JP2010130574A - Method and apparatus of parallel transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively use a band at low cost without preparing transceiving equipment and lane for deskew. <P>SOLUTION: The present invention adjusts the amount of skew between parallelized lanes by performing pattern matching utilizing that patterns differ for each lane when a specific byte showing frame synchronization information is parallelized. After a pattern matching signal is detected, a fixed latency and a variable latency are given to the signal and a latency equal to or more than the time needed to set the variable latency is given by the fixed latency. Both the pattern matching signal and out-of-synchronization frame are detected for each lane. When performing parallelization, if a parallel number is n and a bit number to be interleaved is m, n and m are determined so that n times m does not become a measure of the total bit number of a transmission frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a parallel transmission method and a parallel transmission device, and more particularly to a parallel transmission method and a parallel transmission device for adjusting a skew between lanes in which optical signals are parallelized and transmitted.

  Up to now, the speed of optical fiber transmission has been increased by time division multiplexing, but the problem that the transmission distance is limited by the wavelength dispersion of the optical fiber has become apparent.

  As one means for solving this problem, it is conceivable to use a dispersion compensation device such as a dispersion compensation fiber. However, it is desirable to avoid the use from the viewpoint of device size, device cost, and additional loss. As one of the solutions, a method of developing high-speed signals in parallel and transmitting them in parallel with a plurality of optical subcarriers has been studied. However, in parallel transmission, generally, variations occur in the reception end arrival time of each optical subcarrier. These variations are caused by, for example, propagation delays differing for each optical subcarrier due to wavelength dispersion of the optical fiber, paths passing for each optical subcarrier, and the like. However, since the signal transmitted by each optical subcarrier is originally a bulk signal, the original data cannot be restored if the delay time varies. Therefore, in parallel transmission, it is necessary to compensate (deskew) this variation at the receiving end.

  SFI-5 (Serdes Framer Interface Level 5) will be described as a deskew method. FIG. 20 shows a deskew method using SFI-5.

  In SFI-5, it is defined as a 16 parallel electrical interface between a framer IC and a SerDes (Serializer-Deserializer) IC that performs parallel-serial conversion. The SFI-5 deskew algorithm can also be applied to optical parallel transmission.

The operation will be described below. In SFI-5, in addition to 16 lanes for transmitting parallel signals, another lane is provided as a deskew lane. On the transmission side shown in FIG. 20A, the signals of 16 parallel lanes are sequentially copied for each block, and the copied signals are sequentially written to the deskew lane. The first lane 1 signal is copied, the lane 2 signal is copied next, the 16th lane signal is copied in this order, and then the lane 1 copy is resumed. On the receiving side shown in FIG. 20B, the deskew lane signal is compared with the lane 1 signal, and the buffer memory for the lane 1 signal is adjusted until the bit strings are complete. Similarly, the skew from lane 2 to lane 16 is adjusted. When SFI-5 is used, deskewing is possible regardless of the main signal protocol (for example, see Non-Patent Document 1).
http://www.oiforum.com/public/documents/OIF-SFI5-01.0.pdf

  However, in the prior art, it is necessary to add one lane for deskew, and in particular in optical parallel transmission, it is necessary to add a set of the number of times of optical transmission / reception, which generally increases the circuit scale. Furthermore, since an extra optical transmission band is required, the capacity of the main signal that can be transmitted by one optical fiber in a limited band is limited. In this method, as the number of parallels becomes smaller, the band use efficiency becomes worse. When the number of parallels is 2, a band of 1/3 is actually used for deskew.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a parallel transmission method and a parallel transmission device that can effectively use a band at low cost without preparing a transmission / reception device and a lane for deskew. And

  FIG. 1 is a diagram for explaining the principle of the present invention.

