An improvement of time-varying interference mitigation techniques through collaborative reception schemes

In wireless communications, the cooperative communication (CC) technology\npromises performance gains compared to traditional Single-Input Single Output\n(SISO) techniques. Therefore, the CC technique is one of the nominees for 5G\nnetworks. In the Decode-and-Forward (DF) relaying scheme which is one of the CC\ntechniques, determination of the threshold value at the relay has a key role\nfor the system performance and power usage. In this paper, we propose\nprediction of the optimal threshold values for the best relay selection scheme\nin cooperative communications, based on Artificial Neural Networks (ANNs) for\nthe first time in literature. The average link qualities and number of relays\nhave been used as inputs in the prediction of optimal threshold values using\nArtificial Neural Networks (ANNs): Multi-Layer Perceptron (MLP) and Radial\nBasis Function (RBF) networks. The MLP network has better performance from the\nRBF network on the prediction of optimal threshold value when the same number\nof neurons is used at the hidden layer for both networks. Besides, the optimal\nthreshold values obtained using ANNs are verified by the optimal threshold\nvalues obtained numerically using the closed form expression derived for the\nsystem. The results show that the optimal threshold values obtained by ANNs on\nthe best relay selection scheme provide a minimum Bit-Error-Rate (BER) because\nof the reduction of the probability that error propagation may occur. Also, for\nthe same BER performance goal, prediction of optimal threshold values provides\n2dB less power usage, which is great gain in terms of green communicationBER\nperformance goal, prediction of optimal threshold values provides 2dB less\npower usage, which is great gain in terms of green communication.\n

This article outlines one way to address these problems by using the notion of cooperation between wireless nodes. In cooperative communications, multiple nodes in a wireless network work together to form a virtual antenna array. Using cooperation, it is possible to exploit the spatial diversity of the traditional MIMO techniques without each node necessarily having multiple antennas. Multihop networks use some form of cooperation by enabling intermediate nodes to forward the message from source to destination. However, cooperative communication techniques described in this article are fundamentally different in that the relaying nodes can forward the information fully or in part. Also the destination receives multiple versions of the message from the source, and one or more relays and combines these to obtain a more reliable estimate of the transmitted signal as well as higher data rates. The main advantages of cooperative communications are presented.

<p>Constant evolution requirements of Wi-Fi and cellular standards to meet the demands of better power efficiency, longer range and higher throughput of wireless networks has drawn attention to multiple antenna transmitters and receivers, i.e., multi-input multi-output(MIMO) systems. This research falls in the larger context of distributed MIMO, or DMIMO systems, wherein groups of cooperating transceivers organize themselves into virtual antenna arrays which can, in principle, emulate any MIMO technique that a centralized array can support.</p><p>Beamforming and nullforming are techniques that can be employed by centralized or distributed antenna array, and can be building blocks for MIMO communication systems; these impart directionality to the array and can help cater to the demands of today's wireless networks. In beamforming, a set of distributed transmitters in a wireless network cooperatively transmit a common message signal in such a way that their individual transmissions add up to a desired SNR level at the set of designated receivers while in nullforming, cooperative transmission ensures that the individual transmissions cancel each other at the set of designated receivers. The key bottleneck in the practical realization of DMIMO is synchronization. Distributed nullforming specifically poses challenges that call for special attention. Here, we develop a set of scalable algorithms for beamforming and nullforming using distributed transmitters by forming a virtual antenna array and overcome the involved challenges in a purely distributed fashion.</p><p>Under a per-antenna power constraint and assuming equal-gain channels, an ideal N-antenna beamformer provides an N squared-fold coherent power gain on target. Ideal nullforming on the other hand results in zero power on the target. These properties motivate applications in cooperative jamming or communications, where the goal is to maximize the net transmitted power using multiple transmitters while simultaneously protecting a designated receiver. For example, in a cognitive radio system where the transmit array is a secondary user of licensed spectrum which seeks to communicate with a set of secondary receivers (beam targets) without causing any interference at primary receivers (null targets). Another possible application is a cellular network where adjacent Base Stations form a transmit array and coordinate their transmissions to avoid cochannel interference. Recent algorithms on wireless security critically rely on nodes blanketing a landscape with full power jamming signals while protecting a cooperating receiver through nullforming. So a third application can be electronic warfare where a transmit array broadcasts strong jamming signals that disable an enemy's communication infrastructure while protecting friendly stations (null targets) from interference due to the jamming signal. The joint beam and nullforming specifically can be more generally thought of as a fundamental building block for increased spatial spectrum reuse and toward achieving the full spatial multiplexing gains available from MIMO techniques with distributed antenna arrays.</p>

A new cooperative communication algorithm for improving connectivity in the event of network failure in VANETs

