Femtocells, despite their name, pose a potentially large disruption to the carefully planned cellular networks that now connect majority of planet's citizens Internet and with each other. Femtocells - which by end 2010 already outnumbered traditional base stations at time publication are being deployed rate about five million year both enhance interfere this network in ways not yet well understood. Will femtocells be crucial for offloading data video from creaking network? Or will prove more...

This paper introduces an iterative multiuser receiver for direct sequence code-division multiple access (DS-CDMA) with forward error control (FEC) coding. The is derived from the maximum a posteriori (MAP) criterion joint received signal, but uses only single-user decoders. Iterations of system are used to improve performance, dramatic effects. Single-user turbo code decoders utilized as FEC and complexity study presented. Simulation results show that performance approaches even moderate...

Abstract A code‐division multiple‐access system with channel coding may be viewed as a serially‐concatenated coded system. In this paper we propose low complexity method for decoding the resulting inner code (due to spreading sequence), which allows iterative (turbo) of pair. The per‐bit proposed decoder increases only linearly number users. Performance within fraction dB single user bound heavily loaded asynchronous CDMA is shown both by simulation and analytically.

This paper studies the information-theoretic secrecy performance in large-scale cellular networks based on a stochastic geometry framework. The locations of both base stations and mobile users are modeled as independent two-dimensional Poisson point processes. We consider two important features networks, namely, information exchange between cell association, to characterize their impact achievable rate an arbitrary downlink transmission with certain portion acting potential eavesdroppers. In...

We view the asynchronous random code division multiple-access (CDMA) channel as a time-varying convolutional code. study case where users encode their data, and, therefore, single user transmitters and CDMA appear concatenation of two coding systems. At receiver we employ serial turbo decoding strategies. Unlike conventional codes both inner outer may be selected, in our case, is due to which assume random. Nevertheless, system resembles decoder single-user performance obtained even for...

Coherent OFDM detection requires accurate channel state information (CSI). Mobile radio channels are both time and frequency dispersive, especially at high vehicular speeds, which makes estimation a challenging problem in system design. Conventional preamble-based pilot-aided require numerous reference signals, significantly compromises the throughput. This paper proposes novel low complexity iterative turbo technique use of preamble, pilots soft decoded data an fashion to improve...

Small cell network (SCN) offers, for the first time, a low-cost and scalable mechanism to meet forecast data-traffic demand. In this paper, we propose non-uniform SCN deployment scheme. The small base stations (BSs) in scheme will not be utilized region within prescribed distance away from any macrocell BSs, defined as inner region. Based upon analytical framework provided work, downlink coverage single user throughput are precisely characterized. Provided that size is appropriately chosen,...

In orthogonal frequency division multiplexing (OFDM) systems, coarse frame timing can be acquired from one or more training symbols preceding every OFDM burst. The existing literature studied the case where there was only symbol consisting of identical segments. We generalize synchronization methods to take advantage multiple and require segments highly correlated but not necessarily identical. construct a series component metrics, for each pair segments, combine them linearly minimize false...

In this paper, we investigate the system performance of a multi-cell multi-user (MU) hybrid millimeter wave communications in multiple-input multiple-output (MIMO) network. Due to reuse pilot symbols among different cells, channel estimation is expected be degraded by contamination, which considered as fundamental bottleneck conventional MU massive MIMO networks. To analyze impact contamination performance, first derive closed-form approximation normalized mean-squared error algorithm...

This paper investigates a multiple-access communication receiver system that receives coded data modulated using either direct-sequence code division multiple access or narrowband binary phase shift keying, with an antenna array in multipath propagation environment. We describe iterative improves the initial estimates from array, and therefore reduces interference. Simulation results show bit error rate performance approaches obtained when only one user's signal is incident on array. occurs...

The performance of adaptive antenna array processors is known to decline severely in the presence imperfections and uncertainties. Hence robustness an processor against uncertainties important issue. Diagonal loading correlation matrix a popular technique applied standard Frost increase system. This paper presents number robust beamforming algorithms using efficient realization techniques. techniques do not use presteered allow designer specify frequency response look direction steer main...

Heterogeneous cellular networks consisting of microcell, picocell, femtocell, distributed antennas and relays codeployed in space frequency with carefully planned tower-mounted base stations, increase the complexity network structure, which makes a tractable analysis model difficult to obtain. In this paper, we extend original for downlink heterogeneous scenario directional antennas, from coverage probability (or equivalently outage probability) randomly located mobile user can be derived....

