MULTIPLEXING SCHEMES FOR OFDMA

• US 20130016603A1
• Filed: 09/14/2012
• Published: 01/17/2013
• Est. Priority Date: 10/21/2005
• Status: Abandoned Application

• Current Assignee: Hang Zhang, Jianglei Ma, Kelvin Kar-Kin Au, Mo-Han Fong, Peiying Zhu, Robert Novak, Sophie Vrzic, Wen Tong
• Original Assignee: Hang Zhang, Jianglei Ma, Kelvin Kar-Kin Au, Mo-Han Fong, Peiying Zhu, Robert Novak, Sophie Vrzic, Wen Tong
• Inventors: Novak, Robert, Zhang, Hang, Vrzic, Sophie, Fong, Mo-Han, Au, Kelvin Kar-Kin, Ma, Jianglei, Zhu, Peiying, Tong, Wen
• Application Number:
  US13/616,294
• Publication Number:
  US 20130016603A1
• Time in Patent Office: Days
• US Class Current: 370/216
• CPC Class Codes: H04L 1/0013 Rate matching, e.g. puncturing or repetition of code symbols
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0067 Rate matching H04L1/0013 and H04L1/08 take precedence
• CPC Class Codes: H04L 1/14 in which the signals are sent back to the transmitter to be checked ; echo systems
• CPC Class Codes: H04L 1/1614 using bitmaps
• CPC Class Codes: H04L 1/1867 Arrangements specially adapted for the transmitter end
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0042 intra-user or intra-terminal allocation
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/0064 Rate requirement of the data, e.g. scalable bandwidth, data priority
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

Methods and systems are provided for allocating resources including VoIP (voice over Internet Protocol) and Non-VoIP resources. In some embodiments, multiplexing schemes are provided for use with OFDMA (orthogonal frequency division multiplexing access) systems, for example for use in transmitting VoIP traffic. In some embodiments, various HARQ (Hybrid Automatic request) techniques are provided for use with OFDMA systems. In various embodiments, there are provided methods and systems for dealing with issues such as Handling non-full rate vocoder frames, VoIP packet jitter handling, VoIP capacity increasing schemes, persistent and non-persistent assignment of resources in OFDMA systems.

Claims

1. A method comprising:

persistently allocating an OFDM transmission resource to a wireless station;

blanking a minimum rate sub-packet within the persistently allocated OFDM transmission resource; and

using the unused retransmission resource for allocation to other wireless stations.

2. The method of claim 1 applied for downlink transmission from a base station to a plurality of wireless stations, the method further comprising:

the base station receiving a NAK from the wireless station in response to blanking the sub-packet;

the base station echoing receipt of the NAK with an ACK to indicate no resource is being assigned for retransmission.

3. The method of claim 2 wherein echoing receipt of the NAK with an ACK to indicate no resource is being assigned for retransmission to that wireless station comprises transmitting an ACK-NAK-echo bitmap indicating ACK/NAK status.

4. The method of claim 1 further comprising transmitting keep-alive reduced rate frames.

5. The method of claim 4 further comprising:

using a same amount of frequency/time resource for the minimum rate frames as for full rate frames so as to increase probability of successful transmission, and using freed up retransmission resources for allocation to other wireless stations.

6. The method of claim 1 wherein the minimum rate is ⅛

rate.

7. A method of transmitting sub-packets within VoIP frames comprising:

persistently allocating a resource to a wireless station while there are non-blanked sub-packets to send/receive to/from that wireless station;

when there are no non-blanked sub-packets to send/receive for a given wireless station, re-assigning the unused resource to other wireless stations, or a different data stream for the same wireless station, in a non-persistent manner.

8. The method of claim 7 wherein the resource assignment is identified by specific resource/channel/node index or OFDMA sub-carrier and symbol indices.

9. The method of claim 7 applied for downlink transmission from a base station to a plurality of wireless stations, the method further comprising:

an original wireless station with a persistent allocation of the blanked transmission decoding the sub-packet transmitted on its persistent resource allocation, and if successfully decoded using a layer 2 protocol to detect a mismatch on a user ID and discarding the sub-packet;

the base station ignoring any HARQ ACK/NAK received from the original wireless station with the persistent allocation.

