LTE like you have never seen before, or you will never see at all…

19 Jun

We can be sure that the hunger for data transmission will grow rapidly and that the mobile networks will not be able to deliver the expected capacity. On top of the current avalanche of the data created and consumed by humans we will soon see a completely different order of magnitude of the traffic Not only traffic generated by the machines in so-called Internet of Things or Internet of Everything.

A year ago, 3GPP consortium was approached by the mighty Qualcomm with the proposal to include in the next release of the 3GPP specs the extensions of LTE Advanced framework into two very interesting options promising both dramatic increase of networks capacity and the local peering interfaces.

Promised land

The most rare resource in the mobile world are the frequencies operators can use to build their networks. Based on the old paradigm of licensing, giving the exclusivity of the spectrum usage to a certain entity are in fact the foundation of cellular carriers business model. They pay fortunes for the license and are the only landlords of the assigned band. Also the protocols running there (GSM/3G/4G/LTE) behave like the only kid on the block expecting no interference in the area and enforcing the exclusivity rights.

Quality of service predictability is linked to the exclusivity and the binary access to a given spectrum resource, at a given location and a given time.”

However the licensing model assigns very small spectrum to an operator. Those can be even highly-priced 5 MHz pieces! Very often the frequencies are fragmented and do not allow aggregation of the transmission channels which is vital to increase the data throughout. And since rarely operators decide to merge their frequency assets (like formation of Everything Everywhere by Orange and T-Mobile in the UK or NetworkS! in Poland), there seems to be no way out from the spectrum trap.

But wait a minute! There is a great open field out there – the unlicensed bands. Originating back from back in 1985, when so-called “junk bands” of 2.4 and 5.8 GHz were declared free to use by anyone, they are right now occupied mostly by WiFi (IEEE 802.11). Subsequently the set of the unlicensed frequencies got expanded and right now almost entire 5 GHz range is available – 775 MHZ of continuous spectrum. Recently released TV broadcasting bands (sub 1 GHz) are tested for long-range rural internet access and 60 GHz (massive 7 GHz cluster) is already used as either point-to-point connectivity or short-range multimedia streaming at home (802.11ad standard).

The free spectrum is not only home for WiFi, but also a place of co-existence of many other protocols – Bluetooth, Zigbee. Over time the base rules of the game were defined to guarantee problem-free common usage of the frequencies with good neighbours trying to limit the impact of their actions on the others lives.

How will a selfish kid like LTE behave in this good neighbourhood? It’s not like having a racetrack just for yourself. It’s more like driving a car in the city, where streets are available to everyone who is able to understand the rules and play by those rules. Will LTE learn the traffic or crash spectacularily?

The key to success

The proposal from Qualcomm defines LTE-U extension to use the U-NII-3 part of the 5 GHz band, which has highest EIRP emission power allowed. While in 2.4 GHz regulatory bodies limit EIRP to 100 mW (Europe) or 200 mW (USA), the U-NII-3 enjoys the rights to go as high as 1000 mW outdoors.
Yes – 1 watt of power…

However, the LTE will not move entirely to the unlicensed area. The postulate is to keep the control channel still operational in the reserved frequency so that “the crucial signaling information is always communicated properly.” Which also means that only true MNO will be able to deploy the technology. It’s a big goodbye kiss to the enterprises hoping they could build private LTE networks without licensing cost…

In fact the LTE-U proposal is built on another LTE Advanced standard extension called “carrier aggregation”. It allows using multiple communication channels to transfer data in parallel. Originally it was designed to solve the problem of the “frequency mosaic”. Instead of exchanging and merging the frequencies with the other players to gain higher bandwidths, mobile operators will be able to use the radio resource they have right now “as-is”. LTE-U is simply saying that instead of the owned frequencies, some channels will be formed in the 5 GHz band. Carrier aggregation is pretty adaptive structure, so we can end up in multiple, dynamically changing topologies where all links work in licensed channels, all work in unlicensed spectrum or we have a mixture. System shall adapt to the congestion of the mobile network and availability of the unlicensed frequencies.

Here is the key to the co-existence of the selfish LTE kid with WiFi – effective sensing of available resources without pre-empting all of them. Qualcomm argues that there will be no noticeable degradation of the competing WiFi networks, while allegedly more efficient LTE-U encoding will deliver larger capacity than neighboring 802.11 systems.

Feasibility of the LTE-U

Control channel for LTE-U still needs to be realized via licensed band so the technology is possible to be implemented only in the existing LTE coverage areas. Carriers already struggle with the overwhelming investments that are necessary for LTE rollouts. Will they be willing to add more money to the budget for the promised added capacity, seamless aggregation the unlicensed downlink channels and ability to transition VoLTE calls? Especially that in order to use the LTE-U, their subscribers will need to have fully-compatible terminal with newest chipset, which will not happen overnight.

