adjacent interferers. Since adjacent interferers typically produce additional interference, it can be advantageous to ensure that sequences that are already orthogonal for short sequence lengths are assigned to adjacent interferers. For example, LTE Release 8 CRS can be multiplied by Hadamard or Walsh Hadamard sequences.

  According to another exemplary embodiment of the method, the second reference signal is assigned to a specific bandwidth of the frame.

  Specifically, a second reference signal, such as a common LTE advanced reference signal, is transmitted only in a predetermined portion of the total spectral bandwidth. That is, the second reference signal is transmitted only using a specific resource such as a specific frequency subband. In this way, the overhead caused by the transmission of the reference signal can be reduced or limited by limiting the coordination to a specific bandwidth corresponding to a specific subband, such as this part of the spectrum. Of course, this particular subband or these particular subbands can be changed during transmission. Specifically, the eNB can semi-statically assign this frequency subband or the position and size of these frequency subbands. For example, a quasi-static definition of the number of frequency subbands used, i.e. a configuration change defining the frequency subbands used, can be used, which can be useful for adaptation to different radio conditions. Specifically, when the radio conditions deteriorate, the number of frequency subbands used for transmitting the first reference signal and / or the second reference signal can be increased, and vice versa.

  According to another exemplary embodiment of the method, the first subband is used to transmit the first reference signal type in the first frame and / or the second reference signal type is Use the second subband to transmit in one frame, use the third subband to transmit the first reference signal type in the second frame, and / or the second reference signal The fourth subband is used to transmit the type in the second frame.

  That is, by changing the subband used for transmission of the first and / or second reference signal for each frame, all frequency bands can be used cooperatively. In this case, the scheduler can take into account that some parts of the spectrum, i.e. all frequency bands, have CSI information older than the other parts of the spectrum. In particular, the third subband and / or the fourth subband are the subband (s) that have not been used for transmission of the reference signal (first or second type) over a predetermined period, and the predetermined period. The subbands satisfy a predetermined criterion, such as the subband (s) corresponding to the channels that were not estimated over time. In this way it can be ensured that all channels are estimated equally or at least more equally.

  According to another exemplary embodiment of the method, only a part of the subframe is used for transmission of the first type and / or the second type of reference signal.

  Specifically, other parts of the subframe can be used for transmission of payload data. The payload data is based on the first communication system or based on the second communication system regardless of whether the reference signal transmitted in the subframe is of the first type or the second type. Can be sent.

  According to another exemplary embodiment of the method, a first type of reference signal and a second type of reference signal are combined.

  For example, a common CRS of a Release 8 UE can be combined with a common LTE advanced CRS in a subframe that transmits the LTE advanced CRS. In particular, so-called maximum ratio combining (MRC), taking into account the possibility that LTE advanced multi-cell channel estimation may be out of date in some cases, i.e. considering information on channel estimation performed at the end of the LTE advanced communication scheme. ) Method can be used. A more sophisticated synthesis scheme that takes into account the different structures and properties of the common CRS according to LTE Release 8 and the structure and properties of the LTE Advanced reference signal may be enabled. For example, while the performance of Common Release 8 CRS is affected by multi-cell interference, the LTE advanced reference signal will have a lower temporal localization. Fast iterative decoding techniques can be used to derive maximum performance from the combination of both types of channel estimates. By performing such synthesis, the overall channel estimation accuracy can be increased.

  According to another exemplary embodiment of the method, the first type and / or the second type of reference signal is used to track the movement of network elements of the communication network.

  Specifically, a first type of reference signal, such as a Release 8 reference signal, can be used to track moving network elements such as UEs, mobile phones, laptops, PDAs, etc., thereby improving channel estimation performance. Therefore, the performance of data transmission can be improved when the UE is moving, especially when the UE is moving at a slightly higher speed.

  According to another exemplary embodiment, a method is provided to a second network element regarding the availability and / or location and / or density of transmitted first and / or second type reference signals. The method further includes the step of transmitting a control message to notify.

