As cloud applications and 5G use cases increase the demand for additional spectrum, there has emerged interest in spectrum sharing between terrestrial and satellite (SAT) networks. This paper assesses Dynamic Exclusion Zones (DEZ) and Power Control for spectrum coexistence between 5G Networks and SAT Digital Broadcasting Stations (DVB-S2). Relying on a baseband Software Defined Radio (SDR) based emulation on the COSMOS testbed, we propose a spectrum sharing control model that leverages a joint Dynamic Radio Resource Management (RRM) algorithm (Power Control with DEZ) for optimized control. Furthermore, the model combines RRM strategies with artificially generated atmospheric attenuation and path losses for robust control in a standard communication environment. Evaluating our implementation with a ETSI Rural Macro case study, we emphasize our system’s effective power control to preserve DVB-S2 Receiver Packet Error Rate (PER) performance, while maintaining a satisfactory 5G network PER. Against varying weather conditions, our results reveal joint RRM strategies can restore link performance within 73% to 99% of the ideal (no-interference) in a single base station (BS) interference scenario and 82% of the ideal against multiple BS conditions.

Dynamic Spectrum Access (DSA) is a key mechanism for meeting the ever-increasing demand for emerging wireless services. DSA involves managing and assigning available spectrum resources in a way that minimizes interference and allows RF coexistence between heterogeneous devices and systems. Such co-existence mechanisms, if they are to succeed when heterogeneous RF devices managed by different entities need to operate in a given area and frequency band (licensed and/or unlicensed), require a common mechanism for expressing the boundaries of spectrum use of each device so that spectrum use deconfliction methods can be built and verified. Spectrum Consumption Models (SCMs) – defined in the IEEE 1900.5.2 standard – offer a mechanism for RF devices to: (i) declare the characteristics of their intended spectrum use and their interference protection needs; and (ii) determine compatibility (non-interference) with existing devices. In this paper, we propose a novel SCM-based Spectrum Deconfliction (SD) algorithm that dynamically configures RF operational parameters (e.g., center frequency and transmission power) of a target transmitter-receiver pair aiming to minimize interference with existing devices/systems. We also propose sequential and distributed DSA methods that use the SD algorithm for assigning spectrum in large-scale networks. To evaluate the performance of our methods in terms of computation time, spectrum assignment efficiency, and overhead, we use two custom-made simulation platforms. Finally, to experimentally demonstrate the feasibility of our methods, we build a proof-of-concept implementation in the NSF PAWR COSMOS wireless testbed. The results reveal the advantages of using SCMs and their capabilities to conduct spectrum assignments in dynamic and congested communication environments.

Full-duplex (FD) wireless can significantly enhance spectrum efficiency but requires effective self-interference (SI) cancellers. RF SI cancellation (SIC) via frequency-domain equalization (FDE), where bandpass filters channelize the SI, is suited for integrated circuits (ICs). In this paper, we explore the limits and higher layer challenges associated with using such cancellers. We evaluate the performance of a custom FDE-based canceller using two testbeds; one with mobile FD radios and the other with upgraded, static FD radios in the PAWR COSMOS testbed. The latter is a lasting artifact for the research community, alongside a dataset containing baseband waveforms captured on the COSMOS FD radios, facilitating FD-related experimentation at the higher networking layers. We evaluate the performance of the FDE-based FD radios in both testbeds, with experiments showing 95 dB overall achieved SIC (52 dB from RF SIC) across 20 MHz bandwidth. We conduct network-level experiments for (i) uplink-downlink networks with inter-user interference, and (ii) heterogeneous networks with half-duplex and FD users, showing FD gains of$1.14\times $–$1.25\times $and$1.25\times $–$1.73\times $, respectively, confirming analytical results. We also evaluate the performance of an FD jammer-receiver, demonstrating a strong dependence on relative transmit power levels and modulation schemes.

Private 5G networks will soon be ubiquitous across the future-generation smart wireless access infrastructures hosting a wide range of performance-critical applications. A high-performing User Plane Function (UPF) in the data plane is critical to achieving such stringent performance goals, as it governs fast packet processing and supports several key control-plane operations. Based on a private 5G prototype imple-mentation and analysis, it is imperative to perform dynamic resource management and orchestration at the UPF. This paper leverages Mobile Edge Cloud-Intelligent Agent (MEC-IA), a logically centralized entity that proactively distributes resources at UPF for various service types, significantly reducing the tail latency experienced by the user requests while maximizing resource utilization. Extending the MEC-IA functionality to MEC layers further incurs data plane latency reduction. Based on our extensive simulations, under skewed uRLLC traffic arrival, the MEC-IA assisted bestfit UPF-MEC scheme reduces the worst-case latency of UE requests by up to 77.8% w.r.t. baseline. Additionally, the system can increase uRLLC connectivity gain by 2.40× while obtaining 40% CapEx savings.

This paper investigates the optimization of memory sampling in status updating systems, where source updates are published in shared memory, and reader process samples the memory for source updates by paying a sampling cost. We formulate a discrete-time decision problem to find a sampling policy that minimizes average cost comprising age at the client and the cost incurred due to sampling. We establish that an optimal policy is a stationary and deterministic threshold-type policy, and subsequently derive optimal threshold and the corresponding optimal average cost.

