GB2472537A

GB2472537A - Selecting a network connection for data communication

Info

Publication number: GB2472537A
Application number: GB1019136A
Authority: GB
Inventors: Caleb Carroll; Nick Barker
Original assignee: Nomad Spectrum Ltd
Current assignee: Nomad Spectrum Ltd
Priority date: 2008-10-15
Filing date: 2008-10-15
Publication date: 2011-02-09
Anticipated expiration: 2028-10-15
Also published as: GB201019136D0; GB2472537B

Abstract

A method of selecting, from connections to first and second devices, a connection to be used for data communication, the method comprising: receiving first specific data indicating an operating characteristic of said first device, receiving second specific data indicating an operating characteristic of said second device, processing said first specific data to generate first data in a generic form, processing said second specific data to generate second data in said generic form, and selecting one of said first and second devices based upon the first and second data in generic form. An embodiment describes a connection control unit (CCU) 2 on a train 1 which connects to base stations A, B en route to provide network connectivity to passengers using mobile computing devices. The CCU maintains a database of the operating status of base stations. Faulty base stations which do not provide Internet connectivity are not selected. The CCU also selects a base station to connect to based on data in generic form allowing different access technologies to be compared. A predicted future availability of a base station is also used to make a selection.

Description

NETWORK COMMUNICATION

The present invention relates to a methods for network communication, and more particularly to methods for selecting a connection which should be used for data communication.

Computers are commonplace in modern society. Many computers are now connected to a worldwide network known as the Internet which allows computers to exchange data with one another. In particular, users can use computing devices to access the worldwide web which provides a vast quantity of information which can be downloaded to a user's computer.

With the increased portability of computers, and the increasing sophistication of mobile devices such as mobile telephones and palmtop computers, there is a growing demand for Internet connectivity while on the move. One response to this demand is based upon devices having built-in long-range telecommunications capabilities, such as devices which make use of mobile telephone networks. While such solutions can be effective, they typically suffer from problems of low bandwidth and incomplete geographic coverage. The problem of low bandwidth is a particular issue when a user wishes to access content comprising a large quantity of data (for example video content). The problem of incomplete geographic coverage is particularly problematic when a user is moving, given that data communication may be interrupted when a signal is lost (for example when a train enters a tunnel).

An alternative method of providing Internet connectivity to mobile devices is based upon the use of access points. Such access points may be provided, for example, in public buildings such as libraries and cafes, and can be accessed by mobile computing devices which are located within a predetermined range of the access point. One common technology used to allow mobile computing devices to connect to such access points is specified by IEEE standard 802.11, and is commonly referred to as WiFi. The use of access points in this way is advantageous in that it allows higher bandwidth connections to be established.

The limitations of systems based upon the connection of mobile devices to mobile telephone networks has led to the proposal that public transport vehicles, such as trains or buses, may be beneficially provided with wireless access points, such that mobile computing devices used by passengers travelling in the vehicle can be provided with Internet connectivity by establishing a connection with the access point.

The provision of Internet connectivity to a vehicle can be specially tailored to cope with the routes travelled by the vehicle, such as through tunnels and cuttings. More power is available on the vehicle than on a mobile computing device, meaning that systems fitted to vehicles can generally support larger, higher gain antennas than those that are generally installed in portable user devices such as mobile telephones.

Furthermore, greater computational power can be used in signal processing in a device associated with a vehicle given that there is room for larger, more powerful processing devices.

Different types of communication links can be used to provide data communication to a vehicle, the communication link being selected to be appropriate to the locations through which the vehicle travels. Furthermore, if a vehicle's route is known, the communication links can be managed to provide a higher level of service with greater bandwidth, lower latencies, and fewer losses of connection than if the communications were made directly to individual users using a mobile telephone network. It follows that the provision of a wireless access point on board a vehicle has considerable advantages. Such provision does, however, bring challenges.

It is known to place a number of base stations along a known route, for example alongside a train track. It is further known to connect each base station to a home server via appropriate connections, for example land-based cables. The home server may be connected to the Internet via standard means, for example via cable or via a digital subscriber line (DSL). A communication control unit is placed on the vehicle.

As the vehicle travels along the route, the communication control unit wirelessly connects to a particular base station. In this way, the communication control unit can connect to the Internet through the home server, routed via the base stations and any intermediate devices in the network. The communication control unit is adapted to distribute the Internet connection to devices within the vehicle, allowing users to connect to the Internet whilst onboard the vehicle.

