JP3235041B2 - TDD wireless communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master station and a plurality of slave stations having a TD.
TDD (Time Division) using MA-TDD
on Duplex) wireless communication system. Here, TDMA stands for time division multiple access,
TDD stands for time division duplex communication in which one frequency is used for transmission and reception in a time division manner.

[0002]

2. Description of the Related Art Conventionally, when a master station and a plurality of slave stations perform wireless communication, antennas of the master station and the slave stations are omnidirectional as in the first embodiment shown in FIG.

[0003] Therefore, in a propagation path where multiple waves exist, fading occurs when a slave station moves or when an object moves between the master station and the slave station.
It has been difficult to obtain high quality signal transmission characteristics.

FIG. 1B shows a second conventional example in which both the master station and the slave stations have a plurality of directional antennas. Therefore, the probability of receiving a multiplex wave is low because the beam width of the antenna is narrow,
Fading is less likely to occur, and high-quality signal transmission is possible. However, in this case, it is necessary to sequentially switch a plurality of antennas from the master station to transmit a signal, and also to sequentially switch the plurality of antennas to receive and select an optimum antenna in the slave station, and to transfer the result to the master station. Therefore, there is a disadvantage that the antenna switching control in the master station and the slave station becomes complicated.

[0005]

DISCLOSURE OF THE INVENTION The present invention is disadvantageous in that an omni-directional antenna is used for a conventional master station and a slave station, in that high-quality signal transmission cannot be performed. It is an object of the present invention to provide a TDD wireless communication system in which the control complexity, which is a drawback when a directional antenna is used, is solved.

[0006]

SUMMARY OF THE INVENTION The present invention provides a TDMA-TD
In order to easily realize high-quality signal transmission in the D communication system, the main feature is to use an omnidirectional antenna for the master station and a plurality of directional antennas for the slave station. The conventional technology includes an antenna configuration, its switching control method, and TDMA-
The TDD slot assignment control method and the signal transmission method are different.

[0007]

According to the present invention, a non-directional antenna is used for the master station and a directional antenna is used for the slave station. Therefore, a simple antenna selection method is possible. On the other hand, the method of using the TDMA-TDD frame is controlled according to the traffic or signal format. Therefore, high-quality, high-efficiency signal transmission, which is the object of the present invention, can be realized with a simple configuration.

[0008]

FIG. 2 shows a configuration example of a master station and a slave station according to an embodiment of the present invention.
02 is a transmitting / receiving device, 203 is a control device, 210 is a slave station,
211-A is a slave station antenna-A, 211-B is a slave station antenna-B, 211-C is a slave station antenna-C, 212 is an antenna changeover switch, 213 is a transmission / reception device, 214 is a control device, and 215 is a memory. is there.

FIG. 3 shows a frame format according to an embodiment of the present invention. Reference numeral 301 denotes a slot for a frame synchronization signal, which is transmitted from a master station to a slave station (hereinafter referred to as "downlink") and is composed of one slot. You. Reference numeral 302 denotes a downlink control signal slot, which is used for transmitting a downlink control signal and the like, and is composed of 5 slots. Reference numeral 303 denotes a data slot, which is used when a slave station transmits a data signal (hereinafter, uplink) or a downlink data signal to the master station, and is configured with 10 slots. Reference numeral 304 denotes an uplink control signal slot, which is used when transmitting an uplink control signal, and is composed of 5 slots. Reference numeral 305 denotes a slot composed of a total of 21 slots, which is defined as one TDMA-TDD frame.

[0010]

FIG. 4 is a diagram showing the timing of transmission / reception signals of the master station and the slave station in the present invention. In the following, the negative side of the polarity indicates the reception timing, and the positive side of the polarity indicates the transmission timing for convenience.

Reference numeral 400 is a time chart of a transmission / reception signal of the master station, 401 is a transmission timing of a frame synchronization signal, 402 is a transmission timing of a downlink control signal, 403 is a transmission / reception timing of a data signal, and 404 is a reception timing of an uplink control signal. It is.

As shown in FIG. 1, the master station transmits frame synchronization signals 401-1, 401-2, and 4 at period T (21 slots).
.., 401-n are repeatedly transmitted.

Reference numeral 410 denotes an antenna switching status in the slave station 1;
For 411-2, 212-B for the antenna and 411-B
In 3, the antenna 212-C is selected.

