Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-04-12
2002-05-07
Cumming, William (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
Reexamination Certificate
active
06385455
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related in general to digital communication systems, and more particularly to a method and system for selecting a communications parameter for communicating with a concentrated subscriber unit having multiple subscriber terminals sharing a transceiver.
BACKGROUND OF THE INVENTION
In many communications systems, transceivers in an infrastructure system are designed to communicate with subscriber units distributed throughout a communications system service area. One example of such a communications system is a wireless cellular communications system, wherein the cellular infrastructure system provides communication services to subscriber units in various locations throughout the cellular system coverage area.
In some communications systems, selected subscriber units may be fixed in a particular location, rather than mobile and free to move about the coverage area. When a subscriber unit is fixed, and several subscriber units are used in the vicinity of that same location, an opportunity arises for subscriber units to share communications resources, such as sharing a transceiver in a wireless communications system.
With reference now to
FIG. 1
, there is depicted a communications system
20
wherein subscriber units
22
-
26
communicate with infrastructure
28
. Infrastructure
28
may be coupled to the public switched telephone network (PSTN)
30
so that subscriber units
22
-
26
may communicate with others connected to PSTN
30
. Within infrastructure
28
, base station controller
32
may be coupled to base stations
34
and
36
, wherein base station controller
32
provides base stations
34
and
36
with control and traffic data. If communications system
20
is a cellular communication system, supporting mobile subscriber units, base station controller
32
may be used to route communication traffic to a selected base station for serving each particular subscriber unit.
As shown at subscriber unit
26
, some subscriber units may be “concentrated subscriber units” that support multiple subscriber terminals
38
. A subscriber terminal may be thought of as a communications interface to communications system
20
. For example, if concentrated subscriber unit
26
is a fixed wireless terminal, terminals
38
within concentrated subscriber unit
26
may provide a local loop telephone system interface for coupling to a telephone handset, such as telephone
40
. Note that if telephones
40
are in the same vicinity, such as in the same building, subscriber terminals
38
may all share transceiver
46
in order to communicate with base station
36
. Thus, in a concentrated subscriber unit, S number of subscriber terminals
38
may share transceiver resources provided by T number of transceivers, wherein S is greater than T. This sharing of transceiver resources reduces the cost and complexity of concentrated subscriber unit
26
.
When communications system
20
grows to support a larger number of subscriber units, the communications system will need to add additional capacity to service those subscribers. Capacity may be added by increasing the number of transmission frequencies, or otherwise increasing the number of channels available to subscribers, wherein such channels and frequencies are used in various ways known in the art to separate data intended for one subscriber from another subscriber. In the example of communications system
20
, base stations
34
and
36
each transmit on two carrier frequencies, illustrated at first carrier
42
and second carrier
44
.
For the most part, subscriber terminals
38
appear to infrastructure
28
as separate subscriber units that can be tuned to separate frequencies and set to separate channels, like subscriber units
22
and
24
. However, a problem exist with concentrated subscriber unit
26
when transceiver
46
is supporting subscriber terminals
38
that have been instructed to tune to different frequencies, such as first and second carriers
42
and
44
. The problem occurs because transceiver
46
is typically designed to receive and transmit on a single carrier frequency. Thus, concentrated subscriber unit
26
works better when subscriber terminals
38
are instructed, as group, to select the same communication parameter, such as the same carrier frequency. By operating subscriber terminals
38
as a group, the benefits of sharing a transceiver
46
are maximized.
In communications system
20
, subscriber units
22
-
26
and infrastructure
28
may agree upon a formula for selecting communications parameters, such as carrier frequency or other channel designation parameters. This formula for selecting communications parameters is used to reduce the number of messages transferred between infrastructure
28
and subscriber units
22
-
26
, and to randomly distribute the selection of communication parameters so that capacity of the system is increased, and the success of accessing the communications system is increased. This random distribution attempts to spread subscriber units evenly among the carrier frequencies, for example.
In the prior art, communication parameters are selected by performing a hashing function on an identification number associated with the subscriber unit or subscriber terminal. For example, to select one of two carrier frequencies, both infrastructure
28
and subscriber unit
22
will input an ID number associated with subscriber unit
22
into a hashing function that hashes the ID number to produce a number indicating one of the two carrier frequencies that is being used to communicate between infrastructure
28
and subscriber unit
22
. If four carrier frequencies are available, the hashing function outputs an indicator having one of four values so that one of four carrier frequencies may be selected.
Typically, the subscriber unit identification number is based on the telephone number associated with the subscriber unit. In concentrated subscriber unit
26
, it is desirable to have a different phone number for each terminal unit
38
. Furthermore, it may be desirable to have sequential phone numbers assigned to terminal units
38
. The problem occurs in the prior art when the ID numbers for terminal units
38
hash, as a group, to more than one carrier frequency, or more carrier frequencies than transceiver
46
can support.
One solution to this problem, is described in U.S. Pat. No. 5,544,223, which shows a communications system that includes a database for recording which subscriber units are concentrated subscriber unit and which subscriber units are not. The disadvantages of this system include transmitting additional messages to indicate that a subscriber unit is a concentrated subscriber unit, and the recording, in a database, the subscriber unit status. This system requires additional overhead in messaging and data storage.
Thus, it should be apparent that a need exist for an improved method and system for selecting a communication parameter, such as a carrier frequency, for communicating with a concentrated subscriber unit in a communication system, wherein the number of overhead messages is reduced and a database indicating a concentrated subscriber unit is not required.
BRIEF SUMMARY OF THE INVENTION
Thus there is a particular need for a method and system for selecting a communication parameter, such as a carrier frequency, for communicating with a concentrated subscriber unit in a communication system, wherein the number of overhead messages is reduced and a database indicating a concentrated subscriber unit is not required. Briefly, in accordance with an embodiment of the present invention, a subscriber terminal identification number in one of multiple subscriber terminals is determined. Next, N number of selected digits in the subscriber terminal identification number are set equal to predetermined values to produce a modified subscriber terminal identification number. The modified subscriber terminal identification number is then hashed using a hashing function to produce a communication parameter indicator. The communication para
St. Clair Jon Quin
Willey William Daniel
Cumming William
May Steven A.
Motorola Inc.
Terry Bruce
LandOfFree
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