![Muhammad Ali Jinnah University, Islamabad Campus, Pakistan
Blocked Calls Cleared
–
–
–
–
–
Calls arrive as Poisson distributed
All users may request service at any time
A
- generated traffic
C
- number of channels
Grade of Service (Erlang B formula):
AC
GOS Pr[blocking ] C C! k
A
k!
k 0
Cellular Concept
EE6733 Cellular Mobile Communications
Week 5-6-7; Fall - 2013
© Dr. Noor M Khan
EE, MAJU
45](https://image.slidesharecdn.com/1382450767maju-cell-2013-fall-week-5-6-7-cellularconcept-trunking-131103002339-phpapp01/85/cellular-concept-including-trunking-cells-etc-45-320.jpg)
![Muhammad Ali Jinnah University, Islamabad Campus, Pakistan
Blocked Calls Delayed
• If a channel is not available immediately the
call request may be put in a queue and
delayed until a channel becomes available
• Erlang C formula:
Pr[delay 0]
Cellular Concept
AC
A
C
A C!1
C
EE6733 Cellular Mobile Communications
Week 5-6-7; Fall - 2013
C 1
k 0
Ak
k!
© Dr. Noor M Khan
EE, MAJU
47](https://image.slidesharecdn.com/1382450767maju-cell-2013-fall-week-5-6-7-cellularconcept-trunking-131103002339-phpapp01/85/cellular-concept-including-trunking-cells-etc-47-320.jpg)
![Muhammad Ali Jinnah University, Islamabad Campus, Pakistan
Grade of Service for Delayed
Calls
GOS Pr[delay t ]
Pr[delay 0] Pr[delay t | delay 0]
Pr[delay 0] e
Cellular Concept
EE6733 Cellular Mobile Communications
Week 5-6-7; Fall - 2013
C A t
H
© Dr. Noor M Khan
EE, MAJU
48](https://image.slidesharecdn.com/1382450767maju-cell-2013-fall-week-5-6-7-cellularconcept-trunking-131103002339-phpapp01/85/cellular-concept-including-trunking-cells-etc-48-320.jpg)
![Muhammad Ali Jinnah University, Islamabad Campus, Pakistan
Average Delay in a Queued
System
• The average delay D for all calls in a queued
system is:
H
D Pr[delay 0]
CA
– Where the average delay in the queue is H/(C-A)
• H – average duration of a call
• C – number of channels
• A – total offered traffic
Cellular Concept
EE6733 Cellular Mobile Communications
Week 5-6-7; Fall - 2013
© Dr. Noor M Khan
EE, MAJU
49](https://image.slidesharecdn.com/1382450767maju-cell-2013-fall-week-5-6-7-cellularconcept-trunking-131103002339-phpapp01/85/cellular-concept-including-trunking-cells-etc-49-320.jpg)
cellular concept.. including trunking, cells etc
- 1. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Cellular Concept and Trunking Lecturer: Prof. Dr Noor M Khan Department of Electronic Engineering, Muhammad Ali Jinnah University, Islamabad Campus, Islamabad, PAKISTAN Ph: +92 (51) 111-878787 Ext. 129 (Office), Ext. 186 (ARWiC Lab) email: noor@ieee.org, noormkhan@jinnah.edu.pk MSC Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU PSTN 1
- 2. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Cellular Concept • Simple Solution – Single high powered transmitter on a tall tower – Good coverage but very low capacity – No frequency reuse • High Capacity Solution – Cellular concept solves problem of low capacity – Replaces a single high power transmitter (large cell) with many low power transmitters (small cells) – Much smaller and more efficient mobile units Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 2
- 3. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Operation • The Cellular Concept is a system level idea: – Each base station is allocated a portion of the total number of channels available to the entire system – Nearby base stations are assigned different groups of channels – All channels are assigned to a relatively small number of neighboring base stations • The level of interference between base stations (and the mobile users) is controlled Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 3
- 4. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Scalability • Frequency can be re-used as many times as necessary as long as interference between cochannel stations can be kept within acceptable limits. • As the demand increases, the number of base stations can be increased (with a corresponding decrease in transmitter power) • This fundamental principal is the foundation of all modern wireless communication systems. Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 4
- 5. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Frequency Re-use • The process of selecting and allocating channel groups for all base stations within a system is known as frequency re-use or frequency planning B G C A F B G D E C A F B G D E Cellular Concept C A F D E EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 5
- 6. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Comments on Hexagonal Cells • Hexagon geometry approximates omnidirectional base station with free space propagation • When hexagons are used base stations can either be – in the center (center excited) - omni directional antennas or – on 3 of the six cell vertices (edge excited) sectored directional antennas Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 6
- 7. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan On Hexagonal Cells..? • Hexagon geometry approximates omni-directional base station with free space propagation Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 7
