Wi-Fi router range: the long and the short of it | The Seattle

The development of short range wireless systems, specially Bluetooth and wireless area that is local (WLAN) has captured the industry’s imagination, if not the market that was initially predicted. Bluetooth technology originated in Europe, with early research and development driven by European-based companies. In this special supplement Microwave Journal reviews current European activity, global expansion and globally competing technologies to find out whether going wireless is sold with strings connected.
No cables — what an attractive proposition! Consider the savings in cabling costs and flexibility offered if an office’s computers were served by a WLAN. Just imagine being able to eliminate the mass that is tangled of presently essential to connect a PC, not merely towards the network, but additionally to its peripherals such as for instance the keyboard, mouse and printer. Meanwhile, the mobility of cellular and technology that is cordless promoted tips for a generic short range wireless access solution for various devices.
These are all desirable aims however the interest in and development of short range wireless information networking hasn’t simply been prompted by the requirement to office that is disentangle from trailing wires. The impetus that is real result from the desire and expectation of individuals and companies to help you to get into data and information very nearly anytime, anywhere, anyplace. Laptop-based users and access that is broadband homes are more of the elements converging to drive ideas of a short range wireless access solution as well. Ally that with the prospect of vast numbers of cell phones becoming Internet enabled with users wanting to link up to laptops, headsets, hands-free kits and LAN access points, and a market that is lucrative guaranteed so long as the technology is available to implement it.

With such a big and untapped market there has been no shortage of contenders vying to provide that technology. This article looks at two of the leading contenders, Bluetooth and WLANs. Issues covered add how Bluetooth has generated on its European origins and early development to capitalize on Europe’s Global System for Mobile Communications (GSM) to enable it and synergize with it, together with the opportunities that 3G could offer. By mapping WLAN development and deployment that is global is considered as both a competing technology and development market in its own right.
Since Ericsson originally devised the technology in 1994 Bluetooth has grabbed the imagination & most of the headlines. The organization proceeded taking care of the project alone until February 1998, whenever it shared its research with Nokia, Intel, IBM and Toshiba to found the Bluetooth Special Interest Group (SIG). The main purpose of the SIG is to protect the integrity of the technology and control its development. Its in charge of the official certification procedure that most devices must complete before they can be called having a Bluetooth compliant product. Without official certification, a product cannot claim to be Bluetooth-enabled or use the Bluetooth trademark. The official certification process ensures that designers maintain the standard and make sure interoperability.
The specification that is commercial Bluetooth 1.0, was issued in July 1999 and ratified in February of this year. The growth of activity in the technology is illustrated by the fact that there are currently some 2000 companies working on or products that are developing with this specification. From the European origins — it’s named after a century that is 10th King — Bluetooth has inevitably become of worldwide interest to both manufacturers and prospective users.
The attraction is that Bluetooth could possibly offer cost that is low small physical size (single chip) and low power consumption over throughput and range. Allied to its capability to function in noisy radio environments and offer transmission that is high. These features, together with help for real-time traffic of both vocals and data, allow it to be an attractive wireless networking technology for individual digital assistants (PDA), mobile phones and laptops.
Licensed range is high priced, particularly in Europe ([greater than] $100 billion taken care of 140 MHz). A significant benefit of Bluetooth is it runs at the internationally available unlicensed commercial, systematic and medical (ISM) 2.4 GHz frequency band, allowing compatibility that is worldwide. Figure 1 shows the European 3G spectrum cost vs. the WLAN spectrum (83.5 MHz in the 2.4 GHz band and 455 MHz in the 5 GHz band) at no cost. Bluetooth technology that is wireless in a multiple piconet topology (see Figure 2) that supports point-to-point and point-to-multipoint connections. With the current specification, as much as seven servant devices can be set to talk to a master radio in a single unit. As Figure 3 illustrates, several of these piconets are founded and connected together in advertising hoc scatternets to allow communication among continually configurations that are flexible. All devices in the piconet that is same priority synchronization, but other devices could be set to enter.

Bluetooth’s baseband technology supports both synchronous connection orientated (SCO) links for voice and asynchronous connectionless (AC) links for packet data. Both utilize time division duplex (TDD) as the access technique for full duplex transmission. Voice coding is accomplished using a slope that is continuously variable (CVSD) modulation strategy, under which vocals packets are never retransmitted. The master device controls the link bandwidth and chooses how much bandwidth to give each slave and slaves needs to be polled before transmission.
