Preface

So, yet another book on Wi-Fi and Bluetooth? While deciding which contents should be included in this book, a quick web search was made, which showed that there are possibly thousands of different books involving some aspects of explaining Wi-Fi and Bluetooth. Yes indeed, Wi-Fi and Bluetooth are very mature technologies. It is true that people have been using these technologies for quite a long time and have become extremely familiar with them. To some degree, we can even say that they are old technologies. After all, the name Wi-Fi has been with us since 1997, and Bluetooth even earlier, since 1989. Of course, we were not very familiar with these terms at the time of their first release, but both technologies started coming into the spotlight when the first smartphones were introduced in the middle of the 2000s and these technologies allowed us to connect to the Internet or with various computer peripherals without additional costs.

Then, what more is there to explain about these technologies? As redundant and old-fashioned as these topics may seem, we cannot simply neglect them in the future of next-generation networks. For beginners, these technologies may just seem like very old things that exist in our everyday lives (like a refrigerator, television or a coffee machine). However, inside the core of the technology, there have already been many modifications and enhancements for both Wi-Fi and Bluetooth, and more will occur in the future. Due to the ever-changing properties of these technologies (which is in fact essential, because the services, applications and user-demands also drastically change over time), it is quite difficult to keep up with this pace, especially for researchers and engineers whose jobs require them to have current knowledge. Therefore, there is a need to update the information on Wi-fi and Bluetooth every so often and organize it into detailed manuscripts, such as this book. The summarized information normally provided by the likes of online encyclopedias is not enough detail for some advancements. With this in mind, this book tries to provide readers with insight into these technologies and where they are headed in the future of next-generation networking.

As the title says, this book focuses on two wireless communication technologies, Wi-Fi and Bluetooth. At this point, some people may wonder, why these two technologies are bound together into one single book. After all, they have many differences in their most fundamental concepts and objectives. First of all, Wi-Fi is a wireless local area network (WLAN) technology, while Bluetooth is a wireless personal area (WPAN) technology. Different areas of networks have different objectives, as WLAN’s main objective is to provide a wireless alternative to ethernet (LAN without W), while most can agree WPAN’s main priority is low-power, low-rate communication. Second, Wi-Fi’s most common usage for current applications is to provide high-speed connection to the Internet, while Bluetooth is often utilized more for ad hoc connection between devices and peripherals while prioritizing energy efficiency. Finally, the technical structure of the two is very different. The main body of Wi-Fi is built based on the IEEE 802.11 standard, which defines the physical (PHY) and medium access control (MAC) layers of the stack-layered network architecture. In the current Internet, Wi-Fi is used in conjunction with other commonly used Internet technologies such as Transport Control Protocol (TCP)/Internet Protocol (IP) and Hyper-Text Transfer Protocol (HTTP). On the other hand, Bluetooth generally defines all aspects of the network architecture, starting from the physical connection all the way up to the service itself.

However, despite all of these differences, the two technologies also have many common aspects. Let us try to counter the aforementioned arguments with regard to their differences, one by one. First of all, while Wi-Fi and Bluetooth still “technically” belong in their respective networking areas of WLAN and WPAN, their actual usage in various services and applications extend far beyond this restriction. To elaborate, various amendments and new versions of each technology have been continuously produced over time. Some amendments of IEEE 802.11 allow Wi-Fi to extend its network range to kilometers; some make it reduce power consumption for smaller networks. Likewise, enhancements in Bluetooth now allow it to create many forms of network, which can be considered much larger than a typical WPAN. In fact, their amendments and adaptations into various services have broadened their potentials so much that they are even considered competitors to each other in various service aspects.

To take an example which will be detailed later on, service of wireless and indoor localization is an excellent case of the competition between the two technologies (there are other competitors too, such as Ultra Wide Band (UWB) and even the good old global positioning system (GPS), though the lack of performance for GPS in indoor environments is precisely the reason why Wi-Fi and Bluetooth gained attention). Both technologies are currently used for indoor localization, with specific advantages and disadvantages for respective technologies. For example, Wi-Fi is now capable of providing longer and stronger signals from multiple antenna arrays, which makes the localization more resilient to fading and noise problems. Bluetooth, on the other hand, utilizes redundant signals to improve accuracy but also at the same time maintains a high level of energy efficiency. Thus, these two technologies are compared and compete against each other, or in many cases are even used together in collaboration.

Second, even though the network architecture, which defines the stack layers of Wi-Fi and Bluetooth, is completely different, how they approach the wireless resource is something to be compared. For example, one of the several wireless radio frequencies bands that Wi-Fi operates in is the range of 2.4 GHz, which is in fact the only frequency band used by the Bluetooth physical layer. The definition of channels within the frequency band is different, as Wi-Fi requires larger frequency channels for faster transmission, while Bluetooth uses a larger number of smaller channels for reliability and energy efficiency. However, the problem is that the channels between Wi-Fi and Bluetooth collide with each other, which induces interference and noise. As Wi-Fi operates on a Carrier Sense Multiple Access (CSMA)-based resource access and Bluetooth on a different, Time Division Multiple Access (TDMA)-based access, the interference with each other in the same physical domain is bound to affect the service between them. In fact, just as a simple example, one 80 MHz Wi-Fi channel is capable of interfering with nearly 20 Bluetooth low-energy channels. This also means that interference induced from one Bluetooth channel can actually distort all the data encoded in the 80 MHz Wi-Fi channel as well (though this depends on the encoding mechanism, the possibility exists). Therefore, how Wi-Fi and Bluetooth has evolved over time always had to consider some aspects of competing for the same frequency. Also, the path of evolution that they will continue to take in the future is also intertwined.

Finally, as of right now we may not be able to fully predict the future of both Wi-Fi and Bluetooth, but after reading this book we should at least be able to understand some of their potential directions of evolution. All technologies develop according to the requirements and expectations of the consumers and manufacturers (basically, the manufacturers MUST understand the demands of the users, to create suitable products that the users will pay money for). If there is bound to be a future “killer” application that requires some form of wireless connection, then Wi-Fi and Bluetooth will both evolve to facilitate this requirement, but both within their own capabilities and advantages. Deciding downright which is the better technology in general, is impossible. However, in the perspective of a specific application with requirements, we can analyze and compare the two technologies to select which is more suited to support this specific task. In this regard, even with all their differences, the destinies of the two technologies will continue to be intertwined. This in fact is likely be the future not just for Wi-Fi and Bluetooth, but for all wireless communication and networking technologies, including cellular Long-Term Evolution (LTE) and 5G, near field communication (NFC), UWB, wide area networks, mmWave technologies and light-based communication. As scientists or engineers who act as the architects of future IT applications, how they can accurately analyze and evaluate them, and use the appropriate technologies in integration will be the key aspect in the future. Even though this book is unable to cover all aspects of future wireless communications, it chooses to focus on these two trendy technologies that are still in their prime of development.

To fully understand their roles and places in future wireless communications, first we need to know more about them. This is not just to understand the technical details. Of course, understanding the core technological aspects of “what” the technology exactly is, is important as this allows us to fully understand their objectives and the differences between the two technologies. However, it is just as important to understand “how” and “why”. How and why did the Wi-Fi evolve into the current state? Why did Bluetooth evolve from its classic mode to the low-energy mode? This book will go through the details of the technical...