A synchronous CDMA network has three mobile users: Alice, Bob and Carol. Alice is already assigned with a 4-bit spreading code (1,1,1,1). Answer the following two questions: (20 marks) 1. Develop a spreading code for Bob and Carol so that the three of them can transmit data at the same time without any interference. (8 marks) 2. The raw data Alice wishes to transmit is (1,1); Bob wishes to transmit (0,0); Carol wishes to transmit (0,1). Show the encoding and decoding results based on the spreading codes you just developed in part (1). Assume a binary data 0 will be encoded as signal 1 and a binary data 1 will be encoded as signal +1