An asynchronous channel that transmits data can support an asymmetric link of 721 kbps in either direction and permit 57.6 kbps in return. For a symmetric link the channel can support 432.6 kbps. Since Bluetooth devices can support three sound stations running at 64 kbps, or one information channel, they could attain information rates as high as 1Mbps. The Bluetooth 1.0 specification requires 1 mW transmitters with a nominal antenna power of 0 dBm to operate up to 10 m (type of sight). An increased energy transmitter of 100 mW (+20 dBm) contained in the specification increases the number to 100 m, although this will require a separate PA antenna driver. The compromise is increased expenses and power usage.
Bluetooth utilizes regularity hopping spread spectrum (FHSS) technology, where the system will frequency hop 1,600 times a second, delivering short time division multiplexed packets with each hop. With spread spectrum hopping, the sequence is random and the receiver must hunt down the chosen transmission frequency after each hop. Before any connections in a piconet are created, all devices are in standby mode which allows for the device to listen on 32 hop frequencies defined for each unit, for messages every 1.28 seconds. The text begins whenever one device initiates an association and becomes the master associated with piconet. A link is made by a web page message then an inquiry message followed by a page message is sent if the address is known, and if it is not. The devices synchronize and connect then. At the point of connection each device assumes a media access control (MAC) address to distinguish them.
The Bluetooth specification that is technical be clear, product roll-out less so. The marketing machines did their job in creating awareness but in the process raised expectations that have yet to be fulfilled. All too quickly allegations, particularly in the media, of over hype and over elaborate market forecasts were hitting the headlines. However, last year saw a significant number of product launches together with the initial shipments of products bearing the Bluetooth logo. There has been consolidation for the half that is first of year with all the end of 2001 seeing significant predictions.
Frost & Sullivan forecasts global deliveries of Bluetooth-enabled products to attain over 11 million devices in 2001, equaling $2.5 billion in profits, while Micrologic analysis is more conservative along with its estimation that the marketplace will reach five million devices in 2001 and 1.2 billion in 2005. Such variations in figures tend to muddy the waters and emphasize the unpredictability of the market, but in such an technology that is embryonic is possibly understandable.
This might be a true point made by Michael Wall, research analyst at Frost & Sullivan, who has stated: “Although the delays in the development of Bluetooth are beginning to prompt a backlash from certain sections of the media, industry observers have to take the infancy of Bluetooth as an industry standard technology into consideration when assessing the status of this marketplace. Apart from Ericsson, the pioneers that are original perhaps the most progressive designers weren’t drawn to the project until 1998. Other communications that are mobile such as the GSM took longer to produce than will be allowed for Bluetooth.”
Semiconductor chipset development is an integral take into account the technology’s progress, with a selection of development models emerging in the Bluetooth semiconductor industry. Two distinct manufacturing routes are now being taken. There are either those offering complete integrated solutions through the silicon wafer level to your consumer product degree or those providing part of the amount of a chipset, that is, baseband, radio and software.
Debate continues over the most choice that is effective of technology for Bluetooth. The diversity of silicon technologies and solutions architectures being used has emphasized the software protocol stack. It has become one of the most crucial elements of the solution, especially with regards to achieving interoperability and can be increasingly crucial as semiconductor companies come nearer to establishing their products on the market.
A number of smaller design services companies have entered the Bluetooth software market offering complete or partial protocol stacks to semiconductor developers alongside some of the big names. In the same vein Bluetooth has offered a number of smaller, highly innovative fabless semiconductor developers, such as Cambridge Silicon Radio and Silicon Wave, an opportunity to build early market share with fast time-to-market solutions. Amongst the larger integrated Bluetooth designers, Philips Semiconductors has been the main player to offer solutions in volume. It is expected that a number that is large of is being offered by the finish of 2001.
Market success can be dependant on a chicken and egg combination of chipset supply. Observers have warned that restrictions in the supply of chipsets to smaller product developers may cause delays in the time-to-market of new innovative applications that will provide future revenue streams for chipset companies. Despite such words of care Frost & Sullivan forecasts that the sum total shipments of Bluetooth chipsets will be over 956 million in 2006, while the total market for these chipsets is predicted to be over $2.3 billion in 2006. Further up the value chain from chipsets the early offerings that are bluetooth fairly generic wireless community access items, such as for instance Computer cards along with other add-on products, along with access points (AP).
Also, in European countries, a significant number of Bluetooth mobile phones were launched at the CeBIT exhibition in Germany in March 2001 with many more expected over the summer. However, the market cocktail has become more intriguing because of 30 market developments. At a time when the cost that is huge of licenses is impacting in the telecoms stock exchange while the gear required to roll-out Universal Mobile Telecommunication System (UMTS) systems have not yet arrive at fruition, lots of the services prepared for 3G mobile could be delivered by currently available technologies which run in unlicensed (free) regularity bands.
