Time-Domain CDM for LTE-Advanced CQI Feedback
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Solution Overview
Problem
The existing 3GPP LTE system faces challenges in effectively accommodating the increased demand for channel quality indicator (CQI) feedback in LTE-Advanced systems, particularly due to high overhead in Rel-8 PUCCH CQI transmission mode, which limits the number of UEs that can transmit CQI information concurrently.
Innovation Solution
Implementing a time-domain code division multiple access (CDM) mode where multiple user equipments (UEs) transmit their CQI information on the same time-frequency resource, using orthogonal time-domain frequency-spreading codes to enable efficient transmission of varying sizes of CQI blocks without frequency hopping or with frequency hopping, allowing multiple UEs to share the same resource blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple UEs transmit CQI concurrently on PUCCH using CDM mode, then the number of supported UEs is limited to 12, but the CQI feedback overhead increases when more UEs need to transmit
Solution Approach 1:
The patent transitions from frequency-domain CDM (FD-CDM) to time-domain CDM (TD-CDM) by applying orthogonal sequences in the time domain across multiple slots. This dimensional shift allows more UEs to share the same physical resource blocks by utilizing the time dimension, thereby increasing the number of supported UEs while maintaining efficient resource utilization and reducing feedback overhead.
Solution Approach 2:
The patent changes the spreading factor parameter from traditional frequency-domain implementation to time-domain implementation with different orthogonal sequence lengths (e.g., 2, 4, 8). By adjusting the spreading factor and orthogonal sequence parameters in the time domain, the system can accommodate a larger number of UEs transmitting CQI information concurrently on the same time-frequency resources without increasing overhead.
2Adaptability or versatility
If CQI transmission uses Rel-8 PUCCH mode, then the structure is simple, but it cannot accommodate the increased CQI feedback demand in LTE-Advanced systems
Solution Approach 1:
The patent segments the CQI transmission process into multiple time slots, with each slot containing reference signals and data symbols. By dividing the transmission into temporal segments and applying TD-CDM across these segments, the system can support more UEs and larger CQI payloads while maintaining a structured, manageable framework that builds upon the existing Rel-8 PUCCH format.
Solution Approach 2:
The patent creates a universal CQI transmission mechanism that works for both legacy and LTE-Advanced scenarios. The TD-CDM approach using orthogonal sequences in the time domain provides a flexible framework that can accommodate varying CQI payload sizes and support multiple UEs, making the transmission mode adaptable to different system requirements without requiring completely separate mechanisms.
3Productivity
If CQI bits are transmitted without time-domain CDM, then the transmission is simple, but the resource utilization efficiency is low
Solution Approach 1:
The patent merges multiple UEs' CQI transmissions by combining their signals in the time domain using orthogonal sequences. Multiple UEs share the same physical resource blocks simultaneously, with their signals separated at the receiver through correlation with the known orthogonal sequences. This merging approach dramatically improves resource utilization efficiency by allowing concurrent transmissions on the same resources.
Solution Approach 2:
The patent introduces orthogonal sequences as an intermediary mechanism that enables multiple UEs to share the same time-frequency resources. These sequences act as unique identifiers for each UE's transmission, allowing the base station to separate and decode individual CQI messages from the combined signal through correlation operations, thereby achieving efficient multi-user support.
Data Source
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AI summary
Provide are a method, a system and an apparatus for transmitting channel quality indicator information of multiple user terminals. The method includes: at least two user terminals transmit their own channel quality indicator information using the same time and frequency resources, wherein the time and frequency resources include at least one frequency-domain unit in frequency domain and at least two sets of data time-domain units in time domain, each set of data time-domain units including at least two data time-domain units; and the channel quality indicator information of each user terminal is transmitted on at least one set of data time-domain units by means of time-domain Code Division Multiple Address. Therefore, it is possible to adjust the transmitted bits according to size of the channel quality indicator information.