18-04-2011, 09:58 AM
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INTRODUCTION
1.1 HISTORY OF WIRELESS COMMUNICATION
In the history of wireless technology, the demonstration of the theory of electromagnetic waves by Heinrich Rudolf Hertz in 1888 was important. The theory of electromagnetic waves was predicted from the research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that electromagnetic waves could be transmitted and caused to travel through space at straight lines and that they were able to be received by an experimental apparatus.
David E. Hughes, induced electromagnetic waves in a signaling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals.
In 1885, T. A. Edison uses a vibrator magnet for induction transmission.
In 1888, Edison deploys a system of signaling on the Lehigh Valley Railroad.
In 1891, Edison attains the wireless patent for this method using inductance
The first generation (1G) and second generation (2G) of mobile telephony were intended primarily for voice transmission. The third generation of mobile telephony (3G) will serve both voice and data applications. There really is no clear definition of what 4G will be. It is generally accepted that 4G will be a super-enhanced version of 3G, when all networks are expected to embrace Internet protocol (IP) technology. During the last year, companies such as Ericsson, Motorola, Lucent, Nortel and Qualcomm came up with "3G-plus" concepts that would push performance of approved, though still emerging, standards beyond current ones
1.2 WHAT IS WIRELESS COMMUNICATION
Wireless does not mean sparks, noise, or a lot of switches. Wireless means communication without the use of wires other than the antenna, the ether, and ground taking the place of wires. Radio means exactly the same thing: it is the same process. Communications by wireless waves may consist of an SOS or other messages from a ship at sea or the communication may be simply the reception of today’s top 10 music artists, or connecting to the Internet to check your email.
Any form of communication that does not require the transmitter and receiver to be in physical contact.
Electromagnetic wave propagated through free-space, Radar, RF, Microwave, IR, Optical Simplex: one-way communication (e.g., radio, TV), Half-duplex: two-way communication but not simultaneous (e.g., push-to-talk radios), Full-duplex: two-way communication (e.g., cellular phones) are all examples of wireless devices.
1.3 NEED OF THE SPECIFIC TALK
Wireless networks continue to develop, usage has grown in 2010. Cellular phones are part of everyday wireless networks, allowing easy personal communications. Inter-continental network systems use radio satellites to communicate across the world. Emergency services such as the police utilize wireless networks to communicate effectively. Individuals and businesses use wireless networks to send and share data rapidly, whether it be in a small office building or across the world. The present usage of the 3G networks lead to the rise of Wireless and the advancement and development will soon be seen through the usage of the upcoming 4G wireless technology.
1.4 NEXT GENERATION WIRELESS
Recent advances in wireless technology have led to the proliferation of wireless devices, ranging from wireless LAN to cellular phones. Wireless has pervaded into our daily lives; it has become common to find people carrying a tiny handheld, with which they make a phone call, text, surf the web, and download music on their way to work. While it is difficult to precisely predict the future of wireless technology, it seems apparent that the trend in which wireless technology has emerged and developed is unalterable.
There are several notable aspects of this trend. First, there will be lots of wireless of all kinds. Wireless technology has gradually replaced wired systems, mainly communication systems such as phones and computers, and this trend will continue. This means there will be an increase not only in the number of devices, but also in the number of kinds of devices. Second, the demand for mobility and portability will keep increasing. Mobility and portability that wireless enables are the key driving forces of wireless technology. Future wireless technology must support various devices that impose more diverse and intense mobility and portability requirements. Third, there will be greater demand for integrated services. Current wireless systems depend heavily upon the wired infrastructure, and it was this integration of wireless and wired systems that have played a crucial role in wireless success. In future networks, such as infrastructure-less ad hoc networks, the integration and interoperability among wireless devices, in addition to the wireless-wired interoperability, will be important as well.
For wireless success to continue, future wireless technology must provide necessary features to keep the trend, characterized as above, going. This is reflected in the concept of Next Generation Wireless, which has emerged to characterize the paradigm shift towards more flexible and ubiquitous wireless communication systems. Following this concept, flexibility and interoperability is considered as our keywords, and to investigate the underlying technologies that must be developed in order to achieve them
CHAPTER 2
RELATED WORK
2.1 FLEXIBLE AND INTEROPERABLE WIRELESS NETWORKS
The ways in which people use wireless have become diversified, different technologies have been developed, each supporting a specific use. Cellular systems provide wide area voice and data services, WiFi (i.e. IEEE 802.11 family) systems provide a wireless means of creating local area networks (LANs), and Bluetooth is tailored to enable personal area networks (PANs), and the list goes on. While the miniaturization of radio hardware has enabled engineers to install multiple radios in a device to support multiple technologies (e.g. Apple’s iPhone 3GS [2] comes with 3G, WiFi, and Bluetooth interfaces), such parallel brewing of technologies will hinder further innovation, mainly due to the following two limitations:
1. A separate radio hardware architecture must be devised for every single technology that gets developed.
2. Devices that use different protocols cannot directly communicate with each other.
The first limitation addresses the flexibility issue, while the second refers to the interoperability issue. We define these terms more precisely as follows:
Definition 1 (Flexibility): A wireless device is flexible if it can support multiple wireless modes with a single hardware configuration, and can switch from one mode to another seamlessly.
Definition 2 (Interoperability): Two (or more) wireless devices are interoperable, if one can communicate with another device that employs a different protocol.
Flexibility deals with the device design, while interoperability addresses the issue of networking the devices. We argue that new platforms such as software defined radios (SDRs), radios that can be reconfigured in software at any given time, will enable the flexible transformation of a device from one wireless mode to another Ideally, one should be able to configure a SDR to use it as an IEEE 802.11 transceiver, and later transform the same radio into a Bluetooth device.
While putting SDRs into a practical use is identified as a challenging task due to performance and cost reasons, there have been great interests in developing high-performance SDRs, and we envision that they will closely mimic hardware radios in the near future. Under such vision, the focus of our work is on exploiting such flexible and adaptive platforms to construct interoperable networks among wireless devices of heterogeneous nature. Such a feat can be accomplished by enforcing a minimal set of requirements on every device, while keeping the link-layer protocol designs intact.
2.2 SOFTWARE DEFINED RADIO MODEL
Now let’s take an assumption of a simple SDR model, which is illustrated in Fig. 1. In this model, a SDR consists of multiple modules, where a module is a pre-defined package of signal processing and algorithmic components that implements a particular wireless technology (e.g. IEEE 802.11). A module accepts a data stream from the network layer, processes it accordingly, and outputs the signal to the transceiver. We assume there is only one transceiver shared by all modules; that is, at most one module must be active at a time. This is enforced by the controller, which is responsible for managing the modules and appropriately reconfiguring the SDR, based on some preset rules or user control.
