Market trend of QR code
After the 1970s, the emergence of point-of-sales information systems (Point f sale, POS) and bar code (Barcode) solved the problem that traditional retailers did not have a good tool to count the sales and inventory of goods, and also make barcodes (Barcode). It has been popularized, but new problems have followed. The problem is that Barcode has a limited capacity, and Barcode itself can represent up to 20 words in English. The demand for "Code itself if it can contain more information" is increasing.
In 1994, DENSO WAVE INCORPORATED disclosed the QR code. The name of the QR code is derived from Quick Respo nse Code (QR Code, hereinafter referred to as QR code), also known as 2D Barcode. The QR code can hold a large capacity of about 7000 English digits. It can handle Chinese characters and the reading speed is more than 10 times faster than other encodings.
In 2002, mobile phones with two-dimensional code reading function began to go on the market. This kind of graphics containing many information attracted people. It is very convenient to visit mobile websites through reading, or get various offers, so the QR code quickly Popular in society. According to independent research firm Forrester Research, Inc., on average, 15% of consumers in the US, UK, France, and Germany are already using mobile phones to scan QR codes, and the percentage continues to grow.
LED display basic working principle
The LED display is a display composed of modules. The resolution of the length, width and size can be adjusted as required. However, the input source is fixed resolution. Generally, it is scaled by multimedia playback software, which makes the original image easy. The ratio changes.
The basic working principle of the LED display is line scanning, which illuminates the first line one after the other, and the second line, etc., from top to bottom, completely presents one frame of image, which is called static scanning. Considering the cost of the chip and the demand for the brightness of the light, the line scan is divided into 1~32 lines of scanning, but has the disadvantages of poor display effect and large brightness loss. The poor display performance includes a decrease in the refresh rate of the LED display.
Application limit of QR code on LED display
The QR code can guarantee the reading when the display of the QR code is clear and conforms to the standard. This can be via the LCD screen (E-mail), Internet (Website), etc. (Liquid Crystal Display, LCD) ) There will be no problems when displayed. When applied to applications such as magazine printing, product packaging, business cards, etc., the QR code provides error correction for the above applications to be dirty, damaged, etc., and can correct up to about 30% to ensure reliable settings. Read.
However, as the basic operation principle of the above-mentioned LED display line scanning, when the two-dimensional code is applied to the LED display screen, the following error conditions are likely to occur and cannot be read.
1. Position detection patterns
The QR code can be quickly read from any direction of 360°. The mystery lies in the three positioning patterns in the QR code. It can be explained that the QR code is not affected by the background pattern, and the reading is fast and stable. However, when the LED display performance is not good enough to achieve a high refresh rate (indoor LED display: refresh rate >500Hz / outdoor LED display: refresh rate >1000Hz), the three positioning patterns cannot be fully presented, so it cannot be effectively positioned. .
2. QR code whose modules are distorted
When the LED display is not effective, high gray scale (>14bit) cannot be realized, and when the screenless processor is reduced or enlarged, it is easy to cause the deformation of each code module, although the appearance is the same as the ordinary two-dimensional. The code is the same, but it's actually hard to read, and sometimes it can't be read.
Two-dimensional code application LED display example - "traditional switch type"
LED display screens can be divided into "traditional switch type" and "Scrambled PWM type" depending on the driver chip. Take the accumulation technology chip as an example. The "traditional switch type" driver chip includes JIX5020, MBI5024, etc. "Traditional switch type The driver chip selects three performances of "refresh rate", "grayscale" and "brightness of LED". For general application, in order to obtain high LED brightness, "high LED brightness mode" will be selected. Even the refresh rate and grayscale performance deteriorate (indoor LED display: brush rate frequency <500Hz / outdoor LED display: refresh rate <1000Hz). When the QR code is applied to the "High LED Light Brightness Mode", scanning with a mobile phone may result in an inability to scan correctly.
"Traditional Switch Type" Driver Chip - Low Grayscale, High Refresh (High Refresh Rate Mode)
The "traditional switch type" driver chip includes JIX5020, MBI5024, etc. The "traditional switch type" driver chip is practical, and the control system can select "high refresh rate mode". Take the 1:16 scan LED display as an example. The LED driver chip of the "traditional switch type" technology broadcasts a two-dimensional code picture (as shown in Figure 6, the original image on the lower left).
