WO2009115862A1

WO2009115862A1 - Method, apparatus and computer program product for reselection candidate selection in a multi-rat environment

Info

Publication number: WO2009115862A1
Application number: PCT/IB2008/051027
Authority: WO
Inventors: Toni Kalevi Johannes Majuri
Original assignee: Nokia Inc
Current assignee: Nokia Inc
Priority date: 2008-03-18
Filing date: 2008-03-18
Publication date: 2009-09-24
Anticipated expiration: 2010-09-18

Abstract

An apparatus for providing reselection candidate selection in a multi-RAT environment may include a cell manager and a cell selector. The cell manager may be configured to receive measurement results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology and determine an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell. The cell selector may be configured to enable reselection to either of the first and second candidate cells based on the arrangement.

Description

METHOD, APPARATUS AND COMPUTER PROGRAM PRODUCT FOR RESELECTION CANDIDATE SELECTION IN A MULTI-RAT

ENVIRONMENT

TECHNOLOGICAL FIELD

Embodiments of the present invention relate generally to candidate cell selection and, more particularly, relate to an apparatus, method and a computer program product for enabling reselection candidate selection in a multiple radio access technology (RAT) environment.

BACKGROUND

The modern communications era has brought about a tremendous expansion of wireline and wireless networks. Computer networks, television networks, and telephony networks are experiencing an unprecedented technological expansion, fueled by consumer demand. Wireless and mobile networking technologies have addressed related consumer demands, while providing more flexibility and immediacy of information transfer.

Current and future networking technologies continue to facilitate ease of information transfer and convenience to users. Such increased ease of information transfer and convenience to users has recently been accompanied by an increased ability to provide mobile communications at a relatively low cost. Accordingly, mobile communication devices are becoming ubiquitous in the modern world. With the rapid expansion of mobile communications technology, there has been a related rapid expansion in those services that are demanded and provided via mobile communication devices.

Over the history of mobile communications, there have been many different generations of systems developed to enable the use of such communication devices. The first generations of these systems were sometimes developed independently and, at least initially, were not necessarily usable in cooperation with other systems. However, cooperation between communication system developers began to be employed so that new technologies could be enabled to have the potential for synergistic cooperation with other technologies in order to increase overall capacity. Thus, a mobile terminal operable in second generation (e.g., 2G) systems such as GSM (global system for mobile communications) or IS- 95, which replaced the first generation of systems, may in some cases be useable in cooperation with newer generation systems such as third generation systems (e.g., 3G) and others that are currently being developed (e.g., E-UTRAN). The ability of a particular mobile terminal to access multiple systems or communicate via multiple radio access technologies (multi-RAT) is sometimes referred to as "multi-radio access" (MRA). However, current cell reselection (e.g., due to signal loss or signal strength reduction in a current serving cell) in a multi- RAT environment may not result in selection of the best available cell being selected. In this regard, for example, in an exemplary single RAT situation, an evaluation timer may be used by a mobile terminal to evaluate measurement results received at periodic intervals from cells received by the mobile terminal. In one example, the evaluation timer may begin if received measurement results indicate that a particular received cell is better than the current serving cell (e.g., based on a comparison of signal strength or other parameters (e.g., C values such as C2, C32, etc.) between the current serving cell and neighbor or candidate cells received). If the particular received cell is better than the current serving cell for a predetermined period of time (e.g., 5 seconds), the evaluation timer may time out or expire and a reselection may occur to select the particular received cell as the new serving cell. However, in a multi-RAT environment in which an evaluation timer is used, a different evaluation timer (or at least a different timing operation) typically operates for each cell. As such, for any given cell, the start time of evaluation timer operation may be different. Thus, for example, the evaluation timer may expire for one particular cell associated with a corresponding particular RAT before the corresponding timer expires for others. Also in multi-RAT environment the number of simultaneously running timers can be huge.

Currently, if the evaluation timer expires for a particular cell before expiration of other expiration timers, cell reselection may only occur to the particular cell. In other words, consideration with regard to which cell to reselect is limited to that cell within the particular RAT that had the evaluation timer expire first. As an example, if a mobile terminal is capable of MRA via communicating with 2G, 3G and/or E-UTRAN cells and the 2G cell evaluation timer expires first, the mobile terminal would currently perform cell reselection to the candidate cell that operate in 2G. Thus, even if one or more of the 3G and/or E-UTRAN cells are better cells (e.g., having fulfilled the reselection criteria, but the evaluation timers are still running) than the 2G candidate.

Accordingly, it may be desirable to develop a mechanism by which mobile terminals may perform cell reselection in a multi-RAT environment in a manner that may overcome at least some of the disadvantages described above.

BRIEF SUMMARY OF EXEMPLARY EMBODIMENTS A method, apparatus and computer program product are therefore provided that may enable reselection candidate selection in a multi-RAT environment. In this regard, for example, in response to any one of the RATs encountering a stimuli that may trigger a reselection operation (e.g., timing out of an evaluation timer for one particular cell in one particular RAT), the mobile terminal may rank candidates from same and different RATs against each other to enable selection of a candidate from any of the RATs based on the ranking. As such, in an exemplary embodiment, when a reselection period expires for any one cell associated with a particular RAT, all candidates received for the same and different RATs may be evaluated against each other to provide a comprehensive ranking of candidate cells for reselection determinations. In some embodiments, if reselection results in selection of a cell in a different RAT than the prior serving cell, the comprehensive ranking may be provided to the different or new RAT associated with the new serving cell.

