MXPA00005713A - Initialization of handsets in a multi-line wireless phone system for secure communications - Google Patents

Abstract

A wireless telephone system, having one or more wireless handsets and a base unit. Each handset has a handset transceiver, and the base unit has a base transceiver and a handset docking station, which has a wired interface. The base unit digitally communicates over an RF channel with a handset via its handset transceiver only if the handset has previously been initialized by the base unit. The handset is initialized via the wired interface when it is physically docked in the docking station.

Description

INITIALIZATION OF HEADPHONES IN A MULTI-LINE WIRELESS TELEPHONE SYSTEM TO ENSURE THE COMMUNICATIONS BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to multi-line wireless telephone systems, and in particular, to providing secure communications in a time division multiplexed (TDM) wireless telephone system.

Description of Related Art The use of telephones and telephone systems, including wireless telephone systems, is widely spread. In wireless telephone systems, a wireless telephone handset unit communicates via analog or digital radio signals with a base unit, which is normally connected via a conventional telephone line to an external telephone network. In this way, a user can use the wireless headset to engage in a telephone call with another user through the base unit and the telephone network. Multi-line wireless telephone systems are being used in different situations, such as business with many phone users. These systems employ a headset that communicates with up to N handsets in a simultaneous manner, typically with digital communication schemes, such as an extended-spectrum time division multiple access (TDMA). In a TDMA system, a single radio frequency channel is used, and each headset transmits and receives data during a dedicated slice or time slot within a cycle or global time. It is desirable to provide different features, such as features and capable of private branch exchange (PBX), in a multi-line wireless telephone system. A problem that can be found in these situations is the violation of security. For example, an unauthorized third party may use an "illicit" wireless headset to communicate through the base unit. Without adequate security, these and other types of security breaches can occur. Patent Application Number 0,034,998 (Philips NV), March 1, 1989, discloses a wireless telephone system where one. The base station stores a security address code assigned to a plurality of headphones, and the headphones also store the code assigned to each handset and transmitted to the handset by the base unit during recharging. U.S. Patent No. 5,625,888 (Rüther et al.), April 29, 1997, describes a process for combining transmitting / receiving devices of a wireless communication system to form a communication unit. U.S. Patent No. 5,371,783 (Rose et al.), December 6, 1994, describes a method for continuously monitoring the status of a radio frequency link. European Patent Application Number 0,301,573 (Nippon Electric Co.), February 1, 1989, describes the registration of new cordless telephones in an existing system.

