Investigation on Structure of Interference Canceller for IDMA-Based Random Access

Non-orthogonal multiple access (NOMA) has become the key technology in 5G communication. NOMA can achieve multi-user multiplexing in transmit power domain by allocating different power, which can effectively improve the spectral efficiency, but also causes the multiple access interference of the receiver signal. The parallel interference cancellation (PIC) technology is applied to NOMA system in order to solve the problem of high-delay and error propagation in the successive interference cancellation (SIC) algorithm. PIC can effectively compensate for the deficiency of SIC algorithm but it has high complexity. Combined with the advantages of SIC and PIC, a joint interference cancellation (JIC) method is proposed. The performance and complexity of the three algorithms are simulated and analyzed. The results show that JIC can effectively reduce the delay and improve the error propagation problem in the case of low complexity.

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.

A hybrid Interference cancellation (HIC) technique employing both Parallel and Successive Interference Cancellation (PIC/SIC) is proposed for Overloaded Direct Sequence Code Division Multiple Access (OCDMA) system under imperfect synchronization. Two types of receivers are proposed to efficiently mitigate the multiuser interference (MUI). In type I receiver, the MUI within group-1 users are first cancelled using Parallel Interference Cancellation (PIC). Then the multistage Successive Interference Cancellation (m-SIC) is performed on the resultant output of PIC to efficiently cancel the interference of group-2 users on group-1 users. The type II receiver is designed by performing PIC immediately followed by SIC and this combined process is repeated till a major chunk of multi user interference is cancelled. The BER performance of type II receiver is proved to be better than other cancellation techniques such as PIC, SIC and the proposed type I receiver.

In this paper, let's exhibit the exploitation of Gaussian Approximation (GA) based detection algorithm for Non-Orthogonal Coded Access (NOCA). NOCA belongs to one candidate solution of Non-Orthogonal Multiple Access (NOMA), recently discussed for future wireless communications towards 5th Generation (5G) New Radio (NR) standard. It is well known that GA based detection algorithm was very elegantly introduced in Interleave Division Multiple Access (IDMA). As being an iterative detection approach, the computational requirement belongs to one of the major focuses of GA based detection algorithms. Thus, in this paper, the efficiency in sense of complexity, suitable use cases of GA based detection will be investigated with respect to NOCA and IDMA by link level simulations. Numerical results reveals that both IDMA and NOCA are suitable for sporadic traffic. Especially, NOCA exhibits high detection efficiency for earlier iterations, and IDMA exhibits the capability of overloading and performance convergence under very low Signal-to-Noise Ratio (SNR).

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.

Interleave division multiple access (IDMA) is a potential candidate for the future fifth generation (5G) systems. In this paper, we propose a novel architecture for IDMA system with low latency while maintaining low complexity. In the conventional architecture, the IDMA receiver sequentially processes deinterleaving, despreading, spreading and interleaving for multiuser detection. The proposed architecture, which is called the interleaved domain, can perform multi-user detection directly without deinterleaving the received frame. Because of this, the interleaving is no longer needed in the interference cancellation loop resulting in the decrease of latency by half and the increase of throughput by twice. In VLSI implementation results, the proposed architecture has reduced circuit area and power consumption by 53% and 58% compared to the conventional architecture on the same throughput condition.

This paper presents a non-orthogonal multiple access (NOMA) concept for cellular future radio access (FRA) towards the 2020s information society. Different from the current LTE radio access scheme (until Release 11), NOMA superposes multiple users in the power domain although its basic signal waveform could be based on the orthogonal frequency division multiple access (OFDMA) or the discrete Fourier transform (DFT)-spread OFDM the same as LTE baseline. In our concept, NOMA adopts a successive interference cancellation (SIC) receiver as the baseline receiver scheme for robust multiple access, considering the expected evolution of device processing capabilities in the future. Based on system-level evaluations, we show that the downlink NOMA with SIC improves both the capacity and cell-edge user throughput performance irrespective of the availability of the frequency-selective channel quality indicator (CQI) on the base station side. Furthermore, we discuss possible extensions of NOMA by jointly applying multi-antenna/site technologies with a proposed NOMA/MIMO scheme using SIC and an interference rejection combining (IRC) receiver to achieve further capacity gains, e.g., a three-fold gain in the spectrum efficiency representing a challenging target for FRA.

Nonlinear interference cancellation multiuser detection algorithms have less BER and are less complex than linear multiuser detection methods. We present a hybrid switched mode detector that uses existing interference cancellation methods i.e. Parallel Interference Cancellation (PIC) and Successive Interference cancellation (SIC) based on channel conditions. This proposed detector takes decisions based on number of users on the channel and switches either to SIC method or PIC method. The switching mechanism is exploited by performance complexity tradeoff between matched filter detector and nonlinear interference cancellation methods.

