Learn about wireless wide area networking technologies. Learn about wireless wide area networking technologies.
Learn about wireless metropolitan area networking technologies.
Learn about wireless personal area networking technologies.
Very few rules and standards apply to wireless wide area networks (WWANs), wireless metropolitan area networks (WMANs), and wireless personal area networks (WPANS), and we have very little control over our data or communications. This chapter offers information about these networks, including any applicable standards, incarnations, components and architecture, special features, and special interest groups (SIGs). Note that the information in this chapter is by no means a complete or thorough coverage of these technologies, but it highlights the features that you, as a wireless network administrator, might find especially interesting.
A WAN can span a large geographical area—a country, multiple countries, and even continents. The Internet is a classic example of a WAN. A Wireless Wide Area Network (WWAN) is a class of WAN technologies that uses mostly cellular and satellite infrastructures to enable interconnectivity over a WAN via several services, such as Global System for Mobile (GSM) communication and several incarnations of GSM, the Universal Mobile Telecommunications System (UMTS), and Long Term Evolution (LTE).
NOTE A wireless network administrator may not have much control over the type of hardware and other implementation details of WWANs in use at his or her site, because these things are often determined by third-party service providers. However, the information about WWAN is included in this chapter because you’ll find it useful to understand the technologies powering your networks. This knowledge can, for example, help when you’re selecting or negotiating with service providers that will implement the actual technologies. It can also help in integrating these WWAN technologies with the existing network infrastructure that you control.
GSM is a widely used digital cellular voice and data service that was initially conceived as standard that could be readily adopted by different countries and existing standards. And it has met and surpassed this initial requirement, because GSM is now adopted as a base standard in more than 80 percent of the world’s mobile phone market.
GSM is considered a second generation (2G) cellular technology. The ability of wireless client devices to be truly mobile is a distinguishing feature of the 2G cellular technologies.
True mobility was made possible by the use of cells in mobile network designs. A cell is simply an imaginary boundary within which wireless radio frequency (RF) coverage is managed and provided by a base station. The grouping of various and consecutive cells is where the name “cellular” comes from. Various cells working in conjunction to provide expanded and seamless RF coverage to a wireless client provides mobility for the client.
Various GSM network operators own and manage their own cells, and these network operators often use sharing (also known as roaming) agreements that allow users to use their mobile devices anywhere GSM coverage is available—all at a cost, of course.
Figure 7-1 shows the relationship of the cells in cellular network and a wireless client device. Part A of the figure shows how mobility can be restricted to areas around the single cell tower. Part B shows how mobility can be enhanced when more cells are added to the scenario and mobile users can roam between cells.
Figure 7-1. Relationship of cells in a cellular network and wireless client device
Second-generation GSM networks operate in the 900 MHz and 1.8 GHz frequency bands in Africa, Australia, Europe, Middle East, and Asia (excluding Japan and South Korea), and parts of South America. They operate in the 850 MHz and 1.9 GHz frequency bands in North America, Latin America, and parts of South America. A more complete map of the GSM frequency bands in use in every country can be found at www.worldtimezone.com/gsm.html.
GSM networks comprise several components: a mobile station (MS), a base station system (BSS), and a network switching system (NSS).
Mobile Station The MS is the one part of the GSM network over which the user has some control (to the extent that the user is allowed to choose the color and sometimes ringtone of the wireless device). This is the part that can sometimes cost a lot of money, too. It includes any wireless client device that we intend to connect to the operator-controlled GSM network. Good examples of a MS are cell phones or a WWLAN adapter card connected to a laptop. The MS talks to the BSS (discussed next).
Every MS is uniquely identified by a International Mobile Equipment Identity (IMEI) number that is hard-coded into the GSM client device and therefore not easily transferable between devices. Among other details, the IMEI number describes the organization that registered and allocated the unique IMEI number, the model, and the vendor-assigned serial number of the GSM device.
The first time a user subscribes to the services of a GSM network operator, he or she is issued a Subscriber Identity Module (SIM) card. The SIM card is a type of smart card that stores information designed to identify a user or account uniquely on any GSM network. The SIM card is tied to the user but is portable between devices. The SIM card stores the International Mobile Subscriber Identity (IMSI), the current subscription information, user authentication data, and a simple contact database for the user (an address book). The IMSI is unique world-wide.
