Time-Varying Orthogonal Cover Codes for CFO Interference Randomization
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Solution Overview
Problem
Wireless communication systems face interference issues due to phase impairments like carrier frequency offset (CFO) when using fixed orthogonal cover codes (OCCs), leading to un-decodable transmissions and reduced performance.
Innovation Solution
Implement an interference randomization scheme by assigning OCC codewords to user equipments (UEs) using pseudo-random permutation matrices across transmission time intervals, randomizing the OCC codewords to average out interference caused by CFO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed orthogonal cover codes (OCCs) are used for multiplexed UE communications, then device complexity is reduced and ease of operation is improved, but interference from phase impairments like CFO increases and reliability deteriorates
Solution Approach 1:
The patent applies dynamics by transitioning from fixed OCC assignments to dynamic, time-varying OCC assignments. The OCC codeword is selected differently for each transmission time interval based on a pseudo-random sequence, making the system adaptive to changing channel conditions and interference patterns rather than static
Solution Approach 2:
The patent changes the parameter of OCC selection from fixed to variable. By introducing time-varying OCC assignments where the selected codeword changes based on transmission time interval and pseudo-random sequences, the system modifies its operational parameters to avoid persistent interference from phase impairments
2Productivity
If fixed OCCs are used across transmission time intervals, then device complexity is reduced, but interference averaging is prevented and productivity decreases
Solution Approach 1:
The patent applies preliminary action by pre-generating and storing pseudo-random sequences before the actual data transmission. These sequences are prepared in advance to determine OCC selections for future transmission time intervals, allowing the system to benefit from interference randomization without adding complexity during real-time transmission
Solution Approach 2:
The patent uses copying by generating pseudo-random sequences that replicate statistical properties of random interference patterns. These sequences are copied or reused across different UEs and time intervals to achieve interference averaging without requiring truly random, unpredictable assignments
3Reliability
If fixed OCCs are used, then ease of operation is improved, but interference from CFO cannot be averaged out and reliability worsens
Solution Approach 1:
The patent applies self-service by enabling each UE to autonomously select its own OCC codeword for each transmission time interval based on its assigned pseudo-random sequence. The UE independently determines the appropriate OCC without requiring complex network coordination for each selection, simplifying the overall system operation
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for selecting a first orthogonal cover code (OCC) codeword from an OCC matrix for a transmission occurring during a first transmission time interval based on a first pseudo-random codeword allocator function, such as a first pseudo-random permutation matrix, corresponding to the first transmission time interval; and sending the transmission during the first transmission time interval using the first OCC codeword.