Naomi J. Alpern , Robert J. Shimonski , in Eleventh Hour Network+, 2010
Wireless
WISPs provide Internet access anywhere that it has coverage. Many locations that have very little access to a good last mile source utilize this technology to connect to the Internet. Homes also use this very often to get Internet access. You can access the Internet from an antenna in your local PC, no matter where you are, as long as you can access an antenna and have a clear shot to the antenna you want to connect with.
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Wireless wide area network (WWAN) WWANs are network traffic encapsulated in mobile communications technology such as Worldwide Interoperability for Microwave Access (WIMAX), Universal Mobile Telecom System (UMTS), code division multiple access (CDMA) 2000, Global System for Mobile (GSM), or 3G networks to name just a few. The mobile telecommunication cellular network allows users with WWAN cards or built-in cellular radios (GSM/CDMA) to surf the Web, send, and receive e-mail and in general perform any networking function as if physically connected to a WAN. Its characteristics are as follows:
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Transmission rates are greatly reduced when compared with physical connections.
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WIMAX is based on Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.16 standards or Broadband Wireless Access.
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An acceptable rule of thumb is that WIMAX will sustain 70 Mbps transmission rates at approximately 30 miles.
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As distance increases, throughput decreases and vice versa.
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Competition for access point connectivity is reduced through scheduling such that once the WIMAX device connects to the access point, it is assigned a set time to communicate with the access point from then on.
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Satellite Satellite dishes are starting to gain popularity as a way to access the Internet. Many times (as is the case with cable), your carrier or ISP will provide you with television service or some other form of service, so you can use the satellite dish for multiple purposes. In addition, the dish is less intrusive into your home because it's mounted with very little need for wires or a run to a CO. A typical satellite-based network is shown in Figure 7.2. Characteristics of satellite are as follows:
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A satellite is used to allow a user with a laptop, personal digital assistant (PDA), or PC with wireless satellite capabilities to connect to the Internet from anywhere within the coverage area.
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It includes usage of low Earth orbit (LEO) and medium Earth orbit (MEO) satellites.
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LEOs are primarily used with Internet-based satellite communications and are typically located at about 1,800 to 2,000 miles above Earth.
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MEOs are located at about 9,000 to 10,000 miles above Earth.
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There are also geosynchronous Earth orbits (GEOs), which are typically used for the carrier's or ISP's trunk lines.
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GEOs are located at about 22,000 to 23,000 miles above Earth.
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Wireless systems and satellites are commonly used in geographical areas that are far from a CO or when extreme flexibility is needed.
Architecture of a Wireless Wide-Area Network (WWAN)
Vijay K. Garg , in Wireless Communications & Networking, 2007
7.3 Logical Channels
A WWAN uses a variety of channels in which the information is carried. In GSM, these channels are separated into physical channels and logical channels [10, 11]. The physical channels are determined by the time slots, whereas the logical channels are determined by the information carried within the physical channels. It can be further summarized by saying that several recurring time slots on a carrier constitute a physical channel. These are then used by different logical channels to transfer information. These channels may either be used for user data (payload) or signaling to enable the system to operate.
In GSM logical channels (see Figure 7.4) are used to carry traffic and control information. There are three types of logical channels: traffic channels (TCHs), control channels (CCHs), and the cell broadcast channel (CBCH). The traffic channels are used to transmit user information (speech or data). The control channels are used to transmit control and signaling information. The cell broadcast channel is used to broadcast user information from a service center to the mobile stations listening to a given cell area. It is a unidirectional (downlink-only, base station to mobile station), point-to-multipoint channel used for a short-information message service. Some special constraints are imposed on the design of the CBCH because of the requirement that this channel can be listened in parallel with the broadcast control channel (BCCH) information and the paging messages.
Figure 7.4. GSM logical channel.
The control channels consist of broadcast channel (BCH), common control channel (CCCH), and dedicated control channel (DCCH). The broadcast channels are used for such functions as correcting mobile frequencies, frame synchronization, control channel structure, and so on. They are point-to-multipoint, downlink-only channels. These channels consist of BCCH, frequency correction channel (FCCH), and synchronization channel (SCH).
