Efficient paging in a wireless communication system

• US 20050277429A1
• Filed: 06/10/2004
• Published: 12/15/2005
• Est. Priority Date: 06/10/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Rangan, Sundeep, Hande, Prashanth
• Granted Patent: US 7,711,377 B2
• Time in Patent Office: Days
• US Class Current: 455/458
• CPC Class Codes: H04W 68/025 Indirect paging
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Methods and apparatus for efficient two-stage paging wireless communications systems are described. Wireless terminals are assigned to paging groups. A few first paging message information bits are modulated (using non-coherent modulation) into a first paging signal and communicated from a base station to wireless terminals. WTs wake-up, receive the first paging signal and quickly ascertain whether its paging group should expect a second paging signal, if so, the WT is operated to receive the second paging signal; otherwise, the WT goes back to sleep conserving power. The base station modulates (using coherent modulation) a number of second message information bits into a second paging signal and transmits the signal to WTs. From the information in first and second paging signals, a WT can determine that it is the paged WT and process the paging instructions. The intended paged WT can transmit an acknowledgement signal on a dedicated uplink resource.

Claims

1. A method of paging a wireless terminal in a communications system including multiple wireless terminals, the method comprising:

modulating, using a first type of modulation, a first number of bits of information to generate a first paging signal, said first paging signal conveying said first number of bits of information, said first paging signal including information indicating if there is a paging message;

modulating, using a second type of modulation, a second number of bits of information to generate a second paging signal, said second type of modulation being different from said first type of modulation, said second paging signal including, when there is a paging message, at least a portion of said paging message when said first paging signal indicates that there is a paging message;

transmitting said first paging signal; and

transmitting said second paging signal.

2. The method of claim 1, wherein said first and second numbers of information bits are different, said second number of information bits being larger than said first number of bits.

3. The method of claim 2, wherein said first paging signal is transmitted in a time period which is less than 4 symbol times in duration, said second paging signal being transmitted at least two symbol times after completion of the transmitting of said first paging signal, and where a symbol time corresponds to a time period used to transmit a symbol.

4. The method of claim 1, wherein said first number of bits of information is one.

5. The method of claim 1, wherein said first paging signal indicates if there is a paging message for at least one wireless terminal in a wireless terminal group including multiple wireless terminals.

6. The paging method of claim 5, wherein said second type of modulation requires use of communications channel information to demodulate the information modulated with said second type of modulation.

7. The method of claim 6, further comprising:

periodically repeating said steps of transmitting said first and second paging signals.

8. The method of claim 1, wherein said first paging signal indicates if there is a paging message for at least one wireless terminal in a wireless terminal group and wherein said wireless terminal group is one of a plurality of wireless terminal groups, some of said plurality of wireless terminal groups being multicast groups including a plurality of wireless terminals.

9. The method of claim 1, wherein said first type of modulation method is non-coherent modulation.

10. The method of claim 9, wherein said second type of modulation is coherent modulation.

11. The method of claim 10, wherein said non-coherent modulation type is one of on/off modulation, orthogonal modulation, and differential modulation.

12. The method of claim 10, wherein said second type of modulation is one of quadrature phase shift keying and quadrature amplitude modulation.

13. The method of claim 1, wherein said first and second paging information signals are transmitted at different points in time, said second paging information signal being transmitted at a first fixed time offset from the time said first paging information signal is transmitted.

14. The method of claim 13, wherein said second paging information signal includes information used to identify a wireless terminal in said system.

15. The method of claim 14, wherein said second paging signal includes sufficient information to uniquely identify a wireless terminal within a group of wireless terminals.

16. The method of claim 1, wherein said first signal indicates that there is no paging message for any wireless terminals in a first group of wireless terminals but that there is a paging message for at least one wireless terminal in a second group of wireless terminals.

17. The method of claim 1,

wherein said system supports a maximum number of wireless terminals which can be registered to receive pages in said system at a point in time;

and

wherein the first number of bits is less than the number of bits required to uniquely identify each of said maximum number of wireless terminals.

18. The method of claim 1, wherein information included in said first paging message in combination with information included in said second paging message uniquely identify a wireless terminal in said system.

19. The paging method of claim 1,

wherein transmitting said first paging signal includes transmitting said first paging signal into a communications channel, and

wherein said first modulation method is a modulation method which does not require communications channel information to be used to demodulate said modulated information.

20. The method of claim 1, wherein said first paging signal indicates a group of communications devices, said second paging signal indicating which particular paging device in the group of communications devices the paging message is directed to.

21. A base station for communicating with wireless terminals, said base station including:

first paging signal type generation means for periodically generating paging signals of a first type using a non-coherent modulation method, said paging signals of a first type indicating whether a paging message will be transmitted to at least one wireless terminal in a group of wireless terminals;

means for generating a paging signal of a second type using a coherent modulation method, said type signal including at least a portion of a paging message; and

means for transmitting said first and second type paging signals.

