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Contractive interference functions introduced by Feyzmahdavian et al. is the newest approach in the analysis and design of distributed power control laws. This approach can be extended to several cases of distributed power control. One of the distributed power control scenarios wherein the contractive interference functions have not been employed is the power control in MIMO systems. In this paper,...
In this paper, we consider one of the main disadvantages of Ergodic Interference Alignment, i.e., delay. We propose two methods to solve the open problem of finding the best choice of user sets in order to minimize the delay. With these methods we are able to find the best JAP-B scheme which aims to trade off rate for delay in Ergodic Interference Alignment. First, we provide the solution based on...
Long Term Evolution (LTE) is a standard for wireless communication of high speed data for mobile phones and data terminals. LTE is capable of delivering large data rate on the order of several megabits per second, which is even larger than the current 3G systems. This is very challenging as the wireless networks are subjected to interference, multipath and poor propagation channel characteristics...
In this paper, the problem of Downlink Multi-User MIMO (DL MU-MIMO) transmission from two interfering transmitters, each equipped with M antennas to multiple users each equipped with K antennas is considered. It is assumed that all users receive a single data stream of rank one from only one of the transmitters. A novel transmission/reception scheme is proposed based on the idea of Interference Alignment...
In this paper, we elaborated on a new interference alignment technique for downlink multi-user system in a MIMO-X channel with multiple antennas. We considered two transmitters, each equipped with M antennas, and L users, each equipped with K antennas. Here, we consider a MIMO-X scenario that some users are receiving transmissions from both transmitters. The proposed approach is focused on rank-1...
Power Line Communications (PLCs) enable new and highly convenient networking functions in the framework of Smart-Grids and use an already built-in network. A Multiple Input Multiple Output (MIMO) architecture can strongly improve the PLC performances and links' reliability. In this contribution the effect of self-interference generated by relay nodes has been considered and the MIMO potentials for...
A MIMO interference network with L users is investigated in this paper. We compare the sum-rate performance of interference management approaches applied to this network. The minimum mean square error (MMSE) algorithm optimizes the beamforming vectors by maximizing the signal-to-interference-plus-noise ratio (SINR). Another approach, minimum leakage interference alignment (ML-IA), minimizes the leakage...
The concept of interference alignment has been studied mainly from an information-theoretic and signal processing point of view, focusing on scenarios with a high degree of coordination among nodes often achieved by means of transmission scheduling. However, many real-world networks employ random access policies rather than deterministic scheduling, and it is therefore important to understand how...
Multiple-Input Multiple-Output (MIMO) communications have shown great promise in providing high spectral efficiency for wireless ad hoc networks. In this paper we study the problem of joint routing, scheduling, power control and bit rate selection in MIMO-based ad hoc network with the goal of maximizing the system throughput that satisfies a given end-to-end traffic demand. We formulate this cross-layer...
A multi-cell hybrid channel state information (CSI) feedback scheme was proposed, which has an ideal nested hierarchical structure to support not only the advanced multi-cell MIMO precoding, but also the traditional single-cell single-user and multi-user precoding transmissions. A quantization scheme for the multi-cell hybrid CSI feedback was provided, using codebook based vector-quantization for...
Hierarchical femtocell architectures have become popular recently because of their potential to provide increased coverage and capacity in cellular systems. However, introduction of femtocells might reduce the overlay macrocell system performance due to increased interference caused to macrocel-lular users. With MIMO precoding, the Least Interference (LI) technique can be employed at the femtocellular...
This paper presents results from a novel OFDMA multi-cell mobile broadband system level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Without suitable interference management, multi-billion dollar networks can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been...
In previous works, MIMO beamforming in multiuser wireless systems is typically formulated in two ways: one is minimizing the total transmit power with individual signal-to-interference-plus-noise ratio (SINR) constraints for each user; and the other one is maximizing the minimum SINR among all the users with a total transmission power constraint. However, although the total transmit power is optimized,...
The virtual MIMO (V-MIMO) and coordinated multipoint transmission (CoMP) are adopted by the LTE system to extend the uplink spectral efficiency. V-MIMO makes use of spatial multiplexing to increase system throughput while CoMP by means of mitigating inter cell interference (ICI) significantly achieve the same effect. In this paper, we present an orthogonality based proportional fair scheduling (OPF)...
Channel reciprocity is regarded as one of the most important advantages of TDD systems. However, the RF front-ends contribute to the channel experienced, and their TX/RX mismatches might cause reciprocity error, and thus degrade system throughput. Therefore, channel reciprocity calibration is a crucial issue. Among the existing calibration methods, Over-the-air (OTA) calibration is a promising approach...
Antenna gain mismatch between transmitter and receiver circuits has been regarded as an obstacle for exploiting channel reciprocity between uplink and downlink channels in time-division duplex (TDD) multiple-input multiple-output (MIMO) systems. To the best knowledge of the authors, little work to date has been on about the impact of antenna mismatches on the precoding vector. Motivated by this fact,...
An interference management method for coordinating downlink transmission in a Multiple-Input Multiple-Output (MIMO) cellular network is proposed. The problem is to efficiently manage inter-cell interference in a multi-cell environment, by so-called transmitter cooperation, in order to reduce the diminishing effects of interference on the networks performance. To allow for application in deployable...
Multi-cell MIMO technique theoretically promises large improvement in spectral efficiency and fairness in cellular networks and is regarded as the key enabling technique for solving the troublesome issue of inter-cell interference. To evaluate its practical performance in the cellular network, we have implemented the real-time downlink multi-cell MIMO trial system operating over bandwidth of 20 MHz...
We consider the use of Blind Interference Alignment (BIA) in a cellular environment as a means for supporting downlink Multi-User MIMO (MU-MIMO) transmission without the need for channel state information at the transmitter (CSIT). This “CSIT-blind” characteristic of BIA is of particular interest for Frequency Division Duplex (FDD) systems, since it allows one to eliminate overheads and impairments...
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