In this letter, we propose a set of Space-Time Block Codes (STBC) equipped with 4 transmit antennas to transmit one additional information bit achieving rate-9/8. To maintain full rank property of the coding gain matrix, one new orthogonal STBC code with full rate is proposed in this letter. Simulation results show that this method achieves good bit error rate (BER) performance with a small gap compared to that of the rate-1 case and throughput in the high SNR region.

Adaptive hybrid genetic algorithm concatenated with improved parallel interference cancellation, i.e. adaptive hybrid genetic algorithm parallel interference cancellation (AHGAPIC) was proposed. A study is conducted on the application of AHGAPIC to soft decoding high rate multi-user detection with diversity reception for dual-rate wideband DS-CDMA spread spectrum communications, aiming to mitigate the effect of multiple access interference. The relevant research has revealed that the local search capability of hybrid genetic algorithm (HGA) is still not good enough. Therefore, first, two evolutionary operations, i.e. inversion and insertion are merged into HGA to constitute a novel algorithm. With its moderate local search capability, this new algorithm can search for the global optimum region according to the information entropy, and then it is made adaptively vary its probabilities of crossover and mutation depending on the fitness values of the solutions to form the adaptive hybrid genetic algorithm (AHGA). Second, AHGA is utilized to effectively identify the better and better binary string to maximize the log-likelihood function of dual-rate multi-user detection. As AHGA converges to the optimum region, the control factor of the improved parallel interference cancellation (IPIC) detector is set to be the ratio of the average fitness value to the maximum fitness value of the population of AHGA. Finally, equipped with both the control factor and the binary string with the maximum fitness value as the initial data, the IPIC detector can rapidly find out the approximately optimum soft decoding vector. Then, it can obtain the approximately global optimum estimate point on the basis of the soft decoding rule, corresponding to the transmitted data bits. A lower bound of computational complexity has been achieved through simulations and qualitative analyses. The property of the proposed algorithm to converge rapidly leads to lower computational complexity. Emulation results have shown that the AHGAPIC soft decoding high rate multi-user detector is superior to other suboptimum detectors considered in this paper in terms of two points. They are the mitigation of multiple access interference and the resistance to near-far effects. Its performance is close to the sequential group optimum multi-user detector but with a shorter time delay.

In order to improve the forward link capacity of cdma2000 HRPD (High Rate Packet Data) or CDMA2000 1xEV-DO, it is significant to overcome multi-path interference. This paper focuses on FDE (Frequency Domain Equalization) with MMSE (Minimum Mean Square Error) criterion. On top of that, backward compatibility with HRPD should be maintained, in other words common channels such as the pilot channel should not be changed. Thus, the PN (Pseudo Noise) spread pilot block without CP (Cyclic Prefix) signals has to be dealt with for FDE. However, this will cause the conventional channel estimation accuracy to deteriorate. In order to improve the estimation accuracy of the conventional method, this paper presents a MRC (Maximal Ratio Combining) spectrum estimator, IPI (Inter-Path Interference) canceller, and path searcher. The results obtained from computer simulations reveal that the proposed method can improve the PER (Packet Error Rate) performance significantly. If compared with Rake combiner and TDE (Time Domain Equalization) with NLMS (Normalized Least Mean Square) scheme, the maximum data rates at a fixed PER of 1% can be increased by 5 to 8 times and 1.25 to 2.67 times, respectively.

In this paper, first, we propose two of the high rate methods based on Morii-Kasahara cryptosystem. Method A-I is based on Schalkwijk algorithm. Method A-II is based on the extended Schalkwijk algorithm, which is proposed in this paper. We then show that these proposed methods can yield a higher rate compared with ElGamal cryptosystem. Next, we also propose two methods for a fast encryption by dividing the message vector into several pieces. Regarding each of the divided vectors as an index, we can realize a fast transformation of the index into a limited weight vector. In Method B-I, Schalkwijk algorithm is used for the fast transformation. In Method B-II, the fast transformation is realized with the method of table-lookup. These methods can realize a faster encryption than Method A-I, Method A-II and Morii-Kasahara cryptosystem. The security of these proposed methods are based on the security of Morii-Kasahara cryptosystem.

We propose a soft decision Viterbi decoding scheme and a self-interference cancellation method applicable to a Parallel Combinatory CDMA (PC-CDMA) system. In this decoding scheme, branch metric is calculated for every bit by weighting the output levels of the PC-CDMA correlators so as to enable an effective soft decision capability to the system. The effectivity of this scheme is then further enhanced by the use of a simple pseudo-random bit interleaving scheme. Moreover, to increase the capacity of the PC-CDMA system, we propose a simple self-interference cancellation method for self-induced cross-correlation arising from the multipath environment. This further enhances the efficacy of the decoding scheme because the false contributions of the self-induced cross-correlation component are removed from the branch metric prior to soft decision Viterbi decoding. Finally, we simulated a possible PC-CDMA system with a user data rate of 1.92Mbps, transmitting it at a chip rate of 3.84Mcps and at 7.68Mcps under a multipath-Rayleigh fading interference environment. For a chip rate of 7.68Mcps, BER after Viterbi decoding is less than 3.2e-7 even without the use of interference cancellation. For a chip rate of 3.84Mcps, BER after Viterbi decoding with interference cancellation is 1.0e-4.