MMSE‐based groupwise successive interference cancellation scheme for multirate CDMA systems

We present a successive interference cancellation (SIC) scheme for a multicarrier (MC) DS CDMA system. In every subband, the SIC receiver successively detects the interferers' signals and substracts them from the user-of-interest. A comparison is made among SIC, matched filter detection with an equal gain combiner (MF-EGC), matched filter followed by maximal-ratio combining (MF-MRC) and minimum mean-squared error (MMSE) receivers with optimal tap coefficients. For this latter receiver, we determine the performance both when the number of taps equals the processing gain, denoted by N, and when the number of taps is roughly one-half of the processing gain. By analysis and simulation, it is shown that the SIC has better ability to suppress multiple-access interference (MAI) than do MF and [N/2]-tap MMSE in single carrier (SC) CDMA, and MF-EGC, MF-MRC and [N/2]-tap MMSE in MC CDMA, and this translates to increased capacity and better fading resistance. Further, SIC and N-tap MMSE yield approximately the same performance in SC CDMA, but SIC has a poorer performance than does an N-tap MMSE in MC CDMA. In addition, we derive results for the performance degradation that a SIC scheme experiences in MC CDMA due to both phase and timing tracking errors. It is shown that with small tracking errors, SIC can still retain a performance advantage over MF-EGC and MF-MRC, although the advantage of SIC decreases with increasing tracking errors.

In this paper we introduce a successive interference cancellation (SIC) scheme for direct sequence optical code division multiple access (DS-OCDMA) systems using pulse position modulation (PPM). Considering double-padded modified prime code (DPMPC) as a signature sequence code, results show that the system has better performance in terms of both capacity and bit error rate (BER) as compared to the one without cancellation scheme, where the system with SIC scheme can support up to 88 users while the system without SIC scheme can support only 38 users at similar BER=10

We present a successive interference cancellation (SIC) scheme for a multicarrier (MC) direct-sequence code-division multiple-access (CDMA) system, using band-limited spreading waveforms to prevent self-interference. In every subband, the SIC receiver successively detects the interferers' signals and substracts them from the user-of-interest. A comparison is made among SIC, a minimum mean-squared error (MMSE) receiver, and matched filter (MF) detection with maximal-ratio combining (MRC). We also consider suboptimal combining using pilot symbol-assisted modulation (PSAM) to make the system more realistic. Analytic bit-error probabilities for SIC, MMSE, and MF in correlated Rayleigh fading channels are derived. The theoretical results for SIC, MMSE, and MF are shown to agree well with simulations. In particular, SIC and MMSE are shown to achieve better performance than MF with MRC; when the number of users is small, SIC provides better performance than does MMSE. Further, the correlation among different subcarriers is studied, and only large subcarrier correlation coefficients result in an obvious worsening of performance. Finally, we derive results for the performance degradation that an SIC scheme experiences in MC CDMA due to phase and timing tracking errors. It is shown that SIC can still retain a performance advantage over MF-MRC, although the advantage of SIC decreases with increasing tracking errors, especially when subcarrier correlation coefficients are small.

Performance analysis of multicell multiuser MIMO MC DS/CDMA system with MMSE user-ordered SIC technique

The multiuser detection is a signal processing tech- nique which enhances the performance and capacity in DS- CDMA technology. Since its complexity issue was too expensive to handle, there was focus on the suboptimal detectors. In this paper we propose a hybrid method called adaptive differential interference cancellation method (ADIC) which is a hybrid of the differential interference cancellation method and which is then combined in a adaptive way to determine a weight matrix which will map the outcome of the differential interference cancellation method to come out with a better performance. This paper also looks into the computational cost of different methods using the floating point operation (flops) which is a good estimation of the comparative computational cost if not the exact one. I. INTRODUCTION The conventional DS-CDMA match filter detector fails to combat these issues due three prominent drawbacks: unrealis- tic ucorrelated code, near-far problem (even with strict power control (1)), and tough multiple access interference (MAI). Many advanced signal processing approaches have been made to improve the performances of these kinds of detectors. In this paper we will study the different approaches that were made in this field and implement these methods to reach a conclusion about the detection methods. As the name of the topic suggests the focus of our work will be study and propose cost effective better performing multiuser detection method. We will explore Multiuser Detection Techniques in Synchronous CDMA environment. Multi-user detection deals with the development and ap- plication of joint demodulation and interference cancellation cancellation techniques for improved detection of a desired set of digital signals in the presence of multiple access interfer- ence, intersymbol interference and noise. Since veterbi forward dynamic algorithm (2) is used in case of Optimum multiuser detection (3) the complexity grows in with the increase in the number of users. Hence the complexity is immense which increases exponentially with the increase in the number of users. Looking ahead for lower complexity hence lesser cost of implementation, the paper proposes the use of sub-optimal linear detectors (4). The sub-optimal detector the paper next focuses on is Decorrelator type of Detector (5) which is optimal in least squares. This detector out performs the optimal detector in many respects. Then the Minimum Mean Square Error (MMSE) linear detector is proposed which tries to minimize the squared error from the required transformation. It is one of the most popular detectors in use due to its easiness to implement and its lower complexity. But then in the above detection methods the decisions made were based on certain linear transformation criterion and there are missing efforts to check the performance in between the detection process to improvise the transformation method better detection. So then the paper proposes Adaptive multiuser detection. Then the paper focuses on Interference cancellation methods which utilize the feedback to reduce Multiple Access Interference (MAI) in the detected bits. Under the Interference Cancellation umbrella the Successive Interference Cancellation (SIC) (6), (7) method is explored and simulated to observe the results. Then the next method which performs better than SIC and more commonly used in real life, called Parallel Interference Cancellation (PIC) (6), (8) is also implemented. Before going ahead to implement the final proposed detection method, this paper implements Differential Interference Cancellation (DIC) (9) method. And then this paper finally proposes an Inter- ference Cancellation method called the Adaptive Differential Interference Cancellation Multiuser Detection method which is cost effective in comparison to other Interference Cancellation methods as we will require lesser hardware (multipliers as in the SIC or Parallel Interference Cancellation (PIC)) for that matter. More ever since we are using adaptive method the desired BER can be further reduced. This proposed method will be discussed in detail in the following section.

We present a lattice reduction (LR) aided successive interference cancellation (SIC) scheme combined with linear pre-equalization in the correlated multi-user MIMO system. The LR-aided SIC schemes have been extensively studied to detect multiple users' symbols due to the nearly optimal performance. However, the LR algorithm and the sequential detecting method inherently incur considerable computational complexity overhead although it is of a polynomial order. To reduce their computational complexities, we decouple the entire system into multiple lower dimensional subsystems using linear pre-equalization based on the correlation among the users. We then utilize the LR-aided SIC parallel in each subsystem. Furthermore, to combine the LR-aided SIC with pre-equalization optimally, we modify the LR-aided SIC scheme, handling the residual interferences after pre-equalization.

As the promising novel multiple access scheme for the 5th generation (5G) wireless communication system, pattern division multiple access (PDMA) technology can improve the spectral efficiency and support the massive connection based on the reasonable unequal diversity between users. Compared with traditional multiple access technologies, PDMA brings more serious multiple address interference to hinder the multiuser detection. The universal detection algorithm with low complexity and high performance is one of the main challenges of PDMA technology. In this paper, we proposed a new iterative detection and decoding algorithm, which is a successive interference cancellation (SIC) iterative processing based on the minimum mean square error (MMSE) detection and channel decoding algorithm. It is essentially a SIC iterative processing based on some users' information has been correctly decoded by the MMSE detection and the channel decoder. The proposed multiuser detection algorithm can prevent the error propagation by the cyclic redundancy check (CRC). The simulation results show that the proposed algorithm can get significant performance gains over traditional multiuser detection algorithms.

In DS/CDMA systems, overcoming near/far effects and fading is imperative for satisfactory performance. One way to combat the near/far effect is to use stringent power control, as is done in most of the commercial systems. Another approach is Multi-User Detection (MUD). In addition to mitigating the near/far effect, MUD has the more fundamental potential of raising capacity by canceling Multiple Access Interference (MAI). This paper analyses the convergence behavior and performance of successive interference cancellation (SIC) for CDMA systems. This analysis will be generalized for Parallel Interference Cancellation (PIC) also. In this paper a Hybrid Interference Cancellation (HIC) receiver is designed by combining the successive and Parallel Interference Cancellation algorithms, so that the advantages of both the schemes are utilized effectively. The Hybrid Interference Cancellation scheme results in a simple, faster and reliable receiver. With the help of simulations, it is shown that this hybrid approach outperforms the other Multi-User Detection schemes.

Equalisation is one of the most important algorithms to improve the Bit-Error-Rate (BER) performance in communication systems. In general, equalisation can be classified into two categories: linear and non-linear equalisation. The linear equalisers include Zero Forcing (ZF), and Minimum Mean Square Error (MMSE) equalisers. The non-linear equalisers include ZF and MMSE equalisers that are based on Successive Interference Cancellation (SIC). The ZF equaliser suffers from noise enhancement. The MMSE equaliser can mitigate the noise enhancement using the estimated Signal-to-Noise Ratio (SNR). The ZF-SIC and MMSE-SIC equalisers suffer from error propagation, and high computational complexity, respectively. In this paper, the Orthogonal Frequency Division Multiplexing (OFDM) system is modulated and demodulated using Inverse Discrete Wavelet Transform (IDWT), and DWT instead of Inverse Discrete Fourier Transform (IDFT) and DFT, respectively. Also, we propose a Joint Low-complexity Regularised ZF-SIC (JLRZF-SIC) equaliser that jointly performs the equalisation, and Carrier Frequency Offset (CFO) compensation with lower complexity using banded matrix approximation. The proposed JLRZF-SIC equaliser can accomplish the equalisation, and CFO compensation processes with low-complexity compared to the corresponding MMSE-SIC equaliser. Simulation results show that the proposed JLRZF-SIC equaliser outperforms different linearand non-linear equalisers.

