SYSTEM AND METHOD FOR RADIO FREQUENCY CARRIER AGGREGATION

• US 20150146805A1
• Filed: 11/25/2014
• Published: 05/28/2015
• Est. Priority Date: 11/26/2013
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: PlusN LLC
• Inventors: Terry, John David
• Granted Patent: US 9,401,823 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0242 using matrix methods
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2618 Reduction thereof using auxiliary subcarriers
• CPC Class Codes: H04L 27/2621 Reduction thereof using phase offsets between subcarriers
• CPC Class Codes: H04L 27/2624 by soft clipping
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2649 Demodulators
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/367 using predistortion
• CPC Class Codes: H04L 45/24 Multipath
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04W 84/12 : WLAN [Wireless Local Area Networks]

Abstract

A system and method for aggregation of a plurality of wireless communication signals in a common radio frequency transmitter. A multiple subchannel multiplexed (MSM) signal within a frequency band, and having a communication protocol with pilot signals estimating a channel state and efficient signal demodulation with a mobile receiver is combined with another signal. An automated digital processor at the transmitter modifies the MSM to meet at least one fitness criterion of the combined signal, selected from among alternatives that will maintain good reception of all transmitted signals within system protocols, without requiring transmitting additional side information specifying the modification. The range of alternates include modifications that disrupt the pilot signals. The fitness criterion may include minimizing the peak-to-average power ratio of the combination, and a signal modification may comprise a cyclic permutation of a portion of the time-domain representation of a signal, while maintaining compatibility with prior pilot signals.

Claims

1. A method for controlling a combined waveform, representing a combination of signals, the signals comprising at least one multiple subchannel multiplexed signal having information modulated in respective subchannels, with a modulated signal, comprising:

receiving information to be communicated from a transmitter to a receiver through the at least one multiple subchannel multiplexed signal according to a predetermined protocol, the multiple subchannel multiplexed signal comprising pilot signals, within at least one subchannel for at least a portion of time, having predefined characteristics sufficiently independent of the information to be communicated, to permit receiver prediction of a communication channel state with respect to varying communication channel conditions;

storing a model of the receiver with respect to a combination of the multiple subchannel multiplexed signal with the modulated signal in a memory, the model being for predicting a receiver ability to demodulate the information and a receiver ability to predict the channel state, over a range of at least one parameter representing available alterations in the state of the combination; and

defining, with an automated processor, the combination signals which is predicted to permit sufficient receiver estimation of the channel state to demodulate the information from respective subchannels and which further meets at least one fitness criterion distinct from the receiver estimation of the channel state and being dependent on both the multiple subchannel multiplexed signal and the modulated signal, with respect to at least two different values for the at least one parameter.

2. The method according to claim 1, further comprising forming a plurality of sets of combined waveforms, each combined waveform representing a respective combination of the multiple subchannel multiplexed signal with the modulated signal at a respective value of the at least one parameter, and said defining comprises selecting a respective defined waveform which meets the at least one fitness criterion.

3. The method according to claim 2, wherein the at least one fitness criterion comprises a peak to average power ratio.

4. The method according to claim 1, wherein the modulated signal is modulated with second information, wherein the automated processor further defines the combination of the multiple subchannel multiplexed signal with the modulated signal in a manner which is predicted to permit demodulation of the second information from the modulated signal.

5. The method according to claim 1, wherein a first combination and a second combination based on different values of the at least one parameter differ with respect to a relative timing of a modulation of frequency components of a first signal with respect to a second signal.

6. The method according to claim 1, wherein a first combination and a second combination, having different values of the parameter, differ with respect to a relative phase of frequency components of a respective signal.

7. The method according to claim 1, wherein the at least one multiple subchannel multiplexed signal comprises at least one orthogonal frequency division multiplexed signal, and the modulated signal comprises an orthogonal frequency division multiplexed signal.

8. The method according to claim 1, wherein the at least one multiple subchannel multiplexed signal is an orthogonal frequency division multiplexed stream which is compatible with at least one protocol selected from the group consisting of an IEEE 802.11 protocol, an IEEE 802.16 protocol, a 3GPP-LTE downlink protocol, LTE-Advanced protocol, a DAB protocol and a DVB protocol, wherein a receiver compliant with the at least one protocol can demodulate the at least two respectively different combinations without requiring additional information to be transmitted outside of said protocol.

9. The method according to claim 1, wherein the at least two different values of the at least one parameter correspond to signals that differ respectively in a cyclic time shift in a modulation sequence.

10. The method according to claim 1, wherein meeting the fitness criterion comprises analyzing with respect to a predicted error rate of a reference receiver design for at least one of the signals.

11. The method according to claim 1, wherein the defined combination of signals is communicated as a digital representation of an intermediate frequency representation.

12. The method according to claim 1, wherein the predistorting compensates for at least a portion of one or more of an analog non-linearity, a transmission channel impairment, and a receiver characteristic of an analog radio communication system communicating using the combination of signals.

13. The method according to claim 1, wherein each of the at least two signals comprises an orthogonal frequency domain multiplexed signal having a cyclic prefix, the at least one parameter comprises a cyclic time shift, and said defining comprises defining at least two alternate representations which differ in a respective cyclic time shift.

