3 WiFi Technology 1 Preface Wireless communication is becoming the standard in the business world. Remote wireless Internet connections and wireless computer networks are appearing on the scene and will dramatically impact the way business does in the future. It has truly become a wireless world. In the past five years, Wi-Fi (also known as b, g and a ) has emerged as the dominant standard for wireless LANs (WLANS) worldwide. Anyone can set up a Wi-Fi network and cover an area of typically feet with Internet access hundreds of times faster than a modem connection. It has become the TCP/IP of wireless, a single networking standard for all developers, equipment manufacturers, service providers and users. As with TCP/IP, any innovation in Wi-Fi benefits everyone else in the Wi-Fi community. This study aims to give an overview over WLANs from different point of views. For example, Part-1 handles the technical aspects of WLANs, including its network topology, radio topology, brief explanation of the IEEE standards and securing the WLAN, that s plus comparing WiFi with other technologies, for example 3G and Bluetooth. Part-2 discusses WiFi as a Market/Business model. This part presents some case studies for existing models that are already used in USA and Europe. This part must be taken into consideration, when establishing a well-defined WiFi market in Egypt. Part-3 discusses the regulatory aspects of WiFi. This part takes an overlook over the regulators of the advanced countries and how they deal with introducing WiFi to the market.
4 WiFi Technology 2 Index A- Part 1. Technical aspects of WLANs 1.1. Introduction Wi-Fi Network Topology Network Components Designing the WLAN Layout WLAN Network Implementation Consideration 1.3. Wi-Fi Radio Topology IEEE PHY Layer IEEE MAC Layer IEEE Network Layer 1.4. IEEE standards Wi-Fi Security Wi-Fi Vs Other technologies WiFi and Bluetooth WiFi and 3G B- Part 2. Marketing Study for WLANs Roadmap for WiFi Business Model for WiFi C- Part 3. Regulatory aspects of WLANs
5 WiFi Technology 3
6 WiFi Technology Introduction. The Market for wireless communication has grown rapidly since the introduction of b wireless local area networking (WLAN) standards, which offer performance more nearly comparable to that of Ethernet. WLAN (or WiFi) was created specifically to operate as a wireless Ethernet. It is an open-standard technology that enables wireless connectivity between equipments and local area networks. Public access WLAN services are designed to deliver LAN services over short distances, typically 50 to 150 meters. In these cases, WLANs are connected to a local database, and give the end user access through a kiosk or portable device. Internet access through public WLANs is a new and very hot trend, providing many benefits and conveniences over other types of mobile Internet access. First, performance is 50 to 200 times faster than dial-up Internet connections or cellular data access. Second, users do not have to worry about cords, wires or sharing an access point, such as a phone jack. A global directory that would provide users with a search engine to locate the closest access point. Even without the directory, WLAN devices make it very easy to connect. Most WLAN- enabled devices have a software utility that indicates a user s proximity to a WLAN access point. Service providers place an antenna, or access point, at a designated hot spot. The antenna transmits a wireless signal to the adapter card in a user s computer or device. Users connect to the WLAN through a page in their Internet browser. Coverage extends over a 50 to 150 meter radius of the access point. Connection speeds range from 1.6 Mbps, which is comparable to fixed DSL transmission speed, to 11 Mbps. New standards promise to increase speeds to 54 Mbps. Today s WLANs run in the unlicensed 2.4 GHz and 5 GHz radio spectrums. The 2.4 GHz frequency is already crowded it has been allocated for several purposes besides WLAN service. The 5 GHz spectrum is a much larger bandwidth, providing higher speeds, greater reliability, and better throughput. Note that the terminology WLAN and WiFi are used interchangeably through out the document. Wi-Fi devices The cost of Wi-Fi components is dropping rapidly. Wi-Fi radio chips which cost around $100 in 2000 now cost only $15, and fierce competition amongst commodity radio manufacturers promises to push this price even lower. A future with ubiquitous Wi-Fi networks in homes, offices and in public spaces will be filled with all kinds of Wi-Fi enabled devices: Laptops According to market research firm In-Stat, 5.7% of all notebooks were shipped with built-in Wi-Fi radios in 2002, and this share will rapidly grow to 35% in 2003, and to 90% by This coming only a few years after Wi-Fi became a
