Unit 4 - Cellular System Design, Capacity, Handoff, and Outage

Transcription

1 Unit 4 - Cellular System Design, Capacity, Handoff, and Outage Course outline How to access the portal Assignment. Overview of Cellular Evolution and Wireless Technologies Wireless Propagation and Cellular Concepts Cellular System Design, Capacity, Handoff, and Outage Cellular Geometry & System Design Cellular System Capacity, Trunking Handoff & Mobility Handoff Part, Classification of Signal Variation Shadowing, Outage, Multipath Quiz : Assignment Lec0_notes Lec_notes Lec_notes Lec_notes ) Which of the following is not a valid cluster size ( assume hexagonal cells)? point ) Consider a N-cell reuse pattern (hexagonal geometry) with base stations at the point centre of each cell with omni-directional antennas. What would be the D/R ratio required if a minimum value of C/I = 8dB must be ensured. Assume path loss exponent n =. and only tier interferers ) Consider a N-cell reuse pattern (hexagonal geometry) with base stations at the point centre of each cell with omni-directional antennas. What would be the value of N that will ensure that a minimum C/I = 8dB is maintained. Assume path loss exponent n =. and only tier interferers are present. 9 Lec4_notes Feedback for week /

2 Assignment Solutions Week 4 - Multipath Fading Environment Week 5 - BER Performance in Fading Channels 4) Consider a cellular system with N= (hexagonal cells, BTS(base station) at the point centre of cell with omnidirectional antenna) with path loss exponent n =. Assume that MS(mobile station) is at the worst case C/I situation (at a vertex). Compute via geometric estimation the C/I due to tier interferers only. Hint: Since N= is small, you need to calculate the distance of the MS from all the tier interferers via geometric estimation. Week 6 - Wide Sense Stationary Uncorrelated Scattering (WSSUS) Channel Model 5.5 db 6.5 db 4. db 8.6 db Week - Computer simulation of Rayleigh fading, Antenna Diversity Week 8 - Fading Channels - Diversity and Capacity Week 9 - Capacity and Introduction to CDMA Week 0 - Introduction to CDMA Week - CDMA Receivers Week MATLAB 5.5 db 5) Consider a cellular system with N= with hexagonal cells. Antenna sectorization point is introduced in the system. What is the number of tier interferers if 0 degree sectorization is employed. Assume that the base station is at the center of the cell and evaluate for the worst case interference ) Repeat problem 5 if 60 degree sectorization is employed. Again evaluate for the point worst case interference 4 ) Which of the following is the most favourable action for a cellular system to take point which receives high RSSI but low RxQual (SINR)? Frequency hopping Intracell handover Intercell handover either (a) or (b) either (a) or (b) 8) A cellular service provider implements a digital TDMA system which requires a point minimum signal-to-interference ratio of 5 db. Assume that only Tier- interferers need to /

3 be considered and the approximation that all Tier- interferers are equidistant from the mobile station. What is the optimal value of N considering omni-directional antennas? (Assume a path loss exponent of n = 4) 4 9) Consider a cellular system consisting of 5 users. Each user makes an average point of calls per hour. Each call, on average, lasts for 4 minutes. What is the total offered traffic (in Erlang)? ) What is the maximum system capacity per channel in Erlangs when providing a point blocking probability of % with C = 40 channels (Use the Erlang-B calculator given in ) ) ( For questions and use the following information). A cellular system has point a cluster size N. It is given that a total of 00 voice channels are available, and users are uniformly distributed over the geographic area covered by the cells. Each user generates 0.04 Erlangs of traffic. Assuming that blocked calls are cleared and that the target blocking probability is %. (Use the Erlang-B calculator given in ) What is the maximum number of users per cell that can be supported for cluster size N = 4? /

4 5 ) For the system in previous question, what should be the reduction in offered traffic to maintain the same Grade-of-Service (GOS) if one channel in each cell is reserved for handoff traffic. (Assume cluster size is N = 4 ) point 0.9 Erl. Erl.5 Erl.8 Erl 0.9 Erl ) (Rappaport.) For a N = system with blocking P = % and average call point length of two minutes, find the capacity loss (in terms of No. of users per cell) due to trunking for 60 channels / cell when going from omni-directional antenna to 60 degree sectored antennas. Assume blocked calls are cleared and the average user call rate is call per hour (Use the Erlang-B calculator given in ) 4 users /cell 40 users /cell 609 users /cell 98 users /cell 609 users /cell 4) Which of the following fact is true about the maximum per-channel capacity for a given Pr(blocking)? (Hint : You may use the Erlang-B calculator given in The plot of per-channel capacity versus No. of Channels used is point a concave downwards function a convex downwards function neither concave nor convex Constant a concave downwards function 5) (Q.5-6) Assume that you re travelling in Hyperloop, a High-Speed-Train at a point speed of 60 m/s. Base stations are located at regular intervals along the rails. Assume that you re connected to BTS-A and moving away from BTS-A towards BTS-B. The two base stations, A and B are separated by a distance of km. (Refer. Lec / Slide for picture) The User Equipment, i.e, your mobile phone has a receiver sensitivity of -00 dbm. Neglect the height of the base station towers, and assume Free-Space-Path-Loss model. Assume that the carriers of A and B are around.4 GHz. What is the minimum transmit power required at the base stations to avoid Call-drop. 4/

5 Assume that all base stations work at the same transmit power. Assume that instantaneous hand-off is possible for this problem. dbm 0 dbw 0 dbm dbw 0 dbm 6) Let s say a Hand-off takes about s on an average since initiation, and BTS point transmit power is dbm, what is the Hand-off margin required in db to avoid Call-drops while in the moving train. (Again, UE is moving from BTS-A to BTS-B) db.5 db 0. db 0 db.5 db ) Assuming that the size of the cells and the total number of available channels point are fixed. Increasing the cluster size improves the C/I and at the same time, increases Erlang capacity. This statement is False True Insufficient information to make the statement True under some conditions False 8) A mobile phone receiver operates in a bandwidth of MHz at 00 K and has a point noise figure 4 db. The receiver is present on the cell edge and minimum db SNR is required for reliable communication. Consider log normal shadowing effects with σ = 5 db. Carrier frequency = GHz. To achieve 90% coverage probability, find the mean received power. Make use of the data Q(-.86) = 0.9 Hint: Q(-x) = - Q(x). Q function calculator: dbm dbm -50 dbm -05. dbm 5/

6 -0.6 dbm 9) A mobile phone receiver operates in a bandwidth of MHz at 00 K and has a point noise figure 4 db. The receiver is present on the cell edge and minimum db SNR is required for reliable communication. Consider log normal shadowing effects with σ = 5 db. Given there is maximum power constraint of mw that a base station can transmit., find the maximum radius of the cell for 90% coverage probability. Assume free space path loss model. Carrier frequency = GHz. Make use of the data Q(-.86) = 0.9 Hint: Q(-x) = - Q(x). Q function calculator: 50 km 45.4 km.4 km km.4 km 0) Consider GHz. If the user is moving at 0 m/s towards the base station, find the maximum Doppler shift. point. Hz. Hz Hz 6.66 Hz Hz ) In a normalized U-V coordinate system, consider two points with the following coordinates: point Point A (,) and Point B (5,4). What is the actual distance between points A and B if the side of each hexagon is R= km 5. km 9. km 8 km None of the above 5. km 6/

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