JP4586933B2 - Transmitting apparatus, receiving apparatus, and communication system - Google Patents

Description

  The present invention relates to a transmission apparatus, a reception apparatus, and a communication system applied to a mobile communication system and the like, and more particularly, to an improvement in a data format that is modulated and transmitted using, for example, an Orthogonal Frequency Division Multiplexing (OFDM) transmission system. Is.

  In recent years, the demand for mobile communication using a mobile phone or the like has been greatly increased, and it is used not only for small-capacity communication such as voice but also for transmission of larger-capacity information.

In the mobile communication system, as shown in FIG. 16, a plurality of base stations BS are arranged in a plane, and each base station BS communicates with a mobile station MS near the base station.
Hereinafter, a range in which each base station can communicate with a mobile station is referred to as a cell.

In such a mobile communication system, a frequency channel used in each cell uses a frequency channel different from that of an adjacent cell in order to avoid interference.
However, when the same frequency channel is used in a cell further outside the adjacent cell, that is, in a cell farther away, the received signal received by the mobile station MS in the cell from the base station BS constituting the cell However, since the signal strength is stronger than the interference wave coming from far away, there is not much problem even if the same frequency channel is used.

However, if there is too much space between cells using the same frequency channel, a larger number of frequency channels are required, and the frequency cannot be used effectively. That is, the interference problem due to the use of the same frequency channel and the frequency utilization efficiency are in a trade-off relationship.
Therefore, when designing a communication system, it is necessary to improve frequency utilization efficiency by constructing a system that is resistant to interference.

As a modulation scheme having high frequency utilization efficiency and not easily affected by multipath interference, there is an OFDM modulation scheme.
In the OFDM modulation scheme, transmission signal symbols that have undergone primary modulation (OPSK, 16QAM, etc.) are subjected to inverse Fourier transform by collecting 2 to the power of 2 and, as shown in FIG. Is a modulation scheme constituting n-th power subcarrier.
In a mobile communication system that employs an OFDM modulation scheme or the like, each mobile terminal station communicates with a base station that is closest to the location of the mobile terminal station.

For example, in a communication system employing the OFDM transmission system, as shown in FIG. 18, a period obtained by adding the guard period TGD to the effective symbol period TSBL is one time slot period TSLT, and a plurality of time slots are bundled as one frame FRM. It is transmitted from the base station BS. In the example shown here, one frame FRM is composed of three time slots.
The base stations BS are synchronized with each other and transmit frames at the same timing.

The guard period TGD added to the effective symbol period TSBL is for reducing intersymbol interference due to multipath and fading.
One time slot using the guard period TGD is, for example, as shown in Japanese Patent Laid-Open No. 7-99486, at the beginning of the effective symbol period, the end of the effective symbol period, or a predetermined period having the beginning and end. For example, the signal is connected to the opposite end of the effective symbol period, specifically, the same signal as the last signal of the effective symbol period is connected to the beginning of the effective symbol period, or the same signal as the first signal of the effective symbol period is used The signal is connected to the end of the period, or the same signal as the signal at the beginning and end of the effective symbol period is connected to the end and the head of the effective symbol period.

In a receiving system of a mobile station that receives such an OFDM signal, as shown in FIGS. 19A, 19B, and 19C, a correlation with a signal obtained by delaying the OFDM signal by an effective symbol period is obtained. Thus, by detecting the peak of the correlation result, it is possible to know the start position of the effective symbol period, in other words, where the guard period is in the time slot.
The OFDM demodulator can perform an FFT (Fast Discrete Fourier Transform) operation by knowing the head position of the effective symbol period.

An example of this type of OFDM demodulator is disclosed in Japanese Patent Laid-Open No. 8-107431.
This OFDM demodulator obtains the correlation between the received OFDM signal and a signal obtained by delaying this signal by an effective symbol period, and performs interval integration on this result. In the interval integration, as shown in FIG. 20, the correlation result is divided for each time slot period, and this is interval integrated.
Then, by performing cumulative addition for each slot period in order from the time when synchronization is started, that is, by performing interval integration, as shown in FIG. 20 (E), the peak of the correlation value appears at a specific place in the time slot period. Appear. The uncorrelated part is averaged as interval integration is performed.
Thus, by performing interval integration, the difference between the non-correlated interval and the correlated interval appears more clearly, and by detecting the peak, reliable synchronization becomes possible.

JP-A-8-107431

  As described above, in a communication system using an OFDM signal with a guard period added, intersymbol interference due to multipath and fading can be reduced, but the mobile station receives an OFDM signal with a guard period added. In addition, interference may occur depending on conditions.

Here, the reception status of a certain mobile station is considered.
The mobile station receives the co-channel interference wave IFW in addition to the desired wave DSW. Usually, since the received signal intensity of the desired wave DSW is much stronger than the interference wave IFW, there is no problem.
However, the received signal strength of the desired wave DSW and the interference wave IFW changes from moment to moment due to fading associated with movement of the mobile station .
The fading of the desired wave DSW and the interference wave IFW, that is, how the received signal strength of the desired wave DSW and the interference wave IFW fluctuates is generally uncorrelated, so when the received signal strength of the desired wave DSW is small, The received signal strength of the interference wave IFW may increase. At this time, reception may be disabled due to interference.
In general, since the distance to the base station that is the source of the interference wave IFW is longer than the base station that is the source of the desired wave DSW, the interference wave IFW arrives at the mobile station slightly later than the desired wave DSW. To do.

  For example, based on the example shown in FIG. 18, an example in which a co-channel interference wave IFW from a distant base station using the same channel happens to arrive as an interference wave IFW due to fluctuations in received signal strength due to fading. To consider. Here, as shown in FIG. 18B, the incoming interference wave IFW is only for the frame.

As shown in FIG. 18A, frames of the desired wave DSW arrive continuously.
On the other hand, as shown in FIG. 18B, the interference wave IFW arrives slightly later than the desired wave DSW, and therefore, as shown by 1 and 2 in FIG. Will interfere with each other.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the number of repetitive cells, that is, to reduce the distance between base stations using the same channel and to effectively use a radio channel. Is to provide a transmission device, a reception device, and a communication system capable of reducing frame loss due to co-channel interference.

  In order to achieve the above object, a transmission apparatus according to the present invention reduces frame loss due to interference to a transmission processing pre-stage unit that uses transmission information as a transmission time slot and n (n is an integer including 1) time slot sequences. A frame generation unit that generates a frame by adding a frame guard period for suppression, and a post-transmission processing stage unit that transmits the generated frame as a radio signal.

