| Mobile Phone Technologies | ||
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| Mobile Phone Evolution | Mobile phone technology has been on a steady path of evolution since the release of the first “1G” analogue phones in teh 1980's. But just as it was with landline services, the transmission of data over the mobile network has been an important add on. Initially data use was a small component, but today, with the explosion of broadband services, mobile data is a key driver in the ongoing evolution of the technology. 3G networks still dominate the global market, but here in Australia, 3G networks have been closed and users moved to 4G, and the frequencies the 3G systems operated on re-purposed for 5G networks - and there is certainly a flurry of government and media interest in 5G. As this happens, it is important that, as users of the M2M or machine to machine communications segment (a small part of the whole market) you have a clear picture of the evolution of mobile technologies. |
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| 1G | The first mobile phone systems are now referred to as "1G". Early handsets were huge by modern standards - anyone wanting to use a phone in a car, ended up with a "Bag phone", a wondeful take on a portable device, which featured a corded handset tethered to a box in a bag, containing the battery and electronics. The 1G system was very simple: calls were sent on a fixed number of channels and anyone with a scanner could monitor calls. In a famous episode, former Victorian Premier Jeff Kennett, was recorded whilst being heavily critical or John Howard, who would go on to be the country's longest serving Prime Minister. The biggest downside of the 1G system was the high call cost, with many users footing bills of $1000 per month for the privilege of making calls on the run. But the 1G networks introduced the world to the convenience of mobile calling and "cellular" networks were here to stay. The Americans label the technology "cellular" because each mobile phone tower controls calls within a fixed area or cell. If you are moving, when you get close to the edge of a cell, you will be handed over to the next tower or cell. The system works best when any area is serviced well by multiple cells and is at its worst when you are covered by a singel cell. |
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| 2G | As the market outgrew 1G, the new 2G systems were introduced. These had higher capacity and you could no longer eavesdrop on calls with a scanner. As technology developed, formal standards were developed and any country wishing to invest in mobile infrastructure could rely on handsets and base stations being able to inter-operate. The only limitation was that different countries adopted different operating frequencies based on how their radio spectrum was being used and allocated. One way that 2G systems improved on 1G was by increasing the capcity of the system. And one way this was achieved was by sharing channels based on the time it took a signal to get from the base station to the hand-set. The area around a tower was divided in to segments, each of 250m in radius. If you travelled out in a straight line, your signal would arrive in the first slot, then 250m would go into the 2nd slot etc. All the way out until you reached the last slot - by which time you should have been handed over to the next cell. If there was no next cell, the call would drop. This system of "timing advance" sets the 35km range limit which still exists on the latest networks. Australia ended up with a non-standard "CDMA" network that was developed locally and which was free of the timing advance system. It would operate as long as there was signal - which gave it a range of 60 to 70km. In another fortuitous move, designers looking to take advantage of some spare space in the system, decided to add the capacity to send short messages in text form. They had no way of forecasting just how popular the system would become. When messasging was introduced, messages cost about 30c to send, whereas today, messages are bundled with every plan. |
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| 3G | 3G systems were introduced in 2012 and the 2G towers shut down soon thereafter. Technically there was no reason the servcies could not co-exist - shutting down 2G was purely a business decision. Telstra initially promised rural customers a service with equivalent range to the CDMA system which they had grown to depend on. Their plan was to double the number of timing slots, extending range from 35 to 70km. However when Telstra appointed Sol Trojillo and his crew of ex US honchos to run the organisation, these plans were quashed in favour of keeping the networks standard and avoiding the development of an Australia only solution. Sadly Telstra forgot to tell the sales people, who were still promising the extended range, right up to the 3G launch. After a lot of back-pedalling, Telstra were forced to commit to a large number of extra base stations in order to plug the coverage gaps. Some users never achieved the same coverage as they had with the CDMA network. The launch of the third generation of mobile technologies came at a time when there was also rapid growth in the market for M2M systems. This started with the conversion of fire alarms and building security systems from traditional landlines to mobile phone based systems. Mobiles offered a lower operating cost and much lower installation costs: no longer did cables have to be run from the building’s PABX cabinet to the alarm systems. Cellular or mobile modems could just be dropped in to the alarm cabinet and connected to power. While previous generations of modems had been dial on demand, 3G heralded the widespread use of permanent connections. This paralleled the shift in home and business Internet connections, which had moved from "dial-up" to the always-on style ADSL services. With a dial up system, the modem would dial the Internet Service Provider (ISP) each time they wanted to access the Internet. Users would then be charged according to the amount of time they spent on line. A broadband modem by comparison would remain permanently connected and users were charged for the amount of data they sent, not how much time they spent on line. This change was a primary factor in the growth of M2M systems: while sending data over a dial up system may cost hundreds of dollars a year, the use of a permanent connection dropped this to a $60 dollars. 3G data systems also offered considerably higher speeds than their 2G predecessors. But the priority for 3G systems was still the handling of voice calls. Data was still considered as an add on service. The future however was soon evident as broadband users who were able to switch from a traditional analogue landline phone, to a service provided over their Internet connection: something known as VOIP of Voice Over Internet Protocol. Early services performed very badly, with frequent dropouts and speech delays. But, as the speed of the underlying network improved, VOIP phones offered a way of having a landline phone at a much lower cost than with a standard landline service. And without having to run additional cables. The technology behind VOIP has now matured to the point where, as Australia has rolled out its National Broadband Network (NBN), home and business landlines are now all provided as VOIP service. Most users have ditched their home phone and run a "Naked" service i.e. INternet access without a handset. |
