**3.5 Proposed enhancement in E-Model**

In this section we propose some new equations developed by us using MATLAB could be added to E-Model equations to enhance E-Model performance. It is noticed that the most affected parameter in case (2) when trying to find the best coder in different packet losses condition is the Ie which is expected as the PL is affecting the Ie parameters as shown in Figure10.

90 Mobile Networks

Table 12 shows that G.711 with Back ground link utilization 90 % was the combination chosen as the all coders gave the same number of calls and G.711 gave the highest R-value which means the highest quality. With Back ground link utilization 92%, 94% and 95%, G.723.1 became the chosen coder. With back ground link utilization 95% G.711 became not

This chapter utilized the E-Model to assist with the selection of parameters important to assure the QoS of VoIP in IMS Networks. These parameters include the voice coder, allowable packet loss and the allowable background link utilization. It was based on the concept that maximization of the link usage with respect to the number of calls which is important to the user. It was shown that an optimization of the E-Model is possible and

All of the three cases found that G.723.1 is optimal depending on the Circumstances. G.723.1 looks more favorable due to the fact that G.723.1 uses less bandwidth per audio stream. In case 2 , G.723.1 with 0.5%, 1% and 1.5% packet loss was optimal but with packet loss 2 % it was not feasible and G.729 was the optimum coder. In case3 , G.711 coder was selected in case of background link utilization of 90% but in all other cases till 95% G.723.1 was the optimal coder giving the maximum number of calls with R Value more than 70%. The ability to analyze various coders, delay, packets loss and the effect of background link utilization is vital to the QoS of VoIP in IMS network. The optimization of the E-Model provides a tool

In this section we propose some new equations developed by us using MATLAB could be added to E-Model equations to enhance E-Model performance. It is noticed that the most affected parameter in case (2) when trying to find the best coder in different packet losses condition is the Ie which is expected as the PL is affecting the Ie parameters as shown in

feasible as its R value was below 70 and the feasible coders were G.729 and G.723.1.

useful. Table 13 reviews the total results of the optimization problem.

**3.4 Discussion of E-Model optimization results** 

Table 13. The total results of the optimization problem.

that is useful for this purpose.

Figure10.

**3.5 Proposed enhancement in E-Model** 

Fig. 10. PL % and Ie vs. Coder – case (2)

Case 2 required additional analysis because not all of the packet loss percentages have been tested and recorded. A polynomial fit was completed for each of the three coders. For G.711, the following polynomial was generated, where x represents the level of packet loss and y represents the level of impairment (Ie).Figure 11, shows a graph of the observed results versus the curve fit.

Fig. 11. G.711 Polynomial Fit

The following equation was driven and could be added to enhance E-Model for some codecs.

For G.711, the following polynomial was generated, where x represents the level of packet loss and y represents the level of impairment (Ie).

$$\mathbf{y} = 0.0046 \,\mathbf{x}\mathbf{3} \text{ - } 0.156 \mathbf{x}\mathbf{2} + \mathbf{3}.8\mathbf{x} \text{ - } 0.00035\tag{46}$$

For G.729, the following polynomial was generated, where x represents the level of packet loss and y represents the level of impairment (Ie). Figure 12, shows a graph of the observed results versus the curve fit.

For G.729A, the following polynomial was generated where x represents the level of packet loss and y represents the level of impairment (Ie):

$$\mathbf{y} = 0.0081\mathbf{x} \mathbf{3} - 0.22\mathbf{x} \mathbf{2} + 4.4\mathbf{x} + 11\tag{47}$$

Design and Analysis of IP-Multimedia Subsystem (IMS) 93

Voice traffic in IMS will be served using Internet protocol (IP) which is called Voice over IP (VoIP). This chapter uses the "E-Model" developed by ITU-T as design tool to select network and voice parameters like coding scheme, packet loss limitations, and link utilization level

The objective function for all cases is to maximize the number of calls that can be active on a link while maintaining a minimum level of voice quality (R> 70).The cases considered are: 1. Find voice coder given link bandwidth, packet loss level, and link utilization level. 2. Find voice coder and packet loss level given link bandwidth and background link

3. Find voice coder and background link utilization level given link bandwidth and packet

In case 1, we found that G.723.1 is the optimized coder as it gives the maximum number of calls keeping its R factor more than 70. The quality of speech is generally higher with G.729A and G.711. But G.729A and G.711 uses more bandwidth than G.723.1. In Case 2, both G.729A and G.723.1 were sensitive to changes in packet loss, but G.711 was not as sensitive. In Case 3, voice quality was not sensitive to changes in the link load until the link load grew

The chapter also provides new equestrians can be added to enhance E-Model to relate

23.228 T 2009 IP Multimedia Subsystem (IMS) – Stage 2 (Release 9), Technical specification group core network and terminals, 3rd Generation Partnership Project. 24.229 T 2009 IP multimedia call control protocol based on Session Initiation Protocol (SIP)

group core network and terminals, 3rd Generation Partnership Project. 29.208 T 2007 End-to-end Quality of Service (QoS) signalling flows. Technical specification groupcore network and terminals, 3rd Generation Partnership Project. 29.328 T 2008 IP Multimedia Subsystem (IMS) Sh interface; Signalling flows and message

Calhoun, P.; Loughney, j.; Guttman,E.; Zorn,G.& J. Arkko, J.(2003).Diameter Base Protocol.

Chebbo, H.(2003).Traffic and Load Modelling of an IP Mobile Network. 4th International Conference on 3G Mobile Communication Technologies, London, UK, June 2003. Fathi, H.; Chakraborty, S. & Prasad, R. (2006). Optimization of SIP Session Setup Delay for

Fathi, H.; Chakraborty, S. & Prasad, R. (2006). On SIP session setup delay for VoIP services

RFC 3588, Internet Engineering Task Force, (September 2003).

and Session Description Protocol (SDP); Stage 3 (Release 9). Technical specification

contents. Technical specification group core network and terminals, 3rd Generation

VoIP in Wireless Networks, IEEE Transactions on Mobile Computing, vol. 5, no 9,

over correlated fading channels, IEEE Transactions on Vehicular Technology, vol.

OPNET and MATLAB are the optimization tool that is used in this chapter.

packet loss to the level of Equipment Impairment (Ie) with different codecs.

in IMS Network.

utilization.

loss level

above approximately 94%.

Partnership Project.

pp. 1121–1132, (September 2006)

55, no 1, pp. 286–295, January 2006.

**4. References** 

Fig. 12. G.729A Polynomial Fit

For G.723.1, the following polynomial was generated, where x represents the level of packet loss and y represents the level of impairment (Ie). Figure 14, shows a graph of the observed results versus the curve fit.

Fig. 13. G.723.1 Polynomial Fit

For G.723.1, the following polynomial was generated where x represents the level of packet loss and y represents the level of impairment (Ie):

$$\mathbf{y} = 0.084 \mathbf{x} \mathbf{3} - 0.74 \mathbf{x} \mathbf{2} + 5.2348 \mathbf{x} + 15 \tag{48}$$
