Division Multiple Access Research Articles

Design of concatenative complete complementary codes for CCC-CDMA via specific sequences and extended Boolean functions

A complete complementary code (CCC) consists of M sequence sets with size M. The sum of the auto-correlation functions of each sequence set is an impulse function, and the sum of cross-correlation functions of the different sequence sets is equal to zero. Thanks to their excellent correlation, CCCs received extensive use in engineering. In addition, they are strongly connected to orthogonal matrices. In some application scenarios, additional requirements are made for CCCs, such as recently proposed for concatenative CCC (CCCC) division multiple access (CCC-CDMA) technologies. In fact, CCCCs are a special kind of CCCs which requires that each sequence set in CCC be concatenated to form a zero-correlation-zone (ZCZ) sequence set. However, this requirement is challenging, and the literature is thin since there is only one construction in this context. We propose to go beyond the literature through this contribution to reduce the gap between their interest and our limited knowledge of CCCCs. This paper will employ novel methods for designing CCCCs and precisely derive two constructions of these objects. The first is based on perfect cross Z-complementary pair and Hadamard matrices, and the second relies on extended Boolean functions. Specifically, we highlight that optimal and asymptotic optimal CCCCs could be obtained through the proposed constructions. Besides, we shall present a comparison analysis with former structures in the literature and examples to illustrate our main results.

Fast-Convergence Digital Signal Processing for Coherent PON Using Digital SCM

It is foreseeable that the 100 Gb/s/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> and beyond passive optical network (PON) will be required in future optical access networks to meet the explosive growth of data traffic. The coherent optical systems could be a promising solution for the future beyond 100G PON. Coherent PON using digital subcarrier multiplexing (DSCM) can provide flexible bandwidth allocation to a large number of access subscribers by dividing subcarriers of the DSCM signal into time slots for time-and-frequency division multiple access. When the optical network unit is allocated a new subcarrier, digital signal processing (DSP) should converge fast in the allocated time slot to ensure a low handoff latency for real-time bandwidth allocation. However, the traditional coherent DSP is hard to realize fast convergence due to blind and complex algorithms. In this paper, we design a specific training sequence (TS) structure and propose data-aided DSP to achieve fast convergence for coherent PON. The feasibility of the proposed scheme is experimentally verified in an 8 Gbaud/SC×8 SCs 400 Gb/s-net-rate coherent PON using DSCM with 16 quadrature amplitude modulation. The experimental results show that fast convergence is jointly realized by the proposed TS structure and data-aided DSP using a 416-symbol TS with a 52 ns duration. The receiver sensitivity at the 20% soft-decision forward error correction limit is approximately -27 dBm and an optical power budget of about 35.5 dB is achieved with a booster amplifier.

Evaluation of ACF, CCF, RAC, RCC and MF Properties of Different Spreading Sequences Used in DS-CDMA Systems

This paper investigates the different sequences that can be used in direct sequence divisionmultiple access (DS- CDMA) systems. The auto-correlation, cross correlation, the mean square correlationmeasurements ( RAC, RcC ) and merit factor (MF) are used for evaluating the performance of differentspreading sequences. The results obtained small set of Kasami sequences is the most effective of binarysequences families in terms of correlation measure, but this set suffers from the limited number ofsequences. Overall among orthogonal category, Orthogonal Gold sequences and Golay complementarysequences are a better candidate in synchronous CDMA applications.

IRDB: Towards enjoying spatial, rate, and beam‐channel diversity in wireless networks for multimedia applications

AbstractThis work studies the problems of routing, beam‐channel selection, space/time division multiple accessing, and admission control for multi‐rate wireless networks equipped with directional antennas. The spatial diversity obtained by directional antennas enables neighboring nodes to use a same physical wireless channel simultaneously. On‐demand multimedia flows are considered, where each accepted multimedia request develops a bandwidth‐guaranteed tree. We propose a cross‐layer algorithm, named “interference and rate‐aware directional broadcasting (IRDB),” to efficiently improve the resource allocation in the network. In order to build the routing tree, the proposed algorithm jointly uses all three spatial, channel, and rate diversities. We also introduce an efficient interference‐ and rate‐aware metric for covering more neighboring nodes at the highest possible rate. As an advantage, it not only reduces the resource consumption, but also decreases interference. IRDB greedily schedules a new admitted session without re‐routing or violating the quality of service constraints of current sessions. Numerical results show that the proposed IRDB scheme achieves improved performance in terms of occupied time slots and call acceptance rate.

