METHOD AND APPARATUS FOR WIRELESS
INTERSYSTEM HANDOVER
FIELD OF THE INVENTION
[0001] The present invention relates to a method and apparatus for measurement event synchronisation of a portable radio communication apparatus providing multiple radio access technologies, and more particularly to a method and apparatus for measurement event synchronisation of a portable radio communication apparatus, comprising multiple and operatively interconnected radio access technology devices.
DESCRIPTION OF THE PRIOR ART
[0002] A multiple RAT (Radio Access Technology) terminal is a kind of communication apparatus recently introduced, that comprises two or more radio access technology devices based on different access technologies. A more specific example of a multiple RAT terminal is a dual RAT terminal, that includes two radio access technology devices based on for example the GSM (Global System for Mobile Communication) and the WCDMA (Wide band Code Division Multiple Access) technologies. This new kind of communication apparatuses provide great flexibility for end users, to have only one terminal for usage in different countries and regions providing digital cellular system infrastructures based on different radio access technologies.
[0003] An additional dimension and further advantage for multiple RAT terminal users are achieved in single regions providing multiple digital cellular system infrastructures based on different radio access technologies. This multiple capability holds out the further advantage, that the most suitable radio access technology of the multiple RAT terminal can be selected for communication in each situation.
[0004] For mobility functionality, i.e the user of the terminal crosses cell boarders, a multiple or dual RAT terminal needs to perform base station signal level and identification measurements on both systems, for example WCDMA and GSM systems. This is performed by inter-system measurements that consist at least partly of finding and determining the identity of base stations for the respective system. When connected to one system, the terminal has to support measurements on another system. One way of implementing a dual RAT terminal is to have two seperate radio sets, one for each RAT device, that operate independent of each other. This solution has, however, drawbacks with respect to size, RF (Radio Frequency) performance, and interference between radio devices that are arranged or located close to each other.
[0005] It is however desirable to utilise parts of the radio resources, i.e components common for both technologies, at least for reduced power consumption and miniaturisation purposes. In this kind of dual RAT system the two different radio access technology units will work together in a quasiparallel manner, wherein one of the units is active and the other one is non-active or passive. Measurements on the passive system cannot be carried out while the terminal is receiving/transmitting on the connected or active system. These measurements can be performed either when there are gaps in the reception/transmission of the connected system or in parallel with the reception of the connected system when only down-link gaps are required.
[0006] The inter-RAT measurements consist in part of finding and determining the identity of base stations. Each WCDMA base station can be identified in any measurement gap, provided that it has a minimum length, but independent on the specific placement of the gap in time. In contrast, identification of a specific GSM base station can only take place during particular time slots, which make the particular timing of the measurement gap important. This fact implies that identification of GSM base stations requires some degree of planning, whereas WCDMA base station identification can be performed without knowing the exact timing of the measurement gap.
[0007] With or without common radio resources, there is a particular problem associated with a situation, where a dual RAT terminal is camping on a scheme belonging to a GSM network and where the terminal does not support WCDMA measurements to be performed while the GSM RAT device is either receiving or transmitting.
[0008] Moreover, it is difficult to schedule in advance how the GSM idle gaps should be distributed between the GSM RAT device and WCDMA RAT device, since the need for GSM measurement gaps is not predictable. Hence, it is not possible to inform the WCDMA RAT device in advance of when the WCDMA measurement gaps will occur.
[0009] From a complexity point of view, it is preferred not to plan the measurements of both systems in one scheme, i.e planning activity in WCDMA time format and GSM activity in GSM timeformat each with a separate low layer software and hardware support. The only common planning needed is to ensure that the GSM RAT device and the WCDMA RAT device do not use the same GSM idle gaps for measurements. The cell measurements of the two access technologies are otherwise not dependent on each other. Moreover, the WCDMA RAT device does not require access to several succeeding GSM idle gaps. Therefore, it is preferred that the WCDMA RAT device and the GSM RAT device plan their own activities independently.
SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a method for measurement event synchronisation of terminals with multiple radio access technologies.
[0011] This object is achieved by a method for measurement event synchronisation of a portable radio communication apparatus providing multiple radio access technologies, characterized by the steps of identifying an idle gap between transceiver activities of a first radio access technology device, and sending an execute signal to a second radio access technology device for initiating inter-radio access technology measurements of said second radio access technology device to be performed during said gap.
[0012] A more specific object of the invention is to provide an apparatus for working said method.
[0013] This specific object of the invention is achieved by a portable radio communication apparatus providing multiple radio access technologies, comprising a first radio access technology device and a second radio access technology device, wherein the first and second radio access technology devices are operatively interconnected. The portable radio communication apparatus further comprises a controller adapted to identify an idle gap between transceiver activities of the first radio access technology device, and send an execute signal to the second radio access technology device for initiating inter-radio access technology measurements of the second radio access technology device to be performed during the gap.
