Base station system and method for compensating traffic channel signal strength measurements in a cellular radio telecommunication network
A Base Station System (BSS) and method for compensating traffic channel signal strength measurements to provide improved handover decisions. Each active mobile station in a given cell is instructed to measure and report signal strengths of the mobile station's active traffic channel, broadcast channels from neighboring cells, and a broadcast channel from the given cell over a predefined period of time. An offset value calculator analyzes the signal strength measurements of the active traffic channel and the given cell's broadcast channel, and calculates an updated value for a compensation offset factor. The updated value is then used within a handover algorithm to determine when to hand over mobile stations during future connections on the active traffic channel.
1. A method of compensating traffic channel signal strength measurements for improved handover decisions in a cellular radio telecommunication network, said method comprising the steps of:
collecting by a Base Station System (BSS), signal strength measurements taken by a plurality of active mobile stations operating within a given cell, said measurements including signal strength measurements of the mobile stations' active traffic channels, broadcast channels from neighboring cells, and a broadcast channel from the given cell;
instructing the mobile stations to stop measuring the signal strength of the broadcast channel from the given cell when a predefined event occurs;
analyzing by the BSS, the collected signal strength measurements from the active mobile stations to determine for the given cell, a unique compensation offset factor for each traffic channel, wherein the unique compensation offset factor for a given traffic channel is based on a mean value of all the signal strength differences between the given traffic channel and the broadcast channel of the given cell, as collected from a plurality of mobile stations served by the given traffic channel; and
making future handover decisions for mobile stations served by the given traffic channel by utilizing the unique compensation offset factor for the given traffic channel to define a cell border between the given cell and a neighboring cell.
2. The method of claim 1 , further comprising, prior to collecting the signal strength measurements, the step of instructing all of the active mobile stations in the given cell to measure the signal strength of the given cell's broadcast channel.
3. The method of claim 2 , wherein the step of instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes instructing all of the active mobile stations to add the given cell's broadcast channel to each mobile station's neighbor cell list.
4. The method of claim 2 , wherein the step of instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes instructing all of the active mobile stations to measure and report to the BSS, the signal strength of the given cell's broadcast channel for a predefined time period.
5. The method of claim 2 , wherein the step of instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes instructing all of the active mobile stations to measure and report to the BSS, the signal strength of the given cell's broadcast channel until the mobile stations are instructed otherwise.
6. The method of claim 1 , further comprising the steps of:
determining whether the unique compensation offset for a given traffic channel should be updated; and
if the unique compensation offset for the given traffic channel should be updated, determining an updated unique compensation offset factor by analyzing the signal strength measurements of the active traffic channel and the given cell's broadcast channel collected over a new predefined time period from the plurality of mobile stations served by the given traffic channel.
7. The method of claim 6 , wherein the step of determining whether the unique compensation offset should be updated includes receiving a request from a system operator to update the unique compensation offset for the given traffic channel.
8. The method of claim 6 , wherein the step of determining whether the unique compensation offset should be updated includes determining whether an update timer has expired.
9. The method of claim 1 , further comprising the steps of:
handing over a given mobile station to the neighboring cell; and
instructing the given mobile station to measure and report the signal strength of the broadcast channel from the neighboring cell, wherein the neighboring cell is the given mobile station's new serving cell.
10. The method of claim 1 , wherein the step of analyzing the collected signal strength measurements from the active mobile stations to determine a unique compensation offset factor includes:
calculating the unique compensation offset factor utilizing a linear function of the mean value of all the signal strength differences between the given traffic channel and the broadcast channel of the given cell, as collected from the plurality of mobile stations served by the given traffic channel.
11. In a cellular radio telecommunication network, a Base Station System (BSS) that compensates traffic channel signal strength measurements to provide improved handover decisions, said BSS comprising:
a receiver that receives signal strength measurements taken by all active mobile stations operating within a given cell, said measurements including signal strength measurements of the mobile stations' active traffic channels, broadcast channels from neighboring cells, and a broadcast channel from the given cell;
a transmitter for instructing the mobile stations to stop measuring the signal strength of the broadcast channel from the given cell when a predefined event occurs;
a measurement database that collects the signal strength measurements from the receiver;
an offset value calculator that retrieves the measurements from the database, analyzes the signal strength measurements of the active traffic channels and the broadcast channel of the given cell, and calculates for the given cell, a unique compensation offset factor for each traffic channel, wherein the unique compensation offset factor for a given traffic channel is based on a mean value of all the signal strength differences between the given traffic channel and the broadcast channel of the given cell, as collected from a plurality of mobile stations served by the given traffic channel; and
a handover algorithm for making future handover decisions for the mobile stations served by the given traffic channel by utilizing the unique compensation offset factor for the given traffic channel to define a cell border between the given cell and a neighboring cell.
12. The BSS of claim 11 , further comprising means for instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel.
13. The BSS of claim 12 , wherein the means for instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes means for instructing all of the active mobile stations to add the given cell's broadcast channel to each mobile station's neighbor cell list.
14. The BSS of claim 12 , wherein the means for instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes means for instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel until instructed otherwise.
15. The BSS of claim 12 , wherein the means for instructing all of the active mobile stations to measure the signal strength of the given cell's broadcast channel includes means for instructing all of the active mobile stations to measure and report to the BSS, the signal strength of the given cell's broadcast channel for a predefined time period.
16. The BSS of claim 15 , further comprising means for determining whether the unique compensation offset for a given traffic channel should be updated, wherein the offset value calculator, in response to a determination that the unique compensation offset for the given traffic channel should be updated, calculates an updated unique compensation offset factor by analyzing the signal strength measurements of the active traffic channel and the given cell's broadcast channel collected over a new predefined time period from the plurality of mobile stations served by the given traffic channel.
17. The BSS of claim 16 , wherein the means for determining whether the unique compensation offset value for the given traffic channel should be updated includes an update timer.
18. The BSS of claim 11 , wherein the offset value calculator calculates the unique compensation offset factor utilizing a linear function of the mean value of all the signal strength differences between the given traffic channel and the broadcast channel of the given cell, as collected from the plurality of mobile stations served by the given traffic channel.