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“Provide additional radio capacity 
with no additional increase in radio 
spectrum” 
SHUSHRUTHA K S 
Admissions in India 2015
 Early mobile radio system was to achieve a large 
coverage areas by using high powered transmitter with 
an antenna mounted on a tall tower 
 In this case it is impossible to reuse those same 
frequencies throughout the system 
 Since any attempts to achieve frequency reuse would 
result in interference 
Admissions in India 2015
 Cellular concept is a system level idea which calls for 
replacing a single , high power transmitter with low power 
small transmitters with each providing coverage to only a 
small portion of service area 
 Each base station is allocated a portion of total no of channels 
available to entire system 
 Nearby base station are assigned different groups of channels 
so that all the available channels are assigned to a relatively 
small no. of neighboring base stations 
 Nearby BS are assigned different groups of channel so that 
interference bt. BS is minimized 
Admissions in India 2015
Cluster of 7 cells 
Cells 
•seven groups of channel from A to G 
•footprint of a cell - actual radio coverage 
•oAmdnim-diirsecstiioonnals a ninte nInnad vi.as. d2ir0ec1ti5on al antenna
possible radio coverage of the cell 
idealized shape of the cell 
segmentation of the area into cells 
cell 
◦ use of several carrier frequencies 
◦ not the same frequency in adjoining cells 
◦ cell sizes vary from some 100 m up to 35 km depending on user 
density, geography, transceiver power etc. 
◦ hexagonal shape of cells is idealized (cells overlap, shapes depend on 
geography) 
◦ if a mobile user changes cells 
 handover of the connection Admissions in India 2015 to the neighbor cell
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 
“The design process of selecting and allocating channel 
groups for all of the cellular base station within a system is 
FREQUENCY REUSE/PLANNING” 
Admissions in India 2015
• Consider a cellular system which has a total of S duplex channels. 
• Each cell is allocated a group of k channels, k  S 
. 
• The S channels are divided among N cells. 
• The total number of available radio channels 
S = kN 
• 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 
C = MkN = MS 
• 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 
1/ N 
Admissions in India 2015
• Hexagonal geometry has 
– exactly six equidistance neighbors 
– the lines joining the centers of any cell and each of its neighbors are 
separated by multiples of 60 degrees. 
• Only certain cluster sizes and cell layout are possible. 
• The number of cells per cluster, N, can only have values which satisfy 
N = i2 + ij + j2 
• Co-channel neighbors of a particular cell, ex, i=3 and j=2. 
Admissions in India 2015
Eg for i=1,j=1 Eg for i=2,j=1 
Admissions in India 2015 
The factor N is called the cluster size and is given N=i2+ij+j2
i=1, j=2 , N=1+2+4=7 Admissions in India 2015
To find the nearest co-channel 
neighbor of a particular cell 
1.Move ‘i’ cells along any chain 
of hexagons 
2.Then turn 60 degrees counter-clockwise 
Method of locating co-channel cells in a cellular system. In this example, N = 19 (i.e., I = 3, j = 2). (Adapted 
from [Oet83] © IEEE.) 
and 
3.Move ‘j’ cells. 
Admissions in India 2015
 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. 
Admissions in India 2015
Techniques to provide more channels per coverage area 
is by 
 Cell splitting 
 Cell sectoring 
 Coverage zone approches 
Admissions in India 2015
 Cell splitting increases the capacity of cellular system 
since it increases the number of times the channel are 
reused 
 Cell splitting - defining new cells which have smaller 
radius than orginal cells by installing these smaller 
cells called MICROCELLS between existing cells 
 Capacity increases due to additional number of 
channels per unit area 
“Cell splitting is process of subdividing a congested cell into 
smaller cells each with its own base station(with 
corresponding reduction in antenna Admissions in India 2015 height and tx power)”
CELL SPLITTING 
Split congested cell into smaller cells. 
– Preserve frequency reuse plan. 
– Reduce transmission power. 
microcell 
Reduce R to R/2 
Admissions in India 2015
• Transmission power reduction from to 
• Examining the receiving power at the new and old cell boundary 
• If we take n = 4 (path loss) and set the received power equal to each 
other 
P 
P t1 
t2 = 
• 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 
t1 P t2 P 
n 
r t P µ P R- 1 [at old cell boundary] 
n 
r t P [at new cell boundary]µ P (R / 2)- 2 
16 
Admissions in India 2015
CELL SPLITTING 
•Splitting cells in each CELL 
•Antenna downtiliting 
Admissions in India 2015 
Illustration of cell splitting within a 3 km by 3 km square
2.7.2 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 
Admissions in India 2015
• Interference Reduction 
position of the 
mobile 
interference 
cells 
Admissions in India 2015
2.7.3 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 
Admissions in India 2015
Channel Assignment Strategies 
• Frequency reuse scheme 
– increases capacity 
– minimize interference 
• Channel assignment strategy 
– fixed channel assignment 
– dynamic channel assignment 
• 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 
• Dynamic channel assignment 
– channels are not allocated to cells permanently. 
– allocate channels based on request. 
– Admisresdiuocen tsh ei nlik Ienlihdoioad 2of0 b1lo5ck ing, increase capacity.

