11.2 The Tunnel HO Zone

One of the most challenging components of any tunnel design are the handover zones; big mistakes are often made in that crucial part of the system, when considering the HO zone as any other handover zone in the network. It is very important to understand the potential challenges and pitfalls at an early stage in the project. Often, RF planning is concentrated around the signal level inside the tunnel, and though this is one of the most important parameters and factors for success there are other important parts of the design that must be considered carefully. It will be a major issue if the design and implemention solution do not ensure the smooth and seamless handover of traffic to and from the tunnel system when the vehicles move from the outside network into and out of the tunnel service area. The initial design of the handover zone is theoretical and typical RF desktop work, but the handover zone design is greatly dependent on installation limitations, so it is crucial to define the antenna locations for the tunnel HO antennas, etc. at an early stage in the project. Therefore, close cooperation with the construction team on the tunnel project itself is important at an early stage in the project. We like to consider the RF coverage system to be a crucial part of the project, however the reality is different. Remember that the radio coverage system is normally a minor part of the construction of a tunnel, therefore the specifications and limitations of ...

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