Patent Application
20130331125
The present invention relates to a cooperative localisation process and related apparata. In particular, the present invention relates to a process and related apparata that enable estimating the position of radio apparata that do not have access to localisation systems, or where these are not working or are ineffective, and in which the acquisition of data for calculating the unknown positions takes place through the cooperation of apparata that are present in the surrounding area.
In recent years, determining the position of apparata has grown in importance, due both to interest in services known as LBS (Location Based Services) and to accompany emergency calls with caller position data. Various processs and systems have been studied and implemented for determining the position of radio apparata, some of which are based on satellite systems, such as GPS (Global Positioning System), GLONASS (GLObal NAvigation Satellite System), GALILEO (currently being implemented by the EU) and COMPASS (currently being implemented by China), while other are based on terrestrial radio systems, and cellular systems in particular.
The most well-known terrestrial processs for determining the position of a terminal are:
identification of the radio cell from which the terminal signal originates;
determination of the area of coverage common to the radio stations that simultaneously receive the terminal's signal;
identification of the radio cell from which the terminal's signal originates combined with an estimate of the distance of the terminal from the radio base station;
triangulation, or rather determination of the directions of origin of the terminal's signal in at least two other radio stations, with calculation of the intersection of the corresponding lines;
multilateration, or rather estimation of the distance of the terminal from at least three radio base stations, the geographic coordinates of which are known, with calculation of the point that satisfies said distances;
Some of the above-listed terrestrial processs use the estimate of distances of the terminal from the radio stations, which can be obtained using various techniques:
any other technique that enables obtaining the same result.
In other cases, the terrestrial processs use three or more distance differences between the terminal and two radio stations and the intersections of the hyperbolae that these differences define. As a rule, these differences are calculated by observing the difference in time that the radio signals employ for travelling along the two different propagation paths (Observed Time Difference, OTD), with variants of the techniques dependent on the process used for synchronising the stations or to take into account the time lag between their clocks.
However, the known solutions indicated above have certain technical problems and drawbacks. In particular, satellite localisation systems require a number of satellites to be electromagnetically visible from the apparatus to be localized and entail long, initial acquisition times. With the A-GPS (Assisted-GPS) system, the cell stations provide the terminals with preliminary data on the satellite system with which the terminals can increase GPS signal reception sensitivity and shorten the initial acquisition, but times remain very long when GPS is unavailable because the propagation of the signals transmitted by the satellites is blocked by natural or artificial obstacles.
Similarly, excluding techniques that refer to just one radio station, in many places localisation systems based on cellular networks cannot be used because there is not always electromagnetic visibility between the apparatus to be localized and at least two radio stations (required by the above-mentioned, rather imprecise triangulation technique) or three radio stations, needed for hyperbolic or multilateration systems. There again, techniques that refer to just one radio station normally offer inadequate accuracy, and so it must be concluded that in many places both satellite localisation systems and terrestrial ones are not available or do not provide an estimate of terminal position with sufficient accuracy.
To compensate these shortcomings, processs have been proposed that, for estimating the position of an apparatus that cannot access localisation systems, use the position data of other apparata that are in the vicinity. The process described in patent EP1206152 belongs to this category. According to this process, the terminal to be localized has a radio transceiver system that enables it to establish two-way connections with other terminals that are in the vicinity. By means of said radio transceiver system, the terminal to be localized has the nearby terminals send it data regarding their respective positions and estimates the distance of each one of them with an evaluation of propagation attenuation. The terminal to be localized estimates its position on the basis of this data.
In a first embodiment of the process, the unknown position is calculated as the mean of the positions of the terminals that have provided their position. In this case, there is no guarantee on the accuracy of the calculated position, as there is no information on the relative position of the terminal to be localized with respect to those that are in the vicinity, particularly if it is assumed that the terminal to be localized, like the surrounding ones from which it waits for data, has a localisation system that it momentarily cannot access. In this case, terminals very close to the one to be localized are probably also unable to determine their own position by means of an external localisation system. It is therefore likely that the positions from which the mean is calculated correspond to points further away from the terminal to be localized, and not arranged uniformly around it, but more likely arranged in an irregular and unbalanced manner. Furthermore, the estimate of the distances made on the basis of propagation attenuation can be misleading, especially if conditions are considered where signals are propagated inside buildings or in areas with natural or artificial obstacles. For example, a terminal close by, but separated by a wall or a ceiling can appear further away than a terminal whose signals arrive through a window from a distant external point. By applying the process of patent EP1206152, it is therefore probable that a terminal inside a building calculates that it is on the outside instead.
In a second embodiment of the process of patent EP1206152, the unknown position is calculated with multilateration of the distances and positions of the terminals that have communicated their position data. In this case, it is necessary to have at least three terminals, which know their own position and are electromagnetically visible to the terminal to be localized; the probability of this occurring might not be very high. Then, should three terminals be found in these conditions, as mentioned above, it is likely that they are not close to the terminal to be localized and that the determination of the distance from them by measurement of the power of the signals received from them is misleading. Therefore, the process of patent EP1206152 does not appear to be reliable.
The object of the present invention is that of resolving the above-stated problems of the prior art by providing a cooperative localisation process and related apparata that enable calculation of the position of one or more apparata that request their positioning without having access to localisation processs.
The above-stated objects and other objects and advantages of the invention, as shall emerge from the following description, are achieved with a cooperative localisation process that forms the subject matter of claim 1.
Furthermore, the above-stated objects and other objects and advantages of the invention are achieved with radio communication apparata that form the subject matter of claims 17 to 20.
Preferred embodiments and non-trivial variants form the subject matter of the dependent claims.
It is understood that all the appended claims form an integral part of the present description.
