Seismic Response of Structures with Underground Stories Considering Non-Linear Soil-Structure Interaction

Most of the research conducted for soil-structure interaction analysis of structures are assuming the linear behavior of soil. It is well known that during strong ground excitations the soil adjacent to the structure behaves highly non-linear. The nonlinear soil behavior affects the soil-structure interaction in a complex way especially because of the inadequacy in modeling the unbounded soil medium. In the case where an elastic soil behavior is assumed, the surface motion will be amplified proportionally to the input motion. However, in reality the amplitude and frequency content of the response are modified due to the soil’s stiffness degradation and higher energy dissipation. The present work deals with the influence of soil non-linearity, introduced by hysteretic behavior of near-field soil, on the soil-foundation-structure interaction phenomena. The objective is to reveal the beneficial or detrimental effects of the non-linear SSI concerning both the drift and settlement of structures with underground stories. To examine the effect of non-linear soil-structure interaction a realistic non-linear soil model is incorporated into the finite difference FLAC software. To better understanding the non-linear dynamic SSI, interface elements are also used between the near-field soil and basement walls. For a practical structure throughout a parametric study, some non-linear seismic analyses are performed to demonstrate the effectiveness of the affecting parameters in response of the structure. The results showed much difference on seismic response of structure such as drift, settlement and developing pressure around the basement walls when the non-linear soil-structure interaction is considered

Sl-EDGE: Network Slicing at the Edge

Network slicing of multi-access edge computing (MEC) resources is expected to be a pivotal technology to the success of 5G networks and beyond. The key challenge that sets MEC slicing apart from traditional resource allocation problems is that edge nodes depend on tightly-intertwined and strictly-constrained networking, computation and storage resources. Therefore, instantiating MEC slices without incurring in resource over-provisioning is hardly addressable with existing slicing algorithms. The main innovation of this paper is Sl-EDGE, a unified MEC slicing framework that allows network operators to instantiate heterogeneous slice services (e.g., video streaming, caching, 5G network access) on edge devices. We first describe the architecture and operations of Sl-EDGE, and then show that the problem of optimally instantiating joint network-MEC slices is NP-hard. Thus, we propose near-optimal algorithms that leverage key similarities among edge nodes and resource virtualization to instantiate heterogeneous slices 7.5x faster and within 0.25 of the optimum. We first assess the performance of our algorithms through extensive numerical analysis, and show that Sl-EDGE instantiates slices 6x more efficiently then state-of-the-art MEC slicing algorithms. Furthermore, experimental results on a 24-radio testbed with 9 smartphones demonstrate that Sl-EDGE provides at once highly-efficient slicing of joint LTE connectivity, video streaming over WiFi, and ffmpeg video transcoding

Hybrid transmission scheme and relay selection in LTE-advanced network: Graph-based approach

This paper proposes a dynamic resource block allocation scheme in relay-assisted bidirectional LTE-Advanced networks which consists of three nodes: User Equipment (UE), Base Station or eNodeB (eNB) and an intermediate Relay Node (RN). In this work, an enhanced three-time-slot per cycle timedivision duplexing (TDD) transmission protocol is proposed to the LTE-Advanced frame architecture. In such a protocol, UEs and the eNB can choose between different transmission schemes: direct transmission, pure Cooperative relaying (CoR scheme) using an intermediate relay station, or via the combination of Network Coding and Cooperative Relaying (NC/CoR scheme). A graph-based framework is proposed to solve the NP-hard combinatorial optimization problem. Our problem is transformed into a maximum weighted clique problem and used to provide optimal achievable rate regions for the hybrid transmission scheme, resource block assignment and relay selection. The proposed hybrid transmission scheme determines the best transmission strategy among direct transmission, CoR and NC/CoR in each three-time-slot cycle based on the system channel information as well as the queue length information. The simulation results show that our optimization algorithm significantly outperforms conventional schemes for both SISO and MIMO systems

Optimal server assignment in multi-server queueing systems with random connectivities

In this paper, we provide complementary results on delay-optimal server allocation in multi-queue multi-server (MQMS) systems with random connectivities. More specifically, we consider an MQMS system where each queue is limited to get service by at most one server during each time slot. It is known that maximum weighted matching (MWM) is a throughput-optimal server assignment policy for such a system. In this paper, using dynamic coupling argument we prove that for a system with i.i.d. Bernoulli arrivals and connectivities, MWM minimizes, in stochastic ordering sense, a range of cost functions of the queue lengths such as total queue occupancy (which implies minimization of average queueing delay). Finally, we propose a low complexity heuristic server assignment policy for MQMS systems namely least connected server first/longest connected queue (LCSF/LCQ) and through simulations we show that it performs very closely compared with the optimal policy in terms of average queueing delay

Joint Resource Allocation and Relay Selection in LTE-Advanced Network Using Hybrid Co-Operative Relaying and Network Coding

