SC-FDM-IDMA Scheme Employing BCH Coding

International Journal of Electrical and Computer Engineering (IJECE)
Vol. 7, No. 2, April 2017, pp. 992~998
ISSN: 2088-8708, DOI: 10.11591/ijece.v7i2.pp992-998  992
Journal homepage: http://iaesjournal.com/online/index.php/IJECE
SC-FDM-IDMA Scheme Employing BCH Coding
Roopali Agarwal, Manoj K. Shukla
Electronics Engineering Department, H. B. T. I., Kanpur, India
Article Info ABSTRACT
Article history:
Received Jul 1, 2016
Revised Oct 7, 2016
Accepted Oct 20, 2016
In OFDM-IDMA scheme, intersymbol interference (ISI) is resolved by the
OFDM layer and multiple access interference (MAI) is suppressed by the
IDMA layer at low cost . However OFDM-IDMA scheme suffers high peak-
to-average power ratio (PAPR) problem. For removing high PAPR problem a
hybrid multiple access scheme SC-FDM-IDMA has been proposed. In this
paper, bit error rate (BER) performance comparison of SC-FDM-IDMA
scheme, OFDM-IDMA scheme and IDMA scheme have been duly
presented. Moreover, the BER performance of various subcarrier mapping
methods for SC-FDM-IDMA scheme as well as other results with variation
of different parameters have also been demonstrated. Finally simulation
result for BER performance improvement has been shown employing BCH
code. All the simulation results demonstrate the suitability of SC-FDM-
IDMA scheme for wireless communication under AWGN channel
environment.
Keyword:
BCD code
OFDMA
SC-FDMA
Copyright © 2017 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Manoj K. Shukla,
Electronics Engineering Department,
H. B. T. I.,
Kanpur, India.
Email: manojkrshukla@gmail.com
1. INTRODUCTION
In the literature, it has been reported by researchers that SC-FDMA-IDMA scheme may be used for
the “Long Term Evolution” (LTE) of radio transmissions from cellular phones to base stations i.e. for uplink
communication. OFDM-IDMA scheme may mostly be employed for downlink communication. This scheme
has shown its unsuitability for uplink communication due to high PAPR (Peak to Average Power Ratio).
High PAPR requires high resolution DAC and ADC as well as extremely linear transmitter circuitry because
any nonlinearity may cause inter-modulation distortion raising phase noise which may further result in inter-
carrier interference (ICI).
In this paper, the performance evaluation of SC-FDM-IDMA scheme has been presented employing
BCH codes. Section II provides concept of SC-FDM-IDMA while a glimpse of BCH codes has been
explained in section III. In section IV and V the simulation results and conclusion for this work have been
presented.
2. SC-FDM-IDMA SCHEME
As a special case of CDMA system, IDMA system relies on interleaving as the only means to
distinguish the signals from different users. The IDMA system adopts a very simple chip-by-chip iterative
multi-user detection (MUD) strategy for extracting user-specific signals from received composite signal. The
computational complexity of the MUD in IDMA systems is a linear function of the number of users. The
IDMA scheme significantly outperforms conventional CDMA scheme in the terms of spectral efficiency,
receiver complexity and the combination of coding gain and diversity gain [1], [2].

IJECE ISSN: 2088-8708 
SC-FDM-IDMA Scheme Employing BCH Coding (Roopali Agarwal)
993
In this paper, SC-FDMA scheme has been considered instead of OFDM scheme to combine with
IDMA technique as a solution for LTE uplink, known as SC-FDM-IDMA scheme. This hybrid multiple
access scheme inherits many attractive features of SC-FDMA and IDMA schemes. On the one hand, SC-
FDMA scheme has lower PAPR because of its inherent single carrier structure. On the other hand, IDMA
scheme has a simple and effective iterative MUD in addition to other merits including simple treatment of
inter-symbol interference, multiple access interference, and effective mitigation of cross-cell interference. In
the simulations, different subcarrier mapping for SC-FDM-IDMA systems, i.e., localized subcarrier mapping,
interleaved subcarrier mapping, have been duly iterated [3]. Numerical results show that SC-FDM-IDMA
scheme performs better than OFDM-IDMA scheme for unlinking. Moreover, the BER performance of SC-
FDM-IDMA scheme approaches OFDM-IDMA scheme.
In the presented system data„d‟ of user „k‟ with data length „m‟ is transmitted for each chip „j‟.
After forward error correction coding in coder „C‟ block data is duly interleaved before DFT and subcarrier
mapping operations. Further data is passed through IDFT block before its transfer to channel with AWGN
disturbances. On the receiver side, received combined data is reconverted to the compatible data suitable for
ESE Block [4]. Here, low complexity ESE algorithm is used for signal detection. This algorithm is derived
through Gaussian approximation based on the assumption that the interfering symbols are independent of
each other. This assumption is reasonable when the coded block is long enough due to user-specific
interleavers. Since ISI is only present in the first Lg samples of received sequence R(n), n = Lg, … ,N −1 ,
these Lg samples are removed before FFT operation. Further, on received combined data FFT operation if
performed [5-10].
Figure1. SC-FDM-IDMA System
After FFT operation
̅ ∑
where v=0,………….N-1
Then, it implements subcarrier de-mapping, yielding Xm where m is the data length for specific
user. After IDFT operation, producing r
( ) ∑ ̅̅̅̅
where v=0,………….M-1
c1
Subcarrier
Mapping
FFT
Subcarrier
De-Mapping
ESE
Пk
user-1 IDFTDFTП1
user-k IDFT
Subcarrier
MappingDFTПkc
User-1 DEC
П1
П1
-1
IDF
T
User-k DEC Пk
-1
c
y1
yk
noise(AWGN)

