Handover/Roaming Control Server
Original Publication Date: 2001-Jun-04
Included in the Prior Art Database: 2001-Jun-04
This paper proposes the introduction of a new network entity, the Handover Roaming Control Server (HRCS). The function of the HRCS is to allow non-standardized inter-working amongst all networks types, using existing intra-network mobility procedures. Possibilities for inter-networking are greatly enhanced without the need for modifications to the Core Network.
Handover/Roaming Control Server
by John O'Hare
This paper describes an alternative approach to roaming and handover across networks. For example, a user who receives a call on their mobile (in an area of poor cellular coverage) has the option to intercept that call from any regular land phone.
The same concept can also be applied to provide inter-working across different generations of the same network family, for example between 2G, 2.5G and 3GETSI/3GPP networks.
Problem(s) To Be Solved
Traditionally, separate solutions have been developed to cater for intra-system and inter-system mobility. Intra-system mobility is concerned with the need to locate and maintain a call to a user, anywhere within the jurisdiction of the operators network. Inter-system mobility is concerned with the need to terminate and maintain a call to a user when moving across network boundaries e.g. between two GSM networks operated by different operators.
Today there are several approaches to inter-system mobility, where the controlling functionality is contained within both the involved core networks and mobile device. When a new Core (or Core variant) is deployed, changes are normally required to the existing Cores to which handover is required, as well as extensive changes in the new Core. In some cases standardization efforts are not politically possible due to competing standards e.g. UMTS to
CDMA One. In a 2G (second generation mobile network, this functionality is typically contained in a MSC (Mobile Switching Center), where updates are both cumbersome and expensive.
With an ever-increasing variety of networks being introduced (e.g. R97/98 GPRS, R99 GPRS, R99 UMTS, R2000 UMTS etc. in the GSM arena alone), the trend for convergence of voice and data and the user's desire to have the ubiquitous access across different access networks, there is an opportunity for more efficient network inter-working.
Proposed Solution to the Problem(s)
The proposed improved solution is the introduction of a new element called the HRCS
(Handover Roaming Control Server), which sits outside of the Core network. In order to provide handover/roaming capabilities between GSM (Circuit Switch) and UMTS, the HRCS would appear as an RNC (Radio Network Controller) to the UMTS core while appearing as a BSC to the GSM core. While there are no physical cells controlled by the HRCS, the RNC Terminator and BSC Terminator (functions within the HRCS) appear as a regular RNC at BSC to the UMTS and GSM core networks respectively. The term Terminator is used throughout the text, to refer to those entities within the HRCS, which are visible to the networks being inter-worked.
The HRCS may contain any number of Terminators (e.g. RNC, BSC, CBSC), which "fool"
each of the connected networks, into thinking that the HRCS is part of its own network. The HRCS, inter-works bearer and signaling traffic between the Terminators, when handing over or roaming to an external network.
The benefits of the HRCS approach are: