Anup Kumar Paul

Detour Path Angular Information Based Range-Free Localization in Wireless Sensor Network

Range-free localization algorithm continues to be an important and challenging research topic in anisotropic Wireless Sensor Networks (WSNs). Designing range-free localization algorithms without considering obstacles or holes inside the network area does not reflect the real world conditions. In this paper, we have proposed Detour Path Angular Information (DPAI) based sensor localization algorithm to accurately estimate the distance between an anchor node and a sensor node. We utilized the Euclidean distance and transmission path distance among anchor nodes to calculate the angle of the transmission path between them one by one. Then the estimated hop distance is adjusted by the angle between the anchor pairs. Based on the angle of the detoured path (which is the key factor for accuracy), our algorithm determines whether the path is straight or detoured by anisotropic factors. Our proposed algorithm does not require any global knowledge of network topology to tolerate the network anisotropy nor require high sensor node density for satisfactory localization accuracy. Extensive simulations are performed and the results are observed to be in good agreement with the theoretical analysis. DPAI achieved average sensor localization accuracy better than 0.3r in isotropic network and 0.35r in anisotropic network when the sensor density is above 8.

NEXT-FIT: Available Bandwidth Measurement over 4G/LTE Networks -- A Curve-Fitting Approach

Available bandwidth (ABW) estimation in wireless networks is a critical issue for quality-of-service (QoS) provisioning. Nowadays, a network path often contains at least one wireless link e.g., mobile users having wireless connection to the Internet through laptop PCs or smartphones. Most of the existing tools for measuring ABW have been developed and evaluated in wired networks. Since the characteristics of wired links and wireless links differ in many respects, such as fluctuations incapacity and stability due to the shared and unreliable nature of the wireless links, ABW estimation tools also need to be evaluated for network paths containing at least one wireless link. In this paper, we have extended our previous work, New Enhanced Available Bandwidth Estimation Technique (NEXT) by introducing a parameter-independent curve-fitting technique to detect the ABW from a one-way queuing delay signature and conducted a real test over a radio interface in a 4G/LTE mobile communication network. For the experiments, a commercial 4G/LTE mobile network of a Japanese mobile operator was used. Extensive simulations over an IEEE 802.11 network were also performed. Simulation results as well as real-world experimental results demonstrate that it is feasible to achieve reliable estimates under certain circumstances. Our extended approach, which we call NEXT -- FIT, has very good ABW estimation results under conditions of different packet sizes, dynamic wireless link rates, and channel noises.

NEXT: New enhanced available bandwidth measurement technique, algorithm and evaluation

This paper presents a unique probing scheme and a rate adjustment algorithm that can be used for estimating the available bandwidth (ABW) of an end-to-end network path more accurately and non-intrusively. The proposed algorithm is based on the well-known concept of self-induced congestion and it features a unique probing train structure in which there is a region where packets are sampled more frequently than in other region. This high-density region enables our algorithm to find the turning point more accurately. When the dynamic ABW is outside of this region, we readjust the lower rate and upper rate of the packet stream to fit the dynamic ABW into that region. We appropriately adjust the range between the lower rate and the upper rate using spread factors, which enable us to keep the number of packets few and thus we measured the ABW non-intrusively. Simulation results show that our algorithm outperforms PathChirp, a state of the art measurement algorithm, estimating the ABW with greater accuracy and stability in presence of different cross traffic sources.

Localization in Wireless Sensor Networks: A Survey on Algorithms, Measurement Techniques, Applications and Challenges

Localization is an important aspect in the field of wireless sensor networks (WSNs) that has developed significant research interest among academia and research community. Wireless sensor network is formed by a large number of tiny, low energy, limited processing capability and low-cost sensors that communicate with each other in ad-hoc fashion. The task of determining physical coordinates of sensor nodes in WSNs is known as localization or positioning and is a key factor in today’s communication systems to estimate the place of origin of events. As the requirement of the positioning accuracy for different applications varies, different localization methods are used in different applications and there are several challenges in some special scenarios such as forest fire detection. In this paper, we survey different measurement techniques and strategies for range based and range free localization with an emphasis on the latter. Further, we discuss different localization-based applications, where the estimation of the location information is crucial. Finally, a comprehensive discussion of the challenges such as accuracy, cost, complexity, and scalability are given.

An AQM based congestion control for eNB RLC in 4G/LTE network

In the context of a heterogeneous mobile environment, we analyze the eNodeB (eNB) Radio Link Control (RLC) buffer overflow problem for the 4G/LTE network, and show the benefits of deploying Active Queue Management (AQM) strategies at wireless access links. In order to satisfy the increasing demands of wireless mobile communications, LTE has been proposed as an all-IP-based network to bring higher peak data rates and better spectral efficiency. One of the LTE system performance optimization points is the RLC buffer management mainly at the downlink. RLC buffers at the eNB hold user data before it is selected by a MAC scheduler for transmission over the radio interface. A buffer management scheme is required to keep the RLC buffer occupancy to a minimal level without a noticeable degradation in user application performance. This is a challenging issue for the mobile network operator and has to be thoroughly investigated. When the traffic load is low, the available bandwidth is underutilized and when the traffic load is high, the end-to-end delay becomes large. This paper presents a minimal adjustment to RED called Smart RED (SmRED) in which the packet dropping probability is adjusted based on the traffic load to achieve optimal end-to-end performance. Additionally, the migration from RED to SmRED in a real network needs very little work because of its simplicity. Finally, for a delay-sensitive data stream, a cross layer approach based on SmRED is proposed to make it more practical.