JP5787684B2 - Time division duplex wireless communication system - Google Patents

Description

  The present invention relates to a time division duplex wireless communication system that performs TDD (Time Division Duplex) wireless communication in a synchronized communication network.

  When a wireless communication system is applied to a part of a synchronous network using SONET / SDH (one of the international standards for high-speed digital communication systems) or T1 / E1 (one of the standards for high-speed digital lines), A synchronous clock needs to be transmitted to a wireless device, and conventionally, an FDD (Frequency Division Duplex) frequency communication system has been used (see, for example, Patent Document 1). This is because, in the FDD system, the transmission signal is a continuous modulation signal, and therefore, by using a clock recovery circuit including a voltage controlled oscillator (VCO) or the like in the demodulator, it is easy and stable from the continuous modulation signal. This is because a synchronous clock can be transmitted.

JP 2008-211587 A

  By the way, the TDD system that can adaptively control the transmission band of the uplink and the downlink symmetrically or asymmetrically according to the data traffic may be more advantageous than the FDD system in terms of frequency utilization efficiency. That is, in the FDD scheme, two frequency channels are required, whereas in the TDD scheme, vertical communication is possible with one frequency channel.

  However, in the TDD system, a transmission signal is a burst modulation signal, and a method of reproducing a received symbol by interpolating the burst modulation signal instead of reproducing the clock itself by a demodulator is adopted (references). , Yoichi Matsumoto, Masahiro Morikura, Shuzo Kato, “Burst Mode Fully Digitized High-speed Clock Recovery Circuit—Storage Clock Recovery System”, IEICE Transactions B-II Vol. J75-B-II No. 6 pp. 354-362 May 1992). For this reason, it is difficult to stably transmit a synchronous clock, and it is difficult to apply it to a synchronous network. Further, even if a clock recovery circuit having a voltage controlled oscillator similar to the FDD method is used, the clock cannot be recovered in the no-signal period between the burst modulation signal and the burst modulation signal. It is difficult to stably transmit a synchronous clock.

  Accordingly, an object of the present invention is to provide a time division duplex wireless communication system capable of stably transmitting a synchronous clock in time division duplex wireless communication.

In order to achieve the above object, the invention described in claim 1
A master radio device connected to the first communication network and a slave radio device connected to the second communication network are connected so as to be able to perform radio communication by a time division duplex method,
In the main radio device,
A synchronous clock extracting unit for extracting a synchronous clock from transmission data received from the first communication network which is a synchronous network;
A radio processor clock generator for generating a radio processing clock that is frequency synchronized with the synchronizing clock,
A transmission data extraction unit that extracts transmission data from the first communication network based on the synchronous clock;
Radio transmission processing for generating a radio frame based on the radio processing clock generated by the radio processing clock generation unit and the transmission data extracted by the transmission data extraction unit and transmitting the radio frame as a modulation signal to the slave radio device And
A wireless transmitter having
In the slave radio device,
A received burst detector for detecting the position of a burst signal based on the modulated signal from the main radio device;
A radio frame period detection unit that calculates a detection period of a burst signal from the main radio apparatus based on a detection position by the reception burst detection unit, and generates a radio frame clock based on the detection period;
A synchronous clock regenerator that generates a regenerative synchronization clock that is frequency-synchronized with the radio frame clock generated by the radio frame period detector;
A regenerative synchronization clock transmission unit for transmitting the regenerative synchronization clock generated by the synchronous clock regeneration unit to the second communication network;
A wireless receiver having
This is a time division duplex wireless communication system.

  According to the present invention, when the main radio apparatus receives the synchronization clock from the first communication network, the radio processing clock generation unit of the radio transmission unit generates the radio processing clock frequency-synchronized with the synchronization clock, and transmits it. The data extraction unit extracts transmission data from the first communication network based on the synchronous clock. Then, based on the generated wireless processing clock and the extracted transmission data, a wireless frame is generated by the wireless transmission processing unit, and the modulated signal is transmitted to the slave wireless device. Here, the reciprocal number (frequency) of the period of the radio frame generated based on the radio processing clock has a relationship of a predetermined multiplication number and a frequency division ratio with respect to the frequency of the synchronous clock from the first communication network. .

