Alain Mourad

Xhaul: toward an integrated fronthaul/backhaul architecture in 5G networks

The Xhaul architecture presented in this article is aimed at developing a 5G integrated backhaul and fronthaul transport network enabling flexible and software-defined reconfiguration of all networking elements in a multi-tenant and service-oriented unified management environment. The Xhaul transport network vision consists of high-capacity switches and heterogeneous transmission links (e.g., fiber or wireless optics, high-capacity copper, mmWave) interconnecting remote radio heads, 5G points of attachment (5GPoAs, e.g., macro- and small cells), centralized- processing units (mini data centers), and points of presence of the core networks of one or multiple service provider(s). This transport network shall flexibly interconnect distributed 5G radio access and core network functions, hosted on network centralized nodes, through the implementation of a control infrastructure using a unified, abstract network model for control plane integration (Xhaul Control Infrastructure, XCI); and a unified data plane encompassing innovative high-capacity transmission technologies and novel deterministic-latency switch architectures (Xhaul packet Forwarding Element, XFE). Standardization is expected to play a major role in a future 5G integrated front haul/backhaul architecture for multi-vendor interoperability reasons. To this end, we review the major relevant activities in the current standardization landscape and the potential impact on the Xhaul architecture.

New Frequency-Time Scheduling Algorithms for 3GPP/LTE-like OFDMA Air Interface in the Downlink

This paper proposes new frequency-time schedulers for 3GPP/LTE-like system in the downlink. 3GPP/LTE DL is OFDMA-based with adaptive modulation and coding (AMC) and frequency-time scheduling to enhance spectral efficiency and aggregate system throughput. Time-frequency scheduling and AMC can be implemented jointly or separately i.e. sequentially AMC after scheduling. Two novel schedulers are proposed in this paper with respectively joint and separate implementation of scheduling and AMC. Through system level performance evaluation, results show that the first scheduler with separate AMC and scheduling implementation outperforms the second scheduler (with joint AMC implementation) in terms of trade off between fairness and capacity and implementation complexity.

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.

5G-Crosshaul: An SDN/NFV control and data plane architecture for the 5G integrated Fronthaul/Backhaul

This paper presents the control and data plane architecture design for a 5G transport solution 5G-Crosshaul with the aim of integrating the fronthaul and backhaul network segments in a common transport stratum. The control plane relies on the Software-defined networking/Network Functions Virtualization concept to control and orchestrate the different elements of the network the 5G-Crosshaul control infrastructure. The data plane is based on an mixed optical/packet-based forwarding entity the 5G-Crosshaul forwarding element that leverages the benefits of optical passthrough with the statistical multiplexing of packet-based transmission, working on top of a common frame format for both, fronthaul, and backhaul traffic the 5G-Crosshaul common frame. In addition to the main architecture design, this work includes the impact of providing multi-tenancy support into the architecture of the overall system, in order to share the costs of building and operating the infrastructure among different operators.

Joint Transmit Antenna and space-time coding selection for WiMAX MIMO systems

In this paper the combination of Transmit Antenna Selection with Linear Dispersion Code Selection is studied. Two optimization criteria are proposed (bit error rate minimization and throughput maximization). The performance of the proposed spatial link adaptation scheme is evaluated under low mobility environments concluding that maximum spatial diversity is achieved as well as a smooth transition between codes with low spatial multiplexing rate and high spatial diversity (suitable for low SNR), to codes with high multiplexing rate but low diversity order (suitable for high SNR) maximizing the overall system throughput1.

System level evaluation for WiMAX IEEE 802.16m

This paper presents a system level simulator for the evaluation of WiMAX IEEE 802.16m technologies in a multi-cellular environment. This simulator is a quite powerful tool which allows quantifying the benefits of proposed air interface technologies on overall system performance using several metrics. As a case of study, the paper conducts performance evaluation of WiMAX IEEE 802.16m contiguous and distributed sub-channelization modes. The results obtained show a clear advantage for the distributed mode in term of system throughput but not in term of number of simultaneously active users. Similarly, many different cases of study can be further conducted using this simulation platform, which will yield crystal clear conclusions on the performance of WiMAX IEEE 802.16m system.

Towards a unified fronthaul-backhaul data plane for 5G The 5G-Crosshaul project approach

The paper presents a study of key aspects in the design of a flexible unified data plane capable of integrating both fronthaul and backhaul transport in future 5G systems. In this study, we first review candidate access and multiplexing technologies from the state of the art and assess their capability to support legacy and new fronthaul and backhaul traffic. We then propose a new design framework for the targeted flexible unified data plane, featuring a primary packet-switching path supported by an auxiliary circuit-switching for extreme low latency scenarios. This comprises a summary of the first results achieved in the 5G-Crosshaul EU project since its kick-off in July 2015.

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).