This paper presents a new and simple decoding algorithm for layered space time block codes such as the two independent Alamouti's codes which are also called the double space-time transmit diversity (DSTTD) system. By using group interference suppression and successive interference cancellation, we can treat DSTTD as two independent space-time block codes (STBC). We can then decode both of these STBC's through a simple maximum likelihood (ML) detector with null space-based interference cancellation. We also compare the proposed interference cancellation (IC) scheme with the conventional MMSE IC scheme. The performance of the proposed IC scheme is comparable to that of the MMSE IC scheme while the complexity of the proposed scheme is lower than that of the MMSE IC scheme.

In body area networks, various sensors are attached to clothing or on the body or even implanted under the skin. The sensors measure such as heart beat, the record of prolonged electrocardiogram, blood pressure, and so on. In this paper, an improved Successive interference cancellation (SIC) scheme based on zero correlation zone sequences is proposed. Here ZCZ is used as a random code for TH PPM UWB system. Nodes in a WBAN are connected through wireless communication channel within a very close range. The decrease in internode distance leads to interference between devices. To reduce this interference, an enhanced successive interference cancellation scheme based on ZCZ with optimal ordering is adopted. Because of zero correlation property of ZCZ, the performance of TH PPM UWB system through WBAN channel with ZCZ sequences outperforms performance of existing zero correlation duration code. In this paper, performance of UWB system for various modulation schemes are compared. Performance of UWB/MIMO (\n\t\n\t\t\n\t\t\t\n\t\t\t\t2\n\t\t\t\t×\n\t\t\t\t2\n\t\t\t\n\n\t\t\n\t\n) system employing SIC with optimal ordering using ZCZ codes also compared with pseudorandom (PN) and ZCD codes. Simulation results are obtained using sample biological functions as input to the proposed TH PPM UWB/MIMO (\n\t\n\t\t\n\t\t\t\n\t\t\t\t2\n\t\t\t\t×\n\t\t\t\t2\n\t\t\t\n\n\t\t\n\t\n) system with m-ZCZ codes in WBAN environment with multiple devices.

In this paper, the authors propose a widely-linear (WL) receiver structure for multiple access interference (MAI) and jamming signal (JS) suppression in direct-sequence code-division multiple-access systems. A vector space projection (VSP) scheme is also considered to cancel the JS before detecting the desired signals. They develop a novel multiple-candidate successive interference cancellation (MC-SIC) scheme which processes two consecutive user symbols at one time to process the unreliable estimates and a number of selected points serve as the feedback candidates for interference cancellation, which is effective for alleviating the effect of error propagation in the successive interference cancellation (SIC) algorithm. WL signal processing is then used to enhance the performance of the receiver in non-circular modulation scheme. By bringing together the techniques mentioned above, a novel interference suppression scheme is proposed which combines the WL MC-SIC minimum-mean-squared error (MMSE) algorithm with the VSP scheme to suppress MAI and JS simultaneously. Simulations for binary phase shift keying modulation scenarios show that the proposed structure achieves a better MAI suppression performance compared with previously reported SIC MMSE receivers at lower complexity and a superior JS suppression performance.

This paper focuses on the usage of Equalization-Based receivers for Wideband Code-Division Multiple Access (WCDMA) Multiple Input, Multiple Output (MIMO) Bell Labs Layered Space Time (BLAST)-type systems. The main receivers on trial are the Zero-Forcing and Minimum Mean Square Error (MMSE) algorithm-based receivers and their variants, employing Parallel interference cancellation (PIC) and Iterative Partial Cancellation (IPC) schemes. To assess its performance in an existing system, the uncoded Universal Mobile Telecommunications System (UMTS) High-Speed Downlink Packet Access (HSDPA) standard was considered (using solely QPSK modulation) alongside the reference UMTS environments. The BER performance is assessed both by simulation and by semi-analytical processing.

The effect of unequal power reception in cellular MIMO networks

Turbo equalization schemes based on minimum mean square error (MMSE) criteria available in the literature for multiple-input multiple-output (MIMO) systems are computationally expensive, as they require a relatively large matrix inversion. In this paper, we propose a low complexity turbo equalization (TE) scheme with successive interference cancellation for orthogonal frequency division multiplexing (OFDM) based MIMO receiver systems (TE-SIC-MIMO). TE-SIC-MIMO leverages on the soft feedback symbol estimate to selectively remove the intercarrier interference (ICI) and co-antenna interference (CAI) from the received data, thus turning the system matrix into an easily invertible form. Extrinsic Information Transfer (EXIT) chart analysis supplemented with numerical simulation results shows that TE-SIC-MIMO performance under static and rapidly time varying multipath conditions is mostly on par with MMSE turbo equalization scheme available in the literature, that is based on a sub-matrix of the system matrix at signal-to-noise ratios (SNR) of practical interest. However, the computation complexity of TE-SIC-MIMO turns out to be much lesser than the TE scheme considered.