Making the case for wireless; a wireless primer
March 1, 2003
For Those Who Thought Wireless Would Displace and Kill the Wired Network, It Will Probably Happen at the Same Speed as Computers Have Eliminated the Need for Paper in Modern Offices. Then Again, It Doesn’t Have to Be An Either/Or Situation.
In the current business world, organizations are constantly reminded about the progress made by the wireless technology as well as its potential.
There are numerous wireless technologies satisfying various needs. Customers faced with such a large variety of choices may be confused about services available from public network carriers and those available through private networks.
They are asking themselves a number of questions. Should I cable or not cable? Can I live with wireless only? How durable will my investment be?
If we look back in time, what were we trying to achieve when we took a decision to invest in a properly designed structured cabling system?
First, attempting to invest in an infrastructure that could stand the test of time by being as independent from the application layer as possible.
Secondly, as the speed of networks was increasing constantly, we were looking at maximum bandwidth.
Lastly, we were looking for a system that was easy to manage, since most business customers keep moving and rearranging their staff to better adapt with markets demands.
Structured cabling systems kept delivering on the promises and as a result, became the type of investment an IT manager relies on and tends to forget once installed.
They became more or less a commodity. The quality now relates more to the skills of the installation team rather than the quality of the products themselves.
They have evolved with the technology demands and even faster to a degree. As an example, Category 5e still meets most current needs. Fiber to the desk is not even required due to the capacity of copper cabling, and standards have not really changed, but simply evolved with the technology.
There has been a good symbiosis between the network’s needs as defined by the various IEEE’s committees and the practical cabling solutions coming from the work of the EIA/TIA.
Connectors, patch cords, panels, etc. are still adequate and more importantly, the technology is backward compatible with the older category releases. This is primarily due to the fact that structured cabling has remained a pure level 1 (Physical) layer component of the OSI model.
Still, now there is wireless to consider. Now more than ever, the new generation of wireless connectivity devices are moving to the level three layer and in some instances, to the level four with some transport protocols, even though some companies such as Symbol are introducing products that now separates the basic physical layer (the RF component) from the control layers.
Wireless services offered by the telecommunications carriers are mainly characterized by wide geographical coverage, but are somewhat limited in bandwidth, usually around 19.2 kpbs.
Those services are particularly suitable for applications that are transaction-based — the type of short request and short confirmation (stock information, part number, confirmation request, authorization request etc) with a limited content of information.
The second category is the Wireless LAN and is specific to in-building or campus-based applications.
The infrastructure is private, i.e. owned by the customer. This architecture is currently using equipment in the ISM band and has relatively high bandwidth capacity (up to 11 Mpbs currently under 802.11b, and moving towards 54 Mbps and more for the 802.11a and soon coming 802.11g standards).
On the other hand, the compromise is on the area covered, which is limited to the reach of the cells created with the Access Points — roughly 40-60 metres from the AP location.
The most current standard, the one that has the largest quantity of network deployed — from retail stores to industrial sites — is the 802.11b.
The new 802.11a offers interesting promises, but will not be interoperable with 802.11b, despite hardware migration plans announced by some manufacturers.
Some companies will offer clip-on equipment allowing the two technologies to co-exist without having the burden to re-wire the AP to the network, but the two technologies operate in different frequency bands.
While the more recent 802.11g under development will function in the same band as the 802.11b, we have yet to see how interoperability versus “coexistence” will be handled by different products.
One of the main characteristics of the 802.11b standard is the rate adaptability. Whereas in the previous protocol, if the mobile station was getting out of range, it would lose the signal, in the new standard, the data rate adjusts itself to compensate for the weakness of the radio signal in pre-determined bands.
Though 802,11x are the standards of discussion, one cannot ignore other very important applications such as Bluetooth standard and Wireless Wide Area Network (WWAN).
A great deal has been written about Bluetooth, which is starting to be deployed in many applications.
The WWAN is more of an application than a standard, as equipment available in the market is non-interoperable. This is, however, not an issue since equipment is used to create private LAN-to-LAN extension in a point-to-point (or sometimes multipoint) mode.
