WO2013114415A1

WO2013114415A1 - Method and system for use of rfid tags as a communication channel in an rfid area network (ran)

Info

Publication number: WO2013114415A1
Application number: PCT/IT2013/000026
Authority: WO
Inventors: Antonio IERA; Carlo SPINELLA SILVERIO
Original assignee: Università Degli Studi Mediterranea Di Reggio Calabria
Priority date: 2012-01-30
Filing date: 2013-01-29
Publication date: 2013-08-08
Also published as: ITRC20120002A1

Abstract

The invention relates to a communication system which comprises a server and a plurality of RFID technology readers and tags and in which there are defined local RFID, RAN (RFID Area Networks) technology networks, consisting of a group of RFID readers and tags with functions for performing data exchange in unicast or broadcast mode within the generic RAN, as well as a method for using RFID tags as a "communication channel" for data exchange of varying nature within said communication system.

Description

Method and system for use of RFID tags as a communication channel in an RFID Area Network (RAN)

Summary of the invention

The present invention relates to a communication system which comprises a server and a plurality of RFID technology readers and tags and in which there are defined RFID technology local networks, RAN (RFID Area Networks), consisting of a group of RFID readers and tags with functions for performing data exchange in unicast or broadcast mode within the generic RAN, as well as a method for using RFID tags as a "communication channel" for data exchange of varying nature within said communication system.

BACKGROUND

In accordance with the recommendations stipulated in the EPC Tag Data Standard ver. 1.6 dated 2011, the memory of a Tag Gen2 is divided into four blocks: (i) Reserved Bank or Bank 00, (ii) EPC Bank or Bank 01, (Hi) TID Bank or Bank 10, (iv) User Bank or Bank 11 (Fig. 1). Bank 00 contains the lock function (protection of a memory area) and kill function (permanent deactivation of the tag) which can be accessed by means of 32-bit passwords, while Bank 10 contains general information about the size and characteristics of the tag (model, producer, etc.). The EPC Bank contains both control information and Business Data (Fig. 2), both in support of the so-called EPC code which uniquely identifies the object to which the RFID tag is attached. In fact, the following fields may be identified:

• CRC (16 bit): allows verification of any errors on the remaining memory blocks and is generated automatically by the RFID tag;

• Protocol Control (PC) (16 bit): control information divided into:

1. Length (5 bit): represents the number of 16-bit words included overall both in the PC field and in the EPC field;

2. User Memory Indicator (UMI) (1 bit): indicates whether Bank 11 is present and contains data;

3. XPC Indicator (XI) ( 1 bit): indicates whether an XPC is present;

A.Number System Identifier (NSI) (9 bit): other control information divided into:

4.1Toggle (1 bit): allows applications of the EPC global type (Toggle=0) to be distinguished from applications of the ISO type (Toggle=l). 4.2 Attribute I AFI (8 bit): if Toggle=0 the present field is considered to be of the Attribute type, used to determine whether the physical object to which the tag is attached requires special management of any kind (for example dangerous material); if Toggle=l the present field is considered to be of the AFI (Application Family Identifier) type for indicating a non EPC global application in accordance with the standard ISO/IEC 15961.

• EPC (variable length): unique identifier code of the object to which the tag is attached; in the case of an EPC global application the EPC code is considered, while in the case of an ISO application the Individual Unique Identity is considered.

• Extended Protocol Control (XPC) (variable length): "padding bits" used to complete any 16-bit words.

The AFI contains information about the type of application for which the RFID tag is intended. It defines the type of data which is stored in the tags such that they may be differentiated and therefore filtered for different application areas. The ISO/IEC 15961 specifies both the AFI and the ASF (Application Sub Family). AFI and ASF are assigned by the GS1 (Application Identifiers - AIs), by the ANSI MH- 10 (Data Identifiers - DIs), and by the ATA/IATA (Text Element Identifiers - TEIs).

Finally we shall consider the User Bank block, i.e. the memory part into which a user may enter information regarding the object to which the tag is fixed. The main standard which governs encoding and decoding of the User Bank is ISO/IEC 15962:2004. In Version 1.6 of the EPC Tag Data Standard it is specified how the ISO/IEC 15962:2004 is applied to the second generation RFID tags. At a logic level, the contents of the User Bank is a set of name-value pairs where the name part is an OID (Object Identifier defined using ASN.l syntax) and the value is a character string. Possible examples of OID notation are:

• (iso(l) standard(O) rfid-data-protocol( 15961)} (ASN.l notation);

• 1.0.15961 (dot notation);

• /ISO/Standard 15961 (OID-IRI notation);

• urn:oid:1.0.15961.ff (URN notation - RFC3061).

