Feedback and CSI requests

Abstract

There is provided a receiver device arranged to receive, from a transmitter device, a data packet comprising a control portion and a payload portion, the control portion comprising a feedback request indicator. The receiver device is arranged to detect a feedback request indicator; attempting to decode a payload portion of the data packet; transmitting an acknowledgement to a transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested; and if the feedback request indicator indicates that an acknowledgement for the data packet is not requested, processing the data packet without transmitting the acknowledgement.

Description

Technical Field

[0001] The present invention relates to feedback in communication systems. Background Art

[0002] A common problem in wireless communications between two devices, such as between a base station and a user equipment, is detecting and correcting errors in the transmitted data, for example due to interference or fading in the physical communication channel between the two devices.

[0003] Some radio protocols utilize hybrid automatic repeat request (HARQ) technology to detect and correct errors, where the receiving device provides feedback to the transmitting device to indicate whether a data packet has been (or can be) successfully decoded. If the decoding is or will be successful, the HARQ feedback includes a positive acknowledgement (ACK), and if the decoding fails or will fail, the HARQ feedback includes a negative acknowledgement (NACK). The negative acknowledgement triggers the transmitter device to retransmit the data. In the NB-IoT communication protocol, the evolved Node B (eNB) can specify specific OFDM time and frequency resources used by the user equipment (UE) to provide HARQ feedback.

[0004] Using acknowledgment signals such as HARQ feedback can help ensure reliable communication between two devices. However, having to wait for acknowledgment can stall the transmission of further packets. This problem is particularly severe when the two communicating devices are far apart due to increased transmission latency. However, the effects of noise and interference can be particularly significant over long distances, so simply disabling HARQ feedback may require very conservative operation at low data rates. Some devices can handle multiple HARQ processes in parallel, which can alleviate stalls in some cases, but requires additional resources.

[0005] An improved approach would be needed. Summary of the invention

[0006] According to a first aspect of the present invention, there is provided a receiver device, which is configured to: receiving, from a transmitter device, a data packet including a control portion and a payload portion, the control portion including a feedback request indicator; Detection feedback request indicator; Try to decode the payload portion of the packet; If the feedback request indicator indicates that an acknowledgement is requested for the data packet, transmitting an acknowledgement to a transmitter device; and If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, then the data packet is processed without transmitting an acknowledgement.

[0007] According to a second aspect of the present invention, there is provided a communication system, comprising: a transmitter device; and Receiver device; Wherein, the transmitter device is configured as: transmitting a data packet to a receiver device, the data packet comprising a control portion and a payload portion, the control portion comprising a feedback request indicator; and Wherein the receiver device is configured as follows: receiving the data packet from a transmitter device; Detection feedback request indicator; Try to decode the payload portion of the packet; If the feedback request indicator indicates that an acknowledgement is requested for the data packet, transmitting an acknowledgement to a transmitter device; and If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, then the data packet is processed without transmitting an acknowledgement.

[0008] According to a third aspect of the present invention, there is provided a method for operating a communication system, the method comprising: The transmitter device transmits a data packet to the receiver device, the data packet comprising a control portion and a payload portion, the control portion comprising a feedback request indicator; and Receiver Device: receiving the data packet; Detection feedback request indicator; Try to decode the payload portion of the packet; If the feedback request indicator indicates that an acknowledgement is requested for the data packet, transmitting an acknowledgement to a transmitter device; and If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, the data packet is processed without transmitting an acknowledgement to a transmitter device.

[0009] Therefore, those skilled in the art will recognize that the feedback request indicator allows feedback to be dynamically requested at the packet level, thereby providing greater flexibility to the communication system. For example, a transmitter device can use the feedback request indicator to request feedback when transmitting critical packets (such as resource control signaling) and disable feedback when transmitting non-critical packets, thereby alleviating stalls while still ensuring that critical packets are correctly received. In many communication systems, most traffic can be classified as non-critical, allowing for significant performance improvements.

