qam modulation

design, and DMT by the Amati communications company invented, the difference is the way to send data. ANSI Standard T1.413 is based on DMT, DMT has become an international standard, and Cap is a great decline. Recently, many of the g.lite standards are very good, but DMT and g.lite two kinds of standards have their own strengths, respectively, applicable to different fields. DMT is a full speed ADSL standard, which supports the high speed downlink/uplink rate of 8mbps/1.5mbps, but the DMT requi

receive backup antenna. The downlink interference measurement can be carried out in the coverage area of the base station. You can use directional or indefinite antennas. It may take a long time to measure the interference of a base station that cannot interrupt the business. Measure interference in the business silent clearance. The best way to locate the radio frequency deviation of the base station is to use the base station transmitter tester to test the RF indexes such as power, frequency

the 249 MHz band and is divided into 25 uplink channels and downlink channels in a 4 kHz width. The input data is transmitted to the subchannel after being encoded by TCM and modulated by QAM, therefore, theoretically, the uplink speed can reach 1.5 Mbps and the downlink speed can reach 14.9 Mbps. Considering interference, the actual transmission rate is generally 640 Kbps and 8 Mbps. We usually download about 250 Kbyte at the actual rate of 2 m ADSL

the tuning demodulator constitutes a different digital set-top box, for example, the satellite set-top box (dvb-s) for QPSK demodulation, A wired digital set-top box (dvb-c) for QAM demodulation and a terrestrial transmission digital set-top box (DVB-T) for OFDM demodulation. At present, the market is more popular tuning demodulator manufacturers have Thomson, Sharp, and so on, although some manufacturers in the domestic production of tuning demodula

testThe significance test of the so-called regression coefficient is the test hypothesis H0:bj=0, ...,m). under the conditions of the establishment of H0, there are:tj= b~j/(cjja~) ^ (a) ~ T (n-m-1)which CJJ is the first J+1 element on the main diagonal of the c= (xTx) 1 . For a given significance level, the value of Tj is computed and the table is judged to accept or reject H0. 2. the significance of regression equation testthe significance test of regression equation is about H0:b0=b1= ... =

Electrical signals (that is, the full-TV signal we need to modulate) it is a fixed frequency that is set by the state, that is, the total source of the signal we want to modulate. From electrical signals to light signals: the popular understanding is to be modulated by the signal loaded into the light-emitting diode, with its strong and weak changes to control the luminous intensity of the light-emitting diode changes, and then by the same module of the photosensitive transistor received by some

networkThe input of a double-tuned merge network must be a double-tone sequence. If you want to turn it into a sort network for any input sequence, you first need to convert the input sequence to a double-tone sequence. The main idea is: the sequence of length 2n is regarded as an ordered sequence of n 2 elements, and any two ordered sequence can be composed of a 4-element double-modulation sequence, then a double-

each channel (8 MHz) is time-division multiplexing transmission, the channels are still transmitted in frequency-division multiplexing mode. 1.2 orthogonal frequency division multiplexing Orthogonal Frequency Division Multiplexing is a multi-carrier digital modulation technique. All OFDM carrier frequencies have equal frequency intervals, which are an integer multiple of the basic oscillation frequencies. Orthogonal means that the signal spectrum of

audio and data transmission standards. LMDS work in millimeter bands, 20 GHz ~ For 40 GHz frequencies, the licensed frequencies are 24 GHz, 28 GHz, 31 GHz, and 38 GHz. Among them, 28 GHz has more licenses, and the frequency band has a relatively loose spectrum range, it has the potential to provide multiple services. Currently, the fixed broadband wireless access system uses three types of air interfaces: IP address-based, ATM cell-based, and TDMA-based time slot allocation. It has a theoretica

. What are the characteristics of 802.11ax? What does it bring to wireless? 802.11ax accelerates wireless connections, which many people think. Indeed, 802.11ax delivers a higher transmission rate. It introduces a higher-order modulation and encoding scheme 1024QAM. Compared with the highest 256QAM in 802.11ac, the encoding and modulation efficiency is higher. The association rate of each 80 Mbps bandwidth