  The term “channel” can mean any type of transmission path that can be used to transmit data packets, in particular distinguishable from other transmission paths. That is, individual “channels” can form communication network resources that can be used to transmit data independently of other resources. Such a “channel” can be formed by a resource block (RB) including several subcarriers. For example, the RB can be composed of 12 subcarriers and 14 OFDM symbols.

  In this application, the term “data packet” can mean any kind of data that can be transmitted in detail, either via cable or line or wireless. In particular, the term “data” may include digital or analog data related to a call or transmission of data used in connection with computer communications, such as a program, photo, music title, and the like. In particular, specific data can be formed by one or more data packets.

  To summarize exemplary aspects of the present invention, for multi-cell channel estimation, one or more of the 10 subframes of an LTE radio frame is reserved completely or partially for LTE Advanced CRS. A method can be provided that allows for improved multi-cell channel estimation combined with full backward compatibility. This method can provide full design flexibility for multi-cell CRS for LTE Advanced. At the same time, AP0,. . . 3 and AP5 can be ensured by continuously transmitting release 8 compatible reference signals. Also in the subframe carrying LTE Advanced CRS, the eNB can transmit a reference signal grid as defined in the current standard.

  Thereafter, other resource elements that would otherwise carry the R8 data signal can be used for a new CRS in LTE Advanced. Specifically, Hadamard sequences can be applied to CRSs of different cells to minimize inter-cell crosstalk between reference signals from different cells. In a simple scheme, a particular subframe can carry a combination of LTE Release 8 CRS and LTE Advanced reference signal in other REs not occupied by R8 RS. In this case, in this particular subframe, the Release 8 UE cannot recognize these newly defined reference signals because the eNB does not simply schedule the Release 8 UE. The resulting additional overhead can be on the order of 10% (1 out of 10 subframes). Furthermore, quasi-static definitions of other configurations with more or fewer subframes for LTE Advanced CRS may be useful for adaptation to different radio conditions.

  The above-defined exemplary aspects and exemplary embodiments of the present invention, as well as further aspects, will be apparent from the example embodiments described below and will be described with reference to the example embodiments. Hereinafter, the present invention will be described in more detail with reference to exemplary embodiments, but the present invention is not limited thereto.

It is a figure which shows roughly the potential gain of the difference in a cooperation degree. Fig. 2 schematically shows a basic solution for coordinated transmission. It is a figure which shows the conventional cellular layout schematically. It is a figure which shows schematically assignment to the cell of a Hadamard sequence. FIG. 7 schematically illustrates different sequences of multi-cell performance. It is a figure which shows roughly the sub-frame containing the common R8 and LTE advanced reference signal. FIG. 6 schematically illustrates another transmission scheme that includes a common R8 and LTE advanced reference signal.

  The illustrations in the drawings are schematic. Identical or similar elements are given identical or similar reference signs.

  In the following, some basic principles of a data transmission method and a communication network element according to an exemplary embodiment will be described with reference to FIGS.

  FIG. 1 schematically illustrates the potential gain of the degree of cooperation difference. That is, FIG. 1 shows the spectral efficiency over different coordination levels in bits / second and hertz (bits / S * Hz). In detail, some schemes are shown for some degree of cooperation. The spectral efficiencies of the “ScaleNet” results 101 and 102 represent the results of an optimal MU-MIMO system that recognizes complete channel state information (CSI) without coordination. In addition, “Fo” lines 103 and 104 represent the theoretical upper limit of individual cooperation levels, while line “Fe” 105 represents the data rate based on × 2 between cooperating extended Node B (eNB). Represents the results of a 5 MHz system with varying. From FIG. 1, it can be clearly seen that the spectral efficiency increases as the cooperation level increases. This is especially true for the “Fo” line, but the “Fe” line 105 also increases from uncoordinated to a 10 MHz backhaul, a 20 MHz backhaul, 3 cells, and a complete or infinite backhaul. Also, 106 indicates the result of 3GETproject representing an active IF management scheme with a size 3 collaboration area (CA).