The present invention will now be described in greater detail by some preferred embodiments, provided by non-limitative way of example and with reference to the attached drawings, where:
a shows a diagram representing an example of a first development stage of a location network;
b shows a diagram representing an example of a second development stage of a location network;
c shows a diagram representing an example of a third development stage of a location network;
d shows a diagram representing an example of a fourth development stage of a location network;
a shows a chart representing a table of the distances regarding the example in
b shows a chart representing a table of the distances regarding the example in
c shows a chart representing a table of the distances regarding the example in
d shows a chart representing a table of the distances regarding the example in
a shows a data table regarding the example in
b shows a data table regarding the example in
c shows a data table regarding the example in
d shows a data table regarding the example in
The following terms and related definitions will be used further on in the description:
relay apparatus: an apparatus that acts as a relay for connections between other apparata;
controller (controller apparatus): the cooperator apparatus (see below) that currently has the role of managing the localisation procedure;
cooperator (cooperator apparatus): an apparatus that cooperates in the localisation process;
explorer (explorer apparatus): an apparatus instructed by the controller to emit a search signal and to return the data collected from the replies to said signal to the controller;
active cooperator: a cooperator apparatus capable of carrying out the controller function, the explorer function and also the relay apparatus function;
passive cooperator: a cooperator apparatus not equipped with the specific means of the present invention's process and therefore unable to act as a controller, apparatus, an explorer apparatus or a relay apparatus, but equipped with telecommunications systems that permit active cooperator apparata, equipped with the same telecommunications systems as the passive cooperator apparatus, to estimate the distance and/or receive and/or derive absolute position data from the passive cooperator apparatus;
inert cooperator: a cooperator apparatus equipped with means that enable active cooperators to detect its presence, to estimate the distance from it and to indirectly obtain data regarding its position, cross-referencing data originating from the inert cooperator with data originating from at least one other source of information;
location grid: a set of cooperator apparata and the radio links through which they interconnect, which form a grid of adjacent triangles of known sides;
node: an apparatus that is located at an apex of one of the triangles of the location grid;
location network: the set of cooperator apparata and their possible connections;
distance table: a data matrix containing the distances that separate the cooperator apparata, with the related uncertainties and the times to which the measurements refer;
data table: a table that contains sundry data regarding the individual cooperator apparata, as described in the following.
The active cooperator apparata are preferably equipped with the following specific means:
a suitable radio transceiver system for transmitting and receiving the messages and data necessary for implementing the process according to the present invention;
means for estimating the distances between apparata with reciprocal electromagnetic visibility according to the requirements of the present invention;
digital memories for storing at least the distance table and the data table;
processing means for executing computer programs, processing received data and carrying out the necessary numerical calculations for implementing the process according to the present invention.
In addition, they are preferably equipped with:
calculation means able to implement optimization algorithms for carrying out coordinate calculations having data that is redundant or missing and affected by uncertainties.
The following symbols are used in the text that follows and in the attached figures:
HM: maximum number of radio links from an cooperator apparatus to the controller apparatus beyond which a cooperator apparatus cannot assume the role of explorer;
NM: maximum number of apparata that can be involved in the positioning procedure, beyond which the location network development procedure terminates;
Ta: duration of receiver switch-on in the sleep mode cycle;
Tc: duration of the receiver's sleep mode cycle;
TE: minimum time interval that must elapse between two assignments of the role of explorer for the same apparatus;
TL: time limit beyond which confirmation of interest in calculating the position is requested;
Tp: duration of the alert code, sent in the preamble of the search signal to alert the receivers;
Ts: duration of receiver switch-off in the sleep mode cycle;
TW: time interval, starting from the most recent time when an apparatus has been engaged in transmission or reception, after which the receiver of the apparatus passes to sleep mode.
In general, as shall be seen further on in greater detail, the process according to the present invention is based on the creation of a location grid composed of adjacent triangles, the apexes of which are known as the nodes of the grid and are where the apparata that cooperate in the positioning are situated. In addition to the apparata that are at the nodes of the grid, there are also apparata that can directly or indirectly establish connections with these nodes and cooperate in the positioning process, but do not belong to the grid because they do not have a sufficient number of constraints to constitute the apex of a triangle. The set of all the apparata that cooperate in the calculation of the requested positions (cooperator apparata) and the connections that they can establish constitute the location network. With regard to the radio links through which the cooperator apparata can establish connections, the distance between the corresponding apparata is estimated. This distance estimate can be obtained through any technique, such as any of those previously mentioned for example. The choice of this technique has no importance for the purposes of the present invention and will therefore be ignored throughout the treatment that follows.
The location network is gradually expanded in successive steps so as to obtain sufficient data, through the apparata that are gradually added, to position the location grid and, in consequence, its nodes, finishing with also calculating the position of the node-apparatus to be localized.
One of the apparata of the location network assumes the controller function of the localisation process. Preferably, the controller function is assigned to one of the apparata for which the position needs to be determined, but it can also be assigned to apparata that do request positioning. The controller function can be moved from one apparatus to another during the location network creation and development phase.
The creation and development of the location network takes place through the successive transmission of appropriate “search signals” by the cooperator apparata upon receiving special search commands issued by the controller apparatus and possibly forwarded through intermediate apparata, which function as relay apparata. The apparata that respond to the search signals (called responding apparata) are added to the set of cooperator apparata and the controller is informed of their existence and the direct connections that they have with the other cooperator apparata by the response messages that the explorer apparata receive from the responding apparata and which they forward to the controller, if necessary through the above-stated relay apparata.
The topology of the connections between the cooperator apparata is preferably of the tree type, but can also be of another type (for example, a grid). In the exemplifying case of a tree structure, the root of the connections tree preferably coincides with the controller apparatus that manages both the connections and the creation of the location network and that, once development of the location network is completed, calculates the position of each of the apparata that requests it and communicates it to them.
Development of the location network ends in one of the following cases:
when a sufficient amount of position and distance data is found that enables the position and spatial orientation of the location grid to be geometrically determined, or
when a predetermined numeric limit NM of cooperator apparata is reached or exceeded, in order to avoid involving an excessive number of apparata, or
when a predetermined time limit TL, running from when the process was started, is exceeded.
A limit HM is also defined on the number of radio links necessary for connecting a cooperator apparatus to the controller apparatus. If a number of radio links greater or equal to said limit HM is needed to connect a given apparatus, said given apparatus is barred from emitting search signals. This bar normally limits the number of radio links necessary for connecting a cooperator apparatus to the controller apparatus to HM, as other cooperators cannot be added in cascade to said given cooperator apparatus. This limit can be exceeded, for example, if the connection of a cooperator apparatus to the controller is set up through relay apparata and, due to a change in propagation conditions, one of said relay apparata becomes excluded from the location network and transit through it is replaced by cascaded relaying through another two or more apparata.
If development of the location network ends without having acquired an adequate number of data points to geometrically determine the position of the apparata that have requested it, correlations are applied with radio limits and with the map of the area where the location network is located in order to reduce the uncertainties.
The radio transceiver system with which the connections between the apparata are created can be made ad hoc or be one of those known, as long as it enables estimating apparatus-to-apparatus distances with sufficient accuracy. In addition, it can also be non-homogeneous, or rather the location network can contain connections implemented by mutually different systems and standards of transmission and reception (GSM/GPRS, UMTS, LTE, Bluetooth, Wi-Fi, RFID, etc.). In fact, it is sufficient to be able to establish connections between pairs of apparata and therefore it is sufficient that the apparata have, two by two, the same transmission and reception system, on condition that there are apparata equipped with means to act as an interface between apparata that use different transmission systems. For example, if a first set of apparata uses the Wi-Fi P2P transmission and reception system and a second set of apparata used the ZigBee system, any apparatus belonging to this first set can interconnect to any apparatus belonging to this second set if at least one apparatus exists that has both Wi-Fi P2P and ZigBee.
