LTE-A Pro for Public Safety Services – Part 3 – The Challenges

There is unfortunately an equally long list of challenges PMR poses for current 2G legacy technology it uses that will not go away when moving on the LTE. So here we go, part 3 focuses on the downsides that show quite clearly that LTE won’t be a silver bullet for the future of PMR services:

Glacial Timeframes: The first and foremost problem PMR imposes on the infrastructure are the glacial timeframe requirements of this sector. While consumers change their devices every 18 months these days and move from one application to the next, a PMR system is static and a time frame of 20 years without major network changes was the minimum considered here in the past. It’s unlikely this will significantly change in the future.

Network Infrastructure Replacement Cycles: Public networks including radio base stations are typically refreshed every 4 to 5 years due to new generations of hardware being more efficient, requiring less power, being smaller, having new functionalities, because they can handle higher data rates, etc. In PMR networks, timeframes are much more conservative because additional capacity is not required for the core voice services and there is no competition from other networks which in turn doesn’t stimulate operators to make their networks more efficient or to add capacity. Also, new hardware means a lot of testing effort, which again costs money which can only be justified if there is a benefit to the end user. In PMR systems this is a difficult proposition because PMR organizations typically don’t like change. As a result the only reason for PMR network operators to upgrade their network infrastructure is because the equipment becomes ‘end of life’ and is no longer supported by manufacturers and no spare parts are available anymore. The pain of upgrading at that point is even more severe as after 10 years or so when technology has advanced so far that there will be many problems when going from very old hardware to the current generation.

Hard- and Software Requirements: Anyone who has worked in both public and private mobile radio environments will undoubtedly have noticed that quality requirements are significantly different in the two domains. In public networks the balance between upgrade frequency and stability often tends to be on the former while in PMR networks stability is paramount and hence testing is significantly more rigorous.

Dedicated Spectrum Means Trouble: The interesting questions that will surely be answered in different ways in different countries is whether a future nationwide PMR network shall dedicated spectrum or shared spectrum also used by public LTE networks. In case dedicated spectrum is used that is otherwise not used for public services means that devices with receivers for dedicated spectrum is required. In other words no mass products can be used which is always a cost driver.

Thousands, Not Millions of Devices per Type: When mobile device manufacturers think about production runs they think in millions rather than a few ten-thousands as in PMR. Perhaps this is less of an issue today as current production methods allow the design and production run of 10.000 devices or even less. But why not use commercial devices for PMR users and benefit from economies of scale? Well, many PMR devices are quite specialized from a hardware point of view as they must be more sturdy and have extra physical functionalities, such as a big Push-To-Talk buttons, emergency buttons, etc. that can be pressed even with gloves. Many PMR users will also have different requirements compared to consumers when it comes the screen of the devices, such as being ruggedized beyond what is required for consumer devices and being usable in extreme heat, cold, wetness, when chemicals are in the air, etc.

ProSe and eMBMS Not Used For Consumer Services: Even though also envisaged for consumer use is likely that group call and multicast service will be limited in practice to PMR use. That will make it expensive as development costs will have to be shouldered by them.

Network Operation Models

As already mentioned above there are two potential network operation models for next generation PMR services each with its own advantages and disadvantages. Here’s a comparisons:

A Dedicated PMR Network

• Nationwide network coverage requires a significant number of base stations and it might be difficult to find enough and suitable sites for the base stations. In many cases, base station sites can be shared with commercial network operators but often enough, masts are already used by equipment of several network operators and there is no more space for dedicated PMR infrastructure.

• From a monetary point of view it is probably much more expensive to run a dedicated PMR network than to use the infrastructure of a commercial network. Also, initial deployment is much slower as no equipment that is already installed can be reused.

• Dedicated PMR networks would likely require dedicated spectrum as commercial networks would probably not give back any spectrum they own so PMR networks could use the same bands to make their devices cheaper. This in turn would mean that devices would have to support a dedicated frequency band which would make them more expensive. From what I can tell this is what has been chosen in the US with LTE band 14 for exclusive use by a PMR network. LTE band 14 is adjacent to LTE band 13 but still, devices supporting that band might need special filters and RF front-ends to support that frequency range.

