Wireless Device

QoS in Wireless Networks

XiPeng Xiao , in Technical, Commercial and Regulatory Challenges of QoS, 2008

Energy Constraint

Wireless devices, particularly handheld and mobile devices that are battery operated, are energy constrained because they lack a continuous source of power. This means that the algorithms and protocols for wireless transmission must be energy efficient. The devices may additionally be constrained by their processing capability, making the design of such systems even more challenging.

Therefore, the goal of wireless QoS is to optimize use of limited resources and meet the requirements of different applications by providing ways to control access to, and use of, the wireless medium, based on the characteristics of the application. Since each application has its own requirements for delay, bandwidth, jitter, and loss, the QoS capability must cater to these needs. For example, applications that require high reliability, such as data or email that need delivery of error-free files, must be delivered with low loss and error rates. Similarly, applications that require low delay (for example, voice) may be given higher priority to use the medium, while applications that require higher bandwidth (for example, video) may be assigned longer transmit times or more efficient modulation schemes at the physical layer.

In the next two sections, we examine how these issues are tackled in two popular wireless standards, the IEEE 802.11 Wi-Fi standard for wireless LANs, and the IEEE 802.16 standard for wireless MANs.

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Wireless Technology Overview

Jennifer Ann Kurtz , in Hacking Wireless Access Points, 2017

Wireless Devices, Simplified

Our wireless devices are wonders to behold. Consider a typical smartphone. It is first and foremost a computer with an operating system. As with any computer, the rules of security hygiene apply: Keep your operating system up to date, use anti-virus (AV) software, and do not use easily guessable passwords.

The smartphone typically supports one or two technologies associated with the mobile carrier, a Wi-Fi connection so the smartphone can use a home network or commercial hotspot (in order to save minutes or megabytes associated with mobile carrier limits), and a Bluetooth connection to support a wireless headset and hands-free communications while operating an automobile or treadmill.

How does a smartphone vendor know what features to provide in its products? It reviews a set of technology standards with its mobile carrier partners to determine what features are mandatory for the product to function and what features provide a competitive advantage to the vendor. We will talk about technology standards in the next section.

With few exceptions, users typically refuse to pay more for devices with additional security features. Vendors and carriers may have security features turned off or set to minimum capabilities out of the box so that naïve users do not complain about being unable to access certain sites or features. This means that we as individuals and corporate or governmental staff must determine how to use mobile technology responsibly and in compliance with prevailing policy in our respective environments. We can determine what security features our smartphone has and what settings provide the appropriate security for our devices.

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RF Propagation, Antennas, and Regulatory Requirements

Shahin Farahani , in ZigBee Wireless Networks and Transceivers, 2008

5.10.3 Brief Overview of European Regulations

The wireless devices sold in Europe must receive Conformité Européenne (CE) marking, which is French for European Conformity; they need to comply with Electromagnetic Compatibility (EMC) Directive 89/336/EEC [15]. The European Radio-communications Committee (ERC) Recommendation [16] is a good starting point for understanding European regulations for low-power radio operation.

In European regulatory documents the signals are divided into two categories of narrowband and wideband signals. IEEE 802.15.4 signals are in the wideband category because, per ETSI EN 300 328 document [13], signals modulated via frequency-hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) are considered wideband signals. The emission limits are defined with dBm/Hz units, but actual measurements are taken over a larger bandwidth, such as 100   KHz or 1   MHz.For instance, the –80 dBm/Hz emission limit is equivalent to –30 dBm/100   KHz:

- 80 dBm / Hz + 10 × log 10 ( 10 ) 5 = - 80 dBm / Hz + 50 = - 30 dBm / 100 Hz

Maximum in-band transmission power is 100   mW ERP when FHSS is used. For DSSS, the maximum transmit power is 10 mW/MHz. ERC Recommendation 70-30 [16] imposes a maximum active mode duty cycle of 1% (in any one-hour window) for operations in the 868   MHz band. In contrast with the FCC, the ETSI specifies two separate sets of spurious emission requirements for standby and operating modes. European regulations are summarized in Tables 5.6 and 5.7.

