Comparison of hybrid FDMA/CDMA systems in frequency selective Rayleigh fading (original) (raw)

Capacities of hybrid FDMA/CDMA systems in multipath fading

Proceedings of MILCOM '93 - IEEE Military Communications Conference

A hybrid FDMAKDMA scheme is described and analyzed. The performance of the hybrid system is then compared with that of a wideband CDMA system occupying the same t o t a l bandwidth 8s the hybrid system. It is found that, while the hybrid system has ppatics which may be desirable in certain situations, such as the ftexibility of using a non-contiguous spectrum, in a multipath fading environment, a wideband CDMA system has greater capacity than the hybrid.

MFSK-based modulations for hybrid DS/FH-CDMA systems operating in slowly Rayleigh fading channels

IEEE Transactions on Vehicular Technology, 1997

ABSTRACT This paper presents an analytical evaluation of a direct-sequence/frequency-hopped code-division multiple-access (DS/FH-CDMA) system in a Rayleigh fading environment. The modulations under consideration are noncoherent M-ary-frequency-shift keying (MFSK) and an MFSK-based joint-frequency phase modulation utilizing differential binary phase-shift keying (PSK). Multiple-access interference has been taken into account, and the spectral efficiency for uncoded as well as convolutionally coded systems has been calculated

Design and performance of multicarrier CDMA system in frequency-selective Rayleigh fading channels

Vehicular Technology, IEEE Transactions …, 1999

This paper presents the advantages and disadvantages of a multicarrier code-division multiple-access (MC-CDMA) system. The transmitter/receiver structure and the bandwidth of transmitted signal spectrum are compared with those of a conventional direct-sequence (DS) CDMA system, and an MC-CDMA design method, how to determine the number of subcarriers and the length of guard interval is discussed. The bit error rate (BER) lower bounds for DS-CDMA and MA-CDMA systems are derived and their equivalence is theoretically demonstrated. Finally, the BER performance in downlink and uplink channels with frequency-selective Rayleigh fading is shown by computer simulation.

Spectral efficiency for a hybrid DS/FH code-division multiple-access system in cellular mobile radio

IEEE Transactions on Vehicular Technology, 2001

The spectral efficiency of a hybrid cellular direct-sequence/frequency hopping code-division multiple-access (DS/FH-CDMA) system operating in a Rayleigh-fading environment is examined. In this work, spectral efficiency is evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, on the condition that this is estimated in an average sense. The analysis covers the downlink assuming a static model of operation and a direct-sequence/slow-frequency hopping (DS/SFH) as well as a direct-sequence/fast-frequency hopping (DS/FFH) scheme. As it is shown, the spectral efficiency of cellular DS/FFH-CDMA operating in a Rayleigh-fading environment is greater than that of broad-band DS-and DS/SFH-CDMA systems operating under normalized conditions. This is justified by the combination of path-diversity reception as achieved by conventional coherent RAKE receivers and the frequency diversity that is inherently present in FFH transmission.

Analysis of extended ofdm-cdma system

2001

This paper proposes a hybrid extended OFDM-CDMA modulation technique which can be used principally in mobile communication. It supports the advantages of both of the OFDM and the CDMA systems. The detailed specification is set down. The examination is partitioned into two divisions that are the transmitter and the receiver. The channel which has been used by the simulation is set to linear time-varying filter channel. The performance of these system has been tested by extensive simulations and compared with the OFDM and the CDMA. In very noisy multipath channel the proposed hybrid scheme works efficiently and gives good Bit Error Rate value.

Broadband MC DS-CDMA using space-time and frequency-domain spreading

Proceedings IEEE 56th Vehicular Technology Conference, 2002

In this contribution multicarrier direct-sequence codedivision multiple-access (MC DS-CDMA) using space-time spreading (STS) assisted transmit diversity and frequency-domain (F-domain) spreading is investigated in the context of broadband communications over frequency-selective Rayleigh fading channels. We consider the attainable capacity extension of broadband MC DS-CDMA with the advent of using Time-Frequency-domain (TF-domain) spreading. The BER performance of STS assisted broadband MC DS-CDMA using Binary Phase Shit Keying (BPSK) modulation and TF-domain spreading is investigated by simulation for a range of parameter values. Both the correlation based singleuser detector and the decorrelating multiuser detector are considered. Our study shows that the number of users supported by the broadband MC DS-CDMA system is determined by the product of the T-domain spreading factor and the F-domain spreading factor, while it is independent of the frequency diversity order. Furthermore, when multiuser detection assisted F-domain spreading is considered, the broadband MC DS-CDMA system is capable of supporting a substantially increased number of users, while maintaining a similar bit error ratio (BER) performance to that of the broadband MC DS-CDMA system using no F-domain spreading.

Performance of switched selection transmission diversity in FDD/DS-CDMA system

2008 National Radio Science Conference, 2008

In this paper, the performance of Switched Selection Transmission Diversity in FDD/DS-CDMA system will be investigated. This performance will be evaluated by considering the effect of space distance between the diversity antennas and the maximum Doppler frequency (f d) on bit error rate (BER) performance under optimum conditions. This performance is not clarified until now. Moreover, the effect of error on Feedback Antenna Selection bit on uplink will be studied. Rayleigh fading will be assumed. The proposed scheme significantly decreases the average transmit power at the Base Station or the Mobile Station and shows robustness against the BER performance degradation compared with the conventional scheme.

ANALYSIS THE PERFORMANCE OF MULTI-CARRIER CDMA SYSTEM WITH FADING AND INTERFERENCE

Users moving at vehicular speed communicate over a wireless channel that exhibits time-variant frequency-selective characteristics due to multipath propagation and doppler effects. Multi Carrier Code Division Multiple Access (MC-CDMA) is a relatively new concept to improve the performance over multipath links. MC-CDMA is a modulation method that uses multi carrier transmission of DS-CDMA type signals and an MC-CDMA transmitter spreads the original data stream in the frequency domain over different sub carriers using a given spreading code. The MC-CDMA offers better frequency diversity to combat frequency selective fading. In this paper we evaluate the performance results of MC-CDMA in terms of bit error rate, power, length, code length and no. of subscriber.

Study and Simulation of DS-CDMA over Communication Channels

Performance of synchronous DS-CDMA systems over multipath fading channel and AWGN Channel is evaluated. The synchronous DS-CDMA system is well known for eliminating the effects of multiple access interference which limits the capacity and degrades the BER performance of the system. This paper investigated the bit error rate (BER) performance of a synchronous DS-CDMA system over AWGN and Rayleigh channel, which is affected by the different number of users, as well as different types spreading codes. The promising simulation results explore the comparative study of different DS-CDMA system parameter and showed the possibility of applying this system to the wideband channel. In this paper, Rayleigh channel and AWGN Channel are introduced and investigated the bit error rate (BER) performance of a synchronous DS-CDMA system over these channels. In the DS-CDMA system, the narrowband message signal is multiplied by a large bandwidth signal, which is called the spreading of a signal. The spreading signal is generated by convolving a GOLD sequence code with a chip waveform whose duration is much smaller than the symbol duration.