Available only to EBU Members – the latest EBU BPN 107 provides an introduction to layer division multiplexing.
This technology results from the cooperation between the Communications Research Centre (Canada), the Electronics and Telecommunications Research Institute (Korea) and the University of the Basque Country (Spain).
Layer Division Multiplexing (LDM) is based on spectrum overlay technology and allows broadcasters to transmit on the same RF television channel multiple data streams with different robustness and data capacity, synchronised in time and frequency. Signal cancellation is used to retrieve the upper layer (UL) signal first, cancel it from the received signal, and then start the decoding of the lower layer signal (LL).
The UL needs to be a very robust signal with a Signal to Noise Ratio (SNR) threshold close to 0 or even negative. The ideal reception target would be portable and mobile reception (from deep indoor to harsh mobile and slow mobile).
The LL is a high data rate signal injected from 3 to 6 dB below the UL signal and ideal for transmitting High Definition (HD) and Ultra-high Definition (UHD) services to fixed or portable terminals. DVB-T2/NGH can be used as the lower layer system.
Simulations have shown that when comparing LDM with other techniques such as Time Division Multiplexing (TDM), a clear enhancement of capacity transmitted and of SNR is achieved (for the cases analysed, 30% and 5 dB, respectively). The advantage comes from the fact that LDM uses 100% of the spectrum and 100% time resources for all layers.
The major complexity of LDM relies on the receiver side which would require latency and memory requirements to perform cancellation.