COMPENDIUM A wireless telephone system, which has one or more wireless headsets and a base unit. Each headset has a headset transceiver, and the base unit has a base transceiver, and a headset platform station, which has a wired interface. The base unit communicates digitally over a radiofrequency channel with a handset by means of its headset transceiver only if the handset has been previously initialized by the base unit. The handset is initialized by means of the wired interface when it is physically robbed at the platform station.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a TDMA multi-line wireless telephone system, for initializing the system wireless headphones, in accordance with one embodiment of the present invention. Figure 2 is a schematic representation of the message format for an initialization message exchange between the base unit and a handset of the telephone system of Figure 1, by means of a wired link, to initialize the handset, in accordance with one embodiment of the present invention. Figure 3 is a flow diagram illustrating the initialization of the handset made by the system of Figure 1, from the point of view of the base station, in accordance with one embodiment of the present invention. Figure 4 is a flow diagram illustrating the initialization of the handset made by the system of the Figure 1, from the point of view of the headset being initialized, according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED MODE Referring now to Figure 1, a block diagram of the multi-line TDMA multi-line digital wireless telephone system 100 is shown, in accordance with one embodiment of the present invention. The TDMA system 100 comprises a base unit 110, which has receiver and transmitter units 112 and 111, respectively, and is coupled to the external telephone network 116 via telephone lines 115. The base unit 110 also comprises the platform station 118, to receive a wireless headset, and provide a wired interface between the base unit 110 and the headset. In addition, the base unit 110 also has a controller / microprocessor 113 for controlling and monitoring the overall functions of the base unit 110. The system 100 also comprises N wireless headphones 120- ^, 120 ^, ... 120 ^. Each has a transmitter and receiver unit (transceiver), such as transmitter 121 and receiver 122 of handset 120-j_. In one embodiment, the receiver unit 112 comprises N logical receivers, and the transmitter unit 111 comprises N logical transmitters, such that the receiver and transmitter units 112 and 111 provide N logical transceiver units, one for each of The N wireless headphones. At any given time, M headphones (0 <M <, N) are operating or active (i.e., in the process of conducting a telephone call). The telephone system provided by the system 100 preferably operates in the unlicensed 900 MHz band, and preferably provides features such as those of a small PBX, in conjunction with the PC 140. In one embodiment, the system 100 employs a combination of time division multiplexing (TDM), such as TDMA, and frequency band selection to overcome sources of interference, and to maintain reliable links between the base station and the headphones. In a digital TDMA scheme, each headset transmits or receives only data during its own "slice of time" or slot. Accordingly, the system 100 provides a wireless network between the base station 110 and each handset 120j_ (1 <i> N). In one embodiment, N = 4, such that the system 100 comprises a maximum of 4 wireless headphones, each having unique time slots in the TDMA time dedicated to them. As explained above, the lack or violation of security in this system is undesirable. Accordingly, the telephone system of the present invention is configured to minimize this problem, and to provide secure and robust communications between the headphones and the base unit. In the present invention, the base unit 110 is configured in such a way that it communicates only with headphones that can provide certain unique identifier (ID) information, or security code. This identification information may include information such as the slot number assigned to the handset (for example, one of the numbers 1 to 4 in a system of 4 lines, 4 slots, 4 headphones), as well as the handset serial number, and / or the serial number of the base (or security codes based on the serial number), and the like. Only the headphones 120. which have been initialized by the base unit 110 will be able to provide this information to the base unit 110; therefore, all uninitialized headphones will not be able to communicate as part of the telephone system 100. In an alternative mode, in addition to the use of security codes, such as the serial number, and the slot number, a code is employed programmable mixer by the user. In this mode, during initialization, the handset user is asked to enter a random mixing seed. This mixing seed is then stored both in the headset and in the base unit, and it is used to mix all future TDMA communications between the two. Because only the initialized handset and the base unit know the mixing seed, an unauthorized handset or other transceiver device will not be able to go to the channel or use the handset slot. Accordingly, the user-programmable mixer provides an extra layer of security. In an alternative embodiment, the mixing code or seed can be selected automatically by the base unit and / or the handset, without asking the human user for input. The system 100 is configured in such a way that the base unit 110 has a physical platform station 118 or receptacle / port where the uninitialized handset 120j_ can be physically placed, to provide a wired link and interface between the headset 120 and the headset. base unit 110. Then the base unit initializes the handset via the wired link. Because the physical location of the base unit and its platform station or port can be controlled, and access to them can be limited to authorized persons, and because a headset must physically be docked at the platform station with In order to enter the initialization, only an authorized person can initialize a headset. Accordingly, in the present invention, only the headsets that have been initialized by the handset via the wired link, as a result of actions of an authorized user, may have telephone communications with the telephone system, thereby providing security of the communication. The