Performance Of Cooperative Communication Research Articles

Codeswitching: A Bilingual Toolkit for Opportunistic Speech Planning.

The ability to engage in fluent codeswitching is a hallmark of the flexibility and creativity of bilingual language use. Recent discoveries have changed the way we think about codeswitching and its implications for language processing and language control. One is that codeswitching is not haphazard, but subject to unique linguistic and cognitive constraints. Another is that not all bilinguals codeswitch, but those who do, exhibit usage patterns conforming to community-based norms. However, less is known about the cognitive processes that regulate and promote the likelihood of codeswitched speech. We review recent empirical studies and provide corpus evidence that highlight how codeswitching serves as an opportunistic strategy for optimizing performance in cooperative communication. From this perspective, codeswitching is part and parcel of a toolkit available to bilingual codeswitching speakers to assist in language production by allowing both languages to remain active and accessible, and therefore providing an alternative means to convey meaning, with implications for bilingual speech planning and language control more generally.

Cooperative communications with optimal wireless energy harvesting

In this paper, we analyze the performance of cooperative communications with radio frequency energy harvesting (EH). Different relay selection techniques are studied with optimal harvesting duration. The frame with duration T is decomposed in 3 slots. The duration of first slot is $${\alpha }T$$ , and it is dedicated for energy harvesting $$(0<\alpha <1)$$ . The duration of second and third slots is $$(1-\alpha )T/2$$ . The second and third slots are dedicated to source and relay transmission. When harvesting duration, $$\alpha $$ T, increases, the packet error probability (PEP) decreases since the harvested energy is large. However, the available time for transmission, $$(1-\alpha )T/2$$ , decreases. If harvesting duration is small, the PEP is high due to a low harvested energy. In this paper, we choose the value of harvesting duration to enhance the throughput. The proposed optimal harvesting duration allows up to 4 dB gain with respect to $$\alpha =1/3$$ , i.e., same duration used for EH and source transmission.

Incentive Mechanisms for Cooperative Wireless Networks with Adverse Selection and Moral Hazard

Cooperative communication is a promising technique to improve utilization of the wireless spectrum resource. However, due to the limited wireless network resource, the selfish relay nodes may be unwilling to offer their relay help without any extra incentive. In this work, we study a contract-based mechanism for incentivizing cooperative relay in the presence of the dual asymmetric information. By modelling multi-user cooperative relay as a labour market, a principal-agent model is proposed with the combination of relay power, basic wage and relay bonus in the continuous type scenario. And an optimization problem of multi-user relay incentive is formulated to achieve the twin objectives of ability-discrimination and effort-incentive. Numerical results show that the optimal contract design scheme is effective in improving the performance of cooperative communication.

Performance Analysis of Cooperative Communication in Decentralized Wireless Networks With Unsaturated Traffic

In this paper, we investigate the performance of cooperative communication in decentralized wireless networks under unsaturated traffic conditions with randomly positioned single-hop source-destination pairs and relays, where interference is the main performance-limiting factor. The traffic unsaturation and concurrent cooperative transmissions introduce a correlation between the interferer density and the packet retransmission probability, and a correlation of interference power in both space and time domains, which complicate the interference characterization. Based on queueing theory and stochastic geometry, the stationary interferer density is derived by solving a fixed-point equation, which is proved to have a unique solution. According to the relay selection scheme, we characterize the correlation of interference power in two consecutive time-slots by identifying the densities of source and relay retransmissions. Based on the interferer density and interference correlation, we derive the outage probability and average packet delay of the cooperative scheme, while taking into account the dynamic traffic arrivals, interference correlation, relay selection scheme, and spatial node distribution. The performance analysis is validated by extensive simulations. The analytical results provide useful insights on cooperative communication in large-scale networks.

Relay selection for maximizing the number of successive transmission in cooperative networks

Relay selection has an important effect on improving the performance of cooperative communication system. However, the frequent operation of relay selection can bring enormous control message overhead, and then decrease the performance of cooperative communication. To reduce the relay selection frequency, in this paper, we propose a relay selection scheme to choose the best relay considering successive packets transmission. In this scheme, through the parameters of data transmission rate, the length of data packet and the estimated channel state information, the best relay is selected to maximize the number of successive packets transmission while guaranteeing the given outage probability. It is proven by numerical results that the proposed relay selection scheme can support the successive packets transmission in cooperative wireless networks and the maximum number of successive packets transmission is affected by the different network parameters, i.e. packet length, data transmission rate, signal to noise ratio and Doppler frequency. Compared to previous relay selection schemes by simulation results, it is shown that the proposed relay selection scheme can improve the throughput performance efficiently.

