ns3::Backoff Class Reference

The backoff class is used for calculating backoff times when many net devices can write to the same channel. More...

#include "backoff.h"

Collaboration diagram for ns3::Backoff:

Public Member Functions
	Backoff (Time slotTime, uint32_t minSlots, uint32_t maxSlots, uint32_t ceiling, uint32_t maxRetries)
	Constructor. More...
	Backoff (void)
int64_t	AssignStreams (int64_t stream)
	Assign a fixed random variable stream number to the random variables used by this model. More...
Time	GetBackoffTime ()
void	IncrNumRetries (void)
	Increments the number of retries by 1. More...
bool	MaxRetriesReached (void)
void	ResetBackoffTime (void)
	Indicates to the backoff object that the last packet was successfully transmitted and that the number of retries should be reset to 0. More...

Public Attributes
uint32_t	m_ceiling
	Caps the exponential function when the number of retries reaches m_ceiling. More...
uint32_t	m_maxRetries
	Maximum number of transmission retries before the packet is dropped. More...
uint32_t	m_maxSlots
	Maximum number of backoff slots (when multiplied by m_slotTime, determines maximum backoff time) More...
uint32_t	m_minSlots
	Minimum number of backoff slots (when multiplied by m_slotTime, determines minimum backoff time) More...
Time	m_slotTime
	Length of one slot. More...

Private Attributes
uint32_t	m_numBackoffRetries
	Number of times that the transmitter has tried to unsuccessfully transmit the current packet. More...
Ptr< UniformRandomVariable >	m_rng
	Random number generator. More...

Detailed Description

The backoff class is used for calculating backoff times when many net devices can write to the same channel.

Definition at line 37 of file backoff.h.

Constructor & Destructor Documentation

Backoff() [1/2]

ns3::Backoff::Backoff

(

void

)

Definition at line 28 of file backoff.cc.

References m_ceiling, m_maxRetries, m_maxSlots, m_minSlots, m_numBackoffRetries, m_rng, m_slotTime, ns3::MicroSeconds(), and ResetBackoffTime().

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Backoff() [2/2]

ns3::Backoff::Backoff	(	Time	slotTime,
		uint32_t	minSlots,
		uint32_t	maxSlots,
		uint32_t	ceiling,
		uint32_t	maxRetries
	)

Constructor.

Parameters

slotTime	Length of one slot
minSlots	Minimum number of backoff slots
maxSlots	Maximum number of backoff slots
ceiling	Cap to the exponential function
maxRetries	Maximum number of transmission retries

Definition at line 41 of file backoff.cc.

References m_ceiling, m_maxRetries, m_maxSlots, m_minSlots, m_numBackoffRetries, m_rng, and m_slotTime.

Member Function Documentation

AssignStreams()

int64_t ns3::Backoff::AssignStreams

(

int64_t

stream

)

Assign a fixed random variable stream number to the random variables used by this model.

Return the number of streams (possibly zero) that have been assigned.

Parameters

stream

first stream index to use

Returns

the number of stream indices assigned by this model

Definition at line 98 of file backoff.cc.

References m_rng, NS_LOG_FUNCTION, and ns3::RandomVariableStream::SetStream().

Referenced by ns3::CsmaNetDevice::AssignStreams().

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GetBackoffTime()

Time ns3::Backoff::GetBackoffTime

(

void

)

Returns

The amount of time that the net device should wait before trying to retransmit the packet

Definition at line 53 of file backoff.cc.

References ns3::UniformRandomVariable::GetValue(), m_ceiling, m_maxSlots, m_minSlots, m_numBackoffRetries, m_rng, and m_slotTime.

Referenced by ns3::CsmaNetDevice::TransmitStart().

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IncrNumRetries()

void ns3::Backoff::IncrNumRetries

(

void

)

Increments the number of retries by 1.

Definition at line 92 of file backoff.cc.

References m_numBackoffRetries.

Referenced by ns3::CsmaNetDevice::TransmitStart().

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MaxRetriesReached()

bool ns3::Backoff::MaxRetriesReached

(

void

)

Returns

True if the maximum number of retries has been reached

Definition at line 86 of file backoff.cc.

References m_maxRetries, and m_numBackoffRetries.

Referenced by ns3::CsmaNetDevice::TransmitStart().

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ResetBackoffTime()

void ns3::Backoff::ResetBackoffTime

(

void

)

Indicates to the backoff object that the last packet was successfully transmitted and that the number of retries should be reset to 0.

Definition at line 80 of file backoff.cc.

References m_numBackoffRetries.

Referenced by Backoff(), ns3::CsmaNetDevice::TransmitAbort(), and ns3::CsmaNetDevice::TransmitStart().

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Member Data Documentation

m_ceiling

uint32_t ns3::Backoff::m_ceiling

Caps the exponential function when the number of retries reaches m_ceiling.

Definition at line 52 of file backoff.h.

Referenced by Backoff(), GetBackoffTime(), and ns3::CsmaNetDevice::SetBackoffParams().

m_maxRetries

uint32_t ns3::Backoff::m_maxRetries

Maximum number of transmission retries before the packet is dropped.

Definition at line 57 of file backoff.h.

Referenced by Backoff(), MaxRetriesReached(), and ns3::CsmaNetDevice::SetBackoffParams().

m_maxSlots

uint32_t ns3::Backoff::m_maxSlots

Maximum number of backoff slots (when multiplied by m_slotTime, determines maximum backoff time)

Definition at line 47 of file backoff.h.

Referenced by Backoff(), GetBackoffTime(), and ns3::CsmaNetDevice::SetBackoffParams().

m_minSlots

uint32_t ns3::Backoff::m_minSlots

Minimum number of backoff slots (when multiplied by m_slotTime, determines minimum backoff time)

Definition at line 42 of file backoff.h.

Referenced by Backoff(), GetBackoffTime(), and ns3::CsmaNetDevice::SetBackoffParams().

m_numBackoffRetries

uint32_t ns3::Backoff::m_numBackoffRetries

private

Number of times that the transmitter has tried to unsuccessfully transmit the current packet.

Definition at line 113 of file backoff.h.

Referenced by Backoff(), GetBackoffTime(), IncrNumRetries(), MaxRetriesReached(), and ResetBackoffTime().

m_rng

Ptr<UniformRandomVariable> ns3::Backoff::m_rng

private

Random number generator.

Definition at line 118 of file backoff.h.

Referenced by Backoff(), AssignStreams(), and GetBackoffTime().

m_slotTime

Time ns3::Backoff::m_slotTime

Length of one slot.

A slot time, it usually the packet transmission time, if the packet size is fixed.

Definition at line 62 of file backoff.h.

Referenced by Backoff(), GetBackoffTime(), and ns3::CsmaNetDevice::SetBackoffParams().

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The documentation for this class was generated from the following files:

• src/csma/model/backoff.h
• src/csma/model/backoff.cc