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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, 16215 Alton Parkway, Irvine, CA 92619 Voice: 949 585 6168

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slide1

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, 16215 Alton Parkway, Irvine, CA 92619

Voice: 949 585 6168

E-Mail: [email protected]

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 P802.15. 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

qpsk and o qpsk system model

+

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

slide3

+

Contents of

are defined in Draft P802.15.3/D0.3

CAZAC Preamble with QPSK Modulation

Received sequence

after A/D

(T/2 spaced)

Overall Symbol Response

Periodic CAZAC

Preamble

CAZAC property holds

J. Karaoguz

slide4

+

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

slide5

Received signal level = -71 dBm

AWGN level = -95 dBm

SNR for channel estimation = 24 dB

Channel Estimation with QPSK

Channel Estimation with O-QPSK

Channel Estimation Using CAZAC Preamble

J. Karaoguz

slide6

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

slide7

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

slide8

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 802.15.3 PHY layer preamble is transmitted in QPSK format
  • Finally, based on the contribution IEEE 802.15-01/225 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 802.15.3 base mode is further warranted

J. Karaoguz

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