present invention is described in more detail below, with reference to Figures 2 to 4. Referring now to Figure 2, a schematic representation of the message format 200 for an initialization message exchange between the base unit 110 is shown. and an earphone 120_ of the telephone system 100 of Figure 1 via a wired link, for initializing the handset 120. in accordance with one embodiment of the present invention. The message format 200 comprises a plurality of fields 201-209 for the exchange of information between the base unit 110 and a handset 120 ^, by means of the wired link provided by port 118, which are exchanged for the purpose of initializing the handset . The messages sent to a handset docked 120j_ from the base unit 110, have the format of message 200, as well as the messages sent to the base unit 110 from a docked headset 120¿. Port 118 can also be duplicated as the recharging port or the stand where the earphone can be placed to recharge its battery. Whenever an uninitialized handset 120 is placed on port 118 and is to be initialized, the base unit 110 provides information to the handset, and vice versa, to initialize the handset, so that future TDMA communication can be conducted. In one embodiment, this information includes a security code or ID 205, a slot number 204, and a mixing seed 207. In one embodiment, the security code is based on the serial number of the handset, and is preferably a 32 bit number. The security code may be identical to the serial number, or a part or subset thereof. In an alternative mode, the security code is based on the serial number for the base unit, instead of, or in addition to, that of the handset. The security code is used to authenticate the handset each time messages are exchanged between the base and a handset. In addition to the time slot mechanism, this security code provides a secure exchange of messages from the base to the handset. The slot number for the handset is a 3-bit number, which is assigned by the base unit 110, and is transmitted via the wired link to the handset. The slot number is a unique time slot number, which distinguishes the earphone 120 ^ from other earphones in the system 100. The blender seed is an 8-bit number, also based on the serial number of the base unit, or in an alternative way, programmable by the user through a serial computer interface or other input (for example, the wireless telephone keypad), and is used to generate the code that randomizes the transmitted information spectrum. Because this coding employs a deterministic mapping, which is known only to the handset transceivers and the base unit, it can provide additional security, as described further. In one embodiment, the message format is a 72-bit field 200 that has an unused field 208 for future expansion, as shown in Figure 2. The message number field 201 is a 4-bit field, a module generated at each end of a transmission, which helps keep track of the other end's state. This field is also used for positive recognitions. The message type field 202 is a 4-bit field, used to indicate different types of messages that may possibly be exchanged between the base and the headphones. The new / existing field 203 is a 1-bit field that indicates whether the handset is a new handset or an existing handset, where 0 = new handset. For packets originating from the base unit 110, this field will always be set to 0. As described above, the local number field 204 is a 3-bit field indicating the local number (slot) assigned to an existing handset . This number is ignored if the new / existing field 203 is set to 0. The 32-bit identification field 205 indicates the security code or identification, which is derived from the factory-designated identification for the headset 120j_. This will form the basis for secure communications between the base and the registered headphones with the base (that is, initialized). A 5-bit acknowledgment message field 206 contains the 4-bit message number being recognized, plus 1 acknowledgment bit. In this format, bits 0-3 represent the message number that is being recognized, and bit 4 represents the negative acknowledgment if it is 0, and positive acknowledgment if it is 1. Recognition generation is based on CRC verification at the receiving end. The mixer seed field 207 is an 8-bit field used to seed the mixer into the radio frequency link. It forms an additional layer of security. This can be generated by default from the factory code, or it can be programmed through the serial computer interface by a user. The CRC code field 209 is an 8-bit cyclic redundancy check code for error detection and correction. Referring now to Figure 3, there is shown a flow chart 300 illustrating the initialization of the handset 120j_ performed by the system 100 of Figure 1 under the control of the CPU 113, from the point of view of the base station 110, in accordance with one embodiment of the present invention. A headset placed or "docked" on port 118 can already be initialized and docked only for recharging. Alternatively, an uninitialized handset (that is, either a "new" handset that has never been initialized, or a handset previously initialized for a different base unit) can be docked at port 118 in order to initialize the handset. handset for base 110. Additionally, an already initialized handset can be docked at port 118 for the purpose of reprogramming or changing some of the initialization parameters, i.e., reinitializing the handset. In the latter cases, the headset may still need recharging. Accordingly, the base unit 110 first groups the relevant input / output device to detect the presence of the handset on the recharging support, that is, port 118 (step 301). When a headset 120i is docked at port 118 (i.e., the recharging stand), the base unit 110 first checks to see if the headset battery voltage level 120j_ is above a certain threshold that would allow normal operation of the headset. earphone (step 302). If not, no additional processing steps take place until the handset is recharged to a sufficient voltage. Once the threshold voltage requirement is met (step 302), the base unit 110 initiates the message protocol, according to the message format 200, sending the initial message through the wired interface of port 118 to the handset. 