**2.3 xDSL quality model**

We have discussed the maximum attainable rate which highly depends on DSL technologies, copper quality, relative distance from DSLAM/MSAN to the modem in user side and the channel modes implementation. However in the commercial point of view, the xDSL data rate is further limited by subscription profiles. An ISP usually offers various lines speed to the customer along with the broadband services. The penetration of fix broadband and line speed may vary from country to country depend on the penetration rate and the purchase power for individual line speeds.

We use Europe market as an example. According to Figure 6, as January 2010, there were about two-thirds of fixed broadband lines in the European region offered line speeds between 2 – 10 Mbps. While low speed broadband lines ranging from 144 kps – 2 Mbps represent only 16% of all fixed broadband lines, the penetration of high speed broadband link above 10 Mbps is about 23% of all fixed broadband. In terms of growth, most net fixed broadband additions in 2009 were for high speeds above 10+ Mbps. Most EU countries experienced a reduction in the proportion of low-speed fixed broadband lines.

Indonesia represents a development country. The growth rate of broadband Indonesia projected up to 49%, but the penetration rate is estimated the lowest in Asia. In this broadband business the majority market (67%) is served by TELKOM Group with its 144 Mobile Networks

ADSL Delay (ms) Interleave ADSL Delay (ms) Fast ADSL 2+ Delay (ms) Interleave ADSL 2+ Delay (ms) Fast

**transmission delay (ms)**

64

128

**2.3 xDSL quality model** 

384

512

1000

purchase power for individual line speeds.

2000

3000

4000

5000

6000

since wider frequency bandwidth is required to produce more throughput.

7000

8000

Fig. 5. Average delay transmission of ADSL/ADSL2+ over various bandwidth profile

9000

It can be seen from the graph that the delay at 64 kbps bandwidth is about 40 ms for fast mode and about two times for interleave. As the bandwidth increases the delay decreases

We have discussed the maximum attainable rate which highly depends on DSL technologies, copper quality, relative distance from DSLAM/MSAN to the modem in user side and the channel modes implementation. However in the commercial point of view, the xDSL data rate is further limited by subscription profiles. An ISP usually offers various lines speed to the customer along with the broadband services. The penetration of fix broadband and line speed may vary from country to country depend on the penetration rate and the

We use Europe market as an example. According to Figure 6, as January 2010, there were about two-thirds of fixed broadband lines in the European region offered line speeds between 2 – 10 Mbps. While low speed broadband lines ranging from 144 kps – 2 Mbps represent only 16% of all fixed broadband lines, the penetration of high speed broadband link above 10 Mbps is about 23% of all fixed broadband. In terms of growth, most net fixed broadband additions in 2009 were for high speeds above 10+ Mbps. Most EU countries

Indonesia represents a development country. The growth rate of broadband Indonesia projected up to 49%, but the penetration rate is estimated the lowest in Asia. In this broadband business the majority market (67%) is served by TELKOM Group with its

experienced a reduction in the proportion of low-speed fixed broadband lines.

10000

**data rate (kbps)**

11000

12000

13000

14000

15000

16000

17000

18000

19000

20000

21000

22000

23000

24000

Fig. 6. Fixed Broadband Lines by Technology, January 2010 [7]

Telkom xDSL and Telkomsel mobile broadband. According to the market survey conducted in Jakarta 2011, the fixed broadband line subscription lower than 1 Mbps represent about 72.1 % of population. The line speeds above 3 Mbps represents 9.1% of population and the subscription of 2 Mbps link is about 18.8%.

By considering both technical characteristics and line speed penetration, we propose xDSL backhaul quality model for reference purpose for femtocell deployment. The model can be summarized in Table 1.

Low speed backhaul has relatively high penetration rate especially in Telkom Indonesia which is above 60%. By using fast mode, it will allow to offer high speed internet access up to 4 Mbps. In terms of line speed, this type of backhaul can accommodate almost 100% subscribers with line speed below 3 Mbps. In European region, it will address only 16% subscribers with line speed below 2 Mbps.


