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Blog

LTE Spectrum Fragmentation … Problems For M2M?

Introduction

In a post in this blog some months back, I wrote on LTE spectrum usage and its impact on M2M deployment using LTE.

Since then, with more research (on radios, spectrum, etc.) I have become more concerned that this issue is going to have a very significant impact on M2M deployments in the future, and not just in the short-term future either!

Numerous people have commented about the problem with this fragmentation on LTE deployments, but the problem is even worse for M2M deployments.

The Available Bands

Lets begin by looking at the bands that have been allocated by the ITU for cellular technologies in 3GPP Release 10 (all numbers are in MHz):

Band

Uplink low (MHz)

Uplink high (MHz)

Downlink low (MHz)

Downlink high (MHz)

Bandwidth (MHz)

FDL low FUL low (MHz)

1

1920

1980

2110

2170

60

190

2

1850

1910

1930

1990

60

80

3

1710

1785

1805

1880

75

95

4

1710

1755

2110

2155

45

400

5

824

849

869

894

25

45

6

830

840

875

885

10

45

7

2500

2570

2620

2690

70

120

8

880

915

925

960

35

45

9

1749.9

1784.9

1844.9

1879.9

35

95

10

1710

1770

2110

2170

60

400

11

1427.9

1447.9

1475.9

1495.9

20

48

12

699

716

729

746

17

30

13

777

787

746

756

10

-31

14

788

798

758

768

10

-30

17

704

716

734

746

12

30

18

815

830

860

875

15

45

19

830

845

875

890

15

45

20

832

862

791

821

30

-41

21

1447.9

1462.9

1495.9

1510.9

15

48

22

3410

3490

3510

3590

80

100

23

2000

2020

2180

2200

20

180

24

1626.5

1660.5

1525

1559

34

-101.5

25

1850

1915

1930

1995

65

80

33

1900

1920

1900

1920

20

Tdd

34

2010

2025

2010

2025

15

Tdd

35

1850

1910

1850

1910

60

Tdd

36

1930

1990

1930

1990

60

Tdd

37

1910

1930

1910

1930

20

Tdd

38

2570

2620

2570

2620

50

Tdd

39

1880

1920

1880

1920

40

Tdd

40

2300

2400

2300

2400

100

Tdd

41

2496

2690

2496

2690

194

Tdd

42

3400

3600

3400

3600

200

Tdd

43

3600

3800

3600

3800

200

Tdd

Note: this list does not include the proposed Band 26 (IDEN 800 MHz spectrum used by Nextel prior to the Sprint acquisition). Sprint has proposed some portion of Band 26 for both ANSI-2000 CDMA and some for FDD LTE.

The list above is already showing 34 different spectrum bands!

And this is not counting the Sprint proposal for Band 26 and others that may be in the early proposal stages.

Admittedly, not all of them will be used in any given single country, since that depends on the various regulatory bodies within each country. Some may never see services deployed in the US, since other entities are using them.

Certainly within each country, many bands are being considered, and used, for service deployment.

Many Bands Used/Planned

Unfortunately, the United States is likely to have the largest number of possible bands with LTE deployments.

Current Service and Announcements in the US

So far, services and announcements are:

  • Verizon: 700 MHz (different block/class from AT&T).
  • AT&T: 700 MHz (different block/class from Verizon).
  • MetroPCS: 1.7 GHz / 2.1 GHz.
  • Sprint: 1.9 GHz Block G, 800 MHz later (proposed Band 26).
  • T-Mobile: 1.7 GHz /2.1 GHz (if it can quickly and cleanly move HSPA+ users to 1.9 GHz).
  • Clearwire: 2.5 GHz (TDD LTE).

Future Service Bands in the US

Plus, all these Carriers are likely to re-farm other spectrum (800 MHz, 1.9 GHz bands, etc.) to change to LTE in those frequencies over time. In the case of 1.9 MHz PCS, they also have different blocks available in different markets (remember that the 1.9 GHz PCS band is split into 6 blocks: A through F).

