Synchronizing Broadcast Streams in Soft Handoff Sectors

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Solution Overview

Problem

Current 3G wireless communication networks face challenges in synchronizing the transmission of broadcast streams across sectors during soft handoff, leading to potential buffer overflow and underflow issues, which affect the quality of services like real-time streaming video and interactive gaming.

Innovation Solution

The method involves synchronizing the transmission of broadcast streams by using time stamps in data packets to compute frame transmission start times across base stations, with automatic resynchronization procedures to prevent buffer overflow and underflow by dropping or delaying packets based on latency thresholds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If autonomous soft handoff is implemented between sectors transmitting broadcast streams, then mobile users can receive seamless broadcast content while moving between sectors, but transmission synchronization between sectors becomes complex and difficult to maintain

Engineering Contradiction:

Improveautonomous soft handoff capabilityVSAvoidtransmission synchronization complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a synchronization message as an intermediary carrier that transports timing information between sectors. This message contains frame number, time stamp, and synchronization indicator fields that mediate the synchronization process, allowing sectors to independently adjust their transmission timing based on received synchronization information without direct complex coordination protocols

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs copying by having each sector transmit identical broadcast stream data along with copied synchronization information from the synchronization message. The mobile station receives multiple copies of the same broadcast content from different sectors, and the synchronization mechanism ensures these copies are transmitted in coordinated time slots, enabling seamless handoff without requiring the mobile station to process complex synchronization protocols

Inventive Principle:

Principle #26Copying

2Reliability

If broadcast streams are transmitted at fixed rate and constant power across multiple sectors, then service quality is maintained, but buffer overflow and underflow issues occur during handoff transitions

Engineering Contradiction:

Improveservice quality consistencyVSAvoidbuffer overflow and underflow

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-synchronizing the transmission timing of broadcast streams across all sectors before handoff occurs. The synchronization message is transmitted in advance to establish a common timing reference, and sectors adjust their transmission schedules proactively based on this reference, preventing buffer overflow and underflow during handoff transitions rather than reacting to them after they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through the synchronization message mechanism that continuously monitors and communicates timing status between sectors. The synchronization indicator field in the message provides feedback about synchronization status, allowing sectors to detect and correct timing deviations that could lead to buffer overflow or underflow, maintaining reliable service quality during dynamic handoff conditions

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If time synchronization is implemented between sectors, then seamless broadcast reception during soft handoff is achieved, but transmission timing coordination requires complex protocols and signaling

Engineering Contradiction:

Improvebroadcast stream synchronizationVSAvoidtiming coordination protocol complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The synchronization message serves as a simplified intermediary that encapsulates all necessary timing coordination information in a standardized format. It contains frame number, time stamp, and synchronization indicator fields that convey synchronization status without requiring complex protocol exchanges between sectors, reducing the complexity of timing coordination while maintaining stable broadcast stream synchronization

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting transmission timing parameters based on the synchronization information received. Sectors modify their frame transmission start times and timing advance values according to the synchronization indicator and time stamp in the synchronization message, achieving stable synchronization through parameter adjustment rather than complex protocol negotiation

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7626975B2Method of synchronizing broadcast streams in multiple soft handoff sectors

Publication Date: 2009.12.01 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Transmission of broadcast streams in multiple sectors is synchronized based on time stamps or sequence numbers in data packets received at the base station. The base stations use the time stamps to calculate a frame transmission start time and start position for the data packets. The base station monitors the packet latency of data within its buffer based on the time stamp in the data packets and initiates a resynchronization procedure if the packet latency exceeds predetermined bounds.