Wireless Communication: Encoding, Error Control, Multiplexing and Multiple Access

This article covers various techniques used in wireless communication such as encoding, error control, multiplexing and multiple access. It explains TDM, FDM, CDMA, ASK, FSK, PSK, OFDM and IEEE 802.11ac wireless LAN standard. It also includes calculations and diagrams to help understand the concepts better.

[Date] WIRELESS
COMMUNICATION

CONTENTS
Part I: Encoding and error control............................................................................................................ 2
a) Calculate the data rate required for robot to remote controller communication?..........................2
b) Explain 3 types of suitable encoding techniques could be used to encode the status string.............2
Encoding Techniques: -.............................................................................................................. 2
Bi-polar encoding:...................................................................................................................... 3
c) At a specific occurrence, the sensors gave information as quickening 5 m/s2, snag at
48 cm, all engines working (i.e. engine usefulness 1111), and battery is 75%...............3
I) Write the status string in parallel for this case........................................................................ 3
ii)Represent the status string on ASK, FSK, and PSK encoding strategies...................................3
d) Calculate the CRC for the status string determined in c) with polynomial divisor
11001101....................................................................................................................... 4
e) Briefly clarify some other mistake control and stream control methods that Sam can
use to guarantee the precision of robot control..............................................................5
Error Control:............................................................................................................................. 5
Flow and Error control procedures:............................................................................................ 6
Part II: Multiplexing and multiple access........................................................................................... 7
a) Explain TDM, FDM and CDMA multiplexing techniques with appropriate diagrams. 8
CDMA: -...................................................................................................................................... 9
b) Main air interface within the modification from 3G to 4G and WiMAX. make a case for
however OFDM is completely different from on top of techniques and therefore the
special feature of signals utilized by OFDM..................................................................10
C)IEEE 802.11ac wireless LAN customary uses forty MEGACYCLES per second total
information measure in OFDM theme...........................................................................11
I)For FORTY-EIGHT subscribers what ought to be the subcarrier information measure
(FB)?....................................................................................................................................... 11
ii)Propose an acceptable subcarrier bit time of T to attain orthogonality? ...................11
iii. make a case for however OFDM overcomes the problem of entomb image
interference (ISI)?................................................................................................................. 12
Part III: Wi-Fi................................................................................................................................... 13
a) DESIGN the network specifying the locations of access points and distributions
system showing the backbone network........................................................................13
b) Calculate the BSS and ESS sizes............................................................................14
c) Calculate the turnout for the DS............................................................................16
d) advocate an appropriate IEEE substandard for the network and provides reasons for
wherever selection........................................................................................................ 16
A list of IEEEs substandard that can be used by SAN...............................................................16
e) advocate appropriate security ways for the network................................................17
REFERENCES: -............................................................................................................................... 18
References................................................................................................................... 18
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STUDENT ID 1

PART I: ENCODING AND ERROR CONTROL
Sam is a computer science student and working on a new micro robot design. The robot
continuously sends every two seconds a status string comprising the accelerometer
reading (4 bits), ultrasound obstacle detection (6 bits), motor functionality (4 bits) and
battery power level (2 bits).
A) CALCULATE THE DATA RATE REQUIRED FOR ROBOT TO REMOTE CONTROLLER
COMMUNICATION?
Ans. Data transfer rate is that the rate that an exact quantity of information is
transferred over a given amount in time. a method this may be done is by a
straightforward equation exploitation what quantity knowledge has been transferred
and the way long it took in total to transfer that knowledge. So, equation is that: "Data
Transfer" divided by "Time Taken". therefore, on condition that measuring system
transmit four bits/sec then the desired rate for automaton to remote controller
communication is zero.5 byte/sec.
B) EXPLAIN 3 TYPES OF SUITABLE ENCODING TECHNIQUES COULD BE USED TO ENCODE
THE STATUS STRING.
Ans:
ENCODING TECHNIQUES : -
The propagated NRZ codes is used to divide the property giving to us that the voltage
levels are always consistent, but a little interim in their nature. ASV = bit 1 and LLV = bit
0.
The two varieties are as per the following:
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STUDENT ID 2

