Random Access Preamble Resource Selection for PRACH-PUSCH Conflicts
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Solution Overview
Problem
In two-step random access in communication systems like LTE and NR, conflicts arise between PRACH and PUSCH time-frequency resources, leading to network devices failing to receive random access preambles and uplink data due to overlapping resources.
Innovation Solution
A terminal device determines a PRACH time-frequency resource within a set that does not conflict with the PUSCH time-frequency resource set, either by ensuring no overlap in time or frequency domain, or by maintaining a threshold interval, and sends the random access preamble on this resource.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PRACH and PUSCH time-frequency resources are configured in the same slot and overlap in frequency domain to reduce latency and signaling overheads, then random access efficiency is improved, but resource conflict occurs between terminal devices sending preambles and other terminal devices sending uplink data
Solution Approach 1:
The patent segments the time-frequency resources by introducing separate time slots for PRACH and PUSCH transmissions. Terminal devices are configured with specific PRACH slots for preamble transmission, while PUSCH resources are allocated in different slots, thereby dividing the originally overlapping resources into distinct segments that eliminate conflicts while maintaining overall system efficiency.
Solution Approach 2:
The patent resolves the two-dimensional (time-frequency) resource conflict by introducing a third dimension - the slot dimension. By configuring PRACH and PUSCH in different time slots, the system transforms the resource allocation problem from a two-dimensional overlap issue into a three-dimensional separated structure, eliminating conflicts while preserving the benefits of two-step random access.
2Loss of time
If two-step random access is used to reduce latency and signaling overheads, then access speed is improved, but network devices cannot normally receive random access preambles and uplink data due to resource conflicts
Solution Approach 1:
The patent applies preliminary action by pre-configuring terminal devices with specific PRACH slot information before random access transmission. The network device provides configuration parameters indicating which slots are designated for PRACH, allowing terminal devices to proactively select conflict-free resources for preamble transmission, thereby ensuring reliable reception while maintaining low latency.
Solution Approach 2:
The patent introduces configuration information as an intermediary between the terminal device and the physical layer transmission. This configuration data acts as a mediator that guides terminal devices to select appropriate PRACH slots, indirectly resolving the reception reliability issue by preventing resource conflicts before they occur, while preserving the fast access characteristics of two-step random access.
Data Source
AI summary
In the field of communication technologies, a random access preamble sending method and a communication apparatus are provided to avoid a problem that a conflict exists between a PRACH time-frequency resource occupied by a terminal device for sending a random access preamble and a PUSCH time-frequency resource occupied by another terminal device for sending uplink data, and consequently a network device cannot normally receive the random access preamble and the uplink data. The method includes: a terminal device receives configuration information sent by a network device, where the configuration information includes configuration information of a PRACH time-frequency resource set and configuration information of a PUSCH time-frequency resource set. The terminal device determines, in the PRACH time-frequency resource set, a PRACH time-frequency resource that does not conflict with the PUSCH time-frequency resource set. The terminal device sends a random access preamble on the determined PRACH time-frequency resource.