In particular, the process according to the present invention comprises at least one phase of creating and developing a location network, the description of which is provided by means of a simple illustrative example, in which the need to calculate the position of just one apparatus that does not have access to a localisation systems is assumed. The description will be subsequently extended to cover situations that are more complex.
a shows a first stage of the illustrative example of the location network creation and development phase, aimed at determining the geographic coordinates of the apparatus represented by circle 119.
In the illustrative example, it is assumed that apparatus 119 receives a request, from the user or an entity connected by a telecommunications system, to determine its position when it cannot access any localisation system or when this system is unable to localize the apparatus, for whatever reason. In these conditions, apparatus 119 assumes the role of controller and, following a search command received by its radio transmission and reception system specific to the process according to the present invention, it emits a first search signal, containing a message with the following meaning: “I am 119. Apparata that receive this message should reply with a report indicating the respondent's identification code and, if known, data that enables identifying their respective absolute position”.
Generally speaking, if a preferred radio system is used for implementing the present invention, such as Wi-Fi Direct for example, the simple arrival of a response from a responding apparatus enables the explorer to estimate the distance separating them. In the case where other radio systems are used, the search signal could include a request to send the necessary data for estimating said distance (for example, transmission power and/or information on the time of emission of the response).
It is also advantageous for the search signal to contain a request for other auxiliary data, which will be described in greater detail further on, if known to the respondent and knowledge of which is useful for the task performed by the controller 119. If permitted by the radio system, the search signal should preferably contain a request for all data potentially useful to locating the apparatus to be localized, which should preferably be contained in a single response message. This permits the time employed and the number of messages needed for acquiring localisation information to be minimized. However, due to the particular radio system used and/or the characteristics of the communicating apparata, multiple exchanges of round-trip messages might be necessary to enable the explorer to acquire all the data considered necessary from the respondent, which it must then send to the controller apparatus in a generic exploration step of the process.
Returning now to this first step of expanding the location network of the illustrative example, apparatus 119 assumes the role of the only explorer and also of the only cooperator apparatus. For greater clarity, the apparata in
In this illustrative example, the first message emitted by explorer apparatus 119 is answered by apparata 107, 111, 127 and 123, which thus assume the role of cooperators. With the responses from these apparata, in this case received directly without the aid of intermediate apparata, and by means of any distance estimation technique, apparatus 119 also acquires the distances 112, 118, 121 and 122 that respectively separate it from apparata 107, 111, 127 and 123. The distances are then placed in the distance table, which with regard to the situation under examination is shown in
The times specified in the distance table, like those specified in the data table described further on, take into account the transmission delays and misalignments between the clocks of the apparata. The process of taking these factors into account is dealt with further on.
The numerical values provided in the attached figures are purely for illustrative purposes and do not refer to any real situation.
In addition to the identification code of each respondent, the controller apparatus 119 also acquires certain data regarding the individual responding apparata, which is transmitted by them and collected in the data table.
The second column of data table indicates whether or not the apparatus has made a positioning request. In this column, as in the other entries in the attached tables, symbol “Y” is affirmative, while symbol “N” is negative.
In general, as shall be seen in the following, the apparata must in any case be identified and positioning can be requested for one or more of them.
Amongst the criteria used in developing the location network, there is one that tends to make the apparata for which positioning is requested appear at the nodes of the location grid.
The third column indicates whether or not the apparatus is a node of the grid. This information is used as one of the selection criteria for the apparatus to be ordered to emit a search signal, similar to the first search signal, as will be seen further below.
The fourth column contained the number of radio links that separate the apparatus under consideration from the controller apparatus. As has been mentioned, apparata with a number of radio links greater or equal to HM (maximum number of radio links from the controller apparatus) are barred from emitting search signals. In this column, the “zero” value identifies the controller apparatus, while the absence of values could only arise in fault situations.
The fifth column indicated whether or not the apparatus is mobile. This information is used to establish possible needs to update data.
The next eight columns hold the localisation and speed data, each followed by a respective uncertainty. These are followed by the time column, which indicates the time when the data in the row was updated. As there are a number of data items on each row, the data update time of a row is assumed to be that of the oldest updated data item.
After the time column, there are other columns with “auxiliary data” of various types and different uses. For example, it is possible to find:
list of the users and entities requesting localisation;
addresses where the results should be sent;
time when the apparatus most recently assumed the role of explorer;
type of apparatus (mobile phone terminal, Wi-Fi access point, cordless phone, domestic appliance, etc.);
availability of satellite localisation systems;
availability of terrestrial localisation systems;
availability of distance measurement processs.
This information can determine preference criteria in selecting the apparata to be ordered to emit said search signals.
At each stage of the positioning procedure, by means of a special data-processing program, the controller apparatus analyses the collected data and establishes the next step to take. In the example being illustrated, controller apparatus 119 analyses the data in the data table in
This expansion step can take place in many alternative ways, for example, that of requesting the emission of the second search signal to all the respondents to the first search signal, or to a subset of the respondents, or to just one of these respondents in particular. Each selected explorer will therefore be reached by a special search command addressed to it, emitted by the controller apparatus and possibly forwarded by intermediate relay cooperator apparata. In the illustrative example that is being considered, it is assumed that it is expedient to limit as much as possible the number of apparata involved in the procedure, as well as the number of messages that are transmitted via radio. By applying this criterion, the controller commands just one of said respondents in the previous step to emit a second search signal.
Various criteria can be applied to selecting the apparatus to be ordered to emit the second search signal, according to the current situation. Some of these criteria are applied during this illustration, but purely by way of non-limitative example, it being understood that many other criteria can be applied either individually or in combination.
First of all, the controller checks which apparata have a number of radio links that separate them from controller apparatus 119 that does not exceed limit HM, which, by way of example, is assumed to be five. The value of HM can be predetermined or be set upon starting the process. Given the values indicated in the table in
In the state characterized by the data in the distance table indicated in
It should be underlined that there can be numerous and different selection criteria, but, as will be understood from following this illustration of the process, the use of different criteria and the adoption of different decisions is not, in general, prejudicial to achieving the result, but can only bring about a different number of steps and a different number of apparata involved in the process.
Therefore, continuing with the illustration and the assumption that it is apparatus 123 that emits a second search signal,
Apparatus 123 transfers all of the above-stated information directly to apparatus 119, the procedure controller, and apparatus 119 updates the distance table, as shown in
From analysis of the distance table in
To determine the position of apparatus 119 it is now sufficient to just calculate the position of this triangle, which however is constrained by just one fixed point (apparatus 125) at a single distance (124), and consequently cannot be geometrically positioned. Processing therefore continues with a further expansion of the location network.
