Downlink Pilot Transmission Orthogonal Sequence Configuration
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Solution Overview
Problem
In the 3GPP Long Term Evolution-Advanced (LTE-A) system, the power of dedicated pilots across different OFDM symbols varies due to the use of Walsh codes, affecting orthogonality and channel estimation.
Innovation Solution
Dedicated pilots are transmitted in the Code Division Multiplexing (CDM) mode or hybrid CDM and Frequency Division Multiplexing (FDM) mode, with orthogonal sequence sets configured over resources according to a preset frequency-domain granularity and rule, ensuring the same sequence set is used for each frequency-domain granularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Walsh codes are adopted as pilots in the CDM mode, then orthogonality between pilots of multiple streams is ensured, but the power sum of pilots over different OFDM symbols differs causing power variation across OFDM symbols
Solution Approach 1:
The patent applies local quality by making the orthogonal sequence configuration frequency-dependent. Different frequency-domain granules (subcarriers or resource blocks) are assigned different orthogonal sequence sets, allowing the system to maintain orthogonality locally while balancing power distribution across different OFDM symbols through frequency-selective sequence assignment
Solution Approach 2:
The patent changes the parameter of orthogonal sequence configuration from a uniform system-wide setting to a frequency-selective setting. By varying the orthogonal sequence sets across different frequency-domain granules, the system dynamically adjusts the pilot characteristics to achieve both orthogonality and power stability across multiple OFDM symbols
Data Source
AI summary
A method, apparatus and system for downlink pilot transmission solve the problem of power differences among OFDM symbols caused by Walsh Codes. The transmission method is that dedicated pilots are transmitted in the manner of code division multiplexing (CDM) or hybrid of CDM and frequency division multiplexing (FDM), wherein the dedicated pilots are configured with orthogonal sequence sets according to a preset frequency-domain granularity and rules on the resources for transmitting the dedicated pilots, and the same orthogonal sequence set is employed for the dedicated pilots in each frequency-domain granularity.