Reference numeral 420 denotes a reception level at the slave station. As shown here, the antenna 212-
The level received at A is the highest, followed by antenna 212-B at 421-2 and antenna 212-B at 421-3.
The level received at 12-C is the lowest. Therefore, the slave station 1 can determine that the antenna 202-A is optimal at the time of receiving the frame synchronization signal 401-3,
This result is stored in the memory 215. Thereafter, the antenna is selected with reference to this memory.

In FIG. 1, the above-mentioned judgment is made before n frames, so that the best antenna 212-A is switched in 412-1.

Hereinafter, since the slave station switches the antenna by repeating this operation, the maximum antenna can be promptly selected even when the slave station moves or the surrounding environment changes.

In the above embodiment, although it is possible to immediately respond to a change in the reception level by switching the antennas, since it responds to a fading drop, the error may increase. Therefore, in order to reduce the error, the slave station may receive the signals a plurality of times and perform an averaging process on these signals.

[0018]

[Data transfer method in the present invention] This will be described with reference to FIG. The master station periodically turns on the synchronization signal 4 at 501 after turning on the power.
01 is transmitted. The slave station receives this signal and selects the best antenna at 502 in the manner described above. Thus, the preparation for transmitting and receiving the data signal between the two stations is completed.

The master station determines in 503 whether there is a downlink data signal, and if there is a data signal, performs downlink data transmission from the master station to the slave station by the method 504 described later. Thereafter, the slave station determines at 505 whether or not there is an uplink data signal, and if there is an uplink data signal, performs uplink data transfer at 506. After the data transfer is completed, the slave station determines at 507 whether or not there is an antenna having a higher quality than the currently used antenna. If there is a higher quality antenna, the antenna is changed at 508. Thus, the data transfer is completed.

[0020]

[Downlink Data Transfer Method] The downlink data transfer 504 in FIG. 5 will be described with reference to FIG. The calling signal 601 is transmitted from the master station in the downlink control slot of the n-th frame. Upon receiving this signal in 602, the slave station transmits a response signal 603 in the uplink control slot. Upon receiving this signal at 604, the master station transmits an assignment signal 605 in the downlink control slot of the (n + 1) th frame. Information such as data on the start position of the data slot and data on the number of slots is encoded in the assignment signal. When the slave station receives this signal at 607, it prepares for data reception.

It is also possible to include such information included in the assignment signal in the call signal and omit the assignment signal.

The master station sends downlink data 608 (here, 5 slots) in the data slot of the (n + 1) th frame. Upon receiving this signal at 609, the slave station transmits a reception completion signal 610 in the uplink control slot of the (n + 1) th slot. The master station receives this signal at 611, and the downlink data transfer is completed.

If the data to be transferred is within 10 slots, the data transfer is completed in the (n + 1) th frame, and the reception completion signal is similarly performed. Also, if the data to be transferred is 1
When the number of slots is one or more, the n + 2th and subsequent frames are used, and the reception completion signal is transferred in the uplink control slot of the frame in which the last data transfer was performed.

[0024]

By the uplink data transfer method] FIG 7 the description of the above Ri data transfer 506 of FIG. The master station transmits a request signal 701 in the uplink control slot of the n-th frame. Upon receiving this signal at 702, the slave station transmits an assignment signal 703 in the downlink control slot of the (n + 1) th frame.
Information such as data on the start position of the data slot and data on the number of slots is encoded in the assignment signal. When the slave station receives this signal at 704, it prepares for data reception.

The slave station sends uplink data 705 (here, 5 slots) in the data slot of the (n + 1) th frame. Upon receiving this signal at 706, the master station transmits a reception completion signal 707 in the downlink control slot of the (n + 2) th slot. The slave station receives this signal at 611, and the uplink data transfer is completed.

If the data to be transferred is within 10 slots, the data transfer is completed in the (n + 1) th frame, and the reception completion signal is performed similarly. Also, if the data to be transferred is 1
When the number of slots is one or more, the n + 2th frame and thereafter are used, and the reception completion signal is transferred in the downlink control slot of the frame next to the frame in which the last data transfer was performed.

[0027]

First Embodiment The frame format in the first embodiment is to allocate one slot to the uplink control slot 304 shown in FIG. 3 for one slave station. In this case, the first slot is assigned to the slave station 1. , The second slot is used by the slave station 2, the third slot is used by the slave station 3, the fourth slot is used by the slave station 4, and the fifth slot is used by the slave station 5.

