Range Expansion Technique Research Articles

An Evolutionary Game Theory Approach for Joint Offloading and Interference Management in a Two-Tier HetNet

In this paper, we present a price-based approach for offloading macro users to small-cells in a two-tier heterogeneous network (HetNet). We have constructively exploited the small-cell density in a HetNet to harness offloading opportunities for macro users (MUs), the goal of which is to solve two problems simultaneously. It aims to shun the MUs, who have a lower received data rate due to the interference perceived from the small-cell tier. The scheme also fends off congestion in a macrocell, by offloading macro users to the small-cell tier. We have proposed a novel threshold pricing scheme, which a macrocell adopts, with a view to influencing low data rate MUs to join a small-cell network. Small-cell networks also charge a price, which includes an access price and an interference compensation price, proportional to the number of MUs who choose the small-cells instead of the macrocellular network. We assume that the small-cells adopt existing cell range expansion techniques to accommodate MUs. We formulate an evolutionary game to model and analyze the behavioral dynamics of the large number of MUs under the proposed pricing strategies of both networks. Replicator dynamics is used to find the evolutionary equilibrium of the evolutionary game. Sequentially, we provide the proof of the existence, uniqueness and stability of the evolutionary equilibrium through extensive analysis. Numerical results are provided to demonstrate that the proposed pricing strategies are able to shape the network dynamics by fine-tuning the rate-threshold and price. The ability to control the macrocell population share by itself with an application of the proposed pricing scheme remains the prime contribution of this paper.

Pricing‐based Stackelberg game for spectrum trading in self‐organised heterogeneous networks

In this study, the spectrum trading problem in a self-organised and two-tier heterogeneous cellular network is studied and the bandwidth sharing problem incorporated with cell range expansion technique is formulated as a Stackelberg game. Maximising the revenue of macro eNodeB (MeNB), affording minimum required bandwidth for each home eNodeB (HeNB), enhancing per femto-user throughput, and providing better quality of service for macro-users nearby each femto-cell are the main objectives of this investigation. The authors propose an iterative scheme in which MeNB and HeNBs make decisions autonomously. The MeNB as the spectrum provider decides on the unit-bandwidth price with the objective to maximise its revenue. Each HeNB, on the other side, decides on the amount of requested bandwidth as well as the number of possible nearby macro-users which will support to take advantage of MeNB discounting. The designed discounting strategy is applied for the extra bandwidth request of HeNBs to encourage them in supporting nearby macro-users. It is shown analytically that the proposed scheme converges to a unique Nash equilibrium which is Pareto optimal. Evaluating the authors’ game through different simulations demonstrates that it is all beneficial for both MeNB and HeNBs and the social welfare is maximised in the network.

An Intelligent Pico Cell Range Expansion Technique for Heterogeneous Wireless Networks

Background/Objectives: Due to high transmission power emitted by macro cell, very few users will be offloaded to nearby pico cell which leads to underutilization of pico cells in Heterogeneous Networks (HetNet). Method/Statistical Analysis: Cell Range Expansion (CRE) is a technique to virtually expand the coverage range of pico cell. With the help of CRE, user equipment will add a bias value to actual signal strength received from pico cell and thereby offload their traffic from macro cell to pico cell. But, at the same time adding bias value will lead to additional downlink interference which becomes severe for choosing higher bias value. Findings: Optimal bias value reduces the number of outage mobile stations but it depends on several factors which are hard to find such as the distribution of mobile stations over the cells, resource shared between pico and macro cells, mobility pattern and so on. In this paper, we are proposing a solution of Intelligent Pico Cell Range Expansion (IP-CRE) which calculates the effective bias value for each mobile station independently, by using a fuzzy logic inference system. Our proposed solution takes multiple attributes like signal strength of pico and macro cells, speed and direction of mobile stations, battery level and traffic requirements as input parameters and the output will be an effective bias value for each mobile station. We analyzed the effectiveness of the bias value by varying the number of connected Pico cell User Equipment (PUE) in the expansion region. Application/Improvements: Our observations from the simulation experiments demonstrate that the proposed scheme reduces the number of outage UE and increases the number of offloaded UE in Het Net.

