Store and forward handoff
View Patent ↗In a cellular spread-spectrum communications network, a system and method for handing off a remote unit from a first base station to a second base station without loss of data. The remote unit receives a first spread-spectrum signal having a first signal quality from the first base station and transmits data to the first base station at a first data rate and a first power level. Responsive to monitoring the first signal quality and comparing the first signal quality to a plurality of signal qualities of a respective plurality of received-spread-spectrum signals, the remote unit initiates handoff when any of a number of predetermined criteria are met. Upon initiating handoff to the second base station, the remote unit stores the data that would otherwise have been transmitted. Once handoff is complete, the remote unit transmits the stored data to the second base station at a second data rate and a second power level, with the second data rate greater than the first data rate and the second power level greater than the first power level. Once the stored data has been transmitted, the remote unit transmits data to the second base station at a data rate and power level comparable to the first data rate and the first power level.
1. In a wireless communications system having a central control unit, a plurality of base stations and a wireless remote station, with the wireless remote station communicating with a first base station at a first normal data rate, a handoff method at the wireless remote station comprising:
ceasing transmission to the first base station upon determining to handoff to a second base station;
storing data intended for transmission from the wireless remote station, during the cessation of transmission;
synchronizing to a signal received from the second base station;
upon synchronizing, transmitting the stored data to the second base station at a temporary data rate, thereby transferring the stored data to the second base station; and
upon completing transfer of the stored data to the second base station, transmitting further data intended for transmission from the wireless remote station to the second base station at a normal second data rate, the normal second data rate being different from the temporary data rate.
2. The method as set forth in claim 1 , wherein the temporary data rate is faster than the normal second data rate.
3. The method as set forth in claim 2 , wherein the temporary data rate is faster than the normal first data rate.
4. The method as set forth in claim 3 , wherein the second normal data rate is substantially similar to the first normal data rate.
5. The method as set forth in claim 1 , wherein each transmitting of data comprises processing data with at least one chip sequence signal to produce a spread-spectrum signal and transmitting the spread-spectrum signal.
6. The method as set forth in claim 5 , wherein:
the data transmitted comprises packet data; and
the spread-spectrum signal comprises a spread-spectrum packet signal.
7. The method as set forth in claim 1 , wherein the data transmitted comprises packet data.
8. A wireless remote station for wireless communications, comprising:
a wireless transmitter, for transmitting data to a first base station at a first normal data rate;
a wireless receiver, for receiving a plurality of received-spread-spectrum signals radiated from a plurality of base stations;
a processor, responsive to a determination to handoff to a second base station, for causing a cessation of the data transmission to the first base station; and
a memory, coupled to the processor, for storing all data intended for transmission from the wireless remote station during the cessation of transmission; wherein:
the processor is for completing handoff to the second base station;
the wireless transmitter, responsive to handoff completion, is for transmitting the stored data to the second base station at a temporary data rate, thereby transferring the stored data to the second base station; and
the transmitter, upon completing the transfer of the stored data to the second base station, is further for transmitting further data intended for transmission from the wireless remote station to the second base station at a normal second data rate, the normal second data rate being different from the temporary data rate.
9. The wireless remote station as set forth in claim 8 , wherein the temporary data rate is faster than the normal second data rate.
10. The wireless remote station as set forth in claim 9 , wherein the temporary data rate is faster than the normal first data rate.
11. The wireless remote station as set forth in claim 9 , wherein the second normal data rate is substantially similar to the first normal data rate.
12. The wireless remote station as set forth in claim 8 , wherein the wireless transmitter comprises a spread-spectrum transmitter for processing data with at least one chip sequence signal to produce a spread-spectrum signal for each data transmission.
13. The wireless remote station as set forth in claim 8 , wherein the wireless transmitter comprises a wireless packet data transmitter.