Square Complex Orthogonal Designs with Low PAPR and Signaling Complexity

TL;DR

This paper introduces new square complex orthogonal designs with no zero entries for specific numbers of transmit antennas, reducing PAPR and hardware constraints without increasing signaling complexity, and demonstrates their superior performance under peak power constraints.

Contribution

The paper provides explicit constructions of zero-free SCODs for certain antenna configurations, improving PAPR and hardware efficiency while maintaining signaling complexity.

Findings

Constructed zero-free SCODs for 2^a transmit antennas.

Outperform standard codes under peak power constraints.

Maintain performance parity under average power constraints.

Abstract

Space-Time Block Codes from square complex orthogonal designs (SCOD) have been extensively studied and most of the existing SCODs contain large number of zero. The zeros in the designs result in high peak-to-average power ratio (PAPR) and also impose a severe constraint on hardware implementation of the code when turning off some of the transmitting antennas whenever a zero is transmitted. Recently, rate 1/2 SCODs with no zero entry have been reported for 8 transmit antennas. In this paper, SCODs with no zero entry for $2^a$ transmit antennas whenever $a+1$ is a power of 2, are constructed which includes the 8 transmit antennas case as a special case. More generally, for arbitrary values of $a$, explicit construction of $2^a\times 2^a$ rate $\frac{a+1}{2^a}$ SCODs with the ratio of number of zero entries to the total number of entries equal to $1-\frac{a+1}{2^a}2^{\lfloor log_2(\frac{2^a}{a+1}) \rfloor}$ is reported, whereas for standard known constructions, the ratio is $1-\frac{a+1}{2^a}$. The codes presented do not result in increased signaling complexity. Simulation results show that the codes constructed in this paper outperform the codes using the standard construction under peak power constraint while performing the same under average power constraint.