Mapping user data onto a time-frequency resource grid in a coordinated multi-point wireless communications system

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DESCRIPTION

User data mapping in a time-frequency resource mesh in a coordinated multipoint wireless communication system

Technical field

The present invention relates generally to wireless telecommunication systems, and more particularly relates to the mapping of user data in an Orthogonal Frequency Division Multiplexing (OFDM) mesh of resources in an English Wireless communication system that uses coordinated multipoint transmissions.

Background

In the so-called Long Term Evolution (LTE) systems currently under development by members of the 3rd Generation Collaboration Project (3GPP - 3rd Generation Partnership Project, in English), downlink transmissions are specified according to a scheme of Multiple Access by Division of Orthogonal Frequency (OFDMA - Orthogonal Frequency - Division Multiple Access, in English). Therefore, the physical resources available in the downlink are divided into a frequency time mesh. In general, the time dimension of the downlink physical resource allocated to a particular base station (an Evolved Node B, or eNodeB, in 3GPP terminology) is divided into subframes of one millisecond each; Each subframe includes a number of OFDM symbols. For a normal cyclic prefix length, suitable for use in environments where multi-path dispersion is not expected to be extremely severe, a subframe consists of fourteen OFDM symbols. A subframe consists of twelve OFDM symbols if an extended cyclic prefix is ​​used. In the frequency domain, the physical resources allocated to an eNodeB are divided into adjacent subcarriers, separated by fifteen kilohertz, varying the precise number of subcarriers according to the bandwidth of the assigned system. For the purpose of resource planning (ie, allocation of resources for use in a given mobile telephone station), time-frequency downlink resources are referenced in units called "resource blocks" (RBs - Resource Blocks, in English); Each resource block is divided into twelve adjacent subcarriers and half of a subframe. The term "pair of resource blocks" refers to two consecutive resource blocks, that is, they occupy a subframe of a full millisecond.

The smallest element of the time mesh - LTE frequency, that is, a subcarrier of an OFDM symbol, is called a resource element. There are several different types of resource elements, which include the resource elements used as reference signals (RS - Reference Signals), as well as resource elements for transporting data symbols (for example, coded information that includes symbols). The reference signals allow channel estimation, which can also be used for coherent demodulation of the received signals and can also be used for various measurements. Each reference signal defines a so-called antenna port - since a specific RS is used for each port, a given antenna port is considered by mobile phone stations (user equipment, or UEs, in 3GPP terminology) as a separate channel However, an antenna port is a logical entity that can

or not correspond to a single physical antenna. Thus, when an antenna port corresponds to multiple physical antennas, the same reference signal is transmitted from all physical antennas.

The specific reference signals for a cell (also known as common reference signals) as well as the specific reference signals for a UE (specific reference signals for a user equipment, also known as dedicated reference signals) are supported in the current LTE specifications. In a given eNodeB, 1, 2, or 4 specific reference signals can be configured for a cell. However, only a specific reference signal for a UE is available under current specifications.

Figure 1 illustrates a portion of the LTE time-frequency mesh for cases of 1, 2 and 4 specific antenna ports for a cell (which may correspond, for example, to eNodeBs that use 1, 2 and 4 antennas of transmission, respectively). More particularly, Figure 1 illustrates a pair of resource blocks, that is, twelve subcarriers on a single frequency, for each antenna port. The structure illustrated in Figure 1 is generally repeated over the entire bandwidth of the system.

In Figure 1, reference symbols 110 are highlighted in the illustration of the resource block pair for the case of antenna port 1. Other reference symbols, for additional antenna ports, are shaded but not highlighted in each. of the different meshes. Thus, as can be seen, the reference signals for the different antenna ports are carried in the OFDM symbols 0, 4, 7 and 11 (i.e. the first and fifth symbols of each of the two intervals of the subframe) , to antenna ports one and two. The four-port case includes additional reference symbols also in OFDM 1 and 8 symbols.

In any given eNodeB, the grid of real resources may appear slightly different from what is illustrated in Figure 1 because the pattern of the reference signal may be offset in frequency over an integer number of subcarriers. The specific offset depends on the cell identifier (ID); The number of unique lags available depends on the number of specific antenna ports for a cell that are configured. A

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Thorough examination of Figure 1 will reveal that there are six lags that lead to unique reference symbol patterns in the case of a specific antenna port for a cell. The configurations for the specific antenna ports for a cell two and four will each support three different lags, such as, in these cases, a frequency offset of 3 subcarriers between the reference symbols of different antenna ports.

