gsm dynamic pbt solution white paper v1!1!20070925

8/19/2019 GSM Dynamic PBT Solution White Paper V1!1!20070925

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GSM Dynamic PBT Solution White Paper

Huawei Technologies Co., Ltd.

All rights reserved.

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GSM Dynamic PBT White Paper For internal use only

2009-3-26 Huawei Technologies Proprietary of 7

GSM Dynamic PBT Solution White Paper

1 Introduction to the Coverage Enhanced Technology

1.1 Latest Coverage Enhanced Technology

With the development of GSM, operators are more and more focusing on the

construction and operation cost of a network. With the competition more toughly,operators require the quickly setup of a network. In order to save the total cost ofownership (TCO), quickly set up a network by reducing the number of sites and win

the competition, the leading GSM operators have adopted the latest coverage

enhanced technology and the strategy that the wireless technology of 3G is used in2G.

In 2006, Huawei launched the leading double density BTS in the GSM field. Based

on the double density transceiver (TRX), Huawei also launches the technologiessuch as power boost technology (PBT), transmit diversity (TD) and 4-way receive

diversity (4WRD). The PBT emerges and enlarges the double-transceiver unit(DTRU) power amplifier unit (DPAU) of two TRXs. Thus the output power of TRXscan reach from 60W to 100W and the downlink gain can reach round 3dB. Throughtwo single polarization antennas or a set of dual-polarization antenna, along with the

transceiver with two TRXs, the TD transmits the same downlink signals and obtainsthe downlink gain ranging from 3dB to 5dB. Through two single polarizationantennas or a set of dual-polarization antenna, along with the transceiver with two

TRXs, the 4WRD operates the four diversity combination and obtains the uplinkgain ranging from 3dB to 5dB. If operators adopt Huawei ICC technology, the uplinkgain can be increased. The static sensitivity of Huawei GSM TRXs in the DTRUreaches -112.5dBm, which plays a leading role. Therefore, together with the 4WRDand ICC, the uplink sensitivity can reach -118dBm.

1.2 Market Value of the PBT

In the industry, all the PBT, TD and 4WRD are realized by two TRXs combined into

one TRX. Thus the coverage is enhanced and the number of sites is reduced, whichis the coverage mode in the first stage of setting up a network. With the developmentof the network, the capacity becomes a bottleneck. To obtain large capacity,

operators can convert the coverage mode into the capacity mode and delete theconfigurations of PBT, TD and 4WRD. To meet the requirement of coverage,operators can add sites. What's more, operators can adopt the strategy that thecoverage enhanced technology is used for partly TRXs and common configurations

for other TRXs in a same cell. Operators can also adopt the concentric cell strategyto balance the capacity and coverage.

For the coverage enhanced technologies such as PBT, TD and 4WRD used in the

actual network, if the coverage mode is converted into the capacity mode for one site,operators need not adjust the hardware but modify the configurations through theremote console. There is no special requirement for terminals. Therefore, it is easy to

realize these technologies. Operators can save the maintenance personnel, quickly set

up a network and win the terminal user market.








The downlink coverage enhanced technologies, such as PBT and TD, can be used

together with the DFCU/DFCB to meet the site requirements. In the situation that the

coverage is limited, operators can use the TD to obtain the downlink gain in theS1/1/1 and S2/2/2; while use the TD or PBT in the S3/3/3 and S4/4/4. However, inmany cases, the PBT is more suitable, because the TD requires many antenna feeders.

For the configuration higher than S4/4/4, operators can use the DFCU/DFCB. TheDFCU/DFCB can be flexibly configured and expanded with TRX capacity. TheDFCU/DFCB has small insert loss. In the S6/6/6, the insert loss is only 3dB. Thecommon insert loss is more than 6dB.

1.3 Evolvement of the PBT

The PBT is required for quickly setting up a network and saving the TCO for

operators. Similar to the technology of other manufacturers, the PBT can work basedon only the unit of TRX when used in a TRX. In actual situations, an unexpectedhigh traffic may be present. Therefore, if the PBT can balance the coverage andcapacity (traffic), its market value will be improved.

For the investment of operators:

The user distribution of a cell can be regarded as an average distribution. According

to the network planning and the statistics on the call quality, there are 20% users of acell who receive poor signals. That is, 80% users can make calls of strong signals.For the 80% users, the signals need not be enhanced. Operators need to consider howto enhance the signals for the 20% users. The PBT and TD are not suitable in the

situation, because that 50% capacity is used for the 20% users is wasteful to theinvestment.

Poor Covered Area

Good Covered Area

In general, the channel usage does not exceed 80% and 20% of the time slot is in idle

except in the high traffic time. Therefore, operators expect to full use the 20% idlechannel.

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As required, the PBT is evolved flexibly and intelligently. It is Huawei that launchesthe dynamic PBT.

2

Dynamic PBT

2.1 Introduction to the Dynamic PBT

The dynamic PBT means that some pairs of channels within the DTRU module can

work under PBT, instead of all of the channels. Compared with the current PBT, thedynamic PBT is more specific.

The user in a call occupies a dedicated timeslot. The call quality can be monitored

through the measurement report. When the call signal is lower than the threshold, thedynamic PBT is started to distribute the same timeslot of an adjacent transceiver to

the user. The signals that the two timeslots send are the same, as well as the phases.After the two timeslots are combined, the signal can be enhanced by 6dB. Thus thecall quality is improved.

