JP3063747B2 - ATM wireless transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM radio transmission system, and more particularly to a base station which assigns an asynchronous transfer mode (ATM) cell to a continuous signal of a downlink radio frame and transmits the signal to each terminal station. The present invention relates to an ATM wireless transmission system for allocating a burst signal to an uplink wireless frame and transmitting the burst signal to a base station.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional ATM radio transmission system. As shown in FIG.
The wireless transmission methods are ATM terminals 31 and 33, wireless terminals 32 and 34, a wireless base station 35, and an ATM network 100.
It is composed of The uplink radio channel from the radio terminals 32 and 34 to the radio base station 35 is a TDMA (time division multiple access) system, and the downlink radio channel from the radio base station 35 to the radio terminals 32 and 34 is a continuous radio frame. This is a system in which ATM cells are multiplexed on a signal.

In FIG. 4, a base station 35 is connected to an ATM network 10.
The ATM cell (downlink) received from 0 is added to error correction, a synchronization bit, and the like, is continuously allocated to a downlink wireless frame, and is transmitted to a wireless transmission path. Here, as shown in FIG. 5A and FIG. 6A, the downlink radio frame transmitted by the radio base station 35 has a data portion (DA
TA) and additional bits (GAP: gap) of bit number Z are combined in a time-series manner, and are X bits.

[0004] The radio terminals 32 and 34 receive the downlink radio frame, establish synchronization and correct errors, and transmit the frame to the ATM terminals 31 and 33 without changing the frame configuration.
As shown in FIG. 6A, the ATM terminals 31 and 33 reproduce an ATM cell (downstream) from a downstream radio frame and transmit an ATM cell (upstream) based on the ATM cell (downstream). The wireless terminals 32 and 34 are
An M cell (uplink) is received and transmitted to the base station 35 in a configuration to which error correction, a synchronization bit, and a guard bit are added.

[0005]

However, in the above-mentioned conventional ATM radio transmission system in which an ATM cell is reproduced without using speed conversion, an ATM cell (downstream) sandwiches an additional bit (GAP) on the transmission side. In some cases, as shown in FIG. 6A, there is a shift of up to the number of additional bits Z as shown in FIG. On the other hand, the ATM terminals 31 and 33 determine the position at which burst allocation is performed for the uplink radio frame based on the reception timing of the reproduced ATM cell (downlink), and FIG.
As shown in (1), since the ATM cell (uplink) is transmitted with the bit width A, the fluctuation of the reproduction interval of the downstream ATM cell causes the transmission timing of the ATM cell (uplink) to fluctuate. Exceeding the permissible bit value causes collisions with signals sent by other stations,
The transmission system is adversely affected.

[0006] The present invention has been made in view of the above points,
It is an object of the present invention to provide an ATM wireless transmission system capable of suppressing fluctuations of a downstream ATM cell reproduction interval and thereby suppressing fluctuations of upstream ATM cells.

Another object of the present invention is to provide an ATM cell capable of suppressing the fluctuation of an ATM cell due to an additional bit within one bit.
It is to provide a TM wireless transmission system.

Another object of the present invention is to provide an ATM wireless transmission system capable of simplifying a circuit configuration.

[0009]

In order to achieve the above object, the present invention provides a base station comprising a first bit length data section and a second bit length data section.
A downlink radio frame consisting of a gap, which is a redundant bit having a bit length of, is continuously transmitted to a plurality of terminal stations in frame units, and each of the plurality of terminal stations receives the downlink radio frame, establishes synchronization and corrects errors. After the correction, a plurality of downlink ATM cells are reproduced from the data section, and the downlink ATM cells are reproduced.
In an ATM wireless transmission system that transmits uplink ATM cells to a base station in bursts at a transmission timing based on cell reception timing, each of a plurality of terminal stations divides a received downlink radio frame into N (where N is N is a natural number smaller than the first bit length of 2 or more) to generate a plurality of N-bit divided downlink radio frames composed of a divided data portion and divided redundant bits. The downlink ATM cell of the divided data portion is reproduced from the divided downlink radio frame, and the uplink AT is transmitted at the transmission timing based on the reception timing of the downlink ATM cell.
And transmitting means for transmitting a signal having a configuration in which redundant bits are added to the M cells to the base station in a burst manner.

