The two most important phenomena impacting telecommunications over the past decade have been explosive parallel growth of both the internet and mobile telephone services. The internet brought the benefits of data communications to the masses with email, the web, and ecommerce; while mobile service has enabled “follow-me anywhere/always on” telephony. The internet helped accelerate the trend from voice-centric to data-centric networking. Data already exceeds voice traffic and the data share continues to grow. Now these two worlds are converging. This convergence offers the benefits of new interactive multimedia services coupled to the flexibility and mobility of wireless. To realize the full potential of this convergence, however, we need broadband access connections.
Here we compare and contrast two technologies that are likely to play important roles: Third Generation mobile (“3G”) and Wireless Local Area Networks (“WLAN”) . The former represents a natural evolution and extension of the business models of existing mobile providers. In contrast, the WiFi approach would leverage the large installed base of WLAN infrastructure already in place. We use 3G and WiFi as shorthand for the broad classes of related technologies that have two quiet distinct industry origins and histories.
Speaking broadly, 3G offers a vertically -integrated , top -down , service – provider approach to delivering wireless internet access , while WiFi offers an end -user -centric , decentralized approach to service provisioning. We use these two technologies to focus our speculations on the potential tensions between these two alternative world views. The wireless future will include a mix of heterogenous wireless access technologies. Moreover, we expect that the two world views will converge such that vertically-integrated service providers will integrate WiFi or other WLAN technologies into their 3G or wire line infrastructure when this make sense. The multiplicity of potential wireless access technologies and /or business models provided some hope that we may be able to realize robust facilities – based competition for broadband local access services. If this occurs, it would help solve the “last mile” competition problem that has been deviled telecommunication policy.
SOME BACKGROUND ON WiFi AND 3G
3G:
3G is a technology for mobile service providers. Mobile services are provided by service providers that own and operate their own wireless networks and sell mobile services to and -users. Mobile service providers use licensed spectrum to provide wireless telephone coverage over some relatively large contiguous geographic service area. Today it may include the entire country. From a user’s perspective, the key feature of mobile service is that it offers ubiquitous and continuous coverage. To support the service, mobile operators maintain a network of interconnected and overlapping mobile base stations that hand-off customers as those customers move among adjacent cells. Each mobile base station may support user’s upto several kilometers away. The cell towers are connected to each other by a backhaul network that also provides interconnection to the wire line Public Switched Telecommunications Network (PSTN) and other services. The mobile system operator owns the end-to-end network from the base stations to the backhaul networks to the point of interconnection to the PSTN. Third
Generations (3G) mobile technologies will support higher bandwidth digital communications. To expand the range and capability of data services that can be supported by digital mobile systems, service providers will have to upgrade their networks to one of the 3G technologies which can support data rates of from 384Kbps up to 2Mbps.
WiFi
WiFi is the popular name for the wireless Ethernet 802.11b standard for WLANs . WiFi allows collections of PCs, terminals ,and other distributed computing devices to share resources and peripherals such as printers, access servers etc. One of the most popular LAN technologies was Ethernet.
HOW ARE WiFi AND 3G SAME
From the preceding discussion, it might appear that 3G and WiFi address completely different user needs in quiet distinct markets that do not overlap. While this was certainly more true about earlier generations of mobile services when compared with wired LANs or earlier versions of WLANs , it is increasingly not the case. The end- user does not care what technology is used to support his service. What matter is that both of these technologies are providing platforms for wireless access to the internet and other communication services.
Wifi
Wi-Fi ( /ˈwaɪfaɪ/) is a branded standard for wirelessly connecting electronic devices. A Wi-Fi device, such as a personal computer, video game console, smartphone, or digital audio player can connect to the Internet via a wireless network access point. An access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Multiple overlapping access points can cover large areas.
“Wi-Fi” is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Wi-Fi is used by over 700 million people, there are over 4 million hotspots (places with Wi-Fi Internet connectivity) around the world, and about 800 million new Wi-Fi devices every year.[citation needed] Wi-Fi products that complete the Wi-Fi Alliance interoperability certification testing successfully can use the Wi-Fi CERTIFIEDdesignation and trademark
See also: Wi-Fi Alliance.
The Alliance enforces its use to identify a range of connectivity technologies based on the IEEE 802.11 standards from the Institute of Electrical and Electronics Engineers including wireless local area network (WLAN) connections, device to device connectivity [such as Wi-Fi Peer to Peer AKA Wi-Fi Direct], Personal area network (PAN), local area network (LAN) and even some limited wide area network (WAN) connections. Derivative terms, such as Super Wi-Fi, coined by the U.S. Federal Communications Commission (FCC) to describe proposed networking in the UHF TV band in the US, may or may not be sanctioned by the alliance.
