HARQ Feedback Timing Across Multi-RAT Networks
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Solution Overview
Problem
In wireless communication systems using multiple radio access technologies like LTE and HSPA, there is a challenge in transmitting feedback information such as HARQ ACK/NAK and CQI reports across different RATs with varying subframe timings and transmission time intervals, leading to congestion and performance imbalances due to the lack of a method for uplink carrier configuration for secondary RATs.
Innovation Solution
A method in user equipment and radio base stations to determine the timing of HARQ responses by mapping virtual uplink timing from secondary RATs to primary RATs, allowing for the transmission of feedback information on the primary RAT uplink, even if the secondary RAT is not configured with an uplink carrier, using techniques like bundling responses and adjusting timing based on drift thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spectrum is partitioned to different technologies (e.g., 10 MHz for HSPA and 10 MHz for LTE), then both technologies can be deployed simultaneously, but peak rates are limited and load imbalance occurs
Solution Approach 1:
The patent combines HSPA and LTE carriers into a unified carrier aggregation framework where resources from both RATs are pooled together. This allows the system to achieve peak rates comparable to having all spectrum available to a single technology, while maintaining the ability to support both HSPA and LTE deployments simultaneously through resource sharing and coordinated scheduling.
2Ease of operation
If HSPA carriers are allocated more bandwidth to handle loaded traffic, then load balancing improves, but LTE carriers receive less spectrum and cannot offer competitive performance
Solution Approach 1:
The patent implements dynamic resource allocation across HSPA and LTE carriers based on real-time traffic conditions and channel quality. The system can flexibly adjust the amount of spectrum and processing resources assigned to each RAT, allowing LTE to receive more resources when traffic is light while maintaining load balancing capabilities when HSPA carriers are congested.
3Reliability
If feedback timing is determined separately for each RAT, then timing requirements for each technology are met, but timing misalignment causes feedback transmission conflicts and increased complexity
Solution Approach 1:
The patent establishes a universal feedback timing mechanism that works across both HSPA and LTE carriers. By defining a common reference point and standardized timing relationships that apply to all carrier types, the system ensures timing guarantees are met for both RATs while using a single coordinated approach rather than separate timing mechanisms for each technology.
Data Source
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AI summary
The invention relates to a method in a user equipment 4 for determination of timing of a Hybrid Automatic Repeat re-Request, HARQ, response. The user equipment 4 operates in a communication network 1 comprising a primary radio access technology system 2 and a secondary radio access technology system 3. The user equipment 4 receives on at least one downlink carrier on the first radio access technology system 2 and on at least one downlink carrier on the second radio access technology system 3. The method comprises determining a downlink timing related to the secondary radio access technology system 3; determining an uplink timing related to the primary radio access technology system 2; and determining an uplink time instance for transmission of the HARQ response on an uplink carrier of the primary radio access technology system 2, wherein the HARQ response relates to data received on the downlink carrier on the secondary radio access technology system 3 and wherein the uplink time instance for transmission of the HARQ response is based on an uplink timing for a HARQ response on the secondary radio access technology system 3 and the downlink timing related to the secondary radio access technology system 3. The invention also relates to user equipment, radio base stations and methods therein.