TECHNICAL FIELD:

[0001] The exemplary and non-limiting embodiments . of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to beamforming to radio receivers which are on a fast moving platform such as a bullet train.

BACKGROUND:

[0002] These teachings are relevant to wireless communication in a high-speed mobility scenario, and in particular facilitate a base station (BS) to effectively control beamforming operation when receivers are in a high-speed mobility scenario.

[0003] Figure 1 illustrates one exemplary wireless communication scenario in which there is a high speed train 102 with multiple cabinets (sometimes termed carriages or railroad cars) traveling along a track 101. Each cabinet carries a wireless gateway (GW) device which provides communication service to user-end devices (such as mobile phones, laptop/tablet computers, and the like) in that respective cabinet. Each GW device may be considered to have at least two interfaces, one providing connection links such as wireless local area network (WLAN) to the user-end devices, and one communicating 103 with an external access device such as a BS 108 of a cellular network. This enables the user-end devices to exchange data with external networks via the wireless GW devices. Currently it is not uncommon for high-speed trains to move at speeds of 300 kilometers per hour or more,

[0004] Beamforming is wireless communications technique by which the directional orientation and beam width of the transmit antenna is controlled to emit its electromagnetic (radiofrequency RF) wave towards the direction of the intended receiver. Beamforming has the potential to significantly increase the transmit gain as compared to transmissions from an omni-directional antenna. Improved gain results in an extended wireless communication range and improved communication efficiency. Certain wireless cellular systems such as 2G, 3G, LTE and WIMAX employ beamformmg in the downlink (network towards mobile user devices) from their respective base stations so they transmit with a directional signal. To do this effectively the BS needs to estimate the angle of arrival (AOA) for the downlink beam it will transmit.

[0005] Much of the prior art respecting beamforming of cellular communications may be considered to fall into two distinct approaches for estimating the downlink AOA: global positioning service (GPS) and fixed sensors. Examples of prior art GPS solutions can be seen at US patent publications US 2008/0268865 and US 2009/0111469. The key feature of GPS is to have the GPS receiver estimate its geographic position according to the radio signals received from GPS satellites, so adopting GPS for the purpose of beamforming to a train-mounted GW would entail installing a GPS receiver on the train and having a communication system on the train report the train's geographic location to the BS. From time-lapsed GPS position it might also report speed and direction. The inventors see two problems with GPS positioning to resolve beamforming on a fast platform such as a high speed train: position inaccuracy and latency in fixing the GPS position due to both processing delay and more fundamentally round trip time for signals between the GPS receiver and the GPS satellites. These problems become more significant in a high speed mobility scenario.

[0006] Li the sensor approach a number of different sensors are used individually or combined to track location of the train. A variety of different types of sensors can be used for this purpose, such as an induction coil, pressure sensor, accelerometer, and inertial sensor. While the sensor system does not have the round trip latency inherent in GPS there are other drawbacks. When a sensor system detects a passing train, it measures the mobility parameters of carriages. These alone are not sufficient for beamforming since the BS needs to transmit to particular receivers, not to the carriages. Thus the sensor system needs to identify corresponding receiver identifiers (IDs) as well to inform the BS which mobility parameters describe which receivers. [0007] One approach to bridge this gap is explored in a paper by X. Zhang and M, Tentzeris entitled APPLICATIONS OF FAST-MOVING RFID TAGS IN HIGH-SPEED RAILWAY SYSTEMS [International Journal of Engineering Business Management, Vol. 3, No. 1(201 1), pp. 27-31]. In this approach a radiofrequency identifier RFID reader is installed on the rail and the train carries RFID tags. When the train passes the reader, the reader interrogates the tag and reads out the tag ID which is translated to the on-board mobile receiver ID. The Zhang paper and its internal references admit to the difficulty in reading out RFID tags when the reader and tags are in relative motion. The reading is affected by the surrounding RF interface, data collision where there are multiple readers or tags, Doppler effect, and aging of equipment to name a few. Zhang et al conclude that with a passive RFID tag and a train running at a speed of less than lOOkmph, the miss rate is up to 5 percent. Additionally, the system sensitivity highly relies on the skill of equipment installation workers. For example, the orientation of the reader has to be ensured.

[0008] A RFID tag miss means the measured mobility parameters are useless. High speed motion implies that the read process has to be done very quickly. It is not reliable to read tags when the train is fast moving, and so Zhang et al teach that the RFID tag system would be insufficient for a high speed train scenario, which as noted above would result in relative movement between RFID reader and tag of 300 kmph or more.

