Tag : antenna

Wi-Fi Systems

Wi-Fi Systems

In addition to 3G, Wi-Fi based-systems may be used to provide broadband wireless. Wi-Fi is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to
Emergence of Standards-Based Technology

Emergence of Standards-Based Technology

In 1998, the Institute of Electrical and Electronics Engineers (IEEE) formed a group called 802.16 to develop a standard for what was called a wireless metropolitan area network, or wireless MAN. Originally, this group
Second-Generation Broadband Systems

Second-Generation Broadband Systems

Second-generation broadband wireless systems were able to overcome the LOS issue and to provide more capacity. This was done through the use of a cellular architecture and  implementation of advanced-signal processing techniques to improve
First-Generation Broadband Systems

First-Generation Broadband Systems

As DSL and cable modems began to be deployed, wireless systems had to evolve to support much higher speeds to be competitive. Systems began to be developed for higher frequencies, such as the 2.5GHz
Evolution of Broadband Wireless

Evolution of Broadband Wireless

The history of broadband wireless as it relates to WiMAX can be traced back to the desire to find a competitive alternative to traditional wireline-access technologies. Spurred by the deregulation of the telecom industry
Transmit Diversity Gain in LTE

Transmit Diversity Gain in LTE

Transmit diversity gain can be used when transmitting broadcast information from multiple antennas. This effectively produces, by design, frequency diversity in the transmitter. The gain obtained from transmit diversity can be approximated with the
BEAMFORMING in LTE

BEAMFORMING in LTE

If some knowledge of the downlink channels of the different transmit antennas, (more specifically some knowledge of the relative channel phases) is available at the transmitter side, multiple transmit antennas can be used to
Propagation Path

Propagation Path

Radio wave can be propagated from the transmitting antenna to the receiving antenna in many ways: perpendicular incidence wave or ground refraction wave, diffraction wave, troposphere reflection wave, ionosphere reflection wave, as shown in
Propagation of Electromagnetic Wave

Propagation of Electromagnetic Wave

When the radio wave propagates in the air, the electric field direction changes regularly. If the electric field direction of radio wave is vertical to the ground, the radio wave is vertical polarization wave
Radio Wave Spectrum

Radio Wave Spectrum

The radio waves are distributed in 3Hz ~ 3000GHz. This spectrum is divided into 12 bands, as shown in the above table. The frequencies in each specific band present unique propagation features: The lower
How Open-Loop Transmit Diversity in Wimax?

How Open-Loop Transmit Diversity in Wimax?

Transmit spatial diversity is a newer phenomenon than receive diversity and has become widely implemented only in the early 2000s. Because the signals sent from different transmit antennas interfere with one another, processing is