Power efficient wireless transmission

• US 20070191051A1
• Filed: 01/26/2007
• Published: 08/16/2007
• Est. Priority Date: 01/27/2006
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Corporation
• Inventors: Suonvieri, Jukka
• Granted Patent: US 7,831,273 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04W 52/16 Deriving transmission power values from another channel
• CPC Class Codes: H04W 52/322 Power control of broadcast channels
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A solution for power efficient transmission in a wireless telecommunication system is provided. The telecommunication system utilizes a time slot based data transmission scheme. According to the provided solution, at least a portion of time slots is allocated to a broadcast control channel on a given frequency and to at least one different channel. The transmit power levels of the time slot or time slots allocated to another channel or other channels than the broadcast control channel are then adjusted on the basis of contents of the time slots. The broadcast signal is then transmitted with a given transmit power level on a time slot allocated to the broadcast control channel, and a signal or signals on other time slots are transmitted with the adjusted transmit power level.

Claims

1. A method, comprising:

allocating, in a wireless telecommunication system in which the data transmission on a given frequency band is divided into a plurality of time slots, at least a portion of the time slots of the frequency band to a broadcast control channel and at least one different channel;

adjusting a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel;

transmitting a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel, and

transmitting a signal with the adjusted transmit power level in the time slot of the different channel.

2. The method of claim 1, further comprising decreasing the transmit power level of a time slot for which there is no payload data allocated for transmission and transmitting a signal in the time slot with a lower transmit power level than that of the broadcast signal.

3. The method of claim 1, wherein the power level adjustment is performed together with a conventional downlink power control scheme associated with traffic channels.

4. The method of claim 1, wherein the transmit power level adjustment is performed in a base station of a radio access network of the wireless telecommunication system.

5. The method of claim 4, further comprising activating the transmit power level adjustment upon detection of a break in a mains power supply.

6. The method of claim 1, further comprising switching the power level adjustment on or off upon reception of a corresponding command and assigning the same power level to signals in every time slot in the frequency band when the power level adjustment has been switched off.

7. The method of claim 1, further comprising adjusting handover parameters related to a mobile terminal in the service area of the radio access network on the basis of the power adjustment being currently used in order to compensate for a reduction in the transmit power level for handover purposes.

8. The method of claim 7, further comprising:

receiving handover measurement values from the mobile terminal, each measurement value being associated with a base station of the radio access network and describing the power level of a radio signal received by the mobile terminal from the corresponding base station, and

weighting each handover measurement value by increasing the handover measurement value in proportion to the degree of power adjustment, if the base station utilizes the power adjustment.

9. The method of claim 7, further comprising:

receiving a handover measurement value from the mobile terminal, the handover measurement value describing the power level of a radio signal received by the mobile terminal from a candidate base station;

obtaining, from stored information concerning the behavior of the mobile terminal, knowledge on a serving base station time slot during which the mobile terminal measured the handover measurement value;

receiving from the mobile terminal timing information observed by the mobile terminal and indicating a time difference between frame clocks of a serving base station and the handover candidate base station for which the handover measurement value was measured;

compensating the received handover measurement value according to the knowledge on the transmit power level of the handover candidate base station during the measurement of the handover measurement value, and

determining, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.

10. The method of claim 9, further comprising:

determining the number of time slots of the handover candidate base station during which the mobile terminal measured the handover measurement value,

determining the transmit power level of the candidate handover base station for each time slot during which the mobile terminal measured the handover measurement value, and

compensating the received handover measurement value according to the transmit power levels of the time slot or time slots during which the mobile terminal measured the handover measurement value.

11. A system, comprising:

a controller configured to divide data transmission on a given frequency band into a plurality of time slots and allocate at least a portion of the time slots of the frequency band to a broadcast control channel and at least one different channel, and

a transmitter configured to adjust a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel, transmit a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel, and transmit a signal with the adjusted transmit power level in the time slot of the different channel.

12. The system of claim 11, wherein the transmitter is configured to adjust the transmit power level by decreasing the power level of a time slot for which there is no data or a control signal allocated for transmission and to transmit the signal in the time slot with a lower transmit power level than that of the broadcast signal.

13. The system of claim 11, wherein the transmitter is configured to implement the transmit power level adjustment together with a conventional downlink power control scheme associated with the traffic channels.

