1. Introduction

We bet you ever asked yourself: COFDM digital video transmitter andOFDM digital video transmitter, which one is better? And what are the differences between them? In this article we will help you to have the clearest idea on which option to choose.

2. What is COFDM technology?

COFDM(Coded Orthogonal Frequency Division Multiplexing). Firstly let’s explain the meaning of “coded”.

Coded means channel coding(Source coding is used to solve the efficiency problem and channel coding is used to ensure the reliability of transmission). Before modulating OFDM, the digital code stream need to be encoded firstly. The detailed operation steps as follows:

2.1. Forward Error Correction(FEC)

For example, there are 100bits data need to be modulated and then transmitted. We need to convert it into 200bits. In this way, even though there are 100bits data have problem during transmission.  However finally we are still able to demodulate the correct data. In short, it is necessary to increase redundancy before modulation to improve the reliability of transmission, which is called forward error correction(FEC). In COFDM system, it's a very important parameter.

2.2. Guard Interval

In order to resolve the multi-path problem (signal through multiple transmission paths to the receiving end), insert a guard interval between the transmitted data bits. As shown in the following figure:

Guard interval is also a key point in COFDM technology.

2.3.Conclusion

The difference between COFDM and OFDM is before orthogonal modulation, COFDM adopt increase the error correction coding and guard interval to ensure the signal transmission efficient and correct. However OFDM modulation technology does not have these two parameters.

3. Apply COFDM and OFDM technology to wireless video transmitter

Currently COFDM is widely used in DVB (Digital Video Broadcasting), DVB-T, DVB-S, DVB-C etc for high speed UAV data transmission. 

With the technology development, there are more and more drones and UAV serving for people in different project. IFLY focuses on designing, developing and selling wireless communication solutions for commercial drones and robotics.

The solutions are 800Mhz, 1.4Ghz, 2.3Ghz, 2.4Ghz and 2.5Ghz

5km-8km, 10-16km and 20-50km video and digital Bi-directional Serial Data Links with COFDM technology.

The top flying speed our system support is 400km/h. During such high speed the system can also ensure the vide signal stable transmission.

For short range 5-8km, OFDM is used for UAV/FPV or Multi rotor video transmission for video, Ethernet signal and serial data such as FIP-2405 and FIM-2405.

4. Key Features

• Different models for 5-50km range

• Low Latency end to end 33ms

• Support MAVLINK TELEMETRY

• 40℃~+85℃ working temperature

• Mini size & Light Weight

• ASE128 and AES256 Encrypted & Secured

• Compatible with Pixhawk fly controller

• HDMI Video and IP Video Input

• Ethernet port supports TCP/IP/UDP

• ISM Frequency 800Mhz/1.4G/2.3G/2.4G/2.5Ghz for your option

• Transmitting Video & Bi-directional Data in one RF Channel

• Video Output to display and PC simultaneously

  
  

IFLY will keep serving the commercial and industrial drone market with the best technologies and products. And we are confident that IFLY will establish itself as the leading brand in this industry.