The present invention (Claim 1) is a parallel transmission method for performing deskew between parallel lanes on the receiving side of a parallel optical transmission system,
A pattern detection step (step 1) in which the pattern detection means detects a pattern of frame synchronization information of the transmission frame for each input parallel lane;
A relative position detecting step (step 2) in which the relative position detecting means detects the relative position of the head of the pattern detected for each parallel lane;
A delay amount determining step for determining a skew between the parallel lanes based on the information on the relative position of the head of the pattern for each parallel lane;
A deskew instruction means for determining a different delay amount for each parallel lane so as to compensate for the skew (step 4);
And
In the deskew instruction step (step 4),
The delay amount is determined by the sum of a fixed delay longer than the time required for setting the deskew and a variable delay that changes according to the skew amount to be compensated.

  As described above, after detecting a parallelized signal using pattern matching, a fixed delay and a variable delay are added to the signal, and a delay longer than the time required for variable delay setting is added to the signal by using a fixed delay. Even when the skew changes, since the deskew resetting by the variable delay is completed before the signal arrives, there is an effect that the synchronization is not lost during the operation.

Further, the present invention (Claim 2) detects a loss of frame synchronization based on frame synchronization information of a transmission frame;
The step of providing all possible delay amounts until frame synchronization is established based on the frame synchronization information is further performed.

  As described above, by detecting both the pattern matching signal detected for each lane and loss of synchronization, even when pattern matching is erroneously performed in each lane, the delay amount is changed based on the out of frame synchronization information. Frame synchronization can be established.

The present invention (Claim 3) is a parallel transmission method for performing deskew between parallel lanes on the receiving side of a parallel optical transmission system,
A pattern detecting step for detecting a pattern of frame synchronization information of the transmission frame for each parallel lane;
A relative position detecting means for detecting the relative position of the head of the pattern detected for each parallel lane;
A delay amount determining means for determining a skew between the parallel lanes based on information on a relative position of the head of the pattern for each parallel lane;
A deskew instruction step in which the compensation means determines a different delay amount for each parallel lane so as to compensate the skew; and
And
In the deskew step,
When the number of parallels is n (n is an integer of 2 or more) and the number of interleave bits when performing serial-parallel conversion is m (m is a natural number), n × m is a divisor of the total number of bits in one frame of the transmission frame. Other than.

  As described above, when performing parallel processing, when the number of parallels is n and the number of interleave bits is m, the pattern matching signal is determined by determining n and m so that n × m is not a divisor of the total number of bits of the transmission frame. Becomes longer than the frame period, and a skew longer than the frame period can be detected.

  FIG. 2 is a principle configuration diagram of the present invention.

The present invention (Claim 4) is a parallel transmission apparatus that performs deskew between parallel lanes on the receiving side of a parallel optical transmission system,
Pattern detection means 10 for detecting a frame synchronization information pattern of a transmission frame for each input parallel lane;
A relative position detecting means 20 for detecting the relative position of the head of the pattern detected for each parallel lane;
A delay amount determining means 30 for determining the skew between the parallel lanes based on the information of the relative position of the head of the pattern for each parallel lane;
A deskew means 49 for determining a different delay amount for each parallel lane so as to compensate for the skew;
Have
The deskew means 40 is
Means for determining a delay amount by a sum of a fixed delay longer than a time required for setting the deskew and a variable delay that changes in accordance with a skew amount to be compensated;

The present invention (Claim 5) includes means for detecting loss of frame synchronization based on frame synchronization information of a transmission frame;
And a means for giving all possible delay amounts until frame synchronization is established based on the frame synchronization information.

The present invention (Claim 6) is a parallel transmission apparatus that performs deskew between parallel lanes on the receiving side of a parallel optical transmission system,
Pattern detecting means for detecting a frame synchronization information pattern of a transmission frame for each parallel lane;
A relative position detecting means for detecting the relative position of the head of the pattern detected for each parallel lane;
A delay amount determining means for determining a skew between parallel lanes based on information on a relative position of a head of a pattern for each parallel lane;
A deskew means for determining a different delay amount for each parallel lane so as to compensate for the skew;
Have
Deskew means
When the number of parallels is n (n is an integer of 2 or more) and the number of interleave bits when performing serial-parallel conversion is m (m is a natural number), n × m is a divisor of the total number of bits in one frame of the transmission frame. Other than.

