Yazar "Yilmaz, Ali Ozgur" seçeneğine göre listele

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    Differential Network Coding in Wireless Networks
    (IEEE, 2009) Ozdemir, Ozgur; Yilmaz, Ali Ozgur
    In this paper a three-terminal communication scenario where two users exchange information by employing differential binary modulation and network coding via a relay is considered. The transmission is divided into three slots in time where the first and second slots are allocated to the transmission of differential encoded data of the users. After demodulation, the relay broadcasts the bit-wise XOR-ed and differential encoded pocket to the users in the third slot. The optimum detector and a simplified decision algorithm are derived based on the maximum likelihood rule. The numerical results for Rayleigh fading show that both of the proposed algorithms provide full diversity order. The simulations also demonstrate that the proposed differential network coded transmission not only offers a sum-rate gain of up to 4/3 compared to classical bi-directional relaying with four communication slots but also provides better BER performance as the signal to noise ratio increases.
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    Joint Network-Channel Coding with Repeat Accumulate Codes for Wireless Relay Networks
    (IEEE, 2009) Ozdemir, Ozgur; Yilmaz, Ali Ozgur
    This paper presents two different repetition based joint network channel coding schemes for a three-terminal communication system where two-users want to exchange information via a relay. The transmission is divided into three slots in time where the first and second slots are allocated to the RA (Repeat Accumulate) encoded data of the users. In the first scheme we propose, the relay decodes the received signals and transmits a bit-wise XOR-ed packet using RA coding in the third slot. In the second scheme, the relay demodulates the received signals without decoding and estimates the RA code symbols of each user, then transmits the XOR-ed symbol packet. Unlike the schemes in the literature, the introduced decoding algorithms do not require the relay to decode entire codeword without errors and remove the need for channel feedback without sacrificing the diversity order. The maximum-likelihood decision rule for transmission without channel coding is also derived.