Category Archives: Technology

TD-LTE: 4G Technology

LTE akin to 4G Technnology.

As a technology, LTE is almost indistinguishable from WiMAX. The standards evolution steps are not in sync, which means that at any time the latest version of one of the two technologies may be a bit ahead, but the endless comparisons have failed to conclusively show that one technology is better than the other. As for the market opportunity, LTE was developed by mobile operators–along with their vendors–and there has never been any doubt that the great majority would adopt LTE, not WiMAX.

What is LTE ?

TD-LTE , or Time Division Long Term Evolution, caters to peak download speeds of 100 Mbps on mobile phones, compared to the 20 Mbps for 3G and 40 Mbps for Wimax. LTE brings to the table additional spectrum, more capacity , lower cost, and is essential to take mobile broadband to the mass market.

There are two versions of LTE. FDD-LTE uses the FDD paired spectrum with two separated channels, one for the uplink and one for the downlink, which is the type of spectrum most mobile operators have. TD-LTE uses TDD unpaired spectrum channels that combine uplink and downlink, and split resources on the basis of real-time demand. Voice is inherently symmetric in the uplink and downlink so it is well suited for FDD spectrum allocations. Data traffic benefits from TDD spectrum, as it is typically asymmetric but the degree of uplink/downlink asymmetry is not fixed. The development of TD-LTE was initially pushed by China Mobile and regarded as a mainly Chinese standard, similarly to TD-SCDMA.

The appeal of TD-LTE has widened well beyond China. The recent announcement of Qualcomm to bid for TDD spectrum in India to support a TD-LTE deployment confirms the emergence of TD-LTE as global technology, likely to command a substantial market share.

Why LTE ?

There are four main factors driving a growth in support for TD-LTE:
  • The FDD LTE and TD-LTE versions of the 3GPP standard are very similar. As a result, devices can support both the FDD and TDD interfaces through a single chipset–i.e., without any additional cost. This is a hugely important new development: TD-LTE will benefit from the wide availability of FDD LTE devices that will be able to support TD-LTE as well. Unlike WiMAX, TD-LTE does not need to prove to have a substantial market share to convince vendors to develop devices. Vendors do not need to develop new devices, they simply need to add TD-LTE support to the existing ones.
  • There is a lot of TDD spectrum available, and in most cases it is cheaper and under-utilized. 3G licenses frequently have TDD allocations and upcoming 2.5 GHz auction in most cases contemplate TDD bands.
  • The increasing availability of base stations that can be cost-effectively upgraded will make it possible and relatively inexpensive for WiMAX operators to transition to TD‑LTE using the same spectrum allocation. The transition will still require substantial efforts and be justified only in some cases, but it will make it easier for WiMAX operators to have roaming deals and to have access to the same devices that LTE operators have.
  • Industry commitment to WiMAX 16m, the ITU-Advanced version of WiMAX and successor to the current WiMAX 16e, is still limited.
Implementation of LTE

In the near term very little will change. TD-LTE is still being developed and it will take time before it gets deployed beyond core markets like China and possibly a few others like China. In Europe, for instance, mobile operators will deploy LTE in the FDD spectrum and only when they will need additional capacity they are likely to move to TDD. Unlike FDD LTE, TD-LTE will move from initial deployments in developing countries, with a later introduction as a mature technology in developed countries–a quite interesting trend reversal.


LTE in India

US-based Qualcomm and Sweden’s Ericcson aim to piggyback on TD-LTE , hoping that it will help them gain a toe-hold in India, the world’s fastest growing mobile market . Qualcomm is to participate in the broadband wireless access (BWA) spectrum auction. However, Qualcomm will need an Indian partner for its TD-LTE foray in the country since foreign direct investment is limited to 74%. If it does secure its bid in the auction, India could well become the first country after China to roll out TD-LTE .


Through the use of integrated multimode devices that support TD-LTE as well as 3G and 2G technologies, TD-LTE will take advantage of the 3G and 2G ecosystems, thereby creating economies of scale to enable a broad choice of wireless broadband devices at affordable price points for Indian consumers.



Wireless World – Soon a Reality

What the future holds….
Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in, freeing us from that final, ubiquitous power wire. Some of these devices might not even need their bulky batteries to operate.

Various methods of transmitting power wirelessly have been known for centuries. But it wasn’t until the rise of personal electronic devices that the demand for wireless power materialized.

Perhaps the best known example is electromagnetic radiation, such as radio waves. While such radiation is excellent for wireless transmission of information, it is not feasible to use it for power transmission. Since radiation spreads in all directions, a vast majority of power would end up being wasted into free space.

One can envision using directed electromagnetic radiation, such as lasers, but this is not very practical and can even be dangerous. It requires an uninterrupted line of sight between the source and the device, as well as a sophisticated tracking mechanism when the device is mobile.

The Solution: WiTricity

Researchers at Massachusetts Institute of Technology recently demonstrated a technology that can wirelessly transfer electricity across a room, an important step toward accomplishing this vision of the future.  They were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance. The team called their invention WiTricity, short for “wireless electricity.”

The WiTricity setup consisted of two copper coils, oscillating at the same frequency and trading energy across the two meter divide via their electromagnetic field. While one of the coils was attached to a power supply, acting as the transmitter, the other one was connected to the bulb and acted as the receiver. The key to wireless power is resonance.

The key: Magnetically coupled resonance

The science behind the magic is based on the fact that two objects at the same resonant frequency can effectively exchange energy. Think of a wineglass that shatters when an opera singer hits just the right note. When the voice matches the glass’s resonant frequency—the tone you hear when you tap the glass—the glass efficiently absorbs the singer’s energy and cracks.

In any system of coupled resonators there often exists a so-called “strongly coupled” regime of operation. If one ensures to operate in that regime in a given system, the energy transfer can be very efficient. While these considerations are universal, applying to all kinds of resonances (e.g., acoustic, mechanical, electromagnetic, etc.), the MIT team focused on one particular type: magnetically coupled resonators. The team explored a system of two electromagnetic resonators coupled mostly through their magnetic fields; they were able to identify the strongly coupled regime in this system, even when the distance between them was several times larger than the sizes of the resonant objects. This way, efficient power transfer was enabled.

Magnetic coupling is particularly suitable for everyday applications because most common materials interact only very weakly with magnetic fields, so interactions with extraneous environmental objects are suppressed even further. “The fact that magnetic fields interact so weakly with biological organisms is also important for safety considerations”.


The investigated design consists of two copper coils, each a self-resonant system. One of the coils, attached to the power source, is the sending unit. Instead of irradiating the environment with electromagnetic waves, it fills the space around it with a non-radiative magnetic field oscillating at MHz frequencies. The non-radiative field mediates the power exchange with the other coil (the receiving unit), which is specially designed to resonate with the field. The resonant nature of the process ensures the strong interaction between the sending unit and the receiving unit, while the interaction with the rest of the environment is weak.

“The crucial advantage of using the non-radiative field lies in the fact that most of the power not picked up by the receiving coil remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost.”

As long as the device (eg. laptop) is in a room equipped with a source of such wireless power, it would charge automatically, without having to be plugged in. In fact, it would not even need a battery to operate inside of such a room. In the long run, this could reduce our society’s dependence on batteries, which are currently heavy and expensive.

Still a long way to go…..

At the first glance, it might sound great. But its harmful effects like cancer on humans, especially in case of high voltage transfer and questions to its efficiency still need strong answers before implementing.
However, scientists across the globe believe that “If it works and it’s safe, it will be one of the greatest achievements ever.”

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