A Novel Modified Artificial Bee Colony for DOA Estimation

Aims: We consider the Direction of Arrival (DOA) estimation for code division multiple access (CDMA) signals. Background: Solving this problem requires non-linear optimization and thus the speed of convergence becomes crucial. Objective: A novel Modified Artificial Bee Colony (MABC) has been proposed. We use secondorder Taylor series expansion of the cost function to ameliorate the searchability of artificial bee colony (ABC) for finding the globally optimal solution. Methods: The main idea is to harness the exploration and exploitation features. The optimum point of second-order Taylor expansion of cost function is used as a velocity factor of the ABC algorithm. Results: The proposed technique is used for solving the DOA estimation problem of a CDMA system. Simulation results confirm the performance improvement of our proposed algorithm. Conclusion: The cost function of the DOA estimation usually leads to a non-linear optimization problem. Using evolutionary algorithms can improve convergence rate of such problems.

Iterative Invertible Clipping Method for PAPR Reduction in Wireless MC-CDMA Communication Systems

Background &amp; Objective: One of the disadvantages of Multi-carrier Code Division Multiple Access (MC-CDMA) system is the high value of Peak to Average Power Ratio (PAPR). This paper proposes an approach called Iterative Invertible Clipping Method (IICM) to address the PAPR for MC-CDMA signal based on wireless communication system characteristics. This is mainly concentrated in clipping function making use of a polynomial of degree three at the transmitter, and its inverse at the receiver, to recover the original signal. Method: A Fast Fourier Transform (FFT)-based frequency domain filter is employed to reduce the overall peak regrowth which is supported by measuring the Adjacent Channel Power Ratio (ACPR) after soft clipping and filtering. This technique is compared with Ragusa method using a polynomial of degree 5. Result: The simulated results of the proposed method showed better performance in terms of PAPR reduction, Bit Error Rate (BER), and computational complexity requiring two iterations only. The Complementary Cumulative Complementary Density Function (CCDF) is served to measure and improve PAPR performance of the system. Conclusion: The channel coding process is applied to strengthen the obtained results in the Additive White Gaussian Noise (AWGN) channel and fading channel (Rayleigh). The High-Power Amplifier (HPA) is used for validation purposes.

Multiple Access MmWave Design for UAV-Aided 5G Communications

Unmanned aerial vehicles (UAVs) have tremendous potential to improve wireless network capacity, but are challenging to operate in ultra-dense networks, mainly due to the strong interference received from the dominated lineof- sight channels of the UAVs. By forming multiple highly directional beams, millimeter-wave (mmWave) communication technology allows concurrent user transmissions via beam-division multiple access (BDMA), and thus has emerged as a promising solution to mitigate interference for the fifth generation (5G) UAV communication. However, due to the limited number of beams generated in practical mmWave communication systems, conventional BDMA cannot meet the ever increasing capacity requirement. A new multiple access technique is intensely desired. In this article, we integrate mmWave communication with UAV-aided 5G ultra-dense networks, and design a novel link-adaptive constellation- division multiple access (CoDMA) technique. We discuss key challenges in efficient multiple access technique design, and then investigate design principles on new multiplexing methods and beamwidth optimization for interference management in UAV-aided dynamic networks. We further apply flexible constellation division in rateless codes, and put forward the system-level design of CoMDA with beamwidth adaptation to unleash the multiplexing gain. Finally, we show that our design can successfully enable multiple-user access within a single beam without causing any intra-beam interference while efficiently mitigating interference from adjacent beams. We also demonstrate that the proposed design is adaptive to the UAV network dynamics, and can greatly improve the system throughput.

