Kokusai Denshin Denwa Co., Ltd.

Masayoshi Ohashi

Toshinori Suzuki

Seiichiro Sakai

Akira Yamaguchi

Toshio Mizuno

Yoshio Takeuchi

Fumio Watanabe

Yutaka Yasuda

Yoshihiko Nodera

An interworking apparatus for roaming among a plurality of mobile network having different inter-network signaling protocols is connected to the plurality of mobile networks and has a database record for holding network identity information for identifying a mobile network to which at least one mobile user (mobile station and another mobile terminal such as IC device) to be traced is visited.

Interworking apparatus for roaming among different mobile networks

The radio communication system has at least one first radio station such as a base station and a plurality of second radio stations such as mobile stations. The base station at least possesses a public key, and each of the mobile stations possesses a public-key cryptography function for using the public key and an identity itself. An identity confidentiality method includes steps of generating a time-varying public key at the base station based upon a predetermined time initial, and repeatedly broadcasting, from the base station, the generated time-varying public key to all the mobile stations. The mobile stations cipher their respective identities with the broadcasted time-varying public key so that the encrypted/identities of the mobile stations, which are sent to the base station, remain confidential. After enciphering their identity, the mobile stations wait to be called. When a mobile station is to be called, the base station enciphers the mobile station's identity with the time-varying public key and pages the enciphered identity to all mobile stations.

Identity confidentiality method in radio communication system

Authentication system

In the preliminary authentication stage, the mobile station (35) is authenticated by sending from the home network (30) to the roamed network (31), a plurality of pairs of first random numbers (RNDa.sub.1, . . . , RNDa.sub.n) and calculation results (SRESa.sub.1, . . . , SRESa.sub.n) of the cipher function (f), which calculation is performed at the home network using the secret key (ki) and the first random numbers (RNDa.sub.1, . . . , RND.sub.an), by sending, from the roamed network to the mobile station, third random numbers formed by coupling second random numbers (RNDb.sub.1, . . . , RNDb.sub.m) produced at the roamed network with the first random numbers (RNDa.sub.1, . . . , RNDan), by sending, from the mobile station to the roamed network, calculation results (SRESa.sub.1, . . . , SRESa.sub.n, SRESb.sub.1, . . . , SRESb.sub.m)) of the cipher function (f), which calculation is performed at the mobile station using the secret key (ki) and the sent third random numbers, and by confirming, at the roamed network, coincidence of the calculation results (SRESa.sub.1, . . . , SRESa.sub.n) sent from the mobile station with the calculation results (SRESa.sub.1, . . . , SRESa.sub.n) sent from the home network. In the main authentication, the mobile station is authenticated by using a pair of the second random number (RNDb.sub.1, . . . , RNDb.sub.m) and of the calculation result (SRESb.sub.1, . . . , SRESb.sub.m) with respect to the second random number (RNDb.sub.1, . . . , RNDb.sub.m), sent from the mobile station.

Authentication method for mobile communications

A communication system includes a bidirectional tree network having a base end and a plurality of terminating ends, a central apparatus connected to the base end, a plurality of terminating equipment connected respectively to the terminating ends, and a plurality of subscriber terminals accommodated respectively in the terminating equipment. Each of the terminating equipment has a multiplexer for multiplexing information transmitted from the subscriber terminal accommodated therein to the central equipment, and a signal selection device for discriminating and selectively receiving only information which is destined for the subscriber terminal accommodated in this terminating equipment from information transmitted from the central apparatus to all the subscriber terminals via the tree network. The central apparatus has an exchange equipment for discriminating destination of information transmitted from the subscriber terminals via the tree network, and a loop back device for scrambling the information transmitted from the subscriber terminals via the tree network so that the scrambled signal can be decoded only by a signal selection device corresponding to the discriminated destination and for sending back the scrambled information to the tree network.

Communication system using a bidirectional tree structure network

A syndrome sequential decoding system for error correction of a convolutional code has a syndrome former for providing a syndrome sequence from a received sequence, a syndrome buffer memory for storing the syndrome sequence, an estimated error buffer memory for storing an estimated error sequence, a syndrome register for representing a syndrome state under searching, a comparator for testing if content of the syndrome register is all zero, and an algorithm controller. The algorithm controller controls the syndrome register, calculates a path metric and raises a flag in the estimated error buffer memory for showing an estimated error bit position. The syndrome sequential decoding system also includes an exclusive-OR circuit for correcting an information bit error according to the output of the estimated error buffer memory. When the content of the syndrome register is all zero, it shows that a currently searching path merges with the maximum likelihood path. Then a decoded sequence up to this point is explicitly determined. Moreover no further search will be required as long as the following syndromes remain zero. When the content of the syndrome register becomes nonzero, the normal path search restarts at this point. A back search limit pointer is provided on the estimated error buffer memory and a syndrome buffer memory to show the limit of the depth of back search.

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Saitama, Japan

Masayoshi Ohashi