Base Station System The BSS component of a GSM network is an amalgamation of components owned and managed by the network operator. It usually comprises the base station controller (BSC) and the base transceiver stations (BTS)—the radio transmitters, receivers, and antennas that serve each cell.
The BSC is the brains behind the BTS. It stores the configuration data used for managing the BTS. For example, it controls the RF power levels in the BTS, which in turn connects the cell to the NSS, from which it gets its own instructions.
The MS connects to the BSS which in turn connects to the Network Switching System, discussed next.
Network Switching System The NSS is a central component of any GSM infrastructure. It comprises several parts that perform different complicated functions, such as call processing, subscriber-related functions, and interfacing the mobile phone network with the traditional Public Switched Telephone Network (PSTN).
The Third Generation Partnership Project (3GPP), one of the major GSM SIGs, is committed to the maintenance and development of GSM’s technical specifications (www.3gpp.org). It does this by helping to unite various telecommunications standards bodies all over the world.
Another GSM SIG, the GSM Association (GSMA) represents the interests of the mobile communications industry all over the world (www.gsmworld.com). Its focus is to drive the growth of the mobile communications industry by helping to develop and create new opportunities for its members (manufacturers and suppliers of GSM-based technologies). Its objective is clearly different from that of the 3GPP, which is more concerned with standards issues.
The original GSM standard has undergone many evolutions and revisions—too many to mention them all here. One standard, General Packet Radio Service (GPRS), is of particular interest to us as wireless network administrators. It was designed to handle data and other multimedia applications, unlike the 2G technologies, whose focus was mainly voice applications.
GPRS GPRS is a standard used for communicating over cellular networks. It is often referred to as a two-and-a-half–generation (2.5G) cellular technology. GPRS is based on packet-switching, which offers several advantages from the perspective of a wireless mobile user interested in wireless data communications. One such advantage is cost— packet-switched services are generally cheaper than their circuit-switched counterparts, and billing is often based on the amount of actual data transferred. Packet-switched networks allow the communication medium to be shared among different users, so no expensive circuits need to be dedicated to the user. This sharing can also be a disadvantage, however, because a fixed bandwidth is not always guaranteed or available to individual users.
From the perspective of the wireless network administrator, GPRS-based devices can support the following features:
Internet Protocol (IP) versions 4 and 6
Wireless Application Protocol (WAP)
Data transfer rates of 56–114 kbit/ps
GPRS can be used for data communications in a wide variety of devices, such as mobile phones, GPRS expansion cards for laptops or personal computers, and remote terminals such as point-of-sale systems.
When used for data communications, GPRS-based devices make extensive use of the notion of an Access Point Name (APN), a simple and distinct name that is meaningful only within the cellular service provider’s network. The APN is distinct from access points (APs) used for purely WLAN communications, but, generally speaking, they both help to provide wireless clients access to resources available on a network.
The APN used in GPRS services specifies the external network or services that a wireless mobile device can access. These are usually one of two types: WAP APNs or Internet APNs.
The WAP APN provides access to the mobile provider’s WAP content, which is often filtered and reformatted to meet WAP specifications. A sample WAP APN for a cellular service provider named Wireless WANS ‘R’ US 1234, Inc., could be wap.wwrs1234.com.
The Internet APN provides the mobile device access to the standard Internet-based services such as e-mail and web browsing.
A sample Internet APN for a cellular service provider named Wireless WANS ‘R’ US 1234, Inc., could be internet.wwrs1234.com.
The Universal Mobile Telecommunications System (UMTS) is a third-generation (3G) cellular standard that has several implementations that go by different monikers or brands. Example UMTS implementations are Freedom of Mobile Multimedia Access (FOMA) and Wideband Code Division Multiple Access (W-CDMA).
The BTS component of 2G GSM networks is replaced by a new component called Node B in 3G UMTS networks. The functionality provided by the BSC in 2G GSM networks is provided by a component called the Radio Network Controller (RNC) in UMTS.
The UMTS Forum (www.umts-forum.org) can be considered a UMTS SIG with very clear objectives. The Forum’s objective is to help all UMTS stakeholders understand and profit from the opportunities of 3G/UMTS networks.
