jist.swans.mac
Class Mac802_11

java.lang.Object
  jist.swans.mac.Mac802_11

All Implemented Interfaces:

JistAPI.Proxiable, JistAPI.Timeless, MacInterface, MacInterface.Mac802_11

public class Mac802_11
extends java.lang.Object
implements MacInterface.Mac802_11

Implementation of IEEE 802_11b. Please refer to the standards document. For consistency, many of the variable names, constants and equations are taken directly from the specification.

Since:

SWANS1.0

Version:

$Id: Mac802_11.java,v 1.62 2005/02/10 16:52:28 barr Exp $

Author:

Rimon Barr <barr+jist@cs.cornell.edu>

Nested Class Summary

private static class

Mac802_11.SeqEntry Local class to used manage sequence number records.

Nested classes/interfaces inherited from interface jist.swans.mac.MacInterface

MacInterface.Mac802_11

Field Summary

protected int	bandwidth link bandwidth (units: bytes/second).
protected long	bo backoff time remaining.
protected long	boStart backoff start time.
protected short	cw current contention window size.
static short	CW_MAX Maximum collision window (for backoff).
static short	CW_MIN Minimum collision window (for backoff).
static long	DIFS Distributed inter frame space.
static boolean	DSSS Physical specification constant: 802_11b-1999 Supplement 2_4GHz Direct Sequence.
static long	EIFS Extended inter frame space.
static boolean	FHSS Physical specification constant: 802_11b-1999 2_4GHz Frequency Hopping.
protected MacAddress	localAddr mac address of this interface.
protected byte	longRetry long retry counter.
static byte	MAC_MODE_DIFS mac mode: waiting for difs or eifs timer.
static byte	MAC_MODE_SBO mac mode: waiting for backoff.
static byte	MAC_MODE_SIDLE mac mode: idle.
static byte	MAC_MODE_SNAV mac mode: waiting for virtual carrier sense.
static byte	MAC_MODE_SNAV_RTS mac mode: waiting for virtual carrier sense to RTS.
static byte	MAC_MODE_SWFACK mac mode: waiting for ACK packet.
static byte	MAC_MODE_SWFCTS mac mode: waiting for CTS packet.
static byte	MAC_MODE_SWFDATA mac mode: waiting for DATA packet.
static byte	MAC_MODE_XACK mac mode: transmitting ACK packet.
static byte	MAC_MODE_XBROADCAST mac mode: transmitting broadcast DATA packet.
static byte	MAC_MODE_XCTS mac mode: transmitting CTS packet.
static byte	MAC_MODE_XRTS mac mode: transmitting RTS packet.
static byte	MAC_MODE_XUNICAST mac mode: transmitting unicast DATA packet.
protected byte	mode current mac mode.
protected long	nav virtual carrier sense; next time when network available.
protected boolean	needEifs whether last reception had an error.
protected NetInterface	netEntity Network upcall entity interface.
protected byte	netId network interface number.
protected Message	packet packet currently being transmitted.
protected MacAddress	packetNextHop next hop of packet current being transmitted.
static long	PIFS Point coordination inter frame space.
static long	PLCP_HEADER Length of PLCP Header at 1Mb/s.
static long	PREAMBLE Length of PHY preamble.
protected boolean	promisc whether mac is in promiscuous mode.
static long	PROPAGATION Air propagation delay.
protected RadioInterface	radioEntity Radio downcall entity reference.
protected byte	radioMode radio mode used for carrier sense.
static byte	RETRY_LIMIT_LONG Retransmissions attempted for long packets (those with RTS).
static byte	RETRY_LIMIT_SHORT Retransmissions attempted for short packets (those without RTS).
static long	RX_TX_TURNAROUND Receive-Transmit turnaround time.
protected MacInterface.Mac802_11	self Self-referencing mac entity reference.
protected short	seq sequence number counter.
static short	SEQ_CACHE_SIZE Sequence number cache size.
static short	SEQ_INVALID Invalid sequence number.
protected Mac802_11.SeqEntry	seqCache received sequence number cache list.
protected byte	seqCacheSize size of received sequence number cache list.
protected byte	shortRetry short retry counter.
static long	SIFS Short interframe space.
static long	SLOT_TIME Minimum time to sense medium.
static long	SYNCHRONIZATION PHY synchronization time.
static int	THRESHOLD_FRAGMENT Threshold packet size for fragmentation.
static int	THRESHOLD_RTS Threshold packet size to activate RTS.
protected byte	timerId timer identifier.
static long	TX_DIFS Transmit start DIFS.
static long	TX_SIFS Transmit start SIFS.

