August 6, 2020

The Best Long-Range Outdoor WiFi Antennas

The growth of short range wireless systems, specially Bluetooth and wireless local area networks (WLAN) has captured the industry’s imagination, if not the market that was initially predicted. Bluetooth technology originated in Europe, with early development and research driven by European-based companies. In this special supplement Microwave Journal reviews current European activity, global expansion and globally competing technologies to discover whether going wireless includes strings attached.
No cables — what an proposition that is attractive! 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 currently necessary to connect a PC, not just towards the system, but in addition to its peripherals such as for example the keyboard, mouse and printer. Meanwhile, the flexibility of cellular and cordless technology has promoted a few ideas for a generic short range wireless access solution for various devices.
These are all desirable aims however the curiosity about and development of quick range wireless data networking has not simply been prompted by the need to office that is disentangle from trailing wires. The real impetus has result from the desire and expectation of an individual and organizations to be able to get into data and information very nearly anytime, anywhere, any place. 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 lucrative market is guaranteed provided that the technology can be acquired to implement it.

With such a sizable and untapped market there has been no shortage of contenders vying to provide that technology. This article looks at two of the contenders that are leading Bluetooth and WLANs. Issues covered include how Bluetooth has built 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 global deployment it is thought to be both a competing technology and growth market in its very own right.
Since Ericsson initially devised the technology in 1994 Bluetooth has grabbed the imagination and most of the headlines. The organization proceeded working on 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 purpose that is main of SIG would be to protect the integrity associated with the technology and control its development. It is responsible for the official certification procedure that most products must finish before they may be known as having a Bluetooth compliant product. Without certification, a product cannot claim to be Bluetooth-enabled or make use of the Bluetooth trademark. The official certification process means that designers maintain the standard and ensure 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 on this specification. From its European origins — it is named after a 10th century Norwegian King — Bluetooth has inevitably become of global interest to both manufacturers and prospective users.
The attraction is the fact that Bluetooth can provide low cost, 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 support for real-time traffic of both vocals and data, ensure it is an attractive wireless technology that is networking individual digital assistants (PDA), mobile phones and laptop computers.
Licensed spectrum is high priced, particularly in Europe ([greater than] $100 billion paid for 140 MHz). A significant benefit of Bluetooth is it runs at the internationally available unlicensed industrial, systematic and medical (ISM) 2.4 GHz frequency musical organization, enabling 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) free of charge. Bluetooth wireless technology operates 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 slave devices is set to communicate with a master radio in a single device. As Figure 3 illustrates, a number of these piconets are founded and connected together in advertising hoc scatternets allowing communication among constantly flexible configurations. All devices in the piconet that is same priority synchronization, but other products are set to enter.

Bluetooth’s baseband technology supports both connection that is synchronous (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 continuously variable slope delta (CVSD) modulation method, under which vocals packets are never retransmitted. The master product controls the link bandwidth and chooses how much bandwidth to give to each servant 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. The channel can support 432.6 kbps for a symmetric link. Since Bluetooth devices can support three vocals channels operating at 64 kbps, or one information channel, they can attain data prices as high as 1Mbps. The Bluetooth 1.0 specification calls for 1 mW transmitters with a antenna that is nominal of 0 dBm to operate up to 10 m (line of sight). An increased power transmitter of 100 mW (+20 dBm) within the specification increases the range to 100 m, although this will need a separate PA antenna motorist. The compromise is increased costs and power consumption.
Bluetooth makes use of frequency spread that is hopping (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. Every 1.28 seconds 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. The connection begins whenever one device initiates an association and becomes the master of this piconet. A connection is created 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 first half of this 12 months utilizing the end of 2001 seeing significant predictions.
Frost & Sullivan forecasts worldwide deliveries of Bluetooth-enabled items to reach over 11 million units in 2001, equaling $2.5 billion in revenues, while Micrologic Research is more conservative with its estimation that the marketplace shall 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 were not drawn to the project until 1998. Other mobile communications technologies such as for instance the GSM took longer to produce than will be allowed for Bluetooth.”
Semiconductor chipset development is a vital aspect in the technology’s progress, with a variety of development models appearing within the semiconductor industry that is bluetooth. Two distinct manufacturing routes are now being taken. There are either those offering complete integrated solutions from the silicon wafer level to your consumer product degree or those providing part of the amount of a chipset, that is, baseband, radio and pc software.