In one exemplary embodiment, a method of providing reselection candidate selection in a multi-RAT environment is provided. The method may include receiving measurement reports corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology, determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell, and enabling reselection to either of the first and second candidate cells based on the arrangement. In another exemplary embodiment, a computer program product for providing reselection candidate selection in a multi-RAT environment is provided. The computer program product may include at least one computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable program code portions may include a first executable portion, a second executable portion and a third executable portion. The first executable portion may be for receiving measurement reports corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology. The second executable portion may be for determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell. The third executable portion may be for enabling reselection to either of the first and second candidate cells based on the arrangement. In another exemplary embodiment, an apparatus for providing reselection candidate selection in a multi-RAT environment is provided. The apparatus may include a cell manager and a cell selector. The cell manager may be configured to receive measurement reports corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology and determine an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell. The cell selector may be configured to enable reselection to either of the first and second candidate cells based on the arrangement.

In another exemplary embodiment, an apparatus for providing reselection candidate selection in a multi-RAT environment is provided. The apparatus includes means for receiving measurement reports corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology, means for determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell, and means for enabling reselection to either of the first and second candidate cells based on the arrangement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is a schematic block diagram of a mobile terminal according to an exemplary embodiment of the present invention; FIG. 2 is a schematic block diagram of a wireless communications system according to an exemplary embodiment of the present invention;

FIG. 3 illustrates an example of multiple candidate cells in a multi-RAT environment according to an exemplary embodiment of the present invention; FIG. 4 illustrates a block diagram showing an apparatus for providing reselection candidate selection in a multi-RAT environment according to an exemplary embodiment of the present invention;

FIG. 5 illustrates an example of phase based ranking according to an exemplary embodiment of the present invention;

FIG. 6 illustrates an example of reselection based on the ranking or arrangement developed using the operations described above in reference to FIG. 5 according to an exemplary embodiment of the present invention; and

FIG. 7 is a flowchart according to an exemplary method of providing reselection candidate selection in a multi-RAT environment according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout.

FIG. 1 , one aspect of the invention, illustrates a block diagram of a mobile terminal 10 that would benefit from embodiments of the present invention. It should be understood, however, that a mobile telephone as illustrated and hereinafter described is merely illustrative of one type of mobile terminal that would benefit from embodiments of the present invention and, therefore, should not be taken to limit the scope of embodiments of the present invention. While several embodiments of the mobile terminal 10 are illustrated and will be hereinafter described for purposes of example, other types of mobile terminals, such as portable digital assistants (PDAs), pagers, mobile televisions, gaming devices, laptop computers, cameras, video recorders, audio/video player, radio, GPS devices, or any combination of the aforementioned, and other types of voice and text communications systems, can readily employ embodiments of the present invention.

In addition, while several embodiments of the method of the present invention are performed or used by a mobile terminal 10, the method may be employed by other than a mobile terminal. Moreover, the system and method of embodiments of the present invention will be primarily described in conjunction with mobile communications applications. It should be understood, however, that the system and method of embodiments of the present invention can be utilized in conjunction with a variety of other applications, both in the mobile communications industries and outside of the mobile communications industries. The mobile terminal 10 may include an antenna 12 (or multiple antennas) in operable communication with a transmitter 14 and a receiver 16. The mobile terminal 10 may further include an apparatus, such as a controller 20 or other processing element, that provides signals to and receives signals from the transmitter 14 and receiver 16, respectively. The signals include signaling information in accordance with the air interface standard of the applicable cellular system, and also user speech, received data and/or user generated data. In this regard, the mobile terminal 10 is capable of operating with one or more air interface standards, communication protocols, modulation types, and access types. By way of illustration, the mobile terminal 10 is capable of operating in accordance with any of a number of first, second, third and/or fourth-generation communication protocols or the like. For example, the mobile terminal 10 may be capable of operating in accordance with second-generation (2G) wireless communication protocols IS-136 (time division multiple access (TDMA)), GSM (global system for mobile communication), and IS-95 (code division multiple access (CDMA)), or with third-generation (3G) wireless communication protocols, such as Universal Mobile Telecommunications System (UMTS), CDMA2000, wideband CDMA (WCDMA) and time division-synchronous CDMA (TD- SCDMA), with fourth-generation (4G) wireless communication protocols or the like. As an alternative (or additionally), the mobile terminal 10 may be capable of operating in accordance with non-cellular communication mechanisms. For example, the mobile teπninal 10 may be capable of communication in a wireless local area network (WLAN) or other communication networks described below in connection with FIG. 2.

It is understood that the apparatus, such as the controller 20, may include circuitry desirable for implementing audio and logic functions of the mobile teπninal 10. For example, the controller 20 may be comprised of a digital signal processor device, a microprocessor device, and various analog to digital converters, digital to analog converters, and other support circuits. Control and signal processing functions of the mobile terminal 10 are allocated between these devices according to their respective capabilities. The controller 20 thus may also include the functionality to convolutionally encode and interleave message and data prior to modulation and transmission. The controller 20 can additionally include an internal voice coder, and may include an internal data modem. Further, the controller 20 may include functionality to operate one or more software programs, which may be stored in memory. For example, the controller 20 may be capable of operating a connectivity program, such as a conventional Web browser. The connectivity program may then allow the mobile terminal 10 to transmit and receive Web content, such as location-based content and/or other web page content, according to a Wireless Application Protocol (WAP), Hypertext Transfer Protocol (HTTP) and/or the like, for example.

The mobile terminal 10 may also comprise a user interface including an output device such as a conventional earphone or speaker 24, a ringer 22, a microphone 26, a display 28, and a user input interface, all of which are coupled to the controller 20. The user input interface, which allows the mobile terminal 10 to receive data, may include any of a number of devices allowing the mobile terminal 10 to receive data, such as a keypad 30, a touch display (not shown) or other input device. In embodiments including the keypad 30, the keypad 30 may include the conventional numeric (0-9) and related keys (#, *), and other hard and soft keys used for operating the mobile terminal 10. Alternatively, the keypad 30 may include a conventional QWERTY keypad arrangement. The keypad 30 may also include various soft keys with associated functions. In addition, or alternatively, the mobile terminal 10 may include an interface device such as a joystick or other user input interface. The mobile terminal 10 further includes a battery 34, such as a vibrating battery pack, for powering various circuits that are required to operate the mobile terminal 10, as well as optionally providing mechanical vibration as a detectable output.