120 (step 303). This message is a signature on the message that is indicated in the message type field 202 with 0. This initiates a sequence of events that are described from the point of view of the base unit 110 in Figure 3, and from the point view of handset 120 ^ in Figure 4. All messages exchanged between handset and base are of an asynchronous nature. The general goal of this procedure is to allow a normal recharge, or initialize an uninitialized handset. In the initial message, the base unit 110 fills the following fields: message number field 201, message type field 202 (where the signature in the message = 0), and the CRC field 209. (If the CRC does not In this case, the base unit 110 sends a retransmission message to the handset (not shown in Figure 3). CRCs need recognition, even when not indicated in Figure 3). At this point, the base unit 110 waits for recognition from the handset 120j_ (step 304). If an acknowledgment is not received before a stopwatch gives time out, the procedure starts again (steps 305, 306, 301). If a recognition is received before the time out (step 304), then the base unit 110 can determine whether the docked handset is "new", or has already initialized (step 311). The headset 120., in step 311, may have one of three states: it may be a new headset, it may already be initialized by the base unit 110, or it may have been initialized previously by a different base unit. In the event that the handset message indicates a new handset (in which case, the handset message contains the handset identification in field 205), the base needs to verify whether it has a total number or slot available (step 312). For example, in a system of four headphones, if four headphones are already initialized, and therefore, registered with the base unit 110, there will be no available slot. If the base unit 110 has a local number available, then the base unit 110 will assign it to the headset by updating the message fields (step 313). In this case, the base unit 110 fills the following fields for the message: message number field 201, message type field 202, unique system identification field 205, local slot number assignment field 204, field of mixer seed 207, and CRC field 209. In this case, field ID 205 contains the serial number of base unit 110. If it is determined that handset 120 is new, but there is no slot available (step 312), the base unit 110 assumes that the user is trying to replace an existing headset with the headset 120_. In this case, the user is asked to provide information about which local number needs to be replaced. This is done by a message sent from the base to the headset, which then displays a Local Number request, and an audio warning (step 321). Once a response with a valid slot number is received from the handset as a result of this question (steps 322, 323), the base unit 110 completes the local slot number assignment, and fills in the fields specified for the message (step 313). If no answer is received from the handset, a timeout is issued, and the base starts at the top of its execution (step 324). When the handset 120_ is not a new handset (step 311), the base unit 110 verifies the 32-bit identification, the local number, and the mixing seed transmitted by the handset 120.¡_. If these numbers match the information stored in the memory of the base unit 110, the base program is exited (step 331). If there is a bad coupling, then the base sends a reprogram message (message mole = 8) to the handset (steps 331, 332). This message is filled in the following fields: message number field 201, message type field 202, and CRC field 209. If the base unit 110 receives an acknowledgment. positive, follow the processing chain as if you were dealing with a new headset, so you can reinitialise the headset (steps 333, 312). In case you receive a negative acknowledgment or give time out, leave the service routine (steps 333, 334, 335). Referring now to Figure 4, there is shown a flow diagram 400 illustrating the initialization of the earpiece 120 ^ performed by the system 100 of Figure 1, from the point of view of the earphone 120 ^, in accordance with a modality of the present invention. As will be appreciated, the processing flow in the handset 120 'is a mirror of that of the unit 110, described above with reference to Figure 3. Once the initial signing message is received correctly from the base (step 403), the headset 120j_ responds with an acknowledgment that includes the old / new information and the related handset (step 404). In particular, if the handset is new, it responds (step 404) with a message that fills the following fields: message number field 201, message type field 202 (= 1), new / existing handset field 203 (= 0; "new"), and CRC field 209. If the handset 120j_ has already been initialized, it responds with a message that has the following fields filled: message number field 201, message type field 202, new / existing handset field 203 (= 1; "pre-initialized"), unique identification field of system 205, local slot number assignment field 204, mixing seed field 207, and CRC field 209. The remainder of the processing chain shown in the Figure 4 (steps 405 et seq.) Is a reflection of the actions requested by the base. As discussed above, the 120 ^ headset needs to have an answer for each of the possible states it may be in. In particular, depending on its initial state (which is one of three possible conditions discussed in the previous section), the base may request the following actions: local slot number assignment (step 406); that the user provide local message assignment (step 407); or bad identification coupling of the handset against the base (step 408) (involving a request for a possible reprogramming of the handset based on the user's request). This allows a headset to be recharged in another base, with the user requesting this action only. Also, in the case where only a loading function is performed, not a single ring tone when the action is finished. All other actions of the handset upon completion will result in a unique ring tone (step 425), which signals to the user that the handset and base have finished their actions. It will be understood that those skilled in the art can make different changes in the details, materials, and configurations of the parts that have been described and illustrated above for the purpose of explaining the nature of this invention, without departing from the principle and scope of the invention. as described in the following claims.

