KR-20260066723-A - Communication receiver test using periodic signals

Abstract

The system (100) includes a testing transmitter (102) comprising a pseudo-random number bit sequence (PRBS) generator and a signal generation circuit. The PRBS generator is configured to generate a PRBS. The signal generation circuit is configured to generate a test signal comprising a repetition of a truncated portion of the PRBS, wherein the period of the repetition is shorter than the period of the PRBS.

Inventors

• 나디리 오어
• 안홀트 미카

Assignees

• 레팀 인코포레이티드

Dates

Publication Date

20260512

Application Date

20240904

Priority Date

20230907

Claims (16)

1. As a system, It includes a testing transmitter, and the testing transmitter is: A PRBS generator configured to generate a pseudo-random bit sequence (PRBS); and A system comprising a signal generation circuit configured to generate a test signal including a repetition of the cut portion of the above PRBS, wherein the period of the repetition is shorter than the period of the above PRBS.
2. A system according to claim 1, characterized in that when generating a test signal, the signal generation circuit (102) is configured to generate (i) a repetition of a truncated portion of a PRBS that serves as a payload and (ii) a packet sequence including additional symbols.
3. In paragraph 1 or 2, A receiver circuit configured to receive and decode a test signal; A system characterized by further including a testing circuit configured to generate a reference signal identical to a repetition of a cut portion of PRBS and to evaluate the performance of a receiver circuit by comparing the reference signal with a test signal decoded by a receiver circuit.
4. In paragraph 3, A system characterized in that the testing circuit of the receiver is configured to generate a reference signal composed of a repetition of the cut portion of the PRBS.
5. A system according to paragraph 3, characterized in that the test signal generated by the transmitter is configured such that additional symbols are inserted between repetitions of the truncated portion of the PRBS, and the testing circuit of the receiver is configured to exclude the additional symbols from comparison with the reference signal.
6. As a testing transmitter, An encoder configured to encode an input data sequence into an unterminated forward error correction (FEC) code; and A test sequence generation circuit configured to generate a periodic FEC cycle test sequence of a preset periodic length that forms a valid unterminated encoded data stream according to the FEC-coded portion of the PRBS when repeatedly encoded by an encoder; and A testing transmitter characterized by including a test sequence generation circuit configured to generate a periodic FEC cyclic test sequence having a preset period length, which forms a valid unterminated encoded data stream according to the FEC-coded portion of the PRBS when repeatedly encoded by an encoder.
7. A testing transmitter according to claim 6, characterized in that each cycle of the FEC cyclic test sequence starts in the same state of the encoder.
8. A testing transmitter according to claim 6 or 7, characterized in that the test sequence generation circuit is configured to insert a cyclic redundancy check (CRC) code within the FEC cyclic test sequence.
9. As a method for generating a test signal, A step of generating a pseudo-random bit sequence (PRBS); A test signal generation method comprising the step of generating a test signal configured by repeating a cut portion of PRBS, wherein the repetition period generates a test signal shorter than the period of PRBS.
10. A method for generating a test signal according to claim 9, wherein the step of generating the test signal comprises (i) a repetition of a truncated portion of a PRBS serving as a payload, and (ii) a step of generating a sequence of packets including additional symbols.
11. In paragraph 9 or 10, in the receiver subject to test, Step of receiving and decoding a test signal; A step of generating a reference signal identical to the repetition of the truncated portion of PRBS; A test signal generation method characterized by further including a step of evaluating the performance of a receiver circuit by comparing a test signal decoded by a receiver with a reference signal.
12. A test signal generation method according to claim 11, characterized in that the reference signal generation includes the step of generating a repetition of the truncated portion of the PRBS.
13. In Paragraph 11, The test signal includes additional symbols inserted between repetitions of the truncated portion of the PRBS; A test signal generation method characterized by including a step of excluding additional symbols when comparing with the above reference signal.
14. As a method for generating a test signal, A step of operating an encoder that encodes an input data sequence into an unterminated Forward Error Correction (FEC) code; A test signal generation method characterized by including the step of generating a periodic FEC cycle test sequence of a preset period length, which forms a valid unterminated data stream according to an FEC code when repeatedly encoded by an encoder.
15. A test signal generation method according to claim 14, characterized in that each cycle of the FEC cyclic test sequence starts in the same state of the encoder.
16. In paragraph 14 or 15, A test signal generation method characterized by including the step of inserting a Cyclic Redundancy Check (CRC) code into the FEC cyclic test sequence generation.