According to the present invention, the downlink radio frame received by the N divider is divided into N, that is, a plurality of divided downlink radio frames in N-bit units smaller than the first bit length are generated, and the gap is divided into divided downlink radio frames. In order to reproduce the downstream ATM cell after distributing the number of bits of the gap, the upstream ATM cell is transmitted at the transmission timing based on the reception timing of the reproduced downstream ATM cell.
A signal having a configuration in which a redundant bit is added to a cell can be transmitted to a base station in a burst manner.

That is, according to the present invention, a frame generated by adding an N divider for dividing a downlink radio frame to a portion for converting a downlink radio frame into a downlink ATM cell at a terminal station and removing a gap, which is a redundant bit, is provided. By allocating the empty space to the divided individual radio frames, the downlink ATM cells can be reproduced after the number of bits of the gap is dispersed.

In the present invention, it is desirable to set the first bit length to a multiple of the second bit length for simplifying the circuit configuration of the N divider.

The N-divider of the present invention delays the received downlink radio frame by one bit each, and cascade-connects a total of (Z-1) (where Z is a second bit length). The delay element, the received downlink radio frame, and the output delay downlink radio frame of each of the (Z-1) delay elements are input, and one of them is selected to output a divided downlink radio frame. From the selector and the non-delayed downlink radio frame input to the selector, (Z-
1) Select signal generating means for controlling a selector so that Z downlink radio frames up to a bit delay downlink radio frame are sequentially switched and output in the order of delay time in units of N bits of the downlink radio frame. I do. According to the present invention, it is possible to generate a divided radio frame including a gap one bit at a time.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration diagram of an embodiment of an ATM wireless transmission system according to the present invention. In this figure, this embodiment is different from ATM terminals 11 and 1 in FIG.
3, the radio terminals 12 and 14, the N dividers 16 and 17 built in the radio terminals 12 and 14, the radio base station 15, and the ATM communication network 100 connected to the radio base station 15, respectively. It is configured. The radio link (uplink) from the radio terminals 12 and 14 to the radio base station 15 is TDM
A method is a method in which ATM cells are multiplexed on a continuous signal of a wireless frame in a wireless line (downlink) from the wireless base station 15 to the wireless terminals 12 and 14.

The wireless base station 15 continuously assigns ATM cells (downstream) received from the ATM network 100 to downstream wireless frames to which redundant bits such as error correction and synchronization bits have been added, and transmits them to the wireless transmission path. Here, the wireless base station 1
5 is X (for example, 190 bytes), the number of bits in the data portion is Y, and the number of redundant bits to be added (hereinafter, also referred to as additional bits or gaps) is Z. In this embodiment, the frame configuration is such that the number of bits Y in the data part is a multiple of the number of additional bits Z, that is, the number of bits Y in the data part is divisible by the number of additional bits Z. Here, for example, Y is 188
The byte Z is 16 bits (= 2 bytes).

The wireless terminals 12 and 14 receive the above-mentioned downlink radio frame, establish synchronization and correct errors,
The downlink radio frame is divided into N by N dividers 16 and 17. The ATM terminals 11 and 13 reproduce the data sequence from the divided frames, ignoring the additional bit (GAP), into ATM cells (downstream), and generate ATM cells (upstream) based on the reception timing of the ATM cells (downstream). And outputs it to the wireless terminals 12 and 14. Wireless terminals 12 and 1
4 generates an uplink radio frame having a configuration in which redundant bits such as an error correction, a synchronization bit, and a guard bit are added to an input ATM cell (uplink) and transmits the frame to the radio base station 15.