At the physical layer, the first few bits are an DSFID (Data Storage Format Identifier) representing the format of the data saved in the remaining memory block specified in the ISO/IEC 15961 and in the ISO/IEC 15962. It is typically 8-bit, but may also be extended further, as specified in the standard. The DSFID consists of 3 fields: • Access Method, (2 bit)

• Extended Syntax Indicator (ESI), (1 bit)

• Data Format, (5 bit)

The access methods are the fundamental encoding rules for data compaction and formatting. The standard ISO/IEC 15962 stipulates, in fact, different access methods: (00) No-Directory, (01) Directory, (10) Packed Objects, (11) Tag Data Profiles. When the DSFID specifies the access method (10), then the format of the remaining part of the User Memory is Packed Objects. This format maximizes the compression of the data, therefore minimizing the amount of data to be stored in the tags and the amount of data exchanged in the interface air, at the expense of more complex encoding. The Packed Objects mechanism offers advantageous performance and functionalities to the ISO/IEC 15962:2004 so much so that it is envisaged incorporating it in the next version of the ISO/IEC 15962.

The bit ESI indicates whether a second DSFID byte is present or not, while the Data Format field represents the format of the Packed Objects and coincides, according to the standard RFC3061, with the field ff of the URN notation. Encoding in the Packed Objects format consists in an Application Interface (AI) sequence which includes one or more compacted name-value pairs.

US 2007/262849 Al describes an integrated RFID reader which combines active and passive RFID technology in order to allow automatic identification of each object equipped with an active or passive RFID tag. The integrated RFID reader uses a single antenna or a double antenna and two transceivers with a firmware module for reading and receiving data from active and passive tags.

The technical problem which is posed is therefore that of developing a communication system which uses RFID technology for data packet exchange via a virtual communication channel and an associated method for data packet exchange within this communication system.

DESCRIPTION OF THE INVENTION

The present invention will now be described in detail with reference to examples of embodiment and the accompanying figures. In said figures:

Figure 1: shows a diagram of the structure of the memory blocks of an RFID tag of the type EPC Class 1 Gen2; Figure 2: shows a diagram of the structure of the block EPC BANK of an RFID tag of the type EPC Class 1 Gen2;

Figure 3: shows a schematic representation of the hierarchical relationship between the component parts of an example of a communication system according to the present invention;

Figure 4: shows a schematic representation of examples of embodiment of RFID technology networks (RANs) within the example of the communication system according to Fig. 3;

Figure 5: shows a diagram of the structure of the block EPC BANK of an RFID tag of the type EPC Class 1 Gen2 intended for use in the communication system according to the invention;

Figure 6: shows a schematic representation of an example of an AFI defined according to the present invention;

Figure 7: shows an exemplary diagram of the structure of the block TID BANK of an RFID tag of the type EPC Class 1 Gen2;

Figure 8: shows an example of a definition table according to the invention for the field User Memory Size of the TID Bank of an RFID tag of the type EPC Class 1 Gen2;

Figure 9: shows the diagram of an example of the structure of the block USER BANK of an RFID tag of the type EPC Class 1 Gen2 intended for use in the communication system according to the invention;

Figure 10: shows an example of the table ISO/IEC 15961 Format 24 defined according to the method of the present invention;

Figure 11: shows an example of the decision table for the number of Cluster Packed Object (AI blocks) to be used for encoding a Packed Object;

Figure 12: shows an example of the structure and of a number of substructures of a Cluster Packed Object according to the invention;

Figure 13: shows an example of the Discovery Table present in an RFID reader belonging to the communication system according to the invention;

Figure 14: shows an example of a number of operations performed during an addressing step according to the method of the present invention;

Figure 15: shows a table containing the meaning of a number of messages used during the communication step of the method according to the invention;

Figure 16: shows examples of read operations carried out successfully in a communication step of the method according to the invention;

Figure 17: shows examples of unsuccessful read operations during a communication step of the method according to the invention; Figure 18: shows examples of interaction between Master and Tag in an example of a communication system according to the invention, during a control step;

Figure 19: shows examples of interaction between Reader and Tag in an example of a communication system according to the invention, during a control step.

Let us consider an environment in which N RFID Readers and M RFID Tags of the type EPC Class 1 Gen2 are present. Of these N RFID Readers, a number must consist of type class A (referred to below as Master) and the remainder of type class B (referred to below as ALE Client Reader). Class A reader is understood as meaning a device with more complex logic and hardware, often characterized by several communication interfaces (RFID, IEEE 802.11, IEEE 802.3, UMTS, Bluetooth, etc.). Class B reader instead is understood as meaning a device with logic and hardware of minimum complexity, characterized mainly by basic operations such as reading and writing of the tags by means of the single RFID communication interface. Moreover, a higher entity Master Control (MC) is defined, the Masters interacting therewith by means of one of the interfaces other than the RFID interface for the management of their addresses (Fig. 3). The Master Control is a server device with which the Masters are associated by means of their IP address or MAC address, according to one of the most common connectivity standards (IEEE 802.11, IEEE 802.3, Bluetooth, etc.), chosen as required. The addressing and synchronization logic by means of the IP address or MAC address is therefore dependent on the connectivity standard available on the Master. The added value of the Master Control defined in this invention is that of issuing to each Master a unique sequential 5-bit address, referred to below as ID Master, in order to optimize the resources and procedures for data storage on the RFID tags. The Master Control therefore performs a NAT (Network Address Translation) operation from IP or MAC address to ID Master.

