JPS6370631A - Time division multiple access communication system - Google Patents

Abstract

PURPOSE:To improve the frame utilizing efficiency by recovering a clock synchronized with a master station by a clock recovery circuit and synchronizing the frequency switching with a frame timing clock from the master station so as to reduce a guard time. CONSTITUTION:A reception signal fed to a reception input terminal 11 is inputted to a descrambler 16 and a frame detection circuit 17 via a frequency converter 12 and a demodulator 15 and a reception data is outputted from the descrambler 16 and the frame signal is outputted from the circuit 17. Moreover, the output of the demodulator 15 is supplied also to the clock recovery circuit 22 to recover the clock synchronized with that of the master station. The clock is fed to a frequency switching control circuit 18, which counts the recovered clock based on the detection frame signal and the selection circuit 13 is controlled in the optimum timing during the guard time. Thus, the frequency is switched in synchronism with the frame timing and the clock from the master station, then the guard time is decreased and the frame utilizing efficiency is improved.

Description

Detailed Description of the Invention "Field of Industrial Application" This invention enables the effective use of devices and radio waves by making it possible to transmit and receive signals across a plurality of different carriers in a time-sharing manner using one set of transceivers. The present invention relates to a so-called frequency hopping TDMA (time division multiple access) communication device.

``Prior art'' In satellite communications, a satellite station is configured to be able to transmit and receive multiple carrier waves, but at each ground station,
It is not economical to provide transceivers for all of the carrier waves, and from this point of view, ground stations use a plurality of carrier waves by switching the carrier waves to be transmitted and received for each burst.

This method is called a frequency hopping method. Conventionally, this type of device was used for satellite communications and was constructed as shown in FIG. As shown in FIG. 6, the reception input terminal 11 receives carrier waves Fl, F2 . A burst signal is added for each Fs. This signal is transmitted to frequency converter 1
2, it is converted into an intermediate frequency signal by the selection circuit 13.
oscillators 14a, 14 according to different carrier frequencies.
b, 14C is selected, its output is applied to the frequency converter 12, and the receiving frequency is changed by controlling the selection circuit 13. The output of the frequency converter 12 is converted into a baseband signal by a demodulator 15 and output via a descrambler 16.

On the other hand, the output of the demodulator 15 is branched to the frame detection circuit 1.
Added to 7. A frame signal from the reference ground station is detected by the frame detection circuit 17, and the output of this frame detection circuit 17 is applied to the frequency switching control circuit 18, which determines the frequency to be received for each burst (time slot) based on this. Receiving frequency memo IJ that stores information
A frequency switching control signal is output from l9 to the slow death circuit 21. The delay circuit 21 controls the signal delay time from the frequency converter 12 to the frequency switching control circuit 18 and the frame so that the frequency switching signal is applied to the selection circuit 13 in synchronization with the carrier wave switching timing of the burst (time slot). Add a delay by the time difference with respect to the period.

In other words, as shown in FIG. 97, the frequency switching control circuit 18 counts the clock of the clock light emitter 31 of its own station using the detection frame as a reference, and each time the counted value reaches a predetermined counted value, the counted value Predetermined frequency information is extracted from the reception frequency memory 19 using the address as an address, and is latched into the latch circuit 33 to control the selection circuit 13. This frequency switching signal occurs within a guard time of 1 g between valley bursts. The operation is as described above, and each burst is received across pre-assigned carrier waves. In satellite communications, the distance from multiple ground stations changes depending on the position of the satellite station. Therefore, as shown in FIG. 6, it is necessary to provide a relatively large guard time Tg between bursts (time slots) to allow for burst switching errors, and to add a clock recovery code to the beginning of each burst. When frequency hopping is performed, the frequency switching operation can be performed during the time period in which this clock recovery code is being received.

On the other hand, in TDMA communication in fixed wireless communication, the positional relationship between the master station and slave stations remains unchanged, so a time equivalent to 1 to 2 bits is sufficient as the guard time Tg for burst separation. All four units communicate in sync. In this fixed wireless communication, as in satellite communication, the band used is narrowed and the transmission power is reduced to make the transmitter economical.In order to secure the same communication path, the number of carrier waves is multiple, and multiple carrier waves are used. It is conceivable that the master station is provided with a transceiver for the carrier wave, and that each slave station performs frequency hopping for each burst (time slot). The present invention provides frequency hopping TDMA communication using such fixed wireless communication.