The N dividers 16 and 17 incorporated in the radio terminals 12 and 14 have the same configuration, for example, as shown in the block diagram of FIG. In the figure, the N divider 16 or 17 is composed of (Z-1) cascaded delay elements 21 _{1 to} 21 _Z-1 and a delay element 2
11. A selector 22 for selecting one of the output radio frames of _{11 to} 21 _Z-1 and a frequency divider 23 for dividing the clock.
And the output signal of the frequency divider 23,
2 for outputting a select signal to the counter 2.

Next, the operation of this embodiment will be described with reference to FIG.
A description will be given with reference to FIG. The radio base station 15 shown in FIG. 1 stores the data portion of the bit number Y composed of the ATM cell (down) received from the ATM network 100 and the additional bit (gap) of the bit number Z composed of the error correction and the synchronization bit. Fig. 3
A downlink radio frame as shown in (A) is generated and transmitted to a radio transmission path.

As described above, this downlink radio frame has a frame configuration in which the number of bits Y of the data part is divisible by the number of bits Z of the additional bit (gap). In the above data portion, the ATM cell has a fixed length of 53 bytes, but if the number of bits Y in the data portion is 188 bytes, only one part of the ATM cell is arranged in the data portion, and the ATM cell spans the gap. The rest is placed in the next data part. The gap includes an error correction bit generated by using the 188-byte data (a plurality of ATM cells and a part of one ATM cell) as a generation element.

The radio terminals 12 and 14 receive the above-mentioned downlink radio frame, establish synchronization and correct errors,
The downlink radio frame is divided into N by N dividers 16 and 17. That is, each of the N dividers 16 and 17
As shown in FIG. 2, directly while supplied to the selector 22, and supplied to the delay element 21 ₁ of the above downlink radio frame received reproduced as data 1 as shown in FIG. 3 (B) 1
Delay by bit period T.

[0021] Here, the delay element 21 ₁ delay element 21 ₂ -
21 _Z-1 and are connected in cascade, downlink radio frames retrieved is 1 bit period T delay from the delay element 21 _1, while being supplied as the data 2 to the selector 22, delay element 21 ₂ through 21 _Z- will be inputted is delayed by one bit period T, respectively to the next stage by _one. As a result, a downstream radio frame delayed by a total of kT (k bit shift) is taken out from the delay element 21 _k (k = 2, 3,..., Z−1), and is output as selector (2) as data (k + 1).
2 is supplied. FIGS. 3C and 3D show delay elements 2
1 ₁ and data 2 and the data Z output from the delay element 21 _Z-1 shown schematically.

On the other hand, the frequency divider 23 shown in FIG. 2 divides the clock by N to generate a frequency-divided N clock.
4 The counter 24 generates a select signal for sequentially selecting data 1 to data Z every N bits based on the N frequency-divided clock and supplies it to the selector 22. Thus, as schematically shown in FIG. 3E, the selector 22 selects data 1 when the select signal is from the 1st to Nth count, and selects data 2 when the select signal is from (N + 1) to 2Nth count. , And thereafter, data 3, data 4,. . . Are sequentially selected, and data Z is selected from {(Z−1) N + 1} to the X-th count.

As described above, the selector 22 outputs the state shown in FIG.
As schematically shown in (F), data 1 from the 1st bit to the Nth bit, data 2 from the Nth bit to the (2N-1) th bit,. . . , From the (Z-1) th bit to Y
A divided data signal is obtained by sequentially combining the data Z up to the bit and the first bit of the gap (GAP).

Therefore, since the last bit of each data other than the data Z portion of the divided data signal is the first bit of the next data, the last bit of each data can be regarded as a substitute for the gap. Since the last bit of the data Z portion is the first bit of the actual gap, the divided data signal has a configuration in which the data portion of the radio frame is divided into N and the gap is inserted one bit at a time. FIG.
As schematically shown in (F), when the data Z portion in the divided data signal is output, the gap portion of the remaining (Z-1) bits is ignored, and the first bit of the next radio frame is selected by the selector. 22.

