Adaptive Beamforming and Adaptive Modulation-Assisted Network Performance of Multiuser Detection-Aided FDD and TDD CDMA Systems

The network performance of a frequency division duplex and time division duplex (TDD) code division multiple access (CDMA)-based system is investigated using system parameters similar to those of the Universal Mobile Telecommunication System. The new call blocking and call dropping probabilities, the probability of low-quality access, and the required average transmit power are quantified both with and without adaptive antenna arrays (AAAs), as well as when subjected to shadow fading. In some of the scenarios investigated, the system’s user capacity is doubled with the advent of adaptive antennas. The employment of adaptive modulation techniques in conjunction with AAAs resulted in further significant network capacity gains. This is particularly so in the context of TDD CDMA, where the system’s capacity becomes poor without adaptive antennas and adaptive modulation owing to the high base station (BS) to BS interference inflicted as a consequence of potentially using all time slots in both the uplink and downlink of the emerging wireless Internet. Index Terms—Adaptive beamforming, adaptive modulation, code division multiple access (CDMA) systems, Universal Mobile Telecommunication System Terrestrial Radio Access (UTRA), wireless network performance

Dynamic Channel Allocation Techniques Using Adaptive Modulation and Adaptive Antennas

This contribution studies the impact of adaptive quadrature amplitude modulation (AQAM) on network performance when applied to a cellular network, using adaptive antennas in conjunction with both fixed channel allocation (FCA) and locally distributed dynamic channel allocation (DCA) schemes. The performance advantages of using adaptive modulation are investigated in terms of the overall network performance, mean transmitted power, and the average network throughput. Adaptive modulation allowed an extra 51% of users to be supported by an FCA 4-QAM network, while in conjunction with DCA, an additional 54% user capacity was attained. Index Terms—Adaptive antennas, adaptive modulation, adaptive arrays, beam-steering, DCA, dynamic channel allocation

Adaptive Antenna Array Assisted Dynamic Channel Allocation Techniques

Abstract—The performance of base station adaptive antenna arrays (AAAs) is investigated in conjunction with fixed channel allocation (FCA) and dynamic channel allocation (DCA) schemes. Locally distributed DCAarrangements are studied and benchmarked against standard FCA, in the context of both line-of-sight (LOS) and multipath propagation environments. One-, two-, four-, and eight-element AAAs are employed using the sample matrix inversion (SMI) beamforming algorithm, in both the up- and the down-link. In most investigated scenarios, the locally optimized least interference algorithm (LOLIA) exhibited the best overall compromise in terms of a set of combined metrics, such as the forced termination probability, new call blocking probability, and the probability of a low quality access. Index Terms—Adaptive antennas, adaptive array, beamforming, dynamic channel allocation (DCA), network capacity, wireless networks

The Network Performance of Multi-rate FDD-Mode UMTS

The performance of a multi-rate mobile cellular network using the Frequency Division Duplex (FDD) mode of the Code Division Multiple Access (CDMA) based Universal Mobile Telecommunication System (UMTS) is investigated. The new call blocking and call dropping probabilities and the tolerable network load are studied in the context of a multi-rate FDD-mode UMTS network incorporating dynamic threshold assisted soft handovers and shadow fading

Comparative Study of Adaptive Beam-Steering and Adaptive Modulation-Assisted Dynamic Channel Allocation Algorithms

Abstract—A range of dynamic channel allocation (DCA) algorithms, namely, distributed control and locally distributed control assisted DCA arrangements, are studied comparatively. The so-called locally optimized least interference algorithm (LOLIA) emerges as one of the best candidates for future mobile systems, supporting more than twice the number of subscribers in comparison to conventional fixed channel allocation (FCA). It can also cope with unexpected large increases in teletraffic demands while requiring no tedious frequency planning. This is achieved at the cost of more complex call setup and control, and the requirement of fast backbone networks for base station–base station signalling. Adaptive antennas are shown to significantly enhance the capacity of both the LOLIA and FCA-based networks, especially when used in conjunction with adaptive modulation techniques. Index Terms—Adaptive arrays, adaptive modulation, beam steering, dynamic channel allocation (DCA), smart antennas, wireless networking