  On the other hand, when the slave radio apparatus receives the modulation signal from the main radio apparatus, the position of the burst signal is detected by the reception burst detection section of the radio reception section, and the burst signal of the burst signal is detected by the radio frame period detection section based on this detection position. A detection cycle is calculated and a radio frame clock is generated. Subsequently, the synchronization clock recovery unit generates a recovery synchronization clock that is frequency-synchronized with the radio frame clock, and the generated recovery synchronization clock is transmitted to the second communication network by the recovery synchronization clock transmission unit. Here, the frequency of the reproduction synchronization clock generated based on the radio frame clock has a relationship of a predetermined multiplication number and a frequency division ratio with respect to the inverse number (frequency) of the detection period of the burst signal from the main radio apparatus. .

  According to the first aspect of the present invention, the detection period of the received burst signal in the slave radio apparatus is equal to the period of the radio frame in the master radio apparatus. For this reason, the synchronous clock transmitted from the first communication network to the main radio apparatus is transmitted to the second communication network in frequency synchronization via the sub radio apparatus. That is, in the time-division duplex wireless communication, the synchronous clock can be stably transmitted from the first communication network to the second communication network.

It is a schematic block diagram which shows the radio | wireless transmission part of the main radio | wireless apparatus in the time division duplex system radio | wireless communications system which concerns on Embodiment 1 of this invention. It is a schematic block diagram showing a radio reception unit of a slave radio device in the time division duplex radio communication system according to Embodiment 1 of the present invention. It is a figure which shows (a) PP type radio frame format and (b) P-MP type radio frame format in embodiment of this invention. It is a schematic block diagram which shows the radio | wireless receiving part of a slave radio apparatus in the time division duplex system radio | wireless communications system which concerns on Embodiment 2 of this invention.

  The present invention will be described below based on the illustrated embodiments.

(Embodiment 1)
1 and 2 show a radio transmission unit 1 of a main radio apparatus and a radio reception of a sub radio apparatus in a time division duplex radio communication system (hereinafter simply referred to as “communication system”) according to this embodiment. 3 is a schematic configuration block diagram showing a unit 2. FIG. This communication system is a system that performs time-division duplex wireless communication in a synchronized communication network, a main wireless device connected to a first communication network (synchronous network), and a second communication network A slave radio device connected to the (synchronous network) is connected to be communicable wirelessly by a time division duplex method. Here, the primary radio apparatus includes a radio reception unit, and the slave radio apparatus includes a radio transmission unit, which synchronizes the first communication network and the second communication network, as will be described later. In order to perform an operation equivalent to that of a normal wireless device after being taken, the wireless transmission unit 1 and the wireless reception unit 2 will be mainly described below.

  Further, in this embodiment, a case will be described in which the synchronization clock of the first communication network is used as a reference clock, and this synchronization clock is transmitted to the second communication network via the master radio device and the slave radio device. The wireless connection form between the wireless device and the slave wireless device may be a P-P (Point to Point, 1-to-1) type or a P-MP (Point-to-Multi Point, 1-to-many) type. Also good.

  That is, when defining a line from the main radio apparatus to the sub radio apparatus as a downlink and a line from the sub radio apparatus to the main radio apparatus as an uplink, both the PP type and the P-MP type are as shown in FIG. In addition, the burst length of upper and lower lines may change dynamically. However, it is assumed that the period T of the radio frame, that is, the timing and period of the beginning of the burst modulation signal in the downlink from the main radio apparatus to the sub radio apparatus is constant. In the case of the P-MP type, the main radio apparatus may be referred to as a base station, and the plurality of sub radio apparatuses may be referred to as slave stations.

  As shown in FIG. 1, the radio transmission unit 1 of the main radio apparatus mainly includes a synchronous clock extraction / reproduction unit 11, a radio processing clock generation unit 12, a transmission data extraction unit 13, and a radio transmission processing unit 14. I have.

  The synchronous clock extracting / reproducing unit 11 extracts and reproduces the synchronous clock from the transmission data when the synchronous clock is superimposed on the transmission data from the first communication network. The wireless processing clock generation unit 12 and the transmission data extraction unit 13 are input. Here, in addition to the transmission data, when a synchronous clock is transmitted / input from the first communication network, it is not necessary to provide the synchronous clock extracting / reproducing unit 11.

  The radio processing clock generation unit 12 generates a radio processing clock of the radio transmission unit 1 that is frequency-synchronized with the synchronization clock input from the synchronization clock extraction / regeneration unit 11, and includes, for example, a PLL (Phase Locked Loop, Phase synchronization) circuit. The generated wireless processing clock is input to the wireless transmission processing unit 14.

