Monday 2 December 2013

LTE-U: First step towards 'Operator-neutral' Small Cells

3GPP member companies have decided to take the Small Cells vs WiFi fight back into the Wi-Fi camp by unveiling the initiative to have LTE in the unlicensed band (officially known as LTE-U but another interesting term uLTEA has been proposed unofficially too). 

Mike Roberts wrote an interesting post on ITM Blog:
Qualcomm has launched a radical initiative to deploy LTE Advanced in the unlicensed 5GHz band, which has traditionally been the preserve of Wi-Fi devices. If the initiative gains support, it could be a hammer blow to carrier Wi-Fi, though Qualcomm says it is still a strong supporter of all types of Wi-Fi, given its Qualcomm Atheros division, which is a leading producer of Wi-Fi chipsets. 
Qualcomm CEO Paul Jacobs unveiled the company’s initiative for LTE Advanced in unlicensed spectrum at its financial-analyst day in New York on Nov. 20. It was interesting timing, considering that the main annual carrier Wi-Fi event, the Wireless Broadband Alliance’s Wi-Fi Global Congress, was taking place on the same day on the other side of the world, in Beijing. 
The chipset giant followed the announcement by its CEO with detailed presentations on the initiative at Informa’s LTE North America event in Dallas on Nov. 21-22. The essence of Qualcomm’s proposal is that it is complicated to integrate LTE and Wi-Fi to create carrier Wi-Fi, so a better option could be to use LTE Advanced to extend LTE into unlicensed spectrum, thus eliminating the need for Wi-Fi in that context....So how does Qualcomm plan to square this circle and offer reliable mobile services in unreliable unlicensed spectrum? By using LTE Advanced to create a hybrid system operating in both licensed and unlicensed spectrum at the same time. Specifically, Qualcomm is proposing a system that uses the carrier-aggregation (CA) feature of LTE Advanced to aggregate licensed LTE spectrum with unlicensed spectrum in the 5GHz band. The unlicensed spectrum, which would be aggregated with licensed spectrum on the downlink only, would only be used for data services. The licensed spectrum would be used for uplink and downlink and would support network control as well as voice and data services. Given the power limits placed on devices using the unlicensed 5GHz band, uLTEA would be used mainly in small cells, similar to Wi-Fi.

'All about 4G' did a good quick write-up on this topic from standards perspective, as follows:
Qualcomm has recently floated the idea of deploying LTE in unlicensed bands, particularly focusing on the 5GHz band, which is currently used mostly for WiFi. According to a document (RP-131635) submitted to the upcoming 3GPP plenary meeting, the proposal is to deploy LTE as Supplemental Downlink (SDL) in 5725-5850 MHz in USA, with the PCell (Primary Cell) always operating on a carrier in a licensed band. Verizon has also submitted a Work Item Proposal (RP-131680) to to introduce the new band for SDL usage. There’s also a Study Item proposal from Ericsson (RP-131788) is the rapporteur to study the modifications necessary to the LTE radio.

One of the big issue (though small cell vendors often play it down) that has been delaying the rollout of Small Cells has been interference management in co-channel deployment cases. The operators are worried about ad-hoc small cells creating interference with the properly planned and optimized Macro cells (though in practice its not as bad as they think it is). With LTE-U, this issue can be put to rest.

I can see LTE-U, if adopted, can also help create new business models around Small cells. Neutral Small cells, deployed in the hotspots like stadiums, shopping malls, etc. can serve users of all networks. The signalling can take care of each user connecting to its own network using backhaul.

Femto as a Service (FaaS) and Small Cells as a Service (SCaaS) would probably become a common approach as there would be no concerns about which spectrum is being used. 
There would be a small concern about interference between Wi-Fi and Small cells. Most of the existing Wi-Fi and other devices that use unlicensed spectrum use the 2.4GHz band with a few using 5GHz band now. If LTE-U uses the 'Listen Before Talk' approach, other technologies can be enhanced to probably do the same. Another thing worth remembering is that there is nearly 300MHz of spectrum in 5GHz band available universally. In certain countries the available spectrum can be as much as 500MHz. This should be enough for LTE-U as well as other technologies in the unlicensed spectrum.

The complete Qualcomm presentation is embedded below and is available to download from here:

1 comment:

  1. Interesting article from Rethink Wireless on this topic:

    Qualcomm has declared a phony war on WiFi and it’s one that the company cannot win, although it can probably win enough of a head start on rivals to make a bit more cash, to go with its dominance of cellular chips. The movement has been hinted at in the past, but was only really spelled out in full as CEO Paul Jacobs addressed financial analysts last week in the US, a message that has been repeated to technology analysts this week.

    In its briefest summary, in an utterly disingenuous presentation by Rasmus “hellboy” Hellberg, Qualcomm’s senior director of technical marketing, the idea was put that LTE can be used in the same spectrum as WiFi, specifically the 5.0 GHz segment of spectrum that typifies later releases of WiFi, and that this, ostensibly will be more efficient than using WiFi. We have nicknamed him Hellboy after the famous movie monster, who keeps other monsters at bay for the good of humanity – except in this case this to keep the monster of WiFi at bay for the good of the cellular technologist and its pay-packet.

    At the same time as suggesting that Qualcomm was only “covering the bases” as lots of operators would want to use existing WiFi, but others might not want to, Hellberg claimed a number of improvements for LTE in 5.0 GHz that WiFi cannot deliver. While we owe it to the debate to go into these later, it is important to understand that this is a poorly disguised move by Qualcomm to keep its great US rival Broadcom at bay, and put it at a disadvantage over its own WiFi subsidiary Atheros, slicing the market into operators loyal to WiFi, and those who want to keep all the protocols in the cozy 3GPP club that standardizes cellular networks.

    If Qualcomm was to pull this off, the result would be an unhealthy artificial chip market, where its closed successes would crowd out the open WiFi and make it work badly, as well as cramping the headroom for a rampant WiFi chip community as much led by Chinese companies as by Broadcom.

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