Coordinated HARQ Transmission for LTE Base Stations
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Solution Overview
Problem
Current coordinated transmission systems in LTE advanced technology face challenges in implementing Hybrid Automatic Repeat Request (HARQ) processes effectively between distributed base stations, particularly in managing communication systems for user data and channel data timing, which is not addressed in existing MIMO technologies.
Innovation Solution
The system designs a coordinated downlink HARQ transmission system where two eNodes-B operate in scenarios that ensure simultaneous and synchronized delivery of new and retransmission data packets to mobile terminals, utilizing successive interference cancellation and X2 interface for efficient data management between serving and coordinated base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coordinated transmission is implemented between distributed base stations, then diversity gain and system performance are improved, but HARQ process management and timing synchronization become complex
Solution Approach 1:
The patent segments the HARQ process into distinct functional components: ACK/NAK signal generation at the terminal, X2 interface communication between base stations, and coordinated retransmission execution. This segmentation allows each component to be managed independently, reducing overall system complexity while maintaining diversity gain benefits
Solution Approach 2:
The X2 interface acts as an intermediary mechanism between distributed base stations, enabling standardized information exchange for HARQ processes. This intermediary layer simplifies coordination by providing a defined protocol for sharing ACK/NAK signals and retransmission status, reducing the complexity of direct peer-to-peer coordination
2Productivity
If simultaneous transmission of new and retransmission data packets is implemented, then throughput is improved, but interference management and timing synchronization become challenging
Solution Approach 1:
The patent implements preliminary timing alignment by establishing synchronized transmission schedules between coordinated base stations before data transmission begins. Retransmission packets are pre-coordinated with new data packets to ensure they arrive at the terminal simultaneously, eliminating timing synchronization challenges during actual transmission
Solution Approach 2:
The system dynamically adjusts transmission parameters including timing offsets and power levels for coordinated base stations. By changing these parameters based on channel conditions and traffic requirements, the system achieves both high throughput and proper timing synchronization without manual intervention
3Reliability
If HARQ retransmission is coordinated between multiple base stations, then error rate is reduced, but data management and control signaling overhead increase
Solution Approach 1:
The patent merges HARQ retransmission control into the existing LTE downlink control framework. ACK/NAK signals and retransmission commands are combined with regular downlink control information, eliminating separate control channels and reducing overall signaling overhead while maintaining low block error rates through coordinated retransmission
Data Source
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AI summary
A wireless communication system in which a plurality of wireless base station devices comprising a first wireless base station device and a second wireless base station device perform a coordinated transmission process to a wireless terminal device, wherein: the first wireless base station device includes a transmission unit that transmits to the wireless terminal device a first control channel which indicates new data or retransmission data; and the wireless terminal device includes: a control channel reception unit that receives the first control channel transmitted from the first wireless base station device; a data reception unit that is capable of receiving not only data transmitted from the first wireless base station device but also data coordinately transmitted from the second wireless base station device using a resource which is indicated by the first control channel received by the control channel reception unit; a control channel transmission unit that transmits a second control channel related to a retransmission of the data received by the data reception unit to at least the first wireless base station; and a reception control unit that controls Hybrid Automatic Repeat reQuest (HARQ) process for data coordinately transmitted by at least the first wireless base station device and the second wireless base station device based on the first control channel which is generated corresponding to the second control channel transmitted by the control channel transmission unit.