Claims (9)

1. A wireless telephone system (100), which comprises: (a) one or more wireless headsets (120), each headset (120_) comprising a headset transceiver (121, 122); and (b) a base unit (110) comprising: (1) an earphone platform station (118) having a wired interface, characterized in that the base unit further comprises: (2) an element for initializing the handset by means of the wired interface, when the handset is physically docked at the platform station, reading from the handset a unique headset security code over a single headset serial number permanently stored in the handset, and storing the unique headset security code locally in the base unit; and (3) a base transceiver (111, 112) to communicate over a channel with each handset (120_) by its headset transceiver only if the base unit determines, after receiving the headset security code for this handset from the headset. headset, that the handset has been previously initialized by the base unit.

2. The system of claim 1, wherein: the initializing element further comprises an element for providing (313) to the handset, a unique base unit security code based on a unique base unit serial number; and the base transceiver is for communicating with a given handset only if (331) the handset provides the base unit with the security code of the base unit and the security code of the handset.

The system of claim 1, wherein the base transceiver comprises an element for establishing a time division multiple access (TDMA) link with each handset by means of the handset transceiver, in accordance with a time of TDMA that assign exclusive audio packet time slots to each handset; the item for initializing further comprises an element for providing the handset with an exclusive audio packet slot number corresponding to its time slot of the audio packet; and the base transceiver is for communicating with a given handset only if the handset provides the base unit with the headset security code and the audio pack slot number.

The system of claim 1, wherein: the base unit and the handset each comprise elements for mixing the digital communications between the base transceiver and the handset according to a unique mixer seed (207) for the handset, which it must be known both by the base transceiver and by the handset; and the item for initializing further comprises an element for providing the headset, and for storing locally in the base unit, the mixing seed for the headset.

The system of claim 1, wherein: each headset is energized by battery, by means of a rechargeable battery; and the platform station comprises a charging element for recharging the battery of a handset physically docked at the platform station.

The system of claim 1, wherein: the base unit comprises an element for determining whether the headset battery physically docked at the platform station has a voltage lower than a threshold level (302), wherein the element for initializing it comprises an element for waiting until after the battery voltage has been recharged above the threshold level (302), before initializing the handset.

The system of claim 1, wherein the handset and the base unit comprise an element for exchanging initialization messages during initialization, according to a message format (200) comprising a plurality of fields.

8. A method for providing communication between a base unit (110) of a wireless telephone system (100) and one or more wireless headphones (120) system, the base unit comprising a base transceiver (111, 112), and a headset platform station (118) having a wired interface, each headset (120) comprising a headset transceiver (121, 122), a method characterized by the steps of: (a) initializing a headset via the wired interface, when the headset is physically docked at the platform station, reading from the handset a unique headset security code based on a unique headset serial number permanently stored in the handset, and storing the unique headset security code locally in the base unit; and (b) conducting digital communications, over a radio frequency channel, between the base unit and the handset, by means of the transceivers of the base unit and the handset, respectively, only if the base unit determines, upon receiving the security code of the headset for that headset from the headset, that the headset has been previously initialized by the base unit.

9. A base unit (110) for communicating with one or more wireless headsets (120), each headset (120j_) comprising a headset transceiver (121,122), which comprises: (a) a headset platform station (118) having a wired interface, characterized the base unit because it also comprises: (b) an element to initialize the headset by means of the wired interface, when the headset is physically docked at the platform station, reading from the earphone a headset security code unique based on a unique headset serial number permanently stored in the handset, and storing the unique headset security code locally in the base unit; and (c) a base transceiver (111,112) to communicate over a channel with each handset (120j_) via its headset transceiver, only if the base unit determines, upon receiving the headset security code for that handset from the handset, that the handset has been previously initialized by the base unit.