LTE Random Access Channel Interference Reduction

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Solution Overview

Problem

LTE systems operating in dynamic and shared spectra face challenges with mobility management and random access procedures due to interference from secondary users and timing uncertainties, particularly in narrow bandwidths like TVWS, where current techniques are inadequate in supporting IDLE mode WTRUs and may interfere with the random access procedure.

Innovation Solution

The implementation of systems and methods to enhance LTE random access transmission by configuring the random access channel (RACH) to reduce secondary interference, including selecting a RACH preamble, determining transmission power, and using Listen Before Talk (LBT) to sense the channel before transmission, along with carrier aggregation and coexistence mechanisms to manage interference from secondary users.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If coexistence gap mechanism is used in LTE standalone solutions, then timing uncertainty is accounted for, but RACH capacity is insufficient to support all IDLE mode WTRUs and secondary users can access the spectrum during gaps

Engineering Contradiction:

Improverandom access procedure reliabilityVSAvoidRACH capacity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs Listen Before Talk (LBT) sensing before the RACH transmission opportunity to detect secondary users. This preliminary action allows the eNodeB to identify interference sources before the random access procedure begins, enabling the WTRU to adjust its transmission strategy accordingly and avoid collisions with secondary users while maintaining sufficient RACH capacity for IDLE mode WTRUs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces dynamic transmission power adjustment based on LBT sensing results. The WTRU determines a transmission power for the RACH preamble based on the sensed channel conditions and detected secondary users. This dynamic adjustment allows the system to adapt to varying spectrum availability and interference levels, resolving the contradiction between maintaining reliable random access and providing sufficient capacity.

Inventive Principle:

Principle #15Dynamics

2Reliability

If coexistence gap mechanism is used, then timing uncertainty is accounted for, but LTE random access procedure timing requirements cannot be met including random access response window

Engineering Contradiction:

Improverandom access procedure reliabilityVSAvoidrandom access response window time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs LBT sensing before the RACH transmission to identify secondary users and determine appropriate transmission timing. This preliminary detection allows the WTRU to schedule its preamble transmission within the available time window, ensuring that the random access response can be received within the required timing constraints while avoiding interference with secondary users.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent modifies the transmission power parameter dynamically based on LBT sensing results. By adjusting the transmission power according to detected secondary users and channel conditions, the system can optimize the timing and power of RACH preamble transmissions to meet LTE random access procedure timing requirements while coexisting with secondary users in the spectrum.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If WTRU transmits RACH preamble with excessive transmit power due to poor path loss estimation, then UL transmission can be received, but interference to other RACH transmissions from the same cell occurs

Engineering Contradiction:

ImproveUL transmission receptionVSAvoidinterference to other RACH transmissions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system performs LBT sensing before RACH transmission to detect the presence and power levels of secondary users. This preliminary action provides the WTRU with information about the current electromagnetic environment, enabling accurate path loss estimation and appropriate transmit power selection that avoids excessive power while ensuring reliable reception.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses LBT sensing results as feedback to adjust the WTRU's transmission power. Based on the detected secondary users and their power levels, the WTRU determines an appropriate transmit power for its RACH preamble, creating a feedback loop that prevents both insufficient power (which would fail to be received) and excessive power (which would interfere with other RACH transmissions).

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10849161B2Random access in dynamic and shared spectrums

Publication Date: 2020.11.24 INTERDIGITAL PATENT HOLDINGS INC

AI summary

Systems and methods for using a communication system in a spectrum are provided. For example, a random access or RACH procedure may be performed where the random access or RACH procedure may be configured to reduce secondary interference and/or to be used in a pixel-based environment. The random access or RACH procedure may include selecting a RACH preamble; sending a RACH preamble and/or format information; determining a transmission power of the RACH preamble and/or the format information; determining a random access radio network temporary identifier (RA-RNTI) and preamble ID associated with the RACH preamble; and/or selecting a physical RACH (PRACH).