  FIG. 2 illustrates a basic solution for coordinated transmission that helps to understand the present invention. In particular, it can be expected that the central unit (CU) will perform joint precoding for the cooperative antenna (COOPA) system, as the name implies, this is the so-called cooperative area (CA) in one of the cooperative eNBs. ) At the center point. Other coordinated eNBs can connect to this CU via high speed and low delay fiber connections.

  In the downlink (DL), the CU can perform common signal precoding such as joint transmission, which basically depends on the precoding matrix W of all data signals of all cooperating user equipments (UE). Matrix multiplication. For zero forcing (ZF), W is the pseudo-inverse H + of the entire channel matrix H. FIG. 2 shows the simplest form of SA for codebook based precoding. In this case, the precoding matrix W is selected from the codebook based on different priority matrix index (PMI) feedback PMI1 and PMI2 from UEs of UE1 and UE2. A similar concept can be applied to the uplink (UL), which is sometimes referred to as joint detection (JD).

  Specifically, FIG. 2 shows data packets d1 and d2 transmitted to UE1 202 and UE2 203. For common signal processing, the data packet is encoded by using the matrix W 204 to form a data signal tx for transmission to the eNB1 205 corresponding to UE1 202 and the eNB2 206 corresponding to UE2 203, and the signal r1 and r2 are received, respectively. The signals r1 and r2 correspond to the multiplication of the channel matrix H, the pseudo inverse H + or W, and the data d transmitted with an offset n.

In the upper left of FIG. 3, a conventional cellular layout 301 composed of a standard set of hexagonal cells can be found. Each cell has a common reference signal (CRS) grid of all antenna elements, ie all physical antennas as defined for LTE Release 8, ie 2 or 4 antenna ports (AP) per sector. It is preferable to broadcast continuously. For the sake of clarity, it should be noted that the term antenna port is generally used in the LTE field and is strongly related to the reference signal transmitted from this port.
In the case of a common reference signal, the AP can be connected to different physical antennas or antenna elements. In the right side 302 of FIG. 3, a grid in the time and frequency direction of one resource block can be seen. The UE can perform CSI estimation based on this CRS grid with an accurate interpolation algorithm.

  In a COOPA system, individual UEs estimate at least these radio channels to those eNBs involved in the CA to which the UE belongs. To further complicate matters, the CSI accuracy of a high performance COOPA system must be better than a conventional cellular system, otherwise the precoding accuracy in the downlink (DL) may be degraded.

  Interference cancellation coupling (IRC) can be viewed as another important element of the COOPA system and can also rely on high quality channel state information (CSI) estimation. In the case of a multi-cell scenario, the same CRS may be transmitted simultaneously in a synchronous network, which may cause large inter-CRS interference between different cells when using a conventional communication system. This problem can be partially overcome by assigning different cell ID specific sequences in the LTE standard. Thus, for estimation over one complete orthogonal frequency division multiplexing (OFDM) symbol that is the length of the sequence, there may be some crosstalk reduction between different common CRSs from different cells. However, due to the frequency selection of the radio channel, it is not possible to provide complete orthogonality between all cells, so the quality of the remaining channel estimation performance remains poor when using conventional channel estimation. There is a case.

  FIG. 4 schematically shows the assignment of Hadamard sequences to cells, particularly for sequences of different lengths. Specifically, the length of the Hadamard sequence increases from the upper left area of FIG. 4 to the upper right area, the lower left area, and the lower right area. FIG. 4 shows that as the sequence length increases, the spatial distance between cells assigned the same Hadamard frequency increases, and FIG. 4 uses different shading for each Hadamard sequence.

