Cellular Network Planning and Optimization Part V: GSM

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FH interference diversity gainWithout FH, neighboring cells with co-channel frequ encies to thecarrier frequency will interfere continuously.The interference can be severe for certain frequenc ies and may leadto information loss.FH means that different frequencies will interfere with the carrier atdifferent time slots.Instead of having a constant level of interference between two cells,the interference is spread among several frequencie s.For a specific carrier, only some time slots will s uffer from highinterference. From a system point of view, strong i nterferers areshared between users and so called interference ave raging isachieved.A GSM network can be planned for average interferen ce instead ofworst case interference.The interference diversity gain is dependent on the number of hoppingfrequencies and interference levels from the interf ering cells. Asignificant interference diversity gain is obtained with as little as 3hopping frequencies.26
FH StrategiesCyclic FHIn cyclic hopping, all interfering cells use the sa me hopping sequence,and a channel will be affected by the same interfer ers all the time. Nointerference diversity is obtained with cyclic hopp ing.Random FHRandom hopping uses sequences that are pseudo-rando mlygenerated => interference diversity is obtained.The physical ways to perform FH in a cell are baseb and hopping andsynthesized hopping.In baseband hopping, every TRX is assigned to a fix ed frequency,while the channel is shifted between the TRXs. The number offrequency carriers must be equal to the number of T RXs.In synthesized hopping, channel stays at a certain TRX, while the TRXshifts among the available frequencies. In the latt er method, thenumber of carriers is greater than or equal to the number of TRXs.Since the number of frequencies can be more than th e number oftransceivers in a cell when synthesized hopping is used, the reusefactor can be changed while the number of TRXs is fi xed.27
Page 1 and 2: Cellular Network Planningand Optimi
Page 3 and 4: General GSM was the first digital c
Page 5 and 6: GSM System architectureOur main foc
Page 7 and 8: Network Switching System (NSS)Mobil
Page 9 and 10: Logical channel structureGSM channe
Page 11 and 12: Channel structure FCCH = Frequency
Page 13 and 14: Frequency reuse Cluster sizes up to
Page 15 and 16: TRXA transmission/reception facilit
Page 17 and 18: Assume thatExample Operator has 5 M
Page 19 and 20: SolutionClosest cluster sizes from
Page 21 and 22: Cell categories Commonly used cell
Page 23 and 24: Frequency hopping (FH) in GSM FH me
Page 25: FH diversity gainChannel power resp
Page 29 and 30: Frequency assignment problem Classi
Page 31 and 32: Frequency assignment problem in FCA
Page 33 and 34: Simplified link budgets33
Page 35 and 36: Recall: SINR and TX powersAccording
Page 37 and 38: Simple DL link budget: Illustrative
Page 39 and 40: Link budget test example We have ma
Page 41 and 42: Link budget example/RX characterist
Page 43 and 44: Allowed propagation lossAllowed pro
Page 45 and 46: How to find detailed technical info
Page 47: Standardization documents 3GPP data

Cellular Network Planning and Optimization Part V: GSM

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