Constructor Summary

Mac802_11(MacAddress addr, RadioInfo radioInfo)
Instantiate new 802_11b entity.

Method Summary

private void	backoff() Perform backoff.
private void	cancelTimer() Cancel timer event, by incrementing the timer identifer.
void	cfDone(boolean backoff, boolean delPacket) Collision free send sequence complete.
private void	clearBackoff() Reset backoff counter to zero.
private void	decCW() Decrease Collision Windows.
private void	doDifs()
static java.lang.String	getModeString(byte mode)
MacInterface.Mac802_11	getProxy() Return proxy entity of this mac.
private short	getSeqEntry(MacAddress from) Return latest seen sequence number from given address.
private boolean	hasBackoff() Return whether there is a backoff.
boolean	hasPacket() Return whether mac currently has a packet to send.
private void	idle()
private void	incCW() Increase Collision Window.
private short	incSeq() Increment local sequence counter.
boolean	isAwaitingResponse() Return whether the mac is currently waiting for a response.
private boolean	isBroadcast() Return whether current packet is to be broadcast.
private boolean	isCarrierIdle() Determine whether channel is idle according to both physical and virtual carrier sense.
private boolean	isRadioIdle()
boolean	isTransmitting() Return whether the mac is currently transmitting.
private void	pauseBackoff() Pause the current backoff (invoked when the channel becomes busy).
void	peek(Message msg) Radio has locked onto a packet signal; mac may have a peek.
private void	radioBusy()
private void	radioIdle()
void	receive(Message msg) Radio has received a packet for mac to process.
private void	receiveAck(MacMessage.Ack ack)
private void	receiveCts(MacMessage.Cts cts)
private void	receiveData(MacMessage.Data msg)
private void	receiveForeign(MacMessage msg)
private void	receivePacket(MacMessage msg)
private void	receiveRts(MacMessage.Rts rts)
private void	resetNav() Clear the virtual carrier sense (network allocation vector).
private void	retry()
private void	retryNo()
private void	retryYes()
void	send(Message msg, MacAddress nextHop) Network layer would like to send the following packet.
private void	sendAck(MacMessage.Data data)
private void	sendCts(MacMessage.Rts rts)
private void	sendData(boolean afterCts)
private void	sendDataBroadcast()
private void	sendDataUnicast(boolean afterCts)
private void	sendPacket()
private void	sendRts()
private void	setBackoff() Set new random backoff, if current backoff timer has elapsed.
private void	setMode(byte mode) Set the current mac mode.
void	setNetEntity(NetInterface net, byte netid) Hook up with the network entity.
void	setPromiscuous(boolean promisc) Set promiscuous mode (whether to pass all packets through).
void	setRadioEntity(RadioInterface radio) Hook up with the radio entity.
void	setRadioMode(byte mode) Update mac regarding new mode of its radio.
private boolean	shouldFragment() Return whether current packet requires fragmentation.
private boolean	shouldRTS() Return whether current packet large enough to require RTS.
void	startTimer(long delay, byte mode) Initiate a timer event.
void	timeout(int timerId) Process mac timeout.
private long	transmitTime(Message msg) Compute packet transmission time at current bandwidth.
private void	updateSeqEntry(MacAddress from, short seq) Update latest sequence number entry for given address.
private boolean	waitingNav() Return whether the virtual carrier sense (network allocation vector) indicates that the channel is reserved.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DSSS

public static final boolean DSSS

Physical specification constant: 802_11b-1999 Supplement 2_4GHz Direct Sequence.

See Also:

Constant Field Values

FHSS

public static final boolean FHSS

Physical specification constant: 802_11b-1999 2_4GHz Frequency Hopping.