 ISSN: 2088-8708
IJECE Vol. 7, No. 2, April 2017 : 992 – 998
994
In the process of IDMA detection, we reformulate the algorithm for QPSK signalling as following.
r(j)=∑khkxk(j)+n(j)
r(j)=hkxk(j)+ζk(j)
( ) ( ) ( )
The received complex signal can be expressed by:
( ) ∑ ( ( ) ( )) ∑ ( ( ) ( )) ( )
Further real and imaginary parts of x are obtained in a similar manner with the help of further analysis.
Step I: ESTIMATION OF INTERFERENCE MEAN AND VARIANCE
( ) ∑ ( ( ) ( )) ∑ ( ( ) ( )) ( )
( ( )) ∑ ( ( ( ) ( ( )))
( ( )) ∑ ( ) ( ( )) ∑ ( ) ( ( ))
( ) ∑ ( ( ( )) ( ( )))
( (̅̅̅̅̅ ( )))
( ) ( ( )) ( ) ( ( )) ( )
( ( ))
Step II: LLR GENERATION & COMBINING
The output of elementary signal estimator block is as follows,
( ( ))
(̅̅̅ ( )) ( (̅̅̅ ( )))
( (̅̅̅ ( )))
where Ψ(j) is the covariance of imaginary and real parts of received signal for j chip. The estimates E(.) and
Var (.) denote the expectation and variance. The DEC carries out APP algorithm. The extrinsic LLRs will be
used in the ESE to update the interference mean and variance in the next iteration [11].
( ( ( )) (
( ( ))
)
( ( )) ( ( ( )))
3. BCH CODE
The BCH codes form a class of cyclic error-correcting codes that are constructed employing finite
fields. One of the key features of BCH codes is a precise control over the number of symbol errors
correctable by the code during its code designing process. In addition to it, BCH can easily be decoded using
an algebraic method known as syndrome decoding. BCH codes operate over finite fields or Galois fields.
BCH codes can be defined by two parameters that are: codeword length (n) and the number of errors to be
corrected, [12-14]. The BCH codes are a class of cycle codes whose generator polynomial is product of
distinct minimum polynomials corresponding to α,α2
,....α2t
, where α ε GF(2m
) is a root of the primitive