  The transmission data extraction unit 13 extracts transmission data from the first communication network based on the synchronization clock input from the synchronization clock extraction / reproduction unit 11. That is, transmission data is extracted from the transmission frame received from the first communication network at the timing and cycle of the synchronous clock, and the extracted transmission data is input to the wireless transmission processing unit 14.

  The radio transmission processing unit 14 generates a radio frame based on the radio processing clock generated by the radio processing clock generation unit 12 and the transmission data extracted by the transmission data extraction unit 13, and generates a radio signal as a modulation signal. To send to. That is, a communication path encoding unit 141, a radio frame generation unit 142, and a modulator 143 are provided, and the input transmission data is encoded by the communication path encoding unit 141, and a radio frame is generated based on the radio processing clock. The unit 142 assembles a radio frame, modulates it with the modulator 143, and transmits it wirelessly to the slave radio apparatus.

  The period T of the radio frame generated by the radio transmission unit 1 is based on a radio processing clock, and the radio processing clock is frequency-synchronized with a synchronization clock from the first communication network. For this reason, the reciprocal (frequency) of the period T of the radio frame has the relationship of the following formula 1 with respect to the frequency F0 of the synchronous clock from the first communication network.

1 / T = (N1 / M1) × F0
Here, N1 is a multiplication number specified by the wireless processing clock generation unit 12 (PLL circuit), and M1 is a frequency division ratio specified by the wireless processing clock generation unit 12.

  As shown in FIG. 2, the radio reception unit 2 of the slave radio apparatus mainly includes a radio reception processing unit 21, a radio frame period detection unit 22, a synchronous clock reproduction unit 23, and a transmission frame generation unit (reproduction synchronous clock transmission). Part) 24. The radio reception processing unit 21 includes an A / D conversion unit 211, a reception burst detection unit 212, a demodulator 213, and a communication path decoding unit 214. Further, the radio reception processing unit 21 is independent. Processing and operation are performed by a wireless processing clock generated by the free-running reference oscillator 25.

  The A / D converter 211 performs A / D conversion on the modulated signal received from the main radio apparatus, and the received burst detector 212 detects the position of the burst signal based on the digital signal from the A / D converter 211. Is. That is, for example, the head position of a burst signal received at intervals of the radio frame period T is detected, and the detected position, that is, the burst detection timing is input to the demodulator 213 and the radio frame period detection unit 22.

  The radio frame period detector 22 calculates a detection period T ′ of the burst signal received from the main radio apparatus based on the input detection position, and generates a radio frame clock based on the detection period T ′. is there. That is, first, the period in which the detection position is input from the reception burst detection unit 212 is calculated as the detection period T ′. At this time, in order to increase the accuracy of the detection cycle T ′, an averaging circuit or the like may be provided, and the detection cycle T ′ may be calculated by averaging the cycles in which the detection positions are input. Next, a radio frame clock is generated based on the detection cycle T ′ and input to the synchronous clock recovery unit 23.

  The synchronous clock reproduction unit 23 generates and reproduces a reproduction synchronous clock that is frequency-synchronized with the radio frame clock generated by the radio frame period detection unit 22, and is configured by, for example, a PLL circuit. Thereby, a reproduction synchronization clock frequency-synchronized with the detection period T ′ is obtained, and this reproduction synchronization clock is input to the transmission frame generation unit 24.

  The transmission frame generation unit 24 transmits the reproduction synchronization clock generated by the synchronization clock recovery unit 23 to the second communication network. In this embodiment, the transmission frame generation unit 24 transmits the reproduction synchronization clock superimposed on the transmission data. . That is, the digital signal from the A / D conversion unit 211 is demodulated by the demodulator 213 according to the detection position from the reception burst detection unit 212 and further decoded by the communication path decoding unit 214 to obtain reception data. Then, the transmission frame generation unit 24 superimposes the reproduction synchronization clock on the received data, assembles the transmission frame so as to correspond to the second communication network, and transmits the transmission data to the second communication network according to the transmission frame. . Here, when outputting and transmitting the reproduction synchronization clock separately from the transmission data, the reproduction synchronization clock generated by the synchronization clock reproduction unit 23 may be output and transmitted.

