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<h6>WT Week 13</h6>

<h1>Cellular Network Technology I</h1>

<p><strong>tldr</strong> - Cellular concept, GSM network architecture, GSM network layer and GSM radio link</p>

<h2>Cellular Phone</h2>

<ul>
	<li>Frequency channels used for radio wave transmission</li>
	<li>Duplex device (has 2 channels to transmit and receive simultaneously)</li>
</ul>

<p><strong>Comparison</strong></p>

<ul>
	<li>LAN: Switch used to interconnect PCs</li>
	<li>Cell phone network: Cell tower via a switching office used</li>
</ul>

<h3>Pop Quiz</h3>

<p><strong>Question</strong> - If a telco has 700 channels, how many users can make use of the cell phone service at the same time?</p>

<p><strong>Answer</strong> - Each user requires 2 channels ∴ max users = 700 / 2 = 350</p>

<h3>Problem - 1 cell tower for whole city</h3>

<ul>
	<li>Not enough channels to support more users</li>
	<li>Cell phones require powerful antennas to reach the cell tower</li>
</ul>

<h3>Solution - Cell Concept</h3>

<ul>
	<li>Divide city into small cells (hexagons)</li>
	<li>Cells can be sized at about 2 x 2 square miles</li>
	<li>Each cell has <strong>base station</strong> (antenna tower and building containing radio equipment)</li>
	<li>Base station uses low-power transmitter</li>
</ul>

<h4>Benefits of Low-power Transmitters</h4>

<ul>
	<li>Allows cellular phones to have longer battery lives</li>
	<li>Allows frequency re-use

		<ul>
			<li>Transmissions from base station do not travel very far outside its cell</li>
			<li>Hence, non-adjacent cells can use same set of frequencies without interference</li>
			<li>By using the same set of frequencies extensively across a big area, it reduces the number of frequencies required to support all users</li>
		</ul>

		<figure><img src="http://i.imgur.com/lmMRF0w.png" alt="Frequency Re-use"/><figcaption>Frequency Re-use</figcaption></figure></li>
</ul>

<h3>Base Station</h3>

<blockquote>
<p>Manages, sends and receives traffic from all mobiles in its geographical area to a distant cellular telephone switch called Mobile Telecommunications Switching Office (MTSO)</p>
</blockquote>

<h3>Mobile Telecommunications Switching Office (MTSO)</h3>

<ul>
	<li>Authenticates wireless customers before establishing connection</li>
	<li>Places calls from land-based telephones to wireless customers</li>
	<li>Switches calls between cells as mobiles travel across boundaries</li>
</ul>

<h3>Cellular Phone Technologies</h3>

<ul>
	<li>Global System for Mobile Communications (GSM)</li>
	<li>Code Division Multiple Access (CDMA)</li>
	<li>Time Division Multiple Access (TDMA)

		<ul>
			<li>Analog and inefficient. Also obsolete</li>
		</ul></li>
	<li>Global System for Mobile Communications (GSM)

		<ul>
			<li>Adopted by Singapore</li>
		</ul></li>
</ul>

<h2>Global System for Mobile Communications (GSM)</h2>

<figure><img src="http://i.imgur.com/8m9ayWa.png" alt="Types of GSM Networks"/><figcaption>Types of GSM Networks</figcaption></figure>
<commit_msg>Fix typo in WT Week13<commit_after><!DOCTYPE html>
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		<meta name="viewport" content="width=device-width, initial-scale=1">
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		<title>WT Week 13</title>
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<body>
	<div class="nav">
		<a href="week11-II.html" id="back" class="top-left-link">< Week 11</a>
		<a href="../../index.html" class="home">Cerebral</a>
		<a href="week14.html" id="next" class="top-right-link">Week 14 ></a>
	</div>

<h6>WT Week 13</h6>

<h1>Cellular Network Technology I</h1>

<p><strong>tldr</strong> - Cellular concept, GSM network architecture, GSM network layer and GSM radio link</p>

<h2>Cellular Phone</h2>

<ul>
	<li>Frequency channels used for radio wave transmission</li>
	<li>Duplex device (has 2 channels to transmit and receive simultaneously)</li>
</ul>

<p><strong>Comparison</strong></p>

<ul>
	<li>LAN: Switch used to interconnect PCs</li>
	<li>Cell phone network: Cell tower via a switching office used</li>
</ul>

<h3>Pop Quiz</h3>

<p><strong>Question</strong> - If a telco has 700 channels, how many users can make use of the cell phone service at the same time?</p>

<p><strong>Answer</strong> - Each user requires 2 channels ∴ max users = 700 / 2 = 350</p>

<h3>Problem - 1 cell tower for whole city</h3>

<ul>
	<li>Not enough channels to support more users</li>
	<li>Cell phones require powerful antennas to reach the cell tower</li>
</ul>

<h3>Solution - Cell Concept</h3>

<ul>
	<li>Divide city into small cells (hexagons)</li>
	<li>Cells can be sized at about 2 x 2 square miles</li>
	<li>Each cell has <strong>base station</strong> (antenna tower and building containing radio equipment)</li>
	<li>Base station uses low-power transmitter</li>
</ul>

<h4>Benefits of Low-power Transmitters</h4>

<ul>
	<li>Allows cellular phones to have longer battery lives</li>
	<li>Allows frequency re-use

		<ul>
			<li>Transmissions from base station do not travel very far outside its cell</li>
			<li>Hence, non-adjacent cells can use same set of frequencies without interference</li>
			<li>By using the same set of frequencies extensively across a big area, it reduces the number of frequencies required to support all users</li>
		</ul>

		<figure><img src="http://i.imgur.com/lmMRF0w.png" alt="Frequency Re-use"/><figcaption>Frequency Re-use</figcaption></figure></li>
</ul>

<h3>Base Station</h3>

<blockquote>
<p>Manages, sends and receives traffic from all mobiles in its geographical area to a distant cellular telephone switch called Mobile Telecommunications Switching Office (MTSO)</p>
</blockquote>

<h3>Mobile Telecommunications Switching Office (MTSO)</h3>

<ul>
	<li>Authenticates wireless customers before establishing connection</li>
	<li>Places calls from land-based telephones to wireless customers</li>
	<li>Switches calls between cells as mobiles travel across boundaries</li>
</ul>

<h3>Cellular Phone Technologies</h3>

<ul>
	<li>Code Division Multiple Access (CDMA)</li>
	<li>Time Division Multiple Access (TDMA)

		<ul>
			<li>Analog and inefficient. Also obsolete</li>
		</ul></li>
	<li>Global System for Mobile Communications (GSM)

		<ul>
			<li>Adopted by Singapore</li>
		</ul></li>
</ul>

<h2>Global System for Mobile Communications (GSM)</h2>

<figure><img src="http://i.imgur.com/8m9ayWa.png" alt="Types of GSM Networks"/><figcaption>Types of GSM Networks</figcaption></figure>

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