BACKGROUND OF THE INVENTION

Technical solutions provided here relate to transmissions of messages and redundancy transmissions, e.g., from a base station (BS) to a user equipment (UE) and/or vice versa.

In general terms, the effort of obtaining fast communications between a large number of transmitters/receivers may result in a reduction of reliability. Accordingly, fast retransmissions are needed.

In ultra-low latency communication, on the one hand, prescheduling (e.g., semi-persistence scheduling (SPS) with very low duty cycle is a key solution. On the other hand, the transmit-time interval (TTI, such as short-TTI), the radio frame size, and the hybrid automatic repeat request (HARQ) retransmission intervals for ultra-low latency communication have to be reduced.

Since most of the ultra-low latency use-cases also need high reliability, this puts a huge challenge on techniques such as the hybrid automatic repeat request, HARQ, design which are directed to support a reduced frame chart and short presentence cycle.

Examples below focus on the design of a semi-persistence incremental redundancy retransmission for ultra-low latency reliable communication in an open-loop or almost open-loop fashion.

Examples below refer to Latency-constrained (mission-critical) communication services, Multilevel QoS services, ultra-reliable communication, enhanced Multiple access (MA) scheme and MA channels.

Technical solutions described here permit to increase reliability of the transmissions, and may therefore be used for unreliable communication channels.

In the conventional technology, it has been attempted to increase reliability using the following strategies:TTI bundling, as sending multiple times (over multiple subframes-TTIs) the same information as a kind of redundancy or diversity (this costs a huge delay and only supported in UL) [6,7]Only using asynchronous HARQ with short TTI; does not guarantee low latency as sequence of retransmission may still occur [1-4]Flooding the transmission with multiple and ACK or a combined ACK is received for multiple of transport-blocks. This is still inducing delay due to latency in response if HARQ can correct very late. Additionally, it does not fit the SPS with short (or even normal) periods. [10]Providing extra hardware like relaying different fragments of the frames, but this might not be feasible in critical mission communication [8].HARQ-ACK bundling and multiplexing for feeding back multiple frames, still induce latency due to sequential retransmission [11]

SUMMARY

According to an embodiment, a method for communicating according to a hybrid automatic repeat request, HARQ, scheme may have the following steps: performing a first data transmission at a first channel; simultaneously to the first data transmission and/or in at least one subsequent physical resource, performing at least one redundancy transmission at a second channel; concluding or postponing the redundancy transmission when a stop condition or a postponing condition is met.

According to another embodiment, a method for receiving a data may have the following steps: receiving a first data at a first channel and, simultaneously and/or subsequently, receiving at least one redundancy data at a second channel, wherein the redundancy data are transmitted up to a concluding or postponing the redundancy transmission when a stop condition or a postponing condition is met; performing a validity check on the first data and/or the at least one redundancy data; and transmitting an acknowledgment, ACK, message if the validity check is positive for at least one of the first data and/or the at least one redundancy data, and/or transmitting a non-acknowledgment, NACK, message if the validity check is negative for the first data and/or the at least one redundancy data.

Another embodiment may have a device configured to: perform communications at a first channel; transmit a first data; subsequently and/or simultaneously, perform at least a redundancy transmission at a second channel; and conclude or postpone the redundancy transmission when a stop condition or a postponing condition is met.

Another embodiment may have a device configured to: receive a first data on a dedicated resource in a first channel and, simultaneously and/or subsequently, receive at least one redundancy data in the first or a second channel, wherein the redundancy data are transmitted up to a concluding or postponing the redundancy transmission when a stop condition or a postponing condition is met; perform a validity check on the first data and/or the at least one redundancy data; and transmit an acknowledgment, ACK, message and/or a non-acknowledgment, NACK, message on the basis of the result of the validity check.

In accordance with examples, a method for communicating according to an automatic repeat request, ARQ, scheme, and/or hybrid ARQ, HARQ, scheme, may comprise:performing a first data transmission;simultaneously to the first data transmission or in a subsequent physical resource, performing at least one redundancy transmission.

Accordingly, reliability is increased.

In accordance with examples, a method may comprise concluding or postponing the data retransmission when a stop condition or a postponing condition is met, the stop condition or the postponing condition comprising at least one of the following conditions or an “OR”-condition of at least two of the following conditions:an acknowledgment, ACK, message is received;a maximum number of retransmissions have been performed;a maximum timer is expired;other transmissions are transmitted or are to be transmitted.

