IEEE P802.11

Wireless Access Method and Physical Layer Specification

DATE:	July 2, 1991

TITLE:	IEEE 802.11 DESIGN GOALS QUESTIONNAIRE

AUTHORS:	Larry Van Der Jagt

Knowledge Implementations, Inc.	Telephone: 914-986-3492

32 Conklin Road	Facsimile: 914-986-6441

Warwick, NY 10990 USA

Chandos A. Rypinski,

Chief Technical Officer

LACE, Inc.	Telephone: 707 765 9627

921 Transport Way	Facsimile: 707 762 5328

Petaluma, California 94954 USA

Table of Contents	Page

INTRODUCTION, GENERAL INSTRUCTIONS AND ASSUMPTIONS	1

APPLICATION DESCRIPTION	2

TRAFFIC DESCRIPTION	2

SYSTEM TOPOGRAPHY DESCRIPTION	3

CONCLUSION	4

ATTACHMENT A:

QUESTIONNAIRE	Q1

I.	APPLICATION	Q1

II.	TRAFFIC DESCRIPTION	Q1

III.	SYSTEM TOPOGRAPHY DESCRIPTION	Q3

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IEEE 802.11 DESIGN GOALS QUESTIONNAIRE

INTRODUCTION, GENERAL INSTRUCTIONS AND ASSUMPTIONS

As part of our efforts to arrive at a set of design goals which can be used to develop and evaluate proposals for the IEEE 802.11 standard, the following questionnaire has been developed.

The intent of this questionnaire is to obtain information about a particular application that the responder is interested in implementing on an IEEE 802.11 LAN and to use those responses to develop a set of system design goals.

In recognition of the fact that individual responders may have a variety of applications in mind, we are asking that an individual questionnaire be filled out for each application.

We recognize that the answers to the questions which are posed in this questionnaire may not be readily available. We hope that the responders will make the investigative effort necessary to find the answers or where answers can only be postulated, to do their best job at presenting reasonable responses. Our objective is to be able to come up with one or more sets of numerical specifications which can serve as design goals for the development of a standard.

Many of the previous presentations, and much of the time which the committee has spent to date, has concentrated on market-oriented functional requirements. There seems to have been fairly broadbased support for one particular market-oriented requirement. In this questionnaire we will assume that the market-oriented requirement that an IEEE 802.11 can operate in some mode without requiring a pre-installed infrastructure will be met. With the exception of this assumption we have attempted to keep this questionnaire unbiased with respect to a particular implementation in an attempt to obtain technical specifications that are not tempered by the constraints of a perceived direction.

For the purposes of this questionnaire we propose the following definitions:

STATION - A device which uses or could benefit from a communication path to other devices.

DIRECTIONALITY FACTOR - A parameter devised to describe the ratio of message traffic being transmitted by the station to the message traffic being presented to a station. If a station receives 100 messages of average length 100 bits/message from other networked devices for every 40 messages of average length 50 bits/message that it transmits (including all messages that are transmitted as responses) the Directionality Factor for the station is 20% (( (transmitted message * average length)/(received messages * average length)) * 100 percent). The Directionality Factor for the network feeding the station is the inverse of this number or 500%

HOST - A station that requires information to further enhance the functionality of an application. For example a data processing machine which produces management reports based on input from other machines on the network.

SERVER - A station whose sole purpose for communicating on a network is to provide a service to other stations on the network. For example a station that has as its sole function the sharing of a hard disk among stations on the network.

PRE-INSTALLED INFRASTRUCTURE - Equipment which is placed into a geographical area to be serviced by an IEEE 802.11 LAN in order to enable communication service in that area. This equipment is typically not associated with a given station although it may contain station hardware which is intended to remain in place for the lifetime of the requirement to provide IEEE 802.11 service in the geography.

BASIC COVERAGE AREA - The geographic area that has communication service available at more than the minimum percentage of its area during more than the minimum percentage the time specified in the PAR for conformance to IEEE 802.11 without the support of pre-installed infrastructure.

LOCAL AREA NETWORK - A group of stations and associated interconnect hardware that has the capability to communicate over a bounded geographic area (typically no larger than a college campus) under administrative control of one entity.

TOTAL COVERAGE AREA - The geographic area served by a local area network. It has communication service available at more than the minimum percentage of its area during more than the minimum percentage the time specified in the PAR for conformance to IEEE 802.11 with the support of all equipment installed including (if it is present) pre-installed infrastructure.

APPLICATION DESCRIPTION

Please provide a brief description of the application for which you are providing data with this questionnaire. The breakup of applications and the determination of the scope that a given example of this questionnaire should address is left to the discretion of the responder. It may be that the responder chooses to provide two instances of this questionnaire for a single application based on perceived differences in the requirements of the application in different environments. For example, the communications needs of a network used only for word processing in a large aerospace-oriented firm with an engineering work floor the size of a football field, populated by engineers with desks and stations on a 20'*20' foot grid, may be substantially different than the communication needs of a network used only for word processing in a law firm in which all of the lawyers (or their secretaries) have individual offices separated by fixed partitions. If the responder finds that he is having difficulty providing one set of answers to the questions asked, perhaps it is necessary to breakdown the application into additional instances of this questionnaire.

