Radio Wave Propagation Models Used in RF Coverage Analysis

by

Paul Ngai

Radio wave propagation can be categorized as LOS (Line Of Sight) and non-LOS modes. LOS is direct point-to-point propagation with no obstructions in between. Non-LOS is indirect propagation in the absence of LOS path which consists of diffraction, reflection and scattering. In the HF band (3 30 MHz), propagation is primarily using sky wave for long distance communications. VHF and UHF (30 MHz 3 GHz) waves travel by LOS and ground bounce propagation. The SHF (3 to 30 GHz) wave uses strictly LOS propagation.

The goal of propagation modeling is to determine the probability of satisfactory performance of a wireless system that depends on radio wave propagation. For RF systems planning, the modeling of propagation is for the purpose of RF coverage analysis. This analysis uses the propagation model and terrain data to predict the RF coverage area of a transmitter, the received signal strength at the end of a wireless link, the path loss from the transmitter to a distance receiver, the antenna tilt angle of the transmitter, the minimum antenna height to establish Line of Sight communication path and channel impairment such as delay spread due to multi-path fading. Propagation models for different applications, environments and terrains had been developed by the US government, private organizations and standard body such as International Telecommunications Union (ITU). These models are based on large amount of empirical data collected for the purpose of characterizing propagation for that application. Since propagation models are created using statistical methods, no single model will exactly fit any particular application. It is a good idea to employ two or more independent models and use the results as bounds on the expected performance. The following are a list of most commonly used near-earth propagation models. Longley-Rice The Longley-Rice model predicts long term median transmission loss over irregular terrain. It is designed for frequency from 20 MHz to 20 GHz and path length from 1 to 2000 Km. The model accounts for terrain, climate, subsoil conditions and ground curvature. Longley-Rice model has two modes, point-to-point and area. The point-to-point mode uses detail terrain data and characteristics to predict path loss, whereas the area mode uses general information about the terrain characteristics to predict path loss. Okumura The Okumura model is based on the measurements made in Tokyo in 1960, between 200 to 1920 MHz. The measured values are used to determine the median field strength and numerous correction factors. The correction factors include adjustment to the degree of urbanization, terrain roughness, base station antenna height, mobile antenna height and localized obstruction. The Okumura model is especially applicable in urban area for general coverage calculation where numerous obstructions and buildings exist. Cost 231 The Cost 231 Model, also called the Hata model PCS extension, is used in most commercial RF planning tools for mobile telephony. The coverage of the Cost 231 model is frequency between 1500 to 2000 MHz, transmitter effective antenna height between 30 to 200 m, receiver effective antenna height between 1 to 10 m and link distance from 1 to 20 km. The Cost 231 model is restricted to application where the base station antenna is above adjacent roof tops. Egli The Egli model is a simplified model based on empirical match of measured data to mathematical formula. Its ease of implementation makes it a popular choice for use in the first analysis. It assumes gentle rolling hill height of approximately 50 feet and no terrain elevation data between the transmitter and receiver is needed for the model. The median path loss is adjusted for the height of transmit and receive antenna above ground. The model consists of a single equation for the propagation loss. ITU ITU terrain model is based on diffraction theory that provides a method to predict median path loss. The model predicts path loss as a function of the height of path blockage and the first Fresnel zone for the transmission link. The model is ideal for modeling line-of-sight link in any terrain and is good for any frequency and path length. The model accounts for obstructions in the middle of the communication link, hence it is suitable to be used both inside cities and open fields. The model is considered valid for losses above 15 dB.

Paul Ngai is an engineering consultant specialized in

Telecommunications Network and Systems

. He is also the principal of Network Systems Technologies LLC (

nstecs.net

), a telecommunications consulting firm provides planning, analysis, design, testing and operation support services.

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Radio Wave Propagation Models Used in RF Coverage Analysis

By Craig Elliott

You have found the perfect home. You are ready to move – yesterday. But you have no idea how to go about in the mortgage world. All home owners learn their way through this maze and you are no exception. Take the time to learn – it is well worth the effort you put into it.

