Control packet signaling mechanism using electronic code division multiple access for packet-based networks

We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical amplifier placed in the receiver terminal of the network. The resulting optical tap power that is required for the successful monitoring of the electronic code division multiple access based control signals are compared with that of the case without the amplifier.     

Performance analysis of electronic code division multiple access based virtual private networks over passive optical networks

A solution for implementing multiple secure virtual private networks over a passive optical network using electronic code division multiple access is proposed and experimentally demonstrated. The multiple virtual private networking capability is experimentally demonstrated with 40 Mb/s data multiplexed with a 640 Mb/s electronic code that is unique to each of the virtual private networks in the passive optical network, and the transmission of the electronically coded data is carried out using Fabry-Perot laser diodes. A theoretical scalability analysis for electronic code division multiple access based virtual private networks over a passive optical network is also carried out to identify the performance limits of the scheme. Several sources of noise such as optical beat interference and multiple access interference that are present in the receiver are considered with different operating system parameters such as transmitted optical power, spectral width of the broadband optical source, and processing gain to study the scalability of the network.     

A New Algorithm for Development of Dynamic Cyclic Shift Code for Spectral Amplitude Coding Optical Code Division Multiple Access Systems

Abstract

This article presents a new code—the dynamic cyclic shift code—for spectral amplitude coding–optical code division multiple access systems. One of the important properties of the dynamic cyclic shift code is that the number of users can be increased without increasing the weight value. System performance was evaluated by using both theoretical analysis as well as the simulation experiment. The analysis results show that the proposed dynamic cyclic shift code can support more users in spectral amplitude coding–optical code division multiple access systems compared to spectral amplitude coding–optical code division multiple access codes. It was ascertained by performance evaluation that the dynamic cyclic shift code possesses ideal properties for use in spectral amplitude coding–optical code division multiple access systems.     

Distributed dynamic spectrum access through multi-agent deep recurrent Q-learning in cognitive radio network

This paper addresses the problem of distributed dynamic spectrum access in a cognitive radio (CR) environment utilizing deep recurrent reinforcement learning. Specifically, the network consists of multiple primary users (PU) transmitting intermittently in their respective channels, while the secondary users (SU) attempt to access the channels when PUs are not transmitting. The problem is challenging considering the decentralized nature of CR network where each SU attempts to access a vacant channel, without coordination with other SUs, which result in collision and throughput loss. To address this issue, a multi-agent environment is considered where each of the SUs perform independent reinforcement learning to learn the appropriate policy to transmit opportunistically so as to minimize collisions with other users. In this article, we propose two long short-term memory (LSTM) based deep recurrent Q-network (DRQN) architectures for exploiting the temporal correlation in the transmissions by various nodes in the network. Furthermore, we investigate the effect of the architecture on success rate with varying number of users in the network and partial channel observations. Simulation results are compared with other existing reinforcement learning based techniques to establish the superiority of the proposed method.     

Adaptive RAKE receiver in chaos based pilot-added DS-CDMA system

This paper presents the theoretical analysis of adaptive multiuser RAKE receiver scheme in frequency selective fading channel for direct-sequence code division multiple access (DS-CDMA) system. Least mean square (LMS) algorithm is used to estimate the channel coefficients. Chaotic sequences are used as spreading sequence and corresponding bit error rate (BER) in closed form is derived for imperfect channel estimation conditions. Performances of chaotic sequences are compared with pseudorandom noise (PN) sequences. Under perfect synchronization assumption, various simulation results are shown to investigate the performance of the proposed system.     

A novel multipriority reservation protocol for plastic optical fiber access network

In this paper, a novel multipriority reservation protocol for plastic optical fiber access network based on optical code division multiplexing access (OCDMA) technology is proposed. Conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels. The protocol is proposed to resolve this problem. By using the reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict can be avoided. The protocol can efficiently support the transmission of multimedia messages that require the different time-delays. At the same time, each optical network unit is equipped with a fixed optical encoder/decoder that is always tuned to channel for control and the tunable optical encoder/decoder that is tuned to any of channel for data. The network throughput and average delay have been investigated by numerical analysis and simulation experiments. It is shown that the multipriority reservation protocol in this POF access net     

