Composite CDM-TDM Pilot Signals for Accurate Channel Estimation
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Solution Overview
Problem
Current 3GPP cellular communication systems face challenges in accurately estimating radio propagation channels due to degradation of orthogonality between pilot and data signals in complex radio environments, particularly in Single Frequency Network (SFN) transmissions, where CDM pilots are less effective.
Innovation Solution
A composite signal is transmitted comprising both a CDM pilot sequence and a TDM pilot sequence, with the TDM pilot sequence having a cyclic prefixed structure, allowing for simultaneous transmission periods and code-domain orthogonality, and utilizing a multiplexing logic unit for construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CDM pilot sequences are used in conventional cellular systems, then user separation is achieved through code allocation, but orthogonality degradation occurs in complex radio environments reducing channel estimation accuracy
Solution Approach 1:
The patent segments the pilot transmission into two distinct components: CDM pilots for code-domain separation and TDM pilots for time-domain separation. This segmentation allows each pilot type to serve its specific function without interfering with the other, thereby maintaining orthogonality and improving channel estimation accuracy in complex radio environments
Solution Approach 2:
The patent merges CDM and TDM pilot sequences into a composite signal structure where both pilot types are transmitted simultaneously. The TDM pilot sequences are inserted at specific positions within the CDM pilot structure, creating a combined signal that leverages the advantages of both multiplexing techniques while preserving their orthogonal properties
2Measurement precision
If TDM pilot sequences with cyclic prefix are transmitted, then channel estimation accuracy is improved, but device complexity increases due to multiplexing logic requirements
Solution Approach 1:
The patent applies preliminary action by pre-defining the insertion positions and structures of TDM pilot sequences within the CDM pilot framework. The cyclic prefix structure is predetermined and systematically integrated into the signal construction process, which simplifies the multiplexing logic implementation by providing clear, pre-established rules for pilot sequence integration
3Reliability
If composite signal with both CDM and TDM pilots is transmitted, then receiver performance is enhanced, but signal structure complexity increases
Solution Approach 1:
The patent applies local quality by assigning different structural properties to different parts of the composite signal. The TDM pilot sequences maintain their cyclic prefix structure at specific time positions, while the CDM pilot sequences maintain their code-domain orthogonality throughout. This localized optimization allows the receiver to process different pilot types using appropriate algorithms for each, improving overall performance without requiring complete restructuring of the entire signal
Data Source
AI summary
A wireless device is configured to produce a signal in a time slot of a frame, wherein the time slots have variable lengths. The signal having a first portion and a second portion, wherein the first portion and the second portion are located in defined time regions in the slot. Further, the first portion having data and a multiplexed first pilot, wherein the multiplexed first pilot is derived from a pseudo random sequence, the second portion having a pilot sequence and a cyclic prefix. The wireless device transmits the produced signal in the time slot.