The mobile terminal 10 may further include a user identity module (UIM) 38. The UIM 38 is typically a memory device having a processor built in. The

UIM 38 may include, for example, a subscriber identity module (SIM), a universal integrated circuit card (UICC), a universal subscriber identity module (USIM), a removable user identity module (R-UIM), etc. The UIM 38 typically stores information elements related to a mobile subscriber. In addition to the UIM 38, the mobile terminal 10 may be equipped with memory. For example, the mobile terminal 10 may include volatile memory 40, such as volatile Random Access Memory (RAM) including a cache area for the temporary storage of data. The mobile terminal 10 may also include other non-volatile memory 42, which can be embedded and/or may be removable. The non-volatile memory 42 can additionally or alternatively comprise an electrically erasable programmable read only memory (EEPROM), flash memory or the like, such as that available from the SanDisk Corporation of Sunnyvale, California, or Lexar Media Inc. of Fremont, California. The memories can store any of a number of pieces of information, and data, used by the mobile terminal 10 to implement the functions of the mobile terminal 10. For example, the memories can include an identifier, such as an international mobile equipment identification (IMEI) code, capable of uniquely identifying the mobile terminal 10. Furthermore, the memories may store instructions for determining cell id information. Specifically, the memories may store an application program for execution by the controller 20, which determines an identity of the current cell, i.e., cell id identity or cell id information, with which the mobile terminal 10 is in communication.

FIG. 2 is a schematic block diagram of a wireless communications system according to an exemplary embodiment of the present invention. Referring now to FIG. 2, an illustration of one type of system that would benefit from embodiments of the present invention is provided. The system includes a plurality of network devices. As shown, one or more mobile terminals 10 may each include an antenna 12 for transmitting signals to and for receiving signals from a base site or base station (BS) 44. The base station 44 may be a part of one or more cellular or mobile networks each of which includes elements required to operate the network, such as a mobile switching center (MSC) 46. As well known to those skilled in the art, the mobile network may also be referred to as a Base Station/MSC/Interworking function (BMI). In operation, the MSC 46 is capable of routing calls to and from the mobile terminal 10 when the mobile terminal 10 is making and receiving calls. The MSC 46 can also provide a connection to landline trunks when the mobile terminal 10 is involved in a call. In addition, the MSC 46 can be capable of controlling the forwarding of messages to and from the mobile terminal 10, and can also control the forwarding of messages for the mobile terminal 10 to and from a messaging center. It should be noted that although the MSC 46 is shown in the system of FIG. 2, the MSC 46 is merely an exemplary network device and embodiments of the present invention are not limited to use in a network employing an MSC.

The MSC 46 can be coupled to a data network, such as a local area network (LAN), a metropolitan area network (MAN), and/or a wide area network (WAN). The MSC 46 can be directly coupled to the data network. In one typical embodiment, however, the MSC 46 is coupled to a gateway device (GTW) 48, and the GTW 48 is coupled to a WAN, such as the Internet 50. In turn, devices such as processing elements (e.g., personal computers, server computers or the like) can be coupled to the mobile terminal 10 via the Internet 50. For example, as explained below, the processing elements can include one or more processing elements associated with a computing system 52 (two shown in FIG. 2), origin server 54 (one shown in FIG. 2) or the like, as described below.

The BS 44 can also be coupled to a serving GPRS (General Packet Radio Service) support node (SGSN) 56. As known to those skilled in the art, the SGSN 56 is typically capable of performing functions similar to the MSC 46 for packet switched services. The SGSN 56, like the MSC 46, can be coupled to a data network, such as the Internet 50. The SGSN 56 can be directly coupled to the data network. In a more typical embodiment, however, the SGSN 56 is coupled to a packet-switched core network, such as a GPRS core network 58. The packet- switched core network is then coupled to another GTW 48, such as a gateway GPRS support node (GGSN) 60, and the GGSN 60 is coupled to the Internet 50. In addition to the GGSN 60, the packet-switched core network can also be coupled to a GTW 48. Also, the GGSN 60 can be coupled to a messaging center. In this regard, the GGSN 60 and the SGSN 56, like the MSC 46, may be capable of controlling the forwarding of messages, such as MMS messages. The GGSN 60 and SGSN 56 may also be capable of controlling the forwarding of messages for the mobile terminal 10 to and from the messaging center.

In addition, by coupling the SGSN 56 to the GPRS core network 58 and the GGSN 60, devices such as a computing system 52 and/or origin server 54 may be coupled to the mobile terminal 10 via the Internet 50, SGSN 56 and GGSN 60. In this regard, devices such as the computing system 52 and/or origin server 54 may communicate with the mobile terminal 10 across the SGSN 56, GPRS core network 58 and the GGSN 60. By directly or indirectly connecting mobile terminals 10 and the other devices (e.g., computing system 52, origin server 54, etc.) to the Internet 50, the mobile terminals 10 may communicate with the other devices and with one another, such as according to the Hypertext Transfer Protocol (HTTP) and/or the like, to thereby carry out various functions of the mobile terminals 10.

Although not every element of every possible mobile network is shown and described herein, it should be appreciated that the mobile terminal 10 may be coupled to one or more of any of a number of different networks through the BS 44. In this regard, the network(s) may be capable of supporting communication in accordance with any one or more of a number of first-generation (IG), second- generation (2G), 2.5G, third-generation (3G), fourth-generation (4G) mobile communication protocols or the like. For example, one or more of the network(s) can be capable of supporting communication in accordance with 2G wireless communication protocols IS-136 (TDMA), GSM, and IS-95 (CDMA). Also, for example, one or more of the network(s) can be capable of supporting communication in accordance with 2.5G wireless communication protocols GPRS, Enhanced Data GSM Environment (EDGE), or the like. Further, for example, one or more of the network(s) can be capable of supporting communication in accordance with 3 G wireless communication protocols such as a UMTS network employing WCDMA radio access technology. Some narrow-band analog mobile phone service (NAMPS), as well as total access communication system (TACS), network(s) may also benefit from embodiments of the present invention, as should dual or higher mode mobile stations (e.g., digital/analog or TDMA/CDMA/analog phones).

