在使用像SCRUM这样的迭代敏捷开发方法时，如何避免等待需求？

We attempt to do agile development at my current job and we succeed for the most part. The main problem seems to be that the developers on the project are always waiting for requirements at the beginning of the sprint and rushing to get get things down by the end. The business analysts who are delivering the requirements are always working non-stop to get the requirements done.We attempt to do agile development at my curren