(12) United States Patent (10) Patent No.: US 8,224.290 B2 Reddy Et Al

USOO8224290B2 (12) United States Patent (10) Patent No.: US 8,224.290 B2 Reddy et al. (45) Date of Patent: Jul. 17, 2012 (54) APPARATUS AND METHOD OF CIPHERING (56) References Cited IN WIRELESS COMMUNICATIONS USER EQUIPMENT OPERATIVE WITH A U.S. PATENT DOCUMENTS PLURALITY OF RADIO ACCESS NETWORKS 6,643,513 B2 * 1 1/2003 Timonen et al. .............. 455,438 7,065,340 B1* 6/2006 Einola et al. ... ... 455,410 7,233,671 B2* 6/2007 Wu ............. ... 380,270 (75) Inventors: Giri Narayana Reddy, Birmingham 2004/0228491 A1* 11, 2004 Wu ......... ... 380,272 (GB); Andrew Farnsworth, Marlbrook 2007, OO72635 A1* 3, 2007 Zhao et al. .. ... 455,5O2 (GB) 2009/01 19190 A1* 5/2009 Realini ........................... 705/30 OTHER PUBLICATIONS (73) Assignee: Research In Motion Limited, Waterloo (CA) 3GPP TS 25.331 v5.19.0 (Dec. 2006), full specification. * cited by examiner (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 Primary Examiner — Wen Huang U.S.C. 154(b) by 642 days. (74) Attorney, Agent, or Firm — Novak Druce + Quigg LLP (21) Appl. No.: 12/179,728 (57) ABSTRACT A method in a wireless telecommunications device operative (22) Filed: Jul. 25, 2008 with a plurality of radio access networks, the method com prising: when operating with a first radio access network (65) Prior Publication Data reading at least one ciphering variable applicable in the sec ond radio access network (e.g. in UMTS reading the value of US 201O/OO22235A1 Jan. 28, 2010 a variable START from the USIM of the device). When at (51) Int. C. least one ciphering variable applicable in the second radio H04M I/66 (2006.01) access network renders ciphering in the second radio access HO4M I/68 (2006.01) network infeasible without further authentication (e.g. in UMTS when the value of START in USIM is equal to a value (52) U.S. Cl. ..................... 455/410; 455/411; 455/432.1; THRESHOLD), using a substitute value for the ciphering 455/432.2:455/432.3:455/425; 455/552.1 parameter (e.g. START) when establishing a connection with (58) Field of Classification Search .................. 455/410, the second radio access network. 455/411,432.1, 432.2, 432.3, 425,552.1 See application file for complete search history. 12 Claims, 5 Drawing Sheets Start ciphered GSM call on multimode device 200 202 Read START from USIM 204 TART-THRESHOLD 222 Send START Send a substitute 206 value for START 207 giphered and handed over sy all terminateds Write THRESHOLD To START in USIM 208 217 Carry out ciphered 3G call and increment START 218 210 212 220 Write START to USM 216 U.S. Patent Jul. 17, 2012 Sheet 1 of 5 US 8,224.290 B2 S Fig. 1 U.S. Patent Jul. 17, 2012 Sheet 2 of 5 US 8,224.290 B2 Establish call with 102 first radio access network Read ciphering parameter of Second radio access network 106 Would ciphering in second radio access network be feasible with iphering parameter2 108 d Use a Substitute Use ciphering parameter cipheringg parameter 112 110 Fig. 2 U.S. Patent Jul. 17, 2012 Sheet 3 of 5 US 8,224.290 B2 Start ciphered GSM call on multimode device 200 202 Read START from USIM 204 TART=THRESHOLD2 N Y 222 Send a substitute 206 -Send START value for START 207 N Y all terminated? N Write THRESHOLD TO START in USIM Y 208 217 Carry out ciphered 3G call and increment START 218 210 Termi 220 Write START to USIM 214 Fig. 3 216 End U.S. Patent Jul. 17, 2012 Sheet 4 of 5 US 8,224.290 B2 -,-.…--.•?---,=• -…• Layer 1 - Physical Layer Fig. 4 U.S. Patent Jul. 17, 2012 Sheet 5 of 5 US 8,224.290 B2 Ogg]]JOd[BIJÐS ZZSKeIds[GI JOSS000Id 899 099 Z99 US 8,224,290 B2 1. 2 APPARATUS AND METHOD OF CPHERING There are thus proposed strategies for apparatus and a IN WIRELESS COMMUNICATIONS USER method of ciphering in wireless telecommunications devices EQUIPMENT OPERATIVE WITH A operative with a plurality of radio access networks. A number PLURALITY OF RADIO ACCESS NETWORKS of such strategies are detailed below. Other aspects and features of the proposed strategy will BACKGROUND become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments 1. Technical Field of apparatus and methods of ciphering in wireless telecom This application relates to mobile telecommunications sys munications user equipment operative with a plurality of tems in general, having particular application in UMTS (Uni 10 radio access networks. Versal Mobile Telecommunications System) in general, and in particular relates to an apparatus and method of ciphering BRIEF DESCRIPTION OF THE DRAWINGS in wireless telecommunications user equipment operative with a plurality of radio access networks. Embodiments will now be described, by way of example 2. Description of the Related Art 15 only, with reference to the attached drawings, in which: In a typical cellular radio system, a wireless telecommuni FIG. 1 shows an