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Appazova S.S. Course on a subject «Systems, channels and communication
networks». Project manager is
Aslanov M.T. After collecting and processing the literature on a given topic in
the course work, you need to identify the underlying problem, think about how
it can be solved. To answer the question that needs to be done to resolve it,
you actually get the goal of the course work, it will be based on the
theoretical and practical part and formed a project plan.the first part of
course work describes systems, channels and communication networks, block diagram, general immunity of radio,
the passage of noise through the path of the receiving device. And also made
the choice and justification of the structural scheme and the circuit diagram.
The second part consists of part of the settlement, where calculated the
necessary data transmission speed and the duration of single elements,
bandwidth filters transmission and reception, the effective value of
interference in the channel, time of entry into synchronism and synchronization
reference time fluctuations.project is implemented in the program Word 2010
environment . This course work consists pages, figures and basic material from
books.
1. Signals, channels and communication networks
telecommunications and computer networking, a communication
channel or channel, refers either to a physical transmission medium such as a
wire, or to a logical connection over a multiplexed medium such as a radio
channel. A channel is used to convey an information signal, for example a
digital bit stream, from one or several senders (or transmitters) to one or
several receivers. A channel has a certain capacity for transmitting
information, often measured by its bandwidth in Hz or its data rate in bits per
second.data from one location to another requires some form of pathway or
medium. These pathways, called communication channels, use two types of media:
cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast
(microwave, satellite, radio, and infrared). Cable or wire line media use
physical wires of cables to transmit data and information. Twisted-pair wire
and coaxial cables are made of copper, and fiber-optic cable is made of
glass.information theory, a channel refers to a theoretical channel model with
certain error characteristics. In this more general view, a storage device is
also a kind of channel, which can be sent to (written) and received from
(read).channel can take many forms. Examples of communications channels
include:
1. A connection between initiating and terminating nodes
of a circuit.
2. A single path provided by a transmission medium via
either
· physical separation, such as by
multipair cable or
· electrical separation, such as by
frequency-division or time-division multiplexing.
3. A path for conveying electrical or electromagnetic
signals, usually distinguished from other parallel paths.
· A storage which can communicate a
message over time as well as space
· The portion of a storage medium, such
as a track or band, that is accessible to a given reading or writing station or
head.
· A buffer from which messages can be
'put' and 'got'. See Actor model and process calculi for discussion on the use
of channels.
. In a communications system, the physical or logical
link that connects a data source to a data sink.
5. A specific radio frequency, pair or band of frequencies,
usually named with a letter, number, or codeword, and often allocated by
international agreement.Examples:
· Marine VHF radio uses some 88
channels in the VHF band for two-way FM voice communication. Channel 16, for
example, is 156.800 MHz. In the US, seven additional channels, WX1 - WX7, are
allocated for weather broadcasts.
· Television channels such as North
American TV Channel 2 = 55.25 MHz, Channel 13 = 211.25 MHz. Each channel is 6
MHz wide. Besides these "physical channels", television also has
"virtual channels".
· Wi-Fi consists of unlicensed channels
1-13 from 2412 MHz to 2484 MHz in 5 MHz steps.
· The radio channel between an amateur
radio repeater and a ham uses two frequencies often 600 kHz (0.6 MHz) apart.
For example, a repeater that transmits on 146.94 MHz typically listens for a
ham transmitting on 146.34 MHz. [1]
All of these communications channels share the property that
they transfer information. The information is carried through the channel by a
signal.channel can be modelled physically by trying to calculate the physical
processes which modify the transmitted signal. For example in wireless
communications the channel can be modelled by calculating the reflection off
every object in the environment. A sequence of random numbers might also be
added in to simulate external interference and/or electronic noise in the
receiver.a communication channel is usually modelled as a triple consisting of
an input alphabet, an output alphabet, and for each pair (i, o) of input and
output elements a transition probability p(i, o). Semantically, the transition
probability is the probability that the symbol o is received given that i was
transmitted over the channel.and physical modelling can be combined. For
example in wireless communications the channel is often modelled by a random
attenuation (known as fading) of the transmitted signal, followed by additive
noise. The attenuation term is a simplification of the underlying physical
processes and captures the change in signal power over the course of the
transmission. The noise in the model captures external interference and/or
electronic noise in the receiver. If the attenuation term is complex it also
describes the relative time a signal takes to get through the channel. The
statistics of the random attenuation are decided by previous measurements or
physical simulations.models may be continuous channel models in that there is
no limit to how precisely their values may be defined. [2] channels are also
studied in a discrete-alphabet setting. This corresponds to abstracting a real
world communication system in which the analog->digital and
digital->analog blocks are out of the control of the designer. The
mathematical model consists of a transition probability that specifies an
output distribution for each possible sequence of channel inputs. In
information theory, it is common to start with memoryless channels in which the
output probability distribution only depends on the current channel
input.channel model may either be digital (quantified, e.g. binary) or analog.
