Escaping Future Bandwidth Bottlenecks: LTE and HSPA on Several Bands

I think everyone in the industry is pretty clear by now that the amount of data that cellular wireless networks will have to carry in the future is going to rise. In my recent book I’ve taken a closer look at theoretical and practical capacity on the cellular level in chapter 3 and I come to the conclusion that from a spectrum point of view, there is quite a lot of free space left in most parts of the world that will last for quite some time to come.

So while alternative approaches like integrating Wi-Fi and femtos into an overall solution will ultimately bring much more capacity, I think it is quite likely that network operators will over time deploy their cellular networks in ever more bands. In Europe, for example, I think it’s quite likely that operators at some point will have networks deployed on the 900, 1800, 2100 and 2600 MHz band simultaneously.

Quite an interesting challenge to solve for networks and especially for mobile devices as they have to support an ever growing number of frequency bands.  Also, those bands should not also be used in tight cooperation instead of just aside each other. Ideally, the resources in the 900 MHz band could be reserved for in-house coverage as radio waves in this band penetrate walls quite well. But as soon as the network or the device detect that other bands can be received quite well, they should automatically switch over to them to leave more capacity for devices used indoors or under difficult radio conditions.

Switching between different frequencies and radio technologies during a call or a session is already done today but mostly based on deteriorating reception levels. So in the future, when using so many bands, I think this reactive mechanism has to be enhanced into a proactive mechanism and switch-overs need to be timed so that the user does not notice an interruption.

Comments

[swordfishBob]

Do you think there could/will be development of a backward-compatible radio for use in mobiles? Presently, a quad-band GSM/UMTS mobile actually contains 7 or 8 radios, one for each frequency/method combination. Add LTE into the mix, will we end up with 12-15 receivers?

[Martin]

Hi,

Not sure how exactly that will be implemented, i.e. which things can be reused on the analogue side but for LTE to become successful, I think there is no other way than to have devices that can do GSM, UMTS and LTE.

Cheers,
Martin

[Carlos]

I think the problem of multiple radios will be solved with SDR. But the truth is we won't see this technology in a handset in a few years.

[Gabriel Brown]

Very complex though. Look at the challenges U.S. UMTS operators have had getting 3G devices for their "odd"(non mainstream) bands, and then getting them working. Lucky both operators are huge.

Imagine the chaos of the potential combinations of bands and technologies in the future!

[Martin]

Hi Gabriel,

Definitely a tough thing to do and we have to see how fast things are moving in that direction.

But wait for Rel 9 where 3GPP is likely to specify simultaneous multi band operation (will write about it soon).

I would even argue that one of the big issues of 3G in North America today is that they still don't get a sufficient number of different models of 3G mobiles for their bands and good pricing. Especially T-Mobile US with their very strange 1700/2100 MHz band.

Cheers,
Martin

[Martin]

Hi Carlos,

Thanks for the comment. SDR is one thing which will surely help but it doesn't help with reducing the dedicated hardware necessary to transmit / receive in different frequency bands. So in addition to SDR, I am interested to see how this can be done in practice.

Kind regards,
Martin

[Ram]

In addition to device issues, operators also need to grapple with cost issues - deploying additional RAN infra alongside multiple bands. Operators will try and optimize their existing infra before lighting up additional spectrum

[hyao]

Things will only get worse once operators have start to roll out HSPA+ and LTE. In the US the big operators have made it very clear that they will use the new spectrum for LTE - 700MHz and 1700/2100MHz. Then the operators will want the device manufactures to support quad band GSM, quad-band UMTS, then another one or two bands for LTE - not to mention Wi-Fi a/b/g, GPS, Bluetooth, and MIMO on certain bands for LTE!

The whole device will be a solid brick full of antennas - and not passing SAR. :-)