- 8. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Simple Calculation • Let S be the total number of duplex channels • Let k be the number of channels in each cell • N cells collectively use the complete set of S available channels. • N is the cluster size (N=4,7 or 12), then S = kN • If a cluster is replicated M times • Total number of duplex channels =MS= MkN • 1/N is called the frequency re-use factor Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 8
- 9. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan More About Cellular Structure • Each cell has exactly six equidistant neighbors • Thus there is only certain cluster sizes and cell layouts possible • It can be shown that the number of hexagonal cells per cluster is given by N = i2 + ij + j2 • i & j are non negative integers Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 9
- 10. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan i & j, Co-Channel Neighbors • To find the nearest co-channel neighbors • Move i cells along any chain of hexagons and then • Turn 60 degrees counter clockwise, and move j cells Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 10
- 11. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Example •i=3, (move 3 cells along any chain of hexagons) •j=2 (turn 60 degrees counter clockwise and move 2 cells); i=3 j=2 •This is the way to find the central cell of the new cluster •Number of cells in the cluster; N=9+3*2+4=19. Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 11
- 12. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Distance D 3 R j 2 i 2 j i R 3N D j=2 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 12
- 13. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Channel Assignment • Channel assignment (Frequency reuse) – efficient utilization of radio spectrum – increased capacity – minimized interference • Channel assignment can be – fixed – dynamic • Affects performance especially handover (handoff) Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 13
- 14. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Fixed Channel Assignment • Each cell is allocated a predetermined set of channels • Any call attempt within the cell can only be served by the unused channels in that cell • Variations that allow channel borrowing exist – A cell is allowed to borrow from its neighbor – MSC supervises the borrowing procedure Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 14
- 15. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Dynamic Channel Assignment • Each time a call is attempted, the serving BS request a channel from the MSC • The lending algorithm take into account – likelihood of future blocking – frequency re-use of candidate channel – other cost functions • Dynamic schemes reduces the call blocking probability and increases system capacity Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 15
- 16. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Implications • Dynamic schemes require the MSC to collect real time data on all channels – Channel occupancy – Traffic distribution – Radio signal strength indications (RSSI) • Makes the MSC more complex, and increases its storage and computational load Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 16
- 17. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Handover (Handoff) – Need to be performed successfully and infrequently as possible and be transparent to users – Need to decide the optimum signal level to perform handover – Generally the level is decided the handover level is set slightly above it = Pr handover - Pr minimum usable Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 17
- 18. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Example Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 18
- 19. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Dwell Time • The time a call may be maintained within a cell, without handover, is called the dwell time. • Dwell time is dependent on a number of factors – propagation – interference – distance from BS etc. • Therefore even a stationary subscriber may have a random and finite dwell time Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 19
- 20. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Mobile Assisted Handover (MAHO) • In analog systems the signal strength was measured by the base station and supervised by the MSC, • The MSC decides if a handover is necessary or not • Digital systems handover decisions are mobile assisted – Mobile measures signal strength and reports to the serving BS – Handover is initiated when power received from the BS of a neighboring cell begins to exceed the power received from the current BS - certain level & duration Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 20
- 21. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Handover 2 • MAHO is faster and more suited for micro cellular environments • It is also possible to have intersystem handover, – Handover from a cell of one MSC to a cell of another MSC • Numerous issues – A local call (initially) may become a long distance call – Need to deal with incompatibility of the MSC Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 21
