Amount of IoT devices, per person: car, fridge, smart watch, TVs, lamps, microcontrollers for smart applications, list goes on.
Companies that do standards, the market, politics, IoT-devices.
Prices for internet wont drop further. Companies can sell other services like streaming.
ITU (International Telecommunication Union), sets requirements for each generation.
3GPP (3rd Generation Partnership Project), a collection of regional telecom standards organizations. They develop the technical specifications, which will meet the ITUs requirements.
Automatic machines, traffic lights, vending machines, control or statistics, etc. Replacements would require to work with no internet connection
There are none, which contributed to its success. GSM is more felxible with a little lower data rate.
Changed:
Same:
Avoidance: Redundancy; have backup MSC for each MSC, duplicate data amongst more databases.
In the VLR.
With the EIR it can blacklist the phones.
The system can localize MS with the cells, because the network always knows in which cell the MS is.
Advantage:
Disadvantage:
Adapts to distances with guard spaces and training data.
Time Advance (TA).
The maximum data rate offered is 114Bit per user, but in reality lower because it can be split amongst user and will also send control data.
Because otherwise the MS would ping-pong between the BTSs equally "weak" signals and keep swapping.
Because it fully breaks the connection.
HLR/VLR
End-to-end encryption.
GSM was the "wireless ISDN", so they only implemented the security that ISDN also had. ISDN didnt have end-to-end.
Through the guard spaces and the 26 training bits (in the normal GSM time-slot).
They started to use more time slots per user for higher data rates, and the GPRS infrastructure was built ontop of the GSM infrastructure.
HSCSD was mainly a software update, it bundles several time slots to get higher user rates, so no new infrastructure needed. But it blocked channels for voice transmissions.
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Packet-switched:
Circuit-switched:
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"Normal" cellular phone networks dont have special features like group calls, walkie talkie etc. without preexisting infrastructure, also no ultra high reliability. But it would be cheaper as you dont need to build special infrastructure for TETRA.
The 3rd gen was defined by certain requirements, not a certain technology. Requirements were:
ITU made these standards and set the goals, companies tried to implement it. ETSI came up with UMTS.
Many different standardization bodies, companies and political interests. Some were already using GSM and added UMTS, some used cdmaOne and went with cdma2000. There was already infrastructure in use and frequencies in use, so the countries picked whatever fitted best for them.
Was focused on higher data rates, multimedia services and working on top of GSM. Spectrum that the ITU thought of wasnt available everywhere. Europe had GSM and Japan cdma2000 in those spectrums. In Europe, a part of this spectrum has been used.
That companies wont get their money back if they didnt cover that percentage in time.
UMTS architecture was based in GSM, so a type of extension, vice verca cdma2000 for cdmaOne.
More users -> more codes in use -> more interference -> each user benefits from more spreading to maintain robustness.
More spreading -> more chips per bit -> lower data rate but higher robustness against noise and interference.
Less spreading -> fewer chips per bit -> higher data rate but lower robustness.
So: higher robustness => more chips per bit => more spreading => fewer data bits per second.
Using "power control" it tells the MSs further away from the BS to transmit with more power, and tells MSs closer to the BS to transmit with less power, so that all signals from the MSs arrive with roughly the same signal strength at the BS.
https://en.wikipedia.org/wiki/Chip_(CDMA)
CDMA
Not a big difference at the core network. Slide 4.88: BSS from GSM and RNS from UMTS can both connect via an interface (Iu) to the CN (Core network) from UMTS. The CN then can forward to ISDN circuit-switched or the internet packet-switched. The CN doesnt notice if it was UMTS or GSM.
Schiller:
Hard handover: There is a specific point in time when the mobile device has to switch to a different frequency and a different time slot. In GSM, we have channels and TDMA frames, so within a frame on a certain frequency, you have a time slot. The handover then means you have to jump to a different channel and a different frequency, and maybe also a different time slot. There is a certain point in time where you really break with one of the networks and jump into the other network. Everything is prepared and you know where to jump, but you have to reestablish everything in the new cell.
