Anand; You raise valid points and in a professionally installed system, the installers would have made sure that the transmit power levels were appropriate. My concerns are for non-professionally installed systems and/or systems with low duty cycle mobile end nodes. Normally, in professional installations we ensure a 20 dB signal margin for end nodes, and populate routers to minimize “choke” points and maximize spectrum reuse. However, in non-professional installs, we cannot assume these nodes will be properly set up. Also, I am concerned that the IEEE 802.15.4 standard for the O-QPSK PHY in the 2450 MHz band does not require transmit power leveling nor multiple power set points, so any use of transmit power control would depend upon proprietary capabilities. Finally, although phyTxPower is not marked as a read-only attribute, it is not described as an attribute that actively controls transmit power, hence its use as such would be proprietary.
Pat Pat Kinney Kinney Consulting LLC IEEE 802.15 WG vice chair, TG chair ISA100.11a WG chair O: +1.847.960.3715 [email protected] <mailto:[email protected]> On 9, Jun2015, at 2:50, S.V.R.Anand <[email protected]> wrote: Hi Pat, Thanks a lot for the insightful comments! The main theme of my mail is to use transmit power control is to enable better spatial re-use of the channels, managed by an external controller. The focus is not much on the power savings. With respect to the effect of power control on CSMA behaviour for the shared timeslots, one comes across literature that talks about optimal power control that trades-off between hidden node and exposed node problems. The latter is for better spatial re-use. As Michel pointed out in his mail, the nodes can use different output power levels. Left to them, this could lead to unpredictable the contention regions, and all the associated unfairness issues as well. A well provisioned power levels managed by a centralized controller can also help support more "deterministic" tracks that use dedicated TX timeslots. For reasons I cited in my earlier mail, don't you think a handle to transmit power control helps in managing the network better, at least in the case of non-CSMA timeslots ? Anand On Monday 08 June 2015 10:49 PM, Pat Kinney wrote: > Reducing transmit power may seem like a great idea but it creates havoc in many systems due to the hidden node problem. A reduction in transmit power will often degrade the effectiveness of the CSMA mechanism which is used in shared timeslots. The reduced effectiveness frequently appears as lost packets, requiring retransmissions, requiring more energy than that saved by reduction of transmit power. However, since the CSMA is not required for TX only timeslots, changing TX power in these timeslots may be done with fewer ill effects. > > Pat > Pat Kinney > Kinney Consulting LLC > IEEE 802.15 WG vice chair, TG chair > ISA100.11a WG chair > O: +1.847.960.3715 > [email protected] <mailto:[email protected]> > > > > > > > On 8, Jun2015, at 10:33, Michel Veillette <[email protected]> <mailto:[email protected]> wrote: > > Hi Anand and Qin > > > > Ill like to introduce the idea of supporting the option of adding the phyTXPower value in an IE within BEACON frames. > > Provisioning the phyTXPower can be an issue when targeting multiple markets with different output power limits. > > Including the phyTXPower within BEACON frames will enable joining nodes to adjust dynamically their output power based on a value managed at the PAN coordinator. > > > > <image001.jpg> > > > Michel Veillette > System Architecture Director > > Trilliant Inc. > Tel: 450-375-0556 ext. 237 > [email protected] <mailto:[email protected]> > > www.trilliantinc.com <http://www.trilliantinc.com/> > > > > > > From: 6tisch [mailto:[email protected] <mailto:[email protected]>] On Behalf Of Qin Wang > Sent: 8 juin 2015 11:08 > To: [email protected] <mailto:[email protected]>; Kris Pister > Cc: [email protected] <mailto:[email protected]> > Subject: Re: [6tisch] 6top and transmit power control > > > > Hi Anand, > > > > Regarding to power management, there is a parameter in the IEEE802.15.4 PIB, i.e. phyTXPower. You can control the transmitting power by changing its value. Is that what you want? If so, I think 6tisch MIB will provide the interface to access phyTXPower, which will be defined in the 6tisch-interface draft. > > > > Thanks > > Qin > > > > > > > > On Saturday, June 6, 2015 2:50 PM, "[email protected]" <mailto:[email protected]> <[email protected]> <mailto:[email protected]> wrote: > > > > Hi Kris, > > Thanks! > > I was not sure if and how such a parameter can be accommodated in the > current scheme of things, although it could be a useful control parameter > from the operator's perspective. > > Anand > > > > > seems like a good idea. > > > > ksjp > > > > On 6/4/2015 4:15 AM, SVR Anand wrote: > >> Dear All, > >> > >> A slight digression from the ongoing ML discussions. Hope the timing > >> is OK! > >> > >> As we all know, transmit power control is one of the powerful knobs > >> that can be > >> used to minimize the interference and thereby improve the wireless > >> network > >> performance and also provide deterministic network. Cell breathing > >> technique > >> used in WLANs comes to our mind. When it comes to 6tisch, one might > >> argue that > >> with 16 channels at our disposal, the interference can be avoided > >> through smart > >> 6top cell management interface without worrying much about transmit > >> power > >> control. However, there can be scenarios where transmit power control > >> might be > >> required, for instance, (i) large scale dense deployments with heavy > >> traffic > >> demands (ii) Co-existing WiFi reducing available non-overlapping > >> channels for > >> 15.4 (iii) prevent wireless leaks beyond the periphery of the > >> deployement > >> region and (iv) OTF scheduling where nodes make local decisions for > >> managing > >> cells, may be more. > >> > >> One possibility is to leave the power management to the nodes. We are > >> then > >> leaving this to implementors to device their own algorithms to handle > >> interference. Alternatively, a centralised controller (NME) knowing the > >> information about conflicting links can adaptively and optimally > >> adjust the > >> operating transmit power of the nodes to avoid the interference and > >> maximize > >> the wireless network performance. > >> > >> If we treat transmit power as one of the controllable parameters along > >> with the > >> cell management parameters, wondering if 6tisch 6top interface MIB is > >> the place > >> to define this. Or this parameter is beyond the scope of 6tisch. > >> > >> Any suggestions ? > >> > >> Anand > >> > > > > > > -- > > This message has been scanned for viruses and > > dangerous content by MailScanner, and is > > believed to be clean. > > > > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > _______________________________________________ > 6tisch mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/6tisch <https://www.ietf.org/mailman/listinfo/6tisch> > > _______________________________________________ > 6tisch mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/6tisch <https://www.ietf.org/mailman/listinfo/6tisch> > > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > _______________________________________________ > 6tisch mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/6tisch <https://www.ietf.org/mailman/listinfo/6tisch> -- This message has been scanned for viruses and dangerous content by MailScanner <http://www.mailscanner.info/>, and is believed to be clean.
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