# Patent

## Title
Dynamic adjustment of keep-alive messages for efficient battery usage in a mobile network

## Abstract

Systems and methods for dynamic adjustment of keep-alive message intervals in a mobile network are disclosed. One embodiment of maintaining an IP connection between a mobile terminal and a network node over a network includes, detecting a rate with which the client-slide request are made from the mobile terminal, detecting a rate with which the client-slide request are made from the mobile terminal, sending, by the network node, keep-alive messages to the mobile terminal in an absence of network traffic through the IP connection between the mobile terminal and the network node, and/or further optimizing the time intervals between the keep-alive messages based on a cost to send the keep-alive messages in the network.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. patent application Ser. No. 13/043,425 filed on Mar. 8, 2011, which claims priority to U.S. Provisional Patent Application No. 61/408,826 entitled “ONE WAY INTELLIGENT HEARTBEAT”, filed Nov. 1, 2010 and is a Continuation-In-Part of co-pending U.S. patent application Ser. No. 12/853,119, entitled “MAINTAINING AN IP CONNECTION IN A MOBILE NETWORK”, filed Aug. 9, 2010, which claims the priority of U.S. patent application Ser. No. 11/471,630, entitled “MAINTAINING AN IP CONNECTION IN A MOBILE NETWORK”, filed Jun. 21, 2006, now U.S. Pat. No. 7,774,007, which claims priority to U.S. Provisional Patent Application 60/707,170, filed Aug. 11, 2005. The disclosures of which are herein incorporated by reference.


BACKGROUND
The invention relates to techniques for maintaining an IP (Internet protocol) connection in a mobile network.
In a packet-switched mobile network, a mobile terminal is not normally assigned a dedicated circuit-switched connection. Instead, the network establishes and maintains a session for the terminal, and data packets are sent when necessary. In order to integrate mobile terminals with office applications, it is becoming increasingly popular to maintain Internet Protocol (IP) connections over packet data channels in packet-switched mobile networks. Maintaining an IP connection to/from a mobile terminal is desirable in order to keep data banks synchronized between the mobile terminal and an office computer, for example.
Maintaining an IP connection in packet-Switched mobile networks involves certain problems. For example, it consumes the mobile terminal's battery. Further, many networks apply operator-defined policies to break connections after a certain period of inactivity. This period can be quite short, such as five minutes. When the IP connection to/from the mobile terminal is disconnected, database synchronization is impossible before connection reestablishment. Connection re-establishment must be initiated from the mobile terminal's side, the network cannot initiate connection re-establishment.
But connection re-establishment involves further expenses in tariff and/or battery consumption. Yet further, since the network cannot initiate reestablishment of the IP connection, network-initiated data synchronization must be initiated by means of an out-band trigger, i.e., signaling independent from the Internet Protocol. A short message service (SMS) and its derivatives are examples of theoretically suitable out-band triggering mechanisms. But a single GSM-compliant short message can only transfer approximately 160 characters, which means that it is impracticable to transfer actual data in the trigger message. This has the consequence that the subscriber must bear the expenses and delays in re-establishing the IP connection.
The mobile terminal can send keep-alive messages in order to prevent the network from disconnecting a temporarily inactive IP connection. A keep-alive message is a message sent for the purpose of preventing the network from disconnecting the IP connection.
The mobile terminal's operating parameters in respect of the keep-alive messages could be optimized for a single network, but connection break-up habits vary between networks and in a single network they may depend on roaming arrangements between operators.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an exemplary network arrangement in which the invention can be used.
FIG. 2 shows a flowchart illustrating an embodiment of the invention.
FIGS. 3A and 3B illustrate a technique for determining a maximum interval between keep-alive messages by means of a cumulative probability function.
FIG. 4 shows a flow chart illustrating an example process for dynamically adjusting keep-alive message intervals in a mobile network.
FIG. 5 shows example processes for computing metrics which can be used to adjust or set time intervals between keep-alive messages.
FIG. 6 shows a diagrammatic representation of a machine in the example form of a computer system within which a set of instructions, for causing the machine to perform any one or more of the methodologies discussed herein, may be executed.



