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View Full Version : Question the meaning of some Huawei expression



wireless_houss
2012-02-07, 10:23 PM
Hi every body, please i'd like to know the meaning of the following expression : Edge HO Underlais/Overlaid cells concentric cells PBGT HO THANX

idxtor
2012-02-08, 12:40 AM
it's just a list of handovers classified by reason.
here is quite useful document about Huawei handover types: http://www.4shared.com/rar/ca9qbS1V/Handover.html

pw: www.finetopix.com

wireless_houss
2012-02-08, 05:28 AM
usuful document
look i knew that it's just a list of handovers classified by reason.
but i need the explaination of these handovers for exemple layer HO happends when we move between diffrent layers.

idxtor
2012-02-08, 07:33 AM
usuful document
look i knew that it's just a list of handovers classified by reason.
but i need the explaination of these handovers for exemple layer HO happends when we move between diffrent layers.

Edge HO is a kind of rescue handover based on signal level. When edge handover is triggered, the signal level of the target cell should exceed that of the service cell by at least one hysteresis value (hysteresis in inter-cell handover). The trigger principle of edge handover is that edge handover is triggered when the Rxlev of service cell is lower than edge handover limit and the P/N criteria is met in the statistic time in order to keep the conversation quality.


Overlaid/Underlaid cells. If a cell is configured with at least two frequencies, it can be split into two subcells - an overlaid subcell and an underlaid subcell. More than one frequency can be assigned to a subcell. In the BSC, subcells can be underlaid or overlaid subcell. The underlaid subcell covers the area from the center (BTS) to the outer border of cell coverage area. The coverage area of an overlaid subcell is significantly smaller. The overlaid subcell depends on the underlaid subcell, due to the fact that it cannot set up a call on its own. The overlaid subcell does not have a frequency carrying the BCCH. Call setup is performed by the underlaid subcell, but the call may then be handed over to the overlaid subcell (on the condition that the MS is in its' coverage area), or may be handed back from the overlaid subcell to the underlaid subcell.
The advantage of the subcell concept is that a second cluster with a smaller frequency reuse distance can be installed on top of an existing cluster, for example, a new 3/9-cluster can be installed using overlaid subcells on top of an existing 4/12-cluster of underlaid subcells. This contributes to the network capacity being increased without adding new frequencies, but “stealing” some frequencies from the underlaid cluster.
Another benefit is that it is not necessary to install new hardware. If a place with high traffic load must be covered, an overlaid subcell may also be used. In this case, an overlaid subcell keeps interference low.


Concentric cell HO is a kind of intra-cell handover. Because the concentric cell is on ordinary cell divided into two service layers/subcells: underlaid subcell and overlaid subcell. Concentric cell can be formed with differene combiner or propagation loss, different TX power, downtilt of antennas or by HO parameters. The main purposes of the concentric cell: maximize coverage area, reduce interference and improve frequency reuse density. If both of subcells act as a co-BCCH cell, the TRXs in the underlaid subcell are on a different frequency band from the TRXs in the overlaid subcell. But all the TRXs in the same subcell are on the same band. In a concentric cell, one BCCH can be saved because the two bands are in the same cell. Thus the capacity is enhanced. Compared with the common dual-band network, the dual-band network using the co-BCCH cell (concentric cell) function has larger capacity. Also, the number of neighbours are also lesser in a concentric cell compared to a dual band cell having 2 BCCH.


PBGT (Power Budget) handover algorithm is based on path loss. It looks for a cell with lower path loss and meeting certain system requirements in real time, and judges whether it’s necessary to perform handover. The biggest difference between the PBGT HO and others is that the triggering condition is path loss but not receiving power. There are two main purposes of this handover algorithm: interference reducing and cell overshooting prevention. Because in urban and other areas with high cell distribution density, the actual radio coverage range is far larger than the distance between BTS. So, if MS keeps the conversation within a cell, it will not be effectively handed over to a neighbour with low transmission power and that will result in interference, etc.