Mobile operators that have 3G license debts to service are under great pressure to maximise income of existing information solutions, and demonstrate that the marketplace has got the appetite for 2.5G and 3G services. Bluetooth mobile phones could be one solution by allowing users access to the Internet on their PDA using the phone as a wireless gateway. Ericsson, for instance, is promoting the bluetooth information that is local (BLIP), which provides Bluetooth access to the Internet, within range of a BLIP access point. Such developments will continue to keep Bluetooth in the headlines and the eye that is public.
WLANs are appearing through the wings as a strong contender to rival Bluetooth. WLANs enable the Ethernet cable from the wall outlet to a device (such as a PC) to be replaced by a wireless link between an access point and a wireless user interface card that is either area of the wireless device or connected to it. The technology is in no way a newcomer, however. In fact, it was back in 1990 when, in the US, the IEEE 802.11 Wireless geographic area Networks Standards Working Team ended up being formed because of the task of developing a global standard for radio gear and systems running within the 2.4GHz unlicensed regularity band for information prices of just one and 2 Mbps.
Over 10 years ago what the first 802.11 standard did, to a degree, ended up being to greatly help unify a confused WLAN marketplace, that has been crowded with proprietary solutions. Even though the specification that is original three different transmission media — frequency hopping spread spectrum (FHSS), direct sequence spread spectrum (DSSS) and infrared (IR) — the major area of development has been for DSSS. DSSS spreads the signal over several frequencies, can switch channels to avoid interference and also makes the harder that is signal intercept than standard wired Ethernet.
The IEEE 802.11 standard was used in 1997. The modulation scheme used when operating at the 1 Mbps rate is binary phase shift keying (BPSK) where each symbol carries one bit and one million symbols per second (1 Msps) are transmitted. Thus, with each symbol storing one bit, the bit-rate achieved is 1 Mbps. Quadrature phase shift keying (QPSK) is the modulation scheme used to yield 2 Mbps. The system is able to transmit two channels simultaneously, and although the symbol rate is still 1 Msps with QPSK mapping two bits per symbol, the result yields 2 Mbps with this technique. Nonetheless, these data prices of just one Mbps and 2 Mbps are somewhat slower compared to the wired LAN equivalents. This aligned with questions over interperability and price, restricted use up and acceptance of the standard as a viable option.
IEEE 802.11B
That all changed in September 1999 when the IEEE ratified a brand new rate that is high for WLANs – IEEE 802.11b, which also goes under the various guises of long range router (Wireless Fidelity) and high rate wireless Ethernet. It is significant because it offers a data that is top-end of 11 Mbps. Each access point can help dozens of connections, although each of them must share 11 Mbps of capacity. There might be three access points employed in the same area, and each typically has an indoor range of 90 m at 1 Mbps and 25 m at 11 Mbps. The IEEE 802.11 b specifies complementary code keying (CCK) as the modulation scheme to achieve this higher data rate. The strategy maps four bits per expression to attain 8 Mbps, which allied to a heightened rate of 1.375 Msps yields a bit rate of 11 Mbps. Consequently, while the true number of symbols sent per second hardly varies from the symbol rate used for IEEE 802.11 LANs, more hits per second are sent. Also, as CCK is a DSSS technique, 802.11 b is backward-compatible with products that meet the origin al 802.11 specification, enabling 802.11b products that are standard interoperate with 802.11 compliant DSSS products by falling back to 1 Mbps or 2 Mbps procedure.
With a business human anatomy to confirm interoperability as well as the interoperability of 802.11b cards being guaranteed, due to there being just two silicon manufacturers worldwide utilizing a similar MAC layer specification, that deficiency in the WLAN offering has been addressed. The increased bit rate of 11 Mbps has also dealt with the performance issue with 802.11b being able to match Ethernet that is standard for. It has resulted in a renewed desire for, and maybe more importantly, investment in the development of 802.11b products by large players who failed to view any involvement in 1 to 2 Mbps products as a option that is viable.
Now, the huge benefits that WLANs offer in terms of mobility and flexibility, allied to increased speed while the dropping costs of Computer cards, has caused it to be an option that is attractive the home market where broadband access is growing for small businesses and particularly for the enterprise customer. Typical applications include the creation of ad hoc LANs, the linking of portables into a wired infrastructure, WLAN bridging and in peer-to-peer networks where PCs with wireless cards can directly exchange data. Instead, an access point allows PCs to keep in touch with fixed Ethernet topologies via an Ethernet hub or switch port. Although WLAN cards are still more expensive than ordinary cable-based Ethernet cards, having a standard means that all manufacturers move to the same technology and prices come down. Today there are cards at around the $200 mark.
