Image Processing Reference
In-Depth Information
TABLE .
Overview on Activities within IEEE .
Group
Subject
Status
am
PHYintheGHzbands
Compl ed
b
m
High rate mode in . GHz band
Completed
c
Extensions for specific MAC ooperations (bridging) IEEE .D
Completed
d
m
Supplements for new regulatory regions, raming extensions
Completed
e
m
Enhancements for QoS
Completed
F
To achieve multi vendor AP interoperability
Withdrawn
g
m
Enhancements of .b data rates
Completed
h
m
Extensions for channel selection for .b
Completed
i
m
Enhancements for security and authentication algorithms
Completed
j
m
Enhancements for the use of .a in Japan
Completed
k
Definition of radio resource management measurements
Conditional
l
Nonexistent
m
Summarizes the extensions a, b, d, e, g, h, i, j in IEEE .-
Completed
n
Higher throughputs using multiple input multiple output (MIMO)
Approved draft
o
Nonexistent
p
For car-to-car or car-to-infrastructure communication
Ongoing
q
Nonexistent
r
Fast roaming
Approved draft
s
Extensve Service Set mesh networking
Ongoing
t
Test methods and metrics recommendation
Ongoing
u
Interworking with non- networks (e.g. cellular)
Ongoing
v
Wireless network management
Ongoing
w
Protected management frames
Ongoing
x
Nonexistent
y
- MHz operation in the United States
Approved draft
z
Extensions to direct link setup
Started
25.4.2 Performance
Next to aspects like individual link throughput, network capacity, and interference robustness, the
transmission environment has to be taken into consideration when considering the use of IEEE .
on the factory floor. As the scenarios envisioned for IEEE . were placed primarily in homes and
offices, some differences occur when looking at the delay spread. While in homes and offices the
delayspreadisassumedtobe
ns, respectively, it can be larger on factory floors.
In [SMLW], delay spreads with root mean square values between and ns were measured.
[OP] considers values of - ns. [Gor]'s values go up to ns.
In case of IEEE .b a conventional rake receiver supports (only) about ns delay spread in
theMbpsmodeandnsinthe.Mbpsversion[vNAM
+
]. When employing an IEEE .b
system with such a conventional receiver on a factory floor inter-symbol and/or inter-chip/codeword
interference (ISI and/or ICI) are likely to degrade the performance. Nevertheless, with more com-
plex receiver algorithms (like presented in [CLMK,LMCW]), IEEE .b can compensate well
for delay spreads of µs and even mobility of the user. Another option of course is to use IEEE
.a or g. Because of the guard interval inherent in the OFDM technology, delay spreads of several
hundred nanoseconds can be easily supported without paying attention to the receiver algorithms
implemented [vNAM
+
].
The overall network performance (or interference performance, as discussed in Section .)—in
contrast to the individual link performance—is not that is often addressed as an issue. he publica-
tions that do exist do not at all support this attitude. In [Lin] it is shown that co-channel interference
with a carrier-to-interference ratio (CIR) of dB still results in a packet loss rate of %-%
(BER
<
ns and
<
−
) and that with a frequency offset of MHz still CIR
dBisrequiredtoachievethesame
result. [Bia,Sad] present how the aggregate throughput in a single network decreases with the
number of users, either due to hidden or exposed terminal problems or due to additional RTS/CTS
overhead. With only stations [Bia] or a hidden node probability of % [Sad], the system
throughput is about halved (!) in case of byte payloads. Only when there are more than
stations is the RTS/CTS implementation justified, while the throughput is still reduced.
Thus, when installing IEEE . in a cellular fashion, some kind of frequency planning should
be performed. Several algorithms have been published (see, e.g., [TMK,HF,CMTK]); for IEEE
=
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