For some reason I'm having trouble posting the question. Here it is hopefully.
Q2.CDMA Communication:
Stations A and B are expected to communicate using Code Division Multiple Access (CDMA).
Binary chipping sequences for A and B are 0 0 1 0 1 0 1 0 and 1 0 1 0 1 0 1 1 respectively.
Message that needs to be transmitted is 1 0
Part A:
Firstly, find out whether stations A and B can form a pair required to communicate using CDMA. Show the procedure in detail.
Part B:
Find out a message encoded using CDMA. Show the procedure in detail.
Part C:
Demonstrate decoding process by Station B for the same encoded message. Show the procedure in detail.
Thanks you guys any help would be greatly appreciated.
Part A: To determine whether stations A and B can form a pair to communicate using CDMA, we need to check if their chipping sequences are orthogonal. Orthogonal sequences are essential in CDMA to avoid interference between multiple users.
In this case, the chipping sequences for station A and station B are:
A: 0 0 1 0 1 0 1 0
B: 1 0 1 0 1 0 1 1
To check if these sequences are orthogonal, we need to calculate their cross-correlation. The cross-correlation between two sequences is the sum of the products of their corresponding elements.
Let's calculate the cross-correlation between A and B:
Correlation = 0*1 + 0*0 + 1*1 + 0*0 + 1*1 + 0*0 + 1*1 + 0*1 = 1 + 1 + 1 + 0 = 3
If the cross-correlation is zero, the sequences are orthogonal. In this case, since the cross-correlation is not zero (it is 3), stations A and B cannot form a pair required to communicate using CDMA. The chipping sequences are not orthogonal, and there will be significant interference between them.
Part B: To encode a message using CDMA, we need to multiply each bit of the message by the corresponding chipping sequence and sum the results.
The message that needs to be transmitted is 1 0. Let's encode it using the chipping sequences of station A and station B:
Encoded Message = (Message Bit 1 * Chipping Sequence A) + (Message Bit 2 * Chipping Sequence B)
Encoded Message = (1 * 0 0 1 0 1 0 1 0) + (0 * 1 0 1 0 1 0 1 1)
Simplifying, we get:
Encoded Message = 0 0 1 0 1 0 1 0 + 0 0 0 0 0 0 0 0
= 0 0 1 0 1 0 1 0
Therefore, the message 1 0 is encoded using CDMA as 0 0 1 0 1 0 1 0.
Part C: To decode the encoded message at station B, we need to multiply the received signal by the chipping sequence of station B and sum the result.
Let's assume the received signal at station B is the encoded message: 0 0 1 0 1 0 1 0.
To decode the message, we multiply the received signal by the chipping sequence of station B:
Decoded Message = (Received Signal * Chipping Sequence B)
Decoded Message = (0 0 1 0 1 0 1 0) * (1 0 1 0 1 0 1 1)
Simplifying, we get:
Decoded Message = 0*1 + 0*0 + 1*1 + 0*0 + 1*1 + 0*0 + 1*1 + 0*1
= 1 + 1 + 1
= 3
Therefore, the decoded message at station B is 3.
Please note that in practical CDMA systems, decoding involves additional signal processing steps, and the final decoded message may not be presented as a single number. This simplified example demonstrates the basic concept of decoding in CDMA.