The mobile terminal 10 can further be coupled to one or more wireless access points (APs) 62. The APs 62 may comprise access points configured to communicate with the mobile terminal 10 in accordance with techniques such as, for example, radio frequency (RF), infrared (IrDA) or any of a number of different wireless networking techniques, including WLAN techniques such as IEEE 802.1 1 (e.g., 802.1 Ia, 802.1 Ib, 802.1 Ig, 802.1 In, etc.), world interoperability for microwave access (WiMAX) techniques such as IEEE 802.16, and/or wireless Personal Area Network (WPAN) techniques such as IEEE 802.15, BlueTooth

(BT), ultra wideband (UWB) and/or the like. The APs 62 may be coupled to the Internet 50. Like with the MSC 46, the APs 62 can be directly coupled to the Internet 50. In one embodiment, however, the APs 62 are indirectly coupled to the Internet 50 via a GTW 48. Furthermore, in one embodiment, the BS 44 may be considered as another AP 62. As will be appreciated, by directly or indirectly connecting the mobile terminals 10 and the computing system 52, the origin server 54, and/or any of a number of other devices, to the Internet 50, the mobile terminals 10 can communicate with one another, the computing system, etc., to thereby carry out various functions of the mobile terminals 10, such as to transmit data, content or the like to, and/or receive content, data or the like from, the computing system 52. As used herein, the terms "data," "content," "information" and similar terms may be used interchangeably to refer to data capable of being transmitted, received and/or stored in accordance with embodiments of the present invention. Thus, use of any such terms should not be taken to limit the spirit and scope of embodiments of the present invention.

Although not shown in FIG. 2, in addition to or in lieu of coupling the mobile terminal 10 to computing systems 52 across the Internet 50, the mobile terminal 10 and computing system 52 may be coupled to one another and communicate in accordance with, for example, RF, BT, IrDA or any of a number of different wireline or wireless communication techniques, including LAN, WLAN, WiMAX, UWB techniques and/or the like. One or more of the computing systems 52 can additionally, or alternatively, include a removable memory capable of storing content, which can thereafter be transferred to the mobile terminal 10. Further, the mobile terminal 10 can be coupled to one or more electronic devices, such as printers, digital projectors and/or other multimedia capturing, producing and/or storing devices (e.g., other terminals). Like with the computing systems 52, the mobile terminal 10 may be configured to communicate with the portable electronic devices in accordance with techniques such as, for example, RF, BT, IrDA or any of a number of different wireline or wireless communication techniques, including universal serial bus (USB), LAN, WLAN, WiMAX, UWB techniques and/or the like.

In some embodiments, the mobile terminal 10 may be capable of receiving communication from multiple cells (e.g., multiple BSs or APs) at any given time. Furthermore, in some embodiments, the system of FIG. 2 could represent a multi- RAT environment. In this regard, for example, the BS 44 may be coupled to the SGSN 56 and the MSC 46 via a base station controller (BSC) 45 that may control the BS 44. The BS 44 and the BSC 45 may be associated with a first RAT (e.g., a 2G RAT). Meanwhile, the SGSN 56 and the MSC 46 may also be coupled to a radio network controller (RNC) 47 of a second RAT (e.g., a 3G RAT). The RNC 47 may in turn be in communication with one or more nodes (e.g., node-Bs) 49, one or more of which may be capable of communication with the mobile terminal 10 at any given time. As such, the mobile terminal 10 may be configured to be able to communicate with (e.g., select a cell associated with) either the first RAT or the second RAT. Furthermore, additional RATs may also be included in the system of FIG. 2 so that the mobile terminal 10 may be enabled to communicate with any of a plurality of different RATs.

In an exemplary embodiment, content or data may be communicated over the system of FIG. 2 between a mobile terminal, which may be similar to the mobile terminal 10 of FIG. 1 , and a network device of the system of FIG. 2 in order to, for example, execute applications or establish communication (for example, for purposes of content or information sharing) between the mobile terminal 10 and other mobile terminals. As such, it should be understood that the system of FIG. 2 need not be employed for communication between mobile terminals or between a network device and the mobile terminal, but rather FIG. 2 is merely provided for purposes of example. Furthermore, it should be understood that embodiments of the present invention may be resident on a communication device such as the mobile terminal 10, and/or may be resident on a server, personal computer or other device, absent any communication with the system of FIG. 2. FIG. 3 illustrates an example of multiple candidate cells in a multi-RAT environment according to an exemplary embodiment. In this regard, as shown in FIG. 3, the mobile terminal 10 may be positioned in a location where the mobile terminal 10 is within range of several base stations, access points and/or nodes. In other words, the mobile terminal 10 may be within or at least proximate to a plurality of communication cells defining a coverage area of corresponding base stations, access points and/or nodes. As such, the mobile terminal 10 may be in a multi-RAT environment where cells associated with different RATs overlap to some degree. As shown in FIG. 3, the mobile terminal 10 may be in communication with a current serving cell 64, but may also be capable of receiving communications transmitted from other cells that may be from the same and/or other RATs. For example, the cells drawn in solid lines may include the current serving cell 64 and neighbor cells or first candidate cells 65, which may be associated with a first RAT (e.g., 2G, 3G, E-UTRAN, 4G or the like). In an exemplary embodiment, the current serving cell 64 and the first candidate cells 65 may each be associated with 2G. Meanwhile, cells drawn in dashed lines may include second candidate cells 66 associated with a second RAT (e.g., 3G). Although, embodiments of the invention do not require three or more RATs, a third RAT (e.g., E-UTRAN) may also have one or more third candidate cells 67 that are receivable by the mobile terminal 10. As such, FIG. 3 merely illustrates one example of what may be considered a multi-RAT environment. According to an exemplary embodiment, all cells received by the mobile terminal 10, other than the current serving cell 64, may be considered candidates for selection if a reselection is desired or required. Thus, for example, if communication with the current serving cell 64 is lost or if parameters associated with such communication suggest or otherwise indicate that reselection may be desirable, the mobile terminal 10 may perform reselection by selecting one of the candidate cells.