"Means for Solving the Problem" According to the present invention, a plurality of carrier waves each provide a plurality of transmission paths with a plurality of time slots (bursts) by time division multiple access (TDMA), and An arbitrary carrier wave is selected for each time slot (burst) and communication is performed using terrestrial fixed wireless communication.The master station transmits and receives each carrier wave with the same lock frequency, same frame timing, and same scrambling operation, and the slave station A carrier wave is selected for each time slot (burst) based on the clock frequency and frame timing from the station and prespecified frequency (carrier wave) switching information, and the scramble operation of the master station is reversed.

That is, in this invention, frequency switching is performed in synchronization with the frame timing and clock from the master station, and differs from the conventional technology in that the state before and after frequency switching, including μ-sock synchronization, is not changed.

"Embodiment" FIG. 1 shows an embodiment of the present invention, and parts corresponding to those in FIG. 5 are given the same reference numerals. The received signal, as shown in FIG.
16 outputs received data, and a frame detection circuit 17 outputs a frame signal. In this invention, the output of the demodulator 15 is branched and supplied to a clock regeneration circuit 22, and a clock synchronized with the master station is regenerated. This clock is also supplied to the frequency switching control circuit 18. Frequency switching control circuit 18
As shown in FIG. 3, the reproduction clock is counted based on the detected frame signal and the selection circuit 13 is controlled at the optimum timing during the guard time.

In terrestrial fixed wireless communications, the master station uses the same clock frequency, same frame timing, and
Transmission and reception are performed using the same scrambling operation, and since the positional relationship between the master station and slave stations is fixed, the guard time between the bursts (time slots) of each station, Tg it, is reduced as shown in Figure 2. Since the PTS is synchronized with the master station's clock, consecutive bursts of any carrier wave and clock phase are received, and there is no risk of the bursts overlapping each other.

As mentioned above, each slave station synchronizes reproduction with the same clock of the master station, uses the frame signal from the master station as a reference, and counts the reproduced clock from the master station to perform burst switching. Even if the guard time Tg is shortened as described above, desired burst (carrier) switching can be performed during the guard time Tg.

The descrambling operation mode for bursts received sequentially is synchronized with the master station, so the desk lamp 216 is reset by the detection frame signal and descrambles continuously between bursts. There is no need to reset.

As shown in the figure g4, the desk 2 synthesizer 16 is activated by the frame signal and the four-way signal from the frequency switching control circuit w118.
The timing signal is also configured to send out a timing signal for resetting at the burst head position, which makes it possible to reduce the number of stages of the comparison signal generation circuit compared to the case where the reset is performed every TDM human frame period. In this case, the master station is configured to start a new scrambling operation for each burst.

"Effects of the Invention" As explained above, according to the present invention, in a frequency hopping TDM human communication system, the frame timing and clock phase are the same between each carrier wave, and the clock timing between bursts is synchronized with a continuous received signal. This TD is suitable for frequency hopping communication with high frame utilization efficiency because the guard time can be reduced by switching the frequency.
It becomes possible to provide a system that allows M people to pass through each other.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a burst block diagram thereof, Fig. 3 is a block diagram showing an example of the frequency switching control circuit in Fig. 1, and Fig. 4 is a block diagram showing an example of the frequency switching control circuit in Fig. 1. A block diagram showing an example of a frequency switching control circuit in another embodiment, FIG. 5 is a block diagram showing a conventional technique, FIG. 6 is a burst block diagram thereof, and FIG. 7 shows a frequency switching control circuit in FIG. FIG.

Claims (1)

[Claims] (1) In a frequency hopping TDMA communication system in which multiple carrier waves each provide multiple transmission paths with multiple time slots using time division multiple access, and communication is performed by selecting an arbitrary carrier wave for each time slot at an arbitrary time. , the master station transmits and receives multiple carrier waves with the same clock frequency, the same frame timing, and the same scrambling operation, and the slave station transmits and receives the clock frequency transmitted from the master station,
A carrier wave is selected for each time slot based on the frame timing and frequency switching information specified in advance for each time slot by a control signal, and transmission and reception are performed by performing an operation opposite to the scrambling operation of the master station. Time division multiple access communication method.