Benefits of Fixed-Mobile Convergence

Throughout this book we analyzed in great detail the technologies behind fixed wireless cellular mobile networks convergence. In doing this, we used the shortened term Fixed-Mobile Convergence (FMC). However, convergence has multiple facets and a long history of expectations, and sometimes marketing hype. The FMC term has been used since the early attempts to integrate voice and data through the convergence of telecommunication and data communications networks. Later, the term was used for the convergence of digitized services such as ISDN. The development of the new wave of land based wireless communications brought the convergence term back as the on-going process of integration of wireless networks and wired networks. Returning to the narrow definition adopted for this book, fixed wireless and cellular mobile networks convergence, we can summarize the goals and benefits of FMC as follows:

• Communications anytime, anywhere, using any wireless technology;

• Continuous communication and operation regardless of the network used;

• Convenience for the user with a single handset and telephone number;

• Improved cost/performance factors by automatic selection of the network with highest available bandwidth and lowest cost;

• High availability by having multiple networks that can be used for transmission;

• Flexibility in the network design by combining indoor and outdoor, and short range and long range communications;

• Support for fixed, nomadic and highly mobile users;

• Service portability across heterogeneous networks.

The achievement of these goals requires positive answers and solutions in the following areas:

• Economics of FMC with adequate Return on Investment;

• Standardization of transparent handover operations;

• Scalability of convergent architectures which is critical in urban and metropolitan areas;

• […]

Cellular Mobile Radio Communications Concepts

In the first chapter we provided an extensive introduction to wireless communications. Major aspects such as general models for wireless communications, architectural components, and networks classification were introduced. We have also discussed, mainly at the level of acronyms, many of the elements that constitute the complex world of wireless communications. This was done in the context of the even larger legacy wired world. Key to wireless communications is the wireless link established between transmitter and receiver. The type of this link will determine the kinds of wireless communications. In this section we will limit analysis to terrestrial mobile cellular radio networks that, in simple terms, are the radio links established between Mobile Stations (MS) such as handsets and the Basic Transmission Stations (BTS).

Initially, the approach to mobile radio was the same as that in radio or television broadcasting, where a BTS was placed at the highest point of the desired area to be covered. As the number of mobile users increased, congestion eventually occurred because of the limited available spectrum. To assure that frequencies can be reused across geographical regions, mobile communication uses the concept of individual micro cellular radio systems. The cells can be created by earth-based radio tower transmitters/receivers or by satellite footprints. Clusters of 7 terrestrial cells provide an area coverage and separation of commonly used groups of frequencies. The number of total channels supported, hence the network capacity, will be determined by the number of clusters that are implemented.

Bluetooth Networking

In Chapter 7 we introduced the WPAN infrastructure and Bluetooth, a technology that supports short range communications and home networking. Initially, Bluetooth's primary function was “cable replacement”, i.e., elimination of short-range wired-based communications. Therefore, most of the Bluetooth applications presented were based on point-to-point and point-to-multipoint wireless links. However, the applicability of Bluetooth has gradually extended, covering various aspects of office automation, industrial process automation, and even mobile ad-hoc networking. Many of these extensions include Mobile-to-Mobile (Mo2Mo) networking, beyond the traditional clustering within piconets. An essential condition of Bluetooth networking is its ability to work in extended ranges, up to 1 km, using omnidirectional antennas. Another condition is low power consumption while maintaining a high data rate. The Bluetooth networking architecture is shown in Figure 12.1.

Bluetooth networks consist of multiple piconets interconnected into larger scatternets, providing a community area network of multiple groups of users. A piconet consists of a single Master Station (MS) and several Bluetooth (B)-enabled devices. Sophisticated home networks can be organized as scatternets where each piconet represents an ad-hoc grouping of Bluetooth-enabled devices with common functionality such as environmental automation, audio/visual systems, and computing systems.

Within a piconet, the master station establishes connections with all the Bluetooth devices, including a smart cell phone that can provide connectivity to a mobile service provider and the Internet. Within scatternets, Bluetooth connections are established between master stations to allow multi-hop routing.

