Questions tagged [digital-communications]

Digital Communication is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel.

171 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
0
votes
0answers
89 views

State definition in Viterbi Algorithm?

An ISI channel of length 'L+1' $\mathbf{h}=[h_0 \space h_1 \space … \space h_L]$can always be modeled as a finite state machine(FSM) of memory 'L'. For a binary input $x\in\{+1,-1\}$,a state can be ...
0
votes
0answers
57 views

Parameter selection for log distance path loss model

I am currently referring to the following book MIMO-OFDM Wireless Communications with Matlab in which the log distance path loss model is given by the equation: $P_{LD}(d)[dB] = PL_F(d_0) + 10nlog(d/...
0
votes
0answers
48 views

Why can CPRI links not be wireless?

I have been studying about CRAN and the CPRI links (fronhaul links) and have observed that CPRI links are always either fiber cable or some electrical interface. Why is this needed? Is it related to ...
0
votes
0answers
94 views

“Time To Lock” in Bit Timing Synchronisation

In the context of bit timing synchronisation in digital communications, what is meant by the requirement that says the "Time to lock to a sampling point should be no more than X symbols"? There seems ...
0
votes
1answer
333 views

Important differences between BCJR and SOVA algorithms?

BCJR algorithm needs noise variance for Gamma (branch metrices) calculation. So I am wondering does SOVA (soft output Viterbi algorithm) needs noise variance?
0
votes
0answers
96 views

How to simulate two OFDM Users with low complexity FFT/IFFT?

have two User one of them sending over freq (0-B] and the other transmit over (B-2B]. Both of them are using OFDM and each one has Nc subcarriers. I wanted to simulate the received signal using Matlab....
0
votes
0answers
59 views

Are there any research value in visible light communication?

My advisor wants me to take the area of visible light communication as my MS project, but I don't know whether there are any research value in this area, it seems most of the tenichnical difficulties ...
0
votes
0answers
90 views

Best strategy for sending digital signal over ultrasound

I'm interested in sending digital data over ultrasound. My initial thought is that it should be first converted to BMC: And then phase shift encoded (PSK): I initially thought to use a Goertzel ...
0
votes
0answers
47 views

How does µlaw encoding work with 16-bit signals?

I am new to DSP, so I wan't to know a couple of things. How does µlaw encoding function on a log scale such that you can input 16-bit signals and get the 8-bit µlaw signal output, after compression, ...
0
votes
0answers
193 views

Line coding for a modulation order that is not power of 2

In case a symbol encodes a non-integer number of bits, how is done the bit-symbol pairing? For example, we have a 3-levels FSK with bit rate of 1Mbps and a sequence 01011001. What is the symbol ...
0
votes
0answers
694 views

How to encode a byte array to sound file and then convert back?

This question is moved from Stack Overflow. Sorry about this noob question, because I never work with matlab and signal processing before. Here is what I want to do: I have a fixed length of byte ...
0
votes
2answers
70 views

MU-MIMO Sensitivity to Line of Sight (LOS)

Why do researchers talk about MU-MIMO being "less sensitive to line of sight" / "LOS Okay"? For example in this video, time=[00:40,00:42] Similarly, "User separation based on spatial channel ...
0
votes
1answer
68 views

Modeling channel response as complex vs splitting I and Q

If I have a communications channel where a digital QAM signal is transmitted, I can either model the channel's impulse response as a complex $h(t)$, or as 2 separate impulse responses $p(t)$ and $q(t)$...
0
votes
3answers
129 views

BER Analysis of Dual hop Decode and Forward Relay

I want to perform fair BER analysis between Two-hop Decode and Forward relay communication (S-->R-->D) and Direct Transmission from S-->D. The links have Rayleigh fading. Now for fair analysis 1) ...
-1
votes
0answers
28 views

law for a random variable

Let: $Y=|X_1+X_2|^2$ with $X_1 \sim N(\mu_1,\sigma_1^2)$ and $X_2 \sim N(\mu_2,\sigma_2^2)$. $X_1,X_2$ are independent complex random variables. Consequently, $Y=Re(X_1+X_2)^2+Im(X_1+X_2)^2$ My ...
-1
votes
1answer
33 views

Spatial diversity: symbol error probability, upper bound

I am trying to understand the calculation upper bound that is given in book. Edit 1: I added 3,44 Can someone explain to me how to come from (5.5) to (5.7) ?
-1
votes
1answer
21 views

multi-user communication

For a multi-user communication, I do many signals $s_i(t)$ with $i \in \{1,...,N \}$, $N$ the user number. The bandwith for each $s_i(t)$ is the same. But when I do the Fourier transform of $s_i(t)$, ...
-1
votes
1answer
47 views

bandwidth for a chirp spread spectrum

For a PSK communication with a symbole time $T$, the bandwidth of the system is $B=\frac{1} {T}$. But for a chirp spread spectrum with the same symbol time $T$ and the bandwidth of the chirp is $...
-1
votes
1answer
57 views

Doppler compensation method for cdma

Do you know of effective and simple methods to compensate for Doppler due to movement for the CDMA protocol?
-1
votes
1answer
486 views

Digital signal and frequency analysis

I am generating a digital signal with software. I have defined the vector $$[0,1,1,1,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0] $$ and my sampling rate is 8 million per second. The frequency spectrum is ...
-1
votes
1answer
132 views

How to write cyclic codes?

I am studying cyclic codes. From what I understood of it, a cyclic code is a special kind of linear code with the property that any codeword cyclic shift is also a codeword. Generally, we start with ...