The BCCH is used to send cell identities, organization information about common control channels, cell service available, and so on. The frequency correction channel is used to transmit frequency correction data bursts that contain the set of all "0." This gives a constant frequency shift of the RF carrier that can be used by the mobile station for frequency correction. The synchronization channel (SCH) is used for time synchronization of the mobile stations. The data on this channel include frame number as well as the base station identity code (BSIC) required by mobile stations when measuring base station signal strength.
The CCCHs include paging channel (PCH), access grant channel (AGCH) and random access channel (RACH). The CCCHs are point-to-multipoint downlink-only channels that are used for paging and access. The PCHs are used to page mobile stations. The mobile stations need to listen for paging during certain times. The AGCHs are downlink-only channels used to assign mobiles to stand-alone dedicated control channels (SDCCHs) for initial assignment. The RACHs are uplink-only channels used by mobile stations for transmitting their requests for dedicated connections to the network.
There are two types of DCCHs: SDCCH and associated control channel (ACCH). The SDCCHs are bidirectional, point-to-point channels that are used for service request, subscriber authentication, ciphering initiation, equipment validation, and assignment to a traffic channel (TCH). The ACCHs are bidirectional, point-to-point channels that are associated with a given TCH and SDCCH. These channels are used to send out-of-band signaling and control data between the mobile station and the base station. Examples of their use are to send signal strength measurements from a mobile station to the base station or to send transmission timing information from the base station to the mobile station. The associated control channels are further divided as slow associated control channels (SACCHs) and fast associated control channels (FACCHs). Figure 7.4 shows all GSM logical channels. Table 7.1 lists briefly the role of each logical channel. For more details, refer to the GSM 04.03, 05.01, and 05.2 series recommendations [4, 5].
Table 7.1. Role of logical channels in GSM.
Logical channel
Role of the logical channel
TCH/F
Full rate traffic channel to carry payload at 22.8 kbps
TCH/H
Half rate traffic channel to carry payload at 11.4 kbps
BCCH
Broadcast network information
SCH
Synchronization of the mobile stations
FCCH
Used for frequency correction
AGCH
Acknowledges channel request from mobile and allocates an SDCCH
FACCH
For time critical signaling over TCH (e.g., for handoff signaling); traffic burst is stolen for a full signaling burst
SACCH
TCH in-band signaling, e.g., for link monitoring
SDCCH
For signaling exchange, e.g., during call setup, registration/location updates
FACCHs
FACCH for SDCCH. The SDCCH burst is stolen for a full signaling burst.
SACCHs
SDCCH in-band signaling, e.g., for link monitoring
Vijay K. Garg , in Wireless Communications & Networking, 2007
12.6 Summary
In this chapter we focused on mobility management in wireless wide area networks (WWANs). Mobility is concerned with radio mobility and network mobility. Radio mobility involves a handoff process, whereas network mobility deals with mobile paging and location update. We presented an application of the simple mobility model based on a fluid flow concept for a wireless network in an urban area with small cells and high user density. Next, we discussed mobile registration procedures and message flows of ANSI-41 standards for North American cellular systems and highlighted differences with the token-based registration scheme used in GSM. We concluded the chapter by explaining different types of handoff (hard, soft, and softer), handoff procedure, and message flows for the intra- and inter-MSC handoff.
Vijay K. Garg , in Wireless Communications & Networking, 2007
1.2 First- and Second-Generation Cellular Systems
The first- and second-generation cellular systems are the WWAN. The first public cellular telephone system (first-generation, 1G), called Advanced Mobile Phone System (AMPS) [8, 21], was introduced in 1979 in the United States. During the early 1980s, several incompatible cellular systems (TACS, NMT, C450, etc.) were introduced in Western Europe. The deployment of these incompatible systems resulted in mobile phones being designed for one system that could not be used with another system, and roaming between the many countries of Europe was not possible. The first-generation systems were designed for voice applications. Analog frequency modulation (FM) technology was used for radio transmission.
In 1982, the main governing body of the European post telegraph and telephone (PTT), la Conférence européenne des Administrations des postes et des télécommunications (CEPT), set up a committee known as Groupe Special Mobile (GSM) [9], under the auspices of its Committee on Harmonization, to define a mobile system that could be introduced across western Europe in the 1990s. The CEPT allocated the necessary duplex radio frequency bands in the 900 MHz region.