· Digital (discrete) or analog
(continuous) channel
· Baseband and passband channel
· Transmission medium, for example a
fibre channel
· Computer network virtual channel
· Simplex communication, duplex
communication or half duplex communication channel
· Uplink or downlink (upstream or
downstream channel)
· Broadcast channel, unicast channel or
multicast channel
Communication keeps a weather forecaster informed of
conditions measured by a multitude of sensors. Indeed, the list of applications
involving the use of communication in one way or another is almost endless.the
most fundamental sense, communication involves implicitly the transmission of
information from one point to another through a succession of processes, as
described here:
1. The generation of a message signal: voice, music,
picture, or computer data.
2. The description of that message signal with a certain
measure of precision, by a set of symbols: electrical, aural, or visual.
3. The encoding of these symbols in a form that is
suitable for transmission over a physical medium of interest.
4. The transmission of the encoded symbols to the desired
destination.
5. The decoding and reproduction of the original symbols.
6. The re-creation of the original message signal, with a
definable degradation in quality; the degradation is caused by imperfections in
the system.
There are, of course, many other forms of communication that
do not directly involve the human mind in real time. For example, in computer
communications involving communication between two or more computers, human
decisions may enter only in setting up the programs or commands for the
computer, or in monitoring the results.of the form of communication process
being considered, there are three basic elements to every communication system,
namely, transmitter, channel, and receiver, as depicted in Figure 1. The
transmitter is located at one point in space, the receiver is located at some
other point separate from the transmitter, and the channel is the physical
medium that connects them. The purpose of the transmitter is to convert the
message signal produced by the source of information into a form suitable for
transmission over the channel. However, as the transmitted signal propagates
along the channel, it is distorted due to channel imperfections. Moreover,
noise and interfering signals (originating from other sources) are added to the
channel output, with the result that the received signal is a corrupted version
of the transmitted signal. The receiver has the task of operating on the
received signal so as to reconstruct a recognizable form of the original
message signal for a user.are two basic modes of communication:
1. Broadcasting, which involves the use of a single
powerful transmitter and numerous receivers that are relatively inexpensive to
build. Here information-bearing signals flow only in one direction.
2. Point-to-point communication, in which the
communication process takes place over a link between a single transmitter and
a receiver. In this case, there is usually a bidirectional flow of
information-bearing signals, which requires the use of a transmitter and
receiver at each end of the link.
1. Elements of a communication
system.
broadcasting mode of communication is exemplified by radio
and television, and the ubiquitous telephone provides the means for one form of
point-to-point communication. Another example of point-to-point communication
is the link between an Earth station and a robot navigating the surface of a
distant planet.these different communication systems as well as others not
mentioned here share a common feature: The underlying communication process in
each and every one of them is statistical in nature. Indeed, it is for this
important reason that much of this book is devoted to the statistical
underpinnings of communication systems. In so doing, we develop an exposition
of the fundamental issues involved in the study of different communication
methodologies and thereby provide a natural forum for their comparative
evaluations.is the study of the transmission of various data through different
systems. We can transfer the information from one region to another with out
any loss of the data. A communication system is a collection of network systems
which includes transmission system, encoder, noisy channel, decoder and
receiving system. All these components perform effectively in a good communication
system. The block diagram representing the communication system is given below.
Figure 2. Digital Communication Model
The functions of the each systems are described here.
Transmitter. Transmitter is the first component in this block diagram. Using
this system we can generate the messages which is to be sent through this
system. Encoder. Encoder is the second element in the communication system. It
performs the encoding of the given data, which means that this system converts
the messages in the form of symbols for transmission purpose. In this system, a
sequence of characters are created in a special format for an effective
transmission. This encoding system is used for security purpose. Noisy
Channel:This is the third block in the block diagram of communication system.
