JP3399348B2 - Wireless transmission method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to wireless communication,
In particular, in a wireless ATM system in which information having different service qualities are mixed, the information is made into cells, and lines are multiplexed by the TDMA method, when a plurality of slots are continuously allocated, the allocated slots are allocated. The present invention relates to a transmission method for efficiently using the.

[0002]

2. Description of the Related Art It is desired that future communication can be applied to a wide variety of services such as voice, data, video and multimedia. ATM is designed to support such services in wired communication. ATM is CBR (invariant bit rate), rt
-VBR (real time variable bit rate), nrt
-VBR (No real-time variable bit rate), AB
It is an exchange technology that can economically provide various services such as R (Available Bit Rate) and UBR (Unspecified Bit Rate) with quality of service (QoS) according to demand. Considering the compatibility between wired communication and wireless communication, it is necessary to design a wireless ATM having characteristics such as wideband transmission, application to various services, and selection of QoS.

In wireless ATM, various transmission speeds are required depending on services. Reference "Dynamic TDMA in Wireless ATM": Ryo Umehira et al., 1997 IEICE General Conference, SB-5-2, pp.737-738), which is efficient in a wide range from low speed to high speed. As a method of allocating a wireless line, a TDMA method is described in which a transmission band is variable depending on the number of slots to be allocated.

FIG. 6 is a diagram showing an example of a wireless communication system. The mobile station 12 and the base station 13 are connected by a wireless line or a wireless line via a satellite, and the ATM terminal 11 is connected to the ATM network 14.

FIG. 7 is a diagram showing a frame configuration example of a wireless communication line from a mobile station to a base station. Separately, a line from the base station to the mobile station and a control line are provided. The mobile station 12 uses the control line to request the base station 13 for the line capacity required for the service of the ATM terminal 11. The base station 13 receives the request from each mobile station 12, allocates a slot to be used to each mobile station, and notifies each mobile station using a control circuit. The mobile station 12 is shown in FIG.
Transmission is performed using the assigned slot of the wireless communication line shown in FIG. In the figure, 1 is a frame, 2 is a slot, 3 is a transmission burst, 4 is a guard time (G), 5 is a system symbol (S), and 6 is an information cell (D).

[0006] The information cell 6 means an information unit including information obtained by decomposing data of various services into a certain length and sequence information for reassembling the disassembled information. AT
An example of an information cell using M cells is shown in FIG. The packet data unit (PDU) of the upper layer is decomposed into a fixed length, and an ATM header composed of path information used by the exchange and information for error detection is added to form an ATM cell. The sequence information used to reassemble the decomposed information is the MAC header added to the ATM cell or the ATM.
It is inserted in an AAL header, a higher layer PDU, etc. that form a cell. Due to the order information, even if the received information cells are out of order or the same information is received multiple times,
The sender information can be restored correctly. By using information such as the slot position in the frame of the received transmission burst, if the information of the transmission source can be correctly restored without inserting the sequence information, the sequence information in the information cell is omitted. Sometimes

The system symbol 5 means information other than information cells including a synchronization symbol called a preamble, information for system management called signaling, a training sequence used for equalization and channel estimation, and the like. The transmission burst 3 is composed of information cells 6 and system symbols 5, and is transmitted at a specific timing in frame 1, which is called slot 2. When a large number of mobile stations transmit the transmission burst 3, a guard time 4 is set between the transmission bursts to avoid collision,
It is normal to space transmission bursts.

When the slot length is T and the information cell length is Td, the transmission efficiency represented by the ratio of the time used for transmitting the information cell to the time occupied by the allocated slot is Td / T. Since the transmission efficiency can be improved by bringing Td close to T, it has been conventionally attempted to shorten the guard time and the system symbol as much as possible.

