Rolling out one seamless 3G network - no longer a challenge
By AvitecAs 3G networks are rolled out around the world, mobile operators are all looking to offer subscribers reliable coverage at an affordable price. They request the same high-capacity data transfer to be provided in rural regions as it does in urban environments. In addition, through providing complete indoor coverage, the operator has good chances to further increase their revenue.
Stockholm-based Avitec may just well have the solution to this challenge. Their recent launch of a very innovative generation of repeaters offers mobile operators unrivalled opportunities by simplifying deployment of a 3G network. In rural areas, EDGE is deployed as complementary coverage to WCDMA and in urban regions indoor coverage of GSM, EDGE or WCDMA is provided through a fiber optic distribution system.
EDGE - The path the mobile internet
The frequency translating concept
By shifting the frequency, the isolation requirements are reduced. In other words, the necessary separation between the pick-up and server antennas can be as low as three meters, which means very short masts can be used. As the isolation is much easier to achieve through operating on two different frequencies, the gain in the remote unit can be significantly increased so that superior output powers are obtained. In other words, large areas can be covered at a minimized cost.
Many operators have licenses on both the 900 and the 1800 MHz band. The cell sizes are generally much larger on the 900 MHz frequencies compared to the 1800 MHz frequencies. Considering this, Avitec has taken the concept of frequency translation one step further. By transmitting the link on the 1800 band, while providing the actual coverage on the 900 band, the isolation requirement is zero. There is no need for any separation between the pick-up and server antennas. Actually, the pick-up and server antenna can be placed back to back! This will further reduce the site costs as the masts are even shorter.
EDGE implies increased demands on isolation
However, by shifting the frequency the isolation requirement, even in an EDGE environment, is only three meters. Output power is uniformly high, resulting in coverage comparable to that of base stations.
With the entrance of packed switched traffic, todayís well established radio planning technique using frequency hopping will lose its importance. Therefore the use of channel selective repeaters will increase, thus enabling higher output power and higher data rates.
Increasing data usage
The FiberDAS has built-in compensation both the Tx and Rx paths for optical loss differences and component parameter variations. Therefore, Tx path gain for each link is known and need not be measured. Also, noise contributions from each Remote Rx path is equalized for best sensitivity. The installation process consists of a limited number of steps including mounting units, plugging in and turning on. By using single mode fiber, no more than 4 dB optical loss is achieved at a maximum 6 000 meters run length.
An active antenna system has the advantage over a passive solution that it enables multi-band usage without having to consider path losses on the higher frequency ranges and on the in-line cable amplifiers. Thereby, the system is easily expandable to encompass additional operators or frequency bands or provide additional coverage.
Total cost of ownership reduced using effective management tools
The advanced supervision tools give the operator immediate and continuous information about the condition of the system. The status of all repeater elements can be viewed at a glance, displaying the repeater elements on multiple maps simultaneously. In a logical tree view, relationships between network elements - base stations and repeaters - are displayed using a hierarchal build-up.
Numerous alarm sources indicate where faults have occurred in a particular repeater, which substantially simplifies maintenance as well as decreases outage time. By continuously monitoring the network utilization, the operator can optimize network growth. "The solution allows us to determine how much network traffic is being handled by a particular repeater during any given period. Operators can easily decide where in the network extra capacity is required," comments HŚkan Samuelsson.
Reliable network through high signal quality
Too strong signals from neighboring cells can lead to reduced signal quality transmitted by the operatorís own base station. An Input Overload Alarm detects input signal levels from neighboring cells. If the signal level is too high, an alarm will be sent to the OMC, thus making sure that the signals transmitted by its own base stations remain high.
An interesting tool found in Avitecís repeaters is the Frequency Scanner that can detect the value of the signal level from a specific neighboring frequency. The goal is to minimize interferences in the network. The information obtained by the Frequency Scanner is of great use when selecting an appropriate site and placement of antenna. Also, in the actual commissioning procedure, correct repeater gain can more easily be set.
A creative solution
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