Design of a Wireless Communication Protocol

1
Design of a Wireless Communication Protocol

• Application Wireless Voting System
• By Elfred Pagán Morales
• Advised By Dr. Manuel Jimenez

2
Objectives

• Design a Centralized reliable wireless networking
  protocol for use in embedded devices
• The protocol should be layered and extensible so
  it can be used in a wide array of applications

3
Development Tools

• Hardware
• Motorola HC08
• Low Power UHF Data Transceiver Kit
• Software
• PE Micro Motorola Development Kit

4
Protocol DefinitionLayer Diagram
5
Protocol Definition

• Protocol Contains four basic layers
• Physical Layer Hardware Interface
• Transport Layer Sends and Receives data
• Session Layer Controls Unit Addressing and
  Individual Communication Sessions
• Application Layer Performs individual
  application commands

6
Physical Layer

• BiM 418F Tranceiver
• Low Power Tranceiver
• 40kbits/s
• Range
• 30m in building
• 120m open ground
• Buffering Logic
• Logic circuit needed to interface the
  microcontroller (Motorola HC08) and the Tranceiver

7
Hardware Interface
Antenna
Radiometrix BiM Transceiver
HC08 Development Kit
8
Transport Layer

• Provides a reliable transmission to all layers
  above it.
• Transmit and Receive Routines
• Error Correction
• Automatic repeat Request
• When a packet is sent the sender waits for an
  acknowledge packet as verification
• If acknowledge is not received in a due time or
  recipient requests a retransmit sender
  retransmits the packet
• After a given amount of retransmits the senders
  stops retransmitting and the other unit is
  assumed offline

9
Transport Layer

• Data Encoding for reliable transmissions.
• Used to maintain synchronization for the
  tranceiver
• Adds Starting and ending Delimiters, and CRC
  bytes to packet
• View of Packet

SD
CS
ED
10
Session Layer

• Network Level Control
• Controls addressing of individual units
• Adds Source and Destination Addresses to Packets
• Routes packets to each unit
• Supports 256 addresses
• 1 server
• 254 individual units
• Broadcast packets

11
Session Layer

• Session Level Control
• Adds session control byte to packet used to issue
  session commands such as open and close session
• Uses a Client/Server model
• Server polls each client until one wishes to
  establish a session
• This is done to avoid unnecessary packet loss
• View Of Packet

DA
SA
SC
12
Application Layer

• Controlled by individual applications
• Each application declares how this entry will be
  used
• Wireless Voting System
• Adds Application Control, Data Size and Data
  Field to packet.
• View of Packet

DATA
DS
AC
13
Application Layer

• Wireless Voting System
• Application Control byte is used to specify the
  purpose of the following data
• Examples
• Send Voting Rules
• Retrieve votes
• Others

14
Packet Design Wireless Voting System
DA
SD
SA
DATA
CS
ED
SC
DS
AC
8 - 263 bytes
_at_ Application Layer Level
_at_ Transport Layer Level
_at_ Session Control Layer Level
15
Current Achievements

• Fully implemented the transport layer
• Reliable Send and Receive subroutines
• Manchester Encoding used to maintain
  synchronization
• Automatic Repeat Request
• Fully Implemented the Session Layer.
• Packet routing
• Session Commands

16
Future Work

• Thoroughly test the protocol
• Interface with Application Layer
• Flash Program to MCU

17
Questions?