Rakuten Mobile of Japan may tout its innovative cloud-native network as the main way it will achieve a lower cost base than rivals, but some of its efficiencies actually stem from more physical and well-established methods. In particular, back in 2018, Rakuten struck deals with four Japanese energy utilities to reduce its energy costs and to reduce its need to build out all its own fiber. One of those partnerships was with Tokyo Electric Power Company (Tepco) and that has now been expanded into a full joint venture to cover base station deployment to boost 4G and 5G coverage. Rakuten is targeting accelerated densification and better rural coverage from the move, as it struggles to build commercial success on its…