The main element towards the progress of WiFi is its wide and deployment that is global and without any hype it has begun. Airports as far afield as Europe, Japan, Hong Kong and the US have installed 802.llb networks, with resort hotels and conference centers additionally being prime regions of development. Also, with all the increased use of laptop computers, the natural synergy between their mobility and the mobility offered by WLANs is propelling the growth of 802.llb. Offering mobility is going to be the key to success of WiFi. For instance, when users have a notebook, they want to be able to use it in the office, at home and on their travels and never having to swap cards. Only a wide deployment of 802.1lb will facilitate that.
Mobile operators also see WLANs as an affordable and way that is easy provide high speed access to densely populated areas. Because they rely on very short-range transmissions, users see improved battery life, and with health risks being a concern there is the advantage that is added of energy use. Once more, at CeBit there have been numerous gear manufacturers showing WiFi elements in the shape of Computer cards, universal serial bus (USB) devices, access points and home gateways. However, at present the Wireless Ethernet Compatibility Alliance (WECA) only recognizes one test house in the US for certification of WiFi products with plans for a test that is european become recognized quickly. Such expansion is crucial for the technology to be viewed as truly global when it comes to development.
The key factor in the growth and development of this WLAN market is the increased information rate of 11 Mbps being afforded by the standard that is 802.llb. However, in October last year the IEEE Standards Board approved P802.llg, a new project within the IEEE 802.1 WLAN Working Group to enhance the data rate of WLANs operating in the 2.4GHz frequency band. The expectation is that the information rates will soon be increased to more than 20 Mbps and the mission associated with the task group is to review proposals. Areas of development increasingly being undertaken that could afford this ‘doubled’ data rate include a modulation that is new that improves the robustness of RF information transmissions. It not just overcomes a lot of the backdrop RF sound and other sourced elements of interference but also offers better performance against multipath disturbance.
On the receiver side, advanced technology that is equalizer in concert with these new modulation algorithms will act to reduce the need to retransmit data packets. This is important because when interference in WLANs causes unrecoverable corruption of a reflected information stream or noisy signals are discarded and therefore are retransmitted which slows the data rate and interrupts the data flow, the machine is less reliable for real-time transmission. With advanced equalizer technologies, reflected or noisy signals are not only discarded or filtered out. Forward error modification (FEC) algorithms may take corrupted signals and reconstruct them, considerably reducing retransmits.
Data prices of over 20 Mbps will open up applications that are new the industry to exploit. As might be expected, interest will likely be light emitting diode by leisure applications. Quicker transmission speeds will enable video that is streaming high definition television and graphics for interactive gaming while also providing the headroom to accommodate new applications when they come on stream. Businesses and enterprises are always screaming out for the means to transmit large amounts of data quickly. Home automation will be another avenue by facilitating the interaction of heating, lighting, air conditioning and security systems.
Such applications are some way off however the WLAN is a growing market as the statistics show. According to the latest figures from IDC worldwide WLAN equipment revenue jumped 80% in 2000, breaking the $1 billion mark. IDC predicts that by the end of 2005 the market will be approaching $3.2 billion. Demand, especially in the US, has been particularly strong in vertical industries such as education, retail and health care. In the coming years, the market will see increased use of WLANs in the home and small- to medium-sized business (SMB) segments together with the growth of broadband. Despite the outlook that is optimistic the general market, particularly in the US, Western Europe and Japan, IDC believes vendors will need to overcome a few obstacles, including resolving standardization issues, educating their partners, improving safety and reducing costs making sure that WLANs are affordable for main-stream sections.
The chipset market for 2.4 GHz WLAN items is set to keep to expand, although growth shall not be as high as for Bluetooth chipsets. Frost & Sullivan anticipates direct sequence 802.11b Chipsets to be in great demand, predicting that the market for them shall be worth over $1.3 billion in 2006. This demand shall be driven by the development in mobile computing and also by falling item expenses.
Bluetooth and WLANs could have profiles that are differing terms of marketing and publicity but it is clear from the market statistics and investment in technical development that both are technologies that are becoming established and set to grow. However, can they coexist technically? Interference has been a topic of debate and concern since the early stages of Bluetooth development and to a extent that is certain became a fear associated with the unknown. What exactly is known is interference between 802.1 lb and devices that are bluetooth occur. In the US the Federal Communications Commission (FCC) requires every device operating in unlicensed bands to have a label stating that it can cause interference. Nonetheless, what’s not known is the potential of this problem. The fact that the products operate in an unlicensed band and projections of mushrooming market growth for Bluetooth and 802.1lb is fueling concerns.
