Phase shifted time slice transmission to improve handover

• US 20040047311A1
• Filed: 09/09/2002
• Published: 03/11/2004
• Est. Priority Date: 09/09/2002
• Status: Active Grant

• Current Assignee: Meta Platforms, Inc. (f/k/a Facebook, Inc.)
• Original Assignee: Nokia Corporation
• Inventors: Pekonen, Harri
• Granted Patent: US 7,058,034 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• CPC Class Codes: H04W 36/00 Hand-off or reselection arrangements
• CPC Class Codes: H04W 36/0007 for multicast or broadcast services, e.g. MBMS multicast or broadcast application services H04W4/06; resource management for broadcast services H04W72/30; connection management for selective distribution or broadcast H04W76/40
• CPC Class Codes: H04W 72/30 Resource management for broadcast services

Abstract

The present invention provides methods and apparatus for a wireless system broadcasting a plurality of data packets to at least one wireless terminal. The wireless system comprises a plurality of base stations that interfaces to a backbone network in order to receive the plurality of data packets from a service source. Data packets are sent to a wireless terminal by a first base station transmitting a first channel burst and by a second base station transmitting a second channel burst, in which corresponding time offsets of the channel bursts, as characterized by amounts phase shifts, are different. Consequently, when the wireless terminal executes a handover from the first base station to the second base station, a probability that some of the data packets are lost, as result of practical network considerations, is reduced.

Claims

1. A method of receiving a plurality of data packets from a wireless system by a wireless terminal, the wireless system comprising a first base station and a second base station, the method comprising the steps of:

(a) determining a first amount of phase shift that is associated with a current first channel burst that comprises a first group of data packets, wherein the first amount of phase shift is associated with the first base station and wherein the first amount of phase shift is different from a second phase shift that is associated with the second base station; and

(b) receiving the current first channel burst in accordance with the first amount of phase shift.

2. The method of claim 1, wherein the first group of packets is associated with a first data service.

3. The method of claim 2, wherein the wireless system serves a digital broadband broadcasting area and the first data service is associated with a digital broadband broadcasting service.

4. The method of claim 2, wherein the first group of packets is associated with a second data service.

5. The method of claim 1, further comprising the steps of:

(c) determining a time period, wherein the time period is a time difference between the current first channel burst and a subsequent first channel burst; and

(d) receiving the subsequent first channel burst at a time that is offset by the time period with respect to the current first channel burst.

6. The method of claim 5, wherein step (c) comprises the step of:

receiving information about the time period in the current first channel burst.

7. The method of claim 1, further comprising the steps of:

(c) determining the second amount of phase shift that is associated with the second base station;

(d) measuring a first signal characteristic of a first signal that is transmitted by the first base station;

(e) measuring a second characteristic of a second signal that is transmitted by the second base station;

(f) if the first signal characteristic satisfies a first predefined criterion and if the second signal characteristic satisfies a second predefined criterion, switching reception from the first base station to the second base station; and

(g) in response to step (f), receiving a second channel burst from the second base station in accordance with the second amount of phase shift, wherein the second channel burst comprises a second group of data packets.

8. The method of claim 7, further comprising the steps:

(h) if numbering of the second group of data packets is not consecutive, rearranging data packets of the second group of data packets so that the numbering is consecutive; and

(i) if duplicate data packets are received within the second group of data packets, discarding one of the duplicate data packets.

9. The method of claim 7, wherein the first signal characteristic and the second signal characteristic correspond to a signal attribute selected from a group consisting of a received signal strength indicator (RSSI) value, a bit error rate (BER), and a packet error rate (PER).

10. The method of claim 7, wherein step (c) comprises the step of:

receiving information about the second amount of phase shift in an initial cell.

11. The method of claim 1, further comprising the steps of:

(c) determining the second amount of phase shift that is associated with the second base station;

(d) measuring a first signal characteristic of a first signal that is transmitted by the first base station;

(e) measuring a second characteristic of a second signal that is transmitted by the second base station;

(f) sending the first signal characteristic and the second signal characteristic to the first base station;

(g) if instructed by the first base station, switching reception from the first base station to the second base station; and

(h) in response to step (g), receiving a second channel burst from the second base station in accordance with the second amount of phase shift, wherein the second channel burst comprises a second group of data packets.

