WO2009109796A2

WO2009109796A2 - Method, apparatus and computer program product for enabling a virtual handoff in a wireless communication system

Info

Publication number: WO2009109796A2
Application number: PCT/IB2008/000485
Authority: WO
Inventors: Xiaoyi Wang; Hao Guan
Original assignee: Nokia Siemens Networks Oy; Nokia, Inc.
Priority date: 2008-03-04
Filing date: 2008-03-04
Publication date: 2009-09-11
Also published as: WO2009109796A8

Abstract

An apparatus for enabling a virtual handoff in a wireless communication system may include a processor. The processor may be configured to enter a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node, and establish communication with a sub-node disposed within a coverage area of the macro node during the sleep window. A method and computer program product for enabling a virtual handoff are also provided.

Description

METHOD, APPARATUS AND COMPUTER PROGRAM PRODUCT

FOR ENABLING A VIRTUAL HANDOFF IN A WIRELESS COMMUNICATION SYSTEM

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to communication technology and, more particularly, relate to an apparatus, method and a computer program product for enabling a virtual handoff in a wireless communication system.

BACKGROUND OF THE INVENTION

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. In order to provide easier or faster information transfer and convenience, telecommunication industry service providers are developing improvements to existing networks. In this regard, wireless communication has become increasingly popular in recent years due, at least in part, to reductions in size and cost along with improvements in battery life and computing capacity of mobile electronic devices. As such, mobile electronic devices have become more capable, easier to use, and cheaper to obtain. Due to the now ubiquitous nature of mobile electronic devices, people of all ages and education levels are utilizing mobile terminals to communicate with other individuals or contacts, receive services and/or share information, media and other content.

Communication networks have been developed and expanded to provide robust support for mobile electronic devices. For example, the Worldwide Interoperability for Microwave Access (WiMAX), is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. WiMAX is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, which is also called Wireless Municipal Access Network (WirelessMAN). WiMAX systems typically provide wireless broadband access to users of electronic devices as an alternative to cable or digital subscriber line (DSL) access. In this regard, base stations (often referred to as BSs or BTSs) typically serve as wireless communication access points for a wireless communication device that may be referred to as a subscriber station (SS). A SS could be a fixed device such as a personal computer (PC) or a mobile terminal such as a cellular telephone, laptop computer, or other mobile communication device. A recent focus in relation to wireless broadband access networks such as WiMAX has been on improving performance with respect to mobile devices. As a result, the concept of making femto base stations available to users has been introduced. A femto BS may be a user installed access point that is located within a larger cell (e.g., macro cell) defined by the coverage area of a network installed BS (e.g., a macro BS). In this regard, the femto BS may provide in-home (or business) mobility with improved data rates and quality of service (QoS) as compared to a macro BS, which may be loaded heavily from communications with other SS and/or may be shielded somewhat by buildings or other obstructions with respect to an in-home user's SS. In many instances, the femto BS may access the network via a wired communication mechanism such as a DSL line. Accordingly, the femto BS does not load the macro BS in whose macro cell the femto BS may be located. According to current structures, when a SS is in a user's home, the SS may communicate with the femto BS and completely offload the user from the macro BS. Thus, in order to support mobility of the SS (e.g., if the SS corresponds to a mobile terminal), the SS must be handed over between the femto BS and the macro BS when the user exits or enters the home environment. However, the handoff may, in some instances, not occur with sufficient speed and efficiency to ensure proper QoS or adequate experience for the user.

In light of the issues discussed above, it may be desirable to provide a mechanism for enabling an improved handoff capability between a macro BS and a femto BS. Accordingly, it may be desirable to develop a mechanism by which at least some of the problems described above may be addressed.

BRIEF SUMMARY OF THE INVENTION A method, apparatus and computer program product are therefore provided that may enable a macro communication node (e.g., a macro BS) and a sub-node (e.g., a femto BS) to provide an improved handoff of a SS (e.g., a mobile terminal). For example, embodiments of the present invention may provide a mechanism by which a virtual handoff may be conducted between the macro node and the sub- node. In this regard, the mobile terminal may be enabled to enter a sleep or idle mode with respect to the macro node. During the sleep or idle mode, the mobile terminal may experience sleep and awake periods. During the awake period, the mobile terminal may communicate with the macro node, while during the sleep period, the mobile terminal may communicate with the sub-node. However, in either a sleep or awake period, the mobile terminal may maintain the connection with the macro node. Accordingly, since communication with the macro node is never completely broken, a handoff (or virtual handoff in actuality) between the macro node and the sub-node may be accomplished in a fast and efficient manner, for example, if the mobile terminal leaves the environment of the sub-node or otherwise loses communication with the sub-node.