Performance analysis of FSO/CDMA system based on binary symmetric wiretap channel

Transmission reliability, security, and efficiency are of great importance to free space optical (FSO) communication. For the first time, the authors obtain optimal parameters for the FSO/code division multiple access (CDMA) system taking into account the transmission reliability, security, and efficiency simultaneously. By establishing the eavesdropping model of the FSO/CDMA binary symmetric wiretap channel (BSWC), the performance of physical-layer security and reliability are evaluated simultaneously. Intercept probability is derived for FSO/CDMA BSWC, considering atmospheric attenuation, atmospheric turbulence, shot noise, thermal noise, background noise and multiple access interference (MAI). The effects of transmission distance, code length, transmission power and a number of interfering users on the physical-layer security and reliability are discussed. It is shown that, in order to meet the legitimate user's reliability and security simultaneously, the number of interfering users and code length must be in a certain interval. Furthermore, the maximum spectral efficiency can be obtained by selecting the transmission rate. These results open a new way of researching the FSO/CDMA system, where security, reliability, and spectral efficiency should be taken into account simultaneously.

Low-Cost Implementation Techniques for Interleave Division Multiple Access

We consider a low-cost code shift division multiple-access (CSDMA) scheme, in which user-specific shifting is used to replace user-specific interleaving in interleave division multiple access (IDMA). We also outline a low-cost Gaussian approximation-based linear minimum mean square error message passing detection technique for CSDMA. We show that CSDMA can offer almost the same performance as the original IDMA in low-density parity-check or turbo coded systems, but with considerably lower implementation cost.

A signal power adaptive regularized sphere decoding algorithm based multiuser detection technique for underdetermined OFDM/SDMA uplink system

SummaryThis work considers a regularized Fincke‐Pohst Sphere Decoder (R‐FSD) to detect the multiuser data of orthogonal frequency division multiplexing/space division multiple access (OFDM/SDMA) uplink system with underdetermined and rank‐deficient channel. Rank‐deficiency of the detected channel coefficients makes error‐free multiuser detection (MUD) a difficult task. In literature, most of the papers deal with either a determined or over‐determined full‐rank system. The method proposed in this work transforms an original ill‐posed least squares (LS) problem to a well‐posed one at the receiver, by using the standard Tikhonov regularization method. This is an efficient, direct, and less complex approach where the channel is modified using a regularization parameter that adapts to the signal power at the receiver. The result obtained is compared with maximum likelihood (ML), zero forcing (ZF), minimum mean squared error (MMSE) and ordered successive interference cancellation (OSIC) based detection techniques.

A common gate LNA with negative resistance for noise reduction

This paper presents a common-gate (CG) low-noise amplifier (LNA) using a novel negative resistance to improve its noise figure (NF). The new negative-resistance CG-LNA (NR CG-LNA) shows superior performance over the conventional CG-LNAs in terms of power consumption, gain and NF. A prototype designed in 180 nm CMOS technology, occupied a silicon area of 0.57 mm2. The post layout simulations show a maximum gain of 20.2 dB, and a minimum NF of 2.3 dB with 8.5-mW of power consumption operating in 1.95 GHz–2.3 GHz bandwidth, which could be used in Wideband Code- Division Multiple Access (WCDMA) applications.

Test method for narrowband F/TDMA-based wireless sensor/actuator networks including radio channel emulation in severe multipath environments

Abstract. A test method for narrowband wireless sensor/actuator networks is presented, facilitating affordable and efficient performance and compliance tests prior to the deployment of the wireless communication systems. Commonly used channel models are examined to derive a worst-case test scenario. Employing frequency/time division multiple access (F/TDMA) techniques and protocol synchronization, a new and efficient test method is suggested, where the equipment under test (EUT) is evaluated under the worst-case scenario. A cost-efficient channel emulator is introduced to emulate fading in multipath environments. Also, industrial interferes can be included in the setup. Furthermore, a procedure to test wireless devices with integrated, non-detachable antennas is presented.

