Portable Full Channel Sounder for Mobile Robotics by Using Sub-Nanosecond Time Synchronization over Wireless

Wireless communications have attracted great interest from the industry due to its lower cost and the possibility of enabling new use cases. The new use cases are commonly related to mobile robotics, such as Unmanned Aerial Vehicles. The design of wireless systems for these use cases requires deep knowledge of the channel behavior. However, the weight and size of full channel sounders exceed the payload of most mobile robots. In addition, full channel sounders usually require wired time synchronization. Hence, channel measurements in these scenarios are constrained to use limited channel sounders, which can only measure some specific parameters (frame error rate, channel attenuation, etc.). In this paper, we present the design and implementation of a portable 802.11-based channel sounder combined with a sub-nanosecond wireless time synchronization algorithm. Thanks to the wireless time synchronization, the channel sounder can be used to periodically take complex baseband Channel Impulse Response samples synchronized to absolute time. From these samples, relevant channel parameters can be extracted, including the Power Delay Profile, Doppler spectrum, and channel delay. The verification of the channel sounder through a wireless channel emulator confirms its feasibility for mobile robotics applications.