Communications and Network, 2013, 5, 10-15
doi:10.4236/cn.2013.53B1003 Published Online August 2013 (http://www.scirp.org/journal/cn)
FER Performance in the IEEE 802.11 a/g/n Wireless
LAN over Fading Channel
Ha Cheol Lee
Dept. of Information and Comm. Eng., Yuhan University, Bucheon City, Korea
Received June, 2013
ABSTRACT
This paper explores and compares FER (Frame Error Rate) of a MAC (Medium Access Control) layer in the IEEE
802.11 a/g/n wireless LAN. It is evaluated under the fading wireless channel, using theoretical analysis method. It is
analyzed by using the number of stations with both variable payload size and mobile speed on the condition that fading
margin and transmission probability are fixed. Especially, in the IEEE 802.11n, A-MSDU (MAC Service Data Unit
Aggregation) scheme is considered and the number of subframe is used as the variable parameter. In the IEEE
802.11a/g wireless LAN, fixed wireless channel is assumed to be Rayleigh fading channel. Mobile wireless channel is
assumed to be flat fading Rayleigh channel with Jake spectrum. The channel is in fading states or inter-fading states by
evaluating a certain threshold value of received signal power level. If and only if the whole frame is in inter-fading state,
there is the successful frame transmission. If any part of frame is in fading duration, the frame is received in error.
Keywords: Wireless LAN; MAC; FER; IEEE 802.11a/g/n
1. Introduction
Over the past few years, wireless LAN has emerged as a
promising applications. IEEE 802.11 a/g/n networks are
currently the most popular wireless LAN products on the
market. The conventional IEEE 802.11 g/a provides up
to 54 Mbps data rate [1]. With the successful deployment
of IEEE 802.11 a/g wireless LAN and the increasing
demand for real-time applications over wireless, the
IEEE 802.11n WG (Working Group) standardized a new
MAC and PHY(Physical) layer specification to increase
the bit rate to be up to 600 Mbps. In IEEE 802.11n wire-
less LAN, frame aggregation not only reduces the trans-
mission time for preamble and frame headers, but also
reduces the waiting time during CSMA/CA (Carrier
Sense Multiple Access with Collision Avoidance) ran-
dom backoff period for successive frame transmissions.
Frame aggregation can be performed either by A-MPDU
(MAC Protocol Data Unit Aggregation) or
A-MSDU[2][3][4]. This paper analyzes the FER in the
IEEE 802.11 a/g/n wireless LAN with fixed and mobile
stations. In Section 2, wireless LAN history and stan-
dards are investigated. In Section 3, FER of wireless
channel is derived with fixed station, and FER of mobile
channel is also derived with mobile station by using
theoretical analysis method. In Section 4, numerical re-
sults of FER are displayed in both fixed and mobile
wireless channel. Finally, it is concluded with Section 5.
2. Wireless LAN History and Standards
Standards in the IEEE project 802 target the physical
layer (PHY) and medium access control (MAC) layer [2].
When wireless LAN was first conceived, it seemed that it
would be just another PHY of one of the available stan-
dards.
The first candidate considered for this was IEEE’s
most prominent standard IEEE 802.3(Ethernet). However,
it soon became obvious that the radio medium is very
different from the well-behaved wire. Due to tremendous
attenuation even over short distances, collisions cannot
be detected. Hence, IEEE 802.3’s CSMA/CD (Carrier
Sense Multiple Access with Collision Detection) could
not be applied. The next candidate standard to be consid-
ered was IEEE 802.4. Its coordinated medium access, the
token bus concept, was believed to be superior to IEEE
802.3’s contention-based scheme. In the mean time, the
standardization body realized that a wireless communica-
tion standard would need its own very unique MAC. Fi-
nally, on March 21, 1991, project IEEE 802.11 was ap-
proved. The first IEEE 802.11 standard was published in
1997. At the lowest PHY layer, it provides a FHSS (Fre-
quency Hopping Spread Spectrum) and a DSSS (Direct
Sequence Spread Spectrum) PHY in the unlicensed 2.4
GHz band, and an infrared PHY at 316–353 THz. Al-
though all three provide a basic data rate of 1 Mb/s with
an optional 2 Mb/s mode, commercial infrared imple-

