Method and apparatus in a telecommunication system

ES 2 587 705 T3

DESCRIPTION

Method and apparatus in a telecommunication system

Technical sector

The present invention relates generally to a method and apparatus for optimizing wireless transmissions in a telecommunication system that requires feedback reporting for received data.

Background

In the 3GPP (Project of association of 3^to generation - 3rd Generation Partnership Project, the mobile packet switched communication systems HSPA (High Speed ​​Packet Access) and LTE (Long Term Evolution). English) have been specified for the radio transmission of data packets between user terminals and base stations in a cellular / mobile phone network. Transmissions from the base station to the user terminal are called "downlink" and transmissions in the opposite direction are called "uplink." In the following description, "terminal" is used to represent in a general way any user equipment, commonly referred to as "UE" (User Equipment - User Equipment, in English) in the above systems, that has wireless communication capability, for example , with base stations in a cellular / mobile phone network.

There are two basic modes of operation available for wireless transmissions: FDD (Frequency Division Duplex) and TDD (Time Division Duplex). In FDD, the downlink and uplink transmissions are made in separate frequency bands, such that packets can be transmitted on the downlink and on the uplink at the same time, without interference between them. In tDd, on the other hand, the downlink and uplink transmissions are made in the same frequency band and therefore must be separated in time to avoid interference.

The TDD mode of operation is flexible in that the duration of the downlink and uplink transmissions can be configured depending on the intensity of the traffic in the respective downlink and uplink directions, thereby allowing connections with transmission schemes. asymmetrical. For intensive downlink connections, the downlink time period can thus be set greater than the uplink time period, and vice versa for uplink intensive connections.

For LTE, a new physical layer based on OFDM (Orthogonal Frequency Division Multiplexing) is currently being standardized in 3GPP on the downlink and SC-FDMA (Carrier Frequency Division Multiple Access). single - Single Carrier Frequency Division Multiple Access) in the uplink. The new physical layer will support both FDD and TDD operation, and there should be a high degree of commonality between these two modes of operation. The SC-FDMA properties on the uplink require that all data transmitted from each terminal basically maintain single carrier properties.

Both FDD and TDD transmissions in operation are generally scheduled in radio frames, and each radio frame is typically divided into multiple subframes. In the following description, the term "subframe" is used to represent in a general way a predefined transmission time interval "TTI" (Transmission Time Interval, in English), in which a portion of information can be transmitted as a "block of data ”, although it is not limited to any particular standard or duration. A data packet can be sent in any number of subframes depending on the size of the packet and the length of the subframe. LTE prescribes that a data packet is typically contained in a single subframe. A subframe can generally contain one or more data blocks, also called "transport blocks" in LTE. Currently, LTE allows two data blocks per terminal in a single downlink subframe.

In LTE, the default radio frame is 10 ms (milliseconds), which is divided into ten predefined subframes of 1 ms each. In FDD mode, where packets can be transmitted on the downlink and uplink simultaneously, there are 10 "DL" (DownLink) downlink subframes and 10 "UL" uplink ( UpLink) available during a radio frame in separate frequency bands F1 and F2, respectively, as shown schematically in Figure 1a. In TDD mode, there are a total of 10 downlink and uplink subframes available during a radio frame, which can thus be transmitted only one at a time on a common F frequency band.

As mentioned above, the downlink and uplink transmissions can be configured in TDD depending on the traffic demand in either direction. For example, the downlink / uplink assignment can be configured for 8 downlink subframes and 2 uplink subframes during a radio frame in the same frequency band F, as shown schematically in Figure 1b. Another possible configuration could be 5 DL subframes: 5 UL subframes, and yet another configuration could be 2 DL subframes: 8 UL subframes. The alternation pattern of the subframes

ES 2 587 705 T3 downlink / uplink can also be optionally configured. For example, the downlink / uplink subframe pattern of Figure 1b could be modified to 8 successive downlink subframes followed by 2 uplink subframes.

A single base station can transmit data packets in subframes on the downlink to one or more terminals, and the terminals can transmit data packets in subframes on the uplink to the base station. Transmission in either direction is typically subject to various disturbances, including propagation fading and interference caused by reflections and other transmissions, such that errors may have been introduced into the data packets when they are received. Thus, the channel between a base station and a terminal is often referred to as a "lossy" channel. Also, errors may appear due to a bad receiver and / or a bad antenna.

When a packet with data is received in a subframe, the receiver at the terminal or base station is configured to check the received packet for errors. A common method of detecting errors involves the calculation of a checksum or the like, which is well known in the art. To allow correction of such errors, the sending data participant must retransmit any erroneously received packets, unless some error correction mechanism can be successfully applied to the data receiving participant. Therefore, the receiving participant is typically required to report back information to the sending data participant for each received packet or subframe, indicating whether the packet was basically received correctly, that is, without errors, or not.

