This application is the national stage of PCT/IT2010/000294, filed Jul. 5, 2010. 
     FIELD OF THE INVENTION 
     The present invention relates to a method and system for determining the state of occupation (occupied/vacant) of a plurality of scheduled areas by vehicles. 
     In particular, the method and system of the invention are arranged to monitor the state of occupation of car parks, for example payment car parks located in cities, or parking spaces for the handicapped. Generally, in its various embodiments, the method and device of the invention can be conveniently used to monitor the state of occupation of areas such as carriageways, loading/unloading areas, etc. 
     BACKGROUND OF THE INVENTION 
     WO 2006/067813 describes an automatic system for monitoring and supervising the access, transit and parking of vehicles in predetermined controlled traffic zones, in particular in car parks provided with a plurality of individual parking spaces. The system comprises: an electronic vehicle identification device positioned on each vehicle, comprising a memory in which the data regarding the vehicle and/or the vehicle owner are memorized, and means enabling these data to be remotely transmitted; an electronic sensing device for the vehicle positioned in each parking space and provided with a suitable means for reading and memorizing the data present in each vehicle and means enabling these data to be remotely transmitted; at least one local data processing unit arranged to receive the information transmitted by the vehicle sensing devices, to process this information and to transmit the processed data; at least one central data processing unit, arranged to receive the information transmitted by the local data processing units, to further process the information and to further transmit the information to other processing units, in particular to data processing centres pertaining to banks or to similar financial institutions, or to directly emit signals enabling a vehicle to gain access to, to transit, or to park within the monitored zone; this automatic system is characterised in that the data transmitted by the vehicle electronic identification device are associated with the data relative to the electronic vehicle sensing device, the result of this association being transmitted to one of the local data processing units, the data processed by the local units being transmitted to the central processing unit, this latter generating a signal regarding the payment of a predetermined tariff for the access and/or transit and/or parking of a vehicle within the controlled zone. MI2008A001875, in the name of the Applicant, describes a system for verifying the state of occupation of a plurality of areas by vehicles, which comprises on board a vehicle a transmitting smart card arranged to transmit, to at least one first receiver-transmitter positioned within the area to be monitored, a first identification signal received from the vehicle. 
     The first receiver-transmitter is connected to a second receiver-transmitter to transmit the first identification signal and a second identification signal for the area monitored. 
     The second receiver-transmitter is connected to at least one electronic processor of an operating centre. 
     The electronic processor is arranged to receive the first identification signal and the second identification signal from the second receiver-transmitter, and to generate information indicative of the vehicle which has occupied the monitored area and of the particular area monitored. 
     SUMMARY OF THE INVENTION 
     The technical aim of the present invention is therefore to provide a more easily implemented and more versatile method and system for determining the state of occupation of a plurality of scheduled areas by vehicles. Another object of the invention is to provide a method and system which enable each abusive utilization of one or more parking spaces or other monitored area to be securely and rapidly identified. 
     A further object of the invention is to provide a method and system which are economical and enable parking services to be managed inexpensively. 
     The technical aim, together with these and further objects, are attained according to the present invention by a method and system for determining the state of occupation of a plurality of scheduled areas by vehicles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Further characteristics and advantages of the invention will be more apparent from the description of a preferred but non-exclusive embodiment of the method and system for verifying the state of occupation of a plurality of scheduled areas by vehicles according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which: 
         FIG. 1  is a schematic view of the system according to the invention; 
         FIG. 2  shows a sensor used in the system of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to said figures, a system for verifying the state of occupation of a plurality of scheduled areas by vehicles comprises a plurality of parking spaces, in each parking space  10  a sensor  11  being located below the wearing course of the parking space  10 . 
     A plurality of sensors  11  are coordinated by a concentrator  12  (communication node or bridge) for the parking area  10 , which sees the sensors  11  and evaluates the signals originating from them. 
     The sensor  11  comprises the electric circuit  20  and a containing capsule  21 . The capsule is buried, covered with a layer of asphalt  22  and then with an adhesive piece  23  to identify the position of the sensor  11 . The electric circuit  20  is powered by a long-life battery (5 years). 
