Text: "Wireless Communications," by Andreas F. Molisch, John Wiley & Sons1.What is the resolution of...

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Text: "Wireless Communications," by Andreas F. Molisch, John Wiley & Sons1.What is the resolution of a Rake receiver? Explain your answer.How can the rake receiver know the phases of multipath gains? Is there near-far problem in downlink CDMA systems? Explain your answer.What are the main reason that spectral efficiency of a CDMA cellular system is better than that those of TDMA or FDMA systems?2.In a spread spectrum system, what is the number of chips per bit when the coding gain is 13.424dB?3.For the following circuit, if a1=1, a2=0, a3=0, a4=0, find an for n=5 to 15. 4.
	
Document Preview: Text: "Wireless Communications," by Andreas F. Molisch, John Wiley & Sons1.What is the resolution of a Rake receiver? Explain your answer.How can the rake receiver know the phases of multipath gains? Is there near-far problem in downlink CDMA systems? Explain your answer.What are the main reason that spectral efficiency of a CDMA cellular system is better than that those of TDMA or FDMA systems?2.In a spread spectrum system, what is the number of chips per bit when the coding gain is 13.424dB?3.For the following circuit, if a1=1, a2=0, a3=0, a4=0, find an for n=5 to 15.DDDD 4.Consider a Single-Cell CDMA system that uses random codes on the uplink.   is the CDMA system bandwidth,  is the noise power spectral density at the base station, and  is the total number of users. For the user,  is the average transmitted power,  is the received power signal at the base station site,  is the data rate and  is the distance between the base station and the  user.  a.) What is the received signal power of the user (the desired user) at the base station?b.) What is the received signal energy per bit of the user (the desired user) at the base station?c.) What is the total received noise power at the base station?d.) What is the average interference plus noise power to the  user at the receiver of the base station?  .e.) If interference due to other users behaves like noise, what is the signal to interference plus noise energy ratio (SINR) to the  user at the receiver of the base station?f.) If the required minimum SINR for each user is , what is the condition of perfect power control (i.e., all users transmit minimum power while all users still maintain successful communications)?

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Text: "Wireless Communications," by Andreas F. Molisch, John Wiley & Sons 
 
1. 
a.) What is the resolution of a Rake receiver? Explain your answer. 
 
The resolution of the Rake Receiver is that the signal coming from the different 
paths (multipath) are resolved into single sound wave by the receiver in single 
phase as the signal comes in different out of phase depending upon the PN codes 
used.
b.) How can the rake receiver know the phases of multipath gains?  
 
The signal received is sampled at a sampling rate which should be twice the 
sampling rate for sufficient statistics for detection and synchronization and then 
fed to the Rake Receiver Fingers. The chip-rate of each finger of the Rake 
Receiver is sampled at the timing instant. After the correlation the complex 
conjugate of the generated spread spectrum is summarized and each finger is 
weighted according to Maximum Ratio Criterion.
c.) Is there near-far problem in downlink CDMA systems? Explain your 
answer.
CDMA near far problem basics 
The CDMA near far problem is there as the handset could be anywhere in the 
boundary region of the Cell. Some might be close and some may be far and other 
even far away. As the signal decay over the distance quite rapidly so strength of 
the signal is quite weak.

Text: "Wireless Communications," by Andreas F. Molisch, John Wiley & Sons1.What is the resolution of a Rake receiver? Explain your answer.How can the rake receiver know the phases of multipath gains?...

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