latform, standard ATCA (advanced telecommunications computing architecture) case, and backplane and flexible modular board structure. This kind of hardware platform structure is suited not only for the TDD mode but also for the FDD mode-not only the AP, but also the MT-and it can be used to research wireless transmission technology and test new wireless network struc- tures. Based on the concept of modular design, the system is divided into various modules according to their functions, SO it is easy to improve a module's design or update its functions without affecting other boards. The main modules are connected by using the peer-to-peer distributed interconnection structure based on the exchange; therefore, it is convenient to add or remove a module and adjust the system scale. The system scale and system performance are scalable. Although extreme reduction of the direct coupling between various factors in the overall infrastruc- ture design has been considered, the system can provide the required abilities of expanded connectivity and processing (for example, two four-element antenna arrays can be united into an eight-element one). The concept of modular MIMO is also proposed to adjust or expand flexibly the number of antenna arrays, the element number of every antenna array, the number of users, and the user data rate. The technology of fully distributed parallel processing is adopted to reduce the dependence on CPUs and to avoid the bottleneck of network throughput and pro- cessing performance introduced by centralized processing technology. As a result, it increases the system's effective throughput capacity and improves the system's flexibility, expandability, and adaptability. The whole trial system is based on SDR (software-defined radio) technology, where the baseband signal is processed in FPGA and DSP while the processing of control, wireless, and network protocols is implemented in programmable com- munication processors. This infrastructure based on SDR can sufficiently meet the system's requirement