Table 5.6. Summary of In-Band Transmit Power Limits

Region Frequency Band Power Limit Comment
United States 902–928   MHz
2400–2483.5   MHz		 1000   mW/MHz
Canada 2400–2483.5   MHz 1000   mW/MHz Some limitations apply based on installation location
Europe 868–868.6   MHz 25   mW Duty cycle < 1% in any 1   h period
2400–2483.5   MHz 100   mW EIRP For FHSS
10   mW/MHz Any other modulation (DSSS, etc.)
Japan 2400–2483.5 MHz 10   mW/MHz Assuming DSSS

Table 5.7. Summary of Spurious Emission Limits for 30   MHz to 12.75   GHz Bands

Frequency Band North America Europe (DSSS or FHSS) Japan
30–88   MHz –55.3   dBm/100KHz –86   dBm/Hz operating –107   dBm/Hz standby/receive –26.02   dBm/MHz
88–216   MHz –51.8   dBm/100KHz
216–960   MHz –49.2   dBm/100KHz
960–1000   MHz –41.2   dBm/100KHz
1000–2387   MHz –41.2   dBm/MHz –80   dBm/Hz operating –97   dBm/Hz standby/receive
2387–2400   MHz –16.02   dBm/MHz
2400–2483.5   MHz Common ISM Band
2483.5–2496.5   MHz –41.2   dBm/MHz –80   dBm/Hz operating –97   dBm/Hz standby/receive –16.02   dBm/MHz
2496.5–12750   MHz –26.02   dBm/MHz

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Looking Ahead: Cisco Wireless Security

Eric Knipp , ... Edgar Danielyan , in Managing Cisco Network Security (Second Edition), 2002

Where in the Authentication/Association Process Does MAC Filtering Occur?

When a wireless device wants to connect to a WLAN, it goes though a two-part process called authentication and authorization. After both have been completed, the device is allowed access to the WLAN.

As mentioned earlier, when a wireless device is attempting to connect to a WLAN, it sends an authentication request to the AP (see Figure 15.4).This request will contain the SSID of the target network, or a null value if connecting to an open system. The AP will grant or deny authentication based on this string. Following a successful authentication, the requesting device will attempt to associate with the AP. It is at this point in time that MAC filtering plays its role. Depending on the AP vendor and administrative setup of the AP, MAC filtering either allows only the specified MAC addresses—blocking the rest, or it allows all MAC addresses—blocking specifically noted MACs. If the MAC address is allowed, the requesting device is allowed to associate with the AP.

Figure 15.4. MAC Filtering

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Cognitive Radio Architecture

Joseph MitolaIII, in Cognitive Radio Technology (Second Edition), 2009

14.6.7 When Should a Radio Transition Toward Cognition?

If a wireless device accesses only a single-RF band and mode, then it is not a very good starting point for CR—it's just too simple. Even as complexity increases, as long as the user's needs are met by wireless devices managed by the network(s), then embedding computational intelligence in the device has limited benefits. In 1999, Mitsubishi and AT&T announced the first "four-mode handset." The T250 operated in time division multiple access (TDMA) mode on 850 or 1900 MHz, in first-generation advanced mobile phone system (AMPS) mode on 850 MHz, and in cellular digital packet data (CDPD) mode on 1900 MHz. This illustrates the early development of multiband, multimode, multimedia (M3) wireless. These radios enhanced the service provider's ability to offer national roaming, but the complexity was not apparent to the user because the network managed the radio resources of the handset.

Even as device complexity increases in ways that the network does not manage, there may be no need for cognition. There are several examples of capabilities embedded in electronics that are not heavily used. For example, how many people use their laptop's speech-recognition system? What about its Infrared Data Association (IrDA) port? The typical users in 2004 didn't use either capability of their Windows XP laptop all that much. So complexity can increase without putting a burden on the user to manage that complexity if the capability isn't central to the way in which the user employs the system.

For the radio, as the number of bands and modes increases, the SDR becomes a better candidate for the insertion of cognition technology. But it is not until the radio or the wireless part of the PDA has the capacity to access multiple RF bands that cognition technology begins to pay off. With the liberalization of RF spectrum use rules, the early evolution of CR may be driven by RF spectrum-use etiquette for ad hoc bands such as the FCC use case. In the not-too-distant future, SDR PDAs could access satellite mobile services, cordless telephone, WLAN, GSM, and 3G bands. An ideal SDR device with these capabilities might affordably access three octave bands, from 0.4 to 0.96 GHz (skipping the air navigation and GPS band from 0.96 to 1.2 GHz), from 1.3 to 2.5 GHz, and from 2.5 to 5.9 GHz (Figure 14.23). Not counting satellite mobile and radio navigation bands, such radios would have access to more than 30 mobile subbands in 1463 MHz of potentially sharable outdoor mobile spectrum. The upper band provides another 1.07 GHz of sharable indoor and RF-LAN spectrum.

Figure 14.23. Fixed spectrum allocations versus pooling with CR.

 (Source: © 1997, Dr. Joseph Mitola III, used with permission.)

This wideband radio technology will be affordable first for military applications, next for basestation infrastructure, then for mobile vehicular radios, and later for handsets and PDAs. When a radio device accesses more RF bands than the host network controls, it is time for CR technology to mediate the dynamic sharing of spectrum. It is the well-heeled conformance to the radio etiquettes afforded by CR that makes such sharing practical.