7 WiFi Technology 5 widely-adopted standard, whereas it took at least ten years for modems and wired ethernet ports to appear as standard equipment on laptops. PDAs -- HP and Toshiba have already introduced PocketPC devices with Wi-Fi built in, and many more Wi-Fi-embedded PDA devices are coming. Cell phones -- Imagine a cell phone with a low cost Wi-Fi radio that could opportunistically connect to Wi-Fi hot spots, taking traffic off of overloaded (and expensive) cellular networks, and sucking in broadband content like streaming video. A more power-efficient Wi-Fi radio is necessary for cell phones with small batteries. Automobiles -- New cars are already packed with data-hungry devices that could make use of Wi-Fi. Soon you will pull into any service station (in the coming years, they will all be hot spots) and top up on your data along with your gas. Download MP3 s, update your navigation system with the latest traffic data, download the day s Wall Street Journal audio edition to listen to on the way to work. When you pull into your garage, your car will dock with your home Wi-Fi network. It could also upload data about itself to your dealer or your insurance company. Gameboys -- Gaming devices will connect to private and public Wi-Fi networks and become a platform for multi-player games. Again, a lowcost add-on to existing products. Consumer electronics devices -- Once super-cheap low-power Wi-Fi chips are available, it isn t a stretch to see them added to all manner of consumer electronics devices. Anything that could benefit from the ability to send and receive information, such as MP3 players (download music in any hot spot) and digital cameras (upload pictures right after you take them wherever you are).
8 WiFi Technology WiFi Network Topology A basic topology of an networks in its simplest form consists of two or more wireless nodes, or stations (STAs), which have recognized each other and have established communications. There are two different cases : Independent Basic service set(ibss) Within an IBSS, STAs with each other on a peer-to-peer level. This type of networks is often formed on a temporary basis, and is commonly referred to as an ad hoc networks. Ad hoc networks allow for flexible and cost-effective arrangements in a variety of work environments, including hard-to-wire locations and temporary setups such as group of laptops in a conference room. The Extended Service Set (ESS) consists of a series of BSSs (each containing an AP) connected together by means of a Distribution System (DS). Although the DS could be any type of network (including a wireless network), it is almost invariably an Ethernet LAN. Within an ESS, STAs can roam from one BSS to another and communicate with any mobile or fixed client in a manner which is completely transparent in the protocol stack above the MAC sublayer. The ESS enables coverage to extend well beyond the range of a WLAN radio. By using an ESS, seamless campus-wide coverage is possible. This service is commonly referred to as infrastructure mode.
9 WiFi Technology 7 Network Components An LAN is based on a cellular architecture where the system is subdivided into cells, where each cell (called Basic Service Set or BSS) is controlled by a Base Station (called Access Point or AP). There are three main links in the WLAN chain that form the basis of the network: Access Point: An AP operates within a specific frequency spectrum and uses an standard specified modulation technique. It also informs the wireless clients of its availability and authenticates and associates wireless clients to the wireless network. An AP also coordinates the wireless clients' use of wired resources. The access points generally have two main tasks: o They acts as a base station to the users. o They acts as a bridge between wireless and wired networks. It s a Physical/Data Link Layer device, it supports 1, 2, 5.5, or 11 Mbps connectivity depending on standard implemented. The coverage area of AP can be up to 375 ft.(114 m.). The number of users an AP supports varies but is generally users. A single access point should also be placed as close as possible to the center of the planned coverage area. If it s necessary to install the access point in an obstructed, for security purposes, an optional range extender antenna can usually be mounted to extend the range of the coverage area. Extender Antenna
10 WiFi Technology 8 Network interface card (NIC)/client adapter: A PC or workstation uses a wireless NIC to connect to the wireless network. The NIC scans the available frequency spectrum for connectivity and associates it to an access point or another wireless client. The NIC is coupled to the PC/workstation operating system using a software driver. Wireless NICs do same function as standard NICs : - change data from parallel to serial. - framing & make packets ready for sending. - determine the time to send or receive it. - transmitting & receiving. Bridge: Wireless bridges are used to connect multiple LANs (both wired and wireless) at the Media Access Control (MAC) layer level. It s used in building-tobuilding wireless connections, wireless bridges can cover longer distances than AP s The coverage range can be up to 25 miles(40 Km).
