The present invention generally relates to broadcast and multicast services for wireless communication networks, and more particularly, to repair services for broadcast and multicast services.
In wireless communication networks, the harsh conditions of the radio communication channel cause errors during transmission of data. Various mechanisms exist to detect and/or correct transmission errors. These techniques include forward error correcting (FEC) codes and automatic repeat request (ARQ) protocols. Both FEC and ARQ operate by adding redundancy to the original information bits to enable detection and/or correction of transmission errors by the mobile station. FEC codes allow the mobile station to correct transmission errors, but the redundant bits reduce the gross bit rate of transmission. An advantage of FEC codes is that no retransmission of information is required to correct errors that occur during transmission unless the error correcting capability of the FEC code is exceeded, and no uplink channel is needed for signaling between the mobile station and the base station. ARQ protocols enable the mobile station to detect frame errors with less redundancy so that a mobile station can request retransmission of incorrectly received frames. Unlike FEC codes, ARQ protocols require an uplink channel for sending retransmission requests. Further, retransmission of missing data consumes bandwidth on the downlink.
A repair service can be used to provide mobile stations with data that was not correctly received in the original transmission. A repair service is similar to ARQ but uses a dedicated point-to-point (PTP) channel to retransmit incorrectly received data rather than a broadcast channel. A mobile station reports missing segments (e.g., blocks, frames, packets, etc.) to initiate a repair transaction. The mobile station typically sends its repair request after download of the data object is completed. The server then retransmits the missing packets to the mobile station. The repair service uses a PTP uplink and downlink channel for each mobile station. The PTP uplink and downlink channels may be a “shared” channel or “packet based” channel, however, the information transmitted over the PTP channel is specific for each mobile station.