LAA RTS CTS Multiplexing for Unlicensed Spectrum Reservation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LTE LAA systems face inefficiencies and high latency in channel reservation due to the limitations of existing RTS/CTS mechanisms, particularly in handling multiple UEs and unlicensed spectrum access, which hinders the effective use of unlicensed spectrum for data transmission.
Innovation Solution
The implementation of a modified LAA RTS/CTS procedure that allows for multiplexing of physical resources across multiple UEs, reducing latency by transmitting RTS and CTS signals in unlicensed spectrum without adhering to licensed band timing constraints, and utilizing multiplexed CTS signals that span only one or a fractional OFDM symbol, enabling efficient channel reservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional LTE timing constraints are applied to RTS/CTS signaling in unlicensed spectrum, then reliability of licensed band communication is maintained, but channel reservation latency increases and spectrum utilization efficiency deteriorates
Solution Approach 1:
The patent changes the timing parameters of RTS/CTS signaling from licensed band constraints (minimum 4ms) to unlicensed band optimized timing (can be completed within one subframe). This involves modifying the duration and scheduling of RTS and CTS messages to accommodate the shorter time available in unlicensed spectrum opportunities, thereby reducing latency and improving spectrum utilization.
Solution Approach 2:
The patent introduces dynamic timing adjustment for RTS/CTS procedures based on unlicensed spectrum availability. Instead of fixed timing constraints, the system adapts the timing of RTS and CTS messages to match the opportunistic nature of unlicensed spectrum access, allowing faster channel reservation when spectrum is available and improving overall efficiency.
2Reliability
If RTS/CTS procedure is implemented for each UE individually in unlicensed spectrum, then channel reservation reliability is improved, but signaling overhead and system complexity increase
Solution Approach 1:
The patent merges multiple RTS/CTS procedures into a single unified procedure for multiple UEs. Instead of executing separate RTS/CTS exchanges for each UE, the system performs one RTS message that can address multiple UEs and collects CTS responses from them, thereby maintaining channel reservation reliability while significantly reducing signaling overhead and complexity.
Solution Approach 2:
The patent makes the RTS message universal by enabling it to serve multiple UEs simultaneously. The RTS message structure is designed to accommodate multiple destination UEs, and the CTS response mechanism is adapted to handle responses from multiple sources, creating a multi-functional channel reservation procedure that reduces overall signaling requirements.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Spectrum reservation circuitry for use in a source electronic device (e.g. eNB or UE) of a wireless communication system is provided. The availability of an unlicensed carrier for use is checked by control circuitry of the source device and a License Assisted Access (LAA) Request to Send signal is transmitted on an unlicensed carrier if it is determined to be available for use. Receive circuitry is configured to receive on an unlicensed carrier, from a destination electronic device an LAA Clear to Send signal in response, depending upon availability of the unlicensed channel at the destination. Corresponding spectrum reservation circuitry is provided for use in a destination device, comprising transmit circuitry to transmit the LAA Clear to Send signal. A corresponding computer program product is provided on a non-transitory medium.