Method and apparatus for maintaining continuous synchrounous encryption and decryption in a wireless communication system throughout a hand-off

Method and equipment for keeping continuous synchronization encryption and decryption during handover in wireless communication system

The present invention generally relates to a radio communication system, and more particularly to a dual-channel radio communication system, which includes a method and equipment for synchronous encryption and decryption.

Synchronous counter-driven encryption techniques for full-duplex digital wireless communication systems are known. This kind of system usually uses separate encryption and decryption devices to encrypt and decrypt the transmitting and receiving channels in each communication unit. In each communication unit, a separate encryption and decryption device is used, which makes the communication unit expensive and bulky, and it also complicates the synchronization between the two devices.

In order to maintain synchronization between two linked communication units, the conventional system must transmit an encrypted synchronization signal (E-sync) while transmitting encrypted information. When the transmitted information is stored data that can be interrupted arbitrarily, Sending an encrypted synchronization signal (E-sync) is not a problem. On the other hand, sending E-sync in a voice communication system becomes difficult to some extent, because the sound information is continuous, and it is impossible to be periodically interrupted by E-sync transmission without generating in the received audio signal. Noticeable intermittent or noise pulses.

Some conventional audio encryption systems periodically "appropriate" bits from the audio information and use the embezzled bits to send E-sync. This theory is: if only infrequently embezzled bits, the lack of these bits will not seriously affect Voice. However, the lost bits will still reduce the voice quality to a certain extent, causing the encryption system to use the misappropriated voice bits in the subjective test method of the voice quality. The encryption mode is regarded as the unencrypted mode, that is, the "clear" mode. .

In wireless communication systems, the problems encountered by conventional encryption technology in handover from one fixed communication unit (PCU) from one fixed communication unit to another fixed communication unit (FCU) are related to the work process of handover. When two communication units are connected, the encryption device of the transmission path of each communication unit provides an encrypted synchronization signal (E-sync) on the encryption device of the corresponding receiving path of the other communication unit. Therefore, after the handover to a new FCU, the encryption synchronization will disappear for a period of time. During this period, the encryption device in the PCU will resynchronize with the new E-sync from the new FCU, and the new FCU will be resynchronized. The encryption device is resynchronized with the E-sync from the PCU.

Since the loss of the encrypted synchronization signal will cause the loss of all communication information during the time of handover and re-synchronization, the conventional encryption system used to send continuous information such as voice will return to the clear mode before each handover. After sufficient time required for encrypted synchronization has completely passed, switch to encrypted mode again. This naturally causes a short period of time when the reliability of the transmitted information is impaired during each handover.

Therefore, there is a need for an encryption technology to overcome the aforementioned conventional encryption technology problems. In other words, there is a need for an encryption technology that can continuously work in encryption mode during handover without loss of information. There is a need for an encryption technology that does not reduce the sound quality, and there is a need for a technology that is less expensive and smaller than conventional encryption technologies.

In a wireless communication system, the method of keeping the synchronous encryption and decryption of information without interruption when the handover is completed includes a set of fixed communication unit (FCUS) and at least one portable communication unit (PCU), the fixed communication unit (FCUS) includes A fixed communication unit (FCU) encrypted synchronization counter (ESC), portable communication unit includes (PCU) a portable communication unit encrypted synchronization counter (PCU EDC), PCU and FCU are used to generate and receive digital structure and include a periodic repeat The synchronization flag is used to synchronize the transmitted signal. This method includes the following steps: a) To receive the handover from the first wireless connection with the first FCU to the PCU connected with the second antenna of the second FCU, between one PCU and the second FCU After the wireless connection is established, a continuous value is loaded into the content of the second FCU ESC in the second FCU. This continuous value includes the value expected to be obtained in the PCU ESC after the handover.

b) After the handover is completed, PCU ESC and FCU ESC start to increase synchronously starting from the continuous value installed in step (a).

Fig. 1 is a block diagram of a radio communication system according to the preferred embodiment of the present invention.