A microwave radiometer (MWR) at NOAA-CESSRST in Manhattan, NYC has experienced interference from nearby sources operating in the 5G FR2 n257 band (26.50--29.50 GHz). In this poster, we produce interference using a mobile 28 GHz IBM Phased Array Antenna Module (PAAM). The mobile PAAM leverages a software-defined radio which offers flexibility in varying center frequency, modulation, gain, bandwidth, time schedule, and more. In this poster, we show preliminary experiments which successfully created controlled interference to a MWR's 28 GHz channel which lead to distortion in some of the MWR final products, such as water vapor profile. We transmitted a 10 MHz bandwidth OFDM signal with varying amplitude, observing the highly sensitive MWR voltage response to fractional dB increments of the transmitter gain. The mobile PAAM is characterized in an anechoic chamber and MWR measurements are taken at various azimuth angles to help estimate the MWR antenna pattern. Future work will develop a Spectrum Consumption Model to help enable coexistence of MWRs and Beyond-5G networks.

We present Wall-Street, a smart surface designed for vehicles to boost 5G mmWave connectivity for passengers. It improves mmWave connections in three ways: (1) it steers outdoor mmWave signals into the vehicle, ensuring all users have coverage; (2) it enables the vehicle to receive data from the current cell while measuring signals from potential handover cells, allowing smooth transitions without interrupting service; (3) during handovers, it combines/splits signals from/to both the current and new cells, creating a make-before-break connection. Our demonstration shows Wall-Street's versatile signal manipulation abilities. These include steering single beams, simultaneously reflecting and transmitting beams for neighboring cell measurements with concurrent communication, and combining or splitting beams for seamless cell transitions.

We present experiments using mobile 28 GHz Phased Array Antenna Modules (PAAMs), demonstrating their ability to perform beam steering with high granularity. The mobile node contains a 64-element IBM 28 GHz PAAM along with a USRP software defined radio, allowing for configuration of the transmit/receive (TX/RX) parameters. These parameters include beam shape, beam steering, and duty cycling. We demonstrate the capabilities of the mobile PAAMs by forming a wireless OFDM link between two mobile PAAMs. We then showcase the beam steering capabilities of the PAAM by performing beam sweeping on the RX PAAM to find the angle of arrival from the TX PAAM. A simple graphical user interface is presented for configuring the PAAMs. A tutorial is available online for users interested in experimentation with 28 GHz PAAMs*.

This paper presents a platform for measuring, evaluating and modeling the energy efficiency aspects of an O-RAN 5G wireless network. We describe our open-source based O-RAN testbed which includes both bare-metal and Kubernetes network functions, in addition to physical network components. We focus on measuring power consumption of servers and workloads of cloudified and virtualized network functions. We show that a combination of different power measurements can be used successfully to achieve the accuracy and granularity required for energy efficiency measurement, evaluation and modeling.

Next generation wireless services and applications, including Augmented Reality, Internet-of-Things, and Smart-Cities, will increasingly rely on Dynamic Spectrum Access (DSA) methods that can manage spectrum resources rapidly and efficiently. Advances in regulatory policies, standardization, networking, and wireless technology are enabling DSA methods on a more granular basis in terms of time, frequency, and geographical location which are key for the operation of 5G and beyond-5G networks. In this context, this paper proposes a novel DSA algorithm that leverages IEEE 1900.5.2 Spectrum Consumption Models (SCMs) which offer a mechanism for RF devices to: (i) "announce" or "declare" their intention to use the spectrum and their needs in terms of interference protection; and (ii) determine compatibility (i.e., non-interference) with existing devices. In this paper, we develop an SCM-based DSA algorithm for spectrum deconfliction in large-scale wireless network environments and evaluate this algorithm in terms of computation time, efficiency of spectrum allocation, and number of device reconfigurations due to interference using a custom simulation platform. The results demonstrate the benefits of using SCMs and their capabilities to perform fine grained spectrum assignments in dynamic and dense communication environments.

We consider a system where the updates from independent sources are disseminated via a publish-subscribe mechanism. The sources are the publishers and a decision process (DP), acting as a subscriber, derives decision updates from the source data. We derive the stationary expected age of information (AoI) of decision updates delivered to a monitor. We show that a lazy computation policy in which the DP may sit idle before computing its next decision update can reduce the average AoI at the monitor even though the DP exerts no control over the generation of source updates. This AoI reduction is shown to occur because lazy computation can offset the negative effect of high variance in the computation time.

We quantify the classification accuracy of Neural Networks (NNs) to specific websites using only the packet size and difference in inter-packet arrival time, which are easily observable via passive attackers in the network. Our flow classification work with NNs is unique in that we do not classify traffic by application type. Rather, we observe the accuracy of various NNs classifying specific web sites using HTTP traffic over TCP. We test a diverse set of neural network structures including a fully connected network (FCN), a convolutional neural network (CNN), a long short-term memory network (LSTM), and an autoencoder network (AE). We found that CNNs consistently had the highest accuracy, typically 80-90% when using 20 million packets as training data. We suspect that individual websites generate unique traffic patterns which are discoverable using NN techniques. Our work has important privacy implications. In particular, our work supports that both packet sizes and inter-packet timing must be randomized to obtain strong web browsing privacy. Many privacy preserving techniques, such as VPNs, will require additional enhancements.

We propose reliability and latency quantities as metrics to be used in the routing tree optimization procedure for Wi-Fi mesh networks. In contrast to state-of-the-art routing optimization methods, our proposal involves directly optimizing the data rates of individual mesh links according to underlying channel conditions such that reliability and latency requirements are satisfied for entire mesh paths. Moreover, to mitigate the channel contention problem that is common in Wi-Fi networks, we propose a multichannel (MC) assignment method. In this method, bandwidth is allocated to the individual mesh nodes based on the expected traffic load that they are expected to handle. Once the bandwidth for each node is determined, specific channels are assigned in a way to avoid co-channel interference. Furthermore, considerable efforts were spent for developing a system-level simulator that captures the features of the physical (PHY) layer and medium access layer defined in the IEEE 802.11 standard (Wi-Fi). Using this simulator, we were able to show that Wi-Fi mesh networks using the proposed routing metric based on reliability and latency quantities significantly outperform the state of the art. Finally, the mitigation of channel contention through the proposed MC assignment method results in further dramatic gains in performance.

