JP2007201927A - Error rate estimation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an error rate estimation device which allows a transmitting side to estimate error rate on the receiving side, efficiently retransmits data to raise throughput and a base station device equipped with the error rate estimation device in a communication system. <P>SOLUTION: The error rate estimation device estimates the error rate on the receiving side by counting the number of retransmitted data to the number of transmitted data and calculating the error rate by the transmitting side in an ARQ (automatic retransmission control) system for detecting errors of the transmitted data to request retransmission. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

 The present invention relates to a technical field of a communication system, and more specifically, an error rate estimation method for efficiently performing data retransmission using an ARQ scheme that detects a transmission data error and requests retransmission, and the error rate estimation. The present invention relates to a system using the method, an error rate estimation apparatus, and a base station apparatus including the error rate estimation apparatus.

Some conventional techniques disclose a circuit that estimates the BER from the spread of the phase distribution of received data on the side that has received data transmitted from the transmitting side. (For example, refer to Patent Document 1.) There is also a method in which a processor uses a valid signal-to-noise ratio value of a received frame as a pointer to a reference table and searches for a BER therefrom. (For example, refer to Patent Document 2.) A method of correcting an error rate using short-time dispersion of received data is disclosed. (For example, refer to Patent Document 3.)
Hereinafter, the prior art will be described with reference to FIG. In the prior art, a phase point distribution detection circuit 51 is provided, and the phase signal of the received data demodulated by the digital demodulator 50 is input to the phase distribution detection circuit 51, and the spread of the phase point distribution from the input phase signal. Is detected, the determination result of the spread of the input phase point is obtained, and a BER (bit error rate) corresponding to the determination result is selected from a memory.

 Further, the following three techniques are known as techniques related to the ARQ (Automatic Repeat Request) system. ARQ refers to retransmission processing in which data that cannot be recovered by error correction is automatically sent again.

 There are three typical ARQs. The first is a method of waiting for confirmation from the partner side every time one packet is sent in the Stop and Wait ARQ method.

 The second is the Go-Back-N ARQ method, which forwards several packets without confirmation. Each packet is numbered, and all of the packets after the packet in error are retransmitted. The third is the Selective Repeat ARQ method, which is almost the same as the Go-Back-N ARQ method, but retransmits only erroneous packets. The above three types of methods are generally known in wired data communication systems, wireless data communication systems, and communication systems that combine wired and wireless communication.

 The radio wave environment in a wireless data communication system is diverse, and even if it is a weak electric field, if the electric field strength is stable, the error rate is low and high-speed data transmission is possible.

However, even in a strong electric field, in an electric wave environment of multipath or frequency selective fading, the electric field strength fluctuates unstable and the error rate becomes high. As a result, since the number of data retransmissions increases, only low-speed data communication can be achieved.
JP 2002-237858 A (first page, FIG. 1) JP 2002-319926 A (first page, FIG. 1) JP-A-8-102727 (first page, FIG. 1)

In the prior art, the receiver side estimates the error rate of the signal received by the own station,
No device has been proposed for estimating the error rate on the receiving side on the transmitting side.

 The present invention has been made in view of the above problems, and an object of the present invention is to perform data retransmission control efficiently while estimating the error rate on the reception side on the transmission side.

  The present invention provides a wireless data communication system in which an error rate of a receiving side device (mobile station device) is estimated by a transmitting side device (base station device) and retransmitted quickly without waiting for a communication status notification from the mobile station. The purpose is to implement control and improve throughput.

  In order to achieve the above object, according to the present invention, at the time of data transmission, an error rate on the reception side is estimated from the number of retransmission data with respect to the number of transmission data in the transmission side device (base station device). In addition, the present invention is an error rate estimation device applicable to a wireless data communication system using an ARQ (automatic retransmission control) system during data transmission.

 Next, at the time of data transmission, the error rate estimation can also be realized by measuring the error rate of the reception data on the transmission side and estimating the error rate as the error rate on the reception side.

 The error rate uses BER (bit error rate), PER (packet error rate), or FER (frame error rate) as an index.

