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1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Comment resolution for CID 249 Date Submitted: September 27, 2011 Source: Khurram Waheed Company [.Freescale Semiconductor, Inc] E-Mail: khurram.waheed@freescale.com Re: Supporting resolution to IEEE 802.15.4g Sponsor Ballot CID 249 Abstract: Resolution to IEEE 802.15.4g Sponsor Ballot CID 249 Purpose: Smart Utility Networks 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. Slide 1 Slide 1

2. CID 249 Comment: 50kb/s; 200 kHz CSM requirement in 2.4GHz band results in unnecessarily tight transceiver performance requirements Commenter’s Proposed Resolution: As per PAR, SUN transceivers are low-cost; it is recommended that 2.4GHz CSM requirements are chosen independent of other bands. An option is to choose either of FSK operating mode 2 or 3 (specified for 2.4GHz band) Slide 2 Slide 2

3. Background of this Comment on 2.4GHz CSM • CSM specification for the 2.4GHz and the restrictions that it imposes on the transceiver design has come up for discussion in the group more than once. • e.g., see document by Michael Schmidt • 15-10-0834-00-004g-transmit-center-frequency-tolerance-for-mr-fsk.pdf • Despite its technical merit, this comment has been bunched with the more contentious comments and has been a victim of inaction by the TG4g members • Probably due to lack of interest by active TG4g members • The current 50kbps in 200kHz channel spacing definition for the 2.4GHz band is even more stringent than the higher data BW options in the standard including MR-OFDM and MR-OQPSK , i.e. • See Technical Justification slide(s) for more details

4. Technical Justification (1/2) • Based on the MR-FSK clock frequency tolerance requirements in section 16.1.5.3, the CSM requirements translate to the following clock frequency tolerances • For both MR-OFDM (section 16.2.4.9) and MR-OQPSK (section 16.3.4.8), the clock frequency tolerance is specified to ≤ ± 20 ppm • The clock frequency tolerance shown above encompasses the frequency tolerance of the crystal reference (after calibration) and its degradation due to voltage, temperature, mechanical shock, agingas well as other sources of frequency error in the transceiver such as PLL frequency resolution and clock skew due to routing, etc.

5. Technical Justification (1/2) • Assuming transceiver error sources to be relatively constant, the above clock frequency tolerance requirements translate to a tighter reference frequency spec (TCXO, VCTCXO, etc.), which translates to a higher platform cost by $0.15 - $0.30 (depending on production volume) • This necessitates a GPS quality reference as there is no Automatic Frequency Compensation (AFC) built into the IEEE 802.15.4 family of standards. • The tighter frequency tolerance requirements using a cheaper crystal reference source will result in a reduced lifespan of devices deployed in 2.4 GHz band (< 5-7 years), which contradicts the intended application space requirements for IEEE 802.15.4g standard • Other complications due to a degraded clock frequency tolerance may include • Challenges with adjacent channel rejection due to significant overlap of the main signal lobes (see slide 18 of 10/0834r0) • Requirement to search for the incoming Rx signal in a relatively wider frequency window (practically clock tolerances scale linearly with carrier frequency)

6. Proposed Resolution Justification • While looking at the tabulated CSM clock frequency tolerance requirements (see slide 4), one can argue that the modulation requirements in the 2.4GHz band should be tightened to match the sub-1 GHz bands requiring ≤ ± 30 ppm clock frequency tolerance • However, 2.4GHz bands provides significant contiguous bandwidth and has been historically used for wider channel BWs and higher data throughputs • It is, therefore, proposed that the frequency tolerance requirements are aligned with the specified MR-OFDM and MR-OQPSK PHYs • The next slides list the options discussed at the September Okinawa meeting along with comments on each by the author of this document

7. Recommended Proposed Resolution(s) • Proposed Resolution #1(Khurram Waheed) • Redefine the CSM in 2.4GHz band to the following • Note the same proposal was proposed by Michael Schmidt in document 10/0834r0. Actually, the clock frequency tolerance gets relaxed to approx 28 ppm • This can be done by redefining the Operating Mode #1 in Table 116 to be in line with above definition • Table 69a for the PHY definition for CSM to be revised as follows

8. Recommended Proposed Resolution(s) • Proposed Resolution #2 (Khurram Waheed) • Redefine the CSM in 2.4GHz band to use the 15.4g draft standard defined operating mode #2 • i.e., Filtered 2FSK 150kbps data rate with modulation index ½ in 400kHz band • This option requires no change in Table 116. 50 kbps in 100kHz will remain as an optional mode • The required clock frequency tolerance will be < ± 22 ppm (using operating mode #2), which aligns well with MR-OFDM and MR-OQPSK. Note that choosing Operating Mode #3 instead for CSM would translate to a clock frequency tolerance < ± 28 ppm • Table 69a for the PHY definition for CSM to be revised as follows:

9. Other Proposed Resolutions • Proposed Resolution #3 (Daniel Popa) • Use the same 50kbps data rate but change the channel spacing to 400kHz • Author’s Comments: • While the above proposal will avoid any adjacent channel rejection degradation (see discussion on slide 5), the system would still require the tighter clock frequency tolerance for accurate demodulation • Proposed Resolution #4 • Do Nothing • Include informative text in section 16.1.5.3 (or in section 8.2 CSM) that “THE CSM requirements in 2.4GHz translate to a clock frequency tolerance requirements of < ± 12 ppm” (i.e., leaving some margin for implementation) • Author’s Comments: • This is an unacceptable status quo and essentially translates to a IEEE 802.15.4g CSM definition in 2.4GHz band , which might never be used.

10. Author Recommendation • The author of this document recommends to choose Proposed Resolution #1 to resolve this comment. • Proposed resolution #2 is also acceptable; However, choice of Operating Mode #2 for CSM is less desirable