20. We have a total bandwidth of 25 MHz and each user requires 30 KHz for voice
ID: 1835996 • Letter: 2
Question
20. We have a total bandwidth of 25 MHz and each user requires 30 KHz for voice communication. (This is how spectrum was used for 1G cellular system.). a. If we use one high power antenna to cover the entire town. What would be the maximum simultaneous user which the system can support? b. If we use 20 low power antennas within the area within 4 clusters; That is, to divide the area into 20 cells and divide the entire band to 4 sub-bands. What would be the maximum number of simultaneous users which the system can support? c. If we use case “b” with three time slots per channel (carrier) what would be the effect on simultaneous number of users supported by that system? d. Change the TDMA 30KHz bandwidth of the above scenarios to GSM 200KHz bandwidth with 8 time slots per carrier (channel) and calculate the number of simultaneous users for this scenario 20. We have a total bandwidth of 25 MHz and each user requires 30 KHz for voice communication. (This is how spectrum was used for 1G cellular system.). a. If we use one high power antenna to cover the entire town. What would be the maximum simultaneous user which the system can support? b. If we use 20 low power antennas within the area within 4 clusters; That is, to divide the area into 20 cells and divide the entire band to 4 sub-bands. What would be the maximum number of simultaneous users which the system can support? c. If we use case “b” with three time slots per channel (carrier) what would be the effect on simultaneous number of users supported by that system? d. Change the TDMA 30KHz bandwidth of the above scenarios to GSM 200KHz bandwidth with 8 time slots per carrier (channel) and calculate the number of simultaneous users for this scenario 20. We have a total bandwidth of 25 MHz and each user requires 30 KHz for voice communication. (This is how spectrum was used for 1G cellular system.). a. If we use one high power antenna to cover the entire town. What would be the maximum simultaneous user which the system can support? b. If we use 20 low power antennas within the area within 4 clusters; That is, to divide the area into 20 cells and divide the entire band to 4 sub-bands. What would be the maximum number of simultaneous users which the system can support? c. If we use case “b” with three time slots per channel (carrier) what would be the effect on simultaneous number of users supported by that system? d. Change the TDMA 30KHz bandwidth of the above scenarios to GSM 200KHz bandwidth with 8 time slots per carrier (channel) and calculate the number of simultaneous users for this scenarioExplanation / Answer
(a): one high power antenna to cover the entire town. We can support 25MHz/30 KHz = 833 simultaneous users.
(b): 20 low power antennas are used. That is, to divide the area into 20 cells. We divide the entire frequency band into 4 sub-bands and assign one to each cell, which has a spectrum of 25 MHz/4 = 6.25 MHz.
lThe number of users supported by each cell is 6.25 MHz/30 KHz = 208.
lIn this question, 4 cells form a cluster. Since there are total of 20 cells, the town is covered by 5 clusters (20/4=5).
lEach cluster will use the entire frequency band, so the number of users per cluster is 833, as calculated earlier, and the total number of simultaneous users for 5 clusters is 833x5 = 4,165.
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