This work proposes an empirical propagation model to obtain the path loss, and therefore determine the average received power, of a signal for a specific outdoor urban scenario with UAVs. The proposed 3D propagation model for terrestrial cellular networks generalizes the LUI model and is valid in the frequency ranges from GSM, UMTS and LTE technologies. We report experimental work in 3D space, considering the height, the antennas base station tilt, sectorization, angle and distances profile. The experimental work included in this study appropriately agrees with the proposed theoretical model; hence, the proposed model is adequate for cellular planning tools.

Increasingly mobile data traffic and high quality service demand has driven standard developments and new mobile technologies deployment at an unprecedented level. Long Term Evolution (LTE) standard and its improved version LTE-Advanced (LTE-A) are two technology standards developed to cope with high levels of mobile data traffic demand. However, traffic and revenue disparity still is a reality, suggesting that traditional network deployment methods - based mainly on macro cellular sites - might prove to be cost ineffective in the long term. From another perspective, and increasingly important for mobile network operators, revenue is also a function of each mobile network deployment's sustainability. This work aims to comprehensively elaborate on those matters by presenting four specific scenarios with a comparative analysis of both macro and femtocell deployments (single and both technology networks). For each scenario, capacity, cost effectiveness and expected carbon emissions are the evaluated key indicators. This kind of analysis provides mobile networks operators with relevant information, enabling them to sustainably adapt business and provisioning models as well as network deployment strategies to current and future technological standards, while minimizing capital and operational expenditure (CAPEX/OPEX). The main contribution is that in short term, mixed macro and femtocell deployment scenarios are the most cost effective and sustainable option, while in mid to long term, as data traffic demand rises, femtocell deployments become the most sustainable, not only from economical and environmental points of view, but also from network coverage stand point.

This paper presents an unified and empirical propagation model to obtain the received power in mixed scenarios, with outdoor and indoor environments, or in a scenario with only one kind of environment, either for an urban, sub-urban or rural scenario, with or without vegetation. This unified model is called the Lisbon University Institute (LUI) one and can be included into planning tools for wireless communication systems. The developed model is suitable for Path Loss prediction in mobile, as well as fixed wireless network systems, e.g., Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access, considering Line-of-Sight or Non-Line-of-Sight propagation conditions.

This paper presents the validation of the unified propagation model, the Lisbon University Institute (LUI) model, which is valid for three wireless technologies: Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access. With this purpose in mind, several experimental trials for those technologies were performed in different scenarios, where mixed environments (outdoor and indoor) were included. This generalized and unified propagation model was tuned by adjusting specific parameters for each different technology, based on the achieved results from the field experiments.

In this paper, we consider iterative frequencydomain receivers for block transmission techniques with rate-1 Space Time Block Coding (STBC) for two or four transmit antennas. We consider both Orthogonal Frequency Division Multiplexing (OFDM) and SingleCarrier (SC) schemes. Since our STBC with 4 transmit antennas is not orthogonal, our receiver includes the cancellation of the residual interference, allowing performances close to the ones of an orthogonal code. Our performance results show that combining STBC with block transmission schemes allows excellent performances, even for channels with small multipath diversity.

In this paper we present an LTE RAN (radio access network) emulator based on a new method for mobile channels modeling. The new method is then used to model the OFDMA downlink of LTE (long term evolution) link level performance under 16-QAM hierarchical modulation. The models have been derived for a quality of service (QoS) corresponding to a block error rate (BLER) of 1%, which is the common value for real-time applications. The results provided by the RAN Emulator are then compared to the statistical distribution of the received sequence in a LTE link level simulation. Further, we presented an analysis of the delay in a LTE transmission with different sources.

Among radio technologies, multiple-input multiple-output (MIMO) systems have attracted wide research interests in recent years. It is widely recognized that MIMO systems can be employed for achieving a high capacity and a high diversity order, for mitigating the effects of various types of interfering signals, and for supporting space-division multiple-access (SDMA). In this study a MIMO assisted cellular system using distributed antennas is proposed and investigated, where a big number of antennas are distributed in the area covered by the system. The proposed system is capable of providing a platform for possibly integrating the conventional cellular systems into the future advanced, high-flexibility, ad-hoc and cooperative wireless networks. This system is considered for MBMS (multimedia broadcast multicast service) that enables mobile operators to deliver rich multimedia to a huge number of subscribers by broadcasting over the radio frequencies assigned to WCDMA.