     The sensor  11 , consisting simply of a transmitter, transmits periodically (for example every 5 seconds) a signal of fixed power containing certain minimum information, for example a number identifying the sensor  11 , and possibly the state of the battery. 
     When a vehicle  13  enters a parking space  10 , the signal transmitted by the sensor  11  positioned in that parking space  10  is altered. 
     The ground sensor  11  represents a simple network node which has two essential characteristics. It has a low power consumption level and a very simple functionality level, given that it transmits a signal to the node  12 . When a metal mass halts in the parking space the signal is altered, i.e. attenuated. 
     The state of occupation can be determined precisely from the intensity of the received signal. 
     In this respect, using a low level algorithm (firmware), the node  12  is able to decide whether the car space is occupied. The totality of nodes  12  in fact forms a second network. The state of occupation is deduced by measuring the signals of the network consisting of the sensors  11 . 
     In the node  12 , the received signal intensity value is firstly filtered using a digital filter. The filtered signal is then passed to a threshold sensing algorithm. 
     An algorithm with a received signal intensity value of fixed threshold was used, for example a received signal reduction of 50% indicates the presence of a car in that position. 
     To determine the state of occupation an algorithm of variable threshold level is preferably used. 
     In this respect, as an alternative, a threshold level variable with time is possible, based on the environmental (radio) conditions. 
     In addition, digital filters can be used characterised by different parameters which can influence the transmitted signal. 
     The concentrator  12  receives the signals of all the sensors  11 , then interprets the variation in the signals received, this resulting in recognition of the state of occupation of a parking space by a vehicle  13 . 
     For very large car parks, many concentrators can be used. The concentrator  12  is installed, for example, on a street lighting column. This type of installation is the best from the point of view of positioning the 2.4 Ghz antenna of the coordinator of a ZigBee network. 
     The concentrator  12  is powered by batteries rechargeable for example by photovoltaic cells. 
     Having recognized the state of occupation of a parking space  10 , the identity of the sensor/parking space and the time of occupation are memorized in the concentrator  12 . When the state of occupation is recognized, a string is defined which basically includes the date, the time of occupation (i.e. unambiguous time information which associates the parking space with the time of occupation). Likewise when the vehicle leaves the occupied space, the concentrator senses that the space is again available and essentially assigns a date and time to the moment of leaving. Hence with each parking space a time table is associated carrying the times of occupation and leaving. This table defines the effective level of occupation of the parking space. 
     The concentrator  12  transmits periodically, for example every 3 minutes, the state of all parking spaces assigned to it, to a remote operating centre  14 . 
     Each concentrator for the various parking spaces communicates with the remote operating centre  14 , which will know the overall parking space occupation state and be able to indicate by suitable means the availability or non-availability of vacant parking spaces. 
     Preferably each vehicle  13  comprises a smart card  15  comprising a display, a switch, a memory in which the identification of the vehicle/owner is stored, and a transmitter which communicates with the concentrator  12 . The smart card  15  does not communicate with the sensor  11  (the sensor is merely a transmitter). 
     The concentrator  12  transmits information to the smart card  15  regarding its own state, hence the smart card  15  also comprises a receiver. 
     The smart card  15  comprises rechargeable batteries (preferably of Li-polymer type) connectable to a battery charger; the smart card is also provided with a microcontroller which handles the communication steps with the concentrator  12 . 
     The smart card  15  also presents an indicator activated by the recognition signal; for example the indicator consists of a coloured (green/red) LED which is activated by the microcontroller when the receiver-transmitter receives the recognition signal. 
     Advantageously, the smart card  15  also presents a biometric reader such as a digital fingerprint reader. 
     In this manner, when a user passes a finger across the digital fingerprint reader, correspondence with one or more stored fingerprints can be checked, to authorize parking, if positive. 
     The remote operating centre  14  communicates with the concentrator  12  to pass information regarding the smart card state. 
     When a vehicle  13  enters a parking space  10 , the smart card  15  communicates with the concentrator  12 . 