10. The method of claim 7 further comprising:

if the wireless station with the non-persistent allocation occupying the unused persistent resource does not require HARQ retransmission, at the retransmission slot, the transmitter sending an ACK indication to indicate there is no resource assigned to the wireless station with the persistent allocation for HARQ transmission;

using an unused retransmission resource for other wireless stations.

11. The method of claim 10 wherein sending an ACK indication comprises setting a corresponding bit in a ACK-NAK-echo bitmap to ‘

ACK’

.

12. The method of claim 7 applied for downlink transmission from a base station to a plurality of wireless stations, the method further comprising, if the wireless station with the non-persistent allocation occupying the unused persistent resource requires HARQ retransmission:

retransmitting the sub-packet for the wireless station with the non-persistent allocation using a different resource than the previous sub-packet, and explicitly signalling the new resource;

the transmitter sending an ACK indication in respect of the persistently allocated resource;

reallocating the unused persistently allocated resource for other wireless stations.

13. The method of claim 7 applied for downlink transmission from a base station to a plurality of wireless stations, the method further comprising, if the wireless station with the non-persistently allocated resource occupying the unused persistent resource requires HARQ retransmission:

retransmitting the sub-packet for the wireless station with the non-persistently allocated resource using the same resource as the previous sub-packet without using any explicit signalling for the retransmission;

the transmitter setting an ACK indicator to ‘

NAK’

to indicate that a resource assigned to the wireless station with the persistent allocation is being used for retransmission.

14. A method of transmitting OFDM signals containing sub-packets within frames comprising:

if there is no packet for a given wireless station at a frame boundary, blanking a persistent allocation for that wireless station;

allocating blanked resources to other wireless stations.

15. The method of claim 14, wherein the frames are VoIP frames and a frame boundary is a VoIP frame boundary.

16. The method of claim 15 further comprising delivering a packet that arrives after the VoIP frame boundary by:

transmitting a sub-packet for the packet in a lower MCS format intended for a reduced number of retransmission trials.

17. The method of claim 15 further comprising delaying packets arriving after a predefined number of retransmission slots until the next VoIP frame.

18. The method of claim 15 further comprising delivering a packet that arrives after the VoIP frame boundary by:

delaying the packet transmission until the next VoIP frame;

combining delayed and current VoIP packets into a composite packet.

19. The method of claim 18 further comprising:

supplementing a persistent allocation with additional non-persistent resources for the next VoIP frame.

20. The method of claim 18 further comprising transmitting the composite packet using assigned persistent resources by changing the MCS accordingly.

21. The method of claim 20 further comprising using the “

missed frame”

to trigger blind detection of MCS for the composite packet in the next frame.

22. The method of claim 15 further comprising delivering a packet that arrives after the VoIP frame boundary by:

delaying the packet transmission until resources become available;

continuing to send packets in sequence without combining multiple voice packets into composite packets;

emptying a layer 2 buffer during blanked transmission times.

23. The method of claim 15 further comprising a base station adding a ‘

de-jitter’

delay to every VoIP packet that arrives at the layer 2 buffer such that the probability of a packet available at every VoIP frame boundary is above a predefined threshold.

24. A method of transmitting sub-packets within frames comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

allocating first sub-packet transmission for a set of wireless stations in a staggered manner throughout a frame.

25. The method of claim 24, wherein the frames are VoIP frames and a frame boundary is a VoIP frame boundary.

26. The method of claim 25 wherein each VoIP frame is comprised of a plurality of slots each containing a respective plurality of OFDM symbols and wherein allocating first sub-packet transmission for a set of wireless stations in a staggered manner throughout a VoIP frame comprises allocating first sub-packet transmission on an approximately statistically equal basis across slots of the VoIP frame.

27. A method of transmitting sub-packets within frames comprising:

transmitting frames using OFDM, each occupying a plurality of OFDM symbols;

dividing wireless stations into a plurality of different classes, each class having a respective different number of maximum HARQ retransmissions such that wireless stations with more reliable CQI estimates are grouped together and allowed fewer re-transmissions;

transmitting the frames containing first sub-packets and retransmission sub-packets subject to the maximum number of HARQ retransmissions for each wireless station.