TRAFFIC DESCRIPTION

Media Usage per

Station Considerations

The questions in this section are intended to aid in determining the burst and average message traffic which will be generated by a typical station in a network running the current application. We have provided these questions as an aid in determining this parameter. It is our intention to calculate media usage per station based on the assumption that the files transmitted will be selected at random in a uniformly distributed way from among all the files that are in the system and transmitted at the frequencies defined in other questions. We will augment these file transfer numbers with other traffic related information supplied in the question about other traffic. In addition, any IEEE 802.11 protocol which is established will introduce additional message traffic overhead. The impact of this traffic on media usage per station will be taken into account as actual protocols are presented for consideration. If the responder to this questionnaire believes that the methodology described above will not yield a reasonable approximation of the media usage per station requirements of the application being described please explain the reason for this belief in the space provided.

This section of questions is divided up into questions concerning file size, questions concerning transfer frequency, and questions concerning transfer destination. As a suggestion many operating systems provide the capability to list directories by size. Listing typical directories on your system by size should help in answering some of these questions.

The questions on destination distribution ask for the Directionality Factor (DF) (a detailed definition of this parameter appears in the definition section above) for communications of each type listed.

The final question in this section deals with other factors not mentioned above. Please list any other known sources of message traffic on the network, such as higher level protocols which require periodic service and provide information regarding the nature of this traffic in terms of typical message size, maximum message size, typical and maximum hourly frequency, typical and maximum five minute frequency, destination distribution, and Directionality Factor.

Traffic Timing

Constraint Considerations

The set of questions presented next is intended to quantify the amount of time a station can wait for communications to occur under a variety of conditions and what the tolerance of a station for variability in these parameters is. We expect that the immediate response of many responders may be that response time is not critical in their application. We request that anyone planning to respond in this manner please make the effort to find out what the timeout and retry parameters are for any existing network they may have installed and to provide this information in response to the questions asked. If you feel that the existing numbers do not accurately reflect the actual requirements of the application please elaborate on why there is a difference.

SYSTEM TOPOGRAPHY

DESCRIPTION

The questions in this section are intended to provide information regarding the density of users in a particular network geography as dictated by needs of the application and the attenuation characteristics of the geography involved. These questions deal with both the question of topography of an individual network and of topography associated with the co-location of networks.

Basic Coverage Area Characteristics

The questions in this section are intended to quantify the requirements for communications without the support of a fixed infrastructure. Please indicate yes or no for each item to indicate whether the application you are describing must operate in geographies with the listed characteristics.

Local Area Network Characteristics

The questions in this section are intended to quantify the size of a given local area network. These questions apply to the total geographic area serviced by a network administration which may be made up of a number of basic coverage areas. Questions regarding the type of topography (i.e. type of partitioning, etc.) should be answered in this section with information related to things that separate Basic Coverage Areas rather than things within a Basic Coverage Area.

Neighborhood Demographics

The questions in this section are intended to quantify the degree of nearness and inter-penetration that needs to be supported in the IEEE 802.11 environment. Questions regarding partitioning apply to partitioning that exists between Total Coverage Areas of adjacent Local Area Networks.

Dynamic Topography Considerations

The questions in this section are intended to quantify the degree to which the network topography is time- dependent and the ways in which it varies on a time dependent basis.

CONCLUSION

Thank you for taking the time and effort to review this document and fill out the attached questionnaire. We have tried to minimize the pain associated with filling out this questionnaire. Unfortunately, as we are sure you are aware, wireless networking has many more parameters than wired networking and hence, the problem of generating design goals is not a simple one. Thank you again for your time in providing this information.

ATTACHMENT A

IEEE 802.11 DESIGN GOALS QUESTIONNAIRE

I.	APPLICATION

What application are you addressing with this instance of this questionnaire?

II. TRAFFIC DESCRIPTION

File Size Distribution

Number of files in your system under 10K bytes in size

Number of files in your system between 10K bytes and 100K bytes in size

Number of files in your system greater than 100K bytes in size

Message Time Distribution

Typical number of files transferred per hour

Maximum number of files transferred per hour

Typical number of files transferred per five minutes

Maximum number of files transferred per five minutes

Destination Distribution

(Note: All directionality factors (DF) are from point of view of your station. If your station does not generate a given type of traffic, please enter N/A.)

DF for station to station transfers within your department

DF for station to station transfers within your premises

DF for station to station transfers outside your premises

DF for station to host transfers within your department

DF for station to host transfers within your premises

DF for station to host transfers outside your premises

DF for station to server transfers within your department

DF for station to server transfers inside your premises

DF for station to server transfers outside your premises

Other Traffic

Traffic Timing Constraint Considerations

How long can a wireless station wait for communication service after its initial request to become part of the network?