DETAILED DESCRIPTION
The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to one or an embodiment in the present disclosure can be, but not necessarily are, references to the same embodiment; and, such references mean at least one of the embodiments.
Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.
The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Certain terms that are used to describe the disclosure are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the disclosure. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that same thing can be said in more than one way.
Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification.
Without intent to further limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.
Embodiments of the present disclosure include systems and methods for dynamic Adjustment of keep-alive message intervals in a mobile network.
The invention is applicable to virtually any mobile network architecture. The mobile network may be based on 3G, 4G, LTE, WiMAX, GPRS, 1xRTT or EVDO technologies, for example. The invention can also be implemented as part of a push-type mobile e-mail system, particularly in a consumer e-mail system, in which optimization of network resources is important because of the large number of users.
An object of the present invention is to provide a method, equipment and a computer program product to so as to alleviate the above disadvantages relating to connection break-up in packet-switched mobile radio networks. The object of the invention is achieved by the methods and equipment which are characterized by what is stated in the independent claims. The dependent claims relate to specific embodiments of the invention.
The invention is based on the following idea. An IP connection is established between the mobile terminal and its correspondent node. During periods of inactivity in the IP connection, keep-alive messages are sent at a predetermined schedule. Keep-alive messages can be quite short, such as 10 bytes, but they prevent the network from detecting the connection as inactive, whereby it is not disconnected. The keep-alive schedule is varied. At least one of the parties monitors the lengths of several periods of inactivity at which the mobile radio network disconnects the IP connection. Based on several monitored lengths of periods of inactivity, a maximum interval between keep-alive messages is determined such that the maximum interval meets some predetermined criterion of statistical confidence. In other words, spurious connection break-ups, which are not avoidable by keep-alive messages, are ignored. The interval between keep-alive messages is set to the determined maximum interval.
FIG. 1 shows an exemplary system architecture which is supported by the owner of the present application. This system supports synchronization of e-mail messages and/or calendar items and/or other information between a host system and a mobile terminal.
Reference numeral 100 denotes a host system that is able to send and receive e-mail messages. Reference numeral 102 denotes a mobile terminal, also able to send and receive e-mail messages. The e-mail messages may originate or terminate at external e-mail terminals, one of which is denoted by reference numeral 104. The invention aims at improving cooperation between the host system 100 and mobile terminal 102 such that they can use a single e-mail account as transparently as possible. This means, for example, that the users of the external e-mail terminals 104, when sending or receiving e-mail, do not need to know if the user of the host system 100 actually uses the host system 100 or the mobile terminal 102 to communicate via e-mail. The transparency also means that e-mail manipulation at the mobile terminal 102 has, as far as possible, the same effect as the corresponding e-mail manipulation at the host system 100. For example, e-mail messages read at the mobile terminal 102 should preferably be marked as read at the host system.
Reference numeral 106 denotes a data network, such as an IP (Internet Protocol) network, which may be the common Internet or its closed subnetworks, commonly called intranets or extranets. Reference numeral 108 denotes an e-mail server and its associated database. There may be separate e-mail servers and/or server addresses for incoming and outgoing e-mail. The database stores an e-mail account, addressable by means of an e-mail address, that appears as a mailbox to the owner of the e-mail account. In order to communicate with mobile terminals 102, the data network 106 is connected, via a gateway 112 to an access network 114. The access network comprises a set of base stations 116 to provide wireless coverage over a wireless interface 118 to the mobile terminals 102.
Reference numeral 110 denotes a messaging centre that is largely responsible for providing the above-mentioned transparency between the host system 100 and the mobile terminal 102. The system architecture also comprises a connectivity function 120, whose task is to push e-mail messages to the mobile terminal. In the embodiment shown in FIG. 1, the connectivity function 120 is considered a physically integral but logically distinct element of the messaging centre 110.