Fig. 2 is a frame content of time division multiplexing and time division duplexing in accordance with the Digi-tal European Cordless Telecommuications (DECT) standard according to the preferred embodiment of the present invention.

Fig. 3 is a block diagram of a fixed communication unit (FCU) according to a preferred embodiment of the present invention.

Fig. 4 is a block diagram of a portable communication unit (PCU) according to the preferred embodiment of the present invention.

Fig. 5 is a block diagram of an encrypted synchronization counter (ESC) according to the preferred embodiment of the present invention.

Fig. 6 is a flowchart of a synchronous encryption and decryption method for generating influence information of a single encryption sequence according to the preferred embodiment of the present invention.

Fig. 7 is a flowchart of a method for keeping the synchronous encryption and decryption of information uninterrupted during handover according to the preferred embodiment of the present invention.

Referring to FIG. 1, a radio communication system according to a preferred embodiment of the present invention includes a set of fixed communication units (FCUS) 102 to provide radio frequency coverage for a set of radio frequency coverage areas 108, 110, 112. The FCU is connected to a public switched telephone network (PSTN) 114 through a set of telephone lines 116. Those skilled in the art know that the wireless communication system according to the present invention is not only used in the Public Switched Telephone Network (PSTN), but also used in telephone systems such as branch offices. Moreover, the system includes at least one portable communication unit (PCU) 120 capable of handover and capable of transmitting and receiving in time division multiplexing and time division duplex (TDMA/TDD) digital formats. The system also includes at least one The wired telephone 124 is used to send and receive calls to and from the portable communication unit (PCU) 120. One portable communication unit 120 can communicate through other portable communication units in one or more fixed communication units (FCIS) 102.

According to the present invention, the use of a communication standard protocol between multiple FCUs and at least one PCU in the wireless communication system is further realized. The standard protocol defines messages and procedures for requesting and reestablishing radio communication links, for sending and receiving signal data, for sending and receiving user communication information, and for defining time division multiplexing and time division duplexing used here Format. An example of a standard protocol like this is the Digital European Cordless Telecommunications (PECT) standard. The DECT standard is defined in the European Telecommunications Standards document préTS-300175 entitled "Digital European Cordless Telecommunications Public Interface". It was formulated by the European Telecommunications Standards Association in August 1991. The application parts 2, 3, and 5 of the document 7 merged into reference files.

Referring to Figure 2, a time division multiplexing/time division duplex frame structure 201 constructed according to the DECT standard according to the preferred embodiment of the present invention includes twelve time slots 202 for fixed communication unit (FCU) transmission and ten Two time slots 203 are used for mobile communication unit transmission. The time slots 202, 203 are organized based on the location of the transmitted and received information. For example, a fixed communication unit 102 (Figure 1) transmits information in the time slot 202 labeled "0" and receives information in the time slot 203 labeled "0". Each time slot 202, 203 contains a synchronization part. 204 and a data section 205. The intermediate synchronization part contains a synchronization flag for link synchronization between a portable communication unit (FIG. 1) 120 and a fixed communication unit 102. The data part 205 includes a control part 206 and a user data part 208. The control part 206 is used to transmit control information, that is, the frame mark of the link between the portable communication unit 120 and the fixed communication unit 102, time slot identification and other control information. , The user data part is used to carry user data, such as speech.

According to the present invention, the synchronization part 204 and the control part 206 are used to synchronize the encryption and decryption of the information carried in the user data part 208, and are also used to synchronize the user signal carried in the control part 206. By using the existing parts 204, 206 of the DECT time slots 202, 203 to synchronize the encryption and decryption processes, there is no need to steal bits from the user data part 208. Therefore, according to the present invention, this encryption and decryption technology will not reduce the voice quality like the conventional encryption and decryption technology that uses bit diverting for synchronization. By obtaining synchronization signals between the fixed communication unit 102 and the portable communication unit 120 (FIG. 1) to synchronize the encryption and decryption circuits, a smaller part needs to be used for synchronization, thereby reducing the portable communication unit (PCU) 120 and the fixed communication unit 102 Cost and volume.