When the call signal is higher than the threshold, the dynamic PBT is canceled torelease the adjacent channel.

When the adjacent channel is occupied, the handover between cells is started. The

call is switched to an idle channel, and then the adjacent channel that becomes idle is

used for the dynamic PBT. During the handover, the call is not dropped because thereceiving signal is strong.

As shown in the following figure, the timeslots of two TRXs are used for different

users. When the receiving signal is strong, the PBT mode is not needed.

Timeslot Capacity

Quality of Signal

Good Covered Poor Covered Out of Coverage

0

1

2

3

4

5

6

7

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When the call of a user who is in an area with poor signals is in poor quality, the

dynamic PBT is started to combine the signals of two adjacent timeslots. If the

adjacent timeslot of the user is occupied, switch the signal of the timeslot to anothertimeslot. After the combination, the transmitting power is improved; the Rx level ofthe terminal and the voice quality is enhanced, as shown in the following figure:

Timeslot Capacity

Quality of Signal

Good Covered Poor CoveredOut of

Coverage

0

1

2

3

4

5

6

7

Dynamic PBT has no special requirement on HW. That is, through SW upgrade and purchasing the function License, customers can deploy this feature in the network.For example, a subscriber is parking his car in the basement. Although he is within

the coverage radius of the site, the signal is weak. If Dynamic PBT used, the systemcan assign two channels to this subscriber and improve the signal quality. DynamicPBT can also deployed together with Half Rate to expand the capacity.

2.2 Market Value of the Dynamic PBT

2.2.1 Dynamically Balancing the Capacity and Coverage

Huawei launches the dynamic PBT using idle timeslot. For the area with poor signals,

such as the edge of a cell, indoor and in-vehicle area, the signal is enhanced. Thenetwork resource is not wasted and the capacity is not reduced. The capacity andcoverage are kept in good balance.

2.2.2 Improving the Performance of the CO-BCCH Concentric Cell

At present, many operators obtaining GSM900 band use the DCS1800 band toabsorb capacity. Because the combination solution and multiple frequency bands are

used in many networks, especially in densely populated areas, as well as the capacityis limited, the concentric cell technology is widely used. However, this technology

has a fatal disadvantage. That is the handover between the overlaid subcell and








underlaid subcell and the assignment are blind. TA is used for reference, which iscaused by the GSM itself.

When the assignment is operated from the underlaid subcell to the overlaid subcell,

the dynamic PBT can be adopted to temporarily widen the coverage of the overlaid

subcell and make the user occupying the overlaid subcell channel. Then operatorscan judge the signal according to the measurement report. If the signal reaches thethreshold, the dynamic PBT is cancelled and a channel is released. If the signal doesnot reach the threshold, two channels are used or handover is operated from the

overlaid subcell to the underlaid subcell. For the latter, the handover is according tothe occupation of the overlaid subcell channel. This solution can improve the performance of the CO-BCCH concentric cell.

2.2.3 Realizing the Same Coverage for the 8PSK and GMSK

In general, the maximum transmitting power in GMSK modulation mode is more

than the maximum transmitting power in 8PSK modulation mode. The EGPRS

requires good-quality signal, while the users using EDGE services are very few. Ifoperators plan the network according to the requirements of EDGE services, the costis very high. Through the dynamic PBT, operators can widen the EDGE coverage tohave the same coverage as the GMSK. Thus the users remote from the BTS can usethe EDGE services.

2.2.4 Improving the Data Service Quality

At present, the data service mainly covers surfing and downloading. Improving the

downlink network quality can speed up the download and increase the satisfactory ofusers. In general, high-end users use more data services. The dynamic PBT canensure the loyalty of high-end users and the ARPU.

2.2.5 Protecting the Investment of Operators

Operators expect to full use the invested equipment. In general, the 20% channel is

in idle status. When the channel usage exceeds 80%, operators need to consider thecapacity expansion. Thus the 20% idle channel is wasteful to the investment. It isvery important for operators to full use the idle resource to provide better services.The most efficient way is to full use the current resource.

2.2.6 Reducing Power Consumption

In general, if the downlink transmitting power is 60W and the combination loss is3dB, the output of the antenna connector is 30W. The other 30W is dissipated as heat.When adopting the dynamic PBT, operators prepare only two sets of 15W output power to obtain the 30W antenna connector. That is, 30W consumption is reduced.Thus the power consumption of the system is obviously reduced.

3 Conclusion

The dynamic PBT is mainly used in the S3/3/3 and its higher configuration. The

BCCH TRX which requires the stable power output cannot adopt this technology.








The dynamic PBT is more applicable to the small-capacity situation, for example, a4-TRX cell.

The dynamic PBT enriches Huawei coverage enhanced solution. It complements

other technologies, such as the PBT, TD and filter combiner unit, to meet different

coverage requirements. The complement can protect the operators' investment tomost extent by full using idle timeslots but not reducing the network capacity.

Copyright2007 Huawei Technologies Co., Ltd. All Rights Reserved.The information contained in this document is for reference purpose only, and is subject to changeor withdrawal according to specific customer requirements and conditions.

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