If the packet was received correctly, the participant receiving the data sends an acknowledgment of receipt “ACK” (ACKnowledgement, in English), and if the packet contained errors, it sends a negative acknowledgment of receipt “NACK” (Negative ACKnowledgement, in English ). Although the terms ACK and NACK are used frequently in this description, "report back information" is used in the following as a generic term for such ACK / NACK messages.

Both HSPA and LTE employ a HARQ (Hybrid Automatic Repeat ReQuest) protocol in their MAC (Medium Access Control) layers. The basic functionality of the processes defined in the HARQ protocol is to correct any erroneously received packets by means of a retransmission based on the feedback reporting mechanism described above. In this context, a report of the feedback is sometimes called a "HARQ status report."

For example, the data-receiving participant may simply discard an erroneously received packet. In more advanced solutions, the receiving party stores the signal representing the erroneously received packet in a temporary memory and combines this stored information with the retransmission. This is often referred to as "soft combining HARQ" which can be used to increase the probability of correctly decoding the transmitted packet. In soft-combined HARQ, the pattern of bits encoded in a particular packet may be different between transmission and retransmission, although obviously they must represent the same information.

The HARQ process is used to associate a potential retransmission with its original transmission in order to allow soft combining at the receiving party of the data. When the receiving participant has reported a correct reception of the data sent in a HARQ process, that data can be used to transmit new data. Consequently, prior to receiving a HARQ status report from the receiving party, the sending party of the data does not know whether to transmit new data or retransmit the "old data". Meanwhile, the issuing participant, therefore, "stands and waits" until the result of the transfer is communicated. In order to still be able to use the link during these waiting periods, multiple HARQ processes can be applied in parallel, allowing continuous transmission.

For example, when a packet is transmitted on the downlink, the receiving terminal checks the packet for errors and sends a report of the information back to the base station. If the base station then detects a NACK, it will retransmit the information in the packet. This mechanism can also be used for packets sent on the uplink. In LTE, the return information required for HARQ with soft combination is transmitted by a single bit that indicates ACK or NACK. The timing relationship between the transmission of the packet from the sending participant and the transmission of the return information report from the receiving participant is typically used to indicate which packet the return information report refers to.

In FDD, the number of available subframes is equal in the downlink and in the uplink, as shown in Figure 1a. Consequently, it is possible to send a return information report for a data block received in a downlink subframe in a given uplink subframe according to a "one-to-one relationship", using a fixed time interval between the receipt and return information. Therefore, the data sending participant can infer to which HARQ process the report of the received feedback refers, based on in which subframe the report was received. In TDD, on the other hand, data blocks in multiple subframes can be received on the downlink before it is possible to send

ES 2 587 705 T3 corresponding feedback reports, or ACK / NACK, on ​​the uplink, such as when the number of assigned downlink subframes is greater than the number of assigned uplink subframes.

In the mapping example in Figure 2, there are 8 downlink subframes but only 2 uplink subframes available. Therefore, the feedback reports for the 8 downlink subframes must be transmitted in the 2 uplink subframes. Depending on how many users have been scheduled in the downlink subframes, the number of feedback reports that need to be transmitted can increase by a factor of 4. Furthermore, if a single terminal is scheduled to receive data in all available downlink subframes, that terminal will need to report the feedback for multiple data blocks received in a plurality of downlink subframes during a single subframe of uplink. Furthermore, more than one data or transport block may be contained in a single received subframe, for example, relating to one or more sessions or different media streams at a high level, where each data block needs a feedback report. separately, so that the number of feedback reports required can be increased even more.

In TDD, the above-described reporting mechanism with a fixed time interval cannot be used in a general way, since the report of the return information for a received subframe cannot be transmitted in a fixed time interval after receiving the subframe. if the corresponding subframe is not available to be transmitted from the receiving data party. Consequently, the reporting of feedback for data in that received subframe must be delayed to at least the first subframe available to be transmitted. Furthermore, the receiving data participant typically requires a certain delay after receiving a subframe, to process the data in it and to determine whether it was received correctly or not, before it is possible to report the feedback for that subframe. subplot. For example, if the receiver needs a delay of at least 1 subframe for processing, a received k subframe cannot be communicated until subframe k + 2 or later.

A simple and obvious solution is to send a return information report for a received subframe in the first available subframe after a minimum delay period for processing. Therefore, if one or more subframes after the delay period are allocated for reception, the reporting of the feedback is further delayed until the first subframe available to be transmitted occurs. As a result, typically, a plurality of feedback reports must be sent in the same subframe. This turns out to be particularly a problem when it is desired to reduce the number of such reports in a single subframe.

