Connections +
Feature

Getting It Fixed

Major new developments have made fixed wireless a viable technology solution for commercial spaces.


February 1, 2001  


Print this page

Over the past ten years, wireless technologies have entered into our lives from many directions. The evolution from pagers to analogue cellular phones to the latest generation of web-enabled PCS phones has changed the ways we work and communicate. And the next generation of enhancements promises even further changes to our lives.

While the word “wireless” often carries the connotation of personal communications devices, there have been equal technological developments in other areas. Wireless devices and appliances are eliminating the boundaries in our living areas and are delivering high-speed multimedia services, whether via satellite or through wireless MDS systems, directly to our homes and businesses. The presence of wireless local area network (LAN) access is becoming commonplace in the home and office, as an increasing number of property managers recognize the value and strive to meet tenants’ demands for the convenience of wireless service.

Major developments have also occurred in the fixed wireless sector of the industry. Fixed wireless deploys the latest wireless technologies to provide an alternative means for telecommunications access to buildings and offices. For the most part, point-to-point fixed wireless services have developed much faster than point-to-multipoint technologies, providing a reliable service delivery platform to offices, factories and educational institutions. Fixed wireless can be used to establish completely wireless metropolitan area networks (MANs) or it can be used in conjunction with fiber cable to connect buildings to the MAN on a wireless basis.

THE FIXED WIRELESS SECTOR

The fixed wireless sector in Canada came into its own in the latter part of the 1990s. In the fall of 1999, Industry Canada auctioned some 1400 MHz of spectrum for fixed wireless use at 24 and 38 GHz. Previously, only limited spectrum had been authorized for fixed wireless use at 28 GHz and, as a result of limited technology availability, it was not widely developed.

Fixed wireless uses spectrum in what is considered the “microwave” portion of the band. It operates at a frequency considerably higher than the 2.5 to 5 GHz range of your home microwave oven, specifically in the 25 to 40 GHz bands. In all of the microwave bands, transmissions are only possible on a “line of sight” basis. Unlike lower frequency transmissions, microwaves can not pass through buildings or even dense vegetation.

At the higher frequencies, relatively small antennas (usually less than 0.5 metres in diameter) are utilized, due to the shorter wavelength of the radio wave (typically in the millimetre range). At microwave frequencies, the prime determinant of the range that signals can be transmitted is the atmospheric “path loss”. On a clear day with low humidity, path conditions are optimal and a low power signal can travel up to 25 kilometres. By comparison, during a heavy spring downpour as the path loss increases, the same signal power level travels a much shorter distance — normally a couple of kilometres under the most severe conditions.

BUT IS IT RELIABLE?

Designing a reliable wireless service for a demanding business customer requires that these factors be incorporated into the design process. Recent technology developments incorporate many new features that further enhance the reliability of fixed wireless services. Perhaps the greatest improvement in the technology results from what is called “adaptive power technology”. Put simply, this technology enables a fixed wireless radio to increase its power automatically to ensure that any increases in path loss are offset by an increase in the power level of the radio. By using increased transmission power, the signal at the receiving end remains fundamentally constant, even though the path loss may have increased as the result of a sudden downpour of rain.

This technology is made possible by the use of microprocessors, built into the radios, to monitor the quality and strength of the received signal. By dynamically monitoring these parameters and adjusting power levels (typically twice a second, if required), these radios are able to maintain the same level of reliability that is achieved through fiber optic cable. Earlier generations of microwave radios were susceptible to signal fade as conditions deteriorated and, in some cases, complete loss of signal occurred. This capability is not new; it is deployed in CDMA cellular telephones where power levels are automatically adjusted up to 800 times per second.

In addition to ensuring reliability, this capability also ensures that the limited channels allocated to fixed wireless can be efficiently re-used in adjacent areas — without the fear of interference. For cellular technology, it ensures that battery life is maximized.

THE ADVANTAGES

The prime attributes of any service must be reliability, security and cost-effectiveness for the user. Clearly, these are attributes that can be achieved using traditional wire connectivity, fiber connectivity or fixed wireless. While virtually every building in a metropolitan area is connected with copper, industry figures indicate that only five to seven per cent of buildings are connected with fiber. Most of these buildings are within the city core.