Such frequency offsets serve at least two purposes. First, they allow a more effective energy enhancement of the resource elements used for reference signals, since these resource elements for adjacent cells are less likely to collide. Second, for the purpose of channel quality measurements, the offset allows inter-cell interference to be measured for the resource elements of the reference signal. Since the interference thus obtained is a mixture of the interference of the reference signal and the interference of the data of other cells, such measurements thus take into account the load of interfering cells, at least to some extent.

As previously mentioned, the reference signals specific to a UE are also supported in the current LTE specifications. The pattern for a specific reference for a UE is illustrated in Figure 2, which also illustrates additional details of the approach of a pair of resource blocks. As seen in Figure 2, a pair of resource blocks comprises a mesh of twelve subcarriers per fourteen symbols of resource elements 220 (in the case of a cyclic prefix of normal length), or two resource blocks together occupying a subframe 210. Subframe 210 in turn comprises an even number range 212 and an odd number range 214. The first one, two, three or four subframe symbols are used for a control channel region 240 (which can carry one or multiple Physical Downlink Control Channels, or PDCCHs (Physical Downlink Control CHannels); The resource block illustrated in Figure 2 is configured with two symbols dedicated to the region of the control channel 240. The specific reference symbols for a UE 230 are also illustrated in Figure 2; These reference symbols appear in the OFDM symbols, 3, 6, 9 and 12. The specific reference signal for a UE effectively defines a fifth antenna port.

The specific reference signal for a UE is associated only with those pairs of resource blocks assigned for the transmission of a Physical Downlink Shared Channel (PDSCH) based on such reference signals ( that is, those transmissions that are mapped to the antenna port 5). Thus, the reference symbols corresponding to a specific reference signal for a UE are not necessarily transmitted in each subframe, or for all pairs of resource blocks within a subframe. Unlike the specific reference signals for a cell, precoding can be applied to the specific reference signals for a UE in the same way that it can be applied to the resource elements that carry data. This makes such precoding effectively invisible to the mobile telephone station, in the sense that any precoding will be effectively included in the channel estimates derived by means of the specific reference signals for a UE. The reference signals specific to a UE thus provide greater flexibility in mapping a data transmission to different antenna configurations. In particular, the use of specific reference signals for a UE facilitates the mapping of a particular downlink transmission to antennas deployed at different sites.

The data on the PDSCH is transmitted to a given mobile telephone station using resource elements corresponding to the pairs of resource blocks assigned to that mobile telephone station for a given subframe. The pairs of particular resource blocks involved in the transmission are dynamically selected and designated to the mobile telephone station as part of the resource allocation content of the associated control channel, PDCCH, transmitted in the region of the subframe control channel . As is evident from Figures 1 and 2, some of the OFDM symbols outside the control channel region are used to transport reference symbols; therefore, not all resource elements in that portion of the resource block pair can be used for PDSCH transmission. In other words, the mapping of the PDSCH over the resource mesh is affected by the positions of the specific reference symbols for a cell.

In a classic cellular deployment, the planned service area is covered by several cell sites in different geographical positions. Each site has one or more antennas that serve an area around the site. Often, a cell site is further subdivided into multiple sectors, where perhaps the most common case is to use three sectors 120 degrees wide. Such a scenario is illustrated in Figure 3. Each sector forms a cell, and a base station associated with that cell is controlling and communicating with mobile phone stations within that cell. In a conventional system, planning and transmissions to mobile telephony stations and reception from mobile telephony stations are largely independent from one cell to another.

Simultaneous transmissions that differ in the same frequencies in different cells close to each other will naturally interfere with each other and thus reduce the quality of reception of the different transmissions in a mobile receiving terminal. Interference is a major obstacle in cellular networks and is controlled primarily in conventional deployment scenarios by carefully planning the network, placing the sites in appropriate locations, tilting the antennas, etc.

