Sangjin Han

Coexistence Performance Evaluation of IEEE 802.15.4 Under IEEE 802.11B Interference in Fading Channels

The IEEE 802.15.4 standard specifies the physical and medium access control layers designed for low-rate wireless personal area networks. Its operational frequency band includes the 2.4 GHz industrial, scientific and medical band, which is also used by other IEEE 802 wireless standards. This paper presents the coexistence model of IEEE 802.15.4 with IEEE 802.1 lb interference in fading channels and proposes two adaptive channel allocation schemes. The first avoids the IEEE 802.15.4 interference only and the second avoids both of the IEEE 802.15.4 and the IEEE 802.11b interferences. Numerical results show that by selecting a channel which gives the maximum signal to noise ratio to the system, the proposed algorithms are effective for avoiding the interferences and for max-imizing the network capacity.

Node distribution-based localization for large-scale wireless sensor networks

Distributed localization algorithms are required for large-scale wireless sensor network applications. In this paper, we introduce an efficient algorithm, termed node distribution-based localization (NDBL), which emphasizes simple refinement and low system-load for low-cost and low-rate wireless sensors. Each node adaptively chooses neighboring nodes, updates its position estimate by minimizing a local cost-function, and then passes this updated position to neighboring nodes. This update process uses a node distribution that has the same density per unit area as large-scale networks. Neighbor nodes are selected from the range in which the strength of received signals is greater than an experimentally based threshold. Based on results of a MATLAB simulation, the proposed algorithm was more accurate than trilateration and less complex than multi-dimensional scaling. Numerically, the mean distance error of the NDBL algorithm is 1.08–5.51 less than that of distributed weighted multi-dimensional scaling (dwMDS). Implementation of the algorithm using MicaZ with TinyOS-2.x confirmed the practicality of the proposed algorithm.

Outage Probability Analysis of WPAN under Coexistence Environments in Fading Channels

The IEEE 802.15.4 standard specifies the physical and medium access control layers designed for low-rate wireless personal area networks (LR-WPAN) with a focus on enabling the wireless sensor networks. Its operational frequency band includes the 2.4 GHz industrial, scientific and medical (ISM) band which is also used by other IEEE 802 wireless standards. This paper analyzes the performance of IEEE 802.15.4 in a coexistence environment with IEEE 802.11b in fading channels. The threshold used to obtain the outage probability is computed based on the mean packet error probability (PEP) which satisfies the performance requirement of IEEE 802.15.4. Numerical results show that the interference from IEEE 802.11b depends primarily on the frequency offset as well as on the receive signal power.

Channel Allocation Algorithms for Coexistence of LR-WPAN with WLAN

This paper presents a coexistence model of IEEE 802.15.4 with IEEE 802.11b interference in fading channels and proposes two adaptive channel allocation schemes. The first avoids the IEEE 802.15.4 interference only and the second avoids both of the IEEE 802.15.4 and IEEE 802.11b interferences. Numerical results show that the proposed algorithms are effective for avoiding interferences and for maximizing network capacity since they select a channel which gives the maximum signal to noise ratio to the system.

The Reverse-Link Capacity Analysis of Multihop Cellular Networks over Multi-Cell Environments

In this paper, a framework of link capacity analysis for the uplink MCN (Multi-hop Cellular Network) is presented, and the goal of which is to increase link capacity while mitigating the effect of interference. An overlaid network architecture is employed as the network topology : the multi-hop (single-hop) network at the outer (inner) region of the cell. In order to verify the improvement in capacity accrued from the inter-network cooperation, inter-network and intra-network interferences are redefined. In a simulation, the MCN exhibits a significant increase of 1.2 ~ 1.8 times in link capacity compared to a cellular network.

Stability margin based design of multivariable controllers

In this paper we describe a new approach to the design of Multi-Input Multi-Output (MIMO) controllers which attain predesigned gain and phase margins. This is achieved by considering the Smith-McMillan form of the n×n plant transfer function with diagonal elements Pi(s), designing Single-Input Single-Output (SISO) controllers Ci(s) for the Smith-McMillan plants with corresponding loop gain margins gi and phase margins φi, i = 1, 2, …., n. Then it is shown that the MIMO controller can be recovered in such a way that the MIMO system achieves gain and phase margins that are the minimum of gain margins and the minimum of phase margins of the scalar unity feedback Smith-McMillan loops. These results are then applied to the design of Proportional-Integral (PI) controllers where achievable gain and phase margins can be exactly quantified. The result is illustrated by examples.