In one exemplary embodiment, a method of enabling a virtual handoff in a wireless communication system is provided. The method may include entering a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node, and establishing communication with a sub-node disposed within a coverage area of the macro node during the sleep window. In another exemplary embodiment, a computer program product for enabling a virtual handoff in a wireless communication system is provided. The computer program product includes at least one computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable program code portions include first and second executable portions. The first executable portion is for entering a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node. The second executable portion is for establishing communication with a sub-node disposed within a coverage area of the macro node during the sleep window.

In another exemplary embodiment, an apparatus for enabling a virtual handoff in a wireless communication system is provided. The apparatus may include a processor. The processor may be configured to enter a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node, and establish communication with a sub-node disposed within a coverage area of the macro node during the sleep window.

In another exemplary embodiment, a method of enabling a virtual handoff in a wireless communication system is provided from the perspective of a macro or sub-node. The method may include maintaining a connection, from a first communication node, with a terminal in a sleep mode. The method may further include communicating, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node. The first window may define a period during which the terminal is not receptive to communications from the second communication node. The method may further include maintaining, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node. The first and second communication nodes may have coverage areas that at least partially overlap.

In another exemplary embodiment, a computer program product for enabling a virtual handoff in a wireless communication system is provided from the perspective of a macro or sub-node. The computer program product includes at least one computer-readable storage medium having computer-readable program code portions stored therein. The computer-readable program code portions include first, second and third executable portions. The first executable portion is for maintaining a connection, from a first communication node, with a terminal in a sleep mode. The second executable portion is for communicating, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node. The first window may define a period during which the terminal is not receptive to communications from the second communication node. The third executable portion is for maintaining, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node. The first and second communication nodes may have coverage areas that at least partially overlap. In another exemplary embodiment, an apparatus for enabling a virtual handoff in a wireless communication system is provided from the perspective of a macro or sub-node. The apparatus may include a processor. The processor may be configured to maintain a connection, from a first communication node, with a terminal in a sleep mode. The processor may be further configured to communicate, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node. The first window may define a period during which the terminal is not receptive to communications from the second communication node. The processor may be further configured to maintain, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node. The first and second communication nodes may have coverage areas that at least partially overlap.

In yet another exemplary embodiment, as system for enabling a virtual handoff in a wireless communication system is provided. The system may include a macro node, a sub-node, a terminal and a network gateway. The macro node may be configured to communicate with terminals within a first coverage area. The sub-node may be configured to communicate with terminals within a second coverage area in which the first and second coverage areas at least partially overlap. The terminal may be capable of communication with the macro node and the sub-node. The terminal may include a processor configured to enter a sleep mode with respect to the macro node during a communication connection between the terminal and the macro node. The sleep mode may define a sleep window during which the terminal is not receptive to communications from the macro node, but maintains the communication connection with the macro node. The processor may also be configured to establish communication with the sub-node during the sleep window. The network gateway may be configured to communicate directly with the macro node and enable indirect communication between the macro node and the sub-node. Embodiments of the invention may provide a method, apparatus and computer program product for employment in mobile environments in which broadband communication services are provided. As a result, for example, mobile terminal users may enjoy improved capabilities for handing off communications between nodes having overlapping coverage areas.

