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Compensation of diagonal isi in ofdm signals

A diagonal and signal technology, which is applied in the field of eliminating inter-symbol interference in OFDM signals and compensating for diagonal ISI. It can solve unresolved problems such as diagonal ISI and achieve significant complexity and capacity savings.

Active Publication Date: 2011-02-02
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] Even though Nyquist pulse shaping filters reduce and / or remove inter-channel and / or inter-block ISI, such filters still do not resolve diagonal ISI

Method used

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  • Compensation of diagonal isi in ofdm signals
  • Compensation of diagonal isi in ofdm signals
  • Compensation of diagonal isi in ofdm signals

Examples

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Embodiment Construction

[0025] Inter-symbol interference (ISI) in transmitted OFDM symbols generally includes a combination of inter-channel ISI, inter-block ISI, and diagonal ISI. figure 1 An exemplary OFDM symbol 12 in a two-dimensional plane representing frequency and time domains. Each moment of time (t k ) included at different subcarrier frequencies (f j ) block 10 of OFDM symbols 12 transmitted on . Blocks 10 of symbols 12 in the frequency-time plane are arranged vertically at subcarrier frequencies f 0 , f 1 , f 2 , f 3 , ... to show. figure 1 Use arrows to show the time instant t due to 4 corresponding to the subcarrier frequency f 2 Demonstrative coupling between different symbol instances induced by the symbol's ISI. Arrows 1 and 2 show that at the same time (t 4 ) at different subcarrier frequencies (f 1 and f 3 Inter-channel ISI caused by symbols transmitted on ). Arrows 3 and 4 show that at different times (t 3 and t 5 ) at the same subcarrier frequency (f 2 Inter-block ...

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Abstract

A method and apparatus for compensating for ISI is described herein. A transmitter (110) and receiver (120) work together to develop pulse shaped OFDM symbols with reduced inter-channel ISI between pulse-shaped OFDM symbols transmitted on different sub-carriers at the same time, and inter-block ISI between pulse-shaped OFDM symbols transmitted on the same sub-carrier at different times. In addition, a pre-compensation element (118) in the transmitter (110) and / or a post-compensation element (128) in the receiver (120) compensate for diagonal ISI occurring between pulse-shaped OFDM symbols transmitted on different sub-carriers at different times.

Description

Background technique [0001] The present invention generally relates to interference cancellation, and more particularly to intersymbol interference cancellation in OFDM signals. [0002] Orthogonal Frequency Division Multiplexing (OFDM) is a digital multicarrier modulation scheme utilizing multiple closely spaced orthogonal subcarrier frequencies. Each subcarrier is modulated with a conventional modulation scheme (eg, quadrature amplitude modulation) at a low symbol rate, maintaining a data rate similar to conventional single-carrier modulation schemes in the same bandwidth. OFDMA allows several users to share the available bandwidth by allocating different subcarriers to different users, thus making users orthogonal to each other. Allocation of subcarriers can be dynamic, for example, assigning a larger number of subcarriers to users with larger amounts of data to transmit. OFDM is deployed or planned for a variety of wireless systems, including IEEE802.16 (WiMAX), some IEE...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L25/03
CPCH04L25/03834H04L25/03343H04L2025/03414
Inventor P·W·邓特
Owner TELEFON AB LM ERICSSON (PUBL)
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