Not every Wi-Fi device is submitted for certification to the Wi-Fi Alliance. The lack of Wi-Fi certification does not necessarily imply a device is incompatible with Wi-Fi devices/protocols. If it is compliant or partly compatible, the Wi-Fi Alliance may not object to its description as a Wi-Fi device though technically only the CERTIFIED designation carries their approval.
Wi-Fi certified and compliant devices are installed in many personal computers, video game consoles, MP3 players, smartphones, printers, digital cameras, and laptop computers. Some of these devices can share their internet connection, becoming a hotspot or “virtual router”.[1]
Wi-Fi technology builds on IEEE 802.11 standards. The IEEE develops and publishes some of these standards, but does not test equipment for compliance with them. The non-profit Wi-Fi Alliance formed in 1999 to fill this void — to establish and enforce standards for interoperability and backward compatibility, and to promote wireless local-area-network technology. As of 2010 the Wi-Fi Alliance consisted of more than 375 companies from around the world.[2][3] Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, gain the right to mark those products with the Wi-Fi logo.
Specifically, the certification process requires conformance to the IEEE 802.11 radio standards, the WPA and WPA2 security standards, and the EAP authentication standard. Certification may optionally include tests of IEEE 802.11 draft standards, interaction with cellular-phone technology in converged devices, and features relating to security set-up, multimedia, and power-saving.[4]
Most recently, a new security standard, Wi-Fi Protected Setup, allows embedded devices with limited graphical user interface to connect to the Internet with ease. Wi-Fi Protected Setup has 2 configurations: The Push Button configuration and the PIN configuration. These embedded devices are also called The Internet of Things and are low-power, battery-operated embedded systems. A number of Wi-Fi manufacturers design chips and modules for embedded Wi-Fi, such as GainSpan.[5]
The term Wi-Fi suggests Wireless Fidelity, resembling the long-established audio-equipment classification term high fidelity (in use since the 1930s[6]) or Hi-Fi(used since 1950[6]). Even the Wi-Fi Alliance itself has often used the phrase Wireless Fidelity in its press releases[7][8] and documents;[9][10] the term also appears in a white paper on Wi-Fi from ITAA.[11] However, based on Phil Belanger’s[note 1] statement, the term Wi-Fi was never supposed to mean anything at all.[12][13]
The term Wi-Fi, first used commercially in August 1999,[14] was coined by a brand-consulting firm called Interbrand Corporation that the Alliance had hired to determine a name that was “a little catchier than ‘IEEE 802.11b Direct Sequence’”.[12][13][15] Belanger also stated that Interbrand invented Wi-Fi as a play on words with Hi-Fi, and also created the Wi-Fi logo.
The Wi-Fi Alliance initially used an advertising slogan for Wi-Fi, “The Standard for Wireless Fidelity”,[12] but later removed the phrase from their marketing. Despite this, some documents from the Alliance dated 2003 and 2004 still contain the term Wireless Fidelity.[9][10] There was no official statement related to the dropping of the term.
The yin-yang Wi-Fi logo indicates the certification of a product for interoperability.[9]
Non Wi-Fi technologies intended for fixed points such as Motorola Canopy are usually described as fixed wireless. Alternative wireless technologies include mobile phone standards such as 2G, 3G or4G.
To connect to a WiFi LAN, a computer has to be equipped with a wireless network interface controller. The combination of computer and interface controller is called a station. All stations share a single radio frequency communication channel. Transmissions on this channel are received by all stations within range. The hardware provides no indication to the sender about whether the transmission was delivered and is therefore called a best-effort delivery mechanism. A carrier wave is used to transmit the data in packets, referred to as Ethernet frames. Each station is constantly tuned in on the channel, so each transmission is noticed. In order to determine whether the channel is free, the carrier wave can be sensed by the hardware; if not present the channel is free for transmission.
Internet access
A Wi-Fi enabled device such as a personal computer, video game console, smartphone or digital audio player can connect to the Internet when within range of a wireless network connected to the Internet. The coverage of one or more (interconnected) access points — called hotspots — can comprise an area as small as a few rooms or as large as many square miles. Coverage in the larger area may depend on a group of access points with overlapping coverage. Wi-Fi technology has been used in wireless mesh networks, for example, in London, UK.[16]
In addition to private use in homes and offices, Wi-Fi can provide public access at Wi-Fi hotspots provided either free-of-charge or to subscribers to various commercial services. Organizations and businesses - such as those running airports, hotels and restaurants – often provide free-use hotspots to attract or assist clients. Enthusiasts or authorities who wish to provide services or even to promote business in selected areas sometimes provide free Wi-Fi access. As of 2008 more than 300 metropolitan-wide Wi-Fi (Muni-Fi) projects had started.[17] As of 2010 the Czech Republic had 1150 Wi-Fi based wireless Internet service providers.[18][19]
Routers that incorporate a digital subscriber line modem or a cable modem and a Wi-Fi access point, often set up in homes and other premises, can provide Internet access and internetworking to all devices connected (wirelessly or by cable) to them. With the emergence of MiFi and WiBro (a portable Wi-Fi router) people can easily create their own Wi-Fi hotspots that connect to Internet via cellular networks. Now iPhone, Android, Bada and Symbian phones can create wireless connections.[20]
One can also connect Wi-Fi devices in ad-hoc mode for client-to-client connections without a router. Wi-Fi also connects places that would traditionally not have network access, for example kitchens and garden sheds.