As in the case of emission of the second search signal, a third search signal is then emitted by just one apparatus. Also in this case, it is found that none of the apparata listed in the data table in
Discussion of the various alternatives and the various selection criteria for the apparatus to be given the task of emitting the third search signal shall not be dwelt upon for motives of brevity, but it should be noted that apparatus 107 is the only one of those at the apexes of said triangle that has not yet emitted any search signal. The controller apparatus 119 therefore decides that apparatus 107 should emit a third search signal, by emitting a specific search command addressed to it.
It is then assumed that apparata 101, 102 and 109 respond to this third search signal, shown in
From analysis of the distance table indicated in
From analysis of the data table in
Similarly to the previous expansions, after checking for exceeding limit HM, the controller apparatus causes a fourth search signal to be emitted, by means of an related search command, selecting apparatus 109 as the addressed explorer, because apparatus 109 is the only one of the nodes on the grid that has not yet emitted any search signals. Transmission of the search command from the controller apparatus 119 to apparatus 109 and the possible responses from the respondents to the explorer in the opposite direction takes place with transit through relay apparatus 123 instead of the alternative of transit through apparatus 107, because when transiting through apparatus 123 certain data regarding apparatus 123, data regarding segment 112, which is less recent than the data regarding apparatus 107 (with regard to this, see the data table indicated in
It is assumed that apparata 103, 117, 120, 125, 123 and 107 respond to this fourth search signal, shown in
From analysis of the distance table indicated in
While in the illustrative example used up till now, the location network creation phase ends at a point where a sufficient amount of data has been acquired to calculate the position of the apparata to be localized, development of the location network can also stop after the following two events:
a) exceeding the limit NM for the number of cooperator apparata;
b) exceeding the time limit TL, running from when the procedure was started.
Stopping in the case of event a) is motivated by the need to avoid involving an excessive number of apparata, which could happen in particularly crowded environments and cause unacceptable levels of interference and radio packet collisions.
During the location network development phase, it can happen however that conditions are identified whereby some cooperators are found to be superfluous (for example, cooperators very close to the controller without localisation data while far-away positioned cooperators have been identified). In these cases, the controller can strike off the superfluous cooperators, or not count them when checking if limit NM is exceeded, as they no longer take part in the calculation procedure.
Stopping in the case of event b) avoids the result arriving when it is no longer of interest, should long waits for distances estimates, the acquisition of geographic coordinate data, the repetition of incorrectly received messages, etc. entail excessive delays.
Also in the case of stoppage following events a) and b), the process proceeds with calculating the positions, using the data acquired up to that moment, as explained the further on.
In the illustrative example used up to now, the role of controller has always remained with apparatus 119. However, in general, during the course of creating the location network, the role of controller can pass from one apparatus to another. The change in controller can be motivated, for example, by the advantages of having the controller in a barycentric position of the location network. Alternatively, the role of controller could systematically pass to the apparatus charged with exploration. On the other hand, it must be taken into account that the passage of the role of controller from one apparatus to another entails the transfer of the distance table and the data table, as well as the updating of the column that indicates the number of radio links that separate the apparatus under consideration from the controller apparatus, and so the advantage of performing a passage of the role of controller is evaluated by an appropriate algorithm, which compares the number of messages needed to perform the transfer of the role of controller with the estimate of the messages that would be saved in the course of the calculation procedure if the transfer was carried out.
During the development of a first location network it can happen that, at a certain point of exploration, apparata are encountered that are part of a second location network, and in particular apparata to be positioned that belong to a second location network. In this eventuality, development of the first and the second location network preferably proceeds in an independent manner. Alternatively, the two networks could be combined, with the advantage of avoiding possible duplications of data requests on the cooperators, but with the drawbacks of:
requiring that the apparata to be localized, if possible, belong to a same location grid, more complex than the two separate ones that could be developed independently;
negotiating selection of the controller of the location network resulting from the merge;
combining and transferring the data collected up to the moment of merging to the sole controller.
In addition, the merging of two networks, implicating the development of a more complex network, probably entails a greater number of exploration steps and a greater probability of exceeding limit NM or time TL.
The preferred alternative that is assumed in the description of the process is that of keeping location networks that possibly meet and interpenetrate separate from each other. An expert in the art can however easily imagine how the merging of location networks takes place and the subsequent development of the location network obtained from this merging.
By keeping the location networks that interpenetrate separate and independent, the apparata that belong to more than one location network respond to the queries of the different controllers in an independent manner. Possible collisions of messages coming from the different controllers are resolved by the radio transceiver system, as described in the following.
The process according to the present invention further comprises a phase of calculating the positions of the apparata to be localized.
If at the end of the location network development process there are apparata to be localized other than the current controller, the coordinates of the apparata to be localized are preferably calculated by the controller and then transmitted to the respective apparata. Alternatively, the controller transfers all of the collected data, or a part thereof including the necessary data for calculating the respective positions, to the apparata involved and the latter individually calculate their own positions from the received data.
When development of the location network terminates, for the purposes of calculating the positions of the apparata to be localized, the following situations can arise:
c) constraint redundancy with respect to the indispensable minimum for calculating the positions with geometrical calculations (as in the illustrative example used up till now);
d) number of constraints equal to that geometrically necessary;
e) number of constraints less than that geometrically necessary.
In case c), calculation of the positions is performed by means of an optimization algorithm that takes into account the reliability of the single data items, the absolute values of the distances found or their ratios, the uncertainties of the estimated data, whether position or distance, and the speeds with which the apparata move (values that, for the described example, can be found in the distance table in
In case d), the calculation of the positions is performed using geometrical rules well known to an expert in the art.
In both case c) and case d), errors can be caused by the following:
uncertainties in the values of collected data;
estimation errors on coordinates and distances;
coordinate and distance values measured at different times and therefore potentially inconsistent after movements of the mobile apparata.
For the above-stated causes of error, the results of the position calculations are generally affected by uncertainties and can have some inconsistency.
In case e), in addition to the causes of uncertainty existing in cases c) and d), there is at least one degree of freedom in the positioning of the apparata to be localized. The existence of degrees of freedom, or rather the lack of constraints, corresponds to areas of uncertainty regarding the positions of the apparata; in order to reduce them, the process of the invention determines limits for the positions of the apparata that are calculated considering the transmission and reception ranges and, if available, plans of the area and the lines of demarcation created by obstacles and objects present in the area.
An example is shown in
The grid of triangles 109, 107, 123, 128 and 125 is geometrically positioned, as its node 125 is positioned and there is the constraint of distance 105 from apparatus 102.
Apparatus 119 is, however, only constrained to the location grid at apparatus 123 by distance 122, and therefore from the geometrical viewpoint, its position can be at any point of the circumference 405, which has apparatus 123 at its centre and a radius equal to distance 122.
