Fast Cell Selection Research Articles

Low-Complexity Design and Implementation of a Software-Defined 5G Energy Detector for Fast Initial Cell Selection

Low-Complexity Design and Implementation of a Software-Defined 5G Energy Detector for Fast Initial Cell Selection

Joint Scheduling and Fast Cell Selection in OFDMA Wireless Networks

In modern broadband cellular networks, the omni-directional antenna at each cell is replaced by three or six directional antennas, one in every sector. While every sector can run its own scheduling algorithm, bandwidth utilization can be significantly increased if a scheduler makes these decisions for all the sectors. This gives rise to a new problem, referred to as joint scheduling, addressed in this paper for the first time. The problem is proven to be NP-hard, but we propose efficient algorithms with a worst-case performance guarantee for solving it. We then show that the proposed algorithms indeed substantially increase the network throughput.

Rapid and Effective Isolation Of (T) Cell Populations By a New Method Avoiding Magnetic Beads

In the last two decades, conventional isolation of therapeutic cells has been carried out using high affinity antibodies and magnetic bead technology. Although good purity and reasonable yields can be obtained in many cases, major disadvantages remain comprising biological interference of non-reversible selection reagents (e.g. stimulation, receptor blockade etc.), the difficulty to purify complex multi-parametric cell populations by positive selection, time consuming protocols as well as limitations in high-throughput processing. We report here on the development of a new non-magnetic and fast cell selection technology applying immune affinity chromatography. Therefore, a matrix consisting of beads coated with Streptactin and low-affinity recombinant Fab-fragments (Fab-Streptamers) directed against defined T cell surface antigens has been generated. Stable and specific target cell retention is achieved by passing whole blood or PBMCs over the affinity matrix. After binding and washing, target cells can be gently retrieved by D-biotin administration. Eluted cells are then passed over a second matrix removing D-biotin and free Fab-Streptamers, subsequently yielding in a label-free authentic cell population for further use. Most importantly, total cell processing times can be kept extremely short; depending on the sample size even down to several minutes. Sequential isolation steps are possible and allow positive selection of complex cell populations like regulatory T cells or central memory T cells defined by several markers in high yields and purities. We are currently integrating this approach into a fully closed separation device for clinical cell purification. In addition, high throughput cell selection for diagnostic or basic research applications can be achieved by embedding the matrix into pipette tips and the use of suitable pipetting robots. Disclosures: No relevant conflicts of interest to declare.

Fast cell selection with efficient active set management in OFDMA networks with femtocells

In 4G wireless networks, only hard handover is defined to support users’ mobility. However, dense deployment of femtocells leads to significant rise in amount of initiated handovers. Thus, inevitable decrease in quality of service (QoS) experienced by users is observed. In this article, we investigate possible introduction of fast cell selection (FCS) to OFDMA-based network with femtocells. The goal is to minimize negative impact of user’s mobility on user’s QoS and to take an advantage of macro diversity. First, we define necessary enhancements in current LTE standards to facilitate implementation of FCS to OFDMA networks. Afterward, impact of FCS on network performance is evaluated. Second, we propose novel algorithm for active set management, which considers specifics of femtocells. As simulation results demonstrate, even FCS with conventional active set management is profitable for the networks performance. Nevertheless, the proposed innovation of active set management procedure further improves efficiency of FCS comparing to existing schemes. We also present the most common content of active set observed from simulations if novel algorithm is exploited.

An Optimal Handover Decision for Throughput Enhancement

This letter proposes an optimal handover decision algorithm from the perspective of throughput enhancement. By considering two handover schemes (soft handover and fast cell selection), the proposed algorithm decides a handover only when a throughput gain exists. In order for this decision to be made, a new measurement parameter, Interference to other-Interferences-plus-Noise Ratio (IINR), is defined. The proposed IINR-based handover decision demonstrates optimal throughput performance, while the legacy signal to interference-plus-noise ratios (SINR)-based handover decision presents a tradeoff between throughput and feedback overhead.

Scheduling performance in downlink WCDMA networks with AMC and fast cell selection

This paper is concerned with the analysis of scheduling performance in downlink WCDMA networks that employ adaptive modulation and coding (AMC) and fast cell selection (FCS). The scheduling schemes investigated include (i) the round robin (RR) scheme, (ii) the maximum carrier-to-interference ratio (C/I) scheme, (iii) the simplified proportional fair (PF) scheme, and (iv) the conventional PF scheme. The channel model includes large-scale signal attenuation and small-scale fading. By using a form analogous to Shannon's channel capacity formula, a logarithmic relationship between the instantaneous data rate and the C/I with AMC is first established. Using the so-called Poisson scheme in which the probabilities of the occurrence of the events in Bernoulli trials depend on the trial index, FCS implementation is then examined in detail. Finally, a complete set of analytical expressions on the average system throughput, the peak data rate and the fairness for the abovementioned scheduling schemes are derived.