City-wide Wi-Fi
In the early 2000s, many cities around the world announced plans for city-wide Wi-Fi networks. This proved to be much more difficult than their promoters initially envisioned with the result that most of these projects were either canceled or placed on indefinite hold. A few were successful, for example in 2005,Sunnyvale, California became the first city in the United States to offer city-wide free Wi-Fi,[21] and Minneapolis has generated $1.2 million profit annually fortheir provider.[22]
In May, 2010, London, UK Mayor Boris Johnson pledged London-wide Wi-Fi by 2012.[23] Both the City of London, UK[24] and Islington[25] already have extensive outdoor Wi-Fi coverage.
In 2010 Mysore became India’s first Wi-fi enabled city and second in the world after Jerusalem. A company called WiFiyNet has setup hotspots in Mysore covering the complete city and a few villages nearby.[citation needed]
Campus-wide Wi-Fi
Carnegie Mellon University built the first wireless Internet network using similar technology at their Pittsburgh campus in 1994, before Wi-Fi branding originated.[26] Many traditional college campuses provide at least partial wireless Wi-Fi Internet coverage.
Drexel University in Philadelphia became the United States’ first major university to offer completely wireless Internet access across the entire campus in 2000.[27]
Direct computer-to-computer communications
Wi-Fi also allows communications directly from one computer to another without the involvement of an access point. This is called the ad hoc mode of Wi-Fi transmission. This wireless ad hoc networkmode has proven popular with multiplayer handheld game consoles, such as the Nintendo DS, digital cameras, and other consumer electronics devices.
Disadvantage of this method is that vendors must not implement speeds greater that 11 Mbps(802.11b)[28] and only WEP encryption is available, not WPA(2).[citation needed]
Similarly, the Wi-Fi Alliance promotes a specification called Wi-Fi Direct for file transfers and media sharing through a new discovery- and security-methodology.[29] Wi-Fi Direct launched in October 2010.[30]
Future directions
As of 2010 Wi-Fi technology has spread widely within business and industrial sites. In business environments, just like other environments, increasing the number of Wi-Fi access points provides network redundancy, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells. Wi-Fi enables wireless voice-applications (VoWLAN or WVOIP). Over the years, Wi-Fi implementations have moved toward “thin” access points, with more of the network intelligence housed in a centralized network appliance, relegating individual access points to the role of “dumb” transceivers. Outdoor applications may use mesh topologies.
Advantages and problems
Advantages
Wi-Fi allows cheaper deployment of local area networks (LANs). Also spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.
Manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices.[citation needed]
Different competitive brands of access points and client network-interfaces can inter-operate at a basic level of service. Products designated as “Wi-Fi Certified” by the Wi-Fi Alliance are backwards compatible. Unlike mobile phones, any standard Wi-Fi device will work anywhere in the world.
Wi-Fi operates in more than 220,000 public hotspots and in tens of millions of homes and corporate and university campuses worldwide.[31] The current version of Wi-Fi Protected Access encryption (WPA2) as of 2010 is widely considered secure, provided users employ a strong passphrase. New protocols forquality-of-service (WMM) make Wi-Fi more suitable for latency-sensitive applications (such as voice and video); and power saving mechanisms (WMM Power Save) improve battery operation.
Limitations
Spectrum assignments and operational limitations are not consistent worldwide: most of Europe allows for an additional two channels beyond those permitted in the U.S. for the 2.4 GHz band (1–13 vs. 1–11), while Japan has one more on top of that (1–14). Europe, as of 2007, was essentially homogeneous in this respect.
A Wi-Fi signal occupies five channels in the 2.4 GHz band; any two channels whose channel numbers differ by five or more, such as 2 and 7, do not overlap. The oft-repeated adage that channels 1, 6, and 11 are the only non-overlapping channels is, therefore, not accurate; channels 1, 6, and 11 do, however, comprise the only group of three non-overlapping channels in the U.S.
Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm (100 mW).
The current ‘fastest’ norm, 802.11n, uses double the radio spectrum compared to 802.11a or 802.11g. This means there can only be one 802.11n network on 2.4 GHz band without interference to other WLAN traffic.
The Internet protocol was designed for a wired network in which packet loss due to noise is very rare and packets are lost almost exclusively due to congestion. On a wireless network, noise is common. This difference causes TCP to greatly slow or break transmission when noise is significant, even when most packets are still arriving correctly.[citation needed]
Reach
See also: Long-range Wi-Fi.
