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Viewing 6 posts - 1 through 6 (of 6 total)
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  • #48031 Reply

    Dear All

    can anyone explain to me what for we use the underlaid and overlaid ?

    #48032 Reply

    underlaid and overlaid cells are used to improve capacity issue primarily.

    #48033 Reply

    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 layer

    #48034 Reply

    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 :))

    #48035 Reply
    Jehad Azzam


    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.

    #48036 Reply

    it can be useful when operator use two bands(900Mhz and 1800Mhz)

Viewing 6 posts - 1 through 6 (of 6 total)
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