Prediction of user traffic in cellular networks is one of the promising ways to improve resource utilization among base stations. In this study, we employ deep learning techniques, specifically a long-short-term memory module to forecast cellular traffic. We consider traffic from neighboring cells and other non-cellular traffic-related attributes such as weather, busy period data from open-source API as features to augment the cellular traffic data and improve prediction. Specifically, we augment cellular traffic data from the City of Milan and its surroundings and we perform two types of analyses: (i) a one-step prediction or a point-by-point forecast of traffic and (ii) a trend analysis which is the forecast of traffic over an extended period. We compare the results with existing statistical methods such as auto-regression integrated moving averages (ARIMA) and exponential smoothing and observe gains in the trend analysis by providing the augmented data, whereas the one-step prediction is not much impacted.

To support experimentation with full-duplex (FD) wireless, we recently integrated two FlexICoN Gen-2 wideband FD radios in the open-access, city-scale NSF PAWR COSMOS testbed. Each integrated FD radio consists of an antenna, a customized Gen-2 RF self-interference (SI) canceller box, a USRP software-defined radio, and a remotely accessible compute node. The RF SI canceller box includes an RF canceller printed circuit board which emulates an integrated circuit implementation based on the technique of frequency-domain equalization. The Gen-2 canceller box can achieve up to 50 dB RF SI cancellation across 20MHz bandwidth. In this demo, we present the design and implementation of the open-acccess, remotely accessible FD radios that are integrated in the indoor COSMOS Sandbox 2 at Columbia University. We also demonstrate example experiments that are available to researchers, where demo participants can observe the visualized performance of the open-access FD radios.

This paper focuses on COSMOS - Cloud enhanced Open Software defined MObile wireless testbed for city-Scale deployment. The COSMOS testbed is being deployed in West Harlem (New York City) as part of the NSF Platforms for Advanced Wireless Research (PAWR) program. It will enable researchers to explore the technology "sweet spot" of ultra-high bandwidth and ultra-low latency in the most demanding real-world environment. We describe the testbed's architecture, the design and deployment challenges, and the experience gained during the design and pilot deployment. Specifically, we describe COSMOS' computing and network architectures, the critical building blocks, and its programmability at different layers. The building blocks include software-defined radios, 28 GHz millimeter-wave phased array modules, optical transport network, core and edge cloud, and control and management software. We describe COSMOS' deployment phases in a dense urban environment, the research areas that could be studied in the testbed, and specific example experiments. Finally, we discuss our experience with using COSMOS as an educational tool.

In order to support experimentation with full-duplex (FD) wireless, we integrated the FlexICoN Gen-2 wideband FD radio with the city-scale PAWR COSMOS testbed [1]. In particular, the implemented FD radio consists of an antenna, a customized Gen-2 RF self-interference (SI) canceller box, a USRP software-defined radio (SDR), and a compute node. The RF canceller box includes an RF SI canceller implemented using discrete components on a printed circuit board (PCB), which emulates its RFIC canceller counterpart. The Gen-2 RF SI canceller achieves 50dB RF SI cancellation across 20MHz bandwidth using the technique of frequency-domain equalization (FDE) [2]. In this abstract, we present the design and implementation of the remotely accessible Gen-2 wideband FD radio integrated with the COSMOS sandbox at Columbia University. We also present an example real-time wideband FD wireless link demonstration using the GNU Radio software.

The Cloud-Enhanced Open Software Defined Mobile Wireless Testbed for City-Scale Deployment (COSMOS) platform is a programmable city-scale shared multi-user advanced wireless testbed that is being deployed in West Harlem of New York City [1]. To keep pace with the significantly increased wireless link bandwidth and to effectively integrate the emerging C-RANs, COSMOS is designed to incorporate a fast programmable core network for providing connections across different computing layers. A key feature of COSMOS is its dark fiber based optical x-haul network that enables both highly flexible, user defined network topologies and experimentation directly in the optical physical layer. The optical architecture of COSMOS was presented in [2]. In this abstract, we present the tools and services designed to configure and monitor the performance of optical paths and topologies of the COSMOS testbed. In particular, we present the SDN framework that allows testbed users to implement experiments with application-driven control of optical and data networking functionalities.

Classification of MIMO wireless signals with no prior information of the number of transmitter antenna elements and channel(s) is of tremendous importance in both military and civilian applications. In this research, we present a novel generalized algorithm for classification of digital modulation combined with the recognition of the number of transmit antennas. Our algorithm is developed to rely on only one receiver equipped with a single antenna and does not require any prior channel knowledge. We have introduced a two- phase classifier system. In the first phase, we use a discrete-wavelet transform on the received complex samples to separate the different modulation classes. Following that, we use the K- nearest neighbor approach coupled with k-means clustering to further classify the signals, utilizing the symmetry and relative distances of the constellation points. The performance of the classifiers at different stages of the algorithm demonstrates a high accuracy in an SNR regime where the packets can be decoded.