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Mba admission in india

  • 2. “Provide additional radio capacity with no additional increase in radio spectrum” SHUSHRUTHA K S Admissions in India 2015
  • 3.  Early mobile radio system was to achieve a large coverage areas by using high powered transmitter with an antenna mounted on a tall tower  In this case it is impossible to reuse those same frequencies throughout the system  Since any attempts to achieve frequency reuse would result in interference Admissions in India 2015
  • 4.  Cellular concept is a system level idea which calls for replacing a single , high power transmitter with low power small transmitters with each providing coverage to only a small portion of service area  Each base station is allocated a portion of total no of channels available to entire system  Nearby base station are assigned different groups of channels so that all the available channels are assigned to a relatively small no. of neighboring base stations  Nearby BS are assigned different groups of channel so that interference bt. BS is minimized Admissions in India 2015
  • 5. Cluster of 7 cells Cells •seven groups of channel from A to G •footprint of a cell - actual radio coverage •oAmdnim-diirsecstiioonnals a ninte nInnad vi.as. d2ir0ec1ti5on al antenna
  • 6. possible radio coverage of the cell idealized shape of the cell segmentation of the area into cells cell ◦ use of several carrier frequencies ◦ not the same frequency in adjoining cells ◦ cell sizes vary from some 100 m up to 35 km depending on user density, geography, transceiver power etc. ◦ hexagonal shape of cells is idealized (cells overlap, shapes depend on geography) ◦ if a mobile user changes cells handover of the connection Admissions in India 2015 to the neighbor cell
  • 7. 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 “The design process of selecting and allocating channel groups for all of the cellular base station within a system is FREQUENCY REUSE/PLANNING” Admissions in India 2015
  • 8. • Consider a cellular system which has a total of S duplex channels. • Each cell is allocated a group of k channels, k S . • The S channels are divided among N cells. • The total number of available radio channels S = kN • 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 C = MkN = MS • 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 1/ N Admissions in India 2015
  • 9. • Hexagonal geometry has – exactly six equidistance neighbors – the lines joining the centers of any cell and each of its neighbors are separated by multiples of 60 degrees. • Only certain cluster sizes and cell layout are possible. • The number of cells per cluster, N, can only have values which satisfy N = i2 + ij + j2 • Co-channel neighbors of a particular cell, ex, i=3 and j=2. Admissions in India 2015
  • 10. Eg for i=1,j=1 Eg for i=2,j=1 Admissions in India 2015 The factor N is called the cluster size and is given N=i2+ij+j2
  • 11. i=1, j=2 , N=1+2+4=7 Admissions in India 2015
  • 12. To find the nearest co-channel neighbor of a particular cell 1.Move ‘i’ cells along any chain of hexagons 2.Then turn 60 degrees counter-clockwise Method of locating co-channel cells in a cellular system. In this example, N = 19 (i.e., I = 3, j = 2). (Adapted from [Oet83] © IEEE.) and 3.Move ‘j’ cells. Admissions in India 2015
  • 13.  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. Admissions in India 2015
  • 14. Techniques to provide more channels per coverage area is by  Cell splitting  Cell sectoring  Coverage zone approches Admissions in India 2015
  • 15.  Cell splitting increases the capacity of cellular system since it increases the number of times the channel are reused  Cell splitting - defining new cells which have smaller radius than orginal cells by installing these smaller cells called MICROCELLS between existing cells  Capacity increases due to additional number of channels per unit area “Cell splitting is process of subdividing a congested cell into smaller cells each with its own base station(with corresponding reduction in antenna Admissions in India 2015 height and tx power)”
  • 16. CELL SPLITTING Split congested cell into smaller cells. – Preserve frequency reuse plan. – Reduce transmission power. microcell Reduce R to R/2 Admissions in India 2015
  • 17. • Transmission power reduction from to • Examining the receiving power at the new and old cell boundary • If we take n = 4 (path loss) and set the received power equal to each other P P t1 t2 = • 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 t1 P t2 P n r t P µ P R- 1 [at old cell boundary] n r t P [at new cell boundary]µ P (R / 2)- 2 16 Admissions in India 2015
  • 18. CELL SPLITTING •Splitting cells in each CELL •Antenna downtiliting Admissions in India 2015 Illustration of cell splitting within a 3 km by 3 km square
  • 19. 2.7.2 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 Admissions in India 2015
  • 20. • Interference Reduction position of the mobile interference cells Admissions in India 2015
  • 21. 2.7.3 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 Admissions in India 2015
  • 22. Channel Assignment Strategies • Frequency reuse scheme – increases capacity – minimize interference • Channel assignment strategy – fixed channel assignment – dynamic channel assignment • 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 • Dynamic channel assignment – channels are not allocated to cells permanently. – allocate channels based on request. – Admisresdiuocen tsh ei nlik Ienlihdoioad 2of0 b1lo5ck ing, increase capacity.

Notas del editor

  1. Fig. 3.2