[0010] The receiver device may attempt to decode the entire payload portion of the data packet before transmitting an acknowledgement. Alternatively, the receiver device may attempt to decode only a portion of the payload portion before acknowledging. In some embodiments, attempting to decode the payload portion may include first evaluating one or more error detection portions (e.g., one or more parity bits or check bits) of the data packet. If the error detection portion indicates that successful decoding is possible, the receiver device may proceed with a full decoding attempt. Conversely, if the error detection portion indicates that successful decoding is not possible, the receiver device may skip the full decoding attempt.

[0011] The receiver device may be arranged to transmit an acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement is requested for the data packet and the attempt to decode the payload portion is or will be successful (i.e. if one or more error detection partial or full decoding attempts of the data packet indicate that the data packet has been successfully received). In other words, the acknowledgement may be a positive acknowledgement. In this case, the transmitter device may interpret the absence of an acknowledgement when an acknowledgement is requested as a negative acknowledgement, indicating that part or all of the data packet was not successfully received.

[0012] The receiver device may be arranged to transmit an acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested and the attempt to decode the payload portion has failed or will fail (i.e. if one or more error detection partial or full decoding attempts of the data packet indicate that the data packet has not been successfully received). In other words, the acknowledgement may be a negative acknowledgement. The transmitter device may be arranged to retransmit the data packet in response to a negative acknowledgement.

[0013] The receiver device may be arranged to send positive and negative acknowledgements as required. In one set of embodiments, the receiver device is arranged to: transmit a positive acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested and the decoding attempt succeeded or will succeed; and transmit a negative acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested and the decoding attempt failed or will fail.

[0014] The acknowledgement transmitted by the receiver device may include a single acknowledgement bit. For example, an acknowledgement bit having a first state (eg, "1") may indicate a positive acknowledgement, while an acknowledgement bit having a second state (eg, "0") may indicate a negative acknowledgement.

[0015] The acknowledgement may include a hybrid automatic repeat request (HARQ) acknowledgement. A positive acknowledgement may include a HARQ ACK and a negative acknowledgement may include a HARQ NACK.

[0016] In one set of embodiments, the receiver apparatus (and the transmitter apparatus) are arranged to communicate using orthogonal frequency division multiplexing (OFDM). The data packets may comprise OFDM data packets consisting of symbols spanning a plurality of time slots and frequency subcarriers. In one set of embodiments, the receiver apparatus is arranged to operate in accordance with a 3GPP Long Term Evolution (LTE) communications protocol, such as a Narrowband Internet of Things (NB-IoT) protocol.

[0017] The transmitter device and the receiver device may be arranged to perform bidirectional communication, i.e. they may each comprise a transceiver device. In other words, in one set of embodiments, the transmitter device comprises a first transceiver device and the receiver device comprises a second transceiver device. In such embodiments, the first transceiver device may also be arranged to receive and acknowledge data packets from the second transceiver device in a similar manner.

[0018] The transmitter device may include a base station, such as an LTE evolved Node B (eNB), such as an NB-IoT eNB. The receiver device may include an end-user device, such as an LTE user equipment (UE), such as an NB-IoT UE. The data packet transmitted by the receiver device may include a downlink data packet. The acknowledgement may be transmitted in an uplink data packet. Conversely, the receiver device may include a base station, such as an LTE evolved Node B (eNB), and the transmitter device may include an end-user device, such as an LTE user equipment (UE).

[0019] The transmitter may be arranged to wait for an acknowledgement of a given data packet (if an acknowledgement has been requested) before sending further data packets (i.e. in case a data packet needs to be retransmitted). In some embodiments, the communication system may be arranged to support multiple parallel acknowledgement processes, i.e. wherein acknowledgements of multiple data packets may be performed simultaneously. However, the applicant has recognised that supporting multiple parallel acknowledgement processes may require additional hardware resources and increase energy usage. Therefore, in one set of embodiments, the receiver device and / or the transmitter device is arranged to support only a limited number of parallel acknowledgement processes. For example, the receiver device and / or the transmitter device may be arranged to support only one acknowledgement process at a time, or to support only two parallel acknowledgement processes.