- 22. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Handover Policy • Ways of handling handover requests – Same as all initial call requests – Give it higher priority – Queue requests • Generally it is more annoying to have a call cut off in mid conversation than being blocked on a new call attempt • Fraction of the total available channels in a cell is reserved for handover requests from ongoing calls - guard channel Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 22
- 23. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Practical Handover Considerations • Cell dragging - pedestrian users that provide a very strong signal to the BS (LOS), but moved to a close range of another base station causing interference • Difficulty in obtaining physical cell sites – Zoning laws (no high rise structures) – Public protest (radiation concerns) e.t.c • Too many handoffs for high speed mobiles (on a vehicle) Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 23
- 24. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Handoff Improvements • First generation mobile 10s to make handoff and = 6-12 dB. ( = Pr handover - Pr minimum usable ) • GSM (II generation) 1-2s to make handoff with = 0-6 dB. • Better system efficiency and handling high speed vehicles Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 24
- 25. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Soft Handoff • Channelized wireless systems (such as GSM) have to switch channels in the process of handoff • There is always risk of losing the connection • IS-95, Code Division Multiple Access (CDMA) system provides Soft Handoff. • Soft Handoff does not mean changing the channel but rather deciding which base station will handle the connection • This is a unique property of CDMA concept. Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 25
- 26. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan CDMA Frequency Reuse Pattern B G C A F B G D E C A F B G D E CDMA C A F D E Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 26
- 27. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Co-channel Interference • There are several cells that use the same set frequencies – co-channel cells • Interference between signals from these cells is called co-channel interference • Unlike thermal noise, this cannot be overcome by increasing the signal power • The co-channel cells must be physically separated Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 27
- 28. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Co-channel Interference – Because the cell size is same, co-channel interference is independent of transmitted power – It is a function of the radius of the cell (R), and the distance to the center of the nearest cochannel cell (D) – For hexagonal geometry, co-channel reuse ratio Q is given by D Q 3N R Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 28
- 29. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Carrier to Interference Ratio – Carrier to Interference ratio (SIR or S/I) is also independent of transmitted power – It is a function of the radius of the cell (R), and the distance to the center of the nearest cochannel cell (D) – For the first tier in hexagonal geometry, Carrier to Interference ratio is usually taken as 4 S 1 D 1 2 3N I 6 R 6 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 29
- 30. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Some Arithmetic Again • Let i0 be the number of co channel interfering cells • then carrier signal to interference ratio (SIR) S S i0 I Ii i 1 • S - desired signal power from desired BS; Ii interference power caused by the ith interfering co-channel cell BS Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 30
- 31. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Received Power • Ave. received signal strength at any point decays as a power law of the distance of separation (d) and is given by d Pr P0 d 0 n d Pr (dBm ) P0 (dBm ) 10n log d 0 • P0 - Power received at a close-in reference point in the far field region of the antenna at a small distance; n - path loss component (2-4) Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 31
- 32. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan SIR – If Di is the distance of the ith interferer, the received power at a given mobile due to the ith interfering cell will be proportional to (Di)-n – When the transmit power of each BS is equal and the path loss exponent is the same S I Rn i0 ( Di ) n i 1 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 32
- 33. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Simpler SIR – Considering only the first layer of interfering cells & if all these BS are equidistant S ( D / R ) n ( 3N ) n I i0 i0 – i0 - number of neighboring/interfering cochannel cells Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 33
- 34. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Interference Limitation Example – i0 =6 number of co-channel cells – N=7 – n=2 S 3N N I 6 2 – Considering only the first layer of interfering cells & if all these BS are equidistant Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 34
- 35. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan 16 2 12 3 18 k 6k Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 35
- 36. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Interference Limitation S I Rn i0 (D ) i 1 S K I n i R n 6 k (kR 3N ) n k 0 Cellular Concept DK kR 3N EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 S ( 3N ) n K I 6 k 1n k 0 © Dr. Noor M Khan EE, MAJU 36