A consumer synchronizer for T-DMB receiver based on cooperative communications in emergency alert systems

Currently, terrestrial digital multimedia broadcasting (T-DMB) systems offer an emergency alert service called automatic emergency alert service (AEAS) in emergency alert systems. The performance of T-DMB receiver for AEAS can be enhanced using cooperative communication techniques. This paper assumes the T-DMB receiver based on a cooperative communication model. Since synchronization is crucial in the performance of cooperative communications, a novel consumer synchronizer is proposed in this paper for the T-DMB receiver based on cooperative communications. The presented synchronizer includes the identification of the selected relays, which is especially required in the best-relay selection for cooperative communications. Furthermore, a channel estimation approach is suggested in the synchronizer, which is suitable for T-DMB receivers under high frequencyselectivity. The experimental results reveal that the proposed synchronizer further enhances the performance of T-DMB receiver based on cooperative communications in emergency alert systems.

Power Allocation in Cooperative Communication System Based on Stackelberg Game

Cooperative communication has great potential to improve the wireless channel capacity by exploiting the antennas on wireless devices for spatial diversity. The performance in cooperative communication depends on careful resource allocation such as relay selection and power control. In this paper, the network is expanded and more than one source is used. What is proposed is a distributed buyer/seller game theoretic framework over multiuser cooperative communication networks in order to stimulate cooperation and improve the system performance. A two-level Stackelberg game is employed to jointly consider the benefits of the source node and the relay nodes in which the source node is modeled as a buyer and the relay nodes are modeled as sellers, respectively. In this work we proposed coded method in which relays amplify and code Source data and send it to destination at the same time and then signal detection occur in destination, but in the codeless network relays send source data separately to destination. So, here coded and codeless networks are compared and contrasted. The stimulation results revealed that the proposed coded method performed better than the codeless ones; furthermore, the research shows that relays near the sources can play a significant role in increasing source node's utility, so every source would like to buy more power from these preferred relays. Also, the proposed algorithm enforces truthful power demands.

부분차등변조 방식을 이용한 협력통신 전송기법

Cooperative communication, which transmit signal via arbitrary number of relays, enhances the overall communication performance by providing virtual Multi-Input Multi-Output (MIMO) gain without imposing multiple antennal limitation in physical system. There are two representative relaying protocols, i.e., Amplify-and-Forward (AF) and Decode-and-Forward (DF), where we analyze the performance of cooperative communication by adopting DF relaying protocol applying partially differential modulation. The performance is based on symbol error rate (SER), and the effect of relay location on the performance is analyzed. We also compare the performance of the proposed scheme with the system which uses differential modulation scheme.

A game-theoretic response strategy for coordinator attack in wireless sensor networks.

The coordinator is a specific node that controls the whole network and has a significant impact on the performance in cooperative multihop ZigBee wireless sensor networks (ZWSNs). However, the malicious node attacks coordinator nodes in an effort to waste the resources and disrupt the operation of the network. Attacking leads to a failure of one round of communication between the source nodes and destination nodes. Coordinator selection is a technique that can considerably defend against attack and reduce the data delivery delay, and increase network performance of cooperative communications. In this paper, we propose an adaptive coordinator selection algorithm using game and fuzzy logic aiming at both minimizing the average number of hops and maximizing network lifetime. The proposed game model consists of two interrelated formulations: a stochastic game for dynamic defense and a best response policy using evolutionary game formulation for coordinator selection. The stable equilibrium best policy to response defense is obtained from this game model. It is shown that the proposed scheme can improve reliability and save energy during the network lifetime with respect to security.

