LTE – Page 3 – RAYmaps

October 7, 2011November 21, 2013Channel Modeling, LTE, WiMAX

LTE Multipath Channel Models

When a wireless signal travels from a transmitter to a receiver it follows multiple paths. The signal may travel directly following the line of sight between the transmitter and receiver, it may bounce off the ground and reach the receiver or it may be reflected by multiple buildings on the way to the receiver. When these copies of the same signal arrive at the receiver they are delayed and attenuated based upon the path length that they have followed and various other factors. A well known technique to model such a wireless channel is to model it as an FIR […]

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 27, 2011November 15, 2011Antennas, LTE, Network Planning, WiMAX

Base Station Antenna Tilt and Path Loss

Path loss is basically the difference in transmit and receive powers of a wireless communication link. In a Free Space Line of Sight (LOS) channel the path loss is defined as: L=20*log10(4*pi*d/lambda) where ‘d’ is the transmit receive separation and ‘lambda’ is the wavelength. It is also possible to include the antenna gains in the link budget calculation to find the end to end path loss (cable and connector losses may also be factored in). Antenna gains are usually defined along a horizontal plane and vertical plane passing through the center of the antenna. The antenna gain can then be […]

September 25, 2011November 15, 2011Network Planning, Random Thoughts

Qualcomm In Muddy Waters In India

Remember Qualcomm CEO Paul Jacobs proudly claiming that his company had prevented WiMAX from getting a hold in India by acquiring BWA licenses in four regions of India. Well now Qualcomm is in a bit of bother as the Department of Telecommunication (DoT) in India has raised objections to the license application filed by Qualcomm. According to news circulating on the internet the DoT has objected to Qualcomm filing four separate applications through its nominee companies in the four regions (Delhi, Mumbai, Kerala and Haryana) it had won the licenses on June 12, 2010. Secondly the DoT has also objected […]

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 […]

September 13, 2011November 15, 2011LTE, Network Planning, WiMAX

Propagation and In-Building Penetration at 700MHz

It is quite well known that wireless signals travel further at lower frequencies. This phenomenon has become particularly important in the context of LTE where a frequency band has been allocated at 700MHz. We would like to quantify the benefits that can be achieved by using this frequency band. Firstly we find the received signal power at 728 MHz (lowest downlink frequency) and at 3600 MHz (highest downlink frequency) in a free space line of sight channel. The transmit power is set to 1 W and omnidirectional antennas are considered at the transmitter and receiver. The received power for these […]

September 11, 2011November 15, 2011HSPA, LTE, Network Planning

4G LTE Coverage within Virginia

Since our last post on Verizon LTE coverage within California, Verizon has removed the LTE Coverage Map from its site. Now it only gives a list of cities that have 4G LTE service (just like T-Mobile). So we now move from the West Coast to the East Coast i.e. Virginia. The state that is home to Virginia Tech, one of the finest schools in the country and a breeding ground for Wireless Engineers. It is thus somewhat of a shock to see that Verizon Wireless has no 4G LTE footprint in the state of Virginia. The only place that it […]

September 9, 2011May 31, 20225G, BER Performance, LTE, Modulation, WiMAX

BER of 64-QAM OFDM in Frequency Selective Fading-II

It is observed that the BER performance of 64-QAM OFDM in the time-varying frequency-selective channel is quite similar to that in the static frequency-selective channel with complex filter taps. It must be noted that with 64-QAM the goal is to achieve higher bit rate, error rates can be improved using antenna diversity and channel coding schemes.

September 3, 2011May 31, 20225G, BER Performance, LTE, Modulation, WiMAX

BER of 64-QAM OFDM in Frequency Selective Fading

The real benefits of OFDM become apparent in a frequency selective channel. The introduction of the cyclic prefix (guard period) allows us to remove the Intersymbol Interference (ISI) in the time domain and frequency domain equalization allows us to overcome the channel variations in the frequency domain.