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.

How Can LTE Reduce the Cost Per Bit?

Recently, a question was asked in the LTE forum on LinkedIn how LTE can reduce the cost per bit compared to todays broadband wireless systems such as HSPA. I found it quite interesting that a lot of people immediately jumped at the greater spectral efficiency as the means to reduce the overall cost. But I think there are also other innovations which will drive down cost:

  • There are no Radio Network Controllers (RNC) anymore, i.e. fewer network components
  • The backhaul network is radically different. While E-1/T-1 connections (cable, microwave) are still heavily used today, LTE will be rolled out with Ethernet over fiber / VDSL and microwave. Huge cost advantage here. It's not spectral efficiency operators worry about today, it's the rising E1/T1 backhaul costs.
  • In all fairness, it has to be said, that current HSPA networks are changing towards this as well in terms of backhaul and network element (e.g. one tunnel architecture) but it is not built in and the RNC is still required.
  • Another reason why LTE has a cost advantage over today's deployed networks is that technology has advanced and allows smaller base stations to be built which require less power, less space. These will be deployed from day 1 and in many cases will be put inside existing base station cabinets or mounted besides.
  •  Also count in remote radio head technology that will probably be used heavily with LTE to drive the cost down.
  • In the mid- to long term, I think LTE access will be the catalyst to have multi radio base stations with a common Ethernet based backhaul thus also driving down the cost of 2G and 3G systems to some extend that will remain in place for the time to come.

Anything else you can think of?

4G and Peak-Rate Marketing

Moray Rumney, Lead Technologist at Agilent Technology is quite outspoken about the negative impact of what he calls "Peak-Rate marketing in telecommunications", i.e. the gap between proclaimed (theoretical) data rates of wireless systems and realistic data rates and capacity achieved in practice. I fully agree with his arguments and will also discuss this topic in my next book. In the latest Agilent Measurement Journal, Moray looks at the topic again, this time from the point of view of how Femto cells could positively influence the data rate and capacity equation in the future. His argument is that the effect of adding a femto layer (Wifi or 3G/4G femto cells) in an overall network architecture increases throughput and overall capacity by orders of magnitude while increasing theoretic peak data rates of macro cells does relatively little in comparison. An article not to be missed, it starts on page 52! Also interesting from a wireless point of view is the article starting on page 25 about resolving design issues in HSPA mobile devices. Earlier issues of the journal can be found here.

IMT-Advanced (4G) Submission and Evaluation Process

News from the ITU (International Telecommunication Union) on 4G, aka IMT-Advanced: In a recent meeting it was decided that technology has now moved sufficiently beyond enhanced 3G systems (such as UMTS HSPA, WiMAX, CDMA1xEvDo also called ‘enhanced IMT-2000 systems’ in ITU terms) that the selection process of suitable technologies for 4G can now begin. In a paper, the ITU describes the steps that will now follow and the time frame they see for the process:

  • 2008 – beginning of 2009: Companies can submit proposal for candidate technologies. I guess 3GPP’s LTE Advanced and IEEE’s WiMAX 802.16m are hot candidates. Let’s see who else will come up with something.
  • Up to 2010: Evaluation of the proposed technologies
  • Mid-2010: Decision will be made which systems will get the IMT-Advanced stamp

A further interesting note is that the new documents now published by the ITU do not specify any new technical details concerning the properties of future 4G systems. Instead, they just reference ITU-R M.1465, which has been around for some time now, which calls for data rates of 100 MBit/s while moving and 1 GBit/s while stationary.

Via LTE Watch