1,013 research outputs found

    Communicating over Filter-and-Forward Relay Networks with Channel Output Feedback

    Full text link
    Relay networks aid in increasing the rate of communication from source to destination. However, the capacity of even a three-terminal relay channel is an open problem. In this work, we propose a new lower bound for the capacity of the three-terminal relay channel with destination-to-source feedback in the presence of correlated noise. Our lower bound improves on the existing bounds in the literature. We then extend our lower bound to general relay network configurations using an arbitrary number of filter-and-forward relay nodes. Such network configurations are common in many multi-hop communication systems where the intermediate nodes can only perform minimal processing due to limited computational power. Simulation results show that significant improvements in the achievable rate can be obtained through our approach. We next derive a coding strategy (optimized using post processed signal-to-noise ratio as a criterion) for the three-terminal relay channel with noisy channel output feedback for two transmissions. This coding scheme can be used in conjunction with open-loop codes for applications like automatic repeat request (ARQ) or hybrid-ARQ.Comment: 15 pages, 8 figures, to appear in IEEE Transactions on Signal Processin

    Outage Probability of Dual-Hop Multiple Antenna AF Relaying Systems with Interference

    Full text link
    This paper presents an analytical investigation on the outage performance of dual-hop multiple antenna amplify-and-forward relaying systems in the presence of interference. For both the fixed-gain and variable-gain relaying schemes, exact analytical expressions for the outage probability of the systems are derived. Moreover, simple outage probability approximations at the high signal to noise ratio regime are provided, and the diversity order achieved by the systems are characterized. Our results suggest that variable-gain relaying systems always outperform the corresponding fixed-gain relaying systems. In addition, the fixed-gain relaying schemes only achieve diversity order of one, while the achievable diversity order of the variable-gain relaying scheme depends on the location of the multiple antennas.Comment: Accepted to appear in IEEE Transactions on Communication

    Cooperative Lattice Coding and Decoding

    Full text link
    A novel lattice coding framework is proposed for outage-limited cooperative channels. This framework provides practical implementations for the optimal cooperation protocols proposed by Azarian et al. In particular, for the relay channel we implement a variant of the dynamic decode and forward protocol, which uses orthogonal constellations to reduce the channel seen by the destination to a single-input single-output time-selective one, while inheriting the same diversity-multiplexing tradeoff. This simplification allows for building the receiver using traditional belief propagation or tree search architectures. Our framework also generalizes the coding scheme of Yang and Belfiore in the context of amplify and forward cooperation. For the cooperative multiple access channel, a tree coding approach, matched to the optimal linear cooperation protocol of Azarain et al, is developed. For this scenario, the MMSE-DFE Fano decoder is shown to enjoy an excellent tradeoff between performance and complexity. Finally, the utility of the proposed schemes is established via a comprehensive simulation study.Comment: 25 pages, 8 figure

    Near-Capacity Turbo Coded Soft-decision Aided DAPSK/Star-QAM for Amplify-and-Forward based Cooperative Communications

    No full text
    Multilevel Differential Amplitude and Phase-Shift Keying (DAPSK) schemes do not require any channel estimation, which results in low complexity. In this treatise we derive the soft-output probability formulas required for a soft-decision based demodulation of high-order DAPSK, in order to facilitate iterative detection by exchanging extrinsic information with an outer Turbo Code (TC). Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. Compared to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme, the 4-ring based TC assisted 64-ary DAPSK arrangement has a power-efficiency improvement of 2.3 dB at a bit error rate (BER) of 10-5 . Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. More specifically, when using a TC block length of 400 modulated symbols, the 64 DAPSK (4, 16) scheme is 7.56 dB away from its capacity curve, while it had a reduced gap as low as 2.25 dB, when using a longer TC block length of 40 000 modulated symbols. Finally, as a novel application example, the soft-decision M-DAPSK scheme was incorporated into an Amplify-and-Forward (AF) based cooperative communication system, which attains another 4.5 dB SNR improvement for a TC block length of 40 000 modulated symbols

