ITC254 Wireless Networks

Answer the following questions:

1. Analyse how digital convergence affects people's use of network devices?

2. Compare and contrast DSSS and FHSS. Which one is more suitable than the other, and for what scenario?

3. Research on the standard 802.15.4 and identify its MAC layer responsibilities.

4. According to the Shannon’s Channel capacity theorem:

Channel capacity C = B*log (1 + S/N), Where B = Bandwidth and S/N = Signal to Noise Ratio.

 

Answer the following questions with respect to the Channel capacity theorem:

a. When the Bandwidth increases, what happens?

b. When the Signal to Noise Ratio increases, what happens?

c. When the Signal to Noise Ration S/N tends to infinity what happens?

d. When the Bandwidth tends to infinity what happens?

5. Scrutinize the following scenario:

Consider a communications system operating in the 5.9 GHz band. Assuming the free space loss model for signal attenuation,

the gain of both transmitting and receiving antenna to be 1 dB, and a noise level of -85 dBm, calculate:

a. The range of communication if the transmission power is 100mW;

b. The transmission power if you wanted a communication range of 3 Km;

6. In the questions below, please provide True or False for the statements; justify your answer with proper argument(s). (No marks for not giving the justification)

a. Data throughput is the same as modulation rate of the signal.

b. Frequency Diversity is achieved by spreading the signal in time by sending multiple copies of the signal at different time instants.

c. Multipath propagation always improves the SNR.

1.How digital convergence network devices being used.

Digital convergence - is the combination of all characteristics and abilities of electronic systems into a more simple and converged media to enhance high rate of interaction of individuals through playing and exchanging information in different ways.

Digital convergence has some effects to network devices being used by individual which include the following.

Digital convergence has affected game plan of journalist ad generally news medias. With the many available social media sites people can now interact with them and read the available news at any time instead of waiting for TV station to deliver the news to them at a particular time of the day. This means that the news is delivered quickly to the public at any time. More so news can be found on an online platform so news reader now days don’t purchase   newspapers frequently.

Due to digital convergence, students now days prefer going to study through online platforms living behind the print media. Many of the schools today prefer teaching through online platforms than using printed media. This has reduced the rate at which print medias are being used.

2.Comparison between DSSS and FHSS.

DSSS is transmission technology mostly used  to transmit wireless networks  in local area while ,data signals are  joined  with high data rate bits  signals at the  sending station for transmission while FHSS  is way in which radio signal are transmitted by frequently switching carries among different frequencies that are available according (Falsafi,2010).

Differences between the two

• FHSS uses frequency hopping to modify the phase of the signal while  DSSS uses pseudo noise. Hopping is where by a large bandwidth of data is divided into a small channel in which data will able to fit in it. The signal will then be sent into different channel. DSSS does this in a very different way where by simple dividing the available signal and introducing a random pseudo code into the signal that automatically changes its appearance. This produces an output that resembles noise but appears as just like other signals.
  
  
• FHSS can easily be synchronized as compared to the DSSS .For information to be to be decoded it must be synchronized with the transmitter. Synchronization in FHSS is more easier since it uses one channel to carry out the process while in DSSS is more complex since a timing has to be done it also implements a search algorithm for the decoding process to take place.
  
  
• DSSS can be used in the positioning of systems while FHSS cannot be used in this systems.

FHSS is the best technology to be used in signal transmission since it can be synchronized in a very little time does enable frequency to be transmitted at a faster speed than DSSS.

3.

15.4  standard

This is methodological standard which explains the functioning of a low rate Wireless personal area network. It simply specifies physical layer and the media access layer of the network (Shiu,2011).

802.15.4 Standard mac layer responsibilities

• It regulates the access number of mediums to share resources
• It performs requirements such as delay and throughput to conserve energy of the wireless network.
• It inherits all the known problems of the underlying physical layer using  a wireless layer.

4.

5.a

Power= 1w

6.

References

Falsafi, A., & Pahlavan, K,2010. A comparison between the performance of FHSS and DSSS for

wireless LANs using a 3D ray tracing program. In Vehicular Technology Conference, 1995 IEEE 45th (Vol. 2, pp. 569-573). IEEE.

Shiu, Y. S., Chang, S. Y., Wu, H. C., Huang, S. C. H., & Chen, H. H. (2011). Physical layer security in

wireless networks: A tutorial. IEEE wireless Communications, 18(2).