 Now, we are going to look at how the architecture evolved over time. What I mean by architecture is that the overall network elements have varied from the classical understanding of the amps and the GSM network to the number of elements and the nature of elements that we see today in LTE and LTEA networks. Looking at different releases, it was release 8 that turned out to be the turning point which necessitated or demanded certain revisit of network elements. And then we'd look at the system architecture evolution. It is a well-known terminology that is attributed to how the core side was revised. So let's look at release 8 in a quick manner. Since we are talking about the contribution of the 3GPP community across three domains that is improvement in radio exercise, having an IP core and having an overlay of services. Release 8 took a significant step in bringing the evolution in the radio part. What it means is that the radio part comprising of the BTS, BSC and base station controller, BTS, etc. were now meant to be revised in such a manner that one of these devices had to be improved such as BTS now being called as node B or E node B that is evolved node B. So the system architecture evolution now considers improvement on the core side that is instead of having multiple elements like a BTS, a BSC, an MSC, then SESN, GGSN, HLR, VLR, SMSC, OSS. Now the core side takes the responsibility of all these things by representing them through an entity known as the packet gateway. So this is with regards to how the core was readjusted or revisited into a comprehensive entity. Having lesser entity means lesser number of nodes which would be now be processing the IP packets which are being delivered from the mobile phone to the IP network and downstream as well. The IMS continues to rule the overlay services. So release it with the modification in the radio and the revision of the core part is considered to be a significant step while continuing on to the LTE and LTEA vision. Release nine actually finished off some standardization activities which were pending from release eight. After all the overall requirements of ITU radio communication or the IMT advanced systems that we have discussed earlier, these all functional requirements cannot be fully met because even at the moment having bit rates of one gigabits per second for users which are mobile either inter node B, inter E node B, if they are moving at such a high rate then providing them such data rate is still hard. So it is usually termed that release nine has been able to achieve up to 3.9G. Subsequent releases like release 10, 11 and 12 have focused on the radio side as well as introducing the concept of machine to machine communication. I would not like to go into much detail into M2M because release 12 onwards 13 and 14 talk about M2M which is a very hot topic these days but focusing on how the evolution take took place from release 10 onwards. The main emphasis was to incorporate better modulation and multiplexing techniques. So orthogonal frequency division multiple access was introduced in LTE and LTEA on the radio side. In the uplink side that is from the mobile station to the network, single carrier frequency division multiple access was introduced. This is an obvious reason because having multiple carriers on a mobile phone sometimes has a direct toll on the overall permissible federal commission of communications FCC recommendations emissions. There is a limit on the total emissions that a mobile phone can make and the battery that can sustain such high electromagnetic emissions for a long time. Both LTE and LTEA still continue to have significant overlap in terms of the core network design, the radio access and IMS continues to be there for providing overlay services.