  In addition, the present invention is a transmission apparatus provided for signal transmission in at least one of a plurality of base stations that communicate with a communication terminal station in each defined area by a signal in accordance with a predetermined modulation scheme. , A transmission processing pre-stage unit that sets transmission information as a transmission time slot, and a frame guard period for suppressing frame loss due to interference to n (n is an integer including 1) time slot sequences. A frame generation unit to generate, and a transmission processing post-stage unit for transmitting the generated frame as a radio signal.

  Further, in the present invention, a timing generation unit that generates a timing for transmitting a frame at the same timing between the base stations based on the inter-base station control signal and the GPS signal for synchronization between the base stations. Have.

  In the present invention, the transmission processing pre-stage unit includes a modulation unit that modulates transmission information in a desired scheme, and the modulation unit selects a modulation scheme based on electric field strength information from a destination terminal station. To do.

  In the present invention, the frame guard period is a no-signal period.

  In the present invention, the transmission processing pre-stage unit generates a time slot by adding a predetermined guard period to the effective symbol period.

  Further, the present invention includes n (n is an integer including 1) time slot sequences in which a guard period is added to an effective symbol period, and for suppressing frame loss due to interference with the time slot sequences. A receiving apparatus for receiving a radio signal in which a frame guard period is added to form one frame, and a reception processing pre-stage unit for receiving the radio signal, and a synchronization position for detecting a leading position of an effective symbol period from the received signal The detection unit, the timing generation unit that controls the operation timing of the functional block from the synchronization position information of the synchronization position detection unit, and the control from the timing generation unit, only the effective symbol period excluding the time guard period and the frame guard period. Retrieving the desired information from the received reception window and the signal winded by the reception window And a that reception processing subsequent section.

  In addition, the present invention provides n (n is 1) in which a guard period is added to an effective symbol period transmitted from a base station that communicates with a communication terminal station in each defined area using a signal in accordance with a predetermined modulation scheme. In order to receive a radio signal including one time slot including a number of time slot sequences and a frame guard period added to the time slot sequence to suppress frame loss due to interference, A receiving device mounted in a communication terminal station, wherein the reception processing pre-stage unit that receives the radio signal, a synchronization position detection unit that detects a leading position of an effective symbol period from the received signal, and synchronization of the synchronization position detection unit The timing generation unit that controls the operation timing of the functional block from the position information, and the time guard period and the frame guard period are controlled by the control from the timing generation unit. Has a receiving window training unit for taking out only the valid symbol period have, a reception processing subsequent unit for restoring the desired information from the window training signal by the receiving window training unit.

Further, the communication system of the present invention interferes with a transmission processing pre-stage unit that uses transmission information as a transmission time slot, and n (n is an integer including 1) time slot sequences in which a guard period is added to an effective symbol period. A transmission device including a frame generation unit for generating a frame by adding a frame guard period for suppressing frame loss due to transmission, a post-transmission processing unit for transmitting the generated frame as a radio signal, and the transmission device Controls the operation timing of functional blocks from the synchronization position information of the synchronization position detection unit, the synchronization position detection unit that detects the leading position of the effective symbol period from the reception signal, and the reception processing pre-stage unit that receives the radio signal transmitted from And a valid symbol excluding the time guard period and the frame guard period by control from the timing generator. It has a receiving window training unit to take out only between, and a receiver device including a reception processing subsequent unit for restoring the desired information from the window training signal by the receiving window training unit.
Communications system.

  Further, the communication system of the present invention includes a plurality of communication terminal stations, and a plurality of base stations that communicate with the communication terminal stations in the prescribed areas, respectively, with signals according to a predetermined modulation scheme, At least one of the plurality of base stations includes a transmission processing pre-stage unit that uses transmission information as a transmission time slot, and n (n is an integer including 1) time slot sequences in which a guard period is added to an effective symbol period. Equipped with a transmission device including a frame generation unit that generates a frame by adding a frame guard period for suppressing frame loss due to interference, and a transmission processing post-stage unit for transmitting the generated frame as a radio signal The mobile terminal station includes a reception processing pre-stage unit that receives a radio signal transmitted from the transmission device, and a synchronization position that detects a leading position of an effective symbol period from the received signal. The output unit, the timing generation unit that controls the operation timing of the functional block from the synchronization position information of the synchronization position detection unit, and the control from the timing generation unit, only the effective symbol period excluding the time guard period and the frame guard period A receiving device is mounted that includes a receiving windowing section to be extracted and a receiving processing post-stage section that restores desired information from the signal winded by the receiving windowing section.

  In the present invention, the transmission device generates a timing for transmitting a frame at the same timing between base stations based on an inter-base station control signal and a GPS signal for synchronization between the base stations. A timing generation unit.

  Further, in the present invention, the transmission processing pre-stage unit of the transmission apparatus includes a modulation unit that modulates transmission information by a desired method, and the modulation unit modulates based on electric field strength information from a destination terminal station. Select a method.

According to the present invention, for example, a timing signal for transmitting a frame at exactly the same timing between base stations from a base station control signal and a GPS signal, for example, in a timing generation unit of a transmitter provided in the base station Is generated.
Then, in the transmission device, for example, a transmission time slot is generated from the transmission information in the pre-transmission processing section and supplied to the frame generation section.
In the frame generation unit, a frame composed of a plurality of time slots and one frame guard, eg, a no-signal period, is generated and supplied to the post-transmission processing unit.
In the latter stage of the transmission process, the generated frame is transmitted as a radio signal.
In this way, each base station provides a frame guard period for the transmission frame, and this frame is transmitted at exactly the same timing.

In addition, for example, in the reception processing pre-stage unit of the reception device mounted on the mobile terminal station, the radio signal transmitted from the transmission device is received and supplied to the synchronization position detection unit.
The synchronization position detection unit detects the start position of the effective symbol period from the received signal, and outputs this synchronization position information to the timing generation unit.
The timing generation unit controls the operation timing of each functional block from the synchronization position information.
Then, in the reception windowing unit, only the effective symbol period is extracted except for the time guard period and the frame guard period under the control of the timing generation unit.
Next, desired information is restored from the windowed signal in the reception processing post-stage.
That is, the received frame signal having the frame guard period is demodulated to reproduce the transmission information.