With the addition of MIMO to IEEE 802.11, many new WLAN devices will have multiple antennas. Though an important benefit of multiple antennas is increased data rate with multiple spatial streams, multiple antennas may be also used to significantly improve the robustness of the system. Multiple antennas enable optional features such as receive diversity, spatial expansion, transmit beamforming, and space-time block coding (STBC). The topic of transmit beamforming is addressed in Chapter 12.

Advanced coding has also been added to 802.11n to further improve link robustness with the inclusion of the optional low density parity check (LDPC) codes and STBC. STBC combines multiple antennas with coding.

To simplify notation in the following sections, the system descriptions for receive diversity, STBC, and spatial expansion are given in the frequency domain for a single subcarrier. This is done since each technique is in fact applied to each subcarrier in the frequency band. It is assumed that, at the transmitter, the frequency domain data is transformed into a time domain waveform as described in Section 4.2. Furthermore, the receive procedure to generate frequency domain samples is described in Section 4.2.4.

To quantify the benefits of these features, this chapter contains simulation results modeling each technique. For each function, the simulation results include physical layer impairments, as described in Section 3.5. The equalizer is based on MMSE. Synchronization, channel estimation, and phase tracking are included in the simulation.

Why Convergence?

In the previous chapters we presented and analyzed all major forms of wireless communications and divided them into two major groups: The world of cellular mobile networks as represented by three generations of networks with the corresponding technologies, and the other, the world of so called “fixed wireless” communications grouping WLAN, WPAN, WiMAX, and Near-Field Sensor Networks. In the pursuit of the ultimate goal of communications “anytime, anywhere, any technology” there is a need for interoperability between the cellular mobile radio networks of the latest generations and any form of fixed wireless networks, i.e., Fixed-Mobile Convergence (FMC), the subject of this book. From the user's perspective, convergence means use of the same mobile cell phone or mobile handset across any type of wireless network and transmission of digital information at the highest available data rate, all at the lowest possible cost.

This chapter will provide an overview of the fixed-mobile convergence concept. We will address the terminology, architectural components, interfaces, protocols, the overall requirements, and the technical forums that have been created to advance fixed-mobile convergence concepts. We will also introduce two major solutions that address this convergence at the standards level. Convergence is also one major aspect of the grand schema of designing the New Generation of Wireless Networks; along with associated architectures, applications, and services. The actual pair solutions of convergence between cellular mobile networks and individual fixed wireless networks will be presented in subsequent chapters.

The high-level characteristics of this integration/convergence are:

• A meshed wireless infrastructure as the conduit for voice, data, and video communications;

• […]

The medium access control (MAC) layer provides, among other things, addressing and channel access control that makes it possible for multiple stations on a network to communicate. IEEE 802.11 is often referred to as wireless Ethernet and, in terms of addressing and channel access, 802.11 is indeed similar to Ethernet, which was standardized as IEEE 802.3. As a member of the IEEE 802 LAN family, IEEE 802.11 makes use of the IEEE 802 48-bit global address space, making it compatible with Ethernet at the link layer. The 802.11 MAC also supports shared access to the wireless medium through a technique called carrier sense multiple access with collision avoidance (CSMA/CA), which is similar to the original (shared medium) Ethernet's carrier sense multiple access with collision detect (CSMA/CD). With both techniques, if the channel is sensed to be “idle,” the station is permitted to transmit, but if the channel is sensed to be “busy” then the station defers its transmission. However, the very different media over which Ethernet and 802.11 operate mean that there are some differences.

The Ethernet channel access protocol is essentially to wait for the medium to go “idle,” begin transmitting and, if a collision is detected while transmitting, to stop transmitting and begin a random backoff period. It is not feasible for a transmitter to detect a collision while transmitting in a wireless medium; thus the 802.11 channel access protocol attempts to avoid collisions.