 In the data transmission, the means for checking the error of the received data on the transmission side uses a parity check or CRC (Cyclic Redundancy Code) check. If the error detection and the error can be corrected, the parity check or CRC The error rate after correcting the error by the check is used as the estimated error rate.

 Next, in the base station, there is an error rate estimation device comprising transmission packet number counting means, retransmission packet number counting means, and PER (packet error rate) estimation calculation means. In addition, the base station is an error rate estimation device including transmission frame number counting means, retransmission frame number counting means, and FER (frame error rate) estimation calculation means.

Finally, an error rate estimation device for sampling an error rate estimation value and predicting a change in which the error rate change rate is calculated using at least one sampling value. Is a base station apparatus.

 There are various error rates depending on the radio communication system. In the present invention, BER (bit error rate), FER (frame error rate), and PER (packet error rate) are used for error rate estimation, but the block error rate is a similar concept. It is obvious to those skilled in the art that the present invention can also be applied.

 According to the present invention configured as described above, the following effects can be obtained.

In a wireless data communication system, it is easy to quickly control various parameters related to data communication by estimating an error rate on the reception side on the transmission side.

  The details of the various parameters are described in Japanese Patent Application No. 2005-334748 by the present inventor. For example, when an error is detected in the CRC check on the data receiving side and the data is retransmitted from the transmitting side, the data is retransmitted at a lower transmission rate than the previous transmission, or the modulation method is stronger in error tolerance than the previous time. Throughput can be improved by resending or resending on a frequency channel different from the previous one.

 The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

First, an overall common data structure and the like will be described with reference to the drawings.

 FIG. 22 shows a basic data structure. The header 60 includes an address part 30 and a control part 31. The data 61 includes an information part 32 and an FCS (frame check sequence) 33. The information part 32 consists of fixed length data, and the FCS 33 shows an example using parity (even / odd) check. FIG. 19 shows a horizontal parity check, which is a type of parity check. 0 and 1 in the solid line frame represent data, and 0 and 1 in the dotted line frame represent horizontal parity. Since the top row is 0, 1, 1, 0, the parity is 0 (even).

 FIG. 23 shows an example in which the information part 36 and the FCS 37 are defined as a frame 63, and a CRC (Cyclic Redundancy Code) check is used for the FCS 37. For the CRC check, a generator polynomial F (x) = x ^ 16 + x ^ 12 + x ^ 5 + 1 is generally used.

 Next, FIG. 24 shows details of the packet structure. The packet 64 is divided into a header and a payload 65. The header 64 includes a reception side address 38, a transmission side address 39, a sequence number 40, an information length 41, an ACK 42 (or NAK), and an FCS 43. The sequence number 40 is added in order to correctly grasp the arrival order of the packets when the packets do not reach due to an error or loss. The information length 41 indicates the length of the information 44 of the payload 65. The length of the information 44 is an arbitrary length. The ACK 42 is a signal transmitted from the receiving side to the transmitting side when the information 44 of the payload 65 is correctly received by the FCS 45. NAK is not shown, but is a signal sent from the receiving side to the transmitting side when it cannot be received correctly.

 The FCS is generally added to both the header and payload. Frame structures and data structures are often covered by a single FCS.

 The Stop and Wait ARQ method used in the present invention is a method of waiting for confirmation from the other party each time one packet is sent. Each time an error occurs in the transmission path, the receiving side device sends a NAK signal to the transmitting side device.

 The Selective Repeat ARQ method is a method in which several packets are forwarded from the transmission side device to the reception side device without confirmation. Each packet is numbered, and the transmission side device has an error according to the NAK signal from the reception side device. This is a method of retransmitting only the packets that become.

 It is obvious to those skilled in the art that various structures such as a frame structure, a data structure, a packet structure, and the like exist depending on the use of the communication system.

 The best embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a functional block diagram showing signal flow and signal transmission / reception on the transmission side (base station) 1 in the first embodiment.

For simplicity, only the transmission system of the base station is shown. The base station has transmission data 2, transmission buffer 3,
It comprises a transmitter 4, transmission control means 8, and error rate estimation device 10. Further, the error rate estimation device 10 comprises retransmission data number counting means 5, transmission data number counting means 6, and error rate calculation means 7.

