qam modulation

become a problem to be solved in the communication field. Cognitive Radio (CR) is an intelligent spectrum sharing technology. It can effectively improve the utilization of spectrum resources by making secondary use of the authorized spectrum. It has become a hot topic in the communication field. In the 802.11 Wireless LAN [1], 802.16 MAN [2] and 3G mobile communication networks [3], Cognitive Radio technology has been applied to increase the system capacity, and began to study the application o

In the previous article, we introduced the principle of the HART protocol of SYM20C15. Here we will mainly explain the working process of SYM20C15. We know that the HART protocol is a communication protocol with modulation and demodulation characteristics. Then we will divide it into the modulation part and the demodulation part to analyze the two. SYM20C15 Workflow SYM20C15 is a low-power modem designed to

Coding2.1 Digital Sound Signal(1). Frequency of Sound:　　　　(2). Sampling--Quantization--code:Sampling frequency: The Nyquist theory states that the sampling frequency should not be less than twice times the maximum frequency of the sound signal, so that the voice can be restored to the original sound as a digital expression, which is called lossless digitization (lossless digitization) Sampling accuracy: Number of bits per sound sample (bps)Amount of data (Bytes/sec) = (sampling frequency (Hz

usage would be confusing. Mute to (temporarily) force volume to is zero, independently from the usual volume controls. Pcm Pulse Code modulation, the most common low-level encoding of digital audio. The audio signal is sampled at a regular interval, called the sample rate, and then quantized to discrete values within a Particular range depending on the bit depth. For example, for 16-bit PCM, the sample values is integers between-32768 and

, it is quite far from the high-definition digital TV.High Definition Digital TV (HDTV) is the future development direction. By now, all analog TVs have been eliminated, and TV Station shooting, recording, and editing devices have also been replaced, what people will see on TV screens will be high-definition TV pictures and more functions. HDTV will bring TV into a new era.Someone asked if the current digital set-top box receives a high-definition digital TV signal? No. After a digital set-top b

The G optical transmission technology based on digital coherent receiving PM-QPSK modulation has a milestone in the long-distance optical transmission technology history. The error correction coding technology can be used to further improve the system performance when modulation, detection, balancing, and multiplexing cannot meet the system transmission performance requirements. To achieve the current trans

sending end. It is typical, for example, a modulation; however, many PCs now use built-in modem. Receiver: receives a signal from the transmission system and converts it to the information processed by the target device. A typical device is a modem. The analog signal from the transmission line is demodulated to extract information, restores the digital bit stream generated by the sender. End point: the end device obtains the sent digital bit stream f

time, and the other device can receive the data. However, the communication parties send and receive messages in turn in accordance with certain communication protocols.3. Full Duplex ModeBoth parties are allowed to send and receive messages at the same time. In this case, device A can receive messages at the same time as Device B. The full duplex mode is equivalent to combining two tickets in the opposite direction. Therefore, it requires two data transmission lines. In computer serial communi

addition, compared with the wireless cellular network of mobile communication, this fixed wireless network shows its superiority in terms of data transmission speed, access reliability, and spectrum usage efficiency. Generally, FWA is designed based on line-of-sight transmission LOS, that is, the radio wave transmission between each user and the Access Point BTS is based on line-of-sight transmission LOS. Each user is equipped with a precisely oriented, narrow, and fine-beam antenna with a high

. The most common Ethernet standard in a data center is 1000Base-T or 1000Base-TX, some data centers have started to adopt 10G Base-T. Therefore, this article will mainly study the relationship between these three standards and off-line crosstalk. This article will begin with the three standard modulation methods, analyze their ultimate signal-to-noise ratio, and then compare the signal-to-noise ratio that can be achieved by the transmission media, fi

HSDPA is a high speed downlink packet access, it is 3GPP in the R5 protocol in order to meet the demand of the upper/lower data business is a modulation and demodulation algorithm, which can not change the already built WCDMA network structure, the downlink data service rate to 10Mbps. This technology is an important technology to improve the downlink capacity and data service rate in the later stage of WCDMA network construction. The application of H

speed of static difference slightly larger. (3) Limited unipolar mode, in addition to the unipolar modulation, the energy-saving braking path is limited. Advantages: The control circuit is simple, if connected to the H-bridge mode, can also turn positive and negative. Disadvantages: Can not brake, not energy braking, the load exceeds the set speed can not provide reverse torque. Speed adjustment static difference is big, the speed performance is ve

There is types of frame structure in the LTE standard, type 1 and type 2. Type 1 uses Frequency Division duplexing (Uplink and downlink separated by Frequency), and TDD uses time division Duplexin G (Uplink and downlink separated in time). This overview covers both LTE FDD Type 1 signals and LTE TDD type 2 signals described in the standard documents listed in The About Opts BHD and bhe:lte modulation analysis topic. This overview isn't a exhaustive de

systems that can be upgraded from cdmaone to smooth. The route of its evolution is Cdmaone--cdma20001x--cdma20001xev. Another mainstream of the third generation of communication technology is the second generation of GSM standard developed by the WCDMA technology, because GSM uses TDMA (time division Multiple Access) modulation mode, and WCDMA uses CDMA (Code Division Multiple Access) modulation, its air c

Hue Change and type The change of tone, namely tonal conversion, is an important subject in the design of color selection in art design, with many kinds of varieties and designs, and the form of modulation is generally fixed deformation adjustment, fixed-color modulation, setting color modulation and so on. 1, fixed deformation adjustment The essence is to mai

digital signal into an analog signal, and the receiver uses the demodulator to convert the received analog signal into a digital signal, which is the modulation and demodulation of the signal.The device that implements the modulation and demodulation tasks is called a modem. When using the frequency band transmission, each side of the communication is connected to a modem, and the digital signal is sent to

transmission rate is equal to twice times of the bandwidth to ensure the non-interference between the front and rear code elements. Rmax (maximum information transfer rate) = B*2 B: Bandwidth B. Noise (bandwidth and signal-to-noise ratio) Calculate with Shannon formula C: (channel capacity) channel error-free maximum information transfer rate, that is, rmax (information transfer rate maximum) B: Bandwidth S/N: Signal-to-noise ratio (db) The most common is the signal to noise ratio 30db, can g

IntroductionThe PDM represents the pulse density modulation. However, a better abbreviation is "1-bit oversampling audio" because it is simply a high-sample-rate, single bitrate digital system. If you are looking for an advantage, it is that the sample rate is several times the audio CD, and a proper way to reduce the word length from 16bit to 1bit, which will be the basis of a PDM system.Most modern digital audio systems use multi-bit PCM (pulse-code

scene of the accident. If a serious accident occurs in the tunnel, a fire may occur, therefore, after an accident occurs in the tunnel, an emergency evacuation broadcast system is urgently needed. FMFM broadcast in the tunnel is a good emergency broadcast. Drivers can obtain evacuation and emergency command information through the radio, this service provides emergency incident command and handling to guide drivers to avoid risks. Therefore, whether in terms of security or service to the work a

means that the carrier frequency is changed according to a certain pattern (sequence) within a very wide band. Information Data D enters Carrier Modulation after it is modulated into a baseband signal with BD bandwidth. The carrier frequency is controlled by the pseudo-random code generator and is randomly changed in the bandwidth BSS (BSS> BD) band, the bandwidth of the baseband signal BD is extended to the bandwidth BSS used for transmitting signal