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 is a schematic diagram showing an apparatus for enabling a virtual handoff in a wireless communication system according to an exemplary embodiment of the present invention;

FIG. 4 illustrates a diagram of an exemplary network architecture including a macro node and a sub-node in accordance with an exemplary embodiment of the present invention;

FIG. 5 is a diagram showing the overlapping nature of cell coverage areas provided by the macro node and the sub-node according to an exemplary embodiment of the present invention; FIG. 6 illustrates an example with regard to communications between a subscriber station, a macro node and a sub-node according to an exemplary embodiment of the present invention;

FIG. 7 illustrates another example with regard to communications between a subscriber station, a macro node and a sub-node according to an exemplary embodiment of the present invention;

FIG. 8 illustrates exemplary messaging that may occur during the performance of a virtual handoff process;

FIG. 9 is a flowchart according to an exemplary method for enabling a virtual handoff in a wireless communication system according to an exemplary embodiment of the present invention; and

FIG. 10 is a flowchart according to another exemplary method for enabling a virtual handoff in a wireless communication system according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

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 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 one embodiment of the mobile terminal 10 is illustrated and will be hereinafter described for purposes of example, other types of mobile terminals, such as portable digital assistants (PDAs), pagers, mobile computers, mobile televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of voice and text communications systems, can readily employ embodiments of the present invention. Furthermore, devices that are not mobile may also readily employ embodiments of the present invention.

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 (TDMA), GSM, and IS-95 (CDMA), or with third-generation (3G) wireless communication protocols, such as UMTS, CDMA2000, WCDMA and TD-SCDMA, LTE or E-UTRAN, with fourth- generation (4G) wireless communication protocols or the like.

It is understood that apparatus such as the controller 20 includes circuitry desirable for implementing audio and logic functions of the mobile terminal 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 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 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.

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 (which may include both user plane and control plane (MME) functions), 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), 3.9G, 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 E-UTRAN or a

Universal Mobile Telephone System (UMTS) network employing Wideband Code Division Multiple Access (WCDMA) radio access technology. Some narrow-band AMPS (NAMPS), as well as 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 wireless LAN (WLAN) techniques such as IEEE 802.11 (e.g., 802.11a, 802.11b, 802.1 Ig, 802.1 In, etc.), 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 USB, LAN, WLAN, WiMAX, UWB techniques and/or the like.

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 execute applications for establishing communication between the mobile terminal 10 and other mobile terminals, for example, via the system of FIG. 2. 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 network device or other device accessible to the communication device. An exemplary embodiment of the invention will now be described with reference to FIG. 3, in which certain elements of an apparatus for enabling a virtual handoff in a wireless communication system are displayed. The apparatus of FIG. 3 may be embodied as or otherwise employed, for example, on a network device such as a server of FIG. 2 or on a subscriber station (SS) such as the mobile terminal 10 of FIG. 1. However, it should be noted that the apparatus of FIG. 3, may also be employed on a variety of other devices, both mobile and fixed, and therefore, embodiments of the present invention should not be limited to application on devices such as those in these exemplary descriptions. It should also be noted that while FIG. 3 illustrates one example of a configuration of an apparatus for enabling a virtual handoff in a wireless communication system, numerous other configurations may also be used to implement embodiments of the present invention. Notably, although FIG. 3 will be described in connection with an embodiment in which the SS is a mobile terminal 10 communicating in accordance with a WiMAX technique, this description is merely provided for exemplary purposes. As such, embodiments of the present invention should also not be limited to application in connection with mobile terminals and/or WiMAX communication techniques.

Referring now to FIG. 3, an apparatus for enabling a virtual handoff in a wireless communication system employing WiMAX techniques 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 nonvolatile 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. 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 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 virtual handoff manager 78. In this regard, for example, the virtual handoff manager 78 may be any device or means embodied in either hardware, software, or a combination of hardware and software that is configured to perform the corresponding functions of the virtual handoff manager 78 as described in greater detail below. In this regard, the virtual handoff manager 78 may be configured to generate and/or receive communications related to establishing and managing connections between a SS (e.g., the mobile terminal 10 of FIG. 4) and both a macro node (e.g., the macro BS 80 of FIG. 4) and a sub-node (e.g., the femto BS 82 of FIG. 4). For example, the virtual handoff manager 78 may define, receive or otherwise access communication parameters including parameters defining particular periods of time for the mobile terminal 10 that correspond to awake or available communication periods and sleep, idle or any other unavailable communication periods with respect to communications with the macro node and the sub-node, respectively. In an exemplary embodiment, communication parameters defining an idle period for one of the macro node or sub-node may correspond to communication parameters defining an available period for the other one of the macro node or sub-node. In other words, for example, if the communication parameters define a particular period as being an idle period for the macro node, the particular period may correspond to an available period for the sub-node. The virtual handoff manager 78 may define, receive or otherwise access the communication parameters for inclusion in, or in response to receipt or transmission of, a request message to enter a sleep mode that may be sent from the SS to the macro node.

