M. Elfituri

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (9)3.81 Total impact

  • M. Elfituri, M. Gheryani
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    ABSTRACT: This paper proposes a coding scheme for cooperative networks in the non-ideal case with system imperfections where the source and relays share their antennas to create a virtual transmit array to transmit towards their destination. We focus on the problem of coding for the relay channels. While the relays may use several forwarding strategies, including amplify-and-forward (AF) and decode-and-forward (DF), we focus on coded DF relaying. In particular, we consider the case when all the nodes estimate the channel state information in the transmission process. We derive upper bounded expressions for the bit error rate (BER) assuming M-ary phase shift keying (M-PSK) transmission. It is shown that the performance is degraded due to the presence of channel estimation error. However, the observations made in ideal scenarios still hold for the non-ideal case. Also our analytical results have shown that a performance close to perfect channel knowledge can be obtained when the number of pilot symbols kp increases. Also, with kp pilot symbols, the performance was shown to approach the perfect channel knowledge case at high pilot to noise ratio (PNR) (Eb/N0). Finally, at low PNR, the proposed scheme cannot provide significant performance improvements.
    Applied Electromagnetics (APACE), 2012 IEEE Asia-Pacific Conference on; 01/2012
  • M. Elfituri, M. Gheryani
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    ABSTRACT: This paper proposes a coherent distributed convolutional-based coding scheme with channel estimation based on pilot signals. Instead of transmitting the second frames on orthogonal sub-channels from the source and relay nodes to the destination, we used Alamouti scheme in the second frame. In particular, we assume that the channel state information is estimated at all nodes involved in the transmission process. Assuming decode-and-forward (DF) relaying, we derived upper bounds on the bit error rate (BER) for M-ary phase shift keying (M-PSK) transmission with channel estimation errors. Our analytical results have shown that a performance close to perfect channel knowledge can be obtained when the number of pilot symbols increases. At low pilot to noise ratio (PNR), the proposed scheme cannot provide significant performance improvements. Finally, the performance of the system degrades significantly. This diversity degradation is attributed to the channel estimation errors made at the relay and destination nodes.
    Applied Electromagnetics (APACE), 2012 IEEE Asia-Pacific Conference on; 01/2012
  • M. Elfituri, A. Ghrayeb, W. Hamouda
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    ABSTRACT: In this paper, we consider antenna/relay selection for coded cooperative networks in an effort to improve their end-to-end performance by improving the detection reliability at the relay nodes. Considering amplify-and-forward (AF) relaying, we analyze a previously proposed distributed coded cooperation scheme in conjunction with antenna/relay selection. Specifically, we derive upper bounded expressions for the bit error rate assuming M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order of the system is maintained for the entire range of symbol error rate of interest, unlike the case without antenna/relay selection. Several numerical and simulation results are presented to demonstrate the efficacy of the proposed scheme.
    IEEE Transactions on Communications 10/2009; · 1.75 Impact Factor
  • M. Elfituri, W. Hamouda, A. Ghrayeb
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    ABSTRACT: In this paper, we consider a coded cooperation diversity scheme that is suitable for L -relay channels that operate in the decode-forward mode. The proposed scheme is based on convolutional coding, where each codeword of the source node is partitioned into two frames that are transmitted in two phases. In the first phase, the first frame is broadcast from the source to the relays and destination. In the second phase, the second frame is transmitted on orthogonal subchannels from the source and relay nodes to the destination. Each relay is assumed to be equipped with a cyclic redundancy check (CRC) code for error detection. Only these relays (whose CRCs check) transmit in the second phase. Otherwise, they keep silent. At the destination, the received replicas (of the second frame) are combined using maximal ratio combining. The entire codeword, which comprises the two frames, is decoded via the Viterbi algorithm. We analyze the proposed scheme in terms of its probability of bit error and outage probability. Explicit upper bounds are obtained, assuming M -ary phase-shift keying transmission. Our analytical results show that the full diversity order is achieved, provided that the source-relay link is more reliable than the other links. Otherwise, the diversity degrades. However, in both cases, it is shown that it is possible to achieve substantial performance improvements over noncooperative coded systems. Several numerical and simulation results are presented to demonstrate the efficacy of the proposed scheme.
    IEEE Transactions on Vehicular Technology 03/2009; · 2.06 Impact Factor
  • M. Elfituri, W. Hamouda, A. Ghrayeb
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    ABSTRACT: We introduce coded cooperation diversity using relay nodes in the decode-and-forward (DF) mode, in which the codewords of the source node are partitioned and transmitted through independent fading channels to both relay and destination nodes, to achieve remarkable gains over a noncooperative system. The main difference between the distributed and the noncooperative space-time coding is that the link between the source and the relay node is not error-free in the distributed case, as opposed to the noncooperative case. In this work, we take into account the errors in the source-relay link and derive upper bounded expression for the symbol error rate on DF relaying in the case of M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order is achieved provided that the source-relay link is more reliable than the other links. Otherwise, the diversity degrades. This is unlike the case when the relay nodes operating in the DF mode are based on symbol-by-symbol decoding and forwarding. We present several numerical examples to support our analytical expression.
