The most essential part of the chupah is bringing the groom and the bride to a designated private room,¹ 339:32) where they eat together in privacy following the kidushin². You must prevent anybody from entering that room so that there may be absolute privacy. This is the real chupah that consummates and completes the marriage.³ 55:5.

footnotes: ¹ It must be designated specifically for the groom, so that it is like his house, into which he is bringing his wife. (Mishnah Berurah ² The act of consecrating the woman to be his wife. ³ Beis Shmuel

In the case of a virgin, this yichud (privacy) consummates the marriage even if it is not fit for cohabitation, if for example, she is a niddah, or if people are going in and out of the room. (When she is a niddah it is mandatory that people should be going in and out of the room for if not, they are forbidden to have privacy prior to their first cohabitation.)

In the case of a widow the marriage is consummated only when their privacy is appropriate for cohabitation, which means she must be menstrually clean, and no one is able to enter the room.

An acquisition may not be made on Shabbos, and therefore if the wedding took place on Friday, great care must be taken that the yichud consummating the marriage be made before Shabbos sets in. And then, when the yichud consummating the marriage was made while it was yet day, he is permitted to have the initial marital relations on Shabbos, regardless if she is a virgin or a widow. But if the yichud was not made while it was yet day (before Shabbos), then he is forbidden to approach her on Shabbos, for their initial marital relations. This is because cohabitation completes the acquisition, and it is forbidden to make an acquisition on Shabbos.