In an exemplary embodiment, as shown in FIG. 3, a plurality of cells (although not necessarily the specific cells shown in FIG. 3) may be received at the mobile terminal 10, and the mobile terminal 10 may be enabled to conduct cell reselection in order to select a cell, e.g., based on certain selection criteria, from a ranking of cells that in some cases includes cells that may be from more than one different RAT. An exemplary embodiment of the invention will now be described with reference to FIG. 4, in which certain elements of an apparatus for enabling reselection candidate selection in a multi-RAT environment are displayed. The apparatus of FIG. 4 may be embodied as or otherwise employed, for example, on the mobile terminal 10. However, it should be noted that the apparatus of FIG. 4, may also be employed on a variety of other devices, both mobile and fixed, and therefore, embodiments of the present invention should not necessarily be limited to application on devices such as mobile terminals. It should also be noted that while FIG. 4 illustrates one example of a configuration of an apparatus for enabling reselection candidate selection in a multi-RAT environment, numerous other configurations may also be used to implement embodiments of the present invention.

Referring now to FIG. 4, an apparatus for enabling reselection candidate selection in a multi-RAT environment is provided. The apparatus may include or otherwise be in communication with a processing element 70, a user interface 72, a communication interface 74 and a memory device 76. The memory device 76 may include, for example, volatile and/or non-volatile memory (e.g., volatile memory 40 and/or non-volatile memory 42). The memory device 76 may be configured to store information, data, applications, instructions or the like for enabling the apparatus to carry out various functions in accordance with exemplary embodiments of the present invention. For example, the memory device 76 could be configured to buffer input data for processing by the processing element 70. Additionally or alternatively, the memory device 76 could be configured to store instructions for execution by the processing element 70. As yet another alternative, the memory device 76 may be one of a plurality of databases that store information in the form of static and/or dynamic information, for example, in association with a particular location, event or service point.

The processing element 70 may be embodied in a number of different ways. For example, the processing element 70 may be embodied as a processor, a coprocessor, a controller or various other processing means or devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit) or FPGA (field programmable gate array). In an exemplary embodiment, the processing element 70 may be configured to execute instructions stored in the memory device 76 or otherwise accessible to the processing element 70. Meanwhile, the communication interface 74 may be embodied as any device or means embodied in either hardware, software, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network and/or any other device or module in communication with the apparatus. In this regard, the communication interface 74 may include, for example, an antenna (or antennas) and supporting hardware and/or software for enabling communications with a wireless communication network. The user interface 72 may be in communication with the processing element 70 to receive an indication of a user input at the user interface 72 and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface 72 may include, for example, a keyboard, a mouse, a joystick, a touch screen display, a conventional display, a microphone, a speaker, or other input/output mechanisms. In an exemplary embodiment in which the apparatus is embodied as a server, the user interface 72 may be limited, or even eliminated.

In an exemplary embodiment, the processing element 70 may be embodied as or otherwise control a cell manager 78 and/or a cell selector 80. The cell manager 78 and the cell selector 80 may each be any means or device embodied in hardware, software, or a combination of hardware and software that is configured to carry out the functions of the cell manager 78 and cell selector 80, respectively, as described herein. In this regard, for example, the cell manager 78 may be configured to receive information from a plurality of cells (e.g., measurement results) and organize or arrange the cells according to predefined criteria. In some embodiments, the cell organization (or ranking) may be performed in response to an evaluation timer 82 timing out for one of the cells associated with a particular RAT. However, other predefined criteria or another reselection initiation stimulus may cause the cell manager 78 to arrange or rank the cells. Meanwhile, the cell selector 80 may be configured to select a candidate cell to which the mobile terminal 10 may switch communications from the current serving cell 64 in the event of initiation of a reselection process. In this regard, the cell selector 80 may be configured to select a candidate cell based on the arrangement or ranking of cells provided by the cell manager 78.

As such, in accordance with an exemplary embodiment, the cell manager 78 may be configured to receive measurement reports corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology and determine an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell. In an exemplary embodiment, the cell selector 80 may be configured to enable reselection to either of the first and second candidate cells based on the arrangement.

The evaluation timer 82, which may be part of the apparatus or merely one or more timers in communication with the apparatus in embodiments in which the stimulus for reselection process initiation is provided by a timer, may include a separate timer for each of a plurality of cells associated with various RATs. As described above, the evaluation timer 82 may begin counting (up or down) in response to receipt of measurement results from a candidate cell that indicate that a particular candidate cell in a particular RAT is better than the current serving cell 64 based on measurement results (e.g., based on a comparison of signal strength (e.g., higher signal strength) or other parameters (e.g., C values such as C2, C32, etc.) between the current serving cell and neighbor or candidate cells received). The measurement results may be periodically, routinely, or continuously provided to the mobile terminal 10 at a corresponding interval for use by the mobile terminal 10 (e.g., by the cell selector 80) in determining whether to select a different cell with which to communicate. If the particular candidate cell is better than the current serving cell 64 for a predetermined period of time (e.g., 5 seconds), the evaluation timer 82 may time out or expire (or reach a particular value if counting up) and a reselection process in accordance with an embodiment of the present invention may be initiated. As such, upon counting for the predetermined period of time, the evaluation timer 82 may communicate with the cell manager 78 and/or the cell selector to receive information regarding when to start/stop timers and to provide information that may be used in connection with initiating the reselection process (e.g., sending an initiation instruction or triggering the sending of an initiation instruction based on a timer timeout).

