http://en.wikipedia.org/wiki/Spectral_efficiency#Comparison_table
Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Sun, Sep 26, 2010 at 2:03 PM, John Scrivner <j...@scrivner.com> wrote: > The actual frequency band has nothing to do with data capacity. The > carrier CHANNEL BANDWIDTH is the important number. If a 6 megahertz > wide channel is used at say 200-206 MHz then any modulation system > used on that carrier should be able to carry the same amount of data > as an equivalent channel at say 600-606 MHz. Note both carriers are 6 > MHz wide. The capacity of the channel is determined by the spectral > efficiency of the system used to modulate and demodulate the > information from the channel's carrier(s). Do a Google search on > Nyquist / Shannon's Law / maximum bits per hertz to get a more > thorough understanding of the concepts. What we see in most of the > current systems we use for fixed wireless broadband are spectral > efficiencies from 0.5 to 10 bits per hertz. Some estimates say that we > will see roughly 17 bits per hertz from WiMAX and LTE deployments in > the coming months / years. This in large part due to the advancements > from MIMO which allows for in-channel reuse of the carrier bandwidth. > John Scrivner > > > On Sat, Sep 25, 2010 at 5:42 PM, Scott Reed <scottr...@onlyinternet.net> > wrote: > > That is not exactly true. Depends on the modulation techniques. And I > > believe there is an upper limit to the number of bits you can get on a > > single cycle of the carrier. > > > > On 9/25/2010 10:32 AM, Mike Hammett wrote: > > > > Just as fast as any other frequency. > > > > ----- > > Mike Hammett > > Intelligent Computing Solutions > > http://www.ics-il.com > > > > > > On 9/24/2010 5:50 PM, RickG wrote: > > > > But how fast can 200 or 300MHz go? > > > > On Thu, Sep 23, 2010 at 7:41 PM, Brian Webster > > <bwebs...@wirelessmapping.com> wrote: > >> > >> But what if you are able to use spectrum around 200 or 300 MHz? That > >> certainly goes through trees. > >> > >> > >> > >> Brian > >> > >> > >> > >> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On > >> Behalf Of Tom DeReggi > >> Sent: Thursday, September 23, 2010 7:32 PM > >> To: WISPA General List > >> > >> Subject: Re: [WISPA] Transmit Antenna Height > >> > >> > >> > >> Yeah, that really sucks. Many areas needing served have thick > forest/trees > >> easilly 70ft tall. > >> > >> A 90ft height, just wouldn't allow enough of the signal to have open > air, > >> and the signal would be going through trees most of the full path. > >> > >> In 900Mhz, the difference between having the tower side over the tree > line > >> and below the tree line can be the difference between a quarter mile > >> coverage and a 7 mile coverage in our market. > >> > >> All be it, 700Mhz does have better NLOS propogation characteristics than > >> 900 does. > >> > >> > >> > >> I would have liked to see that height doubled. > >> > >> > >> > >> However, admittedly, it will allow much better spectrum re-use in areas > >> that have a limited number of channels available. > >> > >> Spectrum reuse is one of the best ways to serve more people. > >> > >> > >> > >> > >> > >> Tom DeReggi > >> RapidDSL & Wireless, Inc > >> IntAirNet- Fixed Wireless Broadband > >> > >> > >> > >> > >> > >> ----- Original Message ----- > >> > >> From: Fred Goldstein > >> > >> To: WISPA General List > >> > >> Sent: Thursday, September 23, 2010 4:36 PM > >> > >> Subject: Re: [WISPA] Transmit Antenna Height > >> > >> > >> > >> This item alone may be the show-stopper, the poison pill that makes it > >> useless to WISPs in much of the country. > >> > >> In places where the routine variation in elevation is more than 75 > meters, > >> there will be houses (subscribers) that are more than 76 meters AAT. I > >> notice this in the areas I'm studying, both in the east and in the upper > >> midwest. > >> > >> In a place like Kansas, nobody is >75m AAT. But in the woody Berkshires > >> of Western Massachusetts, the UHF space is needed to get through the > trees, > >> and a significant share of houses are >75m AAT. Also, if you want to > cover > >> a decent radius, the access point needs to be up the hill too. 75 > meters > >> isn't a mountaintop; it's just a little rise. > >> > >> It makes no sense to absolutely ban fixed use at a site that is 100m AAT > >> if the nearest protected-service contour is, say, 50 miles away. A more > >> sensible rule would be to follow broadcast practice, and lower the ERP > based > >> on height, so that the distance to a given signal strength contour is > held > >> constant as the height rises. Hence a Class A FM station is allowed up > to > >> 15 miles, and if it is more than 300 feet AAT, then it is allowed less > than > >> the 3000 watts ERP that apply at lower heights. > >> > >> Maybe the lawyers want to have more petitions to argue over. > >> > >> At 9/23/2010 04:07 PM, Rich Harnish wrote: > >> > >> > >> 65. Decision. We decline to increase the maximum