1.NRZ-Level: NRZ-L strategy looks simply like the NRZ technique, with the exception
of the primary information one information bit. This is so because NRZ does not usually
contemplate the information but by bit or in extreme modifications, while NRZ-L does
so.
2. NRZ-Inverted: the transition achieved at the start of it is a bit interim in nature
(=bit 1) and bit o is when there is not transition. This is what we call differential coding.
BI-POLAR ENCODING:
Bi-Polar encoding has following attributes:
1. its balance rate is considered to be twice to that of the NRZ and transmission capacity
is also more prominent in nature as compared to NRZ in all senses and ways.
2. Since the changes have been unsurprising in nature and in each piece time, the
collector has the ability to sync itself on the progress i.e., the clock and the flag are
separated.
3. The progress can be towards the start of the program and in the interim too, the time
works at double the exchange rate
C) ALSO, IT WAS NOTED THAT AT CERTAIN OCCURRENCE, THE SENSORS HAVE GIVEN
INFORMATION AS QUCIK AS 5 M/S2, SNAG AT 48 CM, ALL ENGINES WORKING (I.E.
ENGINE USEFULNESS 1111), AND BATTERY IS 75%.
I) WRITE THE STATUS STRING IN PARALLEL FOR THIS CASE
Ans: 010111111
II)REPRESENT THE STATUS STRING ON ASK, FSK, AND PSK ENCODING
STRATEGIES.
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STUDENT ID 3

Ans: ASK refers to the amplitude shift key. It is an innovative adjustment made
procedure, wherein the adequacy of the RF carrier is contrasted as per the baseband
advanced information flag too. Short frequency shift key is known as FSK. It is similar to
the computerised balance system. Here, the recurrence of the RF transporter is altered
according to the baseband information provided.
PSK is a short type of Phase Shift Keying, a balance method where the RF transporter is
often changed for computerised inputs.
fig: Diagrams of ASK, FSK and PSKfor string 0100
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STUDENT ID 4

D) CALCULATE THE CRC FOR THE STATUS STRING DETERMINED IN C) WITH
POLYNOMIAL DIVISOR 11001101.
Ans. Divisor: 11001101, Data word: 11110000000
At that point CRC (cyclic repetition check with polynomial) =
E) BRIEFLY CLARIFY SOME OTHER MISTAKE CONTROL AND STREAM CONTROL
METHODS THAT SAM CAN USE TO GUARANTEE THE PRECISION OF ROBOT
CONTROL.
Ans: Flow Control: Flow control accelerates that extent of information that can be sent
before getting affirmation. It is a standout amongst the most imperative obligations of
the information connect layer. Stream control advises the sender how much information
to send. Stream Control Techniques are Stop-and-pause and Sliding Window.
ERROR CONTROL:
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STUDENT ID 5

Error control in the information connect layer depends on ARQ (programmed rehash
asks for), which is the retransmission of information. The term mistake control alludes
to techniques for fault identification and retransmission. Whenever a blunder is
identified in a trade, indicated outlines are retransmitted. This procedure is called ARQ.
To guarantee dependable correspondence, there necessities to exist stream control
(dealing with the measure of information the sender sends), and mistake control (that
information touches base at the goal blunder free).
Flow and Error control should be done at a few layers. For hub to-hub connections,
stream and mistake control is done in the information interface layer. For end-point to
end-point, stream and blunder control is completed in the vehicle layer. Numerous
elements including line clamour can change or wipe out at least one bits of a given
information unit. Dependable frameworks must have component for identifying and
revising such mistakes. Mistake identification and amendment are executed either at
the information connect layer or the vehicle layer of the OSI demonstrate.
FOLLOWING ARE THE FLOW AND ERROR CONTROL PROCEDURES:
Stop-and-Wait ARQ,
Go-back N ARQ,
Selective Repeat ARQ
(i)Stop & Wait Flow control:
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STUDENT ID 6

The sender needs to sit tight for an affirmation of each edge that it sends. Just when an
affirmation has been gotten is the following edge sent. In Stop&Wait stream control,
beneficiary shows the availability getting information for casing. For each casing that is
sent, there should be an affirmation, which takes a comparable measure of engendering
time to return to the sender. Just a single edge can be in transmission at once. This
prompts wastefulness if spread deferral is any longer than the transmission delay
(ii) Go-back-n ARQ: -
Collector window measure is 1. In this strategy, on the off chance that one casing is lost
or harmed all edges sent, since the last edge renowned are retransmitted.
(ii) Selective Repeat ARQ: new highlights:
In this process only, damage packet is retransmit.
So that Sam can use one of them to ensure the accuracy of robot control.
WIRELESS COMMUNICATION
STUDENT ID 7