Noisy channel is nothing but the medium through which the message is
transmitted. Messages are conveyed through this channel. Different channels
have different strengths and weaknesses. Each channel has its own frequency and
different applications have different operating frequencies. Decoder. Decoder
is used to decode the encoded message and retrieve the actual message. Decoding
must be done correctly . If this part is not performed well then the message
which is received might not be correctThis encoding and decoding will be very
help full in military and mobile communications. Receiver. This is the final
block in block diagram of communication system. This can be said as the target
to which the information need to be delivered.
mobile cellular telecommunications industry closed the 2009
calendar year with 3.6 billion global customers and generating approximately
$700 billion in revenues. The cellular telecommunications industry is poised to
grow to more than $850 billion by 2012 and serve an estimated 5 billion
customers worldwide 1 . And while the global economic downturn is
serious business, it doesn't appear that its impact will be as serious for the
mobile cellular telecommunications industry as some might have
expected.cellular telecommunications industry as a whole is expected to
continue to grow, which is good news for all members of the wireless service
domain. There is, however, a caveat: While strong growth in the sector is
expected, that growth will occur in one specific area: mobile data. This growth
is largely due to the flattening of the voice and Short Message Service (SMS)
markets in the developed world as those markets saturate. to making significant
investments to upgrade the mobile telecommunications infrastructure, it is
important to analyse technology trends and determine the most effective use of
investment resources. Therefore, it is necessary to identify which processors
will best support future growth demands. New processor architectures must offer
single software support, while incorporating heightened levels of communication
security. solution is an advanced communication processor architecture, which
enables equipment manufacturers and service providers to overcome the
challenges associated with future mobile networks. solution in question will
incorporate a communication processor built on proven, programmable, and
scalable elements, and will enable communication companies to increase their
share of the estimated $850 billion market. Impact Analysis. Two of the largest
forces driving the cellular communications industry are demand for mobile
services and mobile broadband access. By analysing mobile applications from two
parameters with regard to the underlying processor or CPU, one can see
associated trends. One parameter is the CPU core performance based on the
application demands. The other parameter is the number of cores or threads that
are demanded by the application. these two parameters against each other
reveals several underlying trends in the processor market. For instance, when
the performance-per-core is plotted against the number of cores required for a
broad range of devices it reveals that some applications are CPU-bound and
require more CPU power. CPU-bound applications tend to be the pure control
plane applications, such as an xGSN control plane card; however, other
applications are threads-bound and require more threads-per-processor.
Threads-bound devices tend to be classic data plane-centric applications, such
as transport cards in an RNC. set of applications that demand a balance of both
core performance and number of cores is key to the market. For example, to meet
the demands of mobile broadband, an RNC user-plane application requires the
right mix of subscriber density, the demand for four to eight cores in a
processor, and subscriber peak throughput (with CPU performance greater than
1.5 GHz). , future communications processors must incorporate the correct
balance of multicore processors and powerful CPU cores.
.2 Challenges of Reinventing the Networking Infrastructure
mobile communications market requires multicore processors to
meet consumer trends. However, today's multicore solutions are narrowly focused
and do not provide the performance and flexibility needed to adequately address
future communication demands.
3. Any-to-any next generation mobile
network
we are seeing is that the capabilities of current
communication processors are either control plane-centric or data plane-centric
and, therefore, do not effectively meet consumer demand for both mobile
services and data-intensive applications. is another challenge facing the
mobile industry. Previous generation cell phones transmitted data over private
networks using Asynchronous Transfer Mode (ATM) communication. However, mobile
communication is transitioning to use public, unprotected, all-IP-based
networks. , equipment manufacturers and service providers must develop new
methods to ensure privacy for their customers. Furthermore, silicon designers
must also contribute by incorporating security engines into their designs to
protect data transmission over public networks.
.3 Leading the Way by Providing Innovative Solutions
need to innovate and should be looking at the networking
space to address the challenges facing the mobile communication industry. A
solution is needed that incorporates proven high-performance computing cores
and has processor cores that are built on standardised Instruction Set
Architecture (ISA) so that equipment manufacturers can use industry-standard
development tools. cores need to be compatible with a widely deployed software
base and enable a Symmetric Multiprocessing (SMP) architecture, which further
supports the development of a portable software architecture. well as this the
solution should use a system-on-chip (SOC) architecture, which is an
ultra-efficient message-passing architecture for intra- and inter- processor
communications. type of architecture provides the deterministic behaviour
essential in next-generation networking applications. Deterministic performance
is needed in order to comply with service level agreements (SLAs) where network
operators must be able to predict the overall system performance of the
networking node irrespective of packet size, system loading, or the type of
protocol. Finally, the processors need to be scalable enabling equipment manufacturers
to implement the solution on a broad range of network applications. asymmetric
multicore approach enables the processors not only to complete data and control
plane operations but also provides solutions for gateway offloads and
enterprise routers that require both multicore and high-performance-per-core
capabilities. Working together, all the key sub-components create synergies,
which enable equipment manufacturers and service providers to excel in the
dynamic mobile communication. the communication industry reveals that mobile
consumers are stretching the traditional data plane and control plane
capabilities of today's networks. Equipment manufacturers and service providers
must develop and install a more robust infrastructure to offer mobile services
and virtually unlimited access to online content. , many existing silicon
solutions fall short in supporting future network operator requirements of
achieving cost reductions while meeting and exceeding performance targets.
