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New robust iterative minimum mean squared error-based interference alignment al...

Teodoro, Sara; Silva, Adão; Castanheira, Daniel; Dinis, Rui; Gameiro, Atílio

Interference alignment (IA) is a promising technique for multiple input multiple output interference channels based systems, achieving the theoretical bound on degrees of freedom. However, these gains are reduced in the presence of imperfect channel state informa- tion (CSI), because of quantisation or channel estimation errors. In this Letter, the authors propose a new robust iterative IA minimum mean squared ...


Low-complexity user selection for rate maximization in MIMO broadcast channels ...

Castañeda, Eduardo; Silva, Adão; Robles, Ramiro; Gameiro, Atílio

We present in this work a low-complexity algorithm to solve the sum rate maximization problem in multiuser MIMO broadcast channels with downlink beamforming. Our approach decouples the user selection problem from the resource allocation problem and its main goal is to create a set of quasiorthogonal users. The proposed algorithm exploits physical metrics of the wireless channels that can be easily computed in s...


Low-bit rate feedback strategies for iterative IA-precoded MIMO-OFDM-based systems

Teodoro, Sara; Silva, Adão; Dinis, Rui; Gameiro, Atílio

Interference alignment (IA) is a promising technique that allows high-capacity gains in interference channels, but which requires the knowledge of the channel state information (CSI) for all the system links. We design low-complexity and low-bit rate feedback strategies where a quantized version of some CSI parameters is fed back from the user terminal (UT) to the base station (BS), which shares it with the oth...


Set optimization for efficient interference alignment in heterogeneous networks

Castanheira, Daniel; Silva, Adão; Gameiro, Atílio

To increase capacity and offload traffic from the current macro-cell cellular system operators are considering the deployment of small-cells. It is expected that both the small and macro-cells will coexist in the same spectrum resulting in unsustainable levels of interference. Interference alignment is considered as an effective method to deal with such interfer- ence. By using interference alignment the small-...


Robust leakage-based distributed precoder for cooperative multicell systems

Castanheira, Daniel; Silva, Adão; Gameiro, Atílio

Coordinated multipoint (CoMP) from long term evolution (LTE)-advanced is a promising technique to enhance the system spectral efficiency. Among the CoMP techniques, joint transmission has high communication requirements, because of the data sharing phase through the backhaul network, and coordinated scheduling and beamforming reduces the backhaul requirements, since no data sharing is necessary. Most of the ava...


Minimum Codebook Size to achieve Maximal Diversity Order for RVQ based MIMO Sys...

Castanheira, Daniel; Silva, Adão; Gameiro, Atílio

Multiple antenna systems provide both capacity and diversity gains relatively to single antenna based networks. These gains rely heavily on the availability of channel state information. In this manuscript we assume that the receiver has accurate channel information, which is quantized and fed back to the transmitter. Sufficient conditions for the feedback rate are provided that guarantee no loss of diversity d...


A novel distributed power allocation scheme for coordinated multicell systems

Silva, Adão; Holakouei, Reza; Castanheira, Daniel; Gameiro, Atílio; Dinis, Rui

Coordination between base stations (BSs) is a promising solution for cellular wireless systems to mitigate intercell interference, improving system fairness, and increasing capacity in the years to come. The aim of this manuscript is to propose a new distributed power allocation scheme for the downlink of distributed precoded multicell MISO-OFDM systems. By treating the multicell system as a superposition of si...


An FPGA implementation of OFDM transceiver for LTE applications

Pereira, Tiago; Violas, Manuel; Lourenço, João; Gameiro, Atílio; Silva, Adão; Ribeiro, Carlos

The paper presents a real-time transceiver using an Orthogonal Frequency-Division Multiplexing (OFDM) signaling scheme. The transceiver is implemented on a Field- Programmable Gate Array (FPGA) through Xilinx System Generator for DSP and includes all the blocks needed for the transmission path of OFDM. The transmitter frame can be reconfigured for different pilot and data schemes. In the receiver, time-domain s...


Performance evaluation of IB-DFE-based strategies for SC-FDMA systems

Silva, Adão; Assunção, José; Dinis, Rui; Gameiro, Atílio

The aim of this paper is to propose and evaluate multi-user iterative block decision feedback equalization (IB-DFE) schemes for the uplink of single-carrier frequency-division multiple access (SC-FDMA)-based systems. It is assumed that a set of single antenna users share the same physical channel to transmit its own information to the base station, which is equipped with an antenna array. Two space-frequency mu...


Frequency shift based multiple access interference canceller for DS-CDMA systems

Gonçalves, Luís; Silva, Adão; Gameiro, Atílio

The cyclostationary properties of Direct Sequence Spread Spectrum signals are well known. These cyclostationary properties imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper we present a Multiple Access Interference Canceller that explores this property and applies to UMTS-TDD. This frequency domain Canceller acts in the spreaded signal in such way that mini...


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    Financiadores do RCAAP

Fundação para a Ciência e a Tecnologia Universidade do Minho   Governo Português Ministério da Educação e Ciência Programa Operacional da Sociedade do Conhecimento União Europeia