*
Clyde A. Lettsome, Ph.D., P.E.
* Digital Communication Overview
* Digital Modulation Techniques
* Frequency Shift Keying
* Binary Phase Shift Keying

* C...
*
Satellite, Television,
Radio Broadcast

Data Storage, Hard
drives, USB drives

Digital
Communications is
Everywhere

Wirel...
* Reduced bandwidth if modulated on an analog
carrier

* Noise Immunity
* Errors may be detected
* Errors may be corrected...
Convert to
Binary

Data Encoding

Modulation

Transmission Medium
Storage Device

Transmission Medium
Storage Device

Demo...
*
* Frequency Shift Keying (FSK) - transmission

method in which the modulating wave shifts
between two predetermined freque...
* Binary Phase Shift Keying (BPSK) - transmission
method in which the modulating wave shifts
between two phases 180o out o...
* What if a bit(s) is(are) messed up during
transmission or storage?

* Examples: atmospheric noise, intrinsic noise,
scra...
*
* Error detection –Retransmit the block
* Parity
* Cyclic Redundancy Check
* Block Codes

* Error correction – Fix errors ...
* Arguably the most common method of error
detection.

* A single bit called parity bit is added to each
transmitted code....
*Will detect error only if an unexpected
parity is received

* Odd parity transmitted code: [1001|1]

* Received code indi...
* Effectively detect 99.95 % errors.
* Block of data (D) is combined with a frame

check sequence (F) to compose a frame t...
Example: Develop a (7,4) cyclic code from a transmitter
where the data to be transmitted(D) = [1100] and divisor
(P) =[101...
Decoding in the receiver
1100010 /1011 = 1110 <-[T]/[P]
1011
1110
1011
1011
1011
00 <-Remainder

*
* The Hamming distance is the number of bits
that are different between allowed
transmitted code words

* d(code block, re...
* Example: Block code example
* Let 0 be represented by 00.
* Let 1 be represented by 11.

* The code block is two bits lo...
* Example: Block code example

* Let 0 be represented by 00000.
* Let 1 be represented by 00111.

* The code block is five...
* Hamming code correct single bit errors
* Example: Consider D=[1001] the minimum number
of parity bits is 3.

(2n ≥ m+n+1...
* Detects and corrects bursts of errors
* Utilizes Interleaving
* Used in extensively CDs and Cell Phone
Transmission

0

...
*
* Example: TDMA Example
* Cell phone A and cell phone B, A would be

given a certain amount of time to transmit.

* After ...
* Example: CDMA Example of a computer
network

Endpoint 1 (computer)
Let 0 equal 0110
Let 1 equal 1001

Endpoint 2 (comput...
Upcoming SlideShare
Loading in …5
×

Wireless digital communication and coding techniques new

2,932 views

Published on

Lecture about some modern digital communication techniques in this lecture. These techniques will include but are not limited to:
- Code Error Detection and correction
- Parity
- Cyclical Redundancy Coding (CRC)
- Hamming Code
- Digital Modulation Techniques
- Frequency Shift Keying (FSK)
- Binary Phase Shift Keying (BPSK)
- Quadrature Phase Shift Keying (QPSK)
- Channel Access
- Time Division Multiple Access (TDMA)
- Code Division Multiple Access (CDMA)

Published in: Technology, Business
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,932
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
106
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Wireless digital communication and coding techniques new