Embodiments of the virtual handoff manager 78 may be located at either one or both of a network device (or server) and a SS (e.g., mobile terminal). In either case, the virtual handoff manager 78 may be configured to define the communication parameters and/or receive communication parameters provided from another location (e.g., another embodiment of the virtual handoff manager

78) and implement communication with the macro node and the sub-node based on the communication parameters defined. The virtual handoff manager 78 may alternatively or further be configured to communicate messages such as request or response messages related to entrance into or exiting from a sleep mode. In this regard, for example, rather than terminate communication with the macro node in situations where communication with the sub-node is desired or possible, the virtual handoff manager 78 may be configured to maintain communication with the macro node in an idle or sleep mode capacity while communications are conducted with the sub-node in an available or active mode capacity.

FIG. 4 illustrates a diagram of an exemplary network architecture including a macro node (e.g., macro BS 80) and a sub-node (e.g., femto BS 82) in accordance with embodiments of the present invention. In the example of FIG. 4, a plurality of femto BSs are shown within a particular building 84, which may be an apartment building. Each femto BS of FIG. 4 serves a particular unit (e.g., apartment) within the building 84 (although the femto BSs could alternatively be located within separate buildings or houses) and the entire building 84 may be within a macro cell served by the coverage area of the macro BS 80. The femto BSs may each be in wireline communication with a communication network 86 (e.g., a telecom network acting as an access serving network) via a DSL line 88 to an Internet service provider (ISP) router 90 that may be communicatively coupled to the network 86. The network may also be coupled to the macro BS 80 and other BSs. The mobile terminal 10 may communicatively couple to the network via either the macro BS 80 or the femto BS 82 according to embodiments of the present invention.

In this regard, for example, in many cases apartment or other buildings may be tall and/or constructed of concrete or other materials that may inhibit efficient or effective communications between the macro BS 80 and the mobile terminal 10 when the mobile terminal 10 is within the building 84. Accordingly, while in the building 84 and within range of the femto BS 82, the mobile terminal 10 may preferably communicate with the femto BS 82. Conventionally, a handover of the mobile terminal 10 from the macro BS 80 to the femto BS 82 may therefore be conducted to improve communications of the mobile terminal 10 when in the building 84. However, channel quality in in-door environments may vary dramatically in some situations. Thus, a normal handover process may be too slow to adapt to such changes. Moreover, as indicated above, since the mobile terminal 10 may leave the building 84 or at least leave the range of the femto BS 82, a user of the mobile terminal 10 may wish to employ an embodiment of the present invention to cause a virtual handoff of the mobile terminal 10. Handoffs (or virtual handoffs) of the mobile terminal 10 may be initiated by manual request of the user of the mobile terminal 10 or by automatic action by the mobile terminal 10 (e.g., in response to sensing a reduction of signal strength from the macro BS 80 below a threshold, in response to sensing a signal strength of the femto BS 82 above a particular threshold, in response to sensing a ratio of signal strengths of the macro BS 80 and the femto BS 82 reaching a particular value, or combinations of the above).

Instead of actually fully handing off the mobile terminal 10 to the femto BS 82 (thereby terminating the connection between the mobile station 10 and the macro BS 80), which may cause slower handoff of the mobile terminal 10 back to the macro cell 80 when mobility is resumed, the mobile terminal 10 may be the subject of a virtual handoff only. In the virtual handoff, the mobile terminal 10 may maintain a connection with the macro BS 80 in a sleep or idle mode, which can be easily and efficiently ended to effectuate a virtual handover of the mobile terminal 10 back to the macro BS 80. In this regard, for example, the mobile terminal 10 (e.g., more specifically the virtual handoff manager 78) may communicate a request to the macro BS 80 to enter the sleep or idle mode. The request may further specify that the sleep or idle mode corresponds to a virtual handoff as described herein. During sleep or unavailable periods of the mobile terminal 10 from a perspective of the macro BS 80, the mobile terminal 10 may access or otherwise communicate with the femto BS 82, for example, for ranging, data transmission, and/or the like.