11 WiFi Technology 9 Designing the WLAN Layout: WLANs can be implemented in a number of ways, depending upon the complexity desired. Generally, WLANs are thought of in three ways: 1) Peer-To-Peer A peer-to-peer network is a WLAN in its most basic form. Two PCs equipped with wireless adapter cards are all that is needed to form a peer-to-peer network, enabling the PCs to share resources with one another. While this type of network requires no administration or pre-configuration, it does not allow either PC to access a central server, inhibiting client/server computing. Applications: Spontaneous and/or collaborative work groups Small/branch offices sharing resources Remote control of another PC Games for two or more players Demos Designing a peer-to-peer network involves three main considerations: 1. The stations must be arranged so that they are all within the proper distance limits. 2. All stations must send and receive on the same transmission frequency. (Most wireless NICs have a factory-set default frequency) 3. The hidden node problem must be avoided so that each station can communicate with all other stations. 2) Client & Access Point In a Client & Access Point network, users not only benefit from extended range capabilities, they are also able to benefit from server resources, as the AP is connected to the wired backbone. The number of users supported by this type of network varies by technology and by the nature and number of the transmissions involved. Generally, they can support between 15 and 50 users.
12 WiFi Technology 10 3) Multiple Access Points Although coverage ranges in size from product to product and by differing environments, WLAN systems are inherently scalable. As APs have limited range, large facilities such as warehouses and college campuses often find it necessary to install multiple access points, creating large access zones. APs, like cell sites in cellular telephony applications, support roaming and AP to AP handoff. Large facilities requiring multiple access points deploy them in much the same way as their cellular counterparts, creating overlapping cells for constant connectivity to the network. As network usage increases, additional APs can be easily deployed.
13 WiFi Technology 11 WLAN Networks Implementation Considerations When implementing a WLAN solution, customers are confronted with a number of options and trade-offs that may make one system more suitable than the next. No one WLAN solution at present can deliver all things to all customers, some, as we have mentioned, deliver higher speeds, some have better range, etc. The following is a list of considerations network managers must confront before implementing a wireless LAN: Interoperability and Compatibility The first, and most important job of any network manager, is to insure that any WLAN products conform to wired infrastructure interconnection standards. Standards-based interoperability makes the wireless portion completely transparent to the rest of the network, and is generally based on Ethernet or Token Ring. Also, older WLAN systems from different vendors may not always interoperate, even if they are using the same technology (DSSS or FHSS) and the same frequency band. A wireless NIC from one vendor may have difficulty connecting to an access point from another vendor, because vendors may adjust their hardware or software to meet their own customization requirements and quality standards. However, the Wireless Ethernet Compatibility Alliance (WECA) now certifies WLAN vendors whose products are interoperable. The WECA seal (Wi-Fi Certification) guarantees that WLAN products from different vendors will work together. Proprietary versus Standard Although WLANs that follow the standards are now widely supported and will likely continue to be so. However, there are actually a few situations today in which a proprietary WLAN is a choice. May be to add stations to an existing WLAN, however, replacing a proprietary WLAN with one that follows the IEEE standard is a more forward-looking choice. Another reason, to implement an Infrared WLAN. The Infrared WLAN doesn t interfere with other communication systems, which makes it the choice to be deployed near sensitive scientific or medical equipment. Also, because infrared signal doesn t penetrate walls, so an infrared WLAN may be suited for a network that handles a sensitive data, such as in government or military applications. Peer-to-Peer versus Infrastructure Mode The decision regarding whether to configure the WLAN for peer-to-peer or infrastructure mode should be based upon the purpose of the network. Peer-to-peer mode should be used when wireless stations need to communicate only with each other. This mode is good for a temporary network. Also it s advisable to connect the peer-to-peer network as a first setup before installing the infrastructure mode. For users that need to access the internet or intranet, or for covering a larger area, the infrastructure made is deployed. Range And Coverage Product design and RF and IR propagation determine the distance over which a signal can transmit information. Objects including walls, metal, desks, and people can affect how signals propagate, and, therefore, the range a signal can travel. As we have mentioned before, IR waves cannot travel through opaque objects and have shorter wavelengths, making them more susceptible to interference,