  1. 1. * Clyde A. Lettsome, Ph.D., P.E.
  2. 2. * Digital Communication Overview * Digital Modulation Techniques * Frequency Shift Keying * Binary Phase Shift Keying * Code Error Detection and Correction Methods * Parity * Cyclical Redundancy Check * Block Error Detection and Correction * Hamming Code * Reed Solomon * Channel Access Methods * Time Division Multiple Access (TDMA) * Code Division Multiple Access (CDMA) *
  3. 3. *
  4. 4. Satellite, Television, Radio Broadcast Data Storage, Hard drives, USB drives Digital Communications is Everywhere Wireless Routers, Cellular networks, Bluetooth * CD, MP3, MPeg
  5. 5. * Reduced bandwidth if modulated on an analog carrier * Noise Immunity * Errors may be detected * Errors may be corrected * Easily manipulate to improve transmission * Time Division Multiple Access (TDMA) * Code Division Multiple Access (CDMA) *
  6. 6. Convert to Binary Data Encoding Modulation Transmission Medium Storage Device Transmission Medium Storage Device Demodulation Data Decoding System dependent * Convert to Original Form
  7. 7. *
  8. 8. * Frequency Shift Keying (FSK) - transmission method in which the modulating wave shifts between two predetermined frequencies. *Figure from Modern Communications by Beasley & Miller *
  9. 9. * Binary Phase Shift Keying (BPSK) - transmission method in which the modulating wave shifts between two phases 180o out of phase. *Figure from Modern Communications by Beasley & Miller *
  10. 10. * What if a bit(s) is(are) messed up during transmission or storage? * Examples: atmospheric noise, intrinsic noise, scratches on CDs, single-event upsets, etc. * Digital coding has many advantages over analog coding * Immunity to noise * Errors can be detected and corrected *
  11. 11. *
  12. 12. * Error detection –Retransmit the block * Parity * Cyclic Redundancy Check * Block Codes * Error correction – Fix errors at the receiver via FEC – Forward Error Correction (Adding more coding bits increases the correction capability but reduces throughput.) * * Block Codes * Hamming Code * Reed Solomon
  13. 13. * Arguably the most common method of error detection. * A single bit called parity bit is added to each transmitted code. * Parity bit makes the code either be even or odd * Even parity makes the total number of ones even * Odd parity makes the total number of ones odd * Example: Code [1001] * Even parity transmitted code: [1001|0] * Odd parity transmitted code: [1001|1] *
  14. 14. *Will detect error only if an unexpected parity is received * Odd parity transmitted code: [1001|1] * Received code indicates error [1101|1] * Received code does not indicate error [1111|1] *Good for random errors (single bit errors but not for burst errors (multiple consecutive errors) *Used with ASCII *
  15. 15. * Effectively detect 99.95 % errors. * Block of data (D) is combined with a frame check sequence (F) to compose a frame to be transmitted (T). * The Frame check sequence is developed by mathematically dividing the block of data by a predetermined divisor (P). * On the receiver side the transmitted frame (T) is divided by the divisor (P). If the remainder is zero then no error is detected. *
  16. 16. Example: Develop a (7,4) cyclic code from a transmitter where the data to be transmitted(D) = [1100] and divisor (P) =[1011]. 1100/1011 = 1110 <-[D]/[P] 1011 1110 1011 1010 1011 010 <-Remainder (Block Check Code) Transmitted(T) = [D R] = [1100010] *
  17. 17. Decoding in the receiver 1100010 /1011 = 1110 <-[T]/[P] 1011 1110 1011 1011 1011 00 <-Remainder *
  18. 18. * The Hamming distance is the number of bits that are different between allowed transmitted code words * d(code block, received block) * d(00000,00100) = 1 * d(00111,00100) = 2 * The greater the Hamming distance the more errors need to be corrected. *
  19. 19. * Example: Block code example * Let 0 be represented by 00. * Let 1 be represented by 11. * The code block is two bits long. * The number of bits that are different between each allowed code word is 2. Therefore the Hamming distance is 2. * If 01 or 10 is received at the receiver then a bit error occurred. * This code can detect one bit error per block but cannot correct a bit error *
  20. 20. * Example: Block code example * Let 0 be represented by 00000. * Let 1 be represented by 00111. * The code block is five bits long. * The number of bits that are different between each allowed code word is 3. Therefore the Hamming distance is 3. * If 00110, 00101, or 00011 is received at the receiver then a bit error occurred. * This code can detect up to three bit error per block and can correct one bit bit error *
  21. 21. * Hamming code correct single bit errors * Example: Consider D=[1001] the minimum number of parity bits is 3. (2n ≥ m+n+1 where m is the length of D and n is the smallest of parity bits that makes the relationship true) * Let P1 = (2,4,5), P2 = (4,5,6), P3 = (5,6,2) and use odd parity. P1 1 P2 0 0 1 P3 1 2 34 567 0 1 0 0 0 1 1  Transmitted *
  22. 22. * Detects and corrects bursts of errors * Utilizes Interleaving * Used in extensively CDs and Cell Phone Transmission 0 1 0 <- 1st Word 0 0 1 <- 2nd Word 0 1 1 <- 3rd Word *
  23. 23. *
  24. 24. * Example: TDMA Example * Cell phone A and cell phone B, A would be given a certain amount of time to transmit. * After that time B is transmitted and the process is repeated * (ABABABABAB……) *
  25. 25. * Example: CDMA Example of a computer network Endpoint 1 (computer) Let 0 equal 0110 Let 1 equal 1001 Endpoint 2 (computer) Let 0 equal 0011 Let 1 equal 1100 * If the system router transmits 01101001, both endpoints receive the information. However, endpoint 1 knows the router is communicating with it because the XNOR and sum of the data equals 4 or 0. 0110|1001 <- Transmitted 0110|1001 <- Stored Codeword 1111|1111 <- 4|4 *

×