[Data Transfer Method] The data transfer method in this embodiment will be described with reference to FIG. 8A. The case where data transfer is performed from two slave stations to the master station will be described. The request signal is sent from the slave station 1 in the first slot of the uplink control slot 801 of n frames, and from the slave station 2 in the second slot of the same slot 801. If the master station receives this signal,
The allocation signal 80 in the downlink control slot of the (n + 1) th frame
2, 803 are sent to slave stations 1 and 2. Thereafter, the slave station 1 sends 5 slots of the uplink data signal 804, then the slave station 2 sends 5 slots of the uplink data signal 805, and the master station sends the reception completion signal 80 in the downlink control slot of the next (n + 2) th frame.
6,807 is sent to both slave stations, and the data transfer is completed.

[Signal Retransmission Method] FIG. 8B shows a modification of the first embodiment of the present invention, in which downlink data 851 and 852 are transmitted from a master station to slave stations 1 and 2. N, N + 1, N + 2 slots are transmitted to the slave station 1 in n frames, and M, M + 1, M + 2 to the slave station 2 in n frames.
Transmitting slots. These signals are received by both slave stations. In the slave station 1, the N + 1 slot is incorrect, and in the slave station 2, the M + 2 slot is incorrect.

Therefore, slave stations 1 and 2 transmit retransmission request signals 853 and 854 to the master station in the uplink control slot of n frames. The master station receives these signals and sends N + frames to the slave station 1 at 855 in the (n + 1) th frame.
1, N + 2 slots are retransmitted to the slave station 2 at 856 with M + 2 slots. This time, since the slave station 1 and the slave station 2 can normally receive the received signal without any error, the reception completion signals 857 and 858 are transmitted in the (n + 1) th frame, and the master station receives this signal. Thus, data transmission from the master station to both slave stations is completed.

It is to be noted that a method of transmitting only an erroneous signal at 855, ie, transmitting only the second slot, is also possible.

[0032] In the present embodiment as shown above, because all of the slave stations is possible to send uplink control signal in any frame <br/>, as described in "Data transfer method", the same frame Even if the request signals are transmitted from a plurality of slave stations within the frame, there is no collision, so that as many data as the number of stations permitted by the data slot in one frame can be packed, efficient signal transmission becomes possible.

As described in "Signal retransmission method", even if a retransmission request signal is transmitted immediately, this signal does not collide with a control signal transmitted by another slave station, so that an efficient signal is transmitted. Transmission becomes possible.

[0034]

Second Embodiment A second embodiment is a method in which a part of the requested slot is fixedly assigned to a plurality of slave stations, and the remaining slots of the requested slot are commonly assigned to the remaining slave stations. In the first slot 304-of the uplink control slot 304.
1 is used by the slave station 1, the second slot 304-2 is used by the slave station 2, and the third slot 304-3 and the fourth slot 304-4 are used.
Are assigned to child stations 3 to 10. Here, slave station 1
And the slave station 2 are stations with relatively large traffic, and the slave stations 3 to
Reference numeral 10 denotes a station having relatively little traffic.

In the present embodiment, since the slave stations 1 and 2 having a lot of traffic can transmit the uplink control signal in an arbitrary frame as in the first embodiment, the signal transmission with the highest priority on the efficiency is performed. It becomes possible. On the other hand, the seven slave stations of the slave stations 3 to 10 share the remaining three slots of the control slot. However, since both stations have little traffic, there is little chance of access and signal collision in the same slot. In the case of a signal collision, the slave station randomly changes the slot to be accessed and retransmits it in the next frame, or retransmits the waiting time randomly in frame units, thereby avoiding collision at a considerable frequency. be able to.

As described above, by allocating the uplink control slot according to the traffic amount, there is an advantage that the high speed and the improvement of the capacity can be realized.

[0037]

Third Embodiment FIG. 9 shows a third embodiment, which is a frame format at the time of data transmission, in which the number of downlink control slots 302 is reduced from the usual 5 slots to 2 slots.
The number of uplink control slots is reduced from the usual five slots to two slots. From this, the data slot is normally 10
It has been expanded from slots to 16 slots.

Therefore, in the present embodiment, data of 16 slots or less can be transferred in one frame. In the case of data of 16 slots or more, for example, 160 slots, data transfer requires 16 frames in a normal case where this embodiment is not used. In this embodiment, the transfer is completed in 10 frames.

As described above, according to the present embodiment,
By expanding the data slot during data transmission,
This has the advantage that high-speed data transmission is possible.

[0040]

Fourth Embodiment FIG. 10A shows a fourth embodiment in which downlink data is transmitted. The master station is 1001 of n frames
Transmits data of 10 slots. 1 in the slave station
002, but the sixth slot 1002
-6 is making an error.