The mobile terminal 102 may be a pocket or laptop computer with a radio interface, a smart cellular telephone, or the like. Depending on implementation, the host system 100, if present, may have different roles. In some implementations the host system 100 is optional and may be a conventional office computer that merely acts as the mobile terminal user's principal computer and e-mail terminal. In other implementations the host system may act as a platform for a single user's connectivity function, in addition to being an office computer. In yet other implementations the host system 100 may comprise the connectivity function for several users. Thus it is a server instead of a normal office computer.
We assume here that the access network 114 is able to establish and maintain a IP connection 122 between the messaging centre 110 and the mobile terminal 102.
FIG. 1 shows an embodiment in which the messaging centre 110 is largely responsible for e-mail transport to/from the mobile terminal 102 via the access network 114, while a separate connectivity function 120 is responsible for data security issues. The connectivity function 120 may be physically attached to or co-located with the messaging centre 110, but they are logically separate elements. Indeed, a definite advantage of the separate connectivity function 120 is that it can be detached from the messaging centre, for instance, within the company that owns the host system 100 or the e-mail server 108. For a small number of users, the connectivity function 120 can be installed in each host system 100, or the host system 100 can be interpreted as a separate server configured to support multiple users. It is even possible to implement some or all the above-mentioned options. This means, for example, that there is one or more messaging centers 110 that offer services to several network operators, or they may be a dedicated messaging centre for each network operator (somewhat analogous to short messaging centers). Each messaging centre 110 may have an integral connectivity function 120 to support users who don't wish to install a separate connectivity function in a host system 100. For users who do install a separate connectivity function 120 in their host systems 100, such connectivity functions bypass the connectivity function in the messaging centre 110 and address the messaging centre 110 directly.
A real e-mail system supports a large number of mobile terminals 102 and IP connections 122. In order to keep track of which e-mail account and which IP connection belongs to which mobile terminal, the messaging centre 110 and the connectivity function collectively maintain an association 124, 124′ for each supported mobile terminal. Basically, each association 124, 124′ joins three fields, namely an e-mail address 124A assigned to the mobile terminal or its user, encryption information 124C and a temporary wireless identity 124D of the mobile terminal in the access network. The embodiment shown in FIG. 1 also employs a terminal identifier 124B which may be the same as the e-mail address 124A of the mobile terminal 102, in which case the association 124 actually associates three information items. Alternatively, the terminal identifier 124B may be an identifier arbitrarily assigned to the mobile terminal. In a preferred implementation the terminal identifier 124B is the mobile terminal's equipment identifier or its derivative. The encryption information 124C is preferably related to the mobile terminal's equipment identity and is preferably generated by the mobile terminal itself, so as to ensure that no other terminal besides the one used for creating the encryption information 124C will be able to decrypt incoming encrypted e-mail messages. The temporary wireless identity 124D may be the identifier of the IP connection 122 to the mobile station.
In the above-described system, the messaging centre 110 and connectivity function 120 were arranged to support a fairly large number of users of e-mail and/or calendar data. In order to satisfy the needs of the present invention, virtually any communication server able to maintain an IP connection to the mobile terminal can be used.
FIG. 2 shows a flowchart illustrating an embodiment of the invention. In an optional step 2-0 the network identifier is registered, which means that the method steps should be performed and the resulting parameters maintained separately for each network. In step 2-2 an IP connection is established between the mobile terminal and its correspondent node. The connection establishment can be entirely conventional. Initially, in step 2-4, the mobile terminal and/or its correspondent node sends keep-alive messages when the IP connection is otherwise idle, i.e., when there is no net user data to send. The keep-alive messages are sent according to a predetermined schedule. The schedule may be empty, which means that the mobile terminal may initially send no keep-alive messages at all. In step 2-6 the mobile terminal and/or its