Each Master defines one or more RAN (RFID Area Networks), i.e. a set of ALE Client Readers and RFID Tags, the Master of which is the coordinator for initialization and management (the RAN is equivalent to a WPAN in the case of Bluetooth or to a WLAN in the case of IEEE 802.11). The ALE Client Readers and the RFID Tags will belong to a RAN in a non-exclusive manner, i.e. they may belong to several RAN coordinated by the same or by a different Master (Fig. 4). This choice leaves room for future implementations, such as the possibility of differentiating the RANs depending on the type of traffic exchanged.

The Discovery Tables are defined in the Masters and in the ALE Client Readers and are used to determine the RFID Tags which a Master may use as a communication channel for transferring data to an ALE Client Reader and vice verse within a RAN. For this purpose the RFID Tag, in particular its User Bank, may be suitably structured. In addition to the standard ISO/IEC 15962, which already regulates encoding and decoding of the User Bank, the method for compression and framing of the Packet Objects is considered.

A new Packed Object and a new AFI (Application Family Identifier - ISO/IEC 15961) are therefore defined. By means of these new data structures, the Master and the ALE Client Readers manage the following steps by means of the RFID Tags:

a. Addressing Step

b. Communication Step

c. Control Step

These three steps embrace the general operating principle of the method proposed. Before describing them, a new AFI, a new Packed Object and the new data structure, i.e. Discovery Table, are defined.

The proposed method ensures full compatibility with the standard EPC Class 1 Gen 2. As a prerequisite, in fact, a number of already standardized memory fields are used, these requiring suitable settings. In particular, these are for the EPC Bank (Fig. 5):

• User Memory Indicator (UMI) - 1 bit. If equal to "1" this indicates that the Bank 11 is present and contains data. If it is equal to "0" and the decimal bits of Bank 11 covering the interval 3 to 7 are equal to "00000" (Data Format field), then the Bank 11 is present but not initialized; if it is equal to "0" without Data Format, the Bank 11 is not present. The proposed method requires the presence of Bank 11.

• Toggle - 1 bit. EPC global applications (bit "0") and ISO applications (bit "1") are distinguished. The proposed method supports ISO applications.

• Attribute/AFI - 8 bit. If the Toggle bit is equal to "1", the EPC bank contains an AFI defined according to ISO 15961 and an Individual Unique Identity. If the Toggle bit is instead equal to "0", then the EPC bank contains Attribute bits and an EPC Code. The proposed method requires the definition of a new AFI, AFI = 24 (in binary 00011000) (Fig. 6).

For the TID Bank (Fig. 7):

• User Memory Size - 16 bit. This is defined as the number of 16-bit words in the User Bank. Based on this value, Fig. 8 is defined, where n is a multiplier which, as we shall see below, will allow the new Packed Object to be adapted depending on the size of the User Bank.

or the User bank (Fig. 9):

• Data Storage Format Identifier (DSFID) - 8 bit. When the DSFID specifies the access method (10), then the format of the remainder of the user memory is of the Packed Objects type. This is in fact the access method used. The third bit indicates the Extended Syntax Indicator which in this case is equal to "0". The last 5 bits define, finally, the Data Format: (i) "00000" in the case where the User Bank is not initialized, (κ/ΊΙΟΟΟ" in the new case of User Bank encoded for "Communication Channel" (Data Format 24). In effect, the new DSFID is 10011000 while the new table ISO/IEC 15961 Format 24 is shown in Fig. 10. From the table it can be seen how a block of AIs, distinguished by the multiplier n, is repeated. This block is referred to as Cluster Packed Object (CPO). Depending on the size of the User Bank, the associated multiplier n and therefore the number of CPOs (AI blocks) to be used for encoding (Fig. 11), are defined. The CPO is therefore regarded as a frame and the Packed Object as a multiframe structure.

The AIs of the new Packed Object defined are now considered in detail:

a. Cluster Map (CM) - l*n bit. This consists of a variable bit number depending on the size of the User Bank. A CPO is associated with each bit. If the bit is "1", then this means that the CPO is already being used, otherwise it is available for writing. Each bit of the CM refers to a precise offset, i.e. indicates the start of the CPO concerned.

b. Priority Level (PL) - 2*n bit. It is possible to define for each CPO up to 4 priority levels. Only 3 priority levels are used, the last level being reserved for future implementations (Fig. 12):

• Priority Level 1 (00): indicates a low priority;

• Priority Level 2 (01): indicates a medium priority;

• Priority Level 3 (10): indicates a high priority;

• (11): for future implementations.

c. ID Reader Source (DDRS) - 5 bit. Identifier of the source reader which could coincide with an ID Master or with a Reader Address Lease previously assigned.

d. ID Reader Destination (IDRD) - 5 bit. Identifier of the destination reader (IDRD=11111 means that the message is broadcast) which could coincide with an ID Master or with a Reader Address Lease previously assigned. e. ID RAN (IDRAN) - 2 bit. Identifier of the RAN

f. Count Success (CS) - 4 bit. Counter for successful read operations.

