| 摘要 |
<p>A code-division-multiple-access (CDMA) system provides a collision avoidance mechanism for packet communications. When mobile stations (15) attempt to establish links with a base station (13), the base station selects one mobile station to transmit data over an intended uplink channel (UL). The base station (13) transmits a predetermined sequence, during the first frame of the data transmission over the downlink (DL) control channel that corresponds to the intended uplink channel (UL). If several mobile stations detect or mis-perceive successful access attempts, those stations begin data transmissions via respective desired uplink channels. At the same time, the mobile stations (15) listen for the known sequence over the various corresponding downlink channels. Upon successful detection of the known sequence, one mobile station continues transmission of its data over the intended channel. However, any contending mobile station (15) that does not detect the known sequence on the appropriate downlink channel (DL) immediately stops its data transmission.</p> |
