qam modulation

industry standard interface specification for RF head to base station, CPRI has made this specification a perfect interface and is the main channel for most RF base station products. In addition, the upcoming 4G/LTE network will also use millimeter wave technology to expand the data pipeline. Millimeter Wave (MM) is a wireless frequency of 60 GHz and above. The bandwidth and data speed of this frequency can reach 200 times of the MHz frequency. Millimeter Wave technology provides key links from

structure, reference signal location, and physical channel types are all unique to LTE. However, LTE still retains the Turbo encoding and QAM modulation methods. PDCP PDCP: Packet Data Convergence Protocol, group Data aggregation Protocol. The PDCP protocol is developed on the WCDMA air interface and expands on the LTE air interface. PDCP is located on the top of the RLC sub-layer. It is the top sub-layer

still in its infancy, long-distance applications still need to be tested, and the popularization of endpoint devices also takes time. At present, there is a VDSL Based on Ethernet, the access technology uses the QAM modulation method, its transmission medium is also a pair of copper lines, within the range of 1.5 kilometers can achieve bidirectional symmetric 10 Mbps transmission, that is, the Ethernet spe

communication receiving and sending machine, because the result of using the Sinc Function orthogonal is the best spectrum efficiency (although the method of suppressing bandwidth can suppress the out-of-band sides of each sub-band, it will lead to the continuation of time domain signals, which causes inter-symbol interference ). Orthogonal Frequency Division Multiplexing (OFDM) builds a high-performance, low-complexity transceiver based on orthogonal characteristics between discrete frequency

The 802.11ac standard is mainly designed to provide high throughput in the 5 GHz band, in addition to bringing fast and high-quality video streams, it also provides almost instantaneous data synchronization jobs and backups for laptops, tablets, and mobile phones. Theoretically, this specification will achieve at least 1 Gbit/s of multi-site WLAN throughput and at least 500 Mbit/s of maximum single-link throughput. This is achieved by expanding the air interface concept adopted by 802.11n: wider

This paper examines the principles of Nyquist and Shannon's theorem, which is the theory of communication engineering. Nyquist: In the absence of noise, the relationship between the code element rate limit B and the channel bandwidth: b=2*h (Baud) Nyquist formula----Noise-free channel transmission capacity formula:c=2*h*log2n (bps)H is the channel bandwidth, in the subject h=3khz n is the number of discrete values obtained for a code element, in which the n=16 (4 phases, the amplitude of each ph

The 802.11AC standard is designed to provide high throughput in 5GHz bands, in addition to bringing fast, high-quality video streaming, and providing almost instantaneous data synchronization jobs and backups for laptops, tablets and mobile phones. In theory, this specification will achieve at least 1gbit/s throughput of multiple-station WLANs and at least 500mbit/s maximum single link throughput. This is accomplished by expanding the concept of the air interface adopted by 802.11n: wider RF ba

use of channel bandwidth, but also avoid using high-speed balancing and anti-Burst Noise errors. OFDM is a special multi-carrier communication solution. The information flow of a single user is serialized/transformed into multiple low-rate bitstreams, and each bitstream is sent using one subcarrier. OFDM does not use a band-pass filter to separate subcarriers, but uses the fast Fourier transform FFT) to select waveforms that can maintain orthogonal even if they are overlapped. OFDM is a high-sp

user is serialized/transformed into multiple low-rate bitstreams, and each bitstream is sent using one subcarrier. OFDM does not use a band-pass filter to separate subcarriers, but uses the Fast Fourier Transform (FFT) to select waveforms that can maintain orthogonal even if they are overlapped. OFDM is a high-speed transmission technology in wireless environments. The frequency response curves of wireless channels are mostly non-flat, and the main idea of OFDM technology is to divide a given c

converter, it determines that it must occupy a certain amount of space and consume a certain amount of power in the system. Therefore, in system solutions that require convenient portability, the static D/A converter has to be replaced with [1].So people choose the so-called "Digital basis" D/A converter. There are two methods for digital D/A conversion: PWM (P Ulse Width Modulation) Pulse Width Modulation

