Technical overview of the scalable wireless IP network
Introduction
These pages provide an overview of RTX' Wireless IP Network Solution including the description of its Network elements and server environment. The main focus is on the Wireless IP Network system architecture and therefore the description does not describe in details any standard IP switching, routing and transmission elements.
Wireless IP Network System
The Wireless IP network system combines modern IP switching and transmission technologies, with mature wireless technologies such as DECT and Wi-Fi. DECT offers a high quality audio experience and Wi-Fi is broadly accepted as wireless data network access technology. This combination brings competitive advantages compared to traditional dedicated circuit switched TDM infrastructure technologies in terms of cost, flexibility and scalability.
The Wireless IP Network can be considered as a wireless extension to existing voice and data infrastructure. Related to the voice service, there is no call control or other service features as such offered by the network. It simply brings out the services offered by an external softswitch in to the wireless terminals and allows the users to use these services when roaming in the network coverage areas (cells).
Each wireless DECT terminal in the network is allocated a virtual SIP User Agent (UA) in a network server. The external softswitch communicates with this UA as an ordinary IP phone, while the DECT terminals are able to roam in the network and make use of the services offered by the softswitch and even able to seamlessly enable handover from one cell to another during a call in progress. Effectively the network offers mobility services similar to traditionally 2G or 3G cellular mobile networks.
Radio cells consist of base stations or repeaters. The base stations contain both a DECT radio and a WLAN Access Point (AP) part. These base stations can be installed either indoor or outdoor to form a micro cellular network. The DECT repeater is a convenient and cost effective device for the network operator to extend radio coverage in rural areas, and still be able to offer full voice service.
The network cells are grouped into clusters (and cluster groups) for efficient network interconnection and management. A cluster consists of one or more dedicated synchronization units and a number of DECT/WLAN base stations. All the network elements are assigned a unique IP address within the network.
The synchronization unit provides IP connection, timing synchronizations signal and power to base stations. The synchronization units are equipped with GPS receivers to achieve global timing synchronization between clusters. The base stations and synchronization units are connected via IP network to servers that controls their operation. The servers configure the base stations to operate in a coordinated manner in the network. The servers keep track of all registered terminals and manage roaming terminals including idle and active terminals with on-going calls. The network control server converts the DECT control protocol to SIP call control protocol used in the external VoIP softswitch. The media stream flows directly between the wired network end-points (base stations and media gateways) and is normally not routed through any network servers. The audio path between base stations and the terminals are implemented with DECT specific ADPCM or PCM codec signals.
The audio media streams flows directly between the base stations and the outside media gateway. For internal calls in the network the media stream normal flows directly between the involved base stations.
The network supports full mobility of terminals in the network. Terminals perform “location registration” at regular intervals and when changing location thereby the network server is able to keep track of the terminals. Incoming calls can be directed to its destination in the network. Handover during conversations in progress are possible between cells within same cluster, as well as cells in adjacent clusters. Hence full mobility is supported in any desired area giving sufficient radio coverage.
|
