HomeMy WebLinkAbout2006 04 10 Reports Cellular
Date: April 10, 2006
The attached was referenced by City Manager
Ronald W. McLemore on April 10, 2006 during
"Reports" .
The City of Winter Springs, Florida
CELLULAR REPORT
March 24, 2006
Prepared by
CONSULTING ENGINEERS
Arthur K. Peters
Gainesville, Florida
Cellular Report Executive Summary
This report has laid the foundation for three important conclusions regarding the present state
of and the future of wireless services in the City of Winter Springs.
1. There is an area in the eastern end of the city that is now receiving inadequate first
cellular service. A new cell site is required somewhere in the shaded area shown on
the attached map. There is some latitude as to exactly where in the shaded area a cell
is placed, leaving the decision to factors based on usual technical cellular siting
considerations such as property availability and signal levels.
2. There is currently no technology that can substitute for cellular communications and
provide the same functionality. New technologies such as Wi-Fi and WLAN systems
need much further development before they can be seamlessly integrated into a public
service. Even though there are now entities trying to prove such systems, it will be
several years before new technologies are adequately stable.
Micro-cells, a cellular technology, using low antennas and pole-mounted equipment
requires that surrounding cells also be small and closely spaced. The cellular
providers in and around Winter Springs have relatively large cells that are widely
spaced. The use of micro-cells here is at least 3-5 years away and must await
substantial reorganization of the present systems.
3. The current Winter Springs Ordinance providing for wireless services needs revision
soon. As currently implemented in the Ordinance, cellular service improvements are
not possible in the city. This is mainly due to the requirement that all four of the sites
specifically designated in the Ordinance be functional before any other sites can be
approved. Two of the designated sites will likely never be used. See the map.
Locations for cellular sites must be based on technical considerations only.
CONSULTING ENGINEERS
Arthur K. Peters
Winter Springs Cell Towers
This report is the result of an analysis and inspection of the cellular service currently
experienced in the City of Winter Springs, Florida. Also included are recommendations
designed to provide good wireless communications services while maintaining tight control
of environmental and lifestyle issues.
Existing Conditions
There are four locations in the City's Code that are specified as sites for telecommunications
towers with a fifth recommended for such use to be located at the proposed site of Fire
Station #3 on SR 434. Other tower locations are permitted under Conditional Use provisions,
but only after the four specified sites have been constructed and are occupied. Presently,
there are no facilities at the Bus Barn or West Wastewater Treatment Plant sites specified in
the Code.
It is my understanding that the City Commission deems this study necessary in part because
specific areas of the City are receiving less than satisfactory service from one or more
cellular providers.
An inspection was made of existing towers located within City limits and for an appropriate
distance outside of the City. Figure 1 shows existing approximate tower locations with an
estimate of the number of cellular providers co-located on each. Also shown are the available
locations mandated by the City's tower ordinance.
Several sites exist at locations outside the City limits, some immediately adjacent to its
border and others well beyond its border. Only those sites that provide service within the City
limits have been considered.
CONSULTING ENGINEERS
Arthur K. Peters
Range Factors
Appendix 1 was created to describe some characteristics of cellular systems and what is
needed to provide adequate service to a community. Most critical is the range of cell sites.
Factors affecting range include those mentioned in Appendix 1 and others such as the
physical environmental. Hills or rolling terrain, trees, types of building materials, building
sizes and weather conditions are a few factors that can affect range. Each of the factors can
also have varying effects on range depending on the frequency of cellular service. For
example, tree leaves, especially pine needles, decrease range differently at one frequency
than at another. Similarly, rain and temperature can change cell ranges depending on the cell
frequency.
Winter Springs has enough trees to have significantly degraded ranges of cell transmissions.
This appears to be significant in the eastern end of the City where reception is reported to be
below standard.
It is essential that adequate overlapping coverage exist between adjacent cells. If money were
no object, cell range could be ignored, as could antenna heights and transmitted power, by
using as many cells as were needed to provide service. Antennas mounted in trees could be
easily disguised and made virtually invisible. Unfortunately, costs for such a service would
be prohibitive.
So, in a practical system, range is maximized as much as possible, especially during early or
immature development. This usually means high antennas and greater transmitted powers.
Cells are added as a system matures and needs greater capacity, each reusing channels or
bandwidth to increase the capacity of the entire system. See Appendix 1. Since interference
occurs destructively in all cellular systems, when cells are added it is necessary to reduce the
size of each existing cell. For example, increasing the number of cells in Winter Springs
requires decreasing the size of existing cells to prevent destructive interference.