IJECE ISSN: 2088-8708 
995
polynomial g(x). An irreducible polynomial g(x) of degree m is said to be primitive if only if it divides
polynomial form of degree n, xn
+1 for no n less than 2m
-1. In fact, every binary primitive polynomial g(x) of
degree m is a factor of x 2m 1
+1.Let mi (x) be the minimal polynomial of αi
. Let
p(x) = p0 + p1x + p2x2
+ ......+ pn-1xn-1
(1)
be a code polynomial with coefficients from GF(2). If p(x) has α, α2
… α2t
as its roots, p(x) is divisible by the
minimal polynomials m1(x), m2(x)… m2t-1(x). The generator polynomial g(x) of the t-error correcting BCH of
length code words n = 2m
- 1 and rate codes k/n is the lowest degree polynomial over GF(2) [15-18]. Thus,
the generator polynomial of the code must be the least common multiple (LCM) of these minimal
polynomials: g(x) =LCM{m1(x),m2 (x),......,m2t (x) (2) In general, for any positive integer m≥3 and t <n / 2 ,
there is a binary BCH code with parameters of code words length n = 2m
- 1, number of parity check bits n-k
≤mt , and minimum distance d0=2t +1≤ dmin . The designed distance of the code is d0 = 2t + 1. The minimum
distance dmin could be larger than d0 [16]. Algorithm for designing BCH codes is:
1. Choose a primitive polynomial of degree m, and construct GF (2m
).
2. Find the minimal polynomial mi(x) of αi
for i = 1, 2… 2t.
3. Obtain g(x).
4. Determine k from n - k, which is the degree of g(x).
5. Find the minimum distance dmin≥2t+1.
First of all, performance of SC-FDM-IDMA scheme is evaluated by changing different parameters.
4. SIMULATION RESULT AND DISCUSSION
For simulation purpose, single cell environment has been scheduled with SC-FDM-IDMA scheme
implemented with one transmitter and one receiver architecture. The signalling scheme is opted to be QPSK.
a. ber performance of SC-FDM-IDMA (IFDMA) with different no. of iterations. In Figure 2, the
performance of SC-FDM-IDMA scheme has been observed in AWGN channel for 8 users. The
simulation results shown by using different number of iterations from iteration 1 to 10 and it can be seen
that system performance improves on increasing the number of iterations.
Figure 2. Values of BER at different no. of iterations vs. Eb/N0 in IFDMA
b. ber performance of SC-FDM-IDMA (IFDMA) scheme with different no. of users simulation result shows
that Values of Bit Error Rate increases on increasing value of no. of user
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
10
-5
10
-4
10
-3
10
-2
10
-1
Eb/No
BitErrorRate
BER values ofIFDMA for different no. ofiterations
IFDMA with n=8,it=1
IFDMA with n=8,it=3
IFDMA with n=8,it=5
IFDMA with n=8,it=10

 ISSN: 2088-8708
996
Figure 3. Values of BER at different no. of users vs. Eb/N0 in IFDMA
c. ber performance of SC-FDM-IDMA (IFDMA) scheme with different no. of iterations & blocks No. of
iterations used 1,3,7 No. of blocks 4,16 and Spreading Factor=2, If value of Iteration is changed from 1 to
3 then it is evident from obtained plot that a large change in values of Bit Error Rate is obtained. Now
value of BER is drastically reduced compared to earlier cases.
Figure 4. Values of BER at different no. of iterations and blocks vs. Eb/N0 in IFDMA
d. ber performance comparison of SC-FDM-IDMA with different subcarrier mapping schemes (LFDMA &
IFDMA) & ofdm-idma with & without bch code.The simulation which has been carried out shows the
comparison between Localized subcarrier mapping and Interleaved Subcarrier Mapping case of SC-FDM-
IDMA and OFDM-IDMA. Here value of spreading factor used is 2 for Interleaved Subcarrier Mapping.
These two Subcarrier mapping schemes defines the way in which subcarriers are assigned to message
signals. No. of users 8 No. of Blocks 5and No. of Iterations=5 .Values of BER in the case of OFDM-
IDMA is maximum in comparison to LFDMA and IFDMA case value of BER increases on changing the
1 2 3 4 5 6 7 8 9 10
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
Eb/No
BitErrorRate
BER values of IFDMA for different no. of users
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
10
-5
10
-4
10
-3
10
-2
10
-1
Eb/No
BitErrorRate
BER values of IFDMA for different no. of blocks and iterations
IFDMA with it=1,block=4

