ePHICH Resource Mapping to Distributed ePDCCH for Interference Reduction
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Solution Overview
Problem
In LTE systems, there is a need for an efficient method to transmit Hybrid Automatic Repeat Request (HARQ) indication information, particularly in New Carrier Type (NCT) cells, where existing designs struggle with allocating enhanced Physical HARQ Indication Channel (ePHICH) resources, especially in Carrier Aggregation systems, leading to interference and reduced frequency diversity gain.
Innovation Solution
The method involves mapping ePHICH resources to a portion of time-frequency resources of a distributed enhanced Physical Downlink Control Channel (ePDCCH) set, allowing ePHICH to be transmitted in a frequency division multiplex manner with PDSCH, and using DMRS for demodulation, ensuring frequency diversity and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ePHICH resources are allocated in NCT cells using existing LTE designs, then HARQ indication can be transmitted, but interference increases and frequency diversity gain is reduced
Solution Approach 1:
The patent maps ePHICH resources to the time-frequency resources of distributed ePDCCH sets, transitioning from traditional PHICH resource allocation to a new dimensional mapping approach. This allows ePHICH to utilize the time-frequency structure of ePDCCH, achieving frequency diversity through distributed resource allocation across multiple physical resource blocks while reducing interference through orthogonal resource separation.
Solution Approach 2:
The patent divides ePHICH resources across multiple distributed ePDCCH set resources, segmenting the HARQ indication transmission across different time-frequency locations. This segmentation provides frequency diversity gain by distributing the signal across multiple independent fading channels, ensuring reliable reception even when some resources experience poor channel conditions.
2Reliability
If ePHICH resources are mapped to distributed ePDCCH set, then frequency diversity is improved, but device complexity increases
Solution Approach 1:
The patent makes the distributed ePDCCH set serve multiple functions: it carries both ePDCCH control information and ePHICH HARQ indications. This multi-functionality reduces the need for separate dedicated PHICH resources, simplifying overall resource allocation while maintaining frequency diversity through the distributed structure already present in ePDCCH design.
Solution Approach 2:
The system utilizes the existing distributed resource structure of ePDCCH for ePHICH transmission, allowing the ePDCCH framework to serve itself for multiple purposes. The UE leverages its existing ePDCCH detection capabilities to also detect ePHICH information, eliminating the need for separate complex detection mechanisms and reducing overall device complexity.
3Productivity
If ePHICH is transmitted in frequency division multiplex manner with PDSCH, then spectrum utilization is improved, but detection difficulty increases
Solution Approach 1:
The patent uses DMRS (Demodulation Reference Signal) as an intermediary to facilitate the detection of ePHICH information transmitted in frequency division multiplex with PDSCH. The DMRS provides channel estimation and demodulation support, enabling the UE to accurately detect ePHICH signals even when multiplexed with data channels, thereby maintaining detection performance while improving spectrum utilization.
Solution Approach 2:
The patent changes the transmission parameters of ePHICH by mapping it to ePDCCH resources with specific time-frequency locations and using DMRS-based demodulation. This parameter change allows ePHICH to be transmitted efficiently in the data region alongside PDSCH, improving spectrum utilization while the altered transmission characteristics maintain detectability through the DMRS assistance.
Data Source
AI summary
A method and an apparatus for transmitting Hybrid Automatic Repeat reQuest (HARQ) indication information are provided. The method includes transmitting, by a UE, uplink data on a Physical Uplink Shared CHannel (PUSCH) according to scheduling of a base station; detecting, by the UE, a new UpLink (UL) grant and enhanced Physical HARQ Indication CHannel (ePHICH) information of the base station for the uplink data according to a synchronous HARQ timing relationship, wherein ePHICH resources used for bearing the ePHICH information are mapped to a portion of time-frequency resources of a distributed enhanced Physical Downlink Control CHannel (ePDCCH) set; and if the UL grant is not detected, the UE retransmitting the uplink data or not transmitting the uplink data according to an indication of the ePHICH information.