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、地理位置顯著的地方, 以及訊號傳播的區域.
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, 單一衰落或乾擾可能導致整個通訊鏈路失敗, 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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15km 30km 80km 150km 遠距離無線圖傳接收器傳輸收發器PA 2W 5W 10W
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10W PA 150KM機載視頻數據鏈遠程無人機無線傳輸發射器接收器寬帶戰術手持
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80KM無線收發器視頻數據RC傳輸系統HDMI SDI遠距離低延遲Vcan1702
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IP 網狀自組織收發器 OFDM 發射器接收器用於無人機 IP 攝像機的無線視頻數據傳輸
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SDI 或 HDMI 轉 IP 編碼器調變器 CVBS H.265 H.264 編碼板 PCBA 乙太網路 RSTP UDP 適用於無人機無人機機器人
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IP mesh video data network transmitter transceiver 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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Mini Size HDMI 編碼器板 Over IP 以太網 RJ45 輸出調製器 H.265 HTTP RSTP UDP ONVIF TCP
COFDM Technology Introduction
COFDM is coded OFDM (編碼正交頻分複用). 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 (只要 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.
Conclusion
總之, 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 視頻發射器模塊 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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30Km 遠距離 COFDM HDMI 無線視頻發射器接收器全套音頻視頻 TX RX 無人機無人機 1080P 908T
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攝像機無線視頻發射器和接收器, HDMI高清H265 264 編碼器 1W/2.5W PA 1080P60 Vcan1726
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30-毫秒無人機無人機HDMI無線視頻發射器超低延遲無線傳輸系統Vcan1729
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COFDM 調製器 解調器模塊 編碼器 解碼器 HDMI CVBS AV 輸入 AES 256 全高清射頻流媒體
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編碼董事會COFDM無線視頻發射器
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COFDM無線以太網透傳模塊100M bps RJ45 FDD視頻數據發送器和接收器
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COFDM數字視頻發射機無線高清視頻發射機接收機無人機無人機安防攝像機的全套傳輸
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手持式無線接收器 7 英寸觸摸屏COFDM接收器數字視頻接收器 7 英寸顯示器