**2.2 xDSL transmission delay**

In order to characterize xDSL as femtocell backhaul, we also test transmission delay of ADSL and ADSL2+ from modem to the DSLAM. The experiment has been done in TELKOM R&D Centre Test Bed (called OASIS). Due to the fact that the measurement conducted in the testbed, it is impossible to varying the cable length to have exact transmission delay observation. For the reason that delay is the inverse of frequency carrier, we measured the delay transmission by varying bandwidth profile. By limiting bandwidth profile, the frequency carrier is set and affects the transmission delay. We did not consider delay due to lost in cable as in the commercial DSL deployment.

The network configuration for this observation can be seen in Figure 4.

Fig. 4. Transmission Delay Measurement in TELKOM R&D Centre's Testbed

The transmission delay of xDSL over various bandwidth profiles can be seen in Figure 5.

Femtocell Performance Over Non-SLA xDSL Access Network 145

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

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

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%

3-10 Mbps Up to 1 Mbps FTTC with ADSL2+,

**Conf.** 

ADSL2 /ADSL2+, fast mode

fast and interleave mode

fast and interleave mode

**Copper Length** 

1 – 4 km

≤ 1 km

≤ 800 m

**Backhaul Types DL att. rate UL att. Rate FTTx/DSL** 

**Low Speed Backhaul** < 2 Mbps Up to 512 kbps FTTE/FTTC with

**High Speed Backhaul** 11-24 Mbps 2 - 5 Mbps FTTC with VDSL2,

Table 1. xDSL Quality Model for Femtocell Deployment

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

subscription of 2 Mbps link is about 18.8%.

subscribers with line speed below 2 Mbps.

summarized in Table 1.

**Medium Speed Backhaul**

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

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 since wider frequency bandwidth is required to produce more throughput.