In the TDMA type wireless communication system, various transmission rates can be supported depending on the number of allocated slots. FIG. 9 is an explanatory diagram when a plurality of slots are assigned. FIG. 9 (1) shows a case in which a transmission burst composed of system symbols and information cells and a guard time are added to the slot length. For example, two slots m and m + 1 for the same mobile station
, The transmission band that can be transmitted in one frame can be doubled as in the case of allocating one slot. When a service with a constant transmission band is mainly used, such as a voice service, the slot length is often made to correspond to the guard time and the total length of system symbols. This is because a transmission burst from a different mobile station and a transmission burst from the same mobile station can be processed without distinction, so that the processing is simple. Further, since the transmission efficiency when allocating one slot is main, deterioration of the transmission efficiency due to addition of an unnecessary guard time or the like can be ignored in the case of the same mobile station.

In the case of a service that mainly allocates a plurality of slots to the same mobile station, the deterioration of transmission efficiency due to the addition of an unnecessary guard time or the like cannot be ignored. For example,
Between the first information cell and the last information cell, as disclosed in Japanese Patent Application Laid-Open No. 7-7488, "High-speed information transmission method by block multiple allocation, related receiving method and receiving apparatus for implementing the method". The transmission efficiency can be improved by substituting the information cell for the system symbol included in.

FIG. 9 (2) shows a method in which an intermediate guard time and system symbol are omitted. However, since two slots are used to transmit two information cells, the transmission efficiency is particularly high as it is. I cannot hope for improvement. It is possible to improve the transmission efficiency by using the guard time and the time vacated by the omission of the system symbol for other information transmission. FIG. 9 (3) shows a case where the slot structure of FIG. 9 (2) is changed. However, if the slot structure is changed, the position of the system symbol changes and the position of the synchronization symbol also changes, so that it becomes difficult to receive the burst unless special processing is performed according to the slot structure.

FIG. 9 (4) shows a method of omitting the intermediate guard time and system symbols and additionally using the time used for transmission of information cells. When the time used for transmission becomes long, it is possible to adopt a channel coding method that is more error-resistant, such as adding a lot of redundant information used for error correction, so that communication quality can be improved.
However, when the number of slots allocated to the same mobile station is arbitrary, it is necessary to use redundant information or a channel coding method of arbitrary length in order to effectively use the time vacated by omission. Further, in this case, it is necessary to change the receiving method for each burst, which complicates demodulation processing.

[0013]

As described above, in the prior art, since the slot length is set in correspondence with the total length of the guard time, the system symbol and the information cell, a plurality of slots can be assigned to the same mobile station. Even if slots are assigned, it is not easy to improve transmission efficiency and communication quality. The present invention has been made to solve the above problems, and provides a transmission method with good transmission efficiency and communication quality when the same mobile station mainly serves to transmit a plurality of information cells. The purpose is to do.

[0014]

According to a first aspect of the present invention, there is provided a radio transmission method according to the TDMA method, wherein a transmission burst is composed of information cells and system symbols, and the TDMA slot length corresponds to the information cell length. The length is set, and the system symbol is transmitted in the slot immediately before the slot for transmitting one or more information cells.

In the radio transmission method according to the second aspect of the invention, the base station allocates the slots for transmitting system symbols and the slots for transmitting information cells by the number of information cells permitted to be transmitted to the mobile station, and consecutive slots are the same. When allocating to a mobile station, one slot is additionally allocated.

In the radio transmission method according to the third aspect of the invention, the mobile station to which consecutive slots are assigned transmits information other than system information using the slots assigned to transmit system symbols.

The radio transmission method according to the fourth aspect of the present invention is a channel coding method in which the information cell transmitted in the previous frame is retransmitted in the slot immediately after the slot for transmitting the information cell.

In the radio transmission method according to the fifth aspect of the present invention, as a channel coding method, a slot for transmitting an information cell and a slot immediately after the corresponding slot are used to transmit information to which redundant information for error correction is added.

In the radio transmission method according to the sixth aspect of the present invention, as the channel coding method, the information cell is transmitted using the slot for transmitting the information cell and the slot immediately after the corresponding slot.

In the wireless transmission method according to the seventh invention, the mobile station to which consecutive slots are allocated has a channel coding method independently determined by the mobile station and is determined by using a system symbol. specify.