A Dynamic Range Expansion Technique Using Dual Charge Storage in a CMOS APS and Multiple Exposures for Reduced Motion Blur

This paper presents a dynamic range expansion technique for CMOS image sensors using dual charge storage in a pixel and multiple exposures. Each pixel contains two photodiodes, PD1 and PD2 whose sensitivity can be set independently by the accumulation time. The difference of charge accumulation time in both photodiodes can be widely controlled to expand the dynamic range of the sensor. It allows flexible control of the dynamic range since the accumulation time in the PD2 signal is adjustable. The multiple exposure technique used in the sensor reduces the motion blur in the synthesized wide dynamic range image when capturing fast-moving objects. It also reduces the signal-to-noise ratio dip at the switching point of the PD1 signal to the PD2 signals in the synthesized wide dynamic range image. To reduce the read out time, a comparator-controlled selective readout of the PD1 and PD2 signals has been tested. The synthesis of the captured images to produce wide dynamic range image is also described. A wide dynamic range image sensor with 320x240 pixels has been implemented and tested. It is found that the use of 4 exposures in one frame for the short accumulation time signals is sufficient for the reduction of motion blur in the synthesized wide dynamic range image, and the signal-to-noise ratio dipping at the switching point of the PD1 to PD2 signals is reduced by 6 dB using 4 short-time exposures.

A Dynamic Range Expansion Technique for CMOS Image Sensors with Dual Charge Storage in a Pixel and Multiple Sampling.

A dynamic range expansion technique for CMOS image sensors with dual charge storage in a pixel and multiple sampling technique is presented. Each pixel contains a photodiode and a storage diode which is connected to the photodiode via a separation gate. The sensitivity of the signal charge in the storage diode can be controlled either by a separation gate which limits the charge to flow into the storage diode or by controlling the accumulation time in the storage diode. The operation of the sensitivity control with separation gate techniques is simulated and it is found that a blocking layer to the storage diode plays an important role for high controllability of sensitivity of the storage diode. A prototype chip for testing multiple short time accumulations is fabricated and measured.

A Dynamic Range Expansion Technique Using Dual Charge Storage in a CMOS APS and Multiple Exposures for Reduced Motion Blur

This paper presents a dynamic range expansion technique for CMOS image sensors using dual charge storage in a pixel and multiple exposures. Each pixel contains two photodiodes, PD1 and PD2 whose sensitivity can be set independently by the accumulation time. The difference of charge accumulation time in both photodiodes can be widely controlled to expand the dynamic range of the sensor. It allows flexible control of the dynamic range since the accumulation time in the PD2 signal is adjustable. The multiple exposure technique used in the sensor reduces the motion blur in the synthesized wide dynamic range image when capturing fast-moving objects. It also reduces the signal-to-noise ratio dip at the switching point of the PD1 signal to the PD2 signals in the synthesized wide dynamic range image. To reduce the read out time, a comparator-controlled selective readout of the PD1 and PD2 signals has been tested. The synthesis of the captured images to produce wide dynamic range image is also described. A wide dynamic range image sensor with 320x240 pixels has been implemented and tested. It is found that the use of 4 exposures in one frame for the short accumulation time signals is sufficient for the reduction of motion blur in the synthesized wide dynamic range image, and the signal-to-noise ratio dipping at the switching point of the PD1 to PD2 signals is reduced by 6 dB using 4 short-time exposures.

Highly Accurate and Precise Measurement Technique for Effective Exposure Dose

A highly accurate and precise measurement technique for effective exposure dose in optical microlithography has been developed. The effective exposure dose can be obtained by a dose monitor mark in a photomask, called the effective dose meter, which consists of multiple segments including grating patterns with a pitch below the resolution limit and different duty ratios gradually. Since the residual thickness of the photoresist after development changes according to the duty ratio, the effective exposure dose can be obtained by monitoring the film thickness for each segment of effective dose meter. It was found that an extremely high dose resolution of less than 0.01% was achieved in this technique. A dynamic range expansion technique has been also proposed, which has wide measurement range and improved repeatability. Across-wafer variation of the effective exposure dose in the current krypton fluoride excimer laser lithography process was measured as a demonstration of these technologies.