If you have an existing network how long will a station wait before its initial registration request times out?

If you have an existing network how many times will a station retry prior to giving up its attempt to register?

How long can a wireless station wait for communication service if it is not provided when it has a message and it is part of a network?

If you have an existing network how long will a station wait before timing out if it is not provided communication service when it has a message and it is part of a network?

If you have an existing network how many times will a station retry if it is not provided communication service when it has a message and it is part of a network?

How long can a wireless station wait for acknowledgment of message transmission if it is part of a network, it has transmitted its message and it requires an acknowledgement?

If you have an existing network how long will a station wait before timing out for acknowledgment of message transmission if it is part of a network, it has transmitted its message and it requires an acknowledgment?

If you have an existing network how many times will a station retry if it is part of a network, it has transmitted its message and it requires an acknowledgment?

Does this application have a requirement for the waiting times in any of the categories listed above (initial registration, service when a message is available for transmission, delivery time of a specific message) not to vary from one attempt to the next, and if so how much variation can be tolerated.

III. SYSTEM TOPOGRAPHY DESCRIPTION

Basic Coverage Area

Please indicate whether or not the application you are reporting on must operate in the type of topography described. Please describe the required topography if "OTHER" is selected. Please note that this section deals with a Basic Coverage Area as defined in the detailed discussion document attached.

Please answer yes or no to each of the following categories:

OPEN AREAS WITH MOVABLE PARTITIONS

ROOM AND HALLWAY WITH PERMANENT PARTITIONS

LARGE UNCLUTTERED ENCLOSED AREAS

LARGE CLUTTERED ENCLOSED AREAS

OTHER

Please indicate the physical size of the geography that this application typically must support. Please note this question applies to a Basic Coverage Area.

Floor Space in Square Feet

Ceiling Height in Feet

Minimum

Typical

Maximum

Please indicate the total number of stations required for this application both wired and wireless. Please note this question applies to a Basic Coverage Area.

Total Number of Stations

Minimum

Typical

Maximum

Please indicate the number of wireless stations required for this application. Please note this question applies to a Basic Coverage Area.

Number of Wireless Stations

Minimum

Typical

Maximum

Local Area Network Characteristics

Please indicate whether or not the application you are reporting on must operate in the type of topography described. Please describe the required topography if "OTHER" is selected. Please note that this section deals with topographical features which divide Basic Coverage Areas from each other. Questions about size should be answered for the total LAN coverage area.

Please answer yes or no to each of the following categories:

OPEN AREAS WITH MOVABLE PARTITIONS

ROOM AND HALLWAY WITH PERMANENT PARTITIONS

LARGE UNCLUTTERED ENCLOSED AREAS

LARGE CLUTTERED ENCLOSED AREAS

OTHER

Please indicate the physical size of the geography that typically must be supported. Please note this question applies to the total LAN.

Area in Square Feet

Vertical Height in Feet

Minimum

Typical

Maximum

Please indicate the total number of stations required for this application both wired and wireless. Please note this question applies to the total LAN.

Total Number of Stations

Minimum

Typical

Maximum

Please indicate the number of wireless stations required for this application. Again please note this question applies to the total LAN.6

Number of Wireless Stations

Minimum

Typical

Maximum

Neighborhood Demographics

If the application you are reporting on must operate with co-located LANs in the immediate vicinity please describe the type of topography separating co-located LANs. If you respond yes to "OTHER", please describe the topography required. Please note that this applies to co-located stations that are not within the administrative bound of each other.

Please answer yes or no to each of the following categories:

OPEN AREAS WITH MOVABLE PARTITIONS

ROOM AND HALLWAY WITH PERMANENT PARTITIONS

LARGE UNCLUTTERED ENCLOSED AREAS

LARGE CLUTTERED ENCLOSED AREAS

OTHER

Please indicate the physical separation that can be expected between co-located LANs. The numbers provided should indicate the distance between the geographic centers of the LANs.

Horizontal Distance in Feet

Vertical Distance in Feet

Minimum

Typical

Maximum

Dynamic Topography Considerations

To what degree can stations executing this application be expected to be relocated within a given LAN while not in operation.

Always Relocated

Sometimes Relocated

Never Relocated

To what degree can stations executing this application be expected to move with a given LAN while in operation.

Always Moving

Sometimes Moving

Never Moving

If stations executing this application move during operation please provide the following information.

Movement Distance in Feet

Movement Speed in Feet/Min.

Minimum

Typical

Maximum

To what degree can stations executing this application be expected to be relocated to a different LAN while not in operation.

Always Relocated

Sometimes Relocated

Never Relocated

To what degree can stations executing this application be expected to move from one LAN to another LAN while in operation.

Always Moving

Sometimes Moving

Never Moving

If stations executing this application move from LAN to LAN during operation please provide the following information.

Movement Distance in Feet

Movement Speed in Feet/Min.

Minimum

Typical

Maximum