In response to receipt of an initiation instruction (e.g., from the evaluation timer 82 after the timeout described above), the cell manager 78 may arrange or rank cells. In some cases, the cell ranking may begin by ranking each cell of the current RAT based on reselection criteria. In an exemplary embodiment, the reselection criteria may be based on parameter values associated with the measurement results received for each cell being better than the corresponding parameter values associated with the current serving cell 64 such as by having higher signal strength, higher C2 value, or the like. In some instances, the ranking of the cells may be accomplished in phases. However, it is not necessary that a phase based ranking be performed. Instead, all cells could be ranked at the same time in some embodiments. FIG. 5 illustrates an example of phase based ranking according to an exemplary embodiment.

In this regard, FIG. 5 A illustrates an example of a first phase of arranging or ranking cells of the same RAT as the current serving cell 64 (e.g., each first candidate cell 65) in accordance with an exemplary embodiment. In an exemplary embodiment, the first candidate cells 65 (e.g., 2G candidate 1, 2G candidate 2, and 2G candidate 3) that meet the reselection criteria may be arranged in order with respect to one, more than one, or a combination of particular parameter values. In some cases, each candidate that meets the reselection criteria may be compared to each other candidate individually in order to assign an ordering of the respective candidates. However, as an alternative, a single parameter value could be the basis of ordering and the candidates could be sorted according to such parameter value. FIG. 5B illustrates an example of a second phase of arranging or ranking next the cells of one other RAT different from the RAT of the current serving cell 64 (e.g., each second candidate cell 66) in accordance with an exemplary embodiment. In an exemplary embodiment, the second candidate cells 66 (e.g., 3G candidate 1 and 3G candidate 2) that meet the reselection criteria may be arranged within the existing order of the first candidate cells 65 with respect to one, more than one, or a combination of particular parameter values. In some cases, each candidate that meets the reselection criteria may be compared to each other candidate individually in order to assign an ordering of the respective candidates. As such, for example, the 3G candidate 1 may be compared to the 2G candidate 1 and if the 2G candidate 1 is better than the 3G candidate 1 , the 3G candidate 1 may be compared to the 2G candidate 2. If the 3G candidate 1 is not better than the 2G candidate 2, then the 3G candidate 1 may be ranked between the 2G candidate 1 and the 2G candidate 2. Other 3G candidates of the second candidate cells 66 may also be ranked in a similar manner. However, as an alternative, instead of comparing in a highest to lowest direction, the comparison could be made in a lowest to highest direction or even in a random order.

FIG. 5C illustrates an example of a third phase of arranging or ranking next the cells of another RAT (e.g., each third candidate cell 67) different from the first RAT of the current serving cell 64 and the second RAT of the second candidate cells 66 in accordance with an exemplary embodiment. In an exemplary embodiment, the third candidate cells 67 that meet the reselection criteria (e.g., E- UTRAN candidate 1) may be arranged within the existing order of the first candidate cells 65 and the second candidate cells 66 with respect to one, more than one, or a combination of particular parameter values. In some cases, each candidate that meets the reselection criteria may be compared to each other candidate individually in order to assign an ordering of the respective candidates. As such, for example, the E-UTRAN candidate 1 may be compared to the 2G candidate 1 and if the E-UTRAN candidate 1 is better than the 2G candidate 1, the E-UTRAN candidate 1 may be listed first in the arrangement or ranking. Other E- UTRAN candidates of the third candidate cells 67 (if any) may also be ranked in a similar manner. The result of ranking or arranging candidates from all available RATs may be considered a candidate list 88. However, the candidate list 88 need not necessarily physically exist in a list format. In other words, the candidate list 88 need not sequentially list the candidate cells in order. Rather, for example, the candidate list 88 may simply provide an identification of the candidate cells and some indication or value associated with each candidate cell that may be used to indicate or infer an ordering or ranking associated with the candidate cells. FIG. 6 illustrates an example of reselection based on the ranking or arrangement developed using the operations described above in reference to FIG. 5. The reselection may be accomplished by the cell selector 80 on the basis of the arrangement of the cells that was made by the cell manager 78 (e.g., using the candidate list 88). As such, the cell selector 80 may determine to which candidate cell the mobile terminal 10 may attempt to switch using the arrangement. In this regard, for example, the first listed candidate or highest ranked candidate may be the candidate cell to which the cell selector 80 initially attempts to reselect or switch communication. If the reselection is unsuccessful, the cell selector 80 may then direct attempts to perform reselection to the next candidate in the candidate list 88. Subsequent reselection failures may cause the cell selector 80 to move iteratively to next cells in the listing of candidate cells (e.g., the candidate list 88).

FIG. 6A illustrates a reselection operation as described above in which reselection is initially attempted to E-UTRAN candidate 1 , which may be considered the best candidate cell. In an exemplary embodiment, after reselection to any cell that is not in the same RAT as the cell in which the mobile terminal 10 is camped prior to the reselection (e.g., in this example, 2G since the current serving cell 64 is a 2G cell), the candidate list 88 (which may also be referred to as a reselection list) may be communicated to the RAT associated with the reselected cell. Accordingly, in the present example, after reselection to the E-UTRAN candidate 1 , the candidate list 88 may be sent to the E-UTRAN RAT (e.g., to a E- UTRAN network control device), which is the target RAT with respect to the reselection. In this regard, in an embodiment in which the apparatus of FIG. 4 is embodied at the mobile terminal 10, sending the candidate list 88 to the target RAT may be done internally (e.g., by communicating the candidate list 88 to a protocol stack associated with the target RAT. However, in an alternative embodiment, the candidate list 88 may be communicated to a particular storage location accessible by the protocol stack associated with the target RAT. Furthermore, in some cases, the storage location could be accessible (or made accessible) by multiple stacks associated with corresponding multiple RATS. In an embodiment, where the apparatus of FIG. 4 is embodied at a network device, the candidate list 88 could be communicated to the mobile terminal 10. By providing the candidate list 88 to the target RAT, the target RAT may be provided with information that may be useful in facilitating future reselections for the mobile terminal 10. As such, the likelihood and/or frequency of unnecessary RAT hopping may be reduced and/or, in error situations, candidate selection may be faster and out of service time may be shorter.