In LTE, each subframe typically includes two slots, each slot in turn consisting of a plurality of OFDM symbols. In the frequency domain, each OFDM symbol can be considered as a set of subcarriers. The subcarrier spacing is typically 15 kHz and the number of subcarriers in the array depends on the frequency carrier bandwidth. Furthermore, the subcarriers are divided into groups of multiple adjacent subcarriers, eg 12 subcarriers. Each group of subcarriers in a range is generally referred to as a "resource block." Within a subframe, these resource blocks are arranged as pairs of resource blocks, in which information can be transported.

As explained above, if a terminal has scheduled data packets in multiple downlink subframes, the terminal is typically required to transmit multiple feedback reports in a single uplink subframe. However, single carrier properties must be maintained in uplink transmissions in accordance with LTE. As a result, a terminal cannot transmit on more than one resource block and simultaneously transmit a single carrier signal, since the corresponding subframes are not in contiguous spectrum, that is, on adjacent frequencies.

Furthermore, if the terminal were to transmit multiple feedback reports within a single resource block, the combined signal would typically not maintain its unique carrier signal at the same time, since feedback reports must be transmitted with different sequences of signals. CDM code (Code Division Multiplexing) within the resource block, therefore not being correlated. In other words, it is typically only possible for one terminal to transmit one report of the return information at a time and still maintain the single carrier properties.

If BPSK (Binary Phase Shift Keying) modulation is used, one bit, i.e. 1 or 0, is carried by each symbol, and the terminal can therefore transmit a report of the return information in an uplink subframe. By using QPSK (Quadrature Phase Shift Keying) modulation, it is possible for a terminal to carry two reports of feedback in one uplink subframe, since QPSK allows two bits per symbol. Even higher modulation schemes, for example 16QPSK, which allows 4 bits per symbol, are considered too sensitive for signal disturbances , generally resulting in unacceptable error rates. An increase in the order of modulation will generally decrease the robustness of the feedback information reports, and it is important that the feedback information reports

ES 2 587 705 T3 returns are correctly detected with a relatively high probability. The probability of error is preferably of the order of 10^-3 to 10^-4. Therefore, a modulation order greater than QPSK is not an attractive solution to the problem of reporting multiple feedback reports during a single uplink subframe.

However, when using a transmission allocation of 8 DL subframes: 2 UL subframes, a terminal that has been scheduled in all downlink subframes would need to send at least four feedback reports in one uplink subframe. . Thus, only two possible feedback reports when using QPSK in accordance with the above are clearly not sufficient. In addition, a terminal can receive two data blocks, for example MAC PDUs (Packet Data Units), in a single downlink subframe, with each data block requiring a report of the information. return. In this case, the terminal would need to send twice as many feedback reports in each uplink subframe, making the limitation of sending only two feedback reports while maintaining single carrier properties even more important.

A potential consequence of the above limitations could be that it is not possible to transmit data to a single terminal in all downlink subframes, which would "artificially" limit DL capacity due to lack of feedback opportunities.

WO2005 / 071887, US2005 / 0220042 disclose methods known in the most advanced art.

Compendium

An object of the present invention is to address at least some of the problems outlined above. Furthermore, an objective is to provide a solution that allows a data receiving participant to transmit several reports of feedback in a single subframe to a data sending participant, without losing the single carrier properties of the transmitted subframe. These and other objectives may be achieved by a method and apparatus in accordance with the independent claims that follow.

Other possible features and benefits of the present invention will be explained in the detailed description that follows.

Brief description of the drawings

The invention will now be explained in more detail by way of exemplary embodiments and with reference to the accompanying drawings, in which:

Fig. 1a is a diagram showing a wireless FDD transmission scheme, according to the prior art;

Fig. 1b is a diagram showing a wireless TDD transmission scheme, according to the prior art;

Fig. 2 is a diagram showing a resource block packing on multiple subcarriers in a subframe, which can be used for the present invention;

Fig. 3 is a block diagram showing how feedback reports for data received from a receiving data participant to a sending data participant can be conveyed, in accordance with one embodiment;

Fig. 4 is a flowchart showing a procedure in a data receiving participant for sending feedback information reports to a data sending participant, according to yet another embodiment;

Fig. 5 is a flowchart showing a procedure at a network node, such as a base station, of receiving feedback information reports from a data receiving participant, in accordance with yet another embodiment;

Fig. 6 is a block diagram showing a terminal acting as a data receiving participant and a network node acting as a data sending participant, according to yet another embodiment.

