Pose estimation is a key challenge in robot manipulation and grasping task. Current object pose estimation approaches based on 3D models and depth sensor information have difficulties to handle transparent objects because of the limitation to capture the accurate depth information. To address these issues, we present a 6DoF pose estimation approach, called GhostPose, which utilizes a novel 3D bounding box prediction network and multi-view geometry with cameras on manipulator robot. Our 3D bounding box prediction network is simple and light-weight by adding a small branch to a one-stage object detector. The network detects 2D projections of 3D bounding box vertices. Then, 3D points are reconstructed from the 2D results of the multiple viewpoints with camera motion information, i.e. extrinsic parameters, calculated from the robot joint angles. We also present generalized pose definition to address pose ambiguity of symmetric objects and keep consistency of geometric properties around feature points across both of the symmetric and asymmetric objects. Comparing with the previous pose estimation approaches, GhostPose is more generalized to environments and object types, because it does not require 3D models, object specific key points, predefined stereo settings and depth map. In experiments, it outperforms a state-of-the-art approach and shows generalized properties by applying to a real manipulator robot grasping system.

Heterogeneous cellular networks which consist of macrocells and small cells can offer significant capacity gain by utilizing the resources of the small cells. However, to achieve this, the interference between the macrocells and the small cells must be carefully managed. In this work, we propose an uplink intercell interference control (ICIC) scheme which is a unified ICIC approach of handover based interference control and rate-split based interference control. The handover based interference control scheme is a win-win strategy which enhances both interfering user's rate and interfered user's rate. On the other hand, the rate-split based interference control scheme is a yield-win strategy where an interfering user sacrifices his rate to save the interfered user's rate. In this paper, we assume that users have their target QoS such as minimum rate when they send their data. The proposed uplink ICIC scheme reduces the interference as best as possible while it guarantees the minimum QoS. Simulation results shows that the proposed ICIC scheme offers enhanced rate or fairness than legacy ICIC schemes which are not considering user QoS. The proposed ICIC scheme works in distributed manner with low-complexity so that it can be applied to self-organizing network and mobile ad-hoc networks as well as heterogeneous cellular networks.

In heterogeneous cellular networks (HCN) which consists of macrocells and numerous picocells, efficient interference management schemes between macrocells and picocells are so crucial to the overall system performance. We propose a dynamic cooperative silencing control (DCS) scheme for intercell interference control (ICIC). It is a low-complex, low-feedback and distributed algorithm using only strongly interfered neighboring users' information. The system simulation shows that the system performance and in particular the cell-edge throughput is significantly increased with the proposed silencing scheme. It offers 420% and 190% higher average spectral efficiency and edge-user spectral efficiency in compared to macrocell only case, respectively.

This paper focuses on interference issues arising in the downlink of a heterogeneous network (HetNet), where small cells are deployed within a macrocell. Interference scenario in a HetNet varies based on the type of small cell access modes, which can be classified as either closed subscriber group (CSG) or open subscriber group (OSG) modes. For these two types of modes, we propose hierarchical interference alignment (HIA) schemes, which successively determine beamforming matrices for small cell and macro base stations (BSs) by considering a HetNet environment in which the macro BS and small cell BSs have different numbers of transmit antennas. Unlike prior work on interference alignment (IA) for homogeneous networks, the proposed HIA schemes compute the beamforming matrices in closed-form and reduce the feedforward overhead through a hierarchical approach. By providing a tight outer bound of the degrees-of-freedom (DoF), we also investigate the optimality of the proposed HIA schemes with respect to the number of antennas without any time expansion. Furthermore, we propose a new optimization process to maximize the sum-rate performance of each cell while satisfying the IA conditions. The simulation results show that the proposed HIA schemes provide an additional DoF compared to the conventional interference coordination schemes using a time domain-based resource partitioning. Under multi-cell interference environments, the proposed schemes offer an approximately 100% improvement in throughput gain compared to the conventional coordinated beamforming schemes when the interference from coordinated BSs is significantly stronger than the remaining interference from uncoordinated BSs.