Debate continues over the absolute most effective choice of silicon 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 interoperability that is achieving can be increasingly crucial as semiconductor companies come closer to establishing their products onto the market.
Alongside some of the big names a number of smaller design services companies have entered the Bluetooth software market offering complete or partial protocol stacks to semiconductor developers. An opportunity to build early market share with fast time-to-market solutions in the same vein Bluetooth has offered a number of smaller, highly innovative fabless semiconductor developers, such as Cambridge Silicon Radio and Silicon Wave. Amongst the larger built-in Bluetooth designers, Philips Semiconductors has been the player that is main offer solutions in volume. It is expected that a number that is large of is going to be being offered by the end of 2001.
Market success are decided by a egg and chicken 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 revenue that is future for chipset companies. Despite such words of caution Frost & Sullivan forecasts that the total deliveries of Bluetooth chipsets is going to be over 956 million in 2006, and also the market that is total these chipsets is predicted to be over $2.3 billion in 2006. Further up the value chain from chipsets the early Bluetooth offerings are fairly generic wireless community access items, such as Computer cards as well as other add-on devices, as well as access points (AP).
Additionally, in Europe, 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 on the telecoms stock exchange as well as the gear necessary to roll-out Universal Mobile Telecommunication System (UMTS) companies hasn’t yet arrived at fruition, many of the services prepared for 3G mobile might be delivered by currently available technologies which operate in unlicensed (free) frequency bands.
Mobile operators that have 3G license debts to service are under some pressure to increase income of existing information services, and display that the market gets 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 gateway that is wireless. 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 public eye.
WLANs are appearing through the wings as a contender that is strong 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 an invisible screen card that is either area of the wireless unit or attached to it. The technology is in no way a newcomer, however. The IEEE 802.11 in fact, it was back in 1990 when, in the US Wireless geographic area Networks Standards Working Group was formed utilizing the task of developing a standard that is global radio gear and companies running into the 2.4GHz unlicensed frequency musical organization for data prices of 1 and 2 Mbps.
Over 10 years ago what the initial 802.11 standard did, to a diploma, ended up being to simply 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 signal harder to intercept than standard wired Ethernet.
The IEEE 802.11 standard was adopted in 1997. The modulation scheme utilized whenever operating during the 1 Mbps rate is phase that is binary 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. Nevertheless, these information rates of just one Mbps and 2 Mbps are notably slower than the wired LAN equivalents. This aligned with concerns over interperability and price, limited take up and acceptance associated with the standard as a option that is viable.
IEEE 802.11B
That most changed in September 1999 once the IEEE ratified a new high rate standard 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 top-end data rate of 11 Mbps. Each access point can support a large number of connections, although all 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. To achieve this higher data rate the IEEE 802.11 b specifies complementary code keying (CCK) as the modulation scheme. The technique maps four bits per expression to attain 8 Mbps, which allied to an increased rate of 1.375 Msps yields a little rate of 11 Mbps. Therefore, 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 standard products to interoperate with 802.11 compliant DSSS items by falling back once again to 1 Mbps or 2 Mbps procedure.
With a market human anatomy to validate interoperability and also the interoperability of 802.11b cards being assured, as a result of 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 standard Ethernet for speed. It has resulted in a renewed desire for, and perhaps more importantly, investment in the development of 802.11b products by large players whom failed to see any participation in 1 to 2 Mbps items as a viable option.
Now, the benefits that WLANs offer with regards to flexibility and flexibility, allied to increased speed and the falling costs of PC cards, has managed to get 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 exchange data directly. Instead, an access point allows PCs to talk to fixed Ethernet topologies via an Ethernet hub or switch port. Although WLAN cards continue to be 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 important thing to your 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 seminar facilities also being prime regions of development. Also, with all the increased use of laptops, the synergy that is natural 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 workplace, at home as well as on their travels without having to swap cards. Only a deployment that is wide of will facilitate that.
Mobile operators also see WLANs as an inexpensive and easy way to 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 added advantage of lower energy usage. Once again, at CeBit there were many gear manufacturers showing WiFi components in the shape of PC 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 soon. Such expansion is essential for the technology to be viewed as truly international regarding development.