  As described above, according to the present invention, deskew is realized by using only the information transmitted by the main signal, so there is no need to provide an additional optical transmitter / receiver or transmission path for deskew, and a large-capacity parallel transmission system. Can be realized at low cost.

  Further, according to the present invention, even when the skew changes during operation, it is possible to follow the change in the skew without causing loss of frame synchronization.

  Further, according to the present invention, frame synchronization of a transmission frame can be finally established even when erroneous synchronization pattern detection occurs in each lane.

  Further, according to the present invention, since the period of the synchronization pattern can be expanded to a plurality of frame periods, it is possible to detect a skew larger than the transmission frame length.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 3 is a configuration diagram of the parallel optical transmission apparatus according to the first embodiment of the present invention.

  The parallel optical transmission apparatus shown in FIG. 1 includes a transmission side framer 100 such as an OTN (Optical Transport Network), a transmission side converter 200, a parallel optical transmitter 300 with a parallel number (parallel number n = 4), a multiplexer 400, an optical A fiber 500, a duplexer 600, four parallel (n = 4) parallel optical transmitters 700, a reception-side converter 800, and a reception-side framer 900 are included.

  In the example of the figure, the case where the parallel number n = 4 is shown. A transmission frame such as an OTN frame generated by the transmission side framer 100 is input to the transmission side converter 200 via the SFI-5 interface. In the transmission-side converter 200, the input 16 parallel signals are converted into 4 parallel signals for each 1 bit or a plurality of bits (the number of interleave bits is m). The four parallel signals output from the transmission side converter 200 are converted into optical signals of four different wavelengths by the parallel optical transmitter 300, and then combined into one optical fiber by the multiplexer 400 to be transmitted to the transmission line optical fiber 500. Is sent out. On the receiving side, the signal is separated into four optical signals for each wavelength by the duplexer 600 and input to the parallel optical receiver 700. The parallel optical receiver 700 converts the four optical signals into electric signals and inputs them to the receiving-side converter 800. The receiving-side converter 800 detects the delay difference between the four parallel signals and compensates for the delay difference, and then converts it to 16 parallel signals for each bit number the same as that on the transmitting side. The receiving-side converter 800 is connected to the receiving-side framer 900 via SFI-5, and a transmission frame such as an OTN frame is terminated at the receiving-side framer. The interface between the framer 900 and the converter 800 may be a standardized interface other than SFI-5 or a serial interface.

  Hereinafter, the receiving-side converter 800 will be described.

  FIG. 4 is a configuration example of the reception-side converter according to the first embodiment of the present invention.

  The reception-side converter 800 shown in the figure includes a buffer 801, a pattern detection circuit 802, a fixed delay circuit 803, a variable delay circuit 804, and a relative position detection circuit 807 arranged one by one. A quantity determining circuit 808, a deskew instruction circuit 809, an interleave circuit 805, and an SFI-5 interface circuit 806 are configured.

  The parallel number of the receiving side converter 800 shown in FIG. Four signals (lanes 1, 2, 3, and 4) input from the parallel receiver 700 are input to the pattern detection circuit 802 via the buffer 801 for each lane. The pattern detection circuit 802 detects a characteristic pattern caused by a frame synchronization pattern of a transmission frame such as an OTN frame for each lane. The relative position detection circuit 807 detects the relative position of the head of the pattern from the pattern detected in each lane, and the delay amount determination circuit 808 detects the delay amount (skew) between the lanes based on the relative position. In the deskew instruction circuit 809, the delay compensation (deskew) amount of each lane is determined based on the delay difference detected by the delay amount determination circuit 808 from the pattern detected in each lane.

  On the other hand, after the signal of each lane passes through the pattern detection circuit 802, the fixed delay circuit 803 determines the deskew amount of each lane from the detected delay difference and sets the delay of the variable delay circuit 804 to a desired value. Delayed. The signal that has passed through the variable delay circuit 804 set to a desired value is converted into 16 parallel signals for each bit or a plurality of bits by the interleave circuit 805. The converted 16 parallel signals are converted into SFI-5 interface signals by the SFI-5 interface circuit 806 and input to the transmission framer.

