Ivan Seskar

Overview of the ORBIT radio grid testbed for evaluation of next-generation wireless network protocols

This paper presents an overview of the ORBIT (open access research testbed for next-generation wireless networks) radio grid testbed, that is currently being developed for scalable and reproducible evaluation of next-generation wireless network protocols. The ORBIT testbed consists of an indoor radio grid emulator for controlled experimentation and an outdoor field trial network for end-user evaluations in real-world settings. The radio grid system architecture is described in further detail, including an identification of key hardware and software components. Software design considerations are discussed for the open-access radio node, and for the system-level controller that handles management and control. The process of specifying and running experiments on the ORBIT testbed is explained using simple examples. Experimental scripts and sample results are also provided.

GENI: A federated testbed for innovative network experiments

GENI, the Global Environment for Networking Innovation, is a distributed virtual laboratory for transformative, at-scale experiments in network science, services, and security. Designed in response to concerns over Internet ossification, GENI is enabling a wide variety of experiments in a range of areas, including clean-slate networking, protocol design and evaluation, distributed service offerings, social network integration, content management, and in-network service deployment. Recently, GENI has been leading an effort to explore the potential of its underlying technologies, SDN and GENI racks, in support of university campus network management and applications. With the concurrent deployment of these technologies on regional and national R&E backbones, this will result in a revolutionary new national-scale distributed architecture, bringing to the entire network the shared, deeply programmable environment that the cloud has brought to the datacenter. This deeply programmable environment will support the GENI research mission and as well as enabling research in a wide variety of application areas.

OMF: a control and management framework for networking testbeds

Networking testbeds are playing an increasingly important role in the development of new communication technologies. Testbeds are traditionally built for a particular project or to study a specific technology. An alternative approach is to federate existing testbeds to a) cater for experimenter needs which cannot be fullled by a single testbed, and b) provide a wider variety of environmental settings at different scales. These heterogenous settings allow the study of new approaches in environments similar to what one finds in the real world. This paper presents OMF, a control, measurement, and management framework for testbeds. It describes through some examples the versatility of OMFs current architecture and gives directions for federation of testbeds through OMF. In addition, this paper introduces a comprehensive experiment description language that allows an experimenter to describe resource requirements and their configurations, as well as experiment orchestration. Researchers would thus be able to reproduce their experiment on the same testbed or in a different environment with little changes. Along with the efficient support for large scale experiments, the use of testbeds and support for repeatable experiments will allow the networking field to build a culture of cross verification and therefore strengthen its scientific approach.

Rate of location area updates in cellular systems

The problem of keeping track of the location of moving subscriber terminals in cellular systems is discussed. A vehicle traffic model is developed on the basis of realistic relationships between important traffic parameters: speed, density and volume. Results for various traffic conditions were obtained for ideal and real street maps and compared with the uniform traffic model. Observations are made about when the uniform traffic model is sufficient.<<ETX>>

MobilityFirst future internet architecture project

This short paper presents an overview of the MobilityFirst network architecture, which is a clean-slate project being conducted as part of the NSF Future Internet Architecture (FIA) program. The proposed architecture is intended to directly address the challenges of wireless access and mobility at scale, while also providing new multicast, anycast, multi-path and context-aware services needed for emerging mobile Internet application scenarios. Key protocol components of the proposed architecture are: (a) separation of naming from addressing; (b) public key based self-certifying names (called globally unique identifiers or GUIDs) for network-attached objects; (c) global name resolution service (GNRS) for dynamic name-to-address binding; (d) delay-tolerant and storage-aware routing (GSTAR) capable of dealing with wireless link quality fluctuations and disconnections; (e) hop-by-hop transport of large protocol data units; and (f) location or context-aware services. The basic operations of a MobilityFirst router are outlined. This is followed by a discussion of ongoing proof-of-concept prototyping and experimental evaluation efforts for the MobilityFirst protocol stack. In conclusion, a brief description of an ongoing multi-site experimental deployment of the MobilityFirst protocol stack on the GENI testbed is provided.

ORBIT testbed software architecture: supporting experiments as a service

This paper presents the software architecture of the ORBIT radio grid testbed. We describe the requirements for supporting the lifecycle of an experiment and how they influenced the overall design of the architecture. We specifically highlight those components and services which will be visible to a user of the ORBIT testbed.

SplitAP: Leveraging Wireless Network Virtualization for Flexible Sharing of WLANs

Providing air-time guarantees across a group of clients forms a fundamental building block in sharing an access point (AP) across different virtual network providers. Though this problem has a relatively simple solution for downlink group scheduling through traffic engineering at the AP, solving this problem for uplink (UL) traffic presents a challenge for fair sharing of wireless hotspots. Among other issues, the mechanism for uplink traffic control has to scale across a large user base, and provide flexible operation irrespective of the client channel conditions and network loads. In this study, we propose the SplitAP architecture that address the problem of sharing uplink airtime across groups of users by extending the idea of network virtualization. Our architecture allows us to deploy different algorithms for enforcing UL airtime fairness across client groups. In this study, we will highlight the design features of the SplitAP architecture, and present results from evaluation on a prototype deployed with: (1) LPFC and (2) LPFC+, two algorithms for controlling UL group fairness. Performance comparisons on the ORBIT testbed show that the proposed algorithms are capable of providing group air-time fairness across wireless clients irrespective of the network volume, and traffic type. The algorithms show up to 40% improvement with a modified Jain fairness index.

Effect of Antenna Placement and Diversity on Vehicular Network Communications

In this paper we present empirical results from a study examining the effects of antenna diversity and placement on vehicle-to-vehicle link performance in vehicular ad hoc networks. The experiments use roof- and in-vehicle mounted omni-directional antennas and IEEE 802.11a radios operating in the 5 GHz band, which is of interest for planned inter-vehicular communication standards. Our main findings are two-fold. First, we show that radio reception performance is sensitive to antenna placement in the 5 Ghz band. Second, our results show that, surprisingly, a packet level selection diversity scheme using multiple antennas and radios, multi-radio packet selection (MRPS), improves performance not only in a fading channel but also in line-of-sight conditions. This is due to propagation being affected by car geometry, leading to the highly non-uniform antenna patterns. These patterns are very sensitive to the exact antenna position on the roof, for example at a transmit power of 40 mW the line-of-sight communication range varied between 50 and 250 m depending on the orientation of the cars. These findings have implications for vehicular MAC protocol design. Protocols may have to cope with an increased number of hidden nodes due to the directional antenna patterns. However, car makers can reduce these effects through careful antenna placement and diversity.

Methods for restoring MAC layer fairness in IEEE 802.11 networks with physical layer capture

In this paper, we experimentally investigate the physical layer capture effect in off-the-shelf 802.11 network cards and confirm that it reduces throughput fairness of traffic flows. We then study the feasibility of using the following PHY and MAC layer approaches to mitigate the disproportionate allocation of throughput in capture dominated scenarios: transmit power control, retransmission lim-its, CWmin adjustment, TxOp adjustment, and AIFS control. The results obtained on the ORBIT indoor wireless testbed 1 show that the 802.11e EDCF parameters provide the most fine-grained con-trol of fairness.

Practical implementation of successive interference cancellation in DS/CDMA systems

This paper addresses the practical implementation of successive interference cancellation (SIC) for DS/CDMA systems. The practical aspects of such an implementation are discussed and an FPGA-based detector employing SIC are presented. An important aspect is the integration of power control and interference cancellation which has several benefits.