# Cocktail Intra-Symbol-Codes: Exceeding the Channel Limit of QPSK Input

## TL;DR

This paper introduces the cocktail intra-symbol-code, a novel modulation scheme that surpasses the traditional channel capacity of QPSK by transmitting multiple signals in parallel and decoding them jointly at the receiver.

## Contribution

It proposes a new modulation method combining constellation design and coding to exceed QPSK channel limits, supported by theoretical capacity analysis.

## Key findings

- Demonstrates the potential to exceed QPSK channel capacity
- Uses a rhombic constellation for improved signal separation
- Provides theoretical analysis under capacity-achieving codes

## Abstract

This paper presents a new method, referred to as the cocktail intra-symbol-code, to reveal the possibility of exceeding the channel limit of QPSK input by transmitting independent signals in parallel manner and separating them the receiver, repetitively. In the proposed modulation scheme, the rhombic constellation is created to work with the modulated signal and the channel code in Euclidean- and Hamming space cooperatively. The theoretical derivations are done under the assumption of using the capacity-achieving codes and the results are shown in terms of the reliable bit rates.