OFDM Wireless Terminal Timing Synchronization for Satellite Links

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Solution Overview

Problem

Existing communication systems face challenges in providing reliable cell phone coverage in remote areas due to the high power requirements for transmitting signals to satellite base stations, which result in bulky devices and inadequate uplink symbol timing synchronization, especially with long round trip delays.

Innovation Solution

The development of methods and apparatus that utilize beacon signals for timing synchronization in OFDM systems, allowing wireless terminals to synchronize with base stations, including satellite-based ones, through a variety of techniques such as single-tone mode operation and access intervals, enabling efficient power use and effective communication over long distances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high power transmission is used to communicate with satellite base stations, then communication coverage in remote areas is achieved, but device size and power consumption increase

Engineering Contradiction:

Improvecommunication coverageVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent changes the transmission parameter from high power to single-tone mode operation, which reduces the peak-to-average power ratio. This allows the device to maintain communication coverage while reducing power consumption and device size requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses periodic beacon signals transmitted at regular intervals to enable timing synchronization. This periodic action allows the wireless terminal to synchronize without requiring continuous high power transmission, thereby reducing overall power consumption while maintaining communication reliability.

Inventive Principle:

Principle #19Periodic action

2Reliability

If high power transmission is used to communicate with satellite base stations, then communication coverage in remote areas is achieved, but device power consumption increases

Engineering Contradiction:

Improvecommunication coverageVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Inventive Principle:

Principle #19Periodic action

3Productivity

If conventional multi-tone OFDM is used for uplink transmission, then data rate is improved, but timing synchronization becomes difficult with long round trip delays

Engineering Contradiction:

Improvedata rateVSAvoidtiming synchronization

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the uplink transmission into two distinct parts: a first portion using single-tone mode for timing synchronization and a second portion using multi-tone OFDM for high-speed data transmission. This segmentation allows each part to be optimized for its specific function, resolving the contradiction between data rate and timing synchronization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs timing synchronization using single-tone mode transmission before the actual high-speed data transmission begins. This preliminary action establishes the timing reference needed for subsequent multi-tone OFDM data transmission, ensuring that the system can achieve both synchronization and high data rates.

Inventive Principle:

Principle #10Preliminary action

4Use of energy by moving object

If single-tone mode is used for satellite communications, then power consumption is reduced, but data rate decreases

Engineering Contradiction:

Improvepower consumptionVSAvoiddata rate

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7974261B2Basestation methods and apparatus for supporting timing synchronization

Publication Date: 2011.07.05 QUALCOMM INC

AI summary

A wireless terminal using OFDM signaling supporting both terrestrial and satellite base station connectivity operates using conventional access probe signaling in a first mode of operation to establish a timing synchronized wireless link with a terrestrial base station. In a second mode of operation, used to establish a timing synchronized wireless link with a satellite base station, a slightly modified access protocol is employed. The round trip signaling time and timing ambiguity between a wireless terminal and a satellite base station is substantially greater than with a terrestrial base station. The modified access protocol uses coding of access probe signals to uniquely identify a superslot index within a beaconslot. The modified protocol uses multiple access probes with different timing offsets to further resolve timing ambiguity and allows the satellite base station access monitoring interval to remain small in duration. Terrestrial base station location/connection information is used to estimate initial timing.