Header cell in top left of data tables

I have one question bugging me about table headers, algorithms and scope.

Assume I am authoring a table and want it to be fully accessible. This
table has both row and column headings ... as an example, imagine it's
a TV guide and the columns represent hours in the day and the rows
represent various channels (the data being what's on).

It's the top left cell that bugs me.

If it contains "Time" then it should be a <th scope="row">
If it contains "Channel" then it should be a <th scope="col">

How can this be unambiguous (to a UA) without @scope?

Often this cell is blank in tables (which is easy, I just use
<td></td> ... even within thead) but when it isn't blank, and it could
go either way ...

thanks
Ben