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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [FSK PHY Channelization and Data Rate Proposal] Date Submitted: [March 19th, 2013] Source: [Andy Bottomley] Company [Microsemi] Address [15822 Bernardo Center Dr, Ste B, San Diego, CA, 92127] Voice:[+01-858-675-3485] FAX :[+01-858-675-3450] E-Mail:[andy.bottomley@microsemi.com ] Re: [In response to TG4n PAR] Abstract: [] 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. Andy Bottomley (Microsemi)

2. FSKPHY Recommendation • To facilitate ultra low power battery powered 802.15.4n devices for hospital sensor applications and other medical low power applications it is recommended that an FSK PHY is adopted. • Adoption of an FSK PHY would be in-line with current PHY amendments (802.15.4g & 802.15.4k) • An FSK PHY is also being proposed for 802.15.4q where power consumption is critical (#15-12-0634-01-004q) • This presentation proposes channel spacing, data rates and modulation indexes for 802.15.4n Andy Bottomley

3. Channel Spacing Proposal • Channel spacing of 500kHz can support data rates of 400kbps facilitating low energy per bit data transfer • Channel spacing of 250kHz can support 200kbps & offers more channels and improved sensitivity modes • Both 500kHz & 250kHz channel spacing coexist well with O-QPSK 2MHz channel spacing Andy Bottomley

4. Modulation Index Definition • fd = max peak deviation frequency • h = modulation index • M = 2 or 4 (2-FSK or 4-FSK) • Example of 2-FSK & 4-FSK with the same modulation index and same data rate Andy Bottomley

5. 2-FSK or 4-FSK? • 2-FSK or 4-FSK could both be used for the 400kbps ‘Low Energy Mode’ • The 99% occupied bandwidth of 2-FSK or 4-FSK @ 400kbps is approximately the same with a modulation index of 0.7 • The Eb/No is the same with a modulation index of 0.7 • The digital timing recovery may consume a little less current for a 4-FSK symbol rate of 200ksps compared to a 2-FSK symbol rate of 400ksps but this may be offset by the extra digital required to support a multi-level demodulator • As there appears to be no significant performance benefit in using 4-FSK over 2-FSK it is proposed that 2-FSK is used for all modes Andy Bottomley

6. Eb/No Sweep of Modulation Index for 2-FSK400kbps ‘Low Energy Mode’ • Channel filter 3dB bandwidth = 500kHz • 3rd order Butterworth channel filter • BT = 1 • 0.7 is the optimal modulation index for an Eb/No of 9.2dB at 0.1% BER Andy Bottomley

7. Eb/No Sweep of Modulation Index for 2-FSK 200kbps Mode • Channel filter 3dB bandwidth = 250kHz • 3rd order Butterworth channel filter • BT = 1 • 0.7 is the optimal modulation index for an Eb/No of 9.2dB at 0.1% BER Andy Bottomley

8. Occupied Bandwidth vs Modulation Index for 2-FSK400kbps mode • Occupied bandwidth increases with modulation index Andy Bottomley

9. Occupied Bandwidth vs Modulation Index for 2-FSK 200kbps mode • Occupied bandwidth increases with modulation index Andy Bottomley

10. Modulation Index Summary & Proposal • Modulation index of 0.7 provides best Eb/No performance: • 9.2dB Eb/No at 1e-3 BER for 2-FSK 200kbps mode • 9.2dB Eb/No at 1e-3 BER for 2-FSK 400kbps mode 2-FSK, 400kbps, Modulation Index 0.7 2-FSK, 200kbps, Modulation Index 0.7 Andy Bottomley

11. Adjacent Channel & Alternate Channel Rejection Requirements • 802.15.4-2011 specifies 0dB & 24dB ACR & ALTCR using a modulated interferer • 802.15.4k draft v3 specifies 10dB & 30dB ACR & ALTCR using a modulated interferer • 802.15.4g draft v7 specifies 10dB & 30dB ACR & ALTCR using a CW at centre of channel • Simulation results in the next slide are used to guide the requirement chosen for 802.15.4n Andy Bottomley

12. ACR& ALTCRSimulation Results for 2-FSK200kbpsMode, 250kHzChannelization • BT = 1 • Modulation index 0.7 • 99% occupied bandwidth 291kHz • 3rd order Butterworth channel filter with 250kHz +/-10% • The modulated interferer is the same as the wanted signal Andy Bottomley

13. Proposal for Channel Rejection Specification • Based on the simulation results it is recommended that the 802.15.4g rejection specification is used: ACR 10dB & ALTCR 30dB using a CW interferer • This facilitates a simple 3rd order channel filter with +/-10% bandwidth tolerance and offers some margin in meeting the requirements Andy Bottomley

14. Overall FSK PHY Proposal • 500kHz channelization to support 400kbps ‘Low Energy Mode’ • 250kHz channelization to support greater number of channels • Spreading option to provide extra robustness to interference • Gaussian filter (BT=1) on TX Note 1: A spreading factor of 8, 4 & 2 to be offered for this mode as an alternative way to generate lower data rates and spread the spectrum Andy Bottomley

15. Supporting Slides Andy Bottomley

16. Comparing Occupied Bandwidth vs Modulation Index for 2-FSK 400kbps & 4-FSK 400kbps • At a modulation index of 0.7 the 99% emission bandwidth is similar Andy Bottomley

17. 4-FSK 400kbps (200ksps) Modulation Index Sweep Andy Bottomley

18. 4-FSK 400kbps (200ksps) Occupied Bandwidth with Modulation Index Andy Bottomley