The capacity of mobile Infostation network can be greatly increased, if, in addition to direct short-range communications between mobile nodes and fixed infostations, nodes also communicate amongst themselves whenever they meet. However, this requires cooperation among mobile nodes that are not necessarily spontaneous for commercial applications. We propose means to create opportunistic cooperation in the context of contention distribution in selfish mobile infostation networks. First, we assume that all nodes have a common interest in all files. We stipulate a social contract such that a bilateral file exchange takes place only when either node obtains something it wants from the exchange. Resulting capacity depends on mobility, the number of files being disseminated, and node density. In addition to the existence of multiuser diversity, our results indicate the existence of data diversity-throughput increases as the number of files of interest to all nodes increases. We also consider the case where nodes have dissimilar interests. Results show that as the level of interest overlap decreases, network performance degrades dramatically. We propose an alternate user strategy in the partially overlapping-interests case and show that network throughput is significantly improved by allowing better use of multiuser diversity. We conclude that through opportunistic cooperation, both data and multiuser diversities exist in noncooperative mobile infostation networks.

A mobile infostation network stipulates all transmissions to occur when nodes are in proximity. In this paper, the effect of transmit range on the capacity of four transmission strategies is studied. We show that a stipulated transmit range improves the capacity compared to the Grossglauser-Tse strategy with an unconstrained transmit range by 25%, and outperforms the non rate-adaptive strategy by 68%. This indicates an optimal trade-off exists between spatial transmission concurrency and spectral efficiency on individual links. The optimal number of neighbors is invariant to node density, and is between 0.6 to 1.2 for our transmission strategies. This should be contrasted to a magic number of 6 to 8 neighbors for multihop networks, where the expected forward progress per hop is maximized. This reflects the different optimization criteria of mobile infostation and multihop ad hoc networks. In addition, the capacity per unit area increases linearly with node density. This is counter-intuitive but can be explained using a rescaling argument drawn from percolation theory.

A mobile infostation network stipulates all transmissions to occur when nodes are in proximity. We evaluate the effect of mobility on highway mobile infostation networks. Each node enters a highway segment at a Poisson rate with a constant speed drawn from a known but arbitrary distribution. Both forward and reverse traffic are considered. For node speed that is uniformly distributed, the expected fraction of connection time, or expected number of connections in queueing terminology, is independent of observer node speed for reverse traffic, while it increases with observer node speed for forward traffic. We also extend our mobility model such that each node changes speed at each highway segment. The long run fraction of connection time of an observer node is dependent on the ratio of transmit range and connection time limit. Forward traffic connection yields better performance when the ratio is small and vice versa. We also compute the optimal transmit range and the corresponding data rate for both traffic types. We conclude that forward traffic connections yield much higher data rate in most scenarios.

In mobile ad hoc networks, it is often more important to optimize for energy efficiency than throughput. In this paper we investigate the effect of transmit range on energy efficiency of packet transmissions. We determine a common range for all nodes such that the average energy expenditure per received packet is minimized. In the first part of this paper, we consider stationary networks. We show that energy efficiency depends on various system parameters that includes path loss exponent of the channel, energy dissipation model and network offered load. In particular, when the path loss exponent is large, energy efficiency decreases when the transmit range increases. Hence, the network should be operated at the critical range that just maintains network connectivity. However, when the path loss exponent is small, operating at the critical range yields inferior throughput and energy efficiency. Our results show that energy efficiency is intimately connected to network connectivity. Three network connectivity regimes are identified as the transmit range of all nodes increases. In the second part, we examine the effect of node mobility on energy efficiency. We show that at normal offered load, an optimal transmit range exists such that energy efficiency is maximized The optimal range turns out to be insensitive to node mobility, and is much larger than the critical range. We show that the energy expenditure can be reduced by 15% to 73% in different mobility scenarios, if the network is operated at the optimal range.

