Synchronizing method in a mobile radio system

Details Synchronizing method in a mobile radio system Synchronizing method in a mobile radio system

1992-12-07

1994-03-08

Gregory, Bernarr E.

Cryptography

Key management

Having particular key generator

380 49, 3701001, 375106, 379 58, 379 59, 379 60, 455 331, 455 332, 455 561, H04L 912

Patent

active

052934233

ABSTRACT:
A synchronizing method in a mobile radio system which operates with Time Division Multiple Access (TDMA) but which lacks global time reference for all base stations and mobiles in the system. The inventive method is intended for ciphered transmission of data and speech in accordance with a given ciphering key (E2). When handing-over a call, the ciphering synchronism is lost. In accordance with the method, subsequent to hand-off (the time t.sub.2), the take-over base station (BS2) signals non-ciphered information (S1) to the mobile (MS) disclosing the number of frames (R1-R13) which shall pass until ciphering can again be commenced, calculated from a given frame (R1). Call information is transmit the following frame (R2), this information now being ciphered with the aid of a ciphering key (E1) different to the original key. This other ciphering key consists of a periodic bit sequence having a period which is equal to one frame interval.

REFERENCES:
patent: 4827507 (1989-05-01), Marry et al.
patent: 5081679 (1992-01-01), Dent
European Search Report for Application No. 9017473.1 of Dec. 4, 1990.

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