14. The system of claim 11, wherein the transmitter is a base station of the wireless telecommunication system and the controller is a base station controller connected to the base station and controlling the operation of the base station.

15. The system of claim 11, wherein the transmitter is configured to activate the transmit power level adjustment upon detection of a break in a mains power supply.

16. The system of claim 11, wherein the transmitter is configured to switch the power level adjustment on or off upon reception of a corresponding command and to assign the same power level to signals in every time slot in the frequency band when the power level adjustment has been switched off.

17. The system of claim 11, wherein the controller is configured to adjust handover parameters related to a mobile terminal in the service area of the radio access network on the basis of the transmit power level adjustment being currently used in order to compensate for the reduction in a power level for handover purposes.

18. The system of claim 17, wherein the controller is configured to receive handover measurement values from the mobile terminal, each measurement value being associated with a base station of the radio access network and describing a power level of a radio signal received by the mobile terminal from the corresponding base station, and to give a weight for each handover measurement value by increasing the handover measurement value in proportion to the degree of power adjustment, if the transmitter utilizes the transmit power level adjustment.

19. The system of claim 17, wherein the controller is configured to receive from the mobile terminal a handover measurement value describing the power level of a radio signal received by the mobile terminal from a candidate base station, obtain, from information stored into a memory unit of the system and concerning the behavior of the mobile terminal, knowledge on a serving base station time slot during which the mobile terminal measured the handover measurement value, receiving from the mobile terminal timing information observed by the mobile terminal and indicating a time difference between frame clocks of a serving base station and the handover candidate base station for which the handover measurement value was measured, compensate the received handover measurement value according to the knowledge on the transmit power level of the handover candidate base station during the measurement of the handover measurement value, and determine, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.

20. The system of claim 19, wherein the controller is configured to determine the number of time slots of the handover candidate base station during which the mobile terminal measured the handover measurement value, determine the transmit power level of the candidate handover base station for each time slot during which the mobile terminal measured the handover measurement value, and compensate the received handover measurement value according to the transmit power levels of the time slot or time slots during which the mobile terminal measured the handover measurement value.

21. A base station controller apparatus, configured to divide data transmission on a given frequency band into a plurality of time slots and allocate at least a portion of the time slots of the frequency band to a broadcast control channel and at least one different channel, to assign a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel, and to control a base station to transmit a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel and a signal with the assigned transmit power level in the time slot of the different channel.

22. A base station, comprising:

a first communication unit connected to a controller of the base station;

a second communication unit configured to transmit and receive radio signals, and

a processing unit configured to receive through the first communication unit a command to allocate at least a portion of the time slots of the frequency band to a broadcast control channel and at least one different channel, control the second communication unit to transmit a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel, adjust a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel, and control the second communication unit to transmit a signal with the adjusted transmit power level in the time slot of the different channel.

23. A base station of a radio access network in a wireless telecommunication system, comprising:

a communication unit configured to transmit a pilot signal to an air interface on a specific pilot channel, and a processing unit configured to adjust the transmit power level of the pilot signal according to a specific transmit power level pattern which describes a variable transmit power level for the pilot signal.

24. A system, comprising:

means for allocating at least a portion of time slots of a frequency band to a broadcast control channel and at least one different channel;

means for adjusting a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel;

means for transmitting a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel, and

means for transmitting a signal with the adjusted transmit power level in the time slot of the different channel.

26. The process of claim 24, the distribution medium including at least one of the following media:

a computer readable medium, a program storage medium, a record medium, a computer readable memory, a computer readable software distribution package, a computer readable signal, a computer readable telecommunications signal, and a computer readable compressed software package.

25. A computer program distribution medium readable by a computer and encoding a computer program of instructions for executing a computer process for data transmission in a wireless telecommunication system in which the data transmission on a given frequency band is divided into a plurality of time slots, the process comprising:

allocating at least a portion of the time slots of the frequency band to a broadcast control channel and at least one different channel;

adjusting a transmit power level of at least one time slot in a different channel on the basis of contents of the time slot in the different channel;

transmitting a broadcast signal with a given transmit power in a time slot allocated to the broadcast control channel, and

transmitting a signal with the adjusted transmit power level in the time slot of the different channel.

27. A method, comprising:

receiving, from a mobile terminal served by a serving base station, reception power level measurement information related to signals received by the mobile terminal from the serving base station and from one or more handover candidate base stations, wherein the base stations transmit signals in time slots with variable transmit power levels;

obtaining knowledge on transmit power levels of the signals measured by the mobile terminal,

compensating the received reception power level measurement information according to the knowledge on the transmit power levels, and

determining, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.

