HARQ Process Management in LTE-A Relay Networks
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Solution Overview
Problem
Current wireless communication systems, particularly in 3GPP LTE-A, lack a method for performing Hybrid Automatic Repeat Request (HARQ) processes between a relay and an evolved Node B (eNB) and between the eNB and a User Equipment (UE), which is essential for reliable data transmission due to channel state variations and errors.
Innovation Solution
The implementation of a method to determine and signal the number of HARQ processes, including the use of virtual subframe indexes and exclusion of non-MBSFN subframes, to manage HARQ processes between the relay and the eNB, and between the eNB and the UE, ensuring efficient data transmission and retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a relay is introduced into the 3GPP LTE-A system to extend coverage and improve network capacity, then the network coverage and capacity are enhanced, but the system lacks defined HARQ processes between the relay and eNB and between the eNB and UE, leading to unreliable data transmission
Solution Approach 1:
The patent introduces a relay node as an intermediary between the eNB and UE, enabling extended coverage while establishing separate HARQ processes for backhaul link (eNB-relay) and access link (relay-UE). This mediator approach allows the relay to perform HARQ operations independently on each link, ensuring transmission reliability despite the added complexity of multi-hop communication.
2Reliability
If HARQ processes are implemented between relay and eNB with separate backhaul and access links, then transmission reliability is improved, but the complexity of determining HARQ process numbers and subframe allocations increases
Solution Approach 1:
The patent segments the communication system into two independent HARQ processes: one for the backhaul link (eNB-relay) and another for the access link (relay-UE). Each HARQ process is independently managed with separate process numbers, timing relationships, and subframe allocations. This segmentation allows the relay to handle HARQ operations on each link independently, reducing the overall management complexity compared to a unified approach.
Solution Approach 2:
The patent enables dynamic configuration of HARQ process parameters, including the number of HARQ processes, subframe offsets, and timing relationships, through higher-layer signaling. This dynamic adaptability allows the system to optimize HARQ operations based on varying channel conditions and traffic requirements, improving reliability without requiring fixed, overly complex predetermined configurations.
3Productivity
If separate HARQ timing relationships are established for backhaul and access links, then transmission efficiency is improved, but the difficulty of coordinating subframe allocations and determining HARQ process IDs increases
Solution Approach 1:
The patent establishes preliminary timing relationships and subframe offset configurations through higher-layer signaling before actual data transmission begins. The eNB and relay pre-agree on HARQ process numbers, subframe offsets, and timing relationships, which are then used for automatic HARQ operations. This preliminary configuration reduces the real-time coordination complexity during actual transmission, improving efficiency while managing the coordination difficulty through advance planning.
Solution Approach 2:
The patent introduces an additional dimension of control by separating HARQ process management into independent backhaul and access link processes, each with its own timing relationships and process identifiers. This dimensional separation allows simultaneous independent optimization of both links without interference, improving overall transmission efficiency while managing coordination complexity through structured multi-dimensional control parameters.
Data Source
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AI summary
The present description relates to a method for performing a HARQ process operation in a wireless communication system and to an apparatus using the method. A base station device which performs a HARQ process operation comprises a transmitter which transmits to a relay an uplink (UL) grant in a downlink backhaul subframe n which is a subframe having an index n among the allocated downlink backhaul subframes, and transmits, if downlink data sent from the relay in accordance with the uplink grant is not successfully received, a non-acknowledgement (NACK) signal in a downlink backhaul subframe n+N which is a downlink backhaul subframe that comes after N which is a predetermined number of HARQ processes counted from the downlink backhaul subframe n among the allocated downlink backhaul subframes.