Detailed description

To describe it briefly, a data receiving participant that transmits explicit feedback information to a data sending participant can convey more implicit feedback information by transmitting the explicit feedback information in a selected feedback information resource, out of a plurality of feedback resources. return information available. The available feedback information resources can be different resource blocks that are allocated to carry feedback information. Each available return information resource is assigned a return information code that comprises at least one bit of

ES 2 587 705 T3 information, such that the actual selection of the return information resource involves said return information code. The information bit or bits in the return information code thus indicates or indicates in a predetermined manner whether or not data has been received successfully, ie ACK or NACK.

For example, if 2 return information resources are available to be selected in a subframe allocated for transmission, called a TX subframe, each return information resource may involve one bit of information: for example 1 indicates ACK or 0 indicates NACK, such that a received subframe with data can be communicated as implicit feedback by selecting a feedback resource. In another example, 4 return information resources are available to be selected in a TX subframe and each return information resource can involve a pair of information bits: 0/0, 1/0, 0/1 and 1 / 1, respectively, such that two received subframes can be communicated as implicit feedback by selecting the feedback resource, and so on.

The present invention can be used to allow multiple feedback reports in a single subframe transmitted from a data receiving participant that has received data in multiple subframes from a data sending participant, without losing single carrier properties. As explained above, it may be necessary to transmit several feedback reports in a single subframe when using an asymmetric TDD transmission scheme and / or multiple streams / sessions in a single subframe.

One skilled in the art will understand that the following embodiments can also be applied in an FDD transmission scheme if the number of required feedback information reports is greater than the number of bits in each available feedback information resource. The data sending participant can be a base station and the data receiving participant can be a terminal, or vice versa.

The use of resource blocks as feedback resources will now be explained in more detail. A typical pattern of arrangement of RB resource blocks in a subframe is shown in Figure 2. In this example, a 1 ms subframe comprises 12 pairs of resource blocks. Information can thus be broadly transmitted in the different resource blocks on the respective subcarriers. In the middle M of the subframe, a data block DB in a resource block RBi can be mapped onto a different resource block RBj according to a frequency hopping scheme to obtain frequency diversity, thereby forming a pair RBi / RBj resource blocks. In other words, the transmission of the data block is shifted to another resource block on another frequency within the full frequency carrier. In this example, the dBi data block on RB1 is moved to M on RB12, the DB2 data block on RB2 is moved to RB11, and so on.

In LTE, feedback reports, or ACK / NACKs, are typically transmitted from a terminal on the physical uplink control channel PUCCH (Physical Uplink Control CHannel) that is assigned to one of the blocks. outermost resources on the frequency carrier, unless user data can be transmitted on other subcarriers time multiplexed with user data. In Figure 2, four resource blocks RB1, RB2, RB11 and RBl2 have been allocated for reporting back or ACK / NACK information from different terminals. Within each resource block, each respective terminal can transmit a return information report in the form of CDM. Thus, multiple orthogonal feedback reports can be transmitted by different terminals within each resource block. In other words, multiple resources are available for reporting feedback within each subframe. In this description, each of these resources is called a feedback resource. Within each feedback information resource, a terminal can transmit either a single bit of information using BPSK modulation or two bits of information using QPSK modulation.

A terminal that receives data packets in multiple downlink subframes may need to transmit multiple feedback reports in a single uplink subframe. However, since the single carrier properties must be maintained in uplink transmissions according to LTE, the terminal cannot transmit, for example, both in resource block RB1 and RB3 and still transmit a single signal. of carrier, since these subcarriers are not in contiguous spectrum, that is to say, in adjacent frequencies.

In addition, due to the properties of the CDM component of the return information report, it is also not possible to transmit in the RB1 and RB2 resource blocks, and still maintain the single carrier properties, since the information transmitted from the same terminal in the RB1 and RB2 are uncorrelated, which implies that the single carrier properties have been lost in this case as well. Rather, a terminal is capable of carrying additional implicit feedback information by transmitting on a selected implicit feedback resource, when there are a plurality of feedback information resources available to the terminal.

FIG. 3 schematically shows how feedback information from a receiving data participant 300 can be conveyed to a sending data participant 302 by means of selecting the feedback resource, in accordance with an example embodiment. The data sending participant 302 sends four data sets to the receiving data participant 300, indicated as "Data 1", "Data 2", "Data 3" and "Data 4", which requires

ES 2 587 705 T3 each a report of the individual return information. Data sets 1-4 may be packets transmitted in the subframes as described above, although the present invention is not especially limited thereto. Throughout this description, the term "data set" is used to generally represent any portion of data transmitted in a subframe or otherwise.