多基地空时码探测信号设计及时反相关检测技术

为实现浅海复杂环境下的多基地声纳多源目标回波分辨,本文设计了一种适用于多入多出垂直阵信道环境下的空时码探测信号,并针对倾斜垂直阵的多途子信道差异问题,提出了信号的时反相关检测技术.空时码探测信号采用伪随机信号调制,具有良好的正交性,能在抗子信道严重衰落的同时,分辨多源目标回波.垂直阵受水流冲击,呈倾斜状态时,其多途子信道不一致性会导致各子信道传递信号无法在接收端聚焦,使阵列增益受损,同时导致时延测量能力下降和信号判决错误率上升,为此本文设计了信道训练信号用以估计多途子信道环境,通过虚拟时间反转镜获得子信道不一致条件下的最佳匹配检测信号,实现对接收信号的时反相关检测.仿真结果表明,本文所设计的探测信号和检测方法,能够克服复杂的信道条件和多途子信道不一致性引起的检测问题,满足多基地声纳探测需求,实现多源目标回波分辨.     

基于相位调制偏振态QKD系统的量子信道校正发送方案

提出了一种基于相位调制偏振态QKD系统的量子信道校正发送的新方案—采用波导型相位调制器研制成电控连续可调光学相移器,它可随相位调制器输入电压的连续改变而产生连续的相移,从而控制输出的偏振态;在其前放置一个半波片,即可校正接收端偏振态量子态在信道中所发生的改变,从而保证信道传送密钥的可用性.通过理论推导和实验研究验证了基于相位调制偏振态QKD系统的量子信道校正发送方案的核心部件的可行性.由于本方案能实现高速调制（GHz）,为解决光纤传输的偏振编码QKD系统中偏振态漂移问题提供了一种新的途径.     

CADF-CSE: Chaotic map-based authenticated data access/sharing framework for IoT-enabled cloud storage environment

Data is an essential asset of an organization or individual in this information age. Secure and resource-efficient data communication has become paramount in the IoT-enabled cloud storage environment. The users must communicate with the cloud storage servers to access, store, and share the data utilizing the public communication channel, which is exposed to various security threats. Moreover, various security frameworks have been presented to render secure data access, storage, and sharing functionalities for the cloud storage environment. Most of them are complicated and incapacitated of resisting various security attacks. Thus, it is imperative to design a secure and resource-efficient data access, storage, and sharing framework for the cloud storage environment. This paper presents a chaotic map-based authenticated data access/sharing framework for the IoT-enabled cloud storage environment (CADF-CSE). CADF-CSE is designed using the chaotic map, authenticated encryption scheme (AEGIS), and one-way hash function (Esch256). The proposed CADF-CSE comprises three significant phases user access control, data storage, and data sharing. The user access control phase enables the user and cloud server to attain mutual authentication followed by the secret session key establishment. Using the established SK during the access control phase user and cloud server exchange information securely across the public Internet. The data storage phase facilitates the data owner to store the data on a cloud server in encrypted form, where encryption is performed with a secret key derived from the user’s biometric. The data-sharing phase enables users to access the data from the cloud server after acquiring mutual permission from the cloud server and the data owner. In addition, an explication of the CADF-CSE through formal and informal analysis shows its resilience to various security attacks. Finally, the performance comparison explicates that CADF-CSE renders better security features while requiring lower computational and communication costs than the related security frameworks.     

A novel 2D-OCDMA system with dynamic optimum decision threshold by estimating the number of active users

A novel two dimensional optical code division multiple access (2D-OCDMA) system with dynamic optimum decision threshold by estimating the number of active users is proposed. The bit-error rates (BER) of the system is analyzed. By using one wavelength as the estimator of the number of active users, which is not assigned to any address code, the number of active users can be obtained. The dynamic optimum decision threshold can be obtained according to the multiple user interference (MUI), which can be obtained by cross-correlation characteristics between address codes and the number of active users.     

