Network capacity analysis for cellular based cognitive radio VANET in urban grid scenario

The spectrum scarcity of VANETs(Vehicular Ad hoc Networks)can be alleviated by spectrum sharing technology.We present a framework of CCR-VANETs(Cellular-based Cognitive-radio Vehicular Ad hoc Networks).In CCR-VANETs,cellular network performs as primary network while VANET shares the downlink spectrum of cellular network.We consider a scalable urban grid scenario in which vehicles detect available spectrum holes and opportunistically access them according to a carrier-sensing multiple-access protocol.To restrict vehicles'interference to primary receivers,we set a square preservation region around each particular street block where an active base station is located.The number of street blocks in the preservation region is calculated with the practical assumption that vehicles only know the locations of primary transmitters.We analyze the aggregate interference power from primary and secondary networks,then derive the lower-bound of downlink capacity for the primary network and lower-bound of V2V(Vehicle-to-Vehicle)channel capacity for the secondary network respectively.The numerical results demonstrate the impacts of di erent network parameters on inter-networks interference level and network capacities.

Determining capacity of multimodal multi-commodities freight transportation network from critical link volumes

The commodity transportation capacity between all origin-destination （ OD ） pairs over the multimodal multi-commodities freight transportation network （MMFTN） is determined. A multi-ob- jectives mathematical model is formulated for determining the OD capacity over the MMFTN accord- ing to a transporting capacity matrix that increased from the reference matrixes. The corresponding incremental factor for estimating the capacity matrix is obtained via the maximal likelihood estima- tion method that samples data of differences between the estimated commodity volumes and carrying capacities of the critical links. The proposed formulations are tested by an experimental highway and railroad freight transportation network in an existing literature. The relevant results of OD capacities are displayed and applicability of the algorithm is certified.

Study on QoS and Communications Capacity in Heterogeneous Network Convergence

To provide any subscriber from anywhere at anytime with services that have both secured Quality of Service(QoS) and simultaneous expansion of network coverage and communications capacity is a key problem that has to be considered and solved in heterogeneous network convergence.Key technologies for a secured QoS and communications capacity analysis under heterogeneous environment are important subjects for research.Key technologies for a secured QoS are mainly on radio resource management algorithms covering Call Admission Control(CAC) algorithm,vertical handover algorithm,heterogeneous resource allocation algorithm and network selection algorithm.The applications of a novel multi-hop in heterogeneous convergence system serve the purposes of network coverage expansion,transmission power reduction,system communication capacity and throughput increase.

Optimization of Development Intensity Index of Regulatory Land under the Constraint of Bearing Capacity of Road Network:A Case Study of Xingtang County

In the process of urban development in China,the vast majority of urban construction is faced with the prominent contradiction between scarce land resources and vigorous construction demand.Moreover,high-density and high-intensity development is ubiquitous.However,the overall development amount of a city is restricted by the bearing capacity of road network to some extent,and there is an upper limit.Based on this,Xingtang County of Shijiazhuang City is taken as the research object,and bearing capacity of road network is selected as research emphasis.With the aid of traffi c planning software TransCAD,simulation and quantitative analysis are conducted,and traffi c demand is forecasted,to analyze impact relationship between land-use planning and traffic planning in regulatory planning.It facilitates later modifi cation and optimization of volume rate in the land development intensity index,thus providing rational basis for programme adjustment,preparation and management of regulatory planning in Xingtang County.

Network Evaluation and Protocol Deployment for Complex Deep-Space Networks Based on DTN

Previous research on deep-space networks based on delay-tolerant networking(DTN)has mainly focused on the performance of DTN protocols in simple networks;hence,research on complex networks is lacking.In this paper,we focus on network evaluation and protocol deployment for complex DTNbased deep-space networks and apply the results to a novel complex deep-space network based on the Universal Interplanetary Communication Network(UNICON-CDSN)proposed by the National Space Science Center(NSSC)for simulation and verification.A network evaluation method based on network capacity and memory analysis is proposed.Based on a performance comparison between the Licklider Transmission Protocol(LTP)and the Transmission Control Protocol(TCP)with the Bundle Protocol(BP)in various communication scenarios,a transport protocol configuration proposal is developed and used to construct an LTP deployment scheme for UNICON-CDSN.For the LTP deployment scheme,a theoretical model of file delivery time over complex deep-space networks is built.A network evaluation with the method proposed in this paper proves that UNICONCDSN satisfies the requirements for the 2020 Mars exploration mission Curiosity.Moreover,simulation results from a universal space communication network testbed(USCNT)designed by us show that the LTP deployment scheme is suitable for UNICON-CDSN.