For example:

  • AT&T is likely to deploy LTE at 1.7 GHz / 2.1 GHz, and eventually convert their current 800 /1900 MHz GSM bands to LTE.
  • Verizon is likely to convert their 800 MHz and 1.9 GHz CDMA to LTE, and also 1.7 / 2.1 GHz that they might acquire from cable companies.
  • Sprint is likely to deploy LTE at some unused 1.9 GHz blocks in some markets.

International Deployments

And, if you include the bands that are planned for LTE deployment overseas, the spectrum fragmentation problem gets even worse. I will not go into any more details herethere are other people that have discussed the potential pitfalls quite well!

By some estimates, it would take a six-band radio to roam in the US and a twelve-band radio (at least!) to successfully roam Internationally (assuming that the business agreements are worked out, of course).

Spectrum Purchases

In the US, the large cellular operators have spent billions purchasing the spectrum at auctions run by the Federal Communications Commission (FCC) for the US Federal Government.

Of course, these large Carriers are the only people with the deep pockets who can afford to make these purchases: in the 700 MHz spectrum auctions, for example, Verizon paid $9.6 billion (plus more billions if you count their recent cable company spectrum purchases that are still facing approval), AT&T spent almost $7 billion (and many billions more for spectrum purchases from other entities), etc.

With the intention of deploying LTE in that spectrum.

Yes, there were some smaller markets which were won by the Tier 2 and Tier 3 Carriers. Unfortunately, they dont have the financial and unit volume clout to get handsets from the traditional handset suppliersparticularly if the Tier 1s flex their muscles a bit with the suppliers.

These small Carriers have asked the FCC to make and enforce rules to mandate interoperability across the entire 700 MHz allocations for example, but without success so far.

AT&T and Verizon have argued against such a mandate for interoperability. They say that the government has no authority to do this (why not?), and that there are technical reasons (what are they?) why such a mandate would slow down LTE deployment for them.

With todays soft (i.e., programmable) radiosparticularly in base station radio technologiesI find these arguments somewhat unacceptable. Indeed, recently, T-Mobile filed with the FCC to support a 700 MHz interoperability mandate, since the FCC is apparently considering such a rule.

Without the FCC taking positive action soon, LTE roaming in the United States is likely to be delayed for years.

(By the way, whatever happened to the concept of a lottery for some spectrum? Like was done for the old 800 MHz cellular bands years ago? It would be nice to see the FCC and the politicians return to that even a little bit! I doubt it though too much money there for the Federal government to not drool over it, I suppose.)

Impact on M2M

Multi-band Radios

Unless an LTE handset or radio can be used at more than one of these LTE bands and blocksparticularly for the ones in the US, it is likely that LTE roaming will be impossible for many years. This has clear implications for long-term M2M Application deployments using LTE, assuming that the M2M Application needs the LTE performance and speeds in the first place!

It would take a six-band LTE radio to roam in the US, and somewhere on the order of a twelve-band LTE radio to roam Internationally!

Assuming that all the business and roaming agreements were in place, of course.

With relatively expensive Smart Phones and handsets, this is likely to occur in time. Although today, suppliers are not providing such six and twelve band chipsetseven if the handset manufacturers wanted to use them.

Please Dont Forget the Antenna!

I have not seen this potentially tricky issue discussed by anybody yet!

Given the relatively complexity of LTE chipsets, the added cost of supporting many bands inside the radio, and even assuming that antennas (you would need multiple antennas inside the handset!) could be effectively designed to cover so many widely separated bands, this is likely to be an effort that will take quite a long time to solve.

Todays LTE handsets could need five or six antennas: GPS, Bluetooth, WiFi (at 2.4 GHz or 5.0 GHz), Near Field Communications (NFC), and two antennas for LTE (for the MIMO antenna requirement)!

