Analog Communication over Wireless Networks

1
Senior Project Computer Engineering - 2005
Analog Communication over Wireless Networks
By Michael Pascucci Advisor Professor
Spinelli

• Purpose
• Voice-over-Internet-Protocol (VoIP) currently
  exists as a free telephone alternative. PCs
  connected over the Internet can access telephones
  using phone numbers converted to IP addresses.
  
  - My project
  allows for portable VoIP, using Microcontrollers
  (cell phones) connected over a
  wireless Internet network addresses.
  
  - Please note Wireless
  RS-232 was used, not Wireless Internet

• Constraints
• Telephone Quality Audio
  
  
  Sample 8000 sample/sec (8 KHz) with 8
  bits/sample
  
  Output at gt 8 KHz
  (in 2n KHz increments)
  - Minimal
  Propagation Delay (lt 200 ms)
  
  - Serial RS232 protocol-transmission
  
  115200 baud rate
  (bits/second) to prevent data loss
  8-n-1 transmission
  format (8 data bits, no parity, 1 start/stop bit)
  - 8 bit
  Analog-to-Digital Converter (ADC) / 12 bit
  Digital-to-Analog (DAC)

Wireless VoIP Cell Phone
Interpolating the signal on output allows a more
accurate reproduction without increasing the
input Sample Rate
Input signal 8 KHz sample rate
Output signal interpolation at 16 KHz
Output signal no interpolation
System Schematic
Dedicated Serial-to-Wireless Devices
(replace with Serial-to-WiFi for use
with the Internet)
Functional Diagram
Analog voice to Digital Digital Data to Serial
Port as IP Packets Serial to Wireless To
Internet
Digital to Analog voice IP Packets from Serial
Port to Digital Data Wireless to Serial From
Internet
Microcontrollers

Headphone to DAC
Headphone to DAC
Mic to ADC
Mic to ADC