Global forward-predicting dynamic routing for traffic concurrency space stereo multi-layer scale-free network

Many real communication networks, such as oceanic monitoring network and land environment observation network,can be described as space stereo multi-layer structure, and the traffic in these networks is concurrent. Understanding how traffic dynamics depend on these real communication networks and finding an effective routing strategy that can fit the circumstance of traffic concurrency and enhance the network performance are necessary. In this light, we propose a traffic model for space stereo multi-layer complex network and introduce two kinds of global forward-predicting dynamic routing strategies, global forward-predicting hybrid minimum queue（HMQ） routing strategy and global forward-predicting hybrid minimum degree and queue（HMDQ） routing strategy, for traffic concurrency space stereo multi-layer scale-free networks. By applying forward-predicting strategy, the proposed routing strategies achieve better performances in traffic concurrency space stereo multi-layer scale-free networks. Compared with the efficient routing strategy and global dynamic routing strategy, HMDQ and HMQ routing strategies can optimize the traffic distribution, alleviate the number of congested packets effectively and reach much higher network capacity.

The Impact of RTS Threshold on Capacity of IEEE 802.11 DCF

Based on delicate mathematical model, the average time in a successful and unsuccessful transmission is worked out. Then the relation between network saturation throughput and RTS threshold is found and expressed in a theoretical formula. Our analysis shows that there is an optimum RTS threshold that can maximize the network capacity. The numerical techniques to find out the optimum RTS threshold are also presented. All these analysis are well validated by computer simulation.

Minimum Cost of Capacity Expansion for Time-Limited Transportation Problem On-Demand

The minimum cost of capacity expansion for time-limited transportation problem on-demand (MCCETLTPD) is to find such a practicable capacity expansion transportation scheme satisfying the time-limited T along with all origins’ supply and all destinations’ demands as well as the expanding cost is minimum. Actually, MCCETLTPD is a balance transportation problem and a variant problem of minimum cost maximum flow problem. In this paper, by creating a mathematical model and constructing a network with lower and upper arc capacities, MCCETLTPD is transformed into searching feasible flow in the constructed network, and consequently, an algorithm MCCETLTPD-A is developed as MCCETLTPD’s solution method basing minimum cost maximum flow algorithm. Computational study validates that the MCCETLTPD-A algorithm is an efficient approach to solving the MCCETLTPD.

Maximizing Networking Capacity in Multi-Channel Multi-Radio Wireless Networks

Providing each node with one or more multi-channel radios offers a promising avenue for enhancing the network capacity by simultaneously exploiting multiple non-overlapping channels through different radio interfaces and mitigating interferences through proper channel assignment. However, it is quite challenging to effectively utilize multiple channels and/or multiple radios to maximize throughput capacity. The National Natural Science Foundation of China（NSFC） Project61128005 conducted comprehensive algorithmic-theoretic and queuing-theoretic studies of maximizing wireless networking capacity in multi-channel multi-radio（MC-MR） wireless networks under the protocol interference model and fundamentally advanced the state of the art. In addition, under the notoriously hard physical interference model, this project has taken initial algorithmic studies on maximizing the network capacity, with or without power control. We expect the new techniques and tools developed in this project will have wide applications in capacity planning, resource allocation and sharing, and protocol design for wireless networks, and will serve as the basis for future algorithm developments in wireless networks with advanced features, such as multi-input multi-output（MIMO） wireless networks.

Delay and Capacity Trade-offs in Mobile Wireless Networks with Infrastructure Support

In this paper,we investigate the trade-offs between delay and capacity in mobile wireless networks with infrastructure support.We consider three different mobility models,independent and identically distributed （i.i.d） mobility model,random walk mobility model with constant speed and L＇evy flight mobility model.For i.i.d mobility model and random walk mobility model with the speed θ（1/n～（1/2））,,we get the theoretical results of the average packet delay when capacityis θ（1）,θ（1/n～（1/2）） individually,where n is the number of nodes.We find that the optimal average packet delay is achieved whencapacity λ（n） 〈（1/（2.n.log_2（1/（（1-e）-（k/n））＋1））,where K is the number of gateways.It is proved that average packet delay D（n） dividedby capacity λ（n） is bounded below by （n/（k·w））.When ω（n～（1/2））≤KO（n（（1-η）·（α＋1））/2）ln n） when K=o（n～η）（0≤η〈1）.We also provethat when ω（1/2）≤K）.

Air route network optimization in fragmented airspace based on cellular automata

Air route network optimization,one of the essential parts of the airspace planning,is an effective way to optimize airspace resources,increase airspace capacity,and alleviate air traffic congestion.However,little has been done on the optimization of air route network in the fragmented airspace caused by prohibited,restricted,and dangerous areas（PRDs）.In this paper,an air route network optimization model is developed with the total operational cost as the objective function while airspace restriction,air route network capacity,and non-straight-line factors（NSLF） are taken as major constraints.A square grid cellular space,Moore neighbors,a fixed boundary,together with a set of rules for solving the route network optimization model are designed based on cellular automata.The empirical traffic of airports with the largest traffic volume in each of the 9 flight information regions in China's Mainland is collected as the origin-destination（OD） airport pair demands.Based on traffic patterns,the model generates 35 air routes which successfully avoids 144 PRDs.Compared with the current air route network structure,the number of nodes decreases by 41.67%,while the total length of flight segments and air routes drop by 32.03% and 5.82% respectively.The NSLF decreases by 5.82% with changes in the total length of the air route network.More importantly,the total operational cost of the whole network decreases by 6.22%.The computational results show the potential benefits of the model and the advantage of the algorithm.Optimization of air route network can significantly reduce operational cost while ensuring operation safety.