In this letter, we propose a successive multiuser detector (SMUD) for contention based OFDMA ranging channel compliant to the IEEE 802.16 (WiMAX) standard. A consists of set subcarriers in specific time slots shared by multiple users, so access interference (MAI) limits performance detectors. Different from existing methods that treat MAI as noise, proposed SMUD successively detects paths active signals and cancels their further detection. This approach significantly suppresses improves both...

In this letter, we propose a successive multiuser detector (SMUD) for contention based OFDMA ranging channel compliant to the IEEE 802.16 (WiMAX) standard. A consists of set subcarriers in specific time slots shared by multiple users, so access interference (MAI) limits performance detectors. Different from existing methods that treat MAI as noise, proposed SMUD successively detects paths active signals and cancels their further detection. This approach significantly suppresses improves both...

Using stochastic geometry, the downlink (DL) and uplink (UL) coverage probabilities are derived for co-channel packet multi-tier heterogeneous cellular networks (HCNs). The spatial locations of base stations (BSs) as well user equipments (UEs) modeled independent homogeneous Poisson point processes. decoupled association is evaluated where UE may connect to different BSs in UL DL transmissions. Unlike most existing works, transmission slots not synchronized, that is, starting ending points...

This paper proposes a coverage-oriented femtocell network deployment scheme, in which the base stations (BSs) can decide whether to be active or inactive depending on their distances from macrocell BSs. Specifically, as areas close BSs already have satisfactory cellular coverage, located inside such are kept inactive. Thus, all femtocells poor coverage areas. Based stochastic geometric framework, probability analyzed with tractable results. Surprisingly, results show that proposed although...

Heterogeneous cellular networks consisting of microcell, picocell, femtocell, distributed antennas and relays co-deployed in space frequency with carefully planned tower-mounted base stations, increase the complexity network structure, which makes a tractable analysis model difficult to obtain. Since traditional system-level simulation suffers from computational being not tractable, recent research focused on using stochastic geometry develop new general models for both single tier...

Acquisition of the code timing in a direct-sequence code-division multiple-access (DS-CDMA) system at base station must take place before signal detection and decoding is possible. Code acquisition under severe multiple-access-interference (MAI) conditions with time-varying codes makes task even more difficult. Inefficient designs lead to large number false alarms and/or missed detections. This requirement needed for conventional single-antenna (1-D) designs, as well multielement antenna...

In this paper we derive a novel extrinsic information transfer (EXIT) function for channel estimator that uses both pilot symbols and soft decoding information. We consider CDMA system with forward error correction employs iterative multiuser detection based on interference cancellation single user decoding. The J is useful in convergence analysis as it provides mapping between mutual variance. functions are derived the flat-fading Rayleigh estimate, allowing priori inputs to estimator,...

In this paper, we develop low-complexity iterative channel estimation techniques for emerging IDMA systems. The estimators make use of pilots as well soft decoded data information. We derive a lower bound error that reflects the reliability data. show perform close to minimum variance unbiased estimator mean square (MSE) approaches bound. Numerical results on MSE and BER performance also proposed are able track time-varying states.

This paper studies the information-theoretic secrecy performance in large-scale cellular networks based on a stochastic geometry framework. The locations of both base stations and mobile users are modeled as independent two-dimensional Poisson point processes. We consider key feature network, namely, information exchange between stations, characterize its impact achievable rate an arbitrary downlink transmission with certain portion acting potential eavesdroppers. In particular, analytical...

In this paper, we consider the 1-bit compressive sensing reconstruction problem in a scenario that sparsity level of signal is unknown and time variant, binary measurements are contaminated with noise. We introduce new algorithm which refer to as Noise-Adaptive Restricted Step Shrinkage (NARSS). NARSS superior terms performance, complexity speed convergence algorithms already introduced literature for from noisy measurements.

This paper presents efficient robust broadband antenna array pattern synthesis techniques with interference cancellation capabilities. The are able to place multiple broad nulls and isolated point at regions of interest for cancellation. new algorithms result in improved performance processors. presented computationally more than the existing techniques. includes numerical simulations that demonstrate compared methods.