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Minimum mean-square error two-stage spread spectrum OFDM self-adaptive code distribution method and system

A minimum mean square error and code allocation technology, applied in multi-frequency code systems, multiplexing code allocation, baseband system components, etc., can solve problems such as drastic channel changes, poor signal correlation, and deep fading

Inactive Publication Date: 2013-03-27
PEKING UNIV
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Problems solved by technology

[0004] At present, MC-CDMA still has two deficiencies: first, when encountering a frequency-selective fading channel, if compared to the channel delay extension, the transmitting end transmits a pulse signal with a narrow time width, and in the frequency domain The transmission bandwidth is relatively large. If the transmission bandwidth is larger than the channel coherence bandwidth, then the correlation between signals becomes worse, and the channel changes drastically within a symbol bandwidth, entering deep fading.
Second, when encountering a time-selective fading channel, if the transmitter transmits a frequency-domain signal with a narrow bandwidth relative to the maximum Doppler frequency shift, the symbol period in the time-domain is longer, and if the sampling interval Greater than the coherence time, the correlation of the signal becomes worse

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  • Minimum mean-square error two-stage spread spectrum OFDM self-adaptive code distribution method and system
  • Minimum mean-square error two-stage spread spectrum OFDM self-adaptive code distribution method and system
  • Minimum mean-square error two-stage spread spectrum OFDM self-adaptive code distribution method and system

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[0026] In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0027] The present invention adopts the two-stage spread spectrum OFDM system of two sets of spread spectrum codes, which can flexibly distribute the spread spectrum codes so that the energy of the transmitted signal can be concentrated on the subcarriers with better channel conditions as much as possible, so as to better compensate for the MC -CDMA defects, improve system performance.

[0028] refer to figure 1 , figure 1 It is a flow chart of the steps of the embodiment of the two-stage spread spectrum OFDM adaptive code allocation method under the minimum mean square error method of the present invention, including:

[0029] The first-stage spreading step 110, modulates the original data stream, and combines every L modulated...

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Abstract

The invention discloses a minimum mean-square error two-stage spread spectrum OFDM self-adaptive code distribution method and a system, wherein the method comprises the steps of first stage spread spectrum, second stage spread spectrum, sending signal modification, signal receiving and signal detecting. In the invention, according to the channel condition, positions of all lines of a spreading code matrix C are regulated, so as to lead the sending signal energy to be centralized on a subcarrier with better channel condition as far as possible, and inhibit interference among users and symbols owning to orthogonality damage. Compared with the traditional MC-CDMA, the BER at the receiving end is greatly improved.

Description

technical field [0001] The present invention relates to DS-CDMA (Direct Sequence-Code Division Multiple Access, Direct Sequence Code Division Multiple Access) technology and MC-CDMA (Multicarrier-Code Division Multiple Access, multi-carrier code division multiple access) technology in the field of wireless communication, in particular to a Minimum mean square error two-stage spread spectrum OFDM adaptive code allocation method and system. Background technique [0002] As a spread spectrum method, Direct Sequence-Code Division Multiple Access (hereinafter referred to as DS-CDMA) obtains a wideband spread spectrum signal by multiplying a narrowband signal carrying information with a high-speed address code signal, and the receiving end Despreading can be realized by using the same address code signal synchronized with the transmitter to control the carrier frequency phase of the input frequency converter. DS-CDMA system has superior anti-narrowband interference characteristic...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L27/26H04L25/02H04L25/03H04J13/18
Inventor 尚勇吴波封晓弢项海格
Owner PEKING UNIV
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