I had signal reception problems until yesterday too after moving to CM 10.1 for more than a month. I discovered that for samsung phones you need to install a modem file separately. With the original 10.1 update, I had XXLRK for baseband modem (about phone settings) and it wasnt reporting GSM signal strength to many of the GSM apps in the google play market like sensorly or OpenSignal. I always got 99asu or no signal reported. I tried DDLP4 (for India) it gave me really good 3G speed, but the dead spots in my house did not go, nor did the incorrect GSM signal reporting. I was suffering zero availability inside my house, and good signal reception outside the front door. Then I located XXLT4.zip modem file (its in a XXLT3 -->latest thread towards the last few pages) and did an install from zip from boot recovery mode of CWM and now I get signal reception inside my home and at my bedside. Only downside is that I only get EDGE GPRS data not 3G. 3G is available outside my front door.
Try the XXLT4 modem zip file and it should improve. Its only 5mb and takes less than 10 secs to flash update.
Google for "n7000 modem xxlt3" and also "android modem for dummies" and ye will find!
PS: I use MIUI v5 which needs CM 10.1