 According to the flowchart of FIG. 2, after the transmission data number counting step S1, the presence / absence of the number of retransmission data is determined at step S2, the number of retransmission data is counted at step S3, and the error rate is calculated at step S4. As described above, the error rate on the receiving side (mobile station) can be estimated on the base station side.

 FIG. 3 is a functional block diagram showing signal flow and signal transmission / reception on the transmission side (base station) 1 in the second embodiment.

For simplicity, only the transmission system of the base station is shown. The base station has transmission data 2, transmission buffer 3,
It comprises a transmitter 4, transmission control means 8, and error rate estimation device 10. Further, the error rate estimating apparatus 10 comprises a retransmission frame number counting means 11, a transmission frame number counting means 12, and an error rate calculating means 7.

 According to the flowchart of FIG. 4, after the transmission frame number counting step S5, the presence or absence of the number of retransmission frames is determined at step S6, the number of retransmission frames is counted at step S7, and the error rate is calculated at step S8. As described above, the error rate on the receiving side (mobile station) can be estimated on the base station side.

 FIG. 5 is a functional block diagram showing signal flow and signal transmission / reception on the transmission side (base station) 1 in the third embodiment.

For simplicity, only the transmission system of the base station is shown. The base station has transmission data 2, transmission buffer 3,
It comprises a transmitter 4, transmission control means 8, and error rate estimation device 10. Further, the error rate estimating apparatus 10 comprises a retransmission packet number counting means 14, a transmission packet number counting means 15, and an error rate calculating means 7.

 According to the flowchart of FIG. 6, after the transmission packet number counting step S9, the presence / absence of the number of retransmission packets is determined in step S10, the number of retransmission packets is counted in step S11, and the error rate is calculated in step S12. As described above, the error rate on the receiving side (mobile station) can be estimated on the base station side.

 Next, an actual error rate change will be described using calculation examples with reference to FIGS. 7 to 9 and FIGS. 10 to 12. FIG. This description is based on the Stop and Wait ARQ (automatic retransmission control) method, and FIGS. 7 and 10, FIGS. 8 and 11, and FIGS. 9 and 12 correspond to each other.

 First, FIG. 7 shows a state in which data is sent from the transmitting side to the receiving side, data 1 is sent correctly, and data 2 is retransmitted because an error is detected and cannot be corrected on the receiving side.

 As the transmission path, any one of a wired transmission path, a wireless transmission path, and a combination of a wired transmission path and a wireless transmission path is used according to the communication system.

Regarding the first embodiment, the number of data at that time is shown in FIG. 10 and is calculated under three conditions of A, B, and C. BER (bit error rate) of condition A. The unit of the number of data is bits. Condition A is when the length of the information part is fixed.

Conditions B and C are not normally used, but are described in comparison with the packet communication in FIG.

 In condition A in FIG. 10, data 1 is 100 bits, data 2 is 100 bits, retransmission of data 2 is 100 bits, and data 3 is 100 bits. At this time, the total number of transmission data is 400 bits, the number of retransmission data is 100 bits, and BER = (100/400) × 100 = 25%.

 In condition B in FIG. 10, data 1 is 100 bits, data 2 is 50 bits, retransmission of data 2 is 50 bits, and data 3 is 100 bits. At this time, the total number of transmission data is 300 bits, the number of retransmission data is 50 bits, and BER = (50/300) × 100 = 16.7%.

 In condition C of FIG. 10, data 1 is 100 bits, packet 2 is 50 bits, retransmission of packet 2 is 50 bits, and packet 3 is 50 bits. At this time, the total number of transmission data is 250 bits, the number of retransmission data is 50 bits, and BER = (50/250) × 100 = 20%.

 Next, a second embodiment will be described. FIG. 8 shows a state in which a frame is sent from the transmission side to the reception side, frame 1 is sent correctly, and frame 2 is retransmitted because an error is detected and cannot be corrected on the reception side.