Industry figures also indicate that over 70 per cent of buildings are within one mile of a fiber cable.

Today, most fixed wireless deployment is on a point-to-point basis. Point-to-multi-point technology has not progressed sufficiently to demonstrate all of the prime attributes required to make it a viable business solution, and it is still in the early stages of maturity.

By establishing a wireless hub site with access to a fiber cable, building managers can reach a significant “footprint” in the city core on a wireless basis. These hubs are normally located on the rooftop of a tall building, with wireless coverage possible as long as “line of sight” can be achieved. Ranges vary from 2.5 km in the heaviest rain zones in Canada (Ontario), to 4.3 km on the East and West coasts, to over 6.5 km on parts of the prairies. The key determinant of range is the expected rainfall rate, based on historical data. In Ontario, this equates to an expectation of up to 100 mm per hour. A wireless hub site in these conditions can then provide the “last mile” service up to 2.5 km.

PROPERTY OWNERS AND TENANTS

Fixed wireless access requires that a small antenna, normally less than 0.5m in diameter, be located on the rooftop of the building served. The antenna will point to the wireless hub site. The antennas can be securely mounted on non-penetrating roof mounts near the edge of the roof or on mechanical mounts affixed to a vertical surface, such as the mechanical penthouse. Unless it is the highest point on the building, there are no additional lightning protection systems required (although the mounts must be grounded).

The antenna is then connected to interface equipment by a single flexible coaxial cable that is not much larger than those used for cable TV. This equipment is housed in a small, secure cabinet, which is located in another part of the building and accessible to the building riser system. It could be located near the top of the building, in the telecommunications room, in the building core, or even in tenant space. The cabinet contains a small radio indoor unit with the service interface and power equipment — usually a rectifier and four small batteries. This feature ensures that the service will continue to operate — even during commercial power failures.

Other equipment that is unique to the customers’ service requirements can also be housed in the cabinet. A single coaxial cable, a cable to the customer equipment, and a power cord for connection to a wall outlet, are required to establish service.

As tenants’ bandwidth demands increase, the need for higher speed telecommunications rapidly exceeds the limits of copper technology. Fixed wireless is currently capable of offering services up to 625 Mbps of bandwidth using a single system, and in multiples of that capacity with each
additional system deployed. Higher bandwidth capability is currently being developed.

Fixed wireless also offers tenants some unique advantages. Most major service disruptions in telecommunication networks occur in the last mile. One of the more frequent modes of service loss occurs when a contractor cuts a cable. If that cable was serving your business, your service will be interrupted — often for several hours — while repairs are made. The loss of telecommunications for that period can be disastrous for a business, from both a customer service and cost perspective. Wireless offers relative immunity to this mode of failure and can be deployed as a “redundant path” where failure cannot be tolerated.

The rapid provisioning capability of fixed wireless also makes it attractive for property managers, allowing them to satisfy tenant bandwidth requirements while avoiding the wait for fiber construction.

LOOKING AHEAD

As bandwidth requirements continue to grow, fixed wireless offers a convenient, cost-effective alternative to traditional information transport technologies. Whether the requirement is for voice, data or multimedia capability, fixed wireless can offer reliable and secure service.

For commercial and residential high-rise dwellers, rapid provisioning capability will mean that it may be the only product in the downtown core that can meet urgent and stringent provisioning schedules. From a building perspective, fixed wireless is a simple and non-invasive means of delivering high and reliable bandwidth to tenants. Fixed wireless technology meets all of the requirements for mission critical telecommunications for today’s demanding enterprises, while providing a diverse connection from existing carrier facilities.CS

Bob MacCallum has over 30 years of experience in the Canadian telecom industry. He is currently Chief Technology Officer and Vice President, Operations of Stream Intelligent Networks Corp. in Toronto, a supplier of high-speed digital communication services. Among other responsibilities, Mr. MacCallum is responsible for the design and commissioning of the network and the operation of the company’s advanced Network Control Centre. He also heads a group responsible for the Network planning and Technology selection for Stream’s hybrid fiber-wireless network.


Print this page

Related