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Performing independent planning between different cells has the advantages that it is simple and requires relatively modest communication capabilities between different sites. On the other hand, cells are affected with each other because those signals that originate from a cell are seen as interference in nearby cells. This indicates that there are potential benefits in coordinating nearby cell transmissions. In several cellular systems, separating frequency and / or time transmissions between neighboring cell sites is commonly used to reduce interference. However, this separation has historically been statically configured. More recently, separation in the domain of space, for example, by means of transmission schemes of multiple advanced antennas, has also been widely exploited, and coordination of neighboring transmissions in the domains of time, frequency and space has been proposed. to mitigate interference. Such coordination has recently received substantial interest in both the academic literature and the standardization of new wireless technologies. Actually, the so-called Coordinated Multi-Point Transmission (COMP), see specification TR 36.814 of 3GPP v0.3.2 (R1090929) is considered one of the key technology components for version 10 of the LTE ( LTE-Advanced) next.

COMP can be classified into two separate but related technologies: coordinated planning and joint transmission, respectively. In the first case, the transmission to a given mobile telephone station originates from a single cell site or sector at the same time, while in the latter case multiple sites and / or sectors are simultaneously involved in the transmission. Thus, for example, several cell sites that cover a group of cells, such as the group of seven circles within the circle of Figure 3, can coordinate their transmissions; A group of cells involved in such coordination is referred to herein as the COMP group.

Obviously, coordination between cell sites requires communication between sites. This can take many forms and the requirements on data rates and latency for such inter-site communication depend largely on the exact coordination scheme used.

Apart from the potential problem of site-to-site communication capability, coordination that takes advantage of time and frequency is easily achieved for OFDM systems such as LTE using the dynamic resource allocation feature, which selects the particular resource block pairs to transmit the PDSCH to a given mobile telephone station in a given subframe. Spatial coordination, on the other hand, implies the use of multiple antennas for transmission; This may include the transmission of antennas at geographically distinct cell sites. By modeling the signals as vector value signals and applying matrix weights of appropriate complex values ​​between the transmission antennas, the transmission may focus on the direction (in the physical space or in a more abstract vector space) of the mobile telephone station , even minimizing interference to other mobile phone stations. This approach increases the signal to noise ratio plus interference (SINR - Signal to Noise plus Interference Ratio, in English) at the mobile phone station, and ultimately improves the overall system performance.

As previously indicated, the mapping of the PDSCH in the resource elements in the LTE frequency time mesh may vary from one cell to another, even if the same resource blocks are used for the PDSCH. One reason is the use of different frequency offset of the reference signal for the specific reference signals for a cell. Another reason is that the number of OFDM symbols used to control signaling can dynamically vary from the first 1 to 4 OFDM symbols and may be different for neighboring cells. Therefore, the particular service cell to which a given mobile telephone station is attached affects the PDSCH mapping to the resource elements in the time-frequency resource mesh, since this mapping is intended to be compatible with how other resources such as the reference signals and the PDCCH in that particular cell are allocated. This can create problems for coordinated multipoint transmission, where certain transmissions to a mobile telephone station need to be carried out from sites / sectors other than the service cell (logic), either simultaneously or as part of a coordinated planning.

The Draft 3GPP; Huawei; CMCC; R1-090129 Further Discussions on Downlink Coordinated Transmission, 20090107 3rd Generation Partnership Project (3GPP), Mobile Competence Center; 650, route des Lucioles; F-06921 Sophia-Antipolis Cedex; France XP050318067; Nr: Ljubljana; 20090107; describes a solution in which the eNB informs the UE about the service cell IDs

Compendium

Some of these problems can be mitigated, in some embodiments of the present invention according to claims 1, 8, 15 and 16, allowing PDSCH transmission (possibly including specific reference signals for an associated UE) according to a mapping of resource that is compatible with the mapping used in a cell other than the service cell. Specifically, in these embodiments it is possible to use a PDSCH data symbol mapping to the time mesh - LTE frequency according to a pattern corresponding to a difference in the frequency of the reference signal different from that used by the cell of service (that is, the cell to which the PDSCH is associated). In some embodiments, the mapping of PDSCH data symbols to the time mesh - LTE frequency can also be adjusted to accommodate a control channel.

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of different size (for example, to accommodate the fact that a neighboring cell uses three OFDM symbols for the PDCCH, while the service cell uses only two symbols).

In support of this approach, appropriate signaling can be added, in some embodiments, to support dynamic adaptation of said PDSCH mapping. More specifically, signaling can be added to inform a receiving mobile telephone station about the mapping used for a particular PDSCH transmission. In other words, this additional signaling informs the mobile telephone station of which of the different possible PDSCH mappings the mobile telephone station should use when extracting PDSCH data symbols from the time mesh - OFDM frequency and decoding the PDSCH . In some embodiments, this additional signaling could be part of the PDCCH, such as the part of the PDCCH that carries the planning information for the mobile telephone station.

