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Comment Resolution for LB#70 TX Spectral Mask CID#123

This document provides comment resolution for LB#70 regarding the transmit spectral mask for MR-FSK modulated signals in IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) submission.

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Comment Resolution for LB#70 TX Spectral Mask CID#123

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Comment Resolution for LB#70 TX Spectral Mask CID #123] Date Submitted: [17 March 2011] Source: [Steve Jillings,] Company: [Semtech] E-Mail: [sjillings@semtech.com] Re: [] Abstract: [] Purpose: [To assist with comment resolution for LB #70] 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. Steve Jillings, Semtech

  2. Background • Question: What is a MR-FSK modulated signal? • Answer: “Filtered” FSK • Question: What is “Filtered” FSK? • Answer: ??? • Assumption: For 15.4g, “Filtered FSK” describes the MR-FSK signal as defined in 16.1.2 of the current draft: • The modulation for the MR-FSK PHY is either 2 or 4 level filtered FSK that meets the transmit spectral mask, as defined in 16.1.5.6. GFSK with a BT value of 0.5 should be used in the 950 MHz band. Steve Jillings, Semtech

  3. 16.1.5.6 Transmit Spectral Mask • The transmit spectral content is the ratio of the total transmitted out-of-channel power to the total transmitted in-channel power in a given integration bandwidth. • The frequency interval shall be equal to 1.5 x R, where R is the symbol rate, expressed in units of hertz. Out-of-channel power shall be measured at two offset frequencies relative to the carrier frequency. The offset frequencies M1 and M2 are defined as follows: • M1 = 1.5 x R x (1+h) • Where h is the modulation index for 2-level modulation and three times the modulation index for 4-level modulation • M2 = 3 x R x (1+h) • The transmit spectral content at M1 and M2 shall be less than –25 dB and –35 dB, respectively. • The modulated signal shall use a PN data pattern of 511 bits or longer. • The spectrum analyzer settings for this measurement shall be as follows: the resolution bandwidth is 1 kHz, the video bandwidth is 1 kHz or greater, and the detector is RMS Steve Jillings, Semtech

  4. For MR-FSK PHY operating mode #1 • BR = 50 kb/s, h = 1, channel spacing = 200 kHz • R = 25 kHz • M1 = 1.5*R*(1+h) = 1.5*25*(1+1) = ±75 kHz • M2 = 3*R*(1+h) = 3*25*(1+1) = ±150 kHz • For MR-FSK PHY operating mode #3 • BR = 200 kb/s, h = 0.5, channel spacing = 400 kHz • R = 100 kHz • M1 = 1.5*R*(1+h) = 1.5*100*(1+0.5) = ±225 kHz • M2 = 3*R*(1+h) = 3*100*(1+0.5) = ±450 kHz Steve Jillings, Semtech

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  7. 15.4g spectral mask and regulatory requirements for license-exempt frequency bands (as of 05/11/2011): • 16.1.5.2 Regulatory compliance • It is the responsibility of the implementer to verify and ensure that the device is in compliance with all regulatory requirements in the geographic region where the device is deployed or sold. Conformance with this standard does not guarantee compliance with the relevant regulatory requirements which may apply. Steve Jillings, Semtech

  8. Question: Just because the transmit spectral mask is as defined, do we expect a MR-FSK “Filtered” FSK signal to occupy all of the mask (potentially out to ±)? • Answer: ??? But there exist in the standard specifications that are meant – for a reason - to address the concerns of the support of legacy products: • Transmitter: Symbol rate tolerance (±300 ppm) • Preamble: Up to 1000 octets • Assumption: A MR-FSK “Filtered” FSK may need to occupy the available spectrum allowed by the spectral mask Steve Jillings, Semtech

  9. CID #123 • Proposal: • Defined Spectral mask does not comply with the FCC requirements for nearly all of the bands listed in table 65 • Provide additional spectral mask definitions and reference individual bands as necessary to comply with individual band regulatory requirements Steve Jillings, Semtech

  10. CID #123 • Proposed Resolution • Accept in Principle • Although proposal is US-centric, the comments apply equally to both ETSI and ARIB regulatory bodies • For license-exempt frequency bands the group should revisit the transmit spectral mask definition of 16.1.5.6 to determine whether a more spectrally efficient mask can be identified that does not orphan legacy devices currently compliant with the draft standard • It is noted that conformance with the spectral mask defined does not guarantee compliance with the relevant regulatory requirements which may apply (Section 16.1.5.2) • For dedicated use bands the standard should always defer to the regulatory requirements of the band in question Steve Jillings, Semtech

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