Phase shift correction in Bpsk!

Hello All,

I have designed BPSK transmitter and receiver in grc.
But Costas loop can able to correct frequency offset, not phase offset.

Here, I attached both transmitter and receiver files.

Transmitter :

1). File sink contains Bpsk symbols {-1,1} (repeat = yes)
2). Samples per symbol : 20
3). RRC pulse lasts for 2 symbol periods

Receiver :

1). Matched filtering
2). Costas loop & Timing recovery
3). saving samples in File sink

and final Symbols are recovered from the samples in matlab.

I’m using uhd + gnuradio + USRP1 + RFX 2400 daughter boards.

Can somebody suggest me how to deal with Phase offset ?
(especially when the gain of Rx is low phase shifts are happening

One more Question : Is Rms value sufficient in SNR Calculation ?

Thanks & Regards