This paper proposes a novel advanced distribution management system (ADMS) solution based on a common operation technology platform implemented on a cloud infrastructure. It introduces a virtualization methodology that is used to transition and deploy a traditional, monolithic ADMS in a cloud environment. First, typical ADMS functional blocks (FBs) are identified and their performance is evaluated with respect to four major metrics: processor, memory, network, and storage utilization. Next, a cloud infrastructure-based ADMS solution is presented, based on a collection of FBs mapped to a set of virtual machines. Finally, the proposed architecture is validated via deployment on a physical hardware platform with two representatively sized distribution networks and emulated workloads. Obtained results show that an ADMS, as a mission-critical system, can be deployed on a cloud infrastructure, providing many benefits of virtualized solutions, without negative impact on system performance.

Increasing data traffic demands over wireless spectrum have necessitated spectrum sharing and coexistence between heterogeneous systems such as radar and cellular communications systems. In this context, we specifically investigate the co- channel coexistence between an air traffic control (ATC) radar and a wide area cellular communication (comms) system. We present a comprehensive characterization and analysis of interference caused by the comms system on the ATC radar with respect to multiple parameters such as radar range, protection radius around the radar, and radar antenna elevation angle. The analysis suggests that maintaining a protection radius of $50$ km around the radar will ensure the required INR protection criterion of $-10$ dB at the radar receiver with $\sim 0.9$ probability, even when the radar beam is in the same horizon as the comms BS. Detailed evaluations of the radar target detection performance provide a framework to choose appropriate protection radii around the radar to meet specific performance requirements.

In the recent years it has become increasingly evident that the current end-to-end host-centric communication paradigm will not be capable of meeting the ongoing demand for massive data rates and ultra-low latency. With the advent of fifth generation of cellular architecture (5G) to support these requirements on the wireless edge of the network, the need for core network solutions to play a complementary role is conspicuous. In this paper we present and tackle some of the challenges of deploying a Future Internet Architecture (FIA), called MobilityFirst (MF), specifically for 5G use case scenarios. We report our findings of the deployment based on a setup on a small- scale testbed (ORBIT) and a nation-wide distributed testbed (GENI), and illustrate some results for the use case of device multihoming, in comparison with current TCP/IP based solution, i.e. Multipath TCP.

This paper presents the design and evaluation of a mobile data service which exploits parallel multi-path transmission over multiple cellular networks to achieve significant performance gains. Multi-network access is motivated by the fact that multi-radio mobile devices are fast becoming a reality, making it possible for end-users to increase their service speed and availability via network diversity. In contrast to previously proposed techniques at the application or transport layers, we propose a novel network assisted architecture for multi-homed (NAMH) cellular access. In the proposed system, network elements such as routers and base stations provide the necessary multihoming functionality including identification of a bifurcation router and dynamic splitting of the data stream corresponding to currently achievable bit-rates on the cellular base stations. A detailed evaluation is provided for the multi-network service with LTE base stations, using both ns3 simulation and trace-driven emulations. The results show that significant gains are achieved with multi-network access with bit-rates of ~1.9x using two LTE networks in parallel. Comparison with the well-known MPTCP method is given, showing gains of about 40% with NAMH for the trace-driven two-network scenario.

In this paper, QoS characteristics such as TCP throughput is investigated for densely deployed mobile wireless LANs (WLANs). Factors affecting throughput characteristics are discussed and evaluated by using real machines such as smartphones and portable APs. In IEEE 802.11 WLANs, a rate adaptation mechanism controls the transmission rate and one of the dominant factors for QoS. In order to understand the behavior of the rate adaptation control, 1 to 18 sets mobile WLANs are examined under different parameters. Since a behavior of the rate adaptation control is a vender specific one and it strongly depends on interference, signal strength and etc., the real terminals such as smartphones were used in the experiments. Performance anomaly drastically reduces the throughput not only in the WLAN which has a terminal with low transmission rate but also in the neighboring WLANs that share the same channel. In order to avoid unnecessary transmission rate degradation by the rate adaptation control, Context Aware multi Rate Control (CARC) is proposed and evaluated. In CARC, Turning the rate adaptation control on/off is controlled according to a context, for example, signal strength. The evaluation results show that the CARC can be cost-effectively implemented and improves the throughput performance of whole WLANs by 3.5 times than that without the application of CARC.

This demo presents the architecture of GENI (Global Environment of Network Innovations) [1] edge cloud computing network in the form of compute and storage resources, a mobile 4G LTE edge and a high speed campus network connecting these components. GENI's edge computing strategy proceeds by deploying self-contained packages of network, computing, storage resources, or GENI Racks [2] connected via high speed fiber to LTE BS(s) across twelve campuses in the US, all interconnected via a nationwide research network. The GENI mobile computing resource manager is based on the Orbit Management framework (OMF) [3] and provides seamless access to the edge computing resources via the GENI Portal for experimentation, scheduling, data collection and processing.

High market demand for wireless networking services and devices has resulted in increased complexity of an infrastructure of networking testbeds because of the scale, diversity and exploitation levels of the involved resources. In this paper, we address the problem of managing the infrastructure of large wireless networking testbed by adopting a semantics-based approach to knowledge-driven system management. A novel data transformation language, fully based on the semantic web standards, is introduced. Using the introduced language, an XML description of testbed services can be transformed to semantically enriched data. Workflow of the transformation is explained on the example of semantic lifting of the ORBIT testbed infrastructure. The example provides experimental evidence for successful application of the proposed approach.

