Dual-mode shared OFDM methods/transmitters, receivers and systems

• US 20040001429A1
• Filed: 04/04/2003
• Published: 01/01/2004
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Yu, Dong-Sheng, Tong, Wen, Ma, Jianglei, Zhu, Peiying, Jia, Ming
• Granted Patent: US 7,551,546 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 5/0017 in which a distinct code is applied, as a temporal sequence, to each frequency
• 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 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A wireless terminal and network terminal are provided for implementing a new uplink OFDM protocol. In the new protocol, the wireless terminal has a first transmit chain for generating and transmitting a low rate mode OFDM transmission in a first frequency band of the OFDM band; and a second transmit chain for generating and transmitting a burst-mode transmission in a second frequency band of the OFDM band, the first frequency band being distinct from the second frequency band. An access channel is provided which is overlaid over the low rate mode transmissions of other users.

Claims

1. A wireless terminal for communicating over a shared OFDM band, the wireless terminal comprising:

a first transmit chain for generating and transmitting a low rate mode OFDM transmission in a first frequency band of the OFDM band;

a second transmit chain for generating and transmitting a burst-mode transmission in a second frequency band of the OFDM band, the first frequency band being distinct from the second frequency band.

2. A wireless terminal according to claim 1 wherein the first transmit chain is power controlled and the second transmit chain is rate controlled.

9. A wireless terminal according to claim 2 wherein the first transmit chain further comprises:

at least one low rate signal source;

for each low rate signal source, at least one distinct orthogonal spreading function adapted to generate a respective spread sequence for each symbol of the low rate signal source by multiplying the symbol by a respective orthogonal spreading function from a set of orthogonal spreading functions;

a combiner for adding together in time the spread sequences to generate a composite sequence to be transmitted using said first frequency band.

10. A wireless terminal according to claim 9 comprising a plurality N of transmit antennas, N>

=2, wherein the first transmit chain comprises a space time encoder adapted to perform space time encoding to generate a respective STC sub-block comprising M symbols for sub-carriers by N transmission intervals to be transmitted on each transmit antenna during each set of N OFDM transmission intervals as said low rate mode OFDM transmission, wherein the composite sequence is input to the space time encoder.

11. A wireless terminal according to claim 9 wherein the set of orthogonal spreading functions comprises Walsh codes.

12. A wireless terminal according to claim 9 wherein the at least one low rate signal source comprises at least one of:

DL (dowlink) channel condition (CQI/CLI) feedback channel;

DL ACK/NAK signalling channel;

UL (uplink) buffer status channel;

UL transmit power margin channel;

UL rate indicator channel;

UL fixed data rate dedicated traffic channel.

13. A wireless terminal according to claim 9 further adapted to apply a variable number of Walsh code channels to the at least one low rate signal source as a function of required data rate and/or need for protection.

14. A wireless terminal according to claim 9 further comprising:

a control channel receiver for receiving power control commands in respect of the low rate mode OFDM transmissions;

a power control function adapted to apply transmit power adjustments to the low rate mode OFDM transmissions as a function of the power control commands.

15. A wireless terminal according to claim 2 further comprising a power control function adapted to:

transmit an initial access attempt on an uplink access channel;

determine a long term estimated downlink power measurement of a signal received over a downlink channel and to initially transmit said low rate mode OFDM transmission a transmit power determined as a function of the estimated downlink power measurement;

control channel receiver for receiving power control commands for increasing/unchanging/decreasing transmit power of the low rate mode OFDM transmission after said initial access attempt.

16. A wireless terminal according to claim 2 further comprising:

a control channel receiver for receiving channel assignment information allowing an identification of where in frequency and when in time to transmit the low rate mode OFDM transmissions.

18. A wireless terminal according to claim 9 further comprising:

a cover code generator adapted to apply a cell specific cover code in generating all low rate mode OFDM transmissions.

21. A wireless terminal according to claim 18 wherein the STC block size is N×

M plus pilot carriers, where M is such that the block size is less than the coherence bandwidth.

22. A wireless terminal according to claim 2 further comprising:

an access channel transmit chain adapted to generate an OFDM access signal occupying a randomly selected slot selected from a plurality of slots comprising a frame, each slot comprising a predetermined block of OFDM time-frequency.

23. A wireless terminal according to claim 22 further comprising:

a control channel receiver for receiving an identity of a plurality of signature definitions for use in a coverage area;

wherein the wireless terminal randomly selects one of the plurality of signatures and applies the signature in generating the access attempt.