 The number of data at that time is shown in FIG. 11 and is calculated under the three conditions of A, B, and C. FER (frame error rate) of condition A. The unit of the number of data is bits. Condition A is when the length of the information part is fixed. Conditions B and C are not usually used, but are described for comparison with the packet of FIG.

 In condition A of FIG. 11, frame 1 is 256 bits, frame 2 is 256 bits, retransmission of frame 2 is 256 bits, and frame 3 is 256 bits. At this time, the total number of transmission data is 1024 bits and the number of retransmission data is 256 bits. FER = (1/4) × 100 = 25%.

 In condition B in FIG. 11, frame 1 is 256 bits, frame 2 is 128 bits, retransmission of frame 2 is 128 bits, and frame 3 is 256 bits. At this time, the total number of transmission data is 768 bits and the number of retransmission data is 128 bits. FER = (1/4) × 100 = 25%.

 In condition C of FIG. 11, frame 1 is 256 bits, frame 2 is 128 bits, retransmission of frame 2 is 128 bits, and frame 3 is 128 bits. At this time, the total number of transmission data is 640 bits and the number of retransmission data is 128 bits. FER = (1/4) × 100 = 25%.

 Next, a third embodiment will be described. FIG. 9 shows a state in which a packet is sent from the transmission side to the reception side, packet 1 is sent correctly, and an error is detected in packet 2, and packet 2 is retransmitted because it cannot be corrected on the reception side.

 The number of data at that time is shown in FIG. 12, and is calculated under the three conditions of A, B, and C. This is the PER (packet error rate) of condition A. The unit of the number of data is bits. Condition A is when the length of the information part is fixed.

 Condition A in FIG. 12 is that packet 1 is 64 bits, packet 2 is 64 bits, retransmission of packet 2 is 64 bits, and packet 3 is 64 bits. At this time, the total number of transmission data is 256 bits and the number of retransmission data is 64 bits. PER = (1/4) × 100 = 25%.

 In condition B of FIG. 12, packet 1 is 64 bits, packet 2 is 32 bits, packet 2 is retransmitted 32 bits, and packet 3 is 64 bits. At this time, the total number of transmission data is 192 bits and the number of retransmission data is 32 bits. PER = (1/4) × 100 = 25%.

 Condition C in FIG. 12 is that packet 1 is 64 bits, packet 2 is 32 bits, packet 2 is retransmitted 32 bits, and packet 3 is 32 bits. At this time, the total number of transmission data is 160 bits, the number of retransmission data is 32 bits, and PER = (1/4) × 100 = 25%.

 When calculated based on the number of data, the error rate changes to 25%, 16.7%, and 20%, but when calculated based on the number of frames and packets, the number of transmitted data and the number of retransmitted data differ. However, the error rates may all be the same (25% in this calculation example).

 Next, an actual error rate change will be described with reference to FIGS. 13 to 18 using calculation examples. This description is based on the method of Selective Repeat ARQ (automatic retransmission control), and FIGS. 13 and 14, FIGS. 15 and 16, and FIGS. 17 and 18 correspond to each other.

 First, a fourth embodiment will be described with reference to FIGS. 13 and 14.

 Data is continuously transmitted from the transmission side to the reception side, and the first four sets (up to the dotted line in FIG. 13) are transmitted together. An error that cannot be corrected in data 2 occurs on the transmission path, and the NAK is transmitted from the reception side. Only 2 are requested for retransmission. In this example, data 2 is retransmitted after the dotted line, and data 5 and data 6 are subsequently transmitted.

 FIG. 14 shows the bit error rate calculated under the three conditions A, B, and C. Condition A is an example in which the first four sets of data are all 100 bits. Since a 100-bit error has occurred in data 2, BER = (100/700) × 100 = 14.3%.

 Condition B is an example in which the first four sets of data are all 50 bits, data 2 has a 50-bit error, 50 bits are retransmitted, and data 5 and data 6 are each transmitted 100 bits. BER = (50/450) × 100 = 11.1%.

 Condition C is that data 1 and data 2 are transmitted by 100 bits, and data 3 and data 4 are transmitted by 50 bits. The error in the transmission path is 50 bits in data 2.