Even though the amount of concern risk turning out to be unwarranted, this has at the least grabbed the eye of wireless standards groups, regulatory bodies and wireless industry participants. They are all well aware that if users do experience interference problems it will harm user confidence within the technology. With so investment that is much is a risk that manufacturers, in particular, cannot take. Global development that is technical is being completed and standards are now being addressed to restrict disturbance. The IEEE 802.15.2 Task Group is coordinating efforts, and the FCC has also put together a set of rules that allow multiple devices to share the spectrum, providing room for considerable innovation in building radios that can resist interference in the US.
Consequently, substantial research to monitor the consequence that WiFi and Bluetooth products operating in the same vicinity have actually using one another is under method. Results do vary and Figures 4 and 5 are examples of a particular study to illustrate the effect. However, what is generally accepted is that if the antennas of the Bluetooth and WiFi devices are kept over 2m apart, then there will be graceful degradation of the two protocols, which will only be noticed by very sensitive users. Move the 2 antennas within a meter, nevertheless, and there may be interference that is significant.
Interference actually becomes a serious issue when both radios are integrated into the same device with the antennas close together. Examples of when the two devices are collocated (that is, separated by less than 10cm) are in a combination PC card and laptops or Internet appliances enabled with both technologies. Also, it is believed that collocated products will play an important role in products such as for instance notebook PCs. A good example is a notebook that has a radio that is bluetooth for connection to a PDA or cell phone and in addition has a WiFi radio integrated for LAN access.
Coexistence is a major issue for such applications and one which the industry is striving to address with standards bodies and wireless companies starting to develop and lobby for a variety of coexistence approaches. These vary from regulatory intervention and special standards task forces such as IEEE 802.15.2 to various technical approaches ranging from simple device ‘collocation without any coexistence mechanisms’ to integrated silicon solutions covering the entire sub-system that is wireless.
Mobilian Corporation, along with industry partners, is a business working on developing a solution and has classified these different technical approaches into a performance and user experience hierarchy, as shown in Figure 6, with each having their strengths and limitations. ‘Collocation without a coexistence mechanism ‘is relatively controversial. It does have the advantage of being a time-to-market that is rapid which provides a single-card guide design only. The close proximity of the two radios with no coexistence system will likely create worst-case scenarios, and certainly will consequently end in significant degradation to both radios’ performance.
Dual-mode radio switching will not need changes to the silicon, and could be fairly quick to market. It includes a coexistence device that needs that while one radio is operational, the other is totally suspended. The operation can primarily be implemented in two ways. In the first, the system simply shuts the radio that is non-operating with no signaling to many other nodes in its network. This could easily result in problems for the network and can drop performance amounts below that of simple ‘collocation without a coexistence system.’ The method that is second signal other network nodes that it is suspending one of its radios. Performance will still be 60 percent lower than that of unhindered radios because of its nature that is modal on/one off), but is a lot better than simply shutting the radios off. Neither method supports switching while Bluetooth vocals (SCO) links have been in procedure.
Driver-level transmit switching generally describes an approach by which application transmit demands are mediated at the motorist level, thereby avoiding simultaneous transmission. Intuitively, this approach degrades throughput by some measure simply due to its modal transmit structure. More important, though, are its limits to avoid collisions with incoming packets. The ensuing transmission of one protocol during reception of the other causes lack of gotten packets, interference and user that is potential. This is caused by the technique’s dependence on the host operating system, which will be generally non-deterministic in its response time (non-real-time). Once again, this approach does not switch quickly sufficient to support Bluetooth SCO links, and also will have difficulties mitigating the disturbance from Bluetooth piconet master/slave polling activities.
While Bluetooth adaptive hopping undoubtedly improves simultaneous performance under limited penetration scenarios, its widespread adoption will likely require intervention from regulatory organizations and standards bodies. Even under a fast-track program, this can be a process that is time-consuming. This time-delay exacerbates the issue that the method’s effectiveness is compromised with higher penetrations of WiFi systems and unmodified Bluetooth devices. Adaptive hopping will likely be initiated as an optional Bluetooth profile, indicating that modified devices will perhaps not utilize the functionality in piconets with unmodified devices. Further, within the presence greater than one piconet that is bluetooth WiFi system, adaptive hopping may be counter effective to coexistence.