See Also:

Constant Field Values

PREAMBLE

public static final long PREAMBLE

Length of PHY preamble.

See Also:

Constant Field Values

PLCP_HEADER

public static final long PLCP_HEADER

Length of PLCP Header at 1Mb/s.

See Also:

Constant Field Values

SYNCHRONIZATION

public static final long SYNCHRONIZATION

PHY synchronization time.

See Also:

Constant Field Values

RX_TX_TURNAROUND

public static final long RX_TX_TURNAROUND

Receive-Transmit turnaround time.

See Also:

Constant Field Values

PROPAGATION

public static final long PROPAGATION

Air propagation delay.

See Also:

Constant Field Values

SLOT_TIME

public static final long SLOT_TIME

Minimum time to sense medium.

SIFS

public static final long SIFS

Short interframe space. Minimum wait time between two frames in the same communication session.

PIFS

public static final long PIFS

Point coordination inter frame space. Wait used by the access point (point coordinator) to gain access to the medium before any of the stations.

DIFS

public static final long DIFS

Distributed inter frame space. Wait used by stations to gain access to the medium.

TX_SIFS

public static final long TX_SIFS

Transmit start SIFS.

TX_DIFS

public static final long TX_DIFS

Transmit start DIFS.

EIFS

public static final long EIFS

Extended inter frame space. Wait used by stations to gain access to the medium after an error.

THRESHOLD_RTS

public static final int THRESHOLD_RTS

Threshold packet size to activate RTS. Default=3000. Broadcast packets never use RTS. Set to zero to always use RTS.

See Also:

Constant Field Values

THRESHOLD_FRAGMENT

public static final int THRESHOLD_FRAGMENT

Threshold packet size for fragmentation. Default=2346. Broadcast packets are not fragmented.

See Also:

Constant Field Values

RETRY_LIMIT_SHORT

public static final byte RETRY_LIMIT_SHORT

Retransmissions attempted for short packets (those without RTS).

See Also:

Constant Field Values

RETRY_LIMIT_LONG

public static final byte RETRY_LIMIT_LONG

Retransmissions attempted for long packets (those with RTS).

See Also:

Constant Field Values

CW_MIN

public static final short CW_MIN

Minimum collision window (for backoff).

CW_MAX

public static final short CW_MAX

Maximum collision window (for backoff).

See Also:

Constant Field Values

SEQ_INVALID

public static final short SEQ_INVALID

Invalid sequence number.

See Also:

Constant Field Values

SEQ_CACHE_SIZE

public static final short SEQ_CACHE_SIZE

Sequence number cache size.

See Also:

Constant Field Values

MAC_MODE_SIDLE

public static final byte MAC_MODE_SIDLE

mac mode: idle.

See Also:

Constant Field Values

MAC_MODE_DIFS

public static final byte MAC_MODE_DIFS

mac mode: waiting for difs or eifs timer.

See Also:

Constant Field Values

MAC_MODE_SBO

public static final byte MAC_MODE_SBO

mac mode: waiting for backoff.

See Also:

Constant Field Values

MAC_MODE_SNAV

public static final byte MAC_MODE_SNAV

mac mode: waiting for virtual carrier sense.

See Also:

Constant Field Values

MAC_MODE_SNAV_RTS

public static final byte MAC_MODE_SNAV_RTS

mac mode: waiting for virtual carrier sense to RTS.

See Also:

Constant Field Values

MAC_MODE_SWFCTS

public static final byte MAC_MODE_SWFCTS

mac mode: waiting for CTS packet.

See Also:

Constant Field Values

MAC_MODE_SWFDATA

public static final byte MAC_MODE_SWFDATA

mac mode: waiting for DATA packet.

See Also:

Constant Field Values

MAC_MODE_SWFACK

public static final byte MAC_MODE_SWFACK

mac mode: waiting for ACK packet.

See Also:

Constant Field Values

MAC_MODE_XRTS

public static final byte MAC_MODE_XRTS

mac mode: transmitting RTS packet.