Wi-Fi networks have limited range. A typical wireless router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. IEEE 802.11n, however, can exceed that range by more than two times.[32] Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor ranges, through use of directional antennas, can be improved with antennas located several kilometres or more from their base. In general, the maximum amount of power that a Wi-Fi device can transmit is limited by local regulations, such as FCC Part 15 in USA.
Due to reach requirements for wireless LAN applications, Wi-Fi has fairly high power consumption compared to some other standards. Technologies such as Bluetooth (designed to support wirelessPAN applications) provide a much shorter propagation range of <10m[33] and so in general have a lower power consumption. Other low-power technologies such as ZigBee have fairly long range, but much lower data rate. The high power consumption of Wi-Fi makes battery life in mobile devices a concern.
Researchers have developed a number of “no new wires” technologies to provide alternatives to Wi-Fi for applications in which Wi-Fi’s indoor range is not adequate and where installing new wires (such as CAT-5) is not possible or cost-effective. For example, the ITU-T G.hn standard for high speed Local area networks uses existing home wiring (coaxial cables, phone lines and power lines). AlthoughG.hn does not provide some of the advantages of Wi-Fi (such as mobility or outdoor use), it’s designed for applications (such as IPTV distribution) where indoor range is more important than mobility.
Due to the complex nature of radio propagation at typical Wi-Fi frequencies, particularly the effects of signal reflection off trees and buildings, algorithms can only approximately predict Wi-Fi signal strength for any given area in relation to a transmitter.[34] This effect does not apply equally to long-range Wi-Fi, since longer links typically operate from towers that broadcast above the surrounding foliage.
]Mobility
The very limited practical range of Wi-Fi essentially confines mobile use to such applications as inventory-taking machines in warehouses or in retail spaces, barcode-reading devices at check-out stands, or receiving/shipping stations. Mobile use of Wi-Fi over wider ranges is limited, for instance, to uses such as in an automobile moving from one hotspot to another. Other wireless technologies are more suitable.[citation needed]
Data security risks
The most common wireless encryption-standard, Wired Equivalent Privacy (WEP), has been shown to be easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2) encryption, which became available in devices in 2003, aimed to solve this problem. Wi-Fi access points typically default to an encryption-free (open) mode. Novice users benefit from a zero-configuration device that works out-of-the-box, but this default does not enable any wireless security, providing open wireless access to a LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). On unencrypted Wi-Fi networks connecting devices can monitor and record data (including personal information), but such networks may use other means of protection, such as a VPN or secure Hypertext Transfer Protocol (HTTPS) over Transport Layer Security.
Interference
For more details on this topic, see Electromagnetic interference at 2.4 GHz.
Wi-Fi connections can be disrupted or the internet speed lowered by having other devices in the same area. Many 2.4 GHz 802.11b and 802.11g access-points default to the same channel on initial startup, contributing to congestion on certain channels. Wi-Fi pollution, or an excessive number of access points in the area, especially on the neighboring channel, can prevent access and interfere with other devices’ use of other access points, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points. This can become a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points.
Additionally, other devices use the 2.4 GHz band: microwave ovens, ISM band devices, security cameras, ZigBee devices, Bluetooth devices and (in some countries) Amateur radio, video senders, cordless phones and baby monitors, all of which can cause significant additional interference. It is also an issue when municipalities[35] or other large entities (such as universities) seek to provide large area coverage.
Hardware
USB wireless adapter
A wireless access point (WAP) connects a group of wireless devices to an adjacent wired LAN. An access point resembles a network hub, relaying databetween connected wireless devices in addition to a (usually) single connected wired device, most often an ethernet hub or switch, allowing wireless devices to communicate with other wired devices.
Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as PCI, miniPCI, USB, ExpressCard, Cardbus and PC Card. As of 2010, most newer laptop computers come equipped with internal adapters. Internal cards are generally more difficult to install.
Wireless routers integrate a Wireless Access Point, ethernet switch, and internal router firmware application that provides IP routing, NAT, and DNSforwarding through an integrated WAN-interface. A wireless router allows wired and wireless ethernet LAN devices to connect to a (usually) single WAN device such as a cable modem or a DSL modem. A wireless router allows all three devices, mainly the access point and router, to be configured through one central utility. This utility is usually an integrated web server that is accessible to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a desktop computer, as is the case with as Apple’s AirPort, which is managed with theAirPort Utility on Mac OS X and Microsoft Windows.[36]
Wireless network bridges connect a wired network to a wireless network. A bridge differs from an access point: an access point connects wireless devices to a wired network at the data-link layer. Two wireless bridges may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes.
