In the Internet of Things (IoT) era, smartphones are expected to frequently interact with IoT devices and even facilitate various IoT applications. Due to limited roles, energy constraints, etc., however, IoT devices may use mission-tailored or proprietary wireless protocols that smartphones do not speak natively. In this paper, we propose a novel approach to the wireless “language barrier” problem between the smartphones and IoT devices of the future. We first demonstrate that smartphones have become powerful enough to process software defined radio (SDR) for some known wireless protocols. Moreover, we show that the SDRs can be packaged as “apps” and be downloaded from app stores for OS-independent deployment. Second, we show different SDR protocols on the smartphone can concurrently run through a shared RF to serve multi-tasked applications on it as might happen in diversified IoT environments. For proof-of-concept, we implement a prototype architecture that has all the SDR logic and supporting middleware on an Android smartphone which uses a USRP as the simple RF-end. Finally, we demonstrate that IEEE 802.11p and IEEE 802.15.4 SDRs on a smartphone, respectively, communicate with a ZigBee sensor mote, a ZigBee smart lightbulb, and a commercial Wireless Access in Vehicular Environment (WAVE) device, concurrently.

Modern automotive software components are often first developed by different suppliers and then integrated under limited resources by a manufacturer. The integration of software components under various resource configurations is prone to timing errors because the components are resources independently designed by the supplier and viewed by the manufacturer as black boxes during the integration stage, so that imposing resource constraints/requirements on their behavior is a challenge. This paper introduces an engineering awareness environment for the analysis of automotive systems with respect to two perspectives: 1) time-aware design models that correspond to the supplier perspective; and 2) resource-aware design models imposed by the manufacturer during integration. To this end, first we propose two timed behavioral models, a time-constrained model (TcM) and a resource-constrained model (RcM) that are extended from a functional model (FM). A timing analysis of applications can hence be conducted incrementally by adopting the separation of concerns principle coming from the model-driven architectures (MDAs). Second, given a basic application component description of AUTomotive Open System Architecture with timing properties, we specify how to define the behavior of the basic components as process terms using a process algebra, algebra of communicating shared resources with value passing (ACSR-VP), in order to exploit the description capability of the language for both timing aspects and resource-constrained aspects of a system. As a result, a timed behavioral model of a system can be seamlessly refined by various resource configurations, and both platform-independent and platform-dependent timing properties of real-time systems can be analyzed in a consistent and efficient manner.

Embedded software should be correctly developed so that it is be compliant with not only functional requirements but also real-time and resource constraints. However, those constraints are often dependent on execution environments that are sometimes revealed in late development phases. In this paper, we propose Timed and Resource-oriented Statecharts (TRoS) to analyze the time and resource-constrained behavior of system in earlier development phases of embedded software development. TRoS extends Statecharts using timed action labeled with resources to represent actions that consume resources. This enables us to describe the competition among processes to use shared resources, and to analyze schedulability of embedded systems. We present a case study of a distance control module that controls train movement to keep the distance between trains for railway control systems.

The already severe inefficiency problem in running VoIP on the IEEE 802.11-based wireless LAN is exacerbated in multi-hop networks due to spatial interference. This paper presents a novel scheme that significantly mitigates the effect of the interference by combining the inter-call aggregation and the pseudo-broadcast technique as used in network coding. As such, the proposed scheme works effectively not just for calls traveling the same routed path but also for calls crossing each other inside the multi-hop networks. We demonstrate through extensive simulation that the IEEE 802.11-based multi-hop network can be boosted up to 700% in terms of the number of supportable VoIP calls, with acceptable QoS, through the proposed scheme.

In this paper, we explore the feasibility of vehicle-to-vehicle (V2V) secure communication using public key cryptography. We implement a prototype and test it extensively in real driving conditions. Measurement data indicate that the system is feasible in terms of delay and loss, and that we can usually expect better performance than typical simulation works predict. However, we find that traffic congestion and the performance of public key cryptography component can pose significant challenges.