The interference alignment (IA) is a promising technique to effectively mitigate interferences in wireless communication systems. To show the potential benefits of such an IA scheme, this letter focuses on a two-cell multiple-input multiple-output (MIMO) Gaussian interfering broadcast channels (MIMO-IFBC) with M transmit antennas and N receive antennas. It corresponds to a downlink scenario for cellular networks with two base stations (BSs) with M transmit antennas per BS, and two users with N receive antennas per user, on the cell-boundary of each BS. In this scenario, we propose a novel IA technique jointly designing transmit and receive beamforming vectors in a closed-form expression without iterative computation. It is also analytically shown that the proposed IA algorithm achieves the optimal degrees of freedom (DoF) of 2N in the case of [¾N] ≤ M <; 2N. The simulations demonstrate that not only the analytical results are valid, but the sum-rate of our proposed scheme also outperforms those of conventional techniques, especially in the high signal-to-noise ratio (SNR) regime.

In fourth generation wireless communication standards, the throughput enhancement for cell edge users is a main issue so that various inter-cell interference (ICI) coordination techniques have been suggested. Since the coordination between different cells requires the resources of cooperating cell, its use should be determined carefully. In this paper, we consider two basic handover schemes (Fast Cell Selection and Soft Handover) for the ICI coordination and propose a new handover decision algorithm from a viewpoint of the improvement of cell edge throughput. For the proposed algorithm, a new measurement parameter named Interference to other-Interferences-plus-Noise Ratio (IINR) is defined and some practical issues are addressed in the OFDMA-based cellular system. Compared to the legacy SINR-based decision algorithm, the proposed IINR-based decision algorithm improves the cell edge throughput with reduced feedback overhead, because it optimally selects mobile stations that have cooperation gains more than cooperation costs.

In today's IEEE 802.11 Wireless LANs (WLANs), e.g., the popular IEEE 802.11 b, stations support multiple transmission rates, and use them adaptively depending on the underlying channel condition via link adaptation. It has been known that when some stations use low transmission rates due to bad channel conditions, the performance of the stations using high rates is heavily degraded, and this phenomenon is often referred to as performance anomaly. In this paper, we model the WLAN incorporating stations with multiple transmission rates in order to demonstrate the performance anomaly analytically. Note that all the previously proposed models of the IEEE 802.11 assume a single transmission rate. We also develop possible remedies to improve the performance. Our solution is basically to control the access parameters such as the initial backoff window, the frame size, and the maximum backoff stage, depending on the employed transmission rate. Throughout simulations, we demonstrate that our analytical model is accurate, and the proposed mechanism can indeed provide the remedies to the performance anomaly by increasing the aggregate throughput up to six times.

Today, IEEE 802.11 wireless LAN (WLAN) has emerged as a prevailing technology for broadband wireless networking. Along with many emerging applications and services, the demands for faster and higher-capacity WLANs have been growing fast. We propose a new medium access control (MAC) scheme for the next-generation high-speed WLANs, such as IEEE 802.11n. The proposed MAC, called multiuser polling controlled channel access (MCCA), is composed of two sub-schemes. The first is multiuser polling, in order to achieve higher network utilization. The second is a frame aggregation scheme, which performs aggregations at both MAC and physical (PHY) layers, and can achieve an even higher throughput gain as a result. From simulations, we confirm that the MCCA scheme enhances the aggregate throughput of non-quality-of-service (non-QoS) traffic by an order of magnitude from 17.4 Mbps to 129.9 Mbps, while the aggregate throughput and QoS requirements continue to be satisfied.

Bluetooth, IEEE 802.11b WLAN and microwave ovens are likely to be the dominant interferers to Bluetooth in the coming year. There is both frequency dynamic and frequency static interference. This paper provides a theoretical analysis on the Bluetooth noncollaborative coexistence mechanisms. The analysis results show that a hybrid method of power control, listen-before-talk (LBT) and adaptive frequency hopping (AFH) can give the best packet collision and system aggregate throughput. LBT is the carry sense in Bluetooth. Before any Bluetooth packet transmission, in the turnaround time of the current slot, the packet sender senses the channel, whether there is any transmission going on or not. If the channel is busy, packet transmission is withdrawn until another time. In the hybrid method, power control mitigates the number of potential interferers, LBT combats transient interference, and AFH combats static interference.