Closed-Loop CSMA Handshaking for MU-MIMO Hidden Node Coordination
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Solution Overview
Problem
Existing carrier sense multiple access (CSMA) schemes in wireless networks face challenges in efficiently scheduling multiple user equipment (UE) devices due to independent LBT processes, leading to hidden node problems and reduced spectral efficiency and user throughput.
Innovation Solution
Implementing closed loop CSMA with multiuser RTS/CTS handshaking, where a base station coordinates carrier sensing across multiple UEs and reports results to optimize MU-MIMO transmissions, using licensed and unlicensed spectrum jointly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If independent carrier sensing is performed by each mobile device, then device autonomy is maintained, but spectral efficiency deteriorates due to hidden node problems and uncoordinated transmissions
Solution Approach 1:
The base station acts as an intermediary that coordinates carrier sensing operations. It sends RTS signals to multiple user equipment, collects CCA results from each device, and schedules transmissions based on aggregated channel state information. This mediator approach resolves the hidden node problem while maintaining device autonomy through centralized coordination.
2Reliability
If traditional CSMA handshaking is used, then channel access coordination is achieved, but latency increases due to sequential single-user RTS/CTS exchanges
Solution Approach 1:
Multiple individual RTS/CTS handshaking sequences are merged into a single coordinated multi-user handshaking process. The base station simultaneously manages carrier sensing for multiple users, aggregates their CCA results, and schedules transmissions in a unified manner, eliminating the need for sequential single-user exchanges and reducing overall latency.
3Reliability
If base stations perform centralized spectrum allocation, then interference coordination is improved, but system complexity increases due to information collection and processing requirements
Solution Approach 1:
The centralized spectrum allocation function is segmented into distributed carrier sensing operations performed by each user equipment. Each device independently performs CCA on the unlicensed channel and reports results to the base station. This segmentation reduces system complexity by distributing the sensing burden while the base station maintains centralized coordination for interference management.
Data Source
AI summary
A closed loop carrier sense multiple access multiuser request to send and clear to send handshaking system is provided to efficiently allocate licensed and unlicensed spectrum for a plurality of mobile devices and across different base stations and mobile network operators. A user equipment device can be connected to a base station device via a first frequency in licensed spectrum, and a second frequency in unlicensed spectrum. The air interface on the first frequency can then be used to coordinate physical and virtual carrier sensing on a second frequency among a plurality of user equipment devices. Moreover, carrier sensing results from a plurality of UEs can be reported a base station device via the first frequency in licensed spectrum. The base station device can then schedule multiple user multiple input, multiple output (MU-MIMO) transmissions to a plurality of UEs on the second frequency in unlicensed spectrum.