Detecting malicious users in dynamic spectrum access scenarios is a crucial problem that requires an intrusion detection system (IDS) that scans spectrum for malicious activities. In this paper we design a spectrum scanning protocol that incorporates knowledge about the scanning effectiveness across different bands, which can increase scanning efficiency. The adversary, however, can also exploit such knowledge to its advantage. To understand the interplay underlying this problem, we formulate a Bayesian model, where the IDS faces a scanning allocation dilemma: if the intruder has no knowledge, then all the bands are under equal threat, while if the intruder has complete knowledge, then less-protected bands are more likely to be threatened. We solve this dilemma and show the optimal IDS strategy switches between the optimal response to these threats. Finally, we show that the strategy might be sensitive to prior knowledge, which can be corrected by adapted learning.

Spectrum sensing is one of the core functionalities of a true cognitive radio (CR) that supports operation over a broad range of frequencies and can autonomously adapt transmission parameters to the operating environment. There are several types of hardware ranging from sophisticated (i.e. Nutaq Radio420X FPGA mezzanine card) to low cost (i.e. WiSpy) that can be used to experiment with spectrum sensing. This hardware is available for use in several testbeds across the world (i.e. ORBIT, w-iLab.t, TWIST and LOG-a-TEC). Each testbed provides a specific mechanism to define, deploy and execute experiments making it difficult for an individual researcher to use more than one testbed. In this work we propose an information model for describing spectrum sensing functionality with the ultimate goal of developing and promoting a Common CR language that can describe the resources in existing GENI and FIRE testbeds.

The lessons already learned from the existing protocols operation are taken into deep consideration during the standardization activities of the potential technologies opted for the future 5th Generation mobile networks. Prior research on wireless technologies in general has clearly shown the need for open programmable experimental facilities which can be used for the implementation and evaluation of novel algorithms and ideas under real world settings, even directly comparable to existing technologies and methodologies. Nevertheless, provisioning of such testbed platforms mandates the respective tools which will enable access to the testbed resources and will expose the maximum possible flexibility in configuring them. In this work, we present our efforts in building such a facility, along with the tools and services that cope with such requirements. The facility upon which we build is the long-established NITOS wireless testbed, which is offering commercial as well as open source LTE components in a 24/7 basis.

This paper investigates Quality of Service (QoS) of the personal mobile wireless LANs (m-WLANs). The situations in the m-WLANs differs from the situations in the normal use of WLANs; the access point (AP) and the associated terminals (TEs) are in proximity. In the m-WLANs, the capture effect (CE) significantly affects on the throughput performance. To measure the impact on the QoS by the CE, the experimental study considering the interference from other power sources (APs and TEs) are required. However, since it is difficult to understand the detailed relationships between the QoS factors, the analytical calculations were also performed. With the experimental and analytical results, we demonstrated that the auto rate fallback algorithm of WLAN causes degradation of the QoS performance. We propose two transmission rates controlling schemes to improve the QoS performance.

Traffic from mobile wireless networks has been growing at a fast pace in recent years and is expected to surpass wired traffic very soon. Service providers face significant challenges at such scales including providing seamless mobility, efficient data delivery, security, and provisioning capacity at the wireless edge. In the Mobility First project, we have been exploring clean slate enhancements to the network protocols that can inherently provide support for at-scale mobility and trustworthiness in the Internet. An extensible data plane using pluggable compute-layer services is a key component of this architecture. We believe these extensions can be used to implement in-network services to enhance mobile end-user experience by either off-loading work and/or traffic from mobile devices, or by enabling en-route service-adaptation through context-awareness (e.g., Knowing contemporary access bandwidth). In this work we present details of the architectural support for in-network services within Mobility First, and propose protocol and service-API extensions to flexibly address these pluggable services from end-points. As a demonstrative example, we implement an in network service that does rate adaptation when delivering video streams to mobile devices that experience variable connection quality. We present details of our deployment and evaluation of the non-IP protocols along with compute-layer extensions on the GENI test bed, where we used a set of programmable nodes across 7 distributed sites to configure a Mobility First network with hosts, routers, and in-network compute services.

With the increasing interest in connected vehicles, it is useful to evaluate the capability of delivering large content over a WiFi infrastructure to vehicles. The throughput achieved over WiFi channels can be highly variable and also rapidly degrades as the distance from the access point increases. While this behavior is well understood at the data link layer, the interactions across the various protocol layers (data link and up through the transport layer) and the effect of mobility may reduce the amount of content transferred to the vehicle, as it travels along the roadway. This paper examines the throughput achieved at the TCP layer over a carefully designed outdoor WiFi environment and the interactions across the layers that impact the performance achieved, as a function of the receiver mobility. The experimental studies conducted reveal that impairments over the WiFi link (frame loss, ARQ and increased delay) and the residual loss seen by TCP causes a cascade of duplicate ACKs to be generated. This triggers large congestion window reductions at the sender, leading to a drastic degradation of throughput to the vehicular client. To ensure outdoor WiFi infrastructures have the potential to sustain reasonable downlink throughput for drive-by vehicles, we speculate that there is a need to adapt how WiFi and TCP (as well as mobility protocols) function for such vehicular applications.

This paper presents a technique for enabling multihoming in the emerging heterogeneous (“hetnet”) mobile wireless access scenarios, where mobile devices have dual wireless interfaces (such as Wi-Fi and LTE) and can use either or both to achieve significant improvements in performance and service quality. A novel network-assisted technique for multihoming is introduced, enabled by the globally unique identifier (GUID) based routing in the proposed MobilityFirst Future Internet architecture, now under development. In particular, the approach shifts the burden of policy expression and data-striping from end-nodes to in-network nodes, and utilizes named object routing with GUIDs to establish multiple paths to destination mobile devices. The proposed multihoming technique uses hop-by-hop backpressure for data striping at the bifurcation router and includes a robust mechanism to reduce reordering of packets at the receive buffer. We quantify the performance gains using detailed NS3 based simulations and present results from a thorough parametric study to determine the effects of datarate, delay and hop-count difference between multiple available paths. We also show that when multiple interfaces are available, simultaneous use of both the interfaces is beneficial only under certain conditions depending on the ratio of the data-rate of the interfaces and the size of the flow.