The bandwidth efficiency of voice over IP (VoIP) traffic on the IEEE 802.11 WLAN is notoriously low. VoIP over 802.11 incurs high bandwidth cost for voice frame packetization and MAC/PHY framing, which is aggravated by channel access overhead. For instance, 10 calls with the G.729 codec can barely be supported on 802.11b with acceptable QoS - less than 2% efficiency. As WLANs and VoIP services become increasingly widespread, this inefficiency must be overcome. This paper proposes a solution that boosts the efficiency high enough to support a significantly larger number of calls than existing schemes, with fair call quality. The solution comes in two parts: adaptive frame aggregation and uplink/downlink bandwidth equalization. The former reduces the absolute number of MAC frames according to the link congestion level, and the latter balances the bandwidth usage between the access point (AP) and wireless stations. When used in combination, they yield superior performance, for instance, supporting more than 100 VoIP calls over an IEEE 802.11b link. The authors demonstrate the performance of the proposed approach through extensive simulation, and validate the simulation through analysis.

The common electronic purse specifications (CEPS) was created as a globally interoperable electronic purse standard. However, it is also well known that numerous significant errors have been found in the design of e-commerce protocols. In this paper model-based verification using Casper, CSP and FDR is addressed, demonstrating how the secrecy properties in the CEPS can be achieved. Vulnerabilities are confirmed and its countermeasure are mentioned. In addition, we confirmed that model-based verification techniques should help identify and analyze error in the design of e-commerce protocols

Algorithmic approach to link adaptation for IEEE 802.11 networks such as Automatic Rate Fallback (ARF) is known to suffer from the inability to differentiate between collision and channel-induced error. In this paper, we propose a novel algorithm called COLA that overcomes the shortcoming and achieves near-optimal throughput over wide range of channel and load conditions. The result is significant since the throughput is achieved without any hardware support. Moreover, COLA does not require any optional or extra-protocol mechanisms support, either, such as RTS/CTS exchange, Clear Channel Assessment (CCS), and promiscuous channel monitoring. Finally, the COLA algorithm has a short critical path of just 10 instructions, and it is free of heuristic parameters, which will facilitate practical use.

ACK thinning refers to the technique to discard or reduce TCP acknowledgements (ACKs) for the purpose of diverting scarce bandwidth to TCP data traffic. Delayed ACK and ACK filtering fall into the category. It has been shown that under some circumstances the technique is effective to boost the TCP throughput on wireless links, in particular the IEEE 802.11 wireless LAN (WLAN). In this paper, however, we show that ACK thinning backfires under congestion due to its cross-layer impact on the 802.11 MAC dynamics. With the ACK filtering example, we demonstrate the phenomenon and analyze the cause. Based on the analysis, we show how the IEEE 802.11 contention window size control solves the problem. Although only the ACK filtering and Delayed ACK are considered in this paper, any other techniques to save on TCP ACK bandwidth usage share the same fundamental issues.

In multi-hop wireless networks, the number of supportable VoIP calls can be surprisingly small due to the increased spatial interference. To mitigate the interference, voice frame aggregation can be used. In this paper, we depart from the traditional approaches that perform aggregation at the voice source, and propose a technique called the self-controlled frame aggregation (SCFA) that runs at wireless routers. The core idea of SCFA is to let the congestion itself control the degree of aggregation. Unlike existing frame aggregation approaches, SCFA does not incur fixed delay cost, since it is used only when and by exactly as much as it is needed. In this paper, we take the example of 802.11-based multi-hop network to show the impact of SCFA, since many emerging multi-hop networks are built on the 802.11 technology. The result shows that SCFA on 802.11-based multi-hop network can boost the number of calls approximately twofold, or extends the hop distance threefold for a given number of calls to carry.

To solve the poor bandwidth efficiency problem of VoIP over IEEE 802.11 wireless LANs (WLANs), the literature frequently suggests elongating voice payload size. Such "voice frame aggregation" can be performed (1) over a single call or multiple calls, (2) at the voice source or at the wireless access point (AP), and (3) with additional repacketization delay or without it. This paper shows that over IEEE 802.11 WLANs, voice frame aggregation should better be done at the AP, over a single call, and without additional delay. We demonstrate through simulation and analysis that this particular implementation choice enables us to support far more VoIP calls on 802.11 WLANs than other choices. For one instance, we show that 100 or more G.729 calls are possible on 802.11b within ITU-T recommended delay bounds.

