1. Field of the Invention
The present invention relates to a receiving method and apparatus in a Multiple-Input Multiple-Output (MIMO) communication system. More particularly, the present invention relates to a receiving method and apparatus employing an enhanced Modified Maximum Likelihood (MML) detection scheme.
2. Description of the Related Art
A Multiple-Input Multiple-Output (MIMO) system, which employs multiple transmission/reception antennas, allows respective transmission antennas to transmit independent signals, so that it is possible to increase an amount of data transmitted at one time. Compared with a Single-Input Single-Output (SISO) system, which uses a single transmission/reception antenna, the MIMO system has an advantage in that it is possible to increase the system capacity. Due to such advantages, recently, the MIMO scheme has been applied to standards of commercialized systems requiring high-speed data communication, which are the standards of Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE).
However, in the MIMO communication system, when mutually different data streams are simultaneously transmitted from the respective transmission antennas, mutual interference occurs between the simultaneously transmitted data streams. Therefore, schemes for enabling a receiving apparatus to detect signals based on the mutual interference have been provided.
A Maximum Likelihood (ML) detection scheme, which is one of a signal detection schemes, is a scheme that makes it possible to acquire optimal performance.
However, the ML detection scheme has a problem in that, as the modulation order of data symbols increases in order to achieve high-speed data transmission, complexity of calculations increases exponentially. In addition, since most commercialized systems employ channel coding, a receiving apparatus does not perform a hard decision with a detection result, but must calculate a Log-Likelihood Ratio (LLR) for a channel decoder, instead of performing, thereby increasing the amount of calculations.
Therefore, a need exists for a detection scheme in a MIMO communication system for reducing complexity of calculations.