Saâd Biaz

ARIADNE: a dynamic indoor signal map construction and localization system

Location determination of mobile users within a building has attracted much attention lately due to its many applications in mobile networking including network intrusion detection problems. However, it is challenging due to the complexities of the indoor radio propagation characteristics exacerbated by the mobility of the user. A common practice is to mechanically generate a table showing the radio signal strength at different known locations in the building. A mobile users location at an arbitrary point in the building is determined by measuring the signal strength at the location in question and determining the location by referring to the above table using a LMSE (least mean square error) criterion. Obviously, this is a very tedious and time consuming task. This paper proposes a novel and automated location determination method called ARIADNE. Using a two dimensional construction floor plan and only a single actual signal strength measurement, ARIADNE generates an estimated signal strength map comparable to those generated manually by actual measurements. Given the signal measurements for a mobile, a proposed clustering algorithm searches that signal strength map to determine the current mobiles location. The results from ARIADNE are comparable and may even be superior to those from existing localization schemes.

Realistic radio range irregularity model and its impact on localization for wireless sensor networks

In the research of wireless communications, prototypes and measurements on real test-beds provide insights and fundamental information for a realistic tuning of simulation models. Recently there has been an increasing interest in exploring one of the critical fundamentals: the realistic radio range irregularity (RRI) model. This research builds on the IEEE 802.11, and investigates such a practical RRI model according to the measurements made under various settings. Using the RRI model, a set of representative localization algorithms are evaluated and compared. Through detailed analysis and extensive simulations, the paper points out how the localization performance is affected by the use of simplistic models. Moreover, some algorithms performing well under simplistic models do not work in real world settings. The RRI model reflects and highlights the weaknesses of those algorithms and allow the design of countermeasures. This paper introduces a constrained-greedy forwarding radio propagation method to remedy the negative effects encountered under actual operating environments.

Rate adaptation with loss diagnosis on IEEE 802.11 networks

Rate adaptation in wireless networking aims to seek the optimal data transmission rate most appropriate for current wireless channel conditions to make full use of the channel potentials. It is important in wireless networks because (1) most of them support multiple data rates, and (2) wireless channel is unstable with fast changes on which a single rate thereby may not be proper for long. Based on a comprehensive survey of the rate adaptation for IEEE 802.1 networks in literature, this work proposes a rate adaptation scheme, dubbed effective rate adaptation (ERA), for IEEE 802.11 networks. ERA takes advantage of the fragmentation technique in IEEE 802.11 standard and utilizes the lowest rate retransmission in diagnosing frame loss cause (collision or channel degradation), diffusing collision, and promptly recovering frame losses. It also adopts an adaptive rate increase threshold concept to exploit channel potentials. Different from other rate adaptation schemes, ERA effectively addresses two challenges in rate adaptation on IEEE 802.11 networks: (1) it does not require RTS/CTS for loss diagnosis purpose; the use of RTS/CTS that are optional in IEEE standard results in inefficiency on channel utilization; (2) it promptly responds to frame failure due to channel degradation, unlike others waiting till the end of a transmission window or cycle. With extensive simulation, ERA shows its unique strength in different lossy environments, especially in collision-prone environments. Copyright

ERA: effective rate adaptation for WLANs

Rate adaptation consists of using the optimal rate for a given channel quality: the poorer the channel quality, the lower the rate should be. Multiple rate adaptation schemes were proposed and studied so far. The first generation rate adaptation schemes perform well in collision free environments and manage quite well strict channel degradation. Under a congestion dominated environment, these schemes poorly perform because they do not differentiate losses due to channel degradation from those due to collisions and unnecessarily decrease the rate in response to collisions. A second generation rate adaptation schemes overcome this limitation. However, these most recent schemes usually require RTS/CTS control frames that are not in general used because they constitute an overhead that may heavily lower network performance especially when frame size is small. This work proposes an effective and practical rate adaptation scheme (ERA) that does not require RTS/CTS control frames. ERA judiciously uses fragmentation in compliance with IEEE 802.11 standard to diagnose the cause of frame loss and to promptly recover from frame losses. Through extensive simulations on ns-2, ERA exhibits a significant throughput improvement over other rate adaptation schemes.

BARA: a sender based rate adaptation in wireless networks

Wireless communications benefit from multiple data rates under unstable channel conditions. More efficiently modulated user information results in higher overall data rates, but more error-prone information is received. Thus, it is highly important to adaptively choose a proper data rate so as to optimize network performance based on instantaneous channel condition. This procedure is named as rate adaptation. This paper presents a sender-based rate adaptation proposal named Beacon Auto Rate Adaptation, dubbed BARA, to determine proper instantaneous data rate, especially in the case where control frames such as RTS/CTS are not available. Beacon Auto Rate Adaptation is a suite of mechanisms. Firstly, periodic mandatory control frame beacon is used to estimate the initial data rate for sender at the beginning of a transmission. Then data rate is appropriately adapted during the transmission. Moreover, an innovative scheme is proposed to minimize the number of retransmission. Our simulation with IEEE802.11 demonstrates that, although the improvement for single node is not remarkable, the throughput for network can improved more than 100% in high density network.