Table 1. xDSL Quality Model for Femtocell Deployment

Femtocell Performance Over Non-SLA xDSL Access Network 147

cannot completely accommodate the HDSPA full buffer in the air interface, so there may be bottleneck in the xDSL link. However if operator carefully analyze the individual bandwidth and QoS requirement for the basic communication services such as voice, http, ftp and video streaming, one can still hope that even low speed backhaul is able to support

During connected mode, the bandwidth required by a FAP depends on service or application. Each service has its own traffic behavior. The aggregate traffic from different users will determine the total traffic occupied by the femtocell. However, in case Indonesian mobile operators, where the market is very competitive, 3G packet data offerings are based on unlimited data schemes. The offering may vary from 64kbps, 128kbps, 384kbps, 1.8Mbps, 3.6 Mbps and 7.2 Mbps. The average bandwidth required by a FAP to support these offerings can be seen in Table 2. The bandwidth is determined in the backhaul interface both for xDSL and Ethernet. As it can be seen from the table, that unlimited data packages of 64kbps, 128kbps from four different UEs can be supported by low speed backhaul category (below 2 Mbps downlink, 512 kbps uplink, according to xDSL case as in Table 1). Offers providing up to 384kbps, 1.8 Mbps, 3.6 Mbps and 7.2 Mbps should consider medium to high bandwidth quality. The constraint will be in uplink streams if the offering is symmetrical

**Services xDSL Ethernet** 

HSDPA 1.8 2.3588 Mbps 2.0967 Mbps HSDPA 3.6 4.7176 Mbps 4.1934 Mbps HSDPA 7.2 9.4352 Mbps 8.3868 Mbps

Table 2. Femtocell bandwidth estimation over xDSL and Ethernet

12.2k CS voice 84.8 kbps 84.8 kbps 62.4 kbps 62.4 kbps 64k CS video 212 kbps 212 kbps 163.2 kbps 163.2 kbps 64k data 83.9 kbps 83.9 kbps 74.5 kbps 74.5 kbps 128k data 167.7 kbps 167.7 kbps 149.1 kbps 149.1 kbps 384k data 503.2 kbps 503.2 kbps 447.3 kbps 447.3 kbps

HSUPA 1.4 1.8346 Mbps 1.6308 Mbps

Those connectivity data offerings are indeed valid for macrocell. The MBS has been designed to anticipate peak data rate by utilizing carrier class backhaul. In case of femtocell, the backhaul is depending on broadband connectivity subscription in the customer side. The worse case situation is that, the backhaul bandwidth may be far below supported peak data rate of associate radio technology (HSPA, WiMAX, LTE, etc). Therefore we propose more realistic bandwidth requirement for a FAP by observing the individual bandwidth consumption of selected services. For this purpose, we measured the bandwidth for 4-unitcalls FAP (FAP which supports 4 simultaneous calls) which is commonly used for

Downlink Uplink Downlink Uplink

femtocell.

between uplink and downlink.

residential femtocell deployment.

The medium bandwidth category (3 – 10 Mbps in downstream direction) is usually used to accommodate IPTV, internet and hosted home video surveillance services. In the upstream direction, 1 Mbps line speed can be considered when the copper length can be maintained less than 600 meter from MSAN location. By this medium speed backhaul, we assumed more than 50% DSL subscribers in most European region can have this line speed. While in Jakarta, IPTV service is still emerging, however in term of the attainable rate, it will potentially cover 30% DSL penetration and it will further increase as the deployment of FTTC is progressing.

Figure 7 illustrates the femtocell backhaul model based on the Table 1. In distance 4 km, backhaul quality will be limited. Theoritically ADSL2+ in 4 km can deliver 9 Mbps, however according to the real implementation it can only deliver 4-5 Mbps. By shortening the copper length using FTTC configuration where now copper length is maximum 1 km, the backhaul quality is much better.

High speed backhaul (up to 24 Mbps) is offered to the customer who requires more bandwidth in both downstream and upstream direction. Currently this type of backhaul addresses more than 23% of all fixed broadband in most European Region. Even though VDSL2+ can offer more than 30 Mbps data rate, the upstream data rate limits the overall performance. We limit the range of this backhaul type up to 800 meter distance in order to achieve 2-5 Mbps speed in the upstream.

Fig. 7. Backhaul Quality Model