     Each smart card  15  communicates not with the local sensor  11 , but only with the concentrator  12 . By virtue of this architecture, a smart card with hardware and software is possible which essentially enables applications to be conceived which are very different from each other. 
     The smart card can essentially be related to a specific condition: for example a smart card can be associated with a person or vehicle for payment by subscription, as in the case of a smart card controlling parking by residents of a building. 
     Possible applications can differ on the basis of: type of user (elderly, disabled, pregnant women, etc.), user category (residents, paying persons) and monitored area (airport areas, proximity to bends, etc). 
     The method of operation is based on a smart card logic flow with acceptance of the occupation space. 
     When the vehicle  13  enters a parking area the concentrator  12  communicates all the vacant parking spaces of the area to the smart card  15 . 
     When a vehicle  13  enters a parking space  10  and parks, the concentrator  12  views the smart card  15  and recognizes the state of occupation relative to a sensor  11 , of the area effectively occupied. 
     The smart card  15  shows on a display the number of the parking spaces recently occupied, seeing that in a given instant more vehicles can enter and occupy respective vacant spaces. 
     From the spaces recently occupied, the user accepts the parking space effectively occupied, indicated for example by markings on the floor or by a card positioned on the side. 
     Acceptance is then for example confirmed by positioning the fingerprint on the reader. 
     Alternatively the system can be based on a smart card logic flow with automatic activation. 
     The state of occupation of the parking space  10  is automatically associated with the smart card  15 , given that a time correspondence exists between the two signals. The analyzed concepts of time correspondence mean that the assigning is non-critical, even if overlapping exists in the arrival time. This is achieved by virtue of an assignment and release algorithm. 
     In this case the reserved parking spaces are associated, uniquely or in a proportion of one to many, with a person or a vehicle. Consequently, when faced with the occupation of a vehicle space, for example assigned to residents of a building, the system has to check whether the state of occupation corresponds to a valid association between the vehicle space and the smart card of the resident. The condition is that the smart card has been issued to a resident, who activates a confirmation of occupation of vehicle spaces which are associated in the system only with the smart card. When this event is activated, the system compares whether the smart card is authorized to park in the vehicle spaces associable with that smart card. If the available space is associated with the residents&#39; smart card, a state of authorized occupation is issued, otherwise the supervising personnel are informed, to indicate the presence of unauthorized parking. 
     In this case a unique relationship must be configured between the smart card and the vehicle number plate or possibly the person, to determine that the occupation takes place effectively by authorized vehicles. Alternatively, it may be sufficient for the smart card to be associated with the parking space independently of whether the vehicle occupies the parking space. In this case the smart card can also be passed to different vehicles. 
     The remote operating centre  14  comprises an electronic processor carrying software able to receive data from the concentrator  12  and generate information indicative of the person or vehicle occupying the monitored area and of the particular area monitored. 
     This information can be used to generate a parking payment, for example via a bank. 
     Alternatively this information can be compared with data contained in a data base of the operating centre  14  to verify whether the person occupying the particular parking space or the particular area is authorized (for example whether inserted in the list of handicapped persons). 
     In a particular embodiment, all communications take place by means of ZigBee protocol. 
     ZigBee is known to be the name assigned to a set of high level communication protocols for low power digital radios based on the IEE 802.15.4 standard. These protocols enable a wireless Personal Area Network (PAN) to be constructed. ZigBee operates in the 2.4 GHz band with a pass band of 250 kbit/s. ZigBee technology enables PANs to be constructed more simply and less costly than other technologies, such as Bluetooth. 
     A ZigBee network typically enables applications to be implemented requiring a non-excessive pass band and a low power consumption and, in particular, with a maximum number of nodes equal to 65,000. 
     A ZigBee network is composed of three different node types. 
     ZigBee coordinator (ZC): this is the device which forms the basis of the network and can act as a bridge towards other networks. In each ZigBee network only one ZC is present. The ZC is able to memorize data relative to the network structure, including data cryptography keys. 
     ZigBee Router (ZR): this is the device which enables data to be passed from one node to another. 
