Telecommunications – Transmitter and receiver at separate stations – Having measuring – testing – or monitoring of system or part
Reexamination Certificate
1999-04-28
2001-03-06
Urban, Edward F. (Department: 2683)
Telecommunications
Transmitter and receiver at separate stations
Having measuring, testing, or monitoring of system or part
C455S067700, C455S067700, C455S452200, C455S436000
Reexamination Certificate
active
06198910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cellular networks and more particularly to management of radio frequency (RF) calls in a mobile telephone system.
2. Description of Related Art
In mobile telecommunication systems, an RF performance of the system is typically managed by responding to unacceptable signal characteristics and independently varying one of the RF management mechanisms. For instance, a system may respond to a poor carrier signal strength-to-interference (C/I) ratio of a call by increasing power. While, this power boost may strengthen the signal of the call being monitored, it may also have a corresponding negative affect on another call by increasing the interference in response to the higher noise levels caused by the higher power level. Another conventional RF management technique may be to switch a call from one channel frequency, with relatively high interference, to another channel with relatively low interference. Current RF management functions, however, are designed to operate independently and asynchronously. As a consequence, these RF management functions sometimes operate at cross-purposes, i.e., improving the signal of one mobile while increasing the interference experienced by other mobiles.
In addition, currently available RF management algorithms are essentially fixed in their behaviors, wherein decisions are based on configuration information and/or averaged measurements. As a result, RF management functions tend to have a large number of parameters which must be continually updated to maintain an optimum performance in the cellular network or telecommunication system. RF management algorithms are also typically associated with a variable parameter such as power level, call mode, and channel assignment. That is, one algorithm is used for power management while another manages channel allocation, and the like. RF management algorithms may also be coordinated to avoid significant interference in their respective operations. For example, handoff requests can be delayed until after power control actions have taken place, thus allowing time for the RF signal strength readings to settle. However, channel allocation, handoff and power control decisions are typically conducted in different places in a cellular network or telecommunications system, rather than at a centralized location, which makes coordinating activities difficult.
The effort to maintain and optimize RF management parameters in a cellular network can be reduced through the use of off-board management systems and expert systems. By analyzing past performance information received from a cellular system and comparing that information against a given set of rules, an expert system can determine when the system is getting “out of tune” and then recommend changes to the various parameters to correct the condition. In some cases, the expert system may also be able to make the changes itself. However, these expert systems utilize past average measured criteria and thus cannot make real-time decisions for specific mobile units to implement an appropriate dynamic corrective action. In addition, expert systems are highly complex, having an ability to crunch all the numbers and performance measurements to optimize performance. Such a system however requires undesired complexity. A more simpler solution is desired for handling RF channel allocation on a cellular network.
The problem in the art is further characterized in that management of the RF channels, particularly in terms of handoff, has become a very complicated and cumbersome process. The means used to decide whether or not a mobile should be assigned to a given channel or moved to a different channel has become a very complicated, large engineering problem. A lot of parameters are associated with the cell sites, in particular, to determine when particular mobiles need to be handoff and help decide where the mobiles need to go. It thus becomes difficult for operators of large networks to manage their system, and optimize behavior properly. This means that the quality over time begins to suffer. The operators are unable to keep up with the complexities of the system over time.
A need exists for a centralized RF management system that operates substantially synchronously across all variables for providing improved management of RF channels in a cellular network.
SUMMARY OF THE INVENTION
The present disclosure, accordingly, provides a method and apparatus for a centralized RF management system in a cellular network and operable in an analog and/or digital modes of operation which can include an analog advanced mobile phone system (AMPS), as well as a digital time division multiple access (TDMA) cellular network, or the like.
The RF management system and method combines multiple parameters in a manner to improve an overall quality of service offered to mobile subscribers, while at the same time greatly simplifying a cellular network operator's RF engineering activities. The end result is a cellular system with higher performance and lower operational costs.
The present invention is based on a “Quality Map” or Q-Map of the cellular system for each mobile thereof. The Q-Map identifies, for a particular mobile at a particular point in time during a call, the estimated quality of service the mobile would receive on each available RF channel in each available mode (i.e. analog, digital) at each available power level. The Q-map is created and updated based on information available from the cellular system, including signal strength measurements, interference, call activity and so on. In addition, each mobile is assigned a quality value (Q-value) that reflects it current quality of service.
When a mobile unit's Q-value falls below an operator defined threshold (Q-min) during a call, the mobile unit's current Q-map is searched for a prescribed channel/mode/power level combination. If that Q-map value is greater than the mobile units current Q-value, the unit is then instructed to take an appropriate action (handoff, change mode, change power level, or a combination of these), resulting in an improved quality of service for the mobile. The mobile's Q-map is updated to reflect the new situation and the quality assessment continues for the duration of the call.
The cellular network operator's optimization decision is simply to decide upon what value to set for the Q-min threshold. The Q-min threshold determines the minimum acceptable quality level for the system, thus allowing the operator flexibility to trade-off quality for resources.
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Haynes and Boone LLP
Jackson Blane J.
Nortel Networks Limited
Urban Edward F.
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