Five advantages of OFDM technology

Instead of CDMA, OFDM technology has become the core technology trend of the next generation of wireless communication because of its advantages. The replacement of CDMA technology by OFDM technology has become the trend of the next-generation wireless communication technology because it has the following five advantages:

High spectrum efficiency

Due to the FFT processing, each sub-carrier can partially overlap, and theoretically it can be close to the nycept limit. The OFDM-based multi-access technology OFDMA (Orthogonal Frequency Division Multiplexing) can realize the orthogonal between users in a cell, thus effectively avoiding interference between users. This enables the OFDM system to achieve high cell capacity.

High bandwidth scalability

Because the signal bandwidth of the OFDM system depends on the number of subcarriers used, the OFDM system has good bandwidth scalability. Small to several hundred kHz, up to several hundred MHz, are easy to implement. In particular, with the broadband (increased from MHz to 20 MHz) of mobile communication, the effective support of the OFDM system for large bandwidth has become its relative to single-carrier technology (such as CDMA) "decisive advantage ".

Multi-path fading Resistance

Because OFDM converts broadband transmission to narrowband transmission on many sub-carriers, the channels on each sub-carrier can be seen as horizontal fading channels, which greatly reduces the complexity of the receiver's balancer. On the contrary, the complexity of multi-path balancing for single-carrier signals increases sharply as the bandwidth increases, making it difficult to support large bandwidth (such as 20 MHz ).

Flexible spectrum resource allocation

The OFDM system can flexibly select suitable sub-carriers for transmission to achieve dynamic resource allocation in the frequency domain, so as to make full use of the frequency diversity and multi-user diversity, in order to obtain the best system performance.

Simple MIMO technology

Because the channels in each OFDM subcarrier can be considered as horizontal fading channels, the extra complexity of multi-antenna (MIMO) systems can be controlled at a lower level (linearly increasing with the number of antennas ). On the contrary, the complexity of a single-carrier MIMO system is proportional to the power of the number of antennas and the product of the number of multi-path, which is not conducive to the application of MIMO technology.

1. OFDM promotes the evolution of wireless networks to full IP addresses
2. MIMO and OFDM: Analysis of Wireless LAN core technologies