Multi-SCS RACH Sequences for Cell Coverage and Timing Resolution

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Solution Overview

Problem

Current 5G New Radio (NR) technology faces challenges in optimizing random access channel (RACH) communication, particularly in achieving balanced coverage and timing resolution while adhering to regulatory power specifications, which affects the design of subcarrier spacing (SCS) configurations.

Innovation Solution

The method involves transmitting a first sequence with a first SCS and a second sequence with a greater SCS, both within specific resource sets, with a cyclic prefix greater than the inverse of the first SCS divided by the sequence length, and configuring power and repetition offsets to support increased cell size and timing resolution without budget coverage loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single subcarrier spacing (SCS) configuration is used in RACH communication, then the system design is simple, but it cannot simultaneously achieve both large cell coverage and fine timing resolution

Engineering Contradiction:

Improvecell size and timing resolutionVSAvoidSCS configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent divides the RACH communication into two separate sequences: a first sequence (e.g., PRACH preamble) transmitted with a first SCS configuration optimized for coverage, and a second sequence (e.g., SRS or DMRS) transmitted with a second SCS configuration optimized for timing resolution. This segmentation allows each sequence to independently optimize for its specific function, resolving the contradiction between coverage and timing resolution requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different SCS configurations are applied to different sequences based on their specific functional requirements. The first sequence uses a larger SCS (e.g., 120 kHz) suitable for coverage-extensive scenarios, while the second sequence uses a smaller SCS (e.g., 60 kHz) suitable for timing-resolution scenarios. This local optimization of quality parameters resolves the contradiction by matching each sequence's characteristics to its intended purpose.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If a larger subcarrier spacing is used, then timing resolution is improved, but cell coverage area decreases

Engineering Contradiction:

Improvetiming resolutionVSAvoidcell coverage area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent segments the RACH procedure into two sequences with different SCS configurations. The first sequence uses a larger SCS to provide fine timing resolution, while the second sequence uses a smaller SCS to extend cell coverage. This segmentation allows the system to achieve both fine timing resolution and large cell coverage simultaneously, resolving the contradiction between these two parameters.

Inventive Principle:

Principle #1Segmentation

3Area of stationary object

If a smaller subcarrier spacing is used, then cell coverage is extended, but timing resolution becomes coarse

Engineering Contradiction:

Improvecell coverage areaVSAvoidtiming resolution

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent divides the RACH communication into two sequences: the first sequence transmitted with a smaller SCS to extend cell coverage, and the second sequence transmitted with a larger SCS to provide fine timing resolution. This segmentation resolves the contradiction by allowing each sequence to optimize for its primary function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different SCS configurations are locally optimized for different sequences based on their functional requirements. The first sequence is configured with smaller SCS for coverage optimization, while the second sequence is configured with larger SCS for timing resolution optimization. This local quality differentiation resolves the contradiction between coverage and timing resolution.

Inventive Principle:

Principle #3Local quality

4Area of stationary object

If power is increased to improve coverage, then cell size increases, but interference with other channels increases

Engineering Contradiction:

Improvecell coverage areaVSAvoidinterference with other channels

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent changes the SCS parameter for different sequences to achieve coverage extension without increasing power. The first sequence uses a smaller SCS which naturally provides better coverage for the same power level, while the second sequence uses a larger SCS for timing resolution. This parameter change resolves the contradiction by achieving coverage improvement through SCS optimization rather than power increase, thereby reducing interference.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11622389B2Method and apparatus for RACH communication with multi subcarrier spacing configuration

Publication Date: 2023.04.04 QUALCOMM INC

AI summary

A UE, as a part of a RACH communication procedure, may transmit a first sequence within a first set of resources having a first SCS and a second sequence within a second set of resources having a second SCS greater than the first SCS. The second sequence is transmitted with a cyclic prefix greater than inverse of the first SCS divided by a sequence length of the first sequence. The first sequence is a first PRACH preamble. The second sequence may be a second PRACH preamble, an SRS sequence, or DMRS. The UE may repeat the transmission of the first sequence for a first number of times and repeat the transmission of the second sequence for a second number of times independent of the first number.