Wireless PAN Architecture

A typical residential network infrastructure, shown in Figure 7.1, consists of three types of network: a local wired loop that connects the residence to the serving telephone company (voice/data or xDSL), a coaxial cable that connects the residence to a cable company (video, data, voice with an alternative for video broadcast using a satellite network), and the AC power lines that connect the residence to the power company.

A home network, also known as a Personal Area Network (PAN), is intended to integrate and standardize the use and interaction of home end-devices and appliances. PAN facilitates and supports the interconnection of multiple computing data devices and peripherals (printers, scanners, digital cameras, video cameras), voice and video communications, music distribution (MP3 and CD players), and use of surveillance devices to command and control appliances (meter reading, temperature and light regulation). Wireless Personal Area Network (WPAN) is the new generation of PANs that uses wireless communication to connect the PAN components. A typical WPAN infrastructure consists of a concentration point in the form of a Residential Gateway (RG) with a connectivity component to a broadband network in the form of a Network Gateway (NG). This is shown in Figure 7.2.

Both wired and wireless communications capabilities can be used for connectivity between the RG and the NG. Connection types include unshielded twisted pairs, coaxial cable, fiber optic, or power lines.

What is Unlicensed Mobile Access or GAN?

Unlicensed Mobile Access (UMA) is an architecture and a set of specifications that provides convergence of cell-based mobile radio GSM/CDMA networks with IP-based fixed wireless access networks. Examples of fixed wireless networks include IEEE 802.11 a/b/g WLANs, IEEE 802.16 WMANs (WiMAX), IEEE 802.20 Ultra Wideband, IEEE 802.15.1 Bluetooth WPANs, and Near-Field Sensor Networks. UMA subscribers are provided with total location, mobility, and service transparency.

UMA development was initiated in January 2004 by a group of mobile service infrastructure providers and mobile handset manufacturers: Alcatel, AT&T Wireless, British Telecom, Cingular, Ericsson AB, Kineto Wireless, Motorola, Nokia, Nortel Networks, O2, Roger Wireless, Siemens AG, Sony Ericsson, and T-Mobile. By mid 2005, key components of the UMA specifications, dealing with user, architecture, protocols, and conformance testing aspects were developed. These specifications were submitted to the 3G Partnership Project (3GPP), as part of a work item called “Generic Access to A/Gb Interfaces”. Since then, these specifications, also known as TS 43.318, have been approved and incorporated in 3GPP Release 6 documentation. Consequently, the UMA initiators have decided to disband the independent working group and to continue their effort under the umbrella of the 3GPP organization. Since its adoption by the 3GPP, the UMA name has been changed to Generic Access Network (GAN). However, the old name is still used in technical and marketing circles, so for this reason, we will continue to use it in this book.

Near-Field Sensor Technologies

Near-Field Sensors (NFS)-based Networking (NFSN) is a generic term for wireless transmission technologies and networks confined to a short proximity between transmitters and receivers, generally a few centimeters, exceptionally 1–3 meters. Conceptually, NFC/NFSN covers digital data communications and multimedia information exchange and can be implemented using a variety of wireless technologies such as Radio Frequency Identification (RFID), Near-Field Communications (NFC), and Ultra Wide Band (UWB).

NFSN solutions, regardless of the technology that is adopted, must satisfy service requirements such as broadband transmission capability, reliability, scalability, simplicity, security, quality of services, manageability, and cost effectiveness. Special applications extend NFSN into movements of physical goods and persons, and even commercial and industrial operations. The array of applications ranges from individual customers/subscribers automatic identification to tracking commercial and industrial operations and chain of supplies of medium and large size businesses, all aimed at enhancing overall productivity. This presents challenges to designers of sensors and receivers, NFSN developers and integrators.

Although NFSN and its representative technologies, RFID, NFC, and UWB, are far from being wide-spread mass applications, the signs of their presence are visible in applications involving major retail organizations in their tracking of major items using RFID technologies, in physical persons that accept RFID tag implants to follow-up on health status information, and in spectrum allocation for UWB technologies across major markets.