howard wusb data flow

8/13/2019 Howard WUSB Data Flow

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Wireless USB Data Flow

John S. HowardSenior Architect

Intel Corporation



2

Agenda Agenda

•

Topology• Wireless USB Channel

•

Hosts• Devices

• Data Communications• Examples



3

Logical Communication TopologyLogical Communication Topology

Client SW Function

USB System

SW

WUSB Host

Controller

WUSB Logical

Device

WUSB “BUS”

Interface

Function Layer

Device Layer

“BUS”

Interface Layer

Actual Communications Flow

Logical Communications Flow

Transmissions

Encrypted

Secure

Relationship

Wireless USB

Host

Wireless USB

Device

Delta Change

(from USB 2.0)

Very Small Change

(Isochronous Only )

Small Change

(Security Framework )

Very LargeChange



Physical Communication

Topology

Physical Communication

Topology

Host

DWAX

DY

DZ Range of Host

~10 Meters (max)

DH

DWA

Root Hub

Device

Hub Device

DeviceDevice



Agenda Agenda

• Topology

• Wireless USB Channel

• Wireless USB Channel (Definition)

• USB Time• Wireless USB Cluster

• Hosts

• Devices

• Data Communications

• Transfer Types / Constraints



Wireless USB ChannelWireless USB Channel

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

C

MM

CWireless USB Channel

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

DRP

WUSB

BeaconPeriod

Beacon

Period

t=0

Superframe n Superframe n+1

t=0 t=0

BeaconPeriod

WiMedia

MAC

WiMedia Physical Layer

Channel Time

• The Wireless USB Channel is encapsulated by the WiMedia ‘channel’

• Uses WiMedia PHY/MAC compliant components

•

WiMedia PHY signaling and frames• WiMedia MAC Headers, Security Encapsulation, etc.

• Wireless USB channel is continuous sequence of linked control packets transmitted by the Hostduring reserved WiMedia channel time

• WUSB time is reserved from WiMedia channel time (DRPs)

• Called MMCs – Micro-schedule Management Commands

• All Wireless USB Data communications are over the Wireless USB Channel



Wireless USB

Channel Control

Wireless USB

Channel Control

M M

C

M S

-

C T A 1

M S

-

C T A n

M S

-

C T A 1

M S

-

C T A

m

M M

C

M S

-

C T A 1

M S

-

C T A o

BP

Super Frame N Super Frame N+1

BG Params

Host Beacon (Layout)

DRP IE

Super Frame N-1

Transaction Group 1 Transaction Group 2 . . . . . Transaction Group n

Media Access Slots (MAS)

M M

C

Next MMC Next MMC Next MMC

M M

C

Next MMC

•

Continuous linked series of MMCs transmitted by Host• Contain:

• Wireless USB Channel Time Stamp

• Time to next MMC

• General Channel Management Info (Host ID, etc.)

• Wireless USB channel time allocation declarations



USB TimeUSB Time

• Wired USB Hosts maintain USB channel time

• In wired USB, HW has 11-bit SOF frame counter providingmillisecond resolution or 1/8th millisecond resolution

• Exported to client drivers through USBDI as 32-bit value

• In wired USB, time values are primarily used for

isochronous traffic

• SOFs (Start Of Frame packets) pass time information to devices

• Wireless USB hosts also maintain USB channel time

• 17-bit 1/8th millisecond counter and 7 bit microsecond counter

• Still exported to client drivers as 32-bit millisecond value

•

Timer used for isochronous and directed beaconing• MMCs used to pass time information



9

WUSB Time Vs.

WiMedia Time

WUSB Time Vs.

WiMedia Time

•

WUSB time is NOT slaved toWiMedia time

• WiMedia superframes will be somenumber of WUSB microseconds

• Host by itself means it will be exactly

64K microseconds• If there is a slow beaconing WiMedia

device, superframe may be a few more

WUSB usecs than 64K



10

Device SynchronizationDevice Synchronization

•

Devices use MMC timestamps tosynchronize their internal usec clocks

• Only done on devices that need clocks

• Ex. Isochronous capable and directedbeaconing

• Device clocks must adjust to host rate



11

MMC Transmission AccuracyMMC Transmission Accuracy

Microsecond X-1 Microsecond X Microsecond X+1

Host Prepares Time Stamp For

Microsecond X

Legal Transmit Window. X +/- 40nanoseconds

Hosts transmit MMCs on Micro-second boundaries



12

USB Time Across HierarchyUSB Time Across Hierarchy

•

Device Wire Adapters synch to upstream USB time and propagateto downstream USB time

