Cellular Concepts by Mian Shehzad Iqbal,
Earlier systems used single high power
transmitter. So no frequency reuse
• Cellular concept solve the problem of spectral
congestion and user capacity without any major
technological changes.
• Replaces single high power transmitter with
many low power transmitters.
• Each base station is allocated portion of
available channels.
• Distribution to neighbors so that minimize
interference.
Hexagonal shape is only logical shape.
Actual coverage of cell is known as
footprint and is determined by
measurements and prediction models.
Cell must be designed to serve the
weakest mobile at edge in footprint.
MSC plays major role by monitoring reuse
distance, cost function and other issues. • MSC
needs to collect real time data on channel
occupancy, traffic distribution and radio signal
strength indications (RSSI) this increases the
storage and computational load but provides the
advantage of increased channel utilization and
decreased probability of blocked calls.
This presentation contains the basic of cellular system.
in which direction the cellular system works and how it changes the network from one bast station to another is simply explained.
how Hand-off occur between two base station is shown via figure to understand well.
the cell system in mobile network and the cell spliting, sectoring, microcell zone concept is also explained well.
Please take a look.
may be it is helpfull for you.
Thank you.
Frequencies management,Channel assignments,
Frequency reuse, System capacity and its improvement: Cell spliting and sectoring, Handoffs & its types, prioritizing handoff, Umbrella cell approach, Cell dragging, Roaming, Co channel and adjacent channel interference, Improving coverage- Repeaters for range extension and microcell zone concept, Examples
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Cellular Concepts by Mian Shehzad Iqbal,
Earlier systems used single high power
transmitter. So no frequency reuse
• Cellular concept solve the problem of spectral
congestion and user capacity without any major
technological changes.
• Replaces single high power transmitter with
many low power transmitters.
• Each base station is allocated portion of
available channels.
• Distribution to neighbors so that minimize
interference.
Hexagonal shape is only logical shape.
Actual coverage of cell is known as
footprint and is determined by
measurements and prediction models.
Cell must be designed to serve the
weakest mobile at edge in footprint.
MSC plays major role by monitoring reuse
distance, cost function and other issues. • MSC
needs to collect real time data on channel
occupancy, traffic distribution and radio signal
strength indications (RSSI) this increases the
storage and computational load but provides the
advantage of increased channel utilization and
decreased probability of blocked calls.
This presentation contains the basic of cellular system.
in which direction the cellular system works and how it changes the network from one bast station to another is simply explained.
how Hand-off occur between two base station is shown via figure to understand well.
the cell system in mobile network and the cell spliting, sectoring, microcell zone concept is also explained well.
Please take a look.
may be it is helpfull for you.
Thank you.
Frequencies management,Channel assignments,
Frequency reuse, System capacity and its improvement: Cell spliting and sectoring, Handoffs & its types, prioritizing handoff, Umbrella cell approach, Cell dragging, Roaming, Co channel and adjacent channel interference, Improving coverage- Repeaters for range extension and microcell zone concept, Examples
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
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This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Thinking of getting a dog? Be aware that breeds like Pit Bulls, Rottweilers, and German Shepherds can be loyal and dangerous. Proper training and socialization are crucial to preventing aggressive behaviors. Ensure safety by understanding their needs and always supervising interactions. Stay safe, and enjoy your furry friends!
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
বাংলাদেশ অর্থনৈতিক সমীক্ষা (Economic Review) ২০২৪ UJS App.pdf
WC PPT UNIT-II.ppt
1. 2.1 Introduction to Cellular Systems
Solves the problem of spectral congestion and user capacity.
Offer very high capacity in a limited spectrum without major
technological changes.
Reuse of radio channel in different cells.
Enable a fix number of channels to serve an arbitrarily large
number of users by reusing the channel throughout the
coverage region.
2. Goals
1. Low power transmitter system
2. Increase network capacity
3. Frequency reuse
3. Idea!
# Partition the region into smaller regions called
cells.
# Each cell gets at least one base station or
tower
# Users within a cell talks to the tower
How can we divide the region into cells?
8. Properties of Cell structure
Advantages of cell structures:
1. More capacity due to frequency reusage
2. Less transmission power needed
3. Deals interference, transmission area locally
Problems:
1.Fixed network needed for the base stations
2.Handover (changing from one cell to another)
necessary
3.Interference with other cells
9. 2.2 Frequency Reuse
• Each cellular base station is allocated a group of radio channels within
a small geographic area called a cell.