Thus, embodiments of the invention include methods, such that they can be implemented in a mobile telephone station, to receive user data in a wireless communication system that employs coordinated multipoint transmission of user data from a first service cell. of the wireless terminal and a second neighbor cell site of the first cell site. In this system, the first cell site maps control signals and user data to time-frequency resources according to a first mapping pattern, while the second cell site maps control data and data. Traffic to resource time frequency according to a second mapping pattern. Control signals may include common reference signals, specific reference signals for a UE, synchronization signals, and others.

An example method includes extracting the user data, according to the first mapping pattern, of the time-frequency resources of a first transmission for the mobile telephone station transmitted from the first cell site, detecting a control element transmitted by one of the first and second cell sites, indicating the control element that the user data associated with the control element is mapped to the time-frequency resources according to the second mapping pattern and, in response to said detection, extract the user data in accordance with the second time resource mapping pattern - frequency of a second transmission for the wireless terminal transmitted from the second cell site. In some embodiments, detecting the control element comprises decoding one or more bits of a received downlink resource allocation message. In some of these and other embodiments, the control element indicates one of a plurality of predetermined offset patterns for common reference signals interspersed between time-frequency resources mapped to user data. In some other embodiments, the control element also indicates that the second mapping pattern maps the user data to one or more OFDM symbols less than the first mapping pattern.

The techniques described herein can be applied to coordinated multipoint transmission using only coordinated planning, such as where the first and second transmissions explained above are transmitted during the first and second mismatched transmission time intervals. In addition, these techniques can be applied where the first and second transmissions overlap at least partially in time, in which case the methods listed above may further comprise separating the first and second transmissions using one of space-time or processing diversity processing of spatial demultiplexing. In some embodiments, the control signals comprise specific reference signals for a user equipment interspersed between the time-frequency resources mapped to the user data, in which case the methods collected above may further comprise extracting the specific reference signals for a user equipment of the second transmission according to the second mapping pattern.

Other embodiments include several wireless terminals, adapted for use in a wireless communication system that employs coordinated multipoint transmission of user data, including the wireless terminals a receiver circuit configured to perform one or more of the techniques of the invention collected. previously and explained in detail in the following. Other embodiments include a transmission node for use at a first cell site in a wireless communication system using coordinated multipoint data transmission, where the transmission node includes a transmitter circuit configured to transmit a control element indicating that the User data associated with the control element is mapped to the time-frequency resources according to a particular predetermined mapping pattern. Methods corresponding to this transmission node are also explained.

Of course, the present invention can be carried out in other ways than those specifically presented herein without departing from the essential features of the invention. With the reading of the following description and the vision of the attached drawings, it will be apparent to the person skilled in the art that the described embodiments are illustrative and not restrictive, and that all changes that come within the meaning and range of equivalence of the claims Attached is expected to be covered in them.

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Brief description of the drawings

Figure 1 illustrates the mesh of time resources - Long Term Evolution (LTE) when a normal cyclic profile is used. The cases of one, two and four antenna ports are illustrated.

Figure 2 illustrates a specific reference signal for a UE in a pair of resource blocks.

Figure 3 illustrates an example cellular network with sites from three sectors.

Figures 4A and 4B illustrate transmissions from the first and second cell sites to a mobile telephone station in an LTE system using coordinated multipoint transmission.

Figure 5 is a flowchart of a process illustrating an example method for receiving user data in a wireless communication system using a coordinated multipoint transmission.

Figure 6 is a schematic illustration of components of a wireless communication system according to some embodiments of the invention.

Figure 7 is a block diagram illustrating functional components of an example processing circuit configured in accordance with some embodiments of the invention.

Detailed description

Although aspects of the present invention are described herein in the context of a Long Term Evolution (LTE) system, as specified by the 3rd Generation Collaboration Project (3GPP - 3rd Generation Partnership Project, in English), it will be apparent to those skilled in the art that the techniques of the invention explained herein can be used in other wireless systems. Thus, although terminology of the 3GPP LTE specifications is used throughout this description, this terminology should not be considered as limiting the scope of the invention only for the system mentioned above. Other wireless systems, including WCDMA, WiMax, UMB and GSM, can also be adapted to take advantage of the techniques described below. In fact, it should also be noted that the use of terms such as base station, eNodeB, mobile phone station and UE should also be considered non-limiting in the sense that their use herein does not imply that the present techniques of the invention are only applicable in systems that use the hierarchical architecture of the 3GPP LTE system. Thus, when the methods and apparatus of the present description are adapted to other systems, the apparatus referred to herein as "base station" or "eNodeB" may correspond to a user device or another wireless terminal, for example, the " device 1 ”, although the apparatus described herein as a“ mobile phone station ”or“ UE ”may refer to another wireless terminal, for example,“ device 2 ”, these two devices communicating with each other on any suitable radio channel.

