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In this paper, we study the impact of an important RF impairment inside direct-conversion receiver, namely the I/Q imbalance, on the performance of OFDM radio link over frequency-selective Rayleigh fading channel. Closed-form expressions for link performance, in terms of detection error rate, ergodic capacity and outage capacity, under both frequency-selective RX I/Q imbalance and noisy frequency-selective...
The MIMO wireless channel offers a rich ground for quality of service analysis. In this work, we present a stochastic network calculus analysis of a MIMO system, operating in spatial multiplexing mode, using moment generating functions (MGF). We quantify the spatial multiplexing gain, achieved through multiple antennas, for flow level quality of service (QoS) performance. Specifically we use Gilbert-Elliot...
In the paper, we consider the end-to-end routing and link scheduling problem for multi-hop wireless sensor networks. The efficient link scheduler under our consideration is intended to assign time slots to different users so as to minimize channel usage subject to constraints on data rate, delay bound, and delay bound violation probability. We also present a coupled robust multi-path routing structure...
We consider the impacts of channel fading on the quality of service (QoS) performance of the IEEE 802.11 system. Traditional 2-D Markov chain models, while suitable for throughput analysis, are unable to capture the QoS performance due to the lack of a proper queueing model. We present a 3-D Markov chain queueing model that incorporates channel fading effects and solve the Markov chain efficiently...
In order to address the long runtimes required to fully simulate hybrid automatic repeat-request (ARQ) systems, such as high-speed downlink packet access (HSDPA), we propose an information-theoretic approach to accelerate the simulation while still maintaining its fidelity. The approach is based on the concept of information-outage probability, and involves the computation of the mutual information...
To fully exploit frequency diversity in cyclic delay diversity orthogonal frequency division multiplexing (CDD-OFDM) system, accurate channel estimation is crucial. Due to the excessive channel delay spread in CDD, traditional in-band pilot assisted channel estimation with limited frequency resolution fails to track the considerable variation in the frequency domain. Alternatively, increasing pilot...
Experimental measurements of shallow water acoustic channels show that the received signal power varies over time as the channel experiences fading. This fact motivates the use of adaptive power (or rate) control as a way to improve the system performance or save the transmit power. In a system with adaptive power control, the transmitter adjusts its power so that the received power remains at a pre-specified...
Distributed spatial diversity systems, such as multi-relay and multi-user networks, have drawn significant attention from the research community. However, their feasibility in a practical environment remains an open concern. Most notably, how to optimize cooperation between multiple users with individual interests and how practical systems issues can erode diversity gains. Whilst existing information...
Periodic packet transmission in fading channel is an important issue in wireless networks, where the nodes can save energy, as it is powered by batteries. In mobile radio communication system, communication takes place over time-varying channels. This time variation is called as fading. Fading is the direct result of multi-path propagation where radio waves propagate along different paths before arriving...
The paper describes the transmission of BPSK signals in an OFDM system with 64-point IFFT at transmitter and FFT at receiver. The channel over which transmission will take place is ISI Rayleigh fading channel given by 2 tap channel model with path delay [0, 0.5] μs. The sampling frequency of OFDM is to be kept at 20MHz. Cyclic prefix for OFDM is calculated for improving bandwidth efficiency of the...
We consider the problem of energy-efficient point-to-point transmission of delay-sensitive data (e.g. multimedia data) over a fading channel. We propose a rigorous and unified framework for simultaneously utilizing both physical-layer centric and system-level techniques to minimize energy consumption, under delay constraints, in the presence of stochastic and unknown traffic and channel conditions...
Opportunistic Dynamic Spectrum Access (DSA) systems are emerging as a key to enable the Department of Defense (DoD) to meet its technology requirements for access to the electromagnetic spectrum. One of the main goals of DSA is to protect incumbent spectrum users from interference that could be caused by DSA emitters. One of the ways to accomplish this is through spectrum sensing as means to enable...
In this paper, we propose to use the Discrete-Time Rake receiver for Cooperative DS-CDMA systems. We compare the Bit Error Rate (BER) performance of the Continuous Time, Discrete Time and Decorrelating Discrete Time Rake receivers (CTR, DTR, DDTR) using Decode and Forward (DF) relaying. The former receiver is the most used and consists in combining the output of correlators locked on the most significant...
With the extensive deployment of 802.11 wireless local area networks (WLANs) and the need for better quality of service (QoS), the 802.11e MAC with service differentiation was developed. Analysing the effect of fading, shadowing and near-far effect on the performance of 802.11 is a fundamental consideration in practical situations since the wireless channels are errorprone.This paper develops a p-persistent...
This paper examines the capacity of a time division duplex (TDD) multiple input single output (MISO) beamforming system with channel estimation error and delay over the time varying fading channel. In TDD system, the base station estimates the channel state information (CSI) at transmitter based on uplink pilots and then uses it to generate the beamforming vector in the downlink transmission. Because...
This paper investigates the downlink system level performance for Layer-3 (L3) and Layer-1 (L1) relays with orthogonal frequency division multiple access (OFDMA) used in LTE-Advanced. Various practical factors are taken into account in the evaluations such as the processing delay and upper-bound of the amplifier gain of the L1 relay, capacity limitation of the backhaul channels, and empty buffer status...
In this paper, we introduce several technologies to adapt orthogonal frequency division multiple access (OFDMA) scheme to satellite environments. Maximizing the commonalities with the terrestrial system is one of the most important factors for cost-effective service delivery, which will finally bring successful deployment of the system. For this purpose, we adopt an orthogonal frequency division multiplexing...
In this paper we present parametrization for pathloss regarding the wideband car-to-car channel at 5.7 GHz. Furthermore, we investigate the power decay of delay-resolved multipath components, categorized in LOS and NLOS paths, and discuss the results. The results show relatively high pathloss exponents and a strong dependency of the exponent on the LOS path, which carries the main part of signal power...
Coordination between two or more multiple access channel (MAC) receivers can enlarge the achievable rate region of the whole system. This paper focuses on coordination by sharing the codebooks of the users between the receivers of MACs. We first define the achievable rate region of the time invariant multiple coordinated MAC (MCMAC) and subsequently derive its achievable rate region. We later express...
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