• Neighboring cells are assigned different channel groups.
• By limiting the coverage area to within the boundary of the cell, the
channel groups may be reused to cover different cells.
• Keep interference levels within tolerable limits.
• Frequency reuse or frequency planning
•seven groups of channel from A to G
•footprint of a cell - actual radio
coverage
•omni-directional antenna v.s.
directional antenna
10. • Consider a cellular system which has a total of S duplex channels.
• Each cell is allocated a group of k channels, .
• The S channels are divided among N cells.
• The total number of available radio channels
• The N cells which use the complete set of channels is called cluster.
• The cluster can be repeated M times within the system. The total
number of channels, C, is used as a measure of capacity
• The capacity is directly proportional to the number of replication M.
• The cluster size, N, is typically equal to 4, 7, or 12.
• Small N is desirable to maximize capacity.
• The frequency reuse factor is given by
S
k
kN
S
MS
MkN
C
N
/
1
CAPACIY EXPANSION BY FREQUENCY REUSE
13. Reuse Distance (Cont’d)
13
The cluster size or the number of cells per cluster is given by
2
2
j
ij
i
N
where i and j are integers.
N = 1, 3, 4, 7, 9, 12, 13, 16, 19, 21, 28, …, etc.
The popular value of N being 4 and 7.
i
j
60o
14. Reuse Distance (Cont’d)
14
(b) Formation of a cluster for N = 7
with i=2 and j=1
60°
1 2 3 … i
j direction
i direction
(a) Finding the center of an adjacent cluster
using integers i and j (direction of i and j can
be interchanged).
i=2
i=2
j=1
j=1
j=1
j=1
j=1
j=1
i=2
i=2
i=2
i=2
15. Reuse Distance (Cont’d)
15
(c) A cluster with N =12 with i=2 and j=2
i=3
j=2
i=3 j=2 i=3
j=2
i=3
j=2
i=3
j=2
i=3
j=2
(d) A Cluster with N = 19 cells with i=3
and j=2
j=2
j=2
j=2
j=2
j=2
j=2
i=2
i=2
i=2
i=2
i=2
i=2
17. • Fixed channel assignment
– each cell is allocated a predetermined set of voice channel
– any new call attempt can only be served by the unused
channels
– the call will be blocked if all channels in that cell are
occupied
2.3 Fixed Channel Assignment
• Borrowing Strategy
• Cell can be allowed to
borrow channels from
neighboring cell if all
its channels are
already occupied
• MSC supervises such
borrowing procedures
18. Dynamic Channel Assignment
• Dynamic channel assignment
– channels are not allocated to cells permanently.
– allocate channels based on request.
– reduce the likelihood of blocking, increase capacity.
– Reduces call blocking which in turn increases the trunking
capacity
– DCA requires the MSC to collect real time data
– Channel Occupancy
– Traffic distribution
– Radio signal quality of all channels on continuous basis
– Data collection is done to manage Handoff
19. 2.4 Handoff Strategies
• When a mobile moves into a different cell while a conversation
is in progress, the MSC automatically transfers the call to a new
channel belonging to the new base station.
• Handoff operation
– identifying a new base station
– re-allocating the voice and control channels with the new base
station.
21. 2.4 Handoff Strategies
• Handoff Threshold
– Minimum usable signal for acceptable voice quality (-90dBm to -
100dBm)
– Handoff margin cannot be too large or
too small.
– If is too large, unnecessary handoffs burden the MSC
– If is too small, there may be insufficient time to complete
handoff before a call is lost.
usable
minimum
,
, r
handoff
r P
P
23. • Handoff must ensure that the drop in the measured signal is not
due to momentary fading and that the mobile is actually moving
away from the serving base station.
• Running average measurement of signal strength should be
optimized so that unnecessary handoffs are avoided.
– Depends on the speed at which the vehicle is moving.
– Steep short term average -> the hand off should be made quickly
– The speed can be estimated from the statistics of the received
short-term fading signal at the base station
Handoff (Contd…)
24. • Dwell time: the time over which a call may be maintained
within a cell, without handoff.