The GSM (renamed Global System for Mobile communications) initiative gave the European mobile communications industry a home market of about 300 million subscribers, but at the same time provided it with a significant technical challenge. The early years of the GSM were devoted mainly to the selection of radio technologies for the air interface. In 1986, field trials of different candidate systems proposed for the GSM air interface were conducted in Paris. A set of criteria ranked in the order of importance was established to assess these candidates.
The interfaces, protocols, and protocol stacks in GSM are aligned with the Open System Interconnection (OSI) principles. The GSM architecture is an open architecture which provides maximum independence between network elements (see Chapter 7) such as the Base Station Controller (BSC), the Mobile Switching Center (MSC), the Home Location Register (HLR), etc. This approach simplifies the design, testing, and implementation of the system. It also favors an evolutionary growth path, since network element independence implies that modification to one network element can be made with minimum or no impact on the others. Also, a system operator has the choice of using network elements from different manufacturers.
GSM 900 (i.e., GSM system at 900 MHz) was adopted in many countries, including the major parts of Europe, North Africa, the Middle East, many east Asian countries, and Australia. In most of these cases, roaming agreements exist to make it possible for subscribers to travel within different parts of the world and enjoy continuity of their telecommunications services with a single number and a single bill. The adaptation of GSM at 1800 MHz (GSM 1800) also spreads coverage to some additional east Asian countries and some South American countries. GSM at 1900 MHz (i.e., GSM 1900), a derivative of GSM for North America, covers a substantial area of the United States. All of these systems enjoy a form of roaming, referred to as Subscriber Identity Module (SIM) roaming, between them and with all other GSM-based systems. A subscriber from any of these systems could access telecommunication services by using the personal SIM card in a handset suitable to the network from which coverage is provided. If the subscriber has a multiband phone, then one phone could be used worldwide. This globalization has positioned GSM and its derivatives as one of the leading contenders for offering digital cellular and Personal Communications Services (PCS) worldwide. A PCS system offers multimedia services (i.e., voice, data, video, etc.) at any time and any where. With a three band handset (900, 1800, and 1900 MHz), true worldwide seamless roaming is possible. GSM 900, GSM 1800, and GSM 1900 are second-generation (2G) systems and belong to the GSM family. Cordless Telephony 2 (CT2) is also a 2G system used in Europe for low mobility.
Two digital technologies, Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) (see Chapter 6 for details) [10] emerged as clear choices for the newer PCS systems. TDMA is a narrowband technology in which communication channels on a carrier frequency are apportioned by time slots. For TDMA technology, there are three prevalent 2G systems: North America TIA/EIA/IS-136, Japanese Personal Digital Cellular (PDC), and European Telecommunications Standards Institute (ETSI) Digital Cellular System 1800 (GSM 1800), a derivative of GSM. Another 2G system based on CDMA (TIA/EIA/IS-95) is a direct sequence (DS) spread spectrum (SS) system in which the entire bandwidth of the carrier channel is made available to each user simultaneously (see Chapter 11 for details). The bandwidth is many times larger than the bandwidth required to transmit the basic information. CDMA systems are limited by interference produced by the signals of other users transmitting within the same bandwidth.
The global mobile communications market has grown at a tremendous pace. There are nearly one billion users worldwide with two-thirds being GSM users. CDMA is the fastest growing digital wireless technology, increasing its worldwide subscriber base significantly. Today, there are already more than 200 million CDMA subscribers. The major markets for CDMA technology are North America, Latin America, and Asia, in particular Japan and Korea. In total, CDMA has been adopted by almost 50 countries around the world.
The reasons behind the success of CDMA are obvious. CDMA is an advanced digital cellular technology, which can offer six to eight times the capacity of analog technologies (AMP) and up to four times the capacity of digital technologies such as TDMA. The speech quality provided by CDMA systems is far superior to any other digital cellular system, particularly in difficult RF environments such as dense urban areas and mountainous regions. In both initial deployment and long-term operation, CDMA provides the most cost effective solution for cellular operators. CDMA technology is constantly evolving to offer customers new and advanced services. The mobile data rates offered through CDMA phones have increased and new voice codecs provide speech quality close to the fixed wireline. Internet access is now available through CDMA handsets. Most important, the CDMA network offers operators a smooth migration path to third-generation (3G) mobile systems, [3, 5, 7, 11].