In wireless networks, it is often assumed that all nodes cooperate to relay packets for each other. Although this is a plausible model for military or mission based networks, it is unrealistic for commercial networks and future pervasive computing environments. We address the issue of noncooperation between nodes in the context of content distribution in mobile infostation networks. We assume all nodes have common interest in all files cached in the fixed infostations. In addition to downloading files from the fixed infostations, nodes act as mobile infostations and exchange files when they are in proximity. We stipulate a social contract such that an exchange occurs only when each node can obtain something it wants from the exchange. Our social contract enables much higher system efficiency compared to downloading from fixed infostations only while not requiring true cooperation among nodes. We show by analysis and simulations that network performance depends on the node density, mobility and the number of files that are being disseminated. Our results point to the existence of data diversity for mobile infostation networks. The achievable throughput increases as the number of files of interest to all users increases. We have also extended the common interest model to the case where nodes have dissimilar interests. Our simulation results show that as mobile nodes change from having identical interests to mutually exclusive interests, the network performance degrades dramatically. We propose an alternative user strategy when nodes have partially overlapping interests and show that the network capacity can be significantly improved by exploiting multiuser diversity inherent in mobile infostation networks. We conclude that data diversity and multiuser diversity exist in noncooperative mobile infostation networks and can be exploited.

In a mobile infostation network, any two nodes communicate when they are in proximity. Under this transmission constraint, any pair of nodes is intermittently connected as mobility shuffles the node locations. In this paper, we evaluate the effect of node mobility on highway mobile infostation networks. Each node enters a highway segment at a Poisson rate with a random speed drawn from a known but arbitrary distribution. Moreover, each node changes speed at each highway segment. Since nodes have different speed, a node may overtake other nodes or be overtaken as time evolves. Using arguments from renewal reward theory, the long run fraction of time an observer node is connected, and the long run average data rate can be derived. In this paper, however, we consider the special case of no speed change in each highway segment. In this case, the performance metrics are functions of the observer node speed. We consider both forward traffic scenarios, in which two nodes moving in the same direction have a transient connection when they are within range from each other, and reverse traffic scenarios in which two nodes travelling in opposite directions are connected transiently when they are in range. For node speed that is uniformly distributed, we reveal that the expected fraction of connection time, or expected number of connections in queuing terminology, is independent of the observer node speed in reverse traffic. In forward traffic, on the other hand, the fraction of connection time increases with observer speed. That is, the network performance improves with node mobility, which is unique to the mobile infostation networking paradigm.

In wireless networks, it is often assumed that all nodes cooperate to relay packets for each other. Although this is a plausible model for military or mission-based networks, it is unrealistic for commercial networks and future pervasive computing environments. We address the issue of noncooperation between nodes in the context of content distribution in mobile infostation networks. All nodes have common interest in all files cached in the fixed infostations. In addition to downloading files from the fixed infostations, nodes act as mobile infostations and exchange files when they are in proximity. We stipulate a social contract such that an exchange occurs only when each node can obtain something it wants from the exchange. We show by analysis and simulations that network performance depends on node density, mobility and the number of files that are being disseminated. Our results point to the existence of data diversity for mobile infostation networks. As the number of files of interest to all users increases, the achievable throughput increases. Moreover, each user has a fairer share of the total network throughput. In particular, the transmission of each channel is only limited by contention, indicating the noncooperation strategy achieves near optimum resource utilization.

This paper presents a dynamic location area assignment (DLA) algorithm. When a mobile unit (MU) exits a location area, a new location area is assigned based on the time-varying mobility statistics recorded by the MU. The overlapping region of the new and the original location area, and the location area size are dynamically adjusted. For any location area size, the expected dwell time of a MU in the assigned location area is maximized. Numerical examples show that the proposed algorithm outperforms conventional strategies under all mobility scenarios.

A hybrid Bloom filter location update algorithm is proposed for wireless cellular systems. This belongs to a new category of algorithms characterized by contention free access of uplink control channels during location update. Two or more mobile units are permitted to register with a base station simultaneously without contention on the uplink channel. The location updating procedure is hybrid in the sense that it could be temporally or geographically triggered. Based on the location information stored in all base stations, Bloom filtering is used to select cells to be paged to locate the targeted mobile unit. The performance of this scheme is compared to other algorithms previous proposed. Numerical results shows that the new algorithm requires less combined location update and paging bandwidth than other algorithms.