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In this paper we deal with the problem of minimizing the complexity of an IR-UWB system by the introduction of Time-Reversal, under a power constraint and fixing a reachable performance in terms of BER. An approximate trade-off in the choice of the number of taps at the transmitter and the number of fingers at the receiver is proposed.
Intra-vehicular wireless sensor networks is a promising new research area that can provide part cost, assembly, maintenance savings and fuel efficiency through the elimination of the wires, and enable new sensor technologies to be integrated into vehicles, which would otherwise be impossible using wired means, such as Intelligent Tire. The most suitable technology that can meet high reliability, strict...
In this paper, the source and relay transmit covariance matrices are jointly optimized for a fading multiple antenna relay channel when the transmitters only have partial channel state information (CSI) in the form of covariance feedback. For full-duplex transmission, we evaluate lower and upper bounds on the ergodic channel capacity. These bounds require a joint optimization over the source and relay...
In this paper, we investigate different HARQ strategies with unreliable feedback channel. In classical approaches, retransmitted packets are different versions of the same user data. In order to improve HARQ performance, we propose to construct redundancy packets by jointly encoding several data packets. This strategy is referred to as HARQ Multiple Packet Incremental Redundancy (MP-IR). It can eliminate...
We develop an efficient relay selection protocol for two-hop transmission in cognitive radio networks where secondary users interfere with a primary user. Our protocol provides joint benefits of two well-known relaying strategies, namely relay sub-set selection and incremental relaying. It aims at minimizing the outage probability for delay-constrained applications by utilizing rateless codes. The...
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...
Current trends in low-cost and low power consumption transmitters in state-of-the-art wireless systems is to use the direct-conversion principle. Such transmitters, however, suffer severely from the I/Q imbalance effect, which introduces mirror-frequency interference and degrades data detection. This paper proposes a novel method for frequency-dependent I/Q imbalance estimation and compensation. The...
This paper proposes a dynamic symbol adaptation scheme for downlink and point-to-point multiple input multiple output (MIMO) systems aiming at the minimization of the overall system bit error rate. The proposed scheme adaptively changes the order or the values of the symbols to be transmitted within a sub-frame of symbols with the objective to enhance the received symbols' power. The adaptation is...
We deal with interference channels with (i) delayed channel state information at the transmitter (CSIT), and (ii) delayed output feedback at the receiver and no CSIT. We extend the algorithm by Maleki et al. [8] for M = 3 users to any M ≥ 3 under the constraint that all the transmitter/receiver pairs are active simultaneously. We propose a retrospective interference alignment algorithm achieving M...
In this paper we consider secure transmission for the multiple-input, multiple-output, single-antenna-eavesdropper systems with perfect information of the main channel and only the statistics of the eavesdropper's channel state information known at the transmitter. We adopt the celebrated artificial-noise (AN) assisted beamforming, which was studied by Goel and Negi with the limitation that the AN...
In the previous works on multiple-input multiple-output (MIMO) interference channels, it is usually assumed that the transmit power is fixed and only MIMO beamforming is applied to mitigate interference. In this paper, we design the transmit powers and beamforming vectors jointly for each transmit-receive pairs (links) to maximize the energy efficiency in MIMO interference channels. Centralized and...
In this paper, we study adaptive transmission mode switching between statistical and instantaneous channel state information (CSI) aided single-user (SU) and multiuser (MU) precoding for a two-user downlink system, where two transmit antennas are equipped at the base station and each mobile user has one receive antenna. In the case where only statistical CSI (SCSI) is available at the transmitter,...
In transmit beamforming multi-antenna systems, the representative quantized channel direction information (CDI) may become outdated due to the feedback delay. Grassmannian predictive coding (GPC) has been shown as an effective method to overcome this problem. However, the existing GPC algorithm is still of practical concern as the quantization resolution may not be ensured at relatively low feedback...
In this paper, a new measure of outage-constrained network area spectral efficiency, coined as stable transmission capacity, is introduced, which is achievable under finite delay and queue-length stability. Specifically, this framework extends the transmission capacity formulation to scenarios with packet retransmissions and transmitters' queues with independent packet arrivals. This approach is applied...
In this paper, we obtain the capacity region for the AWGN Multiple Access Channel (MAC) with transmitters equipped with energy harvesters. We next obtain the sum-of-rates capacity for the flat fading Multiple Access Channel with energy harvesting transmitters. We then develop low delay, adaptive transmission strategies that surprisingly achieve near optimal performance under finite battery resource...
In this paper, we propose a novel preamble design of partial Zadoff-Chu sequences, along with a synchronization scheme, for cooperative MIMO OFDM systems. In our preamble design, the training signals of cooperating terminals are well separated from each other in both time domain and frequency domain to suppress their mutual interference in both domains, whereas they are only separated in either of...
Cooperative Multiple Point (CoMP) transmission aided Distributed Antenna Systems (DAS) are proposed for increasing the received Signal-to-Interference-plus-Noise-Ratio (SINR) in the cell-edge area of a cellular system employing Fractional Frequency Reuse (FFR) in the presence of realistic imperfect Channel State Information (CSI) as well as synchronisation errors between the transmitters and the receivers...
Opportunistic scheduling exploits multiuser diversity for improving the performance of wireless systems. However, it requires instantaneous channel state information (CSI) to be available at the transmitter side. Since acquiring CSI is resource consuming, it always comes at a cost. We consider the problem of efficient channel state estimation in the context of 4G mobile broadband systems. Our proposed...
The point-to-multipoint (PMP) mode is considered a well-adopted transmission type that is supported by the IEEE 802.16 standard. The base station (BS) is served as a centralized coordinator to control and forward packets for mobile stations (MSs) within the network. With the consideration of direct communications, the required bandwidth and packet latency are reduced. However, the inappropriate arrangements...
In cognitive radio networks, unlicensed users need to learn from environmental changes. This is a process that can be done in a cooperative or non-cooperative manner. Due to the competition for channel utilization among unlicensed users, the non-cooperative approach may lead to overcrowding in the available channels. This paper is about a fuzzy logic based decision making algorithm for competition-based...
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