  As described above, the transmission frame from the radio reception unit 2 is assembled based on the reproduction synchronization clock, and the reproduction synchronization clock is frequency-synchronized with the radio frame clock. Further, the radio frame clock has a detection cycle. It is generated based on T ′. For this reason, the frequency F0 ′ of the regenerative synchronization clock generated by the wireless reception unit 2 has the following relationship with respect to the reciprocal (frequency) of the detection period T ′ of the received burst signal.

F0 ′ = (N2 / M2) × (1 / T ′)
Here, N2 is a multiplication number specified by the synchronous clock recovery unit 23 (PLL circuit), and M1 is a frequency division ratio specified by the synchronous clock recovery unit 23.

  Next, the operation of the communication system having such a configuration will be described.

  First, when transmission data is transmitted from the first communication network to the main radio apparatus, a synchronous clock is extracted / regenerated by the synchronous clock extracting / reproducing unit 11, and the radio processing clock generating unit 12 performs frequency synchronization with the synchronous clock. A wireless processing clock is generated. On the other hand, the transmission data extraction unit 13 extracts transmission data based on the synchronous clock, and the radio transmission processing unit 14 generates a radio frame based on the radio processing clock and the transmission data, and transmits it as a modulation signal to the slave radio apparatus. Sent.

  Next, when the modulated signal from the main radio apparatus is received by the slave radio apparatus, the position of the burst signal is detected by the received burst detection unit 212, and the radio frame period detection unit 22 performs the burst based on the detection position. A signal detection cycle T ′ is calculated, and a radio frame clock based on the detection cycle T ′ is generated. Subsequently, the synchronous clock recovery unit 23 generates and reproduces a reproduction synchronous clock that is frequency-synchronized with the radio frame clock, and the transmission frame generation unit 24 adds the reproduction synchronous clock to the reception data obtained by the radio reception processing unit 21. Superimposed and transmission data is transmitted to the second communication network according to the transmission frame.

  Here, as described above, the frequency F0 ′ of the regenerative synchronization clock by the slave radio apparatus has the relationship of Equation 2 with respect to the reciprocal of the detection period T ′ of the received burst signal, and the radio of the master radio apparatus The reciprocal of the frame period T has the relationship of Equation 1 with respect to the frequency F0 of the synchronous clock from the first communication network. Further, the detection period T ′ of the received burst signal in the slave radio apparatus is equal to the period T of the radio frame in the master radio apparatus, and the reproduction synchronization clock transmitted to the second communication network is synchronized with the first communication network. Equal to the clock. As described above, the synchronous clock transmitted from the first communication network to the main wireless device is transmitted to the second communication network in frequency synchronization via the slave wireless device. As a result, the first communication network and the second communication network are synchronized, and thereafter, transmission and reception are performed in a state in which the first communication network and the second communication network are synchronized. It is.

  As described above, according to this communication system, the synchronization clock transmitted from the first communication network to the main wireless device is transmitted to the second communication network in frequency synchronization via the slave wireless device. In time division duplex wireless communication, a synchronous clock can be stably transmitted from the first communication network to the second communication network.

(Embodiment 2)
FIG. 4 is a schematic block diagram showing a radio reception unit of the slave radio apparatus of the time division duplex radio communication system according to this embodiment. In this embodiment, the configuration is different from that of the first embodiment in that a wireless processing clock regeneration unit 26 is provided instead of the reference oscillator 25, and the same reference numerals are given to the same components as those in the first embodiment. The description is omitted.

  That is, in the first embodiment, the reference oscillator 25 which is a free-running oscillator generates a wireless processing clock used by the wireless reception processing unit 21, and the received modulation signal is generated by the A / D conversion unit 211 using this wireless processing clock. Sampling. However, since there may be a frequency deviation between the radio processing clock of the radio transmission unit 1 of the main radio apparatus and the radio processing clock of the radio reception unit 2 of the slave radio apparatus, the position detection of the burst signal by the reception burst detection unit 212 is possible. There is a case where an error of one sampling clock at the maximum occurs.

  This error appears as an error of the detection period T ′ of the slave radio apparatus with respect to the radio frame period T of the master radio apparatus, and the fluctuation (jitter) of the regenerative synchronization clock output to the second communication network that is the synchronization network. Or Wanda). Also, when the frequency deviation of the radio processing clock between the main radio device and the slave radio device is large, or when the frequency of the radio processing clock is small with respect to the radio frame period T, the transmission quality of the synchronous clock is affected. It can happen.