12. The method of claim 11, further comprising the steps of:

(i) if numbering of the second group of data packets is not consecutive, rearranging data packets of the second group of data packets so that the numbering is consecutive; and

(j) if duplicate data packets are received within the second group of data packets, discarding one of the duplicate data packets.

13. The method of claim 1, further comprising the steps of:

(c) determining a third amount of phase shift that is associated with a third channel burst that comprises a third group of data packets, wherein the third amount of phase shift is associated with the first base station; and

(d) receiving the third channel burst in accordance with the third amount of phase shift.

14. The method of claim 1, wherein the first base station is associated with a first center frequency value and the second base station is associated with a second center frequency value.

15. The method of claim 1, wherein the first base station is associated with a first channelization code and the second base station is associated with a second channelization code.

16. The method of claim 2, wherein the first data service is an Internet Protocol (IP) service.

17. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 1.

18. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 7.

19. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 8.

20. A wireless terminal that receives a plurality of data packets from a wireless system, the wireless system comprising a first base station and a second base station, comprising:

a storage buffer;

a timing module;

a radio module that communicates with the wireless system over a radio channel;

a processor that receives an indication from the timing module that a current first channel burst is being transmitted, wherein the current first channel burst contains a first group of data packets, and that stores the first group of data packets into the storage buffer, the processor configured to perform the steps of;

(a) determining a first amount of phase shift that is associated with the current first channel burst that comprises the first group of data packets, wherein the first amount of phase shift is associated with the first base station and wherein the first amount of phase shift is different from a second phase shift that is associated with the second base station; and

(b) receiving the current first channel burst in accordance with the first amount of phase shift.

21. The wireless terminal of claim 20, wherein the wireless system serves a digital broadband broadcasting area and the first group of data packets is associated with a digital broadband broadcasting service.

22. The wireless terminal of claim 20, wherein the processor is configured to perform the further steps of:

(c) determining a time period, wherein the time period is a time difference between the current first channel burst and a subsequent first channel burst; and

(d) receiving the subsequent first channel burst at a time that is offset by the time period with respect to the current first channel burst.

23. The wireless terminal of claim 20, wherein the processor is configured to perform the further steps of:

(c) determining the second amount of phase shift that is associated with the second base station;

(d) measuring a first signal characteristic of a first signal that is transmitted by the first base station;

(e) measuring a second characteristic of a second signal that is transmitted by the second base station;

(f) if the first signal characteristic satisfies a first predefined criterion and if the second signal characteristic satisfies a second predefined criterion, switching reception from the first base station to the second base station; and

(g) in response to step (f), receiving a second channel burst from the second base station in accordance with the second amount of phase shift, wherein the second channel burst comprises a second group of data packets.

24. The wireless terminal of claim 23, wherein the processor is configured to perform the further steps of:

(h) if numbering of the second group of data packets is not consecutive, rearranging data packets of the second group of data packets so that the numbering is consecutive; and

(i) if duplicate data packets are received within the second group of data packets, discarding one of the duplicate data packets.

25. The wireless terminal of claim 20, wherein the processor is configured to perform the further steps of:

(c) determining the second amount of phase shift that is associated with the second base station;

(d) measuring a first signal characteristic of a first signal that is transmitted by the first base station;

(e) measuring a second characteristic of a second signal that is transmitted by the second base station;

(f) sending the first signal characteristic and the second signal characteristic to the first base station;

(g) if instructed by the first base station, switching reception from the first base station to the second base station; and

(h) in response to step (g), receiving a second channel burst from the second base station in accordance with the second amount of phase shift, wherein the second channel burst comprises a second group of data packets.

26. The wireless terminal of claim 20, wherein the processor is configured to perform the further steps of:

(c) determining a third amount of phase shift that is associated with a third channel burst that comprises a third group of data packets, wherein the third amount of phase shift is associated with the first base station; and

(d) receiving the third channel burst in accordance with the third amount of phase shift.

27. A method for broadcasting a plurality of data packets by a wireless system to a wireless terminal, the wireless system comprising a first base station and a second base station, the method comprising the steps of:

(a) mapping a first group of data packets to a current first channel burst;

(b) determining a first amount of phase shift that corresponds to the current first channel burst, wherein the first amount of phase shift is different from a second phase shift that is associated with the second base station; and

(c) transmitting the current first channel burst that corresponds to the first amount of phase shift.

28. The method of claim 27, wherein the wireless system serves a digital broadband broadcasting area and the first group of data packets is associated with a digital broadband broadcasting service.

