HARQ-ACK resource allocation and use for eIMTA

An apparatus comprising:

• one or more processors;
• and
• one or more memories including computer program code, the one or more memories and the computer program code configured, with the one or more processors, to cause the apparatus to perform at least the following:
• receiving a downlink data transmission in a downlink subframe;
• determining one or more resources to be used for transmission of error information for the received transmission in an uplink subframe based at least on a pre-determined association set between one or more downlink or special subframes and an uplink subframe, wherein the association set depends on a downlink reference configuration, wherein the association set for each uplink subframe comprises a grouping of the downlink or special subframes into at least three groups, wherein a first group includes only legacy fixed downlink subframes reserved for legacy UEs, wherein a second group includes special fixed downlink subframes where legacy UEs cannot be scheduled in the downlink, and wherein a third group includes flexible downlink subframes where legacy UEs cannot be scheduled in the downlink, so that collisions between legacy UEs and eIMTA UEs in the uplink are avoided, and wherein an association set is defined only for the subframes which are uplink subframes in a corresponding downlink reference configuration;
• and
• transmitting the error information using the determined one or more resources in the uplink subframe.

A method comprising:

• transmitting a downlink data transmission in a downlink subframe;
• determining one or more resources to be used for reception of error information for the received transmission in an uplink subframe based at least on a pre-determined association set between one or more downlink or special subframes and an uplink subframe, wherein the association set depends on a downlink reference configuration, wherein the association set for each uplink subframe comprises a grouping of the downlink or special subframes into at least three groups, wherein a first group includes only legacy fixed downlink subframes reserved for legacy UEs, wherein a second group includes special fixed downlink subframes where legacy UEs cannot be scheduled in the downlink, and wherein a third group includes flexible downlink subframes where legacy UEs cannot be scheduled in the downlink, so that collisions between legacy UEs and eIMTA UEs in the uplink are avoided, and wherein an association set is defined only for the subframes which are uplink subframes in a corresponding downlink reference configuration;
• and
• receiving error information using the determined one or more resources in the uplink subframe.

An apparatus comprising:

• one or more processors;
• and
• one or more memories including computer program code, the one or more memories and the computer program code configured, with the one or more processors, to cause the apparatus to perform at least the following:
• transmitting a downlink data transmission in a downlink subframe;
• determining one or more resources to be used for reception of error information for the received transmission in an uplink subframe based at least on a pre-determined association set between one or more downlink or special subframes and an uplink subframe, wherein the association set depends on a downlink reference configuration, wherein the association set for each uplink subframe comprises a grouping of the downlink or special subframes into at least three groups, wherein a first group includes only legacy fixed downlink subframes reserved for legacy UEs, wherein a second group includes special fixed downlink subframes where legacy UEs cannot be scheduled in the downlink, and wherein a third group includes flexible downlink subframes where legacy UEs cannot be scheduled in the downlink, so that collisions between legacy UEs and eIMTA UEs in the uplink are avoided, and wherein an association set is defined only for the subframes which are uplink subframes in a corresponding downlink reference configuration;
• and
• receiving error information using the determined one or more resources in the uplink subframe.