Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Low duty cycle UWB piconet] Date Submitted: [March, 2006] Source: [Bin Zhen, Huan-Bang Li and Ryuji Kohno; Company: National Institute of Information and Communications Technology ] Contact: Bin Zhen Voice:+81 46 847 5445, E-Mail: zhen.bin@nict.go.jp] Abstract: [piconet level low duty cycle for coexistence.] Purpose: [UWB coexistence] 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.

Low duty cycle UWB piconet by Bin Zhen, Huan-bang Li and Ryuji Kohno

Agenda for discussion in DOC. 06-0049-00-4a Regulatory requirement is to ensure coexistence by reasonable interference reduction technology, e.g. DAA, LDC. Regulatory issues (1) Necessity of Interference reduction technology, e.g. DAA (2) Introduction and discussion of feasible DAA Doc.06-00133-00-4a (Previous Doc.) (3) Summary of issues in DAA for regulatory compliance 2. Coexistence issues (1) Category of coexistence problem (2) Solution for regulatory requirement, i.e. simple DAA, LDC (3) Definition of LDC: necessary duty cycle in node & PCN etc Doc.06-00134-00-4a (This Doc.)

Solution for regulatory requirement, i.e. simple DAA, LDC Necessity of the reason why LDC is good enough for suppression of interference to coexisting victim radio instead of DAA The reason for using 1% duty cycle in 2.4GHz band is vague Can LDC solve all coexistence problems? If no, what can we do for solution? Why and how is the value of 1% selected? Is the value guaranteed for a device-to-device link or a piconet? If the value is valid for a device-to-device link, then how can we guarantee such a low duty cycle for multiple piconet environments?

LDC nodes Currently, LDC refers activity of a device to be 5% over one second, 0.5% over one hour (EU definition) Victim receivers are interfered as long as the UWB channel is active The victim systems may cover larger area than 4a, e.g. 802.16 Any LDC device in the piconet can be an interferers

High density of LDC nodes In the case of high density of LDC nodes in a piconet, the aggregate interference from the piconet (channel) is still high Assuming 0.5% node duty cycle of a pure ALOHA piconet 0.161 when there are 36 nodes 0.732 when there are 360 nodes The channel free period is randomly segmented into small pieces which is hard to be used

Aggregate channel busy period 360 nodes in the piconets 36 nodes in a piconet Irregular free channel piece Beacon Busy channel Free channel … …. time Channel state Victim packet

Low duty cycle piconet Low Duty Cycle piconet as interference metrics For simple sensors, it is hard to detect victim receiver reliable for the reason of cost, power consumption, etc. Maximal aggregate interference to victim receivers from a piconet can be controlled through total piconet active duration Localize the interference period

Low duty cycle piconet (cont.) LDC piconet is to control the aggregate active period and its distribution in the piconet level, which can be guaranteed by control of active/inactive period to add segmented free channel pieces together reduce traffic in the piconets control number of devices through association increase number piconets to cover the same local area traffic shaping at coordinator and device good MAC to reduce packet collision in the active period channel dependent ALOHA CSMA

Low duty cycle piconet (cont.) Inactive period Active period Active period time … …. Active/inactive period CSMA or channel dependent ALOHA Traffic shaping Inactive period Active period Active period time Piconet in another channel band

Applying LDC piconet to 15.4a Extend concept of active/inactive period to non-beacon enabled network Active period is immediately after the beacon for synchronization Application layer clock synchronization Channel dependent ALOHA whose transmission probability depends on channel condition, e.g. RSSI and LQI obtained from beacon Transmission threshold set by application Suggested parameters At least active/inactive ratio = 1:1 Maximal offered traffic in active period of a piconet 0.18 for pure ALOHA 0.5 for CSMA

Conclusions Low duty cycle piconet Policy based coexistence Active/inactive period to non-beacon enabled network Synchronization in application layer We suggest to have coexistence annex to define the duty cycle of device and duty cycle of piconet LDC device is below 1% (for example) LDC piconet is below 20% for ALOHA network or 50% for CSMA network Any application that cannot be implemented through LDC should adopt DAA

Backup: Analysis on aggregate channel busy period in an ALOHA network Pure ALOHA MAC time 1 2 1 2 Busy period idle period Normalized offered load The last packet arrive at y after the reference packet. That is no packet occurs in (1-y). The probability is The average of busy period of channel is The average of idle period of channel is