# Orthogonal Cocktail BPSK: Exceeding Shannon Capacity of QPSK Input

## TL;DR

This paper proposes a novel method to transmit two independent signals in parallel using QPSK, surpassing Shannon capacity limits by enabling interference-free separation at the receiver.

## Contribution

It introduces a new layered QPSK scheme and partial decoding method that allows exceeding traditional Shannon capacity by transmitting multiple signals simultaneously.

## Key findings

- The method theoretically exceeds QPSK capacity.
- Signals can be separated without interference at the receiver.
- The approach is based on signal layering and partial decoding.

## Abstract

Shannon channel capacity of an additive white Gaussian noise channel is the highest reliable transmission bit rate (RTBR) with arbitrary small error probability. However, the authors find that the concept is correct only when the channel input and output is treated as a single signal-stream. Hence, this work reveals a possibility for increasing the RTBR further by transmitting two independent signal-streams in parallel manner. The gain is obtained by separating the two signals at the receiver without any inter-steam interference. For doing so, we borrow the QPSK constellation to layer the two independent signals and create the partial decoding method to work with the signal separation from Hamming to Euclidean space. The theoretical derivations prove that the proposed method can exceed the conventional QPSK in terms of RTBRs.