Seh Chun Ng, Wuxiong Zhang, Yu Zhang, Yang Yang, and Guoqiang Mao, "Analysis of Access and Connectivity Probabilities in Vehicular Relay Networks," to appear in IEEE Journal on Selected Areas in Communications.
Abstract:
IEEE 802.11p and 1609 standards are currently under development to support Vehicle-to-Vehicle and Vehicle-to-Infrastructure communications in vehicular networks. For infrastructure-based vehicular relay networks, access probability is an important measure which indicates how well an arbitrary vehicle can access the infrastructure, i.e. a base station (BS). On the other hand, connectivity probability, i.e. the probability that all the vehicles are connected to the infrastructure, indicates the service coverage performance of a vehicular relay network. In this paper, we develop an analytical model with a generic radio channel model to fully characterize the access probability and connectivity probability performance in a vehicular relay network considering both one-hop (direct access) and two-hop (via a relay) communications between a vehicle and the infrastructure. Specifically, we derive close-form equations for calculating these two probabilities. Our analytical results,
validated by simulations, reveal the tradeoffs between key system parameters, such as inter-BS distance, vehicle density, transmission ranges of a BS and a vehicle, and their collective impact on access probability and connectivity probability under different communication channel models. These results and new knowledge about vehicular relay networks will enable network designers and operators to effectively improve network planning, deployment and resource management.
Showing posts with label Publications. Show all posts
Showing posts with label Publications. Show all posts
Wednesday, July 14, 2010
Wednesday, July 7, 2010
Conference Paper - Globecom 2010
Seh Chun Ng and Guoqiang Mao, “Analysis of k-Hop Connectivity Probability in 2-D Wireless Networks with Infrastructure Support”, to appear in IEEE Global Communications Conference (GLOBECOM), 2010.
Abstract:
Abstract:
Wireless multi-hop networks with infrastructure support have been actively studied to solve the scalability problem in large scale vehicular and sensor networks that the end-to-end throughput and other performance metrics decrease sharply with the increase in the number of nodes in the network. In the infrastructure-based networks, wireless nodes are allowed to access the base stations either directly or via a multi-hop path. In order to provide meaningful services, it is often desirable to limit the number of hops in the wireless multi-hop path. In this paper, we study a 2-D wireless network where users are Poissonly distributed in a square area and base stations are placed at the four corners of the square area as a typical component of a larger network where users are randomly distributed and base stations are regularly deployed. We obtain analytically the exact and approximate k-hop connectivity probability for k=2, i.e. the probability that all users can access to at least one base station in at most two hops, under a generic channel model. The results are verified by simulations and can be used in network planning, design and resource management.
Tuesday, January 5, 2010
Conference Paper - ICC 2010
Seh Chun Ng, Guoqiang Mao and Brian D.O. Anderson, “Properties of 1-D Infrastructure-based Wireless Multi-hop Networks”, to appear in IEEE International Conference on Communications (ICC), 2010.
Abstract:
Many real wireless multi-hop networks are deployed with some infrastructure support, where the results on ad-hoc networks cannot be readily extended to understand the properties of those networks. In this paper, we study those networks in 1-D. Specifically, we consider two types of nodes in the networks: ordinary nodes and powerful nodes, where ordinary nodes are i.i.d and Poissonly distributed in a unit interval and powerful nodes are arbitrarily distributed within the same unit interval. These powerful nodes are inter-connected via some backbone infrastructure. The network is said to be connected, i.e. any two nodes can communicate with each other, if each ordinary node is connected to at least one of the powerful nodes. We call this type of connectivity type-II connectivity. Exact and simplified
asymptotic formulas for type-II connectivity probability and the average hop count between two arbitrary nodes are obtained. Further we prove that equi-distant powerful nodes deployment delivers the optimum performance which maximizes the type-
II connectivity probability. These results are important for the design and deployment of 1-D infrastructure-based networks and provide useful insights into the analysis of higher dimensional networks.
