5.5 Handover Considerations Inside Buildings
It is important to make sure that the indoor DAS system implemented in the building is prepared for future traffic growth. The best way to prepare this is to have a sector plan for future sectorization of the system. Even if the system is implemented as one sector, you need to look ahead, especially for UMTS, in order to prepare for more sectors.
Well-defined HO zones are important for GSM and UMTS/HSDPA to avoid ‘ping-pong’ HO on GSM, extensive soft HO zones on UMTS and degraded HSPA performance. The focus should be on well-defined and controlled handover zones, preferably placed in areas with low traffic in the building. When the DAS is designed and implemented correctly, the dominance and isolation of the indoor system will insure well-defined handover zones to the outdoor macro network. However, in extreme cases, like a rooftop site on the neighboring building, you will sometimes have to deal with some signal leaking inside the building, even with high signal level from the indoor system.
As a general rule you must try to avoid having the handover zones in large open areas inside the building. Here it can be difficult to design and control the handover zone. Try to take advantage of the natural isolation provided by the building to separate the different sectors or cells. This can be done by using the floor separations as the handover border, or the fire separation zones inside the building (Section 5.3.6). Typically these fire zones ...