  Therefore, in this embodiment, a radio processing clock recovery unit 26 is provided instead of the reference oscillator 25, and the radio frame clock generated by the radio frame period detection unit 22 is input to the radio processing clock recovery unit 26. The radio processing clock reproduction unit 26 is configured by, for example, a PLL circuit, and generates a radio processing clock frequency-synchronized with the radio frame clock. Based on the radio processing clock, the radio processing clock recovery unit 21 (received burst detection) Unit 212) processes and operates. That is, in this embodiment, the radio frame clock based on the detection cycle T ′ is reflected not only in the transmission data but also in the internal processing of the radio reception unit 2, and the internal processing of the radio reception unit 2 is detected in the detection cycle. Synchronize with T ′. Therefore, the reception burst detection unit 212 detects the position of the burst signal based on the reception modulation signal sampled by the radio processing clock generated by the radio processing clock recovery unit 26.

  Here, when the radio transmission unit 1 of the main radio apparatus generates a radio frame, the number of radio processing clocks corresponding to the radio frame period T can be obtained in advance from the ideal value of the frequency of the radio processing clock. For this reason, the radio processing clock reproduction unit 26 may control the frequency of the radio processing clock so that the cycle of the radio frame clock becomes an ideal number of radio processing clocks.

  By generating and reproducing a radio processing clock from the radio frame clock by such a radio processing clock reproduction unit 26 and inputting it to the radio reception processing unit 21, an error in the position detection timing of the burst signal by the reception burst detection unit 212 is reduced. The maximum is less than one sampling clock. As a result, fluctuations in the regenerative synchronization clock output to the second communication network can be reduced. Furthermore, by setting the radio frame period T and the frequency of the radio processing clock so that the frequency of the radio processing clock becomes larger than the radio frame period T, fluctuations in the reproduction synchronization clock can be further reduced.

  As described above, according to this embodiment, the synchronization clock from the first communication network is suppressed from fluctuations via the wireless transmission unit 1 of the main wireless device and the wireless reception unit 2 of the slave wireless device. It is possible to transmit to the second communication network.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above embodiment, the A / D conversion unit 211 is included in the wireless reception processing unit 21, but the A / D conversion unit 211 may be positioned upstream of the wireless reception processing unit 21.

DESCRIPTION OF SYMBOLS 1 Radio transmission part of main radio | wireless apparatus 11 Synchronous clock extraction and reproduction | regeneration part 12 Radio processing clock generation part 13 Transmission data extraction part 14 Wireless transmission processing part 141 Communication path encoding part 142 Radio frame generation part 143 Modulator 2 Slave radio apparatus Radio reception unit 21 Radio reception processing unit 211 A / D conversion unit 212 Reception burst detection unit 213 Demodulator 214 Channel decoding unit 22 Radio frame period detection unit 23 Synchronous clock reproduction unit 24 Transmission frame generation unit (reproduction synchronous clock transmission unit)
25 Oscillator 26 Wireless processing clock recovery unit

Claims (1)

A master radio device connected to the first communication network and a slave radio device connected to the second communication network are connected so as to be able to perform radio communication by a time division duplex method,
In the main radio device,
A synchronous clock extracting unit for extracting a synchronous clock from transmission data received from the first communication network which is a synchronous network;
A radio processor clock generator for generating a radio processing clock that is frequency synchronized with the synchronizing clock,
A transmission data extraction unit that extracts transmission data from the first communication network based on the synchronous clock;
Radio transmission processing for generating a radio frame based on the radio processing clock generated by the radio processing clock generation unit and the transmission data extracted by the transmission data extraction unit and transmitting the radio frame as a modulation signal to the slave radio device And
A wireless transmitter having
In the slave radio device,
A received burst detector for detecting the position of a burst signal based on the modulated signal from the main radio device;
A radio frame period detection unit that calculates a detection period of a burst signal from the main radio apparatus based on a detection position by the reception burst detection unit, and generates a radio frame clock based on the detection period;
A synchronous clock regenerator that generates a regenerative synchronization clock that is frequency-synchronized with the radio frame clock generated by the radio frame period detector;
A regenerative synchronization clock transmission unit for transmitting the regenerative synchronization clock generated by the synchronous clock regeneration unit to the second communication network;
A wireless receiver having
A time-division duplex wireless communication system.