Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-12-22
2003-04-22
Vo, Nguyen T. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S522000
Reexamination Certificate
active
06553235
ABSTRACT:
BACKGROUND
The present invention relates generally to cellular telecommunication systems, and, more particularly, to a method and system for controlling radio channel congestion in a cellular telecommunications system.
The cellular telephone industry has made phenomenal strides in commercial operations in the United States as well as the rest of the world. Growth in major metropolitan areas has far exceeded expectations and is rapidly outstripping system capacity. If this trend continues, the effects of this industry's growth will soon reach even the smallest markets. Innovative solutions are required to meet these increasing capacity needs as well as maintain high quality service and avoid rising prices.
FIG. 1
is a block diagram that illustrates a cellular telecommunications system
100
. The cellular system
100
includes a plurality of radio base stations
140
a-n
,
140
a-n
′, each being connected to a corresponding antenna
130
a-n
,
130
a-n
′. The radio base stations
140
a-n
,
140
a-n
′, in conjunction with the antennas
130
a-n
,
130
a-n
40
, communicate with a plurality of mobile stations (e.g., mobile stations
120
a
,
120
b
,
120
m
,
120
a
′,
120
b
′ and
120
m
′), which are located in one of the cells
110
a-n
,
110
a-n
′. Communication from a base station to mobile stations are transmitted on downlink (DL) radio channels of the base station.
In general, a mobile station communicates with the base station corresponding to the cell in which the mobile station is located or if the system supports soft handovers, a mobile station would communicate with more than one base stations. In
FIG. 1
, for example, mobile stations
120
a
and
120
b
are shown to be communicating with base station
130
a
. The base stations
130
a-n
are, in turn, connected to the radio network controller (RNC)
150
, whereas the base stations
130
a-n
′ are connected to the RNC
150
′. Mobile control node
160
is a switching center that supports the interconnection of the cellular system
100
to a fixed network
170
by landlines or other equivalent connections. The fixed network
170
may comprise a computer-based network (e.g., the Internet), a public switched telephone network (PSTN), an integrated services digital network (ISDN) or a public data network (PSPDN).
As more mobile stations subscribe to these types of systems, the demand for system capacity will increase rapidly, especially in highly populated areas, and one of the most crucial limiting factors for the system DL capacity of the radio channel is the available DL transmit power, P
DL
—
MAX
, of the base stations. Thus, for example, if the number of mobile stations being serviced by a given base station is excessive, the base station may not have sufficient DL transmit power available to provide effective support. Consequently, mobile stations may experience transmission delays and unserved requests due to the congestion of the radio channel.
Therefore, a need exists for a method and system for monitoring potential radio channel congestion and for relieving congestion on one or more radio channels of a cellular system.
SUMMARY
The present invention involves method and system for monitoring potential congestion on radio channels, and when appropriate, relieving the radio channel congestion. In general, the present invention accomplishes this through the use of a radio channel congestion alarm that continuously monitors DL transmit power of a base station and compares the current DL transmit power level to an alarm threshold value. The alarm threshold value, in turn, is adaptively adjusted as a function of the variation over time in DL transmit power of the base station. By adaptively adjusting the alarm threshold value based on the variation over time of the DL transmit power, the method and/or system of the present invention monitors potential radio channel congestion based on the behavior of DL transmit power, which increases the accuracy of the congestion alarm, improves the congestion relief and enhances the system capacity.
When appropriate, the present invention relieves radio channel congestion using a congestion controller. The congestion controller is divided into a fast congestion controller (FCC) located in the base station and a slow congestion controller (SCC) located in a radio network controller. The FCC performs rapid congestion relief actions to mitigate DL radio channel congestion until the SCC permanently resolves DL radio channel congestion.
Accordingly, it is an object of the present invention to more accurately detect potential DL radio channel congestions.
It is another object of the present invention to eliminate false congestion alarms and unnecessary capacity limiting actions.
It is yet another object of the present invention to provide fast congestion relief actions upon detecting potential DL radio channel congestion.
It is another object of the present invention to efficiently relieve DL radio channel congestion without decreasing the system DL capacity.
In accordance with one embodiment of the present invention, the above-identified and other objectives are achieved by a base station comprising a FCC. The FCC monitors potential radio channel congestions by monitoring characteristics of the DL transmission on radio channels of the base station. The FCC comprises a congestion alarm having an alarm threshold value that is adaptively adjusted based on the characteristics of DL transmission. Specifically, the variation over time of the DL transmit power is determined and used to adjust the FCC alarm threshold value. Further, the FCC alarm threshold value can be adaptively adjusted with respect to the variation over time of the DL transmit power, the detected number of users and their offered bit rates.
Further, according to exemplary embodiments of the present invention, upon detecting radio channel congestions, methods and systems for relieving radio channel congestions include temporarily blocking data services in the system. Specifically, when the base station is not servicing any packet data user, the system then temporarily reduces the maximum transmit power allowed for all users' downlink dedicated physical channels (DPCHs). However, when there are packet data users serviced by the base station, the system then temporarily blocks packet data services by rapidly decreasing transmit power of the packet data users' downlink DPCHs.
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Bark Gunnar
Helmersson Ke Wang
Wiberg Niclas
Ly Nghi H.
Telefonaktiebolaget LM Ericsson (publ)
Vo Nguyen T.
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