FIG. 5 illustrates the overlapping nature of the cell coverage areas provided by the macro BS 80 and the femto BS 82, either of which may be in wireless communication with the mobile terminal 10. As further indicated in FIG. 5, the macro BS 80 may be in communication with an access serving network gateway (ASN-GW) 92, which along with the macro BS 80 may be a part of the access serving network (ASN). Notably, although both the macro BS 80 and the femto BS 82 may be in communication with the same ASN-GW, they may not communicate directly with each other. The ASN-GW 92, which may be an example of the apparatus of FIG. 3, may also be in communication with the femto BS 82 via the ISP router 90, which may also provide access to the Internet. As can be seen from FIG. 5, a femto cell 94 defined by the coverage area of the femto BS 82 may be within a macro cell 96 defined by the coverage area of the macro BS 80. However, in some embodiments of the present invention, since when the mobile terminal 10 is in range of the femto BS 82 and may therefore communicate the request to the macro BS 80 to enter the sleep mode, the femto BS 82 may therefore be free to allocate the same cell identification (CID) that was used by the macro BS 80. This may be advantageous due to a limited number of CIDs that may be available for use in some instances.

FIGS. 6 and 7 illustrate specific examples with regard to communications between the mobile terminal 10 and the femto BS 82 and the macro BS 80 according to exemplary embodiments of the present invention. In this regard, FIGS. 6 and 7 illustrate a relationship between active and inactive windows for communication between the mobile terminal 10 and the macro BS 80 and the femto BS 82, respectively, in two different exemplary embodiments. The virtual handoff manager 78 may generate a request for a virtual handoff for communication to the macro BS 80, as described above. The virtual handoff may be characterized by entry of the mobile terminal 10 into a sleep mode with respect to the macro BS 80. The sleep mode may include sleep windows 100 and awake windows 102 (or listening windows), each corresponding to respective periods during which the mobile terminal 10 may be asleep or awake, respectively, with respect to the macro BS 80. During a sleep window, although the connection between the macro BS 80 and the mobile terminal 10 is maintained, active communications are not conducted between the macro BS 80 and the mobile terminal 10 since the mobile terminal 10 will not be listening for messages from the macro BS 80. Meanwhile, during an awake window, active communications (e.g., messages) may be exchanged between the macro BS 80 and the mobile terminal 10 since the mobile terminal 10 will be listening for messages from the macro BS 80.

As shown in FIG. 6, in some embodiments, when the mobile station 10 is in an awake window with respect to the macro BS 80, the mobile terminal 10 may be unavailable to the femto BS 82 (e.g., in an unavailable time 104). Similarly, when the mobile station 10 is in a sleep window with respect to the macro BS 80, the mobile terminal 10 may be available to the femto BS 82 (e.g., in an available time 106). Meanwhile, as shown in an alternative embodiment of FIG. 7, the mobile terminal 10 may also enter a sleep mode with respect to the femto BS 82 defining respective sleep and awake windows during the available time 106 for the femto BS 82.

Several options may be available during the sleep mode. For example, parameters defining characteristics of the sleep cycle (e.g., the duration and frequency of sleep or unavailable and awake or available periods) may be defined to have any suitable values. For example, the awake windows 102 may be kept relatively short with respect to the duration of the sleep windows 100. According to other options, different sleep modes may be provided in various different embodiments. For example, in one exemplary sleep mode, the femto BS 82 may be provided with parameters defining characteristics of the sleep cycle through a backhaul network (e.g., via the ISP router 90) to inform the femto BS 82 of parameters such as initial sleeping window, final sleeping window base, etc. Thus, both the femto BS 82 and the macro BS 80 may be aware of listening and sleeping periods and the mobile terminal 10 may only communicate with the femto BS 82 during sleeping periods (e.g., defined by sleep windows 100) to enable a smooth virtual handoff. During an awake period, the ASN-GW 92 may decide whether the macro BS 80 provides data transmission to the mobile terminal 10 or not.

