R.M. de Moraes

Throughput-delay analysis of mobile ad-hoc networks with a multi-copy relaying strategy

Multiuser diversity has been shown to increase the throughput of mobile ad-hoc wireless networks (MANET) when compared to fixed wireless networks. This paper addresses a multiuser diversity strategy that permits one of multiple one-time relays to deliver a packet to its destination. We show that the /spl theta/(1) throughput of the original single one-time relay strategy is preserved by our multi-copy technique. The reason behind achieving the same asymptotic throughput is the fact that, as we demonstrate in this paper, interference for communicating among closest neighbors is hounded for different channel path losses, even when n goes to infinity. We find that the average delay and its variance scale like /spl theta/(n) and /spl theta/(n/sup 2/), respectively, for both the one and multi-copy relay strategies. Furthermore, while for finite n the delay values in the single-copy relaying strategy are not bounded, our multi-copy relay scheme attains bounded delay.

Many-to-Many Communication: A New Approach for Collaboration in MANETs

We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call many-to-many cooperation, that allows concurrent many-to-many communication. This scheme is based on the integration of multi-user detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to nodal locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. Consequently, the interference is divided into constructive interference (COI) and destructive interference (DEI). We show that, if each node is allowed to expand its bandwidth, both the links Shannon capacity and the per source-destination throughput scale like O(nalpha/2 ) (upper-bound) and Omega[f(n)] (lower-bound), for n nodes in the network, a path loss parameter alpha > 2, and 1 les f(n) < nalpha/2. Many-to-many cooperation allows multi-copy relaying of the same packet, which reduces the packet delivery delay compared to single-copy relaying without any penalty in capacity.

On mobility-capacity-delay trade-off in wireless ad hoc networks

We show that there is a trade off among mobility, capacity, and delay in ad hoc networks. More specifically, we consider two schemes for the mobility of nodes in ad hoc networks. We divide the entire network into cells whose sizes can vary with the total number of nodes or whose size is independent of the number of nodes. By restricting the movement of nodes within these cells, we calculate throughput and delay for randomly chosen pairs of source-destination nodes, and show that mobility is an entity that can be exchanged with capacity and delay. We also investigate the effect of directional antennas in a static network in which packet relaying is done through the closest neighbor, and verify that this approach attains better throughput than static networks employing omnidirectional antennas.

Taking Full Advantage of Multiuser Diversity in Mobile Ad Hoc Networks

Multiuser diversity has been shown to increase the throughput of mobile ad hoc wireless networks (MANETs) when compared to fixed wireless networks. This paper addresses a multiuser diversity strategy that permits one of multiple one-time relays to deliver a packet to its destination. We show that the throughput of the original single one-time relay strategy is preserved by our multi-copy technique. The reason behind achieving the same asymptotic throughput is the fact that, as we demonstrate in this paper, interference for communicating among closest neighbors is bounded for different channel path losses, even when goes to infinity. We show that a significant delay reduction is possible by multi-copy relaying when is finite. Furthermore, we find that the average delay and delay variance for both the one and multi-copy relay strategies scale like and , respectively. We derive an approximation of the delay for multi-copy forwarding scheme and demonstrate that this approximation is very close to simulation results in MANET systems.

A new communication scheme for MANETs

The communication protocols used in wireless ad hoc networks today have been designed to support reliable communication between senders and receivers that compete with other sender-receiver sets for the use of the shared bandwidth. This competition-driven approach prevents wireless ad hoc networks from scaling with the number of nodes. We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call opportunistic cooperation. This scheme is based on the integration of multiuser detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to nodal locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. We show that both the links Shannon capacity and the per source-destination throughput scale like O(n/sup /spl alpha//2/) (upper-bound) and /spl Omega/[f(n)] (lower-bound), for n nodes in the network, a path loss parameter /spl alpha/ > 2, and 1 /spl les/ f(n) < n/sup /spl alpha//2/.

Many-to-many communication for mobile ad hoc networks

We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call many-to-many communication, that allows concurrent multi-packet transmissions (MPTs) and multi-packet receptions (MPRs). Many-to-many communication also permits one-time multi-copy relaying of the same packet, which reduces the packet delivery delay compared to single-copy relaying without any penalty in capacity. Our scheme is based on the integration of multi-user detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to node locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. Consequently, the interference is divided into constructive interference (COI) and destructive interference (DEI). We show that, if each node is allowed to expand its bandwidth, both the links Shannon capacity and the per source-destination throughput scale like O(nalpha/2) (upper-bound) and Omega[f(n)] (lower-bound), for n nodes in the network, a path loss parameter alpha > 2, and 1les f(n) < nalpha/2.

Capacity of MIMO mobile wireless ad hoc networks

We compute the capacity of wireless ad hoc networks when all the nodes in the network are endowed with M antennas. The derivation is based on a new communication scheme for wireless ad hoc networks utilizing the concept of cooperative many-to-many communications, as opposed to the traditional approach that emphasizes on one-to-one communications. We show that the upper bound average asymptotic capacity of each cell is 2/spl pi/P/sub t/MC/sub cell/[1-exp(-C/sub cell///spl theta/)], for network parameters C/sub cell/ /spl ges/ 1, 0 /spl les/ /spl theta/ /spl les/ 1, and transmit power P/sub t/.