Design considerations and network architectures for low-power wide-area networks
Bharat Chaudhari , Suresh Borkar , in LPWAN Technologies for IoT and M2M Applications, 2020
2.2.6 Security and privacy
Security threats arise especially due to heterogeneity of and physical accessibility to devices and the openness of the systems connected to the Internet through LPWAN wireless air interface [5]. Risk of vulnerability to cyberattacks is particularly relevant to IoT LPWAN MTC environments due to the massive number of devices involved. To avoid intrusion and hacking, encryption of both the application payload and the network admission request needs to be considered.
Due to cost and energy considerations, it becomes necessary for LPWAN networks to settle for simpler communication protocols for authentication, security, and privacy. Over the air as an alternative to authentication by personalization is a key facility to assure that end devices are not exposed to any security risks over prolonged duration [6]. This may be comparatively expensive in proprietary LPWAN networks operating in unlicensed bands.
In many networks, strong encryption and authentication schemes such as advanced encryption suite are used for confidential data transport, Diffie-Hellman utilized for key exchange and management, and Rivest-Shamir-Adleman are applied to authenticate digital signatures and key transport [2]. These are based on cryptographic suites with robust protocols. Similarly, for 3rd Generation Partnership Project (3GPP) cellular-based systems, subscription identity module–based authentication technique provides comparatively robust protection.
Automating posture management and use of software updates to patch vulnerabilities may be needed to isolate devices from potential attackers [4]. In order to provide protection and to isolate the device and its application, an overlay network may need to be explored. This provides security since the unique local addresses used in the overlay network do not allow access from outside the overlay.
Fourth Generation Systems and New Wireless Technologies
Vijay K. Garg , in Wireless Communications & Networking, 2007
23.1 Introduction
With the rapid development of wireless communication networks, it is expected that fourth-generation (4G) mobile systems will be launched within a decade. 4G mobile systems focus on seamless integration of existing wireless technologies including WWAN, WLAN, and Bluetooth (see Figure 23.1). This is in contrast with 3G, which merely focuses on developing new standards and hardware. The recent convergence of the Internet and mobile radio has accelerated the demand for "Internet in the pocket," as well as for radio technologies that increase data throughput and reduce the cost per bit. Mobile networks are going multimedia, potentially leading to an explosion in throughput from a few bytes for the short message service (SMS) to a few kilobits per second (kbps) for the multimedia messaging service (MMS), to several 100 kbps for video content. In addition to wide area cellular systems, diverse wireless transmission technologies are being deployed, including digital audio broadcast (DAB) and digital video broadcast (DVB) for wide-area broadcasting, local multipoint distribution service (LMDS), and multichannel multipoint distribution service (MMDS) for fixed wireless access. IEEE 802.11b, 11a, 11g, 11n, and 11h standards for wireless local area networks (WLANs) are extending from the enterprise world into public and residential domains. Because they complement cellular networks, these new wireless network technologies and their derivatives may well prove to be the infrastructure components of the future 4G mobile networks when multistandard terminals become widely available. This is already the case for WiFi in the public "hot-spots," which is being deployed by mobile operators around the world with the aim to offer seamless mobility with wireless wide-area networks.
Figure 23.1. Seamless connections of networks.
The 4G systems will encompass all systems from various networks, public to private, operator-driven broadband networks to personal areas, and ad hoc networks. The 4G systems will be interoperable with 2G and 3G systems, as well as with digital (broadband) broadcasting systems. The 4G intends to integrate from satellite broadband to high altitude platform to cellular 2G and 3G systems to wireless local loop (WLL) and broadband wireless access (BWA) to WLAN, and wireless personal area networks (WPANs), all with IP as the integrating mechanism. Table 23.1 provides a comparison of key parameters of 4G with 3G systems.
Table 23.1. Comparison of key parameters of 4G with 3G.
