Cross-Carrier RACH Configuration for TDD-FDD Aggregation
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently configuring random access channel (RACH) occasions for carrier aggregation configurations involving both time division duplexing (TDD) and frequency division duplexing (FDD) bands due to differing subcarrier spacings and potential interference, leading to inconsistent scheduling and increased latency.
Innovation Solution
RACH occasions are scheduled based on synchronization signal (SS)/physical broadcast channel (PBCH) blocks of the TDD band, with cross-carrier scheduling and time division multiplexing patterns used to avoid unavailable uplink slots and optimize transmission parameters, including power and retransmission strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate RACH configurations are used for TDD and FDD bands, then each band can be optimized independently, but the system complexity and configuration overhead increase
Solution Approach 1:
The patent applies universality by using a single RACH configuration that works for both TDD and FDD bands. The base station transmits a unified RACH configuration that the UE can use regardless of whether it's operating on TDD or FDD carrier aggregation, eliminating the need for separate configurations and reducing complexity while maintaining band-specific functionality through the unified framework.
2Adaptability or versatility
If RACH occasions are scheduled independently for each carrier, then carrier-specific optimization is achieved, but scheduling consistency and resource utilization deteriorate
Solution Approach 1:
The patent merges the RACH scheduling across multiple carriers by establishing a unified RACH occasion structure that spans TDD and FDD carriers. The base station schedules RACH occasions in a coordinated manner across carriers, ensuring consistent timing and resource allocation while allowing each carrier to maintain its specific characteristics through the unified configuration framework.
3Adaptability or versatility
If RACH procedures are performed on each component carrier, then carrier-specific access is enabled, but access latency and procedure overhead increase
Solution Approach 1:
The patent applies preliminary action by having the base station pre-configure and transmit a unified RACH configuration that includes pre-determined RACH occasions across multiple carriers. The UE receives this configuration in advance and can immediately use it for random access on any carrier without needing to perform separate configuration procedures, thereby reducing access latency while maintaining multi-carrier access capability.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. Random access channel (RACH) occasions may be scheduled on each component carrier (CC) of a carrier aggregation (CA) configuration that includes both a time division duplexing (TDD) band and at least one frequency division duplexing (FDD) band based on a synchronization signal/physical broadcast channel block (SSB) received in the TDD band. In some cases, the TDD band may be used to configure the RACH occasions in same and/or different CCs. Additionally or alternatively, the FDD band may configure the RACH occasions on its uplink CC based on SSBs received on other CCs. Additionally, the RACH occasions may be configured such that the UE avoids unavailable uplink slots when transmitting a first RACH message in a RACH occasion.