The main element aspect in the development and development of this WLAN market was the increased data rate of 11 Mbps being afforded by the 802.llb standard. 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 the fact that the information rates are risen to greater than 20 Mbps and also the mission associated with the task group is always to review proposals. Areas of development currently being undertaken that could afford this ‘doubled’ information rate add a modulation that is new that improves the robustness of RF information transmissions. It not just overcomes a lot of the backdrop RF noise and other resources of disturbance but in addition offers better performance against multipath disturbance.
In 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 they are retransmitted which slows the information rate and interrupts the data movement, the system is less reliable for realtime transmission. With advanced equalizer technologies, reflected or noisy signals are not simply discarded or filtered down. Ahead error modification (FEC) algorithms usually takes corrupted signals and reconstruct them, significantly reducing retransmits.
Data rates of over 20 Mbps will open up new applications for the industry to exploit. As might be expected, interest shall most likely be light emitting diode by leisure applications. Faster transmission speeds will enable streaming video for 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 a way off nevertheless the WLAN is a growing market as the statistics show. According to the latest figures from IDC WLAN that is worldwide equipment jumped 80% in 2000, breaking the $1 billion mark. IDC predicts that by the final 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. 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 in the coming years. Despite the optimistic outlook for the overall market, especially in the united states, Western Europe and Japan, IDC believes vendors will need to overcome several obstacles, including resolving standardization problems, educating their partners, improving protection and reducing prices in order that WLANs are affordable for main-stream segments.
The chipset market for 2.4 GHz WLAN items is placed to continue to grow, although growth will 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 will be worth over $1.3 billion in 2006. This demand will be driven by the development in traveling with a laptop and also by dropping product costs.
Bluetooth and WLANs may have differing profiles in 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 certain extent it is a fear associated with unknown. What is known is that interference between 802.1 lb and devices that are bluetooth occur. The Federal Communications Commission (FCC) requires every device operating in unlicensed bands to have a label stating that it can cause interference in the US. Nonetheless, what’s as yet not known is the potential of the problem. The truth that the products operate in an unlicensed band and projections of mushrooming market development for Bluetooth and 802.1lb is fueling concerns.
Even though amount of concern may turn out become unwarranted, this has at the very least grabbed the interest of wireless standards groups, regulatory figures and industry that is wireless. They are all well aware that if users do experience interference problems it shall damage 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 being addressed to limit disturbance. In the US 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.
Consequently, substantial research observe the result that WiFi and Bluetooth products operating in identical vicinity have on one another is under means. Outcomes do vary and Figures 4 and 5 are samples 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. Go the two antennas within a meter, but, and there might be significant interference.
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 role that is important products such as notebook PCs. A good example is a notebook who has a Bluetooth radio integrated for link with a PDA or mobile phone and at exactly the same time has a WiFi radio integrated for LAN access.
Coexistence is a issue that is major 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, together with industry partners, is a company working on developing a solution and has now categorized 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 supplies a single-card guide design only. The proximity that is close of two radios with no coexistence device will likely produce worst-case situations, and will consequently end up in significant degradation to both radios’ performance.
Dual-mode radio switching will not require modifications to your silicon, and may be reasonably quick to advertise. It includes a coexistence mechanism that needs that while one radio is operational, the other is completely suspended. The procedure can primarily be implemented in two ways. In the first, the system simply shuts the non-operating radio off with no signaling to other nodes in its community. This may end up in difficulties for the system and may drop performance amounts below that of simple ‘collocation without a coexistence process.’ The second method does 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 much better than simply shutting the radios down. Neither method supports switching while Bluetooth voice (SCO) links are in operation.
Driver-level transmit switching generally describes an approach by which application send requests are mediated at the driver level, thereby avoiding simultaneous transmission. Intuitively, this approach degrades throughput by some measure simply due to its modal transmit framework. More crucial, though, are its limits to avoid collisions with incoming packets. The resulting transmission of one protocol during reception of the other noteworthy causes loss of received packets, interference and user that is potential. This is caused by the technique’s dependence on the host operating system, that is generally speaking non-deterministic in its reaction time (non-real-time). Once again, this process will not switch quickly sufficient to support Bluetooth SCO links, and will also have problems mitigating the disturbance from Bluetooth piconet master/slave activities that are polling.
While Bluetooth adaptive hopping truly improves performance that is simultaneous 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 time-consuming process. This time-delay exacerbates the situation that the strategy’s effectiveness is compromised with greater penetrations of WiFi systems and unmodified Bluetooth devices. Adaptive hopping will likely be initiated as an optional Bluetooth profile, indicating that modified devices will not use the functionality in piconets with unmodified products. Further, into the existence of more than one Bluetooth piconet or WiFi network, adaptive hopping are counter productive to coexistence.