It is assumed that the receiving data participant 300 has previously obtained information about what transmission resources are available in a particular TX subframe for reporting the feedback, in this case four different feedback resources 304, denoted as FR-i, FR2, FR3 and FR4. This information is typically obtained in connection with the selection or transfer of cells. Feedback resources 304 may be resource blocks in a TX subframe allocated in the manner described above, although the present invention is not limited to any particular type of feedback resources.

Each return information resource 304 has been assigned a specific return information code known to the two participants, in which each code contains two bits of information. This code assignment can be communicated in an assignment message, or it could be preconfigured in the equipment used. In this example, FR1 is assigned to code (0, 0), FR2 is assigned to code (1, 0), FR3 is assigned to code (0, 1) and FR4 is assigned to code (1, 1). These codes can be used to convey implicit return information in the received data in combination with explicit return information, that is, as a combined key determined by the bits of the modulation symbol and the additional bits of the resource selection.

It is further assumed in this example that data receiving participant 300 can send feedback for all 4 received data sets in just one subframe using QPSK modulation, i.e. 2 bits of information can be used to carry explicit feedback information in that subplot. Therefore, 2 bits are available to carry explicit feedback, but 4 feedback reports are needed.

In the present solution, two other bits of implicit return information can be transported by transmitting the explicit return information in one of the 4 available return information resources 304, in such a way that the mere selection of the return information resource indicates two additional feedback reports, that is, the two bits in the respective feedback code. Data receiving participant 300 thus checks each received data set 1-4 for errors and determines whether an ACK or NACK message should be returned to the data sending participant for each data set 1-4. In the example shown in figure 3, data sets 1, 2 and 3 were received correctly but data set 4 was received incorrectly. The feedback reports required for data sets 1-4 can thus be encoded as a key "1, 1, 1, 0", where 1 = ACK and 0 = NACK. Therefore, data receiving participant 300 sends 2 explicit feedback reports "1, 1" for data sets 1 and 2 on FR2 which then represents implicit feedback reports "1, 0" for data sets. data 3 and 4, hence "1, 1, 1, 0".

The coded feedback reports can be carried by different terminals in a subframe according to Table 1 shown below:

Return information resource: Terminal: Associated code: Selected resource: Selected code:

<td>FRi</td><td>fr₃</td><td>fr₃</td><td>FR4</td><td>FR_S</td><td>FR «</td><td>fr₇</td><td>FR_to</td>

<td>TO</td><td>TO</td><td>TO</td><td>TO</td><td>B</td><td>B</td><td>B</td><td>B</td>

<td> 0</td><td> 1</td><td> 2</td><td> 3</td><td> 0</td><td> 1</td><td> 2</td><td> 3</td>

<td></td><td>fr₂</td><td></td><td></td><td></td><td></td><td></td><td>FR_and</td>

<td></td><td> 1</td><td></td><td></td><td></td><td></td><td></td><td> 3</td>

Table 1

In Table 1, eight different feedback resources 1-8 in a given subframe are assigned to two terminals A and B, where resources 1-4 are assigned to the terminal and resources 5-8 are assigned to the terminal. B. Furthermore, the return information resources FR1 and FR5 are assigned to a return information code 0, FR2 and FRe are assigned to a return information code 1, FR3 and FR7 are assigned to a return information code 2, and FR4 and FRs are assigned a feedback code 3. It should be noted that the present invention generally allows any number of feedback information resources assigned for any number of terminals.

Therefore, terminals A, B can transmit explicit return information in a selected return information resource to carry a 0-3 return information code, such as return information.

ES 2 587 705 T3 additional implicit data sender participant. If QPSK modulation is used, two bits of explicit feedback information xo and xi are sent on the selected feedback source. The QPSK modulated symbol will then represent two bits of feedback information: bit 0 and bit 1, and the selection of the feedback resource will represent another two bits of feedback information: bit 2 and bit 3. Each of the 0-3 bits can be 0 OR 1, as shown in Table 2 below:

Return information code 0:

Return information code 1:

Return information code 2:

Return information code 3:

<td>Bit 3</td><td>Bit 2</td><td>Bit 1</td><td>Bit O</td>

<td> 0</td><td> 0</td><td>Xi</td><td>Xo</td>

<td> 0</td><td> 1</td><td>X1</td><td>Xo</td>

<td> 1</td><td> 0</td><td>Xi</td><td>Xo</td>

<td> 1</td><td> 1</td><td>Xi</td><td>Xo</td>

Table 2

Using Tables 1 and 2 for the example in Figure 3, data receiving party 300 transmits a QPSK modulated symbol with xo = 1 and xi = 1 as explicit feedback to indicate successful receipt of data sets. 1 and 2, in the selected return information resource FR2 that represents return information code 1 as implicit return information to indicate the successful reception of data set 3 and the unsuccessful reception of data set 4. Therefore, the 4 feedback reports 4 "1, 1, 1, 0", that is, bits 0-3, are conveyed to the data sending participant as a combined key.

