C-V2X Subframe Resource Allocation for Half-Duplex Conflict Avoidance
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Solution Overview
Problem
The existing C-V2X resource allocation schemes, such as Mode 4 of the LTE sidelink PC5 interface, fail to consider the utilization of other resources in the same subframe, leading to potential transmission conflicts and reception degradation due to half-duplex and near-far problems, where devices cannot receive transmissions in the same subframe and strong signals overpower weaker ones.
Innovation Solution
A method for allocating C-V2X radio resources that determines whether transmitting in a subframe is likely to cause reception degradation, excluding all resources in the subframe if necessary, and iteratively adjusting energy thresholds to ensure sufficient resources are available, considering half-duplex and near-far problems, and accounting for significant allocation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If resources are allocated individually without considering other resources in the same subframe, then resource allocation simplicity is maintained, but transmission conflicts and reception degradation occur due to half-duplex and near-far problems
Solution Approach 1:
The patent merges the evaluation of multiple resources within the same subframe by introducing a subframe-level metric that aggregates resource utilization across frequency. This allows the system to treat resources in the same subframe as a combined entity, preventing half-duplex conflicts by identifying subframes where multiple transmissions would occur and selecting alternative subframes instead.
Solution Approach 2:
The patent transitions from evaluating resources individually in the frequency dimension to evaluating entire subframes by introducing a time dimension perspective. By assessing subframe-level resource utilization and selecting subframes based on overall occupancy rather than individual resource availability, the system resolves near-far problems by avoiding subframes with multiple simultaneous transmissions.
2Productivity
If a device transmits in a subframe, then transmission capability is utilized, but the device is disabled from receiving transmissions in that same subframe due to half-duplex limitation
Solution Approach 1:
The patent segments the resource selection process into two independent stages: first selecting a subframe based on overall subframe-level metrics that account for half-duplex constraints, then selecting specific resources within that subframe. This segmentation ensures that transmission and reception capabilities are properly managed by choosing subframes where the device will primarily transmit, avoiding simultaneous reception attempts.
3Productivity
If multiple devices transmit in the same subframe, then channel utilization is improved, but receiving devices cannot receive all transmissions due to dynamic range limitations from near-far problems
Solution Approach 1:
The patent implements feedback mechanisms where devices monitor subframe-level resource utilization and adjust their resource selection accordingly. By continuously assessing which subframes have low overall occupancy and preferentially selecting those subframes, the system feedback-loop prevents multiple devices from simultaneously transmitting in the same subframe, thereby avoiding near-far problems while maintaining efficient channel utilization.
Data Source
AI summary
Methods and apparatuses are provided for allocating cellular vehicle-to-everything (C-V2X) radio transmission resources for transmitting messages in a C-V2X network from amongst a pool of initial resources from within a plurality of subframes. For each subframe in the plurality of subframes, it is determined whether transmitting in the subframe is likely to cause reception degradation with other C-V2X messages being transmitted in the network, and if yes, all resources in the subframe are excluded prior to allocating a resource for transmission.