Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
1997-07-16
2001-12-11
Ton, Dang (Department: 2663)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S441000
Reexamination Certificate
active
06330232
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the selection of Base Station Transceiver Subsystems (BTS) at a CDMA cell site provisioned with multiple co-located BTSs, each operating independently on a dedicated carrier.
Typically, in present CDMA cellular telephone systems, one CDMA base station transceiver subsystem (BTS) is used for each cell. This is sufficient for low to medium traffic demands; however, under heavy demands additional base station transceiver subsystems are required to provide an acceptable level of service.
In a cellular telephone network employing a plurality of base station transceiver subsystems (BTS), typically, the assignment of a particular BTS which is to handle a call, is made by a base station controller having a selector bank subsystem which runs a radio link manager program for determining which of the BTS systems is to be used for a particular call. Currently, the assignment of a call to a particular BTS is made on the basis of whether or not the excess forward link capacity of the BTS exceeds a pre-set LoCall Blocking Threshold and whether or not there are free traffic channel elements available. In areas where there is high traffic demand, one particular BTS may therefore be called upon to service more calls than another BTS, to the point where no further calls can be handled by the loaded BTS, while excess capacity is still available at the unloaded BTS. Various prior art references deal with issues such as handoff boundary balancing, adding and removing a BTS in a network, etc., however, none appears to deal with the problem of concentrated loads on a particular BTS within a multiple BTS cell site. The present invention addresses this problem.
BRIEF SUMMARY OF THE INVENTION
In accordance with one aspect of the invention there is provided a method of selecting a Code Division Multiple Access (CDMA) base station transceiver subsystem from a plurality of base station transceiver subsystems to handle a call in a cellular telephone network, in response to a call request. The method includes the steps of:
a) receiving a representation of available call capacity from each of the base station transceiver subsystems;
b) determining which of the base station transceiver subsystems has the greatest available call capacity; and
c) enabling the base station transceiver subsystem having the greatest available call capacity to handle the call.
Preferably, the method includes the step of passing an available capacity request message from a selector bank subsystem to the base station transceiver subsystem subsystems.
Preferably, the method includes the step of storing in respective data storage elements representations of available call capacities of each of the base station transceiver subsystems.
Preferably, the method includes the step of transmitting to the base station transceiver subsystem having the greatest available call capacity, an enable message indicating that the selected base station transceiver subsystem is enabled to handle the call.
In accordance with another aspect of the invention, there is provided a method of estimating available call capacity at a CDMA base station transceiver subsystem. The method includes the steps of:
a) determining available power to support additional calls by the base station transceiver subsystem;
b) determining the average power used per channel;
c) dividing a value representing the available power to support additional calls by a value representing the average power used per channel to determine the call capacity available;
d) transmitting an available capacity response message including a representation of the call capacity available.
Preferably, the method includes the step of measuring the power consumed by each channel in use.
Preferably, the method includes the step of cumulatively adding values representing the power consumed by each channel in use to obtain a total forward transmit power usage value.
Preferably, the method includes the step of determining the number of channels in use.
Preferably, the method includes the step of dividing a value representing the total power usage by the number of channels in use to obtain the average power used per channel.
Preferably, the method includes the step of subtracting a value representing the total forward transmit power usage, a value representing a LoCall Blocking Threshold power and a value representing a pilot power of said base station transceiver from a value representing a maximum allowable total transmit power, to obtain a value representing the available power to support additional calls.
In accordance with another aspect of the invention, there is provided an apparatus for selecting a CDMA base station transceiver subsystem from a plurality of base station transceiver subsystems to handle a call in a cellular telephone network, in response to a call request. The apparatus includes a receiver for receiving a representation of available call capacity from each of the base stations, a processor for examining the representations of available call capacity from each of the base stations to determine which of the base stations has the greatest available call capacity and a transmitter for transmitting to the base station with the greatest call capacity, an enable message enabling the base station to handle the call.
Preferably, the transmitter is operable to pass an available capacity request message to at least two base station transceiver subsystems.
Preferably, the apparatus includes data storage elements for storing the representations of available call capacity.
In accordance with another aspect of the invention, there is provided an apparatus for estimating available call capacity at a CDMA base station transceiver subsystem having a plurality of traffic channel elements, a known maximum allowable total transmit power, a known pilot power and a known LoCall Blocking Threshold power. The apparatus includes a channel counter for counting the number of channels in use at any given time, a plurality of sensors for determining the power consumed by each channel in use, a processor for:
a) subtracting a value representing the power consumed by all channels in use, a value representing the known LoCall Blocking Threshold power and a value representing the pilot power from a value representing the known maximum allowable total transmit power to determine the total transmit power available to support additional calls;
b) dividing a value representing the power consumed by all channels in use by the number of channels in use to determine an average power used per channel; and
c) dividing a value representing the total transmit power available to support additional calls by a value representing the average power used per channel to determine an available call capacity of the CDMA base station transceiver subsystem; and
a transmitter for transmitting to a selector bank subsystem an available capacity response message including a representation of the available call capacity.
Preferably, the processor is operable to cumulatively add values representing the power consumed by each channel in use to obtain a total forward transmit power usage value.
In accordance with another aspect of the invention, there is provided a method of selecting a base station transceiver from a plurality of base station transceiver subsystems in a cellular telephone network. The method includes the steps of:
a) transmitting an available capacity request message from a selector bank subsystem to the base station transceiver subsystems;
b) receiving the available capacity request message at the base station transceiver subsystems;
c) at each base station transceiver subsystem:
i) determining the available power to support additional calls by the base station transceiver subsystem;
ii) determining the average power used per channel;
iii) dividing a value representing the available power to support additional calls, by a value representing the average power used per channel to determine a call capacity available; and
iv) transmitting an available capacity response message to the
Foley & Lardner
Haszko Dennis R.
Nguyen Toan
Nortel Networks Limited
Ton Dang
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