It might be a good choice for the smaller players on the market strangled by the lack of spectrum and pressured by the quality demand from their customers. That could be a good selling point for them without otherwise unavoidable huge license fees infrastructure expenses.

On the other hand why shall they wait for the specification to be finalized and equipment to be available, while already they can build WiFi networks delivering the same added capacity, seamless roaming between radio networks and even voice transitioning from VoLTE to VoWiFi and back? Maybe because the intention is to make WiFi and other wireless technologies obsolete and take over full control over previously free area? Another Qualcomm extension to LTE Advanced seems to be a step into such direction.

Direct communication – reinvented

The future uber-connected world with everybody and everything talking to each other will likely consume all possible centralized network resources. Not only licensed , but also the previously mentioned unlicensed spectrum. Hence the concept of direct device-to-device communication without engaging of central management seems to be the way forward for some specific types of applications, like location of devices or social media check-ins or individual/group messaging.

Nowadays such applications are based either on modified Bluetooth protocols or exisiting blanket coverage WiFi networks. Using the characteristics of those systems and add-on modules in the operating systems of our smartphones or tablets, it is possible to locate the user in the indoor environment and trigger some action.

Typical example is the shopping assistance. Wandering in the vast public venue like a shopping mall frequently requires some “indoor navigation” aid. Positioning of the customer gives also the opportunity to analyze the behavior of the visitors and pushing to them marketing messages when they enter certain zones (eg. promo messages when passing by a shop which paid for such advertisement). All based on the assumption that the user has got his WiFi and Bluetooth modules active and his terminal is equipped with the application able to receive such information.

LTE Direct proposed by Qualcomm taps on this opportunity by replacing WiFi/BT communication with yet another LTE Advanced extension. It is using as little as <1% of the network signaling, yet provides direct messaging between user devices. There are two types of messages defined – public and private expressions.

Public expressions are exactly matching the Bluetooth iBeacon functionality. They can be used to locate the user and push any kind of message to his device. The messages are not filtered and do not require applications to be presented to the customer. Excellent marketing tool with larger than iBeacon range (ca. 500 meters instead of 50), promised lower power consumption and better accuracy. Moreover working both outdoors and under roof.

Private expressions are linked with particular messaging/presence app and can be subject to special filtering and privacy settings enforced already on the device chipset level. They can be used to communicate with friends wishing to join the party, seek for people with the same interests at an event or simply as next generation social messaging with geo-location context.

In order to work, LTE Direct still needs licensed spectrum and the LTE control channel. It means that, just like LTE-U, its applicability is strongly dedicated to the mobile carriers and not the enterprises. Exactly opposite to the current beneficiaries of location based services, which are public venues of different kinds: shopping malls, transportation hubs or hospitality properties. One might even interpret such definition of the standard as an attempt to bring back to the operators the opportunity to tap on the revenues right now leaking to such enterprises or OTT (over the top) application owners like Facebook or Google. Bringing back human-to-human communication management (and payments) to the carriers. Especially in the context of classical texting and phone call role diminishing. Finally they could charge again for the actual usage of the network and not just deliver the capacity.

However, there are still some unresolved issues with LTE Direct. While WiFi and Bluetooth work in “neutral host” mode and serve all the user devices, irrespectively of the actual mobile operator and even the ones which are not equipped with cellular interface, LTE Direct requires one common signaling band. The open question remains if the operators will be able to agree on one shared control frequency and under which conditions. Especially that such arrangement shall work for their entire coverage area in order for this extension to be a valid upsell option.

Busines case

Both extensions are part of the new 3GPP releases and expected to approved and possible to implement in 2015-2016 timeframe. As part of the LTE Advanced rollout effort, they require substantial investment in the infrastructure (order of magnitude more expensive than WiFi), but above all – compatible user devices. Low number of termials might limit the business feasibility of such “unlicensed offload” or added-value services, while WiFi and BT are already present in all mobile phones (standard supported globally) and are usable immediately. Also majority of tablets, mobile computers and the expected Internet of Everything devices are SIM-less. This dooms LTE-U/Direct to be just an auxiliary, “nice to have” service for years and only few most desperate operators will decide to go their way.

The WiFi revolution seems to be progressing faster than LTE-A and can make a lot of the mobile carrier business obsolete? We already spend 85% of our time in the coverage of WiFi. Do we really need SIM cards for communication? Do we really need phone calls to talk? Maybe it’s time to kill the phone call? SIM-less future?

Pictures and diagrams are from Qualcomm and Aptilo materials.



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