As described above, according to the present invention, even in a system in which the number of repetitive cells is reduced, that is, the distance between base stations using the same channel is reduced and the radio channel is effectively used, Frame loss can be reduced.
According to the present invention, the number of repeated cells can be reduced while maintaining a required error rate, and there is an advantage that frequency resources can be effectively utilized.

Further, according to the present invention, it is possible to synchronize a radio communication system having a frame guard.
Also, since the insertion point of frame guard can be determined, it is not necessary to send control information for frame synchronization (control information for notifying which is the head of the frame), and more information is transmitted accordingly. be able to.

It is a figure which shows the outline | summary of the OFDM communication system with which the transmitter and receiver which concern on this invention are applied. It is a figure which shows the specific structural example of the OFDM communication system with which the transmitter and receiver which concern on this invention are applied. It is a figure for demonstrating the structure method of the cell in the communication system of FIG. It is a figure which shows the example of allocation of the radio channel which concerns on this embodiment. It is a figure which shows the structural example of the OFDM signal containing the frame guard which concerns on this invention. It is a figure for demonstrating the formation method of the time slot containing the guard of the OFDM signal which concerns on this invention. It is a figure for demonstrating the formation method of the time slot containing the guard of the OFDM signal which concerns on this invention. It is a figure for demonstrating the formation method of the time slot containing the guard of the OFDM signal which concerns on this invention. It is a block diagram which shows one Embodiment of the transmitter mounted in the base station which concerns on this invention. It is a figure which shows the symbol mapping of 16QAM. It is a figure which shows the symbol mapping of QPSK. It is a figure for demonstrating the process of the transmission windowing part which concerns on this invention. It is a figure for demonstrating the process of the flame | frame production | generation part which concerns on this invention. It is a block diagram which shows one Embodiment of the receiver mounted in the mobile terminal station which concerns on this invention. It is a figure for demonstrating the advantage at the time of providing a frame guard. It is a figure for demonstrating a mobile communication system. It is a figure for demonstrating an OFDM modulation system. It is a figure for demonstrating the structural example of the conventional OFDM signal of an OFDM transmission system. It is a figure for demonstrating the signal processing operation | movement of the receiving system of the conventional mobile station. It is a figure for demonstrating the area integration operation | movement of the conventional OFDM demodulator.

  FIG. 1 is a diagram showing an outline of an OFDM communication system to which a transmission apparatus and a reception apparatus according to the present invention are applied, and FIG. 2 is a specific example of an OFDM communication system to which a transmission apparatus and a reception apparatus according to the present invention are applied. It is a figure which shows an example of a typical structure.

The OFDM communication system 1 employs a high speed downlink system as shown in FIG.
In FIG. 1, M1 is a mobile terminal station, B1 is a normal base station, B2 is a high-speed downlink base station, N1 is an existing mobile phone network (existing cellular wired network), and N2 is a data communication network such as the Internet. , N3 respectively indicate data communication networks for the high speed downlink system.
In FIG. 1 and FIG. 2, the high speed downlink system is indicated as “W-OFDM”.

In this OFDM communication system 1, as shown in FIG. 1, the mobile terminal station M1 receives control signals such as packet retransmission control (ARQ: Automatic Request for Repetition) due to a data error from an existing base station B1, network (mobile phone). (Telephone network) Transmit via N1.
The transmission capacity of the high-speed downlink system is very large compared with the transmission capacity of the existing mobile phone system, and a large amount of digital content such as images and videos downloaded by the mobile terminal station M1 is the high-speed downlink system. It transmits at high speed in a short time via the downlink system. All information is exchanged over IP.
The data communication network N3 for the high speed downlink system is also connected to a data communication network N2 such as the Internet. The high-speed downlink data communication network N3 is also connected to the network N1, and various control signals and the like are transmitted from the mobile phone base station B1 via the network N1 to the high-speed downlink system data communication network. To N3.

  An OFDM communication system 1A shown in FIG. 2 includes data communication such as mobile terminal stations (MS) M1 to M3, base stations (BS) B1 to B4, an existing cellular wired network N1, and the Internet. A network N2, a data communication network N3 having a database for an additional downlink, and a control center (MRC; Mobile Routing Center) CTR for an additional downlink network are included as main components.

Base station B1 has an existing cellular function, base station B2 has an additional downlink function, base station B3 has an existing cellular function, and base station B4 has an additional downlink function ing.
The wired network N1 is connected to the base stations B1 and B3 by, for example, wired communication lines L1 and L2.
Control center CTR is connected to base stations B2 and B4 by communication lines L3 and L4.
The control center CTR is connected to the network N1 through the communication line L5, connected to the data communication network N2 through the communication line L6, and connected to the data communication network N3 through the communication line L7.

The OFDM communication systems 1 and 1A having such a configuration are configured based on the following reasons.
In other words, in recent years, the demand for mobile communications has increased greatly, and it is used not only for small-capacity communications such as voice, but also for larger-capacity information transmission such as downloading digital data content represented by the Internet. It has become so.
These digital data communications are characterized in that the amount of information received is overwhelmingly larger than the amount of information transmitted by individuals.
Therefore, a new downlink (downlink: communication from the base station to the mobile terminal station) circuit is added in the form of overlaying on the existing mobile phone network.
This downlink is designed to transmit a larger amount of information than the existing mobile phone network.
In such a mobile communication system, a user communicates a relatively low bit rate signal such as a control signal via an existing mobile phone network, and a high bit rate signal such as digital data to be downloaded is added to the added downlink signal. It is configured to transmit at high speed over the line.

Further, in the OFDM communication systems 1 and 1A, a cell can be configured as shown in FIG. 3, for example.
In FIG. 3, a solid line indicates a range (cell) in which each existing mobile phone base station can communicate with a mobile terminal. A broken line indicates a range in which each base station of a broadband wireless (W-OFDM) communication system additionally provided exclusively for downlink (communication from the base station to the mobile terminal station) can communicate with the mobile terminal station ( Cell).

  Specifically, as shown in FIG. 3 (A), a method of installing and configuring the same cell shape as in a base station of an existing mobile phone system, and as shown in FIG. A method of installing a base station only in an area where there are many, as shown in FIG. 3C, a base station having a smaller output than an existing mobile phone base station is installed in an area where there are many users, A method of configuring with a smaller cell (micro cell), as shown in FIG. 3 (D), a method of installing a base station with a higher output than an existing mobile phone base station and configuring with a cell larger than the cell of the mobile phone, As shown in FIG. 3 (E), a method (overlay cell system) configured by combining the methods of FIG. 3 (B) and FIG. 3 (C), or along the main road as shown in FIG. 3 (F). There is a method of forming a micro cell.

