Hani Mehrpouyan

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The distributed nature of cooperative networks may result in multiple carrier frequency offsets (CFOs), which make the channels time varying and overshadow the diversity gains promised by collaborative communications. This paper seeks to address multiple CFO estimation using training sequences in space-division multiple access (SDMA) cooperative networks.(More)
Multiple distributed nodes in cooperative networks generally are subject to multiple carrier frequency offsets (MCFOs) and multiple timing offsets (MTOs), which result in time varying channels and erroneous decoding. This paper seeks to develop estimation and detection algorithms that enable cooperative communications for both decode-and-forward (DF) and(More)
In multi-relay cooperative systems, the signal at the destination is affected by impairments such as multiple channel gains, multiple timing offsets (MTOs), and multiple carrier frequency offsets (MCFOs). In this paper we account for all these impairments and propose a new transceiver structure at the relays and a novel receiver design at the destination in(More)
Oscillator phase noise limits the performance of high speed communication systems since it results in time varying channels and rotation of the signal constellation from symbol to symbol. In this paper, joint estimation of channel gains and Wiener phase noise in multi-input multi-output (MIMO) systems is analyzed. The signal model for the estimation problem(More)
In this paper, a new discrete-time model of phase noise for digital communication systems, based on a continuous-time representation of time-varying phase noise is derived and its statistical characteristics are presented. The proposed phase noise model is shown to be more accurate than the classical Wiener model. Next, using the this model, non-data-aided(More)
Heterogeneous Networks (HetNets) are known to enhance the bandwidth efficiency and throughput of wireless networks by more effectively utilizing the network resources. However, the higher density of users and access points in HetNets introduces significant inter-user interference that needs to be mitigated through complex and sophisticated interference(More)
This paper addresses the problem of estimating time varying phase noise caused by imperfect oscillators in multiple-input multiple-output (MIMO) systems. The estimation problem is parameterized in detail and based on an equivalent signal model its dimensionality is reduced to minimize the overhead associated with phase noise estimation. New exact and(More)
In this paper we propose a new low feedback and low complexity scheme that adjusts the phases at the relays, thus allowing for the coherent combining of signals from multiple relays in a cooperative multi-input-multi-output (MIMO) system using space division multiple access (SDMA). It is assumed that the channel state information (CSI) is not fed back to(More)
Successful collaboration in cooperative networks requires accurate estimation of multiple timing offsets. When combined with signal processing algorithms, the estimated timing offsets can be applied to mitigate the resulting inter-symbol interference (ISI). This paper seeks to address timing synchronization in distributed multi-relay amplify-and-forward(More)
This correspondence first shows that the Cramer-Rao lower bound (CRLB) derivations in the above paper are incorrect. In addition, contrary to the claims in the above paper, the assumptions of perfect timing offset estimation and matched-filtering at the relays affect the generality of the analytical results and cannot be justified assumption.