Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-05-11
2002-04-16
Swann, Tod R. (Department: 2767)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S552100, C455S419000
Reexamination Certificate
active
06374122
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to communications systems. More particularly, the present invention relates to a method and apparatus for identifying subscriber units in a wireless communication network.
II. Description of the Related Art
Wireless communications systems require the identity of subscribers (or subscriber units, such as wireless telephones, terminals, modems, etc.) to be determined for a number of purposes, including authentication for billing and to maintain secure communications over the connection between the subscriber unit and the party to which the subscriber is attempting to communicate. An electronic serial number (ESN) is a unique 32-bit serial number permanently stored in the subscriber unit equipment by the manufacturer. The ESN uniquely identifies a subscriber unit. The circuitry within the subscriber unit that provides the ESN is usually isolated from fraudulent contact or tampering. Many subscriber units are manufactured such that an attempt to alter the ESN renders the subscriber unit inoperative.
FIG. 1
illustrates the content of an ESN. The ESN
100
consists of a manufacturer's code field
102
and serial number field
104
. The serial number field is twenty-four bits long and designates a serial number
104
uniquely assigned to a particular subscriber unit. The manufacturer's code field is eight bits in length and designates a manufacturer's code uniquely assigned to each manufacturer of subscriber units. The Federal Communications Commission (FCC) has mandated that each subscriber unit be assigned an ESN, so that radio transmissions can be identified, if need be. In combination with the ESN, a mobile identification number (MIN) uniquely identifies a subscriber. The unique combination of the ESN and the MIN is used to register and qualify a subscriber for service. In addition, this combination is used to enable all network functions pertaining to an individual subscriber.
The Telecommunications Industry Association (TIA) standard TIA/EIA IS-41, entitled Cellular Radio Telecommunications Intersystem Operations, provides a standard for intersystem operations among mobile switching centers (MSCs), home location registers (HLRs), visitor location registers (VLRs) for cellular networks to support subscriber mobility. In IS-41, a unique subscriber identification is provided by concatenating the MIN and the ESN. This combination is used primarily for registration and authentication functions.
In code division multiple access (CDMA) systems, as standardized by the TIA in TIA/EIA IS-95-A, entitled Subscriber unit-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System, the electronic serial number is used to set the initial state of the scrambling pseudonoise (PN) generator. In IS-95-A, a 42-bit mask is generated in accordance with the 32-bit ESN. The first ten bits are a fixed sequence and the remaining 32 bits are a predetermined permutation of the subscriber unit ESN. The use of the ESN to provide a mask for the long code is described in U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM”.
In addition, the ESN is used in authentication procedures as specified in TIA/EIA IS-41 (hereafter IS-41). Authentication is a set of functions used to prevent fraudulent access to cellular networks by phone illegally programmed with counterfeit mobile identification number (MIN) and electronic serial number (ESN) information. The functions require no subscriber intervention and provide a robust method of validating the true identity of a subscriber.
The authentication procedure specified in IS-41 is performed in accordance with the performance of a set of calculations, collectively known as the CAVE (cellular authentication and voice encryption) algorithm. The CAVE algorithm is described in U.S. Pat. No. 5,159,634, entitled “CRYPTOSYTEM FOR CELLULAR TELEPHONY”. The authentication process and algorithm are based upon two secret numbers: the authentication key (A-key) and shared secret data (SSD). The A-key is a 64-bit secret number that is a permanently stored in the subscriber unit and securely stored in the authentication center. The A-key is never transmitted over the air, but is used in the generation of the SSD. The SSD is result of a calculation using the A-key, the ESN and a random number shared between the subscriber unit and the network. It is by matching the generated SSD of the network with the generated SSD of the subscriber unit that authentication is performed.
With the number of subscriber units increasing dramatically, there is a need for electronic serial numbers beyond the number provided for using the current numbering scheme. In response to this need, a 56 bit extended electronic serial number (EESN) has been proposed.
FIG. 2
illustrates the organization and content of the proposed EESN. As shown in
FIG. 2
, the EESN
200
has an eight-bit manufacturer's code field
202
that indicates that an EESN is being used. The proposed method would require that a predetermined value be placed in the manufacturer's code field of the EESN
200
. One proposal is to have this predetermined value be equal to 128 decimal. The EESN also has a twenty-four-bit serial number field
204
that designates the serial number assigned to the subscriber unit. An eight-bit reserved field
206
provides additional capacity for expanding the current fields or adding an additional field at a later time. A sixteen-bit extended manufacturer's field
208
designates the manufacturer's code in the EESN. It can be seen that there are an additional eight bits provided in the EESN to designate the manufacturer's code.
However, as described above, many existing operations require a 32 bit ESN. Thus, there is a need felt in the art for a method by which a 56 bit EESN can be used in the authentication, registration and scrambling operations that are to be performed using a 32 bit ESN.
Therefore, there is a need for a method and apparatus that can make wireless infrastructure that is designed to accommodate 32-bit ESNs compatible with newer subscriber units that are assigned a 56-bit EESN.
SUMMARY OF THE INVENTION
The method and apparatus disclosed herein generates a 32 bit digital “amended electronic serial number” (AESN) from a 56 bit “extended electronic serial number” (EESN). The AESN distinguishes each subscriber unit within a wireless system from each other subscriber unit. Two distinct methods are disclosed. In accordance with the both the first and second method, an AESN is only generated when an EESN has been assigned to the subscriber unit by the manufacturer.
In accordance with the first method, a portion of the EESN referred to as the manufacturers code field (“MFR”) is tested to determine whether the subscriber unit has, in fact, been assigned an EESN. If the MFR value (i.e., the value designated in the MFR field) is equal to 128 decimal (“1000 0000” binary), then an EESN is being used. If so, then the least significant 8 bits of a portion of the EESN, referred to commonly as the extended manufacturer's code field (“EMFR”) is appended to the 24 bits of the EESN that are commonly referred to as the “serial number” field (“SN”). Accordingly, the AESN would comprise the 8 least significant bits of the EMFR and the 24 bits of the SN.
In accordance with the second method, each manufacturer would be required to generate, by applying a pseudo-random sequence, the 24 bit serial numbers which must be assigned to subscriber units that are produced by that manufacturer. The “seed” for the pseudo-random sequence is based on the manufacturer's EMFR, and therefore different for each manufacturer. This serial number is then combined with the 8 bit MFR to generate an AESN whether the manufacturer has assigned an EESN or an ESN. That is, the 8 bits of the MFR taken together with the 24 bits of the serial number to comprise an AESN whether the manufacturer has assigned an EESN or a
Greenhaus Bruce W.
Meislahn Doug
QUALCOMM Inc.
Swann Tod R.
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