  In the present embodiment, for example, the cell is configured by the method of FIG. 3A, that is, the method of installing in the same manner as the base station of the existing mobile phone system and configuring the same cell shape.

In the W-OFDM communication system 1A employing the high-speed downlink system, the base stations B1 to B4 are completely synchronized by receiving GPS (Global Positioning System) signals.
An OFDM signal transmitted from a base station in the W-OFDM communication system 1A is transmitted with a frame described later as one unit, and all base stations are configured to transmit a frame at the same timing.

In the W-OFDM communication system 1A, a frequency band different from the frequency band of the existing mobile phone system is assigned.
The frequency band allocated to the W-OFDM communication system 1A is divided into a plurality of radio channels, and for each base station, for example, as shown in FIG. It is assigned in the form as shown.
In the example shown in FIG. 4, the frequency band is divided into 12 radio channels and assigned to each base station (cell). In FIG. 4, numerals 1 to 12 in a regular hexagon each indicate a radio channel number.

Here, a communication example of the OFDM communication system 1A of FIG. 2 will be described.
Download request issued from a mobile terminal station is transmitted existing cellular base stations B1 and B3, via the network N1 comprising a mobile telephone network, the control center CTR in the network system of high-speed downlink system . The control center CTR makes this download request to the data communication network N2 such as the Internet. The digital data content transmitted from the data communication network N2 is delivered from the control center CTR to the mobile terminal station via the high-speed downlink system network network and the base stations B2 and B4.
A control signal such as retransmission control accompanying a data error is also transmitted to the control center CTR in the network network of the high-speed downlink system via the existing mobile phone base station and the mobile phone network. The control center CTR retransmits the digital data content requested by the mobile terminal station to the mobile terminal station via the network and base station of the high-speed downlink system.

Specifically, for example, the mobile terminal station M1 transmits a signal (001) to the base station B1 in accordance with the format of the existing system in order to transmit a data download request to the control center CTR.
This request signal is delivered to the control center CTR via the existing cellular network N1.
The control center CTR that knows the data request obtains the data (121) from the data communication network N2 via the communication line L6, and sends the data (121) via the communication line L3 to the mobile terminal station M1. 111) to the base station B2.
Receiving this data (111), the base station B2 transmits the data (101) to the mobile terminal station M1 in accordance with the additional downlink format.
Thereby, the mobile terminal station M1 can receive the requested data (101).

Alternatively, the mobile terminal station M3 transmits a signal (003) to the base station B3 in accordance with the format of the existing system in order to transmit a data download request to the control center CTR.
This request signal is delivered to the control center CTR via the existing cellular network N1.
The control center CTR that knows the data request obtains the data (123) from the additional downlink dedicated data communication network N3 via the communication line L7, and sends the obtained data (123) to the mobile terminal station M3. The data is transmitted to the base station B4 dedicated to the additional downlink as data (113) via L4.
Receiving this data (113), the base station B4 transmits data (103) to the mobile terminal station M3 according to the format of the additional downlink.
Thereby, the mobile terminal station M3 can receive the requested data (103).

In such an OFDM communication system 1A, as shown in FIG. 5, an OFDM signal transmitted from a transmission device provided in a base station to each of the mobile terminal stations M1 to M3 includes one frame FRM and seven time slot periods TSLT. It is composed of one frame guard period TFGD.
In FIG. 5, TFRM indicates a frame period, TSLT indicates a time slot period, and TFGD indicates a frame guard period.
The frame guard FGD has no signal, and is added to the end of the seven time slot sequences of the frame FRM in the present embodiment.
Each of the base stations B1 to B3 transmits a frame at the same timing with a frame composed of seven time slots SLT and one frame guard FGD as a unit.
In the present embodiment, an example in which the frame guard period TFGD is added to the end of the frame is shown, but it is also possible to provide it at the beginning of the frame, or at the end and the beginning of the frame.

Each time slot SLT constituting the frame FRM is configured by adding a guard GD to the effective symbol period TSBL.
The time slot SLT to which the guard GD is added is a signal of a predetermined period having the beginning or end of the effective symbol period or the beginning and end, as shown in FIGS. 6 to 8, on the opposite end side of the effective symbol period. In the example of FIG. 6, the same signal as the signal at the end of the effective symbol period TSBL is connected to the head of the effective symbol period. In the example of FIG. 7, the same signal as the signal at the beginning of the effective symbol period TSBL is connected to the end of the effective symbol period. In the example of FIG. 8, the same signal as the signal at the beginning and the end of the effective symbol period is connected to the end and the head of the effective symbol period.
The time slot shown in FIG. 5 is configured by the method shown in FIG.

As described above, the OFDM signal transmission apparatus in which the frame is configured as the frame guard period TFGD in the time slot sequence in which the guard period TGD is added to the effective symbol period TSBL is mounted on the base station and transmitted from the transmission apparatus. The mobile terminal stations M1 to M3 that receive the OFDM signal are equipped with a receiving device that can more accurately synchronize the OFDM signal to which the frame guard period is added.

  Hereinafter, specific configurations and functions of a transmission device mounted on a base station and a reception device mounted on a mobile terminal station will be described in order with reference to the drawings.

FIG. 9 is a block diagram showing an embodiment of a transmission apparatus mounted on a base station according to the present invention.
As illustrated in FIG. 9, the transmission device 100 according to the present embodiment includes an encoding unit 101, an interleaving unit 102, a symbol mapping unit 103, a pilot signal insertion unit 104, a serial-parallel conversion unit 105, an IFFT calculation unit 106, a parallel -Serial conversion unit 107, time slot generation unit 108, transmission windowing unit 109, frame generation unit 110, GPS reception unit 111, timing generation unit 112, digital-analog (D / A) conversion unit 113, orthogonal modulation unit 114, And a frequency converter 115.
Encoding section 101, interleaving section 102, symbol mapping section 103, pilot signal insertion section 104, serial-parallel conversion section 105, IFFT calculation section 106, parallel-serial conversion section 107, time slot generation section 108, and transmission window The pre-transmission processing stage is configured by the ning unit 109, and the post-transmission processing stage is configured by the digital-analog conversion unit 113, the quadrature modulation unit 114, and the frequency conversion unit 115.

