Spread Baseband Pilot Carrier for Carrier Tracking

Solution Overview

Problem

Existing communication systems using baseband injected pilot carriers face challenges in enhancing performance without increasing bandwidth or reducing payload throughput, as they often require added bandwidth or reduced throughput due to the integration of pilot symbols with payload data.

Innovation Solution

A system that uses a periodically repeating spread spectrum pilot signal with desired auto-correlation and cross-correlation properties, superimposed over data symbols, allowing for efficient carrier tracking and channel estimation without bandwidth expansion, and enabling direct sequence spread spectrum techniques for improved SNR and timing recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If baseband injected pilot carriers are used to enhance tracking performance, then carrier tracking precision is improved, but bandwidth increases or payload throughput decreases

Engineering Contradiction:

Improvecarrier tracking precisionVSAvoidpayload throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent merges the pilot signal and payload data into a single composite signal by superimposing the spread spectrum pilot onto the data constellation. This combining approach allows both pilot and data to share the same bandwidth resource without requiring separate channels, thereby maintaining payload throughput while enabling accurate carrier tracking through the embedded pilot.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The composite signal serves multiple functions simultaneously: it carries payload data for communication and contains an embedded pilot signal for carrier tracking and channel estimation. This multi-functionality eliminates the need for dedicated pilot channels that would consume separate bandwidth, thus maintaining productivity while achieving precise measurement.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If baseband injected pilot carriers are used to enhance tracking performance, then carrier tracking precision is improved, but bandwidth increases

Engineering Contradiction:

Improvecarrier tracking precisionVSAvoidsignal bandwidth

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent merges the pilot signal and payload data into a single composite signal by superimposing the spread spectrum pilot onto the data constellation. This combining approach allows both pilot and data to share the same bandwidth resource without requiring separate channels, thereby maintaining payload throughput while enabling accurate carrier tracking through the embedded pilot.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the parameters of the pilot signal by spreading it with a pseudo-random sequence, which transforms the pilot's spectral characteristics. This spreading allows the pilot to occupy the same bandwidth as the data signal without causing interference, enabling precise tracking within the existing bandwidth constraints.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If pilot symbols are time multiplexed with payload data, then carrier tracking is enabled, but payload throughput decreases

Engineering Contradiction:

Improvecarrier tracking capabilityVSAvoidpayload throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent merges the pilot signal and payload data into a single composite signal by superimposing the spread spectrum pilot onto the data constellation. This combining approach allows both pilot and data to share the same bandwidth resource without requiring separate channels, thereby maintaining payload throughput while enabling accurate carrier tracking through the embedded pilot.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The pilot signal is continuously present within the composite signal throughout the transmission, rather than being time-multiplexed in separate intervals. This continuous presence allows carrier tracking to occur continuously without interrupting payload data transmission, thereby maintaining maximum productivity while enabling tracking capability.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS7756000B2Spread baseband injected pilot carrier

Publication Date: 2010.07.13 HARRIS CORP

AI summary

A system for communicating includes a transmitter that has an encoder and baseband modulator that encodes and modulates a sequence of data symbols as a payload data constellation to be communicated. A PN sequence generator and baseband modulator form a pilot signal as a training sequence with a periodically repeating spread spectrum sequence. A circuit superimposes the pilot signal over the sequence of data symbols to form a composite communication signal that is transmitted. A receiver receives the composite communication signal and extracts the pilot signal from the composite communication signal.