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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks(WPANs) Submission Title: Comments on FSK spreading sequence Date Submitted: Source: Mi-Kyung Oh, Jae-Hwan Kim, Jae-Young Kim and Sangsung Choi (ETRI) Contact: ohmik@etri.re.kr

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks(WPANs) Submission Title: Comments on FSK spreading sequence Date Submitted: Source:Mi-Kyung Oh, Jae-Hwan Kim, Jae-Young Kim and Sangsung Choi (ETRI) Contact: ohmik@etri.re.kr Voice:+82 42 860 6831, E-Mail: ohmik@etri.re.kr Re: Call for proposals Abstract: Purpose: 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 ETRI

  2. Spreading • Spreading • Selectively used for enhanced reliability • Apply to (PHR+PSDU) • Spreading gain: dependent on spreading factor • Spreading sequence design • Mainly focus on spreading gain & low complexity receiver architecture • Do not need to consider the sample-level timing synchronization since spreading sequence does not apply to preamble & SFD SFD PHY Layer PHR PSDU Preamble Spreading ETRI

  3. Spreading Sequence • Selection criteria • In terms of spreading gain, any spreading sequence pattern will give the same spreading gain in (PHR+PSDU) part • Due to chip-symbol level de-spreading (or correlation) • However, it is desirable that spreading sequence provides some benefits considering characteristics of FSK system • Commercially popular low-complexity FSK receivers are optimally designed for “01” or “10” repetition for CFO estimation/compensation and timing recovery • e.g.) ADF7020, CC1101 ETRI

  4. Spreading Sequence • In P802.15.4k/D1 draft • “01” or “10” repetition sequence Slide 4 ETRI

  5. Benefits of Current Spreading Sequence • 1. Symbol timing synchronization • “01” or “10” repetition sequence provides high frequency of chip-symbol transition which helps chip-symbol timing synchronization (or tracking) in general CDR (Clock & Data Recovery) block of FSK system ETRI

  6. Benefits of Current Spreading Sequence • 2. CFO estimation/update • Preamble: multiples of “01010101” which are best for CFO estimation for FSK system • Generally, CFO estimation is carried out during preamble reception • “01” or “10” repetition sequence enables to perform additional CFO update during PHR & PSDU reception without any additional logic at the receiver ETRI

  7. Benefits of Current Spreading Sequence • 3. Low-complexity de-spreading architecture • “01” or “10” repetition sequence requires the minimal implementation logic when chip-symbol level de-spreading • No sequence memory or no sequence matching is required • Repetitive “Add and Subtract” operation is enough • Scalability: De-spreading logic is independent to SF=2,4,8,16. ETRI

  8. Conclusion • The spreading sequence in P802.15.4k/D1 draft is best when considering both spreading gain and low-complexity FSK receiver ETRI

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