  The encoding unit 101 performs convolutional encoding of, for example, a constraint length K = 9 on the digital data input via the network of the high speed downlink system and outputs the result to the interleaving unit 102. The mobile terminal stations M1 to M3 measure the electric field strength of the base station of the high speed downlink system. The encoding unit 101 controls the encoding rate based on this result, for example, from R = 2176/2488 = 0.8764 to R = 44/1370 = 0.395.

  Interleaving section 102 interleaves the digital data encoded by encoding section 101 and outputs the result to symbol mapping section 103.

The symbol mapping unit 103 controls the symbol mapping method (primary modulation method) based on information such as the electric field strength of the base station of the high speed downlink system measured by the mobile terminal station, The orthogonal Q channel is output to pilot signal insertion section 104.
For example, when the field strength of the base station of the high speed downlink system is stable and strong, the symbol mapping unit 103 uses 16QAM that performs symbol mapping as shown in FIG. When the electric field strength is unstable in time, QPSK (Quadrature Phase Shift Keying) or DQPSK (Differrential QPSK) that performs symbol mapping as shown in FIG. 11 is used as the modulation method.

Pilot signal insertion section 104 inserts a pilot signal of “1” into the in-phase I channel and “0” into the quadrature Q channel supplied from symbol mapping section 103, and outputs the result to serial-parallel conversion section 105.
The pilot signal inserted by the pilot signal insertion unit 104 is used for transmission path estimation and phase correction at the receiving device of the mobile terminal station, and demodulates a modulation signal of a method in which information is added to an amplitude such as 16QAM in the primary modulation method. In this case, it is used to calculate a threshold value that is a reference for amplitude.

Serial-parallel converter 105 converts the symbol data into which the pilot signal is inserted from serial data to parallel data, and outputs the converted data to IFFT calculator 106.
Specifically, the serial-parallel converter 105 divides the input symbol data into 98 symbols, adds a guard symbol to each symbol at the beginning and end of this symbol to make 100 symbols, and In order to make the frequency spectrum appear in the assigned radio channel band, “0” s for 1948 symbols are arranged before and after the 100 symbols to form a total of 2048 symbols, and this parallel symbol data is output to the IFFT computing unit 106.

  The IFFT calculation unit 106 is a calculation unit that performs a 2048-point IFFT calculation. By performing a fast inverse Fourier transform on the parallel 2048 symbol data by the serial-parallel conversion unit 105, the IFFT calculation unit 106 calculates the time axis and the frequency axis. A conversion process is performed and output to the parallel-serial conversion unit 107.

  In the OFDM signal used in this embodiment, for example, the subcarrier interval is 4 [kHz], and the effective symbol period is 250 [μs] which is the reciprocal thereof. Then, 100 subcarriers, that is, frequency band 400 [kHz] as a minimum unit, and 100 subcarriers (400 [kHz]) in units of 1600 subcarriers (400 [kHz] × 16 = 6.4 [MHz]) ) Variable radio channel. The IFFT unit performs 2048 point IFFT calculation.

Here, consider a case where the radio channel bandwidth allocated to the base station is 400 [kHz].
In this case, as described above, the symbol data input to the serial-parallel converter 105 is divided every 98 symbols. One symbol is added to the beginning and end of this symbol to make 100 symbols. Then, “0” for 1948 symbols are arranged before and after the 100 symbols so that a frequency spectrum appears in the radio channel band assigned to the base station, so that a total of 2048 symbols is obtained. The parallel symbol data is input to an IFFT calculation unit 106 that performs 2048-point IFFT, and a fast inverse Fourier transform is performed to perform a conversion process between the time axis and the frequency axis.

The parallel-serial conversion unit 107 converts the parallel data output from the IFFT calculation unit 106 into serial data, obtains 2048-point time-series data, and outputs the data to the time slot generation unit 108.
In the present embodiment, the system clock is set to 8.192 [MHz]. Therefore, the length of the 2048-point time-series data (effective symbol period) is (1 / 8.192 × 10 ⁶ ) × 2048 = 250 × 10 ⁻⁶ [s].

For example, as shown in FIG. 8, the time slot generation unit 108 copies the beginning and end 120 points (14.648 μs) of the time series data of 2048 points for the effective symbol period, respectively, to the end of the effective symbol period. And a time slot is generated and output to the transmission windowing unit 109.
Alternatively, as shown in FIG. 7, for example, the time slot generation unit 108 copies a copy of the first 240 points (29.297 μs) of the 2048-point effective symbol period to the end of the effective symbol period to connect the time slot. Is output to the transmission windowing unit 109.

For example, as shown in FIG. 12, the transmission winding unit 109 performs a winding process on the time slot generated by the time slot generation unit 108 to provide a ramp time dTx at the beginning and end of the time slot period TSLT. Output to the frame generation unit 110.
In this embodiment, the ramp time dTx is 2.44 [μs] for each of the beginning and the end, and is 4.88 [μs] in total. This ramp time dTx is provided to prevent unnecessary spectrum leakage outside the band.

For example, as shown in FIG. 13, the frame generation unit 110 collects seven time slots, and provides a 368-point (44.92 μs) no-signal period (frame guard period) at the end, One frame FRM is generated and output to the digital-analog (D / A) converter 113.
For example, as shown in FIG. 13, the length of one time slot period TSLT is 2288 points (279.3 μs), and the length of one frame period TFRM obtained by adding 7 time slots and the frame guard period TFGD is 16384 points (2 ms). It becomes.

  The GPS receiving unit 111 receives a GPS signal via the receiving antenna 111 a and outputs it to the timing generation unit 112.

The timing generation unit 112 generates the transmission timing of the frame generation unit 110 based on the GPS signal from the GPS reception unit 111 and the inter-base station control signal CTL, and outputs the generated timing signal S112 to the frame generation unit 110.
As described above, in this embodiment, each base station transmits a frame at the same timing. Each base station uses the inter-base station control signal CTL to synchronize the frame transmission timing.
Although this synchronization signal is exchanged via a wired communication network, accurate synchronization between base stations cannot be performed with this signal alone due to the influence of transmission delay of the wired network. For this reason, each base station receives a GPS signal, and performs accurate inter-base station synchronization by using this GPS signal and inter-base station control signal CTL to match the frame transmission timing of each base station.

  The D / A converter 113 converts the digital frame data generated by the frame generator 110 into analog data and outputs the analog data to the quadrature modulator 114.

  The quadrature modulation unit 114 performs quadrature modulation on the frame to be transmitted converted into analog data by the D / A conversion unit 114 according to a predetermined modulation method, and outputs the result to the frequency conversion unit 115.

