PBCH Cyclic Shift Signaling for Faster System Frame Decoding
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Solution Overview
Problem
In LTE systems, the current method for carrying the two least significant bits of the system frame number in PBCH transmissions results in increased decoding delays for terminals due to the need to try multiple scrambling sequences, as information and CRC bits are scrambled differently each time, leading to inefficient information retrieval.
Innovation Solution
The proposed method involves concatenating CRC and information bits, performing interleaving and cyclic shifting to ensure that the terminal can determine the correct cyclic shift without multiple decoding attempts, by ensuring that CRC bits can only be correctly checked when the cyclic shift is accurately determined, thus reducing decoding times and improving information retrieval efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If different scrambling sequences are used for each PBCH transmission to carry the two least significant bits of the system frame number, then the system frame number can be fully transmitted, but the terminal needs to try multiple scrambling sequences to decode the information, increasing the decoding delay
Solution Approach 1:
The patent extracts the two least significant bits of the system frame number from the information payload and transmits them separately through cyclic shift indicators. This separation allows the main information to be decoded without trying multiple scrambling sequences, while the LSBs are carried through the cyclic shift pattern, thus reducing terminal decoding delay while maintaining complete system frame number transmission
Solution Approach 2:
The system frame number is segmented into two parts: the most significant bits are transmitted in the information payload, while the two least significant bits are transmitted through the cyclic shift indicator. This segmentation allows the terminal to decode the main information first and then determine the complete system frame number, avoiding the need to try multiple scrambling sequences
2Measurement precision
If the terminal performs multiple decoding attempts with different scrambling sequences to determine the correct sequence, then the system frame number can be accurately received, but the information acquisition delay is increased
Solution Approach 1:
The patent performs preliminary action by pre-defining four specific cyclic shift values (0, 10, 20, or 30) that correspond to the two least significant bits of the system frame number. The terminal can directly apply these predetermined cyclic shifts without needing to perform multiple trial decodings with different scrambling sequences, thus maintaining accuracy while reducing delay
Solution Approach 2:
The patent changes the parameter used to carry the two least significant bits from scrambling sequence selection to cyclic shift value selection. By mapping the LSBs to specific cyclic shift values (0, 10, 20, 30), the terminal can determine the correct value through a single decoding attempt with the appropriate cyclic shift, rather than multiple attempts with different scrambling sequences
Data Source
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AI summary
An information transmission method and a device are disclosed. The method is applied to a network device and includes: determining CRC bits of to-be-sent information bits; concatenating the CRC bits and the to-be-sent information bits to obtain a first information sequence; interleaving bits in the first information sequence in an interleaving manner or scrambling the bits in the first information sequence in a scrambling manner, to obtain a second information sequence, where the interleaving manner or the scrambling manner is used to ensure that bits at locations of the CRC bits after a cyclic shift cannot check bits at locations of the to-be-sent information bits after the cyclic shift; performing a cyclic shift on the second information sequence to obtain a third information sequence, where a quantity of cyclically shifted bits is used to carry information about some bits of a system frame number; and sending the third information sequence. In embodiments of the present invention, a delay of obtaining information by a terminal may be reduced.