Accordingly, reliability is increased.

In accordance with examples, a method may comprise:before performing the first data transmission and the at least one redundancy transmission, inserting data to be transmitted in a first transmission buffer associated to the first data transmission and inserting redundancy data in a second transmission buffer associated to the at least one redundancy transmission; andevacuating the second transmission buffer when a stop condition and/or a postponing condition is met.

Accordingly, it is possible to avoid useless retransmission with the same strategy that is used to perform the transmissions.

In accordance with examples, a method may comprise performing at least one redundancy transmission according to a chase combining scheme and/or a redundancy forward error correction.

Accordingly, reliability is increased.

In accordance with examples, the data transmissions and redundancy transmissions are in uplink, UL, and a method may comprise performing a listen-before-talk scheme or a scheme based on a sensing or a detection technique for performing the at least one redundancy transmission.

Accordingly, a valid technique for regulating the medium access between different UEs may be performed.

In accordance with examples, a method may comprise:performing redundancy transmissions until a postponing condition is met;waiting for a subsequent (dedicated or non-dedicated) resource at disposal for a redundancy transmission;performing at least one additional redundancy transmission on the subsequent dedicated resource.

Accordingly, efficiency is increased.

For example, several HARQ redundancy transmissions may be performed, and, when there is no possibility anymore, a ARQ retransmission may be operated. Accordingly, there is the possibility of efficiently using the communication channels using HARQ and ARQ transmissions.

In accordance with examples, a method may comprise, in an initial step, measuring metrics at least in part associated to a network status for initiating the subsequent steps when the metrics are under an acceptable threshold.

Accordingly, methods above and/or below may advantageously be initiated only when necessary.

In accordance with examples, a method may comprise performing a scheduling to associate a plurality of dedicated resources to data to be transmitted in uplink, UL, and/or downlink, DL, so as to permit an association, in a first channel and/or a second channel, between the first dedicated resource and least one dedicated or non-dedicated resource subsequent or simultaneous to the first dedicated resource.

Accordingly, HARQ redundancy transmissions may be performed on a grant-free basis, which permits to avoid repetitions of HARQ transmissions when a correct message has been received.

In accordance with examples, a method may comprise measuring metrics at least in part associated to the status of the network, so as to assign more redundancy transmissions to devices suffering of low QoS and/or requesting urgent communications.

Accordingly, the network adapts to the conditions of UEs by permitting the lowest-performing UEs to have some additional resources to use.

In accordance with examples, a method may comprise determining a ranking of priorities, so as to assign more retransmissions to higher-priority transmissions.

In case of urgent communications (e.g., URLLC) more retransmissions are assigned, so as to increase reliability for the devices which perform the most important communications.

In accordance with examples, a method may comprise:performing the first transmission at a first channel; andperforming the at least one redundancy transmission at a second channel.

In some examples, some channels may be reserved, for example, for HARQ transmission.

In accordance with examples, the first channel may comprise dedicated physical resources and the second channel may comprise grant-free physical resources.

In accordance with examples, a method for receiving a data may comprise:receiving a first data and, simultaneously or subsequently, receiving at least one redundancy data;performing a validity check on the first data and/or the at least one redundancy data; andtransmitting an acknowledgment, ACK, message if the validity check is positive for at least one of the first data and/or the at least one redundancy data, and/ortransmitting a non-acknowledgment, NACK, message if the validity check is negative for the first data and/or the at least one redundancy data.

In accordance with examples, a device may be configured to:perform communications, at least some of the communications being according to a scheduling;transmit a first data; andsubsequently or simultaneously, perform a redundancy transmission.

In accordance with examples, the device is a base station or a user equipment.

In accordance with examples, a device may be configured to:receive a first data on a dedicated resource in a first channel and, simultaneously or subsequently, receive at least one redundancy data in the first or a second channel;perform a validity check on the first data and/or the at least one redundancy data; andtransmit an acknowledgment, ACK, message and/or a non-acknowledgment, NACK, message on the basis of the result of the validity check.

In accordance with examples, a device may be configured to define a scheduling for a device/method as above/below.

In accordance with examples, a system may comprise at least two devices, the first device being a base station and the second device being a user equipment, wherein at least one of the two devices is configured to transmit data to the other device according to any of the methods above and/or below and/or operate as any of the devices above and/or below.

A redundancy transmission may be, for example, a complete retransmission of a data and/or transmission of a redundant part of a previous data.