A coherent detection of OFDM signals (Orthogonal Frequency Division Multiplexing) allows good performances in severely time-dispersive channels. However, coherent receivers require good channel estimates, a difficult task when the channel impulse response is long and/or when space diversity techniques are employed. Usually, the channel estimates are obtained with the help of pilot symbols multiplexed with data symbols, which reduces the useful bit rate, decreasing the spectral efficiency of the systems. To avoid this, we consider the use of implicit pilots instead of multiplexed pilots. Since the interference levels between data and pilots might be very high, we propose an iterative receiver with joint detection and channel estimation. Our performance results show that our technique allows the use of low-power pilots, with performances close to the ones with perfect channel estimation, even when space diversity techniques are employed.

Abstract Low rate convolutional and turbo codes that output non‐linear cyclic (NLC) codewords of lengthn = 2m,mbeing a positive integer, are described. These codes have a very low coding rate, which makes them especially suitable for spread spectrum systems where they can be used for simultaneously achieving error correction and bandwidth expansion. Due to the cyclic properties and codeword length of the component codes, branch metrics can be efficiently computed using the fast Fourier transform (FFT), enabling simple implementation of the encoder and decoder. Among the possible NLC base codes, special attention is given to the Tomlinson, Cercas, Hughes (TCH) codes family due to their good autocorrelation properties. It is shown by simulation that the turbo codes schemes studied usually perform better than traditional turbo codes (in this paper the universal mobile telecommunications system (UMTS), rate 1/3 turbo code was used as a reference). This improvement is accomplished at the cost of bandwidth expansion. One of the advantages of the presented solutions over other low rate codes is their ability to improve the synchronization process at the receiver due to the good autocorrelation properties of the available NLC codes (especially TCH codes). A comparison of performance between the UMTS uplink connection and an equivalent system using the proposed codes for a multiuser scenario in a multipath fading channel is presented showing the possibility of capacity increase when using these codes. Copyright © 2006 John Wiley & Sons, Ltd.

With the introduction of MBMS (Multimedia Broadcast Multicasting Services), new requirements are introduced in order to offer MBMS to all users. Due to the low UMTS (Universal Mobile Telecommunication System) resources there is a need to enhance the UMTS networks.This study is about the HSDPA (High Speed Downlink Packet Access) as means of deliver MBMS video streaming and also presents packet scheduler's algorithms that try to guarantee the same bit rate to the users in order to offer a good fairness and capacity.

The transmission of multimedia broadcast and multicast services are expected to be transmitted to all users or groups of users within the cell range. UMTS 3GPP Release 6 standards envisage the support of these types of services over a common channel, thus not clogging up the air interface with multiple dedicated transmissions of the same data. The transmission of services over a single common channel reaching down the cell edge requires a large amount of power in order to satisfy the quality of service (QoS) requirements and the planned coverage. These power requirements can be reduced by the use of well known macro diversity combining techniques such as selective combining (SC) and maximum ratio combining (MRC) which allow a significant signal improvement at the receiver side and a more efficient usage of the available radio resources

The proposed decorrelating multi-user detector (MUD) scheme allows the cancellation of both multiple access interference (MAI) and interpath interference (IPI). The current approach considers the downlink environment of universal mobile telecommunication systems (UMTS), with a RAKE receiver in the mobile station (MS). A comparison is made with a subtractive interference cancellation MUD. Moreover, to improve the performance, we consider a combination of the decorrelating MUD with the subtractive interference cancellation MUD

Due to the multipath propagation, the Wideband-Code Division Multiple Access (W-CDMA) channels are typically frequency-selective. For this reason, conventional Vertical - Bell Laboratories Layered Space-Time (V-BLAST) detection techniques are not suitable for W-CDMA-based MIMO systems (Multiple Input, Multiple Output). In this paper, we consider the use of MIMO schemes within W-CDMA systems and we propose a V-BLAST detector suitable for multipath, frequeny-selective channels where the individual detection of each path is performed using a simple decorrelator, and the resulting signals are combined through an MSE-based (Mean Square Error) multipath combining algorithm. Due to the high sensitiveness of this detector to interpath interference, a Multipath - Parallel Interference Cancellation (MPIC) is also considered, followed by either Successive Interference Cancellation (SIC) and Parallel Interference Cancellation (PIC).

