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IEEE P802.11e A quality transport for IEEE 1394?. Peter Johansson Congruent Software, Inc. Chair, IEEE P1394.1. Why should IEEE 802.11e care?. IEEE 1394 is the transport chosen for consumer electronics equipment

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ieee p802 11e a quality transport for ieee 1394

IEEE P802.11eA quality transport for IEEE 1394?

Peter JohanssonCongruent Software, Inc.

Chair, IEEE P1394.1

Peter Johansson / Congruent Software, Inc.

why should ieee 802 11e care
Why should IEEE 802.11e care?
  • IEEE 1394 is the transport chosen for consumer electronics equipment
    • More rapid deployment in these “entertainment” applications than in computer “productivity” applications
  • Wide-spread deployment of home networks likely for entertainment, not productivity
  • Initial home networks likely to rely on wireless technology

Peter Johansson / Congruent Software, Inc.

wireless home network topology

Kitchen

Bedroom

Wireless

Wireless

Living Room

Bedroom

Office

Wireless home network topology
  • Wireless domain is home network backbone
    • Eliminate (or defer) retrofit costs to existing houses
  • Device clusters (hard-wired) within rooms
  • Wireless bandwidth is a severe constraint
    • Multiple domains may ease the problem

Peter Johansson / Congruent Software, Inc.

alternate home network topology

Wiring Closet

Kitchen

Bedroom

Wireless

Living Room

Office

Bedroom

Alternate home network topology
  • Wireless domain is a leaf connected to the wired home network backbone
  • Mobility support for devices carried from room to room

Peter Johansson / Congruent Software, Inc.

what needs to be done
What needs to be done?
  • Develop methods to mimic IEEE 1394 behaviors within an 802.11 services set
    • Wireless endpoint devices (DTV, DVCR, etc.)
  • Develop methods to connect an 802.11 services set to IEEE 1394
    • Wireless endpoint devices interoperate with wired endpoint devices
    • Wired endpoint devices interoperate with each other via an intermediate 802.11 services set

Peter Johansson / Congruent Software, Inc.

scope of work
Scope of work

1 Investigate the suitability of IEEE 802.11

2 Design a protocol adaptation layer (PAL) specific to IEEE 802.11

3 Specify bridges to interconnect the wired and wireless domains

  • Essentially complete in draft standard IEEE P1394.1

4 Profile the details of P1394.1 specifically applicable to bridges for IEEE 802.11

Peter Johansson / Congruent Software, Inc.

what is a pal

Application

1394 PAL

IEEE 802.11

What is a PAL?
  • A “glue layer” on top of a lower level
  • Hides low-level details of underlying layer
  • Mimics high-level behavior of target protocol
  • For example, IP1394 is a PAL that permits Internet protocol to be carried by IEEE 1394

Peter Johansson / Congruent Software, Inc.

what use is a pal

Application

1394 PAL

IEEE 802.11

What use is a PAL?
  • Leverages applications already developed

Application

IEEE 1394

  • Applications developed for IEEE 1394 expect:
    • Read, write and lock transactions
    • Infrastructure CSRs and configuration ROM
    • Isochronous services

Peter Johansson / Congruent Software, Inc.

wireless products enabled

DVCR

DTV

1394 PAL

1394 PAL

IEEE 802.11

IEEE 802.11

Wireless products enabled
  • Firmware developed for (wired) IEEE 1394 products can migrate to wireless domain
  • Minimize reengineering between wiredand wireless domains

Peter Johansson / Congruent Software, Inc.

1394 pal ground rules
1394 PAL ground rules
  • Shall support IEEE 1394 TRAN layer functions
    • Read, write and lock
  • Shall support isochrony and streaming data
  • Shall coexist with other users of the underlying IEEE 802.11 transport
  • Should behave “like” IEEE 1394
  • Should conceal differences between IEEE 1394 and IEEE 802.11 physical and link layers

Peter Johansson / Congruent Software, Inc.

connect wireless to wired

IEEE 1394

IEEE 802.11

Connect wireless to wired?
  • 1394 PAL for IEEE 802.11 permits wireless devices to talk to each other

?