g. Count Insucce'ss (CI) - 4 bit. Counter for unsuccessful read operations. h. Sequence Number (SN) - 5 bit. Sequence number of the packet (SN=00000 means that the packet has not been segmented, but is unique).

i. Reader Address Lease (RAL) - 5 bit. New reader address issued by a Master for its RAN sequentially.

j. Π) Master (IDM) - 5 bit. Identifier of the Master issued by a higher entity

(Master Control) to which the Master is connected via one of its interfaces.

k. Π) RAN Lease (IDRANL) - 2 bit. Identifier of the RAN. This is different from IDRAN since, as we shall see below, different management steps may be involved

1. Reservation Bits (RB) - 2 bit. Pair of bits which allows management of the Reader-Tag-Reader address:

• 00: the Reader Address Lease has not been assigned; this value will be present in the Discovery Table of a Master;

• 01: the Reader Address Lease has been assigned; this value will be present in the Discovery Table of a Master;

• 10: the Reader Address Lease has been acquired; this value will be present in the Discovery Table of an ALE Client Reader;

• 11: the memory occupied by the triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" is made available for other Masters.

m. Check Bits (CB) - 2 bit. Pair of bits which allows, as we shall see during the control step defined below, updating of the Discovery Tables should a Master or an ALE Client Reader be no longer available;

• 00: the Discovery Table updating mechanism is not considered;

• 01: control of the route on the Discovery Table is required at the request of the Master;

• 10: control of the route on the Discovery Table is required at the request of the ALE Client Reader;

• 11: for future implementations.

n. Payload (PLD) - 76 bit. Exchange data between readers.

Finally, the Discovery Table present on each Master or ALE Client Reader is defined (Fig. 13). This new data structure will be similar to a "routing table" for routes from the Master to the ALE Client Reader and vice versa. ID Tag is the 96- bit identifier (any other size which is considered is of no interest for the proposed method) of the RFID Tag which is obtained directly from the EPC Bank. It is important to consider this field since a Master could extend its RAN to different RFID Tags. The Discovery Table is stored inside the Readers since it is assumed that the memory of the Tag is limited.

ADDRESSING STEP

During this step the Master initializes the RFID Tags (should they not be already initialized) in order to manage the addressing step. By means of this step, in fact, the Discovery Tables of the Master and the ALE Client Reader are "populated", allowing one or more RAN to be defined for each Master as well as, for the same RAN, the definition of several routes for the data exchanged between the same Master-ALE Client Reader pair (by using different RFID Tags). Only some AIs of the CPO are taken into consideration for initialization of the RANs and management of the addresses within them, and in particular:

• Reader Address Lease

• ID Master

• ID RAN Lease

• Reservation Bits

Below operation is described in the form of sequential steps:

1) The Master receives a unique address (ID Master) from the closest Master Control.

2) The Master interrogates the RFID Tags present in its cover range, verifying the UMI:

• if UMI=1, Toggle=l and AFI=00011000, step 4 and step 5 are omitted (the structure is already initialized);

• if UMI=0 and bits [3:7] of the DSFID are "00000" (i.e. is the first Master which writes the Tag), Toggle=l and AFI=00011000 are set and the next steps are performed;

• if UMI=0 and the DSFID does not exist, then the RFID Tag is without User Bank and the next Tag is analyzed (if available);

• if UMI=1 and Toggle≠l or AFI≠00011000, the Tag may be used again as communication channel (if not password protected) by setting UMI=0, Toggle=l and AFI=00011000 and proceeding with the following steps; if password protected, the next Tag (if available) is analyzed. 3) The Master interrogates the User Memory Size of the TID Bank in order to determine how many CPOs are available for use (and therefore the AI range) on the basis of the Packed Object ISO/IEC 15961 Format 24. Therefore, once the multiplier n has been defined, it is possible to determine the AIs to be used for the Tag. For example for 512 bits, n=4 and AI[0:52].

4) The Master initializes the fields of the Packed Object: "Cluster Map", "Priority Level", "ID Reader Source", "ID Reader Destination", "ID RAN", "Count Success", "Count Insuccess", "Sequence Number", "Reader Address Lease", "ID Master", "ID RAN Lease", "Reservation Bits", "Check Bits", "Payload" and "Bit unused" where required. All the fields which are not of interest during this step remain only initialized, while the other fields ("Reader Address Lease", "ID Master", "ID RAN Lease", "Reservation Bits") are defined below.

5) The Master sets UMI=1.

6) The Master issues sequential addresses in "Reader Address Lease" for its RAN "ID RAN Lease", entering the value "00" as "Reservation Bits", for the associated Tag (this entry is stored both in the Tag and in the Discovery Table of the Master). The ALE Client Reader (or another Master) which reads the Tag, after being aligned with the number of CPOs to be used, also performing step 3, checks that the AI "Reservation Bits" is "00" and, if this is the case, extrapolates the AI "ID Master", "Reader Address Lease" and "ID RAN Lease", checks whether it already belongs or not to the RAN of that Master for that Tag and, if this is not the case, updates the corresponding Discovery Table, entering "10" as "Reservation Bits", while the value of "Reservation Bits" on the Tag is changed to "01" (Fig. 14).