Performance analysis of an interference cancellation technique for radio navigation

This study describes the theoretical performance of a successive interference cancellation (IC) technique as an electronic counter countermeasure and verifies its feasibility through experiments. In a radio navigation system using direct sequence/code division multiple access, strong pseudorandom signals can be used as interference sources for unauthorised users when regional radio navigation needs to be denied in a specific area, while authorised users can use both the strong signal and the global navigation satellite system (GNSS) ranging signal for navigation through the IC method. To determine the feasibility of this selective jamming concept, this study investigated its theoretical performance and compared the results with experimental ones. The experimental results show that a maximum jamming-to-signal ratio performance of 57 dB or higher can be achieved, which is similar to the theoretical estimation.

5G: MIMO BDMA System Trends and Technology

Beam Division Multipleaccess(BDMA) is The last techniquecame to create the fifth-generation (5G) and solving the problem in the fourth generation (4G). In which base station (BS) allocates private beam to the mobile station (MS) in the system, to increase the capacity and bandwidth of system. For that antenna beam is divides according to the speed and location of mobile stations. In mobile wireless communication the important thing is how to increased limited frequency of the system, improve data rate and good quality of services for user etc. This paper presents information about BDMA and explain the differenttechnologies,and which we want to making future mobile with more powerful and more in demand.Useful thing in BDMA technique is the large number of users to connect at the same time by direction of orthogonal beam from BS by giving multiple access to MS, and increasing the ability of system to be established very big channel. Direction of antenna beam goes off the desired location of MS, and void are placed in undesired direction depend on work environment.

A New Link Scheduling Algorithm for 60 GHz-WPAN Communication System

With apparent advantages of several GHz license-free spectra, low power consumption, low-cost implementation of CMOS devices, and so forth, 60 GHz wireless communication technology becomes the first choice for short-range high rate wireless communication in future wireless personal area network (WPAN) and wireless local area network (WLAN). While different from common WPAN system with omnidirectional communication, 60 GHz-WPAN system generally adopts directional communication. In this paper, a device (DEV) interconnected mechanism of 60 GHz-WPAN based on switched beamforming technology is structured firstly. Without considering the directional transmission characteristic of 60 GHz communication, most of the 60 GHz-WPAN Medium Access Control (MAC) protocols fail to make full use of the high spatial reuse degree caused by directional communication. In this paper, an average time slot multiplexing allocation (ATSMA) algorithm based on space/time division multiple access (STDMA) solution is proposed, which allows concurrent transmission in a single time slot. The designed link schedule process includes common channel interference (CCI) probing scheme, link coexistence determination scheme, and link schedule algorithm. Extensive simulations are conducted in order to demonstrate the efficiency of proposed scheme. Simulation results demonstrated that the capacity gain is obvious using ATSMA algorithm, no matter whether under omnidirectional antenna or under directional antenna.

Radio Resource Allocation in SC-FDMA Uplink with Resource Adjacency Constraints

Radio Resource Allocation (RRA) in cellular systems is a relevant and difficult task that shouldassign the system resources in the most efficient manner while fulfilling different constraints suchas Quality of Service (QoS). In wireless systems that employ Single Carrier - Frequency DivisionMultiple Access (SC-FDMA) as in Long Term Evolution (LTE) uplink, RRA is even more difficultsince the frequency resources should be assigned in contiguous blocks of subcarriers to eachterminal. In this work we study two important RRA problems in SC-FDMA: the total data ratemaximization and the total data rate maximization with minimum user satisfaction constraints. Weformulate them as optimization problems and show that the optimal solutions are not practical tobe employed in real systems due to the high computational complexity. Therefore, we propose twoefficient heuristic solutions for those problems. By simulation results, we show that both solutionsare near optimal and subject only to small performance degradation compared to the complex andimpractical optimal solutions.