MAC-level switching is the utmost effective associated with style that is modal/switching, and provides performance levels approaching those in no-interference scenarios. It is a technique that is collaborative by trading information involving the two protocols during the MAC level and managing transmit/receive operations correctly. Because MAC-level switching is carried out within the baseband, it is able to switch between protocols at a much faster rate than driver-level approaches. Consequently, it is able to mitigate many of the issues that driver-level cannot that is switching. MAC-level switching does not suffer from transmitting signals into incoming receptions, Bluetooth polling or system that is operating. Nevertheless, its susceptible to adjacent-channel interference and does suffer noticeable degradation. Also, it has a longer development cycle than driver-level approaches because it is located in the baseband.
Simultaneous procedure provides the capacity to automatically identify all available wireless networks, select the ones needed and connect to them seamlessly. By providing coexistence in a highly integrated two-chip solution – an analog front-end chip and a digital baseband chip – it allows simultaneous operation for the two protocols while eliminating disturbance and maintaining reliability and performance. Interference is a concern that is genuine, as has been illustrated, there are measures that can be taken and innovative initiatives under development to provide coexistence particularly for collocated devices. The potential market is too large and too lucrative for every effort not to be made to ensure operation that is smooth.
Bluetooth and WLAN might be competing into the frequency that is same but are they competing for the same applications? Due to its simplicity in not having to be configured, low power, short range and low cost Bluetooth will be focused on small devices such as PDAs and cell phones. To provide access and synchronization of those devices that are personal may also be the need for Bluetooth radios to be included in access points and notebooks.
Another possibility that Bluetooth affords is the deconstruction of products into specific components, enabling brand new form factors and device types. For instance, by having a headset that is separate is no longer the need to include one in a cell phone, which simply becomes a cellular receiver/transmitter interacting with the cellular network, PDAs and laptops. More long-term, a so-called killer application for Bluetooth could well be public access. It is all well to possess synchronization involving the notebook, PDA or cell phone but, whenever in an airport or retail complex, use of the Internet or information regarding the area that is local be valuable. For that to happen, though, there is the chicken and egg situation where a company will not deploy Bluetooth enabled access points unless there are significant variety of devices available on the market to use them and vice versa. Similar is true of the providers of this given information that users will be seeking. Nevertheless, this is an area actively being develop ed.
Public access is a definite application for WLAN and, as has been mentioned, systems are already being globally deployed in airports. Their high data rate being comparable to the wired Ethernet makes them particularly appropriate the enterprise sector for computer networking between PCs and to take advantage of the trend towards laptop mobility. Ease, low priced therefore the facility for expansion also make WLAN suited to little workplace home business office (SoHo) execution plus the expansion of the home broadband access market, especially in the united states, additionally starts up opportunities.
Even when simply a fraction of those applications for Bluetooth and WLAN visited fruition, the slim (80 GHz) 2.4 GHz band will soon become congested. In expectation of the, range will play a role that is crucial the deployment of next-generation, high speed WLANs and has prompted licensing authorities globally to allocate large blocks of license free spectrum in the 5 GHz band. As Figure 7 shows, in Europe, a total of 455 MHz is available in the two blocks from 5.15 to 5.35 GHz and from 5.470 to 5.725 GHz. Similarly, the united states has allocated an overall total of 300 MHz into the two obstructs of spectrum at 5.15 to 5.35 GHz and 5.725 to 5.825 GHz. In Japan, one 100 MHz block at 5.15 to 5.25 GHz has been considered.
Again two different 5 GHz standards are increasingly being developed on either part associated with Atlantic with both specs offering data rates of up to 54 Mbps, and so well placed to offer high speed communication services. Originating in the US the IEEE 802.11a standard was ratified in 1999. The physical layer (PHY) is based on orthogonal frequency division multiplexing (OFDM) and shares a common MAC layer with all IEEE 802.11 standards 802.11b that is including.
Alternatively the European Telecommunications Standards institute (ETSI) is developing performance that is high LAN (HIPERLAN) standards as part of its Broadband Radio Access Network (BRAN) effort. Under its remit is the development of four criteria — HIPERLAN1, HIPERLAN2, HIPERLink (made for indoor radio backbones) and HIPERAccess (intended for fixed exterior use to provide access to a wired infrastructure).
The HIPERLAN1 standard, that is in line with the well-established means of Gaussian minimum shift keying (GMSK) modulation, is complete and was ratified in 1997. HIPERLink and HIPERAccess, on the other hand, are at the early stages of development. It is HIPERLAN2 where current activity is concentrated.
The physical levels of both 802.11a and HIPERLAN2 usage OFDM modulation to achieve high speed transmission rates. This multichannel spread spectrum modulation technique allows individual channels to maintain their distance (or orthogonality) to adjacent channels, enabling data symbols to be reliably extracted and multiple subchannels to overlap in the frequency domain for increased efficiency that is spectral. For instance, within the spectrum allocation for Europe, HIPERLAN2 stations are spaced 20 MHz apart for a total of 19 channels.