• Dwell time depends on
– propagation
– interference
– distance
– speed
Dwell Time
25. Types of Handoffs
Hard handoff: “break before make” connection
Intra and inter-cell handoffs
Hard Handoff between the MS and BSs
26. Types of Handoffs
Soft handoff: “make-before-break” connection.
Mobile directed handoff.
Multiways and softer handoffs
Soft Handoff between MS and BSTs
27. Types of protocols [Handoff
Methods]
4 types of handoff protocols which help in
providing continuous and QOS-guaranteed
service.
Network-controlled handoff (NCHO)
Mobile-assisted handoff (MAHO)
Soft handoff (SHO) and
Mobile-controlled handoff (MCHO)
30. Practical Handoff Consideration
• Different type of users
– High speed users need frequent handoff during a call.
– Low speed users may never need a handoff during a call.
• Microcells to provide capacity, the MSC can become burdened if
high speed users are constantly being passed between very
small cells.
• Minimize handoff intervention
– handle the simultaneous traffic of high speed and low speed users.
31. Practical Handoff Consideration (contd…)
Umbrella cell approach.
• Is used to provide large area coverage to high speed user while
providing small area coverage to low speed users
• Large and small cells can be located at a single location
– different antenna height
– different power level
Advantages
Increases radio coverage
Reduces number handoffs
Provides more no. of
channels
Less MSC intervention
32. Practical Handoff Consideration (contd…)
Cell dragging problem
Pedestrian users provide a very strong signal to
the base station
Occurs in urban environment – when LOS exists
between the subscriber and BS
Average signal strength doesn’t decay rapidly
received signal at the BS > handoff threshold
thus Handoff may not be made
Creates Potential Interference and Traffic
Management – when the user may travel deep
within a neighboring cell
Solution
Handoff Threshold and Radio coverage
33. 2.5 Interference and System Capacity
• Sources of interference
– another mobile in the same cell
– a call in progress in the neighboring cell
– other base stations operating in the same frequency band
– noncellular system leaks energy into the cellular frequency band
– Intracell interference
– Intercell interference
• Two major cellular interference
– co-channel interference
– adjacent channel interference
34. 2.5.1 Co-channel Interference and
System Capacity
• Frequency reuse - there are several cells that use the same set
of frequencies
– co-channel cells
– co-channel interference
• To reduce co-channel interference, co-channel cell must be
separated by a minimum distance.
• When the size of the cell is approximately the same
– co-channel interference is independent of the transmitted power
– co-channel interference is a function of
• R: Radius of the cell
• D: distance to the center of the nearest co-channel cell
• Increasing the ratio Q=D/R, the interference is reduced.
• Q is called the co-channel reuse ratio
35. • For a hexagonal geometry
• A small value of Q provides large capacity
• A large value of Q improves the transmission quality - smaller
level of co-channel interference
• A tradeoff must be made between these two objectives
N
R
D
Q 3
36. • Let be the number of co-channel interfering cells. The signal-
to-interference ratio (SIR) for a mobile receiver can be
expressed as
S: the desired signal power
: interference power caused by the ith interfering co-channel
cell base station
• The average received power at a distance d from the
transmitting antenna is approximated by
or
n is the path loss exponent which ranges between 2 and 4.
0
i
0
1
i
i
i
I
S
I
S
i
I
n
r
d
d
P
P
0
0
0
0 log
10
)
dBm
(
)
dBm
(
d
d
n
P
Pr
close-in reference point
TX
0
d
0
P :measued power
37. • When the transmission power of each base station is equal, SIR
for a mobile can be approximated as
• Consider only the first layer of interfering cells
0
1
i
i
n
i
n
D
R
I
S
0
0
3
)
/
(
i
N
i
R
D
I
S
n
n
• Example: AMPS requires that SIR be
greater than 18dB
– N should be at least 6.49 for n=4.
– Minimum cluster size is 7
6
0
i
38. • For hexagonal geometry with 7-cell cluster, with the mobile unit
being at the cell boundary, the signal-to-interference ratio for the
worst case can be approximated as
Where Q= D/R
39. Adjacent Channel Interference
• Adjacent channel interference: interference from adjacent in
frequency to the desired signal.
– Imperfect receiver filters allow nearby frequencies to leak into the
passband
– Performance degrade seriously due to near-far effect.
desired signal
receiving filter
response
desired signal
interference
interference
signal on adjacent channel
signal on adjacent channel
FILTER
40. Adjacent Channel Interference
• Adjacent channel interference: interference from adjacent in
frequency to the desired signal.