Steady-state security in distribution networks with large wind farms

Aging network assets,forced and unforced outages,and the way the networks are operated in a deregulated market are of significant concerns to integrate large wind farms in a distribution network.In many cases,the constrained network capacity is a potential barrier to the large-scale integration of wind power.This paper probabilistically assesses the steady-state security in a distribution network in the presence of large wind farms.The approach incorporates active distribution network operating conditions,including intermittent power outputs,random outages,demand fluctuations,and dynamic interactions and exchanges,and then assesses the steady state security using Monte Carlo simulation.A case study is performed by integrating large wind farms into a distribution network.The results suggest that intermittent outputs of large wind farms in a distribution network can impact the steady-state security considerably.However,the level of impact of wind farms does not necessarily correlate with the installed capacity of them.

On Error Detection of Intermediate Nodes Offour-Node Network with Small Downstream Links

We investigate the error detection ability of intermedi- ate nodes of zig-zag network with small downstream link. We show that the error detection capability of zig-zag networks in the presence of z malicious edges and 2z-1 limited links from node B to node u. Also, at last we analyze a family of networks, which shows that the upper bound of network is smaller than the bound we expected, indicating that Singleton bound is not the tightest bound in the particular condition of network. According to this result, we design corresponding encode and decode strategy to reach the bound we propose in this paper.

Microporous Organic Nanotube Networks from Hyper Cross-linking Core-shell Bottlebrush Copolymers for Selective Adsorption Study

We report a synthesis of microporous organic nanotube networks（MONNs） by a combination of hyper cross-linking and molecular templating of core-shell bottlebrush copolymers. The intrabrush and interbrush cross-linking of polystyrene（PS） shell layer in the core-shell bottlebrush copolymers led to the formation of micropores and large-sized nanopores（meso/macrospores） in MONNs, respectively, while selective removal of polylactide（PLA） core layer generated mesoporous tubular structure. The size of PLA-templated mesoporous cores and porous structure both at micro-and meso-scale could be controlled by simple tuning of the ratio of core/shell or the PLA core fraction in the bottlebrush precursors. Moreover, the resultant MONNs showed a highly selective adsorption capacity for the positively charged dyes on the basis of multi-porosity and carboxylate group-rich structure. In addition, MONNs also exhibited effective performance in size-selective adsorption of biomacromolecules. This work represents a new avenue for the preparation of MONNs and also provides a new application for molecular bottlebrushes in nanotechnology.

Upper Bound for Unequal Zig-Zag Network with Small Downstream

We consider the problem of characterizing network capacity in the presence of adversarial errors on network links,focusing in particular on the effect of small downstream links,where the downstream link is the directed link of feedback links across the cut of network.In this paper,we present a family of zigzag networks where the inner bound and the outer bound coincide.We also establish tight condition for this family of zig-zag network,and develop encoding scheme and detection and decoding strategy.

The Frame of Knowledge-networking Capability in Virtual Rnterprise and Its Promotion Strategy

Based on Virtual Enterprise （VE）, the knowledge networking capacity （KNC） is researched. The knowledge networking capability is divided into four dimensions, including planning capability, building capabil ity, running capability and updating capability, by analyzing the challenge to the knowledge network. Then, atheoretical framework and a dynamic system are built to the knowledge network and promote a great innovation in virtual enterprise by knowledge flow. farthermore, enhance the strategy of improving knowledge networking ca pacity of virtual enterprise to help the enterprise handle the problem of knowledge network better is proposed. hancing knowledge network, thereby, facilitates virtual enterprise to adapt the market need.

Optimal Relay Assignment and Power Allocation for Cooperative Communications

Cooperative communication for wireless networks has gained a lot of recent interest due to its ability to mitigate fading with exploration of spatial diversity. In this paper, we study a joint optimization problem of jointly considering transmission mode selection, relay assignment and power allocation to maximize the capacity of the network through cooperative wireless communications. This problem is much more challenging than relay assignment considered in literature work which simply targets to maximize the transmission capacity for a single transmission pair. We formulate the problem as a variation of the maximum weight matching problem where the weight is a function over power values which must meet power constraints （VMWMC）. Although VMWMC is a non-convex problem whose complexity increases exponentially with the number of relay nodes, we show that the duality gap of VMWMC is virtual zero. Based on this result, we propose a solution using Lagrange dual decomposition to reduce the computation complexity. We do simulations to evaluate the performance of the proposed solution. The results show that our solution can achieve maximum network capacity with much less computation time compared with exhaustive search, and our solution outperforms existing sub-optimal solutions that can only achieve much lower network capacity.