BER = (100/600) × 100 = 16.7%.

 A fifth embodiment will be described with reference to FIGS. 15 and 16. Frames are continuously transmitted from the transmission side to the reception side, and the first four sets (up to the dotted line in FIG. 15) are transmitted together. An error that cannot be corrected in frame 2 occurs on the transmission path, and a NAK is transmitted from the reception side. Only 2 are requested for retransmission. In this example, frame 2 is retransmitted after the dotted line, and frames 5 and 6 are subsequently transmitted.

 FIG. 16 shows the frame error rate calculated under the three conditions A, B, and C. Condition A is an example in which the first four sets of frames are all 256 bits. Since a 256-bit error has occurred in frame 2, FER = (1/7) × 100 = 14.3%.

 Condition B is an example in which the first four sets of frames are all 128 bits, a 128-bit error occurs in frame 2, 128 bits are retransmitted, and 256 bits are transmitted in frame 5 and frame 6, respectively. FER = (1/7) × 100 = 14.3%.

 Condition C is that frame 1 and frame 2 are transmitted in 256 bits, and frame 3 and frame 4 are transmitted in 128 bits. The error in the transmission path is 256 bits in frame 2. FER = (1/7) × 100 = 14.3%.

 A sixth embodiment will be described with reference to FIGS. 17 and 18. Packets are continuously transmitted from the transmission side to the reception side, and the first four sets (up to the dotted line in FIG. 17) are transmitted collectively. An error that cannot be corrected in the packet 2 occurs on the transmission path, and the NAK is transmitted from the reception side. Only 2 are requested for retransmission. In this example, packet 2 is retransmitted after the dotted line, and packets 5 and 6 are subsequently transmitted.

 FIG. 18 shows the packet error rate calculated under the three conditions A, B, and C. Condition A is an example in which the first four sets of packets are all 64 bits. Since a 64-bit error has occurred in packet 2, PER = (1/7) × 100 = 14.3%.

 Condition B is an example in which the first four sets of packets are all 32 bits, a 32-bit error occurs in packet 2, 32 bits are retransmitted, and 64 bits are transmitted in packet 5 and packet 6, respectively. PER = (1/7) × 100 = 14.3%.

 Condition C is that packet 1 and packet 2 are transmitted in 64 bits, and packet 3 and packet 4 are transmitted in 32 bits. The error in the transmission path is 64 bits in packet 2.

 PER = (1/7) × 100 = 14.3%.

Next, a seventh embodiment will be described. FIG. 20 is obtained by adding a sampling means 18 and an error rate estimated value change rate calculating means 17 to the error rate estimating apparatus of FIG. The change rate calculating means 17 makes it possible to predict a change in error rate, and appropriate transmission parameters (data rate, modulation method, information length, transmission from the transmission side (base station) 1 to the reception side (mobile station), Transmission power etc.) can be selected.

 Hereinafter, the calculation in the error rate estimation apparatus will be described. When the estimated error rate at time T1 is E1, and the estimated error rate at time T2 is E2, the estimated error rate E at time T can be expressed by the following equation. The equation of the straight line passing through the two points is E = ((E2-E1) / (T2-T1)) T + (E1T2-E2T1). If the combinations of (T1, E1) and (T2, E2) are estimated one after another, the combinations of (T, E) can also be calculated one after another. The actual value of T2-T1 is suitably about 0.5 to 5 seconds.

 Since data transmission by packet is discontinuous, it is difficult for the transmitting side (base station) to quickly grasp the mobile environment / radio wave environment where the receiving side (mobile station) is located. By providing the change rate calculation means 17 in the base station 1, the base station 1 becomes more effective.

   FIG. 21 is a flowchart showing the flow of processing. According to the flowchart of FIG. 21, after the transmission data number counting step S13, the presence or absence of the number of retransmission data is determined at step S14, the number of retransmission data is counted at step S15, and the error rate is calculated at step S16. Next, the error rate is sampled in step 17, and the error rate change rate is calculated in step S18. By calculating the rate of change of the error rate, it is possible to estimate a change in the radio wave environment on the receiving side, and it is possible to quickly perform retransmission control and improve throughput.

