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Intercarrier Interference (ICI) is an impairment well known to degrade performance of Orthogonal Frequency Division Multiplexing (OFDM) transmissions. It arises from carrier frequency offsets (CFO), from the Doppler spread due to channel time-variation, and, to a lesser extent, from sampling frequency offsets (SFO). The literature reports several models of ICI due to each kind of impairment. Some...
Main goal of this work is to give insight on the possible performance improvement arising in the wireless local ad-hoc access from the synergic cooperation of two emerging paradigms, multi-antenna and cognitive radios. The target is the competitive maximization of each access rate in presence of multiple-access interference (MAI) induced by the other accessing terminals. Being the radios cognitive,...
The low cost of CDMA cellular repeaters suggests that its use may be always advantageous. However, the interference inserted by such repeaters in the CDMA system must not be neglected. The CDMA repeater inserts thermal noise in the repeated carrier, amplifies the carriers of other Base Stations, and thus can also be a source of interference for the mobile stations served by it. In this paper we perform...
Voice communication is effected by a number of factors especially the rain, as it causes the severe fading of the receive signal level. Fading is a function of frequency, polarization and path length and the actual amount of fading is dependent on the frequency of the signal and the size of the raindrop. This proposed outage prediction model is used not only to predict microwave radio link performance...
In this paper, we propose a fast prediction method adapted to multi-user turbo detection based on linear filtering and successive interference cancellation. Using Gaussian approximation, compression and quality tables, the method provides for each user its expected transmission quality at each iteration according to the linear filter of the multi-user detector (MMSE or Matched Filter) as well as its...
Cognitive radio based dynamic spectrum access network is emerging as a technology to address spectrum scarcity. In this study, we assume that the channel is licensed to some primary (licensed) operator. We consider a sensor network with cognitive radio capability that acts as a secondary (unlicensed) network and uses the channel in underlay mode. The secondary network uses interference temperature...
Body-coupled communications (BCC), in which the human body is used as a communications channel, has been shown to be a promising solution for wireless body-area networks (WBANs). For successful deployment of these BCC-based WBANs, it is necessary to develop a clear understanding of the channel behavior. Therefore, this paper presents the key characteristics of the capacitively-coupled on-body channel...
This paper presents the optimum control interval for intra-cell fractional transmission power control (TPC) for a shared data channel employing frequency domain channel-dependent scheduling and adaptive modulation and coding (AMC) in the evolved UTRA uplink using single-carrier (SC)-FDMA radio access. The simulation results show that the best attenuation factor in the fractional TPC is approximately...
The system capacity of a cellular wireless system consisting of a large number of fixed location base stations (BSs) and random location mobile stations (MSs) is studied. Assuming that the BSs in a multi-cell system are connected to a centralized controller which has access to channel state information (CSI), it is possible to optimize transmissions such that capacity is maximized. This paper discusses...
Power control is a very important issue for any mobile node on a network, because of its limited battery power. If nodes use Code Division Multiple Access (CDMA) to share the available bandwidth, the transmitted power needs to be well controlled, to avoid the rise of noise level on the network and interferences with other nodes. The problem is even more difficult in ad-hoc networks, because there...
In this paper, we analyze the sum rate maximization problem in a two-cell wireless system under peak power and minimum service rate constraints. The optimal power allocation is found to be binary, in the sense that each base station power will have one out of only two possible discrete levels, and the result can greatly reduce the optimization and power control complexity required. A closed-form solution...
The transmitter side precoding shows excellent performance for multiuser multiple input multiple output (MIMO) wireless systems. However, joint transmitter and receiver design might achieve further improvement. The optimum precoding and decoding matrices can be solved iteratively. In this paper, we propose a modified joint iterative algorithm, based on minimum mean square error (MMSE) criterion in...
Cellular radio systems are often limited due to the presence of cochannel interference. Basically, radio systems may be operated by utilizing asynchronous or synchronous downlink transmission from all base stations in the system, where synchronization between terminals and their serving base station is mandatory in both concepts. We provide a comparison between the theoretical achievable spectral...
In this paper we present the mutual information of a bit-interleaved V-BLAST space-time architecture. We assume interference cancellation by successive detection using MMSE equalizers without decoding of the channel codes. The mutual information is dependent on the MIMO channel realization and the detection order. However, the mutual information is very similar to that of an AWGN channel when plotted...
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...
To extend the lifetime of wireless sensor networks a power-aware design of the communication units is required. This can be accomplished by employing power-controllable impulse radio ultra-wideband (IR-UWB) transceivers. In this paper, two distributed power control algorithms are suggested that are based on a variation of IR-UWB specific parameters. The iterative algorithms converge to the optimal...
Cross-layer design for wireless networks aims at optimizing system-wide performance measures by exploiting dependencies between different network layers. In this paper, an opportunistic power assignment algorithms for IR-UWB sensor networks is presented that is especially designed for distributed signal detection under resource constraints. Specifically, the objective is to minimize the global probability...
This paper proposes a multipath routing protocol called cross-layered multipath AODV (CM-AODV), which selects multiple routes on demand based on the signal-to-interference plus noise ratio (SINR) measured at the physical layer. Note that AODV (ad hoc on-demand distance vector) is one of the most popular routing protocols for mobile ad hoc networks. Each time a route request (RREQ) message is forwarded...
Antenna tilt is an effective inter-cell interference reduction technique which has been studied a lot previously in the CDMA-based systems. In this paper, we concentrate on the evaluations of the mechanical antenna downtilt in the uplink LTE networks. The SINR performance and the trade-off between the cell coverage and capacity are studied in a homogeneous scenario. Simulation results in Macro 1 show,...
In LTE uplink, the slow varying path gain and shadowing are compensated by the standardized open loop power control (OLPC). Further optimization of the system performance can be done via closed loop power control commands. In this contribution, it is shown that using such commands to control the interference caused by users to the system, it is possible to achieve a gain in the order of 20% on the...
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