overview of two radio access networks and cation device communicates via one or more radio access a wireless telecommunications device; radio networks (RANs) to one or more core networks. In FIG. 2 is a flow diagram illustrating a first embodiment of UMTS system such devices are typically referred to as User a method applicable to a wireless telecommunications device Equipment (UE) and in GSM such devices are typically operative with a plurality of radio access technologies; referred to as Mobile Stations (MS). Such devices comprise FIG.3 is a flow diagram illustrating a second embodiment various types of equipment Such as mobile telephones (also of a method applicable to a wireless telecommunications known as cellular or cell phones), lap tops with wireless device operative with a plurality of radio access technologies; communication capability, personal digital assistants (PDAS) FIG. 4 is a block diagram illustrating an embodiment of a etc. These may be portable, hand held, pocket sized, installed 25 UMTS protocol stack apparatus provided with a RRC block, in a vehicle etc and communicate Voice and/or data signals in accordance with the present application; with the radio access network. FIG. 5 is a block diagram illustrating a wireless telecom In the following, reference will be made to UMTS, GSM munications device. and to particular standards. However it should be understood The same reference numerals are used in different figures that the invention is not intended to be limited to any particu 30 to denote similar elements. lar mobile telecommunications system. A radio access network covers a geographical area typi DETAILED DESCRIPTION OF THE DRAWINGS cally divided into a plurality of cell areas. Each cell area is served by at least one base station, which in UMTS may be An apparatus and method of ciphering in a wireless tele referred to as a Node B. Each cell is typically identified by a 35 communications device operative with a plurality of radio unique identifier which is broadcast in the cell. The base access networks are described. In the following description, stations communicate at radio frequencies over an air inter for the purposes of explanation, numerous specific details are face with the UEs within range of the base station. Several set forth in order to provide a thorough understanding of the base stations may be connected to a radio network controller present invention. It will be apparent, however, to one skilled (RNC) which controls various activities of the base stations. 40 in the art that the technique may be practised without these The radio network controllers are typically connected to a specific details. In other instances, well-known structures and core network. devices are shown in block diagram form in order to avoid GSM is a so-called second generation public land mobile unnecessarily obscuring the proposed method. telecommunications system. UMTS is a third generation pub The needs identified in the foregoing Background, and lic land mobile telecommunication system. Various standard 45 other needs and objects that will become apparent from the ization bodies are known to publish and set standards for following description, are achieved by, in one aspect, a UMTS, each in their respective areas of competence. For method of ciphering in a wireless telecommunications device instance, the 3GPP (Third Generation Partnership Project) operative with a plurality of radio access networks. In other has been known to publish and set standards for GSM (Global aspects, the invention encompasses apparatus and a com System for Mobile Communications) based UMTS, and the 50 puter-readable medium configured to carry out the foregoing 3GPP2 (Third Generation Partnership Project 2) has been actions. In particular, the method may be implemented in a known to publish and set standards for CDMA (Code Divi mobile telecommunications device, with or without voice sion Multiple Access) based UMTS. Within the scope of a capabilities, or other electronic devices such as handheld or particular standardization body, specific partners publish and portable devices. set standards in their respective areas. 55 FIG. 1 shows an overview of a telecommunications net In telecommunications, typically ciphering is used to work and a multimode wireless telecommunications device reduce the likelihood of unauthorised interception and exami 500. Clearly in practice there may be many such devices nation of the content of data transmitted between the mobile operating with the network but, for the sake of simplicity, device and the network. Signalling protocols are typically FIG. 1 only shows a single wireless telecommunications used to set up ciphering within radio connections and cipher 60 device 500. For the purposes of illustration, FIG.

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