[0020] In one set of embodiments, the communication system is a non-terrestrial communication system (i.e., forming part of a non-terrestrial network (NTN)). The transmitter means may be provided by a satellite, for example in low earth orbit. The receiver means may be a ground device (i.e., located on or near the surface of the earth) arranged to receive data packets from the transmitter means provided by the satellite. For example, the receiver means may be a NTN IoT device. The advantages of the invention may be particularly evident in non-terrestrial communication systems where the transmission distance (and therefore the propagation delay) may be large and therefore stall problems are often most common (e.g., when the system runs out of confirmation procedures to use).

[0021] In one set of embodiments, the control portion comprises an LTE physical downlink control channel (PDCCH), such as a NB-IoT physical downlink control channel (NPDCCH). The feedback request indicator may comprise an ACK / NACK field of DCI format N1. Traditionally, the ACK / NACK resource field only indicates which resources are used for HARQ feedback, but applicants have recognized that it can be beneficially reused to provide dynamic feedback operation.

[0022] An acknowledgement (positive or negative) may be sent as part of a subsequent data packet sent from the receiver device to the transmitter device. For example, the acknowledgement may be sent as part of uplink control information (UCI) in an LTE physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH), such as a NB-IoT physical uplink control channel (NPUCCH) or physical uplink shared channel (NPUSCH). In one set of embodiments, the acknowledgement is sent using NB-IoT physical uplink shared channel (NPUSCH) format 2.

[0023] Acknowledgements (positive or negative) may be sent using fixed (i.e., predetermined) time and frequency resources (e.g., at predetermined time and frequency offsets in an OFDM data packet structure). However, in one set of embodiments, the feedback request indicator specifies the time and / or frequency resources used to transmit the acknowledgement. For example, the feedback request indicator may indicate the frequency and / or time offset in the OFDM data packet structure at which the acknowledgement should be transmitted. The feedback request indicator may identify the subcarrier and / or time slot at which the acknowledgement (e.g., an uplink control signal carrying an ACK / NACK message) is to be transmitted. Allowing dynamic allocation of time and / or frequency resources for acknowledgements may improve the flexibility and performance of the communication system. In some embodiments, the feedback request indicator may be configured to specify only time and / or frequency resources, while the receiver device is configured to interpret the range of time and / or frequency resources (e.g., a single time and / or frequency resource) specified by the feedback request indicator as an indication that feedback is not requested. This may facilitate the application of the present invention in existing communication protocols, because existing control signals (e.g., ACK / NACK resource fields) may be reused for additional acknowledgement control signaling without requiring significant transmitter-side changes.

[0024] As described above, enabling the transmitter device to dynamically request data packet acknowledgments provides greater flexibility and can alleviate communication stalls caused by long round-trip acknowledgment delays. However, since not every data packet may be acknowledged, the communication system may be more susceptible to data loss due to poor communication channel conditions. In some embodiments, feedback may be requested for only a small fraction of data packets (e.g., less than 10% of the data packets). Therefore, in one set of embodiments, the receiver device is configured to: determining channel quality information about a communication channel between the transmitter device and the receiver device; and If the feedback request indicator indicates that channel quality information is requested, the channel quality information is transmitted to a transmitter device.

[0025] Thus, the transmitter device is able to dynamically request and receive updated information about channel conditions. This may allow the transmitter device to identify when channel conditions are deteriorating so that it can take appropriate action (e.g., requesting packet feedback more frequently). The transmitter device may be configured to implement additional error compensation in response to channel quality information transmitted from the receiver device, such as by reducing the code rate of the packet. For example, the transmitter device may be configured to request feedback for the next packet using a feedback request indicator if the channel quality information indicates that channel conditions have deteriorated or are deteriorating. For example, the transmitter device (or an associated network system) may classify the receiver as mobile based on the channel quality information and previous communications.

