What are the highest mbit/s when the dbm is +17.5?
create table table_2394927_1 (max_downstream_throughput___mbit_s__ varchar, power___dbm__ varchar, PRIMARY KEY (max_downstream_throughput___mbit_s__))
select max_downstream_throughput___mbit_s__ from table_2394927_1 where power___dbm__ = "+17.5"