Complex sentence: The South Korean government required that all cellular phones sold in that country include the WIPI platform, which prevented most foreign manufacturers from selling their phones in Korea and handed most of the market to local manufacturers like LG and Samsung.
Split into simpler sentences: The South Korean government requires that all cellular phones sold in that country include the WIPI platform. This has prevented most foreign manufacturers from selling their phones in Korea, and handed most of the market to local manufacturers like LG and Samsung.