We first show that various network attacks can cause fatal inflation of dynamic memory usage on packet processing computers. Considering Transmission control protocol (TCP) is utilized by most of these attacks as well as legitimate traffic, we propose a parsimonious memory management guideline based on the design of the TCP and the analysis of real-life Internet traces. In particular, we demonstrate that, for all practical purposes, one should not allocate memory for an embryonic TCP connection with roughly more than 10 seconds of inactivity.

The notion of worm-killing worm has been in the folklore for some time. However the obvious fear of the killer worm itself being compromised, or of any self-propagating code set loose (possibly over administrative boundaries), has barred serious exploration on the practical aspects of the idea. In this paper, we suspend such concerns momentarily, and investigate its functional validity. This effort is motivated by recent fast worm epidemics exemplified by that of SQL slammer, which was overwhelmingly faster than traditional human-intervened response. Specifically, this paper evaluates the killer worm in terms of the prevention effect and the incurred traffic cost. Above and beyond, we consider supplementary techniques that could boost the performance and mitigate the harmful side-effects of the worm-killing worm.

Martian address filtering refers to a technique that discards IP packets that have an invalid source or destination address. This paper evaluates its effectiveness (or lack thereof) under denial of service (DoS) attack or host scan, in terms of packet-level and flow-level filtering performance. In order to overcome the shortcoming of Martian address filtering, we consider two extensions: unallocated address checking and blacklisting. We demonstrate through trace-based simulation that these techniques can indeed boost filtering performance. We also analyze the performance and the possible side-effects of the extensions.

Purging embryonic connection states after an appropriate time interval is essential for connection-level monitoring devices such as stateful firewalls in order to minimize security holes and improve state lookup performance. This paper investigates what timeout intervals are adequate, based on the analysis of real-life Internet traces. It reveals that (R+T) seconds are useful timeout periods where R=0,3,9 and 1/spl les/T/spl les/2, and that wide implementation of RFC 2988 is behind the phenomenon.

We evaluate a TCP-level method, TCP segment size adaptation, to overcome the impact of wireless uplink losses. The performance improvement obtained can be as large as orders-of-magnitudes, and the required TCP sender code modification is limited to a few lines. The improvement can be further bolstered by combining the adaptation method with retransmission timeout (RTO) backoff containment.

State explosion is a well-known problem that impedes analysis and testing based on state-space exploration. This problem is particularly serious in real time systems because unbounded time values cause the state space to be infinite even for simple systems. The author presents an algorithm that produces a compact representation of the reachable state space of a real time system. The algorithm yields a small state space, but still retains enough information for analysis. To avoid the state explosion which can be caused by simply adding time values to states, our algorithm uses history equivalence and transition bisimulation to collapse states into equivalent classes. Through history equivalence, states are merged into an equivalence class with the same untimed executions up to the states. Using transition bisimulation, the states that have the same future behaviors are further collapsed. The resultant state space is finite and can be used to analyze real time properties. To show the effectiveness of our algorithm, we have implemented the algorithm and have analyzed several example applications.

State explosion is a well-known problem that impedes analysis and testing based on state-space exploration. This problem is particularly serious in real-time systems because unbounded time values cause the state space to be infinite. In this paper, we present an algorithm that produces a compact representation of reachable state space of a real-time system. The algorithm yields a small state space, but still retains enough timing information for analysis. To avoid the state explosion which can be caused by simply adding time values to states, our algorithm first uses history equivalence and transition bisimulation to collapse states into equivalent classes. In this approach, equivalent states have identical observable events although transitions into the states may happen at different times. The algorithm then augments the resultant state space with timing relations that describe time distances between transition executions. For example, the relation @(tr1) + 3 ≤ @(tr2) ≤ @(tr1) + 5 means that transition tr2 is taken 3 to 5 time units before transition tr2 is taken. This is used to analyze timing properties such as minimum and maximum time distances between events. To show the effectiveness of our algorithm, we have implemented the algorithm and are currently comparing it to other existing techniques which generate state space for real-time systems.