Optical fiber requirements for G and G Systems With the rapid development of data communication and interconnection networks, network point-to-point, online applications, and video services have all experienced explosive growth. Massive digital media content has led to a rapid increase of 10 or even times of Internet traffic, this results in 50% ~ The speed of 80% is growing rapidly. At present, the GB system has been commercially used by major carriers. The GB system can further increase t

, presentation layer, and application layer TCP/IP are divided into three layers: network Interface Layer, network layer (IP), and transmission layer (TCP ). Physical Layer features: Provides transparent bit stream transmission between two network physical devices. Physical Layer task: Determine some features of the interface with the transmission media DTE: data terminal equipment, data generation and processing DCT: data communication equipment, data circuit final device. Converts the input da

dynamic adaptive signal modulation mode is used between the base station and the user base station. Base station (BS): The base station provides the connection between the user base station and the IP network. Generally, slice-shaped or omnidirectional antennas are used to provide flexible sub-channel deployment and configuration functions, and constantly upgrade and expand the network according to the user group situation. Terminal: The WiMAX system

bandwidth for the audio file format is 20KHZ. According to the Nyquist theory, only if the sampling frequency is higher than twice times the maximum frequency of the sound signal, the voice of the digital signal can be restored to the original sound, so the audio file sampling rate is generally 40~50khz, such as the most common CD quality sampling rate of 44.1KHZ. The process of sampling and quantifying sound is called Pulse Code modulation (

1. TIMER output PWM basic ConceptPulse width modulation (PWM), an abbreviation for the English "pulse width modulation", is called pulse width modulation, which is a very effective technique for controlling analog circuits using the digital output of a microprocessor. The simple point is the control of the pulse width. Generally used to control the speed of stepp

) Development history: 1. Threshold-based decision 1960~1970 Using the two-state amplitude and envelope demodulation method of EMG signal: After correcting, filtering and modulating the EMG signal, the primary contraction activity of the muscle is corresponding to the peak of the signals, and the hand grasping or stretching action is obtained by comparing the peak value with the threshold size. Key Technologies: Amplitude modulation 2. Based on amplit

device will inevitably generate noise, at least at this stage 24 bit difficult to achieve its expected effect.Features of the audio file format. To play or process audio files in the computer, that is, to the sound file number, mode conversion, the process is also composed of sampling and quantification, the sound that the human ear can hear, the lowest frequency is from 20Hz to the highest frequency 20khz,20khz the ear is not audible, So the maximum bandwidth for audio is 20KHZ, so the sample

transmission process, uses the 0V to represent the numeral 0,5v to represent the number 1, then each code element has two states 0 and 1. Each code element represents a binary number. at this point the number of yards per second and the number of binary code per second is the same, which is called two-phase modulation, the baud rate is equal to the bit rate. if 0V, 2V, 4V, and 6V represent 00, 01, 10, and 11 respectively in the digital transmission,

English abbreviation3g-msc 3rd generation mobile switching centre third-generation mobile exchange center3g-sgsn 3rd generation Serving GPRS Support Node Third Generation Service GPRS Node3GPP 3rd Generation Partnership Project 3-generation cooperation projectAal2o3 ATM adaptation layer type 2 atm adapter Layer 2AAL5 ATM adaptation layer type 5 ATM adapter layer 5Acir adjacent channel Interference RatioACLR adjacent channel leakage power ratioACS adjacent channel selectivity adjacent channel Sel

-off and cut-off conduction switch state, the conversion speed, the frequency is generally about 50kHz, in some technologically advanced countries, can achieve hundreds of or nearly 1000kHz. 　　This makes the switching transistor V power consumption is very small, power efficiency can be greatly improved, its efficiency can reach 80%. Small size, light weight. It is clear from the schematic diagram of the switch-stabilized power supply that there is no cumbersome frequency transformer. Since the