PART II: MULTIPLEXING AND MULTIPLE ACCESS
Multiplexing plays a crucial role in communication because it permits the mix of
multiple streams along. completely different multiplexing techniques area unit used for
numerous applications.
A) EXPLAIN TDM, FDM AND CDMA MULTIPLEXING TECHNIQUES WITH
APPROPRIATE DIAGRAMS.
Ans. Multiplexing could be a technique through that many signals area unit at the same
time transmitted over one link. Multiplexed system involves n range of devices that
share the capability of 1 link that’s however a link (path) will have multiple channels. At
the receiver, the only stream is directed to the Demultiplexer (DEMUX), that is once
more translated into its part transmission and sent to their supposed receivers.
TDM is taken into account to be a digital procedure which might be used once the
transmission medium rate amount is over the information rate requisite of the
transmission and receiving devices. every frame consists of a group of your time slots,
and parts of every supply is allotted a time interval per frame.
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STUDENT ID 8

FDM is Associate in Nursing analogy technique that is enforced only the data measure
of the link is over the united data measure of the signals to be conducted. every
causation device produces signals that modulate at distinct carrier frequencies. The
modulated signals area unit then united into one compound signal that may be
transferred by the link. The signals travel through the information measure ranges
stated as channels.
Signals overlapping are often controlled by mistreatment unutilized information
measure strips for segregating the channels, these area unit called guard bands. Also,
carrier frequencies shouldn't interrupt with the first information frequencies. If any
condition fails to stick, the first signals cannot be recovered.
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STUDENT ID 9

CDMA: -
CDMA uses describe band, a technology that was developed in war II to forestall
enemies from intercepting and electronic jamming transmissions. In unfold spectrum,
an information signal is distributed over a spread of frequencies in Associate in Nursing
allotted frequency spectrum.
CDMA provides an exact quantity of intrinsic security because the transmissions of
multiple user’s area unit mixed along inside the frequency spectrum. Completely
different variations of CDM and CDMA area unit employed in 2G and succeeding
generations of mobile phone technology.
B) MAIN AIR INTERFACE WITHIN THE MODIFICATION FROM 3G TO 4G AND
WIMAX. MAKE A CASE FOR HOWEVER OFDM IS COMPLETELY DIFFERENT FROM
ON TOP OF TECHNIQUES AND THEREFORE THE SPECIAL FEATURE OF SIGNALS
UTILIZED BY OFDM.
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STUDENT ID 10

Ans: WiMAX technology was introduced by the Institute of Electrical and Electronic
Engineers (IEEE). It had a customary selection of 802.16d-2004 (used in mounted
wireless applications) and 802.16e-2005 (mobile wireless) in order to ensure supply of
worldwide microwave access. Since telecommunication industry is extremely involved
with wireless communication, the numerous transmission modes were established for
this purpose to be solved.
Technologies 3G 4G
Design Began 1990 2000
Developed 2002 2010
Cellular Services
Higher Capacity, Broadband Data up to
2Mbps
Higher Capacity, completely IP Based,
Multimedia Data
Versions WCDMA, CDMA-2000 OFDM, UWB
Bandwidth 2 Mbps 10 Mbps - 20 Mbps
Multiplexing CDMA FDMA, TDMA, CDMA
Core Network Packet Network All-IP Networks
C)IEEE 802.11AC WIRELESS LAN CUSTOMARY USES FORTY MEGACYCLES PER
SECOND TOTAL INFORMATION MEASURE IN OFDM THEME.
I)FOR FORTY-EIGHT SUBSCRIBERS WHAT OUGHT TO BE THE SUBCARRIER
INFORMATION MEASURE (FB)?
Ans: In OFDM system, the carrier’s area unit curving to amounted curving signals area
unit known as orthogonal once the product is adequate to 0 over one stage.
II)PROPOSE AN ACCEPTABLE SUBCARRIER BIT TIME OF T TO ATTAIN
ORTHOGONALITY?
WIRELESS COMMUNICATION
STUDENT ID 11