[0009] Another drawback of the sensor approach is that converting tag IDs to mobile receiver IDs is considered to impose a high storage overhead and maintenance effort. After the tag IDs are read the sensor system needs to translate them into receiver IDs. This requires the sensor system has to maintain some database that maps tag IDs to mobile receiver IDs. In a rail system there may be thousands or even tens of thousands of carriages as in the case of the China Railway Bureau, and a RFID tag for each carriage. This means a substantial database which would have to be queried very quickly. This is quite expensive to build and requires a high effort to maintain as being current given that maintenance and repairs are routinely performed on the various carriages. {0010] Another reference that considers sensors in the rail environment is an anonymous Internet publication entitled A WIRELESS SOLUTION OF HIGH SPEED RAIL MONITORING, [ht^://w\vw^eamworks,net.cri/High_Speed_Rail_Solutions.httti l; undated but visited on November 8, 2011]. This document describes a railway infrastructure monitoring system with sensors deployed in groups along the railway. A sensor group may include a vibration sensor, temperature sensor, speed sensor, accelerometer, sedimentation sensor, and stress sensor. The sensor data is sent to the BS over wires or wirelessly. This particular scenario dispenses with the need to read the IDs of carriages.

[0011] The inventors find none of these sufficiently suitable for high speed beamforming purposes, due to the various shortfalls mentioned above.

SUMMARY:

[0012] The foregoing and other problems are overcome, and other advantages are realized, by the use of the exemplary embodiments of this invention. [0013] In a first exemplary embodiment of the invention there is a method comprising: receiving mobility parameters collected by a sensor system of a plurality of sensors; associating the received mobility parameters with an identifier of a radio receiver or group of radio receivers; estimating a position of the radio receiver or group of radio receivers from the received mobility parameters and from trajectory information; and controlling a wireless access node to beamform to the radio receiver or group of radio receivers at the estimated position.

[0014] In a second exemplary embodiment of the invention there is an apparatus comprising at least one processor and at least one memory storing a computer program. In this embodiment the at least one memory with the computer program is configured with the at least one processor to cause the apparatus to at least: receive mobility parameters collected by a sensor system of a plurality of sensors; associate the received mobility parameters with an identifier of a radio receiver or group of radio receivers; estimate a position of the radio receiver or group of radio receivers from the received mobility parameters and from trajectory information; and control a wireless access node to beamform to the radio receiver or group of radio receivers at the estimated position.

[0015] In a third exemplary embodiment of the invention there is a computer readable memory tangibly storing a computer program executable by at least one processor, the computer program comprising: code for associating received mobility parameters, collected by a sensor system of a plurality of sensors, with an identifier of a radio receiver or group of radio receivers; code for estimating a position of the radio receiver or group of radio receivers from the received mobility parameters and from trajectory information; and code for controlling a wireless access node to beamform to the radio receiver or group of radio receivers at the estimated position.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0016] Figure 1 is a schematic diagram illustrating a moving train with multiple carriages, each having a respective radio receiver for providing a wireless link to a base station.

[001 7] Figure 2 is similar to Figure 1 but with sensors arranged along the rail track for reporting mobility parameters of the train to the base station according to an exemplary embodiment of these teachings.

[001 8] Figure 3 is a functional diagram of one sensor system of a plurality of sensors arranged along a railway track according to an exemplary embodiment of these teachings. [0019] Figure 4 is a functional diagram of a base station according to an exemplary embodiment of these teachings. [0020] Figure 5 is a high level illustration of five sensor systems deployed along a railway track and two base stations according to an exemplary embodiment of these teachings. [0021] Figure 6 illustrates trajectory tables for the two base stations of Figure 5 according to an exemplary embodiment of these teachings.

[0022] Figures 7-8 illustrate a mobile operation table at two different times according to an exemplary embodiment of these teachings.

[0023] Figure 9 illustrates a simplified diagram of a two-dimensional correlation for grouping receivers according to an exemplary embodiment of these teachings.

[0024] Figure 10 combines the five sensor systems and two base stations of Figure 5 with the two trajectory tables of Figure 6 for detailing a one-railway track example according to these teachings.

[0025] Figures 11-13 illustrate a mobile operation table at different times for one base station of Figure 10 according to an exemplary embodiment of these teachings.