24. A wireless terminal according to claim 22 wherein each slot comprises four OFDM symbols, and there are 16 different possible signatures.

25. A wireless terminal according to claim 22 further adapted to map the signature onto OFDM carriers based on a Peano-Hilbert plane filling curve.

26. A wireless terminal according to claim 22 wherein the access channel is overlaid over low rate mode OFDM transmissions of other wireless terminals.

27. A wireless terminal according to claim 2 adapted to function in an active and standby state, and further comprising:

a control channel receiver for receiving a system access channel assignment upon entering the standby state, the system access channel assignment being associated with specific sub-carriers and OFDM symbols to be used as a system access channel;

wherein the wireless terminal is further adapted to use the system access channel to transmit a pilot and system access requests while in the standby state.

28. A wireless terminal according to claim 27 wherein the system access channel comprises two or more sub-carriers allocated during certain periodic OFDM symbols.

29. A wireless terminal according to claim 28 wherein the system access channel is used to transmit differentially encoded access requests including at least one state that indicates a request for low rate mode and/or burst mode capacity to be scheduled.

30. A wireless terminal according to claim 2 further comprising:

a second transmit chain for generating and transmitting a burst-mode OFDM transmission transmits occupying an assigned space in OFDM frequency-time.

31. A wireless terminal according to claim 30 wherein:

the second transmit chain comprises a space time encoder adapted to perform space time encoding to generate a signal to be transmitted during a plurality of OFDM transmission intervals as said burst-mode OFDM transmission.

32. A wireless terminal according to claim 30 comprising a plurality N of transmit antennas, N>

=2, wherein the second transmit chain comprises a space time encoder adapted to perform space time encoding to generate for each of a plurality of assigned STC sub-block transmission frequency-time locations a respective STC sub-block to be transmitted on each transmit antenna.

33. A wireless terminal according to claim 32 wherein each STC sub-block further comprises pilot symbols.

34. A wireless terminal according to claim 32 wherein each STC sub-block further comprises N pilot symbols on each end of the STC sub-block on a respective single OFDM sub-carrier.

35. A wireless terminal according to claim 32 further comprising a control channel receiver for receiving a downlink signaling channel containing instructions for burst mode transmission.

36. A wireless terminal according to claim 35 wherein the instructions comprise a definition of the assigned STC sub-block transmission frequency-time space and a coding/modulation primitive.

37. A wireless terminal according to claim 36 wherein the instructions further comprise rate control commands, the wireless terminal being adapted to change the coding/modulation primitive according to the rate control commands.

38. A wireless terminal according to claim 31 further adapted to measure a long term power strength from a serving transmitter and to set a coding/modulation by using multi-level progressive coding and modulation feed forward transmission.

39. A wireless terminal according to claim 31 wherein the second transmit chain comprising a hopping pattern generated which defines said assigned STC sub-block transmission frequency-time locations such that they hop about in frequency within a subset of the shared OFDM band allocated for burst-mode traffic.

40. A wireless terminal according to claim 30 further comprising:

an access channel transmit chain adapted to generate an OFDM access signal occupying a randomly selected slot selected from a plurality of slots comprising a frame, each slot comprising a predetermined block of OFDM time-frequency.

41. A wireless terminal according to claim 30 adapted to function in an active and standby state, and further comprising:

a control channel receiver for receiving a system access channel assignment upon entering the standby state, the system access channel assignment being associated with specific sub-carriers and OFDM symbols to be used as a system access channel;

wherein the wireless terminal is further adapted to use the system access channel to transmit a pilot and system access requests while in the standby state.

42. A wireless terminal according to claim 41 adapted to function in an active and standby state, and further comprising:

a control channel receiver for receiving a system access channel assignment upon entering the standby state, the system access channel assignment being associated with specific sub-carriers and OFDM symbols to be used as a system access channel;

wherein the wireless terminal is further adapted to use the system access channel to transmit a pilot and system access requests while in the standby state.

48. A wireless terminal according to claim 2 adapted to function in an active and standby state, and further comprising:

a control channel receiver for receiving a system access channel assignment upon entering the standby state, the system access channel assignment being associated with specific sub-carriers and OFDM symbols to be used as a system access channel;

wherein the wireless terminal is further adapted to use the system access channel to transmit a pilot and system access requests while in the standby state.

49. A wireless terminal according to claim 48 wherein the system access channel comprises two or more sub-carriers allocated during certain periodic OFDM symbols.