- 37. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Interference Limitation n S ( 3N ) K I 6 k 1n k 0 – Considering K layers of interfering cells – For N fixed, n=2 and the number of layers K; S/I 0 K 1 I lim O( ) K k 0 k Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 37
- 38. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Adjacent Channel Interference 1 – Interference resulting from signals which are adjacent in frequency – Results from imperfect receiver filters which allow nearby frequencies to leak • Particularly serious if an adjacent channel user is transmitting very close to the a receiver – Referred to as the near-far effect • Nearby transmitter captures the receiver Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 38
- 39. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Adjacent Channel Interference 2 • Can be minimized by careful filtering & channel assignment • If the frequency re-use factor is small, the separation between adjacent channels may not be sufficient to keep the adjacent channel interference level within tolerable limits Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 39
- 40. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Adjacent Channel Interference 3 • If a mobile is 20 times closer to the BS than another mobile SIR = (20)-n • For n= 4, this is equal to -52 dB • If the intermediate filter has a slope of 20 dB/octave in the stop-band • Adjacent channel must be displaced 3 times the pass-bandwidth from the center of the receiver frequency band-pass to achieve the 52 dB attenuation P(f) 10m BS 100 m 20dB/oct 200 m 60d B 1 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 2 © Dr. Noor M Khan EE, MAJU 3 f 40
- 41. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Power Control • • • • The power level transmitted by every mobile is controlled by the BS Enables to use the smallest power to maintain good link quality and reduces interference to other cells Increases battery lifetime before recharging ( talk time and stand-by time) CDMA requires very strict power control (1dB) Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 41
- 42. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Trunking • Trunking is a statistical concept which allows a large number of users to share relatively small number of channels providing access on demand from a pool of available channels. • Relatively small number of channels can serve a large number of users since all users are not demanding access and utilization of the system at the same time Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 42
- 43. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Grade of Service • • Grade of Service is a measure of the ability of a trunked system to give access to a user requiring service during the busiest hour (4-6pm, Thu, Fri) Grade of Service is usually measured in two ways 1. Probability that a call is blocked 2. Probability that a call will be delayed more than specified queuing time (some tolerable delay) Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 43
- 44. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Some Traffic Quantities • Au - Traffic intensity Au H • H - average duration of a call • - average number of calls per unit time • For system with U, users total offered traffic intensity A, is A UAu Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 44
- 45. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Blocked Calls Cleared – – – – – Calls arrive as Poisson distributed All users may request service at any time A - generated traffic C - number of channels Grade of Service (Erlang B formula): AC GOS Pr[blocking ] C C! k A k! k 0 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 45
- 46. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Capacity of Erlang B System Capacity in Erlangs for GOS No.of Channels Pr=0.01 0.005 0.002 0.001 2 0.153 0.105 0.065 0.046 5 1.36 1.13 0.900 0.762 10 4.46 3.96 3.43 3.09 20 12.0 11.1 10.1 9.41 40 29.0 27.3 25.7 24.5 100 84.1 80.9 77.4 75.2 Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 46
- 47. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Blocked Calls Delayed • If a channel is not available immediately the call request may be put in a queue and delayed until a channel becomes available • Erlang C formula: Pr[delay 0] Cellular Concept AC A C A C!1 C EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 C 1 k 0 Ak k! © Dr. Noor M Khan EE, MAJU 47
- 48. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Grade of Service for Delayed Calls GOS Pr[delay t ] Pr[delay 0] Pr[delay t | delay 0] Pr[delay 0] e Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 C A t H © Dr. Noor M Khan EE, MAJU 48
- 49. Muhammad Ali Jinnah University, Islamabad Campus, Pakistan Average Delay in a Queued System • The average delay D for all calls in a queued system is: H D Pr[delay 0] CA – Where the average delay in the queue is H/(C-A) • H – average duration of a call • C – number of channels • A – total offered traffic Cellular Concept EE6733 Cellular Mobile Communications Week 5-6-7; Fall - 2013 © Dr. Noor M Khan EE, MAJU 49