[0026] Figure 14 is like Figure 10 but illustrating an example for two independent railway tracks according to an exemplary embodiment of these teachings.

[0027] Figure 15 is like Figure 10 but illustrating an example for one railway track branching to many tracks between the two base stations according to an exemplary embodiment of these teachings.

[0028] Figure 16 is like Figure 2 but showing the base station obtaining scheduling information of train operations according to an exemplary embodiment of these teachings.

[0029] Figure 17 illustrates precise locations of receivers along a train for more precision multiple beamforming according to an exemplary embodiment of these teachings.

[0030] Figure 18 is a logic flow diagram that illustrates from the perspective of the base station the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, in accordance with an exemplary embodiment of this invention.

[0031] Figure 19 is a block diagram of a base station with a higher network node/MME, a gateway and a sensor system, which are exemplary electronic devices suitable for use in practicing the exemplary embodiments of this invention.

DETAILED DESCRIPTION:

[0032] These teachings provide a more reliable and cost effective method, by which the sensor system does not need to know onboard receiver IDs when it reports mobility parameters. Instead, in accordance with an exemplary embodiment it is the BS which automatically associates the mobility parameters with the appropriate receiver IDs.

[0033] The description and examples herein are in the context of downlink beamforming to simplify the concepts detailed herein; these teachings concerning beamforming are equally valid for uplink signaling from the gateways located on the moving platform (for example, the transmitters on the train may engage in beamforming their uplink transmissions based on the position of the BS relative to the moving transmitters). Further, while the majority of the examples are in the context of the moving platform being a train and all gateways in a group are attached to a single train, these are also non-limiting examples only. For example, the moving platform/train may have a radio receiver on each carriage as in the examples below, or only on some but not all carriages, or there may be only a single radio receiver for the entire moving platform/train. [0034] According to these teachings there is a system and method which enables the BS to conduct downlink beamforming towards receivers on a fast moving train or other fast moving mobile platform. With this system, when a train passes by a sensor system, the sensor system measures its mobility parameters and transmits these parameters to the BS, but without the IDs of the receivers which are on that mobile platform. As used herein a sensor system refers to one or more sensors at one discrete location as shown by example at Figure 3. In the train examples there are a plurality of sensor systems, each at different locations along the railway track. These individual sensor systems may or may not be networked together, and each sensor system may communicate with the base stations as a stand-alone entity using a unique sensor system identifier, In accordance with certain exemplary embodiments of the invention the BS identifies the associated mobile receivers and updates their mobility parameters which the BS receives from each individual sensor system. The BS shifts or otherwise rotates its signal beam for the coming time slots in real time based on velocity and speed information of the receivers which is used to estimate the current or future position of the radio receivers (or of the group as a whole).

[0035] The BS also maintains the trajectory information for the mobile platform, the rail pathways in the case of a fast moving train. It also maintains operation status parameters of the receivers or receiver group, including by not limited to the receiver ED, a receiver group ID, the sensor ID which last had an event for this receiver or group ID, the time of that last sensor event, the next event ID, the last BS (prior to handover to the current BS), and the handover time, to name a few. [0036] In the beamforming system the BS groups the various receivers by using one or multiple dimensional correlation, based on all or part of the operation status parameters of the various receivers. This includes but is not limited to those listed above: receiver ED, receiver group ID, last event sensor ID, last sensor event time, next event ID, last BS, and handover time. Alternatively, the grouping can be based on the history or statistics of these parameters.

[0037] In one particular embodiment which may be used in conjunction with or in place of some of the above correlation parameters, the BS obtains the train schedulmg information from the train scheduling server. The BS can then use the scheduling information (such as status of a running train) to identify which mobile receivers are on that train when some new mobility parameter is received from the sensor network. For example, the BS receives the train scheduling information and sees there is a Beijing to Shanghai bullet train scheduled to leave at time 7:20 am. The BS knows the rail path from a trajectory database and expects that train to cross sensor xyz at time 7:20+i. Once the BS gets a report from sensor xyz at time 7:20+* (plus or minus some threshold which assures there is no confusion with an earlier or later train on that same track) the BS knows the sensor report applies to that particular train. From the scheduling database the BS can also know how many carriages are on that train and by extension how many receivers are on it. That train will then be associated with a receiver group, and the IDs of all those receivers can be provided to the BS from a) another BS from which the receiver group was handed over; or b) the scheduling database itself which is populated with the receiver IDs. In either case the initial survey of which receiver IDs are associated to this train may be obtained by a first BS located at or near the Beijing station and has sufficient time to query each receiver to learn which receiver IDs are moving together as a group. A FID reader along each track near the station might also perform this initial grouping and provide the grouping information to the scheduling database.