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Wireless Communications

Michele Zorzi , A. Chockalingam , in Encyclopedia of Physical Science and Technology (Third Edition), 2003

II.C Cordless Systems

Another class of popular wireless devices is that of cordless systems. The first generation of such systems is very simple, consisting of a base which communicates with a single portable unit, and basically represents a wireless extension of the household telephone. Because of their convenience, such systems have been very successful, but they are subject to interference and lack of security. Also, with the emergence of the concept of personal communication services, the desire for digital devices and for increased capability (including some mobility) has been growing.

Second generation cordless systems have therefore been introduced, in which the cordless phone becomes part of a geographically distributed network and can connect to various attachment points, instead of being constrained to its own base equipment. For example, a service called Telepoint has been offered in the U.K., where a cordless phone can connect to the wireless equivalent of public telephone booths.

Probably the most popular of second generation systems is the Digital European (Enhanced) Cordless Telecommunication (DECT) system. It uses radio channels spaced by 1.728   MHz, each with a data rate of 1.152   Mbps and capable of supporting 12 TDMA channels. All carriers are used throughout the system (no frequency reuse plan), and channels are dynamically selected based on channel measurements at the time of connection setup. Speech coding uses ADPCM which does not offer good compression performance (32   kbps per voice channel) but has very good robustness, especially needed in the very hostile environment (there is neither a priori separation between co-channel interferers nor SS protection). The two directions of communications share the same channel by time division duplexing (TDD). A DECT frame is made up of 24 slots, the first 12 carrying base-to-mobile traffic and the latter 12 carrying the mobile-to-base traffic. Control channels are provided by means of a dedicated field in each time slot.

Applications of DECT include residential systems (as with today's cordless phones), cordless PBXs with switching capability, telepoint public access (especially in high-density areas such as airports, train stations, and shopping and business centers), and radio in the local loop.

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Optical Wireless Security

Scott R. Ellis EnCE, RCA , in Network and System Security (Second Edition), 2014

6 Surface Area

Microwave and radio frequency (RF) antennas that are typically used to interconnect remote stations have a radial dispersion of 5 to 25 degrees. The actual wavelength of light for optical wireless is in the near-infrared range of 800–1500   nm.

Narrow beams are usually less than 0.5 degrees. By using the diagram and formula given in Figure 13.4, the approximate spread of the beam can be calculated providing the distance is known.

Figure 13.4. The width of the broadcast at x distance can be calculated using simple trigonometry. Different manufacturers boast different theta and use this formula to calculate the spread based on equipment specifications.

Generally speaking, optical wireless devices operate at the same wavelength as fiber-optic networks. Thus, a small wavelength creates frequencies in the several hundred terahertz (THz) range. This is much higher than commercial microwave communications. The lower power and tighter beam of the wireless optics prevent wide angles of reflection, which can be intercepted in an attack (see checklist: An Agenda for Action When Implementing the Security of FSO). Government organizations were among the first to recognize that the greater ability to control the wireless beam inherently meant a higher degree of freedom. The 128 and 256 advanced encryption standard is frequently used in microwave transmissions; while this is all well and good, many are concerned that it can be broken.

An Agenda for Action when Implementing the Security of FSO

The five items in this checklist are, in the author's experience; the most important and critical things to address (and they are listed in order of priority) in any project that aspires to achieve true security of the physical infrastructure. The easiest way to gain access to classified access is always the first way that will be attempted by those who wish to gain unauthorized access. So, assuming that data access prevention through traditional hacking attacks is in place, the key to security of FSO lies in the following (check all tasks completed):

_____1.

Intrusion alerts: When a signal is lost or disrupted, make sure your management software is capable of pinpointing when and where the interruption occurred.

_____2.

Entrusted access: Make sure that, either real or verified, the people working with the data are not selling it out the back door—that they are incorruptible.

_____3.

Physical security of hardware: Prevent actual physical access by unauthorized personnel.

_____4.

Eavesdropping on transmissions: Make sure that any mechanism that collects the data in transit is thwarted.

_____5.

Data security: Make sure that the data is encrypted, so that should it be intercepted it cannot be understood.

To intercept an optical wireless system, the hacker must know the location of either the origin or the target. The intruder must also have unhindered access to a location where he can set up his electronic equipment without being caught or disturbed. Since this location is usually a commercial location, at an elevation well above ground, the ability to insert becomes tremendously more challenging. FSO devices also employ multiplex, bidirectional signals. If the insertion is occlusive, then the units know when the signal has been disrupted. They will not continue to broadcast without the reverse bias feedback that indicates a successful connection. The interloper will only intercept connections establishing signals.

