Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [802.15.4 Multipath]

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [802.15.4 Multipath] Date Submitted: [July 2004] Source: [Paul Gorday] Company: [Motorola] Address: [8000 W. Sunrise Blvd., Plantation, FL, 33322, USA] Voice:[+1 561 723 4047], E-Mail:[paul.gorday@motorola.com] Re: [ IEEE 802.15.4 ] Abstract: [This contribution presents simulated performance of a simple 802.15.4 (2.4 GHz PHY) receiver in multipath channel conditions.] Purpose: [To encourage discussion.] 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. Paul Gorday, Motorola

2. Motivation • Proposed modifications to 868/915 MHz PHY consider additional multipath tolerance for long-range applications. • Provide benchmark simulation results for the 2.4 GHz PHY, which would also apply to the proposed down-banded version. Paul Gorday, Motorola

3. 2.4 GHz PHY Simulation • Floating point simulation of optimum non-coherent demodulator. • Detection based on largest correlation peak (largest path) … No RAKE or equalizer. • Assume channel is constant throughout packet (quasi-static) and uncorrelated from packet to packet. • Record average packet error rate (PER) vs. Eb/No. Paul Gorday, Motorola

4. 2.4 GHz Channel Model • No channel model was specified by 802.15.4 • Commonly used diffuse exponential model • 802.11 Handbook [1] • 802.15.3a Narrowband Model [2] • ETSI BRAN, HIPERLAN/2 [3] • Many textbooks [e.g., 4] • Detailed channel models are being developed by 802.15.4a for a variety of environments, but are not finished. Paul Gorday, Motorola

5. Diffuse Exponential Model • Diffuse – each delay bin • contains multipath energy • Exponential – average power • decays exponentially • Fading - each delay bin has • independent Rayleigh fading • Single Parameter: • RMS delay spread =  • Mean excess delay  • Max excess delay (10 dB)  2.5 • Max excess delay (20 dB)  5 C = Normalization Constant Ts = Simulation Sample Period Normalized Average Power Depicted:  = 4Ts k (Bin #) Paul Gorday, Motorola

6. Results for 2.4 GHz PHY • Acceptable performance • for   400 ns • RMS delay spread = 400 ns • Mean excess delay 400 ns • Max excess delay (10 dB)  1 s • Max excess delay (20 dB)  2 s • Results scale with chip rate •  half-rate at 915 MHz would • tolerate RMS delay spreads • up to 800 ns Paul Gorday, Motorola

7. 802.11a/HIPERLAN/2 Models [3] Paul Gorday, Motorola

8. IEEE 802.11 Handbook [1] Paul Gorday, Motorola

9. Factory/Office Measurements [4] Tx-Rx separation < 30 m Paul Gorday, Motorola

10. Conclusions • 802.15.4 (2.4 GHz PHY) with simple non-coherent demodulator can tolerate RMS delay spreads up to 400 ns  sufficient for most WLAN applications, more than enough for WPAN applications. • Down-banded, half-rate 2.4 GHz PHY would tolerate RMS delay spreads up to 800 ns. • Additional delay spread tolerance may be achievable with some increase in demodulator complexity. Paul Gorday, Motorola

11. References [1] B. O’Hara and A. Petrick, IEEE 802.11 Handbook – A Designer’s Companion, IEEE Press, 1999. [2] J. Foester, “Channel Modeling Sub-committee Report (Final),” IEEE P802.15-02/490r1-SG3a, Feb. 2003. [3] J. Medbo and P. Schramm, “Channel Models for HIPERLAN/2,” ETSI/BRAN doc. No. 3ERI085B, 1998. [4] K. Pahlavan and A. Levesque, Wireless Information Networks, John Wiley & Sons, 1995. Paul Gorday, Motorola