Cell Broadcast Short Message Service

SMS Cell Broad Cast: (3.41) Cell Broadcast Short Message Service is broadcast service to send information to all MS in cell or in a location which are listening to broadcast channel. Information is in text format and could be related to emergency service, traffic related information, advertisement of service e.t.c. CBS message differs from normal point to point message in terms of channel selection and message encoding format, CBS does not expect any response from MS while in point to point SMS originator expect response from receiver. CBS message can be broadcast cyclically by the BTS as a frequency and for duration, duration and frequency of CBS message transmission would be fixed by provider. Following Function would be done by BSC and BTS to broadcast SMS in cell or in a location. BSC stores message content in local memory to broadcast it, storage if message withing BSC memory is require if message is require to transmit for multiple times for certain duration. BSC schedule storage message on CBCH (Cell Broadcast Channel) logical channel. BSC layer encode CBS message according to specification GSM 3.41. Ex message SMS BROADCAST COMMAND, SMS BROADCAST REQUEST. Generate schedule message and inform MS for broadcast, this is optional procedure. BTS layer encode information for CBS message received from BSC layer via CBCH according to specification GSM 4.12, which is data link layer format. While broadcasting message BSC need to take care of idle mode DRX configuration, during DRX period MS may not listen to CBCH channel to save power so messages sent during this period will be not decoded by MS. In OpenBTS code both BSC and BTS exist as one core need to write CBS scheduler and encoding of BSC and BTS messages. Prerequisite for Testing: BSC is up and configuration of one cell is successful, BSC should transmit SIB parameter, MS should decode SIB parameter by reading BCCH channel. Once Cell configuration is successful, start CBS scheduler to schedule CBS messages on CBCH channel.