PCS rural model:Cost-effectiveness, coverage and clarity
A hybrid of base stations and repeaters may be PCS carriers’ answer to filling in coverage gaps at a cost they can justify and afford. In many of these new markets, coverage, not capacity, will determine survival.
As the cellular and personal communication systems (PCS) industries heat up and competition grows fierce, cost issues are raising important questions. How much do I need to pay for building a network that will ultimately grow my subscriber base? How do we keep the clarity and quality of people’s calls a top priority when land issues and alternative coverage applications cost so much money?
Looking for ways to answer these questions has become as much of a preoccupation as paying the bill for the license. As many carriers are beginning to realize, the answer may be in repeaters.
The situation PCS license holders are currently presented with the reality that PCS is having a hard time living up to its touted benefits. Coverage issues have been at the forefront of the carriers’ problems. These problems begin with the need to have three PCS cells to cover the same area that a cellular cell site does. As a result, PCS build-outs have been characterized as having a predominance of “micro-holes.” To fill these holes, carriers have to justify the huge costs in areas where less air time is used. They are normally unable to justify it, however, without the subscriber base to support the cost. But without the coverage, they cannot build a solid customer base, which is the “Catch-22.” With all of the features and wonders of PCS, ultimately the coverage saturation that most PCS carriers have been able to deploy is simply not enough to satisfy their current and potential consumer bases. In these new markets, coverage, not capacity, will determine the survival of the license holders.
As carriers look toward new solutions to wireless deployment, lower cost architecture alternatives will increase the ability of the carrier to provide quality, competitive digital services_sooner. With an estimated 115 million North American subscribers expected by 2002, or about 8% of the 514 million world subscribers1, PCS carriers need to recover the time lost in false starts or lose precious market opportunities by not delivering. The solution to this equation lies in the best use of available capital to create a network that will deliver quality results.
Four applications are currently available to carriers to extend their coverage: towertop low-noise amplifiers, repeaters, smart antennas and superconducting filters. Each model carries a price tag and, often, features not necessary for the task at hand. One field-proven technology is repeaters. They have consistently offered the market the coverage it needs while augmenting networks cost-effectively.
Coverage advantages It takes about three PCS cells to cover the same area as a cellular cell. The use of microcells to combat this problem has created a situation that leaves carriers with too much wasted capacity, higher operating costs and an unresolved coverage problem.
Repeater Technologies developed a new over-the-air CDMA network repeater, the OA1900C, that extends over-the-air repeater range by as much as 20% in highway applications and by 50% in suburban coverage areas_without sacrificing any of CDMA’s generous capacity. As shown in Table 1 on page 26, the repeater bumps power from the 2W output of previous repeaters to a full 6.3W_greater than a threefold increase. (On the logarithmic dBm scale, that jump measures from 33dBm to 38dBm.) In addition, the repeater requires no switch capacity, unlike base station or microcell options. This feature saves carriers money in up-front and recurring costs.
The optimal feature of this class of repeater is that it has been designed with receive diversity. Most CDMA channel elements feature a RAKE receiver with “four fingers” that each accept incoming signals. These signals are then processed and combined to boost the gain and improve the clarity of the call. Diversity is directly correlated with the frame error rate (FER). The FER with diversity is reduced to less than 1%. Without receive diversity, call clarity deteriorates to greater than 4% FER. Arguably, the most important benefit of a diversity repeater is talk time. When compared to a repeater element without diversity, a diversity repeater will provide, at a minimum, 100% more talk time for a hand-held, battery-operated subscriber terminal_these phones simply don’t need to use as much transmit power to get a quality signal to the repeater antenna.
In addition to clarity issues, capacity is the other part of the story. For example, in rural applications without receive diversity, capacity is adversely affected by 50%-80% on a typical rural highway. Diversity does not compromise capacity, and carriers are able to grow their subscriber bases without worrying about replacing systems.
Repeater Technologies has designed remote diagnostic software, and the company has also been working with various carriers to create models of deployment that reflect the capital expenditure concerns (see Table 2 on page 28) and the equally important need to provide a network that has flawless quality and coverage.
Cost advantages: Rural deployment A recent rural example can be used to illustrate the cost-effectiveness of using a hybrid model of repeaters and base stations. Along Interstate 5, from San Joaquin to Kern County, CA, a hybrid model of repeater and base station was deployed for a 160-mile stretch.
In the hybrid deployment, signals are “cascaded” from the base station to two over-the-air repeaters in each direction. (See Figure 1 on page 26). The hybrid configuration, one base station_four repeaters, was able to cover 61 miles compared to 56 miles for two full base stations on this flat and straight road.
Over the full 160-mile stretch of highway, the base station-only build-out (10 base stations) would run $5.5 million in capital costs alone. On the other hand, the hybrid deployment (four base stations and 14 repeaters) would cost only $3.6 million_a capital savings of $1.9 million, with another $1.3 million in savings over five years for recurring costs. (See Table 3 above.)
Conclusion In the race to beat the critics, PCS carriers need to work with what they have: technology and limited financial resources for deployment. PCS carriers can move forward and build networks and, as a result, strong subscriber bases_build it with repeaters_and they will come.
