| 摘要 |
A data transmission method and system for circuit switched and other services that can be employed in TDMA-based systems, and that supports the use of one or several types of modulation (e.g., 8-PSK modulation), in addition to a "normal" modulation (e.g., GMSK modulation) on a radio interface. An additional modulation/channel coding (e.g., one based on 8-PSK) may be used in the downlink transmission, while the normal modulation/channel coding (e.g., one based on GMSK) may be used in the uplink transmissions, under a variety of different conditions. A first condition arises where the radio conditions allow the use of the additional modulation in both directions, but the mobile station transmitter does not support it. A second condition arises where the radio conditions allow the use of the additional modulation in both directions, and the mobile station supports it, but the user requests a downlink-biased or uplink-biased data transmission service. A third condition arises where the mobile station supports the use of the additional modulation in both directions, but the uplink (or downlink) radio conditions do not permit the use of the additional modulation (e.g., because of link budget limitations.) Also, a lower data rate may be desired on the uplink in order to reduce the power consumption of the mobile station, and/or in the downlink direction to avoid unnecessary interference. This is especially true in the case that one direction or the other has less data to transmit, and the high speed data transmission mode is not required (even if supported). |
