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The emerging evolved UTRA radio system is generally envisioned to support a large number of VoIP users. This is basically enabled by efficient frequency domain packet scheduling together with accurate channel quality feedback information. In this paper, we investigate the performance of VoIP on EUTRA downlink assuming that only limited channel quality feedback information is available. System level...
The on-line Bayesian Cramer-Rao (BCRB) lower bound for the dynamic estimation of a time-varying multi-path Rayleigh channel in 4-QAM OFDM system is considered. In case of negligible channel variation within one symbol and delay related information, true BCRB for data-aided (DA) context, and two closed-form expressions for non-data aided (NDA) context are derived.
The frequency selectivity of wireless communication channels can be characterized by the delay spread Ds of the channel impulse response. If the delay spread is small compared to the bandwidth W of the input signal, that is, DsW ?? 1, the channel appears to be flat fading. For DsW ?? 1, the channel appears to be frequency selective, which is usually the case for wideband signals. In the first case,...
This paper studies the small-scale multipath propagation characteristics of a typical outdoor urban environment. Wideband channel sounding measurements are performed and findings are presented. Channel sounding is carried out at UHF band (250, 300, 350, 400 MHz) for static transmit and receive antennas. The power delay profile, mean delay spread, RMS delay spread, as well as coherence bandwidth have...
Multi-channel MAC protocols are proposed to increase the capacity of wireless network. However, dynamic channel selection mechanism based on channel usage information from one-hop neighbor nodes causes multi-channel hidden node problems in a multi-channel multi-hop wireless network. In this paper, we propose a new approach of channel selection. Nodes snoop data channels during idle times and then...
Power amplifiers in a communication system are inherently nonlinear. Digital predistorters can compensate these nonlinearity effects. In this paper, two memory polynomial predistorters including direct and indirect learning architectures are compared with each other. To the best of our knowledge, no similar comparisons have been published. Both of these architectures are special cases of the self-tuning...
This paper investigates the integration of an effective prediction scheme for bandwidth allocation in a GEO satellite architecture supporting DVB-RCS (Digital Video Broadcasting - Return Channel Satellite) features. The prediction strategy joined to a simple scheduling method implemented in the satellite terminals, allows a good QoS differentiation to the miscellaneous traffic categories.
In this paper, a new combination of a multiple access scheme and spatial diversity offered by relays is proposed. In order to support several users in a system, interleave division multiple access (IDMA) is suggested here due to the capability to deal with asynchronous transmission by the users. The relays apply amplify-and-forward combined with delay-diversity in order to exploit the spatial diversity...
The booming multimedia applications are demanding multi-hop communications in high data rate millimeter wave radio WPANs (Wireless Personal Area Networks). However, unable to make use of space reuse, the IEEE 802.15.3 dependent piconet scheme shows its limit when the number of inter-connected piconet grows. In this paper, we introduce the concept of a bridging device - the via to setup multi-hop link...
In underwater networks, when designing contention-based MAC protocols such as CSMA/CA, a long propagation delay should be considered. Particularly, most protocols like 802.11, the most typical CSMA/CA protocol, which utilize the RTS/CTS handshaking technique with network allocation vector (NAV), determine the NAV using a value of duration field in RTS/CTS. The duration value is determined with a fixed...
In an IEEE 802.11 ad hoc wireless LAN, the listen interval (LI) of a power-saving (PS) station should be fixed at one even there is no data traffic or its remaining battery power is low. However, if the value of LI is allowed more than two (in units of beacon interval), 802.11 power management may completely fail. In this paper, we propose a novel power management protocol, named OFPM, which not only...
In many cases, a mobile user has the option of connecting to one of several 802.11 access point (APs). We consider the case when users multihome, i.e., split their traffic among all available APs, based on the long-term channel characteristics such as burstiness and packet error rate. This type of operation requires a new multi-access control (MAC) protocol, where the user has to decide to which AP...
We propose a method for concurrent OFDM fine time synchronization to different stations with propagation delay differences, and a receiver based delay difference compensation method for MMSE channel estimation, which are needed to enable cooperative MIMO-OFDM transmission. Cyclic prefix removal is done dynamically with respect to the closest station, which allows for intersymbol interference free...
This contribution deals with the Turbo-like noncoherent data-aided (e.g., no blind) synchronization of Ultra-Wideband Impulse-Radio (UWB-IR) terminals operating over broadband channels affected by multipath fading with ??a priori?? unknown number of paths. The synchronizer we develop achieves the data-aided joint estimate of the number of paths and their arrival times without requiring any a priori...
Time reversal (TR) is a transmission technique that relies on pre-processing the signal at the transmitter (TX) by filtering it through a filter, the impulse response of which is a time reversed and phase conjugated version of the channel impulse response (CIR) to the target receiver (RX). TR is known to have remarkable temporal and spatial focusing properties. Specifically temporal focusing indicates...
We propose a parallel a posteriori probability (APP) decoding algorithm for increasing the decoding throughput of turbo codes. The parallel decoding algorithm divides a noisy codeword into multiple sub-blocks which are decoded in parallel. The authors in [1] proposed utilizing the forward and backward variables computed by neighbor sub-blocks in the previous iteration as the initial boundary conditions...
A general method to develop Tanner graphs from tail-biting convolutional codes (CC) is proposed. Recursive systematic convolutional (RSC) and non-RSC codes are considered consistently and it is shown that the elimination of redundant states leads to a graph with low complexity. In addition the graphical representation is extended to derive the condition for which the tail-biting termination is valid...
In this paper, we present MRL-QRP, a multi-agent reinforcement learning based routing protocol with QoS support for wireless sensor networks. In MRL-QRP, sensor node cooperatively computes QoS routes using a distributed value function - distributed reinforcement learning algorithm (DVFDRL). Global optimization can be achieved by using locally observed network information and limited exchanging of...
This paper addresses the trend in wireless sensor network applications of increasing node density and multi-hop communications that result into extremely challenging design constraints. SSAS, an adaptive hybrid localised sink-oriented Routing/MAC protocol is proposed. It offers a self-configuration scalable solution for large random sensor networks and attempts to alleviate multi-hop congestion problems...
Packet disordering and resequencing is a common problem in many real-time applications with stringent timing constraints. A typical scenario is when wireless sensor nodes, interconnected with an ad hoc network, are used to monitor a certain event. In such systems, packets will have to be resequenced before consumption because they were disordered while traversing different paths over the ad hoc network...
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