FIG. 19 illustrates an example of groupcast (or unicast) transmission with repetition transmissions of V2V communication. A Tx wireless device (e.g., Tx UE1) may communicate with a plurality of Rx wireless devices (e.g., Rx UE1, Rx UE2, Rx UE3, Rx UE4, Rx UE5, and Rx UE6) with a groupcast communication for a sidelink communication. The Tx wireless device (e.g., Tx UE1) and the plurality of Rx wireless devices (e.g., Rx UE1, Rx UE2, Rx UE3, Rx UE4, Rx UE5, and Rx UE6) may be in a coverage of a base station. The base station may transmit one or more radio resource control (RRC) messages to the Tx wireless device (e.g., Tx UE1). The one or more RRC messages may comprise configuration parameters for the V2V communication. The configuration parameters may indicate: a plurality of repetition values of a physical sidelink shared channel (PSSCH), and a repetition threshold for the PSSCH. Each of the plurality of repetition values of the PSSCH may indicate a number of PSSCH repetition transmissions for a transport block (TB) of the sidelink communication. The repetition threshold may be a repetition value for a transmission of a transport block. A Tx wireless device and/or a Rx wireless device may control/determine whether a HARQ feedback is required based on the repetition threshold. In an example, the Tx wireless device (e.g., Tx UE1) may transmit a message to the base station to request radio resources for the sidelink communication. In an example, the message may be an RRC message. In an example, the message may comprise frequency information of transmitting and/or receiving sidelink data interested in by the Tx wireless device (e.g., Tx UE1). The configuration parameters may indicate a plurality of radio resources for the Tx wireless device (e.g., Tx UE1). The plurality of radio resources may comprise one or more radio resource pools. The one or more radio resource pools may comprise one or more transmission resources pools. The one or more radio resource pools may comprise one or more reception resources pools. In an example, each resources pool of the one or more transmission resource pools (or the one or more reception resource pools) may comprise at least one of: a control region, and a data region. The Tx wireless device (e.g., Tx UE1) may transmit a transport block via the data region of a transmission resource pool according to control information in the control region of the transmission resource pool. An Rx wireless device (e.g., Rx UE2) of the plurality of Rx wireless devices (e.g., Rx UE1, Rx UE2, Rx UE3, Rx UE4, Rx UE5, and Rx UE6) may receive the transport block via the data region of a reception resource pool of the Rx wireless device according to control information in a control region of the reception resource pool. In an example, the transmission resource pool of the Tx wireless device (e.g., Tx UE1) may have an association relationship with the reception resource pool of the Rx wireless device (e.g., Rx UE2). The association relationship may be a one-to-one mapping relationship. In an example, the configuration parameters may indicate the association relationship to the Tx wireless device and/or the Rx wireless device (e.g., Tx UE1 and/or Rx UE2).