A Commercial Network Is Enhanced For PMR

• High Network Quality Requirements: PMR networks require good network coverage, high capacity and high availability. Also due to security concerns and fast turn-around time requirements when a network problem occurs, local network management is a must. This is typically only done anymore by high quality networks rather than networks that focus on budget rather than quality.

• Challenges When Upgrading The Network: High quality network operators are also keen to introduce new features to stay competitive (e.g. higher carrier aggregation, traffic management, new algorithms in the network) which is likely to be hindered significantly in case the contract with the PMR user requires the network operator to seek consent before doing network upgrades.

• Dragging PMR Along For Its Own Good: Looking at it from a different point of view it might be beneficial for PMR users to be piggybacked onto a commercial network as this ‘forces’ them through continuous hardware and software updates for their own good. The question is how much drag PMR inflicts on the commercial network and if it can remain competitive when slowed down by PMR quality, stability and maturity requirements. One thing that might help is that PMR applications could and should run on their own IMS core and that there are relatively few dependencies down into the network stack. This could allow commercial networks to evolve as required due to competition and advancement in technology while evolving PMR applications on dedicated and independent core network equipment. Any commercial network operator seriously considering taking on PMR organizations should seriously investigate this impact on their network evolution and assess if the additional income to host this service is worth it.

So, here we go, these are my thoughts on the potential problem spots for next generation PMR services based on LTE. Next is a closer look at the technology behind it, which might take a little while before I can publish a summary here.

In case you have missed the previous two parts on Private Mobile Radio (PMR) services on LTE have a look here and here before reading on. In the previous post I’ve described the potential advantages LTE can bring to PMR services and from the long list it seems to be a done deal.

Source: http://mobilesociety.typepad.com/

Innovation Qualcomm: network technology demos

Qualcomm has partners, journalists and analysts in Berlin for its IQ event. There are a number of network-related demos, featuring LTE-A, LTE Broadcast, femtocells and UMTS Direct demos. I’ve briefly summarised a few of them here.

Fractional UMTS
The first one I saw was on Fractional UMTS – F-UMTS – a method of squeezing UMTS into half of a “normal” 5MHz channel, by reducing the baseband chip rate (Mcps).

Qualcomm said that delivering UMTS in half the available channel, allows operators to roll out UMTS where they are spectrum constrained. Essentially, F-UMTS delivers UMTS over half the channel bandwidth normally used, meaning operators can deliver UMTS over 2.5MHz channels – accepting that throughput will be half that of a full channel deployment. So, if you have a 14.4Mbps capable base station and device, you’re going to get a max of 7Mpbs using F-UMTS.

Qualcomm demonstrated two femtocell reference platforms, one at 5MHx channel bandwidth delivering 7.2Mbps and one operating over a 2.5MHz channel tdelivering data at 3.6Mbps, to two handsets. The two handsets, were streaming the same content, with little observable difference between the two.

What’s the advantage? Well, for carriers that are spectrum constrained, or have non-contiguous spectrum that means they can’t upgrade in 5Mhz chunks, Qualcomm says F-UMTS can help deploy UMTS where there is constrained spectrum. Also, it might allow operators to refarm small chunks of 2G spectrum, enabling them to keep the majority of spectrum for 2G. There’s also a small cell application, allowing an operator to use a dedicated channel for femtocells, but again conserving more channel space for the macro layer.

What is required? A software upgrade to the device (all OK for the Snapdragon platform), and to the UMTS base station, as well as to the RNC.

Neighbourhood open mode femtocell concept
This was a demo of a model of residential femtocells working in public access mode. The vendor claims that with just 5% penetration of femtocells, in a given area deployed on a dedicated carrier, all users can achieve a 13 times increase in throughput by benefitting from a less busy macrocell and from other open femtocells as they move around a location.