14 WiFi Technology 12 shortening the distance over which they can transmit and receive information. The RF systems will provide the most range, but sacrifice data rates, while Infrared will support high data rates with limited range. Throughput WLAN throughput rates are a constant source of debate, and invariably come down to product and setup choices. IR, as we have mentioned, supports the highest overall data rates, but implementation is difficult. Between the two RF technologies, it is often quoted that DS systems support a higher data rate than FH systems on the order of 5:2. While this is true in low usage systems, FH systems are capable of dividing the allotted spectrum into more channels than DS systems, and, while supporting slower speeds, can actually support more users and, therefore, experience fewer bottlenecks. Interference WLANs can experience interference from other devices operating on the same frequencies. The ISM bands, set aside for free usage by most governments, often have other devices using these same frequencies in close proximity to WLANs. The 2.4 GHz band, for instance, must compete with microwave ovens for spectrum. While most WLAN technologies are designed to resist these types of interference, it is sometimes unavoidable. In addition, FH and DS systems most often cannot be implemented in the same environment despite the different characteristics of transmission; networks of the same type, yet different vendors, can often interfere with one another. Licensing The regulators of the countries governs radio transmission, including those used by WLANs. WLANs are most often operated in the ISM bands we mentioned previously as they do not require the end user to obtain a license to use the airwaves. Most countries have declared it is important, when choosing a vendor, to make sure that they can deliver a product that will conform to the 2.4 GHz portion of radio spectrum as ISM, but some have not. Products must conform to the spectrum requirements of the country in which they operate. Battery Life Battery life for end-user products varies from vendor to vendor and technology to technology and can be an extremely important consideration when designing a wireless network. All vendors typically employ design techniques to maximize the host computer s battery life, and some are more successful than others. Between DS and FH systems, the battery life issue is tilted in favor of FH systems as they have less bandwidth requirements. Generally, the more bandwidth it takes to transmit a signal, the greater degree of battery drain. Safety And Health Concerns WLAN system output is even less than that of cellular phones and no illness has ever been attributed to WLANs. Yet, there are concerns in hospitals when it comes to WLANs as monitoring devices and some medical devices (heart monitors and pacemakers) operate in the same frequency range. Hospital network administrators must make sure that any products they purchase have a sufficient track record of avoiding interference with these types of devices.
15 WiFi Technology 13 Summary This section presents the basic topology of WLAN networks. There are two main Service Set : o Independent Basic Service Set(IBSS) this represents the Ad hoc network with no base station to serve the users. o Extended Service Set(ESS) this represents the infrastructure mode where more than a Basic Service Set is deployed, to serve more users in a larger area. There are three main links in the WLAN chain that form the basis of the network: o Access Points which acts as the base station to the users, and acts as a bridge between the wireless and wired networks. o Network Interface Cards A PC or workstation uses a wireless NIC to connect to the wireless network. o Bridge Wireless bridges are used to connect multiple LANs. WLANs can be implemented in more than one form, depending upon the complexity desired: o Peer-to-Peer which represents the Ad Hoc (or IBSS) networks. o Client & Access Point where one access point is deployed to serve the users in a certain area.(bss) o Multiple Access point which represents the infrastructure mode (or ESS), where more than one access point is deployed and they are connected to the backbone existing network (for example Ethernet or Token Ring). There are some points must be taken into consideration when designing the WLAN network: o Interoperability and Compatibility. o Proprietary versus Standard. o Peer-to-Peer versus Infrastructure Mode. o Range and Coverage. o Throughput. o Interference. o Licensing. o Battery Life. o Safety And Health Concerns.