Additionally, the very high installations that are typical of optical wireless present additional challenges. But what about light scattered from rain, fog, dust, aerosol, or the like? Optical wireless transmissions use extremely low power levels, but the main reason for discounting this possible attack is the scattering of light in many different directions from the transmitted path.

The amount of radiation that can be collected with a detector capable of processing the signal is well beneath the range of what most detectors would consider noise. Because the beam is a laser, once the beam is scattered, the scattered photons still maintain their cohesion. However, being lasers, they tend to move in a very straight line with little incoherence. Capturing enough of the scattered light would require a collector that encapsulates the entire beam, and even then, it may not be enough. Ultimately, though, if the fog is such that one can see the actual beam (imagine a laser pen shining through fog), then it is conceivable that a collector could be designed that would be able to read the signal and translate its longitudinal section. The most likely scenario is that such an intercept device would only capture useless noise and would be so large as to make it extremely noticeable and unwieldy.

Lastly, a hacker could conceivably parachute onto the roof of a building and set his or her intercept device down on top of or next to the network FSO he or she wished to crack. For this reason, take the following precautions:

•

FSOs should have backstops to prevent overshoot to neighboring office windows or rooftops.

•

They should be mounted in difficult to reach places.

•

They should have physical security such as keycard and/or biometric access.

•

They should be protected by motion detection systems and motion-activated video surveillance.

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Introduction

Parisa Naraei , ... Iman Saberi , in Optimizing IEEE 802.11i Resource and Security Essentials, 2014

1.4 Purpose of the study

Nowadays, the number of wireless devices is growing significantly, but they all used to be computer systems. Wireless technology was not accessible in mobile and portable devices until in recent years. The purpose of this research is to determine the existing issues of the performance in current AES-CCMP encryption methods running on different types of devices and handle it so that an optimized resource usage would be achieved with the required security. Finally, two modes for 802.11-2012 for two different groups of devices will be created and evaluated with current encryption method for AES-CCMP to compare the performance.

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Introducing Bluetooth Applications

In Bluetooth Application Developer's Guide, 2002

Considering Power and Range

Power is a critical consideration for wireless devices. If a product is to be made wireless, unleashed from its wired connection, where will its power come from? Often the communication cable also acts as a power cable. With the cable gone, the subject of batteries is brought into focus, and the inevitable questions arise concerning battery life, standby time, and physical dimensions.

Some devices, such as headsets, have no need for power when they are connected with wires. Audio signals come down a wire and drive speakers directly; a very simple system with no need of extra power connections. When the wires are replaced with a Bluetooth link, suddenly we need power to drive the link, power to drive the microprocessor that runs the Bluetooth protocol stack, and power to amplify the audio signal to a level the user can hear. With small mobile devices you obviously do not want to install huge batteries, so keeping the power consumption low is an important consideration.

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Multimedia transmission over wireless networks fundamentals and key challenges

Gürkan Gür , in Modeling and Simulation of Computer Networks and Systems, 2015

5.2 Cognitive radio networks

A cognitive radio is a smart wireless device that can alter its operational parameters based on interaction with the surrounding environment involving its users. This interaction can either involve passive sensing and decision making locally within the radio, or can include active interactions with other nodes in the network [46]. The cognitive radio networks (CRNs) composed of cognitive radio nodes or nodes equipped with cognitive capabilities lead to smarter networks and communication technologies [48]. In addition to intelligent end-user devices, cognitive networks with the smart core/access network nodes (e.g., cognitive femtocells) can act as an enabler for smart grids, and smart ambient environments such as homes and workplaces, and smart transportation systems).

The agility and cognitive capabilities of CRs allow the optimization of various system and environmental parameters for multimedia transmission [48]. At the PHY layer, transmission power/frequency, waveform, beam profile and processing gain can be dynamically controlled. The MAC layer can consider external data such as localization or internal data such as application requirements for medium access and scheduling. Congestion control parameters and rate control parameters can be optimized at the transport layer. The cognitive engine with memory and sensory input in a cross-layer setting is shown in Figure 25.8. However, there are also fundamental challenges for CRN-based multimedia networking, the most important being the opportunistic nature of CRs. The dynamic spectrum access and secondary user requirements result in unstable and intermittent connection characteristics. Moreover, the interference from other CRs and primary users (PUs) degrade the transmission capacity. These intrinsic features complicate multimedia transmission over these networks and bring forth a challenging objective. The modeling of these systems is also challenging due to complexity stemming from diversity and degrees of freedom considering system parameters, control objectives and mechanisms. Moreover, the network environment in which these systems are embedded is highly dynamic and unpredictable due to the secondary nature of CRs.

Figure 25.8. Cross-layer design in CRNs.

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