7) The Master intervenes periodically to control the AIs for managing the addresses and checks whether the "Reservation Bits" is equal to "01", thus updating the associated Discovery Table and issuing a next address (therefore updates again the "Reservation Bits" to "00"). When it establishes that on the Tag an associated triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" has not been read and therefore modified for a given time period, it may decide to release the resource, entering the value "11" in the respective AI "Reservation Bits". The field "Reservation Bits" is updated to "11" also in the Discovery Table, so as to be able to propose again the corresponding entries of the Discovery Table during a subsequent time period. COMMUNICATION STEP

During this step reading and writing of the Tags are performed for exchange of information between Master and ALE Client Reader. It is necessary to make a distinction between unicast and broadcast communication. "Unicast communication" is understood as meaning an exchange of messages directed from the Master to a single ALE Client Reader which, for each message received, will free the associated resource occupied on the RFID Tag as acknowledgement mechanism. Since exchange of a same message probably takes place on several Tags, then the ALE Client Reader could have to free the resources on several Tags. "Broadcast communication" is instead understood as meaning an exchange of messages directed from the Master to all possible ALE Client Readers which are listening for the same Tag. In this case, following the read operation by each ALE Client Reader, it is not possible to release the corresponding resource as in the case of unicast communication (it is not known who must yet read the message). An algorithm, Memory Resource Management (MRM), is defined for this purpose and will check suitable "counters" and set the time intervals for rereading of the same ALE Client Readers. The MRM will deal with release of the communication resources (i.e. the Tags) also in the case where a Master must write information on a Tag which is already saturated, introducing the concept of priority.

Once it has been verified that Toggle=l and AFI=00011000, both the Master and the ALE Client Reader check the UML

The components of the proposed system have a different behaviour depending on the following cases:

A. UMI=1 and Master

B. UMI=0 and ALE Client Reader

C. UMI=1 and ALE Client Reader

The condition "UMI=0 and Master" is implicitly considered during the addressing step.

A. UMI=1 and Master The Master proceeds in the following manner:

1. It interrogates the User Memory Size of the TID Bank in order to determine how many CPOs may be used (and therefore the AI range) on the basis of the Packed Object ISO/IEC 15961 Format 24. Therefore, once the multiplier n has been defined, it is possible to determine the AIs to be used for the Tag. For example for 512 bits, n=4 and AI[0:52]. 2. It checks whether one of the bits of the CM is set to "0" so as to be able to write on the associated CPO, i.e. AI(0) occurs. Considering n=4, if for example AI(0)=1101 occurs, this implies the possibility of writing on the third CPO. The priority of the message is moreover set, choosing from among the 3 levels available (Priority Level 1, Priority Level 2, Priority Level 3). In the case of broadcast communication, Priority Level 3 is always considered.

3. It defines the fields of the CPO (initialization has already occurred during the addressing step). "ID Reader Source", "ID Reader Destination", "ID RAN", "Count Success", "Count Insuccess", "Sequence Number" and "Bit unused" where required.

4. In the case where the CM is formed by "1" only, it is necessary instead to use the algorithm MRM for any release of resources. 2 bits of the PL correspond to each bit of the CM and distinguish the priority thereof. If the message which the Master wishes to write has a priority which is strictly greater than one of the priorities defined by PL, then the corresponding CPO will be engaged, updating the "Priority Level", otherwise the message "NoWriteAccess" will be returned (Fig. 15). Obviously, the CPO with the lowest priority overall, and not the first CPO with a lower priority, is replaced. In the case of identical lower priorities, the CPI with greater CI value is released.

5. Although the algorithm MRM envisages a gradual release of the resources, ensuring fairness, it is possible for a Master to increase the priority of the message whenever the message "NoWriteAccess " is received.

B. UMI=0 and ALE Client Reader. The RFID Tag is without the User Bank. In this case the message "UserMemoryEmpty" will be returned to the ALE Client Reader (Fig. 15).

C. UMI=1 and ALE Client Reader. The following procedure is adopted:

1. The ALE Client Reader interrogates the User Memory Size of the TID Bank in order to determine how many CPOs are available for use (and therefore the AI range) on the basis of the Packed Object ISC7IEC 15961 Format 24.

Once the multiplier n has been defined, it is possible to determine the AIs to be used for the Tag. For example for 512 bits, n=4 and AI[0:52]. 2. The ALE Client Reader interrogates the AI(0) in order to obtain the Cluster Map and in particular information about which bits are set to "1". The size of the Cluster Map is variable, for example in the case of 512 bits it consists of 4 bits. If all the bits are set to "0", then there is no information to be read and the message "ClusterMapNull" is returned (Fig. 15). If instead there are bits set to "1", then it is required to interrogate for each corresponding CPO the AIs which refer to the IDRD. Assuming that CM=1011, the ALE Client Reader will interrogate AI(3), AI(28), AI(41).