H. C. LEE 11
mentations do not exist. Similar to IEEE 802.3, basic
IEEE 802.11 MAC operates according to a listen-be-
fore-talk scheme, and is known as the DCF (Distributed
Coordination Function). It implements CSMA/CA rather
than collision detection as in IEEE 802.3. Indeed, as col-
lision cannot be detected in the radio environment, IEEE
802.11 waits for a backoff interval before each frame
transmission rather than after collisions. In addition to
DCF, the original IEEE 802.11 standard specifies an op-
tional scheme that depends on a central coordination en-
tity, the PCF (Point Coordination Function). This func-
tion uses the so called PC (Point Coordinator) that oper-
ates during the so-called contention-free period. The lat-
ter is a periodic interval during which only the PC initi-
ates frame exchanges via polling. However, the PCF’s
poor robustness against hidden nodes resulted in negligi-
ble adoption by manufacturers. Having published its first
IEEE 802.11 standard in 1997, the WG received feed-
back that many products did not provide the degree of
compatibility customers expected. As an example, often
the default encryption scheme, called WEP(Wired
Equivalent Privacy), would not work between devices of
different vendors. This need for a certification program
led to the foundation of the WECA (Wireless Ethernet
Compatibility Alliance) in 1999, renamed the WFA
(Wi-Fi Alliance) in 2003. Wi-Fi certification has become
a well-known certification program that has significant
market impact. The tremendous success in the market
and the perceived shortcomings of the base IEEE 802.11
standard provided a basis and impetus for a prolific program
of improvements and extensions. This has led to revisions
of the draft, driven by a complete alphabet of amend-
ments. Wireless LAN standards are shown in Table 1.
Although not interoperable, the DSSS and FHSS PHY
initially seemed to have equal chances in the market. The
FHSS PHY even had a duplicate in the HomeRF group
that aimed at integrated voice and data services. This
used plain IEEE 802.11 with FHSS for data transfer,
complemented with a protocol for voice that was very
similar to the Digital Enhanced Cordless Telecommuni-
cations standard. Neither HomeRF nor IEEE 802.11 saw
FHSS extensions, although plans for a second-generation
Table 1. Wireless LAN products on the market.
Standard Spectrum
Maximum
physical rate/Layer
2 Data rate
Tx Compatible
with
802.11n 2.4/5 GHz 600/100 Mbps MIMO OFDM 802.11b/g/a
802.11b 2.4 GHz 11/6-7 Mbps DSSS 802.11
802.11g 2.4 GHz 54/32 Mbps OFDM
802.11/
802.11b/
802.11n
802.11a 5.0 GHz 54/32 Mbps OFDM None
HomeRF existed that targeted at 10 Mb/s. In contrast, the
high-rate project IEEE 802.11b was started in December
1997 and boosted the data rates of the DSSS PHY to 11
Mb/s. This caused IEEE 802.11b to ultimately supersede
FHSS, including HomeRF, in the market. The first ex-
tension project, IEEE 802.11a, started in September 1997.
It added an OFDM(Orthogonal Frequency Division Mul-
tiplexing) PHY that supports up to 54 Mb/s data rate.
Since IEEE 802.11 a operates in the 5 GHz band, com-
munication with plain IEEE 802.11 devices is impossible.
This lack of interoperability led to the formation of IEEE
802.11 g, which introduced the benefits of OFDM to the
2.4 GHz band. As IEEE 802.11 g’s extended rate PHY
provides DSSS-compatible signaling, an easy migration
from IEEE 802.11 to IEEE 802.11 g devices became
possible. While IEEE 802.11b uses only DSSS technol-
ogy, IEEE 802.11g uses DSSS, OFDM, or both at the 2.4
GHz ISM band to provide high data rates of up to 54
Mb/s. combined use of both DSSS and OFDM is
achieved through the provision of four different physical
layers. These layers coexist during a frame exchange, so
the sender and receiver have the option to select and use
one of the four layers as long as they both support it. The
four different physical layers defined in the IEEE 82.11g
standard are ERP-DSSS/CCK, ERP-OFDM, ERP-DSSS/
PBCC and DSSS-OFDM. From the above four physical
layers, the first two are mandatory and the other two are
optional [1].
As the first project whose targeted data rate is meas-
ured on top of the MAC layer, IEEE 802.11n provides
user experiences comparable to the well known Fast
Ethernet (IEEE 802.3u). Far beyond the minimum re-
quirements that were derived from its wired paragon’s
maximum data rate of 100 Mb/s, IEEE 802.11n delivers
up to 600 Mb/s. Its most prominent feature is MIMO
(Multiple-Input Multiple-Output) capability. A flexible
MIMO concept allows for arrays of up to four antennas
that enable spatial multiplexing or beam forming. Its
most debated innovation is the usage of optional 40 MHz
channels. Although this feature was already being used
as a proprietary extension to IEEE 802.11a and IEEE
802.11g chipsets, it caused an extensive discussion on
neighbor friendly behavior. Especially for the 2.4 GHz
band, concerns were raised that 40 MHz operation would
severely affect the performance of existing IEEE 802.11,
Bluetooth (IEEE 802.15.1), ZigBee(IEEE 802.15.4), and
other devices. The development of a compromise, which
disallows 40 MHz canalizations for devices that cannot
detect 20 MHz-only devices, prevented ratification of
IEEE 802.11n until September 2009. As a consequence
of 20/40 MHz operation and various antenna configura-
tions, IEEE 802.11n defines a total of 76 different MCSs.
Figure 1 provides an overview of the IEEE 802.11 PHY
amendments and their dependencies [2].