  The frequency conversion unit 115 converts the data orthogonally modulated by the orthogonal modulation unit 114 to a required frequency band and transmits the data as an RF (Radio Frequency) signal.

FIG. 14 is a block diagram showing an embodiment of a receiving apparatus mounted on a mobile terminal station according to the present invention.
As illustrated in FIG. 14, the reception device 200 according to the present embodiment includes a frequency conversion unit 201, an orthogonal demodulation unit 202, an analog-digital (A / D) conversion unit 203, a synchronization position detection unit 204, a timing generation unit 205, A reception windowing unit 206, a serial-parallel conversion unit 207, an FFT operation unit 208, a parallel-serial conversion unit 209, a transmission path estimation unit 210, a phase correction unit 211, a demodulation unit 212, a deinterleave unit 213, and a decoding unit 214 Have.
The frequency conversion unit 201, the quadrature demodulation unit 202, and the A / D conversion unit 203 constitute a pre-reception processing unit, a serial-parallel conversion unit 207, an FFT operation unit 208, a parallel-serial conversion unit 209, and a transmission path estimation unit. 210, the phase correction unit 211, the demodulation unit 212, the deinterleave unit 213, and the decoding unit 214 constitute a reception processing post-stage unit.

  The frequency conversion unit 210 extracts only a necessary frequency band from an OFDM signal received from an antenna (not shown), in other words, removes noise components other than the necessary frequency band, and then converts the RF signal to IF (Intermediate Frequency). The IF signal S201 is output to the quadrature demodulator 202.

  The quadrature demodulator 202 separates the in-phase signal I and the quadrature signal Q from the IF signal from the frequency converter 201 and outputs the separated signal to the A / D converter 203.

A / D conversion section 203 converts in-phase signal I and quadrature signal Q from quadrature demodulation section 202 from an analog signal to a digital signal, and outputs this digital signal to synchronization position detection section 204 and reception windowing section 206.
Note that the sampling rate of the A / D conversion unit 203 is 8.192 [MHz], which is the same as the sampling rate of the base station transmitter 100.

  The synchronization position detection unit 204 detects the timing of the FFT operation of the FFT operation unit 208 based on the A / D converted digital signals of I and Q. That is, the start position of the effective symbol period TSBL, in other words, the position of the first point of the digital signal in the effective symbol period TSBL is detected. The synchronization position detection unit 204 outputs this synchronization information to the timing generation unit 205.

  Based on the synchronization information from the synchronization position detection unit 204, the timing generation unit 205 receives the reception winding start position of the reception windowing unit 206, the serial-parallel conversion position of the serial-parallel conversion unit 207, and the FFT calculation of the FFT calculation unit 208. The timing and the parallel-serial conversion unit 209 control the parallel-serial conversion timing, respectively.

Based on the digital signal from the A / D conversion unit 203 and the windowing start position information from the timing generation unit 205, the reception winding unit 206 extracts 2048 points (250 μs) of digital data from the synchronization point, and performs serial-parallel conversion. Output to the unit 207.
Note that the reception window (250 μs) in the reception windowing unit 206 has a shorter time waveform than the transmission window (279.3 μs) in the transmission windowing unit 109 of the base station transmission apparatus 100.

  The serial-parallel conversion unit 207 converts the 2048-point digital data from the reception windowing unit 206 from serial data to parallel data, and outputs the converted data to the FFT operation unit 208.

The FFT operation unit 208 performs conversion processing between the frequency axis and the time axis by performing 2048-point fast Fourier transform based on the FFT operation timing information from the timing generation unit 205, and the parallel-serial conversion unit 209 Output.
That is, a signal converted into a 2048-point time-series signal having a carrier interval of 4 [kHz] and a spectrum of 100 × n (1 ≦ n ≦ 16) subcarriers by this fast Fourier transform processing is 100 ×. It is converted into an n-point (1 ≦ n ≦ 16) digital signal.
Actually, the output of the 2048-point fast Fourier transform is a 2048-point digital signal, but since the band allocated as the system bandwidth is only 6.4 [MHz], the base station transmitter side has 2048 lines. Only a maximum of 1600 subcarriers are used, and the remaining 448 subcarriers have a power of “0”. Therefore, the maximum digital signal actually output is 1600 points, and the remaining value is “0”.

The parallel-serial conversion unit 209 converts the parallel signal output from the FFT operation unit 208 into a serial signal, and simultaneously extracts only a required point in 2048 points and outputs it to the transmission path estimation unit 210.
For example, when the bandwidth allocated for communication between the terminal station and the base station is 400 [kHz], the parallel-serial conversion unit 209 on the receiving terminal side has 100 points corresponding to 400 [kHz]. Extract only.

The transmission path estimation unit 210 receives the output signal of the parallel-serial conversion unit 209, extracts only the pilot signal from the received signal, calculates the phase rotation amount from the I channel component and the Q channel component, and sends it to the phase correction unit 211. Output.
That is, since the base station transmitting apparatus 100 transmits the pilot signal with the I channel as “1” and the Q channel as “0”, the magnitude is “1” on the complex plane and the I axis is the reference. In this case, the phase angle is “0”, and the values of I and Q of the terminal reception device 200 on the complex plane indicate the amount of phase rotation as it is.
Further, the information on the magnitude of the vector on the complex plane is used to determine a threshold when demodulating a multi-level modulation signal such as 16QAM.

  The phase correction unit 211 corrects the phase of the received signal based on the phase rotation amount information from the transmission reasoning unit 210 and outputs the phase-corrected signal to the demodulation unit 212.

Demodulation section 212 performs demodulation corresponding to the modulation scheme of base station transmission apparatus 100 and outputs the result to deinterleaving section 213.
When the modulation method is a modulation method in which information is put on amplitude (vector magnitude on the complex plane) such as 16QAM, information on the reference received power (vector magnitude of the received pilot signal) is used for channel estimation. Obtained from the unit 210, this tone is used as a reference to perform double tone.

  Deinterleaving section 213 deinterleaves the signal demodulated by demodulation section 212 and outputs the result to decoding section 214.

  Decoding section 214 receives the demodulated and deinterleaved signal and decodes it, for example, to obtain a decoded signal.

  Next, operations of the transmission device and the reception device employed in the OFDM communication system having the above configuration will be described.

For example, digital data input to a transmission device 100 of a predetermined base station via a network of a high-speed downlink system is subjected to convolutional encoding with a constraint length K = 9 by the encoding unit 101.
The digital data encoded by the encoding unit 101 is interleaved by the interleaving unit 102 and then input to the symbol mapping unit 103.

