multiple access methods in satellite communication
Multiple Access Protocols for Mobile Communications - GPRS, UMTS and Beyond
Ngày tải lên :
02/03/2013, 16:59
... extremely
large in the case of unconstrained channel access, resulting in a low inherent statistical
multiplexing gain. By combining CDMA with PRMA, it is possible to control the access
of users ... 46
2.6 Summary 48
3 Multiple Access in Cellular Communication Systems 49
3.1 Multiple Access and the OSI Layers 49
3.2 Basic Multiple Access Schemes 53
3.3 Medium Access Control in 2G Cellular Systems ... (P
loss
)
max
in multiples of σ
K
d Hamming distance
d
il
Interleaving depth
d
min
Minimum Hamming distance
e Error correcting capability of an (L, B, e) block code; also 2.718 282
f
CAF
Channel access...
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Advances in Satellite Communications Part 1 pptx
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...
Printed in Croatia
A free online edition of this book is available at www.intechopen.com
Additional hard copies can be obtained from orders@intechweb.org
Advances in Satellite Communications, ... capabilities. In addition, a satellite link engineer has to
consider the constrains of the communication channel; so many radio frequency
calculations are needed, these include link budget analysis, ... 1
Antennas in Satellite Communications
Advances in Satellite Communications
Edited by Masoumeh Karimi and Yuri Labrador
Published by InTech
Janeza Trdine 9, 51000...
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Advances in Satellite Communications Part 2 pptx
Ngày tải lên :
19/06/2014, 19:20
... & King, 1979). As
the wave velocities in a finite helix are hard to calculate, those calculated for the infinite
Advances in Satellite Communications
10
The existence of multiple ... et al., 2006).
In this chapter, we introduce a design of the helical antenna obtained by combining two
methods to improve the radiation properties of this antenna; one is changing the pitch
angle, ... lengths were varied in
order to obtain a wider bandwidth with higher antenna gain. In (Skiljo et al., 2010) the axial
mode bandwidth was examined by means of parameters defining the limits of...
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Advances in Satellite Communications Part 3 doc
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19/06/2014, 19:20
... z
M
μν
(z)
M
μν
(0)=M
in
μν
(0), (9)
Fig. 3. Model of wave propagation in an inhomogeneous random medium.
32
Advances in Satellite Communications
2 Will-be-set-by -IN- TECH
Fig. 1. Spot dancing and wave ... However, because a carrier frequency becomes higher according to the increase in
the required channel capacity of satellite communication links in the next generation, the
analysis of the effects of ... shorter in order to achieve a phase lag of 45°. Instead of infinite
balun, we proposed a stripline structure for impedance matching and the support for helical
wire. Fig. 15 c) shows that matching...
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Advances in Satellite Communications Part 4 pptx
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19/06/2014, 19:20
... for Satellite Communications in Ka-band 19
Fig. 14. Average intensity for the uplink in the beam radius at the transmitting antenna
w
0
= 1.2 m normalized by the intensity on a beam axis in free ... (24)
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Advances in Satellite Communications
12 Will-be-set-by -IN- TECH
3. Results
3.1 Modulus of complex degree of coherence
3.1.1 Uplink
Substituting (24) and (27) into (30), the DOC at the GEO satellite in ... predict that the increase in BER is caused by the decrease in the average received intensity
due to spot dancing shown in Fig. 1.
3.2.2 Downlink
For the downlink, the decrease in the spatial coherence...
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Advances in Satellite Communications Part 5 potx
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19/06/2014, 19:20
... process of representing information in a more compact
form by eliminating redundancies in the original data representation (Pu, 2006). Due to the
presence of redundancies in the original representation, ... antenna in order to satisfy the required
EIRP from the point of view of the decrease in an in uence of atmospheric turbulence on BER
in the uplink.
3.3.2 Downlink
For the downlink, we can obtain BER ... flow information before undergoing
compression in order to increase compression ratio.
Unfortunately, IPzip may not suit for real-time processing as it needs to carry out offline
training to...
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Advances in Satellite Communications Part 6 ppt
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19/06/2014, 19:20
... original form. The
original block of packets will be divided into individual packets according to the original
size of each combined packet. After that, these individual packets are stored in ...
Advances in Satellite Communications
76
Fig. 17. The packet drop rate distribution in Scenario 2.
The proposed scheme succeeds in reducing the packet drop rate by 1 – 90 percent in
Scenario ... scheme in satellite network
topology is shown in Figure 10 below. As stated earlier, the main objective of this research
study is to overcome the limitation and constraints of satellite communication...
