Ghulam Bhatti

Image transmission over IEEE 802.15.4 and ZigBee networks

An image sensor network platform is developed for testing transmission of images over ZigBee networks that support multi-hopping. The ZigBee is a low rate and low power networking technology for short range communications, and it currently uses IEEE 802.15.4 MAC and PHY layers. Both ZigBee networking (NWK) and IEEE 802.15.4 MAC layer protocols are implemented on a single M16C microprocessor. Transport layer functionalities such as fragmentation and reassembly are performed at the application layer, since the ZigBee NWK does not have a fragmentation support. The multiple access scheme is CSMA/CA, therefore only the best effort multi-hop transmission of JPEG and JPEG-2000 images are tested; observations and resulting statistics are presented, and open issues are discussed.

Load balanced routing for low power and lossy networks

The RPL routing protocol published in RFC 6550 was designed for efficient and reliable data collection in low-power and lossy networks. Specifically, it constructs a Destination Oriented Directed Acyclic Graph (DODAG) for data forwarding. However, due to the uneven deployment of sensor nodes in large areas, and the heterogeneous traffic patterns in the network, some sensor nodes may have much heavier workload in terms of packets forwarded than others. Such unbalanced workload distribution will result in these sensor nodes quickly exhausting their energy, and therefore shorten the overall network lifetime. In this paper, we propose a load balanced routing protocol based on the RPL protocol, named LB-RPL, to achieve balanced workload distribution in the network. Targeted at the low-power and lossy network environments, LB-RPL detects workload imbalance in a distributed and non-intrusive fashion. In addition, it optimizes the data forwarding path by jointly considering both workload distribution and link-layer communication qualities. We demonstrate the performance superiority of our LB-RPL protocol over original RPL through extensive simulations.

A TV-centric home network to provide a unified access to UPnP and PLC domains

Universal plug and play (UPnP) aims at connecting home electronic devices, especially audio-video (AV) devices, whereas several protocols based on power-line communications (PLC) technologies target home appliances and security devices for networking. There is a need to have a unified access to, and control of, all devices regardless of the networking technology they use. This paper describes the design and implementation of a system that allows a user to control devices in two different network domains, namely a UPnP domain and a multi-carrier (MC) PLC domain based on a proprietary power line networking technology.

Performance analysis of beacon-enabled IEEE 802.15.4 MAC for emergency response applications

IEEE 802.15.4 standard provides a viable MAC and PHY specification for wireless sensor networks. Performance evaluation of these networks has been reported in literature. Previous works focus largely on analyzing the CSMA/CA traffic and frame delay due to Guaranteed Time Slots (GTS) allocations. In this work, we propose a analytical model to understand and characterize the performance of GTS traffic in IEEE 802.15.4 networks for emergency response situations.We study two crucial performance metrics, latency and frame drop rate, for GTS frames. The results from our analysis closely match with those from simulations of IEEE 802.15.4 MAC reported earlier.

A modified beacon-enabled IEEE 802.15.4 MAC emergency response applications

IEEE 802.15.4 specification for MAC and PHY offers a standard for general purpose wireless sensor networks. The TG4e of IEEE 802.15 is currently engaged in defining a specification particularly suitable for industrial and commercial applications, which impose severe constraints of low latency and high reliability. In this work, we present a simple MAC scheme to address these requirements of emergency response sensing applications for wireless sensor networks. We evaluate the proposed scheme for varying channel and traffic load conditions using simulations. Our results show that the latency and packet loss rate performance of emergency response traffic, consisting of guaranteed time slot (GTS) frames, significantly improves in comparison with the performance of original IEEE 802.15.4 MAC. The proposed MAC was also evaluated for potential adverse impact on the non-critical traffic, which consists of frames that use contention access period (CAP) of the superframe. It is shown that under realistic load conditions, the impact on the CAP traffic is minimal.

Efficient Medium Access Protocol for Wireless Sensor Networks

Efficiency of the medium access protocol is crucial for wireless sensor networks. For sensor nodes that are battery powered, it is sometimes difficulty or impractical to charge or replace exhausted battery. The sensor nodes collaborate for a common application such as environmental monitoring. The low sensing ranges result in dense networks. The medium access protocol (MAC) for wireless sensor network must be energy efficient. In this paper, we propose a timeslot sharing medium access protocol for wireless sensor networks. The proposed medium access protocol allows multiple sensor nodes to share a reserved or guaranteed timeslot for transmission. It also allows more sensor nodes to transmit in the reserved or guaranteed timeslots and fewer sensor nodes to contend for the transmission. The primary goal of timeslot sharing medium access protocol is to minimize the energy consumption of sensor nodes as well as to maximize the total number of nodes allowed in a network.

Multi-Hop Localization Using Mobility (MLM) in Mixed LOS/NLOS Environments

This paper presents a novel technique for multi-hop localization by using mobility (MLM) in mixed line-of-sight/non-line-of-sight (LOS/NLOS) environments. In MLM, nodes equipped with ultra-wideband (UWB) radio first move randomly for collecting time-of-arrival (TOA) measurements and then apply a modified biased Kalman filter (MBKF) designed for mitigating NLOS errors. NLOS bias in the measurements is further mitigated by using the shortest path distance (SPD) selection. Node positions are initialized by using multidimensional scaling (MDS) and then estimated by using iterative trilateration accompanied by an error accumulation management. Our simulation results demonstrate that the positioning accuracy of MLM outperforms previous methods in obstructed building environments with a limited anchor heard (AH).