The controller (in the example, apparatus 119 itself), can however work out that apparatus 119 cannot be on the arc of circumference 405 that runs from near node 128 to near node 125, because this arc is close to the line joining the two nodes 128 and 125, which are mutually electromagnetically visible; therefore, if apparatus 119 were to be on this arc, it could establish a radio link with at least one of the two said nodes 128 and 125, and could estimate the respective distance from them. Similarly, the controller can work out that apparatus 119 cannot be on the arc of circumference 405 that runs from near node 125 to near node 109, or on the arc that runs from near node 109 to near node 107. Therefore, in light of the calculations made up to this point, apparatus 119 must be on the shorter of the two arcs of circumference 405 delimited by nodes 107 and 128.
The controller can also calculate the transmission and reception range of nodes 107 and 128, conservatively calculating it in the case where propagation is impeded by obstructions. In
Finally, if the controller has a map of the area and detects from this the presence of obstacle 401 and the absence of other obstacles between obstacle 401 and node 107, it can calculate that the range of node 107 arrives up to obstacle 401 and therefore that the possible position of apparatus 119 closest to that of node 107 is represented by point 404. The final result of the calculations indicates that apparatus 119 is on the shortest of the two arcs of circumference 405 delimitated by points 404 and 406. Then, taking into account the uncertainties on the position of the grid of three triangles 109, 107, 123, 128 and 125, and of the consequent uncertainties of the positions of nodes 123 and 128 in particular, and also taking into account the uncertainty in measuring distance 122, the controller can calculate the area of uncertainty of the position of apparatus 119.
Lastly, taking into account the probability distribution of the quantities affected by uncertainty, by means of statistical processing known to an expert in the art, the controller calculates the most likely value of the position of apparatus 119 and the statistical parameters that characterize the spatial distribution.
The example described with reference to
Thus, in all three cases c), d) and e) it is possible to calculate and limit positioning uncertainties and geometrical inconsistencies.
If uncertainties in the results and any inconsistencies are within acceptable limits, the controller provides the positioning result to the requesters, otherwise the controller, by multiplying the speed with which the mobile apparata move by the time differences to which current data refers, calculates the uncertainty factors that result from this and evaluates whether it is necessary to update all or just part of the available data. If an update is considered necessary, the controller sends an update request to the cooperator apparata that must update the data for which they are responsible, specifying the time when data acquisition must be performed so that whatever the delays occurring between emission of the request and taking the measurements, the measurements refer to the same instant. Also in this case, the controller takes into account transmission delays and misalignment of the clocks of the apparata, as explained further on, when sending the update request.
Once the data is updated, the controller calculates the requested positions and the related uncertainties. If the uncertainties of the results and any inconsistencies are within acceptable limits, the controller provides the positioning result to the requesters. Otherwise, if time limit TL has not been exceeded, it resumes development of the location network and performs a further exploration step in the network development phase, as already seen above. When this further exploration step terminates, the location network development phase also terminates again and the phase of calculating the coordinates of the apparata to be localized is consequently entered.
Instead, if time limit TL has been exceeded, the procedure continues by providing the requesters with the obtained positioning results and the related uncertainties, together with a warning regarding the reliability of the result and the request for users and entities that requested positioning information to indicate whether or not they are interested in refining the calculations. If interest in refining is expressed by at least one requester, the process is resumed at the step of performing a further exploration to develop the location network. The time limit is reset, preferably to the same value as before TL or to a new value, and the requesters that renounce to positioning are struck off the list of requesters.
If necessary, the reiterations continue until there are no longer any requesters that confirm interest for the result.
Following updates or subsequent developments of the location network due to the changed conditions, caused for example by movements of the mobile apparata, it can happen that previously detected apparata or distances are no longer found. In these cases, the missing apparata and data are removed from the tables and the procedure continues as if they had never existed.
In particular, the flowcharts in
Step 517, represents the wait state of a position calculation request. For simplicity, checks have been omitted regarding the possibility of obtaining the requested position by means of a conventional localisation system, assuming on principle that there is no possibility of accessing any of them, or that they have failed, or have supplied unsatisfactory information the correctness of which it is wished to check by means of an alternative localisation process.
When a location request arrives (step 518), control passes to step 502 where the initial settings are assigned, which can be partially or completely predefined without intervention by the user requesting localisation, or can be assigned by any means of man-machine communication interface. In particular, both the role of controller and the role of explorer are assigned to the apparatus on which the process begins. The time limit TL, beyond which the process stops to ask positioning requesters if they are still interested in the continuation of the calculations, is preferably predefined, but can also be requested from the positioning requester by means of the above-mentioned interface.
With the data set up in step 502, the exploration step 503 is started, from which data on the respondents and the distances that separate the explorers from the respondents are obtained. No check is provided downstream of the exploration step 503 on the possibility of there not being any respondents to the exploration, as this case is implicitly dealt with by the procedure as a whole, as will be seen further on.
Now, assuming that there are respondents to the search signal, whether dealing with the first exploration carried out by the controller at the beginning of the localisation process, or dealing with a generic exploration carried out during the course of the subsequent expansions of the location network, the data collected in the exploration step 503 is analysed in step 505 and, using the results of this analysis, it is checked (step 507) whether there is sufficient data to geometrically calculate the requested positions. If the available data is not sufficient to geometrically calculate the requested positions, it is checked (step 511) whether time TL or limit NM for the maximum number of apparata that can be involved in the procedure have been exceeded. If neither TL nor NM has been exceeded, control passes to the step of selecting the explorers 506 to carry out a new step of expanding the location network. As shall be seen below, the explorer selection step 506 also allows an apparatus that has already assumed the role of explorer in the past to be selected, but only if a time equal to at least TE has passed since this role was last assumed. In general, TE is less than TL and is sized to avoid, on the one hand, an excessively frequent repetition of the cycle formed by steps 503-505-507-511-506, and to allow, on the other hand, to reconsider cooperator apparata as explorers even if they have already had this role, so as to be able to examine changes in environmental conditions following movements of the apparata or other objects.
Returning to the flowchart in
If time TL has not been exceeded, control returns to step 506 to select a new explorer and make another attempt to expand the location network, as already seen. Instead, if time TL has been exceeded, control passes to step 514 where it is checked whether the positioning requesters are interested in refining the calculations. For illustrative simplicity, the steps of sending provisional results to the positioning requesters, presenting the query on interest in refining the results and waiting for the response are not represented in
The cases where there are no respondents to the search signal in the exploration step 503 will now be considered. If there are no respondents to the first search signal emitted by the controller, through analysis of the available data (step 505) and the step 507 of determining the sufficiency or insufficiency of the acquired data to geometrically calculate the positions, control arrives to the step 511 of checking whether time TL or number NM have been exceeded. If neither TL nor NM has been exceeded, control passes to the explorer selection step 506. As no data has changed for the controller, apart from time of the most recent exploration, the role of explorer is reassigned to the same apparatus, namely to the controller itself, but, as has been said, after time TE from the previous assignment of the same role. The cycle of steps 503-505-507-511-506 is thus repeated until different conditions are found, either because the environmental conditions or the distances of apparata present in the vicinity have changed so that some respondent to the search signal is found, or because TL or NM has been exceeded.