Details
3G including 2.5G (EDGE)
4G
Major requirement driving architecture
Predominantly voice driven, data was always add on
Converge data and voice over IP
Network architecture
Wide area cell-based
Hybrid-integration of WLAN (WiFi, Bluetooth) and wireless wide-area networks
Speeds
384 kbps to 2 Mbps
20 to 100 Mbps in mobile mode
Frequency band
Dependent on country or continent (1.8 to 2.4 GHz)
Higher frequency bands (2 to 8 GHz)
Bandwidth
5 to 20 MHz
100 MHz or more
Switching design basis
Circuit and packet
All digital with packetized voice
Access technologies
WCDMA, cdma2000
OFDM and multicarrier (MC)-CDMA
Forward error correction
Convolutional codes rate ½, ⅓
Concatenated coding schemes
Component design
Optimized antenna design, multiband adapters
Smart antenna, software-defined multiband and wideband radios
MCSA/MCSE 70-291: Configuring the Windows 2003 Routing and Remote Access Service LAN Routing, Dial-up Services, and Routing Protocols
Deborah Littlejohn Shinder , ... Laura Hunter , in MCSA/MCSE (Exam 70-291) Study Guide, 2003
Categorizing Wireless Networks
Wireless networks can be categorized according to their scope, similarly to wired networking, as follows:
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Wireless personal area networks (WPANs)
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Wireless local area networks (WLANs)
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Wireless metropolitan area networks (WMANs)
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Wireless wide area networks (WWANs)
WPANs connect personal devices such as personal digital assistants (PDAs), cellular phones, laptop computers, and other devices together to share resources or data over a very limited area. WPANs can operate using either infrared or radio frequency. Bluetooth defines a radio frequency-based WPAN. Bluetooth is a technology that is moving toward IEEE standardization through the IEEE 802.15 working group. It provides wireless connectivity at distances up to 30 feet with capabilities to penetrate walls, briefcases, pockets, and so on. Infrared networking typically is limited to line of sight connectivity at a distance no greater than about three feet. Line of sight means that connectivity cannot be established between devices without an unobstructed path between them.
WLANs enable users to share resources throughout a local area (typically an office or a building). WLANs have evolved through the IEEE 802.11 standard. IEEE 802.11 WLANs started life at transfer speeds of 1 Mbps to 2 Mbps. Through evolution and improvement, 802.11b developed as a standard for 11 Mbps transfer rates and new implementations can operate at 22 Mbps, over areas of approximately 300 feet. Two new standards are evolving at 55 Mbps, 802.11a and 802.11 g. IEEE 802.11a is an existing standard, and 802.11 g is nearing completion as a standard. 802.11a provides better speed but shorter distances than 802.11b, whereas 802.11 g combines the high speed of 802.11a with the greater distance span of 802.11b. 802.11 devices connect to existing wired LANs through wireless access points (WAPs) or to one another in peer-to-peer fashion. Wireless bridges can be used to connect devices to the wireless network or to connect two wireless networks together.
Note
The distances given for wireless networking are based on standard antennas. 802.11 network connectivity can be extended by using special high gain antennas, either omnidirectional (which can extend the range up to a kilometer or more) or directional antennas such as the Yagi (which can extend the range to over five kilometers).
WMANs connect buildings within a campus or city through infrared or radio frequency. Again, the disadvantage to infrared is the line of sight requirements. Clouds, aircraft, or anything else that can block line of sight transmission can disrupt infrared WMANs. Radio frequency WMAN technologies, such as multichannel multipoint distribution service (MMDS) and the local multipoint distribution services (LMDS), already exist but the IEEE 802.16 working group has not finalized on any standards at this point.
WWAN technology has been around for several years now. The current players in this field are Global System for Mobile Communications (GSM), Cellular Digital Packet Data (CDPD), and Code Division Multiple Access (CDMA). Current cellular phones use these second generation (2G) technologies. These antenna and satellite-based technologies exhibit compatibility problems with one another, hindering the ability to roam worldwide and utilize the same technology for connectivity worldwide. In an effort to provide standardization and worldwide roaming capabilities, the International Telecommunication Union is working currently working on the third generation of WWAN technology, known as 3G.
Rajiv Ramaswami , ... Galen H. Sasaki , in Optical Networks (Third Edition), 2010
10-Gigabit Ethernet Physical Layer
10-Gigabit Ethernet physical layer also has the physical coded sublayer (PCS), physical media attachment (PMA) sublayer, and physical media dependent (PMD) sublayer. There are PMDs for fiber optic and copper cables. For fiber optic cables, there are three PCS options: LAN PHY, WAN PHY, and WWAN PHY. Both the LAN PHY and WAN PHY use a (64,66) line code. The WAN PHY was designed for wide-area network applications. It has an extra WAN interface sublayer (WIS) between the PCS and PMA sublayers that encapsulates the Ethernet MAC frame into a simplified SONET frame.