[0038] For added precision in the case of a multi- carriage train, the BS may use relative location information of where exactly on the moving train each of the radio receivers are located, in order to form different beams for the different receivers. For example, if the sensor network is set to record and send the mobility parameters when the leading wheel of the train passes, the BS may access a database for the specifics of what kind of locomotive and carriages are on that scheduled run (and their relative lengths) and know relative distance from that front wheel to each radio receiver. The sensors measure the location of the front wheel and by knowing the train's speed and the distance of each radio receiver from that front wheel the BS can beamform precisely to each radio receiver individually in real time. [0039] The sensor systems are deployed terrestrially along the railway track so that they can accurately detect the mobility parameters of the passing train and its onboard receivers. Each discrete deployment location may have a single sensor or a group of sensors, and each such sensor (or sensors) at a given location is termed herein as a sensor system without loss of generality. The sensor system includes one or more sensors, a control unit and a communications module for sending its data to the BS as shown at Figure 3. The mobility parameters reported by an exemplary sensor system include but are not limited to location, speed, acceleration, and direction. At its most basic each sensor system reports its sensor ID and the precise time the train passed by, and the BS can calculate from that time-sensitive position, along with similar reports from a series of other serially-located sensor systems, the train's location, speed, direction and acceleration. Alternatively, an individual sensor system may have two or more serially installed pressure sensors and from those compute the train's speed, direction and acceleration. This is still one sensor system since there is one report of mobility parameters from those spaced-apart pressure sensors and that report is associated with one sensor system identifier. The BS will associate the received mobility data with the correct receivers via the above one or multi-level correlation and/or scheduling database, and thus control the signal beam dynamically. [0040] Figure 2 illustrates schematically such a plurality of sensor systems with one BS 208. There are two individual sensor systems 202, 204 arranged along the railway track 101, each having a wireless connection with the BS 208 for measuring and reporting the mobility parameters of a passing train. Note that while Figure 2 illustrates wireless links between the sensor systems 202, 204 and the BS 208, these may be implemented instead by wired, optical, microwave or other types of communication links.

[0041] Figure 3 describes the functional modules of an exemplary sensor system 300. The sensor system is composed of one or multiple sensors 302, including but not limited to pressure sensors, coils, and inertial sensors as indicated at Figure 3. The sensor system 300 further includes a communication module 304 to communicate with the BS and a control module 306 for managing operations of the sensor system itself, According to various embodiments of these teachings the sensor system 300 obtains its own location information using any one of multiple approaches or a combination of them, such as but not limited to pre-configured location data, GPS, and A-GPS. Functionally the sensor system 300 operates to detect the presence of carriages (or the train as a whole), their speed, orientation, and other mobility parameters. In the whole collection/plurality of sensor systems every sensor system is uniquely numbered or addressed.

[0042] In the examples below it is assumed that there is a minimum time interval between which any two trains may pass a single sensor system 300. This follows from railway operations in which the railway operator assures that no two trains run through one physical location within a minimal time interval to avoid any possible hazardous conditions. For example, in China any two trains should be separated by 6km if they run on the same track segment or pass by a common switch point. This is equal to 72s at a speed 300kmph.

[0043] Figure 4 describes the functional modules of a BS 400, or at least those relevant to this portion of the description. The BS 400 includes at least a transceiver 402, a sensing event processor 404, a mobility server 406, and a beamforming manager 410. The transceiver module 402 transmits data to receivers on the downlink and receives wireless data from sensor systems on the uplink. The sensing event processor 404 is responsible for receiving mobility parameters from the various sensor systems in its charge. These mobility parameters are generated every time a train passes by a sensor system 300. The sensing event processor 404 then feeds the event, with the data derived from the corresponding mobility parameters, to the mobility server 406.

