Randomized Space-Time Coding for Distributed Wireless Networks

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Solution Overview

Problem

In distributed cooperative wireless networks, existing methods struggle to provide diversity gains without requiring extra control information overhead, especially when the number of cooperating nodes is unknown or random, due to the complexity and randomness of node participation in relay transmissions.

Innovation Solution

The implementation of randomized space-time coding, where each node transmits an independent random linear combination of columns from a space-time code matrix, eliminating the need for centralized code allocation and allowing for decentralized operation, even with a random number of active nodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional space-time coding is used with centralized code allocation, then diversity gains are achieved, but control information overhead increases and system complexity increases

Engineering Contradiction:

Improvediversity gainsVSAvoidcontrol information overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Each relay node independently generates its space-time code sequence using a pseudo-random generator seeded with its own identifier and the space-time code parameter. This self-service approach eliminates the need for centralized code allocation and control information overhead, while still achieving diversity gains through the coordinated random sequences from multiple relays

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention changes the parameter of code allocation from centralized deterministic assignment to decentralized random generation. By using pseudo-random sequences with different seeds at each relay node, the system achieves code diversity without requiring control information exchange, resolving the contradiction between reliability and complexity

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If decentralized random transmission is used, then control information overhead is reduced, but diversity gains may be lost due to random delays and bandwidth requirements

Engineering Contradiction:

Improvecontrol information overheadVSAvoiddiversity gains

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention employs periodic space-time coded transmission where each relay transmits according to a predetermined space-time code structure (such as orthogonal codes) generated locally. This periodic structured transmission ensures that diversity gains are maintained through the mathematical properties of space-time codes, while avoiding the need for random delay resolution and large bandwidth requirements

Inventive Principle:

Principle #19Periodic action

3Reliability

If orthogonal space-time codes are used for decentralized transmission, then diversity is achieved, but spectral efficiency decreases and implementation becomes impractical for large numbers of nodes

Engineering Contradiction:

ImprovediversityVSAvoidspectral efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention uses a universal space-time code structure (such as orthogonal codes) that can be adapted to any number of relay nodes through local pseudo-random sequence generation. Each relay uses the same code structure with a unique seed, allowing the system to scale to large numbers of nodes without requiring different code designs, maintaining both diversity and spectral efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8233558B2Methods and systems for space-time coding for distributed cooperative communicaton

Publication Date: 2012.07.31 CORNELL UNIVERSITY

AI summary

Methods and systems for space-time coding for distributed cooperative communication.