  FIG. 5 shows a result of randomly assigning a sequence unique to a cell ID to a cell on the left side 501, and a result of a pattern with Hadamard fixed on the right side 502. As shown, the mean square error (MSE) that can be obtained for the top five strong interferers is extremely poor even when averaging over 8 subframes each of 1 ms length on a static radio channel. obtain. Furthermore, it can be seen that using the pattern with fixed Hadamard slightly improves the mean square error of the averaging over the 8 subframes.

  6 and 7 schematically illustrate a radio frame including subframes in which common release 8 CRS and LTE Advanced CRS are implemented. Specifically, FIG. 6 shows a frame 601 that includes a subframe 602. Subframe 602 carries a combination of LTE Release 8 CRS 603 and LTE Advanced CRS in other REs not occupied by R8 CRS. The eNB does not simply schedule any Release 8 UE within this particular subframe, so the Release 8 UE will not recognize these newly defined reference signals.

  The resulting additional overhead is on the order of 10% (one of 10 subframes). To accommodate different radio conditions, other configurations quasi-static definitions with more or fewer subframes for LTE Advanced CRS may be useful.

  By transmitting a common LTE Advanced reference signal with only a portion of the total spectral bandwidth, the resulting overhead can be further reduced, thereby limiting coordination to that portion of the spectrum. Two different options shown in FIG. 7 can be considered. According to one option, CRCs are assigned to the same frequency subband 704 in individual frames. Note that the position and size of this frequency subband can be semi-statically assigned by the eNB. The second option is indicated by subband 705. According to this option, the subband used changes from frame to frame. Thereby, all frequency bands can be used cooperatively. In this case, the scheduler can take into account that some parts of the spectrum have CSI information older than other parts of the spectrum.

  Furthermore, by using only a part of the LTE Advanced subframe for transmitting the reference signal, the resulting overhead can be further reduced, and if there is no LTE Advanced reference signal in the entire PRB, to the LTE Advanced UE And other parts can be used for data transmission to the R8 UE.

  In general, LTE Advanced UEs need to know the location of these additional advanced reference signals (aRS) and whether these aRS are actually being transmitted. If the predetermined standardized location of the aRS is fixed, all LTE Advanced UEs can expect these additional aRSs as soon as they are set to COOPA mode with a matched control message. In this case, further control signaling for these additional aRSs can be avoided.

  In a second, more flexible solution, additional broadcast or control messages can be used to inform the LTE Advanced UE about the availability and location / density of these aRSs. Release 8 UEs can simply ignore these broadcast or control messages.

To summarize some of the main advantages of the method according to the exemplary embodiment:
a) Performance improvement of multi-cell channel estimation, which is the most important issue for cooperative transmission schemes because COOPA is highly dependent on the accuracy of CSI estimation.
b) LTE Advanced also discusses the 8x8 MIMO scheme. If multi-cell channel estimation is not possible with high accuracy, these schemes may be subject to the same limitations. Therefore, the same method can be applied to MIMO 8 × 8.
c) For systems that define from scratch, there are many options for optimizing this performance, but LTE Advanced may require backward compatibility to Release 8.
The method according to the exemplary embodiment of the present invention provides this backward compatibility. Since any coordinated transmission scheme needs to rely on accurate CSI knowledge for accurate precoding, actually combining the accuracy of multi-cell channel estimation with release 8 backward compatibility is the biggest urgent issue Can do. Thus, the accuracy of the multi-cell channel estimation without the proposed enhancement may significantly limit the COOPA performance enhancement that should be possible.
d) Another application that requires accurate multi-cell channel estimation is the interference cancellation combining algorithm (IRC). IRC can provide high gain only if there is detailed knowledge of all the interferers to be reduced.
e) While this scheme has a completely new design with only one subframe, the CRS of AP0-3 may be the same as in Release 8, so it is very easy to implement.
f) In addition to CRS, LTE Release 8 and LTE Advanced CRS, Walsh Hadamard sequences can be easily implemented with little implementation effort at the transmitting and receiving sides.
g) One main advantage of the proposed solution is that there is no data transmission in other cells during multi-cell channel estimation, and therefore can provide very high performance multi-cell channel estimation.
h) Low to small additional overhead that can be about 10% and can be significantly lower than 10%, such as 2.5% when further optimized.
i) Excellent channel estimation quality in case of high mobility by being able to receive all LTE advanced reference signals in one subframe and even in less than one subframe.
j) Easy support for Release 8 UEs is possible only by not scheduling Release 8 UEs in LTE advanced subframes.
k) When combined with advanced schemes such as COOPA HARQ or model-based channel estimation that may provide good channel estimation, further performance improvements for fast moving UEs may be possible.
l) Another powerful related improvement can be realized by implementing a combination with optimized interpolation.
m) Channel estimation can be easily combined with channel estimation based on LTE Release 8 CRS.
n) Further improvements can be made possible by including Doppler information, which may lead to specific prediction algorithms.
o) The UE can gain advantages because it only needs to perform measurements in one of the 10 subframes in combination with DRX (discontinuous transmission).