Ans: OFDM could be a comparatively new spectrally economical digital modulation
theme that employs multiple carriers that area unit reciprocally orthogonal to 1 another
over a given interval. every carrier, consisting of a combine of undulation and a cos
wave, is referred as a ‘sub-carrier’. allow us to think about Associate in Nursing OFDM
theme with N sub-carriers. The out their transmission information measure is equally
divided amongst the N sub-carriers. If ‘W’ cycle is that the single-sided transmission
information measures out there, the information measure allotted to every sub-carrier
is W N cycle. The distinction between 2 adjacent sub carriers is named the sub carrier
spacing, that is additionally W N cycle in our example. every sub carrier, upon
information modulation might typically be classified as a narrowband modulated signal
however the OFDM signal could be a band signal for moderate or giant price of ‘N’.
Usually, the modulation operation is dispensed at the baseband level and therefore the
baseband-modulated signal is translated within the frequency domain by frequency up-
conversion to the desired frequency band.
Importance of the ideas of Orthogonality in Digital Communications a. within the style
and choice of data bearing pulses, orthogonality over image period could also be
accustomed advantage for derivation economical symbol-by symbol reception theme. b.
Performance analysis of many modulation reception schemes are often dispensed if the
information-bearing signal waveforms area unit acknowledged to be orthogonal to
every different. c. The ideas of orthogonality are often accustomed advantage within the
style and choice of single and multiple carriers for modulation, transmission and
reception.
III. MAKE A CASE FOR HOWEVER OFDM OVERCOMES THE PROBLEM OF ENTOMB
IMAGE INTERFERENCE (ISI)?
Ans: The Orthogonal Frequency Division Multiplexing (OFDM) was developed so that it
could support higher rates of signal and multi-carrier signals as well. It is said to
minimise the image interference and relate it to more and different multiplexing
schemes too.
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STUDENT ID 12

Different frequencies which wastes countless information measure however OFDM
doesn't contain inter-carrier guard band. On prime of that, OFDM handles multipath
result by changing serial information to many parallel information mistreatment quick
Fourier rework (FFT) and Inverse quick Fourier rework (IFFT).
In OFDM system, the carrier’s area unit curving. 2 amounted curving signals area unit
known as orthogonal once their product is adequate to 0.
Fig: Time and Frequency diagram of Single and Multi-carrier signals
To avoid entomb image Interference (ISI) the Cyclic Prefix (CP) is inserted in OFDM
system before every transmitted image. Directorate for Inter-Services Intelligence is
completely eliminated by the planning once CP length is larger than multipath delay.
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STUDENT ID 13

PART III: WI-FI
Prime Living may be an assets company primarily based in Victoria and that we work
type them as an advisor network engineer. the corporate has determined to open a
brand-new workplace in South Japanese suburbs and also the plan of the building is
shown below. The workplace consists of five areas and on the average eight workers
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STUDENT ID 14

work on every room. The lounge is employed by each workers and customers and on
the average regarding twenty-five devices connect with Wi-Fi. The shoppers need we
have a tendency to to style the network for them with a minimum of a hundred Mbps
rate for all wireless connections. As resources we’ve got one distribution system and
few access points of ten m vary.
A) DESIGN THE NETWORK SPECIFYING THE LOCATIONS OF ACCESS POINTS
AND DISTRIBUTIONS SYSTEM SHOWING THE BACKBONE NETWORK.
Ans: Backbone network: -A backbone can be thought of as a part of a network which
has the ability to connect different data type to give a route for exchange of knowledge
between subnetworks. It will add along various networks within the same building
capacity and can cover extremely large areas too.
B) CALCULATE THE BSS AND ESS SIZES.
Ans: once we tack together were wireless access device, we have a tendency to notice a
field referred to as Service Set ID (SSID). A BSS consists of a bunch of computers and one
AP, that links to a wired computer network. associate ESS consists of quite one AP.
associate ESS lets mobile users roll anyplace at intervals the realm lined by multiple
APs.
 The Access purpose manages the wireless network by broadcasting the Service
Set symbol (SSID) associated any device that has to use the wireless network
should initial send an association request to the Access purpose. The Access
purpose will need any of the subsequent criteria before permitting a consumer
to hitch.
• A matching Service Set symbol (SSID)
• A compatible wireless rate
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STUDENT ID 15

• Authentication credentials
when a consumer has associated itself with the Access purpose, all communications to
and from the consumer can traverse the AP.
The wireless coverage space of associate AP is named the essential spot (BSA), generally
additionally referred as Wireless Cell. associate AP also can be connected to a wired
local area network native space Network through associate transmission port affiliation
in contrast to the freelance Basic Service Set during which the wireless network can't be
connected to the wired network.
The BSS is unambiguously known by the essential Service Set symbol (BSSID) that is
that the Layer a pair of mac address of the BSS access purpose. The wireless network
though is publicised victimisation associate SSID that announces the provision of the
wireless network to devices.
2 or a lot of Access Points are connected to a similar native space Network to produce a
bigger coverage space that permits the consumer to more over from one AP to a
different AP and still be a part of the computer network. This method is understood as
roaming during which a consumer will physically amendment locations and still be
connected to the computer network. once a consumer senses that radio wave from this
AP have gotten weaker, it finds a brand-new AP with stronger signals starts
victimisation that AP. associate ESS usually includes a typical SSID to permit roaming
from access purpose to access purpose while not requiring consumer re-configuration.
The wireless coverage space created by connexion 2 or a lot of Access Points via
distribution system is named associate Extended spot (ESA). Stations at intervals a
similar ESA could communicate with one another, even if these stations are also in
numerous basic service areas and should even be moving between the layer.
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STUDENT ID 16

