"Despite all the problems you describe, *and* the fact the FCC had no intention to facilitate widespread short-range wireless data connectivity, that's what we got with WiFi."
Kevin, my point is, Wi-Fi is *all* you're going to get in that band; its economic value to (mostly corporate) users will ensure that sources of potential interference will be carefully scrutinized. Other applications of 2.4 GHz will have a difficult time overcoming real or percieved interference issues (cf. Bluetooth's PR problems now). Significant (in the economic sense) future innovation is most certainly not going to occur at 2.4 GHz; users of Wi-Fi wouldn't allow it unless it could coexist and, as I've stated earlier, designing low cost, low power wireless devices to do so is a nontrivial task.
The FCC *did* start its regulation of the 2.4 GHz ISM band with the goal of spectrum sharing... that's why spread spectrum is required there in the first place, and why the 15.247 rules are only 3 pages long. All other design requirements of systems using the band must be generated by the equipment designers; one of the problems with the band now is that engineers have almost complete latitude in defining the rules (I know -- I'm one of them). When one designs a network in which all nodes are compatible with each other, for "efficient spectrum utilization," all nodes end up looking the same, and you've just created another single-use band -- whether mandated by the FCC, or occurring through market forces as a de facto industry standard.
(And Keven, you're right: Don't complain about being called "the author" -- many authors of/. material would love to get their names back out of the mud, and up to that level!)
The author is out of touch with the issues now facing those of us now working on IEEE 802.11,.15, and.16 standards. The primary problem 802 has at the moment is that almost all of its draft wireless standards (e.g., 802.11g, 15.1, 15.3, 15.4, etc.) are being planned for the 2.4 GHz ISM band, due to its combination of near-worldwide unlicensed availability, suitable (i.e., relatively wide) bandwidth, and technical practicality (small antennas, possibility of cheap CMOS RF implementation, etc.). The major exceptions are in 802.16, the WirelessMAN(tm) Metropolitan Area Network standards, which typically employ such a high data rate that even the 2.4 GHz band is too narrow; however, even there, the 802.16b task group is developing a standard for the unlicensed 5-6 GHz band.
The difficulty is coexistence, or how all these standards will affect each other when networks using them are placed into service. This concern started as a Working Group issue, and was addressed by coexistence task groups (e.g., 802.15.2, 802.16.2a), but has now bubbled up to the 802 LMSC itself, with the recent formation of the 802 COEX coexistence study group. 802.11 has become the 800-lb. gorilla in the 2.4 GHz band, microwave ovens included, and it is far, far from the truth to say that just because every system involved is spread spectrum the band may automatically be shared among many users.
Spread spectrum offers protection only to the extent of its processing gain which, for direct sequence systems, is defined as the ratio of chip rate to data rate. Present FCC regulations for the 2.4 GHz band specify a minimum of 10 dB processing gain; this requires a chip rate that is 10x the data rate. As one can see, to get significant processing gain one either (a) raises the chip rate, and the associated current drain of the product, to a high value, or (b) reduces the data rate to a low value. Neither of these is attractive when one considers that even a ratio of 40 dB (10,000x) is insufficient in many interference scenarios; worse, the FCC is proposing to eliminate the 10 dB requirement completely so that OFDM (Orthogonal Frequency Division Multiplex) signals, like those proposed for 802.11g, may be used.
CFR 47 15.247 devices, like 802.11 and.15 devices, are sold under the condition that they must accept interference to them caused by other devices. This was essentially a regulatory passing of the buck to the "free market," which has a spotty record in telecom (cf. U.S.' multiple cell phone standards vs. GSM). Since 802.11b has the largest installed base, any standard that follows that produces interference with 11b devices will have a hard time gaining marketplace acceptance; at the same time, brute force technologies to avoid interference, such as the use of processing gain, are insufficient. This leads standard and product designers to design ad hoc coexistence mechanisms to identify and avoid specific, predetermined interferers, an inefficient, piecemeal approach that places later, next-generation devices at a disadvantage over existing ones. The result is that 802.11 derivatives are going to defacto own the 2.4 GHz band in most corporate and (later) home environments; anything new in the band must carry the coexistence burden with it.
So, if 802.11b is the model for "Free airwaves," it's a poor model; it's more MS open spectrum than linux open spectrum.
Ah, but that's the advantage of a small model, with a length on the order of six feet. Getting torque from the wind requires a wind vector differential over a distance equal to the size of the model, and unless one is in a tornado one is unlikely to be in winds that differ significantly (from a structural survivability standpoint) over a distance of six feet. Maintaining proper attitude and directional control, of course, is a separate issue, but not an insurmountable one.
It's no exageration to say that Maynard Hill is the world's greatest living R/C aircraft modeller, so I'd have to say that betting on him is the smart play. He's been doing this type of thing better than anyone else for a long, long time... since the 1950's.
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"Despite all the problems you describe, *and* the fact the FCC had no intention to facilitate widespread short-range wireless data connectivity, that's what we got with WiFi."
