Telecom Student Papers: Mirles - California Western
Fall 2004 Telecom Student Papers: Mirles

Wireless Technology

By Victor Mireles

Adaptive Repeaters

            Mobile technology has expanded rapidly in the past decade.  With the increase in demand in services ranging from traditional voice communications to wireless internet access, companies have tried to keep up with demand by either improving their networks or increasing the number of cell towers.  Yet, such moves have their limitations most notably in the area of in-building coverage.

The Basic Concept of a Repeater

            A promising solution to in-building coverage is the use of adaptive repeaters.  The technology itself is not new.  Repeaters have been used for decades to boost fading signals in traditional analog transmissions such as VHF, UHF and microwave.   A repeater takes a signal, amplifies it, and then retransmit it.   A common problem with repeaters is the tendency to boost all signals, which can lead to interference with other signals.    An adaptive repeater takes only a select signal and modulates it to eliminate distortions and prevent interference with other signals.  

A donor unit houses the main receiving antenna and the computer to modulate and fine tune radio frequencies.  The donor unit is placed in a part of a building or structure where signal coverage is somewhat good.  This donor unit is connected by coaxial cable specially designed to transmit and receive radio signals or is connected by a coverage unit that receives the retransmitted signal.  The cable or coverage unit is laid around areas of a building that have poor to non-existent coverage.  Once in place the area should have coverage comparable to the donor unit picking up the outside signal. 

The system is designed for indoor usage, where connectivity is critical for todayís business environment.   In the past to provide indoor coverage cell carriers built a number of cell towers and smaller sites ringing a certain area to provide coverage in the hope that the signal would penetrate the exterior of the building.   Yet, the solution often creates several problems.  The cost of a single tower or smaller site can cost around $250,000 or more.   Another problem is the procurement of land, and the payment of rent to leased sites, not to mention the potential zoning and regulatory issues.   Even if a company were to navigate the process, most modern buildings compound the problem, with its steel structure which tends limit radio energy.   Also, most modern office building windows have some form of metal and reflect all forms of UV and radio energy.   The use of an adaptive repeater solves most of the providersí problems.

Advantages and Disadvantage of a Repeater Solution

The benefits of the adaptive repeater are based on its compact nature and design.  First, since it is essentially an internal antenna it is not subject to zoning regulations placed on tall towers or other types of antennas.   As long as the retransmission is limited to the building and does not affect the outside environment it is not subject to zoning or licensing regulation.  Second, it is site specific and can be expanded to fit the needs of a particular building or structure. Some models cover up to 25,000 square feet, with other models allow for coverage of 100,000 square feet or more in area.   Further, some models can be used for home applications and rural areas where signals are often weak.  Third, it is adaptable to changes in technology.  Most providers have specific standards, and working in concert with the providers adaptive repeaters can boosts most of the systems with minor changes to the donor unit.   Currently, the system can handle all wireless applications and has the potential to expand to new systems.  Also, providing adaptive repeaters with such technology allows the provider to maximize their existing infrastructure without creating new sites.  However, the system does have a few shortcomings. 

The system itself is expensive, with some models going as cheap as $3500 to some systems costing upwards of $50,000.  The repeater itself does not increase the bandwidth of the signal, but in some cases takes too much of the signal and puts stress on transmission sites.  Lastly, a few providers are holding out on sharing some of their technology needed to maximize the benefit of the system, most notably NEXTEL which runs on a separate platform.   The effect of keeping a propritary cell phone system may result in a situation similar to the PC situation of today where most of the worldís computers use Windows and Apple PCs are relagated to a niche market.  The problem may cause delays in improvements to the system, but the overall effect is unknown.

Economic Outlook of the Business

The economic outlook for the technology is great.  The prices of most systems are falling.  The initial slow grow of repeater technology was based on poor performance and the initial costs.  Most companies, apartment building owners, and some home owners could not justify the costs of increasing the coverage area for the benefit of a few.  Yet, as consumers have increasingly taken to such technologies as instant messaging, Wi-Fi, the demand for decent coverage in all parts of the work environment has made this technology a hot commodity.   Also, the providers ads touting their coverage places a pressure on the companies to provide indoor coverage solutions.   The demand has reached even in places not associated with work environments such as subways, sports arenas and tunnels.

Potential sources of continuing income include the occasional upkeep of the system, providing the necessary software improvements to the system and the sales of the units themselves.  The systems have become less complicated to the point where all it takes is basically a personís cell phone to find a good location and some basic know-how in placing cable and any uninstallation needs.    Also, the desire to have a competitive edge should drive most businesses to adopt some form of the technology.  As the technology improves it should become even more attractive since the publicís desire for coverage even in the deepest recesses of a building will put pressure on landlords to provide some sort of service or equipment and is likely to develop as a prime market. 

            The likelihood of a better technology coming along and destroying the business is unlikely at this time since the alternative is either to build a mini-cell site and go through the regulatory and legal hurdles, or increase the use of satellites which require some form of line of sight.  There may be a time where a new technology will make the problems of in building coverage obsolete, but nothing is currently on the horizon.  Currently the field is open as there are a few companies involved in the technology.  Most providers are forming alliances with the various players in the adaptive repeater business.   The future is bright for the technology because as we demand to be connected everywhere, an adaptive repeater helps fill the gap otherwise left open.

Bibliography

Andrew Miceli, I Canít Hear You, 2001 Wireless Rev. WL 6905214 (Feb 28, 2001)

Repeaters: Range Extenders, Mobile Radio Technology, Oct 2002, at 10.

Donny Jackson, Tunnel Vision, Mobile Radio Technology, Sept 1, 2004, at 9.

Vittore, Falling Costs Put Indoor Coverage in Reach, Wireless Review, Dec 1, 2003, at 23.

Emily Motsay, Carriers Look to In-Building to Enhance Voice as Well as Bring Data,  

RCR Wireless News, Oct 20, 2003, at 20.

Sridhar Pai, In-Building Wireless: The Next Generation, Available at: http://telephonyonline.com/microsites/newsarticle.asp?mode=print&newarticleid=27257

Harold Kinley, Technically Speaking, Mobile Radio Technology, Apr 1, 2004 at 4.