In a dynamic spectrum access system, radios seek robust communications in a communication channel with unknown interfering signals. Cooperative distributed spectrum access radios provide a way to share the spectrum without prior knowledge of other radios' spectrum occupancy. Competitive distributive spectrum access radios provide a solution to deal with malicious radios using the same spectrum. In this thesis, both cooperative and competitive distributed spectrum access radios are designed and implemented. Strategies for the cooperative and competitive distributed spectrum access system are proposed and analyzed. A packet management system is especially designed to deal with feedback and packet management for the dynamic spectrum access system. This thesis proposed a new spectrum sensing technique based on the statistical characteristics of the mean and standard deviation of interference signal energy across frequency. A TDD system based on the GNU Radio software and the Ettus Universal Software Radio Peripheral USRP N210 hardware is also analyzed and implemented. Experiments demonstrate that all the components can achieve their design goals and the cooperative distributed spectrum access system can cooperate well with radios running the same protocol.