Wireless range-extenders or wireless repeaters can extend the range of an existing wireless network. Strategically placed range-extenders can elongate a signal area or allow for the signal area to reach around barriers such as those pertaining in L-shaped corridors. Wireless devices connected through repeaters will suffer from an increased latency for each hop. Additionally, a wireless device connected to any of the repeaters in the chain will have a throughput limited by the “weakest link” between the two nodes in the chain from which the connection originates to where the connection ends.
Distance records
Distance records (using non-standard devices) include 382 km (237 mi) in June 2007, held by Ermanno Pietrosemoli and EsLaRed of Venezuela, transferring about 3 MB of data between the mountain-tops of El Águila and Platillon.[37][38] The Swedish Space Agency transferred data 420 km (260 mi), using 6 watt amplifiers to reach an overhead stratospheric balloon.[39]
Embedded systems
Embedded serial-to-Wi-Fi module
Increasingly in the last few years (particularly as of 2007), embedded Wi-Fi modules have become available that incorporate a real-time operating system and provide a simple means of wirelessly enabling any device which has and communicates via a serial port.[40] This allows the design of simple monitoring devices. An example is a portable ECG device monitoring a patient at home. This Wi-Fi-enabled device can communicate via the Internet.[41]
These Wi-Fi modules are designed[by whom?] so that implementers need only minimal Wi-Fi knowledge to provide Wi-Fi connectivity for their products.
The main issue with wireless network security is its simplified access to the network compared to traditional wired networks such as ethernet.[citation needed]With wired networking one must either gain access to a building (physically connecting into the internal network) or break through an external firewall. Most business networks protect sensitive data and systems by attempting to disallow external access. Enabling wireless connectivity provides an attack vector, particularly if the network uses inadequate or no encryption.[42]
An attacker who has gained access to a Wi-Fi network router can initiate a DNS spoofing attack against any other user of the network by forging a response before the queried DNS server has a chance to reply.[43]
Securing methods
A common but unproductive measure to deter unauthorized users involves suppressing the access point’s SSID broadcast. This is ineffective as a security method because the SSID is broadcast in the clear in response to a client SSID query. Another unproductive method is to only allow computers with knownMAC addresses to join the network.[44] But, intruders can defeat this method because they can often (though not always) set MAC addresses with minimal effort (MAC spoofing). If eavesdroppers have the ability to change their MAC address, then they may join the network by spoofing an authorized address.
Wired Equivalent Privacy (WEP) encryption was designed to protect against casual snooping, but is now deprecated. Tools such as AirSnort or Aircrack-ngcan quickly recover WEP encryption keys. Once it has seen 5-10 million encrypted packets, AirSnort can determine the encryption password in under a second;[45] newer tools such as aircrack-ptw can use Klein’s attack to crack a WEP key with a 50% success rate using only 40,000 packets.
To counteract this in 2002, the Wi-Fi Alliance approved Wi-Fi Protected Access (WPA) which uses TKIP as a stopgap solution for legacy equipment. Though more secure than WEP, it has outlived its designed lifetime and has known attack vectors.
In 2004, the IEEE ratified the full IEEE 802.11i (WPA2) encryption standards. If used with a 802.1X server or in pre-shared key mode with a strong and uncommon passphrase and uncommon SSID (Used to salt the password) WPA2 is still considered secure by many IT professionals.[by whom?]
Piggybacking
Main article: Piggybacking (Internet access)
Piggybacking refers to access to a wireless Internet connection by bringing one’s own computer within the range of another’s wireless connection, and using that service without the subscriber’s explicit permission or knowledge.
During the early popular adoption of 802.11, providing open access points for anyone within range to use was encouraged[by whom?] to cultivate wireless community networks,[46] particularly since people on average use only a fraction of their downstream bandwidth at any given time.
Recreational logging and mapping of other people’s access points has become known as wardriving. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. Providing access to one’s Internet connection in this fashion may breach the Terms of Service or contract with the ISP. These activities do not result in sanctions in most jurisdictions; however, legislation and case law differ considerably across the world. A proposal to leave graffiti describing available services was called warchalking.[47] A Florida court case determined that owner laziness was not to be a valid excuse.[48]
Piggybacking often occurs unintentionally, since most access points are configured without encryption by default and operating systems can be configured to connect automatically to any available wireless network. A user who happens to start up a laptop in the vicinity of an access point may find the computer has joined the network without any visible indication. Moreover, a user intending to join one network may instead end up on another one if the latter has a stronger signal. In combination with automatic discovery of other network resources (see DHCP and Zeroconf) this could possibly lead wireless users to send sensitive data to the wrong middle-man when seeking a destination (see Man-in-the-middle attack). For example, a user could inadvertently use an insecure network to log in to a website, thereby making the login credentials available to anyone listening, if the website uses an insecure protocol such as HTTP.
