To meet the demand for wireless data traffic, which has increased since deployment of 4th-generation (4G) communication systems, efforts have been made to develop an improved 5th-generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post long-term evolution (LTE) system’.
It is considered that the 5G communication system will be implemented in millimeter wave (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To reduce propagation loss of radio waves and increase a transmission distance, a beam forming technique, a massive multiple-input multiple-output (MIMO) technique, a full dimensional MIMO (FD-MIMO) technique, an array antenna technique, an analog beam forming technique, and a large scale antenna technique are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation, and the like.
In the 5G system, a hybrid frequency shift keying (FSK) and Feher's quadrature amplitude modulation (FQAM) and a sliding window superposition coding (SWSC) as an advanced coding modulation (ACM) scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonal multiple access (NOMA) scheme, and a sparse code multiple access (SCMA) scheme as an advanced access technology have been developed.
A communication system supporting a full-duplex scheme may increase system capacity doubles by performing a transmitting operation and a receiving operation on the same frequency at the same time.
In the communication system supporting the full-duplex scheme, there is a self-interference (SI) signal which occurs since a signal transmitted by a transmitting device is received in the transmitting device due to a characteristic of the full-duplex scheme.
So, various schemes for canceling the SI signal have been proposed in the communication system supporting the full-duplex scheme, and a typical one is a scheme for cancelling an SI signal which affects a receiving circuit of a transmitting device in a circuit domain.
The scheme for cancelling the SI signal in the circuit domain may be classified into a digital SI cancellation (SIC) scheme and an analog SIC scheme according to whether magnitude of the SI signal is within a digital dynamic range that the SI signal may be received in a digital domain. The digital SIC scheme denotes a scheme for cancelling an SI signal using a digital signal processing scheme, and the analog SIC scheme denotes a scheme for cancelling an SI signal using both an analog circuit and a digital signal processing scheme. It is general to use the digital SIC scheme and the analog SIC scheme at the same time for cancelling an SI signal in a system level.
Each of the digital SIC scheme and the analog SIC scheme will be described below.
Firstly, the analog SIC scheme will be described below.
In the analog SIC scheme, it will be assumed that a received SI signal includes a finite number of signals received after fixed delay time which a transmitting device already knows after the transmitting device transmits a signal. Under this assumption, the analog SIC scheme may adjust a gain for a transmission signal which is divided from an analog transmitting circuit included in the transmitting device, and cancel an SI signal from a signal received from the transmitting device by applying a circuit with fixed delay time. Here, the gain adjusted through the circuit may be acquired based on an interference characteristic estimated by the transmitting device.
Secondly, the digital SIC scheme will be described below.
The digital SIC scheme detects a channel characteristic from difference between a transmission signal and a reception signal using a signal divided from a digital transmission signal of a transmitting device and a digital reception signal which is received using a digital signal processing scheme in the transmitting device, and cancels an SI signal from the digital reception signal by applying the channel characteristic in reverse.
The digital SIC scheme may cancel only an SI signal which is within a digital dynamic range. So, an SI signal which is not within the digital dynamic range may be cancelled only after an analog SIC operation is performed.
So, a performance of a communication system supporting a full-duplex scheme which uses the digital SIC scheme is determined according to a performance of the analog SIC scheme.
The analog SIC scheme is implemented with a scheme for previously predicting the number of SI signals which are received in a transmitting device after being reflected from the transmitting device, and adding an analog circuit which may cancel each SI signal.
The analog SIC scheme may not cancel an SI signal if a characteristic of the SI signal is different from a characteristic of an SI signal predicted by the analog circuit, or the number of SI signals is greater than the number of SI signals predicted by the analog circuit due to various reasons such as a situation that an SI signal is received from an outside of a transmitting device, and the like.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.