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- Le-Nam Tran, Muhammad Fainan Hanif, Antti Tölli, Markku J. Juntti
- IEEE Signal Processing Letters
- 2012

The problem of maximizing weighted sum rates in the downlink of a multicell environment is of considerable interest. Unfortunately, this problem is known to be NP-hard. For the case of multi-antenna base stations and single antenna mobile terminals, we devise a low complexity, fast and provably convergent algorithm that locally optimizes the weighted sum… (More)

- Dan Nguyen, Le-Nam Tran, Pekka Pirinen, Matti Latva-aho
- IEEE Trans. Wireless Communications
- 2014

We investigate the spectral efficiency of full-duplex small cell wireless systems, in which a full-duplex capable base station (BS) is designed to send/receive data to/from multiple halfduplex users on the same system resources. The major hurdle for designing such systems is due to the self-interference at the BS and co-channel interference among users.… (More)

- Dan Nguyen, Le-Nam Tran, Pekka Pirinen, Matti Latva-aho
- IEEE Transactions on Signal Processing
- 2013

We consider data transmissions in a full duplex (FD) multiuser multiple-input multiple-output (MU-MIMO) system, where a base station (BS) bidirectionally communicates with multiple users in the downlink (DL) and uplink (UL) channels on the same system resources. The system model of consideration has been thought to be impractical due to the… (More)

- Le-Nam Tran, Muhammad Fainan Hanif, Markku J. Juntti
- IEEE Signal Processing Letters
- 2014

We investigate the problem of downlink physical layer multicasting that aims at minimizing the transmit power with a massive antenna array installed at the transmitter site. We take a solution based on semidefinite relaxation (SDR) as our benchmark. It is shown that instead of working on the semidefinite program (SDP) naturally produced by the SDR, the dual… (More)

- Le-Nam Tran, Mats Bengtsson, Björn E. Ottersten
- IEEE Transactions on Signal Processing
- 2012

The block diagonalization (BD) scheme is a low-complexity suboptimal precoding technique for multiuser multiple input-multiple output (MIMO) downlink channels, which completely precancels the multiuser interference. Accordingly, the precoder of each user lies in the null space of other users' channel matrices. In this paper, we propose an iterative… (More)

- Oskari Tervo, Le-Nam Tran, Markku J. Juntti
- IEEE Transactions on Signal Processing
- 2015

This paper studies beamforming techniques for energy efficiency maximization (EEmax) in multiuser multiple-input single-output (MISO) downlink system. For this challenging nonconvex problem, we first derive an optimal solution using branch-and-reduce-and-bound (BRB) approach. We also propose two low-complexity approximate designs. The first one uses the… (More)

- Le-Nam Tran, Markku J. Juntti, Mats Bengtsson, Björn E. Ottersten
- IEEE Trans. Wireless Communications
- 2013

We consider the beamformer design for multipleinput multiple-output (MISO) broadcast channels (MISO BCs) using zero-forcing dirty paper coding (ZF-DPC). Assuming a sum power constraint (SPC), most previously proposed beamformer designs are based on the QR decomposition (QRD), which is a natural choice to satisfy the ZF constraints. However, the optimality… (More)

- Dan Nguyen, Le-Nam Tran, Pekka Pirinen, Matti Latva-aho
- ICC
- 2012

We introduce a full duplex multiuser multiple-input multiple-output (FD MU-MIMO) system, and consider the total throughput maximization problem under a sum power constraint in the downlink (DL) channel and per-user power constraints in the uplink (UL) channel. Due to the nature of asymmetric DL/UL capacity, a trivial method to this problem is to optimize… (More)

In this paper, we investigate different practical automatic repeat request (ARQ) retransmission protocols for twoway wireless relay networks based on network coding (NC). The idea of NC is applied to increase the achievable throughput for the exchange of information between two terminals through one relay. Using NC, throughput efficiency is significantly… (More)

- Le-Nam Tran, Markku J. Juntti, Mats Bengtsson, Björn E. Ottersten
- IEEE Trans. Communications
- 2013

We consider precoder design for maximizing the weighted sum rate (WSR) of successive zero-forcing dirty paper coding (SZF-DPC). For this problem, the existing precoder designs often assume a sum power constraint (SPC) and rely on the singular value decomposition (SVD). The SVD-based designs are known to be optimal but require high complexity. We first… (More)