Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

BER for M array orthogonal signal

Status
Not open for further replies.

tomatokid

Newbie level 6
Joined
Sep 3, 2007
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
i need help in calculating the number of bit errors made per decision for my simulation.

M=8 for my case

For example;

if i send symbol X1, and i receive symbol Y1, no error is made

if i send symbol X1, and i receive symbol Y2, an error is made <--- how to calculate the number of bit errors

if i send symbol X1, and i receive symbol Y6, an error is made <-- whats the respective number of bit errors?

Thanks in advance =)
 

darock

Member level 2
Joined
Mar 4, 2007
Messages
48
Helped
17
Reputation
34
Reaction score
1
Trophy points
1,288
Activity points
1,543
It depends on the the "symbol to bit" encoding. For example with Gray coding, adjacent symbols differ by one bit.

For orthogonal signaling with equiprobable symbols, a symbol error is equiprobable in all (M-1) directions. So any bit to symbol encoding will suffice.

Precisely for orthogonal signalling, Prob of bit error=(2^(k-1)/(2^k-1))*Prob of symbol error

which is roughly 0.5* Prob of symbol error.


I should also mention that this holds only for AWGN channels.

Added after 59 seconds:

Forgot k=log2(M)

M= no of orthogonal signals
 

    tomatokid

    Points: 2
    Helpful Answer Positive Rating

tomatokid

Newbie level 6
Joined
Sep 3, 2007
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
Hi

Thanks for your help.. I have got the correct simulation results...



Since the system is of 8 equal energy, equally likely orthogonal signals, so for same SNR value, i should get the same BER for every signal right?

Is it necessary to use gray coding for my case?
 

darock

Member level 2
Joined
Mar 4, 2007
Messages
48
Helped
17
Reputation
34
Reaction score
1
Trophy points
1,288
Activity points
1,543
any random bit to symbol encoding will suffice because there is no nearest neighbor concept in orthogonal constellations unlike mqam or mpsk.
 

sohiltri

Member level 5
Joined
Dec 16, 2006
Messages
81
Helped
6
Reputation
12
Reaction score
1
Trophy points
1,288
Activity points
1,750
How will u prove that BER for msb bit is less than BER for lsb bits in mqam....
 

tomatokid

Newbie level 6
Joined
Sep 3, 2007
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
darock said:
any random bit to symbol encoding will suffice because there is no nearest neighbor concept in orthogonal constellations unlike mqam or mpsk.

Sorry... I dun really understand... Can explain in more details?
 

darock

Member level 2
Joined
Mar 4, 2007
Messages
48
Helped
17
Reputation
34
Reaction score
1
Trophy points
1,288
Activity points
1,543
@sohilitri


Well, it is not neccesarily true that MSB error prob is less than LSB error probability.

Consider QPSK or 4-QAM as shown in the following.

00 01

10 11

Here both LSB and MSB error are equiprobable.

Then what is the significance of the symbol to bit encoding?

Well, to making error in both the bits is less probable to making error in one of the bits. Therefore symbol to bit encoding can be chosen to minimize the total number of bits in error.
 

sohiltri

Member level 5
Joined
Dec 16, 2006
Messages
81
Helped
6
Reputation
12
Reaction score
1
Trophy points
1,288
Activity points
1,750
Thanks Darock,

But u see in M-QAM ...LSB bits are coded with ASK and MSB bits are coded with PSK...so there is lot of diff....as we know that PSK has min probability error....
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top