Here again, the technology is evolving, and due to modern encoding algorithms, pure line of sight is becoming less of an issue.
In this regard, WWAN is competing with the fiber component of structured cabling, especially when we consider its throughput (100 Mbps Ethernet is commonly available). It’s also particularly suitable in instances where right-of-ways are not obtainable or where physical construction is too expensive.
A few words on the ISM band: This band is “license free”, i.e. an Industry Canada or a FCC license is not required, but power levels must be observed to maintain legality.
Many devices other than LAN equipment are operating in these frequency bands, but often with different encoding schemes, on different channels.
Though interference is usually not a major issue, design considerations must be brought, most specially in dense areas, and the firm implementing a network using this technology must perform minimum verifications.
The connection of a wireless LAN to a wired network: The connectivity is established through a UTP EIA/TIA 568 compatible cable between the various access points to the network hub, switch or router, depending upon the needs and the network configuration.
Some manufacturers offer in-line, non-intrusive power sources to power the Access Points without having to bring AC plugs to every unit.
Comparing the basic attributes of structured cabling to wireless: Even if WLAN is perceived as a potential structured cabling replacement, there are fundamental differences starting to emerge. The most important one is probably the dependency (or independence in the case of cabling) to the application.
Where in a structured cabling infrastructure, engineers are concerned about the number of physical connections, their location and the bandwidth required, a wireless network design has to take the application into account. QOS, bandwidth management and network accessibility are becoming more software controlled than the traditional physical access control of a cabling system.
The decision to invest in a structured cabling system and/ or in a wireless network is influenced by many factors. The first one is right at the conceptual design stage.
Both require different skills and information sources. A cabling design can be finalized on structural plans, but a good wireless design can never be final unless a real site survey has been done.
Building construction materials, shelving, obstacles and other physical considerations may affect wave propagation, create reflections or constitute barriers that may affect the throughput in ways not identifiable on blue prints.
Where in a structured cabling system, bandwidth availability is everywhere the same (or
limited by the active networking equipment), this is not true in the case of wireless.
The design can be adapted to guarantee data rates in some areas, but cost limitations may force a decision to limit this data rate in others where only transactional-based connectivity will be required.
The combined effect of the RF coverage and the data coverage constitutes the basic of a private mini cellular network within the enterprise. In addition to channel management, throughput issues, other physical issues should be taken into consideration such as any outside interference.
Cabling is often planned at the building phase and is considered as part of the construction budget.
If someone decides to replace a portion of the cabled infrastructure with wireless, he or she may have to request budgetary approval from the MIS department, not the real estate division.
If budget allocation was not transferred properly, or not identified up front to the MIS department, some implementation roadblocks may suddenly surface.
In addition, when a cabled infrastructure is in place, it is a given that terminal equipment will come equipped with the appropriate NIC cards. That’s not necessarily true when wireless is involved.
Commonly, extra capacity and future MAC flexibility planning is done at the initial implementation phase in structured cabling installations.
Where adding users on a wireless network may not pose major immediate labour considerations, the long-term management of both infrastructures is considerably different.
One should manage an active network versus a passive one, with all appropriate considerations given to user configurations, software licenses, upgrades etc.
User profile considerations are usually not a major consideration in the selection of a structured cabling system. While one may opt for features such as consolidation points if users are frequently re-arranged on floors, distribution through ceiling or floors is often driven by factors different from the communications ones, being more impacted by electrical or ventilation requirements.
Wireless management is performed usually by MIS managers. To that end, several considerations need to be taken into account such as traffic on the network, bandwidth required, applications, NICs and security.
The latter is a key aspect in the design of a wireless network. Current 802.11b has some native wireless features: DES based on 40 bits encryption is a standard basic, and some companies support either higher bit encryption or a series of proprietary encryption or authentication methodologies.
In summary, both telecommunications infrastructures have a key role to play in modern IT environment.
In fact, they are more a complement of each other than competitive threatening technologies.