This paper presents a study of mobile wireless LAN (WLAN) hotspots which are used to provide cellular-WiFi tethering service to personal devices. A dense deployment scenario for fixed and mobile WLAN is described and potential performance problems due to interference are identified. An analytical model for coexisting fixed and mobile WLAN hotspots with heterogeneous traffic is presented. The model is used to evaluate the performance of a mobile WLAN as it transits through a set of densely deployed fixed access points (APs), and performance problems due to lack of frequency coordination are identified. An adaptive channel assignment (ACA) scheme for improving mobile AP performance is proposed and evaluated. It is shown that significant performance gains can be achieved with ACA with maximum absolute and percentage throughput gains up to 1.24 Mbps and 42.8% respectively. We also show that setting the scanning interval in ACA requires consideration of the speed at which the mobile WLAN is moving in order to compensate for the throughput losses during channel scanning.

Vehicular networking has significant potential to enable diverse range of applications, including safety and convenience. As the number of vehicles and applications using wireless spectrum grow, one can expect to see a shortage of either spatially or temporally available spectrum. In this paper, we advocate that dynamic spectrum access for vehicles be the first step towards solving the spectrum shortage. For this, vehicles must be able to sense the availability of spectrum before attempting to transmit. The existence of other transmitters should be detected in order not to cause or experience interference. However, spectrum sensing in vehicular environments is a challenging task due to mobility, shadowing and other factors that govern vehicular environments. Therefore, spectrum sensing by a single vehicle may not be able to provide accurate information about the spectrum vacancies. Cooperative spectrum sensing, on the other hand, uses spatial diversity and can be employed to overcome the limitations associated with a single sensor/vehicle. In this paper, we investigate cooperative spectrum sensing performance in a vehicular environment for sensing signals transmitted from i) a roadside infrastructure and ii) radios located on other vehicles, by using energy-based detection of a transmitted pilot tone as an example. Our goal is to characterize the limits on detection speed and reliability of simple hard and soft cooperative energy-based schemes for this environment. We show how cooperation reduces sensing time by a factor of five in an AWGN channel. The cooperative sensing time reduction is far more significant in a vehicular environment with fading and shadowing. Finally, we illustrate how infrastructure-to-vehicle scenario favors soft equal gain combining while vehicle-to-vehicle scenario favors hard fusion OR rule.

The increasing density and data rate of unlicensed band wireless devices in small office and home (SOHO) environments has led to significant inter- and intra-radio interference problems. Multiple competing standards such as the IEEE 802.11b/g, Bluetooth and ZigBee, all of which operate in the 2.4 GHz ISM band, can interfere with each other when used in typical indoor environments, potentially causing significant performance degradation. This paper presents detailed experimental results (using the ORBIT radio grid testbed) to quantify the effects of such interference in representative SOHO scenarios. In particular, different topologies, traffic loads and number of interfering devices are emulated to show the impact of multi-radio interference and to characterize each kind of interference. Further, a cross-layer, multi-radio interference diagnosis framework (called “spectrum MRI”) is described with the aim of isolating and classifying multi-radio interference problems using heuristic and model-based methods. A specific example of identifying interference problems which may affect an 802.11g video link is given to illustrate the proposed measurement and diagnosis framework.

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.

The 802.16e standard for broadband wireless access mandates the presence of QoS classes, but does not specify guidelines for the scheduler implementation or mechanisms to ensure air time fairness. Our study demonstrates the feasibility of controlling downlink airtime fairness for slices while running above a proprietary WiMAX basestation (BS) scheduler. We design and implement a virtualized infrastructure that allows users to obtain at least an allocated percentage of BS resources in the presence of saturation and link degradation. Using Kernel virtual machines for creating slices and Click modular router for implementing the virtual network traffic shaping engine we show that it is possible to adaptively control slice usage for downlink traffic on a WiMAX Basestation. The fairness index and coupling coefficient show an improvement of up to 42%, and 73% with preliminary indoor walking mobility experiments. Outdoor vehicular measurements show an improvement of up to 27%, and 70% with the fairness index and coupling coefficient respectively

Frame aggregation is a wireless link optimization mechanism that aims to reduce transmission overheads by sending multiple frames as the payload of a single MAC frame. Static assignment of frame aggregation parameters can result in delay penalties due to variations in traffic type or load levels. Another possible side effect is an increase in packet error rate in noisy environments due to large aggregated frame size. Adaptive aggregation methods have previously been proposed to deal with the above problems independently, but there is still a need for a unified adaptation algorithm that addresses both aspects in an integrated manner. In this study, a backlogged queue (BQ) aggregation approach is proposed that considers both these aspects, and also ensures inter-operability with other WLAN devices that are not capable of frame aggregation. Performance evaluation of the proposed algorithm on the ORBIT testbed shows throughput improvements of up to 56% in the presence of channel noise and 25% in scenarios with high contention over using a simple txop. An experimental case study shows improvement in FTP file transfer times of up to 11% while preserving performance for real time traffic.

