A. Lodhi

Performance comparison of space-time block coded and cyclic delay diversity MC-CDMA systems

Spatial diversity is a widely applied technique for enhancing wireless system performance since it greatly reduces the detrimental effects of multipath fading. Space-time block codes have been considered the best choice for transmit diversity in narrowband environments, but their use in broadband channels is questionable due to their inability to pick up multipath diversity. However, when used in conjunction with an MC-CDMA system, they achieve not only full spatial but also variable multipath diversity depending on the employed spreading. In comparison, cyclic delay diversity is an attractive approach to achieve spatial and multipath diversity. Its simplicity and conformability with current standards makes it desirable for multicarrier systems. Previous studies suggest that CDD is only advantageous with an outer channel code for OFDM systems. In this article, we compare STBCs and CDD applied to an MC-CDMA system in terms of complexity and performance. It is shown that for an MC-CDMA system, CDD benefits from spreading and channel coding that makes it very competitive with STBCs, particularly since it is applicable to any number of transmit antennas with no loss in rate.

Closed-Form Symbol Error Probabilities of STBC and CDD MC-CDMA With Frequency-Correlated Subcarriers Over Nakagami-

The performances of cyclic delay diversity and space-time block-coded multicarrier code-division multiple-access (MC-CDMA) systems operating in a Nakagami-m fading channel with correlated subcarriers are investigated. By using the moment-generating function of the correlated Nakagami-m random variable, explicit closed-form formulas for the exact average symbol error rate (SER) of M-ary signals for an MC-CDMA system employing the aforementioned diversity techniques are derived with a maximum ratio combining detection technique. The average SERs are expressed in terms of higher transcendental functions, such as the Gauss and Appell hypergeometric functions. Both numerical and simulation results are presented, showing excellent agreement.

m

Sensor networks as cooperative spatial diversity (CSD) is implemented and analyzed for cyclic delay diversity (CDD) distributed MC-CDMA system. In such as cooperative system, it is proposed a distributed SISO analysis employing CDD to simplify the system evaluation in terms of probability of errors and maximum achievable throughput [bits/s/Hz]. Furthermore, the moment generating function (MGF) of the correlated Nakagami-m random variable is used and considered for the realistic case of frequency-correlated MC-CDMA subcarries. To this end, an explicit allocation strategy for the distributed diversity is deducted. Simulation results are also presented which show excellent agreement with the analytical framework.

Fading Channels

Orthogonal space-time block codes allow utilising the diversity provided by multiple-input-multiple-output communication channels, thereby decreasing the error probability for a given communication rate. The contribution of this paper is the derivation of closed-form expressions of the symbol error probability of distributed codes deployed over Nakagami flat fading channels with different channel gains and fading parameters

Performance Analysis of Distributed CDD MC-CDMA Sensor Networks with Frequency-Correlated Subcarriers over Nakagami-m Fading Channels

Distributed cyclic delay diversity (DCDD) multistage MC-CDMA system communication system is shown to yield superior performance over traditional link network. The benefits provided by increased frequency selectivity caused by the cyclic delays are evaluated through explicit closed-form formulas for the exact average symbol error rate (SER) of M-ary signals. By using the moment generating function (MGF) of the correlated Nakagami-m random variable and considering a realistic case of frequency-correlated MC-CDMA subcarriers, allocation strategies are derived and analysed in order to maximise the end-to-end throughput. Furthermore, the application of CDD is presented for equal subchannel gains. Monte-Carlo simulations are used to numerically verify the analytical framework, which show excellent agreement.

Closed-Form Symbol Error Probabilities of Distributed Orthogonal Space-Time Block Codes

This paper presents the exact bit error rate (BER) analysis of a cyclic delay diversity (CDD) multicarrier code division multiple-access (MC-CDMA) system. By using the moment generating function (MGF) of the correlated Nakagami-m random variable and considering the realistic case of frequency-correlated MC-CDMA subcarriers (which is often ignored in literature), closed-form BER expressions are obtained with maximum ratio combining (MRC) detection technique for both uplink and downlink scenarios. Simulation results are also presented which show excellent agreement with the analytical framework.

Throughput of Distributed Cyclic Delay Diversity MC-CDMA Relaying over Nakagami-m Fading Channels

Distributed Cooperative Cyclic Delay Diversity (DCCDD) multi-hop relay network is shown to yield superior performance over traditional link network. The benefits provided by increased frequency selectivity caused by the cyclic delays are evaluated through the explicit closed-form BER expressions and maximum achievable throughput [bits/s/Hz]. Towards that end resource allocation strategies in terms of fractional frame duration and transmission power are assigned. By using the moment generating function (MGF) of the correlated Nakagami-m random variable and considering a realistic case of frequency-correlated multicarrier code division multiple-access (MC-CDMA) system, allocation strategies are derived and analyzed in order to maximize the end-to-end throughput. Monte-Carlo simulations are used to numerically verify the analytical framework with maximum ratio combining (MRC) detection technique.

Exact Bit Error Probability of CDD MC-CDMA System with Frequency-Correlated Subcarriers

The performance of a space-time block coded (STBC) multicarrier code division multiple-access (MC- CDMA) system operating in Nakagami-m fading channel with correlated subcarriers is investigated. Independency among MC-CDMA subcarriers is often assumed in literature which leads to idealistic performance bounds. The contribution of this paper is the derivation of closed-form expressions of the symbol error probabilities. We use the moment generating function (MGF) of the correlated Nakagami-m random variable (RV) to calculate the closed-form average symbol error rates (SERs) of binary and M-QAM signals with maximum ratio combining detection technique. Both, numerical and simulation results are presented, showing an excellent agreement.