In the wireless transmission method according to the eighth invention, a plurality of channel coding methods are mixed in one transmission burst, and the channel coding method is changed for each information cell according to the quality of service required for each information cell.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a diagram showing a transmission method according to the first embodiment, in which the mth slot to the (m + 8) th slot of the nth frame are written.
In the figure, S is a system symbol, and D1 to D5 are information cells. One or more information cells and the system symbols transmitted immediately before the information cells constitute a transmission burst. In a slot for transmitting a system symbol, a time other than the system symbol becomes a guard time, and it is possible to prevent transmission bursts from different mobile stations from colliding.

The information cell means an information unit including information obtained by disassembling data of various services into a certain length and sequence information for reassembling the disassembled information. Even if the order of the received information cells is out of order or the same information is received multiple times, the order information allows the information of the transmission source to be correctly restored. By using information such as the slot position in the frame of the received transmission burst, if the information of the transmission source can be correctly restored without inserting the sequence number, the sequence information in the information cell is omitted. Sometimes

The system symbol means information other than information cells including a synchronization symbol called a preamble, system management information called a signaling, a training sequence used for equalization and channel estimation, and the like. The order information of the information cells included in the transmission burst and the channel coding method may be included.

Since the length of the TDMA slot is set to the length corresponding to the information cell length, it is possible to continuously transmit an arbitrary number of information cells without changing the slot structure. When the slot length is T, the information cell length is Td, and the number of information cells to be continuously transmitted is k, the transmission efficiency is represented by the ratio of the time used for transmitting the information cells to the time occupied by the allocated slots. Is kTd /
(1 + k) T. Now, since T = Td, the transmission efficiency is k / (1 + k). This means that the guard time length and the system symbol length, which have been conventionally desired to be shortened, do not relate to the transmission efficiency. In the case of a service whose main purpose is to send information cells continuously, k >> 1, so that the transmission efficiency approaches 1, and it can be seen that high transmission efficiency can be obtained.

Further, since the timing of transmitting the system symbol is always the same with respect to the slot, the position of the synchronizing symbol included in the system symbol is also constant. Therefore, the synchronization symbol can be searched for at a fixed timing, and the transmission burst can be received without special processing.

Embodiment 2. FIG. 2 is a diagram showing a transmission method according to the present embodiment, in which the m-th slot to the m + 8-th slot are written from the nth frame to the (n + 2) th frame. In the figure, S is a system symbol, and D1 to D6 are information cells.

The figure shows an example in which the base station permits the mobile station to transmit two information cells in one frame. The base station allocates two slots of m + 1 and m + 3 as information cell transmission slots and two slots of m and m + 2 as slots for transmitting system symbols. in this case,
This is a case where consecutive slots are allocated to the same mobile station, and the base station further allocates an additional m + 4 1 slot. The mobile station assigned the slot is the n-th
The transmission shall start from the frame. In the nth frame, two information cells D1 and D2 are transmitted. In the (n + 1) th frame, two information cells D3 and D4 are transmitted, and the information cells D1 and D2 transmitted in the previous frame are retransmitted in the slot immediately after the slot for transmitting the information cells. Similarly, in the subsequent frames, the information cells transmitted in the previous frame are retransmitted together with the number of information cells permitted to be transmitted.

By the channel coding method as described above, the base station can realize diversity reception called time diversity. That is, since the same information cell is retransmitted in a certain frame and the next frame, two received waves with different propagation environments can be obtained, and the probability of being unable to receive is greatly reduced by combining the two received waves. Therefore, the communication quality can be improved.

Embodiment 3. FIG. 3 is a diagram showing a transmission method according to the third embodiment. The figure is a drawing in which the mth slot to the mth + 8th slot are written from the nth frame to the (n + 2) th frame. In the figure, S is a system symbol, and D1 to D6 are information cells. Also,
(D1) to (D6) are information cells D1 to D, respectively.
It is redundant information for error correction, which is generated in correspondence with 6.

The figure shows an example in which the base station permits the mobile station to transmit two information cells in one frame. The base station allocates two slots of m + 1 and m + 3 as information cell transmission slots and two slots of m and m + 2 as slots for transmitting system symbols. in this case,
This is a case where consecutive slots are allocated to the same mobile station, and the base station further allocates an additional m + 4 1 slot. The mobile station assigned the slot is the n-th
The transmission shall start from the frame.

