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PHY Considerations for Low Power Body Area Networks (BANs)

This document discusses the options for PHY frequency band in 802.15.6 to promote a discussion on available frequency band options for BANs.

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PHY Considerations for Low Power Body Area Networks (BANs)

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title:[PHY considerations for low power body area networks (BAN)] Date Submitted: [March 17, 2008] Source:[Zhanfeng Jia, Jason Ellis and Amal Ekbal] Company [Qualcomm, Inc.] Address [5775 Morehouse Drive, San Diego, CA 92121] Voice:[+1-858-845-6353], E-Mail:[jason.ellis@qualcomm.com] Abstract: [This document presents an option for 802.15.6 PHY frequency band] Purpose: [To promote a discussion of PHY frequency band options available for 802.15.6] 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.

  2. PHY Considerations for Low Power Body Area Networks (BANs) Draft Contribution for March 2008 IEEE 802.15.6 Meeting Jason Ellis Amal Ekbal Zhanfeng Jia

  3. Key Points • Unlicensed Spectrum • Technology Benefits • Initial Propagation Results • Low Cost Antenna Solutions

  4. Available Unlicensed Spectrum • ISM: 900MHz and 2.4GHz • Very congested • WiFi • Bluetooth • Zigbee • Cordless Phones • Microwave Overs • Misc • UNII: 5GHz – less congested • Some WiFI (802.11a, possible small amount of 11g) • Cordless Phones • Misc • UWB: 3.1-10.6GHz • Newly unlicensed globally, • WiMedia (Wireless USB and Bluetooth 3.0) • Unique properties for communication • 60GHz • Globally unlicensed spectrum • Basis for new very high speed and wireless video standards

  5. The global unlicensed spectrum “window” • Regulatory Status • US UWB legal 3.1-10.6 GHz • EU has legalized 6-8.5GHz • Japan has legalized 7.25-10.25GHz for high data rate (>50Mbps) • Regulators still working on lower data rate • 7.25-8.50 GHz is a globally available “window” of spectrum

  6. A closer look at 7.25-8.5 GHz Benefits • Worldwide unlicensed spectrum • Low in-band interference compared with ISM and UNII • Small antenna sizes lead to small form factors • Doubling frequency halves the antenna in each dimension • Good spatial reuse for dense deployments (e.g. hospitals, cars, buses,) • Multipath capture – • good for use in hospital, ship, container environments • Body area propagation is acceptable • No DAA requirements (detecting victim receivers) on low power BAN technologies • Low complexity, implementable in standard CMOS processes

  7. High Frequency Antennas can be Low Cost • $0.02 Antennas (inexpensive) • Very small • Omni directional antenna • Perform well in 7.25-8.5GHz Source: Antenna picture and gain plots from PUBs, http://timederivative.com/pubs.html

  8. Initial Path Loss Measurements • Measurements with off-the-shelf test-equipment to send and receive impulse waveforms at 7.25 to 9 GHz • Digital Storage Oscilliscope (DSO) captures Tx and Rx waveforms • Signals demodulated in Matlab • Preliminary measurements for (see following slides) • line-of-sight, 2’ • pocket-to-ear • Thru-wall and thru-door

  9. Typical Channel Measurements -1 Line-of-Sight, 2 feet Ear to Opposite Pants pocket 2.5ns 5ns Ep/N0 = 34dB Ep/N0 = 28dB Path loss = 49dB Path loss = 55dB

  10. Typical Channel Measurements -2 Thru-Wall, 4.5’ 5ns Thru-door, 4.2’ 5ns Ep/N0 = 27dB Ep/N0 = 27dB Through interior office wall Path loss = 56dB Through interior office door Path loss = 56dB

  11. Typical Channel Measurements: Pocket to Ear • Using a Software Radio test setup we measured the path loss for various pocket-to-ear scenarios and for different environments • 2 different cases considered: Pant’s pocket to ear on same and opposite sides • Path Loss computed as: • Includes antenna losses (Note: average gain is -2dB at either end) “Pants” pocket to opposite ear

  12. Conclusions • Newly unlicensed spectrum presents an opportunity for global BAN apps • Global “window” presently limited to 7.25GHz – 8.5GHz operation • High frequencies enable high density and high reuse applications • Inexpensive options exist for omni-directional antennas in 7.25-8.5GHz • Initial tests suggest path loss performance is quite reasonable, even at higher frequencies • Suggest 802.15.6 standards committee not preclude consideration of appropriate technology proposals for this band

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