800 Mhz "Cellular" Versus 1900 Mhz "PCS"
It's common knowledge among engineering types about the trade-offs of going to higher frequency transmission, but there has been so much advertising by Sprint PCS about how PCS is "the clear alternative to cellular," that some laymen simply can't believe that PCS (1900 Mhz) is really worse than cellular (800 Mhz). It's indoor coverage that suffers the most with PCS because the outdoor coverage issues can be largely eliminated by simply installing a lot more cells.
http://www.wirelessadvisor.com/waforums/messageview.cfm?catid=16&threadid=5629
states:
800 MHz is a lower
frequency band, US Wireless Companies use frequencies in the 850-864MHz
range (iDEN), and 870-894 (Digital and analog cellular, both TDMA and CDMA). This was the original band for cellular radio systems, dating back to it's first use in 1979 for the USA's first cellular system, and is shared by other radio services, such as SMR, public safety and private radio systems. 800 has some advantages: better in-building penetration as lower frequency radio waves generally travel longer distances (higher you go, radio waves begin to become very directional, and are attenuated by
environmental factors), and are not as attenuated by trees, foliage, etc as 1900MHz. Note that with 800MHz cellular portion, there are two blocks, the "A" block of channels, originally meant for use by companies that were not offering local (wireline) phone service in a given market and a "B" block of channels for use by system owners who provide or are associated with wireline phone service in a given area. iDEN (Nextel and Southern LINC) are really licensed as Digital SMR's, and have channels interleaved with other services in the 851-864MHz band.
1900MHz band, sometimes referred to as "PCS" for Personal Communications System, was a radio service created by the FCC in the early 1990's. The main reason it was opened up for use was to allow for more competition and spectrum for use by the wireless industry. PCS 1900 is EXCLUSIVELY commercial wireless- there are no analog wireless, SMR's or public safety, and much more spectrum available for use for wireless companies. 1900 MHz however, is much more of a challenge as far as coverage and in-building penetration than
800 Mhz. More transmission sites are needed than an 800 system, even with similar technologies (i.e., TDMA, CDMA, etc). This is because the higher frequency radio waves don't travel as far as lower ones, are much more directional, and are attenuated more by trees, foliage, obstructions, etc than 800MHz.
Why are companies going to 1900 Mhz more? Simply it's all that is out there. 800MHz spectrum has been spoken for, most systems have been in operation for years, and incumbent licensees are unlikely to give up their spectrum. The 800MHz networks are more mature, so owners are less likely to want to leave, as a new network at 1900
Mhz would be a large outlay of capital, and more sites would be needed to cover the same geographic areas as their 800 systems do. In short, because there is more available "radio" real estate at
1900 Mhz, it isn't necessarily in the best part of "town" (radio spectrum) than 800MHz is, but in due time the PCS 1900
Mhz systems will have been built out and have coverage similar to 800MHz systems.
http://www.privateline.com/Newsletters/PLNews5.htm
states:
PCS phones are the most
fragile because they use higher frequencies whose radio waves are more
easily disturbed and because they use weaker signals to begin with.
Inside building performance is so unreliable that the newest systems
such as IS-136 permit incorporating base stations within a structure
itself, an expensive arrangement for high rise office buildings and
such.
|
|
|
Return to New York City Cellular Carrier Comparison Return to San Francisco Bay Area Cellular Carrier Comparison |
|
|