  • Not interesting unless wireless devices can also talk to (wired) IEEE 1394 devices

Peter Johansson / Congruent Software, Inc.

wired to wireless via bridges

IEEE 1394

IEEE 802.11

Wired to wireless via bridges
  • Bridge isolates physical and link layer differences in each domain from the other
  • Bridge preserves transaction layer similarities
    • Transaction routes configured autonomously
    • Explicit isochronous stream setup / tear down

Peter Johansson / Congruent Software, Inc.

wired across wireless via bridges

IEEE 1394

IEEE 1394

IEEE 802.11

Wired across wireless via bridges
  • Wireless domain serves as backbone to connect wired clusters in different rooms
  • Reduces installation costs of home network
  • Bandwidth limitations of wireless may limit the longevity of this strategy

Peter Johansson / Congruent Software, Inc.

bridge model

cycle clock

portal 0

portal 1

internal fabric

Bridge model
  • Common cycle clock (synchronized to one portal)
  • Internal fabric implementation-dependent
  • Stores and forwards IEEE 1394 primitives
    • Read, write and lock requests and responses
    • Isochronous stream data
    • Neither a router nor aware of higher-level protocols

Peter Johansson / Congruent Software, Inc.

1394 trade association project scope
1394 Trade Association project scope

Develop a document that specifies methods to a) mimic IEEE 1394 infrastructure (transactions, isochrony, stream data, configuration ROM and CSR architecture) using the facilities of IEEE 802.11 and b) implement IEEE P1394.1 bridge behaviors in the same domain. The methods are to be compatible with the simultaneous use of IEEE 802.11 by other protocols, e.g., Internet protocol.

Peter Johansson / Congruent Software, Inc.

what s needed from ieee 802 11
What’s needed from IEEE 802.11?
  • Isochronous data requires:
    • Scheduled availability of the wireless medium
    • High probability that data payload is successfully delivered
  • In a nutshell: reliable quality of service
  • All other mappings of IEEE 1394 behavior to the 802.11 MAC are reasonably straightforward

Peter Johansson / Congruent Software, Inc.

what does isochronous really mean
What does “isochronous” really mean?
  • iso•chro•nous \ adj [Gk isokronos] (1706) —————————————————————————————Send it soon—and get it right the first time!
  • Isochronous data is generally useless if it is late
    • Either the source or sink has no time to wait
  • Efficient bandwidth utilization may preclude retries
  • iso•chro•nous \ adj [Gk isokronos] (1706) : uniform in time; having equal duration; recurring at regular intervals

Peter Johansson / Congruent Software, Inc.

why does isochronous delivery matter
Why does isochronous delivery matter?
  • Worst-case delivery delay for any packet is bounded and easily calculable
  • Bounded latency is small enough to make interesting real-time applications economical
    • Digital audio: 420 s at 1.5 Mbps (81 bytes)
    • SD video: 383 s at 28 Mbps (1,340 bytes)
  • Larger buffers necessary in wireless domain
    • Additional delay should be less than 20 ms

Peter Johansson / Congruent Software, Inc.

isochronous cycles

cycle n + 1

cycle n

asyncQ

cycle start

ch

ch

ch

ch

asyncP

asyncQ

asyncR

cycle start

ch

cycle n - 1

isochronous

asynchronous

cycle offset (delay)

cycle offset (delay)

nominal 125 µs

cycle synch

cycle synch

Isochronous cycles
  • Cycle start packet adjusts for delay
  • Subaction gap ends cycle

Peter Johansson / Congruent Software, Inc.

isochronous streams
Isochronous streams
  • Owner allocates bandwidth and channel number
    • Cooperative allocation insures low latency
  • Cycle master broadcasts cycle start packet every 125 s, on average
  • Single talker per channel broadcasts zero or one isochronous data packets per cycle
  • Multiple listeners receive isochronous data packets by channel number

Peter Johansson / Congruent Software, Inc.

additional desiderata
Additional desiderata
  • Resource allocation should be designed into the MAC protocols
    • Avoid use of RSVP as the only method to control traffic specifications
  • Dissociate coordination functions from access point functions
  • Design contention algorithms to select a single coordination point from multiple stations capable of performing this function

Peter Johansson / Congruent Software, Inc.

contact information
Contact information

Peter Johansson

Congruent Software, Inc.98 Colorado AvenueBerkeley, CA 94707

(510) 527-3926(510) 527-3856 FAX

PJohansson@ACM.org

Peter Johansson / Congruent Software, Inc.