New design of spectral amplitude coding in OCDMA with zero cross-correlation

A zero cross-correlation (ZCC) code is proposed to reduce the impact of system impairment and multiple access interference (MAI) in spectral amplitude coding optical code division multiple access (SAC-OCDMA) system. Bit-error-rate (BER) performance is derived taking into account the effect of some noises. The key to an effective OCDMA system is the choice of efficient address codes with good or almost zero correlation properties for encoding the source. The use of ZCC code can eradicate phase induced intensity noise (PIIN) which will contribute to better BER. Thus, we demonstrate, theoretically, the performance of optical ZCC code. It is shown that optical ZCC code can accommodate more users simultaneously for the typical error rate of optical communication system of 10⁻⁹. The result indicates that the established system not only preserves the capability of suppressing MAI, but also improves bit-error-rate performance as compared to the conventional coders.     

Hybrid WDMA/OCDM system with the capability of encoding multiple wavelength channels by employing one encoder and one corresponding optical code

<正>A hybrid wavelength division multiple access(WDMA)/optical code division multiplexing(OCDM) system is proposed,where the optical code is not the same as the address of every optical network unit(ONU); rather,the code is a virtual fiber of hybrid passive optical network(PON).To our knowledge,this is the first report analyzing a single encoder/decoder with a single corresponding optical code being exploited to encode/decode multiple wavelength signals simultaneously.This system enables OCDM to become transparent to ONU so that the existing wavelength division multiplexing(WDM) PON can be upgraded. Thus,redesigning the optical line terminal and ONU can be easily accomplished,and greatly decreasing the number of encoder/decoder becomes possible.In experiment,we only employ two encoder/decoder pairs to combine two WDM-PONs in one fiber.Simulation results confirm the feasibility of the proposed system.     

Uplink CFO compensation for FBMC multiple access and OFDMA in a high mobility scenario

We study in this work CFO compensation methods for two multicarrier multiple access techniques in a high mobility scenario. In particular, we consider orthogonal frequency division multiple access (OFDMA) and filter bank multicarrier multiple access (FBMC-MA). The main motivation for this study is not only the different sensitivity these multicarrier techniques have to CFO but also the different methods they use to reduce CFO effect. In a high mobility scenario the CFO is re-estimated to follow its variation. We show that the frequency at which the CFO is re-estimated has a strong influence in the performance and the complexity of the proposed compensation methods. Additionally, we present a low-complexity CFO compensation method for OFDMA that employs a better approximation of the intercarrier interference than previous approaches. Regarding FBMC-MA, we introduce an extension of a CFO-compensation method that allows to consider a multitap channel equalizer. Finally, using simulations, we compare the performance of the compensation methods over several channel and time-varying CFO conditions.     

Multiple access interference cancellation in Manchester-coded synchronous optical PPM-CDMA network

A new interference cancellation technique for direct-detection optical code- division multiple-access (OCDMA) network employing pulse-position modulation (PPM) is proposed in this paper. The multiple access interference (MAI) estimation is achieved by pre-reserving one of optical spreading code sequences at the receiver based on the correlation property of padded modified prime codes (PMPC). The estimated interference is then cancelled out after photo-detection process. Additionally, the transmitted signal is Manchester-coded to further improve the system performance. Based on this proposed interference canceller in a shot-noise limited regime, we have obtained an expression for the upper bound of the bit-error probability (BEP) taking into account effects of both MAI and shot-noise. This BEP is compared with that of a PPM-OCDMA without cancellation. Finally, the receiver structure of the proposed optical network unit (ONU) is fairly simple to compare with the conventional cancellation schemes.     

Analysis of physical layer performance of hybrid optical-wireless access network

The hybrid optical-wireless access network (HOWAN) is a favorable architecture for next generation access network. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. In this paper, the HOWAN architecture is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. Most of the existing works, based on performance evaluation are concerned on network layer aspects. This paper reports physical layer performance in terms of the bit error rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the communication system. It accommodates 8 wavelength channels with 32 optical network unit/wireless access points (ONU/APs). It is demonstrated that downstream and upstream of 2 Gb/s can be achieved by optical backhaul for each wavelength channel along optical fiber length of 20 km and a data rate of 54 Mb/s per ONU/AP along a 50 m outdoor wireless link.     

