Ibrahim A. Hemadeh

Layered Multi-Group Steered Space-Time Shift-Keying for Millimeter-Wave Communications

We propose a novel multi-user multiple-input multiple-output (MIMO) technique termed the layered multi-group steered space-time shift keying (LMG-SSTSK) for the downlink of millimeter wave (mmWave) communications, which combines the concepts of multi-user MIMO, space-time shift keying, beamforming and orthogonal frequency-division multiplexing to simultaneously convey information to multiple users. The LMG-SSTSK tackles the propagation challenges of the high-attenuation mmWave frequencies by sub-dividing the users into multiple groups. The proposed system allows more users to be served simultaneously in the downlink over the same time- and frequency-resources than a system dispensing with the proposed grouping technique.

Multi-Set Space-Time Shift-Keying With Reduced Detection Complexity

In this paper, we propose a novel multi-set space-time shift keying (MS-STSK) technique, where the source bits are conveyed over two components, namely, by activating one out of MQ dispersion matrices of STSK and M antenna combination of the Nt available antennas, in a similar fashion to spatial modulation but activating multiple antennas rather than a single antenna. This system requires a smaller number of RF chains than antenna elements (AEs) to achieve an improved throughput. We opt for STSK as the main building block of our proposed MS-STSK as a benefit of its design flexibility, where STSK is capable of providing the system with both diversity and multiplexing gains. The proposed MS-STSK system achieves both higher data rates and a lower bit error rate than the conventional STSK scheme, which is attained at the cost of increased number of AEs and a high-speed antenna switch. Furthermore, as the symbol rate of the MS-STSK system increases, its performance compared with the STSK scheme is significantly improved because of the enhanced diversity introduced by the additional AEs. Furthermore, we propose a reduced complexity detector for Quadrature Amplitude Modulation (QAM)/Phase Shift Keying (PSK) constellations, which-despite its reduced complexity-is capable of achieving the same performance as the optimal maximum likelihood detector.

Multiuser Steered Multiset Space-Time Shift Keying for Millimeter-Wave Communications

The recently proposed concept of multiset space-time shift keying (MS-STSK) is intrinsically amalgamated with the multiple-input multiple-output (MIMO) philosophy for the sake of enhancing the attainable system throughput. Explicitly, we propose a multiuser steered MS-STSK (MU-SMS-STSK) scheme for the downlink of millimeter-wave (mmWave) communications, which is combined with analogue beamforming (BF) that relies on phase shifters and power amplifiers to overcome the high attenuation of mmWaves. Hence, our MU-SMS-STSK system combines the concepts of MU-MIMO, MS-STSK, BF, and orthogonal frequency-division multiplexing for communicating with multiple users relying on the same time and frequency resources.

Multi-Set Space-Time Shift Keying and Space- Frequency Space-Time Shift Keying for Millimeter-Wave Communications

In this paper, we introduce a novel OFDM-aided multifunctional multiple-input multiple-output scheme based on multi-set space-time shift keying (MS-STSK), where the information transmitted over each subcarrier is divided into two parts: STSK codeword and the implicit antenna combination (AC) index. In MS-STSK, a unique combination of antennas can be activated at each subcarrier to convey extra information over the AC index while additionally transmitting the STSK codeword. Furthermore, inspired by the MS-STSK concept, this scheme is extended also to the frequency domain in the novel context of our multi-space-frequency STSK (MSF-STSK), where the total number of subcarriers is partitioned into blocks to implicitly carry the block’s frequency index. The proposed MSF-STSK scheme benefits from the huge bandwidths available at mmWaves for partitioning the total number of OFDM subcarriers into blocks to convey more information over the frequency domain. Both proposed systems use STSK codewords as the basic transmission block, and they can achieve higher data throughput and better BER performance than STSK. Moreover, given that the system is meant to operate at mmWaves, antenna arrays relying on several antenna elements are employed at both the transmitter and receiver for analogue beamforming with the aid of phase shifters and power amplifiers to overcome the effect of high path loss.

Popularity-Aided Routing Protocol for Mobile Social Networks

A novel Popularity-assisted Routing Protocol (PRP) is proposed for Mobile Social Networks (MSNs). The PRP is designed by exploiting the social characteristics of mobile nodes, which are reflected by the friendship derived from regular node meetings. Moreover, the strength of a nodes friendship is specified by its popularity. In detail, four novel metrics are introduced to reflect the social characteristics of mobile nodes, which include friendship, popularity, popularity rank and relationship. Based on these metrics, the PRP is proposed, which makes use of these metrics for message delivery. The performance of the PRP is investigated and compared with that of some existing routing protocols for MSNs under a Random Waypoint Mobility (RWM) model. Our studies and results show that the metrics for social behaviors are efficient for route discovery. The proposed PRP is capable of achieving the total message reception with considerably low average delay. Additionally, the PRP requires significantly less resource, such as, bandwidth, buffer space and energy, than the other routing protocols considered.

