As a quick recap, Part 1 of this thread covered the differences between traditional cellular handset needs compared to M2M needs:
- M2M Devices Are Different.
- M2M Applications Are Different.
- Network Coverage Needs Are Not The Same.
- Device Longevity.
Part 2 began the simplified history of cellular technologies:
- Early M2M Data Transmission Experiences.
- Introduction of Digital TDMA and CDMA.
- Digital Service Expanded And Changed.
- The AMPS Sunset Requirement.
Part 3 continued the simplified history:
- New Digital Data Transmission Methods.
- Higher Speed IP Data.
- Another Fundamental Technology Change ...
- Spectrum Needs Increased.
- GSM Radio Prices Drop.
This week, I will conclude the simplified history on cellular technology.
3G Data Speeds Increase
With an increasing need for faster data rates, the cellular industry introduced multiple technologies that enhanced the performance of their data networks.
New 3G Data Protocols
The CDMA Carriers who deployed ANSI-2000 EV-DO data networks added EV-DO Rev. A (and renamed the original EV-DO data technology to EV-DO Rev. 0) that increased both the download and the upload data performance for IP data.
The W-CDMA (or UMTS) Carriers deployed, in multiple steps, High-Speed Downlink Packet Access (HSDPA), High-Speed Uplink Packet Access (HSUPA) and, most recently, High-Speed Packet Access (HSPA)and there are also some deployments of HSPA+.
These increases in data rates were, and are, more easily accomplished because of the ability to re-program the soft base-station radios at the cell towers to use these new protocols. Handsets and data cards, however, do not change as easily and Customers wishing to take advantage of the higher speeds must change them.
HSPA coverage is not increasing rapidlyand may even be stopped at most Carriers (i.e., HSPA and UMTS are available in major markets only)since 4G technologies are now the choice for further cellular deployment.
Relatively Little Effect on M2M
It is important to note that these 3G speed enhancements have not had a major impact on M2M deployments for a simple reason: most M2M applications do not need, or cannot make effective use of, the high-performance data that these technologies provide!
Additionally, the increased cost of the radio modules (I will discuss that shortly) for these high-performance data networks cannot be easily justified by most M2M Customers.
Clearly, handset manufacturers and data card manufacturers have benefited from the more frequent changes in technologyconsumers are quite used to the idea of changing and updating their handsets often. Furthermore, the improved performance of the IP data rates (even in 3G) has dramatically expanded the Smartphone market world-wide.
4G Cellular Introduced
In the quest for ever-higher data rates, the cellular industry developed yet newer and faster methods for transmitting data on wireless cellular spectrum. 3G is being replaced by 4G.
Introduction of OFDMA Technologies
Two new technologies were introduced and began deployment. First to market in the US was WiMAX service from Clearwire and Sprint in 2008 with market expansion since then to over 70 of the top US markets today. WiMAX uses a new protocol called Orthogonal Frequency Domain Multiple Access (OFDMA).
Another competing 4G technology is Long Term Evolution (LTE). Although LTE also uses OFDMA, this is not compatible with WiMAX. Thus, radios designed for WiMAX cannot be used for LTE and vice-versa.
In the US, MetroPCS was the first to launch LTE service in 2010 in Las Vegas, and Verizon quickly followed with their initial LTE deployments and coverage expansion during 2011 (although it is not yet complete).
Both WiMAX and LTE are very close to the transmission limits of the bandwidth they are designed to use (as defined by Shannons Law). Thus, further increases in data rate performance will, in all likelihood, be addressed by wider spectrum bands, or by combining multiple channels to aggregate overall performance.
Sidebar: it is interesting to note that commercial deployments of WiMAX and LTE are not yet complete (indeed, barely started at most Carriers!), but the technology and standards side of the cellular industry is already working on WiMAX 2 and LTE Advanced!
All IP Technologies
One important similarity, though, in the two 4G technologies is that both WiMAX and LTE are All IP technologies. The bits and bytes are transported to and from the radios using IP data packets and the network control messages are also modified to fully use IP ... the 2G/3G control messages sent on Signalling System 7 ("SS7") using ANSI-41 and GSM-MAP have been completely abandoned in 4G cellular.
This means that the deployment of the 4G network infrastructure is simpler and less capital intensive than older cellular technologies, allowing for more rapid deployment of service than was possible in the past.