In the nth frame, two information cells D1 and D1
2 is transmitted, but redundant information (D1) and (D2) for error correction is generated for each information cell. Slot m + 1 for transmitting information cell and slot m + 2 immediately after it
Sends D1 and (D1) to which redundant information for error correction is added. Similarly, D2 and (D2) are sent using slot m + 3 and slot m + 4.

As the error correction, there are methods such as multiple transmission and error correction coding. When using multiple delivery,
It is sufficient to send the same information cell. When error correction coding is used, the block length increases, but if a code that doubles is used, slots can be effectively used. However, because it is necessary to send one information block over two slots, it is necessary to
It is necessary to specify to the receiving side to send an information block for each slot.

With the above channel coding method, forward error correction can be performed, the block error rate can be greatly reduced, and the communication quality can be improved.

Fourth Embodiment FIG. 4 is a diagram showing a transmission method according to the fourth embodiment. The figure is a diagram in which the m-th slot to the (m + 8) th slot of the n-th frame are written for two types of channel coding schemes. In the figure, S is a system symbol, and D1 to D4 are information cells.

The figure shows an example in which the base station permits the mobile station to transmit two information cells in one frame. The base station allocates two slots of m + 1 and m + 3 as information cell transmission slots and two slots of m and m + 2 as slots for transmitting system symbols. The base station further allocates an extra m + 4 slot.

In channel coding 1, the information cells D1 and D2 are transmitted using the information cell transmission slot m + 1 and the immediately following slot m + 2. In this case, slot m + 3
And slot m + 4 are not used, but the transmission burst is simplified because only one system symbol is needed. Transmission can be simplified if the acceptable cell error rate is low enough.

In channel coding 2, m + 1 to m + 4 are used to transmit information cells D3 and D4 in addition to the authorized information cells D1 and D2. If the allowable cell error rate is sufficiently low, information can be transmitted quickly.

Embodiment 5. FIG. 5 is a diagram showing a transmission method according to the fifth embodiment. The figure is a diagram in which the m-th slot to the (m + 8) th slot of the n-th frame are written for three types of channel coding schemes. In the figure, S is a system symbol, and D1 to D3 are information cells. (D3) is redundant information for error correction generated corresponding to the information cell D3.

The figure shows an example in which the base station permits the mobile station to transmit three information cells in one frame. The base station allocates three slots of m + 1, m + 3, and m + 5 as information cell transmission slots and three slots of m, m + 2, and m + 4 as slots for transmitting system symbols. In this case, consecutive slots are allocated to the same mobile station, and the base station further adds 1 of m + 6.
Allocate extra slots. The mobile station to which the slot is assigned starts transmission from the nth frame.

Channel coding 1 is the default channel coding method and is a case where one information cell is sent in one transmission burst. Channel coding 2 is a case where one transmission burst transmits three information cells and redundant information generated corresponding to the corresponding information cells. Channel coding 3 includes information cells D1 and D
For No. 2, no redundant information is added, and for information cell D3, two pieces of information cell D3 and two pieces of redundant information (D3) generated corresponding to the corresponding information cell are transmitted.

The mobile station changes the channel coding method according to the quality of service required for each information cell. For example, if the allowable cell error rate required for the information cells D1, D2, D3 may be somewhat bad, channel coding 1 is selected. Information cells D1, D2, D
When the permissible cell error rate required for No. 3 is small, channel coding 2 to which redundant information for error correction is added is selected. If the allowable cell error rate required for the information cells D1 and D2 is large and the allowable cell error rate required for D3 is small, redundant information for error correction is added to the information cells requiring high communication quality. The selected channel coding 3 is selected.

The selected channel coding method is designated in the system symbol S, and the receiving side performs demodulation processing according to the designated channel coding method. For example, in channel coding 2, the transmission burst is continuous from slots m + 1 to m + 6, and it is specified that the information cells and the redundant information are transmitted by using every two slots. For example, in channel coding 3, the transmit bursts are continuous from slots m + 1 to m + 6,
Slots m + 1 to m + 2 are 1 for each slot
Information cells are being transmitted, and slots m + 3 to m + 6 specify that information cells and redundant information are transmitted by using two slots each.

