Smart Grid uses the TCP/IP protocol stack for wide area communications. To ensure low latency end to end communications, the FREEDM project chooses UDP datagram as the preferred technique. However, when many devices are using the same network resources, congestion can happen on intermediate routers. Unlike TCP, which uses ECN as an approach for congestion control, UDP does not have a similar implementation in RFC. Therefore, in the FREEDM project, a user defined ECN protocol is developed. The protocol is implemented in a simulated OPNET router module, and the communications performance with and without the improvement is compared to justify the function. The paper introduces the concept in the communications implementation in the FREEDM project as well as the origin for ECN (Explicit Congestion Notification). An algorithm to adjust the terminal data rate based on the ECN notification mechanism is provided, and its simulation is implemented.

Since the problem of optimal radio channel assignment (RCA) is NP-hard, the existing RCA algorithms have to use heuristic approaches for any networks of practical sizes. However, the algorithms suffer from two major issues, i.e., unable to consider the co-channel interference (CCI), and finding only sub-optimal assignment. In this work, we propose a new strategy to overcome the two challenging issues. (1) To consider CCI among neighboring head routers (HRs) and their terminals, we propose to choose the average effective channel utilization (ECU) of an HR as the basic objective function. The function can be also the sum of the average ECU, for which the optimization target is directly to maximize the overall throughput. (2) We propose to use the simulated annealing (SA) algorithm to find the optimal assignment and use the Gibbs sampling (GS) technique to convert the global optimization problem to a series of local optimization problems. In this way, we propose a distributed optimal assignment, i.e., SA-GS-based RCA (SRCA) algorithm. Our extensive simulation results have demonstrated that SRCA outperforms all the existing RCA algorithms in achieving global optimality with bounded CS.

Actuated signal controllers (ASC) are widely deployed to control various intelligent traffic devices. However, there is not enough research on the security of the communication between a control console and the ASC. The communication protocol is SNMP for the management of the ASC. In this paper we will identity the major security threats against the SNMP-based ASC systems and propose possible defense techniques. First, we address the major attacks against the ASC systems, including UDP flooding attack, man-in-the-middle (MITM) attack, and VLAN hopping attack. Second, we launch these attacks against the ASC systems. Third, we demonstrate how to defend these attacks.

In many implementations of intelligent traffic system (ITS), the actuated signal controller (ASC) is widely deployed to control the traffic lights and other terminals. However, inadequate research has been done on the security for the link that goes between the ASC (e.g., primary device) and many secondary devices controlled by the ASC. The communication of the link is based on the old synchronous data link control (SDLC) protocol. The goal of this work is to identify and defense the major possible attacks against the SDLC-based ASC systems. First, we identify the major threats to an ASC system, including man-in-middle attacks, data tampering, bogus commands, and possible attacks, etc. Second, we develop an architecture for the network that supports a secure ASC, including authentication, data integrity, and confidentiality. Third, within such architecture, we propose the possible solutions to address the security issues, including the encryption and decryption algorithms. Finally, we present an applicable hardware and software framework and demonstrate the effectiveness of the proposed solutions by simulations.

The security of the control network has become a major concern since the wide deployment of smart grid systems. The functions of Intelligent Energy Management (IEM) highly depend on the communication techniques. The IEM is the service agent of smart grid communication network in a limited management zone for distributed and autonomous power system control and operations. In such a smart grid, the power flows are unpredictable. Therefore, the management nodes, i.e., IEM agents, form a communication network that has no fixed infrastructure. For this reason, the IEM network can be considered as an ad-hoc network. In this paper, the newly proposed TQOS (Trustworthiness-based Quality of Service) routing protocol is adopted to ensure that every power system communication session can be established through a secure route [1]. We calculate the performance cost of using certain encryption algorithm for building a secure route. By using Opnet simulator, we find the overall smart grid communication performance under different network conditions, by changing the network scales, packet generation size and rate, and the node processing capability. Our simulation results have demonstrated that the proposed secure and distributed network architecture can be applied to smart grid communications in practice.