In another exemplary sleep mode, the femto BS 82 may be informed of parameters through a backhaul network as above. In some embodiments, parameters defining characteristics of the sleep cycle may be provided by the mobile terminal 10 in the request to enter the sleep mode, while in other embodiments, the parameters may be provided by the macro BS 80 in response to the request. The parameters could alternatively be fixed or stored and therefore accessed by the mobile terminal 10 and/or the macro BS 80 in response to the request. However, in an exemplary embodiment, durations of the awake windows 102 and the sleep windows 100 may be adjusted via request by any one of the macro BS 80, the femto BS 82, and/or the ASN-GW 92. Exemplary reasons that may trigger such a request may include long term channel quality variations at the macro BS 80 in heavy load, QoS of a communication line between the femto BS 82 and the ASN-GW 92 varying significantly, or others. If an adjustment to durations of either the awake windows 102 or the sleep windows 100 occurred, both the femto BS 82 and the macro BS 80 may inform the mobile terminal 10 using messaging such as, for example, a MOB SLP RSP, uplink sleep control header, downlink sleep control extended subheader, or another type of message. This mode may be suitable, for example, if both the macro BS 80 and the femto BS 82 have data for transmission.

In another exemplary sleep mode, the macro BS 80 may periodically define or activate a new sleeping window for a mobile terminal. Every time a new sleeping window is defined, the macro BS 80 may inform the femto BS 82 of the new sleep window's parameters (e.g., sleeping duration) to the femto BS 82 through the backhaul network.

In yet another exemplary sleep mode, the macro BS 80 may command the mobile terminal 10 to enter a sleep window of infinite or undetermined duration. Accordingly, the mobile terminal 10 may communicate with the femto BS 82 during the sleep window and, when and if the macro BS 80 decides to wake the mobile terminal 10, the macro BS 80 may send a message to the femto BS 82 via the ASN-GW 92 to request the femto BS 82 to wake up the mobile terminal 10. In an exemplary embodiment, the ASN-GW 92 may communicate data to either or both of the femto BS 82 and the macro BS 80. Accordingly, for example, if a handover of communication with the mobile terminal occurs between the femto BS 82 and the macro BS 80, a packet number may be used to locate the next packet for transmission. Furthermore, in some embodiments, the mobile station 10 may communicate (e.g., due to the maintaining of the connection with the macro

BS 80) a request to the macro BS 80 to end the sleep mode. The request for ending the sleep mode may be sent either during a sleep window or during an awake window. The mobile terminal 10 need not inform the femto BS 82 of the ending of the sleep mode (which may constitute a handoff back to the macro BS 80) prior to ending the sleep mode. As such, for example, the mobile terminal 10 may inform the femto BS 82 of the ending of the sleep mode after the handoff back to the macro BS 80 has been accomplished.

FIG. 8 illustrates exemplary messaging that may occur during the performance of a virtual handoff process in accordance with an exemplary embodiment of the present invention. In this regard, as indicated at operation 200, a connection may initially be established or existing between an SS (e.g., the mobile terminal 10) and a BS (e.g., the macro BS 80). At operation 202, the SS may send a request to enter a sleep mode to the BS. The BS may send a response to the request at operation 204. The SS may enter sleep mode with respect to the BS and attempt to initially access the femto BS at operation 206. The femto BS typically only does local authorizations. Thus, since the SS has been authorized by the ASN previously, it may be desirable to avoid authorizing the SS all over again. The femto BS may then forward a query for information about the SS to the access service network (ASN) (e.g., the ASN-GW 92) at operation 208. The ASN may communicate a query as to information about the SS to the BS at operation 210. At operation 212, the BS may respond to the query with feedback. The ASN may then provide the information regarding the SS to the femto BS at operation 214. The femto BS may then allocate a CID to the SS at operation 216. As indicated above, the same CID used by the BS may be allocated to the femto BS. A connection between the femto BS and the SS may then be established at operation 218, while the connection between the SS and the BS is maintained as indicated by operation 220. Accordingly, embodiments of present invention may enable fast "handoff ' of the SS in case, for example, femto BS signalling drops due to the maintenance of the connection between the SS and the macro BS. Furthermore, the connection between the macro BS and the SS may provide that a user's QoS is not solely reliant upon femto BS access.

Table 1 below shows an exemplary virtual handoff indication message for use in accordance with an exemplary embodiment.

Table 1.