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| 4G | While 1G, 2G and 3G were primarily voice services, with a layer tacked on for data, the 4G system turns this on its head, with data being the prime system and telephone calls being made using VOIP technologies. Given the transition that had occured in home and business Internet connections, this change was a logical progression. The 4G mobile system offers data rates which are considerably higher than those possible with 2G and 3G systems. This comes about due to a number of factors, one of which is improved modulation techniques (which allow more data to be crammed in to a given transmission) another is the availability of additional bandwidth, which enables each channel to be wider and to hence carry more data. An even bigger contributor to the higher data rates, is the pairing of frequencies: on a typical 4G implemention, devices can transmit on two different bands at once, hence doubling the throughput. In Australia, Telstra operates their 4G pairing on 700 MHz and 1800 Mhz. There is however one very important consideration here: the lower frequency 700 MHz services are capable of traveling much longer distances than the 1800 MHz service, which also suffers from poor ability to penetrate through obstacles such as buildings. Which means that the towers for 1800 MHz need to be much closer together: instead of towers being 20 or 30cm apart, they will be 3 to 5km apart. This high cell density offers another advantage: if the total capacity of a tower is fixed, then by reducing the size of its coverage it will take less users, which in turn means that each user can send more data. Those of you who work in country areas will have witnessed first hand the major consequence of this: if you visit a town, you will get high speed Internet via use of the 700 MHz and 1800 MHz bands. But as soon as you move out of the town boundaries, the 1800 MHz service drops off and you are back to 700 MHz alone. This means that rural users are automatically denied one of the biggest benefits of the 4G system. Some rural towns have it even worse - with "small cell" towers installed which operate only on 1800 MHz, limiting coverage to 5 or so km from the tower. And this is just another example of how badly rural users have been treated. Right up to the closure of the 3G network, rural customers had been complaining about the lack of 4G coverage and they fought unsuccesssfuly to keep the 3G network on, while coverage gaps were filled. But Telstra's push to re-used the 3G channels for urban 5G services won the argument. Leaving a lot of users wondering how the whole experience of coverage going backwards with the rollout of a new system, was allowed to happen all over again. To add insult to injury, not only do rural users not have sufficient coverage, but the Telco's have progressivley wound back the size of the batteries in their towers, so they no longer last 1 to 2 weeks and now run flat after 1 to 2 days. |
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| Narrow Band Data Services | The mobile data systems have evolved to the point where they can now form the basis for reliable high speed Internet access. But what about the segment which does not require high speed or high data volumes? This is the Machine to Machine or M2M market, where energy efficiency is usually more of a concern than speed. For years, the M2M market relied onthe use of standard 3G and 4G data modems. The fact that the modems are operating well under capacity did not matter: they wee cheap and reliable. The availability of low cost monthly data plans was the real driver for growth. The evolution of long range, license free radio systems for M2M applications started to challenge the cosy position of the mobile carriers: suddenly LoRa WAN, SigFox, Weightless and the other new players, could offer systems which did not rely on a “Telco”, were lower cost and far more energy efficient. The threat of losing sales in a market segment which, as a result of the emergence of the “Internet of Things”, motivated the mobile data industry to come up with an alternative. This came through the launch of a new "narrow band" data service aimed at the machine to machine and internet of things markets. Just as has been the tendency with most technological developments, there are two platforms competing for this new market: NB1 and Cat M1. There are advantages and disadvantages of each. But in Australia, one factor is drove early users in the market to Cat M1: it did not require any new hardware and could be added to the 4G towers with just a software upgrade. To offer NB1 rquired new hardware to support it, which meant a longer, more complex and more expensive implementation path. Modems which support Cat M1 and NB1 and are approved for use in Australia, are readily available and both services are available on the 4G networks operated by the carriers. Modem manufacturers have chosen one of two different paths : they will offer a 4G modem which supports standard 4G as well as Cat M1/NB1; or offer a universal Cat M1 / NB1 modem which does not offer 4G voice or high speed data. The first approach offers users the ability to switch easily between services according to the application. But it requires manufacturers to make multiple modems so that they can fit in with a country’s band plan. Offering a universal Cat M1 / NB1 only modem means the modem can be sold anywhere in the world. But as they typically don't a 4G fall-back option, users still need to choose a different modem for applications which require high speed data. With all the discussion