correspondent node keeps track of the periods of time after which the network disconnects the IP connection. The period of inactivity after which the network disconnects the IP connection will be called maximum inactivity period. A problem is that the mobile terminal does not know the true value of the maximum inactivity period; the network operator does not publish it. In an embodiment of the invention, the true value of the maximum inactivity period is approached from either direction (upwards and downwards) by altering the schedule for transmitting the keep-alive messages. On the other hand, it is not economically feasible to simply accept the shorted inactivity period before connection break-up as the value of the maximum inactivity period, because connection break-ups may occur for reasons which are not repeatable. In other words, many of the early connection break-ups occur regardless of the keep-alive messages, and attempting to eliminate such spurious break-ups by more frequent keep-alive messages will only result in increased battery drain and/or telecommunication tariffs.
Accordingly, step 2-8 comprises achieving a desired degree of statistical confidence in respect of the detected maximum inactivity period. In order to achieve statistical significance, the mobile terminal applies a confidence measure, such as variance. In a typical but non-restricting implementation, the mobile terminal may regard the connection break-up as regular if it happens after a certain inactivity period with a variance lower than some predetermined value. For example, the connection break-up may be considered regular if the network has discontinued the IP connection a predetermined minimum number x of times after an inactivity period of t, wherein the distribution oft has a variance var(t) which is smaller than some predetermined value y.
The act of achieving a desired degree of statistical confidence preferably comprises subtracting a safety margin Δt from the detected maximum inactivity period. For example, the safety margin may be expressed in minutes, such as 1-2 minutes, or as a percentage, such as 10-20%. If the detected maximum inactivity period is, say, 15 minutes, the mobile terminal may store a value of 13-14 minutes as a maximum safe interval between keep-alive messages. Let us denote this interval value by TINT.
In step 2-10 the mobile terminal and/or its correspondent node set up a schedule for sending keep-alive messages at intervals no higher than TINT in absence of net user traffic. By sending keep-alive messages via an otherwise idle IP connection at intervals no higher than TINT, the network regards the IP connection as active and, under normal operating conditions, does not disconnect it.
The keep-alive messages can be sent by either end of the connection, i.e., by the mobile terminal and/or its correspondent node, such as a server, in the fixed part of the mobile radio network.
Sending the keep-alive messages at intervals no higher than TINT can be accomplished by means of a timer, which may be a physical timer or a logical one, such as a program thread or process. Each time any message is sent (either a real message or a keep-alive message), a timer with a value TINT is triggered. When the timer expires, a keep-alive message is sent, and the timer is re-triggered.
The optimum value for the safety margin safety margin At depends on the costs (battery-wise and tariff-wise) of sending keep-alive messages and reestablishing disconnected IP connections. It may also depend on the behavior of the network, i.e., the regularity by which it breaks up temporarily inactive connections. If the network's behavior is poorly predictable, and break-ups occurs with a certain safety margin, the safety margin should be increased.
In a further optional step 2-12, the maximum safe interval between keep-alive messages, TINT, is stored together with an identifier of the network in which the TINT was determined, whereby it can be quickly taken into use on re-entry to’ the same network. This value can be stored in the mobile terminal. Instead of storing the value in the mobile terminal, or in addition to it, the mobile terminal may send the value to its home network to be stored in a data base which can be inquired by mobile terminals which are about to begin roaming in a foreign network. The value stored by other mobile terminals in the data base in the home network may override any default value otherwise used by the roaming mobile terminal.
Instead of sending the keep-alive messages from the mobile terminal, or in addition to it, the keep-alive messages may be sent from a stationary server connected to the mobile radio network.
FIGS. 3A and 3B illustrate a technique for determining a maximum interval between keep-alive messages by means of a cumulative probability function. The vertical bars in FIG. 3A, collectively denoted by reference numeral 32, show counts of connection break-up versus interval between keep-alive messages. In this example, one break-up was detected at intervals of 5, 7, 8 and 9 minutes. Two break-ups were detected at an interval of 10 minutes, five at 11 minutes, seven at 12 minutes and, finally, three break-ups at an interval of 13 minutes. No idle connection survived for longer than 13 minutes.