50. A wireless terminal according to claim 49 wherein the system access channel is used to transmit differentially encoded access requests including at least one state that indicates a request for low rate mode and/or burst mode capacity to be scheduled.

51. A wireless terminal according to claim 2 further comprising:

a second transmit chain for generating and transmitting a burst-mode OFDM transmission occupying an assigned space in OFDM frequency-time.

52. A wireless terminal according to claim 51 wherein:

the second transmit chain comprises a space time encoder adapted to perform space time encoding to generate a signal to be transmitted during a plurality of OFDM transmission intervals as said burst-mode transmission.

53. A wireless terminal according to claim 51 comprising a plurality N of transmit antennas, N>

=2, wherein the second transmit chain comprises a space time encoder adapted to perform space time encoding to generate for each of a plurality of assigned STC sub-block transmission frequency-time locations a respective STC sub-block to be transmitted on each transmit antenna.

54. A wireless terminal according to claim 53 wherein each STC sub-block further comprises pilot symbols.

55. A wireless terminal according to claim 53 wherein each STC sub-block further comprises N pilot symbols on each end of the STC sub-block on a respective single OFDM sub-carrier.

56. A wireless terminal according to claim 53 further comprising a control channel receiver for receiving a downlink signaling channel containing instructions for burst mode transmission.

57. A wireless terminal according to claim 53 wherein the instructions comprise a definition of the assigned STC sub-block transmission frequency-time locations and a coding/modulation primitive.

58. A wireless terminal according to claim 57 wherein the instructions further comprise rate control commands, the wireless terminal being adapted to change the coding/modulation primitive according to the rate control commands.

59. A wireless terminal according to claim 51 further adapted to measure a long term power strength from a serving base station and to set a coding/modulation by using multi-level progressive coding and modulation feed forward transmission.

60. A wireless terminal according to claim 53 wherein the second transmit chain comprising a hopping pattern generated which defines said assigned STC sub-block transmission frequency-time locations such that they hop about in frequency within a subset of the shared OFDM band allocated for burst-mode traffic.

3. A wireless terminal for communicating over a shared OFDM band, the wireless terminal comprising:

a first transmit chain for generating and transmitting a low rate mode OFDM transmission in a first frequency band of the OFDM band;

the first transmit chain comprises a hopping pattern generator which causes the first frequency band to hop around in frequency within a subset of the shared OFDM band allocated for low rate mode OFDM transmission.

4. A wireless terminal according to claim 3 wherein:

the first transmit chain comprises a space time encoder adapted to perform space time encoding to generate a signal to be transmitted during each OFDM transmission interval as said low rate mode OFDM transmission.

5. A wireless terminal according to claim 3 comprising a plurality N of transmit antennas, N>

=2, wherein the first transmit chain comprises a space time encoder adapted to perform space time encoding to generate a respective STC sub-block comprising symbols for M sub-carriers by N transmission intervals to be transmitted on each transmit antenna during each set of N OFDM transmission intervals as said low rate mode OFDM transmission.

6. A wireless terminal according to claim 5 wherein:

the first transmit chain comprises a hopping pattern generator which causes the first frequency band to hop around in frequency within a subset of the shared OFDM band allocated for low rate mode OFDM transmission and wherein the hopping pattern generates hops with a unit of hopping equal to a size of the STC blocks.

7. A wireless terminal according to claim 5 wherein each STC sub-block further comprises pilot symbols.

8. A wireless terminal according to claim 5 wherein each STC sub-block further comprises N pilot symbols on a respective single sub-carrier on each end of the STC sub-block.

17. A wireless terminal according to claim 6 further comprising a control channel receiver for receiving channel assignment information allowing an identification of where in frequency and when in time to transmit the low rate mode OFDM transmissions wherein the channel assignment information comprises a hopping pattern identity which allows the wireless terminal to perform hopping in accordance with one of a set of orthogonal hopping patterns.

19. A wireless terminal according to claim 6 further comprising:

at least one channel coder adapted to apply channel coding to low rate signal sources prior to forming STC blocks.

20. A wireless terminal according to claim 19 wherein the channel coders have a block size that covers several hops to achieve diversity gain and inter-cell interference averaging.

43. A wireless terminal for communicating over a shared OFDM band, the wireless terminal comprising:

an access channel transmit chain adapted to generate an OFDM access signal occupying a randomly selected slot selected from a plurality of slots comprising a frame, each slot comprising a predetermined block of OFDM time-frequency.

