# MAC PROTOCOL COMPARISON PERFORMANCE ANALYSIS

Document Sample

MAC PROTOCOL COMPARISON &
PERFORMANCE ANALYSIS

Jian-chuan Lu
visiting scholar
DAWN Lab
EECS of Washington State University

2nd November 2000
Outline of Topics

1.   TDMA vs. CSMA, simple comparison
2.   Single station:
delay, throughput and energy consumption
1.   Interference analysis
2.   Multi-base-station scenario
3.   Improved CSMA/CA
TDMA vs. CSMA
TDMA                                    CSMA
Need central control                  Completely decentralized
Reliable synchronization                   Transmit at “will”
Assume a central station for large area   Can be used either at infrastructured
ad hoc wireless net is not the reality           or ad hoc network
Controlled access                        Random access
application,throughput 1               application, throughput for
CSMA/CD1/(1+3.44 a)
Time delay bounded                          Random delay
Synchronous or asynchronous data        Hard to guarantee delay performance
Asynchronous data
and multicast
Collision free                  There always exists some CW
Transceiver can be turned off at idle    Transceiver must monitor channel
state                            state continuously
System parameters
N: number of nodes                           dcross: propagation cross distance
D: Maximum hop number                        efree: free space propagation constant
Cd: average connection degree                etwo-way: ground propagation
constant
Tf: data frame time interval                   hr: receiver antenna height
Eelec: radio electronics circuit energy(J/bit) ht: transmitter antenna height
i:         data packet length                         islot: bit number in one beacon
slot
l: packet arrival rate                       g:       wave length
d: effective transmission distance      L: system signal loss factor
Nb: number of frames between beacon frame
TDMA SINGLE BASE-STATION
Average delay: (D+1)*Tf/2
Channel utilization: h=(Nb-1)/Nb
Energy consumption in one super frame:
Emax=Nd(ERX+ETX)+ islot. ETX+(N-1)ERX
WHERE:
Nd =1/3. Cd .l .Nb. Tf + l .Nb. Tf
ERX= i . Eelec
i . Eelec+ i* efree*d2      when d< dcross
ETX={
i . Eelec +i* etwo-way *d4    when d> dcross

4 .h .h . L

r   t
d

cross
CSMA/CA Basic access method

DIFS   Contention Window
DIFS
PIFS

SIFS
Busy Medium                 Backoff Window             Next Frame

Defer Access            Decrement Backoff if medium is idle
RTS/CTS 4 way handshake access method

Channel access using RTS/CTS

DIFS

RTS                                 DATA
SRC

SIFS         SIFS
SIFS
DEST                           CTS                                     ACK

DIFS
Contention Window

OTHER                    NAV(RTS)

NAV(CTS)

Defer Access
Collision analysis

Ai(dij’)                               Aj(dij’)
Ai(dij’)                          Aj(dij’)

dij’
dij’
i                      j
dij
m                                             n                                i                  j
dij
m                                        n
dij’
dij’

Hi(dij’)                                                 Hj(dij’)
Hji(dij’)         Hij(dij’)
Hi(dij’)                                            Hj(dij’)
Hij(dij’)
Ps(i.j|m,n)
Ps(i.j|m,n)

Basic access methods                                                   RTS/CTS 4 WAY Access methods
CSMA/CA Performance Analysis

Basic access method
Station I transmits to j at time t
Successful data frame transmission conditions:
(i)     No station Aj(dij’)-Hj(dij’) transmits in the time interval(t- b ,t+ b );
(ii)    No station in Ai(dij’)-Hi(dij’) receives successfully a data frame whose
transmission was initiated in the time interval(t- b ,t+ b );
(iii)   No station in Hij(dij’) transmits during the interval (t,t+l);
(iv)    No station in the set Hji(dij’) transmits in the interval (t+l+DIFS,
t+l+max{DIFS, SIFS+Lack})
CSMA/CA Performance Analysis

RTS/CTS 4 way method
Station I transmits to j at time t
Successful data frame transmission conditions:
(i)     No station Aj(dij’)-Hj(dij’) transmits in the time interval(t- b ,t+ b );
(ii)    No station in Ai(dij’)-Hi(dij’) receives successfully a RTS frame whose
transmission was initiated in the time interval(t- b ,t+ b );
(iii)   No station in Hij(dij’) transmits during the interval (t,t+LRTS);
CSMA/CA Performance Analysis
From paper byHarshal S.Chhaya, Sanjay Gupta of Illionis Institute of Technology
Notation:
A: the area covered by a mobile station
Ai(d): the circular area of radius d around station I
Xi: location of station I
dij: distance between station I and j
dij’= a .dij , a >1 Denote the capture range of station j
a: capture parameter and is a function of the receiver characteristics and signaling format used
Hj(d): the set of stations that are hidden from station j and are in circle of radius d around it
Hij(d): the set of stations that are hidden from station I but not from station j in a circle of radius d around
station j
L: length of a data frame
Ltype: length of a “type” frame
b: propagation delay normalized by the expected length of a data frame, include the carrier sensing delay
G(I,j): exponentially data packet arrival rate generated at station I that is destined to j
Pc: the probability that no exchange of RTS/CTS frame is successful in a given renewal interval
G (i )   G (i, j )
jA

