first of all, the very initial 4G definition is telecommunication system that can achieve 100Mbps and fulfill current market demand for mobile data. Don't be so poisoned by the title as long as it fulfill current market demand. LTE-Adv and WiMax2 will achieve that but nevermind, no bother for that, argue for it whether it is true 4G is pointless, the standard set by ITU is simply causing confusion.
Why LTE? Don't you know smartphones nowadays have many limitations? Sucks videocall, voip, cloud storage and etc application, 3G simply unable to unleash the true potential of smartphones due to unable to cater more real-time applications. Evolving into 4G is a must for Operators, Mobile Apps and Smartphones industry.

so, both LTE and Wimax also considered to be 4G, Wimax is from computer world trying expand to Telecommunication, while LTE from telecommunication trying to expand computer world. Long time ago, Computer and Telecommunication are different world but nowadays they come together as 1.
LTE will be winning because it is Mobile Device Era now, and all Operators will be implementing it

TD-LTE and FD-LTE?
For Example:
Basically for layman, we just think about the Download and Upload is divided by Frequency (FD) or Time (TD), if operator have 20Mhz bandwidth and in 10 seconds.
FD: 10Mhz for Downlink, 10Mhz for Uplink (For full 1s)
TD: 20Mhz for both Downlink and Uplink (But 0.7s for DL and 0.3s for UL)
Both have their pros and cons in term of quality, flexible and capacity.
*Above is just concept illustration, technically will much more complicated than that.

Anyway LTE 1800Mhz alone it still not enough, telco still need to resolve with 2600Mhz. It could be Samsung Galaxy S4, Note 3 or Iphone 5s/6 to able support all LTE channels.

In-device Chipsets are another issues, LTE not only have different channels in different countries, but also TD and FD mode, also wimax and etc, this is the current biggest challenge for phone manufacturers, however, all RND are in the midst of developing chipsets that are able to support all these, but the cost surely be higher and more power consume for phone battery, and phone battery is also current limitations to more powerful smartphones.

4G-LTE also can be simless, because it is run on IP-Based
but Traditional Telco will still require you to have simcard as you will be access to 2G and 3G as well, also the meet their requirement for their Traditional Authentication, Authorization and Accounting server for verify your account.

For new telco who don't have 2G/3G burden, it will be simless like YES and P1, and maybe Puncak Semangat as well.

This post has been edited by shincy: Dec 18 2012, 11:43 AM

Hi, I do comment that was for concept illustration, which I think is the easiest to let someone who don't know RF at all to understand a little, those you mention already goes into further technical details, anyway thanks for your clarification as well.
FD-LTE require a pair of spectrum, that's why FD-LTE Telco required to find partner to have 40Mhz block for effectiveness instead of current 20Mhz block allocated by MCMC, TD-LTE will do its Job at 20Mhz alone. If TD-LTE have same for the 40Mhz, the interference issues could be reduced as well, it is better not discuss further as both have their own goods and challenges, and each challenges can be overcome with efforts and costs, at the end both are about the same for user experience. So it is not FDD better than TDD or TDD better than FDD
It is not all Telco are going for FDD, many also have been considered for TDD as well.

Noted that 1800Mhz only available to M and C

This post has been edited by shincy: Dec 17 2012, 10:36 AM

back to the post where you asked about 20Mhz TD-LTE is as good as 2x20Mhz FD-LTE?
Nope, definitely 2x20Mhz FD-LTE is better than 20Mhz TD-LTE.
but, 20Mhz TD-LTE is of course better than 2x10Mhz FD-LTE in term of downlink only, but who knows we have many cloud apps and UL could be important as well.

In term of quality:
FD-LTE is better since it ensure a single user have enough fixed resource, this is better in maintain a stable and smooth connection especially voice/video call.
In term of capacity:
TD-LTE can flexible allocate resource depend on users demand that connected to same sector. The more users using traffic concurrently, the lesser speed for each users, since resource is divided evenly. It is like P1, more users using = lesser speed

In term of overall spectral efficiency, both almost the same, TD-LTE have TTG and RTG but not forget FD-LTE have guard-band as well.

So, my conclusion is about quality vs capacity. A operator can have both system as well depend on demographic and scenario, as long as chipset support both technology.