4G – Page 2 – RAYmaps

November 7, 2011November 15, 2011LTE

Peak to Average Power Ratio (PAPR)

Peak to Average Power Ratio (PAPR) as the name suggests is the ratio of peak signal power to the average signal power and has received considerable attention in the context of multicarrier signals like OFDM which exhibit a high PAPR. The down side of this high PAPR is that the power amplifier in the transmitter is operated at a relatively lower power level so that the peaks in the signal are not distorted by the saturating amplifier. This is called the amplifier backoff and it plays an important part in wireless system design. Power Amplifier Input Output Behavior The reason […]

November 1, 2011June 16, 2014Channel Modeling

Computationally Efficient Rayleigh Fading Simulator

We had previously presented a method of generating a temporally correlated Rayleigh fading sequence. This was based on Smith’s fading simulator which was based on Clark and Gan’s fading model. We now present a highly efficient method of generating a correlated Rayleigh fading sequence, which has been adapted from Young and Beaulieu’s technique [1]. The architecture of this fading simulator is shown below. This method essentially involves five steps. 1. Generate two Gaussian random sequences of length N each. 2. Multiply these sequences by the square root of Doppler Spectrum S=1.5./(pi*fm*sqrt(1-(f/fm).^2). 3. Add the two sequences in quadrature with each other […]

October 21, 2011June 7, 2012Channel Modeling, LTE, WiMAX

A Rayleigh Fading Simulator with Temporal and Spatial Correlation

Just to recap, building an LTE fading simulator with the desired temporal and spatial correlation is a three step procedure. 1. Generate Rayleigh fading sequences using Smith’s method which is based on Clarke and Gan’s fading model. 2. Introduce spatial correlation based upon the spatial correlation matrices defined in 3GPP 36.101. 3. Use these spatially and temporally correlated sequences as the filter taps for the LTE channel models. We have already discussed step 1 and 3 in our previous posts. We now focus on step 2, generating spatially correlated channels coefficients. 3GPP has defined spatial correlation matrices for the Node-B […]

October 3, 2011November 15, 2011Antennas, LTE, Network Planning, WiMAX

Antenna Radiation Pattern and Antenna Tilt

An introductory text in Communication Theory would tell you that antennas radiate uniformly in all directions and the power received at a given distance ‘d’ is proportional to 1/(d)^2. Such an antenna is called an isotropic radiator. However, real world antennas are not isotropic radiators. They transmit energy in only those directions where it is needed. The Gain of a antenna is defined as the ratio of the power transmitted (or received) in a given direction to the power transmitted in that direction by an isotropic source and is expressed in dBi. Although antenna Gain is a three dimensional quantity, […]

September 17, 2011November 15, 2011LTE, Network Planning

LTE Path Loss at 700 MHz

In the previous post we had compared the path loss of LTE at 728 MHz and 1805 MHz in a free space line of sight channel. This is a very simplistic channel model which tells us that ratio of the received signal strengths at these frequencies can be simply found as: (f1/f2)^2=(1805/728)^2=6.15 That is the received signal strength at 728 MHz is 6.15 times higher than the received signal strength at 1805 MHz. Now let us consider a more realistic channel model known as the COST-231 model. According to this model the path loss (difference between the transmit power and […]

August 22, 2011November 15, 2011LTE

Verizon 4G LTE Deployment Within California

We have previously looked at the birds eye view of 4G LTE coverage within the US. We know that Verizon 4G services are now available to more than 50% of the US population. However, geographically, the service is only available in very small islands of population. Now, we take a closer look at 4G LTE coverage within California. LTE Coverage in CA We see that the coverage is available in most of the population centers such as Sacramento, San Francisco, Oakland, San Jose, Fresno and Bakersfield. Further south the coverage is also available in areas around Los Angeles and San […]

August 19, 2011November 15, 2011LTE

Verizon 4G LTE Deployment within the US

Verizon Wireless 4G LTE is now available to 160 million people with coverage in 117 cities within the US. This has been achieved within eight months of the initial deployment. Verizon hopes to increase the coverage to 185 million people by the end of 2011. The company claims that with its current deployment strategy users can experience data rates of 5-12Mbps on the downlink and 2-5Mbps on the uplink. When users do not have access to the 4G LTE network the phones will automatically switch to 3G which is available around most of the US. LTE Coverage This push to […]