16 WiFi Technology WiFi Radio Topology The IEEE began to address the need for an interoperability standard among wireless LANs in After six drafts, the final proposal was ratified in June of 1997, specifying WLAN operation in the 2.4 GHz frequency range. The proposal specifies two layers, the Physical (PHY) and the Media Access Control (MAC). The physical layer refers to the three technologies supported by the standard, Frequency Hopping Spread Spectrum (FH), Direct Sequence Spread Spectrum (DS), and Infrared (IR). The Media Access Control (MAC) layer is concerned with the rules for accessing the wireless medium IEEE PHYSICAL LAYER The PHY layer is divided into two sublayers : 1. The Physical Medium Dependent (PMD) Sublayer: It includes the standards for the characteristics of the wireless medium (DSSS, FHSS, or IR). It defines the methods for transmitting and receiving data through the medium. 2. The Physical Layer Convergence Procedure (PLCP) sublayer: It reformats the data received from the MAC layer into packets (Frame) that the PMD sublayer can transmit. It listens to the medium to determine when the data can be sent. Spread Spectrum Technology Spread spectrum, a digital technology designed to trade off bandwidth for reliability and security. It comes in two forms, Frequency Hopping Spread Spectrum (FH), and Direct Sequence (DS). Both forms of Spread Spectrum consume more bandwidth than a typical narrowband transmission, but this enables a louder signal, far easier for the receiver to detect than a narrowband signal. Spread spectrum technologies have security advantages over narrowband technologies as well. Although spread spectrum technologies share a common background, there are certain advantages and disadvantages to the two forms implemented in WLAN applications, so we offer here a brief comparison. Frequency Hopping Frequency Hopping Spread Spectrum (FHSS)combines the bandwidth advantages of a narrowband signal with the security and clarity advantages of a wideband signal. FH uses a narrowband carrier, as little as one MHz in WLAN applications, that changes frequencies at a predetermined rate known to both the transmitter and receiver. This rate places the signal on a frequency for a very short period of time, called the dwell time, and then directs it to hop to the next frequency in the sequence. When synchronized in this way, the net effect is to maintain a single logical channel. To an unintended receiver, FH appears as impulse noise and is ignored. Without the hopping algorithm, FH signals are nearly impossible to intercept.
17 WiFi Technology 15 Advantages Limitations Low susceptibility to interference. FH systems are also highly scalable as numerous segments can be placed in the same area. Each access point creates its own LAN segment capable of transmitting multiple transmissions simultaneously. In dense user environments, many access points can be connected with overlapping coverage, enabling load balancing. Load balancing enables the clients to choose the access point that optimizes performance. This provides for both a greater number of users as well as an overall increase in the system performance. It doesn t support more than 2 Mbps. Direct Sequence DS systems spread signals over a wider bandwidth than FH systems. For each signal burst sent by a DS system, a redundant chipping code or chip is generated. Large chips increase the likelihood of recovering the original signal as statistical techniques embedded in the receiver can recover the original data without the need for retransmission. However, longer chipping codes consume more bandwidth than FH transmissions, supporting fewer overall channels, and therefore fewer users. Yet, as the signal is spread over a larger channel, higher data rates can be supported by DS systems, making them ideal for data intensive environments with less overall network traffic. DS systems are also extremely secure.
18 WiFi Technology 16 In order to intercept a DS signal, an intruder would have to know the frequency range in which the signal was being sent, in addition to the algorithm used to decode the chipping sequence. As the transmission amplitude in DS systems is small, it appears as noise to an unintended receiver, making interception extremely difficult. Advantages Secure. DS supports higher data rates, 1, 2, 5.5, 11 Mbps. Limitations The spreading of the chipping code is over an 22 MHz channel. Although this lessens the possibility of interference of the entire signal, it remains more susceptible to interference than FH systems, which are spread over an 83 MHz channel. It also limits the number of overlapping cells in a DS network to three, making continuous coverage in large facilities more difficult than with FH systems. Infrared Infrared technologies use extremely high frequencies, just below visible light in the electromagnetic spectrum, and are therefore unable to penetrate solid objects. Infrared is currently capable of higher data rates than RF, but, due to the range characteristics, it is not yet cost-effective in WLAN environments. Infrared requires directed (line of sight) or diffuse (reflective) capabilities for transmission. Directed WLANs that use line of sight principle, are impractical for mobile users. Instead they are best designed for a setting where the network devices are fixed in a stationary position without the possibility of something interfering with the line of sight. While diffused WLAN doesn t require line of sight. Instead it relies on reflected light. Emitters in a diffused WLAN have a wide-focused beam instead of a narrow beam. Emitters are usually pointed at the ceiling and use it as the reflection point. When the emitter transmits an infrared signal, it bounces off the ceiling and fills the room with the signal. Diffused WLANs covers up to 16 m.
