This paper addresses the performance analysis of an adaptive wireless link with one antenna transmitter and a multiple antenna maximum-ratio combining (MRC) receiver. Two main assumptions are used in this paper: (1) Rayleigh fading correlated channels (i.e., MRC branch correlation) and (2) imperfect (outdated) channel state information at the transmitter (CSIT) side. The main contribution of this work lies in the derivation of analytic expressions (in terms of a series expansion) of the statistics of correct packet reception conditional on the decisions made by the transmitter based on outdated CSIT. The novelty of this derivation is the joint modelling of spatially correlated branches, imperfect CSIT, and adaptive modulation based on threshold-trigger decision. Contrary to common belief, the results presented here suggest that spatial correlation not always affects the performance of the MRC receiver: at low signal-to-noise ratio (SNR), correlation can improve performance rather than degrading it. In contrast, at high SNR, correlation is found to always degrade performance. At high SNR, correlation tends to worse the degrading effects of imperfect CSIT, particularly when the number of antennas increases. Imperfect CSIT causes errors in the assignment of MCSs, thus reducing throughput performance. These errors become more evident in the high SNR regime, particularly when the values of branch correlation and the number of antennas increase.
Abstract-Network diversity multiple access or NDMA is the family of algorithms with the highest potential throughput in the literature of signal-processing-assisted random access. NDMA uses the concept of protocol-induced retransmissions to create an adaptive source of physical (PHY) layer diversity. This adaptive diversity is used to resolve packet collisions (via signal separation) without the explicit need (or as a complement) of a multiple antenna receiver. This paper proposes a further improvement on the modelling of NDMA by considering the effects of imperfect channel and collision multiplicity estimation. In addition, this work considers channel correlation between consecutive retransmissions (i.e., temporal correlation). Conventionally, the analysis of NDMA assumes that any error in the collision multiplicity estimation translates into the loss of all contending packets. This is an optimistic assumption because even when the multiplicity has been correctly estimated, errors can still occur. On the other hand, it is also pessimistic because correct reception can also occur when the multiplicity has been incorrectly estimated. This paper presents a more detailed study of the performance of NDMA considering these more specific detection/reception cases.
The ARTEMIS/ECSEL project DEWI (?Dependable Embedded Wireless Infrastructure?) focusses on the area of wireless sensor / actuator networks and wireless com-munication. With its four industrial domains (Aero-nautics, Automotive, Rail, and Building) and 21 clearly industry-driven use cases / applications, DEWI will pro-vide and demonstrate key solutions for wireless seamless connectivity and interoperability in smart cities and infrastructures, by considering everyday physical environ-ments of citizens in buildings, cars, trains and aeroplanes. It will add clear cross-domain benefits in terms of re-usability of technological building bricks and architecture, processes and methods. DEWI currently is one of the largest funded European R&D projects, comprising 58 renowned industrial and research partners from 11 Euro-pean countries. ( AbstractThe ARTEMIS/ECSEL 1 project DEWI ("Dependable Embedded Wireless Infrastructure") focusses on the area of wireless sensor / actuator networks and wireless communication. With its four industrial domains (Aeronautics, Automotive, Rail, and Building) and 21 clearly industry-driven use cases / applications, DEWI will provide and demonstrate key solutions for wireless seamless connectivity and interoperability in smart cities and infrastructures, by considering everyday physical environments of citizens in buildings, cars, trains and aeroplanes. It will add clear cross-domain benefits in terms of reusability of technological building bricks and architecture, processes and methods. DEWI currently is one of the largest funded European R&D projects, comprising 58 renowned industrial and research partners from 11 European countries. (For further details see www.dewiproject.eu)
This paper presents a new approach for the analysis and characterization of the throughput region of wireless random access protocols enabled with multi-packet reception (MPR) capabilities. The derivation of a closed-form expression for the envelope of the throughput region under the assumption of an arbitrary number of terminals is an open issue in the literature. To partially fill this gap, a new method based on multi-objective optimization tools is herein presented. This innovative perspective allows us to identify the envelope of the throughput region as the Pareto frontier solution that results from maximizing simultaneously all individual terminal throughput functions. To simplify this problem, a modified MPR model is proposed that mimics the conditions of collision model protocols, but it also inserts new physical (PHY) layer features that allow concurrent transmission or MPR. The N-reception model is herein introduced, where collisions of up to N signals are assumed to be always correctly resolved from a population of J terminals, where N can be related to the number of antennas or degrees of freedom of the PHY-layer used at the receiver to resolve a collision. It is shown that by using this model and under the assumption of N = J − 1, the Pareto frontier expression can be obtained as a simple extension of the ALOHA solution. Unfortunately, for cases with N < J − 1, the structure of the resulting determinant matrix does not allow for a simple explicit solution. To overcome this issue, a symmetrical system is proposed, and the solution is obtained by the analysis of the roots of the resulting polynomial expression. Based on this result, an equivalent sub-optimal solution for the asymmetrical case is herein identified for systems where N < J − 1. An extension to more general reception models based on conditional reception probabilities is also presented using the proposed equivalence between the symmetric and asymmetric solutions. The results intend to shed light on the performance of MPR systems in general, and in particular to advance towards the solution of the conjecture of the equivalence between throughput and stability regions in random access. Technologies 2018, 6, 117 2 of 15Multi-packet reception (MPR) is one of the most attractive solutions to improve the performance of future wireless random access networks. Contrary to the conventional collision model used in ALOHA, in MPR systems, concurrent transmissions can be simultaneously decoded. This not only implies a boost of capacity, but also the opening of new interactions between the physical (PHY) and medium access control (MAC) layers. Cross-layer design is thus central to the study of MPR wireless random access protocols [5]. Pioneering works in this area were the studies of the effects of power capture on the stability and capacity of random access (see [6,7]). The first work that can be considered as a modern MPR random access protocol was presented in [8], where the authors proposed a stochastic MPR matrix that captures the reception capabil...
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