PBCH Repetitions for Wireless System Information Acquisition

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Solution Overview

Problem

Current LTE systems face challenges in reducing system information acquisition latency for Machine-Type Communications (MTC) and Internet-of-Things (IoT) devices, particularly in coverage enhancement scenarios, where category M1 and NB1 UEs experience significant delays in acquiring system information, leading to increased handover latency and degraded performance in voice-over-LTE and idle state mobility procedures.

Innovation Solution

The implementation of enhanced Physical Broadcast Channel (PBCH) and Narrowband PBCH (NPBCH) repetitions, which increase the number of PBCH symbols available to UEs, allowing them to decode system information more efficiently across multiple subframes and PRBs, thereby reducing latency in acquiring system information and improving handover and idle state mobility performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If conventional PBCH transmission is used in LTE systems, then device complexity is reduced, but system information acquisition latency increases significantly for MTC and IoT devices

Engineering Contradiction:

Improvesystem information acquisition latencyVSAvoidPBCH repetition structure complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent implements periodic PBCH repetitions across multiple subframes, where the broadcast channel is transmitted repeatedly at regular intervals. This periodic transmission allows MTC and IoT devices to accumulate signal energy over multiple subframes, significantly reducing acquisition latency while maintaining manageable device complexity through standardized repetition patterns.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent segments the system information transmission by dividing it into multiple PBCH repetition instances across different subframes and potentially different PRBs. This segmentation allows devices to gradually acquire information over time rather than requiring all information to be transmitted simultaneously, reducing the instantaneous complexity burden on devices.

Inventive Principle:

Principle #1Segmentation

2Productivity

If PBCH repetitions are increased to reduce acquisition latency, then system information acquisition speed improves, but device complexity increases

Engineering Contradiction:

Improvesystem information acquisition speedVSAvoidprocessing complexity for multiple repetitions

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent merges multiple PBCH repetition instances into a unified acquisition process, where devices can combine signals from multiple repetitions to improve decoding reliability. This merging approach increases acquisition speed by allowing parallel processing of repetitions while managing device complexity through standardized combining algorithms.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs preliminary actions by transmitting PBCH repetitions in advance across multiple subframes before the device needs to complete acquisition. This allows devices to start processing information earlier and accumulate signals progressively, improving acquisition speed while enabling devices to process information incrementally rather than all at once, thus managing complexity.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If handover latency is reduced for voice-over-LTE, then call setup time decreases, but system information transmission requirements become more stringent

Engineering Contradiction:

Improvehandover latencyVSAvoidsystem information decoding reliability

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent uses periodic PBCH repetitions during handover scenarios, ensuring that system information is transmitted repeatedly across multiple subframes. This periodic transmission guarantees that devices can acquire necessary information within the reduced handover latency window while maintaining decoding reliability through multiple transmission opportunities.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent ensures continuity of useful action by maintaining PBCH transmissions throughout the handover process rather than interrupting them. This continuous transmission of system information across subframe boundaries ensures that devices can complete acquisition within the shortened handover timeframe while maintaining reliable decoding through uninterrupted information availability.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS11134432B2System information acquisition enhancements for wireless devices

Publication Date: 2021.09.28 APPLE INC

AI summary

An apparatus of a user equipment (UE) includes processing circuitry configured to decode a master information block (MIB) using a set of physical broadcast channel (PBCH) symbols received within a downlink frame to obtain system frame number (SFN) information. The downlink frame includes multiple copies of the PBCH symbols within at least three subframes of the downlink frame. A system information block (SIB) may be decoded based on the SFN information, to obtain uplink channel configuration information. Random access channel (RACH) procedure may be performed with a base station (BS) based on the uplink channel configuration information, to obtain an uplink resource assignment. A connection setup completion message can be encoded for transmission to the BS using the uplink resource assignment. The set of PBCH symbols can include a set of four legacy PBCH symbols.