Feedback Resource Mapping in Wireless Ad Hoc Networks
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Solution Overview
Problem
Current wireless communication systems in unlicensed shared bands face inefficiencies in channel access and feedback signaling, particularly in asynchronous and contention-based access, which limits spectrum utilization and is not scalable for ad hoc networks like wireless mobile robotics.
Innovation Solution
The solution involves mapping feedback radio resources from data radio resources, spaced by a predetermined interval, allowing for efficient asynchronous/contention-based access and dynamic spectrum allocation, enabling scalable and minimal control signaling in ad hoc wireless networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If feedback is transmitted on the same resource as data transmission (WLAN approach), then feedback can be sent immediately after data reception, but the entire bandwidth must be reserved for both data and feedback, reducing spectrum utilization efficiency
Solution Approach 1:
The patent segments the frequency spectrum by dividing the unlicensed bandwidth into predetermined channels, with feedback resources mapped to specific cyclic shifts within these channels. This allows data and feedback to occupy different frequency resources simultaneously, resolving the contradiction between immediate feedback transmission and spectrum utilization efficiency
Solution Approach 2:
The patent introduces a new dimension for feedback transmission by mapping feedback resources to cyclic shift values rather than using the same time-frequency resources as data. This dimensional separation enables orthogonal multiplexing of data and feedback signals, allowing both to coexist without interfering with each other's spectrum efficiency
2Adaptability or versatility
If distributed channel access is used in unlicensed bands, then multiple devices can share the channel, but transmitting and receiving devices are not synchronized to a global reference, requiring specific synchronization measures
Solution Approach 1:
The patent makes the synchronization sequences universal by designing them to serve multiple functions: initial synchronization, channel identification, and feedback resource indication. This multi-functionality reduces the need for separate synchronization mechanisms, thereby reducing device complexity while maintaining adaptability for distributed channel access
Solution Approach 2:
The receiving device performs self-synchronization by detecting cyclic shifts in synchronization sequences and autonomously determining feedback resources without requiring complex external coordination. This self-service approach reduces synchronization complexity while enabling multiple devices to share the channel effectively
3Adaptability or versatility
If short transmissions are used in unlicensed bands, then multiple devices can share the channel, but the transmission duration is limited, reducing productivity
Solution Approach 1:
The patent enables continuous useful action by establishing a systematic feedback mechanism that operates continuously across multiple transmission intervals. The feedback resource mapping based on cyclic shifts allows for ongoing acknowledgment and retransmission processes, maintaining continuous data flow and improving overall transmission productivity while preserving channel sharing capability
Data Source
AI summary
In an ad hoc network a feedback radio resource maps from a data radio resource to at least one frequency sub-band which the data resource excludes. The feedback resource is also spaced in time from the data resource by a predetermined interval. Feedback (ACK/NACK) for data received in the data resource is then sent in the feedback resource. In various embodiments the sub-band is one or more edges of the data resource channel, or edges of a component carrier. The predetermined interval may be a function of how much of the data resource is occupied by data. The data transmitting device delays sending its data by a time offset from the end of a previous transmission on that channel, or if it does not know the end time it delays until the predetermined interval plus the length of the feedback resource have lapsed. Various synchronization aspects are also disclosed.