I had a conversation with a RAN engineer over on Wireless Advisor about omni antennas, and though I'd post it here just because.
Me: AT&T is planning on rolling out 3G in my area this year. As of now, my area is pure EDGE. However, many cell sites in my area use old omni-directional antennas (2 big antennas atop the cell site). Can they simply upgrade the base station in the cell hut and upgrade the backhaul a bit to get 3G going? Or do they need to replace antennas on top of the tower with ones that can broadcast a 3G signal?
RadioRaiders: Yea, the same antennas can be used for 2G and 3G, so long as the frequency is the same (ex. 850Mhz). if the base station is an old 2g one, then it would need to be swapped out. the newest base stations can house 2G/3G/4G in the same cabinet, just swap the cards for which technology you want.
Me: Very cool. Thanks for the reply! Another quick question, why would a sectorized array be better than an omni site?
Do sectorized sites handle network loads better or what?
RadioRaiders: With an omni antenna, it's one frequency that radiates in a circle. with a 3-sector site, each sector has it's own frequency, so you have 3x the frequencies (more capacity), plus you can direct the antennas to focus in certain directions, like for example along roads. So with sectorized antennas, you get more capacity and better coverage in areas you want to cover.
An omni site might be good to cover large areas with little population since it's cheaper and covers equally in all directions.
Me: Do they need to replace the coax cable that runs from the BS to the antennas when upgrading from EDGE-only to UMTS? Also, my home tower has 2 omni's on it. Does one send-only and the other receive-only? Or do both send and receive on different frequencies?
RadioRaiders: Coax can probably stay. If there's 2 omni's it could be like you said (space diversity), where only one transmits but both receive. with space diversity (2 receiving antennas) it takes both receive signals and combines them to negate any fading dips (makes the receive signal better). the uplink (phone to base-station) is usually the weakest link, so having 2 receive antennas helps reception.
Last edited by TWX; 05-05-2012 at 03:01 PM.
Rejection is not failure.