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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: study of UWB interference issues Date Submitted: September 7th, 2008 Source: Kiran Bynam, Giriraj Goyal , Ranjeet Kumar Patro , Arun Naniyat, EunTae Won

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: study of UWB interference issues Date Submitted: September 7th, 2008 Source: Kiran Bynam, Giriraj Goyal , Ranjeet Kumar Patro, Arun Naniyat, EunTae Won Contact: Kiran Bynam, Samsung Electronics Voice: +91 80 41819999, E-Mail: kiran.bynam@samsung.com Re: [] Abstract: brief study on Interference and co-existence in BAN Networks in UWB Purpose: To discuss the Interference and co-existence problems in BAN 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 in March’08 it would be made publicly available by P802.15. Slide 1 Kiran Bynam, Samsung

  2. Outline • Problems with interference • Overview of Interference of UWB to NB systems • Interference problems to the UWB networks • Future work

  3. Interference aspects • Effects of interference • Loss of performance • Reduction in range • Link unavailability • Types of interference • UWB interference on narrow band • Narrow band interference on UWB • UWB to UWB

  4. NB TRx BAN TRx NB TRx BAN TRx NB TRx NB TRx Interference scenario and implications • BAN Receiver node is receiving the Narrow band interference signals coming from N different sources • Performance of BAN network is limited by the N narrow band interference powers and their power levels

  5. Interference from NB to UWB systems • The signal at the BAN receiver can be defined as • Y(n) = α * s(t) + hUWB (t) * a(t) + nUWB(t) • Where s(t) is the UWB transmit signal • a(t) is the Narrow band signal • nUWB(t) is the noise generated in the UWB receiver • The signal to noise density ratio at UWB receiver can be given as • (C/N)density = PUWB/(NUWB + IUWB /BUWB) • PUWB is the power of the UWB band signal at the input of narrow band receiver • NUWB is the power density of the noise generated in the UWB receiver • IUWB is the power of the other NB interferers in the band of UWB

  6. Lower bounds on UWB power due to NB interference • Prx/D > (Nu+ Iu/Buwb) (Eb/No)min • Where D is the date rate required • (Eb/No)min is the minimum Eb/No required for satisfactory operation • Example in a BAN scenario • At typical interference power of -80 dBm • Minimum Eb/No of 10 dB • Data rate of 10 Mbps • The received power should more than approximately -84.5 dBm

  7. NB to UWB interference Even at very close range, the transmit power should be higher in case of strong interference The continuous interferer signal transmission scenario may be avoided using energy detection at the time of network initialization What is the criteria for meeting performance requirements in the interference conditions? Needs to be verified.

  8. Interference from UWB to NB systems • The signal at the Narrow band receiver can be defined as • Y(n) = α * sNB(t) + hNB (t) * a(t) + nNB(t) • Where sNB(t) is the narrow band transmit signal • a(t) is the UWB band signal • nNB(t) is the noise generated in the UWB receiver • The signal to noise density ratio at NB receiver can be given as • (C/N)density = PNB/(NNB + INB / BNB) • PNB is the power of the narrow band signal at the input of narrow band receiver • NNB is the power density of the noise generated in the narrow band receiver • INB is the power of the UWB interferers in the band of narrow band signal

  9. Effects of UWB Interference on NB • Typical Narrow band signal bandwidth is assumed to be 10 M Hz • The UWB signal in the NB receiver bandwidth will be processed at receiver after getting filtered at the BPF of the receiver • For a typical case when the NB node is at 1 m distance from UWB transmitter • UWB power in 10 MHz band is -71.3 dBm ( assuming a path loss of 40 dB at 1m) • This power is not at all negligible as some of the narrow band receiver sensitivities will be typically below -70 dBm • Results in huge loss of performance or power consumption

  10. UWB Interference on Narrow band • The UWB is typically viewed as the modulation of narrow pulses • Accumulation of more power in the active region of pulses • Leads to higher instantaneous interference to narrow band systems • Is there any restrictions posed by any regulatory body for the UWB devices co-existing with Narrow band devices?

  11. Conclusion • Need to have a Threshold for channel migration so that we can change the channel without spending more power to counter the interference and not sacrificing the performance at low received energy levels. • Is there any thing defined by regulatory? • Should work on power control algorithm so that we radiate only required power and reduce the interference to narrow band systems.

  12. References • UWBRadio deployment challenges – R.A.Scholtz et. al

  13. Thank You

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