In operation, the frame synchronization part of the time division multiple access/time division duplex (TDMA/TDD) circuit (described in order here) in the fixed communication unit (FCU) 102 and the portable communication unit (PCU) 120, so that when the control part 206 When the user signal information is included, the encryption and decryption of the information is possible during the transmission of the control part 206 and the transmission of the user data part 208. The time division multiple access/time division duplex (TDMA//TDD) circuit makes encryption and decryption impossible during transmission of all other parts. achieve.

Referring to Fig. 3, according to a preferred embodiment of the present invention, the fixed communication unit 102 (Fig. 1) includes a radio frequency (RF) transceiver 302 for transmitting and receiving including time division multiple access/time division multiplexing ( TDMA/TDD) format is a radio frequency signal for transmitting and receiving digital information. The radio frequency transceiver is connected to the microprocessor 304 through the bus 306, and the microprocessor 304 is used to control the transceiver 302. The microprocessor 304 is connected to the frame synchronization circuit 307 of the system through the bus 306. The frame synchronization circuit 307 is used to maintain the frame synchronization between all the fixed communication units (FCUS) in the system. The frame synchronization circuit 307 terminal 305 receives the main system synchronization signal. If the different delays between the public switched telephone network 114 and a group of fixed communication units 102 (FIG. 1) are adjusted, the main synchronization signal can be obtained from, for example, the synchronization flag therein.

The radio frequency (RF) transceiver 302 is also connected to a time division multiple/time division duplex (TD-MA/TDD) circuit 308. The TDMA/TDD circuit 308 combines the radio frequency transceiver 302 with a modulo two accumulator 309 to complete The audio-to-digital and digital-to-audio codecs (CODECS) 310 of the fixed communication unit (FCU) 102 that transmit and receive signals are connected. This set of codecs (CDDECS) 310 is connected to a set of telephone interfaces 312, and the telephone interface 312 is used to connect a set of telephone lines 116 to the codecs 310. The modulo two accumulator 309 is connected to the encrypted synchronization counter (ESC) 314. The encrypted synchronization counter (ESC) 314 is operated at the rate of the codec 310 and the time division multiple access/time division multiplexing (TDMA/TDD) circuit 308. Driven by the serial bit rate increasing clock generator 315, the modulo two accumulator 309 is also synchronized with the synchronization signal of the main system through the time division multiple access/time division multiplexing (TDMA/TDD) circuit 308, which is described in the present invention as the pass codec The information between 310 and TDMA/TDD circuit 308 provides encryption and decryption.

Time Division Multiple Access/Time Division Duplex Circuit (TDMA/TDD) 308, Codecs (CODECS) 310, Increasing Clock Generator 315, Encrypted Synchronization Counter (ESC) 314 and Telephone Interface 312 are all connected to provide control via microprocessor 304 On the bus 306. The memory 316 is also connected to the microprocessor to store program control software and two sets of values. One storage location 320 is reserved for the encrypted synchronization counter (ESC) content, and the other storage location 318 is for handover. Complete time reservation, each of the two sets of corresponding storage locations 320, 318 is paired with the corresponding fixed communication unit 102 for receiving and transmitting time division multiplexing/time division duplex (TDMA/TDD) time slots 202 , 203 (Figure 2) is related.

When a pair of receiving and transmitting TDMA/TDD time slots 202, 203 (Figure 2) carries user information, the content value of the encrypted synchronization counter (ESC) at the end of each TDMA/TDD time slot 202, 203 is stored In the corresponding paired receiving and transmitting TDMA-TDD time slots 202, 203, the storage location 320 reserved for the encrypted synchronization counter ESC content value, but the storage location 318 reserved for the handover completion time is not used. The value stored in the location 320 reserved for the contents of the encrypted synchronization counter (ESC) is used to refresh the encrypted synchronization counter (ESC) at the beginning of the next corresponding paired receiving and transmitting time slot 202, 203. According to the present invention, As described above, by using the memory 316, a single encrypted synchronization counter (ESC) provides encryption and decryption of information on all TDMA/TDD time slots 202, 203 used by the entire fixed communication unit, thereby reducing the fixed communication unit ( FCU) cost and volume.