3. Whenever there is no correspondence with the IDRD of each CPO, the message "NoFindlDRD" is returned (Fig. 15). If, instead, the IDRD stored in the Tag coincides with that of the ALE Client Reader, then it is required to verify the AIs "Sequence Number", "ID Reader Source" and "ID RAN" of the corresponding CPOs. Assuming that for AI(3) and for AI(41) there is no matching, but that there is for AI(28), then the field AI(32), the field AI(27) and the field AI(29) are interrogated in order to check whether the ALE Client Reader has already acquired in a preceding read operation the Payload identified by that Sequence Number, by that ID Reader Source and by that ID RAN, respectively.

4. The information may be of the unicast or broadcast type. Let us consider a message of the broadcast type. If the information associated with the triplet "ID Reader Source" - "ID RAN" - "Sequence Number" has been already acquired beforehand by an ALE Client Reader, the message "DuplicatePayload" will be returned (Fig. 15) and the field "Count Insuccess" will be incremented; if this is not the case, the field "Payload" will be interrogated and the field "Count Success" will be incremented. In the case of both Count Insuccess and Count Success the information is not deallocated from the Tag because it potentially continues to be available for other ALE Client Readers. For example, if the triplet AI(27)-AI(29)- AI(32) refers to a Payload which has already been acquired, then AI(31)=0001 (assuming that it has been the second access to the CPO); if, instead, the triplet AI(27)-AI(29)-AI(32) relates to a new Payload, then AI(38) is interrogated and AI(30)=0001 is modified (assuming that it has been the first access). If the information is instead of the unicast type, the ALE Client Reader will modify the bit "0" on the CM. Therefore the fields "Count Insuccess" and "Count Success" intervene only if the message is broadcast (Fig. 16 shows examples of successful read operations). 5. In the case of a broadcast message, whenever an ALE Client Reader performs a read operation on a CPO which requires an increment of the field "Count Insuccess", it checks whether (CS - CI) > 0 by means of its algorithm MRM. If the condition is established, the ALE Client Reader will not perform any further operation, otherwise it will modify the corresponding bit to "0" on the CM in order to free the memory resource on the Tag (Fig. 17 shows examples of unsuccessful read operations). A same reader may access the User Bank for the same CPO only after a given period of time calculated by a generic algorithm (e.g. the exponential backoff algorithm known in literature).

CONTROL STEP

This step relates to updating of the Discovery Table. It may be initiated both by a Master and by an ALE Client Reader. This step allows checking as to whether or not a Master and/or an ALE Client Reader and, implicitly, also a Tag are present within a RAN over time. The following cases may be distinguished:

A. ALE Client Reader no longer present

B. Master no longer present

C. Tag no longer present

A. ALE Client Reader no longer present A Master which wishes to renew its entry in the Discovery Table sends the triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" with "Check Bits" equal to "01". An ALE Client Reader which recognizes the triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" present in its Discovery Table modifies the "Check Bits" on the Tag to "00" so as to communicate to the Master that it is still present (Fig. 18). If the Master verifies instead that the "Check Bits" continues to be "01" for a given period, then it may decide to deallocate the entries relating to that ALE Client Reader from its Discovery Table.

B. Master no longer present An ALE Client Reader which wishes to renew its entry in the Discovery Table sends the triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" with "Check Bits" equal to "10". A Master which recognizes the triplet "Reader Address Lease" - "ID Master" - "ID RAN Lease" present in its Discovery Table modifies the "Check Bits" on teh Tag to "00" so as to communicate to the ALE Client Reader that it is still present (Fig. 19). If the ALE Client Reader establishes instead that the "Check Bits" continues to be "10" for a given period, it may decide to deallocate the entries relating to that Master from its Discovery Table. A temporal reference managed by the clock of the Reader (both Master and ALE Client Reader) is associated, in fact, with each entry of the Discovery Table. A lease time is therefore defined for each entry in the Discovery Table which distinguishes its validity: until the lease time has lapsed, no checking operations are performed for that entry. Upon expiry of the lease time, the corresponding entry is checked and the lease time is renewed (in a similar manner to that which happens with the lease time for the DHCP of Internet networks).

C. Tag no longer present When a Master or an ALE Client reader establishes that a Tag is no longer in their operating range, the entries in the Directory for that Tag are eliminated. A minimum number of interrogations (Thrnumber) which a Master and/or ALE Client Reader must consider before proceeding with updating of the Discovery Table is therefore defined.

To conclude, the Addressing and Control steps share common AIs of the Packed Object ISO/IEC 15961 Format 24, and therefore may not be carried out simultaneously for the same CPO. The communication step is instead independent and uses AIs exclusively and therefore may be always associated simultaneously with the Addressing or Control step for a same CPO. However, in general, several steps may be managed simultaneously on different CPOs of the same RFID Tag.

It is therefore clear how with the communication system and method according to the present invention it is possible to create so-called RAN (RFID Area Networks), consisting of a group of RFID readers and tags with functions for performing data exchange in unicast or broadcast mode within the generic RAN. Within each RAN, in fact, the communication channel used by the Readers consists of the residual memory portions (suitably processed) in RFID Tags present in the coverage area of the said readers; tags which form the physical communication means via which data exchange is performed.

The method according to the invention also defines a protocol for enabling and managing this interaction between RFID readers via RFID tags within the communication system.