Description

Communication receiver test using periodic signals (Refer to related application) This application claims priority to U.S. provisional patent application No. 63/581,005 filed on September 7, 2023, the contents of which are incorporated herein by reference. (Field of Invention) The present invention generally relates to a communication system, and in particular to the testing of a communication receiver. Digital communication systems, particularly digital communication receivers, present significant testing challenges. Background knowledge on testing digital communication systems can be found in Lai, R.’s “Research on Communication Protocol Testing (Journal of Systems and Software, 62(1), 21-46 (2002)), which includes a literature review and focuses on five areas: test sequence generation methods, test coverage, error models and prediction, test tools, and experience reports. Additionally, further background knowledge on communication system testing can be found in "BER Testing of Communication Interfaces" by Yongquan Fan and Zilic, Z. (IEEE Transactions on Instrumentation and Measurement, 57(5) (2008)). The authors propose a multi-purpose bit error rate (BER) testing method to characterize the quality of communication interfaces. This paper presents a BER testing method for Field Programmable Gate Arrays (FPGAs) in both the design and evaluation phases. This method consists of a BER Tester (BERT) core and a new additive white Gaussian noise (AWGN) generator core. Furthermore, the authors propose a pipeline structure that achieves a speed improvement of more than four times by utilizing the central limit theorem. FIG. 1 is a block diagram schematically showing a test system according to an embodiment of the present invention. FIG. 2 is a block diagram schematically showing an OIF 800ZR testing transmitter in Mode A configuration according to an embodiment of the present invention. FIG. 3 is a block diagram schematically showing an OIF 400ZR testing transmitter in Mode B configuration according to an embodiment of the present invention. FIG. 4 is a flowchart schematically illustrating a method for generating a valid periodic test sequence according to an embodiment of the present invention. FIG. 5a is a flowchart schematically illustrating a method for testing a communication test target receiver (RUT) in a first test mode according to an embodiment of the present invention. FIG. 5b is a flowchart schematically illustrating a method for testing a communication RUT in a second test mode according to an embodiment of the present invention. (outline) Modern high-speed digital communication systems are often complex and difficult to test. While the following primarily refers to optical (fiber optic) communication systems, the present invention is not limited to optical communication systems and can be applied to other suitable communication systems using electrical, optical, and electromagnetic signals. In recent years, various proprietary systems and standards for fiber optic communication have emerged. For example, there are the Optical Internet Working Forum (OIF) standards 400ZR/800ZR, openZR+, and OpenROADM. For example, the 400ZR standard uses QAM16 to specify a link range of 80 kilometers without amplification and 120 kilometers with amplification at transmission rates of 60 to 68 Gbaud. For forward error correction (FEC), the 400ZR standard supports a connection-oriented FEC (CFEC) method that combines internal and external FEC codes to improve performance over standard FEC codes. The 800ZR is similar but faster because it uses QAM16 modulation. To test and calibrate communication equipment, each part of the modem must be tested with various signals. On the receiving (Rx) side, testing can be performed using test signals from a compatible transmitter or specialized test equipment. Testing and calibration using test equipment is desirable in that it ensures high quality of transmitted signals and allows for the insertion of incomplete signals or errors to suit the test purpose. A disadvantage of using test equipment is that the transmission distance is generally limited, and therefore, it may be necessary to use periodic signals that are not properly supported by some communication standards. Embodiments of the invention disclosed herein provide an apparatus and method for testing a communication receiver (receiver under test, or RUT) using multiple instances of a relatively short periodic test signal. In one embodiment, the testing transmitter is configured to operate in one of two modes: a first mode (Mode-A) and a second mode (Mode-B). In the embodiment disclosed below, Mode A is used to test the demodulator portion of the RUT using a truncated pseudo-random bit sequence (PRBS) input to the modulator portion of the testing transmitter. The RUT is modified to compare the output of the RUT demodulator with the truncated PRBS sequence and output a mismatch (if any). In another embodiment disclosed below, M