This paper describes experiments which study the effects of both a stationary and a moving vehicle on the 22 MHz 802.11b and the 20 MHz 802.11a channel transfer functions. Our setup enables concurrent measurements of: (1) the complex channel transfer function with a Vector Network Analyzer (VNA), and (2) the Received Signal Strength Index (RSSI) obtained using off-the-shelf 802.11 cards. Our results show that, for the case of the stationary channel, the average RSSI is a several dBs away from the channel loss measured by the VNA, even with meticulous calibration of the 802.11 cards. The VNA measurements show that a vehicle moving in an environment resembling a multi-lane highway can cause a change in the magnitude of the transfer function on the order of tens of dB. The results of the RSSI measurements show that changes in RSSI caused by the passing vehicle are in the order of magnitude of the ones measured with the VNA.

Wireless network emulator testbeds have become increasingly important for realistic, at-scale experimental evaluation of new network architectures and protocols. Typically, wireless network performance measurements are made at multiple layers of the wireless protocol stack, i.e. link layer, MAC layer and network layer. This study highlights the impact of layer 2 frame aggregation that is enabled by default in the software drivers for commodity wireless 802.11 devices while it is still not a part of the core 802.11 standard. Using experimental measurements, it is shown that this feature has an impact across a diverse set of wireless experiments and should be considered while comparing results. Measurements on the ORBIT testbed show that throughput measurements can vary up to a startling 25% for certain packet sizes and the variance in receiver side interframe delays can almost double if MAC aggregation and preset transmission opportunities are not taken into consideration. Further results for VoIP traffic show a deterioration in jitter of up to 8 times when coupled with MAC layer aggregation in 802.11.

This demonstration will show the versatility of an agile cognitive radio platform in a non-cooperative communication scenario. The techniques proposed for an Aggressive Cognitive Radio (ACR) including parking on unused spectrum, monitoring users to predict when they will vacate spectrum and intentional jamming of users to force them off spectrum.

We perform a set of measurements of channel frequency responses at different points in the room that accommodates the ORBIT indoor testbed using a vector network analyzer (VNA). To validate the data collected with VNA we use spectrum analyzer (SA) measurements, as well. Four measurements are performed over non-overlapping 100 MHz bands in the industrial, scientific, and medical (ISM) band, and in the unlicensed national information infrastructure (UNII) band. The fifth measurement spans the coarsely sampled .4 to 6 GHz band. From the measured frequency responses we calculate path loss model parameters. The path loss exponent is between 1.1 and 2 and the dynamic range of the signal is around 25 dB across different bands. Based on the frequency responses measured over the .4 to 6 GHz band we determine multipath intensity profiles (MIP) with fine time granularity. The comparison of MIPs to the ray tracing simulations generated with WiSE software indicates that the surfaces perpendicular to the plane defined by the transmit and receive antennas represent a significant source of reflections. However, the reflections from the floor, dropped ceiling, and roof are suppressed by the antenna elevation patterns.

Recent real-world measurements in dense congested radio environments have pointed out the inefficiency of frame error-based bit-rate adaptation mechanisms, which significantly reduce network capacity by misinterpreting frame errors due to collisions. These effects are likely to be amplified with the heavy use of media applications. Fortunately, traditional SNR-based rate adaptation, and the more recently proposed throughput-based, and collision-aware rate adaptation algorithms are expected to provide more robust performance in these scenarios. To our knowledge, however, their performance has never been experimentally validated in a congested environment. In this paper, we report our implementation experiences with rate adaptation in a dense, congested IEEE 802.11 network. We find that throughput-based adaptation, contrary to expectations, also suffers from poor bitrate selection. Due to an increase in physical layer capture, while using lower bitrates, nodes can increase their individual throughput at the expense of cumulative network throughput. SNR-based rate adaptation performs well in static environments but the lack of sufficient precision in RSSI measurements makes accurate rate selection in dynamic radio environments dfficult. The use of RTS/CTS, in the spirit of collision-aware rate adaptation, shows throughput improvements for frame error-based algorithms and, additionally, for throughput-based algorithms as well. However, results are below expectations likely due to RTS/CTS implementation issues on the Atheros 5212 platform.

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.

We propose an algorithm for the construction of ternary orthogonal variable-spreading-factor (OVSF) codes with zero-correlation zone (ZCZ); this is of particular interest for ternary sequence based UWB (TS-UWB) systems. The conventional approach is to design OVSF codes based on Walsh codes and, in this case, the orthogonality of the corresponding OVSF codes is easily lost when synchronism is lacking or in a multipath scenario. 2D OVSF codes possess ideal correlation properties which significantly improve the interference-rejection capability of multicarrier DS-CDMA systems. However, 2D OVSF code schemes, applied over multiple orthogonal channels, suffer from the disadvantages of a high peak-to-average power ratio (PAPR) and high complexities on transceiver design. The proposed OVSF codes, derived from two-dimensional (2D) OVSF codes, present a ZCZ which allows for significant suppression of multipath and multiuser interference and keeps the transceiver of an impulse based UWB system simple.

The paper describes the design and evaluation of ad-hoc extensions to the IEEE 802.15.3 medium access control (MAC) layer for wireless personal area networks (WPANs). The proposed protocol allows communication between ad-hoc devices without the intervention of any central entity and, at the same time, ensures bounded delays for isochronous traffic. Ad-hoc communication is made possible without the hidden terminal problem. Features from both IEEE 802.15.3 and IEEE 802.11 standards are used - in particular the TDMA structure from 802.15.3 and RTS-CTS based contention from 802.11. The protocol includes certain other ingredients, like a decentralized synchronization procedure using randomized beaconing, periodically interspersed contention periods, bit maps to convey reservation information and a mechanism to estimate and react to channel errors. The MAC has been simulated in ns-2 and simulation results are reported.

