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Self adaptable transmission for OFDMA system

An orthogonal frequency division multiple access and adaptive transmission technology, which is applied in the field of OFDM cellular mobile communication system transmission, can solve the problems of poor adaptive modulation performance, limited channel correlation, and large channel correlation, etc., to achieve improved error Bit rate performance, improved throughput, and low complexity effects

Active Publication Date: 2005-02-23
SOUTHEAST UNIV
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Problems solved by technology

However, in the case of low Doppler frequency shift, due to the high correlation between channels, long interleaving is required, which will bring a large delay
So interleaving is only suitable for large Doppler shift
However, the adaptive modulation method will make the influence of channel fading on the system performance tend to be consistent, and the burst errors will also be randomized.
Adaptive modulation is also limited by the correlation of the channel. Under high Doppler frequency shift, the performance of adaptive modulation will deteriorate.

Method used

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  • Self adaptable transmission for OFDMA system
  • Self adaptable transmission for OFDMA system
  • Self adaptable transmission for OFDMA system

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Embodiment Construction

[0024] Each component in the invention is discussed separately below.

[0025] 1. Interweaving mode

[0026] In step 3, the interleaving mode needs to be determined. Interleaving mainly changes the correlation of adjacent bits, so as to better achieve the effect of diversity. There are many studies on adaptive interleaving. According to the known channel state information (Channel State Information, CSI), the channel is divided into two states, good and bad. Through interleaving, these two states are in the frequency domain of the OFDM system. Interleaving occurs, so that Viterbi decoding is more effective, and using the same predictor at both ends of the transceiver can realize the synchronization of this algorithm. In another literature, the Markov model of the channel is used to study the performance of interleaving under different fading conditions and the influence of interleaving length and depth on the bit error rate, so as to select the appropriate interleaving lengt...

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Abstract

The method includes following steps: 1) the system is initialized; the numbers of cyclic prefix inserted into OFDM system are selected by actual measurement of multi path time delay; according to the cyclic prefix, the frequency inserted into by the frequency domain pilot frequency is determined ; 2) SINAD threshold of each kind modulation mode like BPSK, QPSK, 16QAM, 64QAM is set by high layer protocol, the SINAD value obtained from step 1 is compared with the threshold corresponding to each modulation mode; 3) Doppler shift is estimated out, it is decided that the product of Doppler shift and frame length is which range; 4) for first sub-carrier in each group, the modulation mode is presented by using GRAY CODE, the transmission of signal uses 4 bit; 5) the transmitting end assigns the modulation mode to next frame data according to received TMC instruction.

Description

technical field [0001] The invention relates to an adaptive transmission scheme for an Orthogonal Frequency Division Multiple Access (OFDM) cellular mobile communication system, and belongs to the transmission technical field of the OFDM cellular mobile communication system. Background technique [0002] The ever-increasing demand for wireless multimedia services requires reliable high-speed data communication over wireless channels. The main problem of broadband transmission under mobile multipath channels lies in the ability to resist Inter-symbol Interference (ISI). Multi-carrier communication has attracted great interest due to its ability to resist inter-symbol interference. As a kind of multi-carrier communication technology, OFDM has broad prospects. OFDM is a parallel transmission method that uses many subcarriers to transmit information symbols in parallel to reduce the symbol rate, so that each subcarrier experiences a flat fading chann...

Claims

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Application Information

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IPC IPC(8): H04L27/26
Inventor 尤肖虎方昕潘志文高西奇金润姬朴宇欧
Owner SOUTHEAST UNIV
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