A mobile telecommunications system including mobile terminals of first type and second type configured to transmit uplink data to a network over a radio interface using plural sub-carriers. The mobile terminals of first type configured to transmit uplink data on a first group of the sub-carriers over a first bandwidth and the mobile terminals of second type configured to transmit uplink data on a second group of the sub-carriers within the first group of sub-carrier over a second bandwidth smaller than the first bandwidth. The mobile terminals of first type transmit random access request messages to a base station of the network requesting uplink radio resources on a first random access channel. The mobile terminals of second type transmit random access request messages to the base station of the network requesting uplink radio resources on a second random access channel on sub-carriers within the second sub-carrier group.