Actual times in MMC

and SOFs are thesame

Bus A

Bus B SOF SOF SOF SOF

MMCs during this period have

Timestamp :

Bits13:3 of 1/8th

millisecond value = NBits 2:0 of 1/8

thmillisecond value = 7

Microsecond value = microseconds

from start of 1/8th

millisecond

boundary

MMCs during this period haveTimestamp :

Bits13 :3 of 1/8th

millisecond value = N+1Bits 2:0 of 1/8

thmillisecond value = 0

Microsecond value = microseconds from

start of 1/8th

millisecond boundary

PC

orHWA DWA

HS

Device

Wireless USB USB 2.0

Bus A Bus B

Bus Timings

Example Topology

FrameNumber = N FrameNumber = N FrameNumber = N+1 FrameNumber = N+1

MMCs during this period have

Timestamp :Bits13:3 of 1/8

thmillisecond value = N

Bits 2:0 of 1/8th

millisecond value = 6

Microsecond value = microsecondsfrom start of 1/8

thmillisecond

boundary

1/8th

msec 1/8th

msec 1/8th

msec 1/8th

msec



13

Wireless USB Cluster Wireless USB Cluster

•

Term used to refer to all devicesconnected to and communicatingvia the same Wireless USB Channel

• One Wireless USB Host

• One (or more) Wireless USB Devices



14

Addressing In a Wireless

USB Cluster

Addressing In a Wireless

USB Cluster Address Tag Range

UnAssociated_Device_Address 255 (00FFH)UnAuthenticated_Device_Address_Range 128-254 (0080H-00FEH)

USB_Device_Address_Range 0-127 (0000H-007FH)

• Assigned Address Range (0-254)

• For devices

•

Cluster/Channel Broadcast Address• Destination Address for MMCs (assigned by Host from

128-254 range)

• Stream Index Value

• Assigned by Host



15

Agenda Agenda

•


•

Hosts• Devices

•

Data Communications• Transfer Types / Constraints



16

Host ResponsibilitiesHost Responsibilities

• WiMedia MAC compliant

• Manage / Maintain the Wireless USB Channel

• Maintain WiMedia Reservation

(for WUSB Channel(s)• USB Time

• WUSB Periodic Bandwidth

• WUSB Data Communications

• Device Management (addressing, security, enumeration)

• Endpoint Data Streams (Transfer Pipes)

• WUSB Power Management



17

Hosts

Managing 2-hop Topology

HostsManaging 2-hop Topology

• Case 1: Host has nohidden neighbors

• Only Host needs to

beacon to preservereservation

• Host uses cluster

members to detectthis condition

H

D

D

D

D



18

Hosts

Managing 2-hop Topology (cont).

HostsManaging 2-hop Topology (cont).

•

Case 2 – HiddenNeighbor

•

Host uses clustermembers to detectthis condition andpropagate itsreservations tohidden neighbor

H

D

D

D

D

M



19

Agenda Agenda

•


•

Hosts• Devices

•




20

WUSB Device TypesWUSB Device Types

• Self Beaconing Devices

• Devices are full WiMedia MAC aware

• Directed Beaconing Devices

• Devices are not full WiMedia MAC aware

• Depend on host to make the ‘good citizens’

•

Non Beaconing Devices• Limited transmit and receive range

• Fully encompassed by hosts range

• Not enough detail to be built (yet)



21

Self Beaconing Device

(SBD)

Self Beaconing Device(SBD)

• Provide MAS Availability info

• Which MAS slots are they available to communicate with host

• Listen to beacons, collect DRP info

• Reserved MAS slots by devices other than host’s WUSB Cluster

must be excluded from MAS Availability info

• Host uses GetStatus(MASAvailability)

• Report MAS Availability change

• When device sees a change, send notification to host

• Use host provided DRP IE

• Host will tell device what DRP IE to include in beacon

• After host has determined appropriate non-conflicting DRP



22


MAS Availability Info

Self Beaconing DeviceMAS Availability Info

• Device doesn’t have to continuously manage

• Reasons for device to update

• Receives a GetStatus(MASAvailability)

• Smashed MMCs

• Because it wanted to

•

Reasons for device to send changenotification

• Device detects change as a result of doing any

of above except the first one (GetStatus)



23


Host Interaction with SBD

Self Beaconing DeviceHost Interaction with SBD

• Reasons for Host to request MAS availability info

• Initial device connection

• Device not responding at times

• Because it wanted to

• Receipt of MAS Availability Change notification

• How does host detect hidden neighbors?

