There are various solutions that can be implemented for a particular site. For a design approach, CONSISTEL will select the most cost-effective solution to meet the performance criteria.

Distributed antenna network

A particularly useful application of antennas in indoor systems is the idea of distributed antennas.  The philosophy behind this approach is to split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna, but with reduced total power and improved reliability.  This is possible because less power is wasted in overcoming penetration and shadowing losses, and because a line-of-sight channel is present more frequently, leading to reduced fade depths and reduced delay spread (which is known to be a good indicator of the system error rate performance in wideband systems). Furthermore, the smaller coverage footprint of each antenna element provides for controlled coverage and reduces excessive interference and spillage effects.

A distributed antenna system can be implemented in several ways, a number of which are listed below.

1. Passive coaxial network 

   The network is made up of passive components such as coaxial cable, combiners, splitters, directional couplers, etc. Antennas that are utilized can be of wide-bandwidth to support multi-band and/or multi-system requirements. The advantage of this approach is that the network is simple and requires minimal maintenance. Moreover, it has high-power handling capacity with the possibility of infrastructure sharing between network operators. Such a network is usually driven by a single, dedicated EBTS. To mitigate the effects of cable losses in wide-area deployments, however, multiple low-capacity EBTSs may be deployed in the building at different locations in lieu of a single EBTS. This reduces the trunking efficiency of the network but eliminates the need for active components within the distributed antenna network.

   
   

    

2. Leaky feeder system   

   The ultimate form of a passive distributed antenna system is a radiating cable (leaky feeder) that is a special type of coaxial cable where the screen is slotted to allow radiation along the cable length. With careful design, such cables can produce virtually uniform coverage. This type of system is best suited for applications requiring in-tunnel coverage (such as in subways). The radiating cable in this case is run along the entire length of the tunnel. The cable is either a radiating coaxial cable or radiating wire.

Hybrid Distributed Antenna System

3. Fiber Optic Solution

In this method, RF signals are converted to optical signals before being transmitted to distribution units via optical fibers. Single-mode and multi-mode fibers can be used but multi-mode fiber requires frequency conversion before RF- to-optic conversion. The fiber optic solution is ideal for wide-area deployments such as in buildings with extensive floor areas and high-rise office buildings. The installation cost can be well contained if the existing optical fiber infrastructure within a building can be re-used. This solution is also useful for expanding on an existing distributed antenna system that is operating on coaxial solutions. Little disruption is imposed on the existing network in this case because only a small signal (tapped out using an imbalance coupler) is necessary to drive the fiber network. Monitoring of the system is achieved through sending back a signal via the BTS to the OMC.

Active Distributed Antenna System

 

4. Repeater Solution 

This solution is implemented to expand the coverage of an indoor or outdoor cell. If coverage is to be expanded to an isolated place, a repeater solution can be used. This input signal to the repeater can be sourced either from an existing off-the-air RF signal or fiber-fed from a remote location.

In large buildings, where coaxial cable network is required to use, EBTS power will not be enough to power all the antennas. In this instance, in-line repeaters are used to boost up RF signal.

5. Wireless Office 

In view of the introduction of wireless technology to many facets of today’s business environment, CONSISTEL has allied with its strategic partners to provide value-added in-building solutions such as wireless corporate office. Today, CONSISTEL is capable of providing integration services for wireless systems with many existing communication services within the corporate environment, including ones such as PABX, fax, telephony, and computer LAN.

It is worth mentioning that any of the solutions listed above are not always implemented uniquely. There are instances where the design can be a hybrid one, where two or more types of solutions are integrated to make for a better and more cost-effective solution.

Any of the above in-building solutions can be supported by either a dedicated EBTS, an extension of an existing outdoor EBTS by off-the-air repeater, or a dedicated EBTS with in-line repeater or bi-directional amplifier. The many different types of solutions for in-building RF coverage help the system designer to produce a tailored solution for a given project. However, the final solution has to be meticulously designed not only to meet the coverage and quality requirements but also to make the installation acceptable and implementation cost-effective.