Belkacem Mouhouche

Non-Uniform Constellations for ATSC 3.0

This paper introduces the concept of a non-uniform constellation (NUC) in contrast to conventional uniform quadrature-amplitude modulation (QAM) constellations. Such constellations provide additional shaping gain, which allows reception at lower signal-to-noise ratios. ATSC3.0 will be the first major broadcasting standard, which completely uses NUCs due to their outstanding properties. We will consider different kinds of NUCs and describe their performance: 2-D NUCs provide more shaping gain at the cost of higher demapping complexity, while 1-D NUCs allow low-complexity demapping at slightly lower shaping gains. These NUCs are well suited for very large constellations sizes, such as 1k and 4k QAM.

High order non-uniform constellations for broadcasting UHDTV

This paper investigates high order NonUniform Constellations (NUC) with constellation sizes of up to 4K-QAM for broadcasting over-the-air very high data rate services such as Ultra-High Definition TV (UHDTV). An iterative algorithm is proposed for fast convergence towards the optimal NUC at each Signal-to-Noise Ratio (SNR) operating point. Performance evaluation assuming DVB-T2 as a reference shows significant gains for NUC over uniform constellations, above 1 dB for orders higher than 256-QAM, and up to 2 dB with 4K-QAM. This gain in dB converts into a relative throughput gain of nearly 10% compared to DVB-T2 using 32k FFT size with LDPC code rate 1/2.

FANTASTIC-5G: flexible air interface for scalable service delivery within wireless communication networks of the 5th generation

5th generation mobile networks will have to cope with a high degree of heterogeneity in terms of services, mobility, number of devices and so on. Thus, diverse and often contradicting key performance indicators need to be supported, but having multiple radio access technologies for multi-service support below 6i¾źGHz will be too costly. FANTASTIC-5G will develop a new multi-service air interface through a modular design. To allow the system to adapt to the anticipated heterogeneity, some properties need to be pursued, like simplicity, flexibility, scalability, versatility, efficiency and future proofness. Based on these properties, a selected set of use cases and link and network design will be presented. The paper will also comprise validation and system level simulations through some indicative results and will conclude with the overall impact to 5G standardisation. Copyright

Improving the DVB-T2 BICM performance by newly optimized Two-Dimensional Non-Uniform Constellations

This paper focuses on the potential enhancements of the DVB-T2 standard by the use of newly designed Two-Dimensional Non-Uniform Constellations (2D-NUQAM). In this work, a complete analysis of the DVB-T2 system performance when using the proposed 2D-NUQAM constellations against regular uniform (M-QAM) is presented. Based on the optimization of the Bit-interleaved Coded Modulation (BICM) capacity, the designed constellations provide a potential performance improvement of 1.05 dB for the overall DVB-T2 system performance in high order constellations. All carried out analyses are based on a complete DVB-T2 system specification simulation where equivalent 64-QAM and 256-QAM constellation and all baseline code rates have been evaluated.

Non-orthogonal FQAM for multiple access in the uplink of 5G wireless networks.

5G wireless networks have received a lot of attention recently where different key performance indicators (KPIs) are addressed. Two of the major KPIs are the data throughput and the number of supported users. These KPIs are taken into account in the design of modulation and coding techniques. One of the most promising techniques for interference limited scenarios is frequency quadrature amplitude modulation (FQAM). FQAM improves user throughputs at cell-edge where interference is the limiting factor by using only some of the available frequency subcarriers. However, FQAM was mostly studied in downlink settings. Furthermore, FQAM is an orthogonal multiple access scheme that limits the number of users that can access the frequency resources, where each resource can be used by one user only. In this paper, we propose a new multiple access technique for the uplink of future 5G systems that is based on FQAM but relaxes the constraint of user orthogonality. More than one user can independently access the same set of frequency resources. Since the technique is proposed in the uplink where the computational complexity at the base station is not a major hurdle, we also propose to use iterative multiuser detection and decoding in order to improve the performance and better separate the overlapping users. Simulation results show that this technique significantly increases the number of supported users as well as the total system throughput compared with orthogonal transmission techniques.