[0026] The receiver device may be arranged to determine the channel quality information by measuring the signal-to-noise ratio (SNR) of a received signal (eg a common downlink signal such as a narrowband reference signal (NRS) or a synchronization signal).

[0027] The channel quality information may include various different channel quality indications. The channel quality information may include an absolute indication or measurement of the channel quality, for example, a value indicating the channel quality on a numerical scale. For example, the channel quality information may include the SNR of the received signal. Additionally or alternatively, the channel quality information may include a relative or differential indication or measurement of the channel quality, for example, relative to a previously reported channel quality or channel quality trend (e.g., indicating whether the channel quality is improving or deteriorating) about the channel quality. The channel quality information may, for example, identify whether the SNR of the received signal is increasing or decreasing, and may optionally indicate the magnitude of such increase or decrease. The channel quality information may include an LTE channel state information (CSI) report.

[0028] The channel quality information may consist of a single bit. For example, a bit with a first state (e.g., "1") may indicate "good" or "improved" channel quality, while a bit with a second state (e.g., "0") may indicate "bad" or "degraded" channel quality.

[0029] Alternatively, in one set of embodiments, the channel quality information includes a plurality of bits, e.g., to provide more details about the quality of the communication channel. The channel quality information may include a plurality of bits encoded (e.g., encoded over a sequence of bits or symbols sent to a transmitter) using orthogonal cover coding (OCC). For example, two bits may be encoded over a sequence of bits or symbols carrying uplink control information (e.g., uplink control channel symbols) using OCC.

[0030] As with the acknowledgement, the channel quality information may be sent as part of a subsequent data packet sent from the receiver device to the transmitter device. This may be sent using fixed (i.e., predetermined) time and frequency resources (e.g., at predetermined time and frequency offsets in an OFDM data packet structure). However, in one set of embodiments, the feedback request indicator specifies the time and / or frequency resources at which the channel quality information is to be transmitted. For example, the feedback request indicator may indicate a frequency and / or time offset in an OFDM data packet structure at which the channel quality information should be sent. The feedback request indicator may identify the subcarriers and / or time slots at which the channel quality information (e.g., an uplink control signal carrying the channel quality information) is to be transmitted. Allowing dynamic allocation of time and / or frequency resources for the channel quality information may improve the flexibility and performance of the communication system.

[0031] The receiver device may be configured to transmit the channel quality information together with the acknowledgement. For example, the feedback request indicator may indicate that channel quality information and an acknowledgement are requested for the data packet. The feedback request indicator may indicate that one, both, or neither of the channel quality information and the acknowledgement are requested. In other words, for certain data packets, the transmitter device may request one of: no feedback (no acknowledgement and no channel quality information); acknowledgement but no channel quality information; channel quality information but no acknowledgement; or acknowledgement and channel quality information (i.e., full feedback).

[0032] The receiver device may be configured to combine the channel quality information and the confirmation, for example to improve communication efficiency. For example, the receiver device may be configured to encode the channel quality information and the confirmation into a single transmission. In one set of embodiments, the receiver device is configured to encode the channel quality information using the time and / or frequency resources used to transmit the confirmation (for example, the channel quality information is encoded using at least two time and / or frequency resources that can be used to transmit the confirmation). Therefore, the transmitter may be configured to decode the channel quality information by detecting which time and / or frequency resource the confirmation has been transmitted on (for example, which subcarrier has been used and / or in which time slot the confirmation has been transmitted). For example, the receiver device may be configured to transmit the confirmation using one or more specific time and / or frequency resources that identify the channel quality information. In other words, the receiver device may be configured to select the time and / or frequency resources for the confirmation based on the channel quality. The transmitter device may be configured to perform blind decoding in a set of time and / or frequency resources (for example, a set of transmitter devices specified using a feedback request indicator) to detect the confirmation and / or to decode the channel quality information.