Volumetric Attribute Filtering and Interactive Visualization Using the Max-Tree Representation

The Max-Tree designed for morphological attribute filtering in image processing, is a data structure in which the nodes represent connected components for all threshold levels in a data set. Attribute filters compute some attribute describing the shape or size of each connected component and then decide which components to keep or to discard. In this paper, we augment the basic Max-Tree data structure such that interactive volumetric filtering and visualization becomes possible. We introduce extensions that allow (1) direct, splatting-based, volume rendering; (2) representation of the Max-Tree on graphics hardware; and (3) fast active cell selection for isosurface generation. In all three cases, we can use the Max-Tree representation for visualization directly, without needing to reconstruct the volumetric data explicitly. We show that both filtering and visualization can be performed at interactive frame rates, ranging between 2.4 and 32 frames per seconds. In contrast, a standard texture-based volume visualization method manages only between 0.5 and 1.8 frames per second. For isovalue browsing, the experimental results show that the performance is comparable to the performance of an interval tree, where our method has the advantage that both filter threshold browsing and isolevel browsing are fast. It is shown that the methods using graphics hardware can be extended to other connected filters.

Effect of circuit switched services on the capacity of HSDPA

This paper focuses on the effect of circuit switched (CS) services on high speed downlink packet access (HSDPA) packet services in the context of the UMTS FDD system. An objective of the analysis is to provide guidelines for the UMTS planning process to prioritize services when resources are dynamically shared between circuit and packet services. An analytical model, taking into account some of the features introduced in HSDPA (namely adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ) and fast cell selection) and the interaction between CS services and HSDPA, is proposed to approximate the HSDPA cell capacity. Simulation results to assess the efficiency of the analytical model are also reported.

How to minimize the TCP effect in a UMTS‐HSDPA system?

AbstractThis paper focuses on the interaction between the transmission control protocol (TCP) layer and the radio interface in a 3G wireless system. An analytical model to evaluate the impact of TCP on the UMTS‐HSDPA capacity is presented. A method to minimize the effect of TCP on wireless networks using shared channels is also proposed. High speed downlink packet access (HSDPA) is an evolution of the UMTS standard over the air interface to achieve higher aggregate bit rates through the introduction of adaptive modulation and coding, hybrid automatic repeat request (ARQ), fast scheduling, fast cell selection, and multiple input multiple output (MIMO) (space time coding and blast) techniques. The proposed model is used to evaluate the effect of the TCP protocol on the bit rate of various data services (at 64 and 128 kbps). As expected, the bit rate per flow decreases strongly if the congestion frequency in the wired network increases. However, the overall capacity achieved by HSDPA is not as affected by the TCP layer. Using this result, a method to maintain the bit rate per TCP flow at a given value without loosing much cell capacity is proposed. The findings are supported by simulation results. Copyright © 2005 John Wiley & Sons, Ltd.

Cell Selection Based on Shadowing Variation for Forward Link Broadband OFCDM Packet Wireless Access

This paper proposes cell selection (CS) based on shadowing variation for the forward-link Orthogonal Frequency and Code Division Multiplexing (OFCDM) packet wireless access. We clarify its effects using a broadband propagation channel model in a comparison with fast cell selection (FCS), which tracks the instantaneous fading variation, and with the conventional slow CS, which tracks only the distance-dependent path loss, based on radio link level simulations that take into account time-varying instantaneous fading and shadowing variations. The simulation results show that the achievable throughput with FCS improves slightly in a broadband channel with an increasing number of paths when the average path-loss difference between two cells is greater than 2 dB. Nevertheless, we show that the optimum CS interval becomes approximately 100msec, because the interval can track the time-varying shadowing variation considering low-to-high mobility up to the maximum Doppler frequency of 200 Hz. Consequently, we show that the throughput by employing the CS based on shadowing variation with the selection interval of 100msec is increased by approximately 5 and 15% compared to that using the conventional slow CS with the selection interval of I sec. for the maximum Doppler frequency of 20 and 200 Hz, respectively.