A reliable and secure communication network plays a significant role in Smart grid systems, which aims at coordinating generation, transmission, distribution, and consumption parts in power system. The scope of our work ranges from utility level to end consumption level. The major difficulties in this work can be summarized as follows: 1) Performance requirements from the viewpoint of network have not been clearly defined; 2) Model mapping from power system to communication networks is not straightforward. 3) Network performance has not been well-investigated. This paper proposes a communication network model for a typical program of smart gird. Moreover, application requirements, link capacity and traffic settings have been investigated. Simulation results validate the feasibility of this model and provide useful network performances which can satisfy both the non-real-time and real-time application requirements.

Traffic intersections are plenteous in this world we live in, while the efforts to secure them are not. With a little knowledge in the Department of Transportation one could easily take control of an intersection for a period of time without any interference from authorities. In this paper a proposal to encrypt such SDLC and broadband messages shall be described. DES and MD5 prove to be strong solutions for the 0.5 ms window of encryption time available with the SDLC messaging structure used. For added authentication purposes, RSA is an ideal candidate for the NTCIP configuration.

For the design of mobile ad hoc networks, particularly those consisting of low-cost devices, we propose a new routing algorithm, called ranging-based link availability routing (RBLAR). In order to reduce link breakages during data services, we propose a new link cost, i.e., the unavailability of a link. In order to reduce the cost and complexity of the implementation, we propose to use only ranging information in the link availability, in stead of complete localization information. Based on the new metrics, the routing is formulated as an optimal routing problem, for which a heuristic algorithm is developed. Simulation results have demonstrated that RBLAR significantly improves link connectivity by reducing link breaks and also network performance including packet delivery ratio and throughput, as compared to the existing routing algorithms.

Existing analytical methods to model multistage switch networks cannot be applied to the performance modeling of switch networks with phase-type and bursty traffic because of the problem of state-space explosion and unrealistic assumptions, e.g., uniform traffic and independent destination (UTID). This paper presents an approximate scheme to model and analyze such networks. First, a traffic aggregation technique is proposed to deal with phase-type and bursty traffic, including splitting and merging. For the aggregation of two bursty traffic, a closed-form solution is obtained for buffer state probabilities. For the aggregation of more bursty traffic, a recursive algorithm is derived in terms of the buffer size and number of inputs of a switch. Second, a switch decomposition technique is developed, by which the crossbar of a switch is decomposed from its preceding and succeeding buffers. In this way, a switch network ofNinputs and outputs is converted toNtandem queues, for which the performance can be easily evaluated. Our extensive numerical and simulation examples have shown that the proposed scheme achieves satisfied accuracy and computational efficiency.

Due to the fact that the wireless links in an ad hoc network are susceptible to attacks and the nodal mobility renders the network to have a highly dynamic topology, it becomes critical to detect major attacks against the routing protocols of such networks and also provide some extent of QoS to the network traffic. In this paper, we present a new secure routing protocol (SRP) with quality of service (QoS) support, called trustworthiness-based quality of service (TQOS) routing, which includes secure route discovery, secure route setup, and trustworthiness-based QoS routing metrics. The routing control messages are secured by using both public and shared keys, which can be generated on-demand and maintained dynamically. The message exchanging mechanism also provides a way to detect attacks against routing protocols, particularly the most difficult internal attacks. The routing metrics are obtained by combing the requirements on the trustworthiness of the nodes in the network and the QoS of the links along a route. The simulation results have demonstrated the effectiveness of the proposed secure QoS routing protocol in both security and performance.

In this paper, an efficient technique is presented to model the aggregation of traffic described by Markov Modulated Bernoulli Processes (MMBP), which has been used to describe the burstiness of network traffic. For the aggregation of multiple MMBP traffic, a recursive algorithm is derived to find the parameters of the aggregated traffic models based on the buffer sizes and the number of inputs. By aggregating multiple traffic inputs into one, the complexity of network performance modeling is significantly reduced. Compared to methods by simulations, the proposed technique results in satisfied accuracy with much less computations, which are demonstrated by simulation examples.

The Markov modulated poisson processes (MMPP) are very powerful in describing general network traffic. The main hindrance to the application of MMPP is the state-space explosion problem, that is, the superposition of two traffic processes, described by MMPP with orders of n1and n2, respectively, is also an MMPP process with orders of n1times n2. In this paper, we propose a new method to reduce the state-space of the MMPP traffic models based on the clustering structure of the decaying time constants of the variance-time curve of the counting process. It is found that the time constants of the aggregated traffic equal one minus the product of the eigenvalues of the transition matrix of the individual traffic. If some time constants, e.g., those can be merged time constants (MTCs), are well clustered around a representative time constant (RTC), the states corresponding to these time constants can be merged into the state of the RTC. By defining a condition of matrix product approximation (MPA), we find a new model with reduced dimensions. Our numerical examples and simulations have demonstrated the effectiveness of the proposed technique.