Dynamic indoor localization using wireless ethernet: the ARIADNE system

Location determination of mobile users within a building has attracted much attention lately due to its many applications in mobile networking including network intrusion detection problems. However, it is challenging due to the complexities of the indoor radio propagation characteristics exacerbated by the mobility of the user. A common practice is to mechanically generate a table showing the radio signal strength at different known locations in the building. A mobile users location at an arbitrary point in the building is determined by measuring the signal strength at the location in question and determining the location by referring to the above table using a LMSE (least mean square error) criterion. Obviously, this is a very tedious and time consuming task. This paper proposes a novel and automated location determination method called ARIADNE. Using a two dimensional construction floor plan and only a single actual signal strength measurement, ARIADNE generates an estimated signal strength map comparable to those generated manually by actual measurements. Given the signal measurements for a mobile, a proposed clustering algorithm searches that signal strength map to determine the current mobiles location. The results from ARIADNE are comparable and may even be superior to those from existing localization schemes.

An interference-aware routing metric in multi-radio multi-hop networks

It is generally admitted that the performance of ad hoc networks can be quite poor and disappointing due to high contention and lack of an optimal MAC protocol. Here we investigate one approach to alleviate the contention: allowing nodes to communicate simultaneously on different channels by configuring them with multiple radios. Though simply adding radios improves throughput, a more dramatic enhancement can be obtained when using an interferenceaware routing metric, which improves the TCP throughput by an average of 89% against single radio network.

Airtime ping---pong effect characterization in IEEE 802.11s wireless mesh networks

Airtime is set as the default routing metric for the ongoing IEEE 802.11s wireless mesh networking standard. The metric is designed to minimize channel resource consumption by accounting for loss rate, bandwidth, and channel characteristics. However, the metric exhibits a noticeable ping–pong effect whose nature is still vague, and the very few references to this in the literature condemn it for being a perilous behavior. In this paper, we present a thorough study of the Airtime ping–pong effect, and highlight its correlation to the underlying rate control algorithms. Using different rate control algorithms (e.g., ARF, AARF, ONOE, AMRR and Constant rate), we establish that transmission rate adaptation is the principal cause behind the effect. We show that the effect is an inherent behavior, and that an accurate characterization of it can help improve network performance. We present a ping–pong-aware mechanism that, by detecting when a link undergoes such an effect, adapts the routing protocol for better network performance. The mechanism is O(1), decentralized, and can be easily integrated into the IEEE 802.11s routing protocol.

Airtime Ping-Pong Effect in IEEE 802.11s Wireless Mesh Networks

Airtime is set as the default routing metric for the ongoing IEEE 802.11s wireless mesh networking standard. The metric is designed to minimize channel resource consumption by accounting for loss rate, bandwidth, and channel characteristics. However, the metric exhibits a noticeable ping-pong effect whose nature is still vague, and the very few references to this in the literature condemn it for being a perilous behavior. In this paper, we present a thorough study of the Airtime ping-pong effect, and highlight its correlation to the underlying rate control algorithms. Using different rate control algorithms e.g., ARF, AARF, ONOE, AMRR and Constant rate, we establish that transmission rate adaptation is the principal cause behind the effect. We show that the effect is an inherent behavior, and that an accurate characterization of it can help improve network performance. We present a ping-pong-aware mechanism that, by detecting when a link undergoes such an effect, adapts the routing protocol for better network performance. The mechanism is O1, decentralized, and can be easily integrated into the IEEE 802.11s routing protocol.

Basestation flow control for wired to wireless networks

With the exponential growth of the internet, wireless networks such as satellite networks are becoming increasingly popular. The characteristics of satellite networks such as long latency, large delay-bandwidth product, high bit error rate over satellite links and variable round trip time, severely degrade TCP/IP performance. At the conjunction of the satellite link and the fixed link, the basestation, the difference in capacity between the satellite link and the fixed link causes the basestation to experience congestion losses that adversely impact TCP performance. We propose a technique that substantially reduces the congestion at the base station and enforces fairness among the TCP connections that are sharing the satellite link. The technique does not require any change in the TCP sender or the receiver. The stability of our algorithm is analytically proven and its performance is evaluated using ns-2 simulations. Preliminary results yield almost a null congestion loss rate, a 60% decrease in average queue length, and more than 30% increase in the throughput. Fairness is well enforced.