29. The method of claim 27, wherein the first group of data packets is associated with a first data service.

30. The method of claim 29, wherein the first group of data packets is associated with a second data service.

31. The method of claim 27, further comprising the steps of:

(d) determining a time period, wherein the time period is a time difference between the current first channel burst and a subsequent first channel burst; and

(e) transmitting the subsequent first channel burst at the time period with respect to the current first channel burst.

32. The method of claim 31, comprising the further step of:

(f) including information about the time period in the current first channel burst.

33. The method of claim 27, further comprising the step of:

(d) including information about the second amount of phase shift in the current first channel burst, wherein the second amount of phase shift corresponds to a second group of data packets that is transmitted by the second base station.

34. The method of claim 27, further comprising the steps of:

(d) receiving, by the first base station, a first signal characteristic that is indicative of a first signal that is transmitted by the first base station and that is measured by the wireless terminal and a second signal characteristic that is indicative of a second signal that is transmitted by the second base station and that is measured by the wireless terminal;

(e) determining whether the wireless terminal should be served by the second base station in accordance with the first and second signal characteristics; and

(f) sending an instruction to the wireless terminal to switch base stations in response to step (e).

35. The method of claim 27, wherein the first base station is associated with a first center frequency value and the second base station is associated with a second center frequency value.

36. The method of claim 35, wherein a number of center frequency values in the wireless system is equal to N, and wherein the amount of phase shift is equal to 360 degrees divided by N multiplied by an integer.

37. The method of claim 27, where the first base station is associated with a first channelization code and the second base station is associated with a second channelization code.

38. The method of claim 27, further comprising the steps of:

(d) mapping a third group of data packets to a third channel burst that is associated with the first base station;

(e) determining a third amount of phase shift that corresponds to the third channel burst; and

(f) transmitting the third channel burst that corresponds to the third amount of phase shift.

39. The method of claim 27, wherein the first group of data packets is associated with a first data service and wherein the first data service is an Internet Protocol (IP) service.

40. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 27.

41. A computer-readable medium having computer-executable instructions for performing the steps recited in claim 33.

42. A base station that broadcasts a first group of data packets to a wireless terminal, comprising:

a timing module;

a storage buffer;

a network interfacing module that receives a first group of data packets from a backbone network, wherein the first group of data packets is associated with a digital broadband broadcasting service;

a radio module that communicates with the wireless terminal over a radio channel;

a processor that stores the first group of packets in the storage buffer, receives an indication from the timing module that a current first channel burst should be transmitted, and retrieves the first group of data packets from the storage buffer, the processor configured to perform the steps of;

(a) mapping the first group of data packets to the current first channel burst, wherein the first group of data packets is associated with a first data service;

(b) determining a first amount of phase shift that corresponds to the current first channel burst; and

(c) transmitting, through the radio module, the current first channel burst that corresponds to the first amount of phase shift.

43. The base station of claim 42, wherein the processor is configured to perform the further steps of:

(d) including information about a second amount of phase shift in the current first channel burst, wherein the second amount of phase shift is associated with a second base station and the first data service.

44. A method of receiving a plurality of data packets from a wireless system by a wireless terminal, the wireless system comprising a first base station and a second base station, the method comprising the steps of:

(a) determining a first amount of phase shift that is associated with a first channel burst that comprises a first group of data packets, wherein the first group of data packets is associated with a digital broadband broadcasting service and wherein the first amount of phase shift is associated with the first base station and the first data service;

(b) receiving the first channel burst in accordance with the first amount of phase shift;

(c) determining a second amount of phase shift that is associated with the second base station and the digital broadband broadcasting service;

(d) measuring a first signal characteristic of a first signal that is transmitted by the first base station;

(e) measuring a second characteristic of a second signal that is transmitted by the second base station;

(f) if the first signal characteristic satisfies a first predefined criterion and if the second signal characteristic satisfies a second predefined criterion, switching reception from the first base station to the second base station;

(g) in response to step (f), receiving a second channel burst from the second base station in accordance with the second amount of phase shift, wherein the second channel burst comprises a second group of data packets that is associated with the digital broadband broadcasting service;

(h) if numbering of data packets is not consecutive, rearranging data packets of the second group of data packets so that the numbering is consecutive; and

(i) if duplicate data packets are received within the second group of data packets, discarding one of the duplicate data packets.