Due to global climate change as well as economic concern of network operators, energy consumption of the infrastructure of cellular networks, or “Green Cellular Networking,” has become a popular research topic. While energy saving can be achieved by adopting renewable energy resources or improving design of certain hardware (e.g., power amplifier) to make it more energy-efficient, the cost of purchasing, replacing, and installing new equipment (including manpower, transportation, disruption to normal operation, as well as associated energy and direct cost) is often prohibitive. By comparison, approaches that work on the operating protocols of the system do not require changes to current network architecture, making them far less costly and easier for testing and implementation. In this survey, we first present facts and figures that highlight the importance of green mobile networking and then review existing green cellular networking research with particular focus on techniques that incorporate the concept of the “sleep mode” in base stations. It takes advantage of changing traffic patterns on daily or weekly basis and selectively switches some lightly loaded base stations to low energy consumption modes. As base stations are responsible for the large amount of energy consumed in cellular networks, these approaches have the potential to save a significant amount of energy, as shown in various studies. However, it is noticed that certain simplifying assumptions made in the published papers introduce inaccuracies. This review will discuss these assumptions, particularly, an assumption that ignores the effect of traffic-load-dependent factors on energy consumption. We show here that considering this effect may lead to noticeably lower benefit than in models that ignore this effect. Finally, potential future research directions are discussed.

Energy-Efficient Base-Stations Sleep-Mode Techniques in Green Cellular Networks: A Survey

A semiconductor device, and particularly a high electron mobility transistor (HEMT), having a plurality of epitaxial layers and experiencing an operating (E) field. A negative ion region in the epitaxial layers to counter the operating (E) field. One method for fabricating a semiconductor device comprises providing a substrate and growing epitaxial layers on the substrate. Negative ions are introduced into the epitaxial layers to form a negative ion region to counter operating electric (E) fields in the semiconductor device. Contacts can be deposited on the epitaxial layers, either before or after formation of the negative ion region.

Robust transistors with fluorine treatment

A method for fabricating a semiconductor device includes forming a recess gate over a semiconductor substrate. A gate spacer is formed on a sidewall of the recess gate. The semiconductor substrate in a landing plug contact region is soft-etched to form a recess having a rounded profile. A sidewall spacer is formed over the gate spacer and a sidewall of the recess. An insulating film is formed over the semiconductor substrate. The insulating film is selectively etched to form a landing plug contact hole. A conductive layer in the landing plug contact hole is filled to form a landing plug.

Semiconductor Device and Method for Fabricating the Same

Renewable energy powered sustainable 5G network infrastructure: Opportunities, challenges and perspectives

A thinned semiconductor die is coupled to an integrated heat spreader with thermal interface material to form a semiconductor package. The method for forming the package comprises forming a metallization layer on a backside of a thinned semiconductor die. A thermal interface portion, including a solder layer including a fluxlessly-capable solder such as AuSn, is formed on a topside of the integrated heat spreader. The metallization layer and the solder layer are then forced together under load and heat without flux to bond the semiconductor die to the integrated heat spreader.

Fluxless die-to-heat spreader bonding using thermal interface material

An embodiment of an amplifier system includes a modifiable signal adjustment device with an RF signal adjustment circuit coupled between first and second nodes. The RF signal adjustment circuit includes an adjustable phase shifter and an adjustable attenuator coupled in series with each other. The device also includes a memory and a controller circuit. The controller circuit retrieves a phase shift value and an attenuation value from the memory. The controller circuit then controls the adjustable phase shifter to apply a phase shift corresponding to the phase shift value to an input RF signal received at the first node, and controls the adjustable attenuator to apply an attenuation corresponding to the attenuation value to the input RF signal. Applying the phase shift and the attenuation results in an output RF signal at the second node.

Modifiable signal adjustment devices for power amplifiers and corresponding methods & apparatus

We have demonstrated a 1W 1.8∼2.2GHz high efficiency and high linearity power amplifier that was fabricated in a InGaP hetero-junction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) technology. The 2-stage power amplifier was biased at Class AB with 60mA quiescent current and showed 28dB gain. In conjunction with the linearization active bias circuit, harmonic trap circuits were incorporated with the matching networks to simultaneously achieve good bandwidth response, low distortion and low harmonic spurious output. The power amplifier exhibited a 45dBm output third-order intercept point (OIP3) at 5V power supply. This is one of the highest third-order intercept points reported given such a low quiescent current. The power amplifier can be used as a linear driver amplifier in wireless base station applications as well as an output stage in Femto cell or repeater applications.

High efficiency linear GaAs MMIC amplifier for wireless base station and Femto cell applications

A power amplifier device having a conductive structure overlying a dielectric layer. The conductive structure has a first conductive structure portion that is substantially electrically isolated from a second conductive structure portion. A first plurality of bond wires couple the first conductive structure portion to an amplifying device, while a second plurality of bond wires couple the second conductive structure portion to the amplifying device.

Amplifier apparatus and method thereof

This paper presents a highly integrated, sub 0.5 dB noise figure (NF) low noise amplifier (LNA) targeting 700/900 MHz GSM/CDMA/LTE base station receiver and tower mount antenna (TMA) applications. The amplifier is realized using a GaAs pHEMT process, and is housed in a very small 2 × 2 mm2 low cost plastic surface mount DFN style package. State-of-the art noise performance of less than 0.5 dB NF is achieved through an innovative design methodology and circuit architecture which takes full advantage of the selected GaAs device technology. This work represents one of the best matched LNA noise figures reported to-date in this frequency band. In addition to very low noise performance, the amplifier simultaneously exhibits gain greater than 21 dB, excellent linearity, and is closely matched to 50 Ω at the input and output ports. Very wide bandwidth performance from 300 MHz to beyond 1400 MHz is demonstrated, and performance within this frequency range can be further enhanced through selection of specific off-chip components.

Wide bandwidth GSM/WCDMA/LTE base station LNA with ultra-low sub 0.5 dB noise figure

A thin GaAs Substrate can be provided with a copper back-metal layer to allow the GaAs Substrate to be packaged using conventional plastic packaging technologies. By providing the GaAs Substrate with a copper back-metal layer, the GaAs Substrate can be made thinner than 2 mils (about 50 microns), thereby reducing heat dissipation problems and allowing the semiconductor die to be compatible with soft-solder technologies. By enabling the semiconductor die to be packaged in a plastic package substantial cost savings can be achieved.

M. Miller

Papers

Modifiable signal adjustment devices for power amplifiers and corresponding methods & apparatus

High efficiency linear GaAs MMIC amplifier for wireless base station and Femto cell applications

Amplifier apparatus and method thereof

Wide bandwidth GSM/WCDMA/LTE base station LNA with ultra-low sub 0.5 dB noise figure

Thin GaAs die with copper back-metal structure