Spatial Cognitive Engine Technology

By Jianjun Zhang and Jing Li

Spatial Cognitive Engine Technology discusses the increase in user demand for satellite wireless communication services that has led to the increasing development of spectrum resources and the fixed spectrum allocation mode which makes the utilization rate of spectrum resources lower. As an intelligent spectrum sharing technology, cognitive radio has innovated the traditional spectrum management system and is one of the effective ways to solve the above-mentioned problems. As the core of satellite cognitive radio, the spatial cognitive engine can use artificial intelligence to dynamically configure working parameters according to changes in the communication environment and user needs.

• Describes the concept of cognitive engine from the perspective of the spatial cognitive cycle
• Includes coverage of in-depth research on the input module of the spatial cognition engine, the environmental perception module
• Provides in-depth research that has been conducted on the learning reasoning and optimization decision-making modules of the spatial cognition engine
• Covers the cross-layer optimization of the spatial cognition engine to realize an intelligent and complete satellite communication mechanism

• Language: English
• Publisher: Academic Press
• Release date: Jun 15, 2023
• ISBN: 9780323958684

Jianjun Zhang

Jianjun Zhang, PhD, is a Professor at the Beijing Institute of Spacecraft System Engineering, China Academy of Space Technology, Member of the Youth Science Club of China Electronics Society, Member of the Edge Computing Expert of China Electronics Society, Chairman of the "Space (Aerospace) Information Technology," Professional Committee of China Electronics Society, and Member of the Satellite Application Expert Group of China Aerospace Society. He mainly engaged in satellite navigation system design and advanced spatial information system technology based on cognitive mechanism. He has presided over several major projects such as the National Natural Science Foundation's major research project, the final assembly fund, the 863 project, and the development project of the Science and Technology Commission of the China Academy of Space Technology. He has published more than 50 SCI/EI research papers in international journals and conferences, authorized more than 20 invention patents at home and abroad, and published 3 monographs. He won third prize of the National Defense Science and Technology Progress Award.

Book preview

Preface

The cognitive engine is the core module for realizing the intellectualization of the cognitive loop. Through the artificial intelligence technology, it realizes the perception, analysis, learning, decision-making, feedback, and other links and drives the whole cognitive cycle. The cognitive loop includes observation, judgment, implementation, and learning. The cognitive engine is responsible for managing and integrating the above four functions into a single device. In the closed cognitive loop, the judgment part is the next step of the observation part. This part is based on the analysis of the data obtained from the observation part. Its goal is to determine the corresponding optimal mode. The cognitive engine is considered as the brain of the cognitive loop and can support and process all algorithms including perception, classification, reconfiguration, and even management. The cognitive engine shall link all cognitive loops together to ensure the proper function of the equipment.

Software radio is a kind of radio communication technology based on radio communication hardware and running through software programming. Cognitive radio is an extension of software radio. Cognitive radio is based on software radio, adding independent cognitive and inference engine, knowledge base, and learning engine to achieve cognitive functions.

The cognitive engine in cognitive radio can summarize the known information stored in the knowledge base and the information stored in the radio station for a long time under the given requirements and draw conclusions. The learning engine is mainly used to accumulate knowledge base. Through continuous learning and summary of experience and lessons, the learning engine stores the knowledge obtained into the knowledge base for emergencies. In the working state of radio cognitive technology, the learning engine is not only used in the initial state of the system, but also in the process of regular operation of the equipment.

This book focuses on the research of space cognitive engine technology, gives the realization of satellite cognitive function and the process of combining cognition and radio, obtains information from user domain, radio domain and radio itself, realizes reasoning and learning based on artificial intelligence technology, stores the results of reasoning and learning in the knowledge base, and makes decisions based on the total long-term knowledge of the knowledge base.

Spatial cognitive engine is the core component of intelligent satellite, which realizes the reasoning and learning based on various artificial technologies on the satellite software radio platform and realizes and drives the entire cognitive loop. It can be said that spatial cognitive engine is the brain of satellite, and cognitive engine technology is the core technology to realize satellite intelligence.

Jianjun Zhang

Jing Li

Chapter 1: Cognitive radio

Abstract

This chapter explores the concept of cognitive radio according to the needs of wireless services and discusses its five salient features.

Keywords

Cognitive radio; Features; Perception; Spectrum

1.1. Introduction

With the continuous growth of wireless communication services, the demand for wireless services (such as mobile communications, public safety, radio, and television) continues to increase, making wireless spectrum an important national resource in modern society. Available frequency bands are tightening and the lack of spectrum resources is becoming serious. However, is there really a shortage of spectrum?

