Efficient Computation Offloading Decision in Mobile Cloud Computing over 5G Network

Due to the significant advancement of Smartphone technology, the applications targeted for these devices are getting more and more complex and demanding of high power and resources. Mobile cloud computing (MCC) allows the Smart phones to perform these highly demanding tasks with the help of powerful cloud servers. However, to decide whether a given part of an application is cost-effective to execute in local mobile device or in the cloud server is a difficult problem in MCC. It is due to the trade-off between saving energy consumption while maintaining the strict latency requirements of applications. Currently, 5th generation mobile network (5G) is getting much attention, which can support increased network capacity, high data rate and low latency and can pave the way for solving the computation offloading problem in MCC. In this paper, we design an intelligent computation offloading system that takes tradeoff decisions for code offloading from a mobile device to cloud server over the 5G network. We develop a metric for tradeoff decision making that can maximize energy saving while maintain strict latency requirements of user applications in the 5G system. We evaluate the performances of the proposed system in a test-bed implementation, and the results show that it outperforms the state-of-the-art methods in terms of accuracy, computation and energy saving.     

Joint Power Allocation in Wireless Relay Networks: the Case of Hybrid Digital-Analog Transmission

In conventional digital communication systems, the quality of the received signal does not improve beyond a certain level as the channel quality increases. Such kind of quality saturation effect is caused by the unrecoverable quantization errors produced by source coding. The Hybrid Digital-Analog (HDA) transmission, where the quantization errors are transmitted in an analog mode along with the quantized data in a digital mode, has been recognized as an effective technique to combat the quality saturation effect. In this paper, we introduce HDA transmission in Wireless Relay Networks (WRNs) over Rayleigh slow-fading channels to eliminate the quality saturation effect and achieve graceful improvement for the better channel quality. Our goal is to minimize the end-to-end distortion by optimal power allocation. We note that digital-analog power allocation involved in HDA transmission is coupled with source-relay power allocation in WRNs. Therefore, the joint power allocation problem should be considered. We investigate this problem for two kinds of relays in WRNs, i.e., Amplify-and-Forward (AF) relays and Decode-and-Forward (DF) relays. In the case of AF relays, we find that the joint power problem is concave and thus derive the explicit expressions of the optimal solution. In the case of DF relays, we formulate the joint power allocation problem as a nonlinear fractional programming problem and then propose an efficient algorithm to search the optimal solution. Simulation results show that the proposed joint power allocation schemes outperform existing schemes in terms of end-to-end distortion in both WRNs with AF relays and that with DF relays under various channel conditions.     

RoBiN: Random Access using Border Routers in Cellular Networks

Introducing Machine-to-Machine (M2M) communications over traditional 4G cellular networks make the cellular random access channel more congested and collision-prone. In order to resolve this random access congestion, we propose RoBiN - Random access using Border router in M2M cellular Networks. RoBiN proposes an architectural modification of introducing small cells, called Border Routers (BR), in cellular networks, with complete frequency reuse capability. We formulate the aforementioned challenge in terms of collision probability and system capacity. Subsequently, we propose an efficient solution for M2M communications in cellular networks. Exhaustive mathematical analysis shows that RoBiN significantly improves the random access success probability, by 50 % over existing 4G cellular systems. Simulation results on typical 4G networks corroborate our mathematical analysis and demonstrate almost 15 dB increase in Signal-to-Interference-plus-Noise Ratio (SINR) and 3 times throughput improvements over legacy 4G cellular systems. Furthermore, RoBiN also achieves 50 %?80 % improvement in collision probability over existing time alignment matching work.     

Dynamic burst length controlling algorithm-based loss differentiation in OBS networks through shared FDL buffers

The FDL buffers can have only discrete delay values. Because of this discontinuity, in order to construct the FDL buffers, some parameters such as the offered load, the average data burst length, and the basic delay unit, of which the length of each FDL is consecutive multiples, should be considered. This means that if one or more parameters change, new FDL buffers are required. So, even when one or more parameters change, in order to minimize the effect of the change, a new service differentiation algorithm dynamically controlling data burst length based on a shared-type feed-forward FDL architecture is proposed in this paper. Various results show that the algorithm improves fairness between classes and significantly reduces the fluctuation of the number of delay lines for each class.     

Application of local error method to SSSF simulation of vector propagation in dispersion compensated optical links

A local error method based on an analytical scheme previously developed for the scalar optical fiber channel is applied to the second-order symmetrized split-step Fourier simulation of polarization multiplexed signal propagation through dispersion compensated optical fiber links. It is found that the global simulation accuracy for the vector propagation can be satisfied using the local error bound from a scalar propagation model for the same global error over a large range of simulation accuracy, chromatic dispersion, and differential group delay. Furthermore, carefully designed numerical simulations are used to show that similar local simulation error are obtained for vector simulations and that the similar local error leads to higher computational efficiency compared to other prevalent step-size selection schemes. The scaling of the global simulation error with respect to the number of optical fiber spans is demonstrated, and global error control for multi-span simulations is proposed. Combining the local error and global error control, the developed simulation scheme can significantly speed up the time-consuming simulations in coherent optical fiber communication system analysis and design.     