When a transmission/reception time slot pair does not carry user information and only waits for the start of a link or the completion of an ongoing handover, it corresponds to the waiting time slot pair that is reserved for the memory location 320 of the encrypted synchronization counter ESC content. It is used to store the starting value of a PCU sending that affects the start of the link or the continuous value that affects the ongoing handover. According to the present invention, as long as an ongoing handover points to a TDMA-TDD time slot pair, the memory location 318 corresponding to the TDMA-TDD time slot pair used for the handover completion time is used to control the handover time.

4, according to the preferred embodiment of the present invention, the portable communication unit (PCU) 120 includes a radio frequency (RF) transceiver 402 for transmitting and receiving including time division multiple access/time division duplex (TDMA/TDD) ) The radio frequency signal of the data information transmitted or received in the format. The radio frequency transceiver is connected to the microprocessor 404, and the microprocessor 404 controls the transceiver 402 via the bus 406. The radio frequency transceiver 402 is also connected to a time division multiple access/time division duplex (TDMA/TDD) circuit 408. The TDMA/TDD circuit 408 connects the radio frequency transceiver 402 to the CODEC 410 through a modulo two accumulator 409. Together, the CODEC is used to convert the signals sent and received by the portable communication unit 120 from audio to digital and digital to audio, respectively. The modulo two accumulator is also connected to the encrypted synchronization counter (ESC) 414 driven by the generator 415. The up-clock counter (ESC) 414 uses the codec (CODEC) 410 and time division multiple access/time division duplex (TDMA/TDD). ) The serial data rate of the circuit works, and the CODEC410 is used to provide encryption and decryption of the information transferred between the CODEC410 and the TDMA-TDD circuit 408. By using a single encrypted synchronization counter (ESC) 414 for encryption and decryption of TDMA/TDD information, the cost and volume of the portable communication unit are reduced compared with the conventional encryption and decryption technology using separate transmitting and receiving devices.

The increased clock generator 415 synchronizes with the frame synchronization signal flag received from the radio link of the fixed communication unit (FCU) 102 through the time division multiple/time division duplex (TDMA/TDD) circuit 408, and the frame synchronization signal flag is in the fixed position. The communication unit (FCU) area is synchronized by the main system synchronization signal of the terminal 305 (FIG. 3), and the codec 410 is connected to send information to and from the portable communication unit (PCU) 120 to a user of the portable communication unit 120. One of the users receives the signal on the audio interface. The time division multiple access/time division duplex (TDMA/TDD) circuit 408, CODEC 410, increased synchronous clock generator 415, encrypted synchronous counter (ESC) 414 and voice interface 412 are also connected to the bus 406 controlled by the microprocessor 404, The memory 418 is also connected to the microprocessor 404 to store program control software. It also stores the contents of the encrypted synchronization counter 419 and the value of the handover completion time 420 respectively. The values on the memories 419, 420 are determined by The microprocessor decides to send from a portable communication unit to a fixed communication unit. According to the present invention, these two values are used for the link start value and the link handoff. A display 417 for displaying information sent from the microprocessor 404 is also connected to the microprocessor 404, and a keyboard for receiving control signals input by the user is also connected to the microprocessor 404.

Referring to FIG. 5, according to the present invention, the preferred embodiment of encrypted synchronous counters (ESC) 314, 414 includes a shift register 502 with a parallel data input port 504, and a parallel port enable terminal (PE) of the shift register 502 506: Allow the parallel data input port 504 to load the start value and the continuous value from the microprocessors 304 and 404 (FIG. 3, FIG. 4) into the shift register 502. According to the present invention, the shift register 502 has a clock input terminal 508 driven by an increasing clock generator 315, 415 (Figure 3, Figure 4), and the microprocessor 304, 404 enables the clock enable terminal 510 to allow or disable the The codecs (CODECS) 310, 410 and the time division multiple access/time division duplex (TDMA/TDD) circuits 308, 408 (FIG. 3, FIG. 4) transfer information both for encryption and decryption. The shift register is used as a linear feedback shift register. Its final stage output 512 and intermediate output 518, 514 are fed back to its serial data input terminal 522 through modulo two accumulators 516, 520, and connected in this way, the shift The bit register outputs 512 at the last stage to generate a predefined midline bit sequence, which is used to synchronize the encoding and decoding of the information.

