Ahmad Awada

Field Trial of LTE eMBMS Network for TV Distribution: Experimental Results and Analysis

In recent years, the advances in mobile network technologies have revolutionized the paradigm how the users receive video and audio content. With the rise of smart phones and tablets having large screens, users have become more interested than anytime before in watching linear and non-linear TV programs on their mobile devices. This is because the users can fetch nowadays the content using their mobile devices at anytime and any place they are located. Facing this phenomenon, broadcasters are looking for new means to reach the users of digital natives that are interested in watching TV on their mobile devices. As most mobile devices are based on a global 3rd generation partnership project standard, the enhanced multimedia broadcast multicast system (eMBMS) of long term evolution (LTE) network is foreseen as one potential candidate for delivering broadcast services. In order to investigate the capability and limitations of today’s LTE eMBMS network, a field trial was carried out in Munich, Germany. This paper describes the setup of the field trial and presents a comprehensive analysis of the LTE eMBMS technology with respect to performance and future enhancements. The measurement data is compared against simulation models for field strength and path loss of each transmitter, eMBMS useful field strength and received power, and signal-to-interference and noise ratio (SINR). Moreover, the performance of cyclic prefix (CP) durations that are longer than the standardized values of 16.67 us and 33.33 us is evaluated using the calibrated simulation models. Results have shown that the simulation models can adequately predict the measurement data. Moreover, it is shown that a CP duration of 66.67 us provides a gain in SINR and achieves the best tradeoff in terms of maximum user velocity and performance in networks with limited inter-site distance.

Fast cell select for mobility robustness in intra-frequency 5G ultra dense networks

5th Generation (5G) mobile networks are required to support transmission of capacity demanding services such as real-time remote computing without any interruption. One of the candidate solution for high capacity is Ultra Dense Networks (UDNs). However, UDNs are characterized by fast change of the received signal by a user. The fast change of the signal and high speed of users create too many handovers and connection failures such as handover failures and Radio Link Failures (RLFs). Consequently, conventional handovers and connection failures are the major sources of service interruption. To achieve ultra-reliable communication by tackling the service interruptions, this paper proposes a novel multi-connectivity scheme that uses fast selection of serving cell from a set of prepared cells. A similar feature in Long Term Evolution — Advanced (LTE-A) that is defined under Coordinated Multi-Point (CoMP) transmission is Dynamic Point Selection (DPS). However, in DPS a cell is selected dynamically for transmission of only data signals. Transmission of mobility related control signals is performed through one primary cell which is changed through a conventional handover. Unlike DPS, this paper proposes that the selected cell, from the set of prepared cells, is used for transmission of both data and control signals. Simulation results show that the connection failures due to RLFs are considerably resolved by the proposed scheme.

Evaluation of Context-Aware Mobility Robustness Optimization and Multi-Connectivity in Intra-Frequency 5G Ultra Dense Networks

Practical implementation of context-aware mobility robustness technique and a multi-connectivity scheme are investigated based on the requirements of 5th generation networks. Results show that context-aware mobility robustness considerably reduces connection failures and lowers the signaling overhead from handovers, but it has limitations in supporting ultra high reliability applications. On the other hand, multi-connectivity supports ultra high reliability applications at the expense of signaling overhead.

Impact of Mobility on the Reliability Performance of 5G Multi-Connectivity Architectures

The support of mission-critical use cases is an ambitious goal of the upcoming fifth generation of mobile networks. In addition to challenging requirements regarding reliability and latency, particular use cases need to be supported in high mobility scenarios as well. To avoid extensive system simulations and enable studies of very small outage probabilities, we integrate mobility effects into an existing signal-to-interference- plus-noise ratio (SINR) model by combining the model with results from a mobility simulation. An evaluation of the model corroborates that high mobility can severely deteriorate the reliability performance in traditional single-connectivity architectures. As potential countermeasures, inter- and intra-frequency multi-connectivity are identified. Results show that high reliability of 99.999% or greater becomes possible if a sufficient number of connections is utilized.

A simplified deterministic channel model for user mobility investigations in 5G networks

High frequency bands are considered for the fifth generation (5G) mobile networks to handle the continuous increase in the demand for cellular data traffic. However, the propagation conditions in high frequency bands are more challenging than in low frequency bands, making the radio link more susceptible to obstruction. These new radio aspects impose new challenges on the design of user mobility procedures which shall be tested by means of simulations. Current statistical propagation models lack the accuracy in capturing spatial correlation, channel degradation when the user is obstructed and frequency correlation among different layers. On the other hand, deterministic channel models are too complex and inappropriate for mobility investigations since they require a high computational time. This paper proposes a simplified deterministic channel model which captures the propagation aspects that are relevant for mobility investigations. In addition, a model for signal measurement is proposed considering the impact of analog beamforming which is a key component in 5G networks. Simulations are performed to show the characteristics of the channel and received signal. The results corroborate that the signal degradation due to obstruction is faster for higher carrier frequency and user velocity, and slower for higher diffraction angle.

An improved method for on-demand system information broadcast in 5G networks

We argue for a new method that applies to on-demand system information (SI) broadcast transmissions. The proposed method is targeted for 5G networks, and is based upon utilizing a cut-off value for the modulation and coding scheme used for broadcasting. Two variants of the proposed scheme are presented, namely the reactive and proactive method, depending on whether the user equipment requests an additional (re)-transmission of the SI message before or after the reception of the first transmission. The main advantage of this approach is an increase of the resource usage efficiency, which is evaluated through closed-form expressions. The mathematical analysis is complemented by an extensive set of numerical results, which are corroborated via simulations.

Impact of cyclic prefix configuration on mobility performance of multi-connectivity in 5G networks

Service interruptions from mobility events, such as handovers and connection failures, are some of the major impairments for fulfilling the ultra-reliability requirements in fifth Generation (5G) mobile networks. One of the solutions to tackle the aforementioned challenges is multi-connectivity with Single Frequency Network (SFN) transmission, which refers to noncoherent joint transmission of a signal on the same radio resource in frequency and time. This paper investigates the impact of cyclic prefix configuration on user mobility performance using multiconnectivity with SFN transmission. The performance evaluation is carried out with respect to the number of connection failures, 5-%ile and average throughput. Simulation results have shown that, for a sufficiently long cyclic prefix duration, the multiconnectivity scheme can fully resolve connection failures, and improve 5-%ile and average throughput by around 33% and 9%, respectively, compared to single connectivity.