WCF uses TCPTransport CustomBinding but servicesecuritycontext.current is null

Question

I'm trying to configure my WCF host to use TCP with MtomMessageEncoding , I cannot use netTcpBinding cause it uses binary encoding - the problem is that i want to use the servicesecuritycontext.current.WindowsIdentity in the server side but the servicesecuritycontext.current i tried several security options but nothing works...

I am looking for binding configuration matching to the netTcpBinding with the window security default (so i can get servicesecuritycontext.current.WindowsIdentity) but with other encoding.