Technology providers need to provide solutions that incorporate proven cores,
an innovative SOC architecture, and a scalable platform to simplify the
transition as the communication market changes - ultimately enabling service
providers and equipment manufacturers to excel in the future mobile
communications market.
are frequency-selective devices, which will allow or delay
the signals, lying in certain frequency bands.can be classified according to
their frequency characteristics:
. Filters low frequency (LPF) - miss all of oscillations with
frequencies do not above a certain cut-off frequency and constant component.
. Filters high frequency (LPF) - miss all the fluctuations
not below a certain cut-off frequency.
. Band-pass filter (PF) - miss fluctuations in a particular
frequency band, which is determined by a certain level of frequency response.
. Band-suppressing filters (PPF) - detained fluctuations in a
particular frequency band, which is determined by a certain level of frequency
response.
. Rejector filters (Russian Federation) - a type of PPF,
which has a narrow strip of delay and also called the filter-stopper.
. Phase filters (FF) - of a permanent in the ideal case of a
transfer coefficient at all frequencies and designed to change the phase of the
input signal (in particular for temporary delay of signals).
choice and justification of the filter circuitthe help of
active RC filter cannot be the ideal form of frequency characteristics in the
form shown in figure 1.1 rectangles with a strictly constant coefficient of
transmission in bandwidth, the infinite weakening in the suppression and
infinite steep decline in the transition from bandwidth to the suppression. The
design of the active filter is a search for a compromise between the ideal form
of the characteristics and the complexity of its implementation. This is called
“the problem of approximation“. In many cases, the requirements to the quality
of filtration allow to do the simplest filters of the first and second orders
of magnitude. Some of the schemes such filters are presented below. The design
of the filter in this case be limited to the choice of the scheme with the most
appropriate configuration and subsequent calculation of the values of nominal
values of the elements for the specific frequencies.However, there are
situations, when the requirements for filtering may be much more stringent and
may be required schemes of higher order than the first and the second. The design
of the filters high-order is a more complex task, which is devoted to the
course work.Below are some of the basic scheme of the first of the second order
with a description of the advantages and disadvantages of each of them. I and
LPF-I on the basis of non-inverting amplifier.
Figure 5. Filters on the basis of a noninverting amplifier:
a) HPF-I, b) LPF-I.
advantages of schemes filters can be attributed mainly ease
of implementation and adjustment, disadvantages of low - slope of frequency
characteristics,
LPF-II and the HPF-II with a lot of loop feedback.
Advantages: You can build a low pass filter withRelatively
low sensitive adhering to the deviation of the values of the elements (almost
always less than 1): A relatively small input resistance easy adjustment of
only two parameters and a large range of nominal values of elements, especially
in the large and the rate of transmission.
4.
Implementation of the normalization HPF
Butterworth had a reputation for solving
"impossible" mathematical problems. At the time, filter design
required a considerable amount of designer experience due to limitations of the
theory then in use. The filter was not in common use for over 30 years after
its publication. Butterworth stated that:
"An ideal electrical filter should not only completely
reject the unwanted frequencies but should also have uniform sensitivity for
the wanted frequencies".an ideal filter cannot be achieved but Butterworth
showed that successively closer approximations were obtained with increasing
numbers of filter elements of the right values. At the time, filters generated
substantial ripple in the passband, and the choice of component values was
highly interactive. Butterworth showed that a low pass filter could be designed
whose cutoff frequency was normalized to 1 radian per second and whose frequency
response (gain) was
where ω is the angular frequency in radians
per second and n is the number of reactive elements (poles) in the
filter. If ω = 1, the amplitude response of this type of filter in the
passband is 1/√2 ≈ 0.707, which is half power or −3 dB.
Butterworth only dealt with filters with an even number of poles in his paper.