In order to cope with the degradation of communication quality due to fading of wireless signals when transmitted over long distances, cooperative communication techniques are often applied to long-distance wireless communications due to their relay cooperative forwarding characteristics. A reasonable relay assignment scheme can significantly improve the network throughput. In order to solve the problem of irrational relay resource assignment in the existing relay assignment under the multi-node cooperative communication network, this paper proposes a relay assignment method that balances the communication quality (BQRA). Firstly, a multi-node cooperative communication system model is established, and a node pre-assignment set is established based on node distance. Then, with the goal of maximizing the overall network capacity, the proposed relay assignment method is used to allocate relay nodes for each source node. The effective performance of the proposed method is evaluated through simulation experiments. Simulation results show that the system channel capacity index is slightly better than several other methods. 15% increase in system channel capacity compared to the classical relay assignment method, LIRA.

Cooperative networking, by leveraging the broadcast nature of the wireless channel, significantly improves system performance and constitutes a promising technology for next-generation wireless networks. Although there is a large body of literature on cooperative communications, most of the work is limited to theoretical or simulation studies. To impact the next generation of wireless technologies and standards, it is essential to demonstrate that cooperative techniques indeed work in practice. This article describes two programmable cooperative communication testbeds built at Polytechnic Institute of NYU to achieve this goal. The testbeds are based on open-source platforms and enable implementation of cooperative networking protocols in both the physical and the medium access control layer. Extensive experiments carried out using the testbeds suggest not only that cooperative communication techniques can be integrated into current wireless technologies, but also that significant benefits of cooperation can be observed in terms of network throughput, delay, and video quality in real applications.

Cooperative communication is shown to be an efficient method of combating fading in wireless networks. By ”sharing” their antennas cooperating single-antenna nodes create a virtual multi-antenna system and therefore, benefit from spatial diversity. Network coding being a particular cooperative communication technique provides substantial gains in data rate, especially in networks with many sink nodes. By allowing intermediate nodes of a network to mix the incoming data streams, one can achieve the multicast capacity. Recently, Xiao and Skoglund showed that binary network coding (BNC) is not optimal for multi-user multi-relay networks in terms of diversity and proposed diversity network coding (DNC) scheme that outperforms BNC approach. Following this approach we examine potential diversity gains of using the DNC scheme for multi-source line networks. We show that the DNC technique outperforms both conventional time-orthogonal transmission and the BNC scheme. Further, the problem of optimal scheduling of the transmission is explored. We formulate the optimization problem and propose efficient solutions. Numerical results are presented to support theoretical findings.

이동통신 시스템은 재난경보 방송을 위해 CBS 기능이 정의되어 있으며, 이 CBS 기능의 신뢰성을 향상시키기 위하여 협력통신 기법이 제안되었다. 그러나 협력통신에 필수적인 릴레이가 재난경보 수신에 실패할 경우 재난경보 전송에 심각한 지연이 초래될 수 있다.본 논문에서는 이러한 단점을 극복하기 위하여 T-DMB 기능이 추가된 릴레이를 이용하는 협력통신 기법을 제안한다. 이론적인 해석과 모의실험 결과는 제안된 협력통신 방식이 신속한 재난경보 방송에 적합함을 보여준다. The CBS functionality is defined for emergency alert service in cellular systems. Previously, a cooperative communication technique was proposed for more reliable CBS functionality. However, the relays for cooperative communications may fail in receiving emergency message, which may cause a critical latency. Therefore, we propose a novel cooperative communication technology in this letter, which incudes additional T-DMB functionality in relays. Analytical and empirical evaluations confirm that the proposed method is very suitable for rapid emergency alert broadcast.

In a wireless communication system, a cooperative communication technique is a communication method for improving performance. In the conventional scheme, when a destination user is located in the cell boundary, one base station communicates with a destination user. At a same time, a destination user communicates with other base stations which cooperate with base station. If a distance between a base station and a destination user is far, the quality of communication is degraded by the effect of channel attenuation. Therefore, this paper proposes an enhanced cooperative transmission scheme using the orthogonal frequency multiplexing in the wireless communication system. The proposed scheme uses extra relays between a base station and a destination user. When the channel state of a destination user is bad, other base stations are used. In order to obtain better performance than the conventional scheme, the cooperative decode and forward (DF), and space time cyclic delay diversity (STCDD) and cyclic delay diversity (CDD) are applied in the extra relays. In simulation results, the proposed scheme has higher error and throughput performances than the conventional scheme for obtaining diversity gain when the used modulation scheme is increased. Also, the proposed scheme which uses cooperative DF has slightly better error and throughput performances than the proposed scheme which uses cooperative STCDD and CDD due to less error propagations and resultant higher diversity gain.

