Trends and Challenges in LTE

Now we have spent enough time in discussing how we got to 4G and the basics of wireless. It is time to know whats in store or what is the scope for improvement. As we all know there are going to be some huge technical challenges to cope up with the exploding number of connected devices. These challenges are going to be on both the fronts, network and device. From the network side people have come up with solutions like mobile data offloading to WiFi or Femtocell offloading..

It is interesting to read about challenges in LTE predicted a couple of years ago.
I am writing some of the challenges listed in 2009 in wirelessweek article.

1. Spectrum Harmonization
2. 2G/3G Spectrum Re-farming
3. Voice over LTE
4. Backhaul :  Adding raw capacity, Realizing full mesh backhaul
5. Self Organizing Networks
6. Traffic Management

Surprisingly, many of these are still challenges and many more new challenges have been seen/tackled in these years as networks have been rolled out.

From the device manufacturers side, performance, cost and re-usability of devices remain the major challenges.

Now as we have discussed challenges speculated when LTE was in an infant stage and now when it is rolled out in a large part of the United States.

1. A looming spectrum shortage!! Every operator "just" gets 500MHz band.
2. Bandwidth issues
3. Unlimited data plans : lead to enormous data usage.
4. 2G and 3G networks are still there..It is not entirely LTE.

Here now on,  I am trying to take one problem a month and  read/write as much as I can,

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Understanding LTE

There are several new key enabling technologies in the design of LTE. These are
1. OFDM
2.Multiple antenna techniques
3. SC-FDMA
4. Channel dependent resource sharing
5. IP based Network

These technologies enable this evolution. It is important to know about these technologies if one wants to understand this standard. This is the brief discussion about some of these.

1. OFDM : Hmm..OFDM stands for Orthogonal Frequency Domain Multiplexing. Basically it is a multicarrier system which uses multiple subcarriers for transmitting single data stream.. Now thats something!! :) We have multicarrier system, multiple subcarriers and just single data stream!! Isn't that unfair..The picture after this section will explain it well. This is the flow chart I had created for one of my class projects..This helped me understand the working of OFDM.

2. Multiple Antenna Techniques : Everything related to LTE has to have "multiple" things!! Basically it means that this standard can use multiple antennas to transmit and receive. There are several techniques available to be used. We will discuss these in detail. These techniques include, Transmit diversity, beamforming, multiuser MIMO and spatial multiplexing!!


3. SC-FDMA : SC-FDMA is a multiuser version of SC FDE(Single Carrier Frequency Division Equalization). It is implemented at the uplink.

4. Channel dependent resource sharing : OFDMA provides great deal of flexibility in LTE. Allocation both in frequency and time is permitted here.

5. IP Based Network : LTE standard has been designed to reduce the hierarchical structure of networks. In the previous generations, the levels were more and so was the cost and latency. In this particular standard, there is just MME between SAE Gateway and the eNodeB. This has drastically reduced the latency and increased the cost. 

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