Challenges exist however in selecting which of a plurality of wireless connections to respective base stations the communication control unit should use at a particular time so as to use the best possible communication link. Each base station may allow connection using a particular type of connection technology. For example, one base station may use a 3G cellular network, while another may use IEEE standard 802.16 (WiMax). Each different connection technology may use a different hardware device on board the vehicle, and each such hardware device may use a different metric to indicate signal strength, signal quality or usability of the wireless connection. These fundamental technical differences between the connection technologies used to connect to different base stations make comparisons amongst the plurality of connections to different base stations difficult, if not impossible to make.

It is an object of some embodiments of the present invention to obviate or mitigate at least some of the problems outlined above.

According to a first aspect of the present invention, there is provided a method of selecting, from connections to first and second devices, a connection to be used for data communication, the method comprises: receiving first specific data indicating an operating characteristic of said first device; receiving second specific data indicating an operating characteristic of said second device; processing said first specific data to generate first data in a generic form; processing said second specific data to generate second data in said generic form and selecting one of said first and second devices based upon said first data in said generic form and said second data in said generic form.

Therefore, while in known systems the variety of connection technologies and associated signal strength indicators used by differing devices has meant that it has only been possible to directly compare identical devices in determining which device provides a more robust signal, the first aspect of the invention uses generic data to allow more general comparisons to be made. Thus, while base stations may be provided by many manufactures and employ varying technologies, the first aspect of the invention allows signals received from different base stations to be compared even where those base stations utilize differing connection technologies or originate from different vendors.

Data relating to the first and second devices may be received and processed asynchronously, such that said processing is based upon the most recent data relating to a particular device.

The first data in said generic form may comprise data indicating a predicted future operating characteristic of the first device. The second data in said generic form may comprise data indicating a predicted future operating characteristic of said second device, For example, the first data in said generic form may indicate a confidence that the first device will be available for connection for a particular time period. The second data in said generic form may similarly indicate a confidence that the second device will be available for connection for a particular time period. Where the first data in said generic form indicates a higher confidence than is indicated by said second data in said generic form, a connection to said first device may be preferred, and vice versa.

Processing the first specific data to generate the first data in said generic form may comprise processing the first specific data with respect to at least one threshold, to generate said data indicating said predicted future operating characteristic of said first device.

Additionally or alternatively, processing the first specific data to generate said first data in said generic form may comprise processing a plurality of first specific data values indicative of said operating characteristic of said first device at respective times to determine a rate of change of said first specific data values. Data indicating said predicted future operating characteristic of said first device may then be based upon said rate of change. For example, data indicating that a quality of connection is improving may be used to generate a particular predicted future operating characteristic while data indicating that a quality of a connection is deteriorating may be used to generate a different predicted future operating characteristic.

A determined rate of change may be processed to determine a time for which connection to said first device is likely to be possible. Such processing may comprise reading data representing a series of stored first specific data values, identifying part of said series using a determined rate of change and determining said time for which connection to said first device is likely to be possible based upon a position of said part of said series relative to said series.

Additionally or alternatively, the method may further comprise processing at least some of said plurality of first specific data values to determine a first rate of change of said first specific data values, and processing at least one further first specific data value to determine an updated rate of change of said first specific data values. It may then be determined whether said updated rate of change is within a predetermined range of values defined by said first rate of change, and said data indicating said predicted future operating characteristic of said first device may be based upon said determination.

Generating said data indicating said predicted future operating characteristic may comprise generating a value indicating a relatively high confidence in future availability if said updated rate of change is within said predetermined range of values defined by said first rate of change, and generating a value indicating a relatively low confidence in future availability if said updated rate of change is not within said predetermined range of values. This is because first specific data values which are obtained over a relatively short period of time should follow a straight line, meaning that a constant rate of change indicates that a device is behaving as expected, and unexpected changes in the rate of change are considered to be due to an unexpected event (e.g. noise or obstruction of a signal path).

The first specific data may indicate a parameter of a connection to said first device.

For example, the first specific data may indicate a signal strength or signal quality associated with a connection to said first device. The first specific data may be in a form determined by operating parameters of said first device. That is, the first specific data may be in a form determined by, for example, a communications protocol used to connect to the first device.

The first specific data may indicate a current ability of the first device to receive and/or transmit data. The first specific data may indicate whether said first device has participated in a data transaction in a predetermined time period. Such data may be obtained by use of an echo request data packet -a process sometimes known as "pinging".

The first specific data may indicate a plurality of parameters associated with the first device, For example the first specific data may comprise data indicating signal strength and/or signal quality and data indicating a current ability of the first device to receive and/or transmit data.

The preceding description has been concerned with the first specific data and the first data in the generic form. It will be appreciated that equivalent operations can be carried out to generate the second data in said generic form based upon said second specific data. Such operations can be carried out in addition to or instead of operations on the first specific data of the type described above.