However, the inventive techniques of the present invention will be more readily understood with reference to an LTE system using coordinated multipoint transmission (COMP), where user data is transmitted to a telephone station. mobile from a first cell site (for example, a first eNodeB) serving the mobile telephone station, as well as from a second cell site that is neighboring the first cell site. As explained above, the first cell site maps control signals, especially reference signals, to the LTE time-frequency resource mesh according to a first mapping pattern, while the second cell site maps control signals to the resource mesh according to a second mapping pattern, which differs from the first mapping pattern.

For example, consider a scenario that involves a mobile terminal served by a “logical” A cell, which is normally associated with physical transmissions from the AA sector of the cell, which in turn corresponds to an antenna or array of particular antennas in a First cell site. Sometimes a PDSCH associated with this logical cell A needs to be transmitted for at least one subframe from the cell sector BB, in a second cell site, which is normally associated with a logical cell B. However, the cell sector BB it is also transmitting a broadcast channel, BCH - Broadcast CHannel, in English), corresponding to the logical cell B. Thus, during at least one subframe, the sector BB transmits signals for mobile telephone stations that are served by the logic cell B as well as the coordinated signal transmission associated with the logic cell A. However, if logic cell A is using a reference signal offset different from that of logic cell B (because transmissions from logic cell A are normally mapped to a physical cell site that is neighboring the site of cell that transports cell B transmissions), then the sector BB will transport in some resource elements the transmissions of both the common reference signals for the logic cell B and the transmissions of the PDSCH associated with the logic cell A. Thus, there is a problem of collision of data to reference signal, causing a lot of interference.

In particular, there are several different interference scenarios, although related to each other, derived from coordinated transmission. First, because both the AA sector and the BB sector are transmitting the PDSCH according to the mapping of the logical cell A, at least in some pairs of resource blocks, then

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a strong interference of the signals of the PDSCH of the logical cell A is seen over the specific reference signals for a cell for the logical cell B. Especially for mobile telephone stations with center in the cell, this can be a big problem . Normally, a mobile telephone station near a transmission sector enjoys high SINRs, and can therefore support high data rates. However, with strong interference to the specific reference signals for cell of logic cell B, caused by a coordinated PDSCH transmission corresponding to logic cell A, the precision of the channel estimation in a mobile telephone station with center in The cell is likely to be significantly damaged.

On the contrary, the transmission from the cell sector BB of the specific reference signals for a cell for the logic cell B interferes with the coordinated transmission of the PDSCH for the logic cell A. Compared to the first case, this may be somehow a minor problem, since the PDSCH transmission of the logical cell A is likely to serve a mobile telephone station that is not too far from the border between physical areas. normally covered by the AA and BB cell sectors. (Otherwise, the mobile phone station would probably be associated with logic cell B). Thus, the interference of the reference signals of the logic cell B is not worse than the inter-cell interference normally found in a classical cellular display. However, an important objective of coordinated multipoint transmissions is to avoid low SINRs at the edge of the cell; This interference mechanism works against this objective.

Therefore, it is an object of some embodiments of the invention to mitigate the problems described above. This is achieved by allowing PDSCH transmission (possibly including specific reference signals for an associated UE) in accordance with a resource mapping that is compatible with the mapping used in a cell other than the service cell. Specifically, it should be possible to use a PDSCH data symbol mapping to the time mesh - LTE frequency according to a pattern that corresponds to a frequency offset of the reference signal different from that used by the service cell (it is say, the cell to which the PDSCH is associated). In some embodiments, the mapping of PDSCH data symbols to the time mesh

- LTE frequency can also be adjusted to accommodate a different size control channel (for example, to accommodate the fact that a neighboring cell uses three OFDM symbols per PDCCH, while the service cell uses only two).

