Fazli Subhan

Indoor positioning in Bluetooth networks using fingerprinting and lateration approach

Global Positioning System (GPS) is a well known navigation system for outdoor applications; however this technology does not work in indoor environments. In order to overcome this limitation, Bluetooth technology can be employed. Furthermore, Bluetooth technology provides an accurate and low cost solution for short range wireless communication. Most of the digital devices provide the Bluetooth functionality which also makes it a good candidate for indoor positioning. In this paper, we use Bluetooth devices for indoor positioning and use signal based parameters such as received power level for position estimation. The accuracy of indoor positioning system is greatly dependant on the parameters selected for estimation and the measurements obtained from the environment. However, the measurements are corrupted by various environmental conditions such as temperature, reflection, presence of obstacles, human body and other communication signals. Therefore, we need to filter the measurements. This paper presents an experimental relationship between the received power level and distance using the standard radio propagation model. The idea behind this study is to provide an accurate distance estimate for Trilateration approach. Based on the experiments performed, the average error is minimized from 5.87 meters to 2.67 meters using gradient filter. The use of gradient filter improves the accuracy by 45 %.

Kalman Filter-Based Hybrid Indoor Position Estimation Technique in Bluetooth Networks

This paper presents an extended Kalman filter-based hybrid indoor position estimation technique which is based on integration of fingerprinting and trilateration approach. In this paper, Euclidian distance formula is used for the first time instead of radio propagation model to convert the received signal to distance estimates. This technique combines the features of fingerprinting and trilateration approach in a more simple and robust way. The proposed hybrid technique works in two stages. In the first stage, it uses an online phase of fingerprinting and calculates nearest neighbors (NN) of the target node, while in the second stage it uses trilateration approach to estimate the coordinate without the use of radio propagation model. The distance between calculated NN and detective access points (AP) is estimated using Euclidian distance formula. Thus, distance between NN and APs provides radii for trilateration approach. Therefore, the position estimation accuracy compared to the lateration approach is better. Kalman filter is used to further enhance the accuracy of the estimated position. Simulation and experimental results validate the performance of proposed hybrid technique and improve the accuracy up to 53.64% and 25.58% compared to lateration and fingerprinting approaches, respectively.

Extended Gradient RSSI Predictor and Filter for Signal Prediction and Filtering in Communication Holes

In wireless communication, received signal strength indicator (RSSI) is a measurement of power in the received signal. This parameter is mainly used in radio frequency (RF) based distance estimation, position estimation, and handover mechanisms. In real-time applications such as object tracking, a handover mechanism, distance estimations require continuous reception of RSSI measurements in order to accurately estimate the position of the object. However, there are some constraints such as signal attenuation, signal loss, multi-path effects. These parameters cause variations in RSSI, and hence it becomes weak, which produces communication holes. Communication holes refer to the phenomenon when the signal drops to zero, and there is a communication blockage, which is practically negligible and can be considered as disconnection. This communication hole occurs due to various factors such as multi-path effects, noise, moving out of the coverage zone, device manufacturing faults, and inquiry procedure as well. The main focus of this paper is to address the issue of communication holes in Bluetooth networks. In Bluetooth networks communication holes also occur due to the delay in the inquiry procedure. Therefore, an existing gradient filter is modified based on the most recent measurements received. The proposed extended gradient filter is tested using simulated and real time RSSI measurements and compared with Kalman Filter and Kalman Smoother. The results show better performance in case of communication holes occurrence.

Extended Gradient Predictor and Filter for smoothing RSSI

This paper presents the design of an Extended Gradient Predictor and Filter for smoothing Received Signal Strength Indicator (RSSI). In wireless communication RSSI is a measurement of power in received signal, which is a parameter used for handover and position estimation purpose. In real time applications such as handover and position estimation requires continuous reception of RSSI measurements. Due to the effect of noise, variations occur in the received signal, which sometimes produce communication holes. In that case, RSSI measurements become zero, which produces distance estimation error. In order to minimize the effect communication, an existing Gradient filter is modified based on most recent RSSI measurement received. The advantage of the proposed extended Gradient RSSI predictor and filter is that it predicts and filters RSSI values in the presence of communication holes for real time object tracking. The performance of proposed extended Gradient RSSI predictor and filter is tested using simulated and real-time RSSI measurements using Bluetooth technology, which shows better performance in case of communication holes occur.

Minimizing discovery time in bluetooth networks using localization techniques

Bluetooth is a short range wireless communication protocol. However, the discovery process to establish connection in Bluetooth network is very time consuming process. This paper presents localization techniques for Bluetooth networks. There is an increasing interest in location identification, and communication with other Bluetooth devices within a local area network. The idea behind localization techniques is to address position estimation in Bluetooth networks in order to reduce the time taken for device discovery to establish connection process. In this paper Received Signal Strength Indicator (RSSI) is obtained using Inverse square law. The Received Power (Prx) is obtained indirectly by converting RSSI values to Prx using Friis equation. Positioning is based on Prx and converted to estimate the distance using simple radio propagation model based on Friis equation. The advantage of positioning is to know the object actual position with respect to the distance from the transmitter. The relationship obtained from positioning using Prx will be used to minimize the discovery time in connection establishment process in Bluetooth networks. This work is part of the design process of roaming protocol for Bluetooth networks.

