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Bit and power loading schemes for a single-user multiple-input multiple-output channel using a minimum mean-square error receiver are proposed. Such schemes are derived without the benefit of instantaneous channel state information (CSI) at the transmitter, on the basis of only statistical CSI. They exploit the relationships between the average bit error probability at the receiver and the power allocation...
Hybrid automatic repeat request (HARQ) is a well-known technique for improving system throughput and link performance of wireless communication systems, including cooperative communication systems. In this paper, we exploit the limited feedback applied to the two-source turbo coded cooperation scheme to define a particular cooperative HARQ protocol, called two-level HARQ, where the decision on retransmission...
Characterization of cooperative communications, for the ‘everyday’ body-area-network (BAN) wireless channel is presented. Performance analysis is given based on many hours of empirical data measured on five adult subjects. A decode-and-forward protocol is chosen for the cooperative BAN. Three typical locations for on-body relays/hubs are considered, along with seven typical on-body sensor locations...
The exponential increase in data traffic demand has focused attention on two layer network deployment strategies where low-power pico base-stations are placed within a macro cell coverage area targeting specific capacity demands. Two aspects of such a network are different from a macro-only deployment and are studied in this paper — (i) the choice of antenna geometry and polarization for a non-sectorized...
In Release 8 (R8) LTE a 4 antenna codebook was designed primarily with a uniform linear array (ULA) in mind. The consequence is that when using an array at the base other than a ULA (for example a uniform circular array (UCA)) the performance with codebook feedback will be degraded relative to a codebook optimized for that array structure. In this paper methods for improving the performance of LTE...
In this paper, we define a multi-access interference (MAI) cost that can assess the extra interference, inherent to relaying use and perceived by the whole cellular network. This MAI cost shadows an implicit and smart power control for CDMA uplink communications. In fact, this cost takes into account not only the reception quality required at the serving base station but also the global interference...
The multi-input multi-output (MIMO) system with a subcarrier intensity modulation (SIM) scheme in free-space optics (FSO) has a huge merit for ultra wide band communications mainly due to its diversity gain to be able to mitigate the signal scintillation caused by the atmospheric turbulence. In this study, we have analyzed the performance of the orthogonal space-time block codes (OSTBCs) in FSO links...
To combat Inter-Carrier Interference (ICI) in mobile OFDM systems, ICI can be reconstructed and removed from the received signal with the aid of channel estimation and decision-feedback. Successful ICI cancellation hinges on accurate channel estimation, which includes both the channel gains and ICI gains, the multiplicative coefficients to the neighbor subcarrier signals representing their power leakage...
In this paper, we propose a new definition of energy efficiency with respect to a given target packet error rate (PER). It is shown that some previous reported definitions are actually special cases of our definition. Consequently we use the definition to analyze the energy efficiency of Multilevel quadrature amplitude modulation (MQAM) and find that for a specific transmission there exists an energy...
The paper investigates the use of Radio Environment Maps (REMs) as a tool for Interference Management (IM) in two-tier cellular networks comprising macro- and femto-cells. The REMs are databases that provide, through different instances distributed over network elements, a variety of network- and user-related context information for improving IM and Radio Resource Management (RRM) procedures. In this...
A low-complexity user pairing algorithm for the broadcast phase of the XOR-based network coding is presented. The proposed scheme achieves the same spectral efficiency as an exhaustive search approach based on maximizing the sum-rate when network coding is utilized for all transmissions. The proposed scheme is further complemented with an adaptive switch, per user pair, between network coding and...
We present a new co-operative scheduling approach which provides not only more reliability but also higher effective capacity. Cooperation region is defined for active handoff users between two base stations (BSs) based on the user quality-of-service (QoS) requirements. A proper definition of co-operation or handoff region, where the user can be scheduled in a cooperative manner from more than one...
Current 3GPP specifications for LTE include the use of MIMO as a key technology. MIMO can be seen from two different perspectives: if increased data rates are targeted, for a given value of SNR, one gets improved data transmission; however, from an energy efficiency viewpoint, lower values of SNR are needed for the same reference data rate, therefore, allowing the reduction of the transmitted power,...
Deploying relay nodes is foreseen a cost-efficient solution to combat the severe propagation loss at cell edge. However, relay cell coverage is limited by the low transmit power, limited antenna capabilities and wireless backhaul link bottleneck which may lead to load imbalances and hence low resource utilization efficiency. Further challenges in relay deployments are attributed to increased interference...
Provision of voice services over 3G W-CDMA radio access networks is generally designed as a function of the air interface requirements of circuit-switched (CS) connections. On the other hand, packetized VoIP speech services such as Skype, which is becoming increasingly popular among 3G users, impose a more demanding set of requirements on the radio interface, carrying a penalty in terms of coverage...
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