Reference numeral 34 in FIG. 3B shows a cumulative probability function which illustrates a cumulative probability for the network breaking up an idle connection versus interval between keep-alive messages, given the monitoring data shown in FIG. 3A. As shown by function 34, all idle connection survived for 4 minutes and none survived for longer than 13 minutes. Reference numeral 35 denotes a line of maximum derivative in the cumulative probability function 34. It is reasonable to assume that the line of maximum derivative coincides with the maximum period of inactivity tolerated by the network. Or, if the cumulative probability function 34 is drawn as discrete steps (jumps), the position of line 35 can be determined by the highest jump in line 34.
This maximum period is denoted by reference numeral 36, and its value is approximately 11.5 minutes in this example. A value of 10 minutes for TINT is appropriate, as indicated by dashed line 37. Reference numeral 38 denotes a safety margin between the lines 36 and 37.
Although this example shows that as much as 30% of connections were disconnected after 10 minutes of inactivity, it is reasonable to assume that these disconnections were caused by spurious effects rather than the network's policy to break up idle connections.
FIG. 4 shows a flow chart illustrating an example process for dynamically adjusting keep-alive message intervals in a mobile network.
In process 402, a rate with which the client-slide request are made from the mobile terminal is detected. In process 404, time intervals between the keep-alive messages sent to the mobile terminal are dynamically adjusted based on the rate with which the client-side requests are made. Dynamical adjusting of the time interval can include increasing the intervals by multiplying a current time interval with a constant or adding a constant to the current time interval.
In process 406, keep-alive messages are sent to the mobile terminal in an absence of network traffic through the IP connection between the mobile terminal and the network node. The keep-alive messages can be sent from the network node to the mobile terminal or from a server to the mobile terminal. In addition, a rate of change in the source data queried by client-side requests can be monitored and used in setting or adjusting the time intervals. For example, the time intervals can be adjusted to be proportional to the rate at which the content is changing. In some instances, prior to adjusting the time intervals based on the rate of change of the content, an initial time interval can be set, for example, based on a polling rate of a URL (e.g., the link, website, or other types of content location) loaded on the mobile device.
In process 408, the time intervals between the keep-alive messages are further optimized based on a cost to send the keep-alive messages in the network. The cost can include the cost to re-establish the IP connection in the event of disconnection and/or battery life of the mobile terminal. In process 410, the time interval to the mobile terminal is transmitted with at least some of the keep-alive messages or in a cache update message. In some instances, the keep alive messages can be sent using, one or more of, SMS channel, a signaling channel, and a control channel when radio of the mobile terminal is dormant or otherwise unavailable.
In one embodiment, a maximum interval between keep-alive messages sent between the mobile terminal and the network node to prevent disconnection of the IP connection can be determined based on the periods of inactivity monitored between the mobile terminal and the network node or with another server.
FIG. 5 shows example processes for computing metrics which can be used to adjust or set time intervals between keep-alive messages.
For example, in process 502, a rate of change in source data which is queried by the client-side requests is monitored. In process 504, an average communication rate and/or a deviation rate of the average communication rate between the mobile terminal and the network node is monitored. In process 506, a polling rate of a URL loaded on the mobile device utilizing the IP connection is detected. In process 508, the time interval between keep-alive messages sent to the mobile terminal can be adjusted or set based on any of the metrics determined in processes 502, 504, 506, or any combination thereof.
FIG. 6 shows a diagrammatic representation of a machine in the example form of a computer system within which a set of instructions, for causing the machine to perform any one or more of the methodologies discussed herein, may be executed.
In the example of FIG. 6 the computer system 600 includes a processor, memory, non-volatile memory, and an interface device. Various common components (e.g., cache memory) are omitted for illustrative simplicity. The computer system 600 is intended to illustrate a hardware device on which any of the components depicted in the example of FIG. 1 (and any other components described in this specification) can be implemented. The computer system 600 can be of any applicable known or convenient type. The components of the computer system 600 can be coupled together via a bus or through some other known or convenient device.
