John A. Stine

A paradigm for quality-of-service in wireless ad hoc networks using synchronous signaling and node states

Most limitations in mechanisms geared at achieving quality-of-service (QoS) in wireless ad hoc networking can be traced to solutions based on mapping wireless networks to a wireline paradigm of nodes and links. We contend that this paradigm is not appropriate since links are not physical entities and do not accurately represent the radio frequency (RF) media. Using the link abstraction makes arbitration of the use of the RF media cumbersome leaving only overprovisioning techniques to deliver QoS. In this paper, we argue that an appropriate paradigm should match the physics of the network. The critical resource is electromagnetic spectrum in a space; in turn, this results in a complex paradigm since the part of the spectrum-space that each node wants to use is unique to that node and its destination and will overlap with parts that other nodes may want to use creating interdependences among nodes. This paper describes protocol approaches for access and routing that seek solutions within this wireless paradigm. Access is arbitrated using synchronous signaling and topology is resolved through the dissemination of node states. This approach provides an intuitive framework that provides mechanisms that can be exploited to arbitrate RF media use and implement traffic engineering techniques to deliver QoS. Our proposed approach provides a novel way of tracking the state of the network that can serve as a unified state dissemination mechanism to simultaneously support routing, multicasting, and most QoS heuristics.

Exploiting smart antennas in wireless mesh networks using contention access

Smart antennas can increase the capacity of mesh networks and reduce the susceptibility of individual nodes to interception and jamming, but creating the conditions that allow them to be effective is difficult. In this article we provide a broad review of antenna technologies and identify their capabilities and limitations. We review mechanisms used by medium access control schemes to arbitrate access. These reviews let us identify a small set of conditions that are necessary for smart antenna exploitation. We then review the most common MAC approaches, carrier sense multiple access, slotted aloha, and time-division multiple access, and evaluate their suitability for exploiting smart antennas. We demonstrate that they are not capable of creating the complete set of antenna exploitation conditions while retaining a contention nature. We follow with a discussion of the synchronous collision resolution (SCR) MAC scheme and describe how it creates all the exploitation conditions. We conclude that SCR provides the best support for smart antenna exploitation with the added benefits that there is no requirement for all nodes to be equipped with the same antenna technologies and that smart antennas can be combined with channelization technologies to provide even higher capacities

Spectrum management: the killer application of ad hoc and mesh networking

The traditional approach to managing radio frequency (RF) spectrum concludes with a spectrum management administration identifying how a band of spectrum may be used in a region it administers and who may use it. This approach to spectrum management is encumbered with political process that is challenged to keep pace with the rapid advances in technologies that exploit RF spectrum. Recognizing that this process can stifle innovation, the FCC has proposed new spectrum management models and the use of a measure of interference temperature. Unfortunately, they too result in picking winners and losers and can have detrimental effects on legacy users. In this paper we review these concepts and then describe how ad hoc networks can offer new solutions. Three different spectrum management ideas are described. The synchronous collision resolution (SCR) MAC protocol enables a strict arbitration of spectrum access based on spectrum rights thus enabling a hierarchy of networks in the same spectrum that always guarantees the primary rights holder precedence. Second, it autonomously manages the use of an arbitrary number of channels in the same network all of which support the network achieving a higher capacity. The third and most exciting idea is a new fast command and control model for spectrum management. An underlying ad hoc network built using the nodes state routing (NSR) protocol is used to track and manage the use of spectrum of attached RF emitters. NSR tracks the state of the network by collecting and disseminating the states of the nodes. These states can include relevant information on the spectrum these nodes are using and are observing others use. Thus the network supports tracking and monitoring spectrum use spatially in near real time. Spectrum management utilities built on top of the network could allow users and spectrum managers to rapidly negotiate the use of spectrum for short periods of time in small regions. This finer resolution command and control model supports rapid prototyping of new services while simultaneously giving spectrum managers the ability to identify and turn off emitters that cause harmful interference to higher precedence users. We conclude with proposed standardization and regulatory changes to make this feasible

Cross-Layer Design of MANETs: The Only Option

The current Internet protocol (IP) architecture model for mobile ad hoc network (MANET) routing protocol development ignores cross-layer effects by seeking to emulate as closely as possible the wireline architecture. Nevertheless, cross-layer effects are unavoidable and it is actually desirable to exploit these interactions to achieve greater performance. Further, support for cross-layer information flow is necessary for many of the applications envisioned for MANETs. We review the purpose of the IP architecture and argue that the MANET architecture model is not only unsuitable for exploiting cross-layer effects it also violates the very intent of the IP architecture. By focusing the standardization effort on making routing solutions and placing them at the point of integration, just above IP in the protocol stack, it effectively stifles the IP development goals of supporting local subnetwork optimization and long term innovation. We review issues of cross-layer design and then propose an alternative standardization effort that would preserve the opportunity for innovation while ensuring the integration of MANET subnetworks into larger integrated heterogeneous IP networks. Our proposal places MANET into its own subnetworking layer and then divides standardization into four parts: the interface to the MANET subnetwork, a heterogeneous routing protocol, mechanisms for cross-layer information flow, and a combined logical and spatially hierarchical addressing scheme. We identify several more radical MANET design proposals that depart substantially from the current model. All could be integrated into a larger heterogeneous IP network using our protocol approach

A comprehensive energy conservation solution for mobile ad hoc networks

Multiple energy conserving approaches have been proposed for wireless networks that are exploited by the link layer and network layer protocols. Unfortunately, integrating these approaches in ad hoc networks is difficult. Due to the temporally random nature of access protocols, methods based on entering low energy states cause severe degradation of network capacity and also degrade the performance of routing protocols. Meanwhile, methods used by routing protocols that give preference to shorter links or attempt to balance load to prolong the longevity of the plurality of nodes require commitment to one or the other of these metrics without regard to link layer approaches. We show that through the integrated use of our access and routing protocols, synchronous collision resolution (SCR) and node state routing (NSR), that these types of energy conservation mechanisms can be managed simultaneously. We conclude with a simple simulation of the integrated use of these protocols. The simulations demonstrate that these protocols reduce the rate of energy consumption by the network but that in determining their effectiveness, the end-to-end throughput of the network must be considered.

