JPH0787154A - Frame synchronizing method for multilevel quadrature amplitude modulation system - Google Patents

Abstract

PURPOSE:To improve the frequency use efficiency by using training symbols of equalizers for initial value calculation of a symbol for synchronous timing detection and a tap coefficient and giving a specific constitution. CONSTITUTION:In a signal space diagram adapted to a 16 QAM system, training symbols of equalizers are arranged in the signal space diagram (TS1 to TS16) of the 16 PSK(16-level phase shift keying) system on the outermost circumference (radius =18<1/2>) in accordance with the transmission bit array. Information (control) symbols are arranged in accordance with the 16 QAM signal diagram (Q1 to Q16). Contents of a memory are used for comparison and decision. Consequently, training symbols of equalizers can be used as symbols for frame synchronism, and therefore, symbols only for frame synchronism are unnecessary, and the ratio of information (control) symbols to all symbols is increased, and the transmission efficiency, namely, the frequency use efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for correcting the characteristic variation of a propagation path in a multilevel QAM (Quadrature Amplitude Modulation) system applied to enhance frequency utilization efficiency in digital mobile radio communication. In addition, the present invention relates to a frame synchronization method for a mobile communication system that employs an equalizer.

[0002]

2. Description of the Related Art Recently, in the field of mobile communication, it has become an urgent task to improve the effective use of frequencies as the demand increases. From this point of view, the digital TDMA / multi-level modulation system is adopted, and the practical application of the multi-level modulation system with a larger multi-level number is under study. The multi-valued modulation method is effective from the viewpoint of improving the frequency utilization efficiency, and among them, the multi-valued QAM method is said to have an excellent error rate characteristic against deterioration of the propagation path characteristic. Digital multi-level QA for mobile communication
In order to improve the frequency utilization efficiency by adopting the M method, the propagation characteristics of the propagation path fluctuate due to a fading phenomenon or the like. In order to secure a desired error rate characteristic, adaptive automatic Requires a pesticide. The 16QAM system, which is a typical multilevel QAM system, will be described below as an example. FIG. 3 shows a signal space diagram of the conventional 16QAM system. FIG. 4 shows a conventional frame format. The training symbol portion of FIG. 4 is used for determining the initial value of the tap coefficient of the equalizer, and the nature of the symbol sequence is preferably white (uncorrelated). The synchronous (unique) symbols in FIG. 4 are for frame timing detection, and their arrangement is on the outermost circumference (radius: 18 ^1/2 ) of the 16QAM system spatial signal diagram of FIG. The training symbol and the information (control) symbol are 16QAM in FIG.
They are arranged according to the spatial signal diagram (Q _{1 to} Q ₁₆ ) of the system. Here, in the frame synchronization of the conventional 16QAM system, successive synchronization addition of absolute values of received symbols (absolute values of I and Q signals) is performed in a memory of the number of symbols in one slot in integer slot intervals, The frame timing is detected from a large memory address, the self channel slot is identified from the correlation value between the training symbol of the equalizer and the received signal, and the frame synchronization is established. If necessary, the amount of frequency offset is calculated using the training symbols of the equalizer, and the received signal is corrected to improve the accuracy of identification of the self-channel slot and improve the equalization characteristics. I was trying.

[0003]

However, in the above conventional method, as shown in FIG. 4, in addition to the training symbol sequence for the equalizer, a synchronization (unique) symbol for detecting the synchronization timing is required. Therefore, a redundant symbol is added to cause a decrease in transmission efficiency, that is, a deterioration in frequency utilization efficiency. The present invention has been made to solve the above problems, and an object of the present invention is to provide a digital multi-level QAM system that eliminates the decrease in frequency utilization efficiency and is excellent in transmission efficiency.

[0004]

In order to solve the above problems, a frame synchronization method of a multilevel quadrature amplitude modulation system according to the present invention is a multilevel quadrature amplitude modulation system and is a digital radio system employing an equalizer. In, on the outermost circumference of the signal space diagram, the training symbols for determining the initial value of the tap coefficient of the equalizer are arranged at equal angular intervals, and the initial value of the tap coefficient of the equalizer is set. Training symbols to determine, for frame synchronization,
It is configured to be used together as a symbol for frame timing detection and a symbol for self channel slot detection.