IJECE ISSN: 2088-8708 
997
subcarrier mapping scheme from localized subcarrier mapping scheme to interleave subcarrier mapping
scheme. Value of BER is reduces on applying BCH code in the case of OFDM-IDMA.Value of BER is
zero for all the values of Eb/N0 in the case of LFDMA & IFDMA on applying BCH code. It means that no
error bit is obtained on applying BCH code.This is evident from above table that value of bit error rate
reduces on increasing the values of Eb/N0. This trend is normally followed in all preceding plots as well.
Figure 5. BER performance comparison of SC-FDM-IDMA (LFDMA & IFDMA) & OFDM-IDMA with &
without BCH code
5. CONCLUSIONS
In this paper we have investigated SC-FDM-IDMA Scheme for LTE Uplink and further
improvement in performance is obtained with the help of using BCH code. This improvement in performance
is obtained in the terms of reduced Bit Error Rate. Reduced bit error rate is clearly shown in the Results and
Discussions section of this paper. The plus point of using BCH code is that a high improvement in
performance is obtained without much increase in complexity.
REFERENCES
[1] X. Xiong and Z. Luo, “SC-FDMA-IDMA: A Hybrid Multiple Access Scheme for LTE Uplink,” 7th International
Conference on Wireless Communications, Networking and Mobile Computing (WiCOM), 23-25 Sept., pp. 1-5,
2011.
[2] L. Ping, et al., “Interleave-Division Multiple-Access,” IEEE Transactions on Wireless Communications, vol. 4, pp.
938-947, 2006.
[3] F. Moazzami, “Succesive Co-Channel Interference Cancellation,” Indonesian Journal of Electrical Engineering
and Informatics (IJEEI), vol/issue: 3(1), 2015.
[4] M. K. Shukla, “Performance Evaluation of IDMA Scheme in Wireless Communication,” Ph. D. thesis, 2010.
[5] I. Frank, et al., “Multiple-Access Technology of Choice In 3GPP LTE,” Indonesian Journal of Electrical
Engineering and Informatics (IJEEI), vol/issue: 1(3), 2013.
[6] L. Ping, et al., “The OFDM-IDMA Approach to Wireless Communication Systems,” IEEE Wireless
Communications, pp. 18-24, 2007.
[7] H. G. Myung and D. J. Goodman, “Single carrier FDMA A New Air Interface for Long Term Evolution,” Wiley
Series on Wireless Communications and Mobile Computing.
[8] “SC-FDMA Single Carrier FDMA in LTE,” 915-2725-01 Rev A November 2009.
[9] J. G. Proakis, “Digital Communication,” Mcgraw Hill, New York, 1989.
[10] Basharat, A; Khokhar, I.A.; Murtaza, S; “CDMA versus IDMA for subscriber cell density,” International
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[11] K. Kusume, et al., “IDMA vs. CDMA: Detectors, Performance and Complexity,” IEEE Global
Telecommunications Conference, pp. 1-8, 2009.
[12] L. Ping, et al., “A unified approach to multi-user detection and space time coding with low complexity and nearly
optimal performance,” 40th
Allerton Conference, Allerton House, USA, pp. 170–179, 2002.
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
10
-5
10
-4
10
-3
10
-2
10
-1
Eb/No
BitErrorRate
Comparison of SC-FDMA-IDMA(LFDMA & IFDMA) & OFDM-IDMA with & without BCH code
OFDM-IDMA without BCH code
SC-FDMA-IDMA(IFDMA) without BCH code
SC-FDMA-IDMA(LFDMA) without BCH code
OFDM-IDMA with BCH code
SC-FDMA-IDMA(IFDMA) with BCH code
SC-FDMA-IDMA(LFDMA) with BCH code

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[13] X. Xiong, et al., “IDMA/CDMA: A Hybrid Multiple Access Scheme,” International Conference on MultiMedia and
Information Technology, MMIT, pp. 512-514, 2008.
[14] C. Ding, “Parameters of Several Classes of BCH Codes,” in IEEE Transactions on Information Theory, vol/issue:
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[15] Z. Luo and X. Xiong, “Analysis of the effect of carrier frequency offsets on the performance of SC-FDMA-IDMA
systems,” Consumer Electronics, Communications and Networks (CECNet), 2nd International Conference on, pp.
889 – 893, 2012.
[16] Y. Wang, et al., “Interleaved Concatenations of Polar Codes With BCH and Convolutional Codes,” in IEEE
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[17] M. Ambroze and M. Tomlinson, “Performance of BCH codes with (1 + x)s
error detection,” in Electronics Letters,
vol/issue: 50(1), pp. 32-34, 2014.
[18] http://en.wikipedia.org/wiki/BCH_code.
BIOGRAPHIES OF AUTHORS
Received the B.Tech degree in Electronics & Communication Engineering from MIT,
Moradabad and The M.Tech degree in Digital communication from Bundelkhand Institute of
Engineering and Technology in 2005 and 2010 respectively.She is currently working toward
the Ph.D degree at Harcourt Butler Technological Institute,Kanpur her research interest are
Multiple-Access Scheme in Wireless Communication systems.
Received Bachelor of Engineering in 1989 from Amravati University while Master Degree in
Power Electronics & ASIC Design from Motilal Nehru National Institute of Technology,
Allahabad, India in 2004. Honored with Doctorate from same institute in 2011 while
processing research work on Performance Evaluation of Interleave-Division Multiple-Access
Scheme in Wireless Communication.

SC-FDM-IDMA Scheme Employing BCH Coding

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