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.

Wireless MAN Technologies

Wireless Metropolitan Area Network (WMAN), like WLAN and WPAN, is a generic term for networking confined to a geographical area and a set of specific networking technologies that provide wireless communications in metropolitan areas. WMAN is a new technology that will be a supplement to well-known wired technologies such as Resilient Packet Ring (RPR), Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH), SONET over IP, Gigabit Ethernet, and Wavelength Division Multiplexing (WDM). The area of coverage of WMAN falls between WLAN/WPAN, which are customer premises networks, and Wireless Wide Area Networks (WWAN), which are associated with cellular radio mobile networks. Methods of access to WMANs have some resemblance to those of broadband wired access technologies such as Digital Subscriber Line (DSL) and Data over Cable Service Interface Specifications (DOCSIS).

Conceptually, WMAN networks provide services to metropolitan or regional areas, either urban or rural, within a radius of 50 km. They can be used to connect WLANs/WPANs and provide access to data, voice, video, and multimedia services. Although WMANs provide city-wide coverage, the area may be as small as a university campus or even a group of buildings. WMANs belong to a network operator or a service provider, in many cases a wireless extension of services provided by wired or wireless carriers. WMANs can be implemented using a variety of wireless technologies: Local Multipoint Distributed Service (LMDS), Multi-Channel Multipoint Distributed Service (MMDS), Free Space Optics (FSO), Wireless Local Loop (WLL), and Wireless Interoperable Metropolitan Area Exchange (WiMAX).

Service Management Conceptual Model

In general terms, the notion of service is an abstraction. However, in an actual context such as communication service, it becomes more meaningful. If we add service qualifiers such as availability, speed, security, integrity, and responsiveness, we have something palpable to the user. The ultimate goal of any service is to satisfy the customer. That means services that assure the good functioning of a network, system, processes, and overall business in a cost-effective way. Service Management is an area of management that was designed specifically to address these issues. Service Level Management (SLM) is that part of management that encompasses networks and systems, binding together service providers with users of services. It does this by identifying, defining, tracking, and even proactively monitoring the services.

Communication services are provided on a contractual basis between customers (organizations, businesses, or individual subscribers) and one or multiple service providers. These services are to be delivered with the assurances that the exchange of information on data communication networks will be done under well-defined conditions and with guaranteed performance. A simplified communications service conceptual model is presented in Figure 3.1. Service providers with adequate applications and network infrastructure provide communication service to customer systems. Multiple service providers are usually involved in providing communications services because of the particular media used (wireless, fiber optic, cable, twisted pair), the type of network (access, connectivity, backbone), the type of information (voice, data, video, multimedia), and the communications technologies adopted.

The 802.11n amendment, more so than any previous 802.11 amendment, introduces many optional features geared toward specific market segments that will likely only be deployed in specific classes of devices. Many of the optional features are complex and, given time to market concerns and cost constraints, many implementations will only adopt a subset of the available features, perhaps phasing in features with time or in higher end products. Some features appear in multiple flavors. This is due to the many unknowns present at the time the features where being discussed during the standard development process. Very often there was no single clear direction to take that would clearly suit all situations and so variations were introduced.

The popularity of 802.11 also means that there are a large number of legacy 802.11 devices deployed making interoperability and coexistence with those devices essential.

This chapter discusses various features that help ensure interoperability and coexistence between 802.11n compliant devices as well as legacy 802.11 devices.

Station and BSS capabilities

With the large number of optional features in the 802.11n amendment a fair bit of signaling is required to establish device capabilities and ensure interoperability. Also, care must be taken to ensure that a feature used by one station does not adversely affect the operation of a neighboring station that is not directly involved in the data frame exchange.

Networks and Systems Management Concepts

To administer the enormous number of resources involved in communications, either wired or wireless, from customer premises to backbone networks and across all geographical and administrative boundaries, there is a need for specialized systems designed specifically for management. These systems comprise hardware and software components, applications and corresponding operations used together to monitor, control, operate, coordinate, provision, administer, diagnose and report faults, and account for the network and computing resources that allow communications to take place. As communications systems became an important part of any business, management systems evolved to support whole enterprises, i.e., to provide management of multivendor, multiprotocol and multitechnology network and systems environments. Management systems are more than just simple tools used to manage network and systems resources. They include standardized procedures and sophisticated communications protocols to collect and process the management information.

The high level paradigm of management consists of two entities: the Managing Entity and the Managed Entity. The relationship between managing entities and managed entities can be modeled as manager-agent, client-server, mainframe-terminal, master-slave, or peer-to-peer. In the manager-agent model, the management entity, also called the manager, represents the managing process while the managed entity, also called agent, represents the managed process. These models are depicted in Figure 2.1. Both manager and agent processes are software applications. The manager application provides management functions and services while the agent application provides access to the management information related to managed resources or managed objects.

Fixed-Mobile Convergent Network Management

In Chapters 2 and 3 we provided an extensive introduction to the concepts of network and service management, with no specific reference there to wireless networks or fixed-mobile convergent networks. At this point, we use the layered architecture known as Telecommunications Management Network (TMN) to analyze these concepts. The layered TMN architecture is presented in Figure 18.1.

TMN consists of five logical/functional layers implemented as interconnected management applications. The first three layers, Network Element Layer (NEL), Element Management Layer (EML), and Network Management Layer (NML) deal with network management as a whole and network management sub-divisions such as EML and NEL. The main characteristics of each layer are shown in Figure 18.1.

The next layer, the Service Management Layer (SML), provides management of services, monitors the connectivity between multiple service providers, and deals with specific aspects of service management such as Quality of Service and Service Level Agreements.

Management of convergent networks means management of all those networks that are part of an integrated mobile and fixed wireless network. Network management includes monitoring and controlling the capabilities of all vital network components, including diagnosing faults, modifying configurations, measuring performance, providing billing/charging information, and securing network operations. A high-level depiction of convergent wireless networks management is shown in Figure 18.2.

Convergent network management can be achieved through dedicated network management systems that provide separation of management aspects from the switching and transport aspects.