LTE vs.WiMAX

[Cpl]

Hi, All!
Latest news:
LG shows off the world’s first 4G (LTE) modem

While we’re still waiting for a 4G / LTE network to be commercially launched anywhere in the world, LG has recently showcased the first-ever LTE USB modem.

Presented in Singapore, during CommunicAsia 2009, the new LG modem is capable of providing data transfers of up to 100 Mbps over a mobile network – thus being much faster than any 3G modem currently available.

LG didn’t say when its LTE USB modem will be commercially available, but this clearly depends on whenLTE should be widely deployed around the world in the coming years.

For example, Verizon should start offering LTE services in some US markets as soon as 2010.

[Alan J Weissberger]

Whitepaper comparing LTE vs WiMAX

http://www.comsysmobile.com/pdf/LTEvsWiMax.pdf

[Alan J Weissberger]

From Lynnette Luna of Fierce Wireless: Is voice over LTE a conundrum?
July 6, 2009

I find it odd that the first deployments of Long Term Evolution (LTE) are coming this year despite warnings that the current generation of technology cannot support circuit-switched-based SMS and voice services.

It may sound odd in itself that I'm talking about circuit-switched services being supported on these all-IP networks. After all, LTE is supposed to be a data-only solution in the interim, supporting data cards and dongles. Third-generation systems are supposed to be used for voice.

But Kineto Wireless points out in its new blog that a lack of native SMS over LTE is set to doom even LTE dongle services because operators rely on SMS for back office, customer care, provisioning and management of HSPA-based dongle services. The same systems need to be available for LTE dongle and data card services at launch.

And T-Mobile International has been making the rounds to argue why LTE needs to support voice services from the get go. The operator said that since LTE is supposed to give operators the most spectrally efficient networks, it only makes sense to put all traffic on that network and not rely on less efficient 3G networks. Such support also will entice manufacturers to make LTE phones that will be more appealing to consumers than dongles and data cards.

The 3G Partnership Project (3GPP) hasn't ignored the issue, but the standards body has envisioned that this functionality would be solved by the use of IP Multimedia Subsystem (IMS) architecture. The problem is, we've been writing for some time about the sluggish rollout of IMS.

Others have talked about enabling a circuit-switched fallback capability whereby the mobile device is forced off the LTE network onto 2G and 3G networks for voice and SMS capabilities. This also doesn't seem too promising given the network inefficiency.

T-Mobile International and major handset and equipment vendors have joined forces to promote what they call Voice over LTE via Generic Access (VoLGA). By September, the group hopes to develop a common set of standards, to be submitted to 3GPP, to allow circuit-switched SMS and voice traffic to travel over LTE over a generic access approach. Kineto and some of the wireless industry's biggest vendors are founding members of the group, including Alcatel-Lucent, Ericsson, Huawei, LG Electronics, Motorola, Samsung, Starent and ZTE. Nokia Siemens Network is proposing its own solution.

Steve Shaw, vice president of corporate marketing with Kineto, says VoLGA (I keep thinking of Russia) is garnering support from operators despite the fact that T-Mobile International is the only one to join so far. He said other operators aren't that interested in joining since the group is poised to release technical specs.

Although IMS is the plan for many operators, Shaw said there is no reason that operators can't use VoLGA now and then migrate SMS and voice functionality to IMS down the road. Can a consensus be reached within 3GPP quickly? Some see the VoLGA effort as trying to derail IMS. Moreover, will some networks support VoLGA and others support IMS longer term? What does this mean in terms of cost? And of course, the biggest question is: Could early LTE deployments be delayed because of this issue as industry folks are suggesting?

http://www.fiercewireless.com/story/voice-over-lte-conundrum/2009-07-06?utm_medium=nl&utm_source=internal

[Alan J Weissberger]

Vodafone says LTE deployment will improve on 3G

Long Term Evolution (LTE) technology will be a viable competitor to fixed wireline broadband links, said Professor Michael Walker, group R&D director with Vodafone at the Wireless 2.0 conference in the UK. He noted that the 100 Mbps of FTTH (fiber to the home) is the same as the theoretical maximum throughput of LTE, with wireless Internet providing a better and richer experience. That statement may give some hints as to how Vodafone might position the technology in the market.

With LTE capacity on 20 megahertz of spectrum being an order of magnitude higher than today's HSPA networks, Walker said the first real field trials are showing downlink speeds of 15Mbit/s, with 4.5 spectral efficiency. the center of the LTE cell delivered 20Mbit/s in the field trial with the edge of the cell delivering 1.3Mbit/s.

Vodafone is learning from its disappointments with 3G, said Walker. Having been stung by the experience of paying billions for spectrum in the 3G auctions and then seeing the technology fail to achieve the promised performance, Walker said Vodafone would ensure LTE worked as advertised before committing to deployment time frames or acquiring new spectrum

"3G was going to give 1Mbit/s but in some places you were lucky to get 300Kbit/s. It's not going to be like that with LTE," he said.

http://www.electronicsweekly.com/Articles/2009/07/03/46427/vodafone-says-lte-deployment-will-improve-on-3g.htm

[Cpl]

May be, because Europe expects the LTE tech. in an another bands? Currently, vendors are preparing their solutions in 700-800 MGz band.

[Alan J Weissberger]

Wireless 2.0 summit: No LTE from Vodafone until 2012

Professor Michael Walker, group R&D director at Vodafone, said: "There will be no European LTE networks in 2010 except for a few small ones to demonstrate capabilities to governments. Vodafone roll-out will depend on geography, but won't be before 2012."

http://www.rethink-wireless.com/?article_id=1642

[Alan J Weissberger]

The author you reference states, "As we discuss below, SC-FDMA will also be the uplink modulation scheme of the future WiMAX 802.16m system."