A Distribution System connects multiple Access Points to create associate ESS, whereas
doing thus it provides the wireless stations with the choice of quality. With a wired
network. Network instrumentation outside of the extended service set views the whole
ESS and every one of its mobile stations as one layer a pair of network wherever the
quality of the mobile stations from everything outside the ESS. this enables correct
inter-operation with different network protocols that don't perceive the construct of
quality.
Figure below show a Basic Service assail left aspect associated an Extended Service
assail the correct aspect.
Although not shown within the figure associate Access purpose will act as a bridge
between the wireless and wired LANs, permitting stations on either computer network
to speak with one another.
C) CALCULATE THE TURNOUT FOR THE DS
Ans: turnout of wireless packet transfer usually depends on the signal strength of
wireless communication. The design of Wireless Distribution System ( WDS)
in associate IEEE 802.11-based setting will avoid the decline of wireless signals and
keep the information packet turnout by delivering packets among access points. This
paper focuses on WDS associated proposes a rule of most freelance Set (MIS) to see the
set of access points and scale back its computation time for wireless knowledge packet
transmission and achieving turnout improvement.
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STUDENT ID 17

D) ADVOCATE AN APPROPRIATE IEEE SUBSTANDARD FOR THE NETWORK AND
PROVIDES REASONS FOR WHEREVER SELECTION .
Ans:
A LIST OF IEEES SUBSTANDARD THAT CAN BE USED BY SAN.
Like The 802.11 normal is outlined through many specifications of WLANs. There are
many specifications within the 802.11.
• 802.11 − This pertains to wireless LANs and provides one - or a pair of-Mbps
transmission within the 2.4-GHz band victimisation either frequency-hopping unfold
spectrum (FHSS) or direct-sequence unfold spectrum (DSSS).
• 802.11a − this is often associate extension to 802.11 that pertains to wireless
LANs and goes as quick as fifty-four Mbps within the 5-GHz band. 802.11a employs the
orthogonal frequency division multiplexing (OFDM) encryption theme as critical either
FHSS or DSSS.
• 802.11b − The 802.11 high rate Wisconsin Fi is associate extension to 802.11
that pertains to wireless LANs and yields an affiliation as quick as eleven Mbps
transmission (with a fall back to five.5, 2, and one Mbps reckoning on strength of signal)
within a pair of.4-GHz band. The 802.11b specification uses solely DSSS. Note that
802.11b was truly associate change to the first 802.11 normal further in 1999 to allow
wireless practicality to be analogous to hard-wired local area network connections.
• 802.11g − This pertains to wireless LANs and provides a pair of0+ Mbps within
the 2.4-GHz band.
E) ADVOCATE APPROPRIATE SECURITY WAYS FOR THE NETWORK.
Ans: - Following a structured set of steps once developing and implementing network
security can facilitate we have a tendency to address the numerous considerations that
play a section in security style. several security ways are developed in a very haphazard
method and have did not truly secure assets and to fulfil a customer's primary goals for
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STUDENT ID 18

security. Breaking down the method of security style into the subsequent steps can
facilitate we have a tendency to effectively set up and execute a security strategy:
1. determine network assets.
2. Analyse security risks.
3. Analyse security necessities and trade-offs.
4. Develop a security set up.
5. outline a security policy.
6. Develop procedures for security application policies.
7. Develop a technical implementation strategy.
8. bring home the bacon buy-in from users, managers, and technical workers.
9. Train users, managers, and technical workers.
10. Implement the technical strategy and security procedures.
11. take a look at the protection and update it if any issues are found.
12. Maintain security.
REFERENCES: -
REFERENCES
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STUDENT ID 19

Griner, U., & Arnon, S. (2006). Multiuser diffuse indoor wireless infrared
communication using equalized synchronous CDMA. IEEE Transactions On
Communications, 54(9), 1654-1662. doi: 10.1109/tcomm.2006.881247
Otte, R., Jong, L., & Roermund, A. (2011). Low-power wireless infrared
communications. New York: Springer.
Wolf, M., & Kress, D. (2003). Short-range wireless infrared transmission: the link
buoget compared to RF. IEEE Wireless Communications, 10(2), 8-14. doi:
10.1109/mwc.2003.1196397
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STUDENT ID 20