MIMO Uplink Feedback via Rank and Offset Signaling
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Solution Overview
Problem
In wireless communications networks, especially in MIMO uplink operations, existing grant and E-TFC selection procedures often result in non-optimal transmission performance for user equipment, leading to reduced network performance due to suboptimal power control and interference management.
Innovation Solution
The base station provides feedback to user equipment by transmitting a preferred transmission rank and an offset for secondary streams, which are used to determine the transport block size and transmission rank, optimizing data transmission in MIMO mode through the use of a new Absolute Rank and SIR Offset Channel (A-ROCH) similar to the E-AGCH structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If legacy grant and E-TFC selection procedures are used for MIMO uplink transmissions, then the transmission procedure is simple and compatible with existing systems, but the transmission performance is non-optimal leading to reduced network performance
Solution Approach 1:
The base station provides feedback to the user equipment including a preferred transmission rank and an offset for the secondary stream. This feedback mechanism enables the UE to optimize its transport block size and transmission rank decisions, directly improving transmission performance and network efficiency in MIMO uplink operations.
Solution Approach 2:
The invention introduces new parameters (preferred transmission rank and secondary stream offset) that the base station signals to the user equipment. These parameters enable dynamic adjustment of transmission characteristics, allowing the system to adapt to varying channel conditions and optimize performance for different MIMO transmission scenarios.
2Productivity
If dual-stream transmissions are used in MIMO mode, then data throughput is improved in high SINR environments, but power control and interference management become more complex
Solution Approach 1:
The base station provides specific feedback regarding the secondary stream offset and preferred transmission rank, enabling the user equipment to optimize power allocation and transport block size for dual-stream transmissions. This feedback mechanism simplifies the power control complexity by providing explicit guidance rather than requiring complex UE-side optimization.
3Object-generated harmful factors
If the grant is used to control the power ratio between E-DPDCH and DPCCH, then interference control is achieved, but the transmission becomes non-optimal for MIMO operations reducing overall network performance
Solution Approach 1:
The feedback is segmented into distinct components: a preferred transmission rank indicator and a secondary stream offset. This segmentation allows independent optimization of different transmission aspects - the rank controls the number of streams while the offset specifically adjusts secondary stream power, enabling both interference control and optimized MIMO performance simultaneously.
Data Source
AI summary
Embodiments herein relate to a method in a base station (12) for providing feedback to a user equipment (14) for transmissions of a secondary stream out of a primary and a secondary stream of the user equipment (14) in an uplink Multiple Input Multiple Output mode. The base station (12) transmits to the user equipment (14), a preferred transmission rank and an offset for the secondary stream in a channel, wherein the offset is to be used by the user equipment (14) when deciding transport block size of the secondary stream and the preferred transmission rank is to be used by the user equipment (14) when deciding a transmission rank.