Cooperative multicast resource allocation strategy

In this paper we propose a new cooperative video multicast strategy, the so called Coordinated Multiple Relays (CoMR). The strategy is based on an efficient one-to-many resource sharing technique which exploits the space diversity of the two hop topology. The proposed scheme ensures a) significant gain in terms of coverage provided by relay deployment, b) boosted Signal to Interference and Noise Ratios (SINRs) at the second phase of the two hop transmission due to the positive superposition of synchronous transmissions, and c) the flexibility to switch to non-cooperative mode whenever cooperation is no longer beneficial. The new scheme showed considerable enhancement of both system throughput and user fairness and noticeable improvement in terms of energy efficiency compared to the non-cooperative multicast scheme.

Energy aware buffer aided cooperative relay selection

In this paper we evaluate an energy-aware relay selection mechanism which exploits channel state information and the availability of buffers at relays to perform flexible relaying based on a backpressure-driven optimization model. This model ensures the maximization of the cell throughput while maintains the stability of backlog queues. Performance evaluation is conducted using a System Level Simulator (SLS) which is fully compliant with IEEE 802.16m and supports various relaying scenarios. The Below Roof Top (BRT) relaying scenario is considered in this work. A holistic and flexible energy framework is implemented to capture the energy consumption of the cellular network nodes. The model maps the RF output power radiated at the antenna elements of each node including relays on the network to the total supply power of the node equipment. Two derivatives of the proposed mechanism, half-duplex and full-duplex are proposed and evaluated. Results of the two derivatives on BRT relaying scenario revealed noticeable increases for both cell throughput and system energy efficiency of the cell-edge users compared to the conventional relaying protocol and the non cooperative scheme.

Throughput optimization of precoded OFDM with hierarchical modulation

This paper investigates the throughput optimization of precoded Orthogonal Frequency Division Multiplexing (OFDM) with hierarchical modulation. Using the asymptotic analysis approach we derive the limit bit error rate (BER) of the high priority and the low priority streams. We then use the effective Signal to Interference plus Noise Ratio (SINR) corresponding to each stream to calculate the aggregate throughput achieved by the system. We study the behavior of the throughput as a function of the two design parameters: the coding rate and the constellation ratio. Simulation results show that the asymptotic expressions provide a very good approximation of the BER and that the throughput can be maximized by choosing appropriate values for the design parameters. We conclude on when it is advantageous to use hierarchical modulation and on the optimal values of the constellation ratio and the coding rate to be used for each Signal to Noise Ratio (SNR).

Joint detection and channel estimation for broadcast OFDM systems using hybrid Zadoff Chu pilots

In this paper we propose a hybrid Zadoff-Chu (ZC) based pilot sequence suitable for OFDM broadcast systems. While maintaining the same scattered pilot structure and the same power level as in DVB-T2, we replace the phase values by a ZC combined sequence. This combined sequence can either carry information bits through a repetition of small ZC patterns, or serve just as a very robust fine time domain synchronization mechanism. We present the design methodology for different OFDM systems, the possible ZC patterns sequences valid for signaling and provide a recommended structure for DVB-T2 like systems. Simulation results show that, without degrading the pilot channel estimation, an additional time domain synchronization more robust than P1 of DVB-T2 is achieved in each OFDM symbol. The proposed structure can be used as a design basis for future broadcast systems to build on, where a separate preamble will no longer be needed, thus, reducing the frame overhead.

Multichannel Design of Non Uniform Constellations for Broadcast/Multicast Services

Recent studies have shown the potential performance gain of Non Uniform Constellations (NUC) compared to the conventional uniform constellations. NUC can be a promising candidate in 5G systems to increase the data throughput. In the literature, NUC is designed for a specific SNR value and propagation channel. However, in broadcast/multicast services, the received signal by different users will see independent and different channels. Hence, in this paper, we focus on the potential gain of NUC when jointly optimized for more than one propagation channel. In order to assess the gain, we propose an iterative algorithm to jointly optimize the NUC for different channel conditions. The resulting constellations are then compared to uniform constellation and single channel NUC. The simulation results show that the newly designed constellations outperform the classical single channel NUC across different channel conditions when the average performance (across different channels) is considered.