System and method for reducing adjacent channel interference (ACI) in a multicarrier modulation system

• US 20040252631A1
• Filed: 06/16/2003
• Published: 12/16/2004
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Park, Young-Seo
• Granted Patent: US 6,934,246 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 27/02 Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2082 for offset or staggered quadrature phase shift keying
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/26265 Arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral precoding
• CPC Class Codes: H04L 27/2631 with polyphase implementation
• CPC Class Codes: H04L 27/2698 double density OFDM/OQAM system, e.g. OFDM/OQAM-IOTA system
• CPC Class Codes: H04L 27/363 using non - square modulating pulses, modulators specifically designed for this transmission of non - square QAM H04L27/3494

Abstract

An improved multicarrier modulation system and method, which has the advantages of both isotropic orthogonal transfer algorithm orthogonal frequency division multiplexing (IOTA OFDM) and scalable advanced modulation (SAM), is introduced. The invention is root raised cosine (RRC) OFDM using the most spectrally efficient RRC filter without sacrificing the compact subchannel spacing of OFDM. The invention further provides an adjacent channel interference (ACI) suppression scheme and a modified RRC for better suppressing ACI of RRC OFDM. The ACI suppression scheme can also be applied to SAM with the modified RRC and to IOTA OFDM with a modified IOTA. The invention greatly improves a major problem of conventional OFDM namely ACI due to the use of a wide subchannel filter. Thus, the invention allows OFDM to meet even the strictest ACI requirements, which was not possible by using a conventional raised cosine windowing method.

Claims

1. A system for reducing adjacent channel interference (ACI) in a multicarrier modulation system, comprising:

a generator for generating a spectrally efficient modified pulse for multicarrier modulation; and

at least one processor for adapting the spectrally efficient modified pulse at the edge of subchannel for reducing the ACI product by the total multicarrier signal.

2. A system for reducing ACI in a multicarrier modulation system as in claim 1, wherein the modified pulse has fast fading sidelobes having a substantially low amount of distortion as compared with an unmodified pulse.

3. A system for reducing ACI in a multicarrier modulation system as in claim 1, wherein the spectrally efficient modified pulse at the edge of the subchannel has substantially low amplitude sidelobes.

4. A system for reducing ACI in a multicarrier modulation system as in claim 1, wherein only one side sidelobes of the modified pulse are reduced.

5. A system for reducing ACI in multicarrier modulation system as in claim 1, wherein the number of edge subchannels that use the spectrally efficient modified pulse shape is determined by the spectral characteristic of the original and modified pulse shape and the multicarrier signal structure

6. A system for reducing ACI in multicarrier modulation system as in claim 1, wherein the step of adapting includes meeting standard channel interference requirements.

7. A method for reducing adjacent channel interference (ACI) in multi-carrier modulation system comprising the steps of:

generating a spectrally efficient modified pulse for the multi-carrier modulation; and

adopting the spectrally efficient modified pulse at the edge sub-channels for reducing the ACI of the total multi-carrier signal.

8. A method for reducing ACI in a multi-carrier modulation system, as in claim 7, wherein the spectrally efficient modified pulse is generated having fast fading sidelobes with a substantially low amount of distortion from the original pulse.

9. A method for reducing ACI in multi-carrier modulation system, as in claim 7, wherein the modified pulse has low amplitude sidelobes.

10. A method for reducing ACI in a multi-carrier modulation system, as in claim 7, wherein only one side sidelobes of the modified pulse are reduced.

11. A method for reducing ACI in a multi-carrier modulation system, as in claim 7, wherein the number of edge subchannels that use the spectrally efficient modified pulse shape is determined by the spectral characteristic of the original and modified pulse shape and the multicarrier signal structure.

12. A method for reducing ACI in a multi-carrier modulation system, as in claim 7, wherein the step of adapting includes meeting standard channel interference requirements.

13. A method for reducing adjacent channel interference (ACI) in multi-carrier modulation system comprising the steps of:

generating a spectrally efficient modified pulse with fast fading sidelobes for the multi-carrier modulation;

reducing the amplitude of single side lobes of the modified pulse; and

adapting the spectrally efficient modified pulse at the edge sub-channels for reducing the ACI of the total multi-carrier signal to meet predetermined channel interference requirements.

14. A method for reducing ACI in a multi-carrier modulation system, as in claim 13, wherein the number of edge subchannels that use the spatially efficient pulse shape is determined by the spectral characteristic of the original and modified pulse shape and the multicarrier signal structure.