Ruben, The datasheet isn't going to provide transmission ranges, but you can get a good estimate of the transmission range by looking at the transmission power in dBm. Lets say you experimentally determine that transmitting at power value 3 gives you a 5m transmission range. According to the datasheet, this is -25 dBm (note what the datasheet reports and actual values may vary significantly, especially at very low/high power values). What would the transmission range be at power level 7 (-15 dBm)? Remember that you can estimate signal attenuation due to distance by doubling the distance for every 6 dB of gain the signal experiences (or half the distance for every 6 dB loss). 10 dB / 6 dB = 1.67 (1.67 "doubles" of 5m, 2^1.67 ~= 3.17 and 5m * 3.17 ~= 15.9 m. If your transmission range for a -25 dBm signal is 5m then your transmission distance should be somewhere around 16m for a -15 dBm signal.
Of course this has no consideration for multipath effects, or other obstructions. Another key assumption is that the antenna is isotropic (radiates equally in all directions), meaning that no matter how the antenna is oriented, the transmission range will be the same. This is not true, and rotating the antenna even a few degrees on any axis can result in significantly different RSS values seen at the receiver. If you have more questions about this, look at some of the resources on "Free Space Loss" or "Free Space Propagation" models. Hope this helps, -Paul Rubén Ríos del Pozo wrote: > Hi Paul & Vijay, > > I am also interested in transmission power levels and transmission > range so I have been taking a look at the section Paul refers in the > CC2420 datasheet. However, I cannot see much interesting information > regarding transmission range. > > I am quite interested on these issues for indoor tracking so I need > short range communications. Do any of you have any experimental data > to share with me? Actually, I was quite surprised with Vijay's mail > concerning radio ranges with DCC2420_DEF_RFPOWER values of 1 and 2. > > Thanks in advance, > Ruben > > Paul Johnson escribió: >> Vijay, >> >> Please reference the CC2420 datasheet under the section "Output Power >> Programming" for more details on the programmable transmission power >> levels. >> >> Unfortunately, I doubt you will be able to find a transmission power >> level that will precisely fit your needs. The CC2420 is not going to >> be able to provide the transmission power level granularity that you >> are wanting. >> >> Each time you quadruple the transmission power(6 dB power >> difference), you are doubling your transmission range. The listed >> figures on the datasheet show the minimum power levels: 3, 7 and 11 >> gives -25 dbm, -15 dbm and -10 dbm respectively. You cannot rely on >> the fact that values 4,5,6, etc increase the transmission power >> linearly (or guarentee that the transmission power increases and >> doesn't decrease). >> >> I have done some tests on the mica2 platform which uses the CC1000 >> radio chip and found that going from transmission power level 0xF to >> 0x10, I actually saw a decrease in transmission power level. >> >> -Paul >> >> vijay sankar wrote: >>> I am using the telos motes and tinyos1.x. >>> I want the radio frequency range to be within 200 to 400 cm. I tried >>> this CFLAGS+=-DCC2420_DEF_RFPOWER=1 with different values. But for a >>> value of "1" radio range is around 15-30 cm and for a value of 2 it >>> is around 50 cm and for a value of 3 it is going beyond 5mt. >>> Can any one please let me know if I could set radio frequency range >>> around 200cm. >>> >>> Thanks, >>> Vijay. >>> ------------------------------------------------------------------------ >>> >>> >>> _______________________________________________ >>> Tinyos-help mailing list >>> [email protected] >>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >>> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> Tinyos-help mailing list >> [email protected] >> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