The skilled person will readily understand that the above embodiments can be modified in a number of different ways, for example, using different resource assignments, modulation methods, and feedback encoding schemes, without limitation to the present invention. In the previous examples, the number of return information resources corresponds directly to the number of additional information bits for the implicit return information. However, it should be noted that this idea can be generalized by using "M order" symbols for the case where the data receiving participant, eg the terminal, can choose from M assigned feedback resources. For example, with 3 feedback sources allocated and transmitting a QPSK modulated symbol on the selected resource, the data receiving party can point to up to 3x4 = 12 combined feedback keys or different bit patterns, shown in the table 3 that follows.

<td>Keys to return information</td><td>Bit 3</td><td>Bit 2</td><td>Bit 1</td><td>Bit 0</td>

<td> 0</td><td>OR</td><td> 0</td><td> 0</td><td> 0</td>

<td> 1</td><td> 0</td><td> 1</td><td>OR</td><td> 1</td>

<td> 2</td><td> 1</td><td> 0</td><td> 1</td><td> 0</td>

<td> 3</td><td> 0</td><td> 0</td><td> 1</td><td> 1</td>

<td> 4</td><td> 0</td><td> 1</td><td> 0</td><td> 0</td>

<td> 5</td><td> 1</td><td> 0</td><td>OR</td><td> 1</td>

<td> 6</td><td> 0</td><td> 0</td><td> 1</td><td>OR</td>

<td> 7</td><td> 0</td><td> 1</td><td> 1</td><td> 1</td>

<td> 8</td><td> 1</td><td>Q</td><td> 0</td><td> 0</td>

<td> 9</td><td>to</td><td> 0</td><td> 0</td><td> 1</td>

<td> 10</td><td>to</td><td> 1</td><td> 1</td><td> 0</td>

<td> 11</td><td> 1</td><td> 0</td><td> 1</td><td> 1</td>

Table 3

ES 2 587 705 T3

Using the present solution, the number of feedback information resources that must be allocated to each terminal will increase exponentially with the number of feedback reports, ie bits, that are needed. When many feedback reports are required, that is, bits required. When many feedback reports are needed, the utilization of the feedback facility will be correspondingly low. For example, if a 5-bit combined key is needed to report the return information, and modulation QPSK is used, it is necessary to carry an additional 3 bits, selecting a return information resource. Therefore, it is then necessary to allocate 8 feedback resources to the terminal to cover all 3-bit combinations, resulting in maximum resource utilization to maintain single-carrier properties.

On the network side, the base station to which the terminal is connected must be able to detect on which return information resource the terminal transmits the return information. For example, this could be done using energy detection criteria, that is, detecting the power of a received signal and determining if the power of the received signal is high enough to distinguish it from noise and / or interference. . Alternatively or additionally, the used feedback information resource can be detected by comparing the received signal power on all assigned feedback information resources and selecting the feedback information resource that has the signal power and / or the SINR ( Signal to Noise Ratio - Signal - Noise Ratio, in English) higher. These two approaches could also be combined to increase the probability of a correct detection of the feedback resource.

FIG. 4 is a flowchart illustrating a method of transporting feedback reports for received data sets, from a data receiving participant to a data sending participant, as performed by a data receiving participant. The data sending participant can be a base station and the data receiving participant can be a terminal, or vice versa. It is assumed that the single carrier properties are necessary when transmitting feedback reports, and that the number of feedback reports required is greater than the number of bits available to report the feedback by carrier modulation. This is often the case in the TDD mode of LTE when it is necessary for a terminal to send multiple feedback reports in a single subframe on the uplink for data received on the downlink.

In a first step 400, information is obtained in which the feedback information resources are assigned for the transmission of feedback information reports from the data receiving participant, thereby allowing differentiated feedback information reports by selecting the feedback resource. return information. The return information resources obtained are assigned to different return information codes that can be used as return information reports, as explained above.

It is now assumed that the data receiving participant receives several data sets from the data sending participant, which need feedback information reports. In a next step 402, the explicit and implicit feedback information is determined for the data received from the sending data participant. At this stage, the received data is checked for errors and it is determined whether an ACK message or a NACK message should be sent for each data set. Depending on how many bits are available to the explicit participant, ie by carrier modulation, it is determined that one or more explicit feedback reports are sent by modulation. The remaining feedback reports are determined to be sent implicitly by selecting the feedback resource.

