| 摘要 |
When a detector 44 senses a silent period due to the absence of speech signals from a microphone 38, a mobile station 30 is caused to transmit back to the base station the last sync signal which was received from the base station and stored in a memory 43 of the mobile, whereby the base station can still monitor link quality during silent periods. During a silent period, each TDMA transmission time slot from the mobile includes the returned sync signal as a second sync signal, preceded by a first sync signal added by the mobile (Fig.1c). The base station judges link quality from both the bit error rate of the returned, second sync signal and from the field intensity or bit error rate of the first sync signal. Depending on the judged link quality, the base station may change the allocated radio channel or may cause the radio link to be cut off. |