Adaptive Modulation and Adaptive Antenna Array Assisted Network Performance of Multi-User Detection Aided UTRA-like FDD/CDMA Systems

The adaptive antenna array and adaptive modulation aided network performance of a Frequency Division Duplex (FDD) Code Division Multiple Access (CDMA) based system is investigated using system parameters similar to those of the Universal Mobile Telecommunication System (UMTS). A number of performance metrics, such as the call dropping probability, the average throughput as well as the required average transmit power are quantified. It is demonstrated that the employment of adaptive modulation techniques in conjunction with adaptive antenna arrays resulted in significant network capacity gains in the scenarios investigated

Third-generation systems and intelligent wireless networking - smart antennas and adaptive modulation

Third-Generation Systems and Intelligent Wireless Networking studies the network capacity gains that can be achieved with the advent of adaptive antennal arrays and adaptive modulation techniques in both FDMA/TDMA and CDMA based mobile cellular networks. The employment of adaptive antennas has numerous benefits and advantages. These include reducing the co-channel interference imposed on other system users, increasing the user capacity and the area spectral efficiency, improving the power efficiency, and the number of handover as well as transmission errors. • Provides an overview of the various CEDMA based 3G wireless standards, namely UTRA, IMT 2000 and cdma 2000 • Provides an introduction to near-instantaneously adaptive modulation for single- and multi-carrier modulation or OFDM, as well as CDMA • Quantifies the service-related benefits of adaptive transceivers in wireless video telephoney • Studies the network performance gains using adaptive antenna arrays at the base station in an FDMA/TDMA cellular mobile network • Presents the design of a combined power control and adaptive modulation assisted channel allocation algorithm and its performance in an FDMA/TDMa cellular mobile network • Compares the performance of various UTRA soft-handover techniques, quantifies the network capacity and evaluated the network performance with the aid of adaptive antenna arrays. By providing an all-encompassing self-contained treatment of adaptive modulation, adaptive antennas and adaptive networking, this volume will inspire researchers, practising engineers and advanced students in the areas of wireless communications and networking. Above all, it endeavours to be an informative and stimulating read

Adaptive Antenna Assisted Network Performance of FDD-mode UMTS

The performance of the Frequency Division Duplex (FDD) mode of the Code Division Multiple Access (CDMA) based Universal Mobile Telecommunication System (UMTS) is investigated. The new call blocking and call dropping probabilities, the probability of low-quality access as well as the required average transmit power are quantified both with and without the assistance of adaptive antenna arrays as well as with and without encountering shadow fading. In some of the scenarios investigated the system’s user capacity is doubled with the advent of adaptive antennas

Network Performance of Asynchronous UTRA-like FDD/CDMA Systems using Loosely Synchronised Spreading Codes

In this paper we characterize the capacity of a UTRA-like Frquency Division Duplex (FDD) Code Division Multiple Access (CDMA) system employing Loosely Synchronized (LS) spreading codes. Current CDMA systems are interference limited, suffering from Inter-Symbol-Interference (ISI), since the orthogonality of the spreading sequences is destroyed by the channel. They also suffer from Multiple-Access-Interference (MAI) owing to the non-zero cross-correlations of the spreading codes. LS codes exhibit a so-called Interference Free Window (IFW) , where both the auto-correlation and cross-correlation of the codes become zero. Therefore LS codes have the promise of mitigating the effects of both ISI and MAI in time dispersive channels. Hence, LS codes have the potential of increasing the capacity of CDMA networks. This contribution studies the achievable network performance by simulation and compares it to that of a UTRA-like FDD/CDMA system using Orthogonal Variable Rate Spreading Factor (OVSF) codes