[0044] The mobility server 406 updates its database of mobility parameters associated to receivers (on the train) when new parameters become available. Functionally there may be an Operation/Handover/Grouping (OHG) agerit 408 within the mobility server 406. The OHG agent 408 serves multiple roles, namely it maintains the trajectory information of the track segment in the BS's 400 area in a trajectory table to be detailed further below. The OHG agent 408 also tracks the location of receivers (or at least the train as a whole) along the track 101. This information is stored in the mobile operation table, also to be detailed further below. The OHG agent 408 additionally groups receivers into receiver groups by correlating their mobility characteristics. The concept of receiver group reflects the nature that receivers on one train have identical mobility characteristics. As such, when a new mobility parameter is received, it applies to all receivers of one group.

10045] The beamforming manager 410 receives mobility parameters from the mobility server 406 and calculates the beamforming control parameters. Using the mobility parameters such as direction and speed, it can continuously rotate/shift the signal beam towards the moving receivers.

[0046] Figure 5 illustrates five sensor systems SI 1, S12, S21, S22, and S23 deployed along a railway track, and also two BSs Bl and B2. In this example, sensor systems Sl l and S12 report their sensing data to Bl, while sensor systems S21, S22, and S23 report their sensing data to B2. Bl communicates with the receivers onboard the train when the train is to the left of the vertical dotted line shown in Figure 5, and B2 communicates with those onboard receivers when the train is to the right of that vertical dotted line. When a train passes by the track segment from S12 to S21, the onboard receivers are handed over from Bl to B2.

[0047] Figure 6 illustrates two trajectory tables; one for Bl of Figure 5 and one for B2 of Figure 5. For convenience the sensor system identifiers Sl l, S21, etc. are considered as location flags. The Bl trajectory table indicates that a train may go through Sl l and SI 2 in sequence. The B2 trajectory table indicates that a train may go through SI 2, S21, S22, and S23 in sequence. Note that the first entry in a trajectory table starts from the final or "exit" sensor system of the neighboring BS in the coming direction. For example, the B2 trajectory table has as its first entry SI 2 which is a sensor system prior to the dashed handover line of Figure 5, so while sensor system S12 sends its data to Bl it is listed in the trajectory tables of both Bl and B2. [0048] Figures 7 and 8 are mobile operation tables for B2 as a train moves between sensor systems S21 and S22. The RECEIVER ED column indicates the individual onboard receiver. The GROUP ID column indicates which receiver group the identified receiver belongs. A group of receivers are in this example those on the same one train. The LAST EVENT SENSOR ID indicates the ID of the sensor system that the receiver has most recently passed. The LAST SENSOR EVENT TIME indicates the time when the receiver passed by the last sensor system. The NEXT EVENT ED indicates the sensor system that the receiver is expected to pass by in the near future. It is derived from the B2 trajectory table shown at Figure 6. The LAST BS indicates the BS by which the receiver is served before it joins the current BS. And the HANDOVER ΤΓΜΕ indicates the time when the most recent handover from the LAST BS has taken place. [0049] Assume that the receivers on one train have just handed over from Bl to B2. Figure 7 illustrates a mobile operation table of B2 for this scenario. Mobile receiver ME1 and ME2 belong to the same group G001. They have passed by S 12 at time El, and from the trajectory information they are expected to next pass by S21, They were served by Bl, and handover took place at Tl and T2, respectively. Normally, Tl and T2 are very close if not the same. In the next time instant when the train passes by S21, the sensor system S21 reports mobility parameters to the sensing event processor 404 of B2. The processor 404 further feeds the data to the OHG agent 408 which finds that it is group G001 that was expected to trigger sensing data at S21, so it updates the mobility parameters of ME1 and ME2 which are the members of group G001. At the same time, the OHG agent 408 updates the LAST EVENT SENSOR ED to S21 and the LAST SENSOR EVENT TIME to E3. By checking the trajectory table and the direction information of the mobility data, the OHG agent 404 also updates the NEXT EVENT ED to S22. The new mobile operation table reflecting these updates is illustrated at Figure 8.

[0050] In this particular example of the subject invention, the OHG agent 408 recognizes which receivers belong to the same receiver group (or which receivers are attached to the same train) when the handover is confirmed or finished. There are a few different ways to determine which receivers are grouped together of which a few are explored below, but the end result is that all receivers in each receiver group belong to the same train, and no receivers of one train are grouped into different groups.

[0051] One approach to determining which receivers are in a same group is based on correlating the last BS, the HANDOVER TIME, and the LAST EVENT SENSOR ID in the mobile operation table. Figure 9 illustrates a simplified diagram of two-dimensional grouping. The LAST BS is identified along the horizontal direction and the HANDOVER TIME is identified along the vertical direction. In this example, the receivers with the same LAST BS and HANDOVER TIME within 20 seconds of each other are considered as a group. In another implementation, any existing or yet to be devised correlation method can be used for one-to-multiple dimensional grouping.

