PaulS:
I don't really understand your project description.
How can an LED transmit an 'A'? Why does it need to do it repeatedly? If you didn't hear it the first time, what makes you think you'll hear it the next time?
Why would you want to call the user an office? Being told that the user is IN the office might be useful, IF the blind person's home had an office. If it has more than one, that knowing that you were in one of the offices wouldn't be all that useful.I'm relatively certain that blind people are far more spatially aware than sighted people, so being told "you are in the bathroom" doesn't seem like useful information.
I'm not trying to put down your project. I simply think that you need to do a better job of explaining the whole project.
The system is to be used in new buildings to the user , such as school, malls and hospitals. An led can an A by converting it binary and using on off keying modulating, on for a 1 and off for a zero. Let write a better description so that you can understand better