Random Access Preamble Indexing for Distinct PRACH Occasions
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Solution Overview
Problem
The existing RA-RNTI and MSGB-RNTI calculation methods fail to distinguish PRACH occasions when larger subcarrier spacings are used, exceeding the 16-bit value range, leading to indistinguishable PRACH occasions in the random access procedure.
Innovation Solution
The identification parameter for scrambling is calculated using a first index indicating the position of the slot for transmitting the random access preamble, where at least two slots in the system frame have identical first indices or the number of slots with first indices is less than the total, ensuring the parameter remains within the value range and allows differentiation of PRACH occasions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If larger subcarrier spacings are used for PRACH transmission, then the system can support higher frequency bands (FR2 and above), but the RA-RNTI or MSGB-RNTI value exceeds the 16-bit value range, causing PRACH occasions to become indistinguishable
Solution Approach 1:
The patent divides the slot index into two parts: a first index (t_id) that is reused across multiple slots and a second index (i_id) that provides additional distinction. This segmentation allows the system to maintain unique identification of PRACH occasions while using a limited 16-bit RA-RNTI value range. The first index is determined by the slot position in the system frame, while the second index provides differentiation within slots that have the same first index.
Solution Approach 2:
The patent introduces a second dimension of indexing by adding the second index (i_id) to the existing first index (t_id). This dimensional expansion allows the system to distinguish between PRACH occasions that would otherwise be indistinguishable, effectively mapping a 1D slot index to a 2D index structure that provides sufficient uniqueness within the 16-bit constraint.
2Reliability
If all slots in a system frame are assigned unique indices, then PRACH occasions can be distinguished, but the identification parameter exceeds the maximum value of 65535 representable by 16 bits
Solution Approach 1:
The patent segments the slot indexing into a first index (t_id) and a second index (i_id). The first index is reused across multiple slots, while the second index provides additional distinction. This segmentation allows the system to maintain unique identification of PRACH occasions while keeping the overall identification parameter within the 16-bit value range of 0-65535.
Solution Approach 2:
Instead of assigning unique indices to all slots (excessive action), the patent uses a partial indexing approach where the first index is reused. This allows sufficient distinction between PRACH occasions for reliable random access while avoiding the excessive parameter values that would exceed 16-bit representation.
3Device complexity
If multiple slots have identical first indices, then the identification parameter remains within value range, but PRACH occasions with the same first index cannot be distinguished
Solution Approach 1:
The patent segments the identification into two components: the first index (t_id) that is reused across slots to keep values within range, and the second index (i_id) that provides additional distinction. This segmentation resolves the contradiction by allowing multiple slots to share the same first index while still being distinguishable through the second index.
Solution Approach 2:
The patent adds a second dimension of indexing by introducing the second index (i_id) that differentiates slots with identical first indices. This dimensional expansion allows the system to maintain compact identification parameters while achieving reliable distinction between all PRACH occasions.
Data Source
AI summary
A random access method and apparatus. The apparatus includes: a transmitter configured to transmit a first message containing a random access preamble to a network device; and a detector configured to detect downlink control information transmitted by the network device, the downlink control information being used to schedule a second message containing a random access response, cyclic redundancy check (CRC) of the downlink control information being scrambled by using an identification parameter, and a parameter used for calculating the identification parameter at least including a first index, the first index indicating a position of a slot for transmitting the random access preamble in a system frame, wherein at least two slots in a system frame have identical first index, or the number of slots having the first indices in the system frame is less than the number of slots contained in the system frame and first indices of slots having the first indices are different.