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

Comparison of CDMA and FDMA for the MobileStar(sm) system

Spread-spectrum code division multiple access (CDMA) and single channel per carrier frequency division multiple access (FDMA) systems are compared for spectrum efficiency. CDMA is shown to have greater maximum throughput than FDMA for the MobileStar(sm) system which uses digital voice activated carriers and directive circularly polarized satellite antennas

Dynamical replica theoretic analysis of CDMA detection dynamics

We investigate the detection dynamics of the Gibbs sampler for code-division multiple access (CDMA) multiuser detection. Our approach is based upon dynamical replica theory which allows an analytic approximation to the dynamics. We use this tool to investigate the basins of attraction when phase coexistence occurs and examine its efficacy via comparison with Monte Carlo simulations.Comment: 18 pages, 2 figure

A statistical-mechanical analysis of coded CDMA with regular LDPC codes

We analyze, using the replica method of statistical mechanics, the theoretical performance of coded code-division multiple-access (CDMA) systems in which regular low-density parity-check (LDPC) codes are used for channel coding

Watermarking Using Decimal Sequences

This paper introduces the use of decimal sequences in a code division multiple access (CDMA) based watermarking system to hide information for authentication in black and white images. Matlab version 6.5 was used to implement the algorithms discussed in this paper. The advantage of using d-sequences over PN sequences is that one can choose from a variety of prime numbers which provides a more flexible system.Comment: 8 pages, 9 figure

CDMA signature sequences with low peak-to-average-power ratio via alternating projection

Several algorithms have been proposed to construct optimal signature sequences that maximize the sum capacity of the uplink in a direct-spread synchronous code division multiple access (CDMA) system. These algorithms produce signatures with real-valued or complex-valued entries that generally have a large peak-to-average power ratio (PAR). This paper presents an alternating projection algorithm that can design optimal signature sequences that satisfy PAR side constraints. This algorithm converges to a fixed point, and these fixed points are partially characterized

Impact of Interference Model on Capacity in CDMA Cellular Networks

This presentation introduces code division multiple access (CDMA) networks, average and actual interference models, optimized capacity, and the 2D Gaussian user model

Analisa Call Succes Rate Pada Jaringan Code Division Multiple Access ( Cdma )

Sistem komunikasi seluler adalah sistem komunikasi wireless dimana subscriber bisa bergerak dalam suatu coverage jaringan yang luas, sehingga subscriber yang melakukan komunikasi tidak mengalami dropcall karena di daerah blankspot. CDMA ( code division multiple access ) adalah teknologi multiuser dimana masing-masing user menggunakan code yang unik dalam mengakses kanal yang terdapat dalam sstem. Dimana sistem CDMA memiliki lebar frekuensi yang cukup lebar dan tahan terhadap gangguan. Analisis arus pembicaraan ( traffic ) pada sistem wireless dapat diketahui dengan menganalisa semua parameter-parameter yang ada seperti analisa call attempt, call success, call completion, blok call dan drop call. Dengan analisis ini akan didapatkan berbagai peningkatan guna mengoptimalkan jaringan secara efisien apakah perlu adanya penambahan sirkit atau komponen penunjang lainnya. Dengan adanya analisa tentang arus pembicaraan tersebut akan memberi beberapa keuntungan seperti sinyal yang dihasilkan semakin bagus, sehingga kemungkinan terjadinya dropcall sangat kecil. Setelah melakukan analisa, terdapat 4 BTS yang mempunyai tingkat drop call tinggi yaitu BTS Kubu 2,47%, BTS Seirengas 2,37%, BTS Tlk.Pakedai 2,24%, BTS Wajokhulu 2,20%. maka perlu dilakukan Pengurangan radius cakupan dengan melakukan penurunan daya pancar untuk masing-masing BTS dengan cara mengurangi jarak pancar pada masing-masing BTS, terbukti setelah melakukan pengurangan jarak pancar dapat mengurangi resiko terjadiny drop call. Hasil setelah melakukan penurunan daya pancar yaitu Kubu 1,94%, BTS Seirengas 1,85%, BTS Tlk.Pakedai 1,73%, BTS Wajokhulu 1,69%. Dari tabel dapat dilihat bahwa terbukti terjadi penurunan prosentase drop call yang disebabkan oleh inteferensi yang dikarenakan oleh transmisi daya overhead yang berlebihan dari Base Station tetangga ( neighbour BTS ). Jadi terbukti bahwa pengurangan sinyal overhead dengan pengaturan kembali daya pancar akan menyebabkan penurunan prosentase drop call

Code-division multiple-access in an optical fiber LAN with amplified bus topology: the SLIM bus

A novel optical fiber network with a bus topology and dark signaling (the SLIM bus) using optical code-division multiple-access (CDMA) is proposed. With a new design of delay line correlator the network is shown to eliminate optical beating noise and overcome the main limitations of incoherent optical CDMA in a star topology