Most of the current two-dimensional codes have been designed with the background image. However, when using the "traditional switch type" driver chip to select the "two-dimensional code image" played in the "high refresh rate mode", the use of the mobile phone is in progress due to insufficient gray scale. When scanning,
1. The three positioning patterns and codes in the QR code are confused with the background color, which makes the QR code unable to be significantly reduced.
2. Due to insufficient representation of the color scale, the effect of the shooting and the background image appear serious color patches, which greatly reduces the advertising effect.
LTE CAT4/CAT6 Definition
The full name of LTE CAT is LTE UE-category, which is broken down to explain :LTE refers to 4G LTE network, UE refers to user equipment, and Category is translated as level. Smooth interpretation is the level of 4G LTE network transmission rate that user devices can support, which can also be said to be a technical standard for 4G network speed. Therefore, LTE CAT4/CAT6 means that the user device LTE network access capability level is 4 or 6.
Since the level is different, then its capabilities are certainly not the same, let's take a look at LTE CAT4/CAT6 affect what performance, respectively, what level. Simply put, LTE CAT affects the upper limit of 4G LTE uplink and downlink network speed, which is generally referred to as the maximum upload and download speed that a user device can achieve.
There are not only 4 and 6 levels in LTE CAT, but the table above is our list of currently known LTE CAT levels and the corresponding maximum transmission speed. Among them, LTE CAT4/CAT6 is also the current network transmission technology level of 4G mobile phones, while the faster CAT7 and CAT8 are still in the laboratory stage and have not been commercially developed.
Phones and chips that support LTE CAT4/CAT6
As far as the current 4G mobile phone market is concerned, most mobile phone products are CAT4 technology, and only a small number of new mobile phones use CAT6 technology, such as Huawei Honor 6, Samsung Galaxy S5 advanced version and LG G3 Cat6, and the concept of LTE CAT6 is proposed by Huawei Honor 6.
For the mobile phone LTE CAT4/CAT6 standard, it is directly linked to the mobile phone chip, or, if you know the processor of the mobile phone, you know which technology the mobile phone uses. For the current 4G mobile phone chips, only Huawei Kirin 920 and Qualcomm Snapdragon 805 processors for LTE CAT6, before this 4G chips are LTE CAT4, the future and Kirin 930, Qualcomm Snapdragon 808/810 will support LTE CAT6. Mediatek won't have LTE CAT6 chips until the second half of next year.
Qualcomm Snapdragon 805, 808, and 810 also support LTE CAT6
It is worth mentioning here that Qualcomm Snapdragon 805 and Kirin 920 are not the same in chip design, the LTE CAT6 baseband of Snapdragon 805 is an external Gobi MDM9x35, while Kirin 920 is a direct SoC integration, and the chip is integrated, this point Kirin 920 has ultra-high integration. It has certain advantages in power consumption and cost. As a leading international communications company, Huawei's strength can not be underestimated, but also the pride of our people.
The actual use value of LTE CAT6
Upload, download speed is our use of mobile Internet access the most concerned performance, but it should be clear that the LTECAT standard is the 4G transmission speed limit, and can not improve the transmission speed, in the operator's 4G network speed has not reached the next standard, simply raising the limit is meaningless. At present, the 4G networks of domestic operators are all LTE CAT4 standards, and the peak download speed is 150Mbps, but it is difficult to reach the upper limit of LTE CAT4 in practical applications, and even to reach 100Mbps is very difficult, so at this stage LTE CAT6 has no use value.
In terms of real life applications, LTE CAT6 is not as beautiful as we think. We can do a calculation, according to the formula 1MB/s=8Mbps, the maximum download speed of LTE CAT4 is 18.75MB/s, such a download speed, for 1080P video online playback has no pressure, even 4K online film source still can not occupy such a large bandwidth, So LTE CAT6 has no use either.
To sum up, LTE CAT6 does not have much use value at this stage, and the term is only a gimmick of manufacturers, until the operator 4G standard reaches LTE CAT6, I believe that LTE CAT6 equipment has long been popular. So as for whether the phone is LTE CAT4 or LTE CAT6, you don't have to care.
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