22. The base station of claim 21,

wherein said first paging signal type generation means generates paging signals of the first type, said first type paging signals including a first number of information bits;

and

wherein said second paging signal type generation means generates paging signals of the second type, said second type paging signals including a second number of information bits, said second number of information bits being greater than said first number of information bits.

23. The base station of claim 22, wherein said first paging signal type generation means includes:

a first modulation module for modulating information bits using one of on/off modulation, orthogonal modulation, and differential modulation.

24. The base station of claim 22, wherein said second paging signal type generation means includes:

a second modulation module for modulating information bits using one of quadrature phase shift keying and quadrature amplitude modulation.

25. A method of operating a wireless terminal, the method comprising:

awaking from a sleep mode of operation to receive a first paging signal;

performing a non-coherent demodulation operation on said first paging signal to produce demodulated information;

determining if said demodulated information indicates that a paging message was transmitted; and

if it is determined that said demodulated information indicates that a paging message was transmitted, performing a coherent demodulation operation on a second paging signal.

26. The method of claim 25, further comprising:

if it is determine that said demodulated information indicates that a paging message was not transmitted, returning to a sleep mode of operation.

27. The method of claim 25, further comprising:

when it is determined that said demodulated information indicates that a paging message was transmitted, performing a channel estimation operation prior to performing said coherent demodulation operation.

28. The method of claim 27,

wherein said first paging signal has a duration of less than 4 symbol times, where a symbol time is the amount of time used to transmit a symbol;

wherein said second paging signal has a duration of at least 10 symbols; and

wherein said channel estimation operation is initiated prior to receiving said second paging signal.

29. The method of claim 25, further comprising:

returning to said sleep mode of operation prior to receiving said second paging signaling;

awakening from said sleep mode of operation for another time prior to receiving said second paging signal;

initiating a channel estimation operation prior to receiving said second paging signal; and

wherein said wireless terminal consumes less power while in said sleep mode than when operating in an active mode of operation which occurs upon being woken up from said sleep mode of operation.

30. The method of claim 25, wherein said non-coherent demodulation operation does not use channel information and said coherent demodulation operation uses a communications channel estimate to perform said demodulation operation.

31. The method of claim 25, wherein said first paging signal includes a first number of bits and said second paging signal includes a second number of bits which is greater than said first number of bits.

32. The method of claim 31, wherein information obtained from demodulating said second paging signal includes at least a portion of a wireless terminal identifier, said method further comprising:

determining from said at least a portion of a wireless terminal identifier if said page was directed to said wireless terminal.

33. The method of claim 32, wherein said at least a portion of a wireless terminal identifier in combination with wireless terminal group identification information obtained by demodulating said first paging signal provides a unique wireless terminal identifier which uniquely identifies which wireless terminal, in a communications system in which said wireless terminal is located, said paging message is transmitted.

34. The method of claim 33, wherein said demodulated information obtained by demodulating said second paging signal includes at least a portion of said paging message.

35. A wireless terminal comprising:

means for performing a non-coherent demodulation operation on a first paging signal to recover modulated information indicating whether a paging message corresponding to the first paging signal will be transmitted;

control means for controlling the wireless terminal to receive a second paging signal of a second type at a pre-selected time when information recovered from said first paging signal indicates a paging message corresponding to the first paging signal will be transmitted and for controlling the wireless terminal to enter a sleep mode of operation and remain in said sleep mode of operation until after said pre-selected time when said information recovered from said first paging signal indicates a paging message corresponding to the first paging signal will not be transmitted; and

means for performing a coherent demodulation operation on the received second paging signal to recover modulated information including at least a portion of a paging message.

36. The wireless terminal of claim 35, further comprising:

means for performing a channel estimation operation following receipt of a first paging signal including information indicating a paging message will be transmitted and prior to receipt of said second paging signal.

37. The wireless terminal of claim 36, further comprising:

timing control means for controlling said wireless terminal to enter a sleep mode of operation following receipt of a first paging signal including information indicating a paging message will be transmitted and for awakening said wireless terminal to a more active state prior to said pre-selected time.

38. The wireless terminal of claim 37, further comprising:

control logic for determining if said information obtained by demodulating said second paging signal includes an identifier which corresponds to said wireless terminal; and

control means for taking an action in response to information obtained by demodulating said second paging signal when said information is determined to include an identifier which corresponds to said wireless terminal and for controlling said wireless terminal to enter a sleep mode of operation when it is determined that said information obtained by demodulating said second paging signal does not include an identifier which corresponds to said wireless terminal.

39. The wireless terminal of claim 35, wherein means for performing a non-coherent demodulation operation on a first paging signal to recover modulated information indicating whether a paging message includes at least one of an on/off modulation demodulator, an orthogonal modulation demodulator, and a differential modulation demodulator.

40. The wireless terminal of claim 35, wherein means for performing a coherent demodulation operation on a second paging signal includes at least one of a quadrature phase shift keying modulation demodulator and a quadrature amplitude modulation demodulator.