CONSULTING ENGINEERS
Arthur K. Peters
Winter Springs is presently in a relatively immature cellular state with some areas needing
improved basic service.
Cell Placement
A cellular system may be visualized as a honeycomb where the cells are connected and
uniformly sized. Connection is required to provide complete coverage. Uniformly sized cells
produce the maximum system capacity because interference from cells reusing a system's
bandwidth is well defined and uniform in all cells. When one or more cells are enlarged the
interference is no longer uniform in all cells because larger cells produce higher signal levels
than smaller cells. Nearby smaller cells using the same frequencies or bandwidth will receive
larger amounts of interference from the larger cells. The same situation occurs when smaller
cells are added. The surrounding large cells produce large amounts of interference.
Signal power levels decrease with increasing distance. Conversely, the closer to a cell, the
higher is the signalleveI. This is important to the proper placement of cells. If a cell is
moved, more interference will occur from (and toward) cells in the direction of the move.
To minimize interference due to a moved cell or from introduction of a new cell, surrounding
cells must be modified by, for example, decreasing the powers and/or antenna heights of
surrounding cells. But, decreasing powers and/or antenna heights reduces the coverage areas
of the affected cells which, in turn, can and does cause diminished service to areas previously
well served.
These seemingly conflicting effects are real and must be handled carefully to prevent service
disruptions. This also explains why cells that are similar in size and uniformly positioned
afford the greatest system efficiency and capacity.
Correct cell placement requires consideration of a large number of factors. It is not a simple
process. I do not imply that the process is inflexible. With so many factors under the
designer's control there are opportunities to be somewhat flexible in some circumstances. For
CONSULTING ENGINEERS
Arthur K. Peters
example, antenna patterns can be changed to compensate for terrain obstructions or to
position a cell away from its ideal position. But, these techniques are limited in the amount of
compensation that can be applied.
The upshot of this discussion is that cells must be positioned based on environmental and
system factors. Cell placement cannot simultaneously be arbitrary and correct, or, arbitrary
and efficient.
Deficiencies With The City's Telecommunications Ordinance
The present Code, while permitting towers, places a prohibition on towers until four required
sites are constructed and occupied. These required sites are, in a technical cellular sense,
arbitrarily positioned. Furthermore, two sites are not well placed with respect existing
cellular providers. For example, the two unoccupied sites are so close to existing cells as to
render them useless. Thus, it is unlikely the present cellular providers will ever utilize them.
Under these circumstances it is unlikely that service will be improved in deficient areas. An
area needing service improvements (for some providers) occurs in the eastern part of the
City. Another cell site is required in that area.
Code Recommendations
Because new cells must be fitted into the existing cell site matrix, it is recommended that the
existing Code be amended to eliminate the requirement to construct the remaining
unoccupied sites before other sites can be approved.
If cellular usage increases, as it undoubtedly will, additional cells will be required to meet
increased demand. Those unoccupied sites may someday become desirable when the density
of cells permits their use.
If the Commission does follow the above recommendation, it is likely that it will receive
more applications for towers. Also, it is likely that there will be competing tower applications
CONSULTING ENGINEERS
Arthur K. Peters
at some time. I would direct the Commission's attention to two Ordinances that could be
easily modified for use in Winter Springs. Both Pasco and Alachua Counties have ordinances
using a tiered process of granting tower applications. Both counties were intent on having
tight control over quality of life issues such as visual and aesthetic impact. It occurs to me
that Winter Springs would be similarly interested.
Cellular Alternatives
Appendix 2 was prepared in response to questions posed during my inspection. At the
present time and in the near future there are no technological innovations that would provide
similar utility to cellular.
There are major changes coming in telecommunications, both technological and sociological.
However, the many competing technologies are neither refined nor stable enough for public
consumption in the near term. When they arrive they will be revolutionary. But, like every
other revolution, will take a relatively long time to be fully assimilated. It will take even
longer for them to become as widespread as cellular and perhaps, in some locations, they
may never appear.
Arthur K. Peters, PE
March 24, 2006
CONSULTING ENGINEERS
Arthur K. Peters
Appendix 1 - Cellular System Layout Considerations
A cellular system is limited by the Federal Communications Commission to operate within
an assigned frequency band. In order to maximize its ability to serve large numbers of
customers, a system must reuse that assigned frequency band. Any given cell is capable of
simultaneously serving a relatively small number of conversations, sometimes as few as 30
for an omnidirectional cell.
Such limited systems employ a number of modifications to cells to increase the number of
customers served. For example, a cell is typically broken into three sectors, each with its own
frequency band, effectively increasing the total bandwidth of a cell.