More preferably, in order to obtain greater reliability, the serial bit sequence output at the output port 512 of the last stage is sent to a key stream generation algorithm device 524, which is sent to the key stream generation algorithm device by a microprocessor The devices 304 and 404 (FIG. 3, FIG. 4) are initialized from a key variable provided by a KV port, and a reliable encryption sequence is generated at the final output terminal 526. A device like this is the TRN4836A device produced by Motorola (Inc. ofschaumburg, Iuinois) located in Schaumburg, Illinois. The serial signal output at the final output terminal 526 is accumulated in the modulo two accumulators 309 and 409 (FIG. 3, FIG. 4) to complete the encryption and decryption of the information sent and received by the fixed communication unit 102 and the portable communication unit 120.

More preferably, in the fixed communication unit 102, a separate and unique key variable is used for each time division multiple access/time division duplex (TDMA/TDD) time slot pair 202, 203 (Figure 2), each Separate and unique key variables for each TDMA/TDD time slot pair 202, 203 are stored in the memory 316 (Figure 3), at the beginning of each associated time division multiple access/time division duplex (TDMA/TDD) The microprocessor 304 (Figure 3) is transferred to the KV port 528. As just described, in the fixed communication unit 102, the use of separate and unique key variables for each time slot pair provides a greater degree of encryption reliability , While still allowing the use of a single encryption counter ESC containing a single key power flow generation algorithm device to generate all time division multiple access/time division duplex time slots 202, 203.

Referring to FIG. 6, according to a preferred embodiment of the present invention, the method of influencing the synchronous encryption and decryption of information by generating a single encryption sequence includes receiving in the portable communication unit 120 (FCU) 102 (FIG. 1). Fig. 1) The registration information from the portable communication unit 120 (Fig. 1) when the link is established between the fixed communication unit (FCU) 102 and the registration information contains an encrypted user identification code (CPIN) as a result of receiving the registration information In response, the fixed communication unit 102 decrypts 604 a corresponding user identification code (PIN) with a predefined algorithm, and stores the user identification code in an encrypted synchronization counter (ESC) (ESC) dedicated to the time slot of the fixed communication unit 102 link. 3) In the storage location 320 where the content is reserved, because the user identification code is also stored in the portable communication unit (PCU) 120, the microprocessors 304, 404 in the fixed communication unit 102 and the portable communication unit 120 (Figures 3, 4) The value of the user identification code will be loaded into their respective encryption plus synchronization counter (ESC) (Figures 3, 4) at step 606 at the appropriate time described below.

When the link is established to prepare for user communication, the microprocessor 304 in the fixed communication unit 102 and the microprocessor 404 in the portable communication unit install the user identification code into the 608-step encryption synchronization counters 314, 414, respectively, and at the same time The fixed transmitting unit 102 allows the clock enable terminals 510 of the respective encrypted synchronization counters 314 and 414 at the start time of the next synchronization mark in the signal synchronization part 204 (FIG. 2) sent by the transmission time slot 202 (FIG. 2). Those skilled in the art believe that as long as the same signal is used in the fixed communication unit 102 and the portable communication unit, and the clock enable terminal 510 of the encrypted synchronization count 314, 414 is activated at the same time, the portable communication unit 120 will transmit in the PCU transmission time slot 203. The synchronization part 204 of the signal can also be used to activate the respective increasing clock generators 315, 415.

During the reestablishment of the link, the increased clock generators 315, 415 of the encrypted synchronization counters (ESC) 314, 414 synchronize 609 through the time division multiple access/time division duplex circuits 308, 408 (FIGS. 3, 4), respectively, as a pair of fixed communication The unit 102 (FIG. 1) sends a response of the synchronization mark reproduction of the synchronization part of the signal.