Non-orthogonal multiple access (NOMA) is the solution to accommodate tremendous increase in Internet of things (IoT) applications. In interleave division multiple access (IDMA) systems, NOMA is realized using distinguished interleavers for every user. Here, we suggest a recursive successive interference cancellation (SIC)-based IDMA receiver structure for NOMA systems. With unequal optimum power distribution among multiple users, SIC has been implemented in a recursive manner. Chip-by-chip (CBC) multi-user detection (MUD)-IDMA receiver along with recursive SIC structure has been simulated under different simulation environments. The simulation results suggest the effectiveness of the receiver for dense 5G networks in future.KeywordsInterleave division multiple accessNon-orthogonal multiple accessUnequal power allocationRecursive successive interference cancellation

Non-orthogonal multiple access (NOMA) has been viewed as a promising technology in future cellular network to increase channel capacity and frequency efficiency. This NOMA system utilizes power domain to improve the performance of multiple access. Signal detection of a near user is operated by successive interference cancellation (SIC). With SIC, the near user cancels out the signal of far user and decodes its own data. Thereafter, the near user drops the cancelled data if SIC is successful. On the other hand, the far user still needs that the far user data may be retransmitted in case of far user reception failure, i.e., no-acknowledgement. Therefore, retransmission to the far user via the near user is efficient when the near user reuses its cancelled data. In this paper, we investigate more efficient way to conduct hybrid automatic repeat request (HARQ) in NOMA. If the SIC procedure of near user is successful, there is an effective approach to recycle the interference-cancelled data. This concept contains full duplex MIMO technique on near user to support the far user. It is found that the proposed retransmission method provides improvements in view of outage probability, symbol error rate (SER), and throughput of far user.

A Hybrid Interference Cancellation technique for overloaded CDMA with timing offset error

The non-orthogonal multiple access (NOMA) is one of the fledging paradigms which next generation radio access technologies are sprouting toward. The NOMA with superposition coding (SC) in the transmitter and successive interference cancellation (SIC) at the receiver comes with many desirable features and benefits over orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) adopted by Long-Term Evolution (LTE). In this paper, we study the recent research trends on NOMA in 5G systems. We discuss the basic concept of NOMA and explain its aspects of importance for future radio access. Then, we provide a survey of the state of the art in NOMA for 5G systems in a categorized manner. Further, we analyze the NOMA performances with numerical examples; and provide some avenues for future research on NOMA on a set of open issues and challenges.

Vehicular communication network is a core application scenario in the fifth generation (5G) mobile communication system which requires ultra high data rate and ultra low latency. Most recently, non-orthogonal multiple access (NOMA) has been regarded as a promising technique for future 5G systems due to its capability in significantly improving the spectral efficiency and reducing the data transmission latency. In this paper, we propose to introduce NOMA in D2D-enabled V2X networks, where resource sharing based on spatial reuse for different V2X communications are permitted through centralized resource management. Considering the complicated interference scenario caused by NOMA and spatial reuse-based resource sharing in the investigated NOMA-integrated V2X networks, we construct an interference hypergraph to model the interference relationships among different communication groups. In addition, based on the constructed hypergraph, we further propose an interference hypergraph-based resource allocation (IHG-RA) scheme with cluster coloring algorithm, which can lead to both effective and efficient QoS-guaranteed resource block (RB) assignment with low computational complexity. Simulation results verify the efficiency of our proposed IHG-RA scheme for NOMA-integrated V2X communications in improving the network sum rate.

For ultralow-power Internet of Things, we consider a monostatic multiantenna backscatter communication network (MBCN) supporting massive devices through nonorthogonal multiple access (NOMA) over space division multiple access (SDMA). For the network, we optimize the transmit beamforming (BF) for signal excitation of a reader, reflection coefficients of devices for backscattering and energy harvesting, and receive BF for information decoding at the reader toward the maximum fairness in data collection. We first show that the optimization problem for the MBCN without successive interference cancellation (SIC) has a similarity with the problem considered for a wireless power communication network but the conventional algorithm is not applicable to the MBCN with SIC. Thus, we propose a new alternating optimization algorithm that is applicable to both problems with and without SIC at a lower complexity. Simulation results show that the proposed algorithm provides a remarkable gain over the conventional one for the MBCN with SIC while exhibiting a similar performance for the MBCN without SIC. In addition, NOMA/SDMA enhanced by the proposed algorithm increases the minimum system throughput as well as the total energy harvested in the network by utilizing limited resources more effectively for a larger number of devices.

Interleave Division Multiple Access (IDMA) is a recently proposed technique for multiple access of wireless communication. In this paper we have IDMA for Optical Fiber medium. In IDMA user specific interleaver are assigned to distinguish the various users. Thus, for good BER, low computational complexity, low bandwidth requirement interleaver should be designed cautiously. Although the performance of optical IDMA can be further improved by using various interleaving schemes. In this work the two interleaving scheme (Random Interleaver and Tree Base Interleaver) is compared in terms of computational complexity and memory requirement to store the interleaving sequences.