Cells are placed in a regular pattern to obtain the most theoretically efficient capacity
(number of simultaneous conversions). The cell pattern used by each cellular provider is
rarely the same as other providers, although recently providers are tending to co-locate their
facilities to save costs and avoid problems associated with the acquisition of sites for new
cells.
In current cellular practice cells are not always optimally located. As a result theoretical
efficiencies are not realized. Further, nearby cells reusing the same bandwidth are subject to
interference. A carefully balanced system adjusts transmitting power, antenna radiating
characteristics, antenna heights, coding schemes and other factors to obtain the greatest
practical capacity.
The principal goal is to obtain a regular cell pattern using similar transmitting power, antenna
types and heights and generally providing equal technical factors in every cell. Achieving
this goal is rarely accomplished. A system, whether optimal or not, will obtain some
maximum capacity less than the theoretical maximum.
To further increase capacity a system must further reuse its assigned band. Each reuse
requires a new cell at a new location. As the number of cells increases each cell must be
CONSULTING ENGINEERS
Arthur K. Peters
reduced in size. Normally, this requires antenna height and transmitted power reductions and
sometimes antenna replacements.
Consistent with cell regularization, once a system downsizes some cells, it becomes
unbalanced, with some small and some large cells, producing efficiency reductions due to
interference. Reduced efficiencies will persist until all cells are made equal. Most existing
systems are in this state and will probably never reach the optimum efficiency because
expansion rates are so great.
Finally, a system's frequency band plays large role. Higher frequency bands are typically less
efficient due to lower building (and other object) penetration and reduced signal propagation
distances. This means that systems operating at higher frequency bands must use a greater
number of cells than lower frequency systems.
CONSULTING ENGINEERS
Arthur K. Peters
Appendix 2 - Alternatives To Cellular Systems
The consumer and technical presses abound with descriptions of neat and wonderful devices
with unlimited features that, when they reach a stable and mature state, will provide
everything you ever wanted. However, as will be shown, there is nothing currently available
that will, in the near future, match the universality of ubiquitous cellular service. New
cellular features are being implemented almost faster than one's imagination. These features
are being applied to a mature technology and usually work as advertised.
There is considerable research and testing to combine cellular with new technologies. One,
which has recently received considerable attention, is a technology called Wi-Fi, that was
created from Internet roots. Several manufacturers are now incorporating this technology in
standard cell phones that are to be released in June and July of this year.
Wi-Fi is a maturing technology governed by worldwide standards that presently operates in
the 2.4 and 5 GHz bands. It provides computer access at high rates of speed and is capable of
transmitting pictures, music and other data and entertainment forms. Unfortunately, because
of its high frequencies and low power it is limited to very short service distances, on the
order of 300 feet. (A new, not-yet adopted standard has claimed service ranges of up to 1500
feet.) An advantage of Wi-Fi's short range is that it can be effectively used inside buildings, a
situation that frequently impairs cellular service.
Wi-Fi equipment is relatively cheap and easily installed. People gathering places are prime
candidates for this service. With V oice-over-Internet Protocol (V oIP) there are visions of
providing both services in the standard cell phone that would automatically and seamlessly
transfer from one to the other service as needed. This might provide for uninterrupted calls
when transitioning between cellular service and VoIP. However, there are many technical
issues to overcome including the fact that V olP and cellular service might have different
providers.
CONSULTING ENGINEERS
Arthur K. Peters
A number of cities are interested in installing and using wide-area Wi-Fi systems for their
public safety, administrative and as a revenue producing public service, with or without
cellular connection. This has raised many political issues that are unlikely to be resolved
anytime soon. Further, while customer phones may be equipped to operate both cellular and
Wi-Pi in the next months, fluid and reliable integrated service is probably at least two years
away.
A review of the literature shows no other emerging technology that would eclipse the cellular
- Wi-Fi combination.
For example, people frequently inquire about satellite communications. The military does it.
Civilian users do it with large handsets (with large whip antennas) at great expense. There is
not enough worldwide combined satellite capacity to provide more than a miniscule
percentage of existing, not considering future, consumer cellular needs.
This leads to the inescapable conclusion that until a new technology comes along that
provides equivalent services of the current cellular system, consumer needs will essentially
remain a function of cellular providers and a terrestrial interconnection mechanism,
potentially with added performance enhancements such as Wi-Fi.
~
CONSULTING ENGINEERS
Arthur K. Peters
Big Tree Perk
Winter Springs, Florida
'ower Locations
:es specified in the Code
lre unoccupied sites
currently occupied sites
he number of carriers at a site