A small percentage of Wifi users have reported adverse health issues after repeat exposure and use of Wifi,[49] though there has been no publication of any effects being observable in double-blinded studies. The ubiquity of WiFi has led to calls for more research into the effects of “electronic smog”.[50]
One study speculated that “laptops (WiFi mode) on the lap near the testes may result in decreased male fertility”.[51] Another study found decreased working memory among males during Wi-Fi exposure.[52]
In a BBC article,[53] the World Health Organization (WHO) says “there is no risk from low level, long-term exposure to wi-fi networks” and the United Kingdom’s Health Protection Agency reports that exposure to Wi-Fi for a year results in “same amount of radiation from a 20-minute mobile phone call.”
How WiFi Phones Work
It’s a proverb that there’s nothing new under the sun, and the recent surge in inexpensive Wi-Fi wireless gateways that build clouds of wireless access that bridge to each other without a wire in sight proves the principle. The standard that allows this new integrated feature in cheap access points appears way back in the revised IEEE 802.11 specification from 1999, which helped start this current revolution.
Wireless bridging comes in two forms: the one we’re accustomed to talking about generically, in which a Wi-Fi signal is bridged via an internal router in an access point or gateway to a wired network. The wired network can be as plain as a connection to an external or internal dial-up, DSL, or cable modem. Although this is often called wireless bridging, it’s really wireless-to-wired.
The second form is the “new” flavor, however: wireless-to-wireless bridging using the Wireless Distribution System (WDS). WDS allows packets to pass from one wireless access point to another, just as if the access points were ports on a wired Ethernet switch. WDS bypasses the kind of magical kludgery that Linksys offered with its WET11 bridge or with the WAP11 in pairs or as a bridge/AP combination.
The original WAP11, and similar bridge/access points made by other companies for the consumer market, could provide point-to-point or even point-to-multipoint bridging, but had to be locked into a bridge-only mode. They couldn’t function as an access point and a bridge at the same time, a limitation that newer devices with WDS support have avoided. (It’s still an option if you just want to bridge without offering client access.)
The WET11 and even the newer WET54G work singly, by contract, and they can connect to any access point. They achieve their ability to bridge a number of wired devices—from 30 to 50—by masquerading the wired devices’ MAC (Media Access Control) addresses as their own. This can cause some network confusion, as MAC addresses are meant to be unique, typically.
WDS doesn’t use MAC masquerading nor does it require supporting devices to lock themselves into a bridge-only mode, although some makers are still choosing that option. WDS-enabled access points can service local clients while also bridging traffic to other, similarly enabled access points in a hierarchical tree. One unit can act as a master gateway or the “point” in a point-to-multipoint network; the master is the unit that is typically configured to be connected to the Internet or some sort of robust backbone. Other WDS-equipped gateways all point to each other in a star configuration.
WDS relies on a previously underused element of the Frame Control Field for IEEE 802.11b. With the distribution system (DS) bits both set to 1, the client can provide not just its source address (SA) and the destination address of a frame (DA), but also the addresses of the two intermediate wireless gateways (transmitting and receiving or TA and RA) that are bridging the connection. The WDS-enabled access points broadcast MAC messages across all connected nodes allowing all clients to see all adapters on all connected wireless and wired networks.
Let’s take a typical example. Jim is using a laptop in Building A, while Jane administers a cable modem in Building B. Building A and B are linked by Access Point 1 and 2 via WDS. Access Point 2 is also a relay, which connects with Access Point 3, which is connected via Ethernet to the cable modem that Jane runs.
Jim tries to access the Internet. His wireless adapter transmits a frame with the destination address of Jane’s cable modem. Access Point 1 knows that Jane’s cable modem is on the other side of its bridge based on its MAC table. It rewrites the frame to include itself as the TA and Access Point 2 as the RA.
When Access Point 2, the relay, receives the frame, it knows that the destination is really on Access Point 3, so it rewrites the frame again, turning itself into the TA and Access Point 3 into the RA. The frame arrives at that final access point and hits the cable modem.
In a star configuration, each access point has a list of other WDS-equipped access points that it’s bridging with.
The excitement about this technology comes from three factors: a WDS gateway can act as an AP and a bridge in a single box; WDS is standard, although interoperability isn’t being tested by manufacturers yet; and WDS is cheap, with Buffalo offering its WLA-G54 for as little as $100 street price. In the past, expensive enterprise devices either involved standalone bridges or pricey combined units that worked only with other proprietary gear.
Apple also offers WDS in its AirPort Extreme Base Station ($200 or $250, depending on features); Linksys is using WDS in its revised bridging AP, the WAP54G, but the unit has to be locked into bridge mode even with WDS turned on. (Both the Buffalo and Apple units can be set to ignore local clients and just act as bridges.)
You might want to use WDS in a variety of common scenarios that would otherwise require expensive or unnecessary Ethernet cabling. If you needed two access points to serve your house, for instance, and didn’t want to run Ethernet between them, WDS is an able substitute.