"Method of Switching Antenna If Erroneous" First, a method based on the first antenna switching timing will be described. The slave station uses the antenna 212-A used so far at the antenna switching timing (a) of 410-a.
To the second quality antenna 212-B, and retransmission request signal 1 in the uplink control slot of n frames.
003 is transmitted. The master station sends this retransmission request signal 1004
, A retransmission allocation signal 1005 is transmitted in the downlink control slot of the (n + 1) th frame.

When the slave station receives the assignment signal at 1006, it starts preparing for data reception. The master station retransmits the data of the erroneous signal after the sixth slot in 1007, and the slave station receives this signal in 1008. Since no error occurs this time, a reception completion signal 1009 is transmitted in the uplink control slot of the (n + 1) th frame, and the master station
Receives the same signal and completes the downlink data transfer.

The signal to be retransmitted in step 1007 is only an erroneous signal, that is, the method of transmitting only the sixth slot is the first method.
This is possible in the same manner as the embodiment.

The antenna switching timing is set to 4
As shown in 10-b, a method of setting the boundary (b) between frames is also possible.

[Method of Switching Antenna if Retransmission Assignment Signal is Not Received] This will be described with reference to FIG. 10B.
In the slave station, the sixth slot of the signal 1052 is erroneous, 1053
, A retransmission request signal is sent, but the same signal 1054 is incorrect in the master station. Therefore, the slave station cannot receive the retransmission confirmation signal 1055 at the (n + 1) th frame, nor can it receive the data signal 1056 to be retransmitted. Therefore, after switching to the antenna 212-B of the second quality at the antenna switching timing (c) of 410-c, the retransmission request signal 1057 is transmitted in the uplink control slot of the (n + 1) th frame. In this case, since this signal can be normally received by the master station, the master station sends the retransmission allocation signal 1059 in the downlink control slot of n + 2 frame.
Is transmitted, and the data 1060 after the sixth slot is retransmitted in the same frame.
061 is transmitted to complete the data transfer from the master station to the slave station.

As described above, in the present embodiment, if the signal is wrong, it is highly probable that the propagation condition has deteriorated. By switching to the second quality antenna and performing signal retransmission, This is based on the fact that there is a possibility that the probability of reception without error is high, and has the advantage that signal transmission can be realized more efficiently than signal transmission without switching antennas.

The above-described method is a method of switching the antenna at the slave station when the signal received at the slave station is erroneous. However, when the signal received at the master station is erroneous, retransmission from the master station is performed. A request is sent, and when this signal is received by the slave station, or when the reception completion signal from the master station is erroneously received by the slave station, or when the same signal cannot be received by the slave station, By switching antennas and performing communication, the same effect as described above can be obtained.

[0048]

Fifth Embodiment FIG. 11 shows a fifth embodiment in which downlink data is transmitted.

According to the procedure described above, the calling signal 1101 is transmitted from the master station.
2 and finally, the master station transmits an assignment signal 1103, and preparation for data transfer from the master station to the slave station is completed.

Next, the master station transmits data for one slot a plurality of times (here, three times) at 1104. The slave station receives this signal at 1105, but the second slot 1105-2 and the third slot 1105-3
Is making a mistake. However, at the slave station, at least one
Since the data of the slot has been successfully received, a reception completion signal is notified to the master station at 1106. When the master station receives this signal, it ends the data transfer from the master station.

As described above, the present embodiment utilizes the fact that the reliability can be improved by transmitting the same signal many times, and has an advantage that efficient data transfer can be realized. Further, in the second conventional example, the master station has a plurality of antennas, so when performing broadcast transmission, it is necessary to switch a plurality of antennas one after another and transmit by all antennas. Although it is necessary to transmit slots for the number of antennas, according to the present embodiment, there is only one antenna at the master station, so at least one transmission is sufficient. It has the advantage of being able to send multiple times to improve.

Further, in this embodiment, when there is no traffic, the same data signal can be repeatedly transmitted until traffic occurs. In this case, there is an advantage that the reliability can be further improved.

[0053]

Sixth Embodiment FIG. 12 shows a sixth embodiment of the present invention. Here, instead of a method of transmitting and receiving a call signal, a response signal, an assignment signal, and the like as in the fifth embodiment and transmitting data (usually called connection-type communication),
If there is a data transfer request, and if the next data slot is vacant, data is transferred immediately (connectionless communication).
The data of the slot is transmitted a plurality of times (three times in this embodiment).

