We are getting to the point that we're just taking mobile communications for granted. We shouldn't. The recent Blackout of '03 showed that the mobile network is subject to severe service compromises in the right circumstances. To understand why this is, you have to understand what comprises the network, and what its requirements are. This tip, excerpted from InformIT, defines some of the terms of a mobile network.
Mobility is one of the key factors of wireless networks. It allows users freedom of movement. Depending on the radio technology, mobility can be either limited to pedestrian speeds only or can support communication even at speeds up to 120 Kmph.
However, mobility places a few requirements on the network:
- They must have the ability to locate subscribers.
- They must monitor the movement of the subscribers.
- They must enable handoffs seamlessly as the user moves across cells while sessions are kept alive.
The two key concepts of mobility are roaming and handovers.
Roaming can be defined as the movement of the mobile terminal from one network to another. Network operators have coverage that is either limited in scope or is limited to a country. In order to support global mobility, network operators agree to allow subscribers from other networks to roam into their networks and access services. Roaming agreements between operators enable subscribers to roam on a global basis while being reachable all the time.
Handover is the process of switching a call or session that is in progress from one physical channel to another. Handovers can be classified into intracell and intercell. Intracell handover is the transfer of a call in progress from a channel in one cell to another channel in the same cell. Intercell handover is the transfer of the call or session to another cell.
CDMA systems are considered as make-before-break systems since the characteristics of spread spectrum allow the system to be connected simultaneously to two or more base stations. In contrast, TDMA systems from a handover perspective are termed break-before-make networks. CDMA also classifies handoffs into soft handoffs, softer handoffs, and hard handoffs.
To read the entire article from which this tip comes, click over to InformIT. No registration required. No muss, no fuss. Just good information.