The symbol mappin unit 103 controls the symbol mappin method (primary modulation method) based on the information about the electric field strength of the base station of the high-speed downlink system measured by the mobile terminal station, and performs in-phase with symbol mapping. The I channel and the orthogonal Q channel are output to pilot signal insertion section 104.
Pilot signal insertion section 104 inserts a pilot signal of “1” into the in-phase I channel and “0” into the orthogonal Q channel supplied from symbol mapping section 103 and outputs the result to serial-parallel conversion section 105.

  In the serial-parallel conversion unit 105, the symbol data into which the pilot signal is inserted is divided, for example, every 98 symbols, and one symbol is added to the head and the end of this symbol to make 100 symbols. Then, “0” for 1948 symbols are arranged before and after the 100 symbols so that a frequency spectrum appears in the radio channel band allocated to the base station, and converted into parallel symbol data of 2048 symbols as a whole, and IFFT calculation is performed. Is output to the unit 106.

The IFFT operation unit 106 performs fast inverse Fourier transform on the parallel 2048 symbol data by the serial-parallel conversion unit 105 to perform conversion processing between the time axis and the frequency axis, and the parallel-serial conversion unit 107. Is output.
In the parallel-serial conversion unit 107, the parallel data output from the IFFT calculation unit 106 is converted into serial data, 2048-point time series data is generated, and output to the time slot generation unit 108.

  In the time slot generation unit 108, for example, a copy of the beginning and end 120 points (14.648 μs) of time series data of 2048 points for the effective symbol period is connected to the end and beginning of the effective symbol period, respectively. A time slot is generated and output to the transmission windowing unit 109.

  The transmission windowing unit 109 is a window in which a ramp time dTx is provided for the time slot generated by the time slot generation unit 108 at the beginning and end of the time slot period TSLT to prevent unnecessary spectrum leakage outside the band. Is applied to the frame generation unit 110.

  The frame generation unit 110 collects, for example, seven time slots, and adds a 368-point (44.92 μs) power “0” no-signal period (frame guard period) to the end thereof to generate one frame FRM. And output to the digital-analog (D / A) converter 113.

Each base station synchronizes the frame transmission timing with the inter-base station control signal CTL.
Although this synchronization signal is exchanged via a wired communication network, accurate synchronization between base stations cannot be performed with this signal alone due to the influence of transmission delay of the wired network. Therefore, each base station receives the GPS signal by the GPS receiver 111, and the timing generator 112 generates the transmission timing of the frame generator 110 based on the GPS signal and the inter-base station control signal CTL. It is output to the frame generation unit 110.
The frame generation unit 110 outputs the generated frame to the D / A conversion unit 113 at the transmission timing based on the timing signal S112.

In the D / A conversion unit 113, the digital frame data generated by the frame generation unit 110 is converted into analog data, and then orthogonal modulation is performed by the orthogonal modulation unit 114 in accordance with a predetermined modulation method. The frequency is converted into a band and transmitted.

The OFDM signal transmitted from the base station transmitter 100 is received by the receiver 200 mounted on the mobile terminal station.
A signal received by the receiving apparatus 200 is taken out only in a necessary frequency band by a band filter (not shown), converted into an IF signal by a frequency conversion unit 201, and separated into an I signal and a Q signal by an orthogonal demodulation unit. . The signal separated into I and Q is converted into a digital signal by the A / D converter 203.
The A / D converted digital signals of both I and Q are input to the synchronization position detection unit 204 and the reception windowing unit 206.

The synchronization position detection unit 204 detects the timing of the FFT calculation in the FFT calculation unit 208. Specifically, the start position of the effective symbol period, in other words, the position of the first point of the digital signal in the effective symbol period is detected, and this synchronization information is sent to the timing generation unit 205.
In the timing generation unit 205, based on the synchronization information from the synchronization position detection unit 204, the reception winding start position of the reception windowing unit 206, the serial-parallel conversion position of the serial-parallel conversion unit 207, and the FFT calculation of the FFT calculation unit 208 The timing and the parallel-serial conversion timing are controlled by the parallel-serial conversion unit 209.

The reception windowing unit 206 extracts 2048 points (250 μa) of digital data from the synchronization point based on the digital signal from the A / D conversion unit 203 and the windowing start position information from the timing generation unit. The data is output to the conversion unit 207.
In the serial-parallel conversion unit 207, the 2048-point digital data from the reception windowing unit 206 is converted from serial data to parallel data and output to the FFT operation unit 208.

  The FFT operation unit 208 performs conversion processing between the frequency axis and the time axis by performing 2048-point fast Fourier transform based on the FFT operation timing information from the timing generation unit 205, and the parallel-serial conversion unit 209. Is output.

In the parallel-serial conversion unit 209, the parallel signal output from the FFT operation unit 208 is converted into a serial signal, and at the same time, only necessary points in 2048 points are extracted.
Then, transmission path estimation section 209 extracts only the pilot signal from the received signal, calculates the amount of phase rotation from the I channel component and Q channel component, and outputs it to phase correction section 211.
In the phase correction unit 211, the phase of the received signal is corrected based on the information on the amount of phase rotation and supplied to the demodulation unit 212.

Demodulation section 212 performs demodulation corresponding to the modulation scheme of the base station transmission apparatus. When the modulation scheme is a modulation scheme that puts information on amplitude (vector magnitude on the complex plane) such as 16QAM, the information of the reference received power (vector magnitude of the received pilot signal) is the transmission path estimation. Obtained from the unit 210, and the double tone is performed based on this value.
The signal demodulated by the demodulator 212 is deinterleaved by the deinterleaver 213 and then Viterbi decoded by the decoder 214.

Here, in this communication system, a case where an interference wave for one frame arrives due to fluctuations in received electric field strength due to fading or multipath will be considered in association with FIG.
In this case, a plurality of frames are continuously transmitted as the desired wave DSW. Each base station transmits a frame at the same timing, and the interference wave IFW from a distant base station using the same channel arrives slightly later than the desired wave DSW from a nearby base station.
In the conventional method in which the frame guard is not provided as in the present embodiment, the interference wave IFW interferes with the desired wave DSW2 frame, but in the communication system of the present embodiment using the OFDM signal with the frame guard provided. As shown in FIGS. 15A and 15B, there is no need to give interference to the second frame.