Designing of Roaming Protocol for Bluetooth Equipped Multi Agent Systems

Bluetooth is an established standard for low cost, low power, wireless personal area network. Currently, Bluetooth does not support any roaming protocol in which handoff occurs dynamically when a Bluetooth device is moving out of the piconet. If a device is losing its connection to the master device, no provision is made to transfer it to another master. Handoff is not possible in a piconet, as in order to stay within the network, a slave would have to keep the same master. So, by definition intra-handoff is not possible within a piconet. This research mainly focuses on Bluetooth technology and designing a roaming protocol for Bluetooth equipped multi agent systems. A mathematical model is derived for an agent. The idea behind the mathematical model is to know when to initiate the roaming process for an agent. A desired trajectory for the agent is calculated using its x and y coordinates system, and is simulated in SIMULINK. Various roaming techniques are also studied and discussed. The advantage of designing a roaming protocol is to ensure the Bluetooth enabled roaming devices can freely move inside the network coverage without losing its connection or break of service in case of changing the base stations.

Filters for device-free indoor localization system based on RSSI measurement

Based on wireless sensor networks, device-free indoor localization technique has received much attention in the field of indoor localization system Due to different indoor environmental parameters, multipath fading, human presences and different system configurations, the WiFi-based received signal strength indicator values are affected. This problem leads the researchers to choose any filter or smoothing algorithm to get proper values of received signal strength in the indoor environment. The aim of using the filter or smoothing algorithm is to get a signal value which can clearly identify the changes in the signal values due to interferences caused by various factors in the indoor environment. Wi-Fi based device-free indoor localization technique has become more attractive because its simplicity, as well as it does not require extra hardware. However the implementation of this technique in the indoor environment becomes complex, sometimes because of imprecise and unreliable readings caused by multipath fading. There are various filters designed and tested to remove the inconsistencies occurring in RSSI readings due to the various environmental effects. This paper presents various types of filters which are used for smoothing the raw data received signal strength indicator values and also improving the strength of these values by mitigating multipath fading effects in an indoor environment.

Dynamic Energy-Aware Network Maintenance for Bluetooth

Bluetooth is one of mobile ad hoc network technologies, which allows communication through piconet. A piconet consists of at most eight active devices at the same time. A multiple piconets network is called a scatternet, which is connected through a common node known as a relay. The limited energy available in a Bluetooth-enabled device is a critical issue for the mobile devices to participate effectively in the scatternet. Therefore, to improve the network performance, energy capability of a Bluetooth device should be analyzed periodically, and subsequently to determine its role in the network based on this energy analysis. It is expected that the more energy capable device shall perform more demanding role, i.e. the role of a high performance device shall be selected based on its energy level. In this paper, we discussed the design issues of an efficient Dynamic Energy-Aware Network Maintenance (DENM) technique. The proposed technique dynamically adapts changes in the network and maintains a constructed scatternet, as well as it ensures network stability and reduces overhead. The simulation results showed that the proposed technique outperformed the existing protocols in term of message overhead, transmission delay, and reconstruction time.

WLAN location fingerprinting technique for device-free indoor localization system

Device-free indoor localization (DFIL) system can locate the position of human body in the indoor environment by observing the changes in the received signal strength indicator (RSSI) of the wireless local area network (WLAN). The accuracy of a DFIL system is depreciated, as the change in the indoor environment due to furniture and other infrastructure movement. This paper investigates the development of testbed of the Wi-Fi network for measuring the RSSI in various indoor environment, as the initial step for designing the fingerprinting-based algorithms for Wi-fi network. The database of RSSI fingerprint is created initially and then a fingerprint-based algorithm is developed for locating the position of a human body in the indoor environment. The localization algorithm tests the minimum distance in the RSSI values related to the different test points in the indoor environment. This work further demonstrates that how the fingerprints of RSSI are collected and which network configurations generate the most reliable RSSI measurement. For the first phase of designing the testbed, the configurations of different equipment and various tools are elaborated in the indoor environment. For the second phase the RSSI is measured in different propagation indoor environment. The extensive experiments were performed that allow quantification of how changes in an environment affect accuracy. Thus, it is demonstrated that each link offers a viable approach to developing a more robust system for device-free localization that is less susceptible to changes in the environment.

Dynamic load balancing through backup relay in Bluetooth scatternet

A mobile ad-hoc network (MANET) is a collection of wireless mobile nodes, which creates an infrastructure less temporary network. Bluetooth is a short range, low-cost, low and low power wireless technology. Bluetooth allows communication among electronic devices through its basic network know as piconet. In a piconet one device controls the local network (piconet) know as master and others act as slaves. Multiple piconets may exist in Bluetooth network known as scatternet. The connection among different piconets is provided through a common node known as relay. Relay is connected with more then one master with different hopping pattern relay node forwards data among different piconets. The degree (number of connection) of relay has a serious impact on the network performance. A larger degree of relay increases the packet loss rate and transmission delay. The large degree of relay has to switches among different piconets that increase the scheduling overhead. The paper considers the problem of designing an effective Dynamic Load Balancing (DLB) technique to share the traffic load through Backup Relay (BR). The simulation results show using UCBR and NS-2 the proposed technique avoids bottleneck that reduces the transmission delay, packet loss and increases the throughput plus network lifetime.