As described above, as shown schematically in FIG. 5B, each of the above-mentioned divided data signals is composed of N-bit data portion DATA and 1-bit gap portion GAP. In this configuration, a total of Z pieces of data are combined in time series. Of these Z N-bit data,
The data portion of (N-1) Z bits (= Y bits) in all is a data portion obtained by dividing the Y-bit data portion of the radio frame.

Returning to FIG. 1 again, the ATM terminals 11 and 13 receive the above-mentioned divided radio frame, and ignore the 1-bit additional bit (GAP) from the N-bit divided radio frame. Column is A bits (A is N
It is reproduced to an ATM cell (downstream) of (a natural number smaller than -1). FIG. 6B shows the time relationship between the divided radio frame and the reproduced ATM cell (downstream).

[0027] The ATM terminals 11 and 13 are further provided with an AT based on the reproduction timing of the ATM cell (down).
An M cell (uplink) is generated and output to the wireless terminals 12 and 14 at the timing indicated by the arrow in FIG. The wireless terminals 12 and 14 generate an uplink radio frame having a configuration in which error correction, a synchronization bit, and a guard bit are added to the input ATM cell (uplink), and transmit the generated uplink radio frame to the radio base station 15.

Here, in the ATM radio transmission system for reproducing ATM cells without using speed conversion, ATM cells (downlink)
As described above, the transmission side may incorporate the additional bit (GAP) in the downlink radio frame as described above, but in this embodiment, the data portion of the downlink radio frame is divided into N to form a gap. Because of the dispersion, FIG.
As shown in (B), the gap (GAP) of the divided radio frame is Z ′ bits (Z ′ = 1 in the example of FIG. 5),
It is much shorter than its Z bits before division.

Therefore, in this embodiment, the fluctuation of the reproduction interval of the ATM cell (downstream) when the ATM cell (downstream) is incorporated in the downstream radio frame with the additional bit (GAP) interposed therebetween on the transmission side. Can be greatly reduced from the conventional Z (for example, 16 bits) to Z ′ (here, 1 bit), whereby the fluctuation of the transmission timing of the ATM cell (up) is also reduced as shown by Z ′ in FIG. , FIG. 6 (A)
Compared to the conventional Z, it can be greatly suppressed to within 1 bit. Further, in this embodiment, since the speed conversion, that is, the deletion of the additional bits is not performed in the wireless terminals 12 and 14 that receive the downlink wireless frame, a clock generation source and a PLL circuit are not required, and the circuit configuration is simplified. it can.

The present invention is not limited to the above-described embodiment. For example, the present invention is not limited to a wireless system connected to the ATM network 100, but also includes a transmission system using a continuous signal,
The present invention can be applied to all communication systems in which a transmission method using a frame to which burst allocation has been performed is mixed.

[0031]

As described above, according to the present invention,
The downlink radio frame received by the N divider is divided into N, that is, a plurality of divided downlink radio frames in N-bit units smaller than the first bit length are generated, and the gap is divided into the divided downlink radio frames to determine the number of bits of the gap. , The upstream ATM cells are transmitted at the transmission timing based on the reception timing of the reproduced downstream ATM cells, thereby suppressing fluctuations in the downstream ATM cell reproduction interval. As a result, the fluctuation of the uplink ATM cell can be suppressed, and the collision with the signal transmitted from another station can be avoided.

Further, according to the present invention, the first bit length of the data portion in the radio frame is set to a multiple of the second bit length of the gap. , A divided radio frame including one bit for each gap, and fluctuation of the ATM cell due to the gap can be suppressed within one bit.

According to the present invention, when a downstream radio frame is received and an ATM cell is reproduced, speed conversion, that is, deletion of redundant bits (additional bits) is not performed, so that a clock generation source and a PLL circuit are unnecessary. And the circuit configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram according to an embodiment of the present invention.