As described above, according to the present embodiment, the inter-base station control signal interface for synchronizing the base stations, the receiving antenna 111a that receives the GPS signal, and the GPS that receives the GPS signal. A receiving unit 111, a timing generating unit 112 that controls each functional block in order to transmit a frame at exactly the same timing between the base stations from the inter-base station control signal CTL and the GPS signal, and transmission information as a transmission time slot Pre-transmission processing units 101 to 109, a frame generation unit 110 that generates a frame composed of a plurality of time slots and one frame guard, and a post-transmission processing stage for transmitting the generated frame as a radio signal Units 113 to 115, and a frame guard period is provided in the transmission frame so that each base station can perform this operation at exactly the same timing. A base station transmitting apparatus 100 that transmits a frame; a reception processing pre-stage unit 201 to 203 that receives a radio signal and converts it into a digital signal; a synchronization position detection unit 204 that detects a leading position of an effective symbol period from the received signal; A timing generator 205 that controls the operation timing of each functional block from the synchronization position information; and a reception windowing unit 206 that extracts only the effective symbol period excluding the time guard period and the frame guard period by control from the timing generator; Since the reception processing post-stage units 207 to 214 for restoring desired information from the winded signal are provided, the reception frame signal having the frame guard period is demodulated, and the reception device 200 for reproducing the transmission information is provided. The number of repetitive cells is reduced, that is, the distance between base stations using the same channel is reduced. Illusion, even in a system which attained the effective use of the radio channel, it is possible to reduce the frame loss due to co-channel interference.
And there is an advantage that the number of repeated cells can be reduced while maintaining a required error rate, and frequency resources can be effectively utilized.

In addition, synchronization of an OFDM wireless communication system having a frame guard can be performed more accurately.
In addition, since the synchronization device can determine the insertion point of the frame guard, there is no need to send control information for frame synchronization (control information for notifying which is the head of the frame), and much more information. There is an advantage that can be transmitted.

  DESCRIPTION OF SYMBOLS 1,1A ... OFDM communication system, M1-M3 ... Mobile terminal station (MS), B1-B4 ... Base station (BS), N1 ... Existing cellular wired network, N2 ... Data communication network such as the Internet, N3 ... Additional down A data communication network having a database for a link, CTR ... a control center (MRC) for an additional downlink network, 100 ... a transmitting device, 101 ... an encoding unit, 102 ... an interleaving unit, 103 ... symbol mapping 104: Pilot signal insertion unit, 105 ... Serial-parallel conversion unit, 106 ... IFFT calculation unit, 107 ... Parallel-serial conversion unit, 108 ... Time slot generation unit, 109 ... Transmission windowing unit, 110 ... Frame generation unit 111 ... GPS receiver 112 ... timing generator 113 ... de Tal-analog (D / A) conversion unit, 114 ... quadrature modulation unit, 115 ... frequency conversion unit, 200 ... reception device, 201 ... frequency conversion unit, 202 ... quadrature demodulation unit, 203 ... analog-digital (A / D) Conversion unit 204... Synchronous position detection unit 205... Timing generation unit 206 .. reception windowing unit 207... Serial-parallel conversion unit 208... FFT calculation unit 209 .. parallel-serial conversion unit 210. 211, phase correcting unit, 212 demodulating unit, 213 deinterleaving unit, 214 decoding unit.

Claims (9)

A transmission apparatus in a multiple wireless communication system using one or more subcarriers orthogonal to each other,
A transmission processing pre-stage unit that generates a time slot sequence including one or a plurality of time slots to which a guard period is added to a transmission signal;
A transmission processing post-stage unit that transmits the time slot sequence, and
The length of the time slot sequence is defined to be shorter than the frame length defined by the system,
The transmission processing post- stage unit transmits at least the length of the frame determined by the system and the transmitted time slot sequence from when the tail of the time slot sequence is transmitted to when the beginning of the next time slot sequence is transmitted. A transmission device that stops signal transmission and makes no signal for a period corresponding to the difference in length . The transmission processing pre-stage part is:
The transmission apparatus according to claim 1, wherein a time slot string is generated by connecting a signal identical to a signal at the end of a transmission signal to a head and adding a guard period. The transmission device according to claim 1, further comprising a timing generation unit that extracts signal transmission timing information from a radio signal. A receiving apparatus in a multiple wireless communication system using one or more subcarriers orthogonal to each other,
A reception processing pre-stage unit that receives a time slot sequence including one or a plurality of time slots with a guard period added to a transmission signal;
A synchronization position detection unit that detects the start position of the time slot sequence from the received signal,
The length of the time slot sequence to be received is defined to be shorter than the frame length defined by the system ,
A period corresponding to at least the difference between the length of the frame defined by the system and the length of the received time slot sequence after receiving the tail of the time slot sequence is a non-signal period during which signal transmission is stopped A receiving device. The receiving device according to claim 4, further comprising a winding unit that distinguishes between the guard period and a transmission signal. A multiplex radio communication system using one or more subcarriers orthogonal to each other,
A transmission device for transmitting a radio signal;
A receiving device for receiving a radio signal transmitted from the transmitting device,
The transmitter is
A transmission processing pre-stage unit that generates a time slot sequence including one or a plurality of time slots to which a guard period is added to a transmission signal;
A transmission processing post-stage unit that transmits the time slot sequence, and
The length of the time slot sequence is defined to be shorter than the frame length defined by the system,
The transmission processing post- stage unit transmits at least the length of the frame determined by the system and the transmitted time slot from when the tail of the time slot string is transmitted until the beginning of the next time slot string is transmitted. Stop signal transmission for a period according to the difference in the length of the columns to make no signal ,
The receiving device is:
A reception processing pre-stage unit that receives a time slot sequence including one or a plurality of time slots with a guard period added to a transmission signal in the transmission device;
A synchronization position detection unit that detects the start position of the time slot sequence from the received signal,
The length of the time slot sequence to be received is defined to be shorter than the frame length defined by the system ,
A period corresponding to at least the difference between the length of the frame defined by the system and the length of the received time slot sequence after receiving the tail of the time slot sequence is a non-signal period during which signal transmission is stopped Is a communication system. The transmission processing pre-stage of the transmission device is:
The communication system according to claim 6, wherein a time slot string is generated by connecting a signal identical to a signal at the end of a transmission signal to a head and adding a guard period. The transmitter is
The communication system according to claim 6, further comprising a timing generation unit that extracts signal transmission timing information from a radio signal. The receiving device is:
The communication system according to claim 6, further comprising a windowing unit that distinguishes the guard period from a transmission signal.

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