Yeah, It is possible. I think You should stick to trigger editor.
First, You need a point, where wave will spawn. It simply can be a center of the map.
(Regions->Center of region and select "Entire map").
To create the wave, you need to create units in this point (Create units action), next You need to add these units to unit group.
(Add [last created unit] to unitGroup)
Of course, You need to create unit group variable. After this you can add that unit group to wave.
(AI->add unit group to wave).
To send this wave, you first need to set target for player, who will be sending these waves. As point You can use Player's starting location.
(AI->set target point for attack waves)
(Player->Starting location of Player)
To send this wave use "Send attack wave" trigger.
That's all, I hope it will help :)