Multiple Mode 3G/4G Radios
Since both the new 4G technologies use new protocols, todays handsets and radios must be multi-mode since WiMAX and LTE are not yet fully deployed in all markets.
For CDMA Carriers (Verizon, Sprint, US Cellular, etc.), this means providing radios that work in 4G mode (WiMAX for Sprint/Clearwire and LTE for Verizon, for example) when in 4G coverage, and in CDMA mode when not in LTE coverage.
For GSM Carriers (AT&T, etc.), this means providing radios that work in LTE mode when in LTE coverage, and in UMTS mode (using HSPA for example) when not in LTE coverage. Since UMTS is not deployed everywhere, these radios also use EDGE and GPRS if it is available.
Increased Network Complexities
Dual-mode radios are more difficult to use, since the radio cannot operate in both modes simultaneously. For example, if operating in 3G CDMA mode, the radio must periodically check to see if it has moved into 4G LTE coverage to take advantage of the higher performance.
The network infrastructure must also be enhanced to allow a radio to change modes without difficultyparticular if in the middle of a critical IP data session that needs to be maintained with hand-off between different technologies.
Higher Radio Costs
The increased complexity of the protocols requires higher performance processors in the radios. Thus, cellular chipsets are necessarily much larger for 3G and 4G cellular radios than for 2G cellular radios. In the chip industry, this translates to a higher costthe relationship between increased chip size and increased cost is well-known.
As a result of the requirement to support multiple modes, plus the increased complexity of the transmission protocols, the cost of 3G and 4G radios is high compared to 2G radios. In most cases, this makes large-scale M2M deployments using 3G and 4G technologies difficultI will examine this issue in more detail later.
The Grand Unification(?)
Many Carriers in the US have begun deploying LTE as a new, high-performance wireless data service for their customers. Indeed, even Clearwire and Sprint (the early WiMAX providers in the US) have also committed to provide LTE service.
So, it appears at first blush, that the separation of technologies that occurred with CDMA and GSM deployments is coming to an end: all the Carriers will use LTE everywhere and everything will be smooth-sailing from here on.
Different LTE Flavors
Unfortunately, matters are not this easy!
For example, LTE comes in two flavors: TDD and FDD (described here). Depending on the particular frequency bands chosen by a Carrier (i.e., whether their band is split up-link and down-link or not), it may be easier to implement one flavor rather than the other.
For example, Verizon and AT&T are deploying FDD LTE, using different up-link and down-link bands at 700MHz, but Clearwire is expected to deploy TDD LTE because of the way their spectrum at 2.5GHz is allocated. Sprint plans to deploy FDD LTE in their launch, although this may be followed by TDD LTE when they being using the 800MHz Nextel frequencies for LTE.
Clearly, the choice of TDD LTE and FDD LTE is a factor in the radio module decision for M2M Applications, and which Carriers these radios can be used with ... and increases the confusion for the correct choice for long-term application deployments such as M2M!
LTE Spectrum Differences
Carriers are deploying LTE at different frequency bands because of the specific allocations of spectrum they have acquired.
For example, Verizon and AT&T are deploying LTE at 700MHz initially (although not in the same blocksand, apparently, also requiring that the competitors 700MHz blocks are not supported), and Sprint is deploying LTE at 1.9GHz initially (in a new block G). Clearwire is likely to deploy LTE (the TDD flavor) at 2.5GHz.
Other Carriers are deploying LTE at yet different frequencies. For example, MetroPCS has used 1.7GHz / 2.1GHz for their LTE deployments.
As can be seen in the charts at this site, the number of possible bands that can be used for LTE is quite large. Thus, over time, Carriers will deploy LTE at other frequencies that they own.
For example, AT&T is likely to deploy LTE at 1.7GHz/2.1GHz, and eventually convert much of their current 850MHz GSM service bands to LTE.
Verizon is likely to convert their 800MHz and 1.9GHz CDMA deployments to LTE. Sprint is likely to deploy LTE at their 800MHz Nextel frequencies (this is different from 850MHz cellular A and B blocks) and some unused 1.9GHz blocks.
Thus, 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.
To Be Continued ...
Next week, I will cover the further longevity of 2G cellular and why this is of concern for M2M Application deployments.