Marcos D. Katz

Cooperation in Wireless Networks: Principles and Applications

Cooperation in Wireless Networks: Principles and Applications covers the underlying principles of cooperative techniques as well as several applications demonstrating the use of such techniques in practical systems. The work is written in a collaborative manner by several authors from Asia, America, and Europe. Twenty chapters introduce and discuss in detail the main cooperative strategies for the whole communication protocol stack from the application layer down to the physical layer. Furthermore power saving strategies, security, hardware realization, and user scenarios for cooperative communication systems are introduced and discussed. The book also summarizes the strength of cooperation for upcoming generation of wireless communication systems, clearly motivating the use of cooperative techniques and pointing out that cooperation will become one of the key technologies enabling 4G and beyond. This book puts into one volume a comprehensive and technically rich view of the wireless communications scene from a cooperation point of view.

Cellular Controlled Short-Range Communication for Cooperative P2P Networking

This article advocates a novel communication architecture and associated collaborative framework for future wireless communication systems. In contrast to the dominating cellular architecture and the upcoming peer-to-peer architecture, the new approach envisions a cellular controlled short-range communication network among cooperating mobile and wireless devices. The role of the mobile device will change, from being an agnostic entity in respect to the surrounding world to a cognitive device. This cognitive device is capable of being aware of the neighboring devices as well as on the possibility to establish cooperation with them. The novel architecture together with several possible cooperative strategies will bring clear benefits for the network and service providers, mobile device manufacturers and also end users.

Novel concepts for device-to-device communication using network coding

Device-to-device communication is currently a hot research topic within 3GPP. Even though D2D communication has been part of previous ad hoc, meshed and sensor networks proposals, the main contribution by 3GPP is that the direct communication among two devices is carried out over a dynamically assigned, licensed spectrum; thus, it is under full control of the cellular network. D2D communication creates a market potential for new services, new approaches to efficient spectrum use, and security concepts. This is especially true if D2D communication is extended to larger communication groups organized in meshed clusters. In this article, we discuss the potential and shortcomings of D2D communication as proposed today, advocating for the use of network coding as an enabling technology for enhanced security and communication efficiency using the PlayNCool and CORE protocols as key examples to deliver smarter D2D systems.

Optical wireless communications within fourth-generation wireless systems[Invited]

Feature Issue on Optical Wireless Communications (OWC) It is commonly agreed that the next generation of wireless communication systems, usually referred to as fourth-generation (4G) systems, will not be based on a single access technique but will encompass a number of different complementary access technologies. We outline some of the radio frequency (RF) standards that will be used and assess where optical wireless (OW) communications may play a role. Further, we outline some future research challenges and opportunities.

Combining space-time block coding with diversity antenna selection for improved downlink performance

A closed-loop method combining N-out-of-M antenna selection and space-time block coding from the selected antennas is proposed and studied in this paper. Performance is evaluated for WCDMA parameters in both frequency nonselective Rayleigh fading channels and in frequency selective (Vehicular A) channels. Operation in intra- and inter-cell dominant interference scenarios is considered. Numerical results show that the additional antenna selection procedure brings a supplementary uncoded BER performance improvement in the range of approximately 2-3.5 dB for flat-fading channels and 0.8-1.5 dB for frequency selective channels (@BER=12%). A suboptimum selection scheme requiring only a single bit for antenna selection is also presented. In addition, the impact on performance of errors in the feedback channel is investigated in this paper.

Lean and mean: network coding for commercial devices

With its ability to reduce the number of transmissions in lossy networks as well as its potential to simplify the design and required signaling of communication protocols, network coding has emerged as an attractive solution to harness the power of wireless and cooperative networks in order to provide higher throughput and lower energy expenditure. This article shows that network codings complexity is not an issue for current mobile devices even without hardware acceleration. We provide real-life measurements of energy savings gains of two design styles of network coding, namely, inter- and intra-session network coding using commercial platforms, including Open-Mesh routers and various mobile phones. We demonstrate that the energy per bit invested in coding/decoding operations can be several orders of magnitude smaller than that used for transmission/reception, while also maintaining processing speeds as high as several hundreds of Mb/s or even several Gb/s depending on the device and coding configuration used.

Cooperative and noncooperative spectrum sensing techniques using Welch’s periodogram in cognitive radios

Radio spectrum deployment is growing considerably. With this respect finding unutilized frequency channels for new applications has become much more challenging. The problem can be solved by letting unlicensed systems to dynamically use unexploited licensed bands. This kind of flexible spectrum usage requires telecommunication systems to be equipped by an ability to specify unoccupied parts of radio spectrum. One method to identify temporarily unused parts of radio spectrum is spectrum sensing. In this paper, we focus on spectrum sensing using Welchs periodogram. In particular, we generalize and apply the theoretical analysis of the energy detection to the Welchs periodogram. Furthermore, we extend our study to cooperative spectrum sensing. The results indicate that the cooperation between two radios provides the highest cooperation gain.

Two-dimensional code acquisition in time and angular domains

The extension of conventional delay-domain code acquisition to the angular domain is explored. The uncertainty region is partitioned into a number of delay and angular cells. In single-path channels where the interference is modeled as temporarily and spatially white, there exists an optimum number of angular cells minimizing the mean acquisition time. Mean acquisition times up to three times shorter can be attained with the two-dimensional approach. A rather similar behavior is in general found in Lth-order equal amplitude multipath channels, where paths are contiguous in the delay or angular domains. The strategy employed to search through the uncertainty region may have a considerable impact on acquisition performance. The results reveal that the search should proceed not in the direction of the multipath spread but in the other available domain. Proper selection of the search strategy can reduce the synchronization time by a factor of up to two. Two-dimensional code acquisition in scenarios with spatially nonuniform interference is also investigated. In general, the acquisition performance is degraded by the presence of nonuniform interference in the angular domain.

Energy-Efficient Cooperative Techniques for Multimedia Services over Future Wireless Networks

In this paper we develop and analyze energy- efficient cooperative techniques for multimedia streaming applications in wireless networks. The concept of combined cellular- SR network architecture is coupled here with different video coding schemes for the goal of achieving robust transmission over wireless channels and energy saving. The strategies are analyzed in different technology settings, showing promising power saving potentials in comparison to the state-of-the-art non-cooperative operation.

Adaptive spatial modulation for MIMO-OFDM

In this paper we propose and analyze an adaptive spatial modulation scheme for MIMO-OFDM systems which adaptively and optimally selects one of the following transmission modes: diversity, spatial multiplexing and a hybrid combination of these two modes. Two criterias are used for mode selection, namely, the minimum Euclidean distance and a simple threshold based stochastic method exploiting channel quality estimations. We consider practically implementable antenna configuration with four transmit antennas and two or four receive antennas. Simulation results show that considerable BER performance gains can be obtained by the adaptive spatial modulation system, as compared with systems based on fixed modulation schemes.