Soft handover: The soft one is different. For the soft handover, the connection to multiple base stations is active all the time. So you stay on the same frequency. You have wider bands, it's CDMA, and all the antennas use the same frequency. No jumping (only different carriers). Usually you stay in the same. Then it's rather like multipath propagation. Could be by buildings, could be by several different antennas. So you will be able to automatically choose the 5 strongest paths. So you have different paths and receive the signal, and you basically combine these 5 paths (after delaying them by signal strength). This enables a soft handover, so there's no hard switching. Internally, there is: you have to set up a new path via new RNCs or eNodeBs, but the MS won't notice it.
Schiller: Usually not, but it depends on the type of handover. It notices switches of the main RNC. Only if the main RNC switches, the core will notice. Remember: sometimes the RNC also only forwards to another RNC. The core of course notices if you switch from 2G to 3G (from BSC to RNC).
Schiller: As soon as you introduce IP, the mobile phone network is nothing but a big bit-pipe, and the services can be created at the end. But, why have special services like MMS or SMS if you can just use IP? So as soon as you have higher data rates, you can do a lot more at the end, in the apps. You dont need the networks support anymore. That means the operators dont make any more money. By introducing packet services, network providers killed their revenues.
The point is: you can evolve the feature sets faster than the network. As soon as you have IP, then you can put whatever you like ontop. Recent example: Switch to video conferences, and you notice, it gets ass if the network is ass. A real problem is WLANs with video conferencing. Although you have high data rats, its shakey, latency, packet rates, etc. Compared to fixed networks. Autonomous cars are the reason we want 5G/6G for lower delays for remote controlling. Thats a problem, that you can suddenly use all the apps you used on the internet on a network that was never used for it.
Schiller:
Spectrum + Modulation + MIMO = Transmit more bits per second over the air.
Schiller: We have Megabits per second, and now we use something like TCP. What problems may occur?
The problem is: TCP checks the RTT. How long does it take for my packet until its acknowledged. The setting of the RTT depends on the delay. And the delay of your data traveling from your MS to a server for example. Over fixed network its ms. Over the wireless, 100-150ms. So in the end, we have at least something like 150ms -> 150ms <-. Max datarates using TCP, only depends on RTT and Bit-error-rate. Why?
The problem is, if you use protocols like TCP, they are not adapted to the effects of wireless connections with RTT due to forward error correction, sheduling, etc., so in the end, although you might offer something like 600Mbit/s, you can never use them if you use protocols like TCP. More: Chapter about internet protocols.
In LTE, we bring it down to something like 10ms and even below. Today: Ultra Reliable Low Latency Communications, we'll see it in 5G. Very difficult to achieve.
Remember: High data rates are fine, but its not the complete answer to the problems. We also need low delays, UMTS is not the perfect solution there. One of the reasons why UMTS is not the tech of the future. High delay from MS to servers.
Schiller: Flexibility.
If you think of the frequencies, thats just part of the bands, where LTE is operating, so depending on the country we can use different bands, we see a lot of different frequencies (slide 4.115 isnt showing everything). Many different frequencies, can work in paired or unpaired bands, so FDD or TDD, it can use many different modulation schemes, this makes it attractive. As soon as theres spectrum available, you can squeeze in LTE. Thats because you can use many different bandwidths, 1.4 up to 20MHz. So very flexible.
Second part: Much much simpler architecture. From a very high level view, it is pretty much teh same as in UMTS and GSM, the core. We changed the radio interface (now Uu), we have no CDMA anymore, and we have EPC (Evolved Packet Core), which is now packet switched only. Only packet-switching is much simpler. There are pros and cons for that.
Advantages: You use routers, we know how to operate this and how flexible packet-switching is. We dont need to setup and connect.
Disadvantages: What about quality of service? Some additional mechanisms needed.
But it makes the whole architecture much simpler. Especially if you look inside the EPC. There are very few components. Basically you have routers, and you have some management entities. Only 2 different main components. the MMEs and the routers. Thats it. There is no circuit-switching. More elements, more maintenance, setup, etc., so: bad. Only relying on packet-switching, we dont care how this packet reaches the UE. So we could also use WLAN to connect to the UE. You can offload a part of the traffic to available WLANs (with some conditions). But LTE can also use this unlicensed technology.
