Conceptual Questions: [100 points: 10 points per question] 1 List three main cat

Question

Conceptual Questions: [100 points: 10 points per question] 1 List three main categories for access methods (by MAC layer). 2- What is the main distinction between channel partitioning and random access methods. 3- Which partitioning method (out of TDMA, FDMA, CDMA, Hybrid TDMA/FDMA) is used in GSM and LTE wireless systems? 4 What are the main problems of TDMA or FDMA methods? Illustrate with an example 5- Consider a wireless system, where we have 100 users in the system. The users only use voice service (phone conversation) and their traffic is almost evenly distributed over time. Is TDMA or FDMA an appropriate access method for such a system? Why? 6- Consider the above system, but here the users use their devices mainly for web browsing and their phone use is not evenly distributed over time. Is partitioning method (TDMA or FDMA) an appropriate choice? 7- What is the main difference between OFDMA and OFDMA-SC? 8- Explain SDMA access method. What is the main challenges of using SDMA? 9 What are the main advantages of using frequency hopping? 10- What is the main difference between the contention-based or contention avoidance random access method? Problems [200 points] 11- Consider a communication system with QPSK modulation and bit rate 10 kbps. [15 points] What is the symbol interval length? [5 pts) If the total bandwidth of the system is 1 MHz (in both uplink and downlink) and we use FDMA access, what is the maximum number of users that can communicate in parallel? [5 pts] Repeat part b for OFDMA [5 pts] a) b) c) 12- Consider a CDMA system with the following chip sequences for three users (00001111, 00110011, 01010101). Consider that userl, user2 and user3 are simultaneously sending the following bitstreams respectively (00, 01, 11). Show that the receiver 1 is able to recover the information bits sent by user 1. Hint: Calculate transmitted signal for all users, then find the received signal and finally perform decoding at receiver 1. Assume BPSK modulation (01,1-+115 points 13- Consider the above system with the following chip sequences for three users (00001111, 11110000, 01010101). Does this system work properly? Justify your answer. [10 points] 14- If the number of users in a wireless system is 1200, and each user spends a y 15 minutes a day on the phone (on average). What is the channel utilization rate (system efficiency) if the number of TDMA slots is 50? [20 points 1ms and the probability of a user to 10 users [20 points) 15-In a wireless system with Aloha access method, the transmission interval is T transmit in time [t,t T] is pe1%. Calculate the following quantities in a system with n a) Probability of success for user #7 b) Probability of success for a user: p(user#1 success)--D(user#10 success) c) What is the optimal p that maximizes the success probability? d) What is the exact success probability in this case 16- Consider a system with CSMA-CD, where we use slotted Aloha (with optimal transmission probability) in contention period. If a contention time slot is 10us and a transmission time slot is 1ms, what is the channel utilization rate? [20 points

Explanation / Answer

Hello,
          Please find the answer to the first question attached as under. Please give a thumbs up rating if you find the answer useful! Have a rocking day ahead!

NOTE: You have posted a total of 16 questions in one go, which is impossible to answer by a single expert. Please break up the questions and post as multiple entries.

1. The three main categories for access methods by MAC are:

a. CSMA/CD: Usually used in older technologies for local area networks.

b. ALOHA: Uses medium access and experimental UHF for message communication

c. Soltted ALOHA: It is almost the same as ALOHA, except thgat it uses discrete time based scheduling for packet sending.

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.