Dynamic Relay Control Channel Allocation in LTE Inband Relaying
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Solution Overview
Problem
Inband relaying in LTE-Advanced systems faces interference issues due to simultaneous transmission and reception on the same frequency resource, necessitating signal isolation and design restrictions in the relay control structure, particularly with the use of MBSFN sub-frames which prevent relay nodes from receiving the PDCCH channel from the donor eNB.
Innovation Solution
The implementation of dynamic and semi-static resource allocation methods for embedding relay control data within the PDSCH portion of the base station's sub-frame, using new control channels like PRCFICH, PRHICH, and PRDCCH, which dynamically allocate resources based on the number of relay stations and channel conditions, allowing for efficient communication without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If inband relaying is used where the eNodeB-to-relay link and relay-to-UE link share the same frequency band, then spectrum efficiency is improved, but self-interference occurs between simultaneous transmission and reception
Solution Approach 1:
The patent segments the sub-frame structure into distinct time regions: MBSFN sub-frames for eNodeB-to-relay communication and non-MBSFN sub-frames for relay-to-UE communication. This temporal segmentation allows the relay node to separately handle backhaul and access link transmissions without mutual interference, while still operating in the same frequency band.
Solution Approach 2:
The patent implements periodic alternation between MBSFN sub-frames and non-MBSFN sub-frames in a configured pattern. This periodic switching enables the relay node to systematically alternate between receiving from eNodeB and transmitting to UEs, ensuring that transmission and reception never occur simultaneously on the same frequency resource.
2Object-affected harmful factors
If MBSFN sub-frames are used to create gaps in relay-to-UE transmission for receiving from eNodeB, then interference is avoided, but the relay cannot read the PDCCH of the donor cell requiring a new control channel
Solution Approach 1:
The patent introduces a new relay-specific physical downlink control channel (PDCCH) that acts as an intermediary control mechanism. This new control channel is specifically designed for relay nodes and is transmitted during MBSFN sub-frames, enabling relay nodes to receive control information without needing to access the standard PDCCH that is unavailable during backhaul reception.
Solution Approach 2:
The patent implements dynamic resource allocation for the new relay control channel within the PDSCH portion of MBSFN sub-frames. The control channel resources are dynamically configured based on the number of relay stations and channel conditions, allowing flexible adaptation to varying network requirements while maintaining sub-frame structure compatibility.
Data Source
Figure 1~2a
Figure 2b
Figure 3~4b
AI summary
A relay communications system is described in which a base station is able to dynamically vary or semi-statically vary the number of resource blocks used to carry relay control data within a transmitted sub-frame. Default resource blocks are used to include a first part of the control data and if additional control data is provided, then the first part of the control data identifies that there is additional control data and provides information to allow the additional data to be located within the sub-frame.