FIG 6B illustrates continuation of a reselection operation in response to a failure to reselect the best candidate cell. In this regard, for example, if the reselection of the E-UTRAN candidate 1 of FIG. 6A is unsuccessful, then reselection may be performed with respect to the next candidate in the candidate list 88. As such, in the present example, reselection may be performed to 2G candidate 1. Although 2G was the initial RAT, in some instances, after reselection (e.g., to the E-UTRAN cell) to another RAT, it may be desirable to communicate the candidate list 88 back to the initial RAT since the initial RAT may delete the list in response to the reselection to the other RAT. Thus, the candidate list 88 may be communicated from the mobile terminal 10 to the 2G RAT and the mobile terminal 10 may attempt to camp in the 2G RAT subsequent to reselection of the 2G candidate 1.

FIG. 6C illustrates continuation of a reselection operation in response to a failure to reselect the second best candidate cell (e.g., the 2G candidate 1). In this regard, for example, if the reselection of the 2G candidate 1 of FIG. 6B is unsuccessful, then reselection may be performed with respect to the next candidate in the candidate list 88 (e.g., 3G candidate 1). Again, since the reselection represents a change in RAT, the candidate list 88 may be communicated from the mobile terminal 10 to the 3G RAT and the mobile terminal 10 may attempt to camp in the 3G RAT subsequent to reselection of the 3G candidate 1. In some embodiments, the cell manager 78 may be configured to determine, in response to each reselection attempt, whether the reselection is being done inside the current RAT or in another RAT. If the reselection is being done in another RAT, the cell manager 78 may initiate communication of the candidate list 88 to the new RAT. This process may continue with attempts to reselect each candidate in rank order until a reselection attempt is successful.

Notably, in some situations, when a timer times out in one RAT (e.g., 2G) while the timer is still counting (or possibly has not started) in some other RATs, the RAT ultimately selected for reselection may not include a cell that has been better than the current serving cell for the predetermined time period (e.g., 5 seconds). Accordingly, the cell selector 80 may be enabled to reselect a cell even though the timer corresponding to the cell has not run for the predetermined time period.

FIG. 7 is a flowchart of a system, method and program product according to exemplary embodiments of the invention. It will be understood that each block or step of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by various means, such as hardware, firmware, and/or software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory device of the mobile terminal or server and executed by a built-in processor in the mobile terminal or server. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (i.e., hardware) to produce a machine, such that the instructions which execute on the computer or other programmable apparatus create means for implementing the functions specified in the flowcharts block(s) or step(s). These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowcharts block(s) or step(s). The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowcharts block(s) or step(s). Accordingly, blocks or steps of the flowcharts support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that one or more blocks or steps of the flowcharts, and combinations of blocks or steps in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions or steps, or combinations of special purpose hardware and computer instructions.

In this regard, one embodiment of a method for providing reselection candidate selection in a multi-RAT environment as provided in FIG. 7 may include receiving measurement reports or results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology at operation 100. At operation 1 10, an arrangement of the first and second candidate cells for cell reselection may be determined in response to a reselection triggering event with respect to communication with a current serving cell. Reselection to either of the first and second candidate cells may then be enabled based on the arrangement at operation 120.

In an exemplary embodiment, operation 100 may include receiving measurement reports from a plurality of candidate cells in which at least some of the cells are not associated with the same radio access technology as the current serving cell, and operation 1 10 may include ranking the candidate cells, regardless of their respective radio access technologies, with respect to reselection criteria. Notably, the receipt of measurement results may be accomplished internal to a single device. In some examples, determining the arrangement in response to the reselection triggering event may include ranking only the candidate cells that meet the reselection criteria in response to detecting that a parameter of a cell associated with any particular radio access technology exceeds a corresponding parameter of the current serving cell. Additionally or alternatively, determining the arrangement may include ranking all candidate cells that meet the reselection criteria and are associated with the same radio access technology as the current serving cell and separately incorporating candidate cells associated with each other radio access technology into the ranking. In this regard, according to some embodiments incorporating candidate cells may include individually comparing the candidate cells associated with each other radio access technology to respective candidate cells of ranked candidates among the candidate cells associated with the same radio access technology as the current serving cell to incorporate the candidate cells associated with each other radio access technology into the arrangement.

In an exemplary embodiment, the method may further include an additional operation 130 involving communicating the arrangement to a protocol stack associated with the radio access technology associated with a reselected candidate cell in response to the radio access technology associated with the reselected candidate cell being different than a radio access technology associated with the current serving cell. In one example, enabling reselection to either of the first and second candidate cells based on the arrangement may include enabling selection of the one of the first and second candidate cells that is ranked first with respect to a comparison the respective parameters measured for the first and second candidate cells. In accordance with this example, the method may further include attempting reselection to a next candidate cell in the arrangement in response to failure of reselection of a prior candidate cell in the arrangement at operation 140.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A method comprising: receiving measurement results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology; determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell; and enabling reselection to either of the first and second candidate cells based on the arrangement.

2. The method of claim 1 , wherein receiving measurement results comprises receiving measurement results from a plurality of candidate cells in which at least some of the cells are not associated with the same radio access technology as the current serving cell, and wherein determining the arrangement comprises ranking the candidate cells, regardless of their respective radio access technologies, with respect to reselection criteria.