FIGS. 9 and 10 are flowcharts 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 network device and executed by a built-in processor in the mobile terminal or network device. 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 enabling a virtual handoff in a wireless communication system from the perspective of a subscriber station such as a mobile terminal as illustrated in FIG. 9 may include entering a sleep mode with respect to a macro node during communication between a mobile terminal and the macro node at operation 310. The sleep mode may define a sleep window during which the mobile terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node. The method may further include establishing communication with a sub-node disposed within a coverage area of the macro node during the sleep window at operation 320. In some embodiments, an optional initial operation may also be included as operation 300, which may include generating a request to enter the sleep mode for transmission from the mobile terminal to the macro node. In such embodiments, entering the sleep mode may occur in response to receipt of a response to the request from the macro node. In an exemplary embodiment, operation 300 may include defining parameters including characteristics of the sleep window. The method could also include receiving a request from the sub-node, the macro node or an access service network gateway to alter characteristics of the sleep window or communicating with the macro node and not being receptive to communications from the sub-node during an awake period defined by the sleep mode.

In some embodiments, communicating with the sub-node during the sleep window may further include communicating with the sub-node during at least one portion of the sleep window and not being receptive to communications from the sub-node during at least another portion of the sleep window. Additionally, entering the sleep mode may include entering an infinite duration sleep mode such that the method further comprises receiving a message initiated by the macro node and communicated via the sub-node for the mobile terminal to awaken from the sleep mode. Some embodiments may also provide a message to the macro node during the sleep window to end the sleep mode.

Another embodiment of a method for enabling a virtual handoff in a wireless communication system from the perspective of a communication node such as a macro node or a sub-node as illustrated in FIG. 10 may include maintaining a connection, from a first communication node, with a mobile terminal in a sleep mode at operation 400. At operation 410, the first communication node may communicate with the mobile terminal during a first window such that, while the first communication node communicates with the mobile terminal during the first window, the mobile terminal maintains a connection with a second communication node. The first window may define a period during which the mobile terminal is not receptive to communications from the second communication node. The method may further include maintaining, at the first communication node, connection with the mobile terminal, but not directing communications to the mobile terminal, during a second window defining a period during which the mobile terminal is not receptive to communications from the first communication node at operation 420. The first and second communication nodes may have coverage areas that overlap. In an exemplary embodiment in which the first communication node is a macro node, the method may further include ending the sleep mode in response to receiving a request from the mobile terminal to end the sleep mode.

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. 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: entering a sleep mode with respect to a macro node during communication between a mobile terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node; and establishing communication with a sub-node disposed within a coverage area of the macro node during the sleep window.

2. A method according to Claim 1, further comprising an initial operation of generating a request to enter the sleep mode for transmission from the terminal to the macro node, wherein entering the sleep mode occurs in response to receipt of a response to the request from the macro node.

3. A method according to Claim 2, wherein generating the request further comprises defining parameters including characteristics of the sleep window.

4. A method according to Claim 3, further comprising receiving a request from the sub-node, the macro node or an access service network gateway to alter characteristics of the sleep window.

5. A method according to Claim 1, further comprising communicating with the macro node and not being receptive to communications from the sub-node during an awake period defined by the sleep mode.

6. A method according to Claim 1 , wherein communicating with the sub-node during the sleep window further comprises communicating with the sub- node during at least one portion of the sleep window and not being receptive to communications from the sub-node during at least another portion of the sleep window.

7. A method according to Claim 1, wherein entering the sleep mode comprises entering an infinite duration sleep mode and wherein the method further comprises receiving a message initiated by the macro node and communicated via the sub-node for the terminal to awaken from the sleep mode.

8. A method according to Claim 1, further comprising providing a message to the macro node during the sleep window to end the sleep mode.

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 entering a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node; and a second executable portion for establishing communication with a sub- node disposed within a coverage area of the macro node during the sleep window.

10. A computer program product according to Claim 9, further comprising a third executable portion for an initial operation of generating a request to enter the sleep mode for transmission from the terminal to the macro node, wherein the first executable portion is executed in response to receipt of a response to the request from the macro node.

11. A computer program product according to Claim 10, wherein the third executable portion includes instructions for defining parameters including characteristics of the sleep window.

12. A computer program product according to Claim 11, further comprising a fourth executable portion for receiving a request from the sub-node, the macro node or an access service network gateway to alter characteristics of the sleep window.

13. A computer program product according to Claim 9, further comprising a third executable portion for communicating with the macro node and not being receptive to communications from the sub-node during an awake period defined by the sleep mode.