Both the LAN PHY and WAN PHY operate over short-range (SR), long-range (LR), extended-range (ER), and long reach multimode (LRM) PMDs. The short-range PMD is at 850 nm wavelength at a reach of 82 m on older multimode fiber technology and 300 m on OM3 multimode fiber. The long-range PMD is at 1310 nm wavelength at a reach of 10 km on single-mode fiber and 260 m on OM3 multimode fiber. The extended-range PMD is at 1550 nm wavelengths and at a reach of 40 km on single-mode fiber. Long reach multimode PMD is at 1310 nm wavelength over multimode fiber at distances of 260 m.
The WWAN PHY PCS uses four 2.5 Gb/s links using an (8,10) line code. The PMD is for four wavelengths multiplexed on either multimode fiber (reach of 300 m) or single-mode fiber (reach of 10 km).
10-Gigabit Ethernet on copper cable has short ranges, which is sufficient for applications as interconnects and backplanes. There is a PMD for twisted pair cables with a reach of 100 m which uses multilevel modulation. The 10GBASE-CX4 PMD has a reach of 15 m. It has four parallel channels, each at 2.5 Gb/s, and uses an (8,10) line code. The least expensive copper PMD is CX1, which is for twinax cable (coaxial cable but with two inner conductors) at a reach of 10 m.
Wireless sensor networks applications to smart homes and cities
A. Belghith , M.S. Obaidat , in Smart Cities and Homes, 2016
3.3 Third access technologies architecture
The third architecture is presented in Fig. 2.9. As in the first architecture, the wireless sensors send measurement results to the personal server. Then, the personal server gathers and forwards data to the home server. Unlike in the first architecture, the connection between the personal server and the home server is performed using Wireless Wide Area Network (WWAN) technologies such as 2G, 2.5G, 3G, and 4G. Finally, the home server, connected to the Internet, sends data to the distant server.
Figure 2.9. Third Access Technologies Architecture: Use of WPAN and WWAN
Now, we briefly describe some WWAN technologies. The second generation (2G) of mobile networks started to be deployed in the beginning of the 1990s. The main 2G mobile network, and the most successful, by far, is the GSM [51,102]. The services were limited to voice and Short Message Service (SMS).
The so-called two-and-half generation (2.5G or 2G+) such as General Packet Radio Service (GPRS) [52] and Enhanced Data Rates for GSM Evolution (EDGE) [53,102] added packet data services and increased data rate. This generation is mainly used for Internet-style access and email. The theoretical maximum rate in the GPRS system is 115 Kbps while the EDGE system provides better theoretical maximum rate (up to 384 Kbps) [102].
Nevertheless, users need wireless high-speed Internet access. Moreover, users want to be able to access the Internet from a large area. The 3G system can support multimedia, data, video, and other services along with voice. The main 3G systems are the UMTS [54] and CDMA2000 [55,102]. The first deployment of CDMA2000 and UMTS took place in 2000–01.
Yet, the 3G systems are still in evolution. The first data rates were in the magnitude of 1 Mbps. Nowadays much higher data rates are expected in both uplink and downlink with the High Speed Downlink Packet Access (HSDPA) and the High Speed Uplink Packet Access (HSUPA) evolutions [56] (see, eg, Release 7 of UMTS). Apart from the displayed physical data rates, application-level data rates are smaller. For example, in 2007, the HSUPA could reach 1 Mbps for a File Transfer Protocol (FTP) application [57]. More recent versions of HSUPA have higher figures. The next step after 3G is (evidently) 4G or what is also known as Beyond 3G (B3G).
Long-Term Evolution (LTE) defined by third Generation Partnership Project (3GPP) Release 8 in 2008 is a very promising technology providing a high peak data rate of 163 Mbps in a channel bandwidth of 10 MHz and a low latency of 15 ms [58]. The enhancement of LTE, called LTE-Advanced (LTE-A), aims to reach a peak data rate of 1 Gbps in order to have a fourth-generation (4G) access technology. This technology continues to evolve through Release 13 that is planned to be completed in March 2016 although some features will be added [59]. This release includes advanced features such as supporting Advanced three Band Carrier Aggregation (three in Downlink/one in Uplink).
The different access technologies can be evaluated using experimental tests or simulation tools. Note that a web-based simulation tool, proposed in Ref. [60], provides a simulation environment with Network Simulation 2 (NS-2) [61] and includes WSN and Bluetooth modules that can be used to practically evaluate different access technologies for WSN networks.
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