KT and KT Skylife Develop B.U.S. Technology Combining Satellite and LTE

As the autonomous driving era based on 5G networks arrives, the population enjoying dramas and movies while driving is expected to surge dramatically. In response to this trend, media "mobile service" is anticipated to undergo major upgrades. KT and KT Skylife have joined forces to introduce a hybrid media service that delivers uninterrupted high-definition real-time video even in fast-moving automobiles and premium buses.

KT and KT Skylife held the "Skylife LTE TV" launch event on the 12th (Wednesday) at KT Square in Gwanghwamun, Seoul, and announced that they are introducing the world's first next-generation hybrid media service that allows viewers to enjoy high-definition broadcasts without interruption while on the move.

Skylife LTE TV (SLT) is a service that combines KT's LTE technology with KT Skylife's satellite broadcasting to provide high-definition video regardless of driving conditions. It provides real-time broadcasts via satellite, but switches to LTE broadcast signals when satellite signals weaken due to heavy rain or tunnel entry. Key features include satellite broadcasting's high definition, wide coverage, affordable usage fees, and the advantages of uninterrupted LTE network service.

Existing express buses experienced interruptions in real-time broadcasts when entering tunnels or during adverse weather conditions, drawing complaints from passengers. To resolve this issue, the two companies developed and applied "B.U.S." technology.

BUS is an acronym for Buffering, Unified Intelligent LTE Switching, and Still Cut. Buffering is a technology that delays the received satellite signal by approximately 5 seconds in the set-top box before playback. This ensures that video does not interrupt when entering or exiting shadow areas such as tunnels, even when the broadcast signal switches between satellite and LTE networks.

The Unified Intelligent LTE Switching technology switches broadcast signal reception from satellite to LTE in approximately 1 second when satellite signals are poor, and reverts the reception method from LTE back to satellite when satellite signals improve. Still Cut technology ensures smooth screen continuity by displaying the last frame of the broadcast being viewed at the moment the reception method switches between satellite and LTE.

SLT is evaluated as a media service that overcomes the challenging environment of domestic expressways with numerous tunnel sections. As of the end of last year, 9.8% of domestic expressways (total length 8,876 km) consist of tunnel sections (total length 871 km). The recently opened East-West Expressway (Seoul-Yangyang section) is approximately 60% comprised of tunnels.

Prior to SLT's launch, KT and KT Skylife conducted road tests using 7 vehicles over a 2-month period starting in May on major expressways nationwide including Gyeongbu, Jungang, and Yeongdong routes. The tests successfully achieved uninterrupted real-time broadcast viewing in tunnels where satellite broadcasting and DMB were previously unavailable. Additionally, they plan to update RET (Retransmission) technology this year to overcome temporary packet loss.

RET (Retransmission) is a technology that analyzes screen information stored in the set-top box for 5 seconds and, when the screen becomes corrupted, transmits the corrupted image information from the broadcast center via the LTE network to provide a clean image. It is automatically applied upon set-top box upgrade without hardware modifications.

Along with the SLT launch, KT and KT Skylife are pursuing satellite antenna upgrades. The SLT antenna is reduced to one-fifth the size of existing antennas (45×15cm), measuring 30×4.2cm. The ultra-thin SLT antenna scheduled for launch at year-end measures 25×3cm.

A KT official stated that KT plans to apply its B.U.S. solution and RET technology not only to vehicles but also to high-speed trains like KTX and SRT, and is planning to export the technology overseas.