Both IEEE 802.11a and HIPERLAN2 specify an OFDM physical layer that splits the information signal across 52 separate sub-carriers. 48 provide separate pathways that are wireless synchronous data transfer, while the staying four are employed as a reference to disregard frequency or period shifts associated with the signal during transmission and supply synchronization. Synchronization allows coherent (in-phase) demodulation. The 2 criteria could have this similarity but vary over the layer that is physical 802.11a generally speaking seen as simpler and less complex, while HIPERLAN2 is mote sophisticated (or complicated depending on your standpoint) with wider range.
For HIPERLAN2, mobile terminals such as for instance a laptop computer or handheld devices communicate with access points. To provide continuous coverage, these access points must have overlapping coverage areas. Coverage typically extends 30 m indoors and 150 m in unobstructed environments. By utilizing automatic frequency allocation (AFA) access points monitor the HIPERLAN radio channels around them and automatically select an unused channel. A mobile terminal, after association, will only talk to one AP at each and every time, but it can request to be connected to another if it receives a better signal strength. When a mobile terminal roams from the coverage area of one access point to another, it automatically initiates a handoff to the new access point. The APs associated with the handover ensure that established connections throughout the air interface as well as security associations are transparently shifted from the old to the new. Security support includes both negotiation that is key authentication (conventions such as for example the netw ork access identifier (NAI) and X.509 can be utilized), in addition to encryption using DES or 3-DES.
OFDM modulation can provide transmission rates of 54 Mbps but this is dynamically adjusted to less rate by utilizing modulation that is different depending on the prevalent radio conditions. All traffic is transmitted on connections, bi-directional for unicast traffic and uni-directional towards the mobile terminals for multicast and broadcast traffic. This method makes help for quality of service (QoS), implemented through time slots, direct. QoS parameters include bandwidth, bit error rate, latency and jitter. The original request by a mobile terminal to send data uses specific time slots that are allocated for random access. The access point grants access by allocating specific time slots for a specific period in transport stations. The terminal that is mobile sends data without interruption from other mobile terminals operating on that frequency. A control channel provides feedback to the sender, indicating whether data was received in error and whether it must be retransmitted. The QoS de livered depends on how the HIPERLAN2 network interoperates with the network that is fixed for instance, if it is via packet-based Ethernet, cell-based ATM or IP.
HIPERLAN2 operates as a seamless extension of other networks, so wired network nodes see HIPERLAN2 nodes as other network nodes. All common networking protocols at layer 3 (internet protocol address and IPX, as an example) will operate over HIPERLAN2, permitting all common network-based applications to work, making the technology both community and application separate. Interoperation with Ethernet networks is supported right from the start, but easy extensions also provide support for ATM, PPP, IP and UMTS. The standard has been specified with the clear objective of achieving interoperability plus the industry consortium, HIPERLAN2 Global Forum (H2GF), aims to run tests to validate interoperability among items from member companies.
The most application that is obvious HIPERLAN2 will be in the enterprise LAN environment but networks can also be deployed at ‘hot spot’ areas such as airports and hotels, supplying remote access and Internet services to business people. Its ability to act as an alternative access technology to 3G cellular networks is also a key application. The transmission of video streams in conjunction with datacom applications, HiperLAN2 has potential applications in the home by creating a wireless infrastructure for home devices (for connecting home PCs, VCRs, cameras and printers, for example) as the high throughput and QoS features of HIPERLAN2 support.
HIPERLAN2 almost sounds too good to be true and price-to-market is an issue. For instance, the higher price of silicon for OFDM operation could stall reasonably priced execution. At present, expenses stay reasonably high for 5 GHz OFDM systems, mainly due to the high linearity demands that it places on the power amplifier in the transmitter and the low noise amplifier in the receiver. Consequently, HIPERLAN2 products will likely cost more than lower speed alternatives. Also, some view the fact that HIPERLAN2 is sophisticated and able to support a wide range of applications definitely not as a selling point but as overkill that comes at a price.
IEEE 802.lla
On the other hand, IEEE 802.lla, due to its simplicity and maturity, represents lower costs and a faster time-to-market. However, although 802.1la and HIPERLAN2 have a near identical physical layer, they differ into the MAC layer. Inadequacies include integrated quality of service, guaranteeing performance in work surroundings so when home video that is streaming. Therefore, efforts to close the MAC gap are a priority. Moreover, whereas the IEEE 802.lla and HIPERLAN2 both meet US regulatory spectrum requirements, HIPERLAN2 is truly the only 5 GHz WLAN that satisfies European interference avoidance limitations. Conversely, HIPERLAN2 must restrict the frequency range and power for the US to comply with FCC rules.
