An injector spool supports a plurality of ball injector assemblies having respective ball cartridges adapted to load one frac ball at a time into a ball chamber of a ball launcher of the respective ball injector assemblies to provide a horizontal frac ball injector adapted to be connected to a frac head by frac iron. With the above successive interference cancellation method, accuracy of successive interference cancellation as well as system detection performance is enhanced. An optimal path may be determined based at least in part on a measurement of similarity between one or more points of interest and one or more destinations. The device or application communicates data about the asset to the interface. Cells adjacent to the selected cells are collected according to the cell graph.