Since the channel coding method can be changed according to the required communication quality in this way,
Communication can be performed with just enough communication quality. In the above example, the information cell and the redundant information are transmitted using two consecutive slots, but the information cell and the redundant information may be stored in separate slots for transmission, or the information cell and the redundant information may be integrated. May be stored in two slots for transmission.

[0045]

Since the present invention is constructed as described above, it has the following effects.
In the first invention, it is possible to obtain high transmission efficiency.

In the second aspect of the invention, the probability of unreceivability can be greatly reduced and the communication quality can be improved.

In the third invention, forward error correction can be performed, the block error rate can be greatly improved, and the communication quality can be improved.

In the fourth aspect of the invention, when the allowable cell error rate is sufficiently low, cell allocation can be reduced, so that transmission can be simplified.

In the fifth aspect of the invention, when the allowable cell error rate is sufficiently low, the cell allocation can be reduced, so that information can be transmitted quickly.

In the sixth invention, as the channel coding method, the information cell is transmitted using the slot for transmitting the information cell and the slot immediately after the corresponding slot, so that efficient communication can be performed.

In the seventh aspect of the invention, the mobile station to which consecutive slots are assigned independently determines the channel coding method, so that communication can be performed with a sufficient communication quality.

In the eighth invention, since the channel coding method is changed according to the quality of service required for each information cell, it is possible to perform communication with just enough communication quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a transmission burst and a slot configuration according to the first embodiment of the present invention.

FIG. 2 is a diagram showing a channel coding method according to the second embodiment of the present invention.

FIG. 3 is a diagram showing a channel coding method according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a channel coding method according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a channel coding method according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a wireless communication system.

FIG. 7 is a diagram showing a relationship between a conventional transmission burst and a slot configuration.

FIG. 8 is a diagram illustrating an information cell.

FIG. 9 is a diagram showing a conventional channel coding method.

[Explanation of symbols]

1 frame 2 slots 3 transmission bursts 4 guard time 5 system symbols 6 information cells 11 ATM terminals 12 mobile stations 13 base stations 14 ATM network

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-41833 (JP, A) JP-A-8-8874 (JP, A) JP-A-7-170237 (JP, A) JP-A-6- 141009 (JP, A) JP-A-2-180447 (JP, A) JP-A-2-63229 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04J 3/00 H04B 7 / 26 H04L 12/28 H04Q 3/00

Claims (8)

(57) [Claims] 1. A radio transmission method according to a TDMA method, wherein a transmission burst is composed of information cells and system symbols, and a TDMA slot length is set to a length corresponding to the information cell length, and one or more information cells are transmitted. A wireless transmission method characterized in that a system symbol is transmitted in a slot immediately before a slot to be set. 2. The base station allocates the slots for transmitting system symbols and the slots for transmitting information cells by the number of information cells permitted to be transmitted to the mobile station, and when allocating consecutive slots to the same mobile station, one slot is allocated. The wireless transmission method according to claim 1, wherein the wireless transmission method is redundantly allocated. 3. The mobile station according to claim 2, wherein the mobile station, which is assigned with continuous slots, transmits information other than system information using the slots assigned for transmitting system symbols. Wireless transmission method. 4. The radio transmission method according to claim 2, wherein, as the channel coding method, the information cell transmitted in the previous frame is retransmitted in the slot immediately after the slot for transmitting the information cell. 5. The channel coding method according to claim 2, wherein information to which redundant information for error correction is added is transmitted using a slot for transmitting an information cell and a slot immediately after the corresponding slot. Wireless transmission method. 6. The wireless transmission method according to claim 2, wherein, as the channel coding method, the information cell is transmitted using a slot for transmitting the information cell and a slot immediately after the corresponding slot. 7. The mobile station, to which consecutive slots are assigned, determines a channel coding method independently by the mobile station, and specifies the determined channel coding method using a system symbol. 2. The wireless transmission method described in 2. 8. The method according to claim 2, wherein a plurality of channel coding methods are mixed in one transmission burst, and the channel coding method is changed for each information cell according to the quality of service required for each information cell. Wireless transmission method.