3. The method of claim 2, wherein determining the arrangement in response to the reselection triggering event comprises ranking only the candidate cells that meet the reselection criteria in response to detecting that a parameter of a cell associated with any particular radio access technology exceeds a corresponding parameter of the current serving cell.

4. The method of claim 2, wherein determining the arrangement comprises ranking all candidate cells that meet the reselection criteria and are associated with the same radio access technology as the current serving cell and separately incorporating candidate cells that meet the reselection criteria and are associated with each other radio access technology into the ranking.

5. The method of claim 4, wherein incorporating candidate cells comprises individually comparing the candidate cells associated with each other radio access technology to respective candidate cells of ranked candidates among the candidate cells associated with the same radio access technology as the current serving cell to incorporate the candidate cells associated with each other radio access technology into the arrangement.

6. The method of claim 1 , further comprising communicating the arrangement to a protocol stack associated with the radio access technology associated with a reselected candidate cell in response to the radio access technology associated with the reselected candidate cell being different than a radio access technology associated with the current serving cell.

7. The method of claim 1 , wherein enabling reselection to either of the first and second candidate cells based on the arrangement comprises enabling selection of the one of the first and second candidate cells that is ranked first with respect to a comparison with the respective parameters measured for the first and second candidate cells.

8. The method of claim 7, further comprising attempting reselection to a next candidate cell in the arrangement in response to failure of reselection of a prior candidate cell in the arrangement.

9. A computer program product comprising at least one computer- readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising: a first executable portion for receiving measurement results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology; a second executable portion for determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell; and a third executable portion for enabling reselection to either of the first and second candidate cells based on the arrangement.

10. The computer program product of claim 9, wherein the first executable portion includes instructions for receiving measurement reports from a plurality of candidate cells in which at least some of the cells are not associated with the same radio access technology as the current serving cell, and wherein the second executable portion includes instructions for ranking the candidate cells, regardless of their respective radio access technologies, with respect to reselection criteria.

1 1. The computer program product of claim 10, wherein the second executable portion includes instructions for ranking only the candidate cells that meet the reselection criteria in response to detecting that a parameter of a cell associated with any particular radio access technology exceeds a corresponding parameter of the current serving cell.

12. The computer program product of claim 10, wherein the second executable portion includes instructions for ranking all candidate cells that meet the reselection criteria and are associated with the same radio access technology as the current serving cell and separately incorporating candidate cells that meet the reselection criteria and are associated with each other radio access technology into the ranking,

13. The computer program product of claim 12, wherein the second executable portion includes instructions for incorporating candidate cells by individually comparing the candidate cells associated with each other radio access technology to respective candidate cells of ranked candidates among the candidate cells associated with the same radio access technology as the current serving cell to incorporate the candidate cells associated with each other radio access technology into the arrangement.

14. The computer program product of claim 9, further comprising a fourth executable portion for communicating the arrangement to a protocol stack associated with the radio access technology associated with a reselected candidate cell in response to the radio access technology associated with the reselected candidate cell being different than a radio access technology associated with the current serving cell.

15. The computer program product of claim 9, wherein the third executable portion includes instructions for enabling selection of the one of the first and second candidate cells that is ranked first with respect to a comparison with the respective parameters measured for the first and second candidate cells.

16. The computer program product of claim 15, further comprising a fourth executable portion for attempting reselection to a next candidate cell in the arrangement in response to failure of reselection of a prior candidate cell in the arrangement.

17. An apparatus comprising: a cell manager configured to receive measurement results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology and determine an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell; and a cell selector configured to enable reselection to either of the first and second candidate cells based on the arrangement.

18. The apparatus of claim 17, wherein the cell manager is further configured to: receive measurement results by receiving measurement results from a plurality of candidate cells in which at least some of the cells are not associated with the same radio access technology as the current serving cell, and determine the arrangement by ranking the candidate cells, regardless of their respective radio access technologies, with respect to reselection criteria.

19. The apparatus of claim 18, wherein the cell manager is configured to rank only the candidate cells that meet the reselection criteria in response to detecting that a parameter of a cell associated with any particular radio access technology exceeds a corresponding parameter of the current serving cell.

20. The apparatus of claim 18, wherein the cell manager is further configured to rank all candidate cells that meet the reselection criteria and are associated with the same radio access technology as the current serving cell and separately incorporating candidate cells that meet the reselection criteria and are associated with each other radio access technology into the ranking.

21. The apparatus of claim 20, wherein the cell manager is further configured to incorporate candidate cells by individually comparing the candidate cells associated with each other radio access technology to respective candidate cells of ranked candidates among the candidate cells associated with the same radio access technology as the current serving cell to incorporate the candidate cells associated with each other radio access technology into the arrangement.

22. The apparatus of claim 17, wherein the cell manager is further configured to communicate the arrangement to a protocol stack associated with the radio access technology associated with a reselected candidate cell in response to the radio access technology associated with the reselected candidate cell being different than a radio access technology associated with the current serving cell.

23. The apparatus of claim 17, wherein the cell selector is configured to enable selection of the one of the first and second candidate cells that is ranked first with respect to a comparison with the respective parameters measured for the first and second candidate cells.

24. The apparatus of claim 23, wherein the cell selector is further configured to attempt reselection to a next candidate cell in the arrangement in response to failure of reselection of a prior candidate cell in the arrangement.

25. An apparatus comprising: means for receiving measurement results corresponding to parameters measured in at least a first candidate cell associated with a first radio access technology and a second candidate cell associated with a second radio access technology that is different than the first radio access technology; means for determining an arrangement of the first and second candidate cells for cell reselection in response to a reselection triggering event with respect to communication with a current serving cell; and means for enabling reselection to either of the first and second candidate cells based on the arrangement.