Designing a green optical network unit using ARMA-based traffic prediction for quality of service-aware traffic

The optical access networks (OANs) provide an attractive solution to the bandwidth bottleneck problem of the last mile. However, it has been proved (Baliga et al. in J Lightwave Technol 27(13):2391–2403, 2009; Baliga et al. in IEEE Commun Mag 49(6):70–77, 2011) that the OAN consumes a significant ratio of the total energy consumed in an optical networking scenario. This has provided incentive for inspection of energy-efficient schemes for OANs. It has been demonstrated in the literature that energy consumption figures of an OAN can be improved by either designing efficient hardware or employing better media access control (MAC) protocols. In this paper, we design a MAC protocol for OANs to ensure energy-efficiency in the presence of quality of service (QoS)-aware traffic. The proposed scheme incorporates traffic prediction-based selection of different sleep (energy-efficient) modes of operation, of the optical network units—ONUs (OAN end units). It also implements switching between different sleep modes to maintain high QoS with significant energy-efficiency figures. The discussed scheme requires processing at the ONU only and can work independent of the entire OAN (ONU assisted). Thus, our proposal is an attractive solution for the already deployed networks or even in green field deployment.     

An adaptive and efficient buffer management scheme for resource-constrained delay tolerant networks

Provisioning buffer management mechanism is especially crucial in resource-constrained delay tolerant networks (DTNs) as maximum data delivery ratio with minimum overhead is expected in highly congested environments. However, most DTN protocols do not consider resource limitations (e.g., buffer, bandwidth) and hence, results in performance degradation. To strangle and mitigate the impact of frequent buffer overflows, this paper presents an adaptive and efficient buffer management scheme called size-aware drop (SAD) that strives to improve buffer utilization and avoid unnecessary message drops. To improve data delivery ratio, SAD exactly determines the requirement based on differential of newly arrived message(s) and available space. To vacate inevitable space from a congested buffer, SAD strives to avoid redundant message drops and deliberate to pick and discard most appropriate message(s) to minimize overhead. The performance of SAD is validated through extensive simulations in realistic environments (i.e., resource-constrained and congested) with different mobility models (i.e., Random Waypoint and disaster). Simulation results demonstrate the performance supremacy of SAD in terms of delivery probability and overhead ratio besides other metrics when compared to contemporary schemes based on Epidemic (DOA and DLA) and PRoPHET (SHLI and MOFO).     

Schemes for the identification of tissue types and boundaries atthe tool point for surgical needles

Precise control of automated invasive surgical tools requires real-time identification of tissue types and their deformation. At the focus of this paper is the epidural puncture, for which it is shown that the tissue type and deformation can respectively be determined from laser-based spectroscopy and the change in force required to push the needle through the various tissues. Studies have shown that physiological variations from one patient to another are too great to allow absolute values to be reliably used to indicate the position of the needle tip. However, the pattern of force variation during penetration is shown to be similar between specimens. Interpretation of this information in conjunction with spectroscopic techniques can be used to discriminate between tissues and tissue structure at the needle tip. This paper describes results from an investigation on automatic techniques for interpreting the type and deformation of tissues under tool action     

Robust optimization of transmit/receive beamformer for MIMO downlink with imperfect CSI at base station

A robust scheme is proposed to jointly optimize transmit/receive beamformers for Multiple Input Multiple Output （MIMO） downlinks where the available Channel State Information （CSI） at Base Station （BS） （CSIBS） is imperfect. The criterion is to minimize the sum Mean Square Error （sum-MSE） over all users under a constraint on the total transmit power, which is a non-convex and non-linear problem. Observing from the first order optimization condition that the optimal transmit/receive beamformers are mutually dependent, the transmit/receive beamformers for each user are updated iteratively until the sum-MSE is minimized. Simulation results indicate that the proposed scheme can effectively mitigate the system performance loss induced by imperfect CSIBS.     

Packet loss analysis in optical packet-switched networks with limited deflection routing

We present an approximate analytical method for the evaluation of packet loss probability in synchronous optical packet-switched networks which operate under limited deflection routing with the contention resolution method based on priorities. Packets are lost because they are removed by nodes. They are removed because they experience too many deflections and stay prohibitively long in the network. Such packets have to be removed because they will be ignored by the transmission protocols (like TCP) and because the quality of their optical signal is unacceptable. Presented are results for the network in the topology of the torus of the two-dimensional grid, which operates at a steady state with the uniform load u, . The strength of our analysis is its novel mathematical approach, which is capable of providing very low packet loss probabilities. For the network composed of 100 nodes, we predict the packet loss probability as low as 10⁻⁹ or lower, while simulation provided results only at the order of 10⁻⁶. For a given permissible packet loss probability, our analysis provides the maximal network load and the number of allowed deflections. We verify the analysis with simulation in the cases for which simulation gave results.