In another step 404, a return information resource is selected from among the available return information resources received in step 400, which is assigned to a return information code that corresponds to the implicit return information of the step 402. Finally, the explicit return information is sent in the selected return information resource to indicate the implicit return information, in a step 406. Therefore, both the explicit return information and the implicit return information are transported to the data-sending participant, without losing the unique bearer properties.

Fig. 5 is a flowchart showing a method of receiving feedback reports from a terminal for transmitted data sets, as performed by a network node such as a base station transmitting the data sets. In this case, the network node is thus a data sending participant and the terminal is a data receiving participant. Again, it is assumed that single carrier properties are required when the terminal transmits the feedback reports, and that the number of feedback reports required is greater than the number of bits available to report the feedback via carrier modulation.

In a first step 500, a plurality of feedback information resources are assigned to the terminal for selection when feedback information reports are transmitted to the network node, thereby allowing differentiated feedback information reports by selecting information reports. return. The received return information resources are assigned to different return information codes which the terminal can thus use as return information reports.

ES 2 587 705 T3

In a next step 502, the terminal is notified about which feedback information resources are available to be selected, which were assigned in the previous step 500. The available feedback information resources can be communicated in a suitable control message, for example, during a cell selection or handover procedure when the terminal connects to the base station. This control message may be the message generally known as "RCC CONNECTION ESTABLISHMENT" or a suitable broadcast message on the broadcast control channel BCCH (Broadcast Control Channel). Alternatively, the allocation of feedback resources can be given by the downlink scheduling allocation for the terminal, or by which resources the data is transmitted from the network node, for example, the base station, which will be described in more detail below.

It is now assumed that the network node sends multiple data sets to the terminal, which requires reporting feedback from the terminal. In another step 504, one or more explicit feedback information reports are received from the terminal on one of the feedback information resources assigned in step 500, which has been selected by the terminal to carry more implicit feedback information.

Finally, the implicit return information is detected on the basis of the return information code corresponding to the received return information resource, in a step 506. Therefore, both the explicit return information and the implicit return information have been received. from the terminal, without losing the single carrier properties when the return information is transmitted from the terminal.

FIG. 6 is a block diagram schematically showing a terminal 600 acting as a data receiving participant and a network node 602 acting as a sending data participant, eg, a base station, when terminal 600 sends reports of data. uplink feedback for data received from network node 602 on the downlink in a wireless connection. Again, it is assumed that terminal 600 is required to transmit the feedback reports with single carrier properties.

Terminal 600 comprises a receiving unit 600a adapted to receive "FR info" allocation information from network node 602 about a plurality of available feedback sources for transmitting feedback information reports. The feedback information resources are associated with different feedback information codes that are known to the terminal. The terminal may have obtained the knowledge of which particular feedback code each feedback resource is associated with in a suitable control message from network node 602, for example, during a handoff or cell selection procedure. , or it may have been preconfigured in the terminal.

The terminal 600 further comprises a selection unit 600b adapted to select a return information resource from among the received return information resources for transmission, to convey implicit return information depending on the result of the received data, that is, to implicitly indicate the correct or incorrect reception of the same. The selected feedback information resource has thus been assigned a feedback code corresponding to one or more feedback reports relevant to said received data. Terminal 600 also comprises a transmission unit 600c adapted to send feedback information on the selected feedback information resource to the data-sending participant, thereby implicating the feedback information code assigned to the used feedback information resource.

Receiving unit 600a, selecting unit 600b, and transmitting unit 600c may generally be adapted to perform corresponding functions described in connection with Figures 3-5 above.

The network node 602 comprises a transmission unit 602a adapted to send information "FR info" to the terminal 600 about a plurality of return information resources allocated for the transmission of return information, the return information resources being assigned to and associated with different return information codes.

The network node 602 further comprises a reception unit 602b adapted to receive feedback information about the data transmitted from the terminal in the feedback information resource that has been selected by the terminal to carry implicit feedback information. The network node 602 also comprises a detection unit 602c adapted to detect one or more return information resources on the basis of the return information code assigned to the selected return information resource.

Transmission unit 602a, reception unit 602b, and detection unit 602c may generally be adapted to perform corresponding functions described in connection with Figures 3-5 above. It should be noted that Figure 6 merely shows the different functional units 600a-c and 602a-c in a logical sense, while the skilled person is free to implement these functions in practice using any suitable means of software and hardware.

How the feedback resources for a terminal can be allocated in accordance with the above will now be described in more detail. When using FDD mode in LTE, each downlink data packet directed to a specific terminal will identify which return information resource on the link

ES 2 587 705 T3 upstream is available for a feedback report. In order to map a downlink data packet to a corresponding uplink return information resource, three methods can be used: 1) the return information resource is given by which downlink scheduling allocation channel contains the control information related to the downlink data packet, 2) the uplink return information resource is given by in which resources the data packet itself is transmitted, DL-SCH in LTE, and 3) the uplink return information resource is explicitly signaled by the base station.