If a multi-band handset needs to operate at 700 MHz, 800 MHz, 1700 MHz, 1900 MHz, 2100 MHz, and 2500 MHz, adding good antennasinside the volume-constrained thin handsets that are popular today (the emphasis is on maximizing battery size)becomes quite difficult.

Some years ago, I was taken aback at Steve Jobs keynote on the Apple iPhone that had the external stainless-steel antennas touching the users hands (Are you kidding me? That will not work out well! I was proven right within a few days!), but the multi-band LTE antenna problem is going to be far more of a headache.

At least, in M2M Applications, this might not be a physical space constraint, but the antenna cost could be significantly higher than what is used for 800 / 1900 MHz modules in M2M Devices today.

And ... What about M2M Modules?

Supporting many bands will increase the Module cost somenot a massive amount, of course, but certainly some extra dollars to support multiple power amps, filters, and even multiple antenna connectors.

In M2M Applications, where companies expect to deploy large numbers of Devices, selecting more expensive multi-band radios may not be an option for quite a while.

And, until LTE is deployed everywhere in a given Carrier footprint (without LTE roaming available for some time), using multi-technology radios for a long timeperhaps much longer than multi-technology handsets stay availableis essential for M2M Applications.

When deploying on Verizon or Sprint or US Cellular, etc., the modules would need to be LTE-CDMA capable, and when deploying on AT&T, the modules would have to be LTE-HSPA capable.

The underlying assumption being that roaming could be achieved between Verizon, Sprint, US Cellular, etc. using ANSI-2000 CDMA mode, while still operating in LTE in the home footprint.

Of course, this leaves AT&T out of the above mix, since their other technology is HSPA (with EDGE and GPRS fallbacks today)so they could only roam with T-Mobile, etc.

And, of course, needing dual-technology means that the LTE-CDMA modules will be a bit pricier for some time.

What about LTE-only Handsets and Modules?

Eventually, when the Carriers migrate to LTE-only handsetsrelatively soon, I suspect, in the case of Verizon and AT&Troaming between Carriers becomes impossible without multi-band LTE radios inside the handsets.

This LTE-only handset step (just like was done with ANSI-2000 CDMA handsets that did not include Analog AMPS well before the AMPS Shutdown in February 2008) puts the Carriers into a better position to drop the other technology relatively quickly.

Considering moving an LTE handset between Carriers?

Forget it! After cellular service moved away from Analog AMPS, this became difficult enough with ANSI-136 TDMA and ANSI-95 CDMA deployments years ago. And with the GSM and CDMA separation, it pretty much became impossible.

Even when more than one Carrier deployed ANSI-2000 CDMA at 1.9 GHz in most markets, internal radio setups and configurations made it tough. Samsung, for example, shipped identical versions of some handsets like the SCH-i730: one for use on Verizon and one for use on Sprint!

For M2M deployments, Aeris learned how to make CDMA 800/1900 MHz modules move, over the air, between Carriers, without artificially blocking the capability. In fact, we tell our Customers that if they are truly dissatisfied with our M2M network services, we will help migrate their units, over the air if possible, to a Carrier of their choice!

With LTE, and the current crop of LTE Modules being developed for use at just one or two Carrier-specific LTE bands, this will be well-nigh impossible too. The Grand Unification, that LTE will bring all the Carriers back to using the same technology again (like they used to do with Analog AMPS in the US), is a false hope. Today and for more years to come.

Once a Customer selects a Carrier and radio, they may be with them for years. Given the longevity of M2M Devices once actually deployed in the field, selecting a service provider carefully, becomes a critical step.

With a polite nod to the late Mister Rogers (my apologies to International readers who may not understand the reference): Kids, do you know how to say Monopoly?

So, if you just ran out today and splurged on the latest third-generation Apple iPad for use with Verizon or AT&T (in the US), I hope that you stay happy with the Carrier you selected. Since you will not be able to move service to the other provider any time, now or later not with the same unit, that is!