If respondents to the search signals are found, the situation falls back to the general case described above. Instead, if no respondents are found and TL or NM is exceeded, control passes from step 511 to that of calculating the coordinates (step 508), which obviously does not provide useful results, and so control then passes from step 509 to step 510. As there is clearly no data to update, control passes to step 512. If NM has been exceeded, the process terminates at step 516 with the supply of the achieved results and a warning that the uncertainties are beyond acceptable limits. Instead, if NM has not been exceeded, control passes to step 515 and the procedure continues as in the general case described above.
When there are no respondents to search signals emitted by apparata other than the controller, after the exploration step 503, apart from the more recent time of exploration, only data regarding the distances between the apparata involved in the transmission and reception of the exploration procedure's messages can change, and therefore the geometrical constraints of the location network do not change and the first pass through steps 503-505-507-511 develops as in the case seen above, where there are no respondents to the first search signal broadcast by the controller. Whereas, on step 506, if there are a number of apparata likely to become selected as an explorer, the set of explorer apparata can change and it is possible to return to the previously seen, more general case, where there are respondents to the search signal. Instead, if the role of explorer is reassigned in step 505 to the same apparata, respecting time interval TE from the previous assignment, the exploration is reiterated as in the case of no respondents to the first search signal broadcast by the controller.
If the cycle 503-505-507-511-506 is exited at step 511 due to TL or NM being exceeded, the general case of the positions calculation procedure would be entered at step 508, with all of the alternatives already described above, including the possibility of finding acceptable uncertainties in step 509 and terminating in step 516 with the supply of the results to the apparata interested.
The step of selecting the explorers 503, as already explained in the illustrative example provided above, comprises numerous criteria, which are applied according to the status of the network and data at the time of acquisition. Some examples, neither exhaustive nor limitative, of preferential conditions and criteria for selection of an apparatus for the role of explorer are:
apparatus that has localisation means;
apparatus geographically distant from apparata that have localisation means, but not the possibility of directly acquiring their own position;
apparatus geographically close to apparata that do not have localisation means;
apparatus coincident with a node of the location grid;
apparatus that has not assumed the role of explorer for at least time TE;
fixed apparatus;
mobile apparatus with a low speed of movement.
It should also be remembered that, preferably, the role of explorer cannot be assigned to apparata that have a number of radio links from the controller equal or greater than HM.
The exploration step 503 has been described with the illustrative example explained above. Additional details are given further on in connection with the description of the radio transceiver system.
The data analysis step 505 consists in the application of known mathematical and geometrical criteria with which it is determined whether the found constraints are sufficient to calculate the requested positions by geometrical means.
The data update step, already described with the illustrative example, consists in requesting apparata that have provided potentially out-of-date data to update the measured values, which are then forwarded to the controller apparatus 119 for collection and analysis, according to the processs already described in the foregoing.
The positions calculation step has been described above in the illustrative example, also with regard to
As has been stated in the course of explaining the illustrative example, the positions calculation step (step 508 in
If the number of geometrical constraints is not redundant, control passes to step 604 from where, if the number of geometrical constraints is strictly sufficient, the location network data passes to the positions calculation step 605 for determining the positions by geometrical calculations. Also in this case, the uncertainties of the calculated positions are calculated taking into account the uncertainties of the localisation data and any inconsistencies, as mentioned above with regard to the case of redundant geometrical constraints. The obtained results are output in step 608.
If the number of constraints is found not to be strictly sufficient in step 604, control passes to step 606, where the lack of constraints with respect to the indispensable minimum to geometrically calculate the positions is first of all translated into areas of uncertainty. In the case of the illustrative example represented in
The present invention also relates to a cooperative localisation apparatus comprising at least one radio transceiver system for exchanging data packets between the apparata: usefully, this radio transceiver system need not necessarily be designed ad hoc, but can be one of the known systems, as shown further on, as long as it has the following characteristics:
possibility of direct apparatus-to-apparatus transmission of short data packets;
availability of mechanisms for handling radio packet collisions;
adequate transmission and reception range for the operating conditions contemplated for the application of interest;
possibility of estimating the distances between apparatus and apparatus of the requested positioning service;
possibility of making the receivers operate with low energy consumption.
By way of example, if the process of the present invention is applied for the localisation of mobile phone apparata in emergency situations, the required transmission and reception range could be in the order of 30-40 m indoors and 100-150 m outdoors, while, if the positions of the apparata must have an uncertainty within ±10 m, the uncertainty of the distance measurements must be approximately ±2 m, to take into account the various causes of error that combine with each other, including those induced by anomalous propagation conditions.
Obviously, as already stated, the distances can be estimated using one of the known processs of the art.
With regard to the energy consumption of the receivers, techniques similar to those used in many systems are applied, known to experts in the art with the term “sleep mode”. According to these techniques, the receivers have two modes of operation, an “active mode” in periods when they are engaged in cooperative localisation and a “sleep mode”: in active mode, the circuits of the receivers are constantly powered to promptly respond to requests to provide data or to send messages, while in sleep mode, the circuits of the receivers are cyclically switched on for a time Ta and switched off for a time Ts, in a repeated cycle lasting time Tc, where:
T
c
=T
a
+T
s
as shown in
The receivers pass from sleep mode to active mode when an alert signal, described below, is received, while they pass from active mode to sleep mode after a time equal to TW has passed since the respective apparatus was last engaged in the transmission or reception of messages or data regarding a cooperative localisation procedure. Instead, the receiver of the controller apparatus preferably passes to sleep mode when the cooperative localisation procedure in course terminates.
Instead, the transmitter of each cooperator apparatus is normally always switched off and is only activated for transmitting data packets when:
the apparatus must emit said first search signal at the beginning of the procedure for calculating its own position, as it does not have access to systems that can supply it directly;
the apparatus receives a request from a controller to transmit the necessary messages for the localisation of another apparatus.
The emission of signals by the controller will continue until the calculation step for the positions to be determined ends. As the other apparata do not emit signals unless commanded to do so by the controller, when the controller stops emitting, it follows that all of the cooperator apparata also stop emitting.
The passage of the receivers from sleep mode to active mode can be achieved in various ways.
