Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
1997-12-24
2001-11-20
Chin, Wellington (Department: 2664)
Multiplex communications
Communication over free space
Repeater
C370S335000, C370S320000, C370S342000, C370S441000
Reexamination Certificate
active
06320851
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to code division multiple access (CDMA) communication systems and, more particularly, to a system and method for allocating different bandwidth and chip rates to the forward and reverse channel links.
BACKGROUND OF THE INVENTION
One type of cellular communication system employs a technology known as CDMA (code division multiple access). In this system, users are distinguished from one another by unique codes assigned to them while sharing the same frequency band at the same time. CDMA converts information to be transmitted into a spread spectrum signal by multiplying the information by a pseudo random number (PN). This is what spreads the spectrum. The pseudo random number is a digital piece of data that, for all intents and purposes, appears to be entirely random. This PN is synchronized to the system in the CDMA mobile station by a pilot carrier sent from the base station. The rate at which the PN sequence is generated is known as the PN chip rate. For further description of CDMA and the differences between CDMA, TDMA (time division multiple access), and FDMA (frequency division multiple access), please see “Code Division Multiple Access,” Communications, February 1990, by Fred Baumgartner, hereby incorporated by reference.
FIG. 1
graphically illustrates a CDMA-based communication system comprising a mobile station
10
, a base station
20
, reverse link
30
which represents the electromagnetic wave communication link transmitted from mobile station
10
to base station
20
and forward link
40
which represents the electromagnetic wave communication link transmitted from base station
20
to mobile station
10
.
Current mobile stations used in wireless communications have symmetric forward and reverse channel bandwidths and corresponding symmetric chip rates. The term “symmetric” means that the bandwidths for the forward and reverse channels are the same and that the chip rates in the forward and reverse directions are the same. A CDMA standard, W-CDMA, has recently been proposed to accommodate high speed data (HSD) communication service over an air or wireless link. The HSD service may include various applications such as Internet access, electronic mail service, multimedia applications where more throughput is required for the forward channel than for the reverse channel, etc. Many of these services, such as multimedia applications, require asymmetric bandwidths for the forward and reverse directions. The term “asymmetric” means that the PN chip rates on the forward and reverse links are different from each other.
In present CDMA-based communication systems, all of the mobile stations have symmetric bandwidths for the forward and reverse links. The call setup procedure between a mobile station and a base station is accomplished over a symmetric forward and reverse link. After the call setup procedure is completed, a call is maintained on the same forward/reverse channel.
FIG. 2
illustrates asymmetric channel allocation for the forward and reverse channels wherein F
0
(formed link channel frequency) does not equal F
1
(reverse link channel frequency) and BW
0
(forward link channel bandwidth) is equal to BW
1
(reverse link channel bandwidth). Both call setup and call maintenance are performed over the F
0
, F
1
band.
What is needed are mobile stations that accommodate high speed data communication services by supporting asymmetric forward and reverse channel allocation.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a system and method for allocating asymmetric forward and reverse channels in a CDMA-based communication system. The present invention provides a system and method for allocating asymmetric bandwidths and chip rates to the forward and reverse channels. The present invention also provides a negotiation process between a mobile station and a base station for selecting an optimal bandwidth to be utilized by the mobile station for receiving transmitted information from a base station.
Further, the present invention provides a code division multiple access (CDMA) system comprising a base station operating to support a basic chip rate, a forward channel link chip rate, and a reverse channel link chip rate; and a mobile station in electronic communication with the base station, the mobile station communicating with the base station so as to independently adjust the values of the forward channel link chip rate and the reverse channel link chip rate. The forward channel link chip rate may be less than or equal to a maximum forward value allowed by the base station. The reverse channel link chip rate may be less than or equal to a maximum reverse value allowed by the base station. In addition, the forward channel link chip rate, the reverse channel link chip rate, and the basic chip rate may be equal to each other. The base station may transmit the maximum forward and/or reverse values to the mobile station. In addition, the forward channel link chip rate may be less than or equal to a maximum forward value allowed by the mobile station. Further, the reverse channel link chip rate may be less than or equal to a maximum reverse value allowed by the mobile station. In either case, the mobile station may transmit the maximum forward and/or reverse value to the base station.
The present invention also provides a method of operating a CDMA system comprising the steps of setting up a call to a base station operating to support a basic chip rate, a maximum forward channel link chip rate, and a maximum reverse channel link chip rate by paging the base station with a mobile station; requesting a desired forward channel link chip rate from the base station by the mobile station; transmitting the maximum forward channel link chip rate to the mobile station from the base station; transmitting a revised forward channel link chip rate to the base station from the mobile station; transmitting a start message to the mobile station from the base station; and communicating with the base station using the revised forward channel link chip rate. During the use of this method, the revised forward channel link chip rate may be equal to the basic chip rate. In addition, the revised forward channel link chip rate may be equal to the maximum forward channel link chip rate.
In addition, the method of operating a CDMA system may further comprise the steps of requesting a desired reverse channel link chip rate from the base station by the mobile station; transmitting the maximum reverse channel link chip rate to the mobile station from the base station; transmitting a revised reverse channel link chip rate to the base station from the mobile station; and communicating with the base station using the revised reverse channel link chip rate. In this case, the revised reverse channel link chip rate may be equal to the basic chip rate. Further, the maximum reverse channel link chip rate may be equal to the basic chip rate. The basic chip rate may also be equal to the revised forward channel link chip rate and the revised reverse channel link chip rate. The basic chip rate may also be equal to the maximum forward channel link chip rate and the maximum reverse channel link chip rate.
The present invention also provides a method of operating a CDMA system comprising the steps of setting up a call to a mobile station operating to support a basic chip rate, a maximum forward channel link chip rate, and a maximum reverse channel link chip rate by paging a mobile station with a base station; requesting a desired forward channel link chip rate from the mobile station by the base station; transmitting the maximum forward channel link chip rate to the base station from the mobile station; transmitting a revised froward channel link chip rate to the mobile station from the base station; transmitting a start message to the base station from the mobile station; and communicating with the mobile station using the revised forward channel link chip rate. The revised forward channel link chip rate may be equal to the basic chi
Ahn Jae-min
Kang Heewon
Kim Youngky
Chin Wellington
Han John C.
Pham Brenda H.
Samsung Electronics Co,. Ltd.
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