• MAS Availability info doesn’t match what host sees

• Reservation propagation?

• Host sets DRP for device to include in beacon



24

Directed Beaconing Devices(DBD) Three Functions

Directed Beaconing Devices(DBD) Three Functions

• Transmit a packet at certain times

•

This is how the device transmits a beacon• Count packets at specified time

• This is how a device can do a beacon or channel scan

• Device needs to record when packets were received• Also grab a few bytes from MAC header

• Helps host quickly identify beacons that device sees buthost doesn’t see

• Capture packet at specified time

• This is how a device captures neighbor beacons

• Useful for gathering DRP info

• Device needs to record when packet was received



25

Directed Beaconing DeviceTX Packet - Things Device Needs to Know

Directed Beaconing DeviceTX Packet - Things Device Needs to Know

• What to transmit

•

Packet contents are sent to device through control pipe• SetWUSBData(TransmitData)

• 200 bytes of buffer required

•

When to transmit• Host provides device with two values

• Transmit time (covers 64K milliseconds)

•

Transmit Adjustment (number of usecs to add each period)• SetWUSBData(TransmitParams)

• To transmit or not

•

New Feature Selector: DEV _XMIT_PACKET• State reflected in generic GetStatus



26

Directed Beaconing DeviceTX Packet - Device Behavior

Directed Beaconing DeviceTX Packet - Device Behavior

• Device keeps three values:

•

USB Channel Time: synchronized to time in MMCs• Transmit Time: 16 bits, set by host

• Transmit Adjustment: 4 bits, set by host

•Device Algorithm when enabled:

• When bottom 16 bits of USB Channel time matches TransmitTime, device sends packet

• Device adds Transmit Adjustment to Transmit Time

• Go to 1.

• Host will adjust transmit adjustment ‘on the fly’

•

Information Element in an MMC• Adjustment is the same for all DBD’s TX Packet



27

Directed Beaconing DeviceCount Packets - Basic Operation

Directed Beaconing DeviceCount Packets - Basic Operation

• Device is told when to start counting and when

to stop counting

• Host tells device to start counting

• Device counts packets, saves a little bit of packet dataand records reception time of each

• Host retrieves count info

•

Notes:• Host should not expect USB channel responses from device

while counting packets

• The host must ensure that the device is not enabled for

transmit before enabling device for counting

Di d B D i



28

Directed Beacon DeviceCount Packets - Start/Stop Times

Directed Beacon DeviceCount Packets - Start/Stop Times

• Host tells device when to start counting and for how long

•

Start Time is USB channel time (24 bits)• Stop Time is USB channel time (24 bits)

• Packet filter supported

• “One-hot” decode on packet type

• Values are sent through Control channel

• SetWUSBData(ReceiveParams)

• Host tells device to start counting

• New Feature Selector: COUNT_PACKETS

• One shot behavior. When time period has elapsed, device

is no longer enabled to count

Di t d B i D i



29

Directed Beaconing DeviceCount Packets - Saving Info

Directed Beaconing DeviceCount Packets - Saving Info

• Device counts packets, saves a little bit of packet

data and records reception time of each• Data saved is first six bytes of MAC header

• Packet params, src, destination

• Device records reception time (USB channel time)when each packet was received

• Important for locating beacon periods and detecting

slow devices• LQI recorded also

• Count buffer must be 512 bytes

• Each count takes 10 bytes

Di t d B i D iDi t d B i D i



30

Directed Beaconing DeviceCount Packets - Retrieving Data

Directed Beaconing DeviceCount Packets - Retrieving Data

• Host retrieves count info

• GetStatus(ReceivedData)