Abstract:
Many real wireless multi-hop networks are deployed with some infrastructure support, where the results on ad-hoc networks cannot be readily extended to understand the properties of those networks. In this paper, we study those networks in 1-D. Specifically, we consider two types of nodes in the networks: ordinary nodes and powerful nodes, where ordinary nodes are i.i.d and Poissonly distributed in a unit interval and powerful nodes are arbitrarily distributed within the same unit interval. These powerful nodes are inter-connected via some backbone infrastructure. The network is said to be connected, i.e. any two nodes can communicate with each other, if each ordinary node is connected to at least one of the powerful nodes. We call this type of connectivity type-II connectivity. Exact and simplified
asymptotic formulas for type-II connectivity probability and the average hop count between two arbitrary nodes are obtained. Further we prove that equi-distant powerful nodes deployment delivers the optimum performance which maximizes the type-
II connectivity probability. These results are important for the design and deployment of 1-D infrastructure-based networks and provide useful insights into the analysis of higher dimensional networks.
Conference Paper - WCNC 2010
Seh Chun Ng, Wuxiong Zhang, Yang Yang and Guoqiang Mao, “Analysis of Access and Connectivity Probabilities in Infrastructure-Based Vehicular Relay Networks”, to appear in IEEE Wireless Communications and Networking Conference (WCNC), 2010.
Abstract:
Coverage is an important problem in wireless networks. Together with the access probability, which measures how well an arbitrary user can access a wireless network, in particular VANET, they are often used as major indicators of the quality of the network. In this paper, we investigate the coverage and access probability of the vehicular networks with roadside infrastructure, i.e. base stations. Specifically, we analyze the relation between these key parameters, i.e. the coverage range of base stations, coverage range of vehicles, vehicle density and distance between adjacent base stations, and how these parameters interact with each other to collectively determine the coverage and the access probability. We use the connectivity probability, the probability that all nodes in the network are connected to at least one base station within a designated number of hops, as a measure of the coverage. We derived close-form formulas for the connectivity probability and the access probability for a 1D vehicular network bounded by two adjacent base stations. The analytical results have been validated by simulations. The results in the paper can be used by network operators to design networks with specific service coverage guarantees.
Abstract:
Coverage is an important problem in wireless networks. Together with the access probability, which measures how well an arbitrary user can access a wireless network, in particular VANET, they are often used as major indicators of the quality of the network. In this paper, we investigate the coverage and access probability of the vehicular networks with roadside infrastructure, i.e. base stations. Specifically, we analyze the relation between these key parameters, i.e. the coverage range of base stations, coverage range of vehicles, vehicle density and distance between adjacent base stations, and how these parameters interact with each other to collectively determine the coverage and the access probability. We use the connectivity probability, the probability that all nodes in the network are connected to at least one base station within a designated number of hops, as a measure of the coverage. We derived close-form formulas for the connectivity probability and the access probability for a 1D vehicular network bounded by two adjacent base stations. The analytical results have been validated by simulations. The results in the paper can be used by network operators to design networks with specific service coverage guarantees.
Conference Paper - WCNC 2009
Seh Chun Ng, Guoqiang Mao and Brian D.O. Anderson, “Energy Savings Achievable in Connection Preserving Energy Saving Algorithms”, in IEEE Wireless Communications and Networking Conference (WCNC), 2009, pp. 1-6.
Abstract:
Energy saving is an important design consideration in wireless sensor networks. In this paper, we analyze the energy savings that can be achieved in a sensor network where each sensor is capable of reducing its transmission power from a maximum power $p_m$, compared with that in a sensor network where each sensor can only transmit at a constant power level $p_m$. To achieve a fair comparison, we assume sensors in both types of sensor networks are connected to the same set of neighbors, i.e. no connection is lost as a result of a sensor reducing its transmission power. We further assume that sensors are distributed in a given area following a Poisson distribution with known node density and the radio propagation is described by a log-normal model. Ignoring boundary effect, we establish analytically the probability for a sensor to achieve an energy saving of at least $h$ dB. We also obtain the expected percentage of energy savings which can be substantial. The research reported in the paper helps to answer questions such as whether the energy savings achieved by using a sensor with a variable-transmission-power (and the consequent extension of its lifetime) justify the additional cost involved in manufacturing it.
