Dirty paper coding using sign-bit shaping and LDPC codes
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Citations
Improving the Performance of the Zero-Forcing Multiuser MISO Downlink Precoder Through User Grouping
A dirty paper coding scheme for the Multiple Input Multiple Output Broadcast Channel
A Robust Multi-Level Design for Dirty-Paper Coding
A Low Complexity User Grouping Based Multiuser MISO Downlink Precoder
Dirty Paper Coding for Gaussian Cognitive Z-Interference Channel: Performance Results
References
Nested Turbo Codes for the Costa Problem
Code Designs for MIMO Broadcast Channels
Multi-Level Dirty Paper Coding
Related Papers (5)
Frequently Asked Questions (18)
Q2. What have the authors stated for future works in "Dirty paper coding using sign-bit shaping and ldpc codes" ?
Optimizing the LDPC code using genetic algorithms and asymmetric density evolution [ 12 ] along with joint optimization of shaping code and LDPC code using EXIT charts [ 8 ] are topics for future work.
Q3. What is the SNR for Receiver 1?
The SNR for Receiver 1 is computed as 10 log10 ( PX1PX2+PN1) = 19.1791 dB. SinceDPC is done for User 2, the effective SNR at Receiver 2 is computed as 10 log10 ( PX2 PN2 ) = 19.4574 dB.
Q4. What is the coding strategy for dirty paper?
In a Gaussian dirty paper channel, the received symbolvector Y = [Y1 Y2 · · ·Yn] is modeled as Y = X + S + N,where X = [X1 X2 · · ·Xn] denotes the transmitted vector, S = [S1 S2 · · ·Sn] denotes the interfering vector assumed to be known non-causally at the transmitter and N denotes the additive Gaussian noise vector.
Q5. What is the sign-bit vector for i-th?
The bits that map to the i-th symbol are denoted zia2ia3i · · · ali; the sign-bit vector is denoted z = [z1 z2 · · · zs], and the authors define vectors aj = [aj1 aj2 · · · ajs] for 2 ≤ j ≤ l.
Q6. What is the snr of the proposed design?
Simulation results show that the proposed design performs 1.46dB away from the dirty paper capacity for a block length of n = 40000 at the rate of 3 bits/channel use.
Q7. What is the granular gain of the channel?
The granular gain G(Λ) = 22R/6Sx is computed from the simulations to be 1.282dB [4], where R = 3.5 is the rate before channel coding, and Sx is the transmit power (obtained through simulations).
Q8. What is the sign-bit vector for the i-th block?
Let m′′ = [z mk′+1 · · ·mk] be input to the systematic LDPC encoder to obtain the codeword E(m′′) = [m′′ pT ], where pT is the parity-bit vector for the T -th block.
Q9. What is the meaning of dirty paper coding?
The interfering vector S is used as an input in the encoding process and plays an important role to determine a suitable transmit vector X. A coding strategy for choosing X needs to overcome the imminent addition of S and protect the transmitted information from the addition of the noise N. Such coding strategies are called dirty paper coding (DPC) methods.
Q10. Why is the LDPC decoder shown in Fig.3?
Because of the one-codeword delay, parity bits of the T + 1-th block and message plus shaped bits of the T -th block form a valid LDPC codeword.
Q11. What is the mapping in Fig. 1?
1. The mapping in Fig. 1 is suited for signbit shaping, since a flip of the most significant bit results in a significant change in symbol value for all possible 4-bit inputs.
Q12. What is the noise variance per symbol?
The transmit power is assumed to be upper-bounded by 1nE[|X|2] ≤ PX per symbol, and the interference power is denoted 1nE[|S|2] = PS per symbol.
Q13. What is the capacity of the dirty paper channel?
In [1], Costa shows that the capacity of the dirty paper channel is 12 log ( 1 + PXPN ) i.e. known interference can be canceled perfectly at the transmitter.
Q14. What is the SNR for the receiver?
The total transmit power, power for User 1 and power for User 2 required for a bit error rate of 10−5 (at both receivers) are estimated from the simulation and denoted P , Px1 and PX2 , respectively.
Q15. What is the a priori probability of the distribution of M -PAM symbols?
At the receiver, the authors approximate pi usinga Gaussian distribution with variance PS assuming that the distribution of M -PAM symbols is approximately Gaussian.
Q16. What is the proposed scheme for superposition coding in a two-user Gaussian?
The authors use the proposed scheme for superposition coding in a two-user Gaussian broadcast channel Y1 = X + N1 and Y2 = X + N2 with PN1 > PN2 .
Q17. What is the average power of the symbol a?
The number of replications r is chosen so that the average power of AR is approximately equal to the total average power PX + PS , and the bit mapping of the symbol a + jM (a ∈ A, 1 ≤ j ≤ r) is the same as that for a.
Q18. What is the LLR of the sign bits after a delay?
The s = nlog2M LLRs of the sign bits after a delay on one time step, and then−s output LLRs of the de-interleaver are given as the input to the LDPC decoder.