Complex sentence: Six o'clock live was canceled at the end of 1992, As LWT jointly set up with Cartlon the London_News_Network, which took over the responsibility of all news service in London.
Split into simpler sentences: Six o'clock live was canceled at the end of 1992, As LWT jointly set up London_News_Network with Cartlon. This new company took over the responsibility of all news service in London.