Listen-Before-Talk Channel Reservation for Millimeter Wave Systems
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Solution Overview
Problem
Millimeter wave (mmW) systems face challenges in providing effective channel reservation messages across different radio frequency spectrum bands, leading to interference and reduced data rates due to varying coverage areas and limited transmission capabilities.
Innovation Solution
Implementing a listen-before-talk (LBT) procedure on a sub-6 GHz band to reserve channels, allowing user equipment (UE) to transmit a channel reservation signal on a mmW band, which helps neighboring devices to backoff and reduce interference, enabling efficient downlink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If channel reservation messages are transmitted on the same RF spectrum band as downlink transmissions, then coverage area is maximized, but interference increases and data rates decrease
Solution Approach 1:
The system segments the communication function by separating downlink transmission (on mmW band for coverage) from channel reservation signaling (on sub-6 GHz band for interference avoidance). The UE performs LBT and transmits channel reservation messages on a different RF spectrum band than the downlink transmission band, thus achieving both wide coverage and low interference.
2Reliability
If LBT procedure is performed on mmW band, then channel clearance is ensured, but transmission capacity is reduced due to band limitations
Solution Approach 1:
The system adds a frequency dimension to the LBT procedure by performing listen-before-talk on sub-6 GHz band rather than on the mmW band itself. This allows the UE to ensure channel clearance for mmW downlink reception while utilizing the sub-6 GHz band for reservation signaling, thereby maintaining both reliability and transmission capacity.
3Adaptability or versatility
If cross band pairing is implemented, then communication flexibility is improved, but channel reservation complexity increases
Solution Approach 1:
The UE acts as an intermediary that receives downlink transmissions on mmW band from the serving base station while performing LBT and transmitting channel reservation messages on sub-6 GHz band. This intermediary approach enables cross-band operation where the UE coordinates between two different RF spectrum bands, achieving communication flexibility while managing reservation complexity through standardized LBT procedures.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A method may include receiving, from a base station, a pre-grant message indicating that a downlink transmission is available for transmission to a user equipment (UE) on a first radio frequency (RF) spectrum band, and performing a listen-before-talk (LBT) procedure. The UE may then transmit, based on the LBT procedure indicating a clear channel, a channel reservation signal on a second RF spectrum band, and transmit, to the base station, a response to the pre-grant message on the second RF spectrum band. Another method may include a base station transmitting a pre-grant message to the UE, and receiving a response to the pre-grant message on a second RF spectrum band. The base station may then transmit the downlink transmission to the UE using one or more of a set of transmit beams on a first RF spectrum band.