SBFD PRACH Mask Index Indication for Lower-Latency Access
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Solution Overview
Problem
In 5G NR networks, conventional TDD operation limits random access channel (PRACH) preamble transmissions to uplink slots, leading to increased latency in accessing the network, as downlink slots are not suitable for PRACH transmission.
Innovation Solution
A method for a WTRU to receive RACH configuration, including power thresholds and resource selection criteria, allowing PRACH transmissions in uplink subbands, enabling PRACH preamble transmissions in both uplink and downlink slots through subband non-overlapping full duplex (SBFD) operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PRACH transmissions are restricted to uplink slots only in conventional TDD operation, then interference between uplink and downlink is avoided, but network access latency increases
Solution Approach 1:
The patent segments the frequency spectrum into multiple subbands, allowing different subbands to be used for different transmission directions simultaneously. Specifically, certain subbands are designated for uplink PRACH transmissions while other subbands continue downlink transmissions, enabling parallel operation without full-duplex interference. This frequency-domain segmentation resolves the contradiction by allowing PRACH transmissions in what would traditionally be downlink slots while maintaining interference avoidance through subband isolation.
Solution Approach 2:
The patent transitions from time-division multiplexing (TDD) where uplink and downlink are separated in time to a hybrid approach that introduces frequency-domain dimensioning. By allocating specific frequency subbands for uplink PRACH transmissions within the overall TDD framework, the system adds a frequency dimension to the traditional time-based separation, enabling simultaneous uplink and downlink operations in different frequency resources without increasing time latency.
2Loss of time
If PRACH transmissions are allowed in downlink slots through SBFD operation, then network access latency is reduced, but complexity of resource management increases
Solution Approach 1:
The patent applies local quality by configuring specific subbands with particular properties for PRACH transmissions. Instead of uniformly allowing PRACH transmissions across the entire frequency spectrum in downlink slots, the system designates specific local frequency regions (subbands) with appropriate characteristics for random access. This localized approach simplifies resource management by providing clear, specific configurations for PRACH subbands rather than requiring complex global resource coordination.
Solution Approach 2:
The patent introduces new configuration parameters specifically for SBFD operation, including subband offset indicators, subband size configurations, and PRACH mask indices tailored for frequency-division multiplexed random access. These parameter changes enable precise control over which frequency subbands are available for PRACH transmissions in downlink slots, making the resource management complexity manageable through standardized configuration parameters rather than ad-hoc resource allocation.
3Device complexity
If conventional TDD operation is used with PRACH only in uplink slots, then implementation simplicity is maintained, but network capacity is limited
Solution Approach 1:
The patent makes the downlink slots multi-functional by enabling them to serve both traditional downlink transmission purposes and PRACH transmission purposes through frequency-division multiplexing. By configuring specific subbands within downlink slots for PRACH transmissions, the system allows downlink slots to fulfill multiple functions simultaneously: general downlink data transmission in some subbands and random access transmissions in other subbands. This increases network capacity without requiring completely new slot structures, maintaining implementation simplicity while enhancing functionality.
Data Source
AI summary
A method performed by a WTRU may include receiving a random access channel (RACH) configuration indicating a plurality of RACH occasions. The RACH occasions within respective subsets are frequency division multiplexed. The method includes receiving configuration information indicating at least one transmit power threshold and information indicating resources associated with a mode of operation, and receiving criteria for selecting a RACH occasion that defines a group of RACH occasions from at least one subset that overlap with at least one uplink subband. The method includes sending a preamble transmission using a calculated transmit power in a selected RACH occasion, wherein, on a condition the calculated transmit power exceeds the transmit power threshold, the selected RACH occasion is selected from the defined group of the plurality of RACH occasions that overlap with the at least one uplink subband.