– Imperfect receiver filters allow nearby frequencies to leak into the
passband
– Performance degrade seriously due to near-far effect.
desired signal
receiving filter
response
desired signal
interference
interference
signal on adjacent channel
signal on adjacent channel
FILTER
41. Adjacent Channel Interference
Interference from channels that are adjacent in frequency,
The primary reason for that is Imperfect Receive Filters which cause the
adjacent channel energy to leak into your spectrum.
Problem is severer if the user of adjacent channel is in close proximity.
Near-Far Effect
Near-Far Effect: The other transmitter(who may or may not be of the
same type) captures the receiver of the subscriber.
Also, when a Mobile Station close to the Base Station transmits on a
channel close to the one being used by a weaker mobile: The BS faces
difficulty in discriminating the desired mobile user from the “bleed over”
of the adjacent channel mobile.
42. Near-Far Effect: Case 1
The Mobile receiver is captured by the unintended, unknown transmitter,
instead of the desired base station
42
43. Near-Far Effect: Case 2
The Base Station faces difficulty in recognizing the actual mobile user,
when the adjacent channel bleed over is too high.
43
44. HOW TO MINIMIZE ACI:
• Adjacent channel interference can be minimized
through careful filtering and channel assignment.
• Keep the frequency separation between each channel in
a given cell as large as possible
• Sequentially assigning cells the successive frequency
channels
• A channel separation greater than six is needed to bring
the adjacent channel interference to an acceptable level.
• Also, secondary level of interference can be reduced by
not assigning adjacent channels to neighboring cells.
• For tolerable ACI, we either need to increase the
frequency separation or reduce the passband BW.
45. Power Control for Reducing Interference
• Ensure each mobile transmits the smallest
power necessary to maintain a good quality link
on the reverse channel
– long battery life
– increase SIR
– solve the near-far problem
46. Trunking and Grade of Service
(GOS)
Trunking:
A means for providing access to users on demand
from available pool of channels.
With trunking, a small number of channels can
accommodate large number of random users.
Telephone companies use trunking theory to
determine number of circuits required.
Trunking theory is about how a population can
be handled by a limited number of servers.
47. Terminology:
1. Traffic intensity is measured in Erlangs:
One Erlang: traffic in a channel completely occupied. 0.5
Erlang: channel occupied 30 minutes in an hour.
2. Grade of Service (GOS): probability that a call is blocked
(or delayed).- measure of the ability of a user to access
trunked sys in busiest hour
3. Set-Up Time: time to allocate a channel.
4. Blocked Call: Call that cannot be completed at time of
request due to congestion. Also referred to as Lost Call.
5. Holding Time: (H) average duration of typical call.
6. Load: Traffic intensity across the whole system.
7. Request Rate: (λ) average number of call requests per unit
time.
49. Trunking and Grade of Service
• Each user genrates a traffic intensity of
H: average duration of a call.
: average number of call requests per unit time
• For a system containing U users and an unspecified
number of channels, the total offered traffic intensity A, is
given by
• For C channel trunking system, the traffic intensity, is
given as
u
UA
A
c
A
C
UA
A u
c /
H
Au
u
A
50. Erlang C Model –Blocked calls
cleared
Channel is not available ---call request may be delayed until a
channel becomes available.
It is a measure of GOS – Defined as the probability that a call
is blocked after waiting a specific length of queue.
A type of trunked system queues blocked calls –Blocked Calls
Delayed. This is known as an Erlang C model.
51. Erlang C Formula
The likelihood of a call not having immediate
access to a channel is determined by Erlang C
formula:
52. Improving Capacity in Cellular
Systems
• Methods for improving capacity in cellular systems
– Cell Splitting: subdividing a congested cell into smaller
cells.
– Sectoring: directional antennas to control the
interference and frequency reuse.
– Coverage zone : Distributing the coverage of a cell and
extends the cell boundary to hard-to-reach place.
53. Cell Splitting
• Split congested cell into smaller cells.
– Preserve frequency reuse plan.
– Reduce transmission power.
microcell
Reduce R to R/2
54. Cell Splitting
Cell Splitting is the process of subdividing the congested cell
into smaller cells (microcells),Each with its own base station
and a corresponding reduction in antenna height and
transmitter power.
