Multiplexing CDM Pilot and FDM Data in Wireless Control
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in transmitting control information such as ACK and CQI, particularly in multiplexing multiple user equipment (UE) signals without causing interference and ensuring reliable channel estimation.
Innovation Solution
The technique involves using frequency-domain code division multiplexing (CDM) for pilot signals and frequency division multiplexing (FDM) for data, where UEs are assigned different orthogonal sequences and subcarriers to distinguish their transmissions, allowing for efficient multiplexing and channel estimation across multiple subcarriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If FDM is used for data transmission, then resource utilization is improved, but interference management between multiple UEs becomes more difficult
Solution Approach 1:
The system segments the available spectrum into multiple orthogonal frequency subcarriers and assigns different subsets of subcarriers to different UEs for data transmission. This segmentation allows multiple UEs to transmit simultaneously without interference while efficiently utilizing the available frequency resources.
Solution Approach 2:
Different UEs are assigned different local frequency regions (subcarriers) for data transmission based on their channel conditions and requirements. This localized frequency assignment optimizes resource utilization for each UE while minimizing inter-UE interference through orthogonal frequency separation.
2Measurement precision
If CDM is used for pilot signals, then channel estimation accuracy is improved, but sequence design complexity increases
Solution Approach 1:
The system changes the parameter of orthogonal sequences by using different cyclic shifts of a base Zadoff-Chu sequence to generate pilot sequences for different UEs. This approach maintains good correlation properties for accurate channel estimation while simplifying sequence design through a systematic parameter-based generation method.
Solution Approach 2:
The system uses composite signal structures by combining Zadoff-Chu sequences with cyclic shifts to create pilot sequences that possess both good autocorrelation and cross-correlation properties. This composite approach ensures accurate channel estimation while providing a structured method for sequence design.
3Quantity of substance
If orthogonal sequences are assigned to different UEs, then multiplexing capacity is improved, but sequence resource management becomes more complex
Solution Approach 1:
The system dynamically assigns different cyclic shift values to different UEs based on current channel conditions and traffic requirements. This dynamic assignment allows the system to adaptively maximize multiplexing capacity while managing sequence resources efficiently through a flexible parameter-based approach rather than static allocation.
Data Source
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AI summary
Techniques for sending control information in a wireless communication system are described. In an aspect, a user equipment (UE) may send data for control information in a resource block with frequency division multiplexing (FDM) and may send pilot in the resource block with frequency-domain code division multiplexing (CDM). The UE may determine multiple groups of subcarriers to use to send data in multiple symbol periods of the resource block based on a predetermined pattern or a pseudo-random hopping pattern. Each group may include consecutive subcarriers to support localized FDM. The multiple groups may include different subcarriers to provide frequency diversity and possibly interference averaging. The UE may send modulation symbols for data (e.g., in the time domain) on the multiple groups of subcarriers in the multiple symbol periods. The UE may send a reference signal sequence for pilot on multiple subcarriers in each symbol period for pilot.