A method of operating a user equipment device in a wireless communication system, the method comprising: receiving (602, 702) contention-based configuration data from a base station in the wireless communication system, the contention-based configuration data comprising: zone data that identifies a plurality of contention-based resource zones (302, 304, 306) for a shared channel supported by the base station, each of the contention-based resource zones (302, 304, 306) comprising a respective number of physical resource blocks; and modulation and coding scheme data that identifies modulation and coding schemes assigned to the contention-based resource zones (302, 304, 306), the method being characterized by: the received contention-based configuration data further comprising minimum power headroom data that identifies minimum power headroom values assigned to the contention-based resource zones (302, 304, 306); comparing currently available power headroom of the user equipment device to the received minimum power headroom values to identify a subset of the contention-based resource zones for which the currently available power headroom of the user equipment device satisfies the received minimum power headroom values; and selecting (608, 704), from the subset of the contention-based resource zones, a transmit resource zone to be used for data packet transmission. receiving (602, 702) contention-based configuration data from a base station in the wireless communication system, the contention-based configuration data comprising: zone data that identifies a plurality of contention-based resource zones (302, 304, 306) for a shared channel supported by the base station, each of the contention-based resource zones (302, 304, 306) comprising a respective number of physical resource blocks; and modulation and coding scheme data that identifies modulation and coding schemes assigned to the contention-based resource zones (302, 304, 306), the method being characterized by: the received contention-based configuration data further comprising minimum power headroom data that identifies minimum power headroom values assigned to the contention-based resource zones (302, 304, 306); zone data that identifies a plurality of contention-based resource zones (302, 304, 306) for a shared channel supported by the base station, each of the contention-based resource zones (302, 304, 306) comprising a respective number of physical resource blocks; and modulation and coding scheme data that identifies modulation and coding schemes assigned to the contention-based resource zones (302, 304, 306), the received contention-based configuration data further comprising minimum power headroom data that identifies minimum power headroom values assigned to the contention-based resource zones (302, 304, 306); comparing currently available power headroom of the user equipment device to the received minimum power headroom values to identify a subset of the contention-based resource zones for which the currently available power headroom of the user equipment device satisfies the received minimum power headroom values; and selecting (608, 704), from the subset of the contention-based resource zones, a transmit resource zone to be used for data packet transmission.