For DSSS modulation, the correct statement isa. The DSSS technology is developed by Qualcomm.b. The DSSS technology is better than the FH technology for spectrum spreading.c. A DSSS system based on a PN sequence can effectively combat ISI.d. A DSSS system has higher spectrum efficiency than a non-spread system. A. 错 B. 错 C. 对 D. 错