Handoff of a mobile station between half rate and full rate channels
First Claim
1. A method of communication in a cellular mobile radio system having a plurality of base stations in a plurality of cells for communication with a plurality of mobile stations in the cells, comprising the steps of:
- transmitting a signal between a first base station and at least a first mobile station of the cellular mobile radio system, the signal being transmitted on a half rate channel having relatively slowly repeating time slots per frame or a full rate channel having relatively quickly repeating time slots per frame as compared to the relatively slowly repeating time slots. wherein the bit rates within the time slots of both the half and full rate channels are the same, wherein each bit transmitted in said half rate channel represents more sensitive information than that of a corresponding bit transmitted in said full rate channel;
estimating periodically the quality of the received signal;
assigning the transmission of the signal to a half rate channel if the estimated quality is above a first predetermined value;
assigning the transmission of the signal to a full rate channel if the estimated quality is below the first predetermined value; and
handing off the mobile station between a half rate channel and a full rate channel depending upon the estimated quality.
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Abstract
In a cellular mobile telephone system of the type having TDMA channels, a plurality of mobile station operate at either a full rate or a half rate. If the mobile stations are operating on the periphery of a cell they are assigned to full rate channels. If the mobile stations are operating in the vicinity of the base station, they are assigned to half rate channels. The mobile station are reassigned from full rate to half rate channels depending upon a measured parameters relating to signal strength or quality, such as the bit error rate of communications between the mobile station and the base station. If the measured bit error rate between the mobile station and a neighboring station is less than the bit error rate between the mobile station and its presently assigned base station, the mobile station is handed off to the neighboring base station.
133 Citations
19 Claims
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1. A method of communication in a cellular mobile radio system having a plurality of base stations in a plurality of cells for communication with a plurality of mobile stations in the cells, comprising the steps of:
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transmitting a signal between a first base station and at least a first mobile station of the cellular mobile radio system, the signal being transmitted on a half rate channel having relatively slowly repeating time slots per frame or a full rate channel having relatively quickly repeating time slots per frame as compared to the relatively slowly repeating time slots. wherein the bit rates within the time slots of both the half and full rate channels are the same, wherein each bit transmitted in said half rate channel represents more sensitive information than that of a corresponding bit transmitted in said full rate channel; estimating periodically the quality of the received signal; assigning the transmission of the signal to a half rate channel if the estimated quality is above a first predetermined value; assigning the transmission of the signal to a full rate channel if the estimated quality is below the first predetermined value; and handing off the mobile station between a half rate channel and a full rate channel depending upon the estimated quality. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of controlling communications in a cellular communications system comprising the steps of:
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estimating directly or indirectly parameter values indicative of quality of information transfer on communication channels used for ongoing calls in a cell of a cellular communications system, the communication channels including a half rate channel having relatively slowly repeating time slots per frame and a full rate channel having relatively quickly repeating time slots per frame as compared to the relatively slowly, repeating time slots, wherein the bit rates within the time slots of both the half and full rate channels are the same, wherein each bit transmitted in said half rate channel represents more sensitive information than that of a corresponding bit transmitted in said full rate channel; comparing said estimated parameter values indicative of quality with parameter values set by information transfer quality requirements; changing the communication channel of at least one call from a full rate channel to a half rate channel when the comparison indicates that a half rate channel would provide sufficient quality for the call; and changing the communication channel of at least one call from a half rate channel to a full rate channel when the comparison indicates that a full rate channel will be required to provide sufficient quality for the call. - View Dependent Claims (9, 10, 11, 12)
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13. A method of communication in a cellular mobile radio system having a plurality of base stations in a plurality of cells, comprising the steps of:
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transmitting a speech signal between a first base station and at least a first mobile station of a cellular mobile radio system, the speech signal being transmitted on a half rate channel having relatively slowly repeating time slots per frame or a full rate channel having relatively quickly repeating time slots per frame as compared to the relatively slowly repeating time slots, wherein the bit rates within the time slots of both the half and full rate channels are the same, wherein each bit transmitted in said half rate channel represents more sensitive information than that of a corresponding bit transmitted in said full rate channel; estimating periodically the quality of the received speech signal; assigning the mobile station to a half rate channel of the first base station if the estimated quality of the speech signal is greater than a predetermined amount; and assigning the mobile station to a full rate channel of the first base station if the estimated quality of the speech signal is less than a predetermined amount; and handing off the mobile station between a half rate channel and a full rate channel depending upon the estimated quality. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification