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DMR physical layer four-level modem

A modulation and demodulation, four-level technology, applied in the direction of DC level restoration device/bias distortion correction, electrical components, transmitter/receiver shaping network, etc., can solve problems such as fixed threshold judgment large error

Inactive Publication Date: 2009-08-26
XIDIAN UNIV
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Problems solved by technology

[0007] The existing baseband multi-level judgment method usually adopts a hard judgment method with a fixed threshold. When the receiving level is unstable, the fixed threshold judgment will cause a large bit error

Method used

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  • DMR physical layer four-level modem
  • DMR physical layer four-level modem
  • DMR physical layer four-level modem

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Embodiment Construction

[0055] The implementation of the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, taking the four-level baseband modulation and demodulation in the DMR system as an example. The four-level baseband modulation and demodulation methods described below are all completed in the DSP.

[0056] Refer to image 3 The modulator of the present invention is composed of three units: a symbol mapping unit, an interpolation unit and a shaping filter unit. The symbol mapping unit frames the original binary data according to the format required by the DMR system, and maps the data pairwise to quaternary symbols +3, +1, -1 and -3, and the data rate is reduced from 9.6kb / s to 4800 symbols / sec. The interpolation unit inserts zero values ​​between quaternary symbols. The specific method is to insert seven zeros after each symbol, which is equivalent to sampling eight points per symbol period. After interpolation, the da...

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Abstract

The invention discloses a DMR physical layer four-level modem, belonging to the field of wireless communication technology. The modulator frames original binary data in accordance with a format required by a system and maps the data into quaternary symbols two by two in sequence; zero values are interpolated between the quaternary symbols and root-raised cosine filter is performed on the interpolated data in order to generate band-limited quaternary baseband signals. The demodulator implements a de-DC component treatment on sample data frames of the quaternary baseband signals and carries out matched filtering via a root-raised cosine filter; the filtered data and locally-stored synchronous code waveform are subjected to related operations to find out an optimal extraction / judgment location; afterwards, sampling points of the optimal extraction / judgment location are utilized to calculate dynamic thresholds in a segmenting manner, multilevel judgment is implemented to obtain the quaternary symbols; in the end, the quaternary symbols are reversely mapped to restore binary data information. The invention can implement the framing flexibly in accordance with the requirement of the system and is suitable for a variety of data frames, including a digital communication system of a DMR frame structure.

Description

Technical field [0001] The invention belongs to the technical field of wireless communication, relates to modulation and demodulation in communication, and can be applied to the four-level modulation and demodulation of a DMR trunking digital wireless system. Background technique [0002] DMR (Digital Mobile Radio) is a new digital trunking communication system proposed by the European Telecommunications Standards Institute (ETSI) in 2004. Compared with the TETRA system and the iDEN system, it has the advantages of simple technology and lower cost, and supports from analog to digital transition. In September 2006, ETSI released ETSI TS 102 361 related to the air interface, voice technology, digital service and trunking protocol of DMR. [0003] DMR adopts 4FSK modulation method, which is a constant envelope continuous phase FSK modulation. Compared with the π / 4-DQPSK modulation method adopted by TETRA and the multi-ary quadrature amplitude modulation M-16QAM adopted by the iDEN s...

Claims

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Application Information

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IPC IPC(8): H04L25/03H04L25/06H04L27/26H04B1/707
Inventor 丁婧杨家玮杨懋李伟邱婷王保坤刘勤黄鹏宇张文柱罗继芳谭瑾博
Owner XIDIAN UNIV
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