Both the PvP Arena and World Ops are online multiplayer features and depends on a strong and reliable Internet connection. This is especially true for the PVP arena, where a lot of other players are sending and receiving data at the same time during the match. Weaker or unstable online connections can experience lag or disconnections during the match.
If you are consistently getting disconnected from PvP or World Ops, as a first step please follow the instructions in this article.