I. Field
The present disclosure relates generally to communication, and more specifically to data transmission in a multiple-access communication system.
II. Background
A multiple-access system can concurrently communicate with multiple terminals on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. Multiple terminals may simultaneously transmit data on the reverse link and/or receive data on the forward link. This is often achieved by multiplexing the multiple data transmissions on each link to be orthogonal to one another in time, frequency and/or code domain. Complete orthogonality among the multiple data transmissions is typically not achieved in most instances due to various factors such as channel conditions, receiver imperfections, and so on. Nevertheless, the orthogonal multiplexing ensures that the data transmission for each terminal minimally interferes with the data transmissions for the other terminals.
The number of terminals that may communicate with the multiple-access system at any given moment is typically limited by the number of physical channels available for data transmission, which in turn is limited by the available system resources. For example, the number of physical channels is determined by the number of available orthogonal code sequences in a code division multiple access (CDMA) system, the number of available frequency subbands in a frequency division multiple access (FDMA) system, the number of available time slots in a time division multiple access (TDMA) system, and so on. In many instances, it is desirable to allow more terminals to simultaneously communicate with the system in order to improve system capacity. There is therefore a need in the art for techniques to support simultaneous transmissions for more terminals in a multiple-access system.