It’s also a cheaper and simpler way to provide blanket coverage. Attach some sectorized antennas on opposite ends of an open courtyard or park and use WDS to avoid having to put backhaul or backbone between the two units, even while both of them can offer the optimum strength for client connections.
Remember, however, that the stronger the antenna’s signal, the more directional it becomes. If you wanted to use WDS to span a mile between your home and that of a friend, you could certainly do so, but the WDS devices wouldn’t be able to also serve up access to clients in their vicinity. WDS is more about building a cloud than a long-haul system, and stronger omnidirectional antennas could be part of that.
Still, a pair of Buffalo WLA-G54′s talking WDS might be easier to manage than a pair of WAP54Gs, and more easily swapped in and out if equipment problems emerge.
All of the current home gateways are single network interface devices, which means that the WDS backhaul subtracts from your pool of bandwidth. Even worse, WDS bridges and master units must work over the same Wi-Fi channel, which increases interference and reduces throughput. With enough local devices, you’re sacrificing a lot of bandwidth for routine traffic.
The 802.11g factor does help out, though. If you have the usual DSL speeds on your Internet backhaul, then cutting 20-odd Mbps of net throughput in an ideal 802.11g environment down to a third or fourth or a fifth still won’t hold up traffic upstream or downstream. It may be less ideal in offices, homes, or dorms in which local data needs exceed the equivalent of 10Base-T. (In that case, you could use back-to-back bridged connections in which you use a short wired backbone between two access points and set the back-to-back set to a different channel.)
Still, Wi-Fi traffic is usually in bursts, so even a solid stream of data that’s being relayed from one gateway to another via WDS and starting and ending at a wireless client should be able to achieve 5 to 10 Mbps.
A looming question with WDS is interoperability. WDS isn’t part of the Wi-Fi certification program, and it doesn’t appear as though access points made by different companies use the identical approach for configuration, nor is any maker guaranteeing their gear works with anyone else’s.
I was able to turn an Apple AirPort Extreme Base Station into a master WDS node (see Figure 1), and it automatically discovered a Buffalo WLA-G54 on the same network that had its WDS mode enabled (Figure 2). I entered the AirPort address into the Buffalo list of WDS access points, and selected the Buffalo on the AirPort’s list. After reboots, they both spoke to each other with no hiccups.
| Figure 2: WLA-G54 Configuration |
Mac users might find this information especially appealing, as they can use the WLA-G54 as a cheap alternative to the more expensive AirPort Extreme Base Station. The WLA-G54 is an access point with no gateway features like DHCP service, making it the perfect WDS extender.
WDS can pull some of the complexity, expense, and copper out of any new installation, and it’s worth thinking about whether when you’re building a home, office, or neighborhood network whether a WDS access point, bridge, or relay could fit the pieces together with less stress.
The next generation of WDS devices clearly need two radios, and some enterprise equipment has already taken that tack. Vivato recently announced a two-radio access point meant to fill in the gaps or edges of service that it can offer with its phased-array antenna design; they use WDS for the switch-to-access point communication. Tropos Networks has a mesh system for backhaul that relies on WDS, while an optional second radio offers client wireless access.
It might take a leap of faith for the consumer companies to add two radios, but with the cost of a gateway with WDS in the $100 range, a $175 device with two cards and separate antennas for back haul could be part of the next big expansion of wireless networks.
WiFi Phones
From their user interface to how they work, WiFi phones are a lot like cell phones . Like a basic cell phone, a WiFi phone has a printed circuit board (PCB) that connects:
Both types of phones also send and receive signals as radio waves. The difference is that WiFi phones use different frequencies than cellular phones do. Cell phones use 824-MHz to 894-MHz frequency bands. WiFi phones that use the 802.11b or 802.11g standards transmit at 2.4 GHz. Phones that use the 802.11a standard transmit at 5 GHz.
When you make a call on a WiFi phone, you dial the number of the person you want to call, just like you would with a cell phone. If you’re calling another VoIP user, you may enter a VoIP address instead of a phone number, depending on the service provider’s requirements.
The phone translates the number you dial into packets of data. It uses radio waves to transmit the packets to a wireless receiver. The receiver passes the information over the Internet to the call processor like an ordinary VoIP call. When you begin your conversation, the phone transmits your voice in packets of data as well. Your voice travels just like it does in a VoIP call, although the specifics can differ from one provider to another.
· Does WiMAX Threat WiFi?
Abstract
WiFi (Wireless Fidelity) or often called as WLAN (Wireless Local Area Network) is one of wireless broadband technologies that has been mature. WiFi technology maturity proved by the standardization that has been agreed since long time ago (IEEE 802.11), many supports from vendor, and has been used by various groups.
WiFi network usage has been used by many companies or individuals both for private network and for public area or hotspot. Beside many vendors that can provide Access Point also supported by terminal vendor such as computer, note book, PDA, and handphone that has been completed with WiFi interface inside. Plus the price is reachable, so WiFi spread very quickly. Nowadays, almost in every corner in town or airport has been used WiFi device for hotspot service.
