Analysis and implementation techniques of L1 Inband reset in Common Public Radio Interface

Common Public Radio Interface (CPRI) is a high speed serial link standard which connects the radio equipment control(REC) and the radio equipments(RE) in a radio base station. The layer 1 (L1) Inband Protocol in CPRI defines the signalling information that is directly transported by the physical layer. This protocol is required for the L1 link maintenance, exchanging the time critical signalling of the user data and for the system startup of the link. The L1 Inband protocol transfers the reset notifications between the nodes on the CPRI link along with the other control information viz; protocol version, Control & Management (C&M) start-up information and pointers to C&M data. The physical layer of the CPRI is designed in such a way that a very low bit error ratio is achievable without using any of the expensive forward error correction(FEC) techniques. However, reset being very critical signal CPRI defines its own protection mechanism for reset control bit to be implemented in layer 1 of the CPRI protocol. This paper analyses the reset detection and protection requirements of the CPRI standard. The paper presents the possible software approaches and novel hardware implementation techniques for L1 Inband reset detection and protection in CPRI. This paper also analyses the different techniques and sets recommendations for these implementation techniques.