[0033] In one set of embodiments, the receiver device is configured to transmit an acknowledgement using a first set of time and / or frequency resources to indicate a first channel quality indication, and to transmit the acknowledgement using a second set of time and / or frequency resources to indicate a second channel quality indication. For example, the feedback request indicator may indicate that an acknowledgement and channel quality information are requested, and may identify a pair of time and / or frequency resources used to transmit the acknowledgement and channel quality information. The receiver may then be configured to transmit an acknowledgement using a first resource in a pair of resources to indicate a first channel quality (e.g., to indicate that the channel quality is improving), and to transmit an acknowledgement using a second resource in a pair of resources to indicate a second channel quality (e.g., to indicate that the channel quality is deteriorating). In other words, the receiver device may be configured to signal the channel quality information to the transmitter device by sending an acknowledgement (e.g., HARQ ACK / NACK feedback) using specific resources.

[0034] Features of any aspect or embodiment described herein may be applied to any other aspect or embodiment described herein where appropriate.When different embodiments are mentioned, it should be understood that these embodiments are not necessarily different, but may overlap. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a radio communication system according to an embodiment of the present invention; Figure 2 shows a downlink data packet used in an embodiment of the present invention; Figure 3An uplink data packet used in an embodiment of the present invention is shown; Figure 4 The information indicated by the feedback request indicator field in one embodiment of the present invention is shown; and Figure 5 FIG. 4 shows information indicated by a feedback request indicator field according to another embodiment of the present invention. DETAILED DESCRIPTION

[0036] Figure 1 A radio communication system 100 operating according to the NB-IoT communication protocol is shown. The system 100 includes an evolved Node B (eNB) 102 and a user equipment (UE) 104. In this example, the communication system 100 forms part of a non-terrestrial network (NTN), where the eNB 102 is provided by a satellite (e.g., a low earth orbit satellite) and the UE 104 is a terrestrial NTN IoT device (e.g., a sensor device located at or near the ground).

[0037] In use, the eNB 102 transmits data to the UE 104 using downlink physical channel packets, and the UE 104 transmits data to the eNB 102 using uplink physical channel packets. Downlink and uplink data are sent using OFDM on 12 subcarriers, each of 3.75 kHz or 15 kHz.

[0038] Figure 2 An example downlink data packet 200 is schematically shown in FIG. The downlink data packet 200 includes a control portion allocated to an NB-IoT physical downlink control channel (NPDCCH) 202 (the data packet 200 may include multiple portions allocated to the NPDCCH, only one of which is shown here). The NPDCCH 202 carries downlink control information (DCI), such as resource allocation and decoding information. The downlink data packet 200 also includes a payload portion allocated to an NB-IoT physical downlink shared channel (NPDSCH) 204 (again, only one portion is shown here). The NPDCCH 204 carries the actual user data.

[0039] Figure 3 An example uplink data packet 300 is shown in FIG. The uplink data packet 300 includes a control portion (one example is shown) allocated to a NB-IoT physical uplink shared channel (NPUSCH) format 2 302. The NPUSCH format 2 302 carries uplink control information (UCI).

[0040] The radio signal carrying the downlink data packet 200 from the eNB 102 to the UE 104 may be affected by noise, interference, and fading. Therefore, the communication system 100 uses a dynamic hybrid automatic repeat request (HARQ) mechanism, in which the UE 104 can send feedback to the eNB 102 to indicate that the data packet has arrived correctly, or request the eNB 102 to retransmit the data packet received in error. However, because the eNB 102 is provided by a satellite, the physical distance between the eNB 102 and the UE 104 may be large (e.g., 100 kilometers), resulting in a relatively long round-trip signal time. Therefore, when the transmitter runs out of HARQ processes to schedule (in some examples, there may be only one HARQ process available), it must wait for HARQ feedback for each data packet, which will cause the communication to stall.

[0041] Thus, the communication system 100 uses a dynamic HARQ feedback mechanism in which feedback is not sent for every data packet. The NPDCCH 202 for each downlink data packet 200 includes: a feedback request indicator field 206 that indicates to the UE 104 whether feedback is requested for the data packet 200; and a time frequency resource 304 in the NPUSCH format 2 302 of the uplink data packet 300 for such feedback.

