Rate Adaptation for Incremental Redundancy Secure HARQ

International audienceThis paper studies secure communication based on incremental redundancy (INR) secure hybrid automatic retrans-mission request (HARQ) protocol over block-fading wiretap channels. The transmitter has no instantaneous channel state information (CSI) available from either main channel or the eavesdropper channel, hence the coding rates cannot be adapted to instantaneous channel conditions. We investigate the outage performance for two schemes of INR secure HARQ protocols: case 1) when there exists two reliable multi-bit feedback channels from both legitimate receiver and eavesdropper to the transmitter carrying a function of outdated CSI, case 2) when there is a multi-bit feedback channel only from legitimate receiver. In both cases, we demonstrate that using the information carried via multi-bit feedback channels, the transmitter can adapt the coding rates in order to achieve a better secrecy throughput using a smaller number of transmissions comparing to the ACK/NACK feedback channel model. For some parameters, our rate adaptation protocol achieves a strictly positive secrecy throughput whereas it is equal to zero for the protocol with ACK/NACK feedback. We show that for some set of parameters, the loss of secrecy throughput between case 1 and case 2 is very small compared to the gain provided by both protocols

Integration of Satellites in 5G through LEO Constellations

The standardization of 5G systems is entering in its critical phase, with 3GPP that will publish the PHY standard by June 2017. In order to meet the demanding 5G requirements both in terms of large throughput and global connectivity, Satellite Communications provide a valuable resource to extend and complement terrestrial networks. In this context, we consider a heterogeneous architecture in which a LEO mega-constellation satellite system provides backhaul connectivity to terrestrial 5G Relay Nodes, which create an on-ground 5G network. Since large delays and Doppler shifts related to satellite channels pose severe challenges to terrestrial-based systems, in this paper we assess their impact on the future 5G PHY and MAC layer procedures. In addition, solutions are proposed for Random Access, waveform numerology, and HARQ procedures.Comment: Submitted to IEEE Global Communications Conference (GLOBECOM) 201

The new enhancement of UMTS: HSDPA and HSUPA

During the last two decades, the world of the mobile communications grew a lot, as a consequence of the increasing necessity of people to communicate. Now, the mobile communications still need to improve for satisfies the user demands. The new enhancement of UMTS in concrete HSDPA and HSUPA is one of these improvements that the society needs. HSDPA and HSUPA which together are called HSPA, give to the users higher data rates in downlink and uplink. The higher data rates permit to the operators give more different types of services and at the same time with better quality. As a result, people can do several new applications with their mobile terminals like applications that before a computer and internet connection were required, now it is possible to do directly with the mobile terminal. This thesis consists in study these new technologies denominated HSDPA and HSUPA and thus know better the last tendencies in the mobile communications. Also it has a roughly idea about the future tendencies

Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites

Satellite Communication systems are a promising solution to extend and complement terrestrial networks in unserved or under-served areas. This aspect is reflected by recent commercial and standardisation endeavours. In particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G, Non-Terrestrial Networks aimed at deploying satellite systems either as a stand-alone solution or as an integration to terrestrial networks in mobile broadband and machine-type communication scenarios. However, typical satellite channel impairments, as large path losses, delays, and Doppler shifts, pose severe challenges to the realisation of a satellite-based NR network. In this paper, based on the architecture options currently being discussed in the standardisation fora, we discuss and assess the impact of the satellite channel characteristics on the physical and Medium Access Control layers, both in terms of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB) and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis shows that the main technical challenges are related to the PHY/MAC procedures, in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic Repeat reQuest (HARQ) and, depending on the considered service and architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201

Green Cellular Networks: A Survey, Some Research Issues and Challenges

Energy efficiency in cellular networks is a growing concern for cellular operators to not only maintain profitability, but also to reduce the overall environment effects. This emerging trend of achieving energy efficiency in cellular networks is motivating the standardization authorities and network operators to continuously explore future technologies in order to bring improvements in the entire network infrastructure. In this article, we present a brief survey of methods to improve the power efficiency of cellular networks, explore some research issues and challenges and suggest some techniques to enable an energy efficient or "green" cellular network. Since base stations consume a maximum portion of the total energy used in a cellular system, we will first provide a comprehensive survey on techniques to obtain energy savings in base stations. Next, we discuss how heterogeneous network deployment based on micro, pico and femto-cells can be used to achieve this goal. Since cognitive radio and cooperative relaying are undisputed future technologies in this regard, we propose a research vision to make these technologies more energy efficient. Lastly, we explore some broader perspectives in realizing a "green" cellular network technologyComment: 16 pages, 5 figures, 2 table

A New Adaptive Rate IR-HARQ Combining with AMC

In this paper, we analyze a new cross layer combining scheme of adaptive modulation and coding (AMC) at the physical layer and hybrid automatic repeat request (HARQ) protocol at the data link layer. Our purpose is to improve the performance of the communication system in terms of throughput and errors. We propose a new adaptive HARQ protocol based on the estimated mutual information in addition to signal to noise ratio as channel state information (CSI), which are unavailable at the receiver. Unlike the traditional protocols, the transmitter is aware of the transmission mode only, not the instantaneous CSI, which minimize the load on the feedback channel. The transmission is supposed to be done over block fading channel. Mathematical formulation is improved for the performance criterions, in terms of throughput of the new HARQ, average number of transmissions and the spectral efficiency of the AMC/HARQ. The comparison with the traditional variable rate HARQ shows that our new adaptive HARQ protocol provides an upper bound for the throughput. In addition, the simulation results show that, a small number of transmissions, is enough to reach the maximum spectral efficiency while maintaining the error probabilities under certain acceptable level