The communication system described in the present application is therefore an RFID ecosystem in which devices based on RFID technology alone (i.e. Readers) may, by using the method according to the present invention, exchange data via the pre-existing RFID tags which are arranged in their vicinity and without the aid of further communication technology. Although the subject of the present invention has been described with reference to a particular preferred embodiment, it is understood that the scope of protection of the present application is defined exclusively by the following claims.

Claims

1. Communication system for data packet exchange, characterized in that it comprises:

(i) at least one RFID reader, i.e. Master, provided with a plurality of different communication interfaces;

(ii) at least one RFID reader, i.e. ALE Client Reader, provided with a single RFID communication interface;

(iii) a plurality of RFID Tags enabled for read and write operations;

(iv) a server, i.e. Master Control Server, provided with a plurality of different communication interfaces.

2. Communication system according to Claim 1, wherein the Master Control Server has, associated therewith, at least one of the Master readers, each of which is identified by a unique ID Master address issued by the Master Control which communicates with said Masters by using, from among the plurality of communication interfaces, an interface other than the RFID interface.

3. Communication system according to Claim 1, wherein at least one Master reader defines and coordinates one or more RFID technology local Networks, RAN (RFID Area Networks), with which a set of ALE Client Readers and a set of RFID Tags are associated, each RAN being identified by an IDRAN identifier issued by the Master reader.

4. Communication system according to Claim 3, wherein each ALE Client Reader and/or each RFID Tag is associated simultaneously with different RANs created by the same Master reader and/or by different Master readers.

5. Communication system according to Claim 3, characterized in that the RFID Tags are of the type EPCglobal Classl Gen2 equipped with a user memory block, User Bank, as well as the remaining three memory blocks: Reserved Bank, EPCBank, TID Bank; the data exchange between the Master reader and the ALE Client Readers belonging to the same RAN being performed by means of said RFID Tags.

6. Communication system according to Claim 5, wherein in each Master reader and each ALE Client Reader there is defined a Discovery Table structure comprising: (i) an address of the ALE Client Reader issued by a Master reader sequentially for a given RAN;

(ii) the identifier ID Master of the Master reader issued by a Master Control server;

(iii) an identifier IDRAN of the RAN issued by a Master reader;

(iv) a pair of bits for managing the addresses issued by the Master reader to the ALE Client Reader;

(v) a pair of bits for managing updating of the Discovery Table;

(vi) an identifier of the RFID Tag obtained from the memory block EPC Bank of the EPCglobal EPC Tag Data Standard;

said Discovery Table structure being designed to reserve and keep updated all the possible routes from a Master reader to an ALE Client Reader and vice versa.

7. Communication system according to Claim 5, characterized in that each RFID Tag belonging to the system has an AFI (Application Family Identifier) with decimal value "24", binary value 00011000, stored in the memory block EPC bank of the EPCglobal EPC Tag Data Standard.

8. Method for coordinating and synchronizing data packet exchange within a communication system comprising:

(i) at least one RFID reader, i.e. Master reader, provided with a plurality of different communication interfaces;

(iii) a plurality of RFID Tags enabled for read and write operations;

(iv) a server, i.e. Master Control Server, provided with a plurality of different communication interfaces;

characterized in that the Master Control Server has, associated therewith, at least one of the Master readers, for each of which the Master Control Server performs a NAT (Network Address Translation) operation, issuing a unique ID Master address, and with which it communicates using, from among the plurality of communication interfaces, an interface other than the RFID interface.

9. Method according to Claim 8, wherein a Master reader defines and coordinates one or more RFID technology local networks, RAN (RFID Area Networks), with which a set of ALE Client Readers and a set of RFID Tags are associated, and issues to each RAN an IDRAN identifier.

10. Method according to Claim 9, wherein each ALE Client Reader and/or each RFID Tag is associated simultaneously with different RANs created by the same Master reader and/or by different Master readers.

11. Method according to Claim 8, wherein the data exchange between the Master reader and the ALE Client Readers belonging to the same RAN is performed by using RFID Tags of the type EPCglobal Classl Gen2 equipped with a user memory block, User Bank, in addition to the remaining three memory blocks: Reserved Bank, EPC Bank, TID Bank;

12. Method according to Claim 9, characterized in that a Discovery Table structure is defined and used for each Master reader and for each ALE Client Reader, said structure being designed to reserve and keep updated all the possible routes from a Master reader to an ALE Client Reader and vice versa and being formed by:

(i) an address of the ALE Client Reader issued by a Master reader sequentially for a given RAN;

(ii) the identifier ID Master of the Master reader issued by the Master Control Server;

(iii) an identifier IDRAN of the RAN issued by a Master reader;

(v) a pair of bits for managing updating of the Discovery Table;

13. Method according to Claim 8, characterized in that an AFI (Application Family Identifier) with decimal value "24", binary value 00011000, is defined and the same is stored in the memory block EPC Bank of the EPCglobal EPC Tag Data Standard, wherein the presence of said AFI in the memory block EPC Bank of an RFID Tag indicates that the Tag belongs to the communication system.