See Also:

Constant Field Values

MAC_MODE_XCTS

public static final byte MAC_MODE_XCTS

mac mode: transmitting CTS packet.

See Also:

Constant Field Values

MAC_MODE_XUNICAST

public static final byte MAC_MODE_XUNICAST

mac mode: transmitting unicast DATA packet.

See Also:

Constant Field Values

MAC_MODE_XBROADCAST

public static final byte MAC_MODE_XBROADCAST

mac mode: transmitting broadcast DATA packet.

See Also:

Constant Field Values

MAC_MODE_XACK

public static final byte MAC_MODE_XACK

mac mode: transmitting ACK packet.

See Also:

Constant Field Values

self

protected final MacInterface.Mac802_11 self

Self-referencing mac entity reference.

radioEntity

protected RadioInterface radioEntity

Radio downcall entity reference.

netEntity

protected NetInterface netEntity

Network upcall entity interface.

netId

protected byte netId

network interface number.

bandwidth

protected final int bandwidth

link bandwidth (units: bytes/second).

localAddr

protected MacAddress localAddr

mac address of this interface.

promisc

protected boolean promisc

whether mac is in promiscuous mode.

mode

protected byte mode

current mac mode.

radioMode

protected byte radioMode

radio mode used for carrier sense.

needEifs

protected boolean needEifs

whether last reception had an error.

timerId

protected byte timerId

timer identifier.

bo

protected long bo

backoff time remaining.

boStart

protected long boStart

backoff start time.

cw

protected short cw

current contention window size.

nav

protected long nav

virtual carrier sense; next time when network available.

seq

protected short seq

sequence number counter.

seqCache

protected Mac802_11.SeqEntry seqCache

received sequence number cache list.

seqCacheSize

protected byte seqCacheSize

size of received sequence number cache list.

shortRetry

protected byte shortRetry

short retry counter.

longRetry

protected byte longRetry

long retry counter.

packet

protected Message packet

packet currently being transmitted.

packetNextHop

protected MacAddress packetNextHop

next hop of packet current being transmitted.

Constructor Detail

Mac802_11

public Mac802_11(MacAddress addr,
                 RadioInfo radioInfo)

Instantiate new 802_11b entity.

Parameters:

addr - local mac address

radioInfo - radio properties

Method Detail

getModeString

public static java.lang.String getModeString(byte mode)

getProxy

public MacInterface.Mac802_11 getProxy()

Return proxy entity of this mac.

Returns:

self-referencing proxy entity.

setRadioEntity

public void setRadioEntity(RadioInterface radio)

Hook up with the radio entity.

Parameters:

radio - radio entity

setNetEntity

public void setNetEntity(NetInterface net,
                         byte netid)

Hook up with the network entity.

Parameters:

net - network entity

netid - network interface number

setPromiscuous

public void setPromiscuous(boolean promisc)

Set promiscuous mode (whether to pass all packets through).

Parameters:

promisc - promiscuous flag

setMode

private void setMode(byte mode)

Set the current mac mode.

Parameters:

mode - new mac mode

isAwaitingResponse

public boolean isAwaitingResponse()

Return whether the mac is currently waiting for a response.

Returns:

whether mac waiting for response

isTransmitting

public boolean isTransmitting()

Return whether the mac is currently transmitting.

Returns:

whether mac is currently transmitting

hasPacket

public boolean hasPacket()

Return whether mac currently has a packet to send.

Returns:

whether mac has packet to send.

isBroadcast

private boolean isBroadcast()

Return whether current packet is to be broadcast.

Returns:

whether current packet is to be broadcast.

shouldRTS

private boolean shouldRTS()

Return whether current packet large enough to require RTS.

Returns:

does current packet require RTS.

shouldFragment

private boolean shouldFragment()

Return whether current packet requires fragmentation.

Returns:

does current packet require fragmentation.

transmitTime

private long transmitTime(Message msg)

Compute packet transmission time at current bandwidth.

Parameters:

msg - packet to transmit

Returns:

time to transmit given packet at current bandwidth

hasBackoff

private boolean hasBackoff()

Return whether there is a backoff.

