Could someone help and provide some direction or input on the
following....

I have an application that consists of 2 sensors on each floor of a 10
floor concrete building which has open sides (e.g. Parking deck) ,
collecting a sample of data randomly roughly at the rate of 10
messages a minute.

The data needs to be remotely transferred to a computer on the 1st
floor. A message block is 8-16 bytes in size. In a day roughly 25,000
messages will be sent from the sensors.

The data should be guaranteed to reach the computer(although packets
can be resent if there is an error).

Any kind of radio transmission may be used(AM,FM,802.1x,..). It should
be in an FCC approved band whereby licensing is not required.

The transmitters should transfer the data from the sensors. Only 1
transmitter should be attached to each sensor. The transmitter should
have enough range to transmit the message from the 10th floor to the
1st floor. The transmitter should be roughly the size of a cigarette
packet.

Please provide your suggestions and ideas as I am not a electronics
whiz.
thanx
vivek