Repository logo

Browsing by Author "Gameiro, Atilio"

Now showing 1 - 2 of 2
  • Channel Estimation Schemes for OFDM Relay-Assisted Systems
    Publication . Neves, Darlene; Ribeiro, Carlos; Silva, Adao; Gameiro, Atilio
    The aim of this paper is to adapt and evaluate the performance of two classical pilot-aided channel estimation schemes designed for OFDM systems: least square and minimum mean square error, in a relay-assisted scenario. We consider the Amplify-and-Forward, which is the simplest relay protocol for cooperative systems. Also, we consider the use of a single antenna at all the terminals: base station, user terminal and relay node. In our scenario, it is assumed that some of the user terminals deployed in a certain area could act as relaying-able terminals for the communications of other users. In this communication we show that the classical channel estimation techniques designed for conventional wireless communications can be extended for relay-assisted based systems under some modifications.
    2009-04Conference paper Restricted access Show more
  • Effects of Channel Estimation on Multiuser Virtual MIMO-OFDMA Relay-Based Networks
    Publication . Jiménez, Víctor P. Gil; Ribeiro, Carlos; Gameiro, Atilio; Armada, Ana García
    A practical multiuser cooperative transmission scheme denoted as Virtual Maximum Ratio Transmission (VMRT) for multiple-input multiple-output-orthogonal frequency division multiple access (MIMO-OFDMA) relay-based networks is proposed and evaluated in the presence of a realistic channel estimation algorithm and using low-density parity-check (LDPC) codes. It is shown that this scheme is robust against channel estimation errors. It offers diversity and array gain, keeping the complexity low with a multiuser and multiantenna channel estimation algorithm that is simple and efficient. In addition, the combination with LDPC codes provides improved gains; diversity gains larger than 6dB can be easily obtained with a reduced number of relays. Thus, this scheme can be used to extend coverage or increase system throughput by using simple cooperative OFDMA-based relays.
    2010-11-14Journal article Open access Show more