The risk is apparent utilizing the possibility that the united states and European countries will embrace two standards that are different. The consequence that the corporates’ inability to use one standard and benefit from lower acquisition and support costs could delay deployment of 5GHz wireless LANs somewhat. It really is a serious issue for global development because they are two incompatible WLAN standards. Thus, if 802.lla and HIPERLAN2 wireless terminals were operating in the same area, there would be interference, no coexistence and no interworking. Also, no roaming could be feasible if different access points had been deployed in numerous areas that are public. The end user will have to make a standards option as well as the 5 GHz WLAN market is in danger of being fragmented if different industry players follow different standards.
To prevent this several industry partners have begun a 5 GHz industry advisory group. In the HIPERLAN2 ETSI BRAN group and 802.lla Forum there are sub groups particularly taking a look at what exactly is required to reach one standard. At present, there is work that is much be achieved.
The short range wireless data networking headlines have been dominated by Bluetooth, resulting in unreasonably high expectations over the last few years. What tends to be forgotten is that, in relation to the development of similar technologies, Bluetooth is still embryonic. It is also a victim of its own potential. Articles on the subject wax lyrical about the possibility of consumer appliances being Bluetooth-enabled to have the capacity to ‘talk’ to each other and the merits of so-called ‘hidden computing’ applications. These will allow synchronization of laptops, PDAs and phones that are mobile immediately update calendars, appointments and email whenever within range. Envisaged commercial applications range from the wireless monitoring of transported goods and chemical processes.
Nevertheless, a lot of the early applications are essentially cable replacement or connection substitutes primarily aimed at the cell phone and FDA markets. The industry needs to walk before it can run so it should be, and to a great extent is, concentrating on steady development and addressing ways of ensuring interoperability, standardization and coexistence issues. Bluetooth has its origins in Europe with its initial development focused in Scandinavia, and even though it is really a technology that is global that is where its early deployment will be greatest. Bluetooth has attracted all the players that are key investment is considerable as well as perhaps some of the buzz is justified.
The IEEE 802.llb (WiFi) WLAN standard has been developed steadily without any razzmatazz on the other side of the coin and the Atlantic, but in the same 2.4 GHz unlicensed frequency band. Its high data rate, together with the falling costs of PC cards, allied to the mobility and flexibility it offers has seen significant market growth. It’s well placed to enjoy the increase in the usage of laptop computers and development in house broadband access. Globally, 802.1lb companies are making inroads in ‘hot spot’ applications at airports, seminar facilities and resort hotels, and WiFi items are striking the marketplace. Once more, issues of interoperability, standardization and coexistence are being addressed. However, although the establishment of a test that is registered in Europe will assist acceptance, certification has to be much more extensive.
Utilizing the inevitability that the unlicensed 2.4 GHz band becomes congested, the growth associated with the 5 GHz musical organization for next generation speed that is high is vital. However, the possibility of fragmentation, with separate standards being adopted in the US and Europe is a real threat to worldwide development and could wait implementation considerably. A standards war will gain no one, perhaps undermining self-confidence and making manufacturers cautious about significant investment.
Going wireless has include some strings connected but short range wireless systems have actually a long term future. Its ability to satisfy the industry’s desire for seamless connectivity will ensure continued market growth and development.
Mcdougal would like to thank the individuals that are following organizations due to their aid in compiling this supplement:
* Mobilian Corporation, www.mobilian.com
* Vincent Vermeer, company development supervisor — Wireless Connectivity Division, 3COM (Europe), www.3com.com
* Dr Jamshid Khun Jush, chairman of ETSI BRAN and specialist that is senior LANs at Ericsson, www.ericsson.com
* Martin Johnsson, president HIPERLAN2 Global Forum and WLAN item manager at Ericsson, www.ericsson.com/wlan
* Peter Bates, VP company development, www.bluesocket.com
* Andy Craigen, senior supervisor, Wireless Terminals Applications, Agere techniques
* Bob Heile, chairman IEEE 802.15 Working Group
* The organizers and speakers at the Wireless LAN conference in London in April 2001. Arranged by EF-Telecoms, www.ef-international.co.uk
* Frost & Sullivan, www.frost.com
* Figure 2 and Figure 3 are taken with permission from presentations available on www.ieee802.org/15/ EUROPEAN 3G SPECTRUM AT [greater than]$700 M PER MHz COST $B GERMANY 47.5 UK 32.9 ITALY 11.4 FRANCE 9.3 Note: Table produced from club graph
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