28. The method of claim 27, wherein the frames are VoIP frames and a frame boundary is a VoIP frame boundary.

29. The method of claim 28 further comprising:

if a packet fails after a reduced number of transmissions, the wireless station sending a NAK;

if that wireless station is intended to have only the reduced number of transmissions the transmitter sets an ACK indicator to ‘

ACK’

to indicate no further resource is being allocated for the remainder of the frame such that it is not necessary to signal to each wireless station what class the wireless station belongs to.

30. A method of transmitting sub-packets within frames comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

for some wireless stations, allocating resources over multiples of nominal frames;

for wireless stations being allocated resources over multiples of nominal frames, combining multiple packets into composite packets, and allocating these composite packets with a larger number of retransmissions for improved reliability.

32. The method of claim 30 wherein the frames are VoIP frames.

31. A method comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

for some wireless stations, allocating resources over multiples of nominal frames;

for some wireless stations, transmitting an original sub-packet for a first packet during a first frame, with retransmission sub-packets following as necessary;

transmitting a next original sub-packet for another packet for that wireless station immediately, possibly during the first frame, following the successful reception of the first packet, with retransmissions as necessary which may cross a frame boundary.

33. A method of transmitting sub-packets within frames comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

transmitting to each wireless station with a respective resource allocation size, and a respective MCS;

implicitly indicating MCS to each receiver by employing a unique mapping of MCS to resource allocation size.

34. The method of claim 33, wherein the frames are VoIP frames.

35. The method of claim 33 wherein the following MCS to resource allocation size mapping is employed:

QPSK, code rate ⅓

—

first resource allocation size

QPSK, code rate ⅔

—

second resource allocation size

16 QAM, code rate ⅔

—

third resource allocation size.

36. A method comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

performing full persistent resource allocation for at least one wireless station by allocating resources persistently for both original sub-packet transmissions and retransmission sub-packets.

37. The method of claim 36, wherein the frames are VoIP frames.

38. The method of claim 37 comprising:

performing full persistent resource allocation for some of wireless stations and performing first transmission persistent allocation by allocating a resource persistently only for first transmissions for remaining wireless stations.

39. The method of claim 38 further comprising using a combined bitmap (or other signalling) to signal resource allocation both for wireless stations having full persistent resource allocation and for wireless stations having first transmission persistent allocation.

40. The method of claim 39 using a combined bitmap (or other signalling) to signal resource allocation both for wireless stations having full persistent resource allocation and for wireless stations having first transmission persistent allocation comprises:

designating wireless stations with full persistent allocation as a special user group in the bitmap (or other signalling).

41. The method of claim 40 further comprising segmenting wireless stations with full persistent allocation into groups that have different HARQ sub-packet start points.

42. The method of claim 40 further comprising allocating resource locations for the first transmission persistent allocations immediately after the resource locations of the wireless stations with persistent allocation for all transmissions.

43. The method of claim 40 further comprising re-packing and reassigning resources that were not used by one or both of a) the wireless stations with persistent allocation for all transmissions and b) the wireless stations with persistent allocation for the first sub-packet transmission.

44. The method of claim 43 further comprising:

reassigned wireless stations determining what resources are not assigned to persistent wireless stations by reading the bitmap (or other signalling), and deriving the location of the free resources.

45. The method of claim 40 further comprising using a resource shifting pattern for full persistent resources.

46. The method of claim 40 wherein the resource shifting pattern is a cyclic shift.

47. A method comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

for at least one OFDM resource, allocating the resource as a persistent resource allocation to a group of more than one wireless stations with only one wireless station being given the resource in a given slot.

48. The method of claim 47, wherein the frames are VoIP frames.

49. The method of claim 48 further comprising transmitting a bitmap (or other signalling) in which each of the wireless stations which have the same persistent resource have an individual entry, with multiple positions in the bitmap (or other signalling) referring to the same resource.

50. The method of claim 49 further comprising for each persistent resource allocation to a group of more than one wireless stations, each wireless station of the group of more than one wireless stations attempting to decode the resource, and discarding a result if it is not for that wireless station.

