Random Access with Variable TTI Durations

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Solution Overview

Problem

Current wireless communication systems face challenges in reducing packet data latency, particularly in LTE networks, which can impact system responsiveness and throughput, and the use of short transmission time intervals (TTIs) can lead to reduced uplink coverage and increased random access failures.

Innovation Solution

Implementing a method where a mobile terminal performs random access procedures using both short and long duration TTIs, allowing for parallel execution of these procedures to reduce signaling overhead and interruptions, and triggering a long TTI procedure upon short TTI failure to mitigate coverage issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If short duration TTI is used for random access, then latency is reduced, but uplink coverage is reduced and random access failures increase

Engineering Contradiction:

ImprovelatencyVSAvoidrandom access success rate

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The system dynamically selects between short TTI and long TTI for random access procedures based on current channel conditions and coverage requirements. The network can configure different TTI lengths and the UE adapts its random access transmissions accordingly, making the system flexible rather than fixed to one TTI duration.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the TTI duration parameter from a fixed value to a variable that can be adjusted between short and long durations. This parameter change allows the system to optimize between latency (short TTI) and coverage/reliability (long TTI) by selecting appropriate TTI lengths for different random access scenarios.

Inventive Principle:

Principle #35Parameter changes

2Speed

If short duration TTI is used for random access, then system responsiveness is improved, but signaling overhead increases

Engineering Contradiction:

Improvesystem responsivenessVSAvoidsignaling overhead

Core Design Contradiction:

SpeedVSLoss of information

Solution Approach 1:

The random access procedure is segmented into different phases or attempts, where initial attempts may use short TTI for fast access, and subsequent attempts or alternative procedures use long TTI for more reliable transmission. This segmentation allows the system to benefit from both short and long TTI characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs random access with short TTI partially (for initial attempts or good channel conditions) rather than exclusively, combining it with long TTI attempts when needed. This partial use of short TTI maintains responsiveness while avoiding excessive signaling overhead from purely short TTI-based approaches.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If long duration TTI is used for random access, then uplink coverage is improved, but latency increases

Engineering Contradiction:

Improveuplink coverageVSAvoidlatency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

4Loss of information

If parallel random access procedures are executed, then signaling overhead is reduced, but system complexity increases

Engineering Contradiction:

Improvesignaling overheadVSAvoidsystem complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The invention merges multiple random access procedures (short TTI and long TTI) into a unified framework where they can be executed in parallel or alternatively. The MAC layer is enhanced to handle both procedure types simultaneously, consolidating what would otherwise be separate implementation paths into a single integrated system.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11304237B2Random access with different TTI durations

Publication Date: 2022.04.12 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method of operating a mobile terminal, UE, to perform a random access, RA, procedure may be provided. A short duration RA preamble may be transmitted for the RA procedure, wherein the short duration RA preamble is transmitted using a short duration transmission time interval, TTI. A long duration RA preamble may be transmitted for the RA procedure, wherein the long duration RA preamble is transmitted using a long duration TTI, and wherein the long duration TTI is longer than the short duration TTI.