For IEEE 802.11 wireless LANs (WLAN) with multiple access points (AP), it is critical to allocate the limited number of radio channels dynamically and efficiently. In this paper, we present a new radio channel allocation (RCA) scheme for WLANs with multiple data rates. First, we propose a new algorithm to dynamically estimate the number of active stations by using the least square estimator (LSE), which is unbiased and has minimum variance. Second, we derive an expression to evaluate the impact of the co-channel stations of an AP on the channel utilization of the AP based on the number of equivalent co-channel stations, which is the difference between the numbers of stations that are sensed by and associated with the AP. Third, we develop a new distributed RCA (DRCA) that considers the changing number of active stations, the impact of co-channel interference (CCI), and different traffic demands for different APs, which have not been considered by the existing RCA schemes. Simulation results have demonstrated that DRCA quickly finds optimal or suboptimal channel assignments and improves overall channel utilization for about 15 ~ 50% for different AP layouts, as compared to the existing schemes.

For IEEE 802.11 wireless LANs (WLAN) with multiple access points (AP), it is critical to allocate the limited number of radio channels dynamically and efficiently. This paper proposes a new framework for radio channel allocation (RCA) strategy for WLAN APs with power control capabilities. First, we formulate the RCA as a min-max optimization problem regarding channel utilization with constraints of data rate, channel quality, and transmission power. Second, we derive an expression to evaluate the channel utilization, which incorporates the condition of wireless channel, such as signal-to-noise (SNR) ratio and transmission power, in addition to the transmitting probability of a station. Third, we propose a new RCA algorithm that considers both link adaptation and power control mechanisms, in addition to the impact of co-channel interference (CCI) and multiple data rates, which have not been considered by the existing RCA schemes. Simulation results have demonstrated the effectiveness of the proposed strategy.

For IEEE 802.11 wireless LANs (WLAN) with multiple access points (AP), it is critical to allocate the limited number of radio channels dynamically and efficiently. This paper proposes a new framework for radio channel allocation (RCA) strategy for WLANs to support multimedia traffic. Two techniques are introduced for this purpose: service differentiation in the MAC layer, and link adaptation in the physical layer. First, we formulate the RCA as a min-max optimization problem regarding channel utilization with constraints of transmitting power and data rates. Second, we derive an expression to evaluate the channel utilization, which incorporates the condition of a wireless channel, such as signal-to-noise (SNR) ratio and transmitting power, in addition to the transmitting probability of a station. It also incorporates the differentiations among the stations within an AP on behalf the traffic flows carried by the links between a station and its AP. Third, we propose a new RCA algorithm that considers both link adaptation and service differentiation mechanisms, which have not been considered by the existing RCA schemes. Simulation results have demonstrated the effectiveness of the proposed strategy.

In the development of various large-scale sensor systems, a particularly challenging problem is how to dynamically organize the sensors into a wireless communication network and route sensed information from the field sensors to a remote base station. This paper presents a new energy-efficient dynamic clustering technique for large-scale sensor networks. By monitoring the received signal power from its neighboring nodes, each node estimates the number of active nodes in realtime and computes its optimal probability of becoming a cluster head, so that the amount of energy spent in both intra- and inter-cluster communications can be minimized. Based on the clustered architecture, this paper also proposes a simple multihop routing algorithm that is designed to be both energy-efficient and power-aware, so as to prolong the network lifetime. The new clustering and routing algorithms scale well and converge fast for large-scale dynamic sensor networks, as shown by our extensive simulation results.

