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# Cellular System

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I need the answers to the questions so that my study group can have the correct information in preparation for a group assignment. This is just for reference and will not be submitted for a grade to any school.

Answer the following questions. Explain your answer and show your work in a logical manner. Use any needed formula -- show the formula, the substitutions made, and explain why.

1. A TDMA cellular system uses a 200 KHz bandwidth carrier, which carries 8 channels. What defines or determines each channel, and how much bandwidth does each channel occupy and why?

2. Define what is meant by power efficiency and spectral efficiency for a modulation scheme? What is the measure used for each?

3. Order the following modulation types in terms of spectral efficiency (best to worse) and explain why (be specific, show a number and how you got it): 64-QAM, QPSK, 8-PSK, and BPSK. Assume that the r=0, perfect filtering.

4. Propagation in a wireless channel is sometimes modeled using the propagation index n. Explain how the propagation index n varies and why. If there are two channels, where n=2 for the first one and n=3 for the second one (as for both the same power is transmitted and the same modulation/coding is used), in which channel will the signal be detectable further away and why?

5. Describe why multipath occurs in wireless. Describe fast fading, and some technique to counter it.

6. Describe how direct sequence spread spectrum (DSSS) suppresses interference from other transmissions in the same frequency band.

7. A telephone switching board can handle 120 phones. Assuming the following, determine the outgoing traffic intensity and the number of channels:
* On average 5 calls/hour per phone
* 60% of all calls made are external
* Average call duration time is 4 minutes
* QoS = 0.9%

Please refer to the attachment for multiple choice questions.

https://brainmass.com/computer-science/cpu-utilisation/cellular-system-329512

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## Immune System: Allergies, Treatments and Management

Many of the most devastating human diseases result from an attack of various microbes (viruses, bacteria, fungi) on the human body. The flu epidemic of 1918 killed 22 million Americans and Europeans in just 18 months, and our ongoing war against the HIV virus is still waging. In order to fight against this onslaught, the human body developed a sophisticated system that is able to screen, identify, and destroy invading microorganisms before they cause severe damage to the human body. This system, called the Immune System, continuously monitors our blood stream for the presence of foreign cells or molecules. Once an infection is recorded, the system is able to launch a full-scale attack directed against the specific invader. Organisms with compromised immune systems, or those lacking immune systems, cannot survive for long. Infections that are able to escape or destroy the immune system's surveillance (such as HIV) are extremely dangerous.

You work for a company which creates posters and informational material for doctor's offices. You have to prepare information on the immune system.

The immune system is composed of several types of cells whose coordinated, concerted effort is required for screening, identification, and eventual purging of microbial invasion. This is especially evident when the body launches the Specific Immune Response, comprised of both Humoral and Cell-Mediated Immunity. Create a network diagram (flow chart) showing the components of the Specific Immune Response that shows the interaction and relationships of the cells in both Humoral & Cell-Mediated Immunity.

Sometimes too much of a good thing is not so good. When our immune system detects a foreign molecule and mounts an immune response, it is sometimes unaware that the foreign molecule is actually completely harmless. Many cases of allergies are a result of an aggressive immune response against an organism or molecule that harbors no real threat to our body.

What are the components of our immune system involved in allergic reactions, and how does treatment of allergies manage to control them?

Create a one-page brochure designed to explain the causes of allergies and tips for allergy management to a non-scientific audience

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