of Cat M1 and NB1 it is important to realise that they have a number of deliberate limitations. Cat M1 and NB1 do not use the timing advance function used on standard 4G data channels. It thus does not suffer from the enforced 35km range limit. This is evident in the NB IOT coverage maps which show some very long ranges: basically if you can capture signal you can communicate. The promise of Voice over M1 handsets will, for the first time offer users the type of range they had 20 years ago with the first CDMA systems. Although tested in 2020, Telstra as still not committed to a launch date for the service - and there is a risk now that it will get overtaken by the push for "direct to cell" satellite services. Cat M1 and NB1 are low speed: this means that transmissions that took a fraction of a second on a 4G wil take much longer on Cat M1 and longer again on NB1. This means you need to allow a longer time for each transmission. It also means that over the air firmware updates and sending of configuration files will take much longer. The narrow band services ares intended for infrequent, short transmissions. Some of the normal requirements for regular communications on the paging channel are relaxed, allowing units to go in to deep sleep mode between transmissions, helping to reduce power consumption. Ultimately NB1 devices have a lower power consumption than Cat M1. The trade off is in high latency (up to 7 sec) and the fact that NB1 will not support two way live communications like Cat M1 does. Cat M1 data rates will support devices such as cameras, but are not suitable for video of data streaming. Cat M1 devices are expected to drop off after 300 seconds, so systems which offer features such as keeping devices on line between polls will no longer work. Of all the reasons to look at Cat M1 and NB1, probably the most significant is its range. Normal 2G/3G/4G services carry an enforced range limit of about 35km. That is because the towers use “time division multiplexing” to increase capacity. Because radio waves take a finite time to travel, signals from devices close to the tower arrive before those from devices further away. So the towers allocate 64 individual time slots and each time you move another 500m from the tower, you get handed over to the next slot. Ideally when you get to the last one, you are handed over to another tower. But if there is no tower, you drop out, no matter how strong your signal. The narrow band services do not use the “Timing advance” function and hence are free from the artificial range limitation. So if you can get your antenna mounted high, you can achieve very long range. Coverage maps show many sites extending 60 to 100km, which means you will get narrow band coverage in many locations which previously had no service. Offering voice calls over Cat M1 would provide a significant boost to rural users, but there is still no indication on when (or if) it will be offered. | |
| 5G | 5G is being touted as the future and a lot of 4G users are worried about the prospect of 4G systems being closed down to make way for 5G (as it has with CDMA, 2G and 3G). If 4G marked the switch from systems based on voice to those designed for data, 5G marks the transition between low speed and high speed (in relative terms). But physics plays an important qualifying role here. To increase data rates, designers must use more bandwidth. But competition for space in the low frequency bands is tight, so spectrum managers are allocating new bands to mobile services on much higher frequencies. At the higher frequencies, each channel can occupy more space and hence transmit more data. Techniques such as band pairing can also be used to double throughput. But gaining in one area always causes a compromise in another: the higher the frequency, the shorter the transmission range for a given power. Longer distances also mean higher error rates, so for reliable data transmission, range must be limited. Reducing range alsmo means that each tower needs to service a smaller number of users, allowing each user to send more data. The net effect of all this is a move towards “Small Cells.” With 5G, cells will be placed 500m, 1km or 2km apart. The cell towers can be smaller and cheaper to deploy, but that means a massive increase in the number of cells. So no matter what the hype says, high speed 5G data is going the be limited to large urban centres for quite a while. Even the much vaunted push for self driving cars falls victim to this: as soon as 5G services cease, so too will the functionality need to keep the cars mobile. What this means is that (1) 5G will not offer anything significant for rural customers for a long time and (2) 5G offers absolutely nothing for the M2M market of which we are all a part. But since 5G systems will be rolled out in tandem with 4G systems, we will be able to rely on 4G - in its standard LTE and Cat M1 (LTE M1) guise - for many years to come. In 2023 Cat e / LTE-M and NB IoT / NB1 were formally adopted into the 5G ecosystem, so there future is guaranteed. |
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| 6G | Although the first practical 5G systems are only now being deployed, manufacturers are starting to develop (and promote) 6G. With 6G they are promising end user speeds of 1 gigabit per second (1 GB/s). The realists among you will straight away recognise the trap here: if increased data rates need increasingly high frequencies and high frequencies mean shorter range, then 6G is going to be even shorter range than 5G. Early 5G prototype base stations were the size of a mini-van. The first practical 6G base station will likely be just as big. But before they can be released they will need to be scaled down to briefcase size: otherwise Telco’s will have no way of installing them in the density they will be needed (i.,e. on a 500 to 1000m radius). So 6G too will have great promise for city dwellers but will be of no practical use for anyone shifting data in remote localities. And that after all is where we play. What is interesting for observers of the 5G and 6G race is the new fight between the west (US and Europe) and China. The Chinese manufacturers are allowed to sell handsets in the west, but have been effectively blocked from selling base stations. The argument is based on the risk of the Chinese government gaining access to data from private citizens. One can only ask whether this fear is based on the existing hardware having "back-doors" which allow access to the friendly governments and they don't want the Chinese doing the same thing. |