     ZigBee End DEVICE (ZED): this is the device in minimum configuration. Its functionalities are reduced to the mere capacity to transfer data to ZRs or ZCs. A ZED cannot directly exchange data with another ZED: this can take place via a ZR node or directly via the ZC. 
     The ZigBee standard defines the interconnection protocol, via radio communication, through various devices falling within a Personal Area Network. WPANs (wireless PANs) are used to distribute information along relatively short distances without connection cables; connections made via WPANs relate to small environments or infrastructures, favouring the development of inexpensive and energy efficient solutions for a wide range of applications. 
     A WPAN can include two different types of device: FFD (Full Function Device) and RFD (Reduced Function Device). A device of the first type can operate within the network in three ways: by operating as a network coordinator, as a simple coordinator or, more typically, as a communication terminal. An FFD can dialogue with other devices of both categories, whereas an RFD can communicate directly only with an FFD. 
     In each network, only one of the nodes can be configured as a ZC coordinator, used to initiate, terminate and handle communication between the different peripherals. Depending on the particular application, a WPAN can be configured as two possible types: star or peer-to-peer. In either case, each device within the network possesses an extended 64 bit address, which is used as a universal address, a unique identifier for the device, and different from all other devices of the world; this address can be directly used for communication or, alternatively, an address reduced by 2 bytes can be used, unique for the network to which the devices are connected, attributed by the ZC coordinator each time the device is sensed by it. The network topology used to handle the parking services of the present invention is of star type. 
     A single FFD exists acting as ZC coordinator and is physically located at the concentrator  12 . The nodes formed by the sensors  11  communicate directly with the concentrator  12 . 
     The operation of the system according to the invention is apparent from that described and illustrated, and is substantially as follows. 
     It will be assumed that a determined parking space is initially vacant; in this situation the receiver-transmitter  11  periodically transmits a signal to the concentrator  12  which is able to determine the presence or absence of a vehicle on the monitored area based on the intensity of the received signal. 
     In practice, the sensor  11  transmits to the concentrator  12  a signal having a predetermined power; if the monitored parking space is vacant the concentrator  12  receives a signal of power S 1 , whereas if it is occupied the concentrator  12  receives a signal of power S 2 , where the power S 1  is greater than S 2 . 
     By comparing the received power the ZigBee module is able to evaluate whether and when a parking space has been occupied; this comparison is made at the concentrator  12  or at the operating centre  14 . In practice the comparison and the recognition of the “vacant” or “occupied” state of the parking space is made by software constituting means for sensing the state of occupation of the area being monitored. 
     The concentrator  12  itself periodically communicates with the operating centre  14  via a suitable receiver, by indicating the “vacant” or “occupied” state of the parking space. 
     If this comparison is positive, i.e. if the first signal identifying the person or vehicle is recognized, the operating centre  14  transmits a recognition signal to the concentrator  12  and to the smart card  15 ; this signal causes the LED to light, confirming that the user has been recognized. 
     If the signal is not recognized, a sanction procedure is activated whereby the policing authorities are automatically informed, who then apply a sanction or remove the vehicle. 
     If monitoring payment car parks, these data are associated by the operating centre  14  with a time reference. 
     As the concentrator  12  and the operating centre  14  communicate with each other periodically, for example every 5 minutes, or every minute, or every 30 seconds, the electronic processor is able to know almost in real time the moment in which the parking space is occupied and the moment in which it is left vacant. 
     Consequently on the basis of the data in its possession, the electronic processor is able to emit an invoice to be pair for example by post, or (preferably) is able to initiate an automatic payment procedure via credit card, debit card or by other means.
A method for determining the state of occupation of a plurality of scheduled areas by vehicles, comprising the steps of: associating with each area to be monitored a transmitter which periodically transmits a signal of fixed power; receiving in a concentrator the plurality of signals emitted by said plurality of transmitters; examining said plurality of signals and determining the occupied/vacant state of each area to be monitored; periodically transmitting a signal comprising information on the occupied/vacant state of each monitored area to an operating center; generating information indicative of the state of occupation of a plurality of areas.