The first data in said first generic form may comprise data indicating a current operating characteristic of the first device and a predicted future operating characteristic of the first device. The second data in said generic form may comprise data indicating a current operating characteristic of the second device and data indicating a predicted future operating characteristic of the second device. Selecting one of the first and second devices may then comprise comparing said data indicating the predicted future operating characteristic of said first device with said data indicating the predicted future operating characteristic of said second device. If said data indicating the predicted future operating characteristic of said first device and said data indicating the predicted future operating characteristic of said second device meet a predetermined criterion (e.g. equality or near equality), selecting one of said first and second devices may comprise comparing said data indicating the current operating characteristic of said first device with said data indicating the current operating characteristic of said second device.

If said data indicating the current operating characteristic of said first device and said data indicating the current operating characteristic of said second device meet a predetermined criterion (e.g. equality or near equality), one of said first and second devices may be selected by comparing data indicating a bandwidth of said first device with data indicating a bandwidth of said second device.

The method may be carried out by a client device wishing to select one of a plurality of wireless connections. That is a client device may autonomously establish connections with a plurality of devices and the method may select one of these connections for use in transmitting and/or receiving data. The client device may be located on board a vehicle (such as a train), and the processing described above can then be carried out to allow the client device to select a connection as the vehicle moves. The client device may take any convenient form, and may be a communication control unit.

It is important to properly manage failures in a computer network. It is known that a base station providing wireless connectivity may lose its connection to the Internet but still be able to properly provide wireless connections. This is problematic in that mobile devices may connect to the base station expecting to realise a connection with the Internet, while such a connection will, in fact, be impossible to achieve given the malfunction of the base station or the malfunction of come other component in the path between the base station and the Internet. Traffic sent to a base station wirelessly in this way will be lost and delays will be incurred.

It is known to overcome the problem set out above by providing a system which connects to the base station over the Internet, and which periodically determines whether the base station is properly connected to the Internet. In the event that it is determined that the base station is not properly connected to the Internet, the base station may be shut down. While such a system overcomes the problems set out above to an extent, it is not always possible to achieve if connectivity has been lost, and furthermore requires that the base station provides an appropriate interface to allow such processing to be carried out. Given that base stations are typically provided by a variety of different manufacturers this is not always the case.

Another approach which is known to address the problems set out above involves a base station checking its own connectivity to the Internet and shutting down its wireless interface if a problem is detected. While such an approach again overcomes the problems set out above to an extent, it is disadvantageous in that it requires that functionality is provided at each base station, something that is difficult to achieve given that base stations are provided by a variety of manufacturers.

It is an object of a second aspect of the invention to obviate or mitigate at least some of the problems set out in the immediately preceding paragraphs.

According to a second aspect of the invention, there is provided a method of providing data to a plurality of devices indicating an operating status of a plurality of network devices. The method comprises determining the operating status of the network devices and transmitting data to the plurality of devices indicating said operating status of at least some of said network devices. The transmitted data is usable by the plurality of devices to determine whether a connection should be established with a particular one of said plurality of network devices.

In this way, a particular device is provided with information indicating the operating status of each of a plurality of devices, and this information can be effectively used to ensure that a connection is established with a device having a particular operating status.

The method may further comprise periodically determining the operating status of said network devices and if the operating status of one of said network devices has changed, transmitting update data to the plurality of devices.

Data identifying said plurality of network devices may be stored together with data indicating the operating status of each of said plurality of network devices.

The transmitted data may comprise data indicating inoperable network devices.

Said determining and said transmitting may be carried out by a device which is in communication with each of said plurality of network devices, but separate from each of said plurality of network devices. The operating characteristic may indicate whether each network device currently provides a connection to a predetermined network such as the Internet. For example, in many cases a network device receives data using a first interface, and provides a connection allowing the received data to be passed to another network. The operating characteristic may indicate whether said connection to the other network is functional, and said data can be used by a device to determine whether a connection to a particular network device using the first interface should be established.

According to a third aspect of the invention, there is provided a method of determining whether a connection should be established with a selected one of a plurality of network devices, the method comprising receiving data indicating the operating status of the selected network device and determining whether a connection should be established with the selected network device based upon the received data.

The method may further comprise storing data identifying said plurality of network devices, and storing data indicating the operating status of each of said plurality of network devices. The data may be received from a device connected to but different from the selected network device.

