7 research outputs found
Maximum likelihood detection for decode and forward cooperation with interference
In this paper, we obtain the maximum likelihood (ML) decision for a decode and forward (DF) cooperative system in Nakagami-m fading in the presence of co-channel interference at the relay as well as the destination. Through simulation results, we first show that conventional ML designed for interference free systems fails to combat the deleterious effect of interference. An optimum ML decision for combating interference is then derived for integer m. This receiver is shown to be superior to conventional ML through bit error rate (BER) performance simulations. Further, our results also indicate that optimum ML preserves relay diversity in the presence of interference
Physical Layer Network Coding for the Multiple Access Relay Channel
We consider the two user wireless Multiple Access Relay Channel (MARC), in
which nodes and want to transmit messages to a destination node
with the help of a relay node . For the MARC, Wang and Giannakis proposed a
Complex Field Network Coding (CFNC) scheme. As an alternative, we propose a
scheme based on Physical layer Network Coding (PNC), which has so far been
studied widely only in the context of two-way relaying. For the proposed PNC
scheme, transmission takes place in two phases: (i) Phase 1 during which
and simultaneously transmit and, and receive, (ii) Phase 2 during
which , and simultaneously transmit to . At the end of Phase 1,
decodes the messages of and of and during Phase 2
transmits where is many-to-one. Communication protocols in
which the relay node decodes are prone to loss of diversity order, due to error
propagation from the relay node. To counter this, we propose a novel decoder
which takes into account the possibility of an error event at , without
having any knowledge about the links from to and to . It is
shown that if certain parameters are chosen properly and if the map
satisfies a condition called exclusive law, the proposed decoder offers the
maximum diversity order of two. Also, it is shown that for a proper choice of
the parameters, the proposed decoder admits fast decoding, with the same
decoding complexity order as that of the CFNC scheme. Simulation results
indicate that the proposed PNC scheme performs better than the CFNC scheme.Comment: 10 pages, 5 figure
Physical Layer Network Coding for the K-user Multiple Access Relay Channel
A Physical layer Network Coding (PNC) scheme is proposed for the -user
wireless Multiple Access Relay Channel (MARC), in which source nodes
transmit their messages to the destination node with the help of a relay
node The proposed PNC scheme involves two transmission phases: (i) Phase 1
during which the source nodes transmit, the relay node and the destination node
receive and (ii) Phase 2 during which the source nodes and the relay node
transmit, and the destination node receives. At the end of Phase 1, the relay
node decodes the messages of the source nodes and during Phase 2 transmits a
many-to-one function of the decoded messages. Wireless networks in which the
relay node decodes, suffer from loss of diversity order if the decoder at the
destination is not chosen properly. A novel decoder is proposed for the PNC
scheme, which offers the maximum possible diversity order of for a proper
choice of certain parameters and the network coding map. Specifically, the
network coding map used at the relay is chosen to be a -dimensional Latin
Hypercube, in order to ensure the maximum diversity order of Also, it is
shown that the proposed decoder can be implemented by a fast decoding
algorithm. Simulation results presented for the 3-user MARC show that the
proposed scheme offers a large gain over the existing scheme for the -user
MARC.Comment: More Simulation results added, 12 pages, 10 figures. arXiv admin
note: substantial text overlap with arXiv:1210.049
JOINT NETWORK-CHANNEL CODING WITH C-MRC BASED DEMODULATE AND FORWARD PROTOCOL IN TWO-WAY RELAY CHANNELS
Sayısal aktarma tabanlı işbirlikli telsiz ağlarının sistem karmaşıklığını ve enerji sarfiyatını azaltmak için yapılan araştırma faaliyetleri rölenin aldığı işaretlerde kod çözme yerine kipleme çözme yaptığı kipleme çöz ve ilet tasarımını ortaya çıkarmıştır. Öte yandan işbirlikli en yüksek oranlı birleştirme (İEYOB), iletim verimini düşüren çevrimsel artıklık denetimi (ÇAD) kodlardan faydalanmaksızın sayısal aktarmada hata yayılımı ile mücadele etmede kullanılan yüksek performanslı düşük karmaşıklıklı önemli bir başka tekniktir. Bu çalışmada iki kullanıcının bir röle aracılığı ile veri alışverişi yaptığı iki yönlü röle kanalları için İEYOB tabanlı kipleme çöz ve ilet protokolünü önerilmektedir. İletim süresi, birinci ve ikinci fazların kullanıcıların kodlamasız veya konvolüsyonel kodlamalı verilerinin iletimine tahsis edildiği zamanda üç faza ayrılmıştır. Röle, demodülasyondan sonra bit düzeyinde XOR‟lanmış paketi üçüncü fazda kullanıcılara iletmektedir. Rayleigh sönümlemeli kanallardaki sayısal sonuçlar önerilen yaklaşımın tam çeşitleme seviyesi sağladığını göstermektedir. Research activities to reduce the system complexity and energy consumption of digital relaying based cooperative wireless networks have yielded the demodulate-forward scheme where the relay performs demodulation, instead of decoding, on the received signals. On the other hand, cooperative maximal ratio combining (C-MRC) is another high-performance low-complexity technique used to combat error propagation in digital relaying without exploiting CRC codes which decreases the transmission efficiency. In this study, we propose a C-MRC based demodulate and forward protocol for two-way relay channels where two users exchange information via a relay. The transmission is divided into three phases in time where the first and second phases are allocated to the transmissions of uncoded or convolutionally encoded data of the users. After demodulation, the relay broadcasts the bit-wise XOR-ed packet to the users in the third phase. The numerical results for Rayleigh fading show that the proposed approach provides full diversity gain
On the Diversity Order and Coding Gain of Multi-Source Multi-Relay Cooperative Wireless Networks with Binary Network Coding
In this paper, a multi-source multi-relay cooperative wireless network with
binary modulation and binary network coding is studied. The system model
encompasses: i) a demodulate-and-forward protocol at the relays, where the
received packets are forwarded regardless of their reliability; and ii) a
maximum-likelihood optimum demodulator at the destination, which accounts for
possible demodulations errors at the relays. An asymptotically-tight and
closed-form expression of the end-to-end error probability is derived, which
clearly showcases diversity order and coding gain of each source. Unlike other
papers available in the literature, the proposed framework has three main
distinguishable features: i) it is useful for general network topologies and
arbitrary binary encoding vectors; ii) it shows how network code and two-hop
forwarding protocol affect diversity order and coding gain; and ii) it accounts
for realistic fading channels and demodulation errors at the relays. The
framework provides three main conclusions: i) each source achieves a diversity
order equal to the separation vector of the network code; ii) the coding gain
of each source decreases with the number of mixed packets at the relays; and
iii) if the destination cannot take into account demodulation errors at the
relays, it loses approximately half of the diversity order.Comment: 35 pages, submitted as a Journal Pape