51. The method of claim 50 further comprising:

for at least one persistent resource allocation to a group of more than one wireless stations, reassigning the persistent resource if it is not assigned to any wireless station of the group of wireless stations to other wireless stations not receiving a persistent allocation.

52. The method of claim 51 wherein for wireless stations being reassigned persistent resources, the resource location is derived from the bitmap (or other signalling).

53. The method of claim 49 wherein the same resource can be persistently allocated to multiple wireless stations only for a first HARQ transmission.

54. The method of claim 49 wherein the same resource is persistently allocated to multiple wireless stations for multiple HARQ transmissions.

55. A method comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

performing persistent and/or non persistent OFDM resource allocation to multiple wireless stations;

capping a maximum transmit power to a given wireless station at a level related to the longer term channel conditions.

56. The method of claim 55, wherein the frames are VoIP frames.

57. The method of claim 56 wherein capping a maximum transmit power to a given wireless station at a level related to the longer term channel conditions comprises capping the maximum transmit power according to an inverse relationship to average signal to noise ratio or geometry (path loss and shadowing conditions), of the wireless station.

58. The method of claim 57 wherein capping the maximum transmit power according to an inverse relationship to average signal to noise ratio or geometry (path loss and shadowing conditions), of the wireless station comprises setting the maximum transmit power to a wireless station during power control operation to a fixed value above the inverse of geometry of the wireless station.

59. A method comprising:

assigning a non-shared OFDM transmission resource to a wireless station;

assigning a shared OFDM transmission resource to a wireless station with information from a shared resource allocation scheme.

60. The method of claim 59, wherein assigning a non-shared OFDM transmission resource comprises assigning a non-shared OFDM transmission resource using unicast signalling messages.

61. The method of claim 59, wherein assigning shared resources with information from a shared resource allocation scheme comprises assigning shared resources using a bitmap.

62. The method of claim 59, wherein assigning a shared OFDM transmission resource comprises assigning shared resources of which at least a portion of are unused resources.

63. The method of claim 62, further comprising assigning unused resources to one of:

a wireless station notified of assignment of the unused resources by a signalling scheme;

a wireless terminal that is designated to use the unused resources of a shared resource or resources;

one or more wireless stations designated to use unused portions of one or more shared resources.

64. The method of claim 62, wherein other resources in addition to the unused resources are assigned to the wireless terminal.

65. The method of claim 59, wherein if a portion of a transmission sent within the shared resource is not received and decoded by an intended wireless station, reception of the packet can proceed without it.

66. A method comprising:

assigning a shared OFDM transmission resource to a wireless station with information from one of a unicast signalling method or a part of the grouped resource allocation scheme.

67. A method for transmitting a packet comprising:

transmitting frames using OFDM, each frame occupying a plurality of OFDM symbols;

allocating a first OFDM resource within a frame to an original sub-packet transmission for the packet;

transmitting the original sub-packet transmission using a modulation and coding scheme;

in response to reception information received from a receiver, allocating a second resource space to send a retransmission sub-packet for the packet, said second resource space being different from said first resource space; and

transmitting said retransmission sub-packet using said modulation and coding scheme.

68. A method according to claim 67 wherein the step of allocating a second resource space further includes allocating a second resource space using said reception information.

69. The method of claim 67 further comprising:

signalling a respective user ID for each retransmission.

70. The method of claim 67 further comprising:

transmitting an ACK-NAK-echo bitmap to indicate which wireless stations are receiving allocations for retransmissions.

71. The method of claim 67 further comprising:

transmitting original sub-packets and retransmission sub-packets with a constant frame spacing.

72. A system for transmitting a packet comprising:

radio circuitry; and

a controller operable to;

allocate a first resource space for transmitting a first sub-packet for the packet;

provision said sub-packet for transmission by said radio circuitry using a modulation and coding scheme;

in response to reception information received from a receiver, allocate a second resource space to said data packet, said second resource space being different from said first resource space; and

provision said a second sub-packet for the packet for transmission by said radio circuitry using said modulation and coding scheme.

73. A system according to claim 72 wherein the controller is further operable to allocate a second resource space using said reception information.