FIG. 2 is a block diagram of an embodiment of an N divider in FIG. 1;

FIG. 3 is a time chart for explaining the operation of FIG. 2;

FIG. 4 is a diagram illustrating an example of a conventional system configuration.

FIG. 5 is a diagram illustrating each example of a configuration of a received wireless frame in an ATM terminal.

FIG. 6 is a diagram showing the ATM cell transmission timing in a conventional manner and in the present embodiment.

[Explanation of symbols]

11, 13 ATM terminal 12, 14 wireless terminal 15 wireless base station 16, 17 N divider 21 _{1 to} 21 _Z-1 delay element 22 selector 23 frequency divider 24 counter

Claims (6)

(57) [Claims] 1. A base station transmits a downlink radio frame composed of a data portion of a first bit length and a gap that is a redundant bit of a second bit length to a plurality of terminal stations continuously in frame units, Each of the plurality of terminal stations receives the downlink radio frame, performs synchronization establishment and error correction, and then reproduces a plurality of downlink ATM cells from the data unit,
In an ATM radio transmission system for transmitting an uplink ATM cell to the base station in bursts at a transmission timing based on a reception timing of the downlink ATM cell, each of the plurality of terminal stations transmits the received downlink radio frame to N An N divider that divides (where N is 2 or more and is a natural number smaller than the first bit length) and generates a plurality of N-bit divided downlink radio frames including a divided data portion and divided redundant bits; The downlink ATM cell of the divided data portion is reproduced from the divided downlink radio frame extracted from the N divider, and redundant bits are added to the uplink ATM cell at transmission timing based on the reception timing of the downlink ATM cell. Transmission means for transmitting a signal having the above configuration to the base station in a burst manner. 2. Each of the plurality of terminal stations receives a downlink radio frame from the base station, performs synchronization establishment and error correction, and divides the downlink radio frame into N by the built-in N divider. A wireless terminal for transmitting a signal having a configuration in which redundant bits are added to the uplink ATM cell to the base station in a burst manner, and reproducing a downlink ATM cell of a divided data portion from the divided downlink radio frame from the wireless terminal. 2. The ATM wireless transmission system according to claim 1, further comprising an ATM terminal for supplying said upstream ATM cell to said wireless terminal at a transmission timing based on a reception timing of said downstream ATM cell. 3. The method according to claim 1, wherein the first bit length is set to a multiple of the second bit length.
The ATM wireless transmission system described in the above. 4. The N divider, wherein the received downlink radio frame is an N-bit data unit obtained by overlapping L bits (L is a natural number smaller than the second bit length) every N bits, 2. The data processing system according to claim 1, wherein one of the overlapping L-bit data portions of the adjacent data in each of the N-bit data is output as the N-divided downlink radio frame by dividing the data regarded as the redundant bits. The ATM wireless transmission system described in the above. 5. The N-divider delays the received downlink radio frame by one bit each, and cascade-connects a total of (Z−1) (where Z is the second bit length). A delay element, the received downlink radio frame, and each output delay downlink radio frame of the (Z-1) delay elements are input, and one of the downlink radio frames is selected and the divided downlink radio frame is selected. And a Z delay radio frame from the non-delayed downlink radio frame input to the selector to the (Z-1) -bit delayed downlink radio frame by the delay time in units of N bits of the downlink radio frame. 4. The ATM wireless transmission system according to claim 1, further comprising a select signal generating means for controlling the selector so as to sequentially switch and output the signals. . 6. The base station includes a data portion of the first bit length including a plurality of ATM cells received from an ATM network, and a redundant bit of the second bit length including an error correction and synchronization bit. And one AT in the data section adjacent to the data area.
The ATM radio transmission according to claim 1, wherein the radio base station is a radio base station that generates the downlink radio frame in which M cells are divided and incorporated, and continuously transmits the downlink radio frame to a plurality of terminal stations in frame units. method.