It will be appreciated that aspects of the present invention can be implemented in any convenient way including by way of suitable hardware and/or software. For example, a device arranged to implement the invention may be created using appropriate hardware components. Alternatively, a programmable device may be programmed to implement embodiments of the invention. The invention therefore also provides suitable computer programs for implementing aspects of the invention. Such computer programs can be carried on suitable carrier media including tangible carrier media (e.g. hard disks, CD ROMs and so on) and intangible carrier media such as communications signals.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a network of computing devices; Figure 2 is a graph showing how signal strength varies over time; Figures 3 and 4 are graphs of signal strength indication measurements together with associated tangents; Figure 5 is a schematic illustration of a database; and Figure 6 is a flow chart showing processing carried out using the database of Figure 5.

Figure 1 shows a network which is used to provide data communication to a train 1.

The train I is provided with a communications control unit (CCU) 2 which is arranged to connect to base stations A, B. The base station A is connected to a bearer network 3, while the base station B is connected to a bearer network 4. The CCU 2 and the base stations A, B are provided with wireless communications interfaces to allow wireless communication between the CCU 2 and the base stations A, B, thereby allowing the CCU 2 to connect to the bearer networks 3, 4. The bearer network 3 can suitably be a 3G cellular network, while the bearer network 4 can suitably be an IEEE 802.16 (WiMax) network. It will however be appreciated that the bearer networks 3, 4 can take any suitable form, and can be networks of the same type (e.g. both networks can be 3G cellular networks) or of different types. Each bearer network 3, 4 is connected to the Internet 5.

A Home Agent 6 is also connected to the Internet 5. A virtual private network (VPN) is established between the CCU 2 and the Home Agent 6, so as to allow data packets to be securely exchanged between the CCU 2 and the Home Agent 6.

A host computer 7 is also connected to the Internet 5. The connection of the CCU 2 to the Home Agent 6 through a VPN means that from the point of view of computers connected to the Internet 5 (for example the host computer 7), all traffic is seen to emanate from the Home Agent 6, such that computers connected to the Internet 5 need not be concerned with details of the communication between the Home Agent 6 and CCU 2. Instead, computers connected to the Internet 5 can simply deliver data packets to the Home Agent 6 which can then process received data packets to ensure that such data packets are properly forwarded to the CCU 2 via the appropriate bearer network 3, 4 and base station A, B. The CCU 2 is arranged to provide wireless network connectivity on board the train 1.

In this way passengers travelling on the train 1 can use mobile computing devices (such as laptop and patmtop computers, for example) to connect to the CCU 2 and thereby obtain access to the Internet 5. The connection between the mobile computing devices and the CCU 2 can take any suitable form, but may be in accordance with IEEE standard 802.11 (WiFi).

Each base station A, B has a finite area within which the CCU 2 can connect to that base station, and it is preferred that the finite areas overlap, such that there are areas through which the train travels in which the CCU 2 is able to connect to more than one of the base stations A, B so as to establish a connection with more than one of the bearer networks 3, 4.

As the train 1 travels, the signal strength received at the train from each base station A, B changes. For example, as the train 1 moves away from the base station A in the direction of an arrow X the strength of the signal received from the base station A will typically decrease, while as the train 1 moves towards the base station B, the strength of the signal received from the base station B will typically increase. At some point during movement of the train 1, the change in signal strength from each base station A, B will mean that the CCU 2 should switch base stations. For example, where the CCU 2 is connected to the bearer network 3 via the base station A, at some point during the travel of the train I towards the base station B, the CCU 2 should use a connection to the bearer network 4 via the base station B for data communication given that it will be possible to establish a better connection to the base station B. As each bearer network 3, 4 may use a different connection technology, the CCU 2 may comprise a variety of different connection devices allowing connection using the different connection technologies. In the described embodiment the CCU 2 comprises a 3G connection device 10 and a WiMax connection device 11. It will be appreciated that the CCU 2 may comprise other connection devices in order to allow connection to bearer networks employing other connection technologies. !t will further be appreciated that the functionality of connection devices 10 and 11 may be provided by a single device.

The CCU 2 is arranged to determine base stations with which a connection can be established, and to determine a base station to which connection should most preferably be used for data communication. Given that the CCU 2 is arranged to communicate with different base stations using different connection technologies, the CCU 2 is arranged to generate generic data which allows the desirability of connection to different base stations to be determined, bearing in mind that those different base stations may use different connection technologies.

The current availability of a particular base station is determined by ascertaining whether a particular base station is able to successfully pass data traffic from the CCU 2 to a remote computer, for example a computer connected to the Internet 5.

The current availability of a base station A, B may be defined as whether any data traffic has successfully been passed via base station A, B in a preceding predetermined timeframe. For example, it may be determined whether data traffic was successfully sent to and forwarded from a base station A, B in the last second.