Tactical communications using the IEEE 802.11 MAC protocol

This paper proposes a traffic management protocol built upon the 802.11 MAC that is designed to provide the multiple qualities of service particular to tactical communications. Together, the protocols allow for the integration of voice and data traffic giving priority to voice without preempting data. Additional features allow for more efficient collection and dissemination of position information. The most attractive feature, however, is that the protocols allow mobile stations to conserve power, using one third to one fifth the power used otherwise. The paper presents a study that seeks the design parameters, both at the physical and protocol level, for a network to support a company sized unit. In so doing we present a design methodology and validate the performance of the network using a simulation that is absolutely faithful to the protocol operation. We conduct a sensitivity analysis to explore the effects of the design parameters on network performance.

A Location-Based Method for Specifying RF Spectrum Rights

We provide a method to specify location based spectrum rights that enables spectrum management with finer resolution in space and frequency. This method accounts for the attenuation of transmissions from their source and so reveals the location based opportunities to reuse spectrum. The method uses a concise yet flexible data structure that has six parts: a signal strength, a frequency, a spectrum mask, a power map, a propagation map, and a scaling factor. Through the use of one or multiple of these parts most any type of spatial spectrum use authorization or protection may be defined. The structure allows spectrum to be managed as a spatial resource and so subdivided for spatial reuse or for resale. We provide several examples to demonstrate its versatility in spectrum management. We provide some observations and theorems that are useful in developing algorithms to verify compliance to the rights and restrictions conveyed in the proposed method and to discern when coexistent spectrum use is possible. This method provides a unified approach to define spectrum use that can be used to license spectrum, to optimize spectrum reuse, to negotiate spectrum rights, and to specify spectrum policy. It is ideally suited for over-the-air management of spectrum use.

Enabling Secondary Spectrum Markets Using Ad Hoc and Mesh Networking Protocols

Spectrum management is the process of deciding how radio frequency (RF) spectrum may be used in a geographical region and who may use it. Traditionally, spectrum management has been executed as an administrative and political process with the intent of making lasting decisions. Its lack of responsiveness and resolution causes much spectrum to lay fallow since most users rarely need spectrum continuously and ubiquitously. In this paper, we propose an alternative spectrum management approach that enables management at a greater temporal and spatial resolution using networks and wireless ad hoc and mesh networking technologies. Three different spectrum management ideas are described. The Synchronous Collision Resolution (SCR) MAC protocol enables a strict arbitration of spectrum access based on spectrum rights thus enabling a hierarchy of networks in the same spectrum that always guarantees the primary rights holder precedence. Second, it autonomously manages the use of an arbitrary number of channels in the same network. The third and most exciting idea is a new fast command and control model for spectrum management. An underlying ad hoc network built using the Nodes State Routing* (NSR) protocol is used to track and manage the use of spectrum of attached RF emitters. NSR tracks the state of the network by collecting and disseminating the states of the nodes. These states can include relevant information on the spectrum these nodes are using and are observing others use. Thus the network supports tracking and monitoring spectrum use spatially in near real time. Spectrum management utilities built on top of the network could allow users and spectrum managers to rapidly negotiate the use of spectrum and assist spectrum managers in identifying unused spectrum and emitters causing harmful interference. We conclude with proposed standardization and regulatory changes to make this feasible.

An Approach for Modestly Directional Communications in Mobile Ad Hoc Networks

Abstract Directional antennas are a promising technology for use in mobile ad hoc environments. By consuming smaller volumes than omni directional antennas, directional antennas enable significant increases in network capacity by allowing more simultaneous transmissions to occur within a multihop wireless network. In this paper, we present some of the challenges that face asynchronous directional channel access schemes and describe how these problems can be avoided by taking a synchronous approach. We describe a communications system architecture that enables modestly directional sectored antennas to be effectively exploited in a mobile ad hoc environment. A key part of this architecture is the Directional Synchronous Unscheduled Multiple Access (DSUMA) protocol. By making intelligent decisions regarding the enabling/disabling of sector antennas, DSUMA provides an increased density of transmissions while insuring that collisions do not occur. Our results indicate how the number of sectors per node affects performance in terms of spatial reuse, the likelihood of collisions, and overall network capacity.

Node state multicasting in wireless ad hoc networks

Multicasting is an essential service in wireless ad hoc net-works. Applying multicasting concepts developed for wireline networks is inappropriate since they create stateful solutions (i.e. nodes learn to react to the receipt of a multicast packet) which are short lived when topology varies. They require frequent exchanges among nodes with an attendant overhead that increases dramatically with the size of the network, its volatility, and the number of multicast groups. Nevertheless, most proposals for multicasting in ad hoc networks follow the same approach. Our proposal creates a stateless solution that uses the network state information that is already disseminated as part of the node state routing (NSR) protocol. node state multicasting (NSM) uses this information and various packet formats to enable a rich set of multicasting capabilities. Multicast routing is implemented by explicitly listing end destinations or regions in packet headers. Intermediate nodes assume responsibility for the delivery of packets to the end destinations or regions listed in the header. Routing decisions are based on the NSR routing tables. This approach is very generic and can support both traditional wireline multicast scenarios and additional scenarios typical of wireless applications.