In order to meet the increasing demand for wireless data traffic since the commercialization of 4G communication systems, the development focus is on the 5th Generation (5G) or pre-5G communication system. For this reason, the 5G or pre-5G communication system is called a beyond 4G network communication system or post Long Term Evolution (LTE) system.
In order to accomplish high data rates, consideration is being given to implementing the 5G communication system on the millimeter Wave (mm Wave) band (e.g., 60 GHz band). In order to mitigate propagation loss and increase propagation distance, the 5G communication system is likely to accommodate various techniques such as beamforming, massive MIMO, Full Dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna.
Also, for throughput enhancement of the 5G communication system, research is being conducted on various techniques such as small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, Device to Device (D2D) Communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation.
Furthermore, the ongoing research includes the use of Hybrid FSK and QAM modulation and Sliding Window Superposition Coding (SWSC) as Advanced Coding Modulation (ACM), Filter Bank Multi Carrier (FBMC), Non-Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA).
With the advent of the information age, information processing technology has been advancing to handle the explosively growing amounts of information in various fields. Recently, required data processing capability has been increasing more rapidly than in the past. The increase in quantity and quality of information contributes to the growth of data traffic demand in a wireless communication system. In order to meet such demand, the wireless communication system is advancing to support higher data rates.
The 4th Generation (4G) wireless communication systems, which have just started being commercialized, aim at improving spectral efficiency to increase data rate. However, it is difficult to expect that it will be possible to meet the explosively growing demand for wireless data traffic with spectral efficiency enhancement technology.
In order to overcome this problem, the use of a very broad frequency band can be considered. However, the current cellular mobile communication systems operate below 10 GHz, which makes it difficult to secure broad frequency bandwidth. Although there is a need to secure a broad frequency band in a higher frequency band, this would not solve all of the problems because the propagation loss becomes higher as the frequency becomes higher.
Using a high frequency band is advantageous in terms of securing a broad frequency bandwidth, but it has a drawback in that the propagation distance is shortened, which results in a reduction of coverage. Thus there is a need to resolve this problem of coverage reduction caused by shortened propagation distance.
Beamforming technology is a method for mitigating against the increased propagation loss stemming from the use of a high frequency band and protecting against reduction of the coverage area. Beamforming techniques can be categorized into two types: transmit beamforming technique performed by a transmitter and receive beamforming technique performed by a receiver.
For such transmit and receive beamforming techniques, a plurality of antennas is arranged in an array, and the antennas included in the antenna array are called array elements. The antennas may be arranged in various types of arrays such as a linear array and a planar array.
Transmit beamforming is a technique for increasing directivity by focusing the signals in a specific direction using the plural antennas. Using the transmit beamforming technique, it is possible to increase the signal directivity and thus increase the propagation distance. Furthermore, because there is almost no radiation of the signals in directions other than the focused direction, it is possible to reduce signal interference for the view of the receiver.
Receiving beamforming is a technique to form the receive signals into a beam using a receive antenna array. The receive beamforming technique is capable of increasing the signal reception sensitivity by focusing reception of the signals in a specific direction. It may also be possible to exclude signals arriving in directions other than the corresponding direction. Accordingly, the receiver is capable of increasing the directivity gain and canceling interference of signals received from other directions.