[0005]

According to the frame synchronization method of the multilevel quadrature amplitude modulation system according to the present invention having the above-mentioned structure, in the receiver,
By using the training symbol of the equalizer together with the symbol for synchronization timing detection and the calculation of the initial value of the tap coefficient of the equalizer, a frame format configuration in which redundant symbols are removed can be obtained, so that transmission efficiency, that is, frequency utilization The efficiency can be improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a signal space diagram applied to a 16QAM system which is an example of a multilevel QAM system which is an embodiment of the present invention. Further, the transmission / reception frame format is shown in FIG.

The feature of the present embodiment is that, as shown in FIG. 2, the transmission / reception frame format is made up of only equalizer training symbols and information (control) symbols, so that transmission efficiency can be improved. There is.

In the signal space diagram of FIG. 1, the training symbol of the equalizer of FIG. 2 has 16 PS according to the transmission bit arrangement on the outermost circumference (radius: 18 ^1/2 ).
The signals are arranged in the arrangement of the signal space diagram (TS _{1 to} TS ₁₆ ) of the K (16-value Phase Shift Keying) system.

On the other hand, the information (control) symbols of FIG. 2 are arranged according to the 16QAM signal diagram (Q _{1 to} Q ₁₆ ) of FIG.

In the process of establishing frame synchronization, the absolute value (I,
The absolute value of the Q signal) is added synchronously.

Now, assuming that the propagation path is lossless and has no delay, and assuming that the number of slots for which synchronization is added is k and k is sufficiently large, the contents of the memory corresponding to the training symbol portion of the equalizer are: , K × 18 ^1/2 .

On the other hand, the content of the memory corresponding to the information (control) symbol part is k × 10 ^1/2 .

The actual propagation path has attenuation and delay,
Although the memory content has a value different from that in the ideal state described above, the memory content can be used for comparison judgment of size. Therefore, if the area of the memory content that has been added synchronously exceeds the threshold value,
Timing detection can be performed as the training symbol portion of the equalizer. After correcting the frequency offset, the self channel slot can be detected from the correlation value between the training symbol of the equalizer of the self channel and the received signal.

The present invention is not limited to the above embodiment. The above-mentioned embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to the present invention. It is included in the technical scope of the invention.

[0015]

As described above, according to the frame synchronization method of the multilevel quadrature amplitude modulation (multilevel QAM) system according to the present invention having the above configuration, the training symbols of the equalizer are synchronized with each other in the frame synchronization. Since it can also be used as a symbol for the purpose, a symbol only for frame synchronization becomes unnecessary, and the ratio of information (control) symbols to all symbols in a frame can be increased, thus improving transmission efficiency, that is, frequency utilization efficiency. be able to.

[Brief description of drawings]

FIG. 1 is a signal space diagram of a 16QAM system which is an embodiment of the present invention.

FIG. 2 is a frame format diagram of a 16QAM system which is an embodiment of the present invention.

FIG. 3 is a signal space diagram of a conventional 16QAM system.

FIG. 4 is a frame format diagram of a conventional 16QAM system.

[Explanation of symbols]

a slot b frame P _{1 to} P _n space arrangement of synchronization symbols Q _{1 to} Q _{16 16} QAM system space arrangement of symbols SW training symbol portion TCH information symbol portion TS _{1 to} TS ₁₆ space arrangement of training symbols U synchronization symbol portion

Claims (1)

[Claims] 1. In a digital radio system employing an equalizer in a multi-level quadrature amplitude modulation method, a training symbol for determining an initial value of a tap coefficient of the equalizer is provided with a training symbol which is an outermost circle of a signal space diagram. A training symbol for deciding the initial value of the tap coefficient of the equalizer is arranged at equal angular intervals on the circumference, a symbol for frame timing detection for frame synchronization, and a self-channel slot detection A frame synchronization method of a multi-level quadrature amplitude modulation method, which is also used as a symbol for.