In support of this approach, appropriate signaling may be added, in some embodiments, to support dynamic adaptation of the aforementioned PDSCH mapping. More specifically, signaling can be added to inform the receiving mobile phone station about the mapping used for a particular PDSCH transmission. In other words, this additional signaling informs the mobile telephone station of which of several possible PDSCH mappings the mobile telephone station should use when extracting PDSCH data symbols from the time mesh - OFDM frequency and decoding the PDSCH. In some embodiments, this additional signaling could be part of the PDCCH, such as the part of the PDCCH that carries the planning information for the mobile telephone station.

Figures 4A and 4B provide a general illustration of this technique according to several possible embodiments of the invention. The BS1 corresponds to a first cell site and is the service cell in each of Figures 4A and 4B; The mobile telephone station 410 thus continuously monitors the PDCCH control channel, transmitted from the BS1. On the other hand, the PDSCH may occasionally be transmitted from BS1, as in Figure 4A, or from BS2, at a neighboring cell site, as in Figure 4B. (Of course, a given base station may include radio equipment and corresponding antennas for multiple cell sectors - for simplicity, only a single cell sector for each base station is explained herein.) In embodiments of the In the present invention, the PDCCH carries control signaling that informs the mobile telephone station of which two mappings are used for the current transmission of the PDSCH. Thus, in Figure 4A the PDCCH may indicate that a first mapping, corresponding to the mapping normally used by the BS1, should be used when PDSCH data is extracted from the received signal and the PDSCH is decoded. In Figure 4B, however, the PDCCH may indicate that a second mapping, corresponding to the mapping normally used by the BS2, must instead be used. Since the transmission of the PDSCH can dynamically switch between the BS1 and the BS2, the mobile telephone station 410 also dynamically changes its unmapping process.

The additional signaling described above can be implemented in several ways. In an exemplary embodiment of the present invention, the PDCCH contains a bit field describing the frequency offset of the reference signal that the receiving mobile telephone station must assume has been used in the mapping of the PDSCH to the elements. resource of the resource mesh. In other words, this bit field indicates the mapping pattern that the mobile phone station should use when extracting user data from the time-frequency resource mesh of the received signal. The size of this bit field may vary, in some embodiments, or be fixed, in others.

For base stations configured to use two or four specific antenna ports for a cell, there are only three possible offset of the reference signal, and thus, two bits would be sufficient. On the other hand, systems configured to use specific antenna ports for a cell may require the use of a control element comprising three bits. In any case, assuming that a specific reference signal is being used for a UE, the resource elements used in the transmission of the PDSCH can then be made compatible with the site and / or sector from which the transmission of the PDSCH, avoiding

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thus collisions between the PDSCH data symbols and the specific reference signals for a cell transmitted from the cell site it is transmitting.

A similar approach can be used to take into account the size of the control region for PDSCH transmissions that use specific reference signals for a UE. Thus, in some embodiments of the invention, the PDCCH contains an additional control element that indicates the number of OFDM symbols that the mobile telephone station must assume for the control region when determining to which set of resource elements the PDSCH has been mapped. In some embodiments, this additional control element may be coded together with the control element indicating the frequency offset of the reference signal. Alternatively, this signaling (as well as the signaling indicating the offset of the reference signal) could be carried out by means of high layer signaling, such as Radio Resource Control (RRC) signaling. ).

With the foregoing explanation of the application of the present invention to an LTE system in mind, it will be apparent to those skilled in the art that Figure 5 illustrates a general method, such as can be implemented in a wireless terminal, to receive user data in a wireless communication system that employs coordinated multipoint transmission of user data from a first cell that provides service to the wireless terminal and from a second neighboring cell site of the first cell site. In this system, the first cell site maps control signals and user data to time-frequency resources according to a first mapping pattern, while the second cell site maps control data and traffic data to the resources. of time - frequency according to a second mapping pattern. Control signals may include common reference signals, specific reference signals for a UE, synchronization signals and others.

The method illustrated thus begins, as shown in block 510, with the reception of a transmission from the first cell site. This stage may, of course, include monitoring a control channel from the first cell site to detect a specific resource allocation. In the case of an LTE system, this assignment would designate specific resource blocks addressed to the mobile telephone station.