Due to the high flexibility, mobility and low cost features, wireless ad hoc networks are widely used. A particularly challenging problem is how to feasibly detect and defend the major attacks against routing protocols of such networks that have susceptible links and dynamic topology. Most of the existing secure routing protocols for ad hoc networks either avoid the most challenging internal attacks such as Byzantine behaviors, or have often produced inefficient security mechanisms. In this paper, we develop a new efficient distributed key management scheme and a novel algorithm that can detect the most difficult internal attacks, such as Byzantine attacks. We also present a novel secure quality of service routing (SQSR) protocol, which provides both secure and QoS routing. The simulation results have demonstrated the effectiveness of the proposed routing protocol.

In the design of mobile ad hoc sensor networks, a particularly challenging problem is how to effectively route the information among field sensors to a collection station to meet network performance requirements by using minimum energy consumption. In this paper, we propose to adopt a twotier network architecture based on energy-efficient clustering technique. For the tier-2 network formed by the cluster heads, we develop a multihop routing algorithm, called energy-efficient path availability routing (EEPAR). In the new routing algorithm, the parameters for node mobility and energy consumption are incorporated into routing metrics, including link availability, energy-efficiency, and power-awareness. The extensive simulation results have demonstrated that EEPAR improves network performance in link connectivity, delivery ratio, and node lifetime without sacrificing throughput. as compared to existing routing algorithms.

The basic problem in enhancing the security of a routing protocol is how to verify the correctness of the information a router exchanges with its peers, i.e., to feasibly protect the authenticity and integrity of the routing traffic and provide the means to verify the authority of the participating routers. In this paper, we present some enhancements to the routing protocols that have been used in large-scale backbone networks. First, by using limited key distribution and double message hashing, the routing protocols have improved computational efficiency and the ability to verify the authenticity and integrity of a routing message. Second, we propose a novel algorithm that can detect Byzantine attacks as well as other internal attacks, by using both message and route redundancy during route discovery. Third, we also propose an optimal routing algorithm with routing metrics combining both requirements on a node's trustworthiness and performance. In this way, each node makes secure routing decision based on its trust on its neighboring nodes and the performance provided by these nodes. The proposed enhancements can be applied to both distance-vector and link-state routing protocols, such as RIP, OSPF and BGP.

In this paper, we propose a new energy-efficient routing algorithm for mobile ad hoc sensor networks. The network architecture is based on a two-tier energy-efficient clustering scheme. The number of active nodes is estimated in real-time based on signal power a node received from others. Each node tries to become a cluster head (CH) in an optimal probability that minimizes the total clustering energy consumption. For the multihop routing domain formed by the CHs, we propose a new routing algorithm, that is, path availability routing in sensors (PARIS), by incorporating the availability of mobile links into routing metrics, in addition to energy consumption metrics, to establish multihop routes between a source node and a sink node. It has been shown that the routing algorithm is not only energy-efficient but also avoids link breakages in moderate to high mobility scenarios, while the existing ad hoc routing algorithms fail to maintain the links. Compared to the existing routing algorithms, the proposed routing algorithm is more energy efficient and has 40 ~ 60% less link breakages, therefore significantly increases route reliability and extends network lifetime

As more and more wireless LANs are deployed in many popular locations, there is a need for dynamic radio resource management (RRM) schemes. This paper proposes a new dynamic RRM technique for multiple APs network. First, we develop a real-time algorithm to estimate the number of active stations from the standpoint of an AP, instead of a station. Second, we propose a dynamic RRM algorithm that not only significantly increases network performance but also reduces the co-channel interference. Third, we find the optimal switching probability that minimizes the transient time for an AP to reach its equilibrium state. For uniform traffic conditions, our scheme produces classical optimal frequency assignments. For non-uniform traffic conditions, it produces sub-optimal frequency assignments. Our simulations have shown that the proposed RRM technique adapts to dynamic network conditions and increases the channel throughput up to 65% in less than 20 iterations. The results can be applied to practical WLANs to significantly improve network performance

In this paper, we propose a technique to approximate the traffic aggregation processes described by Markov modulated Poisson processes (MMPP) models. It is found that the decaying time constants of the aggregated traffic process are the product of the eigenvalues of the transition matrix of the individual traffic. If the time constants are well clustered around some representative time constants (RTC's), the corresponding states can be merged in the state space. In the worst case, if the time constants are uniformly distributed over the log-scale, we prove that there exist a minimum number of states that can approximate the traffic aggregation. We develop a clustering algorithm to search for the RTC's and extend the rate limit algorithm to the case that the limit of the arrival rate is unknown.