Cell Splitting increases the capacity since it increases the
number of times the channels are reused.
55. An Example
The area covered by a circle with radius R is four times the
area covered by the circle with radius R/2
The number of cells is increased four times
The number of clusters the number of channels and the
capacity in the coverage area are increased
Cell Splitting does not change the co-channel re-use ratio Q
=D/R
55
56. Transmit Power
New cells are smaller, so the transmit power of the new cells
must be reduced
How to determine the transmit power?
The transmit power of the new cells can be found by
examining the received power at the new and old cell
boundaries and setting them equal
Pr(at the old cell boundary) is proportional to
Pr(at the new cell boundary) is proportional to
58. Application of cell splitting
Not all cells are split at the same time.
Larger transmit power
Some of the channels would not be sufficiently separated
from the co-channel cells.
Smaller transmit power --parts of the larger cells left
uncovered
Two groups:
one that corresponds to the smaller cell and the other for
larger cell reuse requirements
58
59. Application of cell splitting (cont.)
The sizes of these two groups depend on the stage of the
splitting process
At the beginning, fewer channels will be there in the smaller
power group. As the demand grows, smaller groups would
require more channels
Cell splitting continues until all the channels are in the
smaller power group
Antenna Down tilting
To limit the radio coverage of microcells
59
60. • Transmission power reduction from to
• Examining the receiving power at the new and old cell boundary
• If we take n = 4 and set the received power equal to each other
• The transmit power must be reduced by 12 dB in order to fill in
the original coverage area.
• Problem: if only part of the cells are splited
– Different cell sizes will exist simultaneously
• Handoff issues - high speed and low speed traffic can be
simultaneously accommodated
1
t
P 2
t
P
n
t
r R
P
P
1
]
boundary
cell
old
at
[
n
t
r R
P
P
)
2
/
(
]
boundary
cell
new
at
[ 2
16
1
2
t
t
P
P
61. Sectoring
• Decrease the co-channel interference and keep the cell radius R
unchanged
– Replacing single omni-directional antenna by several directional
antennas
– Radiating within a specified sector
64. Sectoring Advantages
1. Reduce interference by reducing the number of interfering co
channels
2. Increase SIR (better call quality).
3. The increase in SIR can be traded with reducing the cluster
size (N) which increase the capacity.
Disadvantages
1. Cost: Increase number of antennas at each base station.
2. Next section: Decrease trunking efficiency due to channel
sectoring at the base station.
3. The available channels in the cell must be subdivided and
dedicated to a specific antenna.
65. Microzones
Multiple zones and a base station make up a cell. Microcell zone
concept:. Large control base station is replaced by several lower
power transmitters on the age of cell. ... Since a given channel is
active only in a particular zone in which mobile is travelling, base
station radiation is localized and interference is reduced.
As a mobile travels within the cell, it is served by the zone with the
strongest signal
This technique is superior to sectoring because antennas are placed
at the outer edges of the cell, and any base station channel can be
assigned to any zone by the base station
65
66. Microcell Zone Concept
• Antennas are placed at the outer edges of the cell
• Any channel may be assigned to any zone by the base
station
• Mobile is served by the zone with the strongest signal.
• Handoff within a cell
– No channel re-
assignment
– Switch the channel
to a different zone
site
• Reduce interference
– Low power
transmitters are
employed
67. ADVANTAGES
No handoffs is required at the MSC
The base station radiation is localized and
interference is reduced. A given channel is active
only in the particular zone in which the mobile is
traveling
The co-channel interference is also reduced
68. Decreased co-channel interference improves signal
quality which leads to an increase in capacity
without any degradation in trunking efficiency
caused by sectoring
For example
We know an (S/I) of 18dB is required for
satisfactory system performance in narrowband
FM
69. Repeaters for Range Extension
Repeaters are radio re-transmitters used to provide coverage
for hard-to-reach areas, such as within buildings or in valleys
or tunnels
Repeaters are bidirectional. Upon receiving signals from base
station, then amplifies and reradiates the base station signals
to the specific coverage region. Also it will send signals to the
serving base station.
The repeaters do not add capacity to the system-it simply
serves to reradiate the base station signal into specific
locations
71. 1.Incoming Call to
Mobile X is given to
MSC
2. MSC dispatches the
request to all base
station
3.. BS broadcast the
MIN, Telephone number
of MobileX,