The next sections discuss some revisions and enhancements to the original UMTS standards. Some of these revisions are the High Speed Packet Access (HSPA) family of technologies, such as High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), and HSPA Evolved (eHSPA)—aka HSPA+. The revisions are referred to as UMTS releases.
HSPA Overview HSPA refers to a family of WWAN mobile technologies that provides mobile broadband access for GSM-based devices. HSPA is considered a post-3G cellular technology. It was specifically designed to offer an easy upgrade path for cellular network operators who want to deploy the post 3G technologies. HSPA-based networks operate in the 850, 1900, and 2100 MHz frequency bands.
High Speed Downlink Packet Access HSDPA is a 3G cellular technology based on the UMTS standard. It is described in the UMTS standard Release 5. Among its other features, HSDPA offers improvements in the downlink speeds of its predecessor (HSPA), with downlink speeds of 14 Mbps.
High Speed Uplink Packet Access HSUPA is a 3G cellular technology described in the UMTS standard Release 6. It is referred to simply as Enhanced Uplink (EUL) in some quarters.
Among its other features, HSUPA offers improvements in the uplink speeds of its predecessor (HSDPA), with uplink speeds of 5.7 Mbps.
HSUPA also supports WLAN integration.
The coverage offered by WLANs is traditionally limited and best suited for indoor use, but the coverage offered by a UMTS network can span several miles and is best suited for outdoor use. The strengths and weaknesses of these two technologies can be used to complement one another.
This particular feature makes it possible for mobile stations (such as cell phones) to use either the cellular provider’s managed WWAN or the user-managed WLAN to make voice calls or for data communications. So, for example, when a user is within the reach of a WLAN or Wi-Fi signal, all voice and data communications can occur via a traditional wireless access point (WAP) or residential gateway router. The possibilities and uses of this feature are many (and, of course, can cause headaches for the wireless network administrator).
HSPA+ Evolved HSPA+ (pronounced HSPA plus), often referred to as HSPA Evolved (eHSPA), is a 3G cellular technology that is described in the UMTS standard Release 7.
Among the many enhancements it offers, HSPA+ is purported to be capable of theoretical downlink speeds of 42 Mbps and uplink speeds of more than 11.5 Mbps. The Multiple Input/Multiple Output (MIMO) antenna technology is used to achieve the enhancements in HSPA+.
LTE is GSM on steroids. The authors and backers of LTE describe it as an evolution of the 3G/HSPA cellular technologies. LTE is designed to be backward-compatible with GSM and HSPA technologies. “Improved spectral efficiency” is one of the strong points touted about LTE, which simply means that the technology can make more efficient use of the available radio spectrum.
LTE is purported to be capable of theoretical downlink speeds of 172 Mbps and uplink speeds of more than 50 Mbps. It will make it possible to deliver rich multimedia and bandwidth-intensive applications over long distances wirelessly.
LTE is a purely IP-based technology.
Almost everybody in the wireless community has interests in the success of LTE— from the network operators (who can make more money with less resources), to the equipment manufacturers (who can charge more for cool new hardware to support the technology), to the consumer (who pays more for the cool new hardware and for access to the better network).
LTE is a highly anticipated technology that is supposed to be a win-win situation for most stakeholders.
A MAN can span a moderately large geographical area. The scope of the area covered by a MAN is often within a city but almost certainly restricted to within a country.
A WMAN refers to wireless technologies that facilitate interconnectivity wirelessly in a metropolitan area. WMANs can be considered mid-range networks. They normally do not use the cellular network infrastructure, but instead make use of some vendor-specific technology.
In some cases, the wireless network administrator may not have much control over the type of hardware and other implementation details of WMANs in use at his or her site, because these aspects are often in the hands of third-party service providers. However the information is included here because it is useful for you to understand the technologies powering those networks. This knowledge can help, for example, when you’re selecting or negotiating with service providers that will implement the actual technologies. It can also help you in integrating these WMAN technologies with an existing network infrastructure.
In the next section we’ll look at one specific technology called WiMAX that is used in building WWAN networks.
NOTE WMAN can also be built by wirelessly connecting two or more WLANs using IEEE 802.11 standard-based equipment and protocols.
Worldwide Interoperability for Microwave Access (WiMAX) is used in building WMAN networks. WiMAX can serve as a capable “last mile” technology, which means that it can be used to bypass the traditional cable or wired infrastructure to provide connectivity between the communications provider and the customer.
