Mobile Reception

Difference between fixed and mobile reception environments

Difference between fixed and mobile reception environments

Antenna height difference (Clearance)
Receiving antenna difference (Antenna gain)
Field strength fluctuations (Multipath fading)

In the fixed reception environment, we generally use a directional antenna like a yagi antenna, and a receiving antenna height is about 10 m. And the receiving antenna is usually set up in a good position that provides stable and high field strength. On the other hand, in the mobile reception environment, we generally use an omnidirectional antenna or a less-sensitive directional antenna. The receiving antenna height is lower than fixed reception, so the radio waves are mostly blocked. It is poor reception condition. A problem associated with mobile reception is frequency selective fading interference caused by a moving vehicle. It was very difficult to receive HDTV program in a moving vehicle, such as a bus or car.

Key technologies for mobile reception

1. Time Interleaving

Time interleaving is very effective for fluctuated signal, this feature is only in ISDB-T, not equipped in DVB-T and ATSC.

2. Space diversity reception

The diversity technology, improves the signal quality. Here, ISDB-T adopts a very unique technology, that is "maximum ratio combining for each OFDM subcarriers", for the robustness against frequency-selective fading.