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Advances in Satellite Communications Part 7 pdf
Ngày tải lên :
19/06/2014, 19:20
... Hybr id Satellite/ Terrestrial Networks 9
The following points must be kept in mind when selecting a GKMA:
• Protection against collusion. GMs and non-members should not be able to join their
knowledge ... to ſgure 3. In the ory, for each single change
in the users’ base, the TEK (K
I
in the ſgure) should be changed. Although grouping changes
occurred in a given time interval and updating TEK once ... spreadsheet included): Industry
Report, 07.04.2011, Available from
http://www.mindbranch.com/listing/product/R1-4772.html
Mitra, M. (2005). Satellite Communication, Prentice-Hall of India Private...
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Advances in Satellite Communications Part 8 pptx
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... Satellite/ Terrestr ial Networks 21
LAN
LAN
Internet terrestre
SsS
Up-link
Down-link
Down-link
Down-link
Down-link
Receiving path
Receiving path
Receiving path
Receiving path
Reaching
path
Return path
Sr
1
Sr
M
Sr
R
Sr
M-1
R
1
R
M
R
M-1
R
R
Fig. ... makes it interesting in the context we are examining
(Tommasi et al., 2009). One more reason of interest for the protocol is its capability to transmit
information to users who can receive information ... transmission of a message M, replicating it in N packets.
P
i
is the i-th reply in the N packets sequence. The delivery of a message is organized in two
phases. During the Winding phase, the sender is restricted...
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Advances in Satellite Communications Part 9 potx
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19/06/2014, 19:20
... properly integrated in the
proposed hybrid architecture. In this line and for completeness some important First
Responders’ open technical communication problems are introduced relating interoperability ... point it is useful
to mention some very basic facts and definitions related to On-line Detection. The subject
enjoys intensive ongoing research since wireless and distributed networks are in ... decisions using identical local decision rules
(Chamberland & Veeravali, 2006).
As stated in (Tsitsiklis, 1993), decentralized schemes are definitely worth considering in
contexts involving geographically...
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Advances in Satellite Communications Part 10 pptx
Ngày tải lên :
19/06/2014, 19:20
... capable in offering) real-time or nearly–real time response times for
rapid information updating and Rapid Mapping activities and Surveillance including the
“very urgent” imaging data downlink ... electrons incident angle, the
surface material (typically aluminum), and the coating process applied to the metallic
surfaces (e.g. silver-plating, alodine coating).
In order to gain a physical insight ... advancements in aviation, sensor and imaging technologies, telemetry, data
fusion and processing, and geo-information/value added products use. The authors are
currently involved in assisting the integration...
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Advances in Satellite Communications Part 11 pot
Ngày tải lên :
19/06/2014, 19:20
... rectangular
waveguides operating in the single-mode regime. In other words, the OMT should in fact be
described using the four-port scattering matrix shown in Fig. 5.1 (Peverini, et al. 2006).
... required to refine the initial solution. In particular, such an approach could lead to
sub-optimum designs owing to the presence of local minima in the pertaining cost function.
In order to overcome ... behavior in
this case. The spacing between the various discontinuities is instead adjusted to obtain a
good matching in the pass-band.
The correct choice between the two architectures mainly depends...
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Advances in Satellite Communications Part 12 potx
Ngày tải lên :
19/06/2014, 19:20
... technology in the user segment for satellite communications will
substitute reflectors providing a more compact and easy to install antenna system, which is
an interesting solution e.g. for satellite ... Feed Chains for High Capacity Satellite Communications Systems
157
5.5 Reverse coupling OMT
The broadband operative condition of some of the above-mentioned OMTs is mainly
obtained inserting ... Roughly speaking, from a functional point of
view the first group of corrugations (called ``throat region'') in the horn is designed in order
to convert the input incident field into the...
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Advances in Satellite Communications Part 13 doc
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19/06/2014, 19:20
... antenna array for satellite tracking in ground station
The aim of using a single antenna for tracking many satellites at the same time avoiding
mechanical movements as well as its inexpensive cost ... obtain the required gain and cover the indicated range, it is required around
15 beams, which can be obtained by integrating the beamforming networks with switches in
the design as presented in ... and c) Miniaturized BLC Prototype.
New Antenna Array Architectures for Satellite Communications
171
RF circuits. The principal patch is fed in quadrature in 2 points separated 90º in order...
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Báo cáo sinh học: " Decentralized estimation over orthogonal multiple- access fading channels in wireless sensor networks-- optimal and suboptimal estimators" pot
Ngày tải lên :
18/06/2014, 22:20
... known CSI at low communication SNR levels. It
is interesting to see that using more training symbols does not improve the performance of the MLE as
expected, because inserting training symbols will ... discussed, inserting training symbols is a heuristic way to improve the performance. It is shown in the
25
Decentralized estimation over orthogonal multiple-
access fading channels in wireless ... Furthermore, since the estimation quality of the first stage is available, we use BLUE to obtain
ˆ
θ for exploiting the quality information instead of using the MLE in the M-step as in the standard...
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