MAC-level switching is the very best of this style that is modal/switching, and provides performance levels approaching those in no-interference scenarios. It is a technique that is collaborative by exchanging information between the two protocols at the MAC level and managing transmit/receive operations consequently. Because MAC-level switching is performed in the baseband, it is able to switch between protocols at a much faster rate than driver-level approaches. Consequently, with the ability to mitigate many of the conditions that driver-level switching cannot. MAC-level switching does not suffer from transmitting signals into incoming receptions, Bluetooth polling or operating system latency. Nonetheless, its susceptible to adjacent-channel interference and does suffer noticeable degradation. Also, because it is located in the baseband, it has a longer development cycle than driver-level approaches.
Simultaneous operation provides the capability to automatically detect 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 an electronic digital baseband chip – it allows simultaneous operation associated with the two protocols while eliminating interference and keeping reliability and performance. Interference is a genuine concern and, 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 are 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 will also be the need for Bluetooth radios to be included in access points and notebooks.
Another possibility that Bluetooth affords is the deconstruction of devices into specific components, permitting new kind factors and unit kinds. For example, insurance firms a separate headset there 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 access that is public. It is all well to possess synchronization between the notebook, PDA or cell phone but, whenever in an airport or plaza, use of the online or details about 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 you will find significant numbers of devices available on the market to use them and vice versa. Exactly the same applies to the providers of the information that users will be seeking. Nevertheless, this is an area actively being develop ed.
Public access is a application that is definite 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 suited to the enterprise sector for computer networking between PCs also to use the trend towards laptop flexibility. Ease, low priced and the center for expansion additionally make WLAN suited to little office office at home (SoHo) execution and the expansion of the house broadband access market, particularly in the united states, additionally starts up opportunities.
Even if just a fraction of those applications for Bluetooth and WLAN arrived at fruition, the slim (80 GHz) 2.4 GHz band will soon become congested. In anticipation 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. 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 as figure 7 shows, in Europe. Similarly, the US has allocated an overall total of 300 MHz within the two blocks 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.
Once more two different 5 GHz standards are increasingly being developed on either side of the Atlantic with both requirements offering information rates as high as 54 Mbps, and for that reason well placed to supply 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.
Instead the European Telecommunications Standards institute (ETSI) is developing high performance radio LAN (HIPERLAN) standards as part of its Broadband broadcast Access system (BRAN) initiative. Under its remit is the development of four criteria — HIPERLAN1, HIPERLAN2, HIPERLink (made for interior radio backbones) and HIPERAccess (designed for fixed exterior use to offer access to a wired infrastructure).
The HIPERLAN1 standard, which can be in line with the well-established technique of Gaussian shift that is minimum (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 activity that is current concentrated.
The physical layers of both 802.11a and HIPERLAN2 use OFDM modulation to quickly attain 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 spectral efficiency. For example, within the spectrum allocation for Europe, HIPERLAN2 channels will soon be spaced 20 MHz apart for an overall total of 19 stations.
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 information transfer, even though the remaining four are employed as a reference to disregard frequency or stage changes of this sign during transmission and offer synchronization. Synchronization allows coherent (in-phase) demodulation. The 2 criteria might have this similarity but vary above the layer that is physical 802.11a generally speaking viewed as easier and less complex, while HIPERLAN2 is mote advanced (or complicated based on your viewpoint) with wider scope.
For HIPERLAN2, mobile terminals such as for example a laptop computer or handheld products 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 channel that is unused. A mobile terminal, after association, is only going to keep in touch with one AP at each stage, but if it receives a better signal strength it can request to be connected to another. When a mobile terminal roams from the coverage area of one access point to another, it automatically initiates a handoff to the access point that is new. The APs involved with the handover ensure that established connections within the air interface as well as security associations are transparently shifted from the old to the new. Security support includes both key negotiation, verification (conventions such as the netw ork access identifier (NAI) and X.509 can be used), also encryption making use of Diverses or 3-DES.
OFDM modulation can provide transmission prices of 54 Mbps but this is often dynamically adjusted to a diminished rate simply by using 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 approach makes help for quality of service (QoS), implemented through time slots, simple. QoS parameters include bandwidth, bit error rate, latency and jitter. The request that is original a mobile terminal to send data uses specific time slots that are allocated for random access. The access point grants access by allocating time that is specific for a particular duration in transportation stations. The mobile terminal then 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 fixed network; as an example, if it’s via packet-based Ethernet, cell-based ATM or internet protocol address.