The processor may be, for example, a conventional microprocessor such as an Intel Pentium microprocessor or Motorola power PC microprocessor. One of skill in the relevant art will recognize that the terms “machine-readable (storage) medium” or “computer-readable (storage) medium” include any type of device that is accessible by the processor.
The memory is coupled to the processor by, for example, a bus. The memory can include, by way of example but not limitation, random access memory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM). The memory can be local, remote, or distributed.
The bus also couples the processor to the non-volatile memory and drive unit. The non-volatile memory is often a magnetic floppy or hard disk, a magnetic-optical disk, an optical disk, a read-only memory (ROM), such as a CD-ROM, EPROM, or EEPROM, a magnetic or optical card, or another form of storage for large amounts of data. Some of this data is often written, by a direct memory access process, into memory during execution of software in the computer 900. The non-volatile storage can be local, remote, or distributed. The non-volatile memory is optional because systems can be created with all applicable data available in memory. A typical computer system will usually include at least a processor, memory, and a device (e.g., a bus) coupling the memory to the processor.
Software is typically stored in the non-volatile memory and/or the drive unit. Indeed, for large programs, it may not even be possible to store the entire program in the memory. Nevertheless, it should be understood that for software to run, if necessary, it is moved to a computer readable location appropriate for processing, and for illustrative purposes, that location is referred to as the memory in this paper. Even when software is moved to the memory for execution, the processor will typically make use of hardware registers to store values associated with the software, and local cache that, ideally, serves to speed up execution. As used herein, a software program is assumed to be stored at any known or convenient location (from non-volatile storage to hardware registers) when the software program is referred to as “implemented in a computer-readable medium.” A processor is considered to be “configured to execute a program” when at least one value associated with the program is stored in a register readable by the processor.
The bus also couples the processor to the network interface device. The interface can include one or more of a modem or network interface. It will be appreciated that a modem or network interface can be considered to be part of the computer system 1900. The interface can include an analog modem, isdn modem, cable modem, token ring interface, satellite transmission interface (e.g. “direct PC”), or other interfaces for coupling a computer system to other computer systems. The interface can include one or more input and/or output devices. The I/O devices can include, by way of example but not limitation, a keyboard, a mouse or other pointing device, disk drives, printers, a scanner, and other input and/or output devices, including a display device. The display device can include, by way of example but not limitation, a cathode ray tube (CRT), liquid crystal display (LCD), or some other applicable known or convenient display device. For simplicity, it is assumed that controllers of any devices not depicted in the example of FIG. 6 reside in the interface.
In operation, the computer system 600 can be controlled by operating system software that includes a file management system, such as a disk operating system. One example of operating system software with associated file management system software is the family of operating systems known as Windows® from Microsoft Corporation of Redmond, Wash., and their associated file management systems. Another example of operating system software with its associated file management system software is the Linux operating system and its associated file management system. The file management system is typically stored in the non-volatile memory and/or drive unit and causes the processor to execute the various acts required by the operating system to input and output data and to store data in the memory, including storing files on the non-volatile memory and/or drive unit.
Some portions of the detailed description may be presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the methods of some embodiments. The required structure for a variety of these systems will appear from the description below. In addition, the techniques are not described with reference to any particular programming language, and various embodiments may thus be implemented using a variety of programming languages.