For those who hoped that wireless would displace and kill wired network, it will probably happen at the same speed as computers have eliminated the need for paper in modern offices.
In other words, until that occurs, there will definitely be room for both.
Jacques Kirouac is president and CEO of Normex Telecom Inc., Cygnal Technologies Inc.’s data network solutions group based in Montreal. Normex specializes in the engineering supply of private wired and wireless infrastructures.
A Wireless Primer
Back when Guglielmo Marconi began experimenting with “Hertzian waves” in 1894, wireless meant “wireless telegraphy” and Marconi called his system the “cable telegraph.”
Hertzian waves later became known as radio waves and the cable telegraph became better known, at least in North America, as the radio.
Even the meaning of wireless itself has changed. Originally, wireless described telecommunications in which radio waves (rather than some form of wire conductor) carried a signal over all or part of a communications path.
The definition of wireless today has broadened to incorporate other parts of the electromagnetic spectrum in which information is transmitted without wires.
These include not only radio frequency (RF) transmission, but also communications via infrared, laser, visible light and acoustic energy.
Wireless communications has blossomed. In a mere 20 years, wireless services have accumulated more than one billion users and combined service revenues of nearly US$400 billion a year.
As wireless use has developed, it has engendered a great multitude of technical terms, jargon, trade names and legal definitions. This terminology is seldom readily understandable and, at best, is often confusing. Nonetheless, wireless technologies are expected to continue to grow dramatically in the next decade and play an increasingly greater role in our lives.
Wireless systems can be categorized in various ways, including, for example, classifications based on network architecture or mobility factors. These differing taxonomies — the way systems are organized — are one reason wireless can be so confusing. One wireless taxonomy bases its nomenclature on the area of spectrum utilized. Examples of this type of organization include:
IR wireless: Devices that use IR include home-entertainment remote-control boxes, wireless local area networks, links between notebook computers and desktop computers, cordless modems, intrusion detectors, motion detectors and fire sensors.
Acoustic wireless: Communication by operating devices that employ acoustic waves. These include military (e.g., surveillance, underwater reconnaissance), government (e.g., earthquake and tsunami warning systems) and commercial applications (e.g., pipeline monitoring, ship traffic control.
An alternative categorization classifies wireless technologies by range. In this arrangement, the apportioning factor is the geographical region covered by the network.
Yet another common method divides wireless systems into categories according to the type of device involved in the communication. These categories, which sometimes overlap, include:
Fixed wireless: Communication using devices at fixed locations such as homes or offices. Standard utility mains typically power fixed wireless systems. Frequencies allotted for fixed wireless systems range from 900 MHz to 40 GHz.
Many types of fixed wireless systems exist and have been developed based upon the frequency of the spectrum utilized.
These systems include private licensed microwave links; private unlicensed links; 38 GHz carrier service; Local Multipoint Communications Systems (LMCS); Multichannel (or Microwave) Multipoint Distribution Service (or System) (MMDS); optical wireless (laser); and Unlicensed National Information Infrastructure band (UNII).
Even satellite service and high altitude aircraft systems proposed to offer round-the-clock wireless service are sometimes considered fixed wireless systems because their ground stations are at fixed locations.
The technical limitations of fixed wireless systems limit them to metropolitan area geographies. Therefore, they are considered MAN technologies.
Mobile wireless: Communication via the operation of devices aboard motorized vehicles via battery power, such as personal communication services (PCS) units and automotive cell phones.
Portable wireless: Communication by means of autonomous, battery-powered devices outside the home, office or vehicle, such as PCS units and handheld cell phones.
Like wireless, broadband also can be defined a number of ways. In its simplest description, broadband is a method of delivering voice, data and video using a wide range of frequencies at high speed over a given period of time.
Broadband wireless is the wireless transmission of such information. Although spectrum licenses can be expensive, often, setting up a wireless transmission system is more economical, more convenient and faster to deploy than laying cable to the user.
