Characteristics & Quality Attributes of Embedded Systems

 

CHARACTERISTICS & QUALITY ATTRIBUTES OF EMBEDDED SYSTEMS

 

Unit Structure

Objectives

1. Introduction

2. Characteristics of Embedded System

3. Quality Attributes of Embedded System

Operational Attributes

Non Operational Attributes

 

OBJECTIVES

After reading this chapter you will:

Understand the characteristics of Embedded system

Understand the attributes related to quality of embedded system.

 

1. INTRODUCTION

The characteristics of embedded system are different from those of a general purpose computer and so are its Quality metrics. This chapter gives a brief introduction on the characteristics of an embedded system and the attributes that are associated with its quality.

 

2. CHARACTERISTICS OF EMBEDDED SYSTEM

Following are some of the characteristics of an embedded system that make it different from a general purpose computer:

 

Application and Domain specific

An embedded system is designed for a specific purpose only. It will not do any other task.

Ex. A washing machine can only wash, it cannot cook

Certain embedded systems are specific to a domain: ex. A hearing aid is an application that belongs to the domain of signal processing.

 

Reactive and Real time

  

 

Certain Embedded systems are designed to react to the events that occur in the nearby environment. These events also occur real-time.

 

Ex. An air conditioner adjusts its mechanical parts as soon as it gets a signal from its sensors to increase or decrease the temperature when the user operates it using a remote control.

 

An embedded system uses Sensors to take inputs and has actuators to bring out the required functionality.

 

Operation in harsh environment

 Certain embedded systems are designed to operate in harsh environments like very high temperature of the deserts or very low temperature of the mountains or extreme rains.

 

These embedded systems have to be capable of sustaining the environmental conditions it is designed to operate in.

 

Distributed

Certain embedded systems are part of a larger system and thus form components of a distributed system.

 

These components are independent of each other but have to work together for the larger system to function properly.

 

Ex. A car has many embedded systems controlled to its dash board. Each one is an independent embedded system yet the entire car can be said to function properly only if all the systems work together.

 

Small size and weight

 An embedded system that is compact in size and has light weight will be desirable or more popular than one that is bulky and heavy.

 

Ex. Currently available cell phones. The cell phones that have the maximum features are popular but also their size and weight is an important characteristic.

 

For convenience users prefer mobile phones than phablets. (phone + tablet pc)

 

Power concerns

 

It is desirable that the power utilization and heat dissipation of any embedded system be low.

If more heat is dissipated then additional units like heat sinks or cooling fans need to be added to the circuit.

 

If more power is required then a battery of higher power or more batteries need to be accommodated in the embedded system.

 

 

3. QUALITY  ATTRIBUTES  OF EMBEDDED SYSTEM

These are the attributes that together form the deciding factor about the quality of an embedded system.

 

There are two types of quality attributes are:-

 

Operational Quality Attributes.

 

These are attributes related to operation or functioning of an embedded system. The way an embedded system operates affects its overall quality.

 

Non-Operational Quality Attributes.

 

These are attributes not related to operation or functioning of an embedded system. The way an embedded system operates affects its overall quality.

 

These are the attributes that are associated with the embedded system before it can be put in operation.

 

Operational Attributes

Response

 

Response is a measure of quickness of the system.

It gives you an idea about how fast your system is tracking the input variables.

Most of the embedded system demand fast response which should be real-time.

 

Throughput

 Throughput deals with the efficiency of system.

It can be defined as rate of production or process of a defined process over a stated

period of time.

In case of card reader like the ones used in buses, throughput means how much transaction the reader can perform in a minute or hour or day.

 

Reliability

 

Reliability is a measure of how much percentage you rely upon the proper functioning of the system .

 

Mean Time between failures and Mean Time To Repair are terms used in defining system reliability.

Mean Time between failures can be defined as the average time the system is functioning before a failure occurs.

 

Mean time to repair can be defined as the average time the system has spent in repairs.

 

Maintainability

 

Maintainability deals with support and maintenance to the end user or a client in case of technical issues and product failures or on the basis of a routine system checkup

 

It can be classified into two types :-

 

Scheduled or Periodic Maintenance

o This is the maintenance that is required regularly after a periodic time interval.

Example :

Periodic Cleaning of Air Conditioners

Refilling of printer cartridges.

 

2. Maintenance to unexpected failure

 

This involves the maintenance due to a sudden breakdown in the functioning of the system.

Example:

 

Air conditioner not powering on

Printer not taking paper in spite of a full paper stack

Security

   Confidentiality,  Integrity and Availability are three  corner stones of       information security.

 

Confidentiality deals with protection data from unauthorized disclosure.

Integrity gives protection from unauthorized modification.

Availability gives protection from unauthorized user

Certain Embedded systems have to make sure they conform to the security measures.

Ex. An Electronic Safety Deposit Locker can be used only with a pin number like a password.

 

Safety

 

Safety deals with the possible damage that can happen to the operating person and environment due to the breakdown of an embedded system or due to the emission of hazardous materials from the embedded products.

 

A safety analysis is a must in product engineering to evaluate the anticipated damage and determine the best course of action to bring down the consequence of damages to an acceptable level.

 

Non Operational Attributes

 

Testability and Debug-ability

 

 It deals with how easily one can test his/her design, application and by which mean he/she can test it.

 In hardware testing the peripherals and total hardware function in designed manner

  Firmware testing is functioning in expected way

 Debug-ability is means of debugging the product as such for figuring out the probable sources that create unexpected behavior in the total system

 

Evolvability

  For embedded system, the qualitative attribute “Evolvability” refer to ease with which the embedded product can be modified to take advantage of new firmware or hardware technology.

 

Portability

 

  Portability is measured of “system Independence”.

 An embedded product can be called portable if it is capable of performing its operation as it is intended to do in various

environments irrespective of different processor and or controller and embedded operating systems.

 

Time to prototype and market

 

Time to Market is the time elapsed between the conceptualization of a product and time at which the product is ready for selling or use

 

Product prototyping help in reducing time to market.

Prototyping is an informal kind of rapid product development in which important feature of the under consider are develop.

In order to shorten the time to prototype, make use of all possible option like use of reuse, off the self component etc.

 

Per unit and total cost

 

Cost is an important factor which needs to be carefully monitored. Proper market study and cost benefit analysis should be carried out before taking decision on the per unit cost of the embedded product.

 

When the product is introduced in the market, for the initial period the sales and revenue will be low

 There won’t be much competition when the product sales and revenue increase.

During the maturing phase, the growth will be steady and revenue reaches highest point and at retirement time there will be a drop in sales volume.