  Let's see what happens to the synchronization pattern of each lane using a specific transmission frame synchronization pattern.

  FIG. 5 is a diagram (part 1) illustrating a synchronization pattern bit string according to the first embodiment of the present invention. This figure shows a frame synchronization pattern bit string of an OTU3 frame, which is one of OTN frames, and a synchronization pattern bit string of four lanes, which are four-parallel expanded with the number of interleave bits m = 1. As shown in FIG. 5A, the OTU-3 frame has a 6-byte (48-bit) frame synchronization pattern at the head of each frame, and this pattern always appears for each frame. The OTN framer performs frame synchronization by detecting this pattern. FIG. 5B shows the result of converting this pattern into four parallel signals (lanes 1, 2, 3, 4) for each bit. It can be seen that a 12-bit characteristic pattern appears for each lane. The receiving-side converter 800 detects this characteristic pattern, thereby detecting the delay difference of each lane and performing delay difference compensation (deskew).

  6 to 10 show synchronization pattern bit strings when the number of interleave bits m = 2, 3, 4, 6, and 12, respectively. In these cases, a characteristic pattern can be obtained in each of the four lanes. Therefore, delay difference compensation (deskew) can be performed by detecting the pattern.

  However, in the examples shown so far, when a delay difference (skew) of half or more of the frame period occurs, a correct delay difference cannot be detected. Next, it will be described that in order to detect a delay difference (skew) of more than half of the frame period, the value of the number of interleave bits m may be selected appropriately.

FIG. 11 is a diagram (No. 7) illustrating the synchronization pattern bit string according to the first embodiment of the present invention. This figure shows a synchronization pattern bit string when the number of interleave bits m = 7. Since the bit number (48) of the transmission frame synchronization pattern is not a multiple of the product of the parallel number n and the interleave bit number m (n × m = 4 × 7 = 28), the number of synchronization pattern bits in each lane is different. Each lane has a characteristic pattern. On the other hand, when attention is paid to one lane, for example, a bit of the transmission frame appears in lane 1 of FIG. OTU3 bit number of one frame of the frame is 4080 × 4 × 8 = 130560 bits, when factoring 130560 = 17 × 5 × 3 × 2 9 becomes not a multiple of ^{28 (= 7 × 2 2)} . Therefore, the synchronization pattern appearing in lane 1 appears not in every transmission frame (130560 bits) but in the least common multiple 913920 (= 130560 × 7) bits of 130560 and 28, that is, every seven transmission frames. As described above, in this example, it can be seen that the detectable delay difference (skew) can be enlarged seven times.

Similarly, FIGS. 12 to 14 show cases where the parallel number n × the number of interleave bits m is not a divisor of the total number of bits of one transmission frame. FIG. 12 shows a case where m = 9, FIG. 13 shows a case where m = 11, and FIG. 14 shows a case where m = 13. The detectable delay difference (skew) is compared with a case where n × m is a divisor of 130560, respectively. It can be magnified 3 times, 11 times, and 13 times. In general, the detectable delay difference (skew) is
± (one frame duration) / 2 × (n × m and the least common multiple of the total number of bits in one transmission frame) / (total number of bits in one transmission frame)
It becomes.

[Second Embodiment]
In this embodiment, another configuration of reception-side converter 800 in FIG. 3 will be described. Since other components are the same as those in the first embodiment, the description thereof is omitted.

  FIG. 15 shows the configuration of the reception-side converter in the second embodiment of the present invention.

  In the configuration shown in the figure, the number of parallels is generally n. 4 is different from the configuration shown in FIG. 4 in that a frame synchronization signal from the reception-side framer 900 connected to the subsequent stage of the reception-side converter 800 is converted into an OOF (Out Of Frame) / LOF (Los Of Frame) in the reception-side converter 800. Input to the detection circuit 831 to detect at least one of OOF and LOF. In the OOF / LOF detection circuit 831, when at least one of OOF and LOF is detected and the state continues for a certain number of protection stages, the delay amount given by the variable delay device 824 is determined again. Transmission frame synchronization cannot be established despite the successful pattern detection for each lane, if a bit error occurs, or if the synchronization pattern for each lane happens to be not the original synchronization pattern, it will be delayed. A case where the difference (skew) exceeds a detectable range can be considered. In these cases, transmission frame synchronization can be finally established by trying all possible combinations of delay amounts for each lane until transmission frame synchronization is established.

