ELEC 456 - Mobile Communications
Assignment #1 - Due Feb. 12, 1999
*** Since this is a long assignment, it may have more value than other assignments ***
- Is cellular radio system capacity limited by noise or by interference?
Explain why this is the case.
- Which of TDMA, CDMA, and GSM cellular systems is inherently suited to data services? Why?
- Briefly describe the major sources of CCI and ACI.
- What is frequency re-use and what factors limit re-use in a practical cellular system?
- Assuming a regular hexagonal tessellation, what are the first five cluster sizes and the corresponding distances between cocells?
- Find the re-use distance D/R if the required CCI is 18 dB with a = 3.5. What is the corresponding minimum cluster size?
- Consider an AMPS-like system using a multiple-channel bandwidth scheme to increase capacity. If we have a total bandwidth of 12 MHz and we split this bandwidth equally between 20 kHz and 30 kHz channels, what is the total number of channels? For a seven-cell cluster, what is the radius of the inner cell (as a fraction of the radius of the outer cell)? The minimum C/Ic for the 20 and 30 kHz bands is 22 dB and 18 dB, respectively. Use a = 4.
- Use Okumura’s model to find the propagation loss in dB for an open area with:
f = 1 GHz, ht = 20 m, Pt = 5W, Gt = 4, Gr = 2, hr = 2 m, d = 10 km.
Check the result using Hata’s formula.
- Using sx2 = 1, plot the Rican PDF p(r) for a = 0, a = 1 and for a = 2. As shown in figure on page 72 of the course notes, be sure to normalize a for the computation and normalize r for the plot axis.
- Find the shadow loss when the wavelength is l = 25 cm, the distance from the obstruction to the mobile is d1 = 1 km, the distance from the base to the obstruction is d2 = 6 km, and the height of the obstruction is h = 10 m. Repeat with d1 = 2 km and d2 = 5 km. Explain the difference between the answers in view of the fact that in both cases the total distance is 7 km.