So although the model requires a dedicated carrier for the femtos, Qualcomm said that even at quite a low penetration rate, operators can benefit from switching femtocells to open access mode. Of course, open access femtocells providing overlapping coverage that is intended to hand off users from cell to cell requires a fair amount of mobility management and interference management. Qualcomm said it is working on a range of SON techniques that it will make available with its small cell reference platforms for OEMs, including items such as self configuration and calibration, range tuning, controlled limit on UE power, macro aware rise settings, active hand-in, beacon based femto discovery, transmit and receive diversity.

Qualcomm has installed 7 femtocells in indoor locations in its San Diego campus. It says that is enough to have given it coverage across much of the campus. Users moving around the site have full mobility, with hand-offs between cell locations.

Certainly small cells are now a key priority area for development within Qualcomm. During his keynote, COO Steve Mollenkopf said, “For further capacity improvements we really think  the opportunity exists to make many, many small cells and really diversify the deployment scenario in the network.”

A mass deployment of small cells would bring R&D challenges with it, he added. “There’s still a lot of innovation needed, for very low cost cell sites, the backhaul problem, interference management, and on the device side to offload onto he right network at the right time. There’s a lot of innovation to happen, but that’s a big priority in our 10 year vision for company,” he added.  Indeed, Qualcomm took a leaf out of one or two NEP playbooks by flashing up the legend, “Small Cells Everywhere” over one of its slides.

LTE Broadcast
Qualcomm has taken many of the assets from its doomed MediaFLO products and programmes, and rolled them into a renewed mobile broadcast offering for LTE using the eMBMS standard.

This demo modelled how an operator could use LTE capacity reserved specifically for eMBMS to deliver broadcast content in certain locations at certain times. Qualcomm demoed two use cases. One was a stadium, where there may be thousands of users interested in viewing the same content. By reserving 30% of available LTE capacity for eMBMS an operator could delive seven channels of broadcast video at 800kbps, Qualcomm said. A unicast service trying to deliver the same content to a similar number of users would fall over with just 2,300 users in the stadium, the demo claimed.

Another use case for LTE cell broadcast is file delivery (Video on Demand uploads) or firmware updates at downtime and non-peak hours. After midnight, an operator could spend an hour or two broadcasting content or updates to devices.

What is required? eMBMS needs to be made active in the LTE chip. Qualcomm said it would have LTE chips with eMBMS available by the end of 2012. The operator obviously needs eMBMS enabled as a software upgrade to the EnodeB (Qualcomm demo’d this with Ericsson at MWC 2012 and is working with other NEPs) and also a Broadcast Multicast Service Centre.

LTE-A
Qualcomm has a live LTE HetNet up and running in San Diego. It is using that deployment to demonstrate some features specified in 3GPP R10 and R11 (LTE-A), such as advanced interference management and the ability to allocate radio resources in an adaptive manner.

Some of the features included here are adaptive network partitioning, range expansion and interference cancellation, using eICIC.

The demo shows how resources could be applied dynamically to a picocell that has more users on it at a given time, with the intelligent base station allocating more subframes to that picocell. When these users move outside that picocell area, and the macro sees more demand, then the macro area network is then re-allocated those sub-frames.

These sorts of solutions, designed with the co-ordinated HetNet in mind, are going to be explored in more detail in Mobile Europe’s next Insight Report, which takes a close look at LTE-A standards and recent technical advances.

LTE Direct
This is a vision of an extension of the UMTS standard that would allows users to discover when they are near to devices belonging to people they know. The idea is that devices would broadcast and receive small signal messages (128k) sent in a reserved timeslot every few seconds. These messages would enable devices to advertise their location and discover other local devices without using location technologies such as GPS  or WiFi localisation. It is also designed to be light on the signalling network, Qualcomm said, with the capability integrated down in the modem.

The inevitable use case we saw was in a shopping mall. User A “discovers” User B is near them in the mall, they meet and have a coffee, or whatever. There was some brand couponing, offers, social media integration type of stuff. You probably get the picture.

Source: http://www.mobileeurope.co.uk/news/blog/9449-qualcommiq-network-demos  11 September 2012