We consider wireless data services characterized by short distances, no shadowing, low power, and low antenna heights, deployed in places where a high frequency of potential users is expected, e.g., toll booths, parking lots, intersections, etc. Within such a system, we expect to see a well-defined geometry of base-to-user radio paths, as well as a predictable user trajectory, neither of which can be assumed for the wide-area cellular case. This offers the promise of a strong deterministic component of the channel response, in addition to a weaker stochastic component. Here, we combine analysis of the former with measurements and modeling of the latter for three typical outdoor scenarios. Comparisons between predicted and measured behavior show excellent agreement.

This paper describes a beacon assisted discovery mechanism for self-organizing hierarchical ad-hoc networks. The discovery protocol, which operates between the medium access control (MAC) and network layers, is responsible for topology formation in the ad-hoc network taking into account performance objectives such as throughput, delay, energy consumption and robustness. The proposed discovery protocol operates by listening to augmented MAC-layer beacons from neighboring radio nodes and then selects a subset of these for routing associations based on specified criteria. A distributed heuristic algorithm for topology formation is considered and compared with upper-bound centralized algorithms with optimization objectives such as maximum throughput, minimum delay or minimum energy. Simulation results (based on ns-2 models) are given for the performance of the proposed discovery methods, demonstrating significant improvements in routing overhead when compared to an ad hoc network without discovery. A proof-of-concept prototype implementation for an IEEE 802.11b-based three-tier hierarchical ad hoc network is briefly described in conclusion.

We study a multiple channel direct sequence ultrawideband (DS-UWB) system which transmits the same information bit over a set of parallel channels corresponding to a set of orthogonal pulses. It is known that by employing a mutually orthogonal (MO) ternary complementary set of spreading sequences, one can efficiently suppress both multipath and multiuser interference. Similar to a multicarrier DS-CDMA system, the multichannel DS-UWB system can have a high peak to average power ratio (PAPR) which may limit its application. In this paper, we analyze the PAPR of the multichannel UWB system by studying its upper bound. The bound illustrates how column sequences of MO complementary set matrices with small out-off-phase aperiodic autocorrelation functions (ACF) allow for lowering the PAPR. Hence, we develop an algorithm to construct the spreading sequence sets which may result in data sequences with reduced PAPR, while at the same time, preserving the complementarity and orthogonality which alleviate the multipath and multiuser interference.

This paper describes the design and implementation of a novel 802.11-based self-organizing hierarchical ad-hoc wireless network (SOHAN), and presents some initial experimental results obtained from a proof-of-concept prototype. The proposed network has a three-tier hierarchy consisting of low-power mobile nodes (MNs) at the lowest layer, forwarding nodes (FNs) with higher power and multi-hop routing capability at the middle layer, and wired access points (APs) without power constraints at the highest layer. Specifics of new protocols used for bootstrapping, node discovery, and multi-hop routing are presented, and the overall operation of the complete hierarchical ad-hoc network is explained. A prototype implementation of the SOHAN network is outlined in terms of major hardware and software components, and initial experimental results are given.

A novel self-organizing hierarchical architecture is proposed for improving the performance and scalability properties of ad hoc wireless networks. This paper presents the results of a simulation study of the performance and throughput capacity of a specific three-tier hierarchical ad hoc network with 802.11 radios, forwarding nodes and access points. The performance of the proposed hierarchical network is evaluated for two well-known classes of ad hoc routing protocols: dynamic source routing (DSR) and ad hoc on-demand distance vector (AODV), and compared with that of a conventional "flat" ad hoc network. The results for an example sensor network scenario have shown significant capacity increases with the hierarchical architecture for both DSR and AODV cases. Modifications to ad hoc routing metrics for energy efficiency are also considered. The scalability properties of the three-tier hierarchy are studied further in terms of the achievable system capacity as a function of the relative densities of sensor nodes, forwarding nodes and access points. It is shown that the capacity of the three-tier hierarchical network scales well when the number of forwarding nodes and access points are increased in the right proportions.

We propose a blind successive interference cancellation receiver for asynchronous direct-sequence code-division multiple-access (DS-CDMA) systems using a maximum mean energy (MME) optimization criterion. The covariance matrix of the received vector is used in conjunction with the MME criterion to realize a blind successive interference canceler that is referred to as the BIC-MME receiver. The receiver executes interference cancellation in a successive manner, starting with the most dominant interference component and successively cancelling the weaker ones. The receiver is compared against various centralized and decentralized receivers, and it is shown to perform well in the presence of estimation errors of the covariance matrix, making it suitable for application in time-varying channels. We also analyze properties of the covariance matrix estimates which are relevant to the performance of the BIC-MME receiver. Further, the BIC-MME receiver is particularly efficient in the presence of a few strong interferers as may be the case in the downlink of DS-CDMA systems where intracell user transmissions are orthogonal. An iterative implementation that results in reduced complexity is also studied.

The integration of multimedia services over wireless channels calls for provision of variable quality of service (QoS) requirements. While radio resource management algorithms (such as power control and call admission control) can provide certain levels of variability in QoS, an alternate approach is to use reconfigurable radio architectures to provide diverse QoS guarantees. We outline a novel reconfigurable architecture for linear multiuser detection, thereby providing a wide range of bit error rate (BER) requirements amongst the constituent receivers of the reconfigurable architecture. Specifically, we focus on achieving this dynamic reconfiguration via a software radio implementation of linear multiuser receivers. Using a unified framework for achieving this reconfiguration, we partition functionality into two core technologies [field programmable gate arrays (FPGA) and digital signal processor (DSP) devices] based on processing speed requirements. We present experimental results on the performance and reconfigurability of the software radio architecture as well as the impact of fixed point arithmetic (due to hardware constraints).