The relation between mod. scheme and users and the bits in slots when using TDMA

[admoon]

i want to ask

if we say BPSK is that mean the number of users is 2 only and if we say 8psk we mean 8 users only or this is wrong?

plz replay

 

[m_pourfathi]

Re: users in modulation

It is wrong! BPSK or 8PSK does not refer to the number of users. They are different kinds of digital modulation. each bit is mapped to a symbol. in 8psk every 3 bits is mapped to one symbol. you can use different kinds of multiple access techniques like TDMA or CDMA or FDMA on any of those modulations, and other factors affect the maximum number of users.

 

[admoon]

Re: users in modulation

ok thats fine but plz if you have an example to relation between number of users and type of mod.

what is the relation between mod. scheme and TDMA or FDMA ?

thanks for replay

 

[m_pourfathi]

Re: users in modulation

There is no relationship between number of users and the modulation type. except that if we use a greater modulation level we may be able to have the same number of users with higher data rate or more users for fixed data rate.
TDMA or time division multiple access, uses different time slots for different users. the number of users depend on the maximum time slots that the transceiver allocate to the communication link and FDMA is the same in the frequency domain. CDMA in code space.

 

[admoon]

Re: users in modulation

thanks for reply

but the question is what is the advantage or disadvantage for increase the level like from BPSK to 8PSK?

and another question what is more effecient to reduce the error and increse S/N
BPSK OR 8PSK? and hoe the data arrange if we talk about TDMA ?

thanks alot

 

[m_pourfathi]

Re: users in modulation

for low signal to noise ratio BPSK is more efficient due to decreasing the BER. for Higher Signal to noise ratios 8PSK would be the better option due to its bandwidth reduction and rate increasing.

 

[admoon]

Re: users in modulation

thanks alot for you

but i just to talk to me if this statment is true

if we use BPSK and TDMA that means 2 bit is used in each time slot for one user ?

if wrong plz try to explain to me the relation between mod. scheme and users and the bits in slots if we use TDMA

thanks again

 

[evil_genious]

users in modulation

hello guys, in 4g technology the main modulation technique is used is OFDM and qam 64 combination. but with this combination wimax standard got 57mbps . but the basic rules or expectation for 4g is 1gbps. what do u guys think about using OFDM and 512qam to achieve 1gbps for per user. back bone bandwith is 100mbps. and is there any practical transciever of OFDM and qam64?any schematic or anydata can anyone upload?

 

[admoon]

Re: users in modulation

plz answer meeeeeeeeeee

 

[m_pourfathi]

Re: users in modulation

Admoon, It doesn't matter if you use TDMA FDMA or any other modulation scheme. every symbol transmitted contains two bits of information. If it uses TDMA different symbols at different times may be used by different users.

Added after 3 minutes:

I don't know if 512 qam is efficient enough for mobile communications. I think they have to use more bandwidth, better coding schemes, better multiple access techniques like SDMA, more advanced equalizers and adaptive receivers. and also MIMO technology should be implemented