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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: [ FSK PHY Channelization and Data Rate Proposal ] Date Submitted: [May 13th , 2013] Source: [Andy Bottomley] Company [ Microsemi ]

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

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  1. Project: IEEE P802.15Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [FSKPHYChannelization and Data Rate Proposal] Date Submitted: [May 13th, 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 low power battery powered 802.15.4n devices for hospital sensor applications and other medical low power applications it is recommended that an FSKPHY is adopted. • Adoption of an FSKPHY would be in-line with current PHY amendments (802.15.4g & 802.15.4k) • This presentation proposes channel spacing, data rates and modulation indexes for 802.15.4n Andy Bottomley

  3. Channel Spacing Proposal • Channel spacing of 500kHz to support data rates of up to 200kbps • Channel spacing of 500kHz to coexist with O-QPSK 2MHz channel spacing • Channel spacing of 500kHz with 2-FSK 200kbps to meet spurious requirements close to edge of Chinese Medical bands Andy Bottomley

  4. Toughest Spurious Requirement Close to Band Edge • Level -54dBm/100kHz • Limits +/-2.5xOBW Example of Spurious Requirement with Proximity to 174-216MHz Band Andy Bottomley

  5. 20dB Occupied Bandwidth Simulation Results • The 20dB occupied bandwidth is required to predict where the edge of the spurious domain begins • Conditions: • 200kbps, 2-FSK • Modulation index = 1 • BT = 0.7 • RBW = 1kHz • SA detector = peak • OBW = 300kHz • Fits well into channel Andy Bottomley

  6. BT filter 0.5 & 0.7 • RBW=100kHz • Spurious Power Simulation Results • Conditions: • Maximum TX power 10dBmERP • 200kbps, 2-FSK, modulation index 1 Gaussian filter BT = 0.5 Gaussian filter BT = 0.7 Andy Bottomley

  7. Spurious Power Simulation Results • With a BT of 0.7 the skirts of the modulated signal are well within the -54dBm/100kHz requirement at the frequency offset of 2.5xOBW (edge of spurious domain) Gaussian filter BT = 0.7 Andy Bottomley

  8. Implications for Synthesizer TX Phase Noise • A spurious requirement of -54dBm/100kHz is approximately -104dBm/Hz • The frequency offset of the spurious domain edge is ~300k x 2.5 = 750kHz • The wanted signal power =10dBm therefore phase noise has to be down at -114dBc/Hz at the spurious domain edge in order to meet the spurious requirement • Phase noise better than -114dBc/Hz is required @ 750kHz offset Andy Bottomley

  9. Spurious Power Simulation Results with Phase Noise • Conditions • 1/f phase noise applied to simulations (10dB/decade) • Results • Phase noise better than -120dBc/Hz recommended @ 750kHz Phase noise -114dBc/Hz @ 750kHz Phase noise -120dBc/Hz @ 750kHz Andy Bottomley

  10. Spurious Power Simulation Result Summary • The toughest spurious power requirement is -54dBm/100kHz (average power) at 2.5xOBW (20dB occupied bandwidth) from centre of channel at maximum TX power • The maximum regulatory fundamental radiated power is specified in ERP and spurious power is specified in conducted power. The simulations and spectral plots assume a 0dBd antenna is used such that the TX power of 10dBmERP is equivalent to a conducted power of 10dBm. • With a TX filter of BT=0.7, 200kbps 2-FSK and modulation index of 1 there is a comfortable margin when passing the spurious requirement (200kHz) • Maximum frequency offset allowed in band is 100ppm (regulatory requirement) which translates to 63kHz max at the highest RF frequency. This offset can easily be accommodated. • The 20dB occupied bandwidth is 300kHz with a BT of 0.7. This allows for a channel filter of ~400kHz Andy Bottomley

  11. Eb/No Sweep of Modulation Index for 2-FSK 200kbps • Channel filter 3dB bandwidth = 400kHz • 3rd order Butterworth channel filter • BT = 0.7 • Eb/No = 10.4dB (with MI=1 & 0.1% BER) Andy Bottomley

  12. Adjacent Channel & Alternate Channel Rejection Requirements • 802.15.4-2011 specifies 0dB & 24dB ACR & ALTCR using a modulated interferer • 802.15.4g-2012 specifies 10dB & 30dB ACR & ALTCR using a CW at centre of channel • Modulated interferer seems to be more appropriate to use as an interferer Andy Bottomley

  13. ACR& ALTCRSimulation Results for 2-FSK200kbpsMode, 500kHzChannelization • BT = 0.7, modulation index = 1, 20dB occupied bandwidth = 300kHz, 3rd order Butterworth channel filter with fc = 400kHz • The modulated interferer is the same as for the wanted signal • Results indicate that meeting the modulated interferer requirement is not a problem. Plenty of margin exists. Andy Bottomley

  14. Variable Data Rates • Lower data rates than 200kbps offer improved RX sensitivity: • If a 50kbps 2-FSK mode is considered and the same 20dB occupied bandwidth as for 200kbps is required then this would require a modulation index of 5. Andy Bottomley

  15. Variable Data Rates • With a modulation index of 5 the Eb/No has degraded by 2.5dB worse than for a modulation index of 1. A modulation index of 1 appears to offer optimal Eb/No. Andy Bottomley

  16. Variable Data Rates – Key assumption • The regulatory requirement for spurious emissions is only related to the maximum data rate mode. The following extract is taken from Rec. ITU-R SM.329-12: • With a constant modulation index and lower data rate the occupied bandwidth will drop commensurately. The edge of the spurious domain will draw closer to the wanted channel (2.5 x OBW). Under these conditions the phase noise requirement on the TX will become harder to meet. Andy Bottomley

  17. Overall FSK PHY Proposal • 500kHz channelization to support 200kbps • Range of data rates 25kbps – 200kbps • TX Gaussian filter BT=0.7 • 2-FSK only Andy Bottomley

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