Convolution Encoder Input Selection for Energy-Shaped WLAN Symbols

Solution Overview

Problem

Conventional IEEE 802.11x transmitters are energy inefficient due to equal probability symbol selection from a hypercube constellation, limiting transmit power reduction in dense user environments, such as vehicular networks, and failing to reach channel capacity.

Innovation Solution

An input selector for convolution encoders that shapes input bits to select symbols from an n-dimensional hypersphere, increasing energy efficiency by generating an encoder input bit stream that ensures symbols with lower energies are transmitted, allowing for rate adaptivity without changing the code rate or constellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If symbols are selected with equal probability from a hypercube constellation, then the transmitter can be simple to implement, but energy efficiency is poor and transmit power cannot be reduced

Engineering Contradiction:

Improveenergy efficiencyVSAvoidtransmitter complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The input selector performs preliminary shaping of the input bit stream before encoding, pre-determining which coded bits will be fixed to specific values. This preliminary action ensures that the encoder generates symbols from a hypersphere constellation with desired energy efficiency properties, while the transmitter structure remains compatible with conventional IEEE 802.11x standards.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the parameter of symbol selection from uniform probability distribution over a hypercube to a shaped distribution over a hypersphere. By modifying the input bit stream to control the encoder state, the system transitions from transmitting symbols with equal probability to transmitting symbols with optimized energy efficiency, achieving up to 1.53 dB improvement.

Inventive Principle:

Principle #35Parameter changes

2Power

If conventional equal probability symbol selection is used, then the transmitter structure is simple, but the transmit power cannot be reduced in dense user environments

Engineering Contradiction:

Improvetransmit powerVSAvoidtransmitter structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The input selector performs preliminary shaping of the input bit stream before encoding, pre-determining which coded bits will be fixed to specific values. This preliminary action ensures that the encoder generates symbols from a hypersphere constellation with desired energy efficiency properties, while the transmitter structure remains compatible with conventional IEEE 802.11x standards.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the parameter of symbol selection from uniform probability distribution over a hypercube to a shaped distribution over a hypersphere. By modifying the input bit stream to control the encoder state, the system transitions from transmitting symbols with equal probability to transmitting symbols with optimized energy efficiency, achieving up to 1.53 dB improvement.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If symbols are selected to maximize energy efficiency, then energy efficiency improves, but the transmitter fails to reach channel capacity

Engineering Contradiction:

Improveenergy efficiencyVSAvoidchannel capacity utilization

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The invention changes the parameter of symbol selection from uniform probability distribution over a hypercube to a shaped distribution over a hypersphere. By modifying the input bit stream to control the encoder state, the system transitions from transmitting symbols with equal probability to transmitting symbols with optimized energy efficiency, achieving up to 1.53 dB improvement while maintaining channel capacity utilization.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10530630B2Encoder input selector

Publication Date: 2020.01.07 NXP BV

AI summary

An input selector for selecting an input of a convolution encoder of a transmitter is disclosed. The input selector comprises a shaper block and an input-select block. The shaper block is configured to receive an input comprising a first number of input bits, the shaper block configured to generate a shaped bit stream corresponding to the first number of input bits. The input-select block is configured to generate an encoder input bit stream for the encoder based on the shaped bit stream, wherein the input-select block generates the encoder input bit stream such that, when input into the encoder, a first bit of the encoder input bit stream sets a state of the encoder in order that a subsequent second bit of the encoder input bit stream causes the encoder to generate a bit of the shaped bit stream at a pre-determined position in an encoder output bit stream.