  This effect increases as the parallel number increases. FIG. 16 shows a pattern synchronization bit string when the parallel number n = 8 and the interleave bit number m = 1, and FIG. 17 shows the pattern synchronization bit string when the parallel number n = 12, and the interleave bit number m = 1. The number of synchronization pattern bits in each lane is 6 bits and 4 bits, respectively, which is shorter than 12 bits in the case of n = 4. When the synchronization pattern length is shortened, the probability that the synchronization pattern appears accidentally in a place that is not originally a synchronization pattern increases. In addition, the same pattern can be seen in different lanes. Although there is no problem in detecting the frame of each lane, it becomes a problem when it is necessary to identify the lane. For example, when each lane is transmitted with a different fiber or when transmitted with a different wavelength within one fiber, each lane can be fixedly associated with each input port of the receiving-side converter on a one-to-one basis. Lane identification is not necessarily required.

  On the other hand, when each lane is made to correspond to the number of bits per symbol of multilevel modulation, it may be impossible to make it correspond to each input port of the receiving-side converter, so it is necessary to identify the lane. In some cases. Even when lane identification is required in this way, by using the frame synchronization information of the transmission framer or LA, trying all possible combinations of the ports where each lane appears and the delay amount of each lane. Finally, transmission frame synchronization can be established.

  FIG. 18 shows a synchronization bit string when the parallel number n = 5 and the interleave bit number m = 1. Although the number of synchronization pattern bits in each lane is not necessarily the same, a characteristic pattern appears in each lane, and it can be seen that the delay difference (skew) between each lane can be detected by detecting the synchronization pattern in each lane. .

  FIG. 19 shows a synchronization bit string when the parallel number n = 5 and the interleave bit number m = 5. This corresponds to the case where the above-mentioned n × m is not a divisor of the total number of bits of one frame of the transmission frame, and the detectable delay amount (skew) can be expanded five times.

  As described above, in the present invention, as a dequeue means at the time of parallel transmission, pattern matching utilizing the fact that when a specific byte indicating SDH / SONET or OTN frame synchronization information is parallelized, a different pattern is used for each lane. By adjusting the amount of skew between the parallel lanes by applying the above, it is not necessary to prepare a transmission / reception device and a lane for deskew.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

  The present invention is applicable to a technique for transmitting optical signals in parallel, and particularly to a technique for performing deskew between parallel lanes of a parallel optical transmission system.

It is a figure for demonstrating the principle of this invention. It is a principle block diagram of this invention. It is a block diagram of the parallel optical transmission apparatus in the 1st Embodiment of this invention. It is a structural example of the receiving side converter in the 1st Embodiment of this invention. It is FIG. (1) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (2) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (The 3) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (The 4) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (5) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (6) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (The 7) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (The 8) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (9) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is FIG. (10) which shows the synchronous pattern bit sequence in the 1st Embodiment of this invention. It is a block diagram of the receiving side converter in the 2nd Embodiment of this invention. It is FIG. (1) which shows the synchronous pattern bit sequence in the 2nd Embodiment of this invention. It is FIG. (2) which shows the synchronous pattern bit sequence in the 2nd Embodiment of this invention. It is FIG. (The 3) which shows the synchronous pattern bit sequence in the 2nd Embodiment of this invention. It is FIG. (The 4) which shows the synchronous pattern bit sequence in the 2nd Embodiment of this invention. It is a figure which shows the deskew method prescribed | regulated by the conventional SFI-5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pattern detection means 20 Relative position detection means 30 Delay amount determination means 40 Deskew means 100 Transmission side framer 200 Transmission side converter 300 Parallel optical transmitter 400 Multiplexer 500 Optical fiber 600 Demultiplexer 700 Parallel optical receiver 800 Reception side converter 801 Buffer 802 Pattern detection circuit 803 Fixed delay circuit 804 Variable delay circuit 805 Interleave circuit 806 SFI-5 interface circuit 807 Relative position detection circuit 808 Delay amount determination circuit 809 Deskew instruction circuit 821 Buffer 822 Pattern detection circuit 823 Fixed delay circuit 824 Variable delay Circuit 825 Interleave circuit 826 SFI-5 interface circuit 828 Relative position detection circuit 829 Delay amount determination circuit 830 Deskew instruction circuit 831 OOF / LOF detection circuit 900 Receiver framer

