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Successful operators: the challenges

By Colin Campbell, Sales Director, REMEC, Inc.

Three of the most important considerations for a mobile network operator are coverage, capacity and quality. This article looks at a technique the most successful operators use to maximise the return on their investment on network infrastructure spending and also how to achieve optimum coverage, capacity and quality.

At some point during the deployment of a network, every operator has considered installing Tower Mounted Amplifiers (TMAs).

Ten years ago, there was a certain degree of trepidation in putting electronics at the top of a tower and having them exposed to all the forces of nature. Network operations managers were concerned that TMAs would not prove to be reliable and very heavy maintenance costs would be incurred in swapping out failed units. As a result of this, many GSM 900 operators chose not to install TMAs from the start of rollout.

As time progressed and GSM succeeded beyond everyone's wildest dreams, capacity began to run out at 900 MHz. At the same time, a desire to use GSM in North America also arose. In order to meet the increasing demand, new operators were licensed to provide GSM service at 1800 MHz and 1900 MHz.

These operators were then faced with the same decision- would they install TMAs or not?

This time there were two aspects weighing heavily against the higher frequency operators. However, a situation also existed that if exploited, could provide a competitive advantage.

The first aspect: At GSM 900 MHz, the maximum range between a base transceiver station (BTS) and a mobile (MS) is 35 km and is governed by propagation time. At double the frequency, the system has a range of around 18 km this is plagued by signal decay as the signal travels from BTS to BTS. GSM 1800/1900 signals also exhibit higher losses than GSM 900 when travelling in the same size of feeder cable. Therefore, at GSM 1800/1900, the network operators needed to install more BTSs to fill in the “holes” in the network. Due to these losses, networks at GSM 1800 MHz generally require four to five times the number of BTSs of a GSM 900 network for the same level of coverage.

The second aspect: The frequencies for the newer GSM systems were so much higher, it was decided that it may be prudent to drop the maximum transmit power of the 1800 MHz MS from 2 Watts to 1 Watt.

As with GSM 900, a link imbalance existed . It was possible for a BTS to reach further on the downlink, than it was on the uplink. By merely increasing the BTS sensitivity, an operator could provide service to a greater range of users from any individual BTS.

A number of operators decided to turn the imbalance situation to their advantage. They specifically selected high output power BTS and balanced the link by fitting TMAs. This provided both a range extension and a sensitivity increase. It also helped eliminate black holes and increase indoor service provision. They were also able to increase the distance between BTSs, thus benefiting from a reduced number of BTSs and having a greater degree of flexibility in site acquisition.Today most GSM 1800/1900 operators use TMAs throughout their networks. In numerous consumer satisfaction surveys, the higher frequency operators have been shown to provide better coverage than operators at lower frequencies who have not installed TMAs.

Since the first TMA deployments ten years ago, the manufacturers have gained vast experience in the production of the super reliable product. Today we see mean time between failures, or “MTBF” figures quoted in millions of hours and TMAs are considered a reliable and essential component in many networks.

As networks mature and user penetration begins to both flatten and saturate, the effects of churn begin to really hurt the lowest quality operators and benefit the best performing operators.

Many operators who have not used TMAs extensively are currently in the process of retro-fitting programs. They acknowledge that their competitors with TMAs have an advantage in network quality, which is helping their competitors reduce churn.

The users on the TMA enabled networks have an improved experience and perception of network quality. They see the following benefits:

  • Better service as they travel. There are more reliable handovers between cells and there are more candidates for handover when capacity may be an issue. In addition, there are less dropped calls.
  • Service in areas where terrain or vegetation would cause problems for lower sensitivity BTS. This also applies to indoor coverage where users can receive and make calls further away from windows and doorways.
  • Fully utilised MS power control. With more sensitive BTS, MS transmission power reduced the user will see talk-time time increase between charges. Service will be more readily available and the MS will be available for longer calls.
With each TMA enabled BTS able to provide increased coverage and a better quality service the operator also sees an overall increase in network capacity. There is no need to hand calls over as quickly and there are more BTS available as handover candidates.

The financial benefits for the TMA enabled networks are difficult to quantify. However, it is readily apparent that there are significant gains in three areas:

  • Coverage Improvement at Deployment. This provides potential for a reduced number of BTS and flexibility with site acquisition, thus saving cash.
  • Network Quality and Capacity. A better performing network allows more talk-time for more users, thus generating cash.
  • Reduced Churn. Customer satisfaction is proven to reduce churn. A 2% reduction would payback the cost of retro-fitting TMAs to a network within one year, thus holding revenue and reducing the need for spend on new customer acquisition.
With an increase in data services and the rollout of UMTS, every operator recognises that system performance on the Radio Access Network is becoming increasingly important. Good performance and user experience of IP services in a wireless environment is critical in ensuring success for the new data products.

The benefits seen by GSM users of TMAs are also available to UMTS Operators. In fact there is even more to gain with UMTS as TMAs fitted to Node Bs will deliver the following:

  • Flexibility in sighting of the Node B, thus helping with site acquisition challenges.
  • A reduction in system noise and interference. This will help maintain cell size, allow more users per cell and increase data rates.
  • An improvement in end-user experience, thus assisting with a faster uptake of new services and rollout and ultimately a reduction in churn.
In deciding to purchase TMAs from a supplier such as REMEC, operators can be assured that they will benefit both on capital expenditures and operating expenditures.

Operators who choose to buy TMAs directly from the supplier benefit from a product that is more likely to fit their exact needs than one offered by the their BTS manufacturer or Node Bs. They are also likely to see significant capital expenditure savings.

With the reliability of TMAs in an IP-68 waterproof package ongoing operating expense savings are also likely to be seen over the lifetime of the network.

For more information, please contact:
Colin Campbell: Colin.campbell@remec.com



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