14. Method according to Claim 13, characterized in that each reader is able to access the block AFI of a tag and recognize whether it belongs to the communication system and can be used for data packet exchange.

15. Method according to Claim 14, characterized in that each reader is able to access the AFI block of a tag, modifying it to the decimal value "24", binary value 000110000, so as to include it in the communication system and use it for data packet exchange.

16. Method according to Claim 12, wherein, in order to store in the memory block User Bank of the EPCglobal EPC Tag Data Standard of each RFID Tag the information necessary for operation of the system, a Cluster Packed Object data structure is used, said structure comprising the following fields:

(i) an identifier of the source reader which may be the identifier of a Master reader or the identifier of an ALE Client Reader;

(ii) an identifier of the destination reader which may be the identifier of a Master reader, the identifier of an ALE Client Reader, or the identifier of a broadcast transmission;

(iii) the identifier IDRAN of the RAN;

(iv) a counter which updates the successful read accesses for each Cluster Packed Object;

(iv) a counter which updates the unsuccessful read accesses for each Cluster Packed Object;

(vi) a numerical field which distinguishes the sequence number of the data packet exchanged;

(vii) the address of the ALE Client Reader issued by a Master reader sequentially for a given RAN;

(viii) the identifier of the Master reader ID Master;

(ix) an additional identifier of the RAN, ID RAN Lease;

(x) a pair of bits for managing the addresses issued by the Master reader to the ALE Client Reader;

(xi) a pair of bits for managing updating of the Discovery Table;

(xii) a data packet which is to be exchanged between a Master reader and an ALE Client Reader.

17. Method according to the preceding claim, wherein the destination reader is enabled to exchange traffic of both the unicast type and the broadcast type.

18. Method according to Claim 16, wherein a new Packed Object is used in order to store in the memory block User Bank of the EPCglobal EPC Tag Data Standard of an RFID Tag the information necessary for operation of the system, said new Packed Object consisting of:

(o) a variable number of Cluster Packed Objects; (i) a variable size field, Cluster Map, which establishes how many Cluster Packed Objects are defined and which of these are free or occupied;

(ii) a variable size field, Priority Level, which establishes the priority level of each Cluster Packed Object;

(iii) a field of unused bits for integrating the data packets used for exchange so as to provide them with a constant length.

19. Method according to Claim 18, characterized in that the choice of the number of Cluster Packed Objects is performed depending on the size of the memory block User Bank envisaged by the EPCglobal EPC Tag Data Standard.

20. Method according to Claim 8, characterized in that it envisages three system operating steps:

(i) an "addressing" step for managing the addresses, in which the Discovery Tables are populated;

(ii) a "communication" step, in which the data packets are exchanged;

(iii) a "control" step in which updating of the Discovery Table is performed.

21. Method according to Claims 20 and 18, wherein the "addressing" step involves the following:

(i) the Master readers and the ALE Client Readers interrogate the field "User Memory Size" of the memory block TID Bank envisaged by the EPCglobal EPC Tag Data Standard in order to align themselves with the number of Cluster Packed Objects according to Claim 18 to be used;

(ii) the Master readers and the ALE Client Readers access the single memory blocks of each single Cluster Packed Object;

(iii) the bit pair, Reservation Bits, for managing the addresses is designed to indicate whether an address has been assigned to an ALE Client Reader or has not been assigned;

(iv) each Master reader issues for a given RAN sequential addresses to be assigned to the ALE Client Readers which can be reached by means of the RFID tags onto which it writes, updating also the associated Discovery Table.

22. Method according to Claims 20 and 18, wherein the "communication" step involves the following:

(i) the Master readers and the ALE Client Readers interrogate the field "User Memory Size" of the memory block TID Bank according to Claim 18 to be used; (ii) the Master readers and the ALE Client Readers access the single memory blocks of each single Cluster Packed Object;

(iii) the Master readers and the ALE Client Readers interrogate the field Cluster Map of a Packed Object according to Claim 16 in order to determine which Cluster Packed Objects are available for the read and write operations;

(iv) a priority level for the type of exchanged data is defined for each single Cluster Packed Object;

(v) the Master readers and the ALE Client Readers proceed with different functional steps depending on whether the memory block User Bank envisaged by the EPCglobal EPC Tag Data Standard is present or not.

23. Method according to Claims 20 and 18, wherein the "control" step involves the following:

(i) the Master readers and the ALE Client Readers interrogate the field "User Memory Size" of the memory block TID Bank envisaged by the EPCglobal EPC Tag Data Standard of an RFID Tag in order to align themselves with the number of Cluster Packed Objects according to Claim 18 to be used;

(iii) the bit pair, Check Bits, is used as an indicator for distinguishing a control procedure initiated by a Master reader from a control procedure initiated by an ALE Client Reader.

24. Method according to Claims 22 or 23, wherein a Memory Resource Management protocol is used for allocating and deallocating the Cluster Packed Objects on the basis of:

- the number of read operations of the Cluster Packed Object which are successful; the number of read operations of the Cluster Packed Object which are unsuccessful; and

- the priority level of each Cluster Packed Object;