Tutorial Set 8
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| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | ___________________________________________________________________________________ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Tutorial Set 8 1) You have a bandwidth of 10 MHz (per direction) in a single-cell system and want to deploy a wireless telephone system. You have the following options: analogue 30-kHz channels (as in AMPS), digital 30-kHz channels (each supporting 3 users as in IS-54), digital 200-kHz channels (each supporting 8 users as in GSM), or CDMA with 10-kbps user signals requiring an E b /N 0 of 6 dB. (a) Compute the achievable capacity (in number of simultaneously active users per cell) for each case. (b) How do the results in (a) change if you use 120° sectorization? (c) How do the results in (b) change if instead of a single cell you have many? (Ignore voice activity factor in all of the above.) (d) For the above case of AMPS-like channelization with 7-cell reuse and 3 sectors per cell, suppose that you need to serve 900 users per cell. If the average duration of a call is 2 minutes, what is the maximum calling rate which guarantees a GOS of 2%? 2) Assume that 50 MHz is available for forward channels, and you will deploy GSM. Each channel is 200 kHz, but using TDMA, 8 simultaneous calls can be made on each channel. How many channels are there per cell? How many forward calls can be made simultaneously for the cellular system depicted in Figure 1? Figure 1: Frequency reuse for N=4. 3) Assume that 18 dB of S/I is required for acceptable system operation. What minimum N is required? Test for n = 3 and n = 4. 4) A 7 cell cluster (with N = 7) has 28 MHz allocated to it for forward channels and each channel is 200 kHz. Assume blocked-called-delayed and a probability of delay of 1%, and each user makes one 10 minute call every 3 hours. What is the number of users that can be supported? 5) Let N = 7, each cell has C = 100 channels, and users who make calls with λ = 0.01 per minute with average holding time 3 minutes. For blocked-calls-cleared and a GOS of 2%, what is the number of users which can be supported in this cell? Next, using 120 degree sectoring, and otherwise identical system parameters, what is the number of users which can be supported in this cell? What percentage reduction in capacity does sectoring with constant N cause? 6) For the same system as in question 5, now assume that with 120 degree sectoring, that N can be reduced from 7 to 4. What number of users can be supported?
description
introduction to mobile communication
Transcript of Tutorial Set 8
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
___________________________________________________________________________________
| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 |
Tutorial Set 8
1) You have a bandwidth of 10 MHz (per direction) in a single-cell system and want to deploy a
wireless telephone system. You have the following options: analogue 30-kHz channels (as in
AMPS), digital 30-kHz channels (each supporting 3 users as in IS-54), digital 200-kHz channels (each
supporting 8 users as in GSM), or CDMA with 10-kbps user signals requiring an Eb/N0 of 6 dB.
(a) Compute the achievable capacity (in number of simultaneously active users per cell) for each
case.
(b) How do the results in (a) change if you use 120° sectorization?
(c) How do the results in (b) change if instead of a single cell you have many? (Ignore voice
activity factor in all of the above.)
(d) For the above case of AMPS-like channelization with 7-cell reuse and 3 sectors per cell,
suppose that you need to serve 900 users per cell. If the average duration of a call is 2 minutes,
what is the maximum calling rate which guarantees a GOS of 2%?
2) Assume that 50 MHz is available for forward channels, and you will deploy GSM. Each channel is
200 kHz, but using TDMA, 8 simultaneous calls can be made on each channel. How many channels
are there per cell? How many forward calls can be made simultaneously for the cellular system
depicted in Figure 1?
Figure 1: Frequency reuse for N=4.
3) Assume that 18 dB of S/I is required for acceptable system operation. What minimum N is
required? Test for n = 3 and n = 4.
4) A 7 cell cluster (with N = 7) has 28 MHz allocated to it for forward channels and each channel is
200 kHz. Assume blocked-called-delayed and a probability of delay of 1%, and each user makes
one 10 minute call every 3 hours. What is the number of users that can be supported?
5) Let N = 7, each cell has C = 100 channels, and users who make calls with λ = 0.01 per minute with
average holding time 3 minutes. For blocked-calls-cleared and a GOS of 2%, what is the number of
users which can be supported in this cell? Next, using 120 degree sectoring, and otherwise
identical system parameters, what is the number of users which can be supported in this cell?
What percentage reduction in capacity does sectoring with constant N cause?
6) For the same system as in question 5, now assume that with 120 degree sectoring, that N can be
reduced from 7 to 4. What number of users can be supported?
