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Understanding Co-Channel and Adjacent Channel Interference in Mobile Communication Networks

This tutorial covers the concepts of co-channel and adjacent channel interference in mobile communication networks, essential for effective cell planning and frequency distribution. It explains omni-directional frequency planning and its implications, mathematical calculations for C/I ratios, and problems related to channel allocation in sectorized systems. By examining different scenarios and mathematical principles, readers will gain insights into optimizing cell frequency usage for improved network performance.

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Understanding Co-Channel and Adjacent Channel Interference in Mobile Communication Networks

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  1. Tutorial 5Mobile Communication Networks Mohamed Esam

  2. 6 4 3 6 4 3 1 2 5 1 6 7 2 5 4 3 6 7 4 3 6 1 4 3 2 5 1 7 2 5 1 2 5 6 7 4 3 6 7 4 3 1 2 5 1 Cell Planning 2 5 7 7

  3. Co-Channel Interference • I  Co-channel Interference • For Omni frequency planning: • It means that the network is extended in all directions This relation is valid only for omni planning.

  4. C/I (User)  Complex math as depends on the user position. • Assume the average position (Base Station position)

  5. Omni planning: 1 1 7 1 3 3 3 4 5 1 2 5 9 2 5 1 7 4 7 7 5 4 7 6 7 6 9 3 4 6 2 9 6 3 4 8 11 8 9 1 11 8 8 9 1 10 1 5 6 10 7 1 5 6 12 3 3 12 2 3 3 4 2 5 2 5 2 1 8 5 2 9 4 1 8 7 4 7 4 7 5 6 6 9 7 6 9 3 4 6 2 11 3 4 8 11 8 9 1 8 1 10 9 1 10 6 5 7 12 3 5 6 12 3 2 3 5 4 2 5 2 2 8 7 9 4 8 7 4 5 6 6 9 6 8 2 N=12 D=6 R 11 8 10 8 N=9 D=27^0.5 R 12

  6. Trapezoidal frequency planning

  7. 4 • Frequencies-Cell distribution: If operator has 21 carrier frequencies in N=7 cell. Cell 1 f1 ,f8 and f15 Cell 2 f2, f9 and f16 Cell 3 f3, f10 and f17 Cell 4 f4, f11 and f18 Cell 5 f5, f12 and f19 Cell 6 f6, f13 and f20 Cell 7 f7, f14 and f21 3 5 1 F1/f8/f15 2 6 7

  8. Adjacent Channel Interference (ACI) • Due to incomplete filtering of unwanted modulation products in FM systems. 1 2 Worst case @ d1=d2 where C/I min= 26dB d2 Due to the distance between the adjacent cells Added by the Rx filters as shown in figure above d1 1 2 d2 d1

  9. 4 • Frequencies-Cell distribution: If operator has 21 carrier frequencies in N=7 cell. Cell 1 f1 ,f8 and f15 Cell 2 f2, f9 and f16 Cell 3 f3, f10 and f17 Cell 4 f4, f11 and f18 Cell 5 f5, f12 and f19 Cell 6 f6, f13 and f20 Cell 7 f7, f14 and f21 3 5 1 2 6 7 Adjacent Interference

  10. 6 Less Adjacent Interference • Here in cell1: • C/Imin = 26 dB (although it’s interfered by two adjacent cells) 4 3 1 2 5 7 7 2 1 C I

  11. Each cell is affected by both Cochannel and Adjacent channel interference, so: • C/I total = the least one • If C/I (Cochannel) > C/I Adjacent: • C/I total= C/I Adj • Else: • C/I total = C/I Cochannel. 6 4 3 6 4 3 1 2 5 1 6 2 5 7 4 3 6 7 3 6 1 4 4 3 2 5 1 7 5 1 2 2 5 6 7 4 3 6 7 4 3 1 5 2 1 2 5 7 7

  12. Problem-2-a • Channels/cell= Total No. of channels/N =10 log(1/6 * ) =5.44 dB 6 4 3 6 4 3 1 2 5 1 6 7 2 5 4 3 6 7 4 3 6 1 4 3 2 5 1 1 F1/f8/f15 7 2 5 1 2 5 6 7 4 3 6 7 4 3 1 2 5 1 2 5 7 7

  13. Pr-3-b: 120 Sectorization • Channels/sector= Total No. of channels/(3*N) =10 log(1/2 * ) = 10.21 dB All cells are sectorized 6 4 3 6 4 3 1 2 5 1 6 7 2 5 4 3 6 7 4 3 6 1 F8 F1 f15 2 4 3 5 1 7 2 5 1 2 5 6 7 4 3 6 7 4 3 1 2 5 1 2 5 7 7

  14. Pr-3-c: 60 Sectorization • Channels/sector= Total No. of channels/(6*N) =10 log(1/1 * ) = 13.22 dB All cells are sectorized 6 4 3 6 1 4 3 1 2 5 6 7 2 5 4 3 6 7 1 4 3 6 1 4 3 2 5 1 7 2 5 2 5 6 7 4 3 6 7 1 4 3 1 2 5 2 5 7 7

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