2017년 4월 14일 금요일

[Data Communications] Homework 2 Solutions

Solutions

From now on, no more reply to your questions via e-mail.

(This semester there are about 150 students in my classes. I am not able to handle students' questions via email. It may take at least 10 minutes to handle one student's question. You know what I mean .. ^^)

If you have any questions related to the midterm exam, please stop by my office.

Thanks,

[Question]

강의자료(long version) 12페이지의 수식을 보면, Nmax = 1/c * B * r이라는 식이 나와있는데, ( 첫번째 식 )
8페이지에 나와있는 data rate, signal rate 관련 식을 보면, S = c * N * 1/r인 식이 나와있습니다. ( 두번째 식 )
두번째 식을 정리하면 N = 1/c * S * r으로 바뀌는데, 이것과 첫번째 식을 비교하면,

Nmax = 1/c * B * r
N = 1/c * S * r이 됩니다.
S signal rate(baud rate)라고 배웠는데, 왜 이렇게 S B가 같게 되는 지 모르겠습니다.

Bandwidth, Signal rate는 단위부터 다른데, 이 부분이 헷갈립니다.


  1. We can say that the baud rate determines the required bandwidth for a digital signal: More changes in the signal mean injecting more frequencies into the signal. (Frequency means change!! change means frequency!! Namely, baud rate and frequency imply that some change rates per second)
  2. From the lecture notes, each level corresponds to one signal element.

  • From 1 and 2, we can roughly say that the bandwidth (range of frequencies) is proportional to the signal rates (baud rate). 
  • Thus, the minimum bandwidth can be given as, 
    • S  is proportional to B. 
    • B_min = c X  N X (1/r) ⇒ B ≤ c X  N X (1/r) ⇒ (1/c) X B X r ≥ N (= N_max)

[Problem 37] Errata

Signal 10V -> 10W
Signal 5mV -> 5mW



2017년 4월 11일 화요일

[Data Communications] A new version of HW2 (Due: April 14)

I just removed redundant questions.

[Guidelines]

Type your homework using the MS-Word or another word processor!!
Otherwise, you will get ZERO point

Please submit your HW to the report box in front of NC Lab, where located at office #318, 자연대연구실험동 (Building# 313). Due time: by 7:00 pm (or much earlier is possible).

HW2


The midterm exam topics of C++, Open S/W, and data communications

The midterm exam of C++

covers the topics addressed in the first class through topics addressed on April 11 (i.e., constructors and destructors).

The midterm exam of Open S/W

covers the topics addressed in the first class through topics addressed on April 11 (i.e., makefile and gdb).

You do not have to study stuff related to the Git!!


The midterm exam of data communications

covers Chapter 1 through Chapter 4's Bipolar line coding schemes.

You do not have to study topics beyond Bipolar line coding schemes (e.g., Multilevel: 2B/1Q ...)

Keep up with your study~

Wish you best luck!!


[C++] Source codes on April 11

Download


2017년 4월 6일 목요일

[C++, Open S/W, Data Communications] Midterm Exam - April 18

Midterm examinations will be conducted on April 18.
They will be taken at the same classroom during the same class hour.
I will let you know what topics you need to study for the upcoming midterm exams.

Keep up with your study!!