目錄
OFDM Technology Introduction
ofdm (Orthogonal frequency-division multiplexing, orthogonal frequency division multiplexing) is a multi-carrier digital modulation technology.
OFDM differs from AM/FM because it can transmit multiple high-speed signals using different frequencies at the same time. The result is bandwidth-efficient use of burst communications amid noise and other interference.
Traditional FDM (frequency division multiplexing) divides the bandwidth into several sub-channels, with guard bands in the middle to reduce interference, and they send data simultaneously. Tuning your receiver to the right station is necessary to watch cable TV or analog wireless broadcasts.
Using interference-free technology makes the use of available spectrum more efficient because guard bands aren’t needed. OFDM systems require much less bandwidth than traditional FDM systems.
OFDM Technical Characteristics
Anti-multipath fading and efficient use of frequency band resources
Based on the cyclic prefix, multipath interference is converted into useful signal multipath reception, reducing the impact of self-coherent interference and inter-symbol interference, and improving the channel’s ability to resist multipath fading. It is particularly suitable for use in high-rise buildings, 人口稠密且地理位置突出嘅地方, 以及信號傳播嘅區域.
Efficient use of frequency band resources
OFDM technology uses FFT/IFFT algorithms to transform frequency domain signals, allowing multiple sub-carrier signals to be transmitted in parallel on a broadband channel, thus improving spectrum utilization efficiency. This is particularly important in wireless environments with limited spectrum resources.
Strong resistance to narrow-band interference
In a single-carrier system, 單次衰落或干擾都可能導致成個通信鏈路失敗, but in a multi-carrier system, only a small portion of the carriers will be interfered with. Error correction codes can also be used for error correction on these sub-channels. This technology can automatically detect which specific carrier under the transmission medium has high signal attenuation or interference pulses, and then take appropriate modulation measures to enable successful communication on the carrier at the specified frequency.
High flexibility
OFDM technology can adjust the number and spacing of sub-carriers in different application scenarios to adapt to different bandwidth requirements and has good flexibility.
OFDM Feature Products
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15公里30公里80公里150公里長途無線視頻發射器接收發送收發器PA 2W 5W 10W
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10W PA 150KM機載視頻數據鏈路遠程冇人機無線傳輸發射接收機寬帶戰術手持
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80KM無線發射器-接收器視頻數據RC傳輸系統HDMI SDI遠程低延遲Vcan1702
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IP網狀自設收發器OFDM發射器接收器冇人機督察攝錄機嘅無線視頻數據傳輸
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SDI或HDMI轉IP編碼器調製器CVBS H.265 H.264編碼板pcba以太網RSTP UDP無人機機械人
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IP網狀視頻數據網絡發射器收發器自組網寬帶電台
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7KM無線視頻數據RC傳輸系統遠程低延遲HDMI SDI 15km OFDM Vcan1643
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迷你尺寸HDMI編碼器板IP以太網RJ45輸出調製器H.265 HTTP RSTP UDP ONVIF TCP
COFDM Technology Introduction
COFDM is coded OFDM (編碼OFDM). Some channel coding is added before OFDM modulation (error correction coding and guard interval are added before orthogonal modulation) to make the signal more reliable and effective transmission.
Applications of COFDM
ofdm, as a high-speed transmission technology that can effectively combat interference between signal waveforms, is more widely used in the field of broadband mobile communications. Pure OFDM wireless transmission systems are rarely used in actual systems, and are basically based on COFDM technology, such as DVB (數字視頻廣播), Lte (4g), and WIFI.
Early COFDM wireless image transmission equipment mostly used improved DVB solutions, but there were problems such as two-way transmission, 頻帶, cost, 等, and it is rarely used in the current market. The bottom layer of common ad hoc network technologies on the market is mostly improved from LTE or WIFI technology.
WiFi technology is mainly used in stationary short-range and common applications. Its pilot subcarriers used for channel estimation are relatively sparse (only 4 pilots under 20Mhz bandwidth). It is not effective in mobile scenarios such as UAV image data transmission and emergency communications. ideal;
LTE is designed for complex high-speed mobile long-distance scenarios, has a high pilot density (200 pilots under 20Mhz bandwidth), has stronger signal recovery capabilities, and is more suitable for areas such as occlusion and high-speed movement.
結論
In summary, COFDM is coded OFDM, which adds channel coding to OFDM to provide communication system bit error performance. Our ad hoc network is based on LTE underlying technology (channel coding technologies such as OFDM multi-carrier, convolutional coding/TURBO coding) and is optimized and designed for complex scenarios such as drones and emergency communications.
COFDM Feature Products
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最佳FPV視頻發射器糢塊170-860Mhz無線射頻音頻視頻發射器,適用於FPV相機3W PA 50km
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30公里長距離COFDM HDMI無線視頻發射器接收器全套音頻視頻TX RX冇人機1080P 908T
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用于攝錄機嘅無線視頻發射器和接收器, 高清高清H265 264 編碼器1W/2.5W PA 1080P60 Vcan1726
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30-毫秒級冇人機HDMI無線視頻傳輸超低延遲無線傳輸系統Vcan1729
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COFDM調製器解調器糢塊編碼器解碼器HDMI CVBS AV輸入AES 256 全高清射頻流
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cofdm 無線視頻發射機嘅編碼板
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COFDM無線以太網透傳糢塊100M bps RJ45 FDD視頻數據收發機
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COFDM數字視頻發射機無線高清視頻發射器接收器全套傳輸冇人機冇人機安全攝像頭
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手持式無線接收器 7 英寸掂屏COFDM接收器數字視頻接收器 7 英寸監視器