Wireless Communications and a Priority

Access Protocol for Multiple Mobile

Terminals in Factory Automation

SUBMITTED BY :-

SANDEEP KR. MAHAWAR

2011UEC1303

EC-3

Contents

INTRODUCTION

WIRELESS ACCESS INFRASTRUCTURE

WIRELESS ACCESS PROTOCOLS

PERFORMANCE EVALUATION AND NUMERICAL RESULTS

CONCLUSION

Introduction

MANUFACTURING automation requires many mobile terminals. A robot is a good

example of mobile terminals in manufacturing automation. Recently, multirobot

systems have received much attention. The main reason for setting up a multirobot

system is because two or more robots are necessary for performing manufacturing tasks, for example, carrying large objects. The problem then arises from the fact

that coordination of these mobile devices becomes important. Recently, using

local area network (LAN) for such operation has become an active research topic.

Since 1980’s, the hardwired, token bus-based manufacturing automation protocol

(MAP) network has been widely accepted for computer integrated manufacturing.

Wireless LAN

A wireless local area network (WLAN) would lessen the

time and cost of factory installation, restructuring and

network maintenance and may allow mobile, hand-held

communication users. In other words, a WLAN is a

relatively low cost network of communicating control

information and data to and from any mobile and fixed

terminals in a factory automation application.

WIRELESS ACCESS INFRASTRUCTURE

The following subsection will describe our proposed

wireless access infrastructure

The Current Standards

Adding Wireless Strategy

CDMA Techniques

The Current Standards

Two widely used standards are the proposed manufacturing

automation protocol (MAP) and Fieldbus (IEC TC65C).

For convenience of documentation and separation of

functionality, MAP is referenced on the seven-layer ISO

model while Fieldbus specifications are partitioned into five-

layer structures.

These two standards characterize two different layer

structures.

Adding Wireless Strategy

The most desirable application of wireless access in factory

integration is communication to and from mobile devices such as

AMR’s and robots that may be clustered in islands of automation.

There exist moving difficulties when these mobile devices are wired to the network. Therefore, we propose that each island can be covered

by a base station. There could be several base stations in each

factory floor, depending on the size of subnetworks and the number

of mobile devices. Each base station controls a radio coverage area

(RCA), and the RCA’s may be nonuniform and partially overlapping.

CDMA Techniques

Most current WLAN products employ the code division

multiple access (CDMA) techniques. The CDMA systems

use spread spectrum technologies that are very suitable

for indoor communication due to their capabilities in anti-

multipath, antijamming, and low probability of

interception and detection. In addition, the capability of

allowing asynchronous, overlapped transmissions may be

the key for commercial applications.

WIRELESS ACCESS PROTOCOLS

Multiple access schemes used in traditional LAN’s include random access

(Aloha), token passing and polling access (token bus or ring), deterministic

access (TDMA/FDMA), and demand access (handshake).

PERFORMANCE EVALUATION AND

NUMERICAL RESULTS

we classify the traffic class into type I and type II. A type-I traffic is the traffic that

carries timely information that has to reach the supervisory computer on time,

otherwise, it becomes useless. This kind of traffic must have priority over the other traffic. Also, it is critical to errors, thus requires more reliable transmission. A type-II

traffic, on the other hand, is less sensitive to delay (latency) and may not be

critical to errors (can be retransmitted).

Probability that an idle type-I unit will generate packet for transmission at next

frame is

Probability that an idle type-II unit will generate packet for transmission at next

frame is

The average delay normalized to a frame period as

The average probability of successful handshaking

CONCLUSION

We can conclude that by using the wireless

communication and suitable protocol, the

installation and maintenance cost can be

reduced without deteriorating its performance,

and it also provides the flexibility in factory

automation planning and restructuring.