Frequency error estimation and frame synchronization in an OFDM system

A technology of frequency error estimation and frequency error, which is applied in the field of frequency error estimation and frame synchronization, and can solve problems such as lowering system efficiency and weak robustness

Inactive Publication Date: 2007-03-14
QUALCOMM INC
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  • Frequency error estimation and frame synchronization in an OFDM system
  • Frequency error estimation and frame synchronization in an OFDM system
  • Frequency error estimation and frame synchronization in an OFDM system

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Embodiment Construction

[0021] The word "exemplary" is used herein to mean "serving as an example, illustration or illustration". Any embodiment or design described herein as "exemplary" is not to be construed as preferred or advantageous over other embodiments or designs.

[0022] FIG. 1 shows a block diagram of a transmitter 110 and a receiver 150 in an OFDM system 100 . In transmitter 110, a transmit (TX) data processor 120 receives, formats, and encodes traffic data (eg, information bits) to obtain encoded data. Encoding increases the reliability of data transmission and may also include error detection (eg, CRC) encoding, forward error correction (eg, convolutional, turbo, and / or block) encoding, or combinations thereof. Typically, each data packet is encoded with a fixed or variable length. Then, the TX data processor 120 interleaves the encoded data to obtain interleaved data. Interleaving provides time and / or frequency diversity against deleterious path effects and can also be performed on...

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Abstract

Frequency error estimation and frame synchronization are performed at a receiver in an OFDM system based on a metric that is indicative of detected pilot power. The metric may be defined based on cross-correlation between two received symbols obtained in two OFDM symbol periods. For frequency error estimation, a metric value is computed for each of multiple hypothesized frequency errors. The hypothesized frequency error for the metric value with the largest magnitude is provided as the estimated frequency error. For frame synchronization, a correlation value is obtained for each OFDM symbol period by correlating metric values obtained for NC (e.g., most recent) OFDM symbol periods with NC expected values. The expected values are computed in a manner consistent with the manner in which the metric values are computed. Peak detection is performed on the correlation values obtained for different OFDM symbol periods to determine frame synchronization.

Description

field of invention [0001] The present invention relates generally to data communication, and more particularly to techniques for frequency error estimation and frame synchronization in Orthogonal Frequency Division Multiplexing (OFDM) communication systems. technical background [0002] OFDM is a multi-carrier modulation technique that can provide high performance in some wireless environments. OFDM effectively divides the entire system bandwidth into several (N sb ) orthogonal subbands, which are also commonly referred to as audio bands, subcarriers, frequency segments, and frequency channels. With OFDM, each subband is associated with a corresponding subcarrier that can be modulated with data. [0003] In an OFDM system, initially, the transmitter encodes, interleaves and modulates a stream of information bits to obtain a stream of modulation symbols. In each OFDM symbol period, at N sb N sb "transmit" symbols, where each transmit symbol may be a data symbol (eg, a mo...

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Application Information

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IPC IPC(8): H04L27/26
CPCH04L27/2657H04L27/2675H04L27/2656H04L27/26H04L7/02
Inventor 拉吉夫·维贾亚恩阿洛克·库马尔·古普塔拉古拉曼·克里希纳姆尔蒂
Owner QUALCOMM INC
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