• Device returns data

formatted as illustrated

# of packets

Packet 1 info

Packet 2 info

Packet 3 info

Packet 4 infoLQI

Reception time

First six bytes

of MAC header




31

Directed Beaconing Device

Capture Packet - Basic Operation

Directed Beaconing DeviceCapture Packet - Basic Operation

• Device is told when to start capturing and when to stop

• Host tells device to start capture

• Device captures, records reception time, and saves

packet during this time• Host retrieves captured packet

• Notes:

• Host should not expect USB channel responses from devicewhile capturing packet

• The host must ensure that the device transmit time and device

capture time don’t conflict




32

Directed Beaconing DeviceCapture Packet - Start/Stop Times

Directed Beaconing DeviceCapture Packet - Start/Stop Times

• Host tells device when to start capturing and when to

stop capturing packets• Start is USB channel time

• Stop is USB channel time

• Packet filter as well

• Values are sent through Control channel

• Set WUSB Data (Receive Params)

• Host tells device to start capture

• Feature Selector: Capture Packet

• One shot behavior. When time period has elapsed, device is

no longer enabled to capture

Di t d B i D iDirected Beaconing De ice



33

Directed Beaconing DeviceCapture Packet - Saving Them

Directed Beaconing DeviceCapture Packet - Saving Them

• Device captures, records reception time, and

saves packet during this time

• One packet, 512 bytes of buffering

• Full packet contents are saved

• Excess bytes are discarded

• Device records reception time (USB channel time)when packet was received

Di t d B i D iDirected Beaconing Device



34

Directed Beaconing DeviceCapture Packets - Retrieving Data

Directed Beaconing DeviceCapture Packets - Retrieving Data

Reception Time

Receive Status

Payload

MAC Header

(10 bytes)

LQI

Bit 0 set if bad FCS

Bit 1 set of buffer overrun

• Host retrieves captured

packets

• New Device Request:Get Status (Received

Data)

• Device returns dataformatted as illustrated



35

Agenda Agenda

• Topology


• Hosts

•

Devices• Data Communications

• MMCs

• Transactions• Device Notifications

• Wireless USB Connection

• Transfer Types / Constraints



36

MMC Information ElementsMMC Information Elements

• Transaction protocol

• Host Channel Identification/Information

• Controls for Analogs to Wired signaling events

• Connect, disconnect, suspend & resume,device reset

• WUSB Channel maintenance

• Communicates to cluster the channeltime allocation



37

Wireless USB TransactionsWireless USB Transactions

Token Data Hndsk Token Data Hndsk

Propagation delaysplus Device Turn Time

OUT IN

MMC

W D R

C T A

( T o k e n O )

H D

R

W D T

C T A

( H n d s k O )

Data O

W D T

C T A

( T o k

e n I )

Data I

‘ C l a s s i c ’ U S B 2

T r a n s a c t i o n

P r o t o c o l

W U S B T r a n

s a c t i o n

P r o t o c

o l

MMC

Transaction Group

WUSB Host Transmission

WUSB Device Transmission

W D T

C T A

( T o k

e n I )

Data I AcK

H

n d s k O

Wireless USB TransactionsWireless USB Transactions



38

Wireless USB TransactionsData Bursting

Wireless USB TransactionsData Bursting

• Transaction data

phases may havemore than one datapacket

• Data Payloads areaMaxPacketSize

•

wMaxPacketSize or • Smaller

• Host decision

Tx Rx

Data A PIDX

ACK

DataC PIDZ DataB PIDY Data A PIDX

ACKAckCode

USB 2.0

Data & Handshake

Transaction Phases

WUSB Data Burst &

Handshake

Transaction Phases

D i N tifi ti



39

Device NotificationsDevice Notifications

• Used for small, infrequent,

asynchronous messagesfrom a Device to the Host

• Some are analogs for WiredUSB signaling events

• Opportunities to transmit

Device Notifications arealso scheduled by theWireless USB Host

• Access type is contention

based

SendingNotification

DNTS Notification Message to Host(Notification-specific)

Notification Response from Host(Notification-specific)