14. The method according to claim 1, wherein each of the at least two signals is received as an orthogonal frequency division multiplexed signal conforming to a communications protocol, at least one of the signals being modified to generate the at least two alternate representations differing according to the at least one parameter, and the at least one fitness criterion comprises a peak to average power ratio of the combined signal, wherein said defining selects a combination representing a lowest peak to average power ratio.

15. The method according to claim 1, wherein the model of the receiver incorporates prior pilot signals in defining acceptable values of the at least one parameter that are selected for further evaluation according to the at least one fitness criterion.

16. The method according to claim 1, wherein the model of the receiver uses extrapolation of prior pilot signals to generate a reference signal during time periods when a current pilot signal is not available.

17. The method according to claim 1, wherein an evaluation of the fitness criterion for the combination is implemented in parallel for the different values of the parameter on a programmable gate array.

18. The method according to claim 1, wherein each of the at least one multiple subchannel multiplexed signal and the modulated signal is received as an orthogonal frequency division multiplexed signal conforming to a communications protocol, at least one of the signals is modified to generate the at least two alternate representations, each of which can be demodulated by a receiver compatible with the protocol without requiring receipt of additional information outside of the communications protocol, and the at least one criterion comprises a peak to average power ratio of the combined signal.

19. The method according to claim 1, wherein:

the multiple subchannel multiplexed signal is an orthogonal frequency multiplexed signal having a plurality of subcarriers at different frequencies which concurrently communicate the information;

the multiple subchannel multiplexed signal and the modulated signal each being within a different communication frequency channel and being processed as a combined analog signal in at least one analog signal processing component having a non-linear distortion;

the multiple subchannel multiplexed signal being according to a predetermined protocol which selectively inserts the pilot signals in a plurality of the subcarriers at different times and at different frequencies to estimate the channel state;

the at least one parameter comprises a cyclic shift of digital data representing the multiple subchannel multiplexed signal, and wherein the model of the receiver predicts an ability of a receiver which complies with an OFDM protocol to at least detect the pilot and estimate the channel state subject to at least two different cyclic shifts; and

the at least one fitness criterion is dependent on the non-linear distortion of the combination of the multiple subchannel multiplexed signal with the modulated signal in the analog signal processing component.

20. An apparatus for controlling a combined waveform, representing a combination of at least two signals, each having a plurality of signal components and conveying information, comprising:

an input port configured to receive information defining the at least two signals;

an automated processor configured to;

transform a first of the signals into at least two representations of the conveyed information within a range of transformations, along with pilot signal information which varies in frequency and which is selectively communicated over time, to permit a receiver to estimate a channel state, having prohibited combinations of transformation parameters and pilot signal information,

combine a transformed representation of a first of the signals with a second of the signals, to define at least two alternate combinations representing the conveyed information, and

select one combination which meets a predetermined criterion and which permits the receiver to at least estimate the channel state; and

an output port configured to output information representing a respective combined waveform comprising the selected one combination of the transformed representation which meets the predetermined criterion.

21. The apparatus according to claim 20, wherein a first of the at least two representations and a second of the at least two representations differ with respect to at least one of (a) a relative timing of a modulation of frequency components of a first signal with respect to a second signal and (b) a relative phase of the frequency components of the first signal with respect to the second signal, and the at least one criterion comprises a peak to average power ratio (PAPR).

22. The apparatus according to claim 20, wherein at least one signal is an orthogonal frequency division multiplexed stream which is compatible with at least one protocol selected from the group consisting of an IEEE 802.11 protocol, an IEEE 802.16 protocol, a 3GPP-LTE downlink protocol, a DAB protocol and a DVB protocol, wherein a receiver compliant with the at least one protocol can demodulate the at least two respectively different combinations of without requiring additional information to be transmitted outside of said protocol.

23. The apparatus according to claim 20, wherein the at least two representations differ respectively in a cyclic time shift in a modulation sequence, and the at least one criterion comprises a peak to average power ratio, wherein an alternate representation which results in a lowest peak to average power ratio is selected for combination.

24. The apparatus according to claim 20, wherein the automated processor is configured to predistort, to compensate for at least a portion of one or more of an analog non-linearity, a transmission channel impairment, and a receiver characteristic of an analog radio communication system communicating using the selected at least one combination.

25. The apparatus according to claim 20, wherein said automated processor is further configured to predistort at least one of an intermediate frequency and a radio frequency representation of the selected at least one combination.

26. A system for controlling a combined waveform, representing a combination of at least one multiple subchannel multiplexed signal according to a predetermined protocol to be communicated from a transmitter to a receiver with a modulated signal, the multiple subchannel multiplexed signal comprising pilot signals, within at least one subchannel for at least a portion of time, having predefined characteristics sufficiently independent of information to be communicated, to permit receiver prediction of a communication channel state with respect to varying communication channel conditions, comprising:

a model of a receiver stored in a memory, dependent on a combination of the multiple subchannel multiplexed signal with the modulated signal in a memory, for predicting a receiver ability to demodulate information and a receiver ability to predict the channel state, over a range of at least one parameter representing an alteration in the state of the combination; and

an automated processor configured to define the combination of the multiple subchannel multiplexed signal with the modulated signal which is predicted to permit sufficient receiver estimation of the channel state to demodulate the information and which further meets at least one fitness criterion distinct from the receiver estimation of the channel state and being dependent on both the multiple subchannel multiplexed signal and the modulated signal, with respect to at least two different values for the at least one parameter.