Dataset - Compressed Sensing-Aided Space-Time Frequency Index Modulation

Dataset supports: Lu, S., Hemadeh, I., El-Hajjar, M., & Hanzo, L. (2018). Compressed Sensing-Aided Space-Time Frequency Index Modulation. IEEE Transactions on Vehicular Technology.

Compressed-Sensing-Aided Space-Time Frequency Index Modulation

In space-time shift keying (STSK), the information is conveyed by both the spatial and time dimensions, which can be used to strike a tradeoff between the diversity and multiplexing gains. On the other hand, orthogonal frequency-division multiplexing (OFDM) relying on index modulation (IM) conveys information not only by the conventional signal constellations as in classical OFDM, but also by the indices of the subcarriers. In this paper, we combine the benefits of STSK and IM in order to strike a flexible tradeoff between the throughput and bit-error performance by transmitting extra information bits in each subcarrier block, while increasing the diversity order. In order to further improve this tradeoff, as well as to decrease the complexity of the detector, compressed sensing is combined with the proposed STSK-aided IM system. We first present the maximum likelihood (ML) detection, which forms the best-case bound on the proposed systems performance. Then, we propose a pair of reduced-complexity detection algorithms capable of approaching the ML detectors performance. Furthermore, in order to attain a near capacity performance, we propose a soft-input soft-output decoder that is capable of exchanging soft information with a channel decoder through iterative decoding.

Joint-Alphabet Space Time Shift Keying in mm-Wave Non-Orthogonal Multiple Access

Flexible modulation schemes and smart multiple-input multiple-output techniques, as well as low-complexity detectors and preprocessors may become essential for efficiently balancing the bit error ratio performance, throughput, and complexity tradeoff for various application scenarios. Millimeter-Wave systems have a high available bandwidth and the potential to accommodate numerous antennas in a small area, which makes them an attractive candidate for future networks employing spatial modulation and space-time shift keying (STSK). Non-Orthogonal Multiple Access (NOMA) systems are capable of achieving an increased throughput, by allowing multiple users to share the same resources at the cost of a higher transmission power, or an increased detection (preprocessing) complexity at the receiver (transmitter) of an uplink (downlink) scenario. In this paper, we propose the new concept of joint-alphabet space time shift keying. As an application scenario, we employ it in the context of the uplink of NOMA mm-Wave systems. We demonstrate with the aid of extrinsic information transfer charts that a higher capacity is achievable when compared with STSK, while retaining the attractive flexibility of STSK in terms of its diversity gain and coding rate. Finally, we conceive quantum-assisted detectors for reducing the detection complexity, while attaining a near-optimal performance, when compared with the optimal iterative maximum A posteriori probability detector.

Dataset of the paper: "Reduced-RF-Chain Aided Soft-Decision Multi-Set Steered Space-Time Shift-Keying for Millimeter-Wave Communications"

This dataset contains the data used for producing Figures 5, 6, 7, 8, 9, 15, 16, 17, 18 and 19 of the paper:Hemadeh, I. et al (2017). Reduced-RF-Chain Aided Soft-Decision Multi-Set Steered Space-Time Shift-Keying for Millimeter-Wave Communications. IEEE Access.

Reduced-RF-Chain Aided Soft-Decision Multi-Set Steered Space-Time Shift-Keying for Millimeter-Wave Communications

Soft-decision-aided multi-set steered space-time shift keying intrinsically amalgamated with channel coding is proposed in order to attain near capacity–performance. Multi-set space-time shift keying (MS-STSK) is a multiple-input multiple-output scheme, which combines the concepts of spatial modulation (SM) and STSK for the sake of achieving high data rates and enhanced system integrity. Furthermore, an MS-STSK is combined with orthogonal frequency-division multiplexing (OFDM) as well as single-carrier frequency domain equalization (SC-FDE) and additionally enhanced by analog beamforming in order to support communications at millimeter-wave (mmWave) frequencies. Given that OFDM-based SM systems cannot directly benefit from the reduced number of RF chains of SM due to the spreading effects of the fast-Fourier transform and they suffer from a high peak-to-average power ratio, we opt for employing the SC-based arrangement. The soft-decision-aided detector of the SC-based MS-STSK is combined with recursive systematic convolutional encoding and iterative detection at the receiver side in order to achieve excellent performance within 1.1 dB and 1.4 dB, respectively, from the capacity limit for the soft-decision MS-STSK system and within 1.1 dB from the capacity limit for the SC-FDE-aided soft-decision MS-STSK. We also use extrinsic information transfer charts for analyzing our systems and evaluate their achievable rates.