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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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  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, 16215 Alton Parkway, Irvine, CA 92619 Voice: 949 585 6168 E-Mail: jeyhan@broadcom.com 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

  2. + 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. + 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

  4. + 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. 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

  6. 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 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. 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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