  The term “comprising” does not exclude other elements or steps, and “one” (an English indefinite article) does not exclude a plurality. Elements described in connection with different embodiments can also be combined. Reference signs in the claims should not be construed as limiting the scope of the claims.

101 ScaleNet result 102 ScaleNet result 103 Fo result 104 Fo result 105 Fe result 201 Central unit 202 User device 1
203 User device 2
204 matrix 205 extended Node B1
206 Extension Node B2
302 Conventional cellular layout 302 Resource block 501 Simulation result pseudo-random 502 Simulation result Hadamard scheme 601 Radio frame 602 Subframe 603 Common reference signal 704 Quasi-static subband 705 Variable subband

Claims (15)

A method for transmitting a reference signal from a first network element to a second network element in a communication network comprising:
Using a first resource of the frame to transmit a first type of reference signal associated with the first communication system;
Using a second resource of the frame to transmit a second type of reference signal associated with a second communication system;
A method comprising the steps of:   The method of claim 1, wherein the first type of reference signal and the second type of reference signal are transmitted in different subframes.   The method according to claim 1 or 2, wherein the first type reference signal and the second type reference signal are transmitted in a common subframe.   The method according to one of claims 1 to 3, wherein the first resource is associated with a first frequency band of a subframe.   In the first frame, the first reference signal is transmitted using the first frequency band, and in the second frame, the first reference signal is transmitted using another frequency band. The method of claim 4.   The method according to any one of claims 1 to 5, wherein the reference signal of the first type and / or the second type is generated by a Hadamard sequence.   The method according to claim 1, wherein the second reference signal is allocated to a specific bandwidth of the frame.   A first subband is used to transmit the first reference signal type in the first frame and / or a second to transmit the second reference signal type in the first frame. , Use a third subband to transmit the first reference signal type in the second frame, and / or use the second reference signal type in the second frame. The method according to any of claims 1 to 7, wherein the fourth subband is used for transmission.   The method according to one of claims 1 to 8, wherein only a part of the subframe is used to transmit the first type and / or the second type of reference signal.   10. A method according to any of claims 1 to 9, wherein the reference signal of the first type and the reference signal of the second type are combined.   11. A method according to any of claims 1 to 10, wherein movement of network elements of the communication network is tracked using the reference signal of the first type and / or the second type.   Further comprising the step of transmitting a control message informing the second network element about the availability and / or location and / or density of the transmitted first and / or second type of reference signal. 12. A method according to any one of claims 1 to 11. A communication network element for transmitting a reference signal, in particular for a cooperative communication network,
A first transmission unit adapted to transmit a first type of reference signal associated with the first communication system using a first resource of the frame;
A second transmission unit adapted to transmit a second type of reference signal associated with a second communication system using a second resource of the frame;
A communication network element characterized by comprising:   A computer program configured to control or implement the method of claim 1 when executed by a processor.   A computer readable medium storing a computer program configured to control or implement the method of claim 1 when executed by a processor.