When defined by the RF section of the electromagnetic spectrum that is employed, broadband wireless includes LMCS, MMDS and PCS. Broadband wireless also includes the transmission of information employing optical wireless technologies.
LMCS: LMCS is a broadband microwave fixed wireless sy
stem that offers one-way and two-way communications. It was designed to provide voice, data and video (wireless cable television) service. It is a point-to-multipoint service, which means that in an LMCS system, a local antenna transmits to receivers at homes and businesses. It provides connections of up to five miles, depending on the terrain and weather conditions.
LMCS requires a clear line-of-sight between the transmitter and the receiver. This means that if a hill, trees, walls or similar obstructions are in the way, its signal can distort or fade. Rain also can scatter and distort the signal.
Some LMCS providers offer two-way wireless transmission. This is called downstream and upstream or “symmetrical” service.
Other providers offer only downstream or “asymmetrical” service and a wire connection is required for upstream service (Standard telephone lines supply the wire connection.). LMCS offers a bandwidth of up to 1.5 Gbps downstream to users, although a more common transmission rate is 38 Mbps downstream. It offers 200 Mbps upstream from the user.
LMCS operates in the 27.5-31.3 GHz frequency band in North America and from 24-40 GHz overseas.
MMDS: MMDS is a broadband microwave fixed wireless system quite similar to LMCS. The primary differences are that MMDS can operate over greater distances, but has less bandwidth than LMCS offers.
Initially, MMDS began as a one-way service to broadcast wireless cable television. However, it could not compete with wireline and satellite cable offerings because quality was problematic and satellite television, in particular, offered a greater number of channels.
While MMDS still provides up to 33 analog and more than 100 digital television channels in some locations, it now is available as a two-way transmission service, supplying voice and data communication applications, such as Internet service. In some cases, the upstream path employs a wire connection.
PCS: PCS is a two-way digital wireless voice and data service similar to cellular telephone (cell) service. In both PCS and cell systems, antennas blanket an area of coverage.
As a user moves around, the nearest antenna acquires the user’s signal and transmits it to a base station connected to the wired telephone network.
PCS and cell systems use separate networks of antennas. PCS differs from cell service in several ways. PCS is digital while cell systems may be both analog and digital. PCS was meant to offer greater geographic coverage and thus, extended personal mobility than cell service, which was designed for use in cars with transmitters located around roads.
Optical Wireless: Optical wireless is a broadband fixed wireless system that offers two-way voice, data and video communication. In an optical wireless system, laser beams transmit information through the air. It also is referred to as atmospheric laser transmission, “free space optics” (FSO) or “free space photonics” (FSP).
In an optical wireless system, two or more laser transceivers with a clear line of sight between them are aligned. A transceiver both transmits and receives signals, so there is full duplex (bi-directional) capability.
Typically, optical wireless systems are used to link buildings and campuses together at distances of up to six kilometers.
Four different optical wireless configurations exist.
The first type is a dedicated point-to-point link between two terminals, such as two buildings. In the second, a point-to-multipoint architecture, a hub is placed on a tall building.
Optical wireless systems are less expensive than RF-based systems because there is no cost for acquiring spectrum licenses. However, atmospheric conditions may impact performance.
While rain, snow, dust and smog can block light transmission and thus, disrupt service; fog presents the greatest problem. Dense fog disrupts and dissipates laser signals because its small, dense moisture particles act like billions of tiny prisms.
In summary, Guglielmo Marconi might well be amazed at the extent to which wireless telecommunications technologies have permeated our lives. Similarly, it is hard for us to conceive of which standards will dominate and what applications will appeal to us in years hence.
What we can expect is that wireless technologies will continue to play a significant role in communications infrastructures and thus, they will have a substantial effect on expanding our ability to convey information.
Joseph Kershenbaum is a technology executive and lawyer who has advised manufacturers and service providers in the telecommunications industry. He can be reached at firstname.lastname@example.org. The author wishes to thank Edward Kershenbaum, formerly with SBC Communications Inc. and the senior technology officer of a number of leading companies, for his assistance with this article.