These alternatives can also be applied using TDD mode. Each data packet sent on the downlink could be coupled to a specific given uplink return information resource, regardless of which terminal the DL data packet is directed to. This means that each terminal will receive an allocated feedback resource per received data packet. If only one data packet is received, a corresponding return information resource will be allocated. If two data packets are received, two corresponding return information resources will be allocated. If four DL data packets are received, four corresponding return information resources will be allocated, and so on.

Table 4 provides an example UL feedback resource mapping with two

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Table 4

In this example, terminal A is scheduled to receive data in both downlink subframe 1 and subframe 2, and therefore the UL 3 and 5 feedback resources, underlined, are assigned to terminal A The feedback information report from that terminal will then include the selection of one of the feedback information resources 3 and 5, depending on which feedback status it needs to report.

Using this approach, both the base station and the terminal will know which feedback resources have been assigned to the terminal for selection. The base station naturally knows what scheduling decisions it has made for the terminal, while the terminal knows what downlink resources it has received.

Although the above description generally refers to the case where a single feedback reporting bit is needed for each received downlink data packet, and where multiple received data packets are communicated in a single subframe of uplink, the present invention can be generally applied to any case where more than two bits of feedback information are needed. For example, this solution could also be used to report the quality of the so-called "soft bits" received, the redundancy version of which must be retransmitted, or if it is mainly some specific part of the data packet that was received erroneously. The term "return information" is used in this description to represent in a general way any type of information related to errors or quality of the data received and / or related to the necessary retransmission.

Although the above description focuses on the TDD mode of LTE, it should also be noted that it could also be used for the half-duplex FDD mode, ie when the terminal cannot transmit and receive at the same time.

An advantage of this invention is that feedback reports, such as ACK / NACK, for multiple received data packets can be carried in a single subframe, while still maintaining the required single carrier properties of the transmitted signals. This will also allow for a higher peak rate in downlink transmissions. If the reporting of the return information for basically only one received data packet can be transmitted for each available uplink subframe as in previously known solutions, it is not possible to schedule a single terminal in all downlink subframes for connections very asymmetric, for example 4 DL: 1 UL, thereby limiting the peak rate for downlink data. Using the present invention, it is possible to schedule a single terminal in all the downlink subframes of a radio frame, thereby achieving a higher downlink peak rate.

ES 2 587 705 T3

Furthermore, any unnecessary retransmission of correctly received data packets can be avoided, since each received data packet is communicated individually, further increasing the peak rate and downlink capacity.

The present solution could also be defined as a method in a user equipment (UE - User Equipment, in English) that operates in a communication system that uses a protocol to correct the block errors that occur in the air interface, the Said protocol involves the transmission of reports of uplink return information from the UE that receives data to the transmitter of said data, comprising the steps of

- receiving from the system more than one resource on which the return information reports can be transmitted, in which each resource is assigned a binary code; Y

- choosing from among the received resources a resource to transmit on it, in which the specific binary code that is assigned to the selected resource is used as return information.

The present solution could also be defined as a user equipment capable of operating in a communication system that uses a protocol to correct block errors that occur at the air interface, said protocol involves the transmission of return information reports. uplink, comprising means for carrying out the above method.

The present solution could also be defined as a user equipment capable of operating in a communication system that uses a protocol to correct block errors that occur at the air interface, said protocol involves the transmission of return information reports. of uplink from the UE that receives data to the transmitter of said data, which comprises the steps of

- providing each UE with more than one resource on which the feedback reports can be transmitted, in which each resource is assigned a binary code;

- allow the UE to choose from among the received resources a resource to transmit on it, in which the specific binary code to which the selected resource is assigned is used as return information, and

- detect the return information based on the detection of the received resource blocks on which the UE transmits.

The present solution could also be defined as a user equipment capable of operating in a communication system that uses a protocol to correct block errors that occur at the air interface, said protocol involves the transmission of return information reports. of the uplink from the UE receiving data to the transmitter of said data, comprising means for implementing the above method.

Although the invention has been described with reference to specific exemplary embodiments, the description is only intended, in general, to show the concept of the invention and should not be taken as limiting the scope of the invention. Although the concepts of 3GPP, LTE, HSPA, MAC, radio frames, subframes, HARQ soft combination and ACK / nAcK messages have been used when describing the above embodiments, any other suitable standard, protocol and similar mechanism can basically be used to achieve the functions described in this specification. In particular, the embodiments described above could also be applied in TDD, as well as half-duplex FDD transmission schemes. The present invention is defined by the following independent claims.