Clear Channel Assessment Timing for Shared Spectrum Access
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Solution Overview
Problem
Conventional clear channel assessment (CCA) procedures in wireless communication systems operating in shared or unlicensed radio frequency spectrum bands are inefficient and do not provide suitable flexibility for capturing and reserving the medium for transmissions, particularly in millimeter wave networks, often requiring lengthy or inappropriate procedures for each device.
Innovation Solution
Implementing enhanced clear channel assessment (eCCA) techniques, including transmitter-based energy detection procedures such as extended and one-shot CCA, allowing base stations and user equipment (UEs) to perform CCA during gaps between control and data transmissions, enabling flexible medium reservation for downlink and uplink communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LBT procedure is performed by both devices before transmitting, then channel access is ensured, but transmission efficiency is reduced and time is wasted
Solution Approach 1:
The patent applies preliminary action by having the first device perform CCA and obtain clearance before the second device transmits. The first device performs CCA in advance (during gap period or before control signal transmission) to determine channel availability, and only if clear does it proceed to transmit control signal and data. This eliminates the need for the second device to perform separate CCA, resolving the contradiction by ensuring channel access assurance through preliminary channel checking while improving transmission efficiency by eliminating redundant CCA operations.
2Reliability
If extended CCA procedure is performed to capture medium, then medium reservation is achieved, but transmission time is delayed
Solution Approach 1:
The patent segments the CCA procedure into two distinct types: extended CCA procedure for initial medium capture and one-shot CCA procedure for subsequent transmissions within transmission opportunity. The extended CCA is performed only when needed to establish initial medium reservation, while one-shot CCA is used for faster subsequent access. This segmentation allows the system to achieve reliable medium reservation when necessary while minimizing transmission delays by using faster CCA procedures for ongoing communications.
Solution Approach 2:
The patent implements dynamics by allowing the CCA procedure type to change based on transmission context. The system dynamically selects between extended CCA (for initial medium capture) and one-shot CCA (for subsequent transmissions) based on whether the device needs to establish new transmission opportunity or continue within existing opportunity. This dynamic adaptation resolves the contradiction by providing robust medium reservation capability through extended CCA when needed while reducing delays through one-shot CCA for ongoing transmissions.
3Speed
If one-shot CCA procedure is performed for scheduled transmission, then transmission speed is improved, but channel availability is not guaranteed
Solution Approach 1:
The patent applies preliminary action by performing extended CCA procedure before the transmission opportunity begins to establish initial channel availability and medium reservation. This preliminary extended CCA ensures that the channel is clear and reserved before the faster one-shot CCA procedures are executed for scheduled transmissions within that opportunity. This resolves the contradiction by guaranteeing channel availability through preliminary extended CCA while enabling faster one-shot CCA procedures to maintain high transmission speed during the reserved opportunity.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. A base station may transmit to a user equipment (UE) a control signal comprising a grant for a downlink transmission. The base station may perform, during a gap between the control signal and the downlink transmission, a clear channel assessment (CCA) procedure on a shared radio frequency spectrum band associated with the downlink transmission. The base station may perform, based at least in part on a success of the CCA procedure, the downlink transmission to the UE over the shared radio frequency spectrum band.