The next advanced of broadband wireless technology is WiMAX (Wireless Interoperability for Microwave Access). The technology almost similar with WiFi which added by capability in coverage area, QoS, NLOS (Non Line of Sight), Security, and the other features.
With the condition above, surely it will cause many questions from the observer and telecommunication player, will WiMAX be competitor for WiFi or can it used to support WiFi in field? The article will try to analyze from two points of view both WiMAX for supporting WiFi and the other side WiMAX with WiFi will give service together.
WiFi and WiMAX Application
With capabilities of WiFi (wireless LAN), user capable connect to the internet network wirelessly. The characteristic very suitable if it used by user in office area, hospital, campus, hotel, airport, and house.
Thereby, WiFi usage generally can be mapped such as below:
Picture 1. Various Wireless LAN applications
It is so different between WiFi and WiMAX. Various applications that can be reached by using WiMAX are:
- Backhaul application
For backhaul application, WiMAX can be used to backhaul WiMAX itself, backhaul hotspot, and the other technology backhaul.
In WiMAX context as backhaul of WiMAX, the application resemble with BTS function as repeater. The aim is to widen coverage of WiMAX.
Generally, hotspot many use ADSL lines as the backhaul to connect the internet connection. With limited cable network, WiMAX can be used as backhaul hotspot.
- Backhaul for another technologies
Another technologies backhaul, WiMAX can be used for cellular backhaul. Picture 2 Illustrates WiMAX for connecting MSC/BSC to cellular BTS.
- Broadband Access
WiMAX can be used as Last Mile technology to serve broadband necessary of subscribers. With more capability in QoS (Quality of Service) WiMAX can be used to serve housing and business subscriber with different service.
- Personal Broadband
WiMAX as personal broadband service provider can be differenced into two target markets. There are nomadic and mobile. Detail illustration as follow:
� Nomadic
For nomadic solution, usually mobility level of WiMAX user is not high and if it moves, it will move in low speed. Usually the device is not as simple as mobile application.
� Mobile
For mobile application, user WiMAX better to use WiFi terminal such as notebook, PDA, or smart phone. The mobility levels equal with WiFi level. The difference is in WiMAX use will be used WiMAX card that put on the terminal. Picture 2 illustrates WiMAX for mobile application.
Integration or Overlay
Can be seen from description above about WiFi and WiMAX, the outline is both of them can be integrated and overlay. If they were integrated, it means between WiMAX and WiFi will support each other. Both of them will be synergized to serve bigger and many more subscribers. If they were overlay or overlap in coverage, so they can be functioned to support each other (if they were in one operator) and will be opponent if they were in different operators.
Various configurations that can be applied by WiMAX and WiFi operators if they were integrated as follow:
- as backhaul
The configuration shown as in picture 2. WiFi network will be cost effective than WiFi for the backhaul. By combining these two technologies, WiMAX functioned as backhaul while WiFi connected directly to the subscriber.
Picture 2. WiMAX as WiFi Mesh Network Backhaul (source: Intel).
- as backhaul inter WiFi Mesh Network
In this step, WiMAX has been used directly as part of WiFi Mesh Network. Subscriber Terminal of WiMAX put on Access Point WiFi Mesh Network so WiFi network automatically be more reliable in wider coverage area and reduce cost connection that caused by cable drawing in each AP installation. The configuration shown as picture 3. The solution principally can increase performance and robust of WiFi network.
Picture 4. WiFi and WiMAX Full Integration (source: Intel)
Combination of both technologies platform gives sufficient solution, especially for data communication system that still become problem nowadays. Access to internet network is profitable application. Various innovations can be created such as free internet to houses, connection service in cultural art community, social professions non profit, etc.
Beside integration concept above, between WiMAX and WiFi also can be competitive to get subscribers. It can be happened if WiMAX and WiFi in different operators and give services in one area. WIMAX Application as personal broadband that will cause competition with WiFi.
Thereby, for consumer it will be easier because they can view network appropriate with their needs. The illustration above describes the consumer notebook where it apparently network WiFi (Hotspot) with WiMAX.
For hotspot operator, WiMAX can be used to make penetration of hotspot implementation easy. Beside as customer loyalty, it also can add brand image for meant operator. But, if the operator is different, so the WiMAX will struggle hotspot market which based on WiFi technology. Quality, price, marketing, and the after sales service will determine where the subscriber will choose.
Conclusion
Some things that have to be concluded with description above as follow:
1. WiMAX can be applied for backhaul, broadband access (wireless DSL) and personal broadband while WiFi capable for private application and for public (hotspot).
2. WiMAX and WiFi can be scenario for synergy and can be threat each other if it operated in different operators.
******************************************************************************************************************************************************************************************************************************************************************************************
