CDMA-CP Broadcast Multicast Transmission Format

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Solution Overview

Problem

Current HRPD broadcast/multicast systems face challenges in efficiently combining signals from different cells/sectors due to sector-dependent spreading codes, leading to sub-optimal performance and non-backward compatibility with CDMA transmission formats, especially in high frequency selective channels.

Innovation Solution

The implementation of a CDMA-CP based transmission format that removes long code spreading and inserts a cyclic prefix (CP) to facilitate efficient combining and equalization of signals across sectors, maintaining backward compatibility with existing CDMA systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If sector-dependent long code spreading is used for broadcast/multicast transmission, then backward compatibility with CDMA systems is maintained, but signal combining performance deteriorates due to interference between signals from different sectors

Engineering Contradiction:

Improvebackward compatibilityVSAvoidsignal combining performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies different spreading code strategies to different signal components: sector-dependent long code spreading is removed for the broadcast/multicast data portion to enable coherent combining, while maintaining CDMA structure for other control channels. This local differentiation resolves the contradiction by optimizing the data transmission path for combining performance while preserving overall system compatibility.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the spreading code parameter from sector-dependent to content-dependent for broadcast/multicast transmissions. This parameter change allows identical content to be transmitted with the same spreading code across sectors, enabling coherent signal combining while maintaining compatibility through the preserved CDMA frame structure and synchronization mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If separate equalization is performed per sector prior to combining, then implementation feasibility is maintained, but performance deteriorates due to sub-optimal combining in high frequency selective channels

Engineering Contradiction:

Improveimplementation feasibilityVSAvoidcombining performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent inverts the traditional processing order by performing combining first and equalization second. Instead of equalizing each sector separately then combining, the system combines signals from all sectors coherently first (enabled by content-dependent spreading), then performs a single equalization operation on the combined signal. This inversion achieves optimal combining performance while maintaining implementation feasibility through the simplified single equalization step.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If OFDM with cyclic prefix is used for broadcast/multicast, then efficient signal combining across sectors is achieved, but backward compatibility with CDMA transmission format is lost

Engineering Contradiction:

Improvesignal combining efficiencyVSAvoidbackward compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent merges the advantages of OFDM cyclic prefix techniques with CDMA transmission structure. It adopts the cyclic prefix concept from OFDM to enable efficient combining, but implements it within the CDMA framework using content-dependent spreading codes. This hybrid approach achieves OFDM-like combining efficiency while maintaining CDMA backward compatibility, as the overall transmission structure and synchronization remain CDMA-based.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces content-dependent spreading codes as an intermediary mechanism that enables efficient signal combining without requiring full OFDM implementation. This intermediary approach provides the benefits of cyclic prefix-based combining in a CDMA environment, serving as a bridge between the two technologies and maintaining compatibility while achieving improved performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If equalizer training is performed in high frequency selective channels, then performance improvement is achieved, but training becomes impossible due to low SNR from interference by stronger sectors

Engineering Contradiction:

Improveequalization performanceVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent performs signal combining as a preliminary action before equalization training. By combining signals from all sectors coherently first (enabled by content-dependent spreading codes), the desired signal strength is enhanced relative to noise and interference before the equalization training process begins. This preliminary combining action creates sufficient SNR for successful equalizer training in high frequency selective channels, eliminating the SNR limitation that would otherwise prevent effective training.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9525977B2Broadcast multicast mode

Publication Date: 2016.12.20 APPLE INC

AI summary

A broadcast/multicast transmission format includes a data portion and a cyclic prefix (CP) coupled to the traffic data portion. A method and system for providing broadcast/multicast transmissions with the application to communication systems that perform broadcast or multicast transmission is also disclosed. The addition of a pilot to the data portion of the transmissions is also disclosed.