WiMAX operates in the 2–66 GHz frequency range.
WiMAX is governed by the details specified in the IEEE 802.16 standards, where it’s called WirelessMAN. Of the several revisions and versions of the standard, two are especially interesting to us here: IEEE 802.16d and IEEE 802.16e.
Two incarnations of the standard are important to wireless network administrators: Fixed WiMAX and Mobile WiMAX.
Fixed WiMAX This first mainstream version of WiMAX was widely adopted. It is especially suited for point-to-multipoint (one-many) applications. Its inner workings are specified in IEEE 802.16d.
Fixed WiMAX is purported to support wireless coverage of up to 30 miles (50 km).
Mobile WiMAX The details of the inner workings of Mobile WiMAX are governed by the IEEE 802.16e standard. It was developed to support mobile wireless clients—in other words, it was designed with the idea that users of the network will not always be in a fixed location and may be in motion while accessing the network.
Mobile WiMAX is purported to support wireless coverage of up to 10 miles (15 km). Smart antenna technology, such as MIMO, is used in Mobile WiMAX to improve gain and provide better throughputs.
NOTE Mobile WiMAX and the Long Term Evolution (LTE) standard provide similar functionality and are also technically similar. In fact, the two are considered competing standards, despite the fact that WiMAX is used mostly for WMAN applications and LTE is used in WWAN applications. Both are considered fourth-generation (4G) wireless network technologies.
Several WiMAX special interest groups exist, including the following:
The WiMAX Forum This group describes itself as an industry-led, nonprofit organization dedicated to certifying and promoting compatibility and interoperability of products based on the IEEE 802.16 standard. The relationship of the WiMAX Forum to WiMAX is similar to the relationship of the Wi-Fi Alliance to WLAN technologies. The WiMAX Forum’s web site is at www.wimaxforum.org/.
Intel Corporation Intel is a big proponent of WiMAX technology. This is understandable because they are possibly the biggest manufacturer of the hardware (chipsets) that implements WiMAX in the world. You can learn more about Intel’s interest in WiMAX at www.intel.com/technology/wimax.
A WPAN is used for facilitating communication between devices in a very small area. The “personal” aspect of this wireless network type came about because the devices in question are often used in the context of a personal space. And as with other communication types discussed thus far, WPAN’s objective is to receive and/or send data.
WPAN can be considered a short-range network because the range and reach of this wireless network type is typically quite limited when compared with that offered by WLANs, WMANs, and WWANs. A WPAN requires little external infrastructure to operate; most WPANs are self-contained.
The IEEE 802.15 standards describe specifications for the inner workings of WPANs.
Several technologies exist for enabling WPANs, such as Bluetooth, ZigBee, Z-Wave, Infrared Data Association (IrDA), and Ultra-Wideband (UWB), to mention a few. The following sections discuss Bluetooth and ZigBee.
Bluetooth technology replaces the cables traditionally used for connecting numerous electronic devices.
Bluetooth uses the frequency-hopping spread spectrum (FHSS) modulation technique. Its devices operate in the 2.4–2.4835 GHz unlicensed frequency range.
The IEEE 802.15.1-2002 and IEEE 802.15.1-2005 standards are good examples of the few Bluetooth standards that emerged from a neutral standards body. Most of the past and future work done regarding the development of Bluetooth is accomplished by the Bluetooth SIG.
Bluetooth devices consist primarily of the same components that make up most wireless RF devices: transmitter and receiver components (the transceiver) and the baseband.
Protocols The Bluetooth standard defines a group of protocols that are used to manage communications between the devices. Most commonly used Bluetooth protocols are listed in Table 7-1.
Profiles Bluetooth devices make use of profiles to determine the services and protocols that are supported by the device. This is a useful but somewhat confusing feature of the technology. It is useful because it makes it easy for hardware manufacturers and Bluetooth software developers to create Bluetooth devices and applications that are very specific in scope. In other words, it helps to keep things simple and possibly bring down the costs of Bluetooth devices because they do not need to support a plethora of features.
The confusion can result on the user side because the unknowing user may assume that all Bluetooth-capable devices can be used for any type of communication with any other Bluetooth device. This is incorrect, however, because to communicate, two Bluetooth devices must be able to speak the same profile.
