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Since the birth of modern communication technology, achieving more reliable communication at lower cost (signal power, signal bandwidth, etc.) has been a core issue in the field of information technology. Channel coding technology is one of the core technologies of the physical layer of wireless communication systems. Its main purpose is to enable digital signals to be reliably transmitted. The channel coding technology corrects the errors generated during the transmission by adding additional check bits on the basis of the transmitted information sequence and using a certain decoding technique at the receiving end to correct the errors generated during the transmission. receive.
Coding and modulation are the most esoteric parts of wireless communication technology and are known as top-level communication technologies. The channel codec is located at the physical layer location in the basic communication framework, and its performance improvement will directly improve the network coverage and user transmission rate. At the 87th meeting of RAN1 (Wireless Physical Layer) of 3GPP, the Huawei-based Polar code was adopted as the control scheme of the control channel, and the LDPC code dominated by Qualcomm was used as the coding scheme of the data channel.
What we should remember is Polar Code, the polarization code. At 0:45 am on November 17, 2016, in the discussion of the 5G short-code scheme of the 87th meeting of 3GPP RAN1, after many hardships, China Huawei's Polar Code scheme finally defeated the powers and became 5G control channel eMBB scene coding final scheme.
The Polar code eventually becomes the coding scheme for the control channel uplink and downlink. The uplink and downlink short code schemes of the data channel belong to the high-pass LDPC code. Polar Code is the first channel coding method known to man that can be strictly proved to reach the Shannon limit. The error correction performance exceeds the widely used Turbo code and LDPC code, and finally becomes the channel control coding scheme. Huawei and the Australian operator Optus completed a 5G network test, using a 73GHz ultra-high frequency band to achieve a transmission rate of up to 35Gbps.
This is the first time that a Chinese company has entered the field of basic communication framework agreements. Compared with the past 2G, 3G, and 4G eras, its greatest significance is to increase the voice of Chinese companies in the global communications field.
What is the polar code polarization codeIn order to achieve reliable signal transmission, coders have proposed a variety of error correction code technologies such as code (RS code), convolutional code, Turbo code, etc. in the past more than half a century, and have achieved in various communication systems. A wide range of applications. However, all the practical coding methods in the past failed to reach the capacity limit of channel transmission given by Shannon in 1948 (also known as Shannon). In 2008, at the International Information Theory ISIT meeting, Arikan first proposed the concept of channel polarization. Based on this theory, he gave the first channel coding method known to man that can be strictly proved to achieve channel capacity, and named it as pole. Polar Code. The Polar code has a clear and simple encoding and decoding algorithm. Through the continuous efforts of channel coding scholars, the error correction performance that current Polar codes can achieve exceeds the currently widely used Turbo codes and LDPC codes.
The polar code was first proposed by Professor Erdal Arikan of Bilken University in Turkey in 2008. The paper theoretically proves for the first time that the polarization code is in the binary input symmetric discrete memoryless channel. It can "reach" Shannon capacity and has low coding and decoding complexity. In a sense, the polarization code "theoretically" solves the problem that has been solved in the field of information theory and coding in the past 60 years.
Although the theory of polarization codes is very beautiful, its actual performance is not ideal from its appearance ("theoretical" refers to the performance when the code length tends to infinity; "actual" refers to the finite length code length). However, in recent years, the actual construction method of the polarization code and the list continuous cancellaTIon decoding technology, the overall performance of the polarization code has achieved the most advanced channel coding technology in some application scenarios. The same or better performance of the Turbo code and the low density parity check code (LDPC code).
Here we will talk about the three main points of the 2*2 matrix as the core polarization code mentioned by Professor Arikan in the invention of the polarization code: (The following three points, or the core innovation of the polarization code in channel coding) .)
1. Upper Convergence Convergence: A channel transformation is constructed. If the transformation is recursively and the transformation result is randomly selected, the Bhattacharya parameter of the transformation result constitutes a stochastic process. Arikan proves that this stochastic process is a captain, and then uses the random variable sequence as in the upper cap to converge and converge as expected, proving that the convergence result is a binary random variable. It is proved that the probability that the binary random variable is 0 is the binary discrete symmetric memoryless channel capacity I. It can be inferred that when the code length n is infinite, the undistorted subchannel with about nI Barth's parameters approximating 0 can be selected, which proves The channel polarization is that the channel capacity is reachable. FoundaTIon and trends inside the polar chapter, there is another proof method, the first class.
2. SC decoding: A good decoding algorithm is needed to have a good code. Shannon and Gallager have proved that most of the codes are good codes, only the lack of good polynomial complexity decoding algorithms. Arikan uses the recursive structure in the channel transform, first translating the result of the "bad" channel, and even freezing the "bad" channel to a decoding result of 0 (reduced bit rate), and then as the basis for "good" channel decoding. The complexity is super linear, very Nice.
Due to the superiority of both theory and practice, the research of polarization codes has become a hot research in the field of information theory and coding and communication. At present, Huawei's positive force pushes the polarization code into the 5G mobile communication standard.
The Polar Code code promoted by Huawei was adopted by 3GPP as the 5GeMBB control channel standard solution, which is an important progress in the research and standardization of 5G mobile communication technology in China.
Standard = voiceWhoever mastered the standard technology has the right to speak and the commanding heights. 30 years ago, Qualcomm used military CDMA technology for civilian communications, launched the IS-95 standard, and became the second generation mobile communication system competing with European GSM. This is the 2G era we often say.
In the 2G era, GSM achieved victory, but Qualcomm's Viterbi decoding algorithm has led the industry to believe that CDMA represents the development direction of wireless communication technology. Therefore, in the 3G era, WCDMA, CDMA2000 and TD-SCDMA all adopt CDMA technology. Today, most of Qualcomm's profits come from patent licenses based on this technology standard.
In the 3G era, although China independently developed TD-SCDMA, it is still technically incomparable. Even in the 4G era, China's TD-LTE has made a certain breakthrough, but its core long code encoding Turbo code and short code tail biting convolutional code are not original Chinese technologies. This led to GM’s infringement of Chinese companies’ infringement and additional patent fees.
The first year of the 5G standard in 2016, and the coexistence of multiple standards in the 3G and 4G eras, 5G is expected to achieve global unified standards, but the right to speak in the standard is bound to compete, it depends on the degree of participation in each link. And the use and confirmation of more technologies by the 5G standard will inevitably allow the company to have more patent reserves in the future.
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