H. C. LEE
12
A key element to the IEEE 802.11 success is its simple
MAC operation based on the DCF protocol. This scheme
has proven to be robust and adaptive to varying condi-
tions, able to cover most needs sufficiently well. Follow-
ing the trends visible from the wired Ethernet, IEEE
802.11’s success is mainly based on over provisioning of
its capacity. The available data rate was sufficient to
cover the original best effort applications, so complex
resource scheduling and management algorithms were
unnecessary. However, this may change in the future.
Because of the growing popularity of IEEE 802.11,
Wireless LANs are expected to reach their capacity lim-
its. Moreover, applications like voice and video stream-
ing pose different demands for quality of service. There-
fore, traffic differentiation and network management
might become inevitable. Figure 2 shows IEEE 802.11
MAC layer amendments
3. FER Analysis
3.1. FER of Fixed Wireless Channel
In IEEE 802.11a/g wireless LAN, fixed wireless channel
isassumed to be Rayleigh fading channel. The probability
of bit error is upper bound by
Figure 1. The IEEE 802.11 PHY layer amendments and
their dependenc ie s[2].
Figure 2. The IEEE 802.11 MAC layer amendments[2].
1
free
b
dd
PB
k


dd P (1)
where
f
ree
d
B is the free distance of the convolutional code, d is the total number of information bit ones on
all weight d paths, d is the probability of selecting a
weight d output sequence as the transmitted code se-
quence, and k is the number of information bits per clock
cycle. Because the weight structure is generally accepted
that the first five terms in equation (1) dominate, equa-
tion (1) can be rewritten as
P
4
1free
free
d
b
dd
PB
k


dd P (2)
The probability of selecting the incorrect path when d
is odd.



1
2
1
ddi
i
dd
i
d
Pp
i



p
(3)
where p is the probability of channel bit error. The prob-
ability of selecting the incorrect path when d is even.