Abstract:
Energy saving is an important design consideration in wireless sensor networks. In this paper, we analyze the energy savings that can be achieved in a sensor network where each sensor is capable of reducing its transmission power from a maximum power $p_m$, compared with that in a sensor network where each sensor can only transmit at a constant power level $p_m$. To achieve a fair comparison, we assume sensors in both types of sensor networks are connected to the same set of neighbors, i.e. no connection is lost as a result of a sensor reducing its transmission power. We further assume that sensors are distributed in a given area following a Poisson distribution with known node density and the radio propagation is described by a log-normal model. Ignoring boundary effect, we establish analytically the probability for a sensor to achieve an energy saving of at least $h$ dB. We also obtain the expected percentage of energy savings which can be substantial. The research reported in the paper helps to answer questions such as whether the energy savings achieved by using a sensor with a variable-transmission-power (and the consequent extension of its lifetime) justify the additional cost involved in manufacturing it.
Journal Paper - IJBDCN 2007
Kuok-Shoong Daniel Wong, Seh Chun Ng, and Wei Lee Woon, "Simultaneous Mobility: Probability of Lost Binding Updates and Mean Time to Occurrence," International Journal of Business Data Communications and Networking (IJBDCN), vol. 3, no. 2, pp. 1 - 12, 2007.
Abstract:
To realize the full potential of mobile multimedia, mobility protocols are needed to handle situations when nodes move while in a multimedia session. Many mobility protocols have been proposed for IP-based networks. In some important cases in using these mobility protocols such as mobile IPv6 with route optimization, a problem can arise when both nodes are mobile and move simultaneously. The problem is that both sides’ binding updates could be lost. A few solutions have recently been proposed. A crucial indicator of the importance of the simultaneous mobility problem, and of its solutions, is the probability of its occurrence. However, previous articles have used only a simple analytical model to estimate the probability of the simultaneous mobility problem occurring. In this article, we present new and more accurate results on the variation of this probability with a number of critical variables.
Abstract:
To realize the full potential of mobile multimedia, mobility protocols are needed to handle situations when nodes move while in a multimedia session. Many mobility protocols have been proposed for IP-based networks. In some important cases in using these mobility protocols such as mobile IPv6 with route optimization, a problem can arise when both nodes are mobile and move simultaneously. The problem is that both sides’ binding updates could be lost. A few solutions have recently been proposed. A crucial indicator of the importance of the simultaneous mobility problem, and of its solutions, is the probability of its occurrence. However, previous articles have used only a simple analytical model to estimate the probability of the simultaneous mobility problem occurring. In this article, we present new and more accurate results on the variation of this probability with a number of critical variables.
Conference Paper - DFMA 2006
Seh Chun Ng and Kuok-Shoong Daniel Wong, "IEEE 802.11b Multi-hop Experiments and Analysis," in Distributed Frameworks for Multimedia Applications (DFMA), 2006, pp. 1 - 7.
Abstract:
IEEE 802.11b has become a prominent standard to provide wireless connections between mobile nodes, and often also through an access point (AP) to a wired LAN. All kinds of traffic may be handled by the wireless networks formed, including multimedia traffic. However, the standard comes with some inherent problems, such as channel interference, the hidden node problem and the exposed node problem. All these problems will affect the quality, bandwidth and performance of the radio links between the mobile nodes and the APs, and consequently also the types of traffic they can support. In addition, the problems also limit the distance between the mobile nodes and APs, and the topology of the wireless network they form. The degradation of service is especially not negligible when the topology involves multi-hops and routing in the network. In this paper, we look at the performance of multi-hop wireless networks and identify some effects of channel interference on the network performance.
Abstract:
IEEE 802.11b has become a prominent standard to provide wireless connections between mobile nodes, and often also through an access point (AP) to a wired LAN. All kinds of traffic may be handled by the wireless networks formed, including multimedia traffic. However, the standard comes with some inherent problems, such as channel interference, the hidden node problem and the exposed node problem. All these problems will affect the quality, bandwidth and performance of the radio links between the mobile nodes and the APs, and consequently also the types of traffic they can support. In addition, the problems also limit the distance between the mobile nodes and APs, and the topology of the wireless network they form. The degradation of service is especially not negligible when the topology involves multi-hops and routing in the network. In this paper, we look at the performance of multi-hop wireless networks and identify some effects of channel interference on the network performance.
Conference Paper - M2USIC 2005
Seh Chun Ng and Kuok-Shoong Daniel Wong, "Performance Analysis on Two-Layer Wireless Networks," in MMU International Symposium on Information and Communications Technologies (M2USIC), 2005.
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