1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Effects of O-QPSK Modulation on a CAZAC Preamble
Date Submitted: 9 May 2001
Source: Jeyhan Karaoguz
Address: Broadcom Corporation, Alton Parkway, Irvine, CA 92619
Voice:
Abstract: This contribution analyzes the adverse effects of O-QPSK modulation on a CAZAC Preamble
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15

2. QPSK and O-QPSK System Model
11/28/2018
QPSK and O-QPSK System Model
Received sequence
after A/D
(T/2 spaced)
Overall Symbol Response
Periodic CAZAC
Preamble +
In-phase
Quadrature-phase
Frequency
Response
J. Karaoguz

3. are defined in Draft P802.15.3/D0.3
11/28/2018
CAZAC Preamble with QPSK Modulation
Received sequence
after A/D
(T/2 spaced)
Overall Symbol Response
Periodic CAZAC
Preamble +
CAZAC property holds
are defined in Draft P /D0.3
Contents of
J. Karaoguz

4. CAZAC property does not hold !
11/28/2018
CAZAC Preamble with O-QPSK Modulation
Received sequence
after A/D
(T/2 spaced)
Overall Symbol Response
Periodic CAZAC
Preamble +
CAZAC property does not hold !
J. Karaoguz

5. Channel Estimation Using CAZAC Preamble
11/28/2018
Channel Estimation Using CAZAC Preamble
Received signal level = -71 dBm
AWGN level = -95 dBm
SNR for channel estimation = 24 dB
Channel Estimation with QPSK
Channel Estimation with O-QPSK
J. Karaoguz

6. Channel Estimation with QPSK Modulation
11/28/2018
Channel Estimation with QPSK Modulation
Channel estimation requires the calculation (and its inversion) of input correlation matrix CHC
where “H” denotes hermitian transpose
QPSK format
For QPSK modulation, the input correlation matrix CHC is well conditioned due to zero-auto
correlation property of CAZAC sequences
J. Karaoguz

7. Problem Statement for O-QPSK
11/28/2018
Problem Statement for O-QPSK
The input correlation matrix CHC for O-QPSK case:
O-QPSK
format
In this case, the input correlation matrix CHC is nearly singular since the CAZAC property is not
maintained resulting in large channel estimation errors as shown previously on page 5
J. Karaoguz

8. 11/28/2018
Conclusions
Zero-auto correlation property of a CAZAC sequence is lost when transmitted in O-QPSK format
Channel estimation using an O-QPSK modulated CAZAC preamble yields unacceptable error performance
We, therefore, propose that the PHY layer preamble is transmitted in QPSK format
Finally, based on the contribution IEEE /225 that shows only slight performance gain for O-QPSK over QPSK with respect to peak-to-average ratio, the use of QPSK modulation for the entire base mode is further warranted
J. Karaoguz