[0052] In another implementation, the grouping of receivers can be based on the history or statistics of some operation status. For example, the grouping can be based on the last three handover time of mobile receivers. Or the receiver grouping may be based on group handover processes, described in various documents such as US Patent 6,490,452 and US Patent Publication US 2010/0144354A1. The key feature of such group handover is that mobile receivers are grouped before the handover has taken place, and the receivers are handed over together when handover is needed. If this is the case, the OHG agent can naturally inherit the group arrangement from the handover process and need not compute on its own members of the group, except perhaps as a check to assure robustness while the train travels and passes through multiple BS operating areas. Another implementation to determine that initial grouping is noted above, while the train is just leaving the station and not yet moving at a rapid speed.

[0053] Figures 10-13 consider an example in which there is one railway track and, similar to Figure 5, it runs from sensor system Sl l toward sensor system S23 in the serial order illustrated, A train sequentially passes by these five sensor systems SI 1, S12, S21, S22, and S23, Sensor systems Sl l and S12 report their mobility parameters to the Bl, while sensor systems S21, S22, and S23 report their measured mobility parameters to the B2. The vertical dashed lines represent the coverage area cutoff of BSs, the handover locations. Similar to that shown at Figure 6, the Bl trajectory table at Figure 10 indicates that a train may go through Sl l and SI 2 in sequence. The B2 trajectory table at Figure 10 indicates that a train may go through SI 2, S21, S22, and S23 in sequence.

[0054] In this example, at one instant in time a first train is running on the track segment between S 12 and S21, and a second train is running on the track segment between S22 and S23. Figure 11 illustrates the mobile operation table of B2. The table has entries for five receivers ME1 through ME5, and they belong to two different groups G001 and G002.

[0055] Now assume there is a third train, carrying mobile receivers M6 and 7, passes by S12 towards S2 , the receivers are handed over f om Bl to B2. After the handover is confirmed, the B2 BS adds one entry in its operation table for each new mobile receiver. Figure 12 illustrates the table of Figure 11 but updated to reflect the two new receivers ME6 and ME7.

[0056] The updated table at Figure 12 stores seven receivers ME1 through ME7, which belong to three groups G001 through G003. Notice that G001 and G003 both run between S 12 and S21. G002 runs between S22 and S23. If the sensing data is received from S21 at time E4, the OHG agent 408 will compares the LAST SENSOR EVENT TIME of groups G001 and G003. Since El is earlier than E3, the OHG agent 408 associates the sensed mobility parameter with G001. The sensing data is used to update the mobility parameters of the receivers which are members of the group G001, and this updated operation table is shown at Figure 13.

[0057] Figure 14 is similar to Figure 10 except showing two (independent) railway tracks each with their own sets of sensor systems, and for each of the BSs a different trajectory table for each track. Bl and B2 provide wireless services to both tracks, and since the tracks are independent the operations relevant to these teachings is similar to the single-track example above. Above was detailed how the mobile operation table was updated as new data came in from a sensor. For the scenario of Figure 4 the operation is similar except each BS Bl and B2 constructs and maintains a mobile operation table for each track.

[0058] Figure 15 is similar to Figure 10 except showing that the single track branches to many (two shown). As with Figure 10, sensor systems Sl l and S12 report their sensing events to Bl, and sensing systems S21 through S26 report their sensing events to B2. The railway track branches out after S 2 into two distinct trajectories. When a train passes by the segment between S12 and S21 or S12 and S24, onboard receivers are handed over from Bl to B2. But despite the branched track, even from the perspective of B2 there is no material difference from the single un-branched track of Figure 10; updating the mobile operations table for B2 is substantially similar except the trajectory table will give two possibilities for the next sensor after S12 which B2 immediately resolves when the sensor ID is reported with the sensing results. When a sensing event takes place at one of the sensor systems served by B2, the OHG agent 408 follows the same rule to update the mobile operation table as detailed above for the single track scenario.

