Myung Gil Kang

Ergodic Interference Alignment With Delayed Feedback

We propose new ergodic interference alignment techniques for K-user interference channels with delayed feedback. Two delayed feedback scenarios are considered - delayed channel information at transmitter (CIT) and delayed output feedback. It is proved that the proposed techniques achieve total 2K/(K+2) DoF which is higher than that by the retrospective interference alignment for the delayed feedback scenarios.

The capacity of a three-user interference channel with a cognitive transmitter in strong interference

This paper analyzes the capacity of a three-user interference channel with a cognitive transmitter which non-causally knows the messages of the other two transmitters. Especially, We derive the capacity region when all interference channel gains are strong and show that the capacity is achieved by superposition coding. From the capacity results for the specific channel conditions, we also analyze the capacity region for three-user Gaussian interference channel with a cognitive transmitter.

The Degrees of Freedom of the Interference Channel With a Cognitive Relay Under Delayed Feedback

This paper studies the interference channel with a cognitive relay under delayed feedback. Three types of delayed feedback are studied: delayed channel state information at the transmitter, delayed output feedback, and delayed Shannon feedback. Outer bounds are derived for the degrees of freedom (DoF) region of the two-user multiple-input multiple-output interference channel with a cognitive relay with delayed feedback as well as without feedback. For the single-input single-output scenario, optimal schemes are proposed based on retrospective interference alignment. It is shown that while a cognitive relay without feedback cannot improve the sum-DoF in the two-user single-input single-output interference channel, delayed feedback in the same scenario can increase the sum-DoF to

Linear Secrecy Capacity Scaling in Dense Networks

4/3

On the diversity multiplexing tradeoff in a 4-user clustered Z-channel

. For the multiple-input multiple-output case, achievable schemes are obtained via extensions of retrospective interference alignment, leading to the DoF regions that meet the respective upper bounds.

Cognitive Relay in Interference Channel with Delayed Feedback: Degree of Freedom Region

We propose a new hierarchical cooperation technique using jamming in dense networks to achieve linear secrecy capacity scaling. To show the effect of the jamming signal in the proposed scheme, we derive the tolerable intensities of eavesdroppers to achieve the linear secrecy capacity scaling for hierarchical cooperation schemes with and without jamming, respectively. Although both hierarchical cooperation schemes can achieve the linear secrecy capacity scaling, only the proposed hierarchical cooperation scheme using jamming can achieve meaningful tolerable intensity of eavesdroppers.

On the achievable diversity multiplexing tradeoff of K-user interference channels

We study a new interference channel called 4-user clustered Z-channel where 4 clusters consisting of two single-antenna nodes each construct a Z interference channel and the connected two clusters form a two-user interference channel. We analyze diversity multiplexing tradeoff (DMT) in this channel by joint decoding. We also propose a new interference alignment scheme requiring only partial channel phase information and analyze DMT for the proposed interference alignment scheme. Eventually, we show that the proposed interference alignment and joint decoding should be switched depending on multiplexing gain for better DMT performance. It is also shown that the hybrid scheme is DMT optimal in the range between 0 and 0.2 and at the point 0.5.

Interference alignment with rate splitting in a three-user interference channel with a cognitive transmitter

This paper studies a two-user single-input single- output (SISO) interference channel with a cognitive relay (ICCR) under delayed feedback. We consider three types of feedback: delayed channel state information at transmitter (CSIT), delayed output feedback, and no feedback. For each feedback information, we derive the optimal degrees of freedom (DoF) region of the two-user ICCR where delayed feedback information is available at all transmitters. We show that while a cognitive relay with no feedback cannot improve the sum DoF beyond 1 in the two-user interference channel, delayed feedback can increase the sum DoF to 4/3.

Apparatus and method for hierarchical rate splitting in hierarchical cell communication system

This paper analyzes diversity multiplexing tradeoff (DMT) of K-user interference channels. We propose a timesharing scheme using both joint decoding and interference alignment (IA), and derive a closed form of its achievable DMT. We show that the achievable DMT is not limited by the maximum of DMTs achieved by joint decoding and IA each but is much better than the maximum of the two. As K increases, the achievable DMT converges, but the DMT improvement by the time-sharing scheme becomes more remarkable. To the best of our knowledge, the time-sharing scheme outperforms any other known schemes in the K-user interference channel in terms of DMT.

Secrecy Capacity Scaling by Jamming-Aided Hierarchical Cooperation in Ad Hoc Networks

This paper proposes a new strategy combining interference alignment (IA) and rate splitting for a three user interference channel with a cognitive transmitter. Although a half of available dimensions are sacrificed to align interference signals from other users in conventional IA, the proposed scheme recycles the sacrificed dimensions with the help of a cognitive transmitter. The achievable rate region and generalized degrees of freedom are derived. Compared with conventional IA, the proposed scheme improves achievable rate and generalized degrees of freedom.