28. The method of claim 27, wherein the knowledge on transmit power levels of the signals measured by the mobile terminal comprises information on time slots during which the mobile terminal measured the reception power level, and transmit power levels of the time slots.

29. The method of claim 28, further comprising:

obtaining the knowledge on the time slots during which the mobile terminal measured the reception power level from stored information concerning the behavior of the mobile terminal, and

receiving from the mobile terminal timing information observed by the mobile terminal and indicating a time difference between frame clocks of the serving base station and a handover candidate base station for which the reception power level measurement was performed.

30. The method of claim 27, further comprising:

determining the number of time slots during which the mobile terminal measured the reception power level of a received signal,

determining the transmit power level for each time slot during which the mobile terminal measured the reception power level, and

compensating the reception power level according to the transmit power levels of the time slot or time slots during which the mobile terminal measured the reception power level.

31. The method of claim 27, wherein the compensation comprises scaling the reception power level received from the mobile terminal proportionally to the difference between a reference transmission power level and a transmission power level of the signal from which the mobile terminal measured the reception power level.

32. The method of claim 31, wherein the reference transmission power level is the maximum transmission power level of the base station for which the reception power level was measured.

33. A base station controller apparatus, comprising:

a communication interface configured to provide a communication connection with one or more base stations controlled by the base station controller apparatus and transmitting signals in time slots with variable transmit power levels under the control of the base station controller apparatus, and

a processing unit configured to receive, through the communication interface reception power level measurement information related to signals received by a mobile terminal from a serving base station and from one or more handover candidate base stations, obtain knowledge on transmit power levels of the signals measured by the mobile terminal, compensate the received reception power level measurement information according to the knowledge on the transmit power levels, and determine, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.

34. The apparatus of claim 33, wherein the knowledge on transmit power levels of the signals measured by the mobile terminal comprises information on time slots during which the mobile terminal measured the reception power level, and transmit power levels of the time slots.

35. The apparatus of claim 34, wherein the processing unit is configured to obtain the knowledge on the time slots during which the mobile terminal measured the reception power level from information concerning the behavior of the mobile terminal and stored into the memory unit and from timing information received from the mobile terminal, which timing information is observed by the mobile terminal and indicates a time difference between frame clocks of the serving base station and handover candidate base stations.

36. The apparatus of claim 33, wherein the processing unit is configured to determine the number of time slots during which the mobile terminal measured the reception power level of a received signal, determine the transmit power level for each time slot during which the mobile terminal measured the reception power level, and compensate the reception power level according to the transmit power levels of the time slot or time slots during which the mobile terminal measured the reception power level.

37. The apparatus of claim 33, wherein the compensation comprises scaling the reception power level received from the mobile terminal proportionally to the difference between a reference transmission power level and a transmission power level of the signal from which the mobile terminal measured the reception power level.

38. The apparatus of claim 37, wherein the reference transmission power level is the maximum transmission power level.

39. A base station controller apparatus, comprising:

communication means for providing a communication connection with one or more base stations controlled by the base station controller apparatus and transmitting signals in time slots with variable transmit power levels under the control of the base station controller apparatus;

memory means capable of storing information;

means for storing into the memory means information on the transmit power levels of the one or more base stations;

means for receiving, through the communication means from a mobile terminal served by a serving base station, reception power level measurement information related to signals received by the mobile terminal from the serving base station and from one or more handover candidate base stations;

means for obtaining knowledge on transmit power levels of the signals measured by the mobile terminal,

means for compensating the received reception power level measurement information according to the knowledge on the transmit power levels, and

means for determining, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.

40. A computer program distribution medium readable by a computer and encoding a computer program of instructions for executing a computer process, comprising:

receiving, from a mobile terminal served by a serving base station, reception power level measurement information related to signals received by the mobile terminal from the serving base station and from one or more handover candidate base stations, wherein the base stations transmit signals in time slots with variable transmit power levels;

obtaining knowledge on transmit power levels of the signals measured by the mobile terminal;

compensating the received reception power level measurement information according to the knowledge on the transmit power levels, and

determining, on the basis of compensated reception power level measurement information, whether or not to initiate a handover procedure for the mobile terminal.