The invention will now be described on the basis of various embodiments with reference to the accompanying drawings in which:
The invention, according to certain embodiments, will now be described based in an exemplary multi-RAT architecture in which an LTE access of 3GPP UTRAN, called E-UTRAN, is provided in combination with other RATs, such as 3G (e.g., UMTS) and/or 2G (e.g., GSM) technology. Multiple overlaid cells are operated, in which the different RATs are used in a common or shared administrative domain of the operator(s), and all cells are available for use by the terminal devices (e.g., UEs). However, it will be apparent from the following description and is therefore stressed that the invention can be applied to any other network architecture with different radio access technologies.
The different RAT APs 21 to 23 provide access for a terminal device 10 (e.g., mobile phones, UEs, or any other form of a variety of different wireless communication devices, such as a mobile radiotelephone, satellite radiotelephone, wireless networking card, or the like) as long as it is located within their respective cellular coverage areas.
For interoperability, the terminal device 10 implements a process that controls selection and reselection of cells associated with the different RAT types, i.e., inter-RAT cell reselection. As an illustration, when the terminal device 10 is in the third cell C3 with a RAT2 (e.g., GSM) idle mode, it may perform signal measurements of the neighboring RAT1 (e.g., UTRAN) cell C1 or LTE cell C2. If the terminal device 10 determines that the neighboring cell C1 provides better signalling conditions, it selects the neighboring cell C1 with RAT1 technology for communication services.
Upon selection of the neighboring cell C1, the terminal device 10 switches to the RAT1 communication mode and attempts to “camp on” the RAT1 cell C1. To successfully camp on the RAT1 cell C1, however, the cell C1 must also satisfy other cell selection criteria. Exemplary cell selection criteria for UTRAN are specified foe example in the 3GPP Technical Specification (TS) 25.304. If the RAT1 cell C1 does not satisfy the cell selection criteria, the terminal device 10 deselects the RAT1 cell C1 and switches back to the RAT2 mode.
In such an overlaid multi-RAT environment, cell reselection criteria are of importance for efficient network operation. According to one embodiment of the invention, a service preference information is provided which indicates which RAT cell should be used for which service purpose of the terminal device 10 so that the utility of the network resources is balanced and optimum while providing high QoS to the terminal device 10 and avoiding inter-RAT handover as much as possible.
From the operators' perspective, LTE access technology is rather used to deliver “new” services with good enhancements in terms of cost, quality and security, which are highly valued by the customers. The following service class table summarizes the LTE service classes for business requirements of the operators:
Based on the above considerations, certain embodiments, as described below, provide a simple and effective means of signaling service-based cell-reselection criteria to the terminal. This enables the network to control the terminal device 10 to access a suitable RAT cell for a certain service in the overlaid multi-RAT environment. This option can be used as a service-based condition for triggering an inter-RAT handover as well.
In the following, it is assumed that the broadcast system information provided by the network to the terminal device 10 contains some information about the overlaid multi-RAT environment. Furthermore, the LTE cell C2 is assumed to be also able to support all kinds of packet services.
According to one embodiment of the invention, the LTE network indicates to the terminal device 10 preferences on service classes (and applications) which should be served with LTE and different RAT cells. For example, services marked as LTE high driver in the above table could be associated to LTE RAT at the first place and other services to the other RATs, e.g., RAT1 and RAT2.
For a network-originated call to the terminal device 10 in idle mode, the terminal device 10 will be paged first via the current RAT cell in which its idle state has been maintained. This may result in an inter-RAT handover triggered by the expected service. But the network can prepare the inter-RAT handover beforehand to reduce the call setup delay.
Thus, in the second to fourth implementation examples, signaling to individual terminal devices can be performed during initial access or registration to a new administrative domain. This way, the subscription profile of the terminal device 10 can be taken into account to configure some QoS differentiation right at this stage. For a terminal-originated call from the terminal device 10 in the idle mode, the terminal device 10 can now use the aforementioned service preference information and the service awareness of the upcoming call to perform cell reselection if needed for using the appropriate RAT. For instance, the terminal device 10 reselects the LTE RAT cell C2 for the LTE-driver services indicated in the above table.
Due to the fact that cells with 3G and enhanced 3G (e.g., LTE) RATs may overlap as indicated in
According to
Based on the information provided in the service preference memory 420, a message generation functionality 410 embeds or adds the specific service preference information e.g., as information element to individual messages, such as those described in connection with
At the terminal device 10, a detection functionality 110 is provided for detecting and interpreting the service preference information added to or embedded in the respective message, and for providing the detected service preference information to a cell selection or reselection functionality 120 configured to initiate a cell selection, reselection or inter-RAT handover based on the detected service preference information.
At this point, it is noted that the functionalities of blocks 110, 120, 410 and 420 described in connection with
Hence, a flexible and rather straightforward signalling option is provided which can be embedded into or added to broadcast system information, UE capability negotiation, or network policy enforcement during initial access and registration or during other suitable opportunities.
To summarize, methods, a system, a network element, a terminal device, and computer program products have been described for cell selection or reselection in a multi-radio network environment involving at least two different radio access technologies. A service preference information which indicates service preferences for different radio access technologies can be set at a network element and can be sent to at least one terminal device. At the terminal device, the service preference information is detected and a serving cell is selected based on the detected service preference information. Thereby, the network is capable of performing service-based control of cell selection or reselection of the terminal device upon initiating access for a certain service in an overlaid multi-RAT environment. This in turn enhances network utility, operation and performance.
It is to be noted that the invention is not restricted to the embodiment described above, but can be implemented in any network environment involving different radio access technologies which can be used selectively. Any signaling means or message can be used for transferring the service preference information to a terminal device. The service preference information may even be obtained based on a retrieval, download or access operation initiated by the terminal device. The embodiment may thus vary within the scope of the attached claims.
Number | Date | Country | Kind |
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EP 06 017 056.0 | Aug 2006 | EP | regional |