G   G (i, j )
i , jA
CSMA/CA Performance Analysis
Assumptions:
.ignore the effect of frames error due to bit error introduced by channel noise;
.limited station mobility;
.all data frame are of identical size
. The transmission from any station that are destined for distinct destinations are independent
Definitions:
Renewal point: the instance of the completion of a successful transmissions and/or a collision
Throughput:        defined as the number of successful transmissions between successive renewal points, divided
by the length of the time interval between the renewal points
Ts: the expected length of time interval between successive observations of the channel being idle more than
DIFS, when in the intervening renewal interval at least one successful transmission occur;
Tc: the expected length of time interval between successive observations of the channel being idle more than
DIFS, when in the intervening renewal interval only collision(s) occur
Tc> 1/G+L+DIFS+ b
Ts= 1/G+L+SIFS+Lack+DIFS+     b
Ps(I,j|m,n),   m,n e A, the probability that the transmission of a data frame from station I to j is successful
given that the transmission of a data frame from station m to n terminated the idle period, ie. Was the first
data frame to be transmitted once the channel had been sensed idle for time greater than DIFS ;
C(I,j) the set at all transmitter-receiver station pairs(m,n) such that   m e Aj(dij’)-Hj(dij’) or n e Ai(dij’)-Hi(dij’)
throughput
S           s (i,
i , j A
j)
ps(i, j )
[G (i, j )  (1  e )  G (m, n)]                                          G ( i . j )

( m , n )C ( i , j )

s(i, j )  G
1 / G  L  DIFS    L  SIFS                                                                        ack

ps(i, j )  exp{                                   
( m , n )C ( i , j )
G (m, n)  L                                   
k Hij ( dij ' )
G (k ) 
max[ 0, SIFS  L  DIFS ]             ack

k Hji ( dij ' )
G (k )}

S   s (i, j )
i , j A

p s (i, j )                  4

[G (i, j )  (1  e )  G (m, n)]                                                            G ( i . j )

( m , n )C ( i , j )

s (i, j )                  G
1 / G  L  SIFS  L  DIFS    (1  pc )(L  SIFS  L  SIFS )
RTS                                           CTS
4

ack

p s (i, j )  exp{   G (m, n)  L
4

( m , n )C ( i , j )

RTS k Hij ( dij ' )
G (k )}
Interference analysis

Local connectivity view
i+1 hop node       i hop node
i -1hop node

A

Outward                                           Inward nodes
nodes

Hybrid multi-base-station architecture
Involved problems

   Hybrid station type, flat architecture, multi hop ad hoc wireless
network. No whole range central control available. Different with
existing cellular and pure ad hoc wireless network;
   End to end multi-mode communication support: B-B,B-S,S-S;
   Sensor node energy limitation;
   Multi-hop ad hoc wireless sensor network route, MAC protocols,
esp. network self-organization, topology finding and adaptation,
collision free MAC protocols. Hidden terminals and efficient
   Base-station random access and mobility support;
   Network delay and throughput optimization.
Hybrid type station , hybrid protocol
Improve CSMA/CA
CSMA/CA with priorities
Elimination of
Each high priority node transmits a burst forrandom bursts
The surviving nodes defer transmission
a geometrically distributed number of slots
for a geometrically distributed number
and listens for one slot, if another burst is                      Listen after burst   of slots while listens to the channel,,if
heard, the node stops contending for the
any channel activities is detected,the
channel
packet transmission is postponed.

0 1 2 3 4

DATA                                                                                            DATA
ACK

ELIMINATION                YIELD
Nodes having a packet with priority
p transmit a burst in slot p+1 , if no
higher priority burst has been
heard                                                 PRIORITIZATION
Listen for priorities 0,1,2,3,or 4

This MAC protocol used in HIPERLAN I standard

Operation of the MAC protocol supporting prioritization and random burst elimination
Our propose:self-organization,MAC and route protocol
Synchronized sensor network frame and slot structure
Our propose:self-organization,MAC and route protocol
architecture:single base-station

DOCUMENT INFO
Shared By:
Categories:
Stats:
 views: 21 posted: 5/29/2010 language: English pages: 20
How are you planning on using Docstoc?