Arboriculture & Urban Forestry 35(4): July 2009 some unintended consequences, such as a gradual avoidance of large trees, for fear they might interfere with aboveground util- ity lines (see Kuhns 2007, for a practical approach). Municipal Wi-Fi networks appear to be a part of city infrastructure that, if properly planned, is entirely compatible with (even) large urban trees. Municipal Wi-Fi represents an opportunity to inte- grate new urban technology into existing or newly planted tre- escapes while ensuring a conflict-free interaction between the two infrastructure components for the entire life of the trees. NOTE ON MEASUREMENT UNITS RF signal strength can be expressed in watts (W), but be- cause the power levels encountered in RF engineering vary over a range of as much as a billion-fold (Dobkin, 2005), logarithmic units called decibels (dB) are most com- monly used to express this change in power (i.e., “gain”): Gain (dB) = 10 · [log10 (measured power/reference power)]. A three-dB change represents a doubling of power, whereas 10 dB change is equivalent to a ten-fold increase or decrease. To make dB values meaningful, a standard “reference power” is agreed upon; in RF engineering it is one milliwat (1 mW = 10-3 W). The resulting units are designated dBm (“deci- bel referenced to 1 mW”), and because the Wi-Fi system uses very low power (i.e., measured power is much lower than the 1 mW reference power), the dBm values for Wi-Fi are nega- tive, varying from the high of about -30 dBm (one microwatt, 10-6 W) to the low of about -90 dBm (one picowatt, 10-12 W). Acknowledgments. We sincerely thank Dr. Daniel Dobkin, whose ex- tensive help with data analysis and in understanding the effects of trees on Wi-Fi signal made this study possible. Many thanks also to Tom Blais and Dr. Jay Kruse of Tropos Networks for describing the details of the municipal Wi-Fi hardware and the network in Mountain View. Bruce Hurlburt and Scott Gilliland of the City of Mountain View’s Forestry and Roadway Landscape Division greatly helped with the selection of study sites. Profs. Nicholas Mills and Perry de Valpine of the University of Cal- ifornia, Berkeley, provided invaluable statistical advice. The manuscript was greatly improved by the thoughtful comments of two anonymous re- viewers. The idea for this study came from Dr. Rajeev Koodli, of Starent Networks, who suggested the potential for the interaction of urban trees and municipal Wi-Fi networks. LITERATURE CITED Costello, L.R., and K.S. Jones. 2003. Reducing Infrastructure Damage by Tree Roots: A Compendium of Strategies. Western Chapter of the International Society of Arboriculture, Cohasset, CA. 119 p. Dalley, J.E.J., M.S. Smith, and D.N. Adams. 1999. Propagation losses due to foliage at various frequencies. pp. 267-270 In Proceedings of the IEEE National Conference on Antennas and Propagation (31 March–1 April 1999, University of York, York, UK). 209 Dobkin, D.M. 2005. RF Engineering for Wireless Networks: Hardware, Antennas, and Propagation. Newness, San Francisco, CA. 448 p. Grabosky, J., and N. Bassuk. 1995. A new urban tree soil to safely in- crease rooting volumes under sidewalks. Journal of Arboriculture 21:197–201. Kim, R. 2008. Cities have to bid bye-bye to free Wi-Fi. San Francisco Chronicle. www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/06/12/ BU681140TT.DTL&feed=rss.business (accessed 9/23/2008). Kuhns, M. 2007. How to Fit Large Trees Into Landscapes. extension.usu. edu/forestry/Presentations/Assets/Large%20Trees%20and%20Com- munities.07.pdf (accessed 9/17/2008). Lesser, L.M. 2001. Hardscape damage by tree roots. Journal of Arbori- culture 27:272–276. Oklahoma City. 2008. Oklahoma City now operational with world’s larg- est municipal Wi-Fi mesh network. www.okc.gov/news/2008_06/ oklahoma_city_wi_fi_mesh_network.html. (accessed 9/23/2008). Perras, S., and L. Bouchard. 2002. Fading characteristics of RF signals due to foliage in frequency bands from 2 to 60 GHz. pp. 267-271 In Proceedings of the 5th International Symposium on Wireless Personal Multimedia Communications (27–30 Oct. 2002, Honolulu, Hawaii). Randrup, T.B., E.G. McPherson, and L.R. Costello. 2001. A review of tree root conflicts with sidewalks, curbs, and roads. Urban Ecosystems 5:209–225. Sydnor, T.D., D. Gamstetter, J. Nichols, B. Bishop, J. Favorite, C. Blazer, and L. Turpin. 2000. Trees are not the root of sidewalk problems. Journal of Arboriculture 26:20–29. Urban, J. 2008. Up By Roots: Healthy Soils and Trees in the Built Environ- ment. International Society of Arboriculture, Champaign, IL. 479 p. Wagar, J.A., and P.A. Barker. 1983. Tree root damage to sidewalks and curbs. Journal of Arboriculture 9:177–181. Igor Laćan (corresponding author) Postdoctoral Researcher University of California, Berkeley Department of Environmental Science, Policy and Management 137 Mulford Hall # 3114, Berkeley, CA 94720–3114, U.S.
[email protected] Joe R. McBride Professor University of California, Berkeley Department of Environmental Science, Policy & Management and Department of Landscape Architecture & Environmental Planning 137 Mulford Hall # 3114, Berkeley, CA 94720–3114, U.S.
[email protected] ©2009 International Society of Arboriculture
July 2009
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
