Multiuser Superposition Transmission Interference Cancellation
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Solution Overview
Problem
Current LTE systems face limitations in achieving high system capacity due to mutual interference in multiuser superposition transmission (MUST) operations, particularly in scenarios where multiple users share the same time-frequency resources, which degrades performance.
Innovation Solution
The implementation of higher-layer signaling for configuring user equipment (UE) to enable MUST operation, allowing dynamic switching between MUST and non-MUST modes, and supporting mixed transmission schemes and precoders among co-channel UEs, with new DCI formats carrying scheduling information and interference cancellation data to manage interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple users share the same time-frequency resources in MUST operations, then system capacity is improved, but mutual interference degrades performance
Solution Approach 1:
The patent converts the harmful mutual interference into a beneficial signal by having users perform interference cancellation. Each user treats the interference from other users' signals as useful information that can be decoded and subtracted from the received signal, thereby eliminating the harmful effect and improving overall system capacity
Solution Approach 2:
The patent applies preliminary action by pre-configuring users with interference cancellation capabilities and providing necessary channel state information before the actual data transmission. This allows users to proactively cancel interference rather than reactively dealing with it, improving the efficiency of MUST operations
2Object-affected harmful factors
If orthogonal precoders are used in MU-MIMO, then interference between users is reduced, but system capacity is limited by wide beamwidth
Solution Approach 1:
The patent changes the parameter of precoder orthogonality from orthogonal to non-orthogonal. By allowing non-orthogonal precoders, the system can form narrower, more directional beams that increase spatial multiplexing capacity while managing interference through user-side cancellation techniques rather than relying on orthogonal separation
3Productivity
If non-orthogonal precoders are used for multiple users, then system capacity is improved, but interference cancellation complexity increases
Solution Approach 1:
The patent applies self-service by having each user equipment perform its own interference cancellation using locally available channel state information and received signal data. This distributes the computational complexity from the base station to individual users, making the system scalable while maintaining high capacity benefits of non-orthogonal transmission
Data Source
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AI summary
Methods of enabling multiuser superposition transmission (MUST) in LTE systems are proposed. MUST operation allows simultaneous transmission for multiple co-channel users on the same time-frequency resources. A higher-layer signaling is used for configuring a UE to enable MUST in each transmission mode (TM). MUST is a sub-TM of each TM. When a UE is configured by higher layer to enable MUST, the UE will monitor new DCI formats supported by the configured TM with new fields carrying scheduling information of another co-channel UE. Dynamic switching between MUST and non-MUST operation is allowed. Mixed transmission schemes and precoders among co-channel UEs are also supported.