About connecting to Active Directory from CentOS7

I've searched several videos on Youtube, articles in other Stack Exchange sites, and some blogs.. but I couldn't make this done yet.. My environment is Windows Server 2012 RC and CentOS7.

1. I succeeded to make an Active Directory and promoted it to Domain Controller.
2. I created a user and a group in Active Directory and set up the Unix Attributes for UID and GID.
3. I can send a ping to the domain controller from the linux.
4. I succeeded to join the realm of the domain controller.(Use realm join command)
5. Also, I can see the realm list.
6. I can see the kerberos ticket with "klist" command.
7. I installed the DNS in the domain controller as well and can see the result from nslookup.
8. I can see the linux hostname in the Active Directory Users and Computers tab.
9. I succeeded to match the time of linux with the one of windows by ntpdate command.

I followed almost all the information I could find, but still I can't search the Active Directory user from my Linux machine..

[root@test1 ~] su - pamtest@korea.com
su: user pamtest@korea.com does not exist

[root@test1 ~]# id pamtest
id: pamtest: no such user

[root@test1 ~]# id pamtest@korea.com
id: pamtest@korea.com: no such user

What do I have to do to solve this.. I'm using sssd instead of winbind. I didn't touch any configuration on Linux such as sssd.conf It's really difficult for me to solve this.. Just please let me know something you might doubt from the list I did..