As a non-limitative example, the search signals and, in general, all signals directed to apparata that have remained inactive for a time greater than TW, are constituted by a preamble followed by the information content. The preamble contains an “alert code” known to all the receivers of the apparata with the characteristic functionality of the process of the present invention, lasting time Tp, less than Ta/n, where n is an integer greater than one. This alert code is repeated for a number of times equal to at least the integer higher than the ratio nTc/Tp. In this way, in the interval Ta of periodic receiver switch-on, n repeats of the alert code occur, of which n−1 are definitely not interrupted, while one might possibly be composed of an initial part of a first repeat and an end part of a second repeat. The possibility of receiving multiple repeats of the alert code in interval Ta allows the probability of non-detection or false detection of the alert code to be reduced. On the other hand, having set the duration of the alert code, the greater the number of repeats that can arrive in interval Ta, the greater will be the duration of Ta. After receiving and decoding the alert code, the receiver passes from sleep mode to active mode.
Each message transmitted over the radio channel contains information on the addressees and, in particular, contains a data field that indicates whether the message is intended for “all” the apparata that receive it or if instead it is intended for only the apparata of a defined set. In this way, apparata that are not amongst the message's addressees do not emit any message, in order to avoid a pointless, domino-effect multiplication of messages not needed for achieving the localisation of apparata that have requested it.
The main types of message are those listed below, by way of non-limitative example:
m01: request all apparata to send a reception acknowledgement, the response for which must be addressed to just the acknowledgement requester;
m02: exploration request, which implicates the emission of a m01 request and returning the collected data to the requester;
m03: data request (distances, polar coordinates, etc.);
m04: request all apparata to send a reception acknowledgement, the response for which must include an m01 request;
m05: reception acknowledgement.
There are also the response messages for these messages m01÷m05 and others not listed for brevity.
The data items available in the data table and in the distance table are characterized by the time when they were detected. These times must refer to a common time, whilst the clocks of the apparata can be misaligned. Techniques known to an expert in the art can be used to align these times to a common reference. For example, each apparatus, instead of transmitting the time according to its own clock when it performed a certain measurement, transmits the amount of its own processing time, defined as the duration of the time interval between the moment when it performed this particular measurement and the time when the signal carrying the value of this particular measurement was emitted from its antenna. To this processing time, the cooperators, which are inserted like repeaters (relay apparata) between the cooperator that originated this value and the controller, each add their own processing time, or rather the time that runs from reception of the signal carrying this value on its receiving antenna to the retransmission of the signal carrying this value from its transmitting antenna. The controller adds its own processing time to these processing times and also adds the time taken by the electromagnetic waves to travel over the radio links through which the signal arrived, as their lengths are known. In this way, the controller calculates the total time between the instant when this particular measurement was taken and the instant when this particular measurement became available for processing. The controller, for example, by subtracting this total time from the time indicated by its own clock, obtains the instant in time of this measurement with reference to the time indicated by its own clock, and it can repeat this for every other measurement. In the case where, during the positions calculation procedure, the role of controller passes from a first apparatus, with a first clock, to a second apparatus, with a second clock, possibly misaligned with respect to the first, the first apparatus converts the times stored in its own data table and distance table into time differences with respect to its clock, assumed as the reference clock, and transmits these tables with these time differences. Transmission takes place in the same way as seen above for transmission of the value of this particular measurement, so that the second apparatus can make all the stored times refer to said second clock.
Symmetrically, when the controller sends a request to a cooperator to update a measurement value at a set time, it does not send the value of this set time with reference to its own clock, but sends the time delay, running from the time when this cooperator receives the request, after which the measurement must be taken. In a similar way to the case seen above regarding the communications of reference times from cooperators to controller, the controller transmits a delay value that takes into account its own processing time and the times taken by radio propagation, while the cooperators through which said request signal is possibly relayed, subtract their own processing time from the delay value found in the message they receive, and forward this request message with said delay value so corrected.
It should be underlined that in the system according to the present invention, any apparatus, fixed or mobile, which is equipped with a specific radio transceiver system for the process of the present invention, can become an active cooperator apparatus, or rather assume the role of controller or explorer.
A preferred embodiment of the system according to the present invention is the implementation of the previously described process in mobile phone terminals that, in addition to having the proper radio transceiver system of the cellular network to which they are affiliated, also have the radio transceiver system known by the name of “Wi-Fi Direct” or “Wi-Fi Peer-to-Peer” or “Wi-Fi P2P”.
As is known to an expert in the art, Wi-Fi P2P enables direct communications between apparata with a range of approximately 40+150 m, depending on the conditions of propagation. Furthermore, its transmission and reception system has quite a good capacity to recover received packets damaged due to poor propagation conditions, signal insufficiency, interference and packet collisions. Wi-Fi P2P therefore has adequate performance for implementation of the process of the present invention.
Many types of mobile phone terminals are already equipped with Wi-Fi and so, with the addition of appropriate software modules, these types of terminals can implement the process of the present invention in combination with the processing, storage and distance calculation means provided for therein. All apparata equipped with Wi-Fi P2P, including Wi-Fi access points, personal computers equipped with Wi-Fi and all peripherals (printers for example) equipped with Wi-Fi for data transfer, can also become cooperators in the step of calculating the position of one or more of said mobile phone terminals.
In the description given above, it has been assumed that the number of apparata involved in the localisation process and the number of messages transmitted via radio preferably have to be minimized. To achieve this objective, the emission of search signals is limited to one apparatus at a time, so as to be able to decide on the need to launch any further exploration steps after having collected and analysed the data of those already carried out. If it is wished to reach the result more rapidly, possibly renouncing to maximum efficiency in terms of number of messages and number of apparata involved, at a certain exploration step, a search signal can be emitted to a number of apparata at the same time, so as to simultaneously collect a larger amount of data.
In the illustrative example it has been assumed that the controller apparatus 119 builds a location network by means of radio messages that the cooperator apparata exchange, and that it checks at each development step of said network whether it is capable of calculating the position of the apparatus to be localized on the basis of the collected data. Furthermore, in the case where calculation is impossible, it is the controller apparatus that actually estimates the position, or positions, to be determined through specific processing and storage means, if necessary using approximation and optimization techniques, according to the completeness and precision of the available data. In alternative, it is possible to make the controller apparatus 119 send the collected data to another apparatus that it can reach, by any means of communication, and transfer the task of performing the calculations to the latter. Said apparatus that performs the calculations then sends the results to the controller apparatus, which maintains control of the procedure and, in particular, establishes whether to terminate the localisation procedure or continue to follow it.