HIPERLAN2 functions 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 (IP and IPX, for instance) will run over HIPERLAN2, allowing all common network-based applications to operate, making the technology both network and application independent. Interoperation with Ethernet companies is supported from the beginning, but extensions that are easy 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 perform tests to verify interoperability among items from member businesses.
Probably the most obvious application for 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. As the high throughput and QoS features of HIPERLAN2 support 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).
HIPERLAN2 almost sounds too good to be real and price-to-market is an issue. As an example, the bigger price of silicon for OFDM procedure could stall reasonably priced implementation. At the moment, costs remain fairly high for 5 GHz OFDM systems, due primarily to the linearity that is high 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 range that is wide of not necessarily as a selling point but as overkill that comes at a cost.
IEEE 802.lla
On the other hand, IEEE 802.lla, because of 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. Deficiencies include built-in quality of service, guaranteeing performance in work environments and when streaming home video. 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 happens to be the only 5 GHz WLAN that satisfies European disturbance avoidance restrictions. Conversely, HIPERLAN2 must limit the frequency power and range for the united states to adhere to FCC rules.
The risk is obvious utilizing the possibility that the US and European countries will embrace two different standards. 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 considerably. It is a issue that is serious global development because they are two incompatible WLAN standards. Thus, if 802.lla and HIPERLAN2 wireless terminals were operating in the same area, there is disturbance, no coexistence with no interworking. Additionally, no roaming is feasible if different access points had been deployed in numerous public areas. The end user will be forced to make a standards option and the 5 GHz WLAN market is at risk of being fragmented if different industry players follow different standards.
In order to avoid this a few 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 evaluating what is necessary to reach one standard. At the moment, there is much work to be performed.
Over the last few years the short range wireless data networking headlines have been dominated by Bluetooth, resulting in unreasonably high expectations. 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 mobile phones to immediately update calendars, appointments and email whenever within range. Envisaged commercial applications are the monitoring that is wireless of goods and chemical procedures.
However, all 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 it should be, and to a great extent is, concentrating on steady development and addressing ways of ensuring interoperability, standardization and coexistence issues before it can run so. Bluetooth has its origins in Europe featuring its initial development concentrated in Scandinavia, and although it’s certainly a technology that is global that is where its early deployment will be greatest. Bluetooth has attracted all the key players, investment is considerable and maybe 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 market growth that is significant. It’s well placed to take advantage of the increase in the utilization of laptops and growth in house broadband access. Globally, 802.1lb networks are making inroads in ‘hot spot’ applications at airports, seminar facilities and accommodations, and WiFi items are hitting the market. Once again, 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 needs to be much more extensive.
With the inevitability that the unlicensed 2.4 GHz band will become congested, the growth associated with 5 GHz band 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 postpone deployment somewhat. A standards war will gain no body, perhaps undermining confidence and making manufacturers cautious with significant investment.
Going wireless has include some strings attached but quick range wireless systems have a term future that is long. Its ability to satisfy the industry’s desire for seamless connectivity will ensure continued market growth and development.
The author wish to thank the following individuals and organizations for his or her aid in compiling this health supplement:
* Mobilian Corporation,
* Vincent Vermeer, business development supervisor — Wireless Connectivity Division, 3COM (Europe),
* Dr Jamshid Khun Jush, chairman of ETSI BRAN and senior specialist Wireless LANs at Ericsson,
* Martin Johnsson, chairman HIPERLAN2 Global Forum and WLAN product manager at Ericsson,
* Peter Bates, VP business development,
* Andy Craigen, senior manager, Wireless Terminals Applications, Agere Systems
* Bob Heile, chairman IEEE 802.15 Working Team
* The organizers and speakers at the Wireless LAN conference in London in April 2001. Organized by EF-Telecoms,
* Frost & Sullivan,
* Figure 2 and Figure 3 are taken with authorization from presentations available on EUROPEAN 3G SPECTRUM AT [greater than]$700 M PER MHz PRICE $B GERMANY 47.5 UK 32.9 ITALY 11.4 FRANCE 9.3 Note: Table created from bar graph
[Graph omitted]
[Graph omitted]
[Graph omitted]
[Graph omitted]