 
2
2
1
2
1
11
22
dd
di d
i
dd
i
d
d
Ppp p
d
i


 


p
(4)
To achieve data rates of 54 Mbps for wireless access,
the IEEE 802.11 a standard utilizes MQAM (6q

,
64M

) with convolutional coding at rate r = 3/4. We
obtain the approximate channel bit error probability for
the sub-channel for MQAM with a square constella-
tion as
th
i






3
3211
2
3
2
3211
2
1
41
3211
221 1
1
21
311
11
bi
ibI
i
i
bi
bI
i
i
qr
dqr M
id
bI
I
qr
dqr M
bI
I
e
M
pqr M
qc M
e
M
qr M
cq M










 
 




 








 














 







(5)
where 22.6 0.1c


 is empirically obtained and d = 1
for HDD. i

is the ratio of direct-to-diffuse signal
power on the sub-channel.
th
i

has 0 in a pure
Rayleigh fading channel and ranges from 0 to 10 in a
composite Rayleigh/Ricean fading channel. bi

is the
ratio of received average energy per bit-to-noise power
spectral density on the sub-channel. The overall p is
the average of the probability of bit error on each of the
N OFDM sub-channels [5, 6].
th
i

H. C. LEE 13
1
1N
i
i
p
N
p (6)
Note that for either no channel fading or for all sub-
channels experiencing the same fading (that is, i


and for all
i
bb ), then i.
i  pp/N
bbo
is
the ratio of received average energy per bit-to-noise
power spectral density ,
E  

is the ratio of direct-to-dif-
fuse signal power. Now, using equation (6) in equation (3)
or (4) and taking the result into equation (2), we obtain
the performance of 64 QAM with HDD over Ricean
fading channels. For basic access mechanism, a data
packet including the PHY header and the MAC header
needs retransmission if any one bit of them is corrupted.
We define a variable which is the probability that a
backoff occurs in a station due to bit errors in packets.
We further assume that bit errors randomly appear in the
packets. So frame error rate is represented by (7).
P
c
1(1 )
p
reamble ACKLPHYMACPL
hh
PP
cb 
  (7)
CSMA/CA is also used as the MAC scheme in IEEE
802.11n wireless LAN, and it has basic and RTS/CTS
access scheme. Although there is a successful RTS/CTS
transmission in the time slot, a frame has to be retrans-
mitted when there is a bit error in a payload. For conven-
ience, we define a variable which is the probability
that a backoff occurs in a station due to bit errors in
packets. We further assume that bit errors randomly ap-
pear in the packets and A-MSDU scheme is used. So
frame error rate is represented by (8).
P
e
1(1 )
L
P
e q (8)
where L is the aggregated MAC frame’s size. For a con-
volutional code with a coding rate kc/nc, the bit error rate,
denoted as q, can be approximated by

1
2
1()1( is odd)
free free
free
ddi
free i
bb free
d
ci
d
qqqd
i
k







 (9)

()1
1
1
2
122
()(1)
22
( is even)
free free
free bb
cfree
free free
free
bb
free
c
free
ddi
di
qq
i
qkd
i
dd
dqq
d
k
d

 








where dfree is the maximum free distance of the convolu-
tional code and qb is the probability of a bit error for the
M-QAM[5].
2( 1)
s
b
M
q
qM  (10)
qs is the SER(Symbol Error Rate) under the Rician fading
channel.
2
min 2
2
min
()
(|| ||)
8
()
()
1
44 8
2
min
1
()
()
18
dH
d
K
sK
qe
d
K








(11)
K is the Rician factor  may be interpreted as the average
SNR at the receive antenna in a SISO fading link. dmin is
the minimum distance of separation of the underlying
scalar constellation. H is MR  MT channel transfer func-
tion and 2
|| ||
H
is the squared Frobenius norm of the
channel [6, 7].
3.2. FER of Mobile Wireless Channel
Mobile wireless channel is assumed to be flat fading
Rayleigh channel with Jake spectrum. The channel is in
fading states or inter-fading states by evaluating a certain
threshold value of received signal power level. If and
only if the whole frame is in inter-fading state, there is
the successful frame transmission. If any part of frame is
in fading duration, the frame is received in error. In the
fading channel fading margin is considered and defined
as ρ = Rreq/Rrms, Where Rreq is the required received
power level and Rrms is the mean received power. Gener-
ally, the fading duration and inter-fading duration can be
taken to be exponentially distributed for ρ<-10dB. With
the above assumptions, let be the frame duration,
then the frame error rate is given by (12).
Tpi
1(
f
i
Ti
FERP tTpi
Ti T
 