The slave station 1 sends this signal to the slave station 2 at 1202.
Are simultaneously received at 1203. Here, in the child station 1, 1202-2 and 1202-3 have made an error,
In the slave station 2, 1203-1 and 1202-2 have errors. However, since one slot has been normally received, data transmission from the master station to the slave station is completed. Here, the reception completion signal is not transmitted from the slave station because of the connectionless communication.

As described above, the present embodiment differs from the fifth embodiment only in the difference in the presence or absence of a connection, and has the same advantages as the fifth embodiment, namely, efficient data transfer and reliability. It has the advantage that it can be improved.

[0056]

As described above, according to the present invention, there is an advantage that high-quality and high-efficiency signal transmission can be realized by a simple antenna configuration and an antenna control system.

[Brief description of the drawings]

FIG. 1 is a conventional example.

FIG. 2 is an embodiment of the present invention.

FIG. 3 shows a frame format of the present invention.

FIG. 4 shows an antenna selection method in a slave station according to the present invention.

FIG. 5 shows a control flow of the present invention.

FIG. 6 shows a downlink data signal transmission method of the present invention.

FIG. 7 shows an uplink data signal transmission method of the present invention.

FIG. 8A shows a data transfer method according to the first embodiment of the present invention.

FIG. 8B shows a signal retransmission method according to the first embodiment of the present invention.

FIG. 9 shows a frame format according to a third embodiment of the present invention.

FIG. 10A shows a fourth embodiment of the present invention.

FIG. 10B shows a case where a retransmission assignment signal cannot be received according to the fourth embodiment of the present invention.

FIG. 11 shows a fifth embodiment of the present invention.

FIG. 12 shows a sixth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 200 master station 201 master station antenna (omnidirectional) 202 transmitting / receiving device 203 control device 210 slave station 211-A, 211-B, 211-C slave station antenna (directivity) 212 antenna changeover switch 213 transmitting / receiving device 214 control device 215 memory

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Satoshi Baba 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (56) References JP-A-4-341020 (JP, A) JP JP-A-5-145484 (JP, A) JP-A-4-354221 (JP, A) JP-A-4-10724 (JP, A) JP-A-3-48943 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H04J 3/00-3/26 H04L 5/22-5/26 H04L 1/02-1/06 H04B 7/00 H04B 7/02-7/12 H04B 7/24-7 / 26 H04Q 7/00-7/04

Claims (2)

(57) [Claims] 1. A time-division duplex communication system using one frequency for time-division transmission and reception between one master station and a plurality of slave stations using a time-division multiple access system, TDMA-TDD. In the TDD wireless communication system, a master station has a single omnidirectional antenna, each slave station has a plurality of directional antennas, and each slave station transmits a frame synchronization signal periodically transmitted from the master station. Receive sequentially using all antennas while switching antennas, evaluate the quality of the received frame synchronization signal by at least one of signal reception level, signal to noise power ratio, signal to interference power ratio and signal error rate, to communicate with the master station the quality of the received signal and selects the highest antenna, data from the slave station to the data signal or the master station to the to the parent station
When the data signal is erroneous, the slave station controls the antenna to be switched to the antenna having the second highest received signal quality, and the TDMA-TDD slot used between the master station and the slave station is An uplink control slot for transmitting a control signal from the master station to the master station, a data slot for transmitting and receiving data between the master station and the slave station, a downlink control slot for sending a control signal from the master station to the slave station, A synchronization slot for transmitting a synchronization signal from a station to a slave station, wherein the uplink control slot is uniquely assigned in advance to all slave stations, and the uplink control slot used by each slave station independently. A TDD wireless communication system, characterized in that: 2. A time-division multiple access system using one frequency for time-division transmission and reception between one master station and a plurality of slave stations and TDMA-TDD. In the TDD wireless communication system, the master station has a single omnidirectional antenna, each slave station has a plurality of directional antennas, and the slave stations sequentially receive signals from the master station while switching antennas. The quality of the received signal is evaluated based on at least one of the signal reception level, the signal-to-noise power ratio, the signal-to-interference power ratio, and the signal error rate, and the antenna having the highest received signal quality is selected, and A TDMA-TDD slot used for communication between the master station and the slave station performs communication, an uplink control slot for transmitting a control signal from the slave station to the master station, and data transmission / reception between the master station and the slave station. Data slot and control signal from master station to slave station And a synchronization slot for transmitting a synchronization signal from the master station to the slave station. Each of the slave control stations independently uses the uplink control slot for a slave station with a lot of traffic. A TDD wireless communication system characterized in that an uplink control slot is fixedly assigned and an uplink control slot commonly used by a plurality of slave stations is assigned to a slave station with little traffic.