Relay selection with outdated channel state information in cooperative communication systems

Relay selection has been considered as an effective method to improve the performance of cooperative communication. However, the channel state information (CSI) used in relay selection can be outdated, yielding severe performance degradation of cooperative communication systems. In this study, the authors investigate how to select relays under outdated CSI in an amplify-and-forward cooperative communication system to improve its outage performance. The authors adopt maximum a posteriori (MAP) estimation to predict the actual signal-to-noise ratio (SNR) of each relay during data transmission and propose a single-relay selection (SRS) strategy based on the MAP estimation (SRS-MAP). To reduce the computational complexity, we approximate the a posteriori probability density of SNR and obtain a closed form of the predicted SNR. Simulation shows that SRS-MAP outperforms the relay selection strategies given in the literature. In order to further improve the outage performance, a new multiple-relay selection (MRS) method for outdated CSI is proposed, and by applying it to existing SRS strategies the corresponding MRS strategies are obtained. The authors find that the MRS strategies perform much better than their corresponding SRS ones and the MRS method improves the outage performance of cooperative communication system more effectively under outdated CSI than under non-outdated CSI.

Performance of transmitter preprocessing aided cooperative relaying with fixed infrastructure relays

In this correspondence, we study the performance of cooperative communications with the aid of multi-user transmitter preprocessing (MUTP), both at the base station (BS) and multi-antenna enabled fixed infrastructure based decode and forward relay stations (RSs), for uplink (UL) and downlink (DL) transmissions where, multi-user interference (MUI) and inter-relay interference (IRI) are the domineering channel impairments. MUTP formulated under instantaneous, statistical and imperfect channel state information assumptions at the RSs and BS for UL and DL respectively is based on singular value decomposition and, further at the RSs for DL is based on minimum mean square error principle. Specifically, we investigate the performance of the considered system in the context of weak and dominant MUI at the RSs in UL and dominant IRI at the mobile stations in DL. Our simulation studies show that MUTP aided system achieves better bit error rate than multiuser detection based system.

Improved Network-Coded Cooperative Transmission with Low-Complexity Adaptation to Wireless Channels

The relay employs network coding to transmit the packets from the source nodes simultaneously, for increasing spectral efficiency in wireless environments. The cooperative transmission based on network coding usually works on decode-and-forward (DF) protocols. However, detection errors at the relay cause error propagation, which degrades the performance of cooperative communications. To overcome this problem, we model the error propagation effect of the DF-based system at the destination as the addition of virtual noise, and then design a low complexity detection method. We derive the achievable diversity gain to evaluate the proposed model and corresponding detection scheme. To extend the proposed model to network-coded systems, we first express the channel conditions between the sources and relay as a single equivalent channel gain. Then, we develop low complexity detection schemes for the network-coded systems. From the error propagation model, we propose a dual mode network coding technique, which exploits different network coding schemes adaptively according to channel qualities. Simulation results show that the proposed model and detection scheme effectively reduce the error propagation effects. Also, the proposed dual mode network coding has gains for all channel conditions and thus gives better BER performance than conventional methods.

Spare node cooperative method for IEEE 802.11 networks

Most of the existing cooperation methods select relay node(s) mainly based on the channel state information, but do not consider whether the selected relay nodes work or not. If the selected relays are invalidated, the performance of cooperative communication will deteriorate. To resolve the above problem, this paper investigates cooperative communication in IEEE 802.11 networks, and proposes a novel Spare Cooperative Method (SCM). SCM chooses a spare cooperation node to enhance the reliability of communication, and uses an enhanced handshaking mechanism to coordinate the access of source nodes and cooperation nodes to the wireless channel. The performance of SCM is comprehensively analyzed in terms of outage probability and saturated throughput. The analysis shows that SCM improves the performance of IEEE 802.11.

Distributed Relay Selection and Power Control for Multiuser Cooperative Communication Networks Using Stackelberg Game

The performance in cooperative communication depends on careful resource allocation such as relay selection and power control, but the traditional centralized resource allocation requires precise measurements of channel state information (CSI). In this paper, we propose a distributed game-theoretical framework over multiuser cooperative communication networks to achieve optimal relay selection and power allocation without knowledge of CSI. A two-level Stackelberg game is employed to jointly consider the benefits of the source node and the relay nodes in which the source node is modeled as a buyer and the relay nodes are modeled as sellers, respectively. The proposed approach not only helps the source find the relays at relatively better locations and buyrdquo an optimal amount of power from the relays, but also helps the competing relays maximize their own utilities by asking the optimal prices. The game is proved to converge to a unique optimal equilibrium. Moreover, the proposed resource allocation scheme with the distributed game can achieve comparable performance to that employing centralized schemes.