[0014] An advantage of the method and apparatus according to the invention is that a low complexity solution is provided with low real time requirements, for the problem of event synchronisation of GSM and WCDMA radio access technologies. Moreover, the method allows an implementation where both RAT devices plan their activities independently of each other. Thereby, the development of platforms for GSM and WCDMA can be performed independently of each other. Another advantage is that the method does not require synchronisation of the clocks in the GSM and the WCDMA RAT devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to explain the invention in more detail and the advantages and features of the invention a preferred embodiment will be described in detail below, reference being made to the accompanying drawings, in which
[0016] FIG. 1A is a schematic block diagram of a first embodiment of a dual-radio access technology terminal according to the invention,
[0017] FIG. IB is a schematic block diagram of the dual-radio access technology terminal in FIG. 1A with circuits/components in further detail,
[0018] FIG. 1C is a schematic block diagram of a second embodiment of a dual-radio access technology terminal according to the invention,
[0019] FIG. 2 is a schematic view of the different levels of communication for measurement event synchronisation between first and second radio access technology devices of the dual-radio access terminal in FIG. 1A,
[0020] FIG. 3 is a schematic view of a cellular mobile telephone network, and
[0021] FIG. 4A and FIG. 4B illustrate flowcharts of two alternative embodiments of the method according to the invention.
DETAILED DESCRIPTION OF THE
INVENTION
[0022] An embodiment of a multiple radio access technology (RAT) terminal utilising common radio resources for size and RF (radio frequency) performance reasons and having means for measurement event synchronisation according to the invention is shown in FIG 1A. In this embodiment, the terminal has two different radio access technology devices and is therefore referred to as a dual RAT terminal or communication apparatus 100. The term terminal or communication apparatus includes portable radio communication equipment. The term portable radio communication equipment includes all equipment such as mobile telephones, pagers, communicators, i.e electronic organizers, smartphones or the like.
[0023] The communication apparatus 100 includes but is not limited to a first radio access technology device 101 based on WCDMA (Wideband Code Division Multiple
Access) and a second radio access technology device 102 based on GSM (Global System for Mobile Communication). The first radio access technology device 101 has a WCDMA radio transmitter/receiver or transceiver 103, which is adapted to establish and maintain WCDMA connections with other communication equipment via a WCDMA base station, described later. The transceiver 103 has a transmitter 104 and a receiver 105, connected to an antenna 106 via an antenna switch 107. The second radio access technology device 102 has a GSM radio transmitter/receiver or transceiver 108, which is adapted to establish and maintain GSM connections with other communication equipment via a GSM base station, described later. The transceiver 108 has a transmitter 109 and a receiver 110, connected to the common antenna 106 via said antenna switch 107.
[0024] The WCDMA transceiver 103 is connected to a controller 111. The controller 111 may be implemented in several different ways, such as in the form of a programmable microprocessor (CPU), an Application-Specific Integrated Circuit (ASIC), or any other electronic logic device that fulfils the functional requirements set out below. Portions of the controller 111 may also be implemented in the form of software program instructions, which are stored in an electronic memory 112 and may be read and executed by the controller 111. The memory 112 is coupled to the controller 111 and may be implemented e.g. as a RAM memory, ROM memory, EEPROM memory, flash memory, etc.
[0025] Similarly, the GSM transceiver 108 is connected to a controller 113. This controller 113 can also be implemented in several different ways, such as in the form of a programmable microprocessor (CPU), an Application-Specific Integrated Circuit (ASIC), or any other electronic logic device that fulfils the functional requirements set out below. Portions of the controller 113 may also be implemented in the form of software program instructions, which are stored in an electronic memory 114 and may be read and executed by the controller 113. The memory 114 is coupled to the controller 113 and may be implemented e.g. as a RAM memory, ROM memory, EEPROM memory, flash memory, etc.
[0026] In this embodiment of the invention the communications apparatus 100 is a mobile telephone that can be used for but is not limited to conventional mobile communications. Additionally it can be used for wideband digital radio communications of advanced Mobile Internet services, multimedia, video and/or other capacity-demanding applications with the WCDMA and GSM mobile telecommunications networks, which preferably operate at about 2 GHz and 900, 1800 and/or 1900 MHz, respectively.
[0027] The dual radio access technology communication apparatus 100 comprises additional circuits and/or components 115 to make the apparatus operate properly. With reference to FIG. IB, these circuits and/or components 115 include but are not limited to an additional controller or central processing unit (CPU) 116 provided for interpretation and execution of program instructions for communication with the first and second radio access technology devices 101, 102 and for controlling the operations of other components and blocks in the apparatus, such as a data and program memory 117, a keypad 118, an LCD driver 119 for driving an LCD display 120, a microphone 121, which is
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