[0059] In the above examples it was assumed that all the mobile receivers are attached to one train or another. If instead the involved BSs serve both onboard receivers and other receivers such as for example automobile-mounted receivers, there are several approaches to distinguish these different receiver types from one another. In one approach the BS can maintain a list of all onboard receivers. In another approach the BS may distinguish the on-board receivers from the auto-mounted receivers because the onboard receiver IDs are specially coded, such as by using a designated segment of IDs. The BS can then distinguish whether a receiver ID is associated or not with a train carriage. The receivers associated with train carriages are treated separately from the other receiver IDs. [0060] Alternatively, the BS can recognize onboard receivers by conducting one or multi- dimensional correlations, or when a train leaves the station and is still slowly moving an initial BS may conduct the multi- dimensional correlation and pass along group information with or immediately prior to handing over the receivers of the train.

[0061 ] In addition to the receiver ID acquisition detailed above, in an exemplary embodiment the BS can obtain this information from other sources, such as the scheduling server or control center 210 of the train operator as shown at Figure 16. The scheduling center 210 maintains complete knowledge of the train operations including some or all of the following: which train is to pass which segment of which track at what time, the number of carriages (or receivers) there are for a given train, and the relative locations of receivers, etc. The BS can make use of this information to determine the association of a given set of mobility data to the receiver IDs when they are reported from the sensor system.

[0062] In one exemplary embodiment the BS makes use of the relative location information of multiple receivers of a train to simplify calculating locations of each individual receiver. Fig, 17 depicts the locations of multiple on-board receivers 1701 through 1704. The relative location of the four receivers 1701 through 1704 is fixed on the train 102. The sensor system reports the mobility parameters of one receiver 1 01, or of the train 102 itself, to the BS which then can derive the locations of all other receivers 1702 through 1704 using the information of the relative locations of those multiple receivers. This relative location information can be preconfigured or collected from external servers; for example the train scheduling server 210 may be adapted to also carry information of relative locations along a carriage at which the radio receiver is mounted. As noted above, in other embodiments there may be only one radio receiver for the entire train, or there may be a radio receiver on some but not all carriages. [0063] While the above examples assume there is a gateway disposed in each carriage of the train, in other embodiments there may instead be a relay node disposed in some or in each carriage, such as one defined by the IEEE 802.16j standard. Or there may be other types of network access devices for existing or emerging radio technology standards, whether in each carriage or less than all carriages of a train.

[0064] One technical effect of certain embodiments of these teachings is that they are quite simple to deploy in existing cellular communication systems, requiring no hardware modification to existing BS and its associated network components, Embodiments according to these teachings are seen to be more reliable than RFID-based systems in a high speed scenario. Embodiments of this invention also does not suffer from the fact that RFID-based beamfo ming may not be operable at all when a RFID reader cannot read the RFID tag in a high speed scenario. RFID-based systems incur some associated hardware cost.

[0065] Further, the disclosed invention is more cost-effective than GPS-based systems. Adding a GPS unit to each receiver incurs a fairly high expense, in that the labor and hardware cost is quite high to modify legacy on-board receivers. Exemplary embodiments of these teachings require no such receiver modification.

[0066] Some engineering work at the network side may be required to implement the exemplary embodiments of these teachings, but minimal collaboration is seen to be needed between the train operators and the wireless network operators to initially deploy the sensor network along the railway.

[0067] Now are detailed with reference to Figure 18 further particular exemplary embodiments from the perspective of the base station, more generically a wireless access node of a wireless communication network. Figure 18 may be performed by the whole base station, or by one or several components thereof such as a modem, a processor in combination with a software program tangibly stored on a memory, or any sub-combination of functional blocks shown at Figure 19. [0068] At block 1802 there are received mobility parameters which have been collected by a sensor system of a plurality of sensors. At block 1804 the received mobility parameters are then associated with an identifier of a radio receiver or of a group of radio receivers, Block 1806 details that a position of the radio receiver is estimated from the received mobility parameters and from trajectory information, and at block 1808 a wireless access node is controlled to beamform to the radio receiver at the estimated position. The estimated position may be a current position or a future position.

