- This topic has 5 replies, 1 voice, and was last updated 15 years, 1 month ago by bala.
2nd July 2007 at 13:47 #48031RFGuest
can anyone explain to me what for we use the underlaid and overlaid ?3rd July 2007 at 06:50 #48032ADGuest
underlaid and overlaid cells are used to improve capacity issue primarily.3rd July 2007 at 06:53 #48033NitinGuest
Yes it is used for capacity purpose. In this we make a two layers named as underlay & overlay. If capcity is increased & quality is good then call will be established on overlay layer. As quality will decrease then immidiately call will handover to underlay layer3rd July 2007 at 07:10 #48034PixGuest
you can find a good overview of “hierarchical” networks in the 3GPP doc 45.022, with a detailed description of all available solutions for different vendors.
Very interesting document for once :))4th July 2007 at 09:59 #48035Jehad AzzamGuest
The main usage for underlaid and overlaid,The traffic capacity of a cellular network can be increased by adding more frequencies or reducing the frequency re-use distance. One approach is to apply a second frequency re-use pattern, using the existing sites, with a tighter frequency reuse as overlay on the existing pattern. These cells should be restricted in size, making shorter re-use distance possible without causing excessive co-channel or adjacent channel interference. They are termed overlaid (OL) subcells, whereas the original cells, now with the OL subcells associated, are termed underlaid (UL) subcells. By having more frequencies per cell, the network capacity is increased.The fundamental idea with OL/UL subcells is that traffic close to the site is moved to the OL subcell, while the traffic closer to the cell border is moved to the UL subcell. By controlling the traffic in this way, the frequencies in the OL subcell can have a tighter reuse.12th July 2007 at 14:07 #48036balaGuest
it can be useful when operator use two bands(900Mhz and 1800Mhz)