Schiller: Especially LTE and UMTS: Main difference on high-level:
In UMTS we use CDMA. Now, for LTE, we are back at FDMA/TDMA. Basically we dropped all of CDMA. We dropped part of the core aswell (circuit-switching). CDMA could do soft handovers, but FMDA/TDMA does hard handovers again. But its not the same handover as in GSM, because were talking about packets now. Its not a hard handover compared to GSM where youve had a connection which you have to switch over. In LTE, it is hard, but you can make it "softer" by: In EPC and also E-UTRAN you can provide the packets not only to the currently active station, but also to the new base station. So that if you hand over, the new packets are already there. They will during that time transmit them to both stations. Its a "seamless" handover.
Schiller: Remember: We are now at FDMA/TDMA.
Imagine tow base stations with their cells overlapping. This is very standard. In neighbouring cells, you cant use the same frequencies. Then you will have interference. So these two base stations have different frequencies. The idea is now: We do not use all the channels, so all the bandwidth we have in a cell with full power, but we use a part of the spectrum only with less power, so we restrict the cell size for certain frequencies, and now these frequencies can be reused, because they do not overlap. So we can reuse them for all the cells with less transmission power. No overlapping, no interference. And only for a minor part of the spectrum we send with more power, and this part of the spectrum will overlap, and they will use different frequencies.
So: We use the same frequencies in a smaller cell around each tower (that means: we send these at lower power). We reuse this part of the frequency. On the parts that overlap, we use another frequency.
Schiller: dropped circuit switching part, kept packet switching, also a bit new functions, new acronyms. but in the end, if you look at the core: Slide 4.119, HSS is the HLR, LTE core is simplified, no RNCs anymore, its all integrated now, thats the core idea.
Schiller: Seamless/lossless handover. Thats what you use them for.
What else? Handover without packet core. Safety if one node fails. You introduce redundant paths.
Relaying. Not all eNodeBs need a direct connection to the core. You can setup a network or make it denser/higher coverage by creating a new cell and connect it to another eNodeB, you dont need a connection to the packet core anymore. Way more flexible radio access network.
Schiller: You assign resource blocks in a static fashion. "Every 10 resource blocks". If you need higher datarates, you assign more of the spectrum. Some max. delay? Just make sure in the sheduler in the eNodeB that you assign in a periodic fashion the resource blocks. Thats the core idea.
Schiller: We are now back at a scheme that is not like GSM, but now we add a flexible way of using the frequencies, its only possible because we use the OFDM technology. This goes deep into electrical engineering. For here enough: We can dynamically assign parts of the spectrum for certain amounts of time. Thats then used for the multiplexing of different data streams for different users. And we can also use different sending powers to different users, so the base station will send different resource blocks with different signal strengths to different users. Thats also soft frequency reuse, not all frequencies are sent with the same power. Only the major part with less power. only some of the frequencies will use high power to reach UEs somewhere out in the cell in the overlapping areas.
Schiller: What's the evolutionary part? So in the early days of LTE you went for higher data rates. Then there was a new demand, so they scaled it down. When IoT showed up, you scaled it down. That's the evolutionary part - it's not a revolution with a new access theme, it's rather that we integrate devices into LTE. Need device-to-device? We integrate it.
Schiller: Long sleep periods are supported. LTE can support narrow band use, so you can replace single channels of GSM.
Some applications need high data rates, that's also possible in LTE. So LTE is extremely scalable when it comes to data rates. This is also reflected in the spectrum use. You can start with 200kHz, 1.4MHz, etc., depending on the available spectrum. LTE can be adapted. That's also why people think that LTE will take over the other standards.
When we talk about WLANs, we will see "why not use LTE for a campus network?". You can use many different frequencies and cell sizes etc. Also IoT works well with ultra low power technologies. Great IoT support.
LTE is quite flexible. Funny thing: Absolutely newest standard for WLANs, you will find LTE technology in there. Quite interesting.
Different applications are reflected in different spectrum use, sleep patterns, data rates, different frequencies. Sometimes for example for smart meters, you have to penetrate walls to get to the basement for water meters or something, then with LTE we can use lower frequencies. More flexible.