The current availability of a base station may be determined by periodically sending an echo request data packet (commonly known as pinging) to the Home Agent 6 (or to another computer connected to the Internet 5) via the base station whose current availability is being determined, and awaiting a response from the Home Agent 6. If a response is received it is determined that the base station of interest is currently available to provide data connectivity, while if no response is received it is determined that the base station of interest is not currently available to provide connectivity.

In some cases, where the CCU 2 is currently connected to a particular base station and where data traffic is being sent via that base station, it may not be necessary to send an echo request data packet to determine current availability. Instead, it may suffice to determine whether the data packets already being sent are successfully reaching the Home Agent 6, for example by monitoring acknowledgement data packets received at the CCU 2.

In some embodiments a base station is given a binary current availability score (either 1' for currently available, or 0' for not currently available) based on receiving a response to a data packet sent via the base station, which data packet can either be an echo request data packet, or a data packet including data to be transmitted from the CCU 2 to the Home Agent 6. It can be seen that the nature of the data indicating the current availability of a base station is independent of the type of base station or communications protocols used, but is instead generic.

In addition to determining the current availability of a particular base station, in some embodiments the CCU 2 is also arranged to generate data indicating predicted future availability of a particular base station. It will be appreciated that such predictions are particularly useful in the selection of a base station with which a connection should be established, given that such a selection should desirably take into account the likely future availability of a connection via a particular base station.

In general terms, the CCU 2 is arranged to determine a strength of a signal received from a particular base station. For example, in some cases the CCU 2 may generate a received signal strength indication (RSSI) for a particular base station based upon the strength of signal received from that base station. In other cases, a signal strength may be obtained by reading an appropriate signal strength value. It will be appreciated that differing connection technologies used for connection to different base stations may provide different signal strength indicators, and that these signal strength indicators are not readily susceptible of direct comparison. Received signal indicators are therefore processed to generate data in a generic form which is more readily susceptible of comparison between different connection technologies and which provides an effective predictor of future availability. Such a predictor of future availability may take the form of a measure of confidence in the ability of a base station to continue to be able to forward data traffic in a predetermined timeframe. In alternative embodiments, the predicted availability may be a period of time for which it is believed that a base station will continue to be able to forward data packets from the CCU 2.

Figure 2 is a graph showing how a signal strength indicator (for example a RSSI) varies with time as the CCU passes through an area which is served by a particular base station.

Four signal strength threshold value are shown on the graph: sig mm and sig max being outer thresholds, and sig hi and sig lo being inner thresholds. If the RSSI of a signal received from a particular base station is between the inner thresholds sig lo and sig hi, the CCU 2 will give that base station a predicted availability score of 2' indicating that there is a high confidence that the base station will be able to accept and forward data packets in the next tirneframe If however the RSSI of a signal received from a particular base station is between the inner and outer thresholds, that is between sig hi and sig max or between sig Ic and sig mm, the CCU 2 assigns that base station a predicted availability of 1 indicating a lower confidence that the base station will be able to accept and forward data packets in the next timeframe. A RSSI between sig hi and sig max results in a lower confidence value being generated because the value sig hi is selected such that higher values are indicative of an anomalous reading, which should be considered to be somewhat suspect meaning that generation of a lower confidence value is appropriate.

If the RSSI of a signal is outside the outer threshold values, (i.e. above sig max or below sig mm) the CCU 2 assigns that base station a predicted availability of 0' indicating a low confidence that the base station will be able to accept and forward data packets in the next timeframe. The value sig max is selected to be the highest value that would ordinarily be expected in normal use. A value above sig max is therefore considered to be indicative of an error condition, and therefore results in generation of a low confidence value.

While the approach described above provides useful predictions of future availability, other factors can also be taken into account. For example, if a plurality of signal strength readings are obtained, a gradient can be derived from the plurality of values.

A positive gradient indicates improving signal strength meaning that it is more likely that a particular base station will have future availability. This is because signal strength provided by a base station over time, as the CCU 2 is moved, generally follows a curve of the type shown in Figure 2. Similarly, a negative gradient indicates that signal strength is diminishing making it is less likely that the particular base station will have future availability. Additionally, where the gradient has a negative value, it will be appreciated that a steeper gradient indicates that future availability is less likely than a shallower gradient.

Figure 3 shows a typical curve 15 of signal strength values over time. Typical growth and decline curves may be calculated for each base station using known information such as the output power of that base station and the connection technology used by that base station.

