12/29/2017 Introduction to Wireless and Cellular Communications - - Unit 2 - Overview of Cellular Evolution and Wireless Technologies

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1 12/29/2017 Introduction to Wireless and Communications - - Unit 2 - Evolution and Wireless Technologies Course outline How to access the portal Evolution and Wireless Technologies Assignment 1 This assignment is based on Lectures 1-4 (Unit 2). Covers Systems Parts I, II, III 5G & other Wireless Technologies 1) For a analogue signal with bandwidth 8 khz, the Nyquist sampling rate will be. Systems - Part 1 Systems - Part 2 Systems - Part 3 5G and other Wireless Technologies Lecture Slides Unit2_notes Quiz : Assignment samples per sec samples per second 4000 samples per second samples per second 2) Consider a speech signal with bandwidth 4 KHz. Assuming Nyquist sampling and subsequent quantization to 6 bits per sample, the data rate of the sampled and quantized stream will be 48 kbps 24 kbps 96 kbps Feedback for week 1 Solutions to Assignment 1 Wireless Propagation and Concepts System Design, Capacity, Handoff, and Outage 48 kbps 3) Consider a cellular signal with carrier frequency f c = 900MHz. Compute the maximum Doppler frequency f D if the transmitter is moving at 72 kmph. 6 Hz 600 Hz 60 Hz 1/6

2 12/29/2017 Introduction to Wireless and Communications - - Unit 2 - Evolution and Wireless Technologies Week 4 - Multipath Fading Environment Week 5 - BER Performance in Fading Channels Week 6 - Wide Sense Stationary Uncorrelated Scattering (WSSUS) Channel Model Week 7 - Computer simulation of Rayleigh fading, Antenna Diversity Week 8 - Fading Channels - Diversity and Capacity 60 Hz 4) Multipath delay spread is the difference in time of arrival of the first and last copy of the signal generated through multipath propagation. If we consider a two component multipath environment and the difference in the path length traversed by the two paths is 300m, then the time difference between the two multipath components in microseconds will be Cannot be computed without specifying the carrier frequency 1 5) A cellular signal is transmitted at a power level of 1 W. The power level in dbw and dbm are: 0 dbw and 30 dbm 1 dbw and 31 dbm 30 dbw and 0 dbm Week 9 - Capacity and Introduction to CDMA Week 10 - Introduction to CDMA Week 11 - CDMA Receivers Week 12 0 dbw and 30 dbm 6) If a WCDMA cellphone has a frontend receiver bandwidth of 5MHz, and Noise figure of 5dB, the receiver Thermal Noise floor in dbm is MATLAB ) If a cdma2000 radio has a receiver thermal noise floor -108 dbm, and the minimum signalto-noise ratio to detect the signal is 5 db, then the receiver sensitivity is -103 dbm -113 dbm Insufficient data -108 dbm -103 dbm 8) A cellular system is designed for a receiver sensitivity of -102 dbm. If the total path loss permitted is 112 db, and a fading margin of 20 db, then the transmit power must be 30 milliwatts 1 Watt 30 Watts 2/6

3 12/29/2017 Introduction to Wireless and Communications - - Unit 2 - Evolution and Wireless Technologies 1 Watt 9) Consider an IoT system with data rate 6.4 Kbps (using BPSK modulation) and GSM which uses GMSK (binary modulation) signaling rate Kbps. Assuming the same transmitted power, and receivers with same Noise Figure, which of the following statements is TRUE GSM system will have better E b N0 than the IoT system IoT system will have better E b N0 than GSM Insufficient information to conclude that GSM system will have better E b N0 than the IoT system / / / IoT system will have better E b / N0 than GSM 10) Consider an IoT system with data rate 6.4 Kbps (using BPSK modulation) and GSM which uses GMSK (binary modulation) signaling rate Kbps. Assuming the same transmitted power, and receivers with the same Noise Figure. Estimate the difference in the E b / N0 of the two systems GSM system is better by 16.3 db IoT system is better by 24.2 db GSM system is better by 24.2 db IoT system is better by 16.3 db IoT system is better by 16.3 db 11) For the same battery capacity, rank the following devices in terms of longest battery life to the shortest battery life : A) One-way communications device (Rx. only) B) Cordless telephone C) phone D) 2-way Long-Range IoT device (Tx and Rx, low rate) (Hint: Transmit power depends on data rate and range) A, B, D, C D, A, B, C A, D, B, C A, D, B, C 12) A cellular phone has a 900 milli-amp-hour (mah) battery. Assume that the cellular phone draws 3 ma in idle mode and 300 ma during a call. what is the maximum possible talk time? 1 hour 3 hours 30 hours Insufficient data 3 hours 3/6

4 12/29/2017 Introduction to Wireless and Communications - - Unit 2 - Evolution and Wireless Technologies 13) A cellular phone has a 900 milli-amp-hour (mah) battery. Assume that the cellular phone draws 3 ma in idle mode and 300 ma during a call. What is the battery life (in hours) if the user makes a 10-minute call every 6 hours? (Hint: Compute the average current drawn from battery) 18 hours 80 hours 108 hours 80 hours 14) A cellular phone has a 900 milli-amp-hour (mah) battery. Assume that the cellular phone draws 3mA in idle mode and 300 ma during a call. What is the battery life in (in hours) if the user makes a 10-min call every hour? (Hint: Compute the average current drawn from the battery) hours 18 hours 3 hours hours 15) A cellular phone has a 900 milli-amp-hour (mah) battery. Assume that the cellular phone draws 3 ma in idle mode and 300 ma during a call. How long would the battery last if no call is made? 300 hours 900 hours 30 hours 300 hours 16) Consider three cellular systems, wherein the signal bandwidth for each system is indicated within brackets - GSM (200 KHz), CDMA2000 (1.25 MHz) and WCDMA (5 MHz). Assume that the base stations transmit at same power over the same distance, and that thermal noise is the only impairment. Which of the following statements is TRUE about the Carrier-to-Noise ratio ( C/N) - signal power / noise pow GSM has the best C/N GSM C/N better than cdma2000 C/N by 7.95 db GSM C/N better than WCDMA C/N by 14 db All of the above All of the above 17) The GSM slot and frame structure are given in Slide 38 of handout. A user gets assigned one time slot per frame. It was shown in the lecture that if a User is assigned one timeslot, the achieved data rate is 22.8 Kbps. What would be the user data rate if the 2 flag bits and the 6 tail bits were converted to data symbols (in addition to the regular (114 bits) data fields)? No change in the data rate 24.4 kbps 4/6

5 W W W W 12/29/2017 Introduction to Wireless and Communications - - Unit 2 - Evolution and Wireless T kbps 24.4 kbps 18) An EDGE system uses a similar slot structure as GSM but 8PSK modulation (3 bits per symbol) and the same symbol rate is ksymbols per second. Compute the user throughput per time slot for the EDGE system kbps 73.2 kbps kbps (= kbps *3) 68.4 kbps 19) For questions 15 to 19 use the below information. If and are IID Gaussian RVs with zero mean and variance, and W and are two RVs satisfying W X 2 + Y 2, and =arctan Y/X. Express X and Y in terms of W and X=Wcos ϕ, Y=Wsin ϕ X=Wsin ϕ, Y=Wcos ϕ X= sin ϕ, Y= cos ϕ 3 points X= sin ϕ, Y= cos ϕ

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