To begin, find out what your credit rating is. There are three credit bureaus in the U.S.A. You are entitled to one free credit report per year and either of the bureaus can provide you with your score. Your credit score will give you a lot of information and it may even help you discover if someone has used your credit or your name without you knowing about it.

Once you know your credit score, then you are in a position to negotiate with your lender. While the interest rate may not be negotiable, several other items relating to your loan may be. You must know what to ask for in the negotiation stage. Remember, to go into escrow to buy a house, you will have points or costs that you must pay toward the loan. Points are actually a charge that the lenders use toward the cost of borrowing the money they will need to finance your loan. Each point equals 1% of total amount you are going to borrow. If you borrow $125,000 and your lender is asking you to pay three points, your total cost to borrow the money is $3,750.00. Ask about lowering the points by a quarter or a half.

In some mortgage loan transactions there are still institutions that charge for their attorney’s legal work on the loan. Point out that some of the other lenders you have talked to no longer charge for this service and ask for a break on the lawyer’s fees. There are document preparation fees and there are the advertisements of other lenders across town. Use the competitive price system to your advantage. Saving a few hundred dollars in up-front escrow costs are a few hundred dollars you might need to put in that skylight that would look great in your new den.

Learn how the mortgage loan industry works; learn its lingo. When you know what the person on the other side of the desk is talking about, then the terms and phrases that they pull out of their hat are not so scary and you can converse and ask questions with confidence.

Fill out your application and begin to get quotes from three or four different lenders. Sometimes, looking at the bottom line is helpful. However, knowing what the escrow costs are and what the long-term mortgage rate is will help you make an important decision: do you want to pay more up front in order to get a better long-term rate or would you prefer to pay less up front and pay a little more each month? Examine the various offers and make sure you know what each charge is for and what it means. If they are professionals in the business, the lender will not mind helping you to understand – they want the other business that you might have for them in the future.

Once you have the quotes and you understand what the programs and costs mean, then you are in a position to choose the lender you prefer. Let the lender know that you have gotten other quotes and start asking them to work with you in the places where the other lenders quote might look better.

There are several laws that you also need to be aware of as you begin to search for a loan. The first one is the Equal Credit Opportunity Act. Another is the Fair Housing Act. Both of these prohibit lenders and sellers from discriminating against any buyer/borrower and they make it illegal to charge more for their services to people of a different backgrounds, belief systems, nationalities, etc. These laws are designed to protect you, the buyer and borrower. You need to know your rights as you begin this process.

Even if you have credit problems, there are still ways to negotiate loans. You might need to explain the circumstances of late pay situation, especially if it was due to the loss of a job or an illness. It is especially important to point out to lenders when you have fixed the situation and show them the plan you have in place now to avoid future situations of the same nature.

You need to learn something about interest rates and the different types of interest rates available. Some interest rates appeal because of their stability while others appeal because of their flexibility. Can you work with the flexibility of an adjustable-rate mortgage or do you feel more comfortable with a fixed-rate loan? Those are questions you need to ask and examine with your financial advisor and your lender.

Once you have your questions answered, pursue the dream for purchasing your home for yourself and your family.

About the Author: Craig Elliott is a freelance writer who writes about topics pertaining to the mortgage industry such as Mortgage Company | Home Mortgage Lender at absolutemortgageco.com

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By Bill Smith

Listed below are some of the top ways to consolidate debt. If executed properly, they have the power to make you debt free.

Self Repayment Plan

Self Repayment Plan is a do it yourself approach to debt consolidation. If you do not want to hire a debt consolidation company and want to consider debt consolidation on your own, self repayment plan is for you. With the correctly cherry picked steps, you will be able to overcome debt. Budgeting plays a very crutial role in self repayment plan. You will need to add up your earnings and expenses in a given month and figure out where the extra green has been spent and aggressively work on reducing the expenses. In some situations, a part time job might just be the answer to pay off your debts and earn a debt free living. If you are determined to find a solution to your debt problems, self repayment plan is your best bet. If the plan is set up correctly and you are motivated enough to follow you, you will start to see results within a few months.