By obtaining signal strength values, and determining a gradient based upon those values in the manner described above, a position on the typical curve can be identified, so as to provide an indication of the extent of likely future availability. More specifically, having identified a particular point on the curve, its value on the time-axis of the graph can be determined, and a prediction can then be made of a time for which the base station will have availability, based upon the point on the time-axis at which the typical curve crosses a predetermined threshold.

Referring again to Figure 3, an example of how gradients can be used to predict future availability can be seen. More specifically, Figure 3 shows four tangents, a, b, c and d to the typical growth and decline curve 15. As the signal received from a base station A, B moves through a, b, c and d the predicted availability score of that signal is decreased. This can be achieved either by locating the relevant position on the typical growth and decline curve 15 and processing the position in the manner described above, or alternatively by determining gradients in the manner described above, and generating data indicating a greater probability of future availability based upon positive gradients than negative gradients (i.e. a gradient indicated by the tangent a results in a higher probability than a gradient indicated by the tangent c or the tangent d) and also by generating data indicating a higher prábability of future availability based upon shallow negative gradients than steep negative gradients (i.e. a gradient indicated by the tangent c results in a higher predicted availability than a gradient indicated by the tangent d).

Further, a maximum negative slew rate may be defined for each base station. By monitoring the rate of change of the signal strengths recorded, the CCU 2 can decrease the predicted availability score of a signal having a negative slew rate greater than that allowed for a particular connection device 10, 11.

Usually, a curve representing the change in strength of a received signal at a train will grow and decline at a relatively low rate where the strength of the signal is sampled at a sampling frequency of at least 1Hz. This is because during a period of I second a train will only have moved a relatively short distance, which is likely to have relatively little effect on the signal strength. For example, where a train travels at a speed of 500km/hour the distance travelled in 1 second will be about 140m. It is assumed therefore, that where a connection device 10, 11 measures a high rate of change for a received signal from a base station A, B, that the high rate of change is due to sampling noise, error or changes in localized conditions (for example, where buildings block the path of the signal to the train). The CCU 2 calculates a correlation coefficient of the measured signal strength indicator at the current time and a previously calculated tangent. As the rate of change is expected to be low, a recently calculated straight-line tangent should have a high correlation coefficient with the last few signal strength measurements. Where a current signal strength indicator measurement and the last calculated tangent for that signal have a correlation coefficient lower than a predetermined threshold, the CCU 2 decreases the predicted availability of that signal.

Figure 4 shows a line 18 showing signal strength indicators measured over time. It can be seen that where two tangents x, y have been calculated, the signal strength measurements fit poorly with the calculated tangents. If, at these points, a predetermined number of subsequent signal strength indicators and the calculated tangents x, y have a correlation coefficient below a given threshold, the CCU 2 decreases the predicted availability of the signal from the measured base station A, B. It will be appreciated that predictions of future availability can be represented in any convenient way. For example, although a scale comprising three discrete values has been described above, a scale comprising a larger number of discrete values could be used, as could an analogue scale.

As described above, it is preferred that the areas in which connections to each base station A, B can be established overlap such that there are areas through which the train 1 travels in which the CCU 2 may connect to more than one base station A, B. As such, the CCU 2 proactively establishes a connection with a base station A, B before the signal from a currently connected base station A, B is lost. The CCU 2 may then choose which of the base stations A, B to use to forward data packets to the Home Agent 6 based upon the predicted availability and/or the current availability of each base station A, B. In one embodiment the CCU 2 chooses base stations with a relatively high probability of future availability determined using the techniques described above over devices with a relatively low probability of future availability. In general terms, various types of signal strength information provided by connection to various base stations can be processed to derive an indicator of predicted future availability. Given that these indicators of predicted future availability are in a generic (rather than device specific) form, information allowing comparison of predicted future availability of a plurality of different base stations is provided. As described, this information can be used to determine a time for which a particular base station is likely to be available.

Where the predicted availability of two base stations is equal, data indicating current availability generated as described above in generic form, can be used to influence which base station is selected for connection. Where two base stations have equal predicted availability and current availability values, the CCU 2 may choose one of the base stations A, B based upon the published bandwidths of the base stations A, B. Parts of the preceding description have been concerned with the selection of a base station based upon a strength of a signal between the CCU 2 and respective base stations. It will be appreciated that in alternative embodiments parameters other than signal strength can conveniently be used. For example, the signal to noise ratio of connections to different base stations can be processed in the manner described above with reference to signal strength so as to select a base station which should be used for communication.

The preceding description has been concerned with selecting one of a plurality of base stations with which a connection should be established. This selection has been based upon the availability of a connection between that base station and the CCU 2.