... that's why spread spectrum is required there in the first place, and why the 15.247 rules are only 3 pages long. All other design requirements of systems using the band must be generated by the equipment designers; one of the problems with the band now is that engineers have almost complete latitude in defining the rules (I know -- I'm one of them). When one designs a network in which all nodes are compatible with each other, for "efficient spectrum utilization," all nodes end up looking the same, and you've just created another single-use band -- whether mandated by the FCC, or occurring through market forces as a de facto industry standard.
/. material would love to get their names back out of the mud, and up to that level!)
Kevin, my point is, Wi-Fi is *all* you're going to get in that band; its economic value to (mostly corporate) users will ensure that sources of potential interference will be carefully scrutinized. Other applications of 2.4 GHz will have a difficult time overcoming real or percieved interference issues (cf. Bluetooth's PR problems now). Significant (in the economic sense) future innovation is most certainly not going to occur at 2.4 GHz; users of Wi-Fi wouldn't allow it unless it could coexist and, as I've stated earlier, designing low cost, low power wireless devices to do so is a nontrivial task.
The FCC *did* start its regulation of the 2.4 GHz ISM band with the goal of spectrum sharing
(And Keven, you're right: Don't complain about being called "the author" -- many authors of
The author is out of touch with the issues now facing those of us now working on IEEE 802.11, .15, and .16 standards. The primary problem 802 has at the moment is that almost all of its draft wireless standards (e.g., 802.11g, 15.1, 15.3, 15.4, etc.) are being planned for the 2.4 GHz ISM band, due to its combination of near-worldwide unlicensed availability, suitable (i.e., relatively wide) bandwidth, and technical practicality (small antennas, possibility of cheap CMOS RF implementation, etc.). The major exceptions are in 802.16, the WirelessMAN(tm) Metropolitan Area Network standards, which typically employ such a high data rate that even the 2.4 GHz band is too narrow; however, even there, the 802.16b task group is developing a standard for the unlicensed 5-6 GHz band.
The difficulty is coexistence, or how all these standards will affect each other when networks using them are placed into service. This concern started as a Working Group issue, and was addressed by coexistence task groups (e.g., 802.15.2, 802.16.2a), but has now bubbled up to the 802 LMSC itself, with the recent formation of the 802 COEX coexistence study group. 802.11 has become the 800-lb. gorilla in the 2.4 GHz band, microwave ovens included, and it is far, far from the truth to say that just because every system involved is spread spectrum the band may automatically be shared among many users.
Spread spectrum offers protection only to the extent of its processing gain which, for direct sequence systems, is defined as the ratio of chip rate to data rate. Present FCC regulations for the 2.4 GHz band specify a minimum of 10 dB processing gain; this requires a chip rate that is 10x the data rate. As one can see, to get significant processing gain one either (a) raises the chip rate, and the associated current drain of the product, to a high value, or (b) reduces the data rate to a low value. Neither of these is attractive when one considers that even a ratio of 40 dB (10,000x) is insufficient in many interference scenarios; worse, the FCC is proposing to eliminate the 10 dB requirement completely so that OFDM (Orthogonal Frequency Division Multiplex) signals, like those proposed for 802.11g, may be used.
CFR 47 15.247 devices, like 802.11 and .15 devices, are sold under the condition that they must accept interference to them caused by other devices. This was essentially a regulatory passing of the buck to the "free market," which has a spotty record in telecom (cf. U.S.' multiple cell phone standards vs. GSM). Since 802.11b has the largest installed base, any standard that follows that produces interference with 11b devices will have a hard time gaining marketplace acceptance; at the same time, brute force technologies to avoid interference, such as the use of processing gain, are insufficient. This leads standard and product designers to design ad hoc coexistence mechanisms to identify and avoid specific, predetermined interferers, an inefficient, piecemeal approach that places later, next-generation devices at a disadvantage over existing ones. The result is that 802.11 derivatives are going to defacto own the 2.4 GHz band in most corporate and (later) home environments; anything new in the band must carry the coexistence burden with it.
So, if 802.11b is the model for "Free airwaves," it's a poor model; it's more MS open spectrum than linux open spectrum.
Robotic aircraft is a popular avocation, viz.: Aerial Robotics Competition, The Association for Unmanned Vehicle Systems International and, in particular, their Unmanned Air Vehicles page. Each of these sites has links to many other projects.
Ah, but that's the advantage of a small model, with a length on the order of six feet. Getting torque from the wind requires a wind vector differential over a distance equal to the size of the model, and unless one is in a tornado one is unlikely to be in winds that differ significantly (from a structural survivability standpoint) over a distance of six feet. Maintaining proper attitude and directional control, of course, is a separate issue, but not an insurmountable one.
... since the 1950's.
It's no exageration to say that Maynard Hill is the world's greatest living R/C aircraft modeller, so I'd have to say that betting on him is the smart play. He's been doing this type of thing better than anyone else for a long, long time