Making ad hoc networks scale using mobility and multi-copy forwarding

Multiuser diversity has been shown to increase the throughput of mobile ad hoc wireless networks (MANET) when compared to fixed networks. We present a different multiuser diversity strategy for packet relaying, which permits more than one-copy (multi-copies) of a packet to be received by relay nodes, thus allowing us to decrease the delay on such networks for a fixed number of total users n. We show that the /spl theta/(1) throughput is preserved by our multi-copy technique when n goes to infinity. In addition, we find that the average delay and variance scale like /spl theta/(n) and /spl theta/(n/sup 2/) respectively for both one-copy and multi-copies techniques. We also show that for a fixed n and by multi-copy forwarding, a maximum bounded delay value can he guaranteed.

Effects of UHF stimulus and negative feedback on nonlinear circuits

We investigate the combined effect of rectification and nonlinear dynamics on the behavior of several simple nonlinear circuits. We consider the classic resistor-inductor-diode (RLD) circuit driven by a low-frequency (LF) source when an operational amplifier with negative feedback is added to the circuit. Ultra-high-frequency (UHF) signals are applied to the circuit, causing significant changes in the onset of LF period doubling and chaos. Measurements indicate that this effect is associated with a dc voltage induced by rectification of the UHF signal in the circuit. The combination of rectification and nonlinear circuit dynamics produce qualitatively new behavior, which opens up a new channel of radio frequency interference in circuits.

Opportunistic Cooperations: A New Communication Approach for MANETs

Opportunistic Cooperations: A New Communication Approach for MANETs Renato M. de Moraes, Hamid R. Sadjadpour J.J. Garcia-Luna-Aceves Department of Electrical Engineering University of California at Santa Cruz (UCSC) Santa Cruz, CA 95064, USA Email: {renato,hamid}@soe.ucsc.edu Department of Computer Engineering at UCSC and Palo Alto Research Center 3333 Coyote Hill Road, Palo Alto, CA 94304, USA Email: jj@soe.ucsc.edu Abstract—We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call opportunistic cooperation. Transmissions are divided in frequency and codes according to nodal locations, and succes- sive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfer- ing sources. We show that both the link’s Shannon capacity and the per source-destination throughput scale like O(n 2 ) (upper- bound) and Ω[f (n)] (lower-bound), for n nodes in the network, a path loss parameter α > 2, and 1 ≤ f (n) < n 2 . I. I NTRODUCTION Communication protocols used in wireless ad hoc networks today are meant to support reliable communication among senders and receivers that are competing with one another for the use of the shared bandwidth. This “competition-driven” view of bandwidth sharing has had profound implications on network architectures and methods used to access the channel and disseminate information. Gupta and Kumar [1] showed that, in a wireless connected network with static nodes, the throughput for each node degrades as the number of nodes in- creases under the competition-driven view of networking. That p is, it scales as Θ(1/ n log(n)), 1 where n is the number of nodes in the network. Grossglauser and Tse [2] analyzed a two-hop, single-relay forwarding scheme for MANETs in which a source passes a packet to a relay that in turn delivers it to the destination when the two nodes are close to each other. This and many subse- quent studies on how to make MANETs scale by using mobil- ity [2], [3], [4], consider each transmission as competing with all the other concurrent transmissions in the network. However, because a relay cooperates with a source by storing the source’s packet until it is close enough to the intended destination, the throughput of MANETs can be increased. 2 Recently, Toumpis and Goldsmith [5] have shown that the capacity regions for ad hoc networks are significantly increased when multiple access schemes are combined with spatial reuse (i.e., multiple simultaneous transmissions), multihop routing (i.e., packet relaying), and SIC, even without performing power This work was supported in part by CAPES/Brazil, by the US Army Re- search Office under grants W911NF-04-1-0224 and W911NF-05-1-0246, by the Basking Chair of Computer Engineering, and by UCOP CLC under grant SC-05-33. 1 Ω, Θ and O are the standard order bounds. log(·) is the natural logarithm. 2 In [2], the per source-destination throughput scales as Θ(1). control. Also, SIC circuits with simple implementation and low complexity have been introduced recently [6], and code divi- sion multiple access (CDMA) [7] and global positioning sys- tem (GPS) [8] technologies have been already integrated into a single IC chip [9]. In this paper, we present an integrated approach to coopera- tive bandwidth sharing in MANETs and propose what we call opportunistic cooperation. 3 We show that with opportunistic cooperation, nodes access the available channel(s) and forward information across a MANET in such a way that concurrent transmissions become useful at destinations or relays. Hence, sender-receiver pairs collaborate, rather than compete, with oth- ers. Therefore, a better network performance is possible. Section II summarizes the basic network model that has been used recently to analyze the capacity of wireless networks [1], [2], [3], [4], [10]. Section III describes the opportunistic co- operation implementation. Section IV presents the the link’s Shannon capacity, the per source-destination throughput, and the bandwidth requirement. Section V concludes the paper. II. N ETWORK M ODEL The term cell denotes the set of nodes located inside a defined area of the network. The receiver range of a node is defined as the radius, measured from the node, which contains all other nodes of the same cell. The cluster associated with a given node is the set of cells reached by the receiver range of this node. Our assumptions are consistent with prior work [1], [2], [10]. Also, in this paper, nodes are considered to have SIC capability. The modeling problem we address is that of a MANET in which n mobile nodes move in a unit square area. To simplify our analysis, we assume that cells have square shapes, each with area equal to a(n) = φn , in which φ ∈ (0, 1) is the cell area pa- rameter of the network. We consider that the communication occurs only among those nodes that are close enough (i.e., in same cell), so that interference caused by farther nodes is low, allowing reliable communication. In other words, the receiver chooses the closest nodes because they present the best chan- nel, in a respective order, due to the assumption of the simple path propagation model, i.e., the receiver takes advantage of 3 The term “opportunistic” is used here to indicate that the number of nodes cooperating with one another in a cell during a communication session is a random variable.