As shown in block 520, the method continues with the extraction of user data from the transmission of data received according to the first mapping pattern, that is, the pattern used by the first cell site for mapping. User data and transmission control data. In some embodiments, the mobile telephone station may determine which mapping pattern should be used for this particular transmission in accordance with conventional methods, such as determining a reference offset of the ID of the broadcast cell transmitted by the first cell site. . In others, the mobile telephone station may determine which mapping pattern should be used to detect one or more specific resource elements, perhaps included in a downlink resource allocation transmitted by the first cell site. This control element (or elements) may (or may) order one of the different possible reference offsets, for example, and / or indicate how many OFDM symbols are dedicated to the downlink control channel.

As shown in block 530, the method continues with the reception of a transmission from the second cell site. It will be apparent to those skilled in the art that the mobile telephone station does not need to "know" that this transmission is arriving from the second cell site, since the mobile telephone station continues to receive its downlink resource allocations from the channel of control transmitted by the first cell site. However, as explained in detail above, this transmission from the second cell site includes traffic and control data signals (such as reference signals) mapped to the time-frequency resources according to the second pattern. mapping, which is different from the first.

As shown in block 540, the mobile telephone station learns that this is the case by detecting a control element indicating that the second mapping pattern is currently being used. As noted above, this control element could be included, for example, in one or more bits of a downlink resource allocation message, or somewhere else in the control channel. In some embodiments, the control element indicates one of a plurality of predetermined offset patterns for common reference signals interspersed between time-frequency resources mapped to user data. In some embodiments, the control element also indicates that the second mapping pattern maps user data to one or more OFDM symbols less than the first mapping pattern, for example, because the second cell site dedicates more symbols of OFDM to the downlink control channel.

In some embodiments, this control element could only be used for transmissions that are mapped according to a pattern other than the "normal" pattern. In other words, the mobile telephone station might be able to determine a default pattern, for example, using the cell ID or other broadcast control information. This default pattern could then be used for all transmissions for which no additional control element has been received, for example, for all transmissions from the service cell site. In these embodiments, the detection of the additional control element would signal to the mobile telephone station that a second mapping pattern should be used instead. However, in other embodiments, this additional control element may be transmitted with each resource allocation, so that the mobile telephone station always determines the appropriate mapping pattern to use from the additional control element.

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In any case, as shown in block 550, the process illustrated in Figure 5 continues with the extraction of user data from the transmission received from the second cell site, in accordance with the second mapping pattern. The illustrated procedure can be repeated as many times as necessary, with dynamic switching between transmissions from the first cell site and the second cell site as the propagation conditions change, when the mobile phone station moves, or when the environment of interference changes.

It will be apparent to those skilled in the art, then, that the techniques explained above facilitate the mapping of PDSCH (or similar) transmissions on a time-frequency resource mesh using a different mapping pattern from that used in the service cell ( that is, the logical cell to which the PDSCH is associated). Similarly, the size of the control region can also be assumed as different. It will be apparent to those skilled in the art that this may be particularly beneficial for PDSCH transmissions using reference signals specific to a UE, since this allows the PDSCH to be transmitted from another cell site other than the one normally used as the site of service cell, completely avoiding collisions with transmissions from another cell site. Coordinated planning with rapid sector selection could thus be implemented without causing high interference to mobile telephone stations that are based on specific reference signals for a cell. Also, the interference from the specific reference for a cell on said PDSCH disappears. Thus, in several embodiments of the method illustrated in Figure 5, the first and second transmissions, from the first and second cell sites, are during mismatched time intervals (i.e., they do not overlap).

On the other hand, the techniques illustrated in Figure 5 can also be applied to COMP systems using joint transmission, in which case the first and second transmissions explained above can be at least partially overlapped in time. In some of these embodiments, the mobile telephone station may be configured to separate the first and second transmissions using space-time diversity processing, space demultiplexing processing, or others.

For joint transmission from multiple cell sites (corresponding to multiple logical cells) that use different frequency shifts of the reference signal, collisions of the reference signal with the PDSCH are unavoidable. However, signaling the offset information of the reference signal frequency for PDSCH mapping according to the techniques described above provides the eNodeB with the opportunity to select a offset for a given PDSCH transmission, which causes the least amount of interference For example, perhaps one of the cells in a COMP group does not have a mobile telephone station based on specific reference signals for a cell for reception of the PDSCH. In this case, using a offset of the resource of the reference signal corresponding to that cell can then reduce the negative impact of the PDSCH transmitted to the reference signals. In addition, the ability to dynamically signal an indicator of the size of the control region for the purpose of mapping the PDSCH may also be beneficial because the size of the control region may vary from one cell site to another within the COMP group, while the PDSCH mapping for mobile phone stations participating in the COMP transmission could be assuming a control region size equal to the maximum control region size used within the COMP group.

