Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-04-07
2004-07-27
Gesesse, Tilahun (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S439000, C370S331000
Reexamination Certificate
active
06768908
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the field of communications and communication systems, and more particularly, to a code division multiple access (CDMA) communication system.
Several types of commercially available CDMA communication systems operate according to communication standards commonly known as IS-95B and IS-95C standards. Such systems evolve from one generation to another. For example, the IS-95B standard followed a previously known IS-95A standard to provide additional capacity while improving performance in many different aspects of the CDMA communication systems. Recently the IS-95C standard, otherwise known as IS2000, has been introduced to meet even a higher demand for capacity and performance. The standards describing the details of IS-95A, IS-95B, IS-95C (IS2000) systems, a copy of each may be obtained by contacting Telecommunications Industry Association in Washington D.C., USA, or visiting the world wide web site at www.tiaonline.org, incorporated by reference herein.
Referring to
FIG. 1
, a simplified block diagram of a communication system
100
with several cell sites coverage areas and certain associated building blocks is shown. Often times CDMA systems operating according to different standards are implemented in coverage areas located side by side, in proximity of each other or in an overlapping coverage area. For example, a cell site
101
having multiple sectors provides communication services according to IS-95B and IS-95-C standards in an overlapping coverage area. Cell site
101
achieves multi-type services by coupling a base transceiver station (BTS)
131
of type IS-95B and BTS
132
of type IS-95C to a base station controller (BSC)
134
. Since BSC
134
controls some aspects of the communication calls made via cell site
101
, BSC
134
may decide which type of service, type B for IS-95B or type C for IS-95C, a mobile user may receive while it is in the coverage area. The mobile user may also select the service type. BSC
134
provides the communication services through the selected communication type by routing the information through the corresponding BTS, for example, either BTS
131
or BTS
132
if the mobile station is in the cell site
101
coverage area.
According to one example of a cell configuration as shown in communication system
100
, a cell site
103
adjacent to cell site
101
may provide only communication services according to IS-95B standards. As such, a BTS
135
serving cell site
103
is of the B type and coupled to BSC
134
. A cell site
102
adjacent to cell sites
103
and
101
may provide communication services according to IS-95C standards. As such a BTS
136
serving cell site
102
is of the C type and coupled to BSC
134
. Other cell site configurations are also possible.
Since mobile stations are also evolving with the standards, a mobile station may operate in a single-mode or dual-mode or other multi-mode. In case of dual-mode operation, the mobile station may operate according to both IS-95B and IS-95C standards. A mobile station (MS)
104
, if it is in a single-mode operation, may receive communication services from cell sites
101
and
102
through BTSs
132
and
136
or cell sites
101
and
103
through BTSs
131
and
135
depending on whether its mode of operation is IS-95C or IS-95B respectively. A dual-mode MS
104
, however, may not be able to efficiently receive communication services from all three cell sites
101
-
103
. At least to some extent, MS
104
in dual mode operation may not benefit from soft hand operation from all three cell sites.
The operation known as soft handoff commonly known to one ordinary skilled in the art allows a mobile station to receive and combine from neighboring base stations different signals to improve receiving quality. The received signals are combined in the receiver to gain improvement in reception and decoding of the transmitted information. The operations relating to the soft handoff are well known to one ordinary skilled in the art in view of the description provided in the IS-95B and IS-95C standards.
When a mobile station receives signals communicated according to a common standard, the soft-combining operation is easily performed. For example, if mobile station
104
is communicating with cell site
101
according to IS-95B standard through BTS
131
and moves to cell site
103
, the soft handoff operation is easily performed because cell site
103
operates through BTS
135
which is of the B type. As such, BSC
134
may easily transmit the information to MS
104
via cell sites
101
and
103
through BTSs
131
and
135
which both are of the B type. However, if mobile station
104
is communicating with cell site
101
according to IS-95B standard and moves to cell site
102
, the soft handoff operation may not be possible because cell site
102
provides only communication services through BTS
136
operating according to IS-95C standard. Moreover, when MS
104
is communicating with cell site
101
through BTS
131
operating according to IS-95B standard, soft handoff operation for signals transmitted from cell site
101
through BTS
132
operating according to IS-95C standard may not be possible or difficult. It is well understood by one ordinary skilled in the art that the terms cell site and sector are interchangeable in the way the communication services are provided.
Therefore, there is a need for a method and apparatus that facilitates soft-combining operation of received signals transmitted according to different CDMA standards.
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Chen Jiangnan (Jason)
Jalloul Louay
Luz Yuda Yehuda
Rotstein Ron
Tenbrook Keith A.
Gesesse Tilahun
May Steven A.
Motorola Inc.
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