The purpose of the current work is to analyze several schemes to combat both the MAI and fading, in the downlink direction. We propose a new predistortion (PD) filtering technique, which can be used to combat the multiple access interference (MAI), combined the selective transmit diversity (STD) for high data rate transmissions over frequency selective Rayleigh fading channels. The proposed PD scheme considers a Rake in the receiver. By predistorting the signals to be transmitted by the base station (BS) with a minimum variance (MV) algorithm, the orthogonality between the desired signal and all interfering signals can be improved. With the PD, the increase in performance is achieved with a small increase in power processing at the BS, avoiding any need to increase complexity at the mobile station (MS).

It is intended to specify a new pre-distortion (PD) filtering technique, which can be used to combat the multiple access interference (MAI), combined with two kinds of transmit diversity (TD), namely the selective transmit diversity (STD) and the space-time transmit diversity (STTD) for high data rate transmissions over frequency selective Rayleigh fading channels. By pre-distorting the signals to be transmitted by the base station (BS) with a minimum variance (MV) algorithm, the orthogonality between the desired signal and all interfering signals can be improved. We combine the PD with STD and with STTD, allowing a reduction in the MAI and combating the fading. The increase in performance is achieved with a small increase in power processing in the BS, avoiding any need to increase complexity in the mobile station (MS).

We present a new space time transmit diversity (STTD) scheme for M/spl ges/4 transmit antennas and one receive antenna. The new diversity scheme belongs to the open loop class and consists of an extension to the work presented by Alamouti (1998) and by Tarokh et al. (1998, 1999). Another hybrid scheme that combines open and close loop classes is also presented. The coding rate of the new scheme is one and in spite of the presence of intersymbol interference it may achieve the full diversity after applying a multi-dimensional orthonormal rotation to the original constellation. For each coding scheme every block with 8 received symbols is detected using a maximum likelihood decoding algorithm to get the estimated maximum likelihood sequence. Q-QAM modulations are analysed.

This paper considers the SIC-subtractive interference cancellation and PIC-parallel interference cancellation with and without the ISI cancellation system-commutation signaling (CS), in a deep Rayleigh fading environment, time and frequency selective, assuming the spreading sequences and the features of the channels of the several interfering users is known. It is shown that SIC and PIC lead to better performance when the CS technique is used together, once these systems subtract the MAI estimated for each user. These estimates improve when the ISI is cancelled, since the MAI estimated depends upon the estimate of the transmitted symbols by each interfering user. A blind detection (without knowledge of spreading sequences nor the features of the channels of the interfering users) with a noise whitening matched filter (NWMF) that combats the MAI through the whitening of the interfering power spectrum (following the single-user philosophy) is also developed.

This work considers asynchronous time division code division multiple access (TD-CDMA) systems with RAKE receivers and one stage of parallel interference cancellation (PIC) or serial interference cancellation (SIC). A general method based on the concept of spherically symmetric signals is presented for the evaluation of the average probability of error of uncoded TD-CDMA systems. Slow frequency-hopping (SFH) with frequency overlap (FO) between adjacent carriers and interference cancellation are also included in the analysis, which considers the multipath Rayleigh fading channel (which models indoor and outdoor vehicular radio propagation). We analyze quadrature phase shift keying (QPSK) modulation with coherent demodulation and multipath (frequency) diversity with maximal ratio combining (MRC). Power control, adaptive SFH, and interference cancellation are employed for improving the bit-error rate (BER) performance. It is found that the scheme with SFH, in spite of the FO, always improves the performance substantially, and interference cancellation, in general, provides the highest BER improvement.

This work deals with the asynchronous DS-CDMA reverse link with multiuser detection (MUD) receivers (two stages of parallel interference cancellation) the channel is multipath Rayleigh faded. The trade-off analysis between MUD and channel coding is the main topic. A comparison is made between the maximum throughputs (in bits/s/Hz) achievable using multiuser detection and single user detection, for both single cell and cellular systems. The effect of imperfect power control is also investigated. As in a DS-CDMA system a fixed bandwidth expansion can be allocated to either error correction coding or modulation signal spreading this trade-off is also analysed in conjunction with MUD vs. coding. We suppose that BPSK modulation with coherent demodulation is employed.

Bandwidth expanding signaling with quasi-orthogonal short codes where the bandwidth expansion factor N/spl les/8, is considered. The evaluation of the average probability of error over channels with multipath induced intersymbol interference (ISI) (which model broadband indoor and outdoor millimeter wave radio propagation) is presented, for two different receivers. Namely the rake receiver with equal gain combining and the postdetection integrator. Both BFSK modulation with noncoherent demodulation and DPSK modulation are analysed.