 Although the present invention has been mainly described in the wireless data communication system, it can also be applied to a wired data communication system, an optical data communication system, and the like.

FIG. 2 is a functional block diagram of an error rate estimation apparatus using a base station and the number of data in the first embodiment of the present invention. 6 is a flowchart of calculation of an estimated error rate using the number of data in the first embodiment of the present invention. The functional block diagram of the error rate estimation apparatus using the base station and frame number in 2nd Embodiment of this invention. It is a flowchart of the estimation error rate calculation using the frame number in 2nd Embodiment of this invention. The functional block diagram of the error rate estimation apparatus using the base station and packet number in 3rd Embodiment of this invention. It is a flowchart of the estimation error rate calculation using the packet number in 3rd Embodiment of this invention. It is a data transition diagram for demonstrating 1st Embodiment of this invention. It is a frame transition diagram for demonstrating 2nd Embodiment of this invention. It is a packet transition diagram for demonstrating 3rd Embodiment of this invention. It is a figure regarding BER for explaining a 1st embodiment of the present invention. It is a figure regarding FER for demonstrating 2nd Embodiment of this invention. It is a figure regarding PER for demonstrating 3rd Embodiment of this invention. It is a data transition diagram for demonstrating 4th Embodiment of this invention. It is a figure regarding BER for explaining a 4th embodiment of the present invention. It is a frame transition diagram for demonstrating 5th Embodiment of this invention. It is a figure regarding FER for demonstrating 5th Embodiment of this invention. It is a packet transition diagram for demonstrating 6th Embodiment of this invention. It is the figure regarding PER for demonstrating 6th Embodiment of this invention. It is explanatory drawing of the parity check common to the whole of this invention. It is a figure of the base station which comprised the error rate change rate calculating means of 7th Embodiment of this invention. It is a flowchart of the base station which comprised the error rate change rate calculating means of 7th Embodiment of this invention. It is explanatory drawing of the data structure common to the whole of this invention. It is explanatory drawing of the frame structure common to the whole of this invention. It is a detailed explanatory view of a packet structure common to all of the present invention. It is a flowchart which shows the conventional Example.

Explanation of symbols

1: Transmission side device (base station device)
2: Transmission data 3: Transmission buffer 4: Transmitter 5: Retransmission data number counting means 6: Transmission data number counting means 7: Error rate calculation means 8: Transmission control means 9: Antennas 10, 13, 16, 18: Error rate Estimating device 11: Transmission data number counting means 12: Retransmission data number counting means 13: Transmission data number counting means 17: Error rate change rate calculating means 18: Error rate sampling means 30, 34: Address part 31, 35: Control part 32 36: Information parts 33, 37, 43, 45: FCS (frame check sequence)
44: Information section 50: Digital demodulator 51: Phase point distribution detection circuit 52: Estimation circuit

Claims (6)

In an error rate estimation apparatus that estimates an error rate in a transmission side apparatus in a communication system, every time a predetermined number of transmission data is transmitted, the transmission predetermined number of data is used as a denominator, based on a request method from a reception side apparatus. An error rate estimation apparatus characterized by estimating a calculation result obtained by dividing the number of retransmitted data as a numerator as an error rate at a receiving apparatus. The error rate estimation device according to claim 1, wherein a request method from a receiving side device operates in a Stop and Wait ARQ method or a Selective Repeat ARQ method. The error rate estimation apparatus according to claim 1, further comprising: a transmission data number counting unit, a retransmission data number counting unit, and an error rate calculation unit. The error rate estimation apparatus according to claim 1, further comprising: a transmission frame number counting unit, a retransmission frame number counting unit, and an error rate calculation unit. The error rate estimation apparatus according to claim 1, further comprising: a transmission packet number counting unit, a retransmission packet number counting unit, and an error rate calculation unit. 2. The error rate estimation apparatus according to claim 1, further comprising an error rate sampling unit and an error rate change rate calculation unit.

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