It is also desirable to ensure that a base station with which a connection is established is able to properly provide a connection to the Internet 5. That is, there is often little point in establishing a strong connection with a base station if that base station is unable to provide a reliable connection to the Internet 5. Indeed, a base station A, B may experience problems with its connection to the Internet 5, such that, while still being able to send and receive data packets to and from the CCU 2, the affected base station A, B cannot forward those data packets on to the Home Agent 6 Where a base station is experiencing problems forwarding data packets to the Home Agent 6, it is preferable that the CCU 2 does not connect to that base station and that a connection to a different base station is established instead.

Referring back to Figure 1, a database 20 is connected to the Home Agent 6 and a local database 21 is connected to the CCU 2. Figure 5 shows the fields of the databases 20, 21 in further detail. It can be seen that the databases 20, 21 contain a record for each base station A, B. Each record contains the base station's IP address and a flag indicating whether or not the base station is functioning within acceptable parameters. Each record may further comprise additional information such as information to aid repair engineers in finding a base station in order to make repairs (for example, the location of the base station, and the type of technology used by the base station). The CCU 2 accesses the local database 21 and uses the flag to determine whether a connection should be established with that base station. That is, where the flag field has a value of 0', this is taken to indicate that the base station is not properly providing Internet connectivity, and as such it is not to be used.

Management of the database 20 associated with the Home Agent 6, and updating of the database 21 associated with the CCU 2 is now described with reference to Figure 6.

At step Si the Home Agent 6 determines whether each base station A, B is functioning correctly. Such a determination may be performed in any appropriate way, for example using the Simple Network Management Protocol (SNMP) and is preferably carried out at predetermined time intervals. If a base station A, B does not respond, or if a problem is detected, for example attenuation of the signal is above a maximum threshold, then the Home Agent 6 updates the flag field in the database 20 corresponding to the affected base station A, B to indicate that there is a problem at step S2. At step S3 the Home Agent notifies an operator responsible for a failed based station that there is a problem. Such a notification can be provided in any convenient way, for example by SMS message or email.

At step S4 a CSV file is created from records of the database 20, and at step S5 a plurality of notifier processes 30 are spawned, one process being spawned for each CCU with which the Home Agent communicates. Each notifier process 30 sends a message to its CCU informing the CCU that the database 20 has been updated, and providing the CSV file created at step S4. The notifier process then awaits an acknowledgement from the CCU to confirm safe receipt of the CSV file.

Upon receiving the message from the Home Agent 6, the CCU updates the database 21 so as to be consistent with the database 20.

When the CCU 2 needs to choose between a base station A, B it consults the database 21. Where a base station A, B is indicated as having a problem, the CCU 2 will not connect to that base station.

It will be appreciated that the database 21 need not contain all of the fields of the database 20. That is, the database 20 needs only enough information to determine that a particular base station A, B should be avoided. It may therefore suffice for the database 20 to contain only the IF addresses and problem flag fields for each base station. In alternative embodiments, the CCU 2 may simply maintain a list of IF address of problematic base stations. It will further be appreciated that the CCU 2 may update the database 21 via any appropriate mechanism. It will be appreciated that base stations need not be identified by using IF addresses, but can be identified in any convenient way, for example using MAC addresses.

In the preceding description it has been explained that the CCU 2 connects to base stations A and B. These base stations can conveniently be provided at the side of a track along which the train travels. In alternative embodiments of the invention the CCU 2 may be configured to communicate with base stations associated with respective mobile telephone networks such that the CCU is configured to connect to different mobile telephone networks as the train moves. Similarly, the CCU 2 can be adapted for connection to satellite networks.

It has been explained in the preceding description that the CCU 2 is arranged to provide wireless network connectivity onboard the train 1 such that passengers travelling on the train I can use mobile computing devices to connect to the CCU 2. It will be appreciated that in some embodiments of the invention the CCU 2 is not adapted to provide wireless network connectivity onboard the train. Such embodiments can be useful in providing telemetry services and closed circuit television.

The preceding description has been concerned with an embodiment in which the CCU is associated with a train. It will be appreciated that the methods described herein are in no way limited to trains, but are instead widely applicable to any situation in which data communication is provided to a moving person or object. In particular, the methods described can be used to provide data communication to other vehicles (e.g. busses and cars).

Although preferred embodiments of the present invention were described above, it will be appreciated that various modifications can be made to the described embodiment without departing from the spirit and scope of the present invention.