permitted transmit > >> antenna height above ground for fixed TV bands devices. As the > Commission > >> stated in the Second Report and Order, the 30 meters above ground limit > was > >> established as a balance between the benefits of increasing TV bands > device > >> transmission range and the need to minimize the impact on licensed > >> services.129 Consistent with the Commission’s stated approach in the > Second > >> Report and Order of taking a conservative approach in protecting > authorized > >> services, we find the prudent course of action is to maintain the > previously > >> adopted height limit. If, in the future, experience with TV bands > devices > >> indicates that these devices could operate at higher transmit heights > >> without causing interference, the Commission could revisit the height > limit. > >> > >> 66. While we expect that specifying a limit on antenna height above > ground > >> rather than above average terrain is satisfactory for controlling > >> interference to authorized services in the majority of cases, we also > >> recognize petitioners’ concerns about the increased potential for > >> interference in instances where a fixed TV bands device antenna is > located > >> on a local geographic high point such as a hill or mountain.130 In such > >> cases, the distance at which a TV bands device signal could propagate > would > >> be significantly increased, thus increasing the potential for > interference > >> to authorized operations in the TV bands. We therefore conclude that it > is > >> necessary to modify our rules to limit the antenna HAAT of a fixed > device as > >> well as its antenna height above ground. In considering a limit for > antenna > >> HAAT, we need to balance the concerns for long range propagation from > high > >> points against the typical variability of ground height that occurs in > areas > >> where there are significant local high points – we do not want to > preclude > >> fixed devices from a large number of sites in areas where there are > rolling > >> hills or a large number of relatively high points that do not generally > >> provide open, line-of-sight paths for propagation over long distances. > We > >> find that limiting the fixed device antenna HAAT to 106 meters (350 > feet), > >> as calculated by the TV bands database, provides an appropriate balance > of > >> these concerns. We will therefore restrict fixed TV bands devices from > >> operating at locations where the HAAT of the ground is greater than 76 > >> meters; this will allow use of an antenna at a height of up to 30 meters > >> above ground level to provide an antenna HAAT of 106 meters. > Accordingly, we > >> are specifying that a fixed TV bands device antenna may not be located > at a > >> site where the ground HAAT is greater than 75 meters (246 feet). The > ground > >> HAAT is to be calculated by the TV bands database using computational > >> software employing the methodology in Section 73.684(d) of the rules to > >> ensure that fixed devices comply with this requirement. > >> > >> 130 The antenna height above ground is the distance from the antenna > >> center of radiation to the actual ground directly below the antenna. To > >> calculate the antenna height above average terrain (HAAT), the average > >> elevation of the surrounding terrain above mean sea level must be > determined > >> along at least 8 evenly spaced radials at distances from 3 to 16 km from > the > >> transmitter site. The HAAT is the difference between the antenna height > >> above mean sea level (the antenna height above ground plus the site > >> elevation) and the average elevation of the surrounding terrain. > >> > >> 67. In reexamining this issue, we also note that the rules currently do > >> not indicate that fixed device antenna heights must be provided to the > >> database for use in determining available channels. It was clearly the > >> Commission’s intent that fixed devices include their height when > querying > >> the database because the available channels for fixed devices cannot be > >> determined without this information.131 We are therefore modifying > Sections > >> 15.711(b)(3) and 15.713(f)(3) to indicate that fixed devices must submit > >> their antenna height above ground to the database. > >> > >> 68. We continue to decline to establish height limits for > >> personal/portable devices. As the Commission stated in the Second Report > and > >> Order, there is no practical way to enforce such limits, and such limits > are > >> not necessary due to the different technical and operational > characteristics > >> of personal/portable devices. > >> > >> -- > >> Fred Goldstein k1io fgoldstein "at" ionary.com > >> ionary Consulting http://www.ionary.com/ > >> +1 617 795 2701 > >> > >> ________________________________ > >> > >> > >> > -------------------------------------------------------------------------------- > >> WISPA Wants You! 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