14. A computer program product according to Claim 9, wherein the second executable portion includes instructions for communicating with the sub- node during at least one portion of the sleep window and not being receptive to communications from the sub-node during at least another portion of the sleep window.

15. A computer program product according to Claim 9, wherein the first executable portion includes instructions for entering an infinite duration sleep mode and wherein the computer program product further comprises a third executable portion for receiving a message initiated by the macro node and communicated via the sub-node for the terminal to awaken from the sleep mode.

16. A computer program product according to Claim 9, further comprising a third executable portion for providing a message to the macro node during the sleep window to end the sleep mode.

17. An apparatus comprising a processor configured to: enter a sleep mode with respect to a macro node during communication between a terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains a communication connection with the macro node; and establish communication with a sub-node disposed within a coverage area of the macro node during the sleep window.

18. An apparatus according to Claim 17, wherein the processor is further configured to perform an initial operation of generating a request to enter the sleep mode for transmission from the terminal to the macro node and wherein entering the sleep mode occurs in response to receipt of a response to the request from the macro node.

19. An apparatus according to Claim 18, wherein the processor is configured to generate the request further by defining parameters including characteristics of the sleep window.

20. An apparatus according to Claim 19, wherein the processor is further configured to receive a request from the sub-node, the macro node or an access service network gateway to alter characteristics of the sleep window.

21. An apparatus according to Claim 17, wherein the processor is further configured to communicate with the macro node and not being receptive to communications from the sub-node during an awake period defined by the sleep mode.

22. An apparatus according to Claim 17, wherein the processor is configured to communicate with the sub-node during at least one portion of the sleep window and not being receptive to communications from the sub-node during at least another portion of the sleep window.

23. An apparatus according to Claim 17, wherein the processor is configured to enter the sleep mode via entering an infinite duration sleep mode and wherein the processor is further configured to receive a message initiated by the macro node and communicated via the sub-node for the terminal to awaken from the sleep mode.

24. An apparatus according to Claim 17, wherein the processor is further configured to provide a message to the macro node during the sleep window to end the sleep mode.

25. A method comprising: maintaining a connection, from a first communication node, with a mobile terminal in a sleep mode; communicating, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node, the first window defining a period during which the terminal is not receptive to communications from the second communication node; and maintaining, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node, the first and second communication nodes having coverage areas that at least partially overlap.

26. A method according to Claim 25, further comprising ending the sleep mode in response to receiving a request from the terminal to end the sleep mode.

27. 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 maintaining a connection, from a first communication node, with a terminal in a sleep mode; a second executable portion for communicating, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node, the first window defining a period during which the terminal is not receptive to communications from the second communication node; and a third executable portion for maintaining, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node, the first and second communication nodes having coverage areas that at least partially overlap.

28. A computer program product according to Claim 27, further comprising a fourth executable portion for ending the sleep mode in response to receiving a request from the terminal to end the sleep mode.

29. An apparatus comprising a processor configured to: maintain a connection, from a first communication node, with a terminal in a sleep mode; communicate, from the first communication node, with the terminal during a first window such that, while the first communication node communicates with the terminal during the first window, the terminal maintains a connection with a second communication node, the first window defining a period during which the terminal is not receptive to communications from the second communication node; and maintain, at the first communication node, connection with the terminal, but not directing communications to the terminal, during a second window defining a period during which the terminal is not receptive to communications from the first communication node, the first and second communication nodes having coverage areas that at least partially overlap.

30. An apparatus according to Claim 29, wherein the processor is further configured to end the sleep mode in response to receiving a request from the terminal to end the sleep mode.

31. A system comprising: a macro node configured to communicate with terminals within a first coverage area; a sub-node configured to communicate with terminals within a second coverage area in which the first and second coverage areas at least partially overlap; a terminal capable of communication with the macro node and the sub- node, the terminal comprising a processor configured to enter a sleep mode with respect to the macro node during a communication connection between the terminal and the macro node, the sleep mode defining a sleep window during which the terminal is not receptive to communications from the macro node, but maintains the communication connection with the macro node, and establish communication with the sub-node during the sleep window; and a network gateway configured to communicate directly with the macro node and enable indirect communication between the macro node and the sub- node.