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A Range and Scaling Study of an FPGA-Based Digital Wireless Channel Emulator

A Digital Wireless Channel Emulator (DWCE) is a system that is capable of emulating the RF environment for a group of wireless devices. A major issue with current designs is that they do not scale to a large enough number of nodes to emulate meaningful network. A reason for this lack of scalability is the large amount of computations and network capacity required for such a system. Previously documented DWCE systems implement a hub-and-spoke configuration that inhibits them from simply adding additional hardware to scale. This paper investigates the use of a FPGA cluster configured as a distributed system to provide the computational and network structure to scale a DWCE to support 1250 wireless devices. This scale is approximately two orders of magnitude larger than any other previously documented system. This paper presents multiple FPGA cluster configurations that use currently available hardware and describes the algorithms used to route the signals through the network and place the computational hardware on each FPGA. The low level VHDL Signal Path Component (SPC) is synthesized and mapped under different parameters to interpolate is resource utilization. One example FPGA build with enough SPCs to fill 80% of the FPGA resources is successfully run through the Xilinx tool-chain to determine the maximum FPGA system clock speed. Finally, the scaling results are presented that detail the maximum sample frequency of various sized DWCE systems which could be used to examine a variety of wireless devices.