DeviceDevice-- specific statespecific state

which results in need towhich results in need to

generate a notificationgenerate a notification

DeviceDevice-- specific statespecific state

dependent on responsedependent on response

from Hostfrom Host

Send Notification Event

Wi l USB C iWi l USB C ti



40

Wireless USB ConnectionWireless USB Connection

• Definition of a connection, including

security components

• Definition of TrustTimeout

• Define Device Reset• Example of Connection Process

•

Example of Reconnection• See Session on Device Power Management

Wi l USB C tiWi l USB C ti



41


• A host and device exchange data using a

secure connection• A process is defined for making the connection secure

• Establishing Trust

• Limited ‘non-secure’ data communications allowed toestablish secure connection

• All data communications in a secure connection are

either encrypted or authenticated• MMC are authenticated by devices belonging to the cluster

• Other data protocol and Device notifications are encrypted

Wi l USB C ti ( t )Wi l USB C ti ( t )



42

Wireless USB Connection (cont.)Wireless USB Connection (cont.)

• Session Keys:

• Wireless USB Cluster has a single Group Key

• Used by devices to Authenticate MMCs

•

Each device in Cluster has a unique symmetricsession key

• Encrypt/decrypt of data, protocol and notification packets

•

Keys only valid while Connection is Secure• TrustTimeout requires re-authentication

(re-establishment of keys)




43

Wireless USB ConnectionConnection Lifetime

Wireless USB ConnectionConnection Lifetime

• A secure connection has a Lifetime

•

Maintenance of the secure connection requires exchange ofsecure information so that the connection can be kept ‘fresh’

• No data received by host or device for TrustTimeout(4 seconds) results in requirement to re-authenticate

• Re-authentication can be initiated by either thehost or device

• Loss of trust is asymmetric

• Device informs host of Loss of Trust by sending aReconnect request

• Host re-establishes trust by performing 4-way

handshake with the Device

A dAgenda



44

Agenda Agenda

• Topology


• Hosts

• Devices

•


Transfer T pe ConstraintsTransfer Type Constraints



45

Transfer Type ConstraintsTransfer Type Constraints

• Same Transfer types as USB 2.0

• Bulk

• Control

• Interrupt

• Isochronous

• Different/new constraints to make moreefficient for Wireless Media



47

Transfer Type ConstraintsControl

a s e ype Co s a sControl

• Retains many/most constraints and behavior of Wired USB

• “Best Effort” service

• Reliable data delivery

•

Maximum Packet Size of 512 (only)• Maximum burst size of 1 data packet per data phase

• Host must use PHY Base rate with Default Control

Pipe (Standard Commands)

• On Flow control event, taken from active list

• Device must notify host when ready




48

Transfer Type ConstraintsInterrupt

ypInterrupt

• Not more than 80% of Wireless USB Channel(combined all periodic)

• Similar purpose and characteristics of Wired USB• Reliable data delivery (protocol)

• Periodic (allocated) Bandwidth service

• Interval = (2bInterval-1) * 128 µs; range : (6 to 16) [~4ms to ~4s]• (host will provide polling @ rate or faster)

• Retries during service interval to reduce PER

• Host may adjust payload packet size (& number of

transactions per interval) to reduce PER

• Use any bit transfer rate supported by device• Host choice

•

On Flow control event, skip to next service interval




49

ypInterrupt (cont.)

ypInterrupt (cont.)

• Two ‘Power Flavors’ of Interrupt Endpoint

•

Normal power• Traditional behavior – including retry/halt policy

• Maximum packet size (1 – 1024) Max burst size : 1

• Retries per service interval : 5 (to achieve PER)

• Low Power

• Intended for low-latency but very low bandwidth

• Device to Host ONLY

• Endpoint responds only when it has data *

• Relaxed retry/halt policy

• Maximum Packet Size of 64 (only) Max burst size : 1

• Retries per service interval : 2 (max)

*must NAK to avoidTrustTimeout




50

ypIsochronous

ypIsochronous

• Not more than 80% of Wireless USB Channel(combined all periodic)

• Similar purpose and characteristics of Wired USB

• Periodic (allocated) Bandwidth service

• Interval = (2bInterval-1) * 128 µs; range : (6 to 16) [~4ms to ~4s]

•

(host will provide polling @ rate or faster)• Retries during service interval to reduce PER

• Host cannot adjust payload packet size

• Maximum Packet Size of 0-3584 Max burst size : 1-16

• At least one retry per service interval

• Use any bit transfer rate supported by device

• Host choice

• On Flow control event, next service interval

Allocation includes

additional 30% of

average

throughput (for

retries)



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