    Energy Harvesting in Cooperative Communications

    Get PDF
    Ühiskommunikatsioon on vĂ”imalik meetod lahendamaks informatsiooni levimist juhtmeta vĂ”rgus mitmikteekonna korral. See vĂ”imaldab laiendada vĂ”rgu katvust ning pakkuda vĂ”imendust kasutades olemasolevat taristut. Praktikas tehakse seda kasutades sĂ”lmpunkte vahereleedena. Nii mitmese ligipÀÀsuga releede sĂŒsteem kui paralleelsete releede sĂŒsteem on vĂ”imalikud kandidaadid tulevastes juhtmeta ĂŒhisvĂ”rkudes nende ĂŒlekandekiiruse efektiivsuse ning parema energiatarbe tĂ”ttu.\n\r\n\rVĂ”imenda-ja-edasta (AF) ning dekodeeri-ja-edasta (DF) on peamised ĂŒhisreleede protokollid, mida kasutatakse ĂŒle releekanalite. Me uurime kĂ€esolevas magistritöös paralleelseid releesid AF ĂŒhiskommunikatsiooni vĂ”rkudes kasutades QPSK signaliseerimist ĂŒle Rayleigh’ kiirelt hajuva kanali koos valge aditiivse Gaussi mĂŒraga. Sihtkohas vastuvĂ”etud signaali detekteerimiseks kasutades vĂ”rgus olevaid tegevuseta kasutatakse maksimaalse suhte ĂŒhendamise (MRC) meetodit. MÔÔtes sihtkohast vastu vĂ”etud ĂŒhendsignaali sĂŒmbolite veasuhet (SER) arvutusliku simulatsiooni abil, uurime me suhet releede arvu ning kommunikatsiooni kvaliteedi vahel.\n\r\n\rSĂŒsteemi energeetiline efektiivsus mÀÀrab selle operatsioonilise jĂ€tkusuutlikkuse. Energiakogumise (EH) meetod on hĂ€davajalik tehnoloogia juhtmeta sĂŒsteemides, kus on piiratud ligipÀÀs usaldusvÀÀrsele elektritoitele ja laadimisvĂ”imalustele. KĂ€esolevas magistritöös uurime me mitmese ligipÀÀsuga releede sĂŒsteeme kasutades EHtehnoloogiat. Me eeldame, et lĂ€hte- ja releesĂ”lmedel pole ĂŒhendatud energiaallikat, kuid on taaslaetav energiatalletus. Seega, iga sĂ”lme kĂ€ivitatakse ligipÀÀsupunkti (AP) edastatud raadiosignaalidelt kogutud energiast ning iga sĂ”lm toimib salvesta-siis- koostööta (STC) reĆŸiimis. Me simuleerime arvutuslikult ĂŒhendusetaseme jĂ”udlust kasutades fĂŒĂŒsilise ĂŒhenduse vĂ”rgukodeerimist EHja DF protokolli olemasolul. KĂ€esolev magistritöö esitab erinevaid energiakogumise meetodeid (EH ja STC) ning nende katkemistĂ”enĂ€osusi. Esitatud skeemid saavutavad SER jĂ”udluse, mis lĂ€heneb pĂŒsiva toiteallikaga jĂ”udlusele ning laiendab oluliselt sĂŒsteemi energiapĂŒsivust, samas sĂ€ilitades pidevat lĂ€bilaskejĂ”udlust.Cooperative communications is a promising technique used to combat the multipath propagation in wireless networks. It can also extend the network coverage and provide the diversity gain by using the existing infrastructure. In practice, this is often achieved by using idle nodes in the network as relays. The multiple access relay system and parallel relay system are appealing candidates for emerging wireless cooperative networks due to bandwidth efficiency and improved power consumption.\n\r\n\rThe amplify and forward (AF) and decode and forwards (DF) protocols are basic cooperative relay protocols used over the relay channels. In this thesis, we study parallel relays in AF cooperative communication networks using QPSK signalling over the Rayleigh fast fading with additive Gaussian noise channels. The maximum ratio combining (MRC) method is employed to detect the received signals at the destination. By simulating the symbol error rate (SER) of the combined received signal at the destination, we study a trade-off between the number of relays and the quality of the communications. \n\r\n\rThe energy efficiency of a system determines its operational sustainability. Energy harvesting (EH) is a crucial technology for a variety of wireless systems that have limited access to a reliable electricity supply or recharging sources. In this thesis, the design of a multiple access relay system (MARS) using EH is considered. We assume that the sources and the relay have no embedded power supply but rechargeable energy storage devices. Thus, each node is powered by harvesting the energy from the RF signals broadcasted by an access point (AP), and it operates in store-then-cooperate (STC) mode. We simulate the link level performance by using the physical layer network coding in the presence of EH with DF protocol. The thesis presents energy harvesting schemes (EH and STC) and outage probability analysis. The schemes presented in this thesis achieve SER performance approaching that of a fixed power supply and contribute significantly to sustaining the energy in the system while maintaining a constant throughput
    • 

    corecore