In alternative embodiments, the machine operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine may operate in the capacity of a server or a client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment.
The machine may be a server computer, a client computer, a personal computer (PC), a tablet PC, a laptop computer, a set-top box (STB), a personal digital assistant (PDA), a cellular telephone, an iPhone, an iPad, any smartphone or tablet device, a Blackberry, a processor, a telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine.
While the machine-readable medium or machine-readable storage medium is shown in an exemplary embodiment to be a single medium, the term “machine-readable medium” and “machine-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable medium” and “machine-readable storage medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the presently disclosed technique and innovation.
In general, the routines executed to implement the embodiments of the disclosure, may be implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions referred to as “computer programs.” The computer programs typically comprise one or more instructions set at various times in various memory and storage devices in a computer, and that, when read and executed by one or more processing units or processors in a computer, cause the computer to perform operations to execute elements involving the various aspects of the disclosure.
Moreover, while embodiments have been described in the context of fully functioning computers and computer systems, those skilled in the art will appreciate that the various embodiments are capable of being distributed as a program product in a variety of forms, and that the disclosure applies equally regardless of the particular type of machine or computer-readable media used to actually effect the distribution.
Further examples of machine-readable storage media, machine-readable media, or computer-readable (storage) media include but are not limited to recordable type media such as volatile and non-volatile memory devices, floppy and other removable disks, hard disk drives, optical disks (e.g., Compact Disk Read-Only Memory (CD ROMS), Digital Versatile Disks, (DVDs), etc.), among others, and transmission type media such as digital and analog communication links.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” As used herein, the terms “connected,” “coupled,” or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling of connection between the elements can be physical, logical, or a combination thereof. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or,” in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.
The above detailed description of embodiments of the disclosure is not intended to be exhaustive or to limit the teachings to the precise form disclosed above. While specific embodiments of, and examples for, the disclosure are described above for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative or subcombinations. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times. Further any specific numbers noted herein are only examples: alternative implementations may employ differing values or ranges.
The teachings of the disclosure provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.
Any patents and applications and other references noted above, including any that may be listed in accompanying filing papers, are incorporated herein by reference. Aspects of the disclosure can be modified, if necessary, to employ the systems, functions, and concepts of the various references described above to provide yet further embodiments of the disclosure.
These and other changes can be made to the disclosure in light of the above Detailed Description. While the above description describes certain embodiments of the disclosure, and describes the best mode contemplated, no matter how detailed the above appears in text, the teachings can be practiced in many ways. Details of the system may vary considerably in its implementation details, while still being encompassed by the subject matter disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the disclosure should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the disclosure with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the disclosure to the specific embodiments disclosed in the specification, unless the above Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the disclosure encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the disclosure under the claims.
While certain aspects of the disclosure are presented below in certain claim forms, the inventors contemplate the various aspects of the disclosure in any number of claim forms. For example, while only one aspect of the disclosure is recited as a means-plus-function claim under 35 U.S.C. §112, ¶6, other aspects may likewise be embodied as a means-plus-function claim, or in other forms, such as being embodied in a computer-readable medium. (Any claims intended to be treated under 35 U.S.C. §112, ¶6 will begin with the words “means for”.) Accordingly, the applicant reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the disclosure.