A low‐complexity turbo MUD for MU–MIMO SC‐FDMA systems

AbstractIn order to provide high‐quality services, current communication systems require high data‐transmission rate and good error performance. Single carrier‐frequency division multiple access (SC‐FDMA) has been adopted as the uplink transmission standard in fourth generation cellular network to enable the power efficiency transmission in mobile station. Multi‐user multiple‐input multiple‐output (MU–MIMO) technologies are adopted in many standards to enhance the data rate and the link robustness. By combining MU–MIMO techniques with the SC‐FDMA modulation scheme, MU–MIMO SC‐FDMA systems can achieve high data rates over broadband wireless channels. For MU–MIMO SC‐FDMA systems, possible detection techniques include zero‐forcing detection, minimum mean squared error detection and maximum likelihood detection (MLD). Among these schemes, MLD is optimal, but its complexity grows exponentially with the number of symbols detected. As a result, there are demands for near MLD schemes that provide similar performance with less complexity. In this paper, we consider the MU–MIMO SC‐FDMA communication and propose a low‐complexity and high‐performance turbo receiver for the systems. Some simulation examples for uplink scenario are given to demonstrate the effectiveness of the proposed scheme. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Algoritimos Heurísticos Aplicados à detecção Multiusuário DS/CDMA DOI: 10.14209/jcis.2005.11

The characteristics of nine heuristic algorithms based on genetic evolution theory and local search, applied to a DS/CDMA (Direct Sequence/Code Division Multiple Access) multi-user detection problem in Flat Rayleigh fading channel are introduced. The algorithms comparisons through the performance versus computational complexity tradeoff are carried out. The computational complexity is determined in terms of the number of operations to reach the Maximum Likelihood (ML) performance. The effects on the performance of the errors in the estimates of the channel coefficients are also considered, as well as the performance degradation due to overload. There are three contributions in this work: a) a compared analysis of the evolutionary, evolutionary with cloning and local search algorithms applied to MuD detector in Flat Rayleigh channels; b) a systematic comparison of these algorithms in terms of the same simulation scenario and performance analysis base; c) a more fair and precise complexity analysis for the MuD detector in terms of the number of the computational operations.

A Novel Multiuser Detector Based on Restricted Search Space and Depth-First Tree Search Method in DS/CDMA Communication Systems

In this paper, we consider an improved and efficient algorithm for the multiuser detection (MUD) in direct sequence/code division multiple access (DS/CDMA) communication systems. The optimum detector for MUD is the maximum likelihood (ML) detector, but its complexity is very high and it calls for an optimization problem that involves an exhaustive search. Consequently, there has been considerable interest in suboptimal multiuser detectors with less complexity and reasonable performance. The idea of reducing the complexity by sub-optimum detectors was efficient and applicable but had some defects. The idea proposed in this paper is the restriction of the search space. This idea comprises using a sub-optimum detector such as ordinary genetic algorithm for which the size of the search space is confined to a predetermined region that is smaller than the whole search space. This limited region includes the objective bit sequence. Then by using depth-first tree search algorithm, we could find the optimum bit stream. We compare our algorithm to the ML detector, the genetic algorithm with conventional detector, and the ant colony optimization (ACO) detector which have been used for MUD in DS/CDMA. Simulation results show that the performance of this algorithm is near the optimal detector with very low complexity, and works better in comparison to other algorithms.

EASO-TDMA: enhanced ad hoc self-organizing TDMA MAC protocol for shipborne ad hoc networks (SANETs)

As very high frequency (VHF) data links are overloaded due to the rise of Automatic Identification System (AIS) applications, additional VHF channels and the development of corresponding communication technologies are necessary. For this reason, shipborne ad hoc networks (SANETs) and the medium access (MAC) protocol for SANETs,ad hoc self-organizing-time division multiple access (ASO-TDMA), have been proposed, which provide ocean-going ships with diverse data services cost-effectively. In this paper, a new MAC protocol for SANETs, enhanced ASO-TDMA (EASO-TDMA), is proposed in order to manage the bottleneck and under-utilization problems resulting fromASO-TDMA and thus enhances the overall performance of SANETs. To accomplish this, in EASO-TDMA, a ship adaptively allocates its time slots according to the number of subscribing ships, which make their communication route to a base station at the shore via the ship, by referring to the routing table. The performance of EASO-TDMA is investigated through simulations and compared with that of ASO-TDMA. The simulation results indicate that EASO-TDMA outperforms ASO-TDMA, regardless of the network conditions, with 25 % higher reception success rate, 25 % lower collision rate, and 21 % higher channel utilization at maximum. In particular, the end-to-end delay of EASO-TDMA is on average 1/12 of that of ASO-TDMA, and this implies that EASO-TDMA can be effective for delay-sensitive data services.