05. Frequency Management and Channel Assignment.pdf

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1. Frequency Management
and Channel Assignment

2. After completing this chapter a student will be able to:
➢Frequency Management
➢ Frequency Spectrum Utilization
➢ Set-up Channels
➢ Channel Assignment

3. Frequency Management
•Frequencymanagement
–Designatingset-upchannelsandvoicechannels
(donebytheFCC),
–Numberingthechannels
(donebytheFCC),and
–Groupingthevoicechannelsintosubsets
(donebyeachsystemaccordingtoitspreference).

4. Channel Assignment
•Meanstheallocationofspecificchannelsto
cellsitesandmobileunits.
•Afixedchannelset–Cellsite-long-term
basis
•Duringacall-Mobileunit-short-termbasis
(handledbyMTSO).

5. Channel Assignment
•Ideallychannelassignmentshouldbebasedon
causingtheleastinterferenceinthesystem.

6. Numbering the Channels
•The total number of channels (January 1988) is
832.
•But most mobile units and systems are still
operating on 666 channels.
•A channel consists of two frequency channel
bandwidths,
–one in the low band
–one in the high band

7. Numbering the Channels
•Two frequencies in channel 1 are
–825.030 MHz (mobile transmit) and
–870.030 MHz (cell-site transmit)
•The two frequencies in channel 666 are
–844.98 MHz (mobile transmit) and
–889.98 MHz (cell-site transmit)

8. Numbering the Channels
•The 666 channels are divided into two groups:
–block A system
–block B system

9. Frequency-ManagementChart

10. Numbering the Channels
•Eachblockhas333channels
•The42set-upchannelsareassignedas
follows.
–Channels313-333blockA
–Channels334-354blockB
•Thevoicechannelsareassignedasfollows.
–Channels1-312(312voicechannels)blockA
–Channels355-666(312voicechannels)blockB

11. Numbering the Channels-
AdditionalSpectrumAllocation
•Newadditionalspectrumallocation-10MHz-
additional166channelsareassigned
•a1MHzisassignedbelow825MHz(or870MHz)
•additionalchannelswillbenumberedupto849MHz
(or894MHz)andwillthencircleback
•Thelastchannelnumberis1023(=2
10
)
•Therearenochannelsbetweenchannels799and991.

12. NewAdditionalSpectrumAllocation

13. Full Spectrum Frequency Management

14. Full Spectrum Frequency Management

15. Grouping into Subsets
•Voicechannelsforeachsystemis312
•Wecangrouptheseintoanynumberofsubsets
21set-upchannelsforeachsystem
•itislogicaltogroupthe312channelsinto21subsets
•Eachsubsetthenconsistsof16channels
•Ineachset,theclosestadjacentchannelis21
channelsaway

16. Grouping into Subsets
•The 16 channels in each subset -connected to
a channel combiner
•Wide separation between adjacent channels -
requirement of minimum isolation
•Each 16-channel subset is idealized for each
16-channel combiner

17. Grouping into Subsets
•Inaseven-cellpatternsystemeachcellcontains
threesubsets,
iA+iB+iC
whereiisanintegerfrom1to7
•Thetotalnumberofvoicechannelsinacellis
about45
•Theminimumseparationbetweenthreesubsetsis7
channels(21/3)

18. Grouping into Subsets
•Ifsixsubsetsareequippedinanomnicellsite,
•Minimumseparationbetweentwoadjacent
channelscanbeonlythree(21/6>3)physical
channelbandwidths
•For Example

19. Techniques for increasing frequency spectrum
•Increasingthenumberofradiochannelsusingnarrow
banding,spreadspectrum,ortimedivision
•Improvingspatialfrequency-spectrumreuse
•Frequencymanagementandchannelassignment
•Reducingtheloadofinvalidcalls
–VoicestorageserviceforNo-Answercalls
–Callforwarding
–CallwaitingforBusy-Callsituations
–Queuing

20. Set-up Channels
•Set-up channels, also called control channels,
•Channels designated to set up calls
•A system can be operated without set-up
channels
•Set-up channels can be classified by usage into
two types
–access channels
–paging channels

21. Access channels -Operational functions
•Power of a forward set-up channel [or forward control
channel (FOCC)]
•The set-up channel received level (Threshold)-RECC
•Change power at the mobile unit(Messages)
–Mobile station control message
–System parameter overhead message
–Control-filler message
•Direct call -retry

22. Channel Assignment to the Cell
Sites-Fixed Channel Assignment
•Set-up channels & Voice channels
•long-term basis

23. Fixed Channel Assignment
•N = 4, 7, 12 Setup-channels
–21 channels
–cell reuse patterns
–Omni-directional antennas
–One channel per cell
–Unused set-up channels
–Avoid interference between block A and B

24. Fixed Channel Assignment
•Voice Channels
–21 subsets
–Min. cochannel & Adjacent channel interference
•3 SAT Tones

25. Channel Assignment to Travelling Mobile Units
•Underlay-overlay
•Frequency Assignment
•Tilted Antenna

26. Channel Assignment to Travelling Mobile Units
Underlaid-overlaidcellarrangements
(a)Undelay-overlayinomnicell
(b)underlay-overlayinsectorizedcells
(c)two-levelhandoffscheme

27. Underlay-Overlay Arrangement

28. Fixed Channel Assignment
•Adjacent-Channel Assignment
•Channel Sharing and Borrowing
•Sectorization

29. Adjacent-Channel Assignment
Adjacentchannelassignment.
(a)Omnidirectional-antennacells
(b)directional-antennacells

30. Channel Sharing and Borrowing
•Channel Sharing
Algorithm

31. Sectorization
•The 120
o
sector cell for both transmitting and
receiving
•The 60
o
sector sell for both transmitting and
receiving
•120
o
or 60
o
sector cell for receiving
sectorization only , and transmitting antenna is
omni-directional

32. Non-Fixed Channel Assignment
Algorithms
•Dynamic Channel Assignment
•Hybrid channel Assignment
•Borrowing channel Assignment
•Forcible-borrowing channel Assignment

33. Simulation Process and Results
Cellularsystem.
Vehicleand radio-
channeldistribution
inthebusyrushhour

34. Simulation Process and Results
•Average Blocking
•Handoff Blocking