[0042] The communication system 100 also facilitates providing periodic channel state information (CSI) updates from the UE 104, i.e., periodic reporting of the channel quality between the eNB 102 and the UE 104. The feedback request indicator field 206 in each downlink data packet 200 indicates whether a CSI update is requested, and which resources in the NPUSCH format 2 302 of the uplink data packet 300 are used for this update. It is particularly useful for the eNB 102 to be able to request periodic CSI updates when HARQ feedback is not used regularly, so as to be able to identify when channel conditions are deteriorating and additional error compensation may be required (e.g., more regular requests for HARQ feedback and / or changes in the code rate of upcoming data packets).

[0043] Dynamic feedback can be implemented in different ways. Figure 4 and Figure 5 Two possible embodiments are described. In these embodiments, the feedback request indicator field 206 is the ACK / NACK resource field in the DCI format N1. The feedback request indicator field 206 consists of four bits (i.e., has sixteen possible values). When HARQ feedback is requested, the UE 104 sends a single acknowledgement bit to indicate whether the data packet was received correctly (ACK) or not received correctly (NACK).

[0044] In one embodiment ( Figure 4), the feedback request indicator field 206 may: a) indicating that HARQ feedback is requested and specifying one resource of eight resources in NPUSCH format 2 302 to be used for HARQ feedback; b) indicating that a CSI update is requested and specifying one resource out of seven resources in NPUSCH format 2 302 for CSI information; or c) Indicates that no feedback is requested.

[0045] If the feedback request indicator field 206 has a value in the first set 402, this indicates that HARQ ACK / NACK feedback is requested (option (a)). There are eight possible values ​​(0, 1, 4, 5, 8, 9, 12, and 13) in the first set 402, which specify eight possible resources for HARQ feedback in the NPUSCH format 2 302. For example, a value of "0" indicates that the HARQ feedback bit (ACK / NACK) should be in the NPUSCH format 2 302 of the uplink data packet 300 on subcarrier index 0 with a time offset k. 0 =13Send.

[0046] If the feedback request indicator field 206 has a value in the second set 404, this indicates that HARQ ACK / NACK is not requested, but CSI update is requested (option (b)). There are seven possible values ​​(2, 3, 6, 7, 10, 11, and 14) in the second set 404, which specify seven possible resources for CSI reporting in NPUSCH format 2 302. For example, the value "2" indicates that the CSI report data should be in NPUSCH format 2 302 of the uplink data packet 300 on subcarrier index 2 with time offset k. 0 =13Send.

[0047] Finally, if the feedback request indicator field 206 has a value in the third set 406, this indicates that no feedback is requested (ie, option (c)). In this example, the third set 406 consists of a single value "15".

[0048] In use, the UE 104 receives a downlink data packet, detects the value of the feedback request indicator field 206 and attempts to decode the user data carried in the NPDSCH 204. In the first step of this decoding, the UE 104 evaluates one or more error detection portions (e.g., one or more check bits or parity bits) of the downlink data packet, which indicate whether the data packet is sufficiently error-free to be successfully decoded.

[0049] If the value of the feedback request indicator field 206 is in the first set 402, the UE 104 transmits an ACK or a NACK to the eNB 102 using resources in the NPUSCH format 2 302 indicated by the value of the feedback request indicator field 206. If the decoding attempt is successful, the UE 104 transmits an ACK (e.g., a "1"), and if the decoding attempt is unsuccessful, the UE 104 transmits a NACK (e.g., a "0").

[0050] If the value of the feedback request indicator field 206 is in the second group 404, the UE 104 does not transmit an ACK or a NACK, but instead transmits a CSI indicator based on the most recent channel quality measurement to the eNB 102 using resources in the NPUSCH format 2 302 indicated by the value of the feedback request indicator field 206. The CSI indicator may be determined, for example, based on a channel quality measurement based on a narrowband reference signal or a synchronization signal received by the receiver.

