An apparatus comprises: a processor configured to: select a first channel from among a plurality of channels in a network, and generate a first message assigning a first grant corresponding to the first channel; a transmitter coupled to the processor and configured to transmit the first message; and a receiver coupled to the processor and configured to receive a second message on the first channel and in response to the first message. A method comprises: selecting a first channel from among a plurality of channels in a network; generating a first message assigning a first grant corresponding to the first channel; transmitting the first message; and receiving a second message on the first channel in response to the first message.