Flip Left-to-Right Approach Based Inverse Tree Interleavers for Unconventional Integrated OFDM-IDMA and SCFDMA-IDMA Systems

Several interleavers have been proposed for conventional interleave division multiple access (CIDMA) systems which provides a mean to control burst errors and to reduce multi user and multiple access interferences. However, CIDMA alone is incapable of completely removing inter-symbol interference and inter-carrier interference problems even in presence of such interleaver. In this paper, a recently developed novel interleaver i.e. ‘flip left–right approach based inverse-tree interleaver’ (FLRITI) or simply ‘inverse tree interleaver’, has been explored for two unconventional integrated interleave division multiple access techniques i.e. single carrier frequency division multiple access cum interleave division multiple access (SCFDMA-IDMA) and orthogonal frequency division multiplexing based interleave division multiple access (OFDM-IDMA). The results and analysis reveal that this unconventional integration of CIDMA with SCFDMA and OFDM techniques in presence of FLRITI improves the overall system performance in terms of bit-error rate, memory footprint and computation complexity. Therefore, it validates the worthiness of FLRITI as a competent interleaver for the communication systems to be used even beyond fourth generation.

ƛ:

Level of repetition coder

K:

Total no. of users

k:

kth specific user

∏_k :

Interleaving pattern for kth user

d_k :

Input data sequence of kth user

\(l\) :

Length of data sequence

C_k :

Chip sequence for kth user

\(\widetilde{{x_{k} }}\) :

Interleaved sequence of kth user

\(X_{k}\) :

Sequence obtained after SCM and IFFT operations

\(F\) :

M × M DFT matrix

M:

Length of chip sequence and/or number of OFDM subcarriers

Ł:

Length of cyclic prefix

\({{\uptau }}_{\text{d}}\) :

Channel delay spread

\({{\uptau }}_{{{\text{e}}\left( { \hbox{max} } \right)}}\) :

Maximum timing-error

L:

Length of MAC

\(r\) :

Resultant output of MAC

\(r_{k}\) :

Received vector for kth user

N :

AWGN

\(\widetilde{H}_{k}\) :

M × M circular channel matrix

\(T_{k}\) :

M × M circular time-shift matrix

H:

Channel matrix

\(H_{k}\) :

Diagonalized channel matrix

\(\xi_{k}\) :

Noise plus interference component

\(e_{ESE }\) :

Output of ESE

\(e_{DEC }\) :

Output of DEC

\(\prod_{LR}^{ - 1}\) :

Inverse interleaving pattern of sequence flipped left-to-right

\(\prod\) :

Mother or reference interleaver

3GPP:

3rd Generation partnership project

APP:

Apriori probability

AWGN:

Additive white Gaussian noise

B4G:

Beyond 4th generation

BER:

Bit error rate

CBC:

Chip-by-chip detection

CDMA:

Code-division multiple access

CIDMA:

Conventional interleave division multiple access

CPI:

Cyclic prefix insertion

CPR:

Cyclic prefix removal

DEC:

Decoder

DFT:

Discrete Fourier transforms

DSCM:

De-mapping of subcarriers

ESE:

Elementary signal estimator

FEC:

Forward error correction

FFT:

Fast Fourier transforms

FLRITI:

Flip left-to-right approach based inverse tree interleavers

ICI:

Intercarrier interference

IDFT:

Inverse discrete Fourier transform

IFFT:

Inverse fast Fourier transform

IDMA:

Interleave division multiple access

IIDMA:

Integrated interleave division multiple access

ISI:

Intersymbol interference

ITBI:

Inverse tree based interleaver

ITI:

Inverse tree interleaver

LLR:

Logliklihood ratio

LTE:

Long-term evolution

MAC:

Multiple access channel

MAI:

Multiple access interference

MUI:

Multiuser interference

OFDM:

Orthogonal frequency division multiplexing

OFDM-IDMA:

Orthogonal frequency division multiplexing based interleave division multiple access

PAPR:

Peak-to-average power ratio

PN:

Pseudo noise

POC:

Probability of occurrence

RI:

Random interleavers

SCFDMA-IDMA:

Single carrier frequency division multiple access based interleave division multiple access

SCM:

Subcarrier mapping

TBI:

Tree based interleaver

TI:

Tree interleaver

Authors and Affiliations

1. Department of Electronics and Communication Engineering, Amity School of Engineering and Technology, Amity University, Noida, 201303, India

   Manish Yadav

2. Department of Electronics and Communication Engineering, Amity Institute of Advanced Research and Studies, Amity University, Noida, 201303, India

   Vinod Shokeen

3. Department of Electronics Engineering, Madhav Institute of Technology and Science (MITS), Gwalior, M.P., 474005, India

   Pramod Kumar Singhal

Corresponding author

Correspondence to Manish Yadav.

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