As is well known to those skilled in the art, if the first serial bit stream and the second pseudo-random serial bit stream with the same rate and synchronization as the bit-serial bit stream in the modulo two accumulator (exclusive OR logic) Gate), a new encrypted serial bit stream will be generated at the output of the modulo two accumulator. If this new (encrypted) serial bit stream is synchronized with and the same as the second pseudo-random) sequence The third pseudo-random serial bit stream of is accumulated in the modulo two accumulator 2, and the output of the modulo two accumulator will generate a serial bit stream exactly the same as the first serial bit stream. Therefore, the present invention provides a method and device for realizing synchronous encryption and decryption of information by generating a single encryption sequence, which is used to control the encryption and decryption that occurs in the fixed communication unit 102 and the mobile communication unit 120.

Referring to FIG. 7, according to the preferred embodiment of the present invention, the method for keeping the encryption and decryption of information uninterrupted during handover includes: the portable communication unit 102 linked with the first fixed communication unit 120 (FIG. 1) determines whether 701 is It is necessary to handover to another fixed communication unit 120, and then select the crossover completion time, the selected handover completion time and the subsequent FCU transmission time slot used by the first fixed communication unit 102 for the link 202 The synchronization flags in the synchronization part 204 (FIG. 2) of the transmitted signal occur at the same time. In the same step 710, the portable communication unit 120 calculates the handover duration value, that is, the desired value of the encrypted synchronization counter (FIG. 4) of the portable communication unit 120 at the time when the selected handover is completed.

In the next step 702, the portable communication unit 120 and the second fixed communication unit 102 establish a second wireless link, and send the duration value and the selected handover completion time. Because the handover completion time coincides with the subsequent synchronization mark in the synchronization part 204 (Figure 2) that is sent by the first fixed communication unit in the FCU transmission time slot 202, and because all the fixed communication units in the system must be synchronized with each other. In the main system synchronization of the port 305 (FIG. 3) in the fixed communication unit 102, the second fixed communication unit 102 can determine the handover time quite accurately.

The second fixed communication unit 102 (FIG. 1) stores the duration value and the handover completion time in step 706, stores the contents of the encrypted synchronization counter (FIG. 3) in the memory location 320, and stores the crossover in the memory location 318 Switch completion time (Figure 3). The memory locations 320 and 318 are respectively related to the time division multiple access/time division duplex (TDMA/TDD) time slots of the second wireless link used by the fixed communication unit 102.

When the selected handover completion time is up, the microprocessor 304 (Figure 3) accesses its memory 316 to restore the persistence value, loads the persistence value into the encryption synchronization counter 314 (Figure 3) in step 708, and then starts the encryption synchronization The increasing clock of the counter (ESC) 314 starts the encrypted synchronization counter ESC of the second fixed communication unit 102, and starts counting with the value reached at the same time by the encrypted synchronization counter 414 (FIG. 4) of the portable communication unit 120.

During the duration of the second wireless link, the increased clock generator 315 of the encrypted synchronization counter 314 of the second fixed communication unit 102 and the increased clock generator 415 of the encrypted synchronization counter 414 of the portable communication unit are respectively time-division multiple access/ The TDMA/TDD (TDMA/TDD) circuits 308, 408 are synchronized with each other, and step 709 responds to the periodic synchronization flag of the synchronization part 204 (FIG. 2) of the signal sent by the second fixed communication unit 102 (FIG. 1).

Therefore, the present invention includes a method and device for realizing synchronous encryption and decryption of information, which controls the encryption and decryption occurring in the fixed communication unit 102 and the portable communication unit 120 by generating a single encryption sequence. Moreover, the present invention includes a method and device for keeping the synchronization encryption and decryption of information uninterrupted during handover. Therefore, the present invention provides an encryption technology that overcomes the above-mentioned problems in the conventional encryption technology. It provides: (a) Encryption technology that can continuously work in encryption mode without loss of information during handover, (b) Technology that does not carry out bit embezzlement and therefore does not reduce voice quality, (c) It is more cost-effective than conventional encryption technology Encryption technology of lower and smaller encryption system.