He may have been unaware that such filters could be designed with an odd number
of poles. He built his higher order filters from 2-pole filters separated by
vacuum tube amplifiers. His plot of the frequency response of 2, 4, 6, 8, and
10 pole filters is shown as A, B, C, D, and E in his original graph.of the
required filter ordersolved the equations for two- and four-pole filters,
showing how the latter could be cascaded when separated by vacuum tube
amplifiers and so enabling the construction of higher-order filters despite
inductor losses. In 1930, low-loss core materials such as molypermalloy had not
been discovered and air-cored audio inductors were rather lossy. Butterworth
discovered that it was possible to adjust the component values of the filter to
compensate for the winding resistance of the inductors.used coil forms of 1.25″
diameter and 3″ length with plug in terminals. Associated capacitors and
resistors were contained inside the wound coil form. The coil formed part of
the plate load resistor. Two poles were used per vacuum tube and RC coupling
was used to the grid of the following tube. of the polynomial Butterworthalso
showed that his basic low-pass filter could be modified to give low-pass,
high-pass, band-pass and band-stop functionality.
Figure 7. The resonant response of a physical system
0 8. The typical response of a resonant low-pass filter and
high -pass filter
The frequency response of the Butterworth filter is maximally
flat (i.e. has no ripples) in the passband and rolls off towards zero in the
stopband. [2] When viewed on a logarithmic Bode plot the response
slopes off linearly towards negative infinity. A first-order filter's response
rolls off at −6 dB per octave (−20 dB per decade) (all first-order
lowpass filters have the same normalized frequency response). A second-order
filter decreases at −12 dB per octave, a third-order at −18 dB and
so on. Butterworth filters have a monotonically changing magnitude function
with ω, unlike other filter
types that have non-monotonic ripple in the passband and/or the stopband.
.4 the Reverse transition from a fixed to a planned
HPFCompared with a Chebyshev Type I/Type II filter or an elliptic filter, the
Butterworth filter has a slower roll-off, and thus will require a higher order
to implement a particular stopband specification, but Butterworth filters have
a more linear phase response in the pass-band than Chebyshev Type I/Type II and
elliptic filters can achieve.third-order low-pass filter (Cauer topology). The
filter becomes a Butterworth filter with cutoff frequency ω c =1 when (for example) C 2 =4/3
farad, R 4 =1 ohm, L 1 =3/2 henry and L 3 =1/2
henry.simple example of a Butterworth filter is the third-order low-pass design
shown in the figure on the right, with C 2 = 4/3 F, R 4
= 1 Ω, L 1 =
3/2 H, and L 3 = 1/2 H. [3] Taking the impedance of
the capacitors C to be 1/ Cs and the impedance of the inductors L
to be Ls , where s = σ + j ω is the complex frequency,
the circuit equations yield the transfer function for this device:
The magnitude of the frequency response (gain) G (ω) is given by
and group delay of the third-order Butterworth filter with ω c =1group delay is defined
as the derivative of the phase with respect to angular frequency and is a
measure of the distortion in the signal introduced by phase differences for
different frequencies. The gain and the delay for this filter are plotted in
the graph on the left. It can be seen that there are no ripples in the gain
curve in either the passband or the stop band.Transition from the transfer
function of the circuitThe log of the absolute value of the transfer function H(s)
is plotted in complex frequency space in the second graph on the right. The
function is defined by the three poles in the left half of the complex
frequency plane.density plot of the transfer function H(s) in complex frequency
space for the third-order Butterworth filter with ω c =1. The three poles lie on
a circle of unit radius in the left half-plane.are arranged on a circle of
radius unity, symmetrical about the real s axis. The gain function will
have three more poles on the right half plane to complete the circle.replacing
each inductor with a capacitor and each capacitor with an inductor, a high-pass
Butterworth filter is obtained.the active HPF of the third orderA band-pass
Butterworth filter is obtained by placing a capacitor in series with each
inductor and an inductor in parallel with each capacitor to form resonant circuits.
The value of each new component must be selected to resonate with the old
component at the frequency of interest.band-stop Butterworth filter is obtained
by placing a capacitor in parallel with each inductor and an inductor in series
with each capacitor to form resonant circuits. The value of each new component
must be selected to resonate with the old component at the frequency to be
rejected.
Input voltage, U in = 0,2 мВ 0,0002factor, К U = 10000 10000resistance, R in = 10 кОм 10000range of amplifi
frequency, f Н .. f В =100…10000000Гц 100
The recession of the amplitude-frequency characteristics on
the b
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