If you are curious why it's not happening, ask the author where he got his information.

[Cpl]

OK
Here is source http://www.circleid.com/posts/20090310_wimax_vs_lte/
And here is the latest draft of IEEE 802.16m:
http://wirelessman.org/tgm/index_older.html
http://ieee802.org/16/tgm/

[Alan J Weissberger]

Where is that quote from? You don't site any of the sources for your information. Never rely on anyone else's comments on an emerging standard. Instead, go to the web site- in this case IEEE 802.16m- to track the progress. If there is no mention of SC-FDMA in the latest draft of IEEE 802.16m-08/003r7 then see if it was discussed in a meeting report or proposed in contributions.

If you identify the source for your comment, ask that person directly where he came up with his or her conclusion.

[Cpl]

What's about this comment?
"...SC-FDMA will also be the uplink modulation scheme of the future WiMAX 802.16m system." But I don't see any mention of SC-FDMA in the latest draft of IEEE 802.16m-08/003r7..."

[Cpl]

Hi, All!
Why LTE uses SC-FDMA in Up-link.
"Both WiMAX and LTE use OFDMA for the downlink and so have broadly similar performance, for any given RF bandwidth and set of conditions. By contrast, the modulation techniques for their uplinks are entirely different.
WiMAX (including Mobile WiMAX) also use OFDM for uplink, while LTE uses a new technique—SC-FDMA (Single Carrier Frequency Division Multiple Access). Hyung G. Myung's site [hgmyung.googlepages.com/scfdma] provides a detailed description of SC-FDMA.
SC-FDMA resembles OFDM in many respects, but involves using a Fourier transform to convert OFDM's separate sub-carriers on separate frequencies into a different, time-domain, form. With OFDMA, several handsets can transmit upstream at the same time, within the same set of 512 sub-carriers, with each handset transmitting data on different sub-carriers. This reduces the frequency diversity of each handset's signal, but enables several of them to transmit upstream at the same time. SC-FDMA also enables simultaneous upstream transmissions, and the receiver is able to separate the separate components from each handset after suitable mathematical transformation.
SC-FDMA, as it is planned to be implemented in LTE, results in a transmission properties with some of the characteristics of both OFDM and DS-CDMA (Direct Sequence Code Division Multiple Access). These are two completely different modulation techniques, and SC-FDMA can be considered as a novel, but useful hybrid of the two.
Both SC-FDMA and OFDM can be used with fast-moving mobile devices, with some compromises in the total achievable data rate. Part of the problem in accommodating fast-moving devices is the Doppler shift resulting from the movement, including from the mobile device's point of view. Another is coping with the rapid changes in propagation environment, such as those due to multipath reflections.
SC-FDMA can also be used with MIMO, as it will be in LTE. As we discuss below, SC-FDMA will also be the uplink modulation scheme of the future WiMAX 802.16m system.
The primary attraction of SC-FDMA over OFDMA is the former's significantly reduced Peak to Average Power Ratio (PAPR). ODMA's output waveform is the sum of hundreds of sub-carriers, each of which is composed of uncorrelated levels of sine and cosine signal. The result of summing a large number of small uncorrelated (essentially random, with respect to each other) numbers is that most of the time, the sum is relatively small too. However, occasionally, when many of the sub-carriers are strongly positive, or strongly negative, the sum is a much larger value than usual.
If these values were numbers in a digital computer system, this would present no problems. However the digital OFDMA signal is converted to an analogue signal by a Digital to Analogue Converter (DAC), and amplified to drive the transmit antenna. The signal propagates through space, being very strongly attenuated and mixed with interference and other noise, where it arrives at the receive antenna. There, it is amplified again and then fed to a high resolution, high speed, Analogue to Digital Converter (ADC). Now in a digital form, the receive signal is analysed by a Fourier Transform operation and many other processes to recover the transmitted data.
Because OFDM signals have a high PAPR, the linear amplifiers which must be used to drive the transmit antenna, and in the receiver, must have a large headroom compared to the average value of the signal they are handling. It is possible to set the amplifier's power supply so that the very highest peaks, which are quite infrequent, will be clipped—but the more clipping which occurs, the greater the distortion, which adds noise to the received signal and makes it harder to discern the finer increments of modulation: four or more levels of sine and cosine in each sub-carrier.
Signals with a high PAPR are most problematic in battery operated transmitters. The RF amplifier must have a relatively high positive and negative power supply in order that its transistors can lift and drop the output waveform linearly to follow the extreme, but relatively infrequent, peaks of the OFDM signal. While the average current used by the amplifier may be quite low, and its average output level also quite low, all this current is drawn from these high voltage supplies.
For a signal with a low PAPR, the same average signal level can be achieved with an amplifier with much lower power supply voltages, because the signal does not have high peaks.
Consequently, to achieve a given average power output, an amplifier with +/- 12 volt supplies might be required for an OFDM signal (allowing for some low, but acceptable, level of noise due to the very highest peaks being clipped) or with the same amplifier with +/- 4 volt supplies for an SC-FDMA signal with a much lower PAPR.
Since the average current drawn by both amplifiers is the same, and the power drawn is the current multiplied by the power supply voltages of the amplifier, in this example, the SC-FDMA transmitter only uses a third of the power of the OFDMA transmitter.
Inefficiency in transmitter amplifiers presents few problems in base-stations, but is a major determinant of battery life in a cellphone or other mobile device. Consequently, considering all the tradeoffs, for LTE it was decided that SC-FDMA was a better choice for the uplink modulation technique.
This is likely to result in LTE being more suitable for handheld devices then WiMAX. This advantage of lower power consumption would not be so important in a device with a bigger battery, such as a laptop—and of course it is no advantage for a mains-powered fixed WiMAX service."
Have a nice day!