Aspects describe maximizing a Euclidean distance for an ACK transmission as a function of the number of bits in a HARQ-ACK and a modulation order. Encoding includes placing escape sequences in the HARQ-ACK, wherein the number of escape sequences is based on the number of bits and the modulation order. Multiple encoded ACK blocks are combined to obtain a vector sequence that is multiplexed with the encoded data and interleaved, such as on a “time-first” manner. Scrambling is performed as a function of the size and the modulation order. For a 1-bit ACK, the scrambling is performed to achieve any two corners in any constellation for transmission for the ACK. For a 2-bit ACK, the scrambling is performed to achieve any four corners in any constellation for transmission for the ACK.

A control unit (208) transmits a response signal on an uplink control channel on the basis of a rule. In the rule, error detection result pattern candidates are associated with multiple resources of the uplink control channel used in the transmission of the response signal and with phase points within each resource, and at least a specific pattern candidate, wherein the pattern for a specific error detection result with respect to downlink data of a first unit band is identical to the error detection result pattern when communication with the base station (100) occurs using only the first unit band, and the error detection results other than the specific error detection result are all NACK or DTX, is associated with the first resource of the multiple resources. In addition, at least the first resource of the multiple resources is arranged within the first unit band.

A method of configuring a positive acknowledgement (ACK) or negative acknowledgement (NACK) in a wireless communication system based on time division duplex (TDD) in which M, M=4, downlink subframes are associated with an uplink subframe. The method is performed by a user equipment receiving a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH). The user equipment receives at least one downlink transport block in the M downlink subframes from a first serving cell. The user equipment determines ACK/NACK states {HARQ-ACK(1), HARQ-ACK(2), HARQ-ACK(3), HARQ-ACK(4)} for the first serving cell. The use equipment determines an ACK/NACK response based on the ACK/NACK states.

A communications system is described in which user devices are allocated sub-carriers on which to transmit uplink data to a base station. ACK/NACK messages for the data transmitted on the uplink are then transmitted by the base station on sub-carriers that depend on the sub-carriers used to carry the uplink data. A direct mapping function is preferably used to determine the sub-carriers to be used for the ACK/NACK messages from the uplink sub-carriers. In another embodiment, the ACK/NACK messages are transmitted to the user devices on sub-carriers that are previously identified to the user devices, preferably by transmitting one or more index values to the user device in a control channel thereof.

A method is provided for sending an acknowledgement frame by a receiving entity. The method includes: subsequent to reception of a data frame sent by a sending entity and including a synchronization field containing an invariant item of information known to the entities and an identification field containing information identifying the sending entity and the receiving entity, sending an acknowledgment frame including a synchronization field; and calculating a signature of a transmission channel between the sending entity and the receiving entity, the synchronization field of the acknowledgment frame being obtained on the basis of the synchronization field of the data frame, by using the signature.

Data transmission in a multicast fashion in which retransmissions are requested by recipients sending feedback to the one sender. Receiving stations are informed about the feedback of another receiving station. This is done by mirroring the feedback of receiving stations to other receiving stations. Due to this, in case, for example, one of the mirrored feedbacks is a negative acknowledgement message, the other receiving stations are informed that it is no longer necessary to provide their feedback, since a retransmission will be initiated anyway. Advantageously, this may allow reduced interference in the direction of the feedback.

Techniques for contention window size (CWS) adaptation (CWSA) are discussed. One example apparatus can comprise a processor that can receive HARQ messages UEs in response to PDSCH transmissions in one or more reference subframes. The HARQ messages can comprise HARQ-ACK values that denote a HARQ-ACK state for a transport block associated with License Assisted Access (LAA) operation, wherein each of the HARQ-ACK states is one of a DTX state, an ACK state, a NACK state, or an “any” state. The processor can also; determine a metric value for each of the HARQ-ACK states; calculate a CWS adjustment metric based on the determined metric values; increase a CWS to a next higher allowed value when the CWS adjustment metric is greater than or equal to a threshold; and reset the CWS to a minimum allowed value when the CWS adjustment metric is less than the threshold.

A method for performing by a mobile station (MS) a retransmission operation in a device to device (D2D) communication system is provided. The method includes performing a data communication with a peer MS using a D2D communication, receiving feedback information for a retransmission operation for data which is transmitted to the peer MS which is transmitted using a resource block mapped to identification information of a D2D connection from the peer MS, determining whether there is need for retransmission of the data based on the feedback information received from the peer MS, and if there is need for the retransmission of the data, retransmitting the data to the peer MS.

A communication method and a terminal and a base station adapted to the method are provided. The communication method of a terminal includes: receiving a message containing information regarding a semi-persistent scheduling (SRS) configuration from a base station; determining whether a sub-frame configured with a non-adaptive re-transmission is identical to a sub-frame configured with an uplink grant according to the SPS configuration; and when: a sub-frame configured with a non-adaptive re-transmission is identical to a sub-frame configured with an uplink grant according to the SPS configuration; and the terminal does not have data to be first transmitted via the sub-frame configured with an uplink grant according to the SPS configuration, performing the non-adaptive re-transmission.

Provided are a method, performed by a first terminal, for adjusting a threshold for determining hybrid automatic repeat request (HARQ) feedback in a wireless communication system, and an apparatus for supporting the same. The method comprises the steps of: transmitting at least one piece of information to a second terminal; receiving, from the second terminal, at least one HARQ feedback in response to the at least one piece of information; determining an ACK or NACK with respect to the at least one HARQ feedback, based on the threshold; receiving, from the second terminal, an HARQ feedback transmission history of the second terminal; and adjusting the threshold, based on the HARQ feedback transmission history of the second terminal and information about the HARQ feedback determined by the first terminal.