Finally, the flexibility of the PDSCH mapping mentioned above could also be used in conjunction with COMP based on specific reference signals for a cell. However, for that case, the mobile telephone station may need to know the cell ID of the cell sites that participate in the transmission of COMP, in order to estimate the channels. Thus, in these cases the frequency offset of the reference signal that the mobile telephone station must use in the mapping of the PDSCH transmissions of the downlink frequency mesh can alternatively be implicitly signaled by the ID of cell, although an indication of the size of the control region would still be explicitly stated unless it can be assumed that the mobile telephone station is capable of decoding the control channel format indicator (PCFICH, in LTE system) by providing the size of the control region of non-service cell sites in the COMP group.

It will be apparent to those skilled in the art that the techniques described above, although generally described in the context of an LTE system, can more generally be implemented in a variety of wireless devices adapted for use in a communication system. wireless that uses coordinated multipoint transmission. Figure 6 is a schematic diagram illustrating the functional components of such a system, including a transmission node 610 connected to a cell site 630, and a wireless terminal 635.

The transmission node 610 includes a receiver section 615 and a transmitter section 620, each of which may be designed, in accordance with well-known design techniques, for compatibility with one or more wireless technology standards (such as LTE). The transmission node 610 further includes a controller section 625, which can again be designed, in accordance with well-known design techniques, to implement one or more wireless technology standards. In particular, controller 625 may be configured to map user data to time resources - downlink frequency according to a first mapping pattern, for transmission to wireless terminal 635. However, controller 625,

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which may include one or more microprocessors or others, configured with appropriate software and / or firmware, may also be configured to transmit an additional control element to the wireless terminal, specifically indicating that the user data associated with the control element is mapped to Time resources - frequency according to the first mapping pattern. As noted above, this control element may be included in or associated with a downlink resource allocation message, so that transmitting the control element comprises transmitting the downlink resource allocation message.

Like the transmission node 610, the wireless terminal 635 can be designed, in accordance with well-known design techniques, for compatibility with one or more wireless technology standards, such as LTE. Thus, in some embodiments, wireless terminal 635 includes a duplexer 650, a radio resource receiver (RX) section (RF) 645, and the RX 640 baseband circuit, each of which in general it can be configured according to conventional means. However, the RX 640 baseband circuit is further configured, in accordance with some embodiments of the invention, to contain one or more of the invention techniques described above. In particular, the RX 640 baseband circuit is configured, in various embodiments of the invention, to extract user data in accordance with a first time-frequency resource mapping pattern of a transmission for the wireless terminal 635 transmitted from a first cell site, to detect a control element transmitted by one of the first and second cell sites, indicating the control element that the user data associated with the control element is mapped to the time-frequency resources according to a second mapping pattern and, in response to the detection of the second mapping pattern of the time resources - frequency of a second transmission for the wireless terminal 635 transmitted from a second cell site.

Figure 7 provides some details of an example receiver circuit 640, which includes one or more processors 710 (which may include one or more microprocessors, microcontrollers, digital signal processors, or others) and other digital hardware 720 (which includes, by example, particularized signal processing logic). Some or both of these 710 processors and other 720 digital hardware may be configured with software and / or firmware stored in memory 730. In particular, this software includes a receiver processing code 740, which comprises instructions for carrying out one or more of the techniques described above. Memory 630 may also include another processing code (not shown), as well as program data 646, configuration data 648 and other control data 649, some of which may be stored in a random access memory (RAM - Random Access Memory, in English) or a quick memory.

More generally, it will be apparent to those skilled in the art that the receiver circuit 640 may comprise any of a variety of physical configurations, such as in the form of one or more application-specific integrated circuits (ASICs - Application Specific Integrated Circuits, in English). Other embodiments of the invention may include computer readable devices, such as a programmable quick memory, a magnetic data storage device, or others, encoded with computer program instructions which, when executed by a suitable processing device, cause the processing device to carry out one or more of the techniques described herein to equalize the signals received at a communications receiver.

The present invention can, therefore, be implemented in other ways than those specifically presented herein without departing from the essential features of the invention. The present embodiments should be considered in all aspects as illustrative and not restrictive, and all changes within the meaning and scope of equivalence of the appended claims are intended to be encompassed in them.