Homa Eghbali

Relay Selection Strategies for Single-Carrier Frequency-Domain Equalization Multi-Relay Cooperative Networks

In this paper, we investigate several relay selection strategies for cooperative Single-Carrier Frequency-Domain Equalization (SC-FDE) with the amplify-and-forward protocol. We consider both maximum likelihood (ML)-SC-FDE and minimum mean square error (MMSE)-SC-FDE receivers. We provide a novel pairwise error probability (PEP)-based selection criterion (SHARM) for frequency selective channels. We further present several selection strategies for cooperative (C) MMSE-SC-FDE receivers, which are motivated by minimizing the instantaneous error rate. These are, norm-based relay selection (NBRS), instantaneous mutual information-based relay selection (CBRS), singular value based relay selection (SVRS), and equalizer output signal quality-based relay selection (EQRS) strategies. We further propose a novel relay selection strategy, selective-to-flat fading relay selection (SFRS), in which from the effective frequency selective source-relay-destination channel link associated with the selected relay, only the channel tab with highest power is passed to the destination terminal. Additionally, to tackle the multiple relay selection problem considering generic mobile scenarios with moderately fast fading channels, in order to select the near best relay subset within the minimum processing time, we apply estimation of distribution algorithm (EDA) and formulate a modified EDA for the relay selection problem. Our results show promising performance of EDA with comparable computational complexity.

A Novel Receiver Design for Single-Carrier Frequency Domain Equalization in Broadband Wireless Networks with Amplify-and-Forward Relaying

In this paper, we propose an efficient receiver design for single carrier frequency-domain equalization (SC-FDE) for relay-assisted transmission scenario over frequency selective channels. Building upon our earlier work, we propose a novel minimum mean square error (MMSE)-based receiver design tailored to broadband cooperative networks. We show that, by incorporating linear processing techniques, our MMSE-based receiver is able to collect full antenna and multipath diversity gains, while maintaining low complexity implementation. Specifically, under the assumption of perfect power control and high signal-to-noise ratio (SNR) for the underlying links and assuming either of source-to-relay (S → R) or relay-to-destination (R → D) links to be frequency selective Rician fading, our performance analysis demonstrates that the proposed receiver is able to achieve a maximum diversity order of min (LSR,LRD) + LSD + 2, where LSR, LRD, and LSD are the channel memory lengths for S → R, R → D, and source-to-destination (S → D) links, respectively. Simulation results demonstrate that our proposed receiver outperforms the conventional cooperative MMSE-SC-FDE receiver by performing close to the matched filter bound (MFB).

Indoor Multi-wall Path Loss Model at 1.93 GHz

This paper studies a multi-wall path loss propagation model for an indoor environment at 1.93 GHz of transmission frequency. The effects of locations, materials, and thickness of the walls are considered in the model. The loss factors are optimized and verified by the measurements. To implement the proposed model, image processing techniques are applied to the architectural floor plan in order to obtain the locations and thickness of the walls. Compared with the actual measurements, the proposed model provides higher accuracy in prediction of the path loss than some of the existing well-known empirical indoor channel models. To test the robustness of proposed model to the noise in the images of floor plans, four types of noise are added to the images when obtaining the locations and thickness of walls. Simulation results indicate that the performance of proposed model, unlike that of an existing model, is not degraded by the noise added to the image of floor plan.

A Low Complexity Two Stage MMSE-Based Receiver for Single-Carrier Frequency-Domain Equalization Transmissions over Frequency-Selective Channels

In this paper, we propose a novel low complexity two-stage minimum mean square error (MMSE)-based receiver for single carrier frequency-domain equalization (SC-FDE) for space-time block coded (STBC) transmissions over frequency selective channels. We demonstrate that the proposed receiver enjoys a remarkably simple decoding scheme. We further show that, by incorporating linear processing techniques, our MMSE-based receiver is able to collect full antenna and multipath diversity gains, while maintaining low complexity, thus, eliminating the need for maximum-likelihood sequence detection (MLSD), which has certainly prohibitive complexity, specially, when the constellation size of the transmitted signals and/or the block length increases. Simulation results demonstrate that our proposed receiver significantly outperforms the conventional SC-MMSEFDE receiver, while maintaining nearly similar complexity.

Differential Decoding for SFBC OFDM Systems in Underwater MIMO Channels

We investigate the use of differential space frequency block codes (SFBCs) with orthogonal frequency division multiplexing (OFDM) over underwater acoustic channels. While SFBC efficiently exploits spatial transmit diversity, differentially coherent detection eliminates the need for extensive signal processing required for channel tracking. System performance is demonstrated using real data transmitted in the 12-26 kHz acoustic band from a vehicle moving at 0.5-2 m/s and received over a 100 m shallow water channel, using 4-QAM and a varying number of carriers ranging from 128 to 2048. Performance results demonstrate the advantage of the differentially coherent SFBC detection over the conventional, coherent SFBC detection which suffers from imperfect channel estimation.

Single-carrier frequency-domain equalization for multi-relay cooperative systems with relay selection

In this paper, we investigate the performance of single-carrier frequency-domain equalization (SC-FDE) for distributed space-time block coded (DSTBC) systems with Non-Regenerative (or amplify-and-forward) relaying over frequency-selective Rician fading channels. Our performance analysis demonstrates that SC-FDE for DSTBC is able to achieve a maximum diversity order of Σ^R<inf>i=1</inf> min (L<inf>SRi</inf>, L<inf>RiD</inf>) + R, where R is the number of relays, L<inf>SRi</inf> and L<inf>RiD</inf> are the channel memory lengths for source to i^th relay (S → R<inf>i</inf>) link and i^th relay to destination (R<inf>t</inf> → D) link, respectively. Furthermore, to overcome the loss in bandwidth efficiency due to the deployment of orthogonal DSTBC, we present and investigate several relay selection strategies for D-SC-FDE over frequency selective channels.

A New Receiver Design for Single-Carrier Frequency Domain Equalization in Broadband Cooperative Wireless Networks

In this paper, we propose an efficient receiver design for single carrier frequency-domain equalization (SC-FDE) for relay-assisted transmission scenario over frequency selective channels. Building upon our earlier work, we propose a novel minimum mean square error (MMSE)-based receiver design tailored to broadband cooperative networks. We show that, by incorporating linear processing techniques, our MMSE-based receiver is able to collect full antenna and multipath diversity gains, while maintaining low complexity implementation. Specifically, under the assumption of perfect power control and high signal-to-noise ratio (SNR) for the underlying links and assuming either of

A new reduced-complexity detection scheme for zero-padded OFDM transmissions

S \to R

A Novel Reduced Complexity MMSE-Based Receiver for OFDM Broadband Wireless Networks

or

Multiuser Two-way relaying with power control for SC-FDE systems

R \to D