)
(12)
where, is inter-fading duration and it
f
t is fading du-
ration. is the mean value of the random variable
and
Ti it
f
T is the mean value of the random variable
f
t.
is the probability that inter-fading duration
lasts longer than . Since exponential distribution is
()Pti Tpi
Tpi
assumed for , it()exp(iTpi Pt TpiTi ) . For Rayleigh fading
channel, the average fading duration is given by (13).
exp()1
2
Ti fd




 (13)
iTTf

is 1
f
N, where
f
N is the level crossing rate,
which is given by 2exp( )fd

 . is the maxi- df
mum Doppler frequency and evaluated as


.

is the
mobile speed and

is wavelength. Frame error rate
can be expressed by (14).
1 exp(2)d
F
ERf Tpi    (14)

H. C. LEE
14
Equation (14) shows that frame error rate is deter-
mined by fading margin, maximum Doppler frequency
and frame duration. Since fading margin and maximum
Doppler frequency are hard to dynamically control, the
only controllable parameter is frame duration to get re-
quired frame error rate. For the RTS/CTS access mode,
the frame duration
p
iTis
H
RTS CTSDATA ACK
TTTT T

 .
H
T is preamble transmission time + PLCP header trans-
mission time + MAC header transmission time.
D
ATAT
ACKT is MSDU transmission time and is ACK frame
transmission time.
R
TS is RTS frame transmission time
and is CTS frame transmission time[6,7].
T
CTS
T
4. Numerical Results of FER over the Fading
Channel
4.1. FER Results with Fixed Stations
In the Figure 3, Pc(P, b

, K) shows FER(Frame Error
Rate) due to b

, the ratio of received average energy per
bit- to-noise power spectral density[6,7]. K means Rician
factor and P means payload size. And as expected, the
FER performance improves with K and the smaller pay-
load size is, the better performance is.
In the Figure 4, qs(ρ,K) shows SER(Symbol Error
Rate) and Pe(K,ρ,ns,P) shows FER(Frame Error Rate)
[6,7]. K means Rician factor and as expected, the FER
performance improves with K and the smaller subframe’
payload size is, the better performance is.
(a) IEEE 802.11a OFDM
(b) IEEE 802.11g ERP-OFDM
(c) 802.11g DSSS-OFDM
Figure 3. Frame error rate of IEEE 802.11a/g fixed LAN
over Rayleigh fading channel.
(a) SER
(b) FER
Figure 4. SER and FER of IEEE 802.11n fixed LAN over
Rician fading channel.
4.2. FER Results with Mobile Stations
In the Figures 5(a)-(c), the symbol fer (,

, P) shows
frame error rate of IEEE 802.11a/g. In the Figure 5(d),
the symbol fer (ns, ,

, P) shows frame error rate of
IEEE 802.11n with the horizontal parameter of sub-
frame’ payload size. In the Figure 5(e), the symbol fer (,
ns,

, P) shows frame error rate of IEEE 802.11n using
the number of subframes as the horizontal parameter. It
is generally identified that the higher mobile speed is, the
C
opyright © 2013 SciRes. CN

H. C. LEE
15
higher FER is. In case of payload size, the same result
mentioned above is also acquired.
(e) IEEE 802.11n OFDM (58.5 Mbps, number of subframe)
Figure 5. Frame error rate of IEEE 802.11a/g/n mobile LAN.
5. Remarks
(a) IEEE 802.11a OFDM (54 Mbps)
This paper explored the FER performance of MAC layer
in the IEEE 802.11a/g/n wireless LAN under the er-
ror-prone channel. The fixed wireless channel was as-
sumed to be Rayleigh fading channel and the mobile
wireless channel was assumed to be flat fading Rayleigh
channel with Jake spectrum. The MAC protocol that they
are based upon is the same and employs a CSMA/CA
protocol with binary exponential back-off. IEEE 802.11
DCF is the de facto MAC protocol for wireless LAN
because of its simplicity and robustness.
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