In essence, the shortage of spectrum exists mainly because the use of wireless spectrum resources is managed and coordinated by the national government, and the fixed spectrum management policy has caused the problem of serious shortage of spectrum resources in the use of wireless spectrum. Except for the very few industrial, scientific, and medical frequency bands, the frequency use policies of countries around the world mostly adopt a license system. However, not all licensed users occupy the licensed frequency bands continuously. Some frequency bands are not employed by users part of the time and some are occupied occasionally. Even if the system spectrum utilization rate is low, it is still unable to allocate the space spectrum to other systems, that is, it is unable to achieve spectrum sharing. Studies have shown that at any given moment, the spectrum used by people accounts for only 2% to 6% of all available spectrum, so wireless communications face the problem of the shortage and waste of spectrum resources.

The root of this problem is that existing wireless communication technology is difficult to adapt to the dynamic changes of the environment. Cognitive science theory provides a good idea for solving this problem. Cognitive science studies the information processing of human perception and thinking, including from sensory input to solving complex problems, and from human individuals to the intelligent activities of human society and the nature of human intelligence and machine intelligence. The cognitive system makes plans, decisions, and executions through observation and learning of the environment, so that the system adapts to the dynamically changing environment [1].

To solve the problem of the insufficient radio-frequency spectrum, the concept of cognitive radio was clearly proposed for the first time in IEEE Personal Communications journal in Aug. 1999 by a consultant for MITRE, Professor Joseph Mitola of the Royal Swedish Institute of Technology. In a broad sense, cognitive radio means that the wireless terminal has sufficient intelligence or cognitive ability to detect, analyze, learn, reason, and plan the history and current conditions of the surrounding wireless environment, and to use the corresponding results to adjust its own transmission parameters. The most suitable wireless resource completes the wireless transmission. Cognitive radio systems employ unused spectrum holes in licensed frequency bands to improve spectrum use and effectively employ various idle channels in different regions and many time periods. This technology was quickly adopted as a possible solution to deal with the spectrum resource crisis. Cognitive radio uses this frequency band to send signals when it detects that a specific authorized frequency band is not used within a specific range, and to ensure that it does not cause significant interference to the transmission of authorized users.

After the concept of cognitive radio was proposed, the US Federal Communications Commission (FCC) opened an additional part of the authorized spectrum to commercial applications, pointing to the need to adopt cognitive radio technology, and established the Wireless Spectrum Policy Task Force in Jun. 2002 to formulate the work policy of smart wireless communications. This policy uses a number of technologies such as cognitive radio, avoids channels in use, and dynamically allocates frequencies. In Dec. 2003, the FCC announced an amendment to Chapter 15 of the FCC Rules (Rule Part l5), which is equivalent to the Radio Wave Act of the United States. Terminals can also use existing wireless frequency bands that need to be licensed. It also legalized the use of cognitive radio in the 5-GHz and TV frequency bands, laying the foundation for the development of cognitive radio.

In 2003, Raytheon, which is engaged in developing high-end military equipment, accepted the contract for the development of the Next Generation Communication (XG) program from the Defense Advanced Planning Agency. The goal of the XG plan is to solve the problem of opportunistic spectrum access comprehensively. In terms of top-level design, the plan has two sets of goals: to develop technologies that can achieve opportunistic spectrum access, and to achieve flexibility in strategies to apply a framework structure. Fig. 1.1 shows the XG plan based on cognitive radio [2].

The XG plan is an autonomous dynamic spectrum use plan. It perceives a wider frequency band and then determines the existence of basic users and describes the characteristics of available timing. Then, it determines the strategy set based on these characteristics and determines an optimal plan, finally coordinating the use of available timing based on the optimal plan.

Through the XG program, the US military has increased its spectrum efficiency 10–20 times. The program promotes the research and application of cognitive radio technology in the field of military communications. Whether it is conducting military exercises overseas or training at home, the issue of spectrum planning has always been a problem that the military field hopes to overcome. With cognitive radio technology, the military will no longer be limited to a static frequency plan, but can fundamentally meet changes in demand.

Figure 1.1  XG plan based on cognitive radio.

In Nov. 2004, the Institute of Electrical and Electronics Engineers (IEEE) 802.22 working group was formally established. Its main task is to develop and establish a set of regional network air interface standards based on cognitive radio technology that uses the temporarily idle spectrum of the existing TV frequency band for wireless communications. The standard is based on cognitive radio technology, which perceives and measures TV frequency bands, uses dynamic spectrum management technology, and finds a free spectrum for redistribution without interfering with the broadcasting TV spectrum.

In Feb. 2005, Simon Haykin published a landmark article on cognitive radio technology, Cognitive radio: brain-empowered wireless communication in IEEE Journal on Selected Areas in Communications, which strongly promoted international cognitive radio technology research [2].

Under the strong advocacy of the FCC, the US National Natural Science Foundation (NSF) funded the cognitive radio project as one of five subnets under the Global Network Interconnection Innovation Environment Project. The funded research content includes new cognitive radio technology validation, a physical layer adaptive wireless network protocol, a spectrum sharing method, dynamic spectrum measurement, and hardware implementation. With funding from the NSF, many university research institutes and research organizations such as the Software Defined Radio Forum have launched research into cognitive radio technology.

