b-mobile release a dedicated SIM card for the Pokemon GO game which release on August 10, 2016 in Japan. Each SIM card includes LTE connection and 1GB mobile data for 30 days. You can buy the card for 1500 Yen (with tax) and you can choose from 3 different types of SIM card: standard SIM, Micro SIM, Nano SIM. If you pay 500 Yen (with tax) 10 days before the 30 days period off you can enjoy the service in the next month also.
With this SIM card and the LTE connection you can enjoy a more stable service for the Pokemon GO from the mobile data side. Of course the card not going to improves the GPS connection of your device.