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A technology of differential coding and modulation method, which is applied in multi-frequency code systems, preventing/detecting errors through diversity reception, etc., to achieve stable and reliable performance.
Inactive Publication Date: 2010-04-28
SHANGHAI JIAO TONG UNIV
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[0005] After searching the existing literature, it was found that Qian Ma et al published a paper entitled "Differential space-time-frequency coded OFDM with maximum multipath diversity" in "IEEE Transactions on Wireless Communications (IEEE Journal of Wireless Communications)". Space-Time-Frequency Coding Orthogonal Frequency Division Multiplexing)", which provides a space-time-frequency differential modulation method, but this technology can only perform differential coding in a single frequency domain or time domain, that is, coding and Differential modulation is performed on the same dimension in the time domain or frequency domain, so that the demodulation of the signal requires the channel to be within the OFDM symbol transmission time period with twice the number of transmit antennas, or the adjacent OFDM sub-bands with twice the number of transmit antennas. Between carriers, the approximation remains unchanged, so this technique is only suitable for channel environments with high time domain correlation or high frequency domain correlation
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Embodiment 1
[0022] Under two transmitting antennas, this embodiment adopts differential space-time-frequency block code mapping, including the following steps:
[0023] In the first step, the mobile terminal of the communication system performs Alamouti code (orthogonal block code) encoding on the information bit sequence to be sent to generate a 2×2 unitary matrix codeword sequence, denoted as {...,D k-1 ,D k ,D k+1 ,...}.
[0024] In the second step, the unitary matrix codeword sequence {..., D k-1 ,D k ,D k+1 ,...} each codeword is transformed into a 2×2 matrix to be transmitted. code word D k As an example, the converted matrix X to be transmitted k for:
[0025] X k = X k - 1 D k = x 11 , k ...
Embodiment 2
[0032] Under two transmitting antennas, this embodiment adopts differential space-frequency-time cyclic code mapping, including the following steps:
[0033] In the first step, the mobile terminal of the communication system performs diagonal cyclic code encoding on the information bit sequence to be sent to generate a 2×2 unitary matrix codeword sequence, which is denoted as {...,D k-1 ,D k ,D k+1 ,...}.
[0034] Specifically, m information bits are used as a group to carry out diagonal cyclic coding to obtain 2 m different cyclic code words. Taking m=2 as an example, the codebook of the cyclic code is:
[0035] D. k ∈{G 0 , G 1 , G 2 , G 3}
[0036] in:
[0037] G 0 = 1 0 0 1 ; G 1 = ...
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Abstract
The invention discloses a differential encoding space-time-frequency modulation method, and belongs to the technical field of wireless communication. The method comprises that: a mobile terminal of a communication system performs space-time encoding on an information bit sequence required to be transmitted to generate a unitary matrix code word sequence; the unitary matrix code word sequence is subjected to differential modulation to generate a matrix sequence to be transmitted; symbols in the matrix sequence to be transmitted are respectively mapped to a space domain, a time domain and a frequency domain so as to acquire a group of space-time-frequency three-dimensional signals; a plurality of groups of transmission signals are acquired through OFDM modulation, and each group of transmission signals is transmitted through a transmitter antenna; and the OFDM modulation and differential demodulation are directly carried out a receiving end, and required information is acquired. Through differential space-time-frequency block code mapping or differential space-time-frequency cyclic code mapping, the encoding and the differential modulation are respectively carried out at different dimensionalities, so that a requirement of a channel on relevance of the time domain and the frequency domain is reduced, and a requirement of reliable signal transmission in high-speed mobile environment in a wideband communication system can be met.
Description
technical field [0001] The present invention relates to a method in the technical field of wireless communication, in particular to a differential coding space-time-frequency modulation method. Background technique [0002] When the signal is transmitted in the wireless environment between the mobile terminal and the base station, it will be interfered by various factors in the wireless channel, such as path loss, shadow fading, fast fading, Doppler frequency shift, etc., especially when the mobile terminal is at high speed While on the move, the channel state changes over time. Therefore, some technologies will be used in the mobile communication system to suppress these interferences and ensure smooth communication, especially smooth communication during movement, such as multiple input multiple output (MIMO) technology, orthogonal frequency division multiplexing (OFDM) technology, diversity technology etc. [0003] MIMO technology can obtain multiple independent transmi...
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