Wireless sensor network is the network of tiny size of sensor nodes. These sensor nodes have sensing capability and transmit the sensed information to sink node. If the energy of sensor nodes is not utilised properly, it results in performance degradation of the network. Sleep scheduling approach and cooperative communication techniques can be employed to enhance the network performance. Cooperative communication follows the relay-based transmission. The nodes turn its radio sleep and awake in sleep scheduling approaches. This paper considers the merits of both techniques and proposes the sleep scheduling-based cooperative data transmission approach for WSN. In this approach, optimal number of virtual cluster heads are calculated by the sink node according to the number of nodes and area of interest. The real cluster head is decided based on the distance and energy of the sensor nodes from the virtual cluster head. The node is paired with each other and follows the sleep scheduling approach. Further, the energy-efficient relay selection and data transmission according to cooperative technique improves the network performance. The simulation analysis shows that the proposed routing protocol outperforms the related existing routing protocols.

Energy efficiency and Quality of Service (QoS) have become major requirements in the research and commercial community to develop green communication technologies for cost-effective and seamless convergence of all services (e.g., data, 3D media, Haptics, etc.) over the Internet. In particular, efforts in wireless networks demonstrate that energy saving can be achieved through cooperative communication techniques such as multihop communications or cooperative relaying. Game-theoretic techniques are known to analyze interactions between collaborating entities in which each player can dynamically adopt a strategy that maximizes the number of bits successfully transmitted per unit of energy consumed, contributing to the overall optimization of the network in a distributed fashion. As for the core networks, recent findings claimed that resource over-provisioning is promising since it allows for dynamically booking more resources in advance, and multiple service requests can be admitted in a network without incurring the traditional per-flow signaling, while guaranteeing differentiated QoS. Indeed, heavy control signaling load has recently raised unprecedented concerns due to the related undue processing overhead in terms of energy, CPU and memory consumption. While cooperative communication and resource over-provisioning have been researched for many years, the former focuses on wireless access and the latter on the wired core networks only. Therefore, this chapter investigates existing solutions in these fields and proposes new design approach and guidelines to integrate both access and core technologies in such a way as to provide a scalable and energy-efficient support for end-to-end QoS-enabled communication control. This is of paramount importance to ensure rapid development of attractive 3D media streaming in the current and future Internet.

The communication based on electromagnetic waves in nonconventional media (underground and underwater environment) is not desirable because of high path loss, large antenna size, and dynamic channel behavior of the media. Magnetic induction (MI) based communication is recently explored technique for such type of media, which exhibits several promising characteristics, such as constant channel behavior, less propagation delay, and stealth underwater operations. In every wireless sensor network (WSNs), energy is a main constraint. The overall energy consumption of the network can be significantly reduced by clustering technique. The efficacy of clustering technique can be further improved by the incorporation of cooperative communication and energy harvesting (EH) techniques. This paper proposes cooperative communication over Rayleigh fading channels, EH-enabled energy-efficient design, and EH-enabled tree-based waveguide topology in MI-based clustered nonconventional WSNs. Furthermore, we perform an analytical modeling to find the total energy consumption and throughput of the network in three different media (dry soil, wet soil, and sea water).

Radar interference into LTE base stations in the 3.5 GHz band

<div class="htmlview paragraph">This research work is concerned with experimental studies of the aerodynamic interference between passenger cars. Aerodynamic interference covers the two cases of vehicles in a convoy and in parallel passing (overtaking). Vehicles are assumed to be moving in open roads. Flow visualization technique is used to clarify the flow behavior, especially wake structure behind interfering passenger cars.</div> <div class="htmlview paragraph">This paper is a trial to further explain the aerodynamic characteristics, usually reported in the form of pressure distributions and drag forces, through visible observations. Visualization images of passenger cars in close interference are presented for the first time. Special attention is paid to the effect of Reynolds number on flow pattern especially in severe interference conditions. Results show that flow structure around interfering cars changes dramatically depending on the gap between the cars and Reynolds number. Interesting flow structures are captured and analyzed.</div>

The bit-stream generated by most source coding algorithms, for voice, audio and images, usually consists of bits of different significance and error sensitivity. By exploiting this property, in the design of a wireless communication system, it is possible to obtain significant advantages. First, the network capacity can be increased, with a smoother quality degradation under heavy traffic or severe interference conditions. Secondly, the application of source sensitivity matched FEC (forward error correction) protection schemes, leads to a higher robustness of source bits to channel impairments. We evaluate the usefulness of prioritized, variable-rate speech encoding schemes, for handling congestion over packet switching systems. The system performance is shown to be sensitive to the fraction of information placed in each priority and to the number of priorities. The applicability of source-sensitivity matched error protection schemes, for variable-rate speech transmission on a radio channel, is also investigated.