Claims (6)

A parallel transmission method for performing deskew between parallel lanes on the receiving side of a parallel optical transmission system,
A pattern detecting step for detecting a pattern of frame synchronization information of a transmission frame for each parallel lane; and
A relative position detecting step for detecting a relative position of the head of the pattern detected for each of the parallel lanes;
A delay amount determining means for determining a skew between the parallel lanes based on information on a relative position of a head of the pattern for each parallel lane;
A deskew step in which a deskew means determines a different delay amount for each parallel lane so as to compensate for the skew; and
And
In the deskew step,
A parallel transmission method characterized in that the delay amount is determined by a sum of a fixed delay longer than a time required for setting the deskew and a variable delay that changes in accordance with a skew amount to be compensated. Detecting out of frame synchronization based on frame synchronization information of the transmission frame; and
Providing all possible delays until frame synchronization is established based on the frame synchronization information;
The parallel transmission method according to claim 1, further comprising: A parallel transmission method for performing deskew between parallel lanes on the receiving side of a parallel optical transmission system,
A pattern detecting step for detecting a pattern of frame synchronization information of a transmission frame for each parallel lane; and
A relative position detecting step for detecting a relative position of the head of the pattern detected for each of the parallel lanes;
A delay amount determining means for determining a skew between the parallel lanes based on information on a relative position of a head of the pattern for each parallel lane;
A deskew step in which a deskew means determines a different delay amount for each parallel lane so as to compensate for the skew; and
And
In the deskew step,
When the number of parallels is n (n is an integer of 2 or more) and the number of interleave bits when performing serial-parallel conversion is m (m is a natural number), n × m is a divisor of the total number of bits in one frame of the transmission frame. A parallel transmission method characterized by being other than the above. A parallel transmission device that performs deskew between parallel lanes on the receiving side of a parallel optical transmission system,
Pattern detecting means for detecting a pattern of frame synchronization information of a transmission frame for each input parallel lane;
A relative position detecting means for detecting a relative position of the head of the pattern detected for each parallel lane;
A delay amount determining means for determining a skew between the parallel lanes based on information on a relative position of a head of the pattern for each parallel lane;
Deskew means for determining a different delay amount for each parallel lane so as to compensate for the skew;
Have
The deskew means is:
A parallel transmission apparatus comprising: means for determining the delay amount by a sum of a fixed delay longer than a time required for setting a deskew and a variable delay that changes in accordance with a skew amount to be compensated. Means for detecting loss of frame synchronization based on frame synchronization information of the transmission frame;
Means for giving all possible delays until frame synchronization is established based on the frame synchronization information;
The parallel transmission apparatus according to claim 4, further comprising: A parallel transmission device that performs deskew between parallel lanes on the receiving side of a parallel optical transmission system,
Pattern detection means for detecting a frame synchronization information pattern of a transmission frame for each parallel lane;
A relative position detecting means for detecting a relative position of the head of the pattern detected for each parallel lane;
A delay amount determining means for determining a skew between the parallel lanes based on information on a relative position of a head of the pattern for each parallel lane;
Deskew means for determining a different delay amount for each parallel lane so as to compensate for the skew;
Have
The deskew means is:
When the number of parallels is n (n is an integer of 2 or more) and the number of interleave bits when performing serial-parallel conversion is m (m is a natural number), n × m is a divisor of the total number of bits in one frame of the transmission frame. A parallel transmission apparatus characterized by being other than the above.

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