    Communications, 2008. ICC '08. IEEE International Conference on; 06/2008
  • M. Elfituri, A. Ghrayeb, W. Hamouda
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    ABSTRACT: In this paper, we consider distributed coding for wireless cooperative networks with antenna/relay selection. The aim of this of work is to find ways to improve the reliability of the source-relay link in an effort to maintain the diversity order available in the system. To this end, we propose to use antenna selection at the relay node whereby the antenna with the best instantaneous received signal to noise ratio is selected. This assumes that the relay node is equipped with multiple antennas, but only one radio frequency (RF) chain is employed. The concept of antenna selection can be extended to relay selection. That is, among the available relay nodes, the one with the best source-relay link reliability is selected. Assuming decode-and-forward (DF) relaying, we analyze the antenna/relay selection in conjunction with a previously proposed distributed coded cooperation scheme based on convolutional codes. Specifically, we derive an upper bounded expression for the symbol error rate assuming M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order of the system is maintained for the entire range of bit error rate of interest, unlike the case without antenna selection. Several numerical and simulation results are presented to demonstrate the efficiency of the proposed scheme.
    Communications, 2008. ICC '08. IEEE International Conference on; 06/2008
  • M. Elfituri, W. Hamouda, A. Ghrayeb
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    ABSTRACT: In this paper, we consider a coded cooperation diversity scheme suitable for relay channels. The proposed scheme is based on convolutional coding, where each codeword of the source node is partitioned into two parts. The first part is transmitted from the source to the relays and destination. The second part is transmitted simultaneously from the source and relay nodes to the destination. All the relay nodes are assumed to be operating in the decode-and-forward (DF) mode. At the destination, the two replicas of the second sub-codeword are combined using maximum ratio combining (MRC). The entire codeword is decoded via the Viterbi algorithm. We analyze the proposed scheme for L-relay channels in terms of its probability of symbol error and outage probability. In that, explicit upper bounds are obtained assuming M-ray phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order is achieved provided that the source-relay link is more reliable than the other links. Otherwise, the diversity degrades. However, in both cases, it is shown that substantial performance improvements are possible to achieve over noncooperative coded systems. Several numerical and simulation results are presented to demonstrate the efficiency of the proposed scheme.
    Signal Processing and Information Technology, 2007 IEEE International Symposium on; 01/2008
  • M. Elfituri, W. Hamouda, A. Ghrayeb
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    ABSTRACT: In this paper, we investigate the performance of a coded cooperation diversity using relay nodes in the decode-and-forward (DF) mode, in which the codewords of the source node are partitioned and transmitted through independent fading channels to both the relay and destination nodes. The application of such a cooperative coding scheme is shown to offer remarkable gains over a noncooperative system. Unlike noncooperative space-time coding, in distributed cooperative coding, the link between the source and the relay node is not error-free. In this work, we take into account the errors in the source-relay link and derive the outage probability of DF relaying for binary phase shift keying (BPSK) transmission. Our analytical results show that the proposed scheme achieves full diversity. This is different from conventional relay systems where the relay nodes operating in the DF mode are based on symbol-by-symbol decoding and forwarding. Numerical results are shown to support our analytical expression.
    Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
  • M. Elfituri, W. Hamouda
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    ABSTRACT: Cooperative diversity provides reliable communications between nodes in a network through relay nodes. In this paper, we introduce a new transmission protocol for relay fading channels. We examine the performance of the proposed protocol using both the amplify-and-forward (AF) and decode-and-forward (DF) modes. Our results prove that using this protocol, one can achieve full spatial diversity at full rate. We also show that our protocol with M relays is equivalent to a delay diversity scheme with M+1 transmit antennas. At the receiver side, a maximum likelihood sequence detector is used to recover the transmitted symbols. Comparing our protocol with existing ones, we noted large performance degradations in all protocols when the relay is operating in the DF mode where detection errors exist. This is different from the AF mode, where diversity is always maintained and only a SNR loss is incurred (relative to the ideal case of error-free relay transmission). This, in turn, suggests that even with the large cost/complexity involved in the DF mode, the ensuing performance may be poor compared to the AF mode. Motivated by this fact, we obtain a bit-error rate upper bound for a multi-relay configuration where all relay nodes operate in the AF mode. At high signal-to-noise ratio (SNRs), this error bound is shown to be tight when compared to simulation results
    Signal Processing Systems Design and Implementation, 2006. SIPS '06. IEEE Workshop on; 11/2006

Publication Stats

43 Citations
3.81 Total Impact Points

Institutions

  • 2006–2009
    • Concordia University Montreal
      • Department of Electrical and Computer Engineering
      Montréal, Quebec, Canada