Fast frequency modulation optical code division multiple access communication system

An optical fast frequency modulation code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code named functional code is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The performance of this system is shown to be better compared with a fast frequency hopping and a spectral amplitude coding systems.     

Multi-Access Channel Based on Quantum Detection in Wireless Optical Communication

In this paper, we propose a novel multi-user access in wireless optical communication based on the quantum detection of the coherent state. In this case, the coherent states are used as the signal carrier and a technique of quantum detection is applied to distinguish between signals from different users. To accomplish this task, two main quantum measurement methods are introduced; one is minimum error discrimination (MED), and the other is unambiguous state discrimination (USD). The theoretical derivation implies that the two methods can both distinguish between the signals from different users efficiently when the average photon number is large enough. Typically, the numerical result shows that in the two-user case, the channel capacity will approach the theoretical maximum limit when the average photon number is greater than 2.5 for MED and 5 for USD in the absence of noise. The MED gains more channel capacity than the USD at the same average photon number. However, the USD wins the error-correction scene with its free-error capability. Furthermore, the detection error probability and channel capacity for the USD with the thermal noise are examined. The result shows that increasing the signal average photon number can continue the USD’s advantage of error-free detection even if in the presence of thermal noise. In addition, compared with non-orthogonal multiple access (NOMA), the bit error rate (BER) against signal-to-noise rate (SNR) performance of USD has been improved.     

Fiber-wireless (FiWi) access network: Performance evaluation and scalability analysis of the physical layer

The fiber-wireless (FiWi) access network is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In this paper, the FiWi access network is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul with data rate of 2.5 Gb/s and wireless fidelity-worldwide interoperability for microwave access (WiFi–WiMAX) technologies at the wireless front-end along a 50 m–5 km wireless links with data rate of 54–30 Mb/s, respectively. The performance of the optical backhaul and the wireless front-end, in the proposed FiWi access network, has been evaluated in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR) of the physical (PHY) layer. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length of 24 km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10⁻⁹.     

Spectral efficient hybrid wireless optical broadband access network (WOBAN) based on transmission of wireless MIMO OFDM signals over WDM PON

In this paper, a spectral efficient hybrid wireless optical broadband access network (WOBAN) is proposed and demonstrated based on the transmission of wireless multi-input multi-output orthogonal frequency division multiplexing (MIMO OFDM) signals over wavelength division multiplexing passive optical network (WDM PON). By using radio over fiber (ROF) techniques, the optical fiber is well adapted to propagate multiple wireless services having different carrier frequencies. It is a known fact that multiple wireless signals having the same carrier frequency cannot propagate over a single optical fiber at the same time, such as MIMO signals feeding multiple antennas in fiber wireless (FiWi) system. A novel optical single-sideband frequency translation technique is designed and simulated to solve this problem. This technique allows four pairs of wireless MIMO OFDM signals with the same carrier frequency for each pair to be transmitted over a single optical fiber by using one optical source per wavelength. The crosstalk between the different MIMO channels with the same frequency is eliminated, since each channel is upconverted on specified wavelength with enough channel spacing between them. Also the maximum crosstalk level between the different MIMO channels with different frequencies is very low around ?76 dB. The physical layer performance of the proposed WOBAN is analyzed in terms of the bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). The proposed WOBAN achieves 7.68 Gb/s data rate for 20 km for the optical back-end and 240 Mb/s for the outdoor wireless front-end.     

Realization of 2-D OCDMA network using EDW code

The attraction towards two-dimensional optical code division multiple access (2D-OCDMA) systems has increased due to its potential in enhancing the performance of optical access networks and producing optical code-based signals. 2D-OCDMA network systems enable better bit-error-ratio (BER) performance as well as increase the number of supportable users in the optical network. Time-spreading wavelength-hopping is one of the many techniques that has been proposed for 2D-OCDMA. In this paper, we present the simulative study of a 2D-OCDMA system. The developed time-spreading, wavelength-hopping network utilizes enhanced double weight (EDW) code which has enhanced properties such as a cross-correlation value of 1 and has a simple encoder/decoder design. The output BER was satisfactory at above 10^?9 at data rate of 1.25 Gbps for 20 km distance with the ITU-T G.652 standard single mode optical fiber for 3 users.