Returns:

whether backoff non-zero.

clearBackoff

private void clearBackoff()

Reset backoff counter to zero.

setBackoff

private void setBackoff()

Set new random backoff, if current backoff timer has elapsed.

pauseBackoff

private void pauseBackoff()

Pause the current backoff (invoked when the channel becomes busy).

backoff

private void backoff()

Perform backoff.

incCW

private void incCW()

Increase Collision Window.

decCW

private void decCW()

Decrease Collision Windows.

waitingNav

private boolean waitingNav()

Return whether the virtual carrier sense (network allocation vector) indicates that the channel is reserved.

Returns:

virtual carrier sense

resetNav

private void resetNav()

Clear the virtual carrier sense (network allocation vector).

isCarrierIdle

private boolean isCarrierIdle()

Determine whether channel is idle according to both physical and virtual carrier sense.

Returns:

physical and virtual carrier sense

incSeq

private short incSeq()

Increment local sequence counter.

Returns:

new sequence number.

getSeqEntry

private short getSeqEntry(MacAddress from)

Return latest seen sequence number from given address.

Parameters:

from - source address

Returns:

latest sequence number from given address

updateSeqEntry

private void updateSeqEntry(MacAddress from,
                            short seq)

Update latest sequence number entry for given address.

Parameters:

from - source address

seq - latest sequence number

send

public void send(Message msg,
                 MacAddress nextHop)

Description copied from interface: MacInterface

Network layer would like to send the following packet. Should be called only after Mac has notified that it is wants a packet.

Specified by:

send in interface MacInterface

Parameters:

msg - packet to send

nextHop - destination mac

doDifs

private void doDifs()

cfDone

public void cfDone(boolean backoff,
                   boolean delPacket)

Description copied from interface: MacInterface.Mac802_11

Collision free send sequence complete.

Specified by:

cfDone in interface MacInterface.Mac802_11

Parameters:

backoff - is a backoff required

delPacket - is processing for this packet complete

sendPacket

private void sendPacket()

sendRts

private void sendRts()

sendCts

private void sendCts(MacMessage.Rts rts)

sendData

private void sendData(boolean afterCts)

sendDataBroadcast

private void sendDataBroadcast()

sendDataUnicast

private void sendDataUnicast(boolean afterCts)

sendAck

private void sendAck(MacMessage.Data data)

retry

private void retry()

retryYes

private void retryYes()

retryNo

private void retryNo()

peek

public void peek(Message msg)

Description copied from interface: MacInterface

Radio has locked onto a packet signal; mac may have a peek.

Specified by:

peek in interface MacInterface

Parameters:

msg - packet currently in flight

receive

public void receive(Message msg)

Description copied from interface: MacInterface

Radio has received a packet for mac to process.

Specified by:

receive in interface MacInterface

Parameters:

msg - packet received

receivePacket

private void receivePacket(MacMessage msg)

receiveRts

private void receiveRts(MacMessage.Rts rts)

receiveCts

private void receiveCts(MacMessage.Cts cts)

receiveAck

private void receiveAck(MacMessage.Ack ack)

receiveData

private void receiveData(MacMessage.Data msg)

receiveForeign

private void receiveForeign(MacMessage msg)

setRadioMode

public void setRadioMode(byte mode)

Description copied from interface: MacInterface

Update mac regarding new mode of its radio.

Specified by:

setRadioMode in interface MacInterface

Parameters:

mode - new radio mode

isRadioIdle

private boolean isRadioIdle()

radioBusy

private void radioBusy()

radioIdle

private void radioIdle()

startTimer

public void startTimer(long delay,
                       byte mode)

Description copied from interface: MacInterface.Mac802_11

Initiate a timer event. Note that only one timer event can be active at a given time.

Specified by:

startTimer in interface MacInterface.Mac802_11

Parameters:

delay - timer duration

mode - new mode

cancelTimer

private void cancelTimer()

Cancel timer event, by incrementing the timer identifer.

idle

private void idle()

timeout

public void timeout(int timerId)

Description copied from interface: MacInterface.Mac802_11

Process mac timeout.

Specified by:

timeout in interface MacInterface.Mac802_11

Parameters:

timerId - timer identifier