The field of wireless communications has undergone several changes, from fixed communications to mobile communications, from analog communications to digital communications, from hardware architecture to software programmable, and from blindness to cognition. The introduction of cognitive science has brought an epoch-making change to the field of wireless communications. Cognitive radio has transformed software radio from a blind executor of prefabricated programs into an intelligent agent in the radio field. It has the ability to meet user needs in various ways. At present, cognitive radio technology has become the research focus of international standardization organizations, research institutions and universities. Countries have invested large amounts of funds to set up research plans and research projects to conduct research into it.

1.2. Concept of cognitive radio

To facilitate an understanding of the concept of cognitive radio, we first distinguish between cognitive radio and software radio. At the American Communication System Conference in 1992, Joseph Mitola clearly put forward the concept of software radio for the first time. Its core idea is that A/D and D/A converters are as close to the antenna as possible. Under ideal conditions, all aspects (Including the physical air interface) can be defined through software. According to the IEEE definition, the basic premise for a radio device to be called a software radio is that part or all of the baseband or radio frequency signal processing can be completed by digital signal processing software, and this software can be modified after leaving the factory. Therefore, software radio focuses on the realization of signal processing in the radio system, whereas cognitive radio emphasizes that the radio system can perceive changes in the operating environment and adjust system operating parameters accordingly. In this sense, cognitive radio is a higher-level concept that not includes signal processing as well as high-level functions for reasoning and planning based on corresponding tasks, policies, rules, and goals [3].

Since the father of software radio, Dr. Joseph Mitola, first proposed the concept of cognitive radio in 1999 and systematically explained the basic principles of cognitive radio, different institutions and scholars have approached the definition of cognitive radio from different angles. The more representative ones include the definitions of Joseph Mitola, the FCC, and Simon Haykin.

Joseph Mitola believes that cognitive radio is a radio station based on software radio. It uses pattern inference to obtain special capabilities in radio-related fields. Cognitive radio uses model-based methods to detect the use of radio-frequency bands in the radio domain, and then uses reasoning based on the situation to express various parameters of radio-frequency signals through the language of radio cognition and intelligently change its own frequency, power, and other parameters to achieve interoperability between networks [3].

The FCC believes that a cognitive radio station is a radio station that can interact with the surrounding environment to change the parameters of the transmitter. The interaction includes active coordination and negotiation with other users, or conservative perception and decision-making by the radio station. The station can judge its own location, sense the working frequency spectrum of neighboring devices, change its own frequency, adjust transmit power, and so forth.

Professor Simon Haykin believes that cognitive radio is an intelligent wireless communication technology that can perceive the surrounding frequency, time, and space and other spectrum environment characteristics, and can adopt a method to understand the environment, location, channel, network, protocol, and user. As well as the internal structure of the device itself, the software radio is transformed from a blind executor of a predefined protocol to an intelligent agent in the radio field. It communicates intelligently with the communication network through the language of radio knowledge and adjusts the transmission parameters in real time to make the system's wireless rules. The wireless rules of the system (a series of radio frequency bandwidth, air interface, related protocols and space and time mode settings suitable for the reasonable use of the wireless spectrum) is adapted to the input radio excitation changes, so that the communication system can achieve high adaptability to the wireless environment and efficiency of spectrum sharing.

Here, it is proposed that cognitive radio is an intelligent wireless communication system that can perceive the surrounding wireless environment and adjust the internal configuration in real time by understanding and learning the environment to adapt to changes in the external wireless environment. Cognitive capabilities enable cognitive radio to capture or perceive information from the working wireless environment, identifying unused spectrum resources (also called spectrum holes) in a specific time and space, and selecting the most appropriate spectrum and operating parameters accordingly.

The goal of cognitive radio research is to achieve high adaptability to the spectrum-centered environment and efficient spectrum use. For this goal, the cognitive cycle shown in Fig. 1.2 is used and includes three steps: spectrum sensing, spectrum management, and spectrum allocation. The function of spectrum sensing is to monitor available frequency bands and detect spectrum holes. The function of spectrum management is to estimate the characteristics of spectrum holes obtained by spectrum sensing. Spectrum allocation selects appropriate frequency bands to transmit data according to the characteristics of spectrum holes and user needs.

1.3. Characteristics of cognitive radio technology

Cognitive radio technology uses an idle spectrum in real time and opportunistically (i.e., with opportunistic spectrum access), without causing interference to authorized users (primary users). The basic principle of opportunistic spectrum access is shown in Fig. 1.3. The basic idea is that the device first senses the surrounding wireless environment and determines the spectrum characteristics, determines the existence of authorized users and describes the available opportunities. Through understanding and active learning of the environment, the device complies with the management policies applied to the spectrum, determines an optimal plan, adjusts the transmission parameters in real time, such as power, carrier modulation and coding, and coordinates the use of communication between nodes. The definition domain applies the interference restriction strategy, and then sends the signal in a way that does not conflict with the authorized user, so as to achieve the goal of optimizing the performance of the communication system