Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Having particular address related cryptography
Reexamination Certificate
1999-12-15
2004-12-14
Barrón, Gilberto (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Having particular address related cryptography
C713S160000, C713S163000, C713S168000, C370S360000, C370S395640
Reexamination Certificate
active
06832314
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to communications methods and apparatus, and more particularly, to communications methods and apparatus using encryption.
Wireless communications systems are commonly employed to provide voice and data communications to subscribers. For example, analog cellular radiotelephone systems, such as those designated AMPS, ETACS, NMT-450, and NMT-900, have long been deployed successfully throughout the world. Digital cellular radiotelephone systems such as those conforming to the North American standard IS-54 and the European standard GSM have been in service since the early 1990's. More recently, a wide variety of wireless digital services broadly labeled as PCS (Personal Communications Services) have been introduced, including advanced digital cellular systems conforming to standards such as IS-136 and IS-95, lower-power systems such as DECT (Digital Enhanced Cordless Telephone) and data communications services such as CDPD (Cellular Digital Packet Data). These and other systems are described in
The Mobile Communications Handbook
, edited by Gibson and published by CRC Press (1996).
FIG. 1
illustrates a typical terrestrial cellular radiotelephone communication system
20
. The cellular radiotelephone system
20
may include one or more radiotelephones (mobile terminals)
22
, communicating with a plurality of cells
24
served by base stations
26
and a mobile telephone switching office (MTSO)
28
. Although only three cells
24
are shown in
FIG. 1
, a typical cellular network may include hundreds of cells, may include more than one MTSO, and may serve thousands of radiotelephones.
The cells
24
generally serve as nodes in the communication system
20
, from which links are established between radiotelephones
22
and the MTSO
28
, by way of the base stations
26
serving the cells
24
. Each cell
24
typically has allocated to it one or more dedicated control channels and one or more traffic channels. A control channel is a dedicated channel used for transmitting cell identification and paging information. The traffic channels carry the voice and data information. Through the cellular network
20
, a duplex radio communication link may be effected between two mobile terminals
22
or between a mobile terminal
22
and a landline telephone user
32
through a public switched telephone network (PSTN)
34
. The function of a base station
26
is to handle radio communication between a cell
24
and mobile terminals
22
. In this capacity, a base station
26
functions as a relay station for data and voice signals.
As illustrated in
FIG. 2
, a satellite
42
may be employed to perform similar functions to those performed by a conventional terrestrial base station, for example, to serve areas in which population is sparsely distributed or which have rugged topography that tends to make conventional landline telephone or terrestrial cellular telephone infrastructure technically or economically impractical. A satellite radiotelephone system
40
typically includes one or more satellites
42
that serve as relays or transponders between one or more earth stations
44
and terminals
23
. The satellite conveys radiotelephone communications over duplex links
46
to terminals
23
and an earth station
44
. The earth station
44
may in turn be connected to a public switched telephone network
34
, allowing communications between satellite radiotelephones, and communications between satellite radio telephones and conventional terrestrial cellular radiotelephones or landline telephones. The satellite radiotelephone system
40
may utilize a single antenna beam covering the entire area served by the system, or, as shown, the satellite may be designed such that it produces multiple minimally-overlapping beams
48
, each serving distinct geographical coverage areas
50
in the system's service region. The coverage areas
50
serve a similar function to the cells
24
of the terrestrial cellular system
20
of FIG.
1
.
Several types of access techniques are conventionally used to provide wireless services to users of wireless systems such as those illustrated in
FIGS. 1 and 2
. Traditional analog cellular systems generally employ a system referred to as frequency division multiple access (FDMA) to create communications channels, wherein discrete frequency bands serve as channels over which cellular terminals communicate with cellular base stations. Typically, these bands are reused in geographically separated cells in order to increase system capacity. Modern digital wireless systems typically utilize different multiple access techniques such as time division multiple access (TDMA) and/or code division multiple access (CDMA) to provide increased spectral efficiency. In TDMA systems, such as those conforming to the GSM or IS-136 standards, carriers are divided into sequential time slots that are assigned to multiple channels such that a plurality of channels may be multiplexed on a single carrier. CDMA systems, such as those conforming to the IS-95 standard, achieve increased channel capacity by using “spread spectrum” techniques wherein a channel is defined by modulating a data-modulated carrier signal by a unique spreading code, i.e., a code that spreads an original data-modulated carrier over a wide portion of the frequency spectrum in which the communications system operates.
Communications in a wireless communications system such as the systems of
FIGS. 1 and 2
typically make use of different addressing modes for messages sent out by base stations over a broadcast control channel. Messages may be sent to a broadcast address of the communications system, i.e. addressed to all the mobile terminals (receiver devices or receivers) served by the system, or sent to an individual address associated with a specific mobile terminal. The use of broadcast (point to multipoint) addresses may avoid undue network traffic when a particular message is of interest to more than one receiver. Receivers supported by such systems are preferably configured with both a broadcast address and an individual address so they may access both types of messages. Such systems may also use encryption to provide greater privacy for communications broadcast on control channels which may be subject to interception by receivers other than the intended recipient.
One problem with such prior art systems is that all mobile terminals having the proper broadcast address may access all messages broadcast with the broadcast address. Thus, it is problematic to conveniently use the same channel to send both messages that are intended to be received generally and those that are intended to be received by only a subset of the potential receivers. This is particularly problematic with the expansion of services available on such communications networks, including the introduction of premium services such as, for example, stock quotes or weather updates. Service providers desire a method to control billing for such premium services and control access to such premium services.
One approach previously suggested to the problem of controlling access to premium services is the use of group addresses. A group address may be described as a broadcast address for a subset of receivers. In such a network, each receiver would have a broadcast address, an individual address and, optionally, one or more group addresses. Premium services may then be transmitted using group addresses associated with the premium service. A disadvantage of this approach to controlling access to premium services is the burden of adding and removing receivers from a group. It also places the burden on the address managing system rather than the channel. Fraud prevention concerns may discourage easy changing of receiver addresses in networks such as cellular telephone networks. Furthermore, the use of the group address approach may be subject to eavesdropping, thus making the group addresses subject to interception by those wishing to obtain premium services without payment or to invade the privacy
Barrón Gilberto
Ericsson Inc.
Myers Bigel & Sibley & Sajovec
Nobahar Abdulhakim
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