A wireless base station employs adaptive modulation to connect to a wireless terminal, and comprises a first processing means and a second processing means. The first processing means determines a target value for the total bit quantity of the traffic to a wireless terminal to be mapped to a wireless resource. The second processing means determines a modulation scheme for the wireless terminal by adaptive modulation, restricting the total bit quantity to be transmitted in association with the target value thereof, such that available resources of the wireless resource are reduced and transmission power density is at a constant level and reduced.