# What is the difference between space time, space time coding and temporal coding?

Status
Not open for further replies.

#### vkekk

##### Full Member level 3
1. What is the difference between Space time and space time coding?

2. what is temporal coding?

3. advantages of QAM compared with QPSK.. what effect if increase 4QAM To 16QAM...

#### salam2000

##### Member level 3
Re: Space time...

with increase the modulation order you can increase the throughout. because you send same number symbol, but each symbol have larger number bit. bit/symbol=log2(M),
with increase Modulation order, the symbol become closer (near) and we need higher SNR to decrease BER.

### vkekk

points: 2

#### vkekk

##### Full Member level 3
Re: Space time...

thanks salam2000

Can i get the advantages of QAM compared to others.

help me the below .....

1. What is the difference between Space time and space time coding?

2. what is temporal coding?

#### salam2000

##### Member level 3
Re: Space time...

Temporal coding use more in medical and bioelectrical, it maybe use also in wireless communication.
the definition of bioelectrical of it is:
-------------------------------------------------------------------------------
The temporal coding is a type of neural coding which relies on precise timing of action potentials or inter-spike intervals. Combined with traditional rate coding models, temporal coding can provide additional information with the same rate. There is no precise definition of temporal code. Actually almost any coding scheme that is not rate coding can be referred to as a temporal code.

Unlike rate coding, the temporal coding model tries to account for short-term stimuli producing a small number of spikes. For example, if a neuron is capable of firing at a maximum rate of 100 spikes per second, then a stimulus <10ms would likely elicit only a single spike. This model is especially important for sound localization, which occurs within the brain on the order of milliseconds.

The discovery of spike timing dependent plasticity, where synaptic efficacy is modulated by the precise timing of spikes, provides strong evidence that temporal codes are used for cortical information transmission.

It should not be confused with the coding of the temporal information.
----------------------------------------------------------------------------------
if you interest to MIMO systems, you can see title of some book about MIMO in this link:
https://www.edaboard.com/viewtopic.php?t=272247&highlight=

also the Tse book and papers are about "trade off between Spatial Multiplexing and Diversity is good.
I think the space-time is a general name use for systems that gained simultaneously from Space and time diversity. but "Space-Time Codings" are some orthogonal code and mapping scheme that use in these systems to reduce the complexity of these systems from exponential to linearity complexity. some schemes like "STBC", layered ST & ... are famous. they are need for separation signals that interference because transmit simultaneously and in same band.

#### mimomod

##### Member level 4
Re: Space time...

vkekk said:
1. What is the difference between Space time and space time coding?

2. what is temporal coding?

3. advantages of QAM compared with QPSK.. what effect if increase 4QAM To 16QAM...
1. In wireless communication, space-time refers to space and time coordinate of the wireless channel. As you might know, wireless channels have three dimensions: time, frequency, and space. Time dimension is well known. Frequency dimension is due to multipath fading (frequency selective channel). Space dimension occurs when you have multiple antennas at the transmitter or/and the receiver. This three dimensions of wireless channels may be exploited by communication systems to improve the quality of transmission. In simplest form, to improve the quality you may transmit a signal in several copies. This multiple copies may be transmitted in multiple time (repetition in time) or multiple space (antenna), or in case of space-time coding this multiple copies are transmitted both in multiple space and time based in specific way. Hopefully, one or few of this copies are in good quality so the receiver can decode the transmitted signal perfectly.

2. Temporal coding in wireless communication refers to coding only in time coordinate. This is the old kind of coding in wireless communication. Reed-Solomon and convolutional coding is a kind of temporal coding.

3. Actually the difference between 4QAM and QPSK is only in rotation of the signal constellation. QSPK signals are at +1, -1, +j, -j, whereas 4QAM signal are at $e^{j \pi /4}$, $-e^{j \pi /4}$, $j e^{j \pi /4}$, and $-j e^{j \pi /4}$, i.e. QPSK signals rotated by $\pi /4$. Rectangular QAM constellation are, in general, sub-optimal in the sense that they do not maximally space the constellation points for a given energy. However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (PAM) signals on quadrature carriers, and can be easily demodulated.

If you increase to higher order modulation scheme, you will have more bits per trasmission of a symbol. This is a good strategy to transmit higher order modulation schemes if SNR is high. But if SNR is low then transmitting higher order modulation may introduce higher bit errors.

May it helps.
best

M.N.Rindani

points: 2