Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-10-06
2001-05-29
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S403000, C455S455000, C455S440000, C370S342000, C375S346000
Reexamination Certificate
active
06240287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to processing of call related operations at base stations of a cellular wireless communication system, and particularly to a processing management scheme that insures a base station will maintain its ability to process user call activities while handling an increasing number of active calls.
2. Discussion of the Known Art
A typical base station of a cellular wireless communication system has processing equipment that controls call-related activities such as, for example, call originations, call terminations, handoffs of active calls to or from the base station, and user registrations and paging. These activities all use or occupy processing time at the base station. For example, at base stations of code division multiple access (CDMA) systems, processing equipment known as a radio control complex (RCC) includes a number of associated hardware units that interface with a system bus with which a core processor unit (CPU) is connected. As user activity in a base station's area of coverage or “cell” increases, the RCC approaches a limit of its maximum capacity to handle both new and ongoing traffic functions. Co-pending U.S. patent application Ser. No. 09/131,390 filed Aug. 7, 1998, entitled “CDMA Base Station Assisted Soft Handoff” and assigned to the assignee of the present invention and application, discloses a scheme for conserving base station processing resources and available forward link power. All relevant portions of the mentioned patent application are incorporated by reference. Specifically, the scheme proposes a reduction of call handoff activity at a CDMA base station. That is, a user who might add a new base station to a list of potential base stations to which the user may be handed off, is maintained by only currently serving CDMA base stations as long as a minimum quality of call service is being provided.
Although a CDMA base station preferably should support multiple carriers at its site to allow for potential subscriber growth, current limitations of base station processors including the mentioned RCC, make it difficult at present to support more than three carriers in a CDMA system. User-related control functions that contribute significantly toward RCC processing time at a CDMA base station include, for example, handoffs of calls to or from the base station, or between sectors of the same base station; subscriber call originations (i.e., attempts by a user to initiate a call via the base station); and user call termination (i.e., connection of a call originating from a wired (telephone) network with which a base station is linked, to a user in the base station's cell). Each handoff typically occupies about 100 milliseconds of processing time at the base station. Each call origination and termination occupies about 75 milliseconds. User registration (i.e., system recognition of a user prior to placing or receiving a call), and paging of a user with operating data from the base station, each occupy about five milliseconds of the base station's processing time. Processing times may vary depending on the CPU used at the base station.
SUMMARY OF THE INVENTION
A technique is provided for allowing a base station of a cellular wireless communication system to manage an increasing number of active users in the base station's cell, without exceeding the capacity of the base station's call processing equipment.
According to the invention, a method of preventing an overload of call processing capacity at a base station of a cellular wireless communication system, includes monitoring a level of call processing at the base station and reducing a present handoff rate for user stations served by the base station when the monitored level of call processing exceeds a first threshold which is less than a maximum capacity of call processing at the base station. When the monitored level of call processing exceeds a second threshold greater than the first threshold, a present rate of call originations or terminations is reduced, while further reducing the handoff rate.
The inventive overload control scheme first reduces unnecessary handoff activities, and then limits so-called new arrival traffic to prevent a processor overload condition when control traffic cannot be reduced sufficiently by a reduction of handoff activity alone.
For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawing and the appended claims.
REFERENCES:
patent: 5245629 (1993-09-01), Hall
patent: 5475861 (1995-12-01), Hall
patent: 5745520 (1998-04-01), Love et al.
patent: 5940430 (1999-08-01), Love et al.
patent: 6085107 (2000-07-01), Persson et al.
Cheng Terry Si-Fong
Huang Ching Yao
Huang Joe
Yu Bee Yun
Hunter Daniel
Law Office of Leo Zucker
Lucent Technologies - Inc.
Tran Pablo
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