44. A wireless terminal according to claim 43 further comprising:

a control channel receiver for receiving an identity of a plurality of signature definitions for use in a coverage area;

wherein the wireless terminal randomly selects one of the plurality of signatures and applies the signature in generating the access attempt.

45. A wireless terminal according to claim 43 wherein each slot comprises four OFDM symbols, and there are 16 different possible signatures.

46. A wireless terminal according to claim 43 further adapted to map the signature onto OFDM carriers based on a Peano-Hilbert plane filling curve.

47. A wireless terminal according to claim 43 wherein the access channel is overlaid over low rate mode OFDM transmissions of other wireless terminals.

61. A network terminal for receiving communications over a shared OFDM band, the network terminal comprising:

a receiver for receiving burst-mode OFDM transmissions over a first subset of the shared OFDM band and for receiving low rate mode OFDM transmissions over a second subset of the shared OFDM band.

62. The network terminal according to claim 61 further adapted to:

extract burst-mode OFDM transmissions of multiple wireless terminals from said first subset and extract low rate mode OFDM transmissions of multiple wireless terminals from the second subset.

63. A network terminal according to claim 61 further comprising:

a control channel output for controlling frequency-time locations with which wireless terminals are to transmit their low rate mode transmissions.

64. A network terminal according to claim 63 wherein the control channel identifies to each wireless terminal a respective orthogonal hopping pattern for low rate mode OFDM transmission.

65. A network terminal according to claim 61 further comprising:

a power control function adapted to determine a quality of low rate mode OFDM transmissions for each wireless terminal transmitting low rate OFDM transmissions and to generate power control signals in respect of the low rate mode OFDM transmissions for each wireless terminal transmitting low rate OFDM transmissions.

66. A network terminal according to claim 65 further adapted to:

for each standby wireless terminal in a state, assign a respective system access channel and transmit an identity of the respective system access channel over a control channel;

the network terminal being further adapted to monitor the system access channels for requests for capacity from wireless terminals in the standby state.

67. A network terminal according to claim 66 further adapted to maintain timing and synchronization using the system access channels for wireless terminals in the standby state.

68. A network terminal according to claim 66 wherein the requests for capacity can be requests for burst-mode or low rate mode capacity.

69. A network terminal according to claim 61 further comprising:

a control channel output for controlling which wireless terminals are to transmit burst-mode OFDM transmissions.

70. A network terminal according to claim 69 wherein control channel output identifies for each wireless terminal to transmit a burst-mode OFDM transmission where in frequency and when in time to transmit the burst-mode OFDM transmission.

71. A network terminal according to claim 69 further adapted to perform adaptive rate control over the burst-mode transmission.

72. A network terminal according to claim 61 further adapted to monitor a random access channel, the random access channel comprising:

a plurality of slots, each slot comprising a plurality of OFDM symbol intervals, and for each slot a plurality M of signatures such that M access attempts can be received during one slot, the slots being overlaid over transmissions of active wireless terminals.

73. A network terminal according to claim 72 further adapted to transmit an identity of the signatures for use on the random access channel.

74. A network terminal according to claim 73 further adapted to grant system access on the basis of detected access attempts on the random access channel.

75. A system comprising:

a plurality of wireless terminals in which each wireless terminal is assigned a respective Walsh code, and each user data element produced by the wireless terminal is transmitted on a respective sub-carrier spread in time over multiple OFDM symbols, with multiple wireless terminals transmitting a respective data element simultaneously on the same sub-carrier.

76. A system comprising a plurality of wireless terminals in which:

for a given wireless terminal, at least one is Walsh code is assigned for each channel for the wireless terminal, and each user data element of any wireless terminal is transmitted on an OFDM symbol sub-band spread in frequency over multiple OFDM sub-carriers, with multiple of the wireless terminal transmitting simultaneously on the same OFDM symbol sub-band.

77. A method of communicating over a shared OFDM band comprising:

generating and transmitting a low rate mode OFDM transmission in a first frequency band of the OFDM band;

generating and transmitting a burst-mode transmission in a second frequency band of the OFDM band, the first frequency band being distinct from the second frequency band.

78. A method according to claim 77 further comprising:

receiving power control commands and controlling transmit power of the low rate mode OFDM transmission as a function of the power control commands;

receiving rate control commands and controlling transmission rate of the burst-mode OFDM transmission as a function of the rate control commands.