E-PDCCH HARQ-ACK Resource Allocation to Prevent PUCCH Collisions
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Solution Overview
Problem
Current wireless communication systems, particularly in LTE Rel. 8 to 10, face limitations in downlink spectral efficiency and HARQ-ACK resource allocation, especially with the introduction of 8-antenna systems and dual-polarized antenna arrays, leading to potential collisions and reduced reliability in HARQ-ACK transmissions.
Innovation Solution
The implementation of an enhanced physical downlink control channel using DMRS-based transmit diversity and a new mechanism for determining HARQ-ACK resources, which avoids collisions by dynamically configuring PUCCH resources and using a HARQ-ACK resource indicator, ensures reliable HARQ-ACK reception and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ-ACK resources are allocated based on legacy PDCCH methods, then resource allocation is simple, but HARQ-ACK collisions occur and reliability decreases
Solution Approach 1:
The patent introduces a new intermediary entity called the Enhanced Physical Downlink Control Channel (E-PDCCH) that mediates between the downlink data transmission and HARQ-ACK resource allocation. The E-PDCCH carries Downlink Control Information (DCI) that includes a HARQ-ACK Resource Indicator (ARI) field, which acts as a mediator to dynamically indicate the specific PUCCH resource for HARQ-ACK feedback, thereby avoiding collisions that occur with legacy resource allocation methods
Solution Approach 2:
The patent implements dynamic HARQ-ACK resource allocation where the PUCCH resource is not fixed but is dynamically selected based on the ARI field in the E-PDCCH. This dynamic mechanism allows the system to adaptively allocate different PUCCH resources for different users and different transmissions, preventing HARQ-ACK collisions while maintaining reliability
2Productivity
If downlink control channel capacity is increased to support 8-antenna systems, then spectral efficiency improves, but resource allocation complexity and collision risk increase
Solution Approach 1:
The patent segments the downlink control channel into a legacy PDCCH and an enhanced E-PDCCH, where the E-PDCCH is specifically designed to support 8-antenna MIMO systems. The E-PDCCH is further segmented into multiple resource blocks and antenna ports, allowing flexible allocation of control resources that scales with the number of antennas while maintaining manageable complexity through structured resource organization
Solution Approach 2:
The patent introduces a new dimension for control channel resources by defining E-PDCCH resources in terms of enhanced resource blocks (ERBs) and antenna ports, rather than just traditional resource blocks. This dimensional expansion allows the system to support 8-antenna configurations by distributing control information across multiple antenna ports and ERBs, thereby increasing spectral efficiency while managing complexity through structured resource organization
3Reliability
If dynamic PUCCH resource allocation is implemented, then HARQ-ACK collisions are avoided, but signaling overhead increases
Solution Approach 1:
The patent makes the E-PDCCH and its ARI field multi-functional: the E-PDCCH serves both as the downlink control channel for scheduling and as the carrier of the HARQ-ACK resource indication. The ARI field within the DCI serves dual purposes by both scheduling uplink resources and indicating PUCCH resources for HARQ-ACK feedback. This multi-functionality reduces signaling overhead by consolidating multiple control functions into a single channel and message structure
Data Source
AI summary
A method and apparatus of wireless communication between a base station and at least one user equipment. The method includes: transmitting an enhanced physical downlink control channel from the base station to the at least one user equipment using a demodulation reference signal antenna port; transmitting message from the base station to the at least one user equipment which is scheduled by the enhanced physical downlink control channel; receiving the message at the at least one user equipment; determining at the at least one user equipment whether the message was correctly received; and transmitting an ACK/NAK signal on an ACK/NAK resource determined from the enhanced physical downlink control channel from the at least one user equipment to the base station indicating whether the message was correctly received by the at least one user.