[0051] If the value of the feedback request indicator field 206 is in the third set 406 (ie, if it is equal to “15”), the UE 104 simply processes the downlink data packet without transmitting any feedback to the eNB 102 .

[0052] In another embodiment ( Figure 5 ), UE 104 provides HARQ ACK / NACK feedback along with CSI information. Feedback request indicator field 206 is again a four-bit field that can take 16 values. In this embodiment, feedback request indicator field 206 can be: a) indicating that HARQ feedback is requested and specifying one pair of resources out of eight pairs of resources in NPUSCH format 2 302 for combined HARQ ACK / NACK and CSI update; or b) Indicates that no feedback is requested.

[0053] The least significant bit (LSB) of the feedback request indicator field 206 indicates whether feedback is requested. If the LSB is equal to 1 (i.e., if the value of the feedback request indicator field 206 is an odd number), the UE 104 is instructed not to send feedback (i.e., not to send HARQ ACK / NACK feedback and not to send CSI reports).

[0054] If the LSB is equal to 0 (ie, if the value of the feedback request indicator field 206 is even or zero), then the UE 104 is instructed to provide HARQ feedback and CSI updates. The remaining three bits are used to specify how this feedback should be transmitted.

[0055] The remaining three bits identify one of eight pairs of resources in NPUSCH format 2 302 for combined HARQ ACK / NACK and CSI feedback (if feedback is enabled). For example, if the remaining three bits are all equal to zero, this identifies the first pair of resources 500 in NPUSCH format 2 302 of the uplink data packet 300: the first resource 502 at subcarrier index 0, with a time offset of k 0 =13; the second resource 504 at subcarrier index 1, with a time offset of k 0 =13.

[0056] The combined HARQ ACK / NACK and CSI feedback is sent to the UE 104 by transmitting HARQ feedback (e.g., "0" or "1") on a designated pair of resources corresponding to the desired CSI report. If the channel quality is improving, the UE 104 sends the HARQ feedback at the first resource 502 of the pair. If the channel quality is decreasing, the UE 104 sends the HARQ feedback at the second resource 504 of the pair. The eNB 102 then performs blind decoding at the appropriate location in the NPUSCH format 2 302 to identify which resource 502, 504 has been used (to identify the CSI report) and to determine the bit positions transmitted in the resource (to identify the HARQ feedback). Encoding the CSI feedback using the time and frequency resources used to transmit the HARQ ACK / NAK can include a particularly flexible use of communication resources because two bits can be transmitted by the UE when only transmitting on a single resource. Although in this embodiment, the amount of uplink (UL) resources used for UE feedback is increased (ie, 2 subcarriers are reserved for one UE), the overall usage of UL control resources in the network may not increase because feedback may be disabled for most downlink packets.

[0057] exist Figure 5 In the illustrated embodiment, the ACK / NACK is combined with a separate indication of whether the channel quality is improving or deteriorating. In a variation of this embodiment, the ACK / NACK itself may also be used to indicate CSI information. For example, as shown in Table 1 below, an ACK sent in a first resource may indicate an SNR increase of 0.5dB, while a NACK sent in a first resource may indicate an SNR decrease of -0.5dB. An ACK sent in a second resource may indicate a larger SNR increase of 2dB, while a NACK sent in a second resource may indicate a larger SNR decrease of -2dB. The CSI information indicated by an ACK / NACK in the same resource is not necessarily symmetrical (for example, an ACK in the first TF resource may indicate no change in the SNR, while a NACK in the first TF resource may indicate a -0.5db change in the SNR).