19 WiFi Technology 17 Personal area networks and peer-to-peer networks of a few feet in distance are suited for infrared technology, as is the implementation of fixed sub-network connections such as LAN bridges. But, as infrared is unable to penetrate opaque objects, we don t believe RF technologies are threatened in the near term for enterprise-wide WLAN solutions. Advantages Limitations Infrared light doesn t interfere with other communication systems as it works in the optical region. Infrared signal doesn t penetrate walls, so the signal are kept inside the room. This makes less interference and prevents eavesdropping. Limited range of coverage (up to 16 m.). Not applicable for mobile users. slow data rate (only up to 4 Mbps). Note: Microwave WLAN technologies are also being used, mainly in WLAN bridge applications. Data rates and range for microwave products fall between RF and IR technologies. Microwave has been inhibited thus far by cost and safety issues, as well as the need for direct line of sight. The FCC has set aside spectrum in the 18.8 to 19.2 GHz bands for use in microwave applications however. A comparison of the features of light-based infrared, FHSS and DSSS wireless networks is summarized in the following table. IR FHSS DSSS Causes No Yes Yes Interfernce Can be No Yes Yes interfered Power Low Moderate Moderate Consumption Coverage Limited Broad Broad BW (Mbps) IEEE MAC LAYER: The Medium Access Control (MAC) Layer addresses the following issues: Accessing the medium The standard uses an access method known as the Distributed Coordination Function (DCF). The DCF specifies the use of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithm as the media access scheme. Association This establishes the wireless links between clients and access points in the network. Association begins by scanning where the station first scans the air to know the access points from beacons sent by the access points. Then the association process begins. Reassociation This is concerned with the handoff of clients as they roam the network.
20 WiFi Technology 18 Authentication The Standard has two ways of addressing authentication. By default the standard is an open system, allowing any client with a wireless connection device to address the network without authentication. The standard does provide, however, for a more secure network with the Wired Equivalent Privacy option, by configuring a Shared Key into the AP and its wireless clients. Only those equipped with the proper key will be allowed to access the AP. Power Management provides for two separate power modes for the operation of wireless clients, Active mode and Power Save mode. Active mode is enabled when a client is transmitting or receiving while Power Save mode is used when there is no communication to the network. The power management is used to preserve the power of laptops as they depend mainly on batteries IEEE Network Layer: Although IEEE specifies the PHY and MAC layer, yet the Network Layer needs enhancements to allow mobility. This enhancement involves the standard protocol of sending and receiving data, TCP/IP. TCP/IP: Each station on the network is assigned a unique IP address, which consists of 4 bytes. 3 bytes of them represents the IP address of the network, and 1 byte represents the host IP (or the station IP). The IP address is unique and fixed to each station, which prevents the mobility and roaming between networks. Mobile IP: Mobile IP provides a mechanism within TCP/IP protocol to support mobility. In mobile IP, computers are given a home address, which is a static address, on their home network. The computer also has a home agent, which keeps track of where the mobile computer is located. When the mobile computer roams to another network (called a Foreign Network),a foreign agent provides routing services to the mobile computer and it assigns him a new, but temporary IP number. So when a data is sent to the mobile computer, to its home address, the home agent forward it to the foreign agent. To respond to the original sender, the mobile computer uses traditional IP routing instead of tunneling back toward its home agent.
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