## Claims

1. A method of maintaining communication between a mobile terminal and a network node over a network, the method comprising:
detecting a rate with which requests are made to or from the mobile terminal;
dynamically adjusting time intervals between the keep-alive messages sent to or from the mobile terminal based on the rate with which the requests are made;
sending, keep-alive messages to or from the mobile terminal in an absence of network traffic between the mobile terminal and the network node;
monitoring the lengths of several periods of communication inactivity between the mobile terminal and the network node;
determining a maximum interval between keep-alive messages based on the several monitored lengths of periods of inactivity such that the maximum interval meets a criterion of statistical confidence; and
setting at least one interval between keep-alive messages to the maximum determined interval.

2. The method of claim 1 wherein detecting the rate with which requests are made includes at least one of:
detecting a rate with which client-side requests are made from the mobile terminal; and
detecting a rate with which server-side requests are made to the mobile terminal.

3. The method of claim 1 wherein the network node comprises a node in a mobile radio network.

4. The method of claim 1, wherein maintaining communication between the mobile terminal and the network node includes routing Internet protocol (IP) packets between the mobile terminal and the network node.

5. The method of claim 4, wherein maintaining communication between the mobile terminal and the network node includes maintaining a transmission control protocol (TCP) connection between the mobile terminal and the network node.

6. The method of claim 1, comprising, in response to detecting a period of communication inactivity, sending keep-alive messages at predetermined and variable intervals.

7. The method of claim 6, wherein the keep-alive messages are sent from the mobile terminal.

8. The method of claim 6, wherein the keep-alive messages are sent from the network node.

9. The method of claim 1, comprising storing the maximum determined interval at the mobile terminal.

10. The method of claim 9, comprising storing the maximum determined interval in association with an identifier of the network.

11. The method of claim 9, wherein the identifier of the network comprises an identifier of a mobile radio network.

12. The method of claim 1, comprising sending the maximum determined interval in association with the identifier of the network to a home network of the mobile terminal for storage and future inquiry.

13. The method of claim 1, wherein meeting a predetermined criterion of statistical confidence includes subtracting a safety margin from the detected maximum inactivity period.

14. The method of claim 13, wherein the safety margin is expressed as a duration of time.

15. The method of claim 13, wherein the safety margin is expressed as a percentage.

16. The method of claim 13, wherein the safety margin is proportional to a predictability of behavior of the mobile radio network.

17. The method of claim 13, wherein the safety margin corresponds to a cost associated with the mobile terminal.

18. The method of claim 17, wherein the cost corresponds to battery life of the mobile terminal.

19. The method of claim 17, wherein the cost corresponds to a tariff for sending keep-alive messages from the mobile terminal.

20. A method for maintaining communication between a mobile terminal and a network node over a network, the method comprising:
observe periods of inactivity between messages that are communicated between a mobile terminal and a network node via a network and observe whether a connection between the mobile terminal and the network node was dropped;
determine, based on the observed information, a maximum delay between messages that does not result in the connection being dropped;
in response to detecting an absence of observed traffic for a period greater than or equal to the determined maximum delay, sending a keep-alive message to prevent the connection from being dropped,
wherein determining a maximum delay that does not result in a dropped connection includes determining a maximum delay that meets a predetermined criterion of statistical confidence that the connection will not be dropped.

21. The method of claim 20, comprising observing whether a sent keep-alive message failed to prevent the connection from being dropped, and in response to a determination that the connection was dropped, reducing the maximum delay until a sent keep-alive message succeeds in preventing the connection from being dropped.

22. The method of claim 21, comprising observing whether a sent keep-alive message failed to prevent the connection from being dropped, and in response to a determination that the connection was not dropped, increasing the maximum delay until a sent keep-alive message fails to prevent the connection from being dropped and then reducing the maximum delay until a sent keep-alive message succeeds in preventing the connection from being dropped.

23. A method for maintaining communication between a mobile terminal and a network node over a network, the method comprising:
defining a maximum allowed period of inactivity between messages that are communicated between a mobile terminal and a network node via a network;
in response to detecting an absence of observed traffic for a period greater than or equal to the determined maximum delay, sending a keep-alive message to prevent a connection from being dropped;
adjusting the maximum allowed period of inactivity based on an observation of whether the keep-alive message succeeded or failed to prevent the connection from being dropped,
wherein adjusting the maximum allowed period of inactivity based on an observation of whether the keep-alive message succeeded or failed to prevent the connection from being dropped includes adjusting the maximum allowed period based on a predetermined criterion of statistical confidence that the connection will not be dropped.

24. The method of claim 23, wherein adjusting the maximum allowed period of inactivity includes reducing the maximum allowed period in response to determining that the keep-alive message failed to prevent the connection from being dropped.

25. The method of claim 23, wherein adjusting the maximum allowed period of inactivity includes increasing the maximum allowed period in response to determining that the keep-alive message succeeded in preventing the connection from being dropped.