[0058] The first TF resource, ACK ACK and 0.5dB rise The first TF resource, NACK NACK and -0.5dB The second TF resource, ACK ACK and 2dB The second TF resource, NACK NACK and -2dB ; Table 1 - CSI information indicated using ACK / NACK

[0059] Although the present invention has been described in detail in conjunction with only a limited number of embodiments, it should be readily understood that the present invention is not limited to these disclosed embodiments. On the contrary, the present invention may be modified to include any number of variants, changes, substitutions, or equivalent arrangements that have not been described heretofore but are commensurate with the scope of the present invention. In addition, although various embodiments of the present invention have been described, it should be understood that various aspects of the present invention may include only some of the described embodiments. Therefore, the present invention should not be considered to be limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A receiver device, configured to: receiving, from a transmitter device, a data packet including a control portion and a payload portion, the control portion including a feedback request indicator; detecting the feedback request indicator; attempting to decode the payload portion of the packet; transmitting an acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested; as well as If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, then the data packet is processed without transmitting an acknowledgement.

2. A receiver device according to claim 1, arranged to transmit a positive acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement for the data packet is requested and an attempt to decode the payload portion succeeded or will succeed.

3. A receiver device according to claim 1 or 2, arranged to transmit a negative acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested and an attempt to decode the payload portion was or will be unsuccessful.

4. A receiver device according to any preceding claim, wherein: The acknowledgement comprises a hybrid automatic repeat request acknowledgement.

5. A receiver arrangement according to any preceding claim, comprising ground equipment arranged to receive data packets from a transmitter arrangement provided via a satellite.

6. A receiver device according to any preceding claim, wherein: The data packets include OFDM packets consisting of symbols spanning multiple time slots and frequency subcarriers.

7. A receiver device according to claim 6, comprising an LTE NB-IoT user equipment.

8. A receiver device according to claim 6 or 7, wherein: The control portion includes an LTE physical downlink control channel, and the feedback request indicator includes an ACK / NACK field of DCI format N1.

9. A receiver device according to any preceding claim, wherein: The feedback request indicator specifies the time and / or frequency resources on which the acknowledgment is to be transmitted.

10. The receiver device according to claim 10, wherein: The receiver apparatus is arranged to interpret the range of time and / or frequency resources specified by the feedback request indicator as an indication that no feedback is requested.

11. A receiver device according to any preceding claim, arranged to: determining channel quality information about a communication channel between the transmitter device and the receiver device; and If the feedback request indicator indicates that channel quality information is requested, transmitting the channel quality information to the transmitter device.

12. The receiver device according to claim 11, wherein The channel quality information comprises a plurality of bits encoded using orthogonal cover coding on a sequence of bits or symbols sent to the transmitter.

13. A receiver device according to claim 11 or 12, wherein: The feedback request indicator specifies time and / or frequency resources on which the channel quality information is to be transmitted.

14. A receiver apparatus according to any of claims 11 to 13, arranged to encode the channel quality information using time and / or frequency resources used for transmitting the acknowledgement.

15. A receiver apparatus according to claim 14, arranged to: transmit the acknowledgement using a first set of time and / or frequency resources to indicate a first channel quality indication; and transmit the acknowledgement using a second set of time and / or frequency resources to indicate a second channel quality indication.

16. A communication system comprising: Transmitter device; as well as Receiver device; Wherein, the transmitter device is configured as: transmitting a data packet to the receiver device, the data packet comprising a control portion and a payload portion, the control portion comprising a feedback request indicator; and Wherein, the receiver device is configured as follows: receiving the data packet from the transmitter device; detecting the feedback request indicator; attempting to decode the payload portion of the packet; If the feedback request indicator indicates that an acknowledgement is requested for the data packet, transmitting an acknowledgement to the transmitter device; and If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, processing the data packet without transmitting an acknowledgement to the transmitter device.

17. A method of operating a communication system, the method comprising: The transmitter device transmits a data packet to the receiver device, the data packet comprising a control portion and a payload portion, the control portion comprising a feedback request indicator; as well as The receiver device: receiving the data packet; detecting the feedback request indicator; attempting to decode the payload portion of the packet; transmitting an acknowledgement to the transmitter device if the feedback request indicator indicates that an acknowledgement of the data packet is requested; as well as If the feedback request indicator indicates that an acknowledgement is not requested for the data packet, processing the data packet without transmitting an acknowledgement to the transmitter device.

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