Some common Bluetooth profiles are listed in Table 7-2.
Table 7-1. Bluetooth Protocols
Network Two or more Bluetooth devices communicate with one another using a piconet, a type of Bluetooth network that comprises one master and one or more slaves. The master is responsible for regulating all access to the Bluetooth RF channel. The bandwidth of the RF channel is shared among the participating Bluetooth devices in the piconet. Each piconet operates in its own frequency-hopping radio channel.
A piconet is exclusive, in that a maximum of only seven active slaves (and one master) are allowed to participate in the network at a time. However, other slaves are allowed to wait outside the piconet until any of the seven slaves leaves the network. These waiting slaves, in a parked state, can join the piconet after a vacancy has been created. Up to 255 devices can exist in an inactive, or parked, state, and the master device can bring these into active state at any time. Active member slaves are referred to as being in an active state.
Table 7-2. Common Bluetooth Profiles
When two or more established piconets are in proximity of each other, they form a scatternet, which forms as a result of the individual piconets having overlapping radio frequency coverage areas. The slaves in one piconet can participate in another piconet in the role of either a master or a slave.
Figure 7-2 shows some Bluetooth network topologies. It shows two separate piconets (Piconet-A and Piconet-B), and it also shows how the two piconets can combine to form a scatternet.
Bluetooth technology has grown and developed a lot over the years since its inception, and, as a result, a few versions are out there (as of this writing): Bluetooth 1.2, 2.0, 2.1, and 3.0.
Figure 7-2. Bluetooth network topologies
A prominent Bluetooth SIG is the aptly named Bluetooth SIG (www.bluetooth.org), a non-profit trade association. Among other things, the group is tasked with publishing Bluetooth specifications, qualifying Bluetooth devices, and promoting the Bluetooth trademark.
Several big-name Bluetooth hardware and software vendors abound and include Ericsson, Intel, Toshiba, Lenovo, Microsoft, Motorola, and Nokia, to name a few.
ZigBee is especially suited for use in embedded applications that require low data rates and low power consumption. ZigBee is targeted for use in wireless monitoring and control systems and automation type applications. Its low cost, low power, and open standards–based attributes are some of its key differentiating points.
ZigBee uses the direct-sequence spread spectrum (DSSS) modulation technique. It operates in different frequency bands in various parts of the world. For example, in Europe, it works in the 868–868.8 MHz range; in North America, it works in the 902–928 MHz range; and worldwide, it works in the 2400–2483.5 MHz range.
ZigBee is based on the specifications described in the IEEE 802.15.4 standards.
From a wireless network administrator’s point of view, the components of a ZigBee network are relatively few and simple.
The players in a ZigBee network can be grouped broadly into two components: the physical components and the logical components. We start with the logical components in Table 7-3. The physical components are shown in Table 7-4.
ZigBee WPANs use a mesh network type of architecture, which is described as a “self-healing” network. This basically means that nodes (ZigBee devices) are pretty smart and knowledgeable about their surroundings and know how to work around faults and other simple kinks in the communication links between its members. ZigBee networks can support up to 64,000 nodes.
A sample wireless network made up of ZigBee devices is shown in Figure 7-3.
As of this writing, few incarnations of the ZigBee suite exist, but two notable ones are the
ZigBee, the original standard, and
ZigBee Pro, with optimizations to accommodate more nodes in a ZigBee network.
ZigBee hardware generally cost less than other competing technologies that perform similar functions, such as Bluetooth. Despite the lower cost, devices using ZigBee have not yet achieved the market penetration and acceptance of the more expensive competition.
Table 7-3. Logical Components of a ZigBee Network
Table 7-4. Physical Components of a ZigBee Network
Figure 7-3. A sample ZigBee network
A prominent ZigBee SIG is the ZigBee Alliance, “an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard,” according to its web site at www.zigbee.org. Sample manufacturers that make ZigBee-based devices include Emerson, Freescale, Ember, and Philips.
Wireless Wide Area Networks (WWANs) include some specific WWAN implementations— specifically, GSM, GPRS, UMTS, and LTE.
Wireless Metropolitan Area Networks (WMANs) include WiMAX networks.
Wireless Personal Area Networks (WPANs) use Bluetooth and ZigBee implementations.
