To implement cooperative algorithms in distributed wireless networks (DWNs) where the devices in the network are able to communicate each other independently, the correlation model of distributed channels are crucial. Although, traditional channel sounders were utilized by existing works to measure and develop the correlation model for indoor distributed channels, it is difficult to implement such a system in large scale of outdoor distributed measurement which requires the numerous transmitter and receiver nodes. Therefore, the well-suited channel sounder prototype for the outdoor DWNs is developed by adopting the standalone system which combines the free GNU radio software and the open source USRP hardware. First, the time-grid of received signal acquisition is introduced and implemented in order to overcome the drawback of the limited data rate within USRP in this work. By this solution, the data rate can be successfully reduced to 1/8 without sacrificing the accuracy of the channel characteristics. Second, the suitable solution of synchronization in large scale of outdoor distributed measurement is pointed out by investigating the properties of existing synchronizers in term of performance, operation, cost and size. Third, the protocol of communication among nodes for obtaining the possible correlation in the distributed channels is pointed out by considering the existing works of modeling the distributed channels versus the specification of the proposed channel sounder. Finally, the prototype of channel sounder is validated and evaluated in the laboratory environment.
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