Transferred from: http://baike.baidu.com/link?url= KEOJCOEXYDZUH8N7BNUGEDUTAGLDGDI7ESJUSZESPUREBK0NI6SFMTPWGIRED-H-L3ZZ7CY6QSHXVHHILK7BCQ the speed at which a microcontroller or computer communicates at the serial port. Refers to the signal is modulated after the change in the unit time, that is, the number of times the carrier parameter changes in the unit time, such as 240 characters per second, and each character format contains 10 bits (a starting bit, 1 stop bit, 8 data bits), the baud rate

Figure 8-4-3 of the voltage controlled oscillator, this characteristic describes the oscillation frequency ω U of the voltage controlled oscillator. Take ω 0 Center, UC with input signal voltage (T) changes. The expression for this feature is (8-4-6) When UC (T) The oscillation frequency ω U of the voltage controlled oscillator varies with time It also changes with time. The phase-locked loop enters the "Frequency traction" and automatically tracks and captures the frequency of the input signa

This article mainly discusses the technical advantages of the wireless LAN Standard IEEE802.11g. Data Transmission Based on OFDM technology With the wide application of wireless LAN technology, users have higher and higher requirements on data transmission rates. However, in the indoor environment, the complex electromagnetic environment, the multi-pass effect, frequency selective fading, and other interference sources make it more difficult to achieve high-speed data transmission in wireless c

there are tags nearby. RFID is usually called a near-pairing system for communication at a very close distance. The range of near-pairing systems is usually 0 to 1 cm. This means that the tag is appended to the reader or pressed to the reader. The advantage of this close distance is that the label battery plant can produce a lot of energy. This energy is sufficient to support tag communication without the need for Built-in power. Near-matching is also conducive to highly confidential occasions.

Spectrum utilization, supporting high speed multimedia services, system capacity, multipath channel interference and other factors are the main starting points for the majority of fixed broadband wireless access devices to select CDMA (Code Division multiplex) or OFDM (Orthogonal Frequency Division multiplexing) as the key technology for point to Point (PMP). And these two technologies have their own strengths in these areas, so the equipment business needs to weigh the pros and cons of the actu

attenuation rateDiffusion60-10 reverb DiffusionThe delay time between INI. dly12.0ms0.1-200.0ms and early reflection.Cut-off frequency of lpf4.0khz1.0khz-16108khz.thru low-pass filterCut-off frequency of hpfthruthru, 32hz-8khz high-pass filter Reverb vocal used for voice and chorus reverbParameter value range descriptionRev. time1.9s0.3-30.0s reverb timeHigh ratio0.50.1-1.0 high-frequency attenuation rateDiffusion60-10 reverb DiffusionDelay Time between INI. dly16ms0.1-200.0ms direct and earl

------------------------------------------------------------------------------- Chorus reverbParameter value range descriptionMod. freq0.8hz0.1-20Hz Modulation SpeedMod. depth40 % 0-100% modulation depthMod. dly1.3ms0-24ms delay time before initiation of modulationRev. time2.4s0.3-30s reverb timeHigh ratio0.70.1-1 high-frequency attenuation rateDiffusion70-10 reverb DiffusionDelay Time between ini. dly30ms

the data is represented by binary or more discrete level values. Therefore, the communication channel maximum transmission rate and channel bandwidth have a clear relationship, so people can use "bandwidth" to replace the "rate." For example, people often use the network's "high data rate" to express the "high bandwidth" of the network. So "bandwidth" and "rate" are almost synonymous in the discussion of network technology. ------------------------------------------------------ bit rate. Baud

amplifier. This product is specially designed to support GSM/edge pam and 3G/3.5g pa. Because the space of the circuit board in the mobile phone is very precious, the designer no longer needs to use two independent step-down converters. FAN5904 supports 3G wireless standards from WCDMA to HSUPA +, as well as the world's popular CDMA 200 1x EV-DO. In addition, the device supports China's 3G standard TD-SCDMA and HSUPA for TD-SCDMA signal modulation fo

downlink data transmission rate of WCDMA network, Is 3GPP in the R5 protocol in order to meet the requirements of the data business asymmetry, it can be in the construction of the WCDMA network structure on the basis of greatly improve the user downlink data Service rate (theoretical maximum can reach 14.4Mbps), This technology is an important technique to improve the downlink capacity and data service rate in WCDMA network construction. (Computer science) 1, HSDPA technology and its new featu