Although Wi-Fi P2P lends itself very well to implementing the process of the invention, in the long term the radio transceiver system could be made ad hoc, or developed also taking into account the specific requirements of security and short message services. There are many Machine-to-Machine applications with these requirements, for which important markets are foreseen and which could advantageously share the radio transceiver system with the process of the present invention. There are also research proposals for a radio-signalling network that satisfactorily handles, in a generalized and universal manner, the transmission and reception of the messages necessary for accessing wireless telecommunications networks and for negotiating the performance of transmission and reception prior to the assignment of traffic channels. The requirements of this type of network blend well with those of the invention under discussion and so, if such a network were to be implemented, the transceivers would be found in a great many apparata, both mobile and fixed, rendering the process of the present invention implementable on a very large scale with minimum marginal costs.
For descriptive simplicity, the description of the invention has assumed that all of the elements belonging to the localisation system and involved in the related localisation process lie on a plane, but it obvious to an expert in the art that the process could be applied equally well to a three-dimensional space, i.e. not considering just longitudes and latitudes, but also the altitudes at which the apparata and points of reference are located.
Again, for descriptive simplicity, the distinctions between active cooperator apparata, passive cooperator apparata and inert cooperator apparata have not been commented on up to now. Nevertheless, in general, these three types of apparatus can be part of the “location network” and cooperate in the positions calculation procedure, and have the below-described characteristics.
Active cooperator apparata are equipped with the following means:
In addition, active cooperators can optionally have data on their own position.
Active cooperator apparata, by having all of the specific means of the process of the present invention, can assume the role of controller, the role of explorer and the role of relay apparatus.
Examples, neither exhaustive nor limitative, of apparata that could become active cooperators are Wi-Fi P2P terminals endowed with the characteristic functionality of the present invention, and mobile phone terminals equipped with Wi-Fi P2P and the characteristic functionality of the present invention.
Passive cooperator apparata are apparata that have data on their own position, but are not equipped with the specific means of the process of the present invention. They therefore cannot assume the role of controller, the role of explorer or the role of relay apparatus.
Passive cooperators are equipped with at least a second two-way radio system, not necessarily different from the first radio system. This second radio system enables:
Examples, neither exhaustive nor limitative, of apparata that could become passive cooperators are:
radio base stations of cellular systems;
radio base stations of WiMax systems;
Wi-Fi Access Points;
Personal computers equipped with one or more bi-directional transmission and reception systems, such as Wi-Fi P2P, Bluetooth, or ZigBee;
in general, all apparata that have means to establish two-way connections with other apparata, but are unable act as a controller or explorer.
In the illustrative example used above to describe the process of the present invention, apparatus 117, shown in
Inert cooperator apparata are apparata only equipped with means that enable active cooperators to detect their presence, to estimate the distance from them and to indirectly obtain data on their position. Said data on the position of an inert cooperator is intended as being found indirectly as the active cooperator, after having read the identification code of the inert cooperator, retrieves the data position of the latter from a database accessible to the active co-operator and not provided directly by the inert cooperator, but acquired from other information sources.
Obviously, inert cooperators cannot assume the role of controller, the role of explorer or the role of relay apparatus. Examples, neither exhaustive nor limitative, of apparata that could become inert cooperators are apparata incorporating RFID (Radio Frequency IDentification) and for which the position can be provided.
Here is an example of inclusion of an inert cooperator in a location network: when an active cooperator equipped with an RFID reader and with the possibility of accessing an “RFID database” assumes the role of explorer, it activates its RFID reader and, upon a command originated by the controller, emits a search signal via the RFID radio system; if the explorer detects the presence of an RFID device, it queries this “RFID database” and, if this database of RFID devices has the absolute position data of this apparatus equipped with RFID, it will include the object identified via this RFID read in the inert cooperators, with the position of said object acquired from said “RFID database”. In addition, the active cooperator estimates its own distance from the RFID device based on the level of the signal it receives and the type of RFID that emits this signal (e.g., unpowered RFID, RFID equipped with internal battery, RFID equipped with a power system connected to an electricity grid) and/or the radio emission characteristics of the RFID device, if known. As the distances within which RFID devices can be detected are normally small, the absolute error on the estimated distance of an RFID is small. Alternatively, the position of the RFID device can also be made available to the explorer in other ways, such as, for example, the transmission of said position in a particular area around the RFID device in messages emitted by other radio transceiver apparata that the explorer can receive and use.
Returning to the illustrative example, let it be assumed that the explorer apparatus 107 in
The classification of the apparata into one of the three above-stated types (active, passive and inert) can optionally be indicated by a specific column of the data table, which has not been previously mentioned for descriptive simplicity. This column is part of the set of columns that are grouped under the “Auxiliary data” heading in the data table shown in
The process and the apparata according to the present invention therefore advantageously enable calculation of the position of apparata in places where localisation systems are not available or where localisation systems are inactive or unreliable. In particular, implementation of the process according to the present invention requires that the apparata that implement the present invention simply have a radio transceiver system that enables establishing direct apparatus-to-apparatus connections and specific application software. For example, Wi-Fi P2P is perfectly suitable as a radio transceiver system and therefore, as Wi-Fi is already present in many telecommunications apparata, including many types of mobile phone terminals, the process of the present invention can be widely implemented by just adding software applications.
The process according to the present invention further enables not only calculating the position of apparata in which the process is implemented, but also the position of apparata that do not have the process of the present invention at their disposal, if these apparata that do not have this process at their disposal can connect to at least one apparatus that has the characteristics of an active cooperator, according to the present invention, and send a request to it to calculate their position. In fact, a transceiver apparatus that can establish radio connections with apparata having the characteristics of active cooperators can be included in a location grid that can be formed by the active cooperators surrounding it. Having calculated the position and orientation of the location grid, and in consequence the position of said transceiver apparatus, the controller apparatus sends the data on said transceiver apparatus's position to it.
Considering that a significant percentage of emergency calls are made from places not reached by localisation systems, by implementing the described process in mobile phone terminals, it is possible to provide accurate data on the caller's position in situations where otherwise there would be no possibility of locating the call's point of origin, other than the rough approximation of the cell from which the call comes.
The described process also enables calculating the position of apparata using just the communication capabilities of the specific radio transceiver system of the present invention. It is therefore possible to locate any apparatus with it, without the need for either localisation systems or other telecommunications systems. For example, any PC equipped with Wi-Fi P2P can determine its own position without establishing any connection with public telecommunications networks.
Finally, the process according to the present invention can be applied for calculating the relative position of a closed set of apparata even in the absence of absolute localisation data, as is obvious to an expert in the art. The relative position of the apparata of this closed set can be displayed on one or more terminals equipped with display means (LCD, OLED, etc.) to offer professional services or services for civil uses, for example, of the Location Based Service (LBS) type. In general, according to the invention, this visualization can also be applied to all cooperator apparata equipped with these display means.
| Number | Date | Country | Kind |
|---|---|---|---|
| TO2011A000284 | Mar 2011 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT2012/000091 | 3/26/2012 | WO | 00 | 8/7/2013 |