Debt Settlement

Debt Settlement involves negotiating with your creditors on your debts. Either you can do it yourself or hire a debt settlement export to do it on your behalf. Debt settlement companies specialize in reducing or eliminating debt via the debt settlement process. A good negotiator will be able to reduce your balance as much as 40%. Most of the reputed debt settlement companies will be candid about their fees but make sure you understand the fee well enough so there are no hidden surprises later on in the debt settlement game.

Debt consolidation loan

If you have multiple debts to be paid off, debt consolidation might work well for you. For example, you may have credit card debts, auto loan, boat home, personal loan, store cards etc. All these can be consolidated into a single loan with a very low interest rate. These loans with low interest rates are debt consolidation loans. The entire purpose of a debt consolidation loan is to lower your monthly interest and thereby reduce your monthly obligation. You can also consider extending your repayment period to lower your monthly obligation on this loan.

About the Author: Bill Smith is a

debt consolidation expert

for Ameri debt consolidation – FREE debt community. Visit us at

americreditservices.com/

Source:

isnare.com

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Submitted by: Bob I. Richards

You could be intimidated about managing investment accounts for customers because you feel you don’t know much about investments. But you needn’t fret because these days, everything is either computerized or sub-contracted out to third-party portfolio managers. Your job is simply to maintain the relationship with the client and somebody else will handle the investing. So as a life agent, you have an untapped source of new income.

If you sell annuities and your clients take the cash out of variable products such as stocks, bonds or mutual funds, you are generally open to the charge that you encouraged your client to liquidate the variable item and therefore gave investment advice with out an investment license. So become a registered investment adviser due to the fact then you DO have a license and can’t get in problems over this charge (the charge that you encouraged the client to see securities does not need to be true in order to cost you plenty in legal fees and perhaps your insurance license).

Don’t squander any more time not getting paid

You’ve been giving men and women advice for years–at no charge to them. Does your legal professional do that? Your Certified Public Accountant? Your doctor? Then why do you? You ought to charge for your time and guidance. As soon as you get a registered investment adviser certificate, you can get paid for your time and guidance. No more 2 hours meetings without getting paid for your time.

Being a registered investment adviser is the least complicated way to collect annual service fees. While the money manager deals with your client’s account, you get a part of the fee each year simply for sustaining the client relationship. It’s likely you got into this business simply because you like people. As a result, maintaining relationships is exactly what you’re good at so get paid for it every year.

Get paid for annual reviews

In case you do retirement planning it is possible to charge a fee for that. Your earnings might be rising as individuals will need to redo their retirement plans which have been decimated. In the same manner, when you do estate planning, planning for college funding or other type of advice-based planning, in this market, it is possible to maintain a good flow of income providing what people want.

Similarly, we have a great deal of people reaching retirement age in this country. They might be ready to harvest assets like real estate or they might be ready to move to a new location. What are the financial ramifications and can you offer fee-based planning? How about the business owners who have had their small business turned the wrong way up? Are there financial projects you’ll be able to provide (e.g. The $5,000 financial make over, where it is possible to provide planning and advice services?

In an age when so many services and products are undifferentiated, like the buying of insurance, you should add other services to maintain value in the eyes of the purchaser. Therefore the more related services you supply, the more valuable you become. For that reason, obtain a registered investment adviser certificate so you’ll be able to be the real adviser.

Simple steps to become an RIA:

1. Contact your state department of securities or other department that handles RIAs

2. Get the application. Complete it and send it in with the fee.

3. In most states, you have to pass the series series 7 exam (you don’t will need a broker dealer and you won’t be a FINRA licensee, you just need to take the exam). It’s straightforward since all you do is take a one week program Monday to Friday and then take the exam and pass it on Saturday. You’re then in the securities business. You may not know much about investing but neither do many securities professionals. Be an affuent life insurance agent and be an RIA.

About the Author: Bob Richards writes on ways for insurance agents to increase their clientele and income. You can subscribe to his articles for

life insurance agents

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