The problem of joint resource allocation and relay selection is studied for bidirectional LTE-advanced relay networks. The bidirectional communication between user equipment (UE) and eNodeB (eNB) is performed via direct transmission, co-operative relaying (CoR), or a combination of network coding (NC) and CoR (NC/CoR). In this paper, an enhanced three-time-slot per cycle time-division duplexing (TDD) scheme is proposed for LTE-Advanced frame architecture to accommodate a hybrid transmission scheme. More specifically, we formulate the problem of joint resource assignment, relay selection, and bidirectional transmission scheme selection as a combinatorial optimization problem with the objective to maximize the total product of backlog and rate (back-pressure principle). Two approaches are considered to solve our combinatorial optimization problem. First, a graph-based framework is proposed in which the problem is transformed into a maximum weighted Clique problem (MWCP). In addition, our problem is also transformed into a three-dimensional assignment problem (3DAP) which is solved using a hybrid ant colony optimization (ACO) algorithm. Using simulations, it is concluded that the hybrid transmission scheme outperforms all conventional nonhybrid schemes. Moreover, the simulation results confirm that while the two proposed solutions provide similar results, the ACO algorithm is faster due to its lower complexity

Ant colony optimization for joint resource allocation and relay selection in LTE-advanced networks

In this paper, we study the problem of optimal resource allocation in relay-assisted bidirectional LTE-Advanced networks. The bidirectional network consists of User Equipment (UE), Base Station or eNodeB (eNB) and a Relay Node (RN). We model the network by using a Two-Way Relay Channel (TWRC) in which UE and eNB can choose between different transmission schemes: direct transmission, pure CoR (CoR scheme), or via the combination of Network Coding and Cooperative Relaying (NC/CoR scheme). In this paper, an enhanced three-time-slot per cycle time-division duplexing (TDD) transmission scheme is proposed for LTE-Advanced frame architecture to accommodate the hybrid transmission scheme. We formulate the joint problem of subcarrier assignment, relay selection, and bidirectional transmission scheme selection as a combinatorial optimization problem to maximize the system total product of backlog and rate (backpressure principle). The problem is then transformed into a three-dimensional assignment problem which is solved using a hybrid ant colony optimization (ACO) algorithm. The simulation results show that our optimization algorithm significantly outperforms conventional schemes for both SISO and MIMO systems

Scheduling for optimal file-Transfer delay using chunked random linear network coding broadcast

We study the broadcast transmission of a single file to an arbitrary number of receivers using Random Linear Network Coding (RLNC) in a network with unreliable channels. Due to the increased computational complexity of the decoding process (especially for large files), we apply chunked RLNC (i.e., RLNC is applied within non-overlapping subsets of the file). In our work, we show the optimality of the Least Received (LR) batch scheduling policy with regards to the expected file transfer completion time. The LR policy strives to keep the receiver queues balanced. This is done by transmitting packets (corresponding to encoded batches) that are needed by the receivers with the shortest queues of successfully received packets. Furthermore, we provide formulas for the expected time for the file transmission to all receivers using the LR batch scheduling policy and the minimum achievable coding window size in the case of a pre-defined delay constraint. Moreover, we evaluate through simulations a modification of the LR policy in a more realistic system setting with reduced feedback from the receivers. Finally, we provide an initial analysis and further modifications to the LR policy for time-correlated channels and asymmetric channels

Optimal joint resource allocation and power control in bidirectional relaying networks

Cooperative relaying (CoR) and network coding (NC) are two promising techniques for improving the performance of next-generation mobile networks. In this paper, a dynamic joint resource allocation and power control scheme is proposed for bidirectional relaying in wireless mobile networks. We consider a bidirectional relaying network consisting of three nodes: user equipment (UE), base station or eNodeB (eNB), and an intermediate relay station (RS). We model the network by a two-way relay channel (TWRC) in which UE and eNB can choose between different transmission schemes: direct transmission, pure CoR (CoR scheme), or via the combination of NC and CoR (NC/CoR scheme). We first study the achievable rate regions for direct transmission, CoR, and NC/CoR and characterize them by a set of linear inequalities. We show that NC/CoR does not always achieve better performance than CoR or direct transmission in terms of achievable throughput. Therefore, we propose a hybrid transmission scheme with adaptive resource allocation to dynamically choose the best transmission strategy and the optimal resource allocation at each bidirectional transmission time frame. This is done on the basis of the system channel state information and the buffer occupancy of UE and eNB. The hybrid approach achieves the convex hull of the union of the rate regions of the direct, CoR, and NC/CoR schemes. Finally, we extend our hybrid approach by considering power control at the RS, and we use simulations to study the effect of power control in the hybrid scheme. It is shown that in both single-input-single-output and multiple-input-multiple-output systems, the hybrid scheme with joint power control and resource allocation improves the throughput and delay performance of the system considerably

Network capacity region of multi-queue multi-server queueing system with time varying connectivities

Network capacity region of multi-queue multi-server queueing system with random connectivities and stationary arrival processes is studied in this paper. Specifically, the necessary and sufficient conditions for the stability of the system are derived under general arrival processes with finite first and second moments. In the case of stationary arrival processes, these conditions establish the network capacity region of the system. It is also shown that AS/LCQ (Any Server/Longest Connected Queue) policy stabilizes the system when it is stabilizable. Furthermore, an upper bound for the average queue occupancy is derived for this policy