1. A method comprising:receiving one or more radio resource control (RRC) messages comprising one or more configuration parameters for a licensed assisted access (LAA) cell, the one or more configuration parameters comprising one or more listen before talk (LBT) configuration parameters;
receiving a downlink control information (DCI) comprising:
an allocation of resource blocks for transmission of uplink data in a subframe;
a first field comprising an index indicating a starting position for the uplink data in the subframe, the index identifying one of a plurality of pre-configured starting positions; and
a second field indicating an ending symbol for the uplink data, the ending symbol being one of a plurality of pre-configured ending symbols;
performing, on the LAA cell and before the starting position of the subframe, an LBT procedure employing the one or more LBT configuration parameters, the LBT procedure indicating a clear channel;
mapping, based at least on the starting position and the ending symbol, the uplink data to resource elements corresponding to the resource blocks allocated for transmission; and
transmitting, the uplink data on the LAA cell, starting at the starting position in the subframe and ending before the ending symbol.