Managing interference in a multi-user interference network is important to achieve a better performance for the network. Hence, studies to find out the performance of interference network in various conditions have been done actively. With interference alignment, a core technique to improve DoF in a multi-user interference networks, studies have shown the optimal performance of K-user MIMO interference channels (ICs), which is $K/2$ DoF. However, although there exist some remarkable results on the performance of one-way ICs, few studies on two-way ICs have been done.\
In this thesis, we study the achievable DoF of two-way ICs with a relay. We propose a new interference management scheme to achieve better performance on such channels. If we use the conventional scheme for the TWIC, the performance shows that the channel can have 1/4 DoF per antenna, under the assumption of half-duplex communication. In this paper we show that the performance can be improved up to 1/3 DoF per antenna by using a conventional relay for the channel. This result gives us two novel outcome. One is showing that the TWIC can have better performance compared to the conventional one, and the other one is showing that the relay can help increase the DoF of ICs.\
Throughout the paper we propose a suitable interference management scheme for 2-by-2 and 3-by-3 TWIC with relay. First, in 2-by-2 TWIC, we use three time slots, two for the user transmission and the other one for the relay broadcasting, to achieve $1/3$ DoF per antenna, where each user has $M$ antennas and the relay has $N=2M$ antennas. Similarily we show that 3-by-3 TWIC can achieve DoF up to $5/18$ DoF per antenna, with $N=3M$ antennas at the relay, by adopting techniques of interference alignment since the there are more than two users. We also show that the 3-by-3 TWIC can achieve 1/3 DoF per antenna with $N>3M$ antennas at the relay.
최근 네트워크를 구성하는 통신 디바이스의 수가 기하급수적으로 증가함에 따라 이들이 서로의 통신에 주는 영향을 고려한 간섭 채널에 대한 연구가 활발히 진행되고 있다. 간섭정렬을 사용하여 $K$ 사용자 간섭 채널에서 총 $K/2$ 자유도를 달성한 기존의 연구와는 달리 본 연구에서는 양방향 간섭 채널을 가정하고 여기서 가질 수 있는 자유도 이득을 보인다. 이미 연구가 활발히 진행된 한방향 간섭 릴레이 채널에서 사용하는 기법을 양방향 간섭 채널에서 사용하면 똑같이 $K/4$ 자유도를 가지지만 본 연구에서 제시하는 기법으로는 $K=2,3$일 때 $K/3$ 자유도를 달성할 수 있음을 보인다. 달성 기법은 두 개의 통신 단계로 이루어지며 정보 교환 단계에서는 사용자들이 정보를 주고받고, 브로드캐스팅 단계에서는 릴레이가 정보를 사용자들에게 뿌려주어 전체에 자유도 이득을 가져온다.