Claims

Claims 1. A method of selecting, from connections to first and second devices, a connection to be used for data communication, the method comprising: receiving first specific data indicating an operating characteristic of said first device; receiving second specific data indicating an operating characteristic of said second device; processing said first specific data to generate first data in a generic form; processing said second specific data to generate second data in said generic form; selecting one of said first and second devices based upon said first data in said generic form and said second data in said generic form.
2. A method according to claim 1, wherein the first specific data is of a first type and the second specific data is of a second different type.
3. A method according to claim 1 or 2, wherein said first data in said generic form comprises data indicating a predicted future operating characteristic of said first device and said second data in said generic form comprises data indicating a predicted future operating characteristic of said second device.
4. A method according to claim 3, wherein: processing said first specific data to generate said first data in said generic form comprises processing said first specific with respect to at least one threshold to generate said data indicating said predicted future operating characteristic of said first device.
5. A method according to claim 3 or 4, wherein processing said first specific data to generate said first data in said generic form comprises: processing a plurality of first specific data values indicative of said operating characteristic of said first device at respective times to determine a rate of change of said first specific data values; and generating said data indicating said predicted future operating characteristic of said first device based upon said rate of change.
6. A method according to claim 5, further comprising: processing said rate of change to determine a time for which connection to said first device is likely to be possible.
7. A method according to claim 6, wherein processing said rate of change to determine a time for which connection to said first device is likely to be possible corn prises: reading data representing a series of stored first specific data values; identifying part of said series using said rate of change; and determining said time for which connection to said first device is likely to be possible based upon a position of said part of said series relative to said series.
8. A method according to claim 5, 6 or 7, further comprising: processing at least some of said plurality of first specific data values to determine a first rate of change of said first specific data values; processing at least one further first specific data value to determine an updated rate of change of said first specific data values; determining whether said updated rate of change is within a predetermined range of values defined by said first rate of change; and generating said data indicating said predicted future operating characteristic of said first device based upon said determination.
9. A method according to claim 8, wherein generating said data indicating said predicted future operating characteristic comprises generating a value indicating a relatively high confidence in future availability if said updated rate of change is within said predetermined range of values defined by said first rate of change, and generating a value indicating a relatively low confidence of future availability if said updated rate of change is not within said predetermined range of values.
10. A method according to any preceding ctaim, wherein said first specific data indicates a parameter of the connection to said first device.
11. A method according to claim 10, wherein said first specific data indicates a signal strength or signal quality associated with the connection to said first device.
12. A method according to claim 10 or 11, wherein said first specific data is in a form determined by operating parameters of said first device.
13. A method according to any preceding claim, wherein said first specific data indicates a current ability of the first device to receive andtor transmit data.
14. A method according to claim 13, wherein said first specific data indicates whether said first device has participated in a data transaction in a predetermined time period.
15. A method according to any preceding claim, wherein: said first data in said first generic form comprises data indicating a current operating characteristic of said first device and a predicted future operating characteristic of said first device; said second data in said generic form comprises data indicating a current operating characteristic of said second device and data indicating a predicted future operating characteristic of said second device; and selecting one of said first and second devices comprises: comparing said data indicating the predicted future operating characteristic of said first device with said data indicating the predicted future operating characteristic of said second device.
16. A method according to claim 15, wherein if said data indicating the predicted future operating characteristic of said first device and said data indicating the predicted future operating characteristic of said second device meet a first predetermined criterion, selecting one of said first and second devices comprises: comparing said data indicating the current operating characteristic of said first device with said data indicating the current operating characteristic of said second device.
17. A method according to claim 16, wherein if said data indicating the current operating characteristic of said first device and said data indicating the current operating characteristic of said second device meet a first predetermined criterion, selecting one of said first and second devices comprises: comparing data indicating a bandwidth of said first device with data indicating a bandwidth of said second device.
18. A method according to any preceding claim, wherein the method is carried out by a client device wishing to select one of a plurality of wireless connections to be used for communication.
19. A method according to claim 18, wherein the client device is located on board a vehicle.
20. A computer readable medium carrying computer readable code arranged to cause a computer to carry out a method according to any preceding claim.
21. A communications device arranged to select, from first and second devices, a device with which a connection should be established, the communications device comprising: a memory storing processor readable instructions; and a processor configured to read and execute instructions stored in said memory; wherein said instructions comprise instructions controlling the processor to carry out a method according to any one of claims 1 to 19.
22. A method of selecting, from first and second devices, a device with which a connection should be established, the method comprising: receiving first data indicating an operating characteristic of a first device; processing said first data to generate data indicating a predicted future operating characteristic of said first device; receiving second data indicating an operating characteristic of a second device; processing said second data to generate data indicating a predicted future operating characteristic of said second device; selecting one of said first and second devices based upon said data indicating a predicted future operating characteristic of said first device and said data indicating a predicted future operating characteristic of said second device.