The results of a UMTS interference field study performed this summer by the EBU and FreeTV Australia are now available. The study consisted of practical compatibility tests between DVB-T reception and UMTS base station and mobile terminal transmissions. The existing UMTS (WCDMA) network in Australia in the 850 MHz band was used for this purpose.
Study objectives
The objectives of the study were twofold:
1. to assess the protection requirements between a UMTS transmission from a base station as an adjacent or image channel to the channel used for DVB-T reception employing an external TV receive antenna or a portable antenna;
2. to assess the protection requirements between a UMTS transmission from a mobile terminal as an adjacent or image channel to the channel used for DVB-T reception employing an external TV receive antenna or a portable antenna.
Main outcomes
The field measurements have provided valuable information about the levels that could be received by the broadcast receiver from the interfering base stations or mobile terminals. The measured levels were used to assess the impact of interfering signals on the wanted broadcast signals. A panel of set-top boxes was used for this. A set of protection measures has been identified that should be used to ensure the protection of the broadcasting service. With regard to the possible interference from the base station transmission, the following measures were identified to be taken at the base station:
- Adequate limitation of the out-of-band emission level of the base station;
- Use of a polarisation which has only one component (preferably vertical) at the base station.
- Adequate reduction of the transmit power of the base station.
With regard to the emission from the mobile terminals, the field study showed that a sufficient frequency guard band is needed to avoid interference on portable DVB-T reception from real UMTS mobile phones. Interference has been shown and recorded on HDTV video for cases where insufficient guard band was used between the broadcast channel and the mobile channel. This helps illustrate the interference effects. For more information, please contect: Walid Sami (EBU) .