Comp [34]49 midterm exam study guide

The midterm is Thursday, October 23, 2008

This will be an OPEN BOOK, OPEN NOTE exam

Material Covered:

Antennas: Stallings Chapter 5, supplemental materials
	Why hackers eat so many pringles
	Antenna gain, effective area: 5.1
	Line-of-sight problems: 5.3
		Attenuation
		Thermal noise
		Eb/No
		Multipath
	Fading & Multipath: 5.4
		You will <b>not</b> need to know the three fading models
		(Gaussian, Rayleigh, Rician) on p 118)
	Forward Error Correction, p 119
	Diversity and interleaving (pp 120-122)
	
Basic modulation techniques: Stallings Chapter 6 Section 2:
	Digital Data, Analog signal
	(with some implicit inclusion of Chapter 2)
	Time domain v Frequency domain
	ASK, FSK, MFSK, PSK, MPSK
	Eb v N0 graphs
	Spectrum (bandwidth) requirements

Error-correcting codes: Stallings Chapter 8: 8.1, 8.2, 8.3
	mod-2 arithmetic (in §8.1, under CRC; see esp. example 8.3)
	CRC
	block codes, Hamming distance
	Cyclic codes: §8.2, p 210, esp. Example 8.8 and Table 8.3
	   BCH codes: p 214, but note that most of the details are under
	   	"cyclic codes"
	Convolution codes: §8.3
		encoding
		decoding
		NOT Viterbi algorithm for error correction
	
"Wi-fi" (802.11) basics: Stallings Chapter 14, sections 2-4
	backoff strategy
	hidden-node issues
		what is the "hidden node problem"?
		How does RTS/CTS address this?
	14.1: Note that LLC is not explicitly used in 802.11; you can ski[pm] this
	14.2: 802.11 services. Important!
	14.3: 802.11 MAC, both DCF and PCF. Backoff, IFS, etc. Also important!
	14.4: 802.11 physical layer: FHSS v DSSS. Just skim the beginning.
	
Spread-spectrum techniques of chapter 7 will *not* be covered.
	
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Some study questions:


1. How is the wi-fi transmission algorithm different from Ethernet?

2. Why doesn't wireless do collision detection?

3. Give an application for using a high-gain wifi antenna

4. Correct a simple block-code error

5. Decode or encode a few bits with a convolution code

6. Frequency (bandwidth) use of ASK

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Some of Stallings' end-of-chapter exercises

5.4, 5.5 (cute) on antenna size v wavelength

5.9, on received power (use the indicated equation in the book)

5.15: Thermal noise problem

Added by me: estimate the thermal noise for wi-fi:
	bandwidth 30 MHz
	Temp 300K (m.o.l.)
How does this compare with ~1 watt transmitter power?
How does it compare with 1milliWatt power at the receiver?

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6.2: use book formulas to calculate Eb/N0 for two cases.
(This is easier than it looks; Eb = energy per bit is computed by
energy rate in watts (given) multiplied by bit length.)

6.4: Again, this is easier than it looks.
Bandwidth Efficiency is defined on p 138, as R/B_T, or
	DataRate / TransmissionBandwidth
(note that this can be >> 1)

6.5 is similar: using the formulas in the section, evaluate the
bandwidth requirement

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Problems from chapter 8: to come!

8.1

8.5: modest manual division

8.9

8.13

8.15

8.17

8.20?

8.21

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14.1: draw a typical timeline of events within a BSS