[0069] Further elements of Figure 18 detail various of the non-limiting embodiments detailed above. Specifically, block 1810 describes that the received mobility parameters are associated with an identifier of the group of radio receivers. Block 1812 summarizes the further step of determining the group of radio receivers by correlating (such as across one or two or more dimensions) an operational status of a plurality of radio receivers. Block 1814 gives further details for block 1812 in that the operational status of the radio receivers comprises a database which tracks in real time for each of the plurality of radio receivers: a) identifier of a sensor system which last had an event with the radio receiver; b) time of a last sensor event for the radio receiver or group; c) identifier of a next sensor system for which the radio receiver is to have an event; d) identifier of a last base station prior to a most recent handover; and e) time of the most recent handover. [0070] Block 1816 details that the associating of block 1804 comprises utilizing scheduling information of a mobile platform to which the radio receiver or group of radio receivers is affixed to choose the radio receiver or group of radio receivers to associate with the mobility parameters. And finally block 1818 summarizes that, if the radio receiver of block 1804 is considered a first radio receiver and there is a further step of estimating a position of a second radio receiver by its relative location with respect to the first radio receiver, and the beamforming of block 1808 is individually to each of the first and second radio receivers at their respective estimated positions simultaneously. [0071 ] Figure 18 is a logic flow diagram which may be considered to illustrate the operation of a method, and a result of execution of a computer program stored in a computer readable memory, and a specific manner in which components of an electronic device are configured to cause that electronic device to operate. The various blocks shown in Figure 18 may also be considered as a plurality of coupled logic circuit elements constructed to carry out the associated function(s), or specific result of strings of computer program code stored in a memory.

(0072] Such blocks and the fiinctions they represent are non-limiting examples, and may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention. [0073] Reference is now made to Figure 19 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 19 a wireless network (BS/access node 22 and mobility management entity MME 24) is adapted for communication over a wireless link 21 with an apparatus, such as a gateway 20 on a rail carriage or other mobile platform. The mobility management entity 24 may provide connectivity with further networks such as for example a publicly switched telephone network PSTN and/or a data communications network/Internet over the SI 1 interface, and is communicatively coupled to other MMEs so all BSs along the railway may be in contact with one another.

[0074] The gateway 20 includes processing means such as at least one micro processor (MP) 20A, storing means such as at least one computer-readable memory (MEM) 20B storing at least one computer program (PROG) 20C, communicating means such as a transmitter TX 20D and a receiver RX 20B for bidirectional wireless communications with the BS 22 via one or more antennas 20F.

[0075] The wireless access node BS 22 also includes processing means such as at least one micro processor (MP) 22A, storing means such as at least one computer-readable memory (MEM) 22B storing at least one computer program (PROG) 22C, and communicating means such as a transmitter TX 22D and a receiver RX 22E for bidirectional wireless communications with the gateway 20 via one or more antennas 22F. The BS 22 receives the measurement parameters collected by the sensor system 26 via a wired or a wireless data link 23 and associates them using unit/program 22G so as to control beamforming by the BS 22 toward the gateway 20. There is also a data and/or control path SI coupling the BS 22 to the mobility management entity 24. Details of an exemplary sensor system are shown at Figure 4.

[0076] Similarly, the mobility management entity 24 includes processing means such as at least one micro processor (MP) 24A, storing means such as at least one computer-readable memory (MEM) 24B storing at least one computer program (PROG) 24C, and communicating means such as a modem 24D for bidirectional communications with the BS 22, with outside networks (through a system architecture evolution SAE gateway or similar) via the interface Sl l . While not particularly illustrated for the gateway 20 or BS 22 those devices are also assumed to include as part of their wireless communicating means a modem which may be inbuilt on an RF front end chip within those devices 20, 22 and which also carries the TX 20D/22D and the RX 20E/22E.

[0077] At least one of the PROGs 22C in the BS 22 is assumed to include program instructions that, when executed by the associated DP 22A, enable the device to operate in accordance with the exemplary embodiments of this invention which are detailed above. In these regards the exemplary embodiments of this invention may be implemented at least in part by computer software stored on the MEM 22B which is executable by the MP 22 A of the base station 22; or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Electronic devices implementing these aspects of the invention need not be the entire base station 22, but exemplary embodiments may be implemented by one or more components of same such as the above described tangibly stored software, hardware, firmware and MP, or a system on a chip SOC or an application specific integrated circuit ASIC or a digital signal processor DSP.

[0078] Various embodiments of the computer readable MEMs 20B/22B/24B include any data storage technology